U.S. Department

of Transportation

Federal Aviation

Administration

FEBRUARY 9, 2012

AERONAUTICAL

INFORMATION

MANUAL

Change 1

July 26, 2012

REPLACES

BASIC DATED

February 9, 2012

Administration

U.S. Department

of Transportation

Federal Aviation

Aeronautical

Information

Manual Official Guide to

 Basic Flight Information and ATC Procedures

An electronic version of this publication is on the internet at

http://www.faa.gov/atpubs
AIM

Record of Changes

Change Number Change Filed Comments
7/26/12 AIM

Explanation of Changes E of Chg−1

Aeronautical Information Manual

Explanation of Changes

Effective: July 26, 2012

a. 1−1−7. Distance Measuring Equipment (DME)

This change explains why slaved compass systems may be

susceptible to heading errors on the ground and alerts pilots

to the fact that the system’s erroneous heading may not

self-correct. It also offers mitigation strategies to avoid a

possible heading misalignment at takeoff.

b. 1−1−15. LORAN

This change addresses the termination of U.S. LORAN-C

signals on 8 Feb 2010 and removes outdated material.

c. 1−2−2. Required Navigation Performance (RNP)

This change updates the guidance to the new terminology

used for these procedures in TBL 1−2−1. U.S. Standard

RNP Levels.

d. 4−1−20. Transponder Operation

This change assigns beacon code 1202 for gliders that are

VFR and not in contact with ATC. The change also adds

beacon code 1255 for aircraft engaged in fire fighting and

beacon code 1277 for authorized SAR missions.

e. 5−1−3. Notice to Airmen (NOTAM) System;

5−1−9. International Flight Plan (FAA Form 7233−4)−

IFR Flights (For Domestic or International Flights);

7−1−4. Preflight Briefing; 

9−1−5. Where and How to Get Charts of Foreign Areas

This change addresses the termination of U.S. LORAN-C

signals on 8 Feb 2010 and removes outdated material.

f. 5−1−4. Flight Plan - VFR Flights

This change updates the VFR Flight Plan section of the

AIM to match requirements of FAA Order JO 7110.10,

Flight Services, and JO 7340.2, Contractions, by

expanding items that may be pertinent in the Remarks field

of a VFR flight plan. Since this particular paragraph

pertains to VFR flight plans, “pertinent to ATC” is deleted

since ATC would not normally see VFR flight plan

remarks, and the deletion is replaced with information that

may aid FSS in search and rescue.

g. 5−1−8. Flight Plan (FAA Form 7233-1) -

Domestic IFR Flights

This change updates the IFR Flight Plan section of the AIM

to match requirements of FAA Order JO 7110.10, Flight

Services, and JO 7340.2, Contractions, by expanding items

that may be pertinent in the Remarks field of an IFR flight

plan, in particular the radiotelephony requirements, plus

notes of explanation concerning radiotelephony.

And, this change addresses the termination of U.S.

LORAN-C signals on 8 Feb 2010 and removes outdated

material.

h. 5−4−16. Simultaneous Close Parallel ILS PRM

Approaches (Independent) and Simultaneous Offset

Instrument Approaches (SOIA)

This change removes the requirement of pilots not

qualified to accept PRM approaches to contact the FAA

Command Center prior to departure.

i. 5−4−18. RNP AR Instrument Approach

Procedures

This change updates the guidance to the new terminology

used for these procedures.

j. 7−1−26. Microbursts

This change removed FWA from the ASR−WSP wind

shear systems in FIG 7−1−16. NAS Wind Shear Product

Systems.

k. 7−6−5. Safety Alerts For Operators (SAFO) and

Information For Operators (InFO); and Appendix

4. Abbreviations/Acronym

This change introduces, explains and updates the guidance

to the new terminology used for Safety Alerts For

Operators (SAFO) and Information For Operators (InFO).

l. Entire publication.

Editorial/format changes were made where necessary, to

include recent organization name changes. Revision bars

were not used when changes are insignificant in nature.

7/26/12 AIM

Page Control Chart 1

AIM Change 1

Page Control Chart

July 26, 2012

REMOVE PAGES DATED INSERT PAGES DATED

Entire Basic Manual .................... 2/9/12 Entire Change 1 ....................... 7/26/12

NOTE−

Because the Pilot /Controller Glossary is an appendix to several other publications it will contain pages dated

2/9/12. The entire AIM including its Pilot/Controller Glossary are printed in its entirety in this Change 1

package.

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Cover 7/26/12

Record of Changes N/A

Exp of Chg−Basic 7/26/12

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Subscription Info 7/26/12

Comments/Corr 7/26/12

Comments/Corr 7/26/12

Basic Flight Info 7/26/12

Publication Policy 7/26/12

Reg & Advis Cir 7/26/12

Table of Contents

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Chapter 1. Air Navigation

Section 1. Navigation Aids

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Section 2. Area Navigation

(RNAV) and Required

Navigation Performance

(RNP)

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Chapter 2. Aeronautical

Lighting and Other Airport

Visual Aids

Section 1. Airport Lighting

Aids

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Section 2. Air Navigation and

Obstruction Lighting

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Section 3. Airport Marking

Aids and Signs

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Chapter 3. Airspace

Section 1. General

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Section 2. Controlled Airspace

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Section 3. Class G Airspace

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Section 4. Special Use 

Airspace

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Section 5. Other Airspace

Areas

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Chapter 4. Air Traffic Control

Section 1. Services Available

to Pilots

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Section 2. Radio

Communications Phraseology

and Techniques

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Section 3. Airport Operations

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Section 4. ATC Clearances

and Aircraft Separation

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Section 5. Surveillance 

Systems

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Section 6. Operational Policy/

Procedures for Reduced Vertical

Separation Minimum (RVSM) in

the Domestic U.S., Alaska,

Offshore Airspace and the 

San Juan FIR

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Section 7. Operational Policy/

Procedures for the Gulf of Mexico

50 NM Lateral Separation

Initiative

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Chapter 5. Air Traffic 

Procedures

Section 1. Preflight

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Section 2. Departure

Procedures

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Section 3. En Route

Procedures

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Section 4. Arrival Procedures

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Section 5. Pilot/Controller

Roles and Responsibilities

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Section 6. National Security

and Interception Procedures

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Chapter 6. Emergency 

Procedures

Section 1. General

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Section 2. Emergency Services

Available to Pilots

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Section 3. Distress and

Urgency Procedures

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Section 4. Two−way Radio

Communications Failure

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Section 5. Aircraft Rescue

and Fire Fighting

Communications

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Chapter 7. Safety of Flight

Section 1. Meteorology

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Section 2. Altimeter Setting 

Procedures

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Section 3. Wake Turbulence

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Section 4. Bird Hazards and

Flight Over National Refuges,

Parks, and Forests

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Section 5. Potential Flight

Hazards

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Section 6. Safety, Accident,

and Hazard Reports

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Chapter 8. Medical Facts 

for Pilots

Section 1. Fitness for Flight

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Chapter 9. Aeronautical

Charts and Related

Publications

Section 1. Types of Charts

Available

9−1−1 7/26/12

9−1−2 7/26/12

9−1−3 7/26/12

9−1−4 7/26/12

9−1−5 7/26/12

9−1−6 7/26/12

9−1−7 7/26/12

9−1−8 7/26/12

9−1−9 7/26/12

9−1−10 7/26/12

9−1−11 7/26/12

9−1−12 7/26/12

9−1−13 7/26/12

Chapter 10. Helicopter

Operations

Section 1. Helicopter IFR

Operations

10−1−1 7/26/12

10−1−2 7/26/12

10−1−3 7/26/12

10−1−4 7/26/12

10−1−5 7/26/12

10−1−6 7/26/12

10−1−7 7/26/12

PAGE DATE

Section 2. Special Operations

10−2−1 7/26/12

10−2−2 7/26/12

10−2−3 7/26/12

10−2−4 7/26/12

10−2−5 7/26/12

10−2−6 7/26/12

10−2−7 7/26/12

10−2−8 7/26/12

10−2−9 7/26/12

10−2−10 7/26/12

10−2−11 7/26/12

10−2−12 7/26/12

10−2−13 7/26/12

10−2−14 7/26/12

10−2−15 7/26/12

10−2−16 7/26/12

10−2−17 7/26/12

Appendices

Appendix 1−1 7/26/12

Env N/A

Appendix 2−1 7/26/12

Appendix 3−1 7/26/12

Appendix 4−1 7/26/12

Appendix 4−2 7/26/12

Appendix 4−3 7/26/12

Appendix 4−4 7/26/12

Appendix 4−5 7/26/12

Pilot/Controller Glossary

PCG−1 7/26/12

PCG A−1 2/9/12

PCG A−2 2/9/12

PCG A−3 2/9/12

PCG A−4 2/9/12

PCG A−5 2/9/12

PGC A−6 2/9/12

PCG A−7 2/9/12

PCG A−8 2/9/12

PCG A−9 2/9/12

PCG A−10 2/9/12

PCG A−11 2/9/12

PCG A−12 2/9/12

PCG A−13 2/9/12

PCG A−14 2/9/12

PCG A−15 2/9/12

PCG A−16 2/9/12

PCG B−1 2/9/12
AIM 7/26/12

Checklist of Pages

CK−6 Checklist of Pages

PAGE DATE

PCG C−1 2/9/12

PCG C−2 2/9/12

PCG C−3 2/9/12

PCG C−4 2/9/12

PCG C−5 2/9/12

PCG C−6 2/9/12

PCG C−7 2/9/12

PCG C−8 2/9/12

PCG C−9 2/9/12

PCG D−1 2/9/12

PCG D−2 2/9/12

PCG D−3 2/9/12

PCG D−4 2/9/12

PCG E−1 2/9/12

PCG E−2 2/9/12

PCG F−1 2/9/12

PCG F−2 2/9/12

PCG F−3 2/9/12

PCG F−4 2/9/12

PCG F−5 2/9/12

PCG G−1 2/9/12

PCG G−2 2/9/12

PCG H−1 2/9/12

PCG H−2 2/9/12

PCG H−3 2/9/12

PCG I−1 2/9/12

PCG I−2 2/9/12

PCG I−3 2/9/12

PCG I−4 2/9/12

PCG I−5 2/9/12

PCG J−1 2/9/12

PCG K−1 2/9/12

PCG L−1 2/9/12

PCG L−2 2/9/12

PCG L−3 2/9/12

PAGE DATE

PCG M−1 2/9/12

PCG M−2 2/9/12

PCG M−3 2/9/12

PCG M−4 2/9/12

PCG M−5 2/9/12

PCG M−6 2/9/12

PCG N−1 2/9/12

PCG N−2 2/9/12

PCG N−3 2/9/12

PCG N−4 2/9/12

PCG O−1 2/9/12

PCG O−2 7/26/12

PCG O−3 7/26/12

PCG O−4 7/26/12

PCG P−1 2/9/12

PCG P−2 2/9/12

PCG P−3 2/9/12

PCG P−4 2/9/12

PCG P−5 7/26/12

PCG Q−1 2/9/12

PCG R−1 2/9/12

PCG R−2 2/9/12

PCG R−3 2/9/12

PCG R−4 2/9/12

PCG R−5 2/9/12

PCG R−6 2/9/12

PCG R−7 2/9/12

PCG R−8 2/9/12

PCG S−1 2/9/12

PCG S−2 2/9/12

PCG S−3 2/9/12

PCG S−4 2/9/12

PCG S−5 2/9/12

PCG S−6 2/9/12

PCG S−7 2/9/12

PAGE DATE

PCG S−8 2/9/12

PCG T−1 2/9/12

PCG T−2 2/9/12

PCG T−3 2/9/12

PCG T−4 2/9/12

PCG T−5 2/9/12

PCG T−6 2/9/12

PCG T−7 2/9/12

PCG T−8 2/9/12

PCG U−1 2/9/12

PCG V−1 2/9/12

PCG V−2 2/9/12

PCG V−3 2/9/12

PCG V−4 2/9/12

PCG W−1 2/9/12

Index

I−1 7/26/12

I−2 7/26/12

I−3 7/26/12

I−4 7/26/12

I−5 7/26/12

I−6 7/26/12

I−7 7/26/12

I−8 7/26/12

I−9 7/26/12

I−10 7/26/12

I−11 7/26/12

I−12 7/26/12

I−13 7/26/12

Back Cover N/A
7/26/12 AIM

Subscription Information

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7/26/12 AIM

Comments/Corrections

Comments/Corrections

Comments, suggested changes, or corrections concerning this publication may be submitted on this form and

mailed to:

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ATC Products and Publications, AJV−362

Attn: AIM Editor, Station 5601

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7/26/12 AIM

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Basic Flight Information and ATC Procedures

Federal Aviation Administration (FAA)

The Federal Aviation Administration is responsible

for insuring the safe, efficient, and secure use of the

Nation’s airspace, by military as well as civil

aviation, for promoting safety in air commerce, for

encouraging and developing civil aeronautics,

including new aviation technology, and for supporting the requirements of national defense.

The activities required to carry out these responsibilities include: safety regulations; airspace management

and the establishment, operation, and maintenance of

a civil−military common system of air traffic control

(ATC) and navigation facilities; research and

development in support of the fostering of a national

system of airports, promulgation of standards and

specifications for civil airports, and administration of

Federal grants−in−aid for developing public airports;

various joint and cooperative activities with the

Department of Defense; and technical assistance

(under State Department auspices) to other countries.

Aeronautical Information Manual (AIM)

Basic Flight Information and ATC Procedures

This manual is designed to provide the aviation

community with basic flight information and ATC

procedures for use in the National Airspace System

(NAS) of the United States. An international version

called the Aeronautical Information Publication

contains parallel information, as well as specific

information on the international airports for use by

the international community.

This manual contains the fundamentals required in

order to fly in the United States NAS. It also contains

items of interest to pilots concerning health and

medical facts, factors affecting flight safety, a

pilot/controller glossary of terms used in the ATC

System, and information on safety, accident, and

hazard reporting.

This manual is complemented by other operational

publications which are available via separate

subscriptions. These publications are:

Notices to Airmen publication - A publication

containing current Notices to Airmen (NOTAMs)

which are considered essential to the safety of flight

as well as supplemental data affecting the other

operational publications listed here. It also includes

current Flight Data Center NOTAMs, which are

regulatory in nature, issued to establish restrictions to

flight or to amend charts or published Instrument

Approach Procedures. This publication is issued

every four weeks and is available through subscription from the Superintendent of Documents.

The Airport/Facility Directory, the Alaska

Supplement, and the Pacific Chart Supplement −

These publications contain information on airports,

communications, navigation aids, instrument landing

systems, VOR receiver check points, preferred

routes, Flight Service Station/Weather Service

telephone numbers, Air Route Traffic Control Center

(ARTCC) frequencies, part−time surface areas, and

various other pertinent special notices essential to air

navigation. These publications are available upon

subscription from the Aeronautical Navigation

Products (AeroNav) Logistics Group, Federal

Aviation Administration, Glenn Dale, Maryland

20769.

Publication Schedule

Basic or Change Cutoff Date

for Submission

Effective Date

of Publication

Basic Manual 8/25/11 2/9/12

Change 1 2/19/12 7/26/12

Change 2 7/26/12 3/7/13

Change 3 3/7/13 8/22/13

Basic Manual 8/22/13 2/6/14
7/26/12 AIM

Flight Information Publication Policy

Flight Information Publication Policy

The following is in essence, the statement issued by

the FAA Administrator and published in the

December 10, 1964, issue of the Federal Register,

concerning the FAA policy as pertaining to the type

of information that will be published as NOTAMs

and in the Aeronautical Information Manual.

a. It is a pilot’s inherent responsibility to be alert

at all times for and in anticipation of all circumstances, situations, and conditions affecting the safe

operation of the aircraft. For example, a pilot should

expect to find air traffic at any time or place. At or

near both civil and military airports and in the vicinity of known training areas, a pilot should expect

concentrated air traffic and realize concentrations

of air traffic are not limited to these places.

b. It is the general practice of the agency to advertise by NOTAM or other flight information publications such information it may deem appropriate; information which the agency may from time to time

make available to pilots is solely for the purpose of

assisting them in executing their regulatory responsibilities. Such information serves the aviation

community as a whole and not pilots individually.

c. The fact that the agency under one particular

situation or another may or may not furnish information does not serve as a precedent of the

agency’s responsibility to the aviation community;

neither does it give assurance that other information

of the same or similar nature will be advertised, nor,

does it guarantee that any and all information

known to the agency will be advertised.

d. This publication, while not regulatory, provides information which reflects examples of operating techniques and procedures which may be requirements in other federal publications or

regulations. It is made available solely to assist pilots in executing their responsibilities required by

other publications.

Consistent with the foregoing, it is the policy of the

Federal Aviation Administration to furnish information only when, in the opinion of the agency,

a unique situation should be advertised and not to

furnish routine information such as concentrations

of air traffic, either civil or military. The

Aeronautical Information Manual will not contain

informative items concerning everyday circumstances that pilots should, either by good practices

or regulation, expect to encounter or avoid.
7/26/12 AIM

Code of Federal Regulations and Advisory Circulars

Aeronautical Information Manual (AIM)

Code of Federal Regulations and Advisory Circulars

Code of Federal Regulations - The FAA publishes the

Code of Federal Regulations (CFRs) to make readily

available to the aviation community the regulatory

requirements placed upon them. These regulations

are sold as individual parts by the Superintendent of

Documents.

The more frequently amended parts are sold on

subscription service with subscribers receiving

changes automatically as issued. Less active parts are

sold on a single−sale basis. Changes to single-sale

parts will be sold separately as issued. Information

concerning these changes will be furnished by the

FAA through its Status of Federal Aviation

Regulations, AC 00−44.

Advisory Circulars - The FAA issues Advisory

Circulars (ACs) to inform the aviation public in a

systematic way of nonregulatory material. Unless

incorporated into a regulation by reference, the

contents of an advisory circular are not binding on the

public. Advisory Circulars are issued in a numbered

subject system corresponding to the subject areas of

the Code of Federal Regulations (CFRs) (Title 14,

Chapter 1, FAA).

AC 00−2, Advisory Circular Checklist and Status of

Other FAA Publications, contains advisory circulars

that are for sale as well as those distributed

free−of−charge by the FAA.

NOTE−

The above information relating to CFRs and ACs is

extracted from AC 00−2. Many of the CFRs and ACs listed

in AC 00−2 are cross−referenced in the AIM. These

regulatory and nonregulatory references cover a wide

range of subjects and are a source of detailed information

of value to the aviation community. AC 00−2 is issued

annually and can be obtained free−of−charge from:

U.S. Department of Transportation

Subsequent Distribution Office

Ardmore East Business Center

3341 Q 75th Avenue

Landover, MD 20785

Telephone: 301−322−4961

AC 00−2 may also be found at: http://www.faa.gov under

Advisory Circulars.

External References - All references to Advisory

Circulars and other FAA publications in the

Aeronautical Information Manual include the FAA

Advisory Circular or Order identification numbers

(when available). However, due to varied publication

dates, the basic publication letter is not included.

EXAMPLE−

FAAO JO 7110.65M, Air Traffic Control, is referenced as

FAAO JO 7110.65.

7/26/12 AIM

Table of Contents i

Table of Contents

Chapter 1. Air Navigation

Section 1. Navigation Aids

Paragraph Page

1-1-1. General ............................................................ 1-1-1

1-1-2. Nondirectional Radio Beacon (NDB) .................................. 1-1-1

1-1-3. VHF Omni-directional Range (VOR) ................................. 1-1-1

1-1-4. VOR Receiver Check ................................................ 1-1-2

1-1-5. Tactical Air Navigation (TACAN) ...................................... 1-1-3

1-1-6. VHF Omni-directional Range/Tactical Air Navigation (VORTAC) ......... 1-1-3

1-1-7. Distance Measuring Equipment (DME) ................................ 1-1-3

1-1-8. Navigational Aid (NAVAID) Service Volumes ........................... 1-1-4

1-1-9. Instrument Landing System (ILS) ...................................... 1-1-7

1-1-10. Simplified Directional Facility (SDF) .................................. 1-1-12

1-1-11. Microwave Landing System (MLS) .................................... 1-1-14

1-1-12. NAVAID Identifier Removal During Maintenance ...................... 1-1-16

1-1-13. NAVAIDs with Voice ............................................... 1-1-17

1-1-14. User Reports on NAVAID Performance ............................... 1-1-17

1-1-15. LORAN .......................................................... 1-1-17

1-1-16. VHF Direction Finder .............................................. 1-1-17

1-1-17. Inertial Reference Unit (IRU), Inertial Navigation System (INS), and

Attitude Heading Reference System (AHRS) ........................ 1-1-18

1-1-18. Doppler Radar ..................................................... 1-1-18

1-1-19. Global Positioning System (GPS) ..................................... 1-1-18

1-1-20. Wide Area Augmentation System (WAAS) ............................. 1-1-29

1-1-21. Ground Based Augmentation System (GBAS) Landing System (GLS) 1-1-34 ......

1-1-22. Precision Approach Systems other than ILS, GLS, and MLS .............. 1-1-34

Section 2. Area Navigation (RNAV) and Required Navigation

Performance (RNP)

1-2-1. Area Navigation (RNAV) ............................................ 1-2-1

1-2-2. Required Navigation Performance (RNP) ............................... 1-2-4

1-2-3. Use of Suitable Area Navigation (RNAV) Systems on

Conventional Procedures and Routes ............................... 1-2-5

Chapter 2. Aeronautical Lighting and 

Other Airport Visual Aids

Section 1. Airport Lighting Aids

2-1-1. Approach Light Systems (ALS) ........................................ 2-1-1

2-1-2. Visual Glideslope Indicators .......................................... 2-1-1

2-1-3. Runway End Identifier Lights (REIL) .................................. 2-1-6

2-1-4. Runway Edge Light Systems .......................................... 2-1-6

2-1-5. In-runway Lighting ................................................. 2-1-6

2-1-6. Runway Status Light (RWSL) System ................................... 2-1-7

2-1-7. Stand­Alone Final Approach Runway Occupancy Signal (FAROS) .......... 2-1-10
AIM 7/26/12

ii Table of Contents

Paragraph Page

2-1-8. Control of Lighting Systems ........................................... 2-1-11

2-1-9. Pilot Control of Airport Lighting ...................................... 2-1-11

2-1-10. Airport/Heliport Beacons ............................................ 2-1-14

2-1-11. Taxiway Lights ..................................................... 2-1-15

Section 2. Air Navigation and Obstruction Lighting

2-2-1. Aeronautical Light Beacons ........................................... 2-2-1

2-2-2. Code Beacons and Course Lights ...................................... 2-2-1

2-2-3. Obstruction Lights .................................................. 2-2-1

Section 3. Airport Marking Aids and Signs

2-3-1. General ............................................................ 2-3-1

2-3-2. Airport Pavement Markings ........................................... 2-3-1

2-3-3. Runway Markings ................................................... 2-3-1

2-3-4. Taxiway Markings ................................................... 2-3-7

2-3-5. Holding Position Markings ............................................ 2-3-12

2-3-6. Other Markings ..................................................... 2-3-16

2-3-7. Airport Signs ....................................................... 2-3-19

2-3-8. Mandatory Instruction Signs .......................................... 2-3-20

2-3-9. Location Signs ...................................................... 2-3-23

2-3-10. Direction Signs .................................................... 2-3-25

2-3-11. Destination Signs .................................................. 2-3-28

2-3-12. Information Signs .................................................. 2-3-29

2-3-13. Runway Distance Remaining Signs .................................... 2-3-29

2-3-14. Aircraft Arresting Systems ........................................... 2-3-30

2-3-15. Security Identifications Display Area (Airport Ramp Area) ............... 2-3-31

Chapter 3. Airspace

Section 1. General

3-1-1. General ............................................................ 3-1-1

3-1-2. General Dimensions of Airspace Segments .............................. 3-1-1

3-1-3. Hierarchy of Overlapping Airspace Designations ......................... 3-1-1

3-1-4. Basic VFR Weather Minimums ........................................ 3-1-1

3-1-5. VFR Cruising Altitudes and Flight Levels ............................... 3-1-2

Section 2. Controlled Airspace

3-2-1. General ............................................................ 3-2-1

3-2-2. Class A Airspace .................................................... 3-2-2

3-2-3. Class B Airspace .................................................... 3-2-2

3-2-4. Class C Airspace .................................................... 3-2-4

3-2-5. Class D Airspace .................................................... 3-2-8

3-2-6. Class E Airspace .................................................... 3-2-9

Section 3. Class G Airspace

3-3-1. General ............................................................ 3-3-1

3-3-2. VFR Requirements .................................................. 3-3-1

3-3-3. IFR Requirements .................................................. 3-3-1
7/26/12 AIM

Table of Contents iii

Section 4. Special Use Airspace

Paragraph Page

3-4-1. General ............................................................ 3-4-1

3-4-2. Prohibited Areas .................................................... 3-4-1

3-4-3. Restricted Areas .................................................... 3-4-1

3-4-4. Warning Areas ...................................................... 3-4-1

3-4-5. Military Operations Areas ............................................ 3-4-2

3-4-6. Alert Areas ......................................................... 3-4-2

3-4-7. Controlled Firing Areas .............................................. 3-4-2

Section 5. Other Airspace Areas

3-5-1. Airport Advisory/Information Services .................................. 3-5-1

3-5-2. Military Training Routes ............................................. 3-5-1

3-5-3. Temporary Flight Restrictions ......................................... 3-5-2

3-5-4. Parachute Jump Aircraft Operations ................................... 3-5-5

3-5-5. Published VFR Routes ............................................... 3-5-5

3-5-6. Terminal Radar Service Area (TRSA) .................................. 3-5-9

3-5-7. National Security Areas .............................................. 3-5-9

Chapter 4. Air Traffic Control

Section 1. Services Available to Pilots

4-1-1. Air Route Traffic Control Centers ..................................... 4-1-1

4-1-2. Control Towers ..................................................... 4-1-1

4-1-3. Flight Service Stations ............................................... 4-1-1

4-1-4. Recording and Monitoring ............................................ 4-1-1

4-1-5. Communications Release of IFR Aircraft Landing at an Airport Without

an Operating Control Tower ....................................... 4-1-1

4-1-6. Pilot Visits to Air Traffic Facilities ..................................... 4-1-1

4-1-7. Operation Take‐off and Operation Raincheck ........................... 4-1-2

4-1-8. Approach Control Service for VFR Arriving Aircraft ..................... 4-1-2

4-1-9. Traffic Advisory Practices at Airports Without Operating Control Towers 4-1-2 ....

4-1-10. IFR Approaches/Ground Vehicle Operations ........................... 4-1-6

4-1-11. Designated UNICOM/MULTICOM Frequencies ....................... 4-1-6

4-1-12. Use of UNICOM for ATC Purposes ................................... 4-1-7

4-1-13. Automatic Terminal Information Service (ATIS) ........................ 4-1-7

4-1-14. Automatic Flight Information Service (AFIS) - Alaska FSSs Only ......... 4-1-8

4-1-15. Radar Traffic Information Service .................................... 4-1-8

4-1-16. Safety Alert ....................................................... 4-1-10

4-1-17. Radar Assistance to VFR Aircraft .................................... 4-1-11

4-1-18. Terminal Radar Services for VFR Aircraft ............................. 4-1-12

4-1-19. Tower En Route Control (TEC) ...................................... 4-1-14

4-1-20. Transponder Operation ............................................. 4-1-15

4-1-21. Hazardous Area Reporting Service .................................... 4-1-18

4-1-22. Airport Reservation Operations and Special Traffic Management Programs 4-1-21 .

4-1-23. Requests for Waivers and Authorizations from Title 14, Code of Federal 

Regulations (14 CFR) ............................................ 4-1-23

4-1-24. Weather System Processor ........................................... 4-1-23
AIM 7/26/12

iv Table of Contents

Section 2. Radio Communications Phraseology 

and Techniques

Paragraph Page

4-2-1. General ............................................................ 4-2-1

4-2-2. Radio Technique .................................................... 4-2-1

4-2-3. Contact Procedures .................................................. 4-2-1

4-2-4. Aircraft Call Signs ................................................... 4-2-3

4-2-5. Description of Interchange or Leased Aircraft ........................... 4-2-4

4-2-6. Ground Station Call Signs ............................................ 4-2-4

4-2-7. Phonetic Alphabet ................................................... 4-2-5

4-2-8. Figures ............................................................ 4-2-6

4-2-9. Altitudes and Flight Levels ........................................... 4-2-6

4-2-10. Directions ......................................................... 4-2-6

4-2-11. Speeds ............................................................ 4-2-6

4-2-12. Time ............................................................. 4-2-6

4-2-13. Communications with Tower when Aircraft Transmitter or Receiver or Both

are Inoperative .................................................. 4-2-7

4-2-14. Communications for VFR Flights ..................................... 4-2-8

Section 3. Airport Operations

4-3-1. General ............................................................ 4-3-1

4-3-2. Airports with an Operating Control Tower .............................. 4-3-1

4-3-3. Traffic Patterns ..................................................... 4-3-2

4-3-4. Visual Indicators at Airports Without an Operating Control Tower .......... 4-3-5

4-3-5. Unexpected Maneuvers in the Airport Traffic Pattern ..................... 4-3-6

4-3-6. Use of Runways/Declared Distances .................................... 4-3-6

4-3-7. Low Level Wind Shear/Microburst Detection Systems .................... 4-3-11

4-3-8. Braking Action Reports and Advisories ................................. 4-3-11

4-3-9. Runway Friction Reports and Advisories ................................ 4-3-11

4-3-10. Intersection Takeoffs ............................................... 4-3-12

4-3-11. Pilot Responsibilities When Conducting Land and Hold Short 

Operations (LAHSO) ............................................ 4-3-13

4-3-12. Low Approach ..................................................... 4-3-15

4-3-13. Traffic Control Light Signals ......................................... 4-3-15

4-3-14. Communications ................................................... 4-3-16

4-3-15. Gate Holding Due to Departure Delays ............................... 4-3-17

4-3-16. VFR Flights in Terminal Areas ....................................... 4-3-17

4-3-17. VFR Helicopter Operations at Controlled Airports ...................... 4-3-17

4-3-18. Taxiing ........................................................... 4-3-19

4-3-19. Taxi During Low Visibility ........................................... 4-3-20

4-3-20. Exiting the Runway After Landing .................................... 4-3-21

4-3-21. Practice Instrument Approaches ...................................... 4-3-21

4-3-22. Option Approach .................................................. 4-3-23

4-3-23. Use of Aircraft Lights ............................................... 4-3-23

4-3-24. Flight Inspection/`Flight Check' Aircraft in Terminal Areas ............... 4-3-24

4-3-25. Hand Signals ...................................................... 4-3-24

4-3-26. Operations at Uncontrolled Airports With Automated Surface 

Observing System (ASOS)/Automated Weather Sensor System(AWSS)/

Automated Weather Observing System (AWOS) ...................... 4-3-28
7/26/12 AIM

Table of Contents v

Section 4. ATC Clearances and Aircraft Separation

Paragraph Page

4-4-1. Clearance .......................................................... 4-4-1

4-4-2. Clearance Prefix .................................................... 4-4-1

4-4-3. Clearance Items ..................................................... 4-4-1

4-4-4. Amended Clearances ................................................ 4-4-2

4-4-5. Coded Departure Route (CDR) ....................................... 4-4-3

4-4-6. Special VFR Clearances .............................................. 4-4-3

4-4-7. Pilot Responsibility upon Clearance Issuance ............................ 4-4-4

4-4-8. IFR Clearance VFR-on-top ......................................... 4-4-4

4-4-9. VFR/IFR Flights .................................................... 4-4-5

4-4-10. Adherence to Clearance ............................................. 4-4-5

4-4-11. IFR Separation Standards ........................................... 4-4-7

4-4-12. Speed Adjustments ................................................. 4-4-7

4-4-13. Runway Separation ................................................. 4-4-9

4-4-14. Visual Separation .................................................. 4-4-9

4-4-15. Use of Visual Clearing Procedures .................................... 4-4-10

4-4-16. Traffic Alert and Collision Avoidance System (TCAS I & II) .............. 4-4-10

4-4-17. Traffic Information Service (TIS) ..................................... 4-4-10

Section 5. Surveillance Systems

4-5-1. Radar ............................................................. 4-5-1

4-5-2. Air Traffic Control Radar Beacon System (ATCRBS) 4-5-2 .....................

4-5-3. Surveillance Radar .................................................. 4-5-7

4-5-4. Precision Approach Radar (PAR) ...................................... 4-5-7

4-5-5. Airport Surface Detection Equipment - Model X (ASDE-X) ............ 4-5-7

4-5-6. Traffic Information Service (TIS) ...................................... 4-5-8

4-5-7. Automatic Dependent Surveillance-Broadcast (ADS-B) Services ......... 4-5-14

4-5-8. Traffic Information Service- Broadcast (TIS-B) ........................ 4-5-17

4-5-9. Flight Information Service- Broadcast (FIS-B) ......................... 4-5-18

4-5-10. Automatic Dependent Surveillance-Rebroadcast (ADS-R) .............. 4-5-20

Section 6. Operational Policy/Procedures for Reduced Vertical

Separation Minimum (RVSM) in the Domestic U.S., Alaska, Offshore

Airspace and the San Juan FIR

4-6-1. Applicability and RVSM Mandate (Date/Time and Area) ................. 4-6-1

4-6-2. Flight Level Orientation Scheme ...................................... 4-6-1

4-6-3. Aircraft and Operator Approval Policy/Procedures, RVSM Monitoring and 

Databases for Aircraft and Operator Approval ....................... 4-6-2

4-6-4. Flight Planning into RVSM Airspace ................................... 4-6-3

4-6-5. Pilot RVSM Operating Practices and Procedures ......................... 4-6-3

4-6-6. Guidance on Severe Turbulence and Mountain Wave Activity (MWA) ....... 4-6-4

4-6-7. Guidance on Wake Turbulence ........................................ 4-6-5

4-6-8. Pilot/Controller Phraseology .......................................... 4-6-6

4-6-9. Contingency Actions: Weather Encounters and Aircraft System Failures 4-6-8 .....

4-6-10. Procedures for Accommodation of Non-RVSM Aircraft ................. 4-6-10

4-6-11. Non-RVSM Aircraft Requesting Climb to and Descent from Flight Levels Above

 RVSM Airspace Without Intermediate Level Off ..................... 4-6-11
AIM 7/26/12

vi Table of Contents

Section 7. Operational Policy/Procedures for the Gulf of Mexico 50 NM

Lateral Separation Initiative

Paragraph Page

4-7-1. Introduction and Background ......................................... 4-7-1

4-7-2. Gulf of Mexico 50 NM Lateral Separation Initiative Web Page: Policy, Procedures 

and Guidance for Operators and Regulators ......................... 4-7-1

4-7-3. Lateral Separation Minima Applied .................................... 4-7-1

4-7-4. Operation on Routes on the periphery of the Gulf of Mexico CTAs ......... 4-7-2

4-7-5. Provisions for Accommodation of NonRNP10 Aircraft (Aircraft Not Authorized 

RNP 10 or RNP 4) ............................................... 4-7-2

4-7-6. Operator Action .................................................... 4-7-2

4-7-7. RNP 10 or RNP 4 Authorization: Policy and Procedures for Aircraft and 

Operators ...................................................... 4-7-2

4-7-8. Flight Planning Requirements ......................................... 4-7-4

4-7-9. Pilot and Dispatcher Procedures: Basic and In­flight Contingency Procedures 4-7-5 .

Chapter 5. Air Traffic Procedures

Section 1. Preflight

5-1-1. Preflight Preparation ................................................ 5-1-1

5-1-2. Follow IFR Procedures Even When Operating VFR ...................... 5-1-2

5-1-3. Notice to Airmen (NOTAM) System ................................... 5-1-2

5-1-4. Flight Plan - VFR Flights ............................................ 5-1-8

5-1-5. Operational Information System (OIS) ................................. 5-1-10

5-1-6. Flight Plan- Defense VFR (DVFR) Flights ............................. 5-1-10

5-1-7. Composite Flight Plan (VFR/IFR Flights) ............................... 5-1-11

5-1-8. Flight Plan (FAA Form 7233-1)- Domestic IFR Flights .................. 5-1-11

5-1-9. International Flight Plan (FAA Form 7233-4)- IFR Flights (For Domestic or

International Flights) ............................................. 5-1-18

5-1-10. IFR Operations to High Altitude Destinations .......................... 5-1-27

5-1-11. Flights Outside the U.S. and U.S. Territories ........................... 5-1-28

5-1-12. Change in Flight Plan ............................................... 5-1-29

5-1-13. Change in Proposed Departure Time .................................. 5-1-30

5-1-14. Closing VFR/DVFR Flight Plans ..................................... 5-1-30

5-1-15. Canceling IFR Flight Plan ........................................... 5-1-30

5-1-16. RNAV and RNP Operations ......................................... 5-1-30

Section 2. Departure Procedures

5-2-1. Pre‐taxi Clearance Procedures ......................................... 5-2-1

5-2-2. Pre-departure Clearance Procedures .................................. 5-2-1

5-2-3. Taxi Clearance ...................................................... 5-2-1

5-2-4. Line Up and Wait (LUAW) ........................................... 5-2-1

5-2-5. Abbreviated IFR Departure Clearance (Cleared. . .as Filed) Procedures 5-2-2 .....

5-2-6. Departure Restrictions, Clearance Void Times, Hold for Release, and

Release Times ................................................... 5-2-4

5-2-7. Departure Control .................................................. 5-2-5

5-2-8. Instrument Departure Procedures (DP) - Obstacle Departure Procedures

(ODP) and Standard Instrument Departures (SID) ................... 5-2-5
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Table of Contents vii

Section 3. En Route Procedures

Paragraph Page

5-3-1. ARTCC Communications ............................................ 5-3-1

5-3-2. Position Reporting .................................................. 5-3-3

5-3-3. Additional Reports .................................................. 5-3-4

5-3-4. Airways and Route Systems ........................................... 5-3-5

5-3-5. Airway or Route Course Changes ...................................... 5-3-7

5-3-6. Changeover Points (COPs) ........................................... 5-3-8

5-3-7. Minimum Turning Altitude (MTA) ..................................... 5-3-8

5-3-8. Holding ............................................................ 5-3-8

Section 4. Arrival Procedures

5-4-1. Standard Terminal Arrival (STAR), Area Navigation (RNAV) STAR, and

Flight Management System Procedures (FMSP) for Arrivals 5-4-1 ............

5-4-2. Local Flow Traffic Management Program 5-4-2 ...............................

5-4-3. Approach Control 5-4-2 ...................................................

5-4-4. Advance Information on Instrument Approach 5-4-3 ..........................

5-4-5. Instrument Approach Procedure Charts 5-4-4 ................................

5-4-6. Approach Clearance 5-4-25 .................................................

5-4-7. Instrument Approach Procedures 5-4-26 ......................................

5-4-8. Special Instrument Approach Procedures 5-4-28 ...............................

5-4-9. Procedure Turn and Hold-in-lieu of Procedure Turn 5-4-28 ....................

5-4-10. Timed Approaches from a Holding Fix 5-4-31 ................................

5-4-11. Radar Approaches 5-4-34 .................................................

5-4-12. Radar Monitoring of Instrument Approaches 5-4-35 ...........................

5-4-13. ILS/MLS Approaches to Parallel Runways 5-4-36 .............................

5-4-14. Parallel ILS/MLS Approaches (Dependent)(See FIG 5-4-19.) 5-4-38 ...........

5-4-15. Simultaneous Parallel ILS/MLS Approaches (Independent)

(See FIG 5-4-20.) 5-4-39 ..............................................

5-4-16. Simultaneous Close Parallel ILS PRM Approaches (Independent) and 

Simultaneous Offset Instrument Approaches (SOIA) (See FIG 5-4-21.) 5-4-41

5-4-17. Simultaneous Converging Instrument Approaches 5-4-47 .......................

5-4-18. RNP AR Instrument Approach Procedures 5-4-47 .............................

5-4-19. Side-step Maneuver 5-4-49 ...............................................

5-4-20. Approach and Landing Minimums 5-4-49 ....................................

5-4-21. Missed Approach 5-4-52 ..................................................

5-4-22. Use of Enhanced Flight Vision Systems (EFVS) on Instrument Approaches 5-4-55 .

5-4-23. Visual Approach 5-4-57 ...................................................

5-4-24. Charted Visual Flight Procedure (CVFP) 5-4-58 ..............................

5-4-25. Contact Approach 5-4-59 ..................................................

5-4-26. Landing Priority 5-4-59 ...................................................

5-4-27. Overhead Approach Maneuver 5-4-59 .......................................

Section 5. Pilot/Controller Roles and Responsibilities

5-5-1. General ............................................................ 5-5-1

5-5-2. Air Traffic Clearance ................................................ 5-5-1

5-5-3. Contact Approach ................................................... 5-5-2

5-5-4. Instrument Approach ................................................ 5-5-2

5-5-5. Missed Approach ................................................... 5-5-2

5-5-6. Radar Vectors ...................................................... 5-5-3
AIM 7/26/12

viii Table of Contents

Paragraph Page

5-5-7. Safety Alert ........................................................ 5-5-3

5-5-8. See and Avoid ...................................................... 5-5-4

5-5-9. Speed Adjustments .................................................. 5-5-4

5-5-10. Traffic Advisories (Traffic Information) ................................ 5-5-4

5-5-11. Visual Approach ................................................... 5-5-5

5-5-12. Visual Separation .................................................. 5-5-5

5-5-13. VFR‐on‐top ....................................................... 5-5-6

5-5-14. Instrument Departures .............................................. 5-5-6

5-5-15. Minimum Fuel Advisory ............................................. 5-5-6

5-5-16. RNAV and RNP Operations ......................................... 5-5-7

Section 6. National Security and Interception Procedures

5-6-1. National Security .................................................... 5-6-1

5-6-2. Interception Procedures .............................................. 5-6-2

5-6-3. Law Enforcement Operations by Civil and Military Organizations .......... 5-6-5

5-6-4. Interception Signals ................................................. 5-6-6

5-6-5. ADIZ Boundaries and Designated Mountainous Areas (See FIG 5-6-3.) 5-6-8 ...

5-6-6. Visual Warning System (VWS) ........................................ 5-6-9

Chapter 6. Emergency Procedures

Section 1. General

6-1-1. Pilot Responsibility and Authority ..................................... 6-1-1

6-1-2. Emergency Condition- Request Assistance Immediately .................. 6-1-1

Section 2. Emergency Services Available to Pilots

6-2-1. Radar Service for VFR Aircraft in Difficulty ............................ 6-2-1

6-2-2. Transponder Emergency Operation .................................... 6-2-1

6-2-3. Direction Finding Instrument Approach Procedure ....................... 6-2-1

6-2-4. Intercept and Escort ................................................. 6-2-2

6-2-5. Emergency Locator Transmitter (ELT) ................................. 6-2-2

6-2-6. FAA K-9 Explosives Detection Team Program .......................... 6-2-4

6-2-7. Search and Rescue .................................................. 6-2-5

Section 3. Distress and Urgency Procedures

6-3-1. Distress and Urgency Communications ................................. 6-3-1

6-3-2. Obtaining Emergency Assistance ...................................... 6-3-2

6-3-3. Ditching Procedures ................................................. 6-3-3

6-3-4. Special Emergency (Air Piracy) ........................................ 6-3-6

6-3-5. Fuel Dumping ...................................................... 6-3-7

Section 4. Two‐way Radio Communications Failure

6-4-1. Two‐way Radio Communications Failure ................................ 6-4-1

6-4-2. Transponder Operation During Two‐way Communications Failure .......... 6-4-2

6-4-3. Reestablishing Radio Contact ......................................... 6-4-2

Section 5. Aircraft Rescue and Fire Fighting Communications

6-5-1. Discrete Emergency Frequency ........................................ 6-5-1
7/26/12 AIM

Table of Contents ix

Paragraph Page

6-5-2. Radio Call Signs .................................................... 6-5-1

6-5-3. ARFF Emergency Hand Signals ....................................... 6-5-1

Chapter 7. Safety of Flight

Section 1. Meteorology

7-1-1. National Weather Service Aviation Products ............................. 7-1-1

7-1-2. FAA Weather Services ............................................... 7-1-1

7-1-3. Use of Aviation Weather Products ..................................... 7-1-3

7-1-4. Preflight Briefing .................................................... 7-1-6

7-1-5. En Route Flight Advisory Service (EFAS) ............................... 7-1-8

7-1-6. Inflight Aviation Weather Advisories ................................... 7-1-9

7-1-7. Categorical Outlooks ................................................ 7-1-19

7-1-8. Telephone Information Briefing Service (TIBS) .......................... 7-1-20

7-1-9. Transcribed Weather Broadcast (TWEB) (Alaska Only) ................... 7-1-20

7-1-10. Inflight Weather Broadcasts ......................................... 7-1-20

7-1-11. Flight Information Services (FIS) ..................................... 7-1-23

7-1-12. Weather Observing Programs ........................................ 7-1-27

7-1-13. Weather Radar Services ............................................. 7-1-34

7-1-14. ATC Inflight Weather Avoidance Assistance ............................ 7-1-38

7-1-15. Runway Visual Range (RVR) ........................................ 7-1-40

7-1-16. Reporting of Cloud Heights .......................................... 7-1-42

7-1-17. Reporting Prevailing Visibility ........................................ 7-1-42

7-1-18. Estimating Intensity of Rain and Ice Pellets ............................ 7-1-42

7-1-19. Estimating Intensity of Snow or Drizzle (Based on Visibility) .............. 7-1-43

7-1-20. Pilot Weather Reports (PIREPs) ...................................... 7-1-43

7-1-21. PIREPs Relating to Airframe Icing .................................... 7-1-44

7-1-22. Definitions of Inflight Icing Terms .................................... 7-1-45

7-1-23. PIREPs Relating to Turbulence ....................................... 7-1-48

7-1-24. Wind Shear PIREPs ................................................ 7-1-49

7-1-25. Clear Air Turbulence (CAT) PIREPs .................................. 7-1-49

7-1-26. Microbursts ....................................................... 7-1-49

7-1-27. PIREPs Relating to Volcanic Ash Activity .............................. 7-1-59

7-1-28. Thunderstorms .................................................... 7-1-59

7-1-29. Thunderstorm Flying ............................................... 7-1-60

7-1-30. Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report

(METAR) ...................................................... 7-1-62

7-1-31. International Civil Aviation Organization (ICAO) Weather Formats ....... 7-1-64

Section 2. Altimeter Setting Procedures

7-2-1. General ............................................................ 7-2-1

7-2-2. Procedures ......................................................... 7-2-1

7-2-3. Altimeter Errors .................................................... 7-2-3

7-2-4. High Barometric Pressure ............................................ 7-2-4

7-2-5. Low Barometric Pressure ............................................. 7-2-4

Section 3. Wake Turbulence

7-3-1. General ............................................................ 7-3-1

7-3-2. Vortex Generation .................................................. 7-3-1
AIM 7/26/12

x Table of Contents

Paragraph Page

7-3-3. Vortex Strength ..................................................... 7-3-1

7-3-4. Vortex Behavior ..................................................... 7-3-2

7-3-5. Operations Problem Areas ............................................ 7-3-5

7-3-6. Vortex Avoidance Procedures ......................................... 7-3-5

7-3-7. Helicopters ......................................................... 7-3-6

7-3-8. Pilot Responsibility .................................................. 7-3-6

7-3-9. Air Traffic Wake Turbulence Separations ................................ 7-3-7

Section 4. Bird Hazards and Flight Over National Refuges, Parks, and

Forests

7-4-1. Migratory Bird Activity .............................................. 7-4-1

7-4-2. Reducing Bird Strike Risks ........................................... 7-4-1

7-4-3. Reporting Bird Strikes ............................................... 7-4-1

7-4-4. Reporting Bird and Other Wildlife Activities ............................ 7-4-1

7-4-5. Pilot Advisories on Bird and Other Wildlife Hazards ...................... 7-4-2

7-4-6. Flights Over Charted U.S. Wildlife Refuges, Parks, and Forest Service Areas 7-4-2 .

Section 5. Potential Flight Hazards

7-5-1. Accident Cause Factors .............................................. 7-5-1

7-5-2. VFR in Congested Areas ............................................. 7-5-1

7-5-3. Obstructions To Flight ............................................... 7-5-1

7-5-4. Avoid Flight Beneath Unmanned Balloons .............................. 7-5-2

7-5-5. Unmanned Aircraft Systems .......................................... 7-5-2

7-5-6. Mountain Flying .................................................... 7-5-3

7-5-7. Use of Runway Half-way Signs at Unimproved Airports .................. 7-5-5

7-5-8. Seaplane Safety ..................................................... 7-5-6

7-5-9. Flight Operations in Volcanic Ash ..................................... 7-5-7

7-5-10. Emergency Airborne Inspection of Other Aircraft ....................... 7-5-8

7-5-11. Precipitation Static ................................................. 7-5-9

7-5-12. Light Amplification by Stimulated Emission of Radiation (Laser)

Operations and Reporting Illumination of Aircraft .................... 7-5-10

7-5-13. Flying in Flat Light and White Out Conditions .......................... 7-5-10

7-5-14. Operations in Ground Icing Conditions ................................ 7-5-12

7-5-15. Avoid Flight in the Vicinity of Thermal Plumes (Smoke Stacks and Cooling

Towers) ........................................................ 7-5-13

Section 6. Safety, Accident, and Hazard Reports

7-6-1. Aviation Safety Reporting Program .................................... 7-6-1

7-6-2. Aircraft Accident and Incident Reporting ............................... 7-6-1

7-6-3. Near Midair Collision Reporting ...................................... 7-6-2

7-6-4. Unidentified Flying Object (UFO) Reports .............................. 7-6-3

7-6-5. Safety Alerts For Operators (SAFO) and Information For Operators (InFO) 7-6-3 .

Chapter 8. Medical Facts for Pilots

Section 1. Fitness for Flight

8-1-1. Fitness For Flight ................................................... 8-1-1

8-1-2. Effects of Altitude ................................................... 8-1-3
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Table of Contents xi

Paragraph Page

8-1-3. Hyperventilation in Flight ............................................ 8-1-5

8-1-4. Carbon Monoxide Poisoning in Flight .................................. 8-1-5

8-1-5. Illusions in Flight .................................................... 8-1-5

8-1-6. Vision in Flight ..................................................... 8-1-6

8-1-7. Aerobatic Flight ..................................................... 8-1-8

8-1-8. Judgment Aspects of Collision Avoidance ............................... 8-1-8

Chapter 9. Aeronautical Charts and 

Related Publications

Section 1. Types of Charts Available

9-1-1. General ............................................................ 9-1-1

9-1-2. Obtaining Aeronautical Charts ........................................ 9-1-1

9-1-3. Selected Charts and Products Available ................................. 9-1-1

9-1-4. General Description of each Chart Series ............................... 9-1-1

9-1-5. Where and How to Get Charts of Foreign Areas ......................... 9-1-12

Chapter 10. Helicopter Operations

Section 1. Helicopter IFR Operations

10-1-1. Helicopter Flight Control Systems .................................... 10-1-1

10-1-2. Helicopter Instrument Approaches .................................... 10-1-3

10-1-3. Helicopter Approach Procedures to VFR Heliports ...................... 10-1-5

10-1-4. The Gulf of Mexico Grid System ..................................... 10-1-6

Section 2. Special Operations

10-2-1. Offshore Helicopter Operations ...................................... 10-2-1

10-2-2. Helicopter Night VFR Operations .................................... 10-2-7

10-2-3. Landing Zone Safety ............................................... 10-2-10

10-2-4. Emergency Medical Service (EMS) Multiple Helicopter Operations ........ 10-2-16

Appendices

Appendix 1. Bird/Other Wildlife Strike Report .................................. Appendix 1-1

Appendix 2. Volcanic Activity Reporting Form (VAR) ............................ Appendix 2-1

Appendix 3. Laser Beam Exposure Questionnaire ................................ Appendix 3-1

Appendix 4. Abbreviations/Acronyms .......................................... Appendix 4-1

PILOT/CONTROLLER GLOSSARY .......................................... PCG-1

INDEX .................................................................... I-1

7/26/12 AIM

Navigation Aids 1−1−1

Chapter 1. Air Navigation

Section 1. Navigation Aids

1−1−1. General

a. Various types of air navigation aids are in use

today, each serving a special purpose. These aids have

varied owners and operators, namely: the Federal

Aviation Administration (FAA), the military services, private organizations, individual states and

foreign governments. The FAA has the statutory

authority to establish, operate, maintain air navigation facilities and to prescribe standards for the

operation of any of these aids which are used for

instrument flight in federally controlled airspace.

These aids are tabulated in the Airport/Facility

Directory (A/FD).

b. Pilots should be aware of the possibility of

momentary erroneous indications on cockpit displays

when the primary signal generator for a ground−

based navigational transmitter (for example, a

glideslope, VOR, or nondirectional beacon) is

inoperative. Pilots should disregard any navigation

indication, regardless of its apparent validity, if the

particular transmitter was identified by NOTAM or

otherwise as unusable or inoperative.

1−1−2. Nondirectional Radio Beacon (NDB)

a. A low or medium frequency radio beacon

transmits nondirectional signals whereby the pilot of

an aircraft properly equipped can determine bearings

and “home” on the station. These facilities normally

operate in a frequency band of 190 to 535 kilohertz

(kHz), according to ICAO Annex 10 the frequency

range for NDBs is between 190 and 1750 kHz, and

transmit a continuous carrier with either 400 or

1020 hertz (Hz) modulation. All radio beacons

except the compass locators transmit a continuous

three−letter identification in code except during voice

transmissions.

b. When a radio beacon is used in conjunction with

the Instrument Landing System markers, it is called

a Compass Locator.

c. Voice transmissions are made on radio beacons

unless the letter “W” (without voice) is included in

the class designator (HW).

d. Radio beacons are subject to disturbances that

may result in erroneous bearing information. Such

disturbances result from such factors as lightning,

precipitation static, etc. At night, radio beacons are

vulnerable to interference from distant stations.

Nearly all disturbances which affect the Automatic

Direction Finder (ADF) bearing also affect the

facility’s identification. Noisy identification usually

occurs when the ADF needle is erratic. Voice, music

or erroneous identification may be heard when a

steady false bearing is being displayed. Since ADF

receivers do not have a “flag” to warn the pilot when

erroneous bearing information is being displayed, the

pilot should continuously monitor the NDB’s

identification.

1−1−3. VHF Omni−directional Range (VOR)

a. VORs operate within the 108.0 to 117.95 MHz

frequency band and have a power output necessary to

provide coverage within their assigned operational

service volume. They are subject to line−of−sight

restrictions, and the range varies proportionally to the

altitude of the receiving equipment.

NOTE−

Normal service ranges for the various classes of VORs are

given in Navigational Aid (NAVAID) Service Volumes,

paragraph 1−1−8.

b. Most VORs are equipped for voice transmission on the VOR frequency. VORs without voice

capability are indicated by the letter “W” (without

voice) included in the class designator (VORW).

c. The only positive method of identifying a VOR

is by its Morse Code identification or by the recorded

automatic voice identification which is always

indicated by use of the word “VOR” following the

range’s name. Reliance on determining the identification of an omnirange should never be placed on

listening to voice transmissions by the Flight Service

Station (FSS) (or approach control facility) involved.

Many FSSs remotely operate several omniranges

with different names. In some cases, none of the

VORs have the name of the “parent” FSS. During
AIM 7/26/12

1−1−2 Navigation Aids

periods of maintenance, the facility may radiate a

T−E−S−T code (- -) or the code may be

removed.

d. Voice identification has been added to numerous VORs. The transmission consists of a voice

announcement, “AIRVILLE VOR” alternating with

the usual Morse Code identification.

e. The effectiveness of the VOR depends upon

proper use and adjustment of both ground and

airborne equipment.

1. Accuracy. The accuracy of course alignment of the VOR is excellent, being generally plus or

minus 1 degree.

2. Roughness. On some VORs, minor course

roughness may be observed, evidenced by course

needle or brief flag alarm activity (some receivers are

more susceptible to these irregularities than others).

At a few stations, usually in mountainous terrain, the

pilot may occasionally observe a brief course needle

oscillation, similar to the indication of “approaching

station.” Pilots flying over unfamiliar routes are

cautioned to be on the alert for these vagaries, and in

particular, to use the “to/from” indicator to determine

positive station passage.

(a) Certain propeller revolutions per minute

(RPM) settings or helicopter rotor speeds can cause

the VOR Course Deviation Indicator to fluctuate as

much as plus or minus six degrees. Slight changes to

the RPM setting will normally smooth out this

roughness. Pilots are urged to check for this

modulation phenomenon prior to reporting a VOR

station or aircraft equipment for unsatisfactory

operation.

1−1−4. VOR Receiver Check

a. The FAA VOR test facility (VOT) transmits a

test signal which provides users a convenient means

to determine the operational status and accuracy of a

VOR receiver while on the ground where a VOT is

located. The airborne use of VOT is permitted;

however, its use is strictly limited to those

areas/altitudes specifically authorized in the A/FD or

appropriate supplement.

b. To use the VOT service, tune in the VOT

frequency on your VOR receiver. With the Course

Deviation Indicator (CDI) centered, the omni−bearing selector should read 0 degrees with the to/from

indication showing “from” or the omni−bearing

selector should read 180 degrees with the to/from

indication showing “to.” Should the VOR receiver

operate an RMI (Radio Magnetic Indicator), it will

indicate 180 degrees on any omni−bearing selector

(OBS) setting. Two means of identification are used.

One is a series of dots and the other is a continuous

tone. Information concerning an individual test signal

can be obtained from the local FSS.

c. Periodic VOR receiver calibration is most

important. If a receiver’s Automatic Gain Control or

modulation circuit deteriorates, it is possible for it to

display acceptable accuracy and sensitivity close into

the VOR or VOT and display out−of−tolerance

readings when located at greater distances where

weaker signal areas exist. The likelihood of this

deterioration varies between receivers, and is

generally considered a function of time. The best

assurance of having an accurate receiver is periodic

calibration. Yearly intervals are recommended at

which time an authorized repair facility should

recalibrate the receiver to the manufacturer’s

specifications.

d. Federal Aviation Regulations (14 CFR Section 91.171) provides for certain VOR equipment

accuracy checks prior to flight under instrument

flight rules. To comply with this requirement and to

ensure satisfactory operation of the airborne system,

the FAA has provided pilots with the following means

of checking VOR receiver accuracy:

1. VOT or a radiated test signal from an

appropriately rated radio repair station.

2. Certified airborne check points.

3. Certified check points on the airport surface.

e. A radiated VOT from an appropriately rated

radio repair station serves the same purpose as an

FAA VOR signal and the check is made in much the

same manner as a VOT with the following

differences:

1. The frequency normally approved by the

Federal Communications Commission is

108.0 MHz.

2. Repair stations are not permitted to radiate the

VOR test signal continuously; consequently, the

owner or operator must make arrangements with the

repair station to have the test signal transmitted. This

service is not provided by all radio repair stations.

The aircraft owner or operator must determine which
7/26/12 AIM

Navigation Aids 1−1−3

repair station in the local area provides this service.

A representative of the repair station must make an

entry into the aircraft logbook or other permanent

record certifying to the radial accuracy and the date

of transmission. The owner, operator or representative of the repair station may accomplish the necessary

checks in the aircraft and make a logbook entry

stating the results. It is necessary to verify which test

radial is being transmitted and whether you should

get a “to” or “from” indication.

f. Airborne and ground check points consist of

certified radials that should be received at specific

points on the airport surface or over specific

landmarks while airborne in the immediate vicinity of

the airport.

1. Should an error in excess of plus or minus

4 degrees be indicated through use of a ground check,

or plus or minus 6 degrees using the airborne check,

Instrument Flight Rules (IFR) flight must not be

attempted without first correcting the source of the

error.

CAUTION−

No correction other than the correction card figures

supplied by the manufacturer should be applied in

making these VOR receiver checks.

2. Locations of airborne check points, ground

check points and VOTs are published in the A/FD.

3. If a dual system VOR (units independent of

each other except for the antenna) is installed in the

aircraft, one system may be checked against the other.

Turn both systems to the same VOR ground facility

and note the indicated bearing to that station. The

maximum permissible variations between the two

indicated bearings is 4 degrees.

1−1−5. Tactical Air Navigation (TACAN)

a. For reasons peculiar to military or naval

operations (unusual siting conditions, the pitching

and rolling of a naval vessel, etc.) the civil

VOR/Distance Measuring Equipment (DME) system

of air navigation was considered unsuitable for

military or naval use. A new navigational system,

TACAN, was therefore developed by the military and

naval forces to more readily lend itself to military and

naval requirements. As a result, the FAA has

integrated TACAN facilities with the civil VOR/

DME program. Although the theoretical, or technical

principles of operation of TACAN equipment are

quite different from those of VOR/DME facilities, the

end result, as far as the navigating pilot is concerned,

is the same. These integrated facilities are called

VORTACs.

b. TACAN ground equipment consists of either a

fixed or mobile transmitting unit. The airborne unit in

conjunction with the ground unit reduces the

transmitted signal to a visual presentation of both

azimuth and distance information. TACAN is a pulse

system and operates in the Ultrahigh Frequency

(UHF) band of frequencies. Its use requires TACAN

airborne equipment and does not operate through

conventional VOR equipment.

1−1−6. VHF Omni−directional

Range/Tactical Air Navigation (VORTAC)

a. A VORTAC is a facility consisting of two

components, VOR and TACAN, which provides

three individual services: VOR azimuth, TACAN

azimuth and TACAN distance (DME) at one site.

Although consisting of more than one component,

incorporating more than one operating frequency,

and using more than one antenna system, a VORTAC

is considered to be a unified navigational aid. Both

components of a VORTAC are envisioned as

operating simultaneously and providing the three

services at all times.

b. Transmitted signals of VOR and TACAN are

each identified by three−letter code transmission and

are interlocked so that pilots using VOR azimuth with

TACAN distance can be assured that both signals

being received are definitely from the same ground

station. The frequency channels of the VOR and the

TACAN at each VORTAC facility are “paired” in

accordance with a national plan to simplify airborne

operation.

1−1−7. Distance Measuring Equipment

(DME)

a. In the operation of DME, paired pulses at a

specific spacing are sent out from the aircraft (this is

the interrogation) and are received at the ground

station. The ground station (transponder) then

transmits paired pulses back to the aircraft at the same

pulse spacing but on a different frequency. The time

required for the round trip of this signal exchange is
AIM 7/26/12

1−1−4 Navigation Aids

measured in the airborne DME unit and is translated

into distance (nautical miles) from the aircraft to the

ground station.

b. Operating on the line−of−sight principle, DME

furnishes distance information with a very high

degree of accuracy. Reliable signals may be received

at distances up to 199 NM at line−of−sight altitude

with an accuracy of better than 1/2 mile or 3 percent

of the distance, whichever is greater. Distance

information received from DME equipment is

SLANT RANGE distance and not actual horizontal

distance.

c. Operating frequency range of a DME according

to ICAO Annex 10 is from 960 MHz to 1215 MHz.

Aircraft equipped with TACAN equipment will

receive distance information from a VORTAC

automatically, while aircraft equipped with VOR

must have a separate DME airborne unit.

d. Aircraft equipped with slaved compass systems

may be susceptible to heading errors caused by

exposure to magnetic field disturbances (flux fields)

found in materials that are commonly located on the

surface or buried under taxiways and ramps. These

materials generate a magnetic flux field that can be

sensed by the aircraft’s compass system flux detector

or “gate”, which can cause the aircraft’s system to

align with the material’s magnetic field rather than

the earth’s natural magnetic field. The system’s

erroneous heading may not self-correct. Prior to take

off pilots should be aware that a heading

misalignment may have occurred during taxi. Pilots

are encouraged to follow the manufacturer’s or other

appropriate procedures to correct possible heading

misalignment before take off is commenced.

e. VOR/DME, VORTAC, Instrument Landing

System (ILS)/DME, and localizer (LOC)/DME

navigation facilities established by the FAA provide

course and distance information from collocated

components under a frequency pairing plan. Aircraft

receiving equipment which provides for automatic

DME selection assures reception of azimuth and

distance information from a common source when

designated VOR/DME, VORTAC, ILS/DME, and

LOC/DME are selected.

f. Due to the limited number of available

frequencies, assignment of paired frequencies is

required for certain military noncollocated VOR and

TACAN facilities which serve the same area but

which may be separated by distances up to a few

miles.

g. VOR/DME, VORTAC, ILS/DME, and LOC/

DME facilities are identified by synchronized

identifications which are transmitted on a time share

basis. The VOR or localizer portion of the facility is

identified by a coded tone modulated at 1020 Hz or

a combination of code and voice. The TACAN or

DME is identified by a coded tone modulated at

1350 Hz. The DME or TACAN coded identification

is transmitted one time for each three or four times

that the VOR or localizer coded identification is

transmitted. When either the VOR or the DME is

inoperative, it is important to recognize which

identifier is retained for the operative facility. A

single coded identification with a repetition interval

of approximately 30 seconds indicates that the DME

is operative.

h. Aircraft equipment which provides for automatic DME selection assures reception of azimuth

and distance information from a common source

when designated VOR/DME, VORTAC and ILS/

DME navigation facilities are selected. Pilots are

cautioned to disregard any distance displays from

automatically selected DME equipment when VOR

or ILS facilities, which do not have the DME feature

installed, are being used for position determination.

1−1−8. Navigational Aid (NAVAID) Service

Volumes

a. Most air navigation radio aids which provide

positive course guidance have a designated standard

service volume (SSV). The SSV defines the reception

limits of unrestricted NAVAIDs which are usable for

random/unpublished route navigation.

b. A NAVAID will be classified as restricted if it

does not conform to flight inspection signal strength

and course quality standards throughout the

published SSV. However, the NAVAID should not be

considered usable at altitudes below that which could

be flown while operating under random route IFR

conditions (14 CFR Section 91.177), even though

these altitudes may lie within the designated SSV.

Service volume restrictions are first published in

Notices to Airmen (NOTAMs) and then with the

alphabetical listing of the NAVAIDs in the A/FD.

c. Standard Service Volume limitations do not

apply to published IFR routes or procedures.
7/26/12 AIM

Navigation Aids 1−1−5

d. VOR/DME/TACAN Standard Service

Volumes (SSV).

1. Standard service volumes (SSVs) are graphically shown in FIG 1−1−1, FIG 1−1−2, FIG 1−1−3,

FIG 1−1−4, and FIG 1−1−5. The SSV of a station is

indicated by using the class designator as a prefix to

the station type designation.

EXAMPLE−

TVOR, LDME, and HVORTAC.

FIG 1−1−1

Standard High Altitude Service Volume

(See FIG 1−1−5 for altitudes below 1,000 feet).

60,000 ft.

100 NM

130 NM

45,000 ft.

18,000 ft.

14,500 ft.

1,000 ft. 40 NM

FIG 1−1−2

Standard Low Altitude Service Volume

(See FIG 1−1−5 for altitudes below 1,000 feet).

NOTE: All elevations shown are with respect

to the station’s site elevation (AGL).

Coverage is not available in a cone of

airspace directly above the facility.

40 NM

18,000 ft.

1,000 ft.
AIM 7/26/12

1−1−6 Navigation Aids

FIG 1−1−3

Standard Terminal Service Volume

(See FIG 1−1−4 for altitudes below 1,000 feet).

25 NM

12,000 ft.

1,000 ft.

2. Within 25 NM, the bottom of the T service

volume is defined by the curve in FIG 1−1−4. Within

40 NM, the bottoms of the L and H service volumes

are defined by the curve in FIG 1−1−5. (See

TBL 1−1−1.)

e. Nondirectional Radio Beacon (NDB)

1. NDBs are classified according to their

intended use.

2. The ranges of NDB service volumes are

shown in TBL 1−1−2. The distances (radius) are the

same at all altitudes.

TBL 1−1−1

VOR/DME/TACAN Standard Service Volumes

SSV Class Designator Altitude and Range Boundaries

T (Terminal) ........ From 1,000 feet above ground level (AGL) up to and including 12,000 feet AGL at radial distances out

to 25 NM.

L (Low Altitude) .... From 1,000 feet AGL up to and including 18,000 feet AGL at radial distances out to 40 NM.

H (High Altitude) .... From 1,000 feet AGL up to and including 14,500 feet AGL at radial distances out to 40 NM. From

14,500 AGL up to and including 60,000 feet at radial distances out to 100 NM. From 18,000 feet AGL

up to and including 45,000 feet AGL at radial distances out to 130 NM.

TBL 1−1−2

NDB Service Volumes

Class Distance (Radius)

Compass Locator 15 NM

MH 25 NM

H 50 NM*

HH 75 NM

*Service ranges of individual facilities may be less than 50 nautical miles (NM). Restrictions to service

volumes are first published as a Notice to Airmen and then with the alphabetical listing of the NAVAID in

the A/FD.
7/26/12 AIM

Navigation Aids 1−1−7

FIG 1−1−4

Service Volume Lower Edge Terminal

1000

500

0

0 5 10 15 20 25

DISTANCE TO THE STATION IN NM

ALTITUDE IN FEET

FIG 1−1−5

Service Volume Lower Edge

Standard High and Low

1000

500

0

0 10 20 30 40

DISTANCE TO THE STATION IN NM

ALTITUDE IN FEET

5 15 25 35

1−1−9. Instrument Landing System (ILS)

a. General

1. The ILS is designed to provide an approach

path for exact alignment and descent of an aircraft on

final approach to a runway.

2. The ground equipment consists of two highly

directional transmitting systems and, along the

approach, three (or fewer) marker beacons. The

directional transmitters are known as the localizer

and glide slope transmitters.

3. The system may be divided functionally into

three parts:

(a) Guidance information: localizer, glide

slope;

(b) Range information: marker beacon,

DME; and

(c) Visual information: approach lights,

touchdown and centerline lights, runway lights.

4. Precision radar, or compass locators located

at the Outer Marker (OM) or Middle Marker (MM),

may be substituted for marker beacons. DME, when
AIM 7/26/12

1−1−8 Navigation Aids

specified in the procedure, may be substituted for the

OM.

5. Where a complete ILS system is installed on

each end of a runway; (i.e., the approach end of

Runway 4 and the approach end of Runway 22) the

ILS systems are not in service simultaneously.

b. Localizer

1. The localizer transmitter operates on one of

40 ILS channels within the frequency range of

108.10 to 111.95 MHz. Signals provide the pilot with

course guidance to the runway centerline.

2. The approach course of the localizer is called

the front course and is used with other functional

parts, e.g., glide slope, marker beacons, etc. The

localizer signal is transmitted at the far end of the

runway. It is adjusted for a course width of (full scale

fly−left to a full scale fly−right) of 700 feet at the

runway threshold.

3. The course line along the extended centerline

of a runway, in the opposite direction to the front

course is called the back course.

CAUTION−

Unless the aircraft’s ILS equipment includes reverse

sensing capability, when flying inbound on the back

course it is necessary to steer the aircraft in the direction

opposite the needle deflection when making corrections

from off−course to on−course. This “flying away from the

needle” is also required when flying outbound on the

front course of the localizer. Do not use back course

signals for approach unless a back course approach

procedure is published for that particular runway and the

approach is authorized by ATC.

4. Identification is in International Morse Code

and consists of a three−letter identifier preceded by

the letter I ( ) transmitted on the localizer

frequency.

EXAMPLE−

I−DIA

5. The localizer provides course guidance

throughout the descent path to the runway threshold

from a distance of 18 NM from the antenna between

an altitude of 1,000 feet above the highest terrain

along the course line and 4,500 feet above the

elevation of the antenna site. Proper off−course

indications are provided throughout the following

angular areas of the operational service volume:

(a) To 10 degrees either side of the course

along a radius of 18 NM from the antenna; and

(b) From 10 to 35 degrees either side of the

course along a radius of 10 NM. (See FIG 1−1−6.)

FIG 1−1−6

Limits of Localizer Coverage

RUNWAY

LOCALIZER

ANTENNA

LOCALIZER

ANTENNA

10 NM 1

18 NM 1M

NORMAL LIMITS OF LOCALIZER

COVERAGE: THE SAME AREA

APPLIES TO A BACK COURSE

WHEN PROVIDED.

NORMAL LIMITS OF LOCALIZER

COVERAGE: THE SAME AREA

APPLIES TO A BACK COURSE

WHEN PROVIDED.

10°

10°

35°

35°

6. Unreliable signals may be received outside

these areas.

c. Localizer Type Directional Aid (LDA)

1. The LDA is of comparable use and accuracy

to a localizer but is not part of a complete ILS. The

LDA course usually provides a more precise

approach course than the similar Simplified

Directional Facility (SDF) installation, which may

have a course width of 6 or 12 degrees.

2. The LDA is not aligned with the runway.

Straight−in minimums may be published where

alignment does not exceed 30 degrees between the

course and runway. Circling minimums only are

published where this alignment exceeds 30 degrees.

3. A very limited number of LDA approaches

also incorporate a glideslope. These are annotated in

the plan view of the instrument approach chart with

a note, “LDA/Glideslope.” These procedures fall

under a newly defined category of approaches called

Approach with Vertical Guidance (APV) described in

paragraph 5−4−5, Instrument Approach Procedure

Charts, subparagraph a7(b), Approach with Vertical

Guidance (APV). LDA minima for with and without

glideslope is provided and annotated on the minima

lines of the approach chart as S−LDA/GS and

S−LDA. Because the final approach course is not

aligned with the runway centerline, additional

maneuvering will be required compared to an ILS

approach.
7/26/12 AIM

Navigation Aids 1−1−9

d. Glide Slope/Glide Path

1. The UHF glide slope transmitter, operating

on one of the 40 ILS channels within the frequency

range 329.15 MHz, to 335.00 MHz radiates its signals

in the direction of the localizer front course. The term

“glide path” means that portion of the glide slope that

intersects the localizer.

CAUTION−

False glide slope signals may exist in the area of the

localizer back course approach which can cause the glide

slope flag alarm to disappear and present unreliable glide

slope information. Disregard all glide slope signal

indications when making a localizer back course

approach unless a glide slope is specified on the approach

and landing chart.

2. The glide slope transmitter is located between

750 feet and 1,250 feet from the approach end of the

runway (down the runway) and offset 250 to 650 feet

from the runway centerline. It transmits a glide path

beam 1.4 degrees wide (vertically). The signal

provides descent information for navigation down to

the lowest authorized decision height (DH) specified

in the approved ILS approach procedure. The

glidepath may not be suitable for navigation below

the lowest authorized DH and any reference to

glidepath indications below that height must be

supplemented by visual reference to the runway

environment. Glidepaths with no published DH are

usable to runway threshold.

3. The glide path projection angle is normally

adjusted to 3 degrees above horizontal so that it

intersects the MM at about 200 feet and the OM at

about 1,400 feet above the runway elevation. The

glide slope is normally usable to the distance of

10 NM. However, at some locations, the glide slope

has been certified for an extended service volume

which exceeds 10 NM.

4. Pilots must be alert when approaching the

glidepath interception. False courses and reverse

sensing will occur at angles considerably greater than

the published path.

5. Make every effort to remain on the indicated

glide path.

CAUTION−

Avoid flying below the glide path to assure

obstacle/terrain clearance is maintained.

6. The published glide slope threshold crossing

height (TCH) DOES NOT represent the height of the

actual glide path on−course indication above the

runway threshold. It is used as a reference for

planning purposes which represents the height above

the runway threshold that an aircraft’s glide slope

antenna should be, if that aircraft remains on a

trajectory formed by the four−mile−to−middle

marker glidepath segment.

7. Pilots must be aware of the vertical height

between the aircraft’s glide slope antenna and the

main gear in the landing configuration and, at the DH,

plan to adjust the descent angle accordingly if the

published TCH indicates the wheel crossing height

over the runway threshold may not be satisfactory.

Tests indicate a comfortable wheel crossing height is

approximately 20 to 30 feet, depending on the type of

aircraft.

NOTE−

The TCH for a runway is established based on several

factors including the largest aircraft category that

normally uses the runway, how airport layout effects the

glide slope antenna placement, and terrain. A higher than

optimum TCH, with the same glide path angle, may cause

the aircraft to touch down further from the threshold if the

trajectory of the approach is maintained until the flare.

Pilots should consider the effect of a high TCH on the

runway available for stopping the aircraft.

e. Distance Measuring Equipment (DME)

1. When installed with the ILS and specified in

the approach procedure, DME may be used:

(a) In lieu of the OM;

(b) As a back course (BC) final approach fix

(FAF); and

(c) To establish other fixes on the localizer

course.

2. In some cases, DME from a separate facility

may be used within Terminal Instrument Procedures

(TERPS) limitations:

(a) To provide ARC initial approach segments;

(b) As a FAF for BC approaches; and

(c) As a substitute for the OM.

f. Marker Beacon

1. ILS marker beacons have a rated power

output of 3 watts or less and an antenna array

designed to produce an elliptical pattern with

dimensions, at 1,000 feet above the antenna, of

approximately 2,400 feet in width and 4,200 feet in
AIM 7/26/12

1−1−10 Navigation Aids

length. Airborne marker beacon receivers with a

selective sensitivity feature should always be

operated in the “low” sensitivity position for proper

reception of ILS marker beacons.

2. Ordinarily, there are two marker beacons

associated with an ILS, the OM and MM. Locations

with a Category II ILS also have an Inner

Marker (IM). When an aircraft passes over a marker,

the pilot will receive the indications shown in

TBL 1−1−3.

(a) The OM normally indicates a position at

which an aircraft at the appropriate altitude on the

localizer course will intercept the ILS glide path.

(b) The MM indicates a position approximately 3,500 feet from the landing threshold. This is

also the position where an aircraft on the glide path

will be at an altitude of approximately 200 feet above

the elevation of the touchdown zone.

(c) The IM will indicate a point at which an

aircraft is at a designated decision height (DH) on the

glide path between the MM and landing threshold.

TBL 1−1−3

Marker Passage Indications

Marker Code Light

OM BLUE

MM AMBER

IM WHITE

BC WHITE

3. A back course marker normally indicates the

ILS back course final approach fix where approach

descent is commenced.

g. Compass Locator

1. Compass locator transmitters are often

situated at the MM and OM sites. The transmitters

have a power of less than 25 watts, a range of at least

15 miles and operate between 190 and 535 kHz. At

some locations, higher powered radio beacons, up to

400 watts, are used as OM compass locators. These

generally carry Transcribed Weather Broadcast

(TWEB) information.

2. Compass locators transmit two letter identification groups. The outer locator transmits the first

two letters of the localizer identification group, and

the middle locator transmits the last two letters of the

localizer identification group.

h. ILS Frequency (See TBL 1−1−4.)

TBL 1−1−4

Frequency Pairs Allocated for ILS

Localizer MHz Glide Slope

108.10 334.70

108.15 334.55

108.3 334.10

108.35 333.95

108.5 329.90

108.55 329.75

108.7 330.50

108.75 330.35

108.9 329.30

108.95 329.15

109.1 331.40

109.15 331.25

109.3 332.00

109.35 331.85

109.50 332.60

109.55 332.45

109.70 333.20

109.75 333.05

109.90 333.80

109.95 333.65

110.1 334.40

110.15 334.25

110.3 335.00

110.35 334.85

110.5 329.60

110.55 329.45

Localizer MHz Glide Slope

110.70 330.20

110.75 330.05

110.90 330.80

110.95 330.65

111.10 331.70

111.15 331.55

111.30 332.30

111.35 332.15

111.50 332.9

111.55 332.75

111.70 333.5

111.75 333.35

111.90 331.1

111.95 330.95

i. ILS Minimums

1. The lowest authorized ILS minimums, with

all required ground and airborne systems components

operative, are:
7/26/12 AIM

Navigation Aids 1−1−11

(a) Category I. Decision Height (DH)

200 feet and Runway Visual Range (RVR) 2,400 feet

(with touchdown zone and centerline lighting, RVR

1,800 feet), or (with Autopilot or FD or HUD, RVR

1,800 feet);

(b) Special Authorization Category I.

DH 150 feet and Runway Visual Range (RVR) 1,400

feet, HUD to DH;

(c) Category II. DH 100 feet and RVR 1,200

feet (with autoland or HUD to touchdown and noted

on authorization, RVR 1,000 feet);

(d) Special Authorization Category II with

Reduced Lighting. DH 100 feet and RVR 1,200 feet

with autoland or HUD to touchdown and noted on

authorization (touchdown zone, centerline lighting,

and ALSF−2 are not required);

(e) Category IIIa. No DH or DH below 100

feet and RVR not less than 700 feet;

(f) Category IIIb. No DH or DH below 50

feet and RVR less than 700 feet but not less than 150

feet; and

(g) Category IIIc. No DH and no RVR

limitation.

NOTE−

Special authorization and equipment required for

Categories II and III.

j. Inoperative ILS Components

1. Inoperative localizer. When the localizer

fails, an ILS approach is not authorized.

2. Inoperative glide slope. When the glide

slope fails, the ILS reverts to a nonprecision localizer

approach.

REFERENCE−

See the inoperative component table in the U.S. Government Terminal

Procedures Publication (TPP), for adjustments to minimums due to

inoperative airborne or ground system equipment.

k. ILS Course Distortion

1. All pilots should be aware that disturbances to

ILS localizer and glide slope courses may occur when

surface vehicles or aircraft are operated near the

localizer or glide slope antennas. Most ILS

installations are subject to signal interference by

either surface vehicles, aircraft or both. ILS

CRITICAL AREAS are established near each

localizer and glide slope antenna.

2. ATC issues control instructions to avoid

interfering operations within ILS critical areas at

controlled airports during the hours the Airport

Traffic Control Tower (ATCT) is in operation as

follows:

(a) Weather Conditions. Less than ceiling

800 feet and/or visibility 2 miles.

(1) Localizer Critical Area. Except for

aircraft that land, exit a runway, depart or miss

approach, vehicles and aircraft are not authorized in

or over the critical area when an arriving aircraft is

between the ILS final approach fix and the airport.

Additionally, when the ceiling is less than 200 feet

and/or the visibility is RVR 2,000 or less, vehicle and

aircraft operations in or over the area are not

authorized when an arriving aircraft is inside the ILS

MM.

(2) Glide Slope Critical Area. Vehicles

and aircraft are not authorized in the area when an

arriving aircraft is between the ILS final approach fix

and the airport unless the aircraft has reported the

airport in sight and is circling or side stepping to land

on a runway other than the ILS runway.

(b) Weather Conditions. At or above ceiling 800 feet and/or visibility 2 miles.

(1) No critical area protective action is

provided under these conditions.

(2) A flight crew, under these conditions,

should advise the tower that it will conduct an

AUTOLAND or COUPLED approach to ensure that

the ILS critical areas are protected when the aircraft

is inside the ILS MM.

EXAMPLE−

Glide slope signal not protected.

3. Aircraft holding below 5,000 feet between

the outer marker and the airport may cause localizer

signal variations for aircraft conducting the ILS

approach. Accordingly, such holding is not authorized when weather or visibility conditions are less

than ceiling 800 feet and/or visibility 2 miles.

4. Pilots are cautioned that vehicular traffic not

subject to ATC may cause momentary deviation to

ILS course or glide slope signals. Also, critical areas

are not protected at uncontrolled airports or at airports

with an operating control tower when weather or

visibility conditions are above those requiring

protective measures. Aircraft conducting coupled or

autoland operations should be especially alert in
AIM 7/26/12

1−1−12 Navigation Aids

monitoring automatic flight control systems. 

(See FIG 1−1−7.)

NOTE−

Unless otherwise coordinated through Flight Standards,

ILS signals to Category I runways are not flight inspected

below 100 feet AGL. Guidance signal anomalies may be

encountered below this altitude.

1−1−10. Simplified Directional Facility

(SDF)

a. The SDF provides a final approach course

similar to that of the ILS localizer. It does not provide

glide slope information. A clear understanding of the

ILS localizer and the additional factors listed below

completely describe the operational characteristics

and use of the SDF.

b. The SDF transmits signals within the range of

108.10 to 111.95 MHz.

c. The approach techniques and procedures used

in an SDF instrument approach are essentially the

same as those employed in executing a standard

localizer approach except the SDF course may not be

aligned with the runway and the course may be wider,

resulting in less precision.

d. Usable off−course indications are limited to

35 degrees either side of the course centerline.

Instrument indications received beyond 35 degrees

should be disregarded.

e. The SDF antenna may be offset from the runway

centerline. Because of this, the angle of convergence

between the final approach course and the runway

bearing should be determined by reference to the

instrument approach procedure chart. This angle is

generally not more than 3 degrees. However, it should

be noted that inasmuch as the approach course

originates at the antenna site, an approach which is

continued beyond the runway threshold will lead the

aircraft to the SDF offset position rather than along

the runway centerline.
7/26/12 AIM

Navigation Aids 1−1−13

FIG 1−1−7

FAA Instrument Landing Systems
AIM 7/26/12

1−1−14 Navigation Aids

f. The SDF signal is fixed at either 6 degrees or

12 degrees as necessary to provide maximum

flyability and optimum course quality.

g. Identification consists of a three−letter identifier transmitted in Morse Code on the SDF frequency.

The appropriate instrument approach chart will

indicate the identifier used at a particular airport.

1−1−11. Microwave Landing System (MLS)

a. General

1. The MLS provides precision navigation

guidance for exact alignment and descent of aircraft

on approach to a runway. It provides azimuth,

elevation, and distance.

2. Both lateral and vertical guidance may be

displayed on conventional course deviation indicators or incorporated into multipurpose cockpit

displays. Range information can be displayed by

conventional DME indicators and also incorporated

into multipurpose displays.

3. The MLS supplements the ILS as the standard

landing system in the U.S. for civil, military, and

international civil aviation. At international airports,

ILS service is protected to 2010.

4. The system may be divided into five

functions:

(a) Approach azimuth;

(b) Back azimuth;

(c) Approach elevation;

(d) Range; and

(e) Data communications.

5. The standard configuration of MLS ground

equipment includes:

(a) An azimuth station to perform functions

(a) and (e) above. In addition to providing azimuth

navigation guidance, the station transmits basic data

which consists of information associated directly

with the operation of the landing system, as well as

advisory data on the performance of the ground

equipment.

(b) An elevation station to perform function (c).

(c) Distance Measuring Equipment (DME) to

perform range guidance, both standard DME

(DME/N) and precision DME (DME/P).

6. MLS Expansion Capabilities. The standard configuration can be expanded by adding one or

more of the following functions or characteristics.

(a) Back azimuth. Provides lateral guidance

for missed approach and departure navigation.

(b) Auxiliary data transmissions. Provides

additional data, including refined airborne positioning, meteorological information, runway status, and

other supplementary information.

(c) Expanded Service Volume (ESV) proportional guidance to 60 degrees.

7. MLS identification is a four−letter designation starting with the letter M. It is transmitted in

International Morse Code at least six times per

minute by the approach azimuth (and back azimuth)

ground equipment.

b. Approach Azimuth Guidance

1. The azimuth station transmits MLS angle and

data on one of 200 channels within the frequency

range of 5031 to 5091 MHz.

2. The equipment is normally located about

1,000 feet beyond the stop end of the runway, but

there is considerable flexibility in selecting sites. For

example, for heliport operations the azimuth

transmitter can be collocated with the elevation

transmitter.

3. The azimuth coverage extends:

 (See FIG 1−1−8.)

(a) Laterally, at least 40 degrees on either side

of the runway centerline in a standard configuration,

(b) In elevation, up to an angle of 15 degrees

and to at least 20,000 feet, and

(c) In range, to at least 20 NM.
7/26/12 AIM

Navigation Aids 1−1−15

FIG 1−1−8

Coverage Volume

Azimuth

APPROACH

AZIMUTH

AZIMUTH

-40°

+40°

20 NM

ESV

ESV

14 NM

+60° MAXIMUM LIMIT

14 NM

-60°

c. Elevation Guidance

1. The elevation station transmits signals on the

same frequency as the azimuth station. A single

frequency is time−shared between angle and data

functions.

2. The elevation transmitter is normally located

about 400 feet from the side of the runway between

runway threshold and the touchdown zone.

3. Elevation coverage is provided in the same

airspace as the azimuth guidance signals:

(a) In elevation, to at least +15 degrees;

(b) Laterally, to fill the Azimuth lateral

coverage; and

(c) In range, to at least 20 NM.

(See FIG 1−1−9.)

FIG 1−1−9

Coverage Volumes

Elevation

ELEVATION ELEVATION

NORMAL

GLIDE PATH

NORMAL

GLIDE PATH

MAXIMUM LIMIT MAXIMUM LIMIT 20,000’

20 NM

30

3

15

o

o

o

o

d. Range Guidance

1. The MLS Precision Distance Measuring

Equipment (DME/P) functions the same as the

navigation DME described in paragraph 1−1−7,

Distance Measuring Equipment (DME), but there are

some technical differences. The beacon transponder

operates in the frequency band 962 to 1105 MHz and

responds to an aircraft interrogator. The MLS DME/P

accuracy is improved to be consistent with the

accuracy provided by the MLS azimuth and elevation

stations.

2. A DME/P channel is paired with the azimuth

and elevation channel. A complete listing of the

200 paired channels of the DME/P with the angle

functions is contained in FAA Standard 022 (MLS

Interoperability and Performance Requirements).

3. The DME/N or DME/P is an integral part of

the MLS and is installed at all MLS facilities unless

a waiver is obtained. This occurs infrequently and

only at outlying, low density airports where marker

beacons or compass locators are already in place.

e. Data Communications

1. The data transmission can include both the

basic and auxiliary data words. All MLS facilities

transmit basic data. Where needed, auxiliary data can

be transmitted.

2. Coverage limits. MLS data are transmitted

throughout the azimuth (and back azimuth when

provided) coverage sectors.

3. Basic data content. Representative data

include:

(a) Station identification;
AIM 7/26/12

1−1−16 Navigation Aids

(b) Exact locations of azimuth, elevation and

DME/P stations (for MLS receiver processing

functions);

(c) Ground equipment performance level;

and

(d) DME/P channel and status.

4. Auxiliary data content: Representative

data include:

(a) 3−D locations of MLS equipment;

(b) Waypoint coordinates;

(c) Runway conditions; and

(d) Weather (e.g., RVR, ceiling, altimeter

setting, wind, wake vortex, wind shear).

f. Operational Flexibility

1. The MLS has the capability to fulfill a variety

of needs in the approach, landing, missed approach

and departure phases of flight. For example:

(a) Curved and segmented approaches;

(b) Selectable glide path angles;

(c) Accurate 3−D positioning of the aircraft in

space; and

(d) The establishment of boundaries to ensure

clearance from obstructions in the terminal area.

2. While many of these capabilities are

available to any MLS−equipped aircraft, the more

sophisticated capabilities (such as curved and

segmented approaches) are dependent upon the

particular capabilities of the airborne equipment.

g. Summary

1. Accuracy. The MLS provides precision

three−dimensional navigation guidance accurate

enough for all approach and landing maneuvers.

2. Coverage. Accuracy is consistent

throughout the coverage volumes. (See

FIG 1−1−10.)

FIG 1−1−10

Coverage Volumes

3−D Representation

3. Environment. The system has low susceptibility to interference from weather conditions and

airport ground traffic.

4. Channels. MLS has 200 channels− enough

for any foreseeable need.

5. Data. The MLS transmits ground−air data

messages associated with the systems operation.

6. Range information. Continuous range information is provided with an accuracy of about

100 feet.

1−1−12. NAVAID Identifier Removal During

Maintenance

During periods of routine or emergency maintenance,

coded identification (or code and voice, where

applicable) is removed from certain FAA NAVAIDs.

Removal of identification serves as a warning to

pilots that the facility is officially off the air for

tune−up or repair and may be unreliable even though

intermittent or constant signals are received.

NOTE−

During periods of maintenance VHF ranges may radiate

a T−E−S−T code (- -).
7/26/12 AIM

Navigation Aids 1−1−17

NOTE−

DO NOT attempt to fly a procedure that is NOTAMed out

of service even if the identification is present. In certain

cases, the identification may be transmitted for short

periods as part of the testing.

1−1−13. NAVAIDs with Voice

a. Voice equipped en route radio navigational aids

are under the operational control of either a Flight

Service Station (FSS) or an approach control facility.

The voice communication is available on some

facilities. Hazardous Inflight Weather Advisory

Service (HIWAS) broadcast capability is available on

selected VOR sites throughout the conterminous U.S.

and does not provide two-way voice communication.

The availability of two-way voice communication

and HIWAS is indicated in the A/FD and aeronautical

charts.

b. Unless otherwise noted on the chart, all radio

navigation aids operate continuously except during

shutdowns for maintenance. Hours of operation of

facilities not operating continuously are annotated on

charts and in the A/FD.

1−1−14. User Reports on NAVAID

Performance

a. Users of the National Airspace System (NAS)

can render valuable assistance in the early correction

of NAVAID malfunctions by reporting their

observations of undesirable NAVAID performance.

Although NAVAIDs are monitored by electronic

detectors, adverse effects of electronic interference,

new obstructions or changes in terrain near the

NAVAID can exist without detection by the ground

monitors. Some of the characteristics of malfunction

or deteriorating performance which should be

reported are: erratic course or bearing indications;

intermittent, or full, flag alarm; garbled, missing or

obviously improper coded identification; poor

quality communications reception; or, in the case of

frequency interference, an audible hum or tone

accompanying radio communications or NAVAID

identification.

b. Reporters should identify the NAVAID, location of the aircraft, time of the observation, type of

aircraft and describe the condition observed; the type

of receivers in use is also useful information. Reports

can be made in any of the following ways:

1. Immediate report by direct radio communication to the controlling Air Route Traffic Control

Center (ARTCC), Control Tower, or FSS. This

method provides the quickest result.

2. By telephone to the nearest FAA facility.

3. By FAA Form 8740−5, Safety Improvement

Report, a postage−paid card designed for this

purpose. These cards may be obtained at FAA FSSs,

Flight Standards District Offices, and General

Aviation Fixed Base Operations.

c. In aircraft that have more than one receiver,

there are many combinations of possible interference

between units. This can cause either erroneous

navigation indications or, complete or partial

blanking out of the communications. Pilots should be

familiar enough with the radio installation of the

particular airplanes they fly to recognize this type of

interference.

1−1−15. LORAN 

NOTE−

In accordance with the 2010 DHS Appropriations Act, the

U.S. Coast Guard (USCG) terminated the transmission of

all U.S. LORAN−C signals on 08 Feb 2010. The USCG also

terminated the transmission of the Russian American

signals on 01 Aug 2010, and the Canadian LORAN−C

signals on 03 Aug 2010. For more information, visit

http://www.navcen.uscg.gov. Operators should also note

that TSO−C60b, AIRBORNE AREA NAVIGATION

EQUIPMENT USING LORAN−C INPUTS, has been

canceled by the FAA.

1−1−16. VHF Direction Finder

a. The VHF Direction Finder (VHF/DF) is one of

the common systems that helps pilots without their

being aware of its operation. It is a ground−based

radio receiver used by the operator of the ground

station. FAA facilities that provide VHF/DF service

are identified in the A/FD.

b. The equipment consists of a directional antenna

system and a VHF radio receiver.

c. The VHF/DF receiver display indicates the

magnetic direction of the aircraft from the ground

station each time the aircraft transmits.

d. DF equipment is of particular value in locating

lost aircraft and in helping to identify aircraft on

radar.
AIM 7/26/12

1−1−18 Navigation Aids

REFERENCE−

AIM, Direction Finding Instrument Approach Procedure,

Paragraph 6−2−3.

1−1−17. Inertial Reference Unit (IRU),

Inertial Navigation System (INS), and

Attitude Heading Reference System (AHRS)

a. IRUs are self−contained systems comprised of

gyros and accelerometers that provide aircraft

attitude (pitch, roll, and heading), position, and

velocity information in response to signals resulting

from inertial effects on system components. Once

aligned with a known position, IRUs continuously

calculate position and velocity. IRU position

accuracy decays with time. This degradation is

known as “drift.”

b. INSs combine the components of an IRU with

an internal navigation computer. By programming a

series of waypoints, these systems will navigate along

a predetermined track.

c. AHRSs are electronic devices that provide

attitude information to aircraft systems such as

weather radar and autopilot, but do not directly

compute position information.

1−1−18. Doppler Radar

Doppler Radar is a semiautomatic self−contained

dead reckoning navigation system (radar sensor plus

computer) which is not continuously dependent on

information derived from ground based or external

aids. The system employs radar signals to detect and

measure ground speed and drift angle, using the

aircraft compass system as its directional reference.

Doppler is less accurate than INS, however, and the

use of an external reference is required for periodic

updates if acceptable position accuracy is to be

achieved on long range flights.

1−1−19. Global Positioning System (GPS)

a. System Overview

1. System Description. The Global Positioning

System is a satellite−based radio navigation system,

which broadcasts a signal that is used by receivers to

determine precise position anywhere in the world.

The receiver tracks multiple satellites and determines

a pseudorange measurement that is then used to

determine the user location. A minimum of four

satellites is necessary to establish an accurate

three−dimensional position. The Department of

Defense (DOD) is responsible for operating the GPS

satellite constellation and monitors the GPS satellites

to ensure proper operation. Every satellite’s orbital

parameters (ephemeris data) are sent to each satellite

for broadcast as part of the data message embedded

in the GPS signal. The GPS coordinate system is the

Cartesian earth−centered earth−fixed coordinates as

specified in the World Geodetic System 1984

(WGS−84).

2. System Availability and Reliability

(a) The status of GPS satellites is broadcast as

part of the data message transmitted by the GPS

satellites. GPS status information is also available by

means of the U.S. Coast Guard navigation

information service: (703) 313−5907, Internet:

http://www.navcen.uscg.gov/. Additionally, satellite status is available through the Notice to Airmen

(NOTAM) system.

(b) The operational status of GNSS operations depends upon the type of equipment being used.

For GPS−only equipment TSO−C129(a), the operational status of nonprecision approach capability for

flight planning purposes is provided through a

prediction program that is embedded in the receiver

or provided separately.

3. Receiver Autonomous Integrity Monitoring

(RAIM). When GNSS equipment is not using

integrity information from WAAS or LAAS, the GPS

navigation receiver using RAIM provides GPS signal

integrity monitoring. RAIM is necessary since delays

of up to two hours can occur before an erroneous

satellite transmission can be detected and corrected

by the satellite control segment. The RAIM function

is also referred to as fault detection. Another

capability, fault exclusion, refers to the ability of the

receiver to exclude a failed satellite from the position

solution and is provided by some GPS receivers and

by WAAS receivers.

4. The GPS receiver verifies the integrity

(usability) of the signals received from the GPS

constellation through receiver autonomous integrity

monitoring (RAIM) to determine if a satellite is

providing corrupted information. At least one

satellite, in addition to those required for navigation,

must be in view for the receiver to perform the RAIM

function; thus, RAIM needs a minimum of 5 satellites

in view, or 4 satellites and a barometric altimeter

(baro−aiding) to detect an integrity anomaly.
7/26/12 AIM

Navigation Aids 1−1−19

[Baro−aiding satisfies the RAIM requirement in lieu

of a fifth satellite.] For receivers capable of doing so,

RAIM needs 6 satellites in view (or 5 satellites with

baro−aiding) to isolate the corrupt satellite signal and

remove it from the navigation solution. Baro−aiding

is a method of augmenting the GPS integrity solution

by using a nonsatellite input source. GPS derived

altitude should not be relied upon to determine

aircraft altitude since the vertical error can be quite

large and no integrity is provided. To ensure that

baro−aiding is available, the current altimeter setting

must be entered into the receiver as described in the

operating manual.

5. RAIM messages vary somewhat between

receivers; however, generally there are two types.

One type indicates that there are not enough satellites

available to provide RAIM integrity monitoring and

another type indicates that the RAIM integrity

monitor has detected a potential error that exceeds the

limit for the current phase of flight. Without RAIM

capability, the pilot has no assurance of the accuracy

of the GPS position.

6. Selective Availability. Selective Availability

(SA) is a method by which the accuracy of GPS is

intentionally degraded. This feature is designed to

deny hostile use of precise GPS positioning data. SA

was discontinued on May 1, 2000, but many GPS

receivers are designed to assume that SA is still

active. New receivers may take advantage of the

discontinuance of SA based on the performance

values in ICAO Annex 10, and do not need to be

designed to operate outside of that performance.

7. The GPS constellation of 24 satellites is

designed so that a minimum of five is always

observable by a user anywhere on earth. The receiver

uses data from a minimum of four satellites above the

mask angle (the lowest angle above the horizon at

which it can use a satellite).

8. The DOD declared initial operational capability (IOC) of the U.S. GPS on December 8, 1993. The

FAA has granted approval for U.S. civil operators to

use properly certified GPS equipment as a primary

means of navigation in oceanic airspace and certain

remote areas. Properly certified GPS equipment may

be used as a supplemental means of IFR navigation

for domestic en route, terminal operations, and

certain instrument approach procedures (IAPs). This

approval permits the use of GPS in a manner that is

consistent with current navigation requirements as

well as approved air carrier operations specifications.

b. VFR Use of GPS

1. GPS navigation has become a great asset to

VFR pilots, providing increased navigation capability and enhanced situational awareness, while

reducing operating costs due to greater ease in flying

direct routes. While GPS has many benefits to the

VFR pilot, care must be exercised to ensure that

system capabilities are not exceeded.

2. Types of receivers used for GPS navigation

under VFR are varied, from a full IFR installation

being used to support a VFR flight, to a VFR only

installation (in either a VFR or IFR capable aircraft)

to a hand−held receiver. The limitations of each type

of receiver installation or use must be understood by

the pilot to avoid misusing navigation information.

(See TBL 1−1−6.) In all cases, VFR pilots should

never rely solely on one system of navigation. GPS

navigation must be integrated with other forms of

electronic navigation (when possible), as well as

pilotage and dead reckoning. Only through the

integration of these techniques can the VFR pilot

ensure accuracy in navigation.

3. Some critical concerns in VFR use of GPS

include RAIM capability, database currency and

antenna location.

(a) RAIM Capability. Many VFR GPS receivers and all hand−held units have no RAIM

alerting capability. Loss of the required number of

satellites in view, or the detection of a position error,

cannot be displayed to the pilot by such receivers. In

receivers with no RAIM capability, no alert would be

provided to the pilot that the navigation solution had

deteriorated, and an undetected navigation error

could occur. A systematic cross−check with other

navigation techniques would identify this failure, and

prevent a serious deviation. See subparagraphs a4 and

a5 for more information on RAIM.

(b) Database Currency

(1) In many receivers, an up−datable

database is used for navigation fixes, airports, and

instrument procedures. These databases must be

maintained to the current update for IFR operation,

but no such requirement exists for VFR use.

(2) However, in many cases, the database

drives a moving map display which indicates Special

Use Airspace and the various classes of airspace, in
AIM 7/26/12

1−1−20 Navigation Aids

addition to other operational information. Without a

current database the moving map display may be

outdated and offer erroneous information to VFR

pilots wishing to fly around critical airspace areas,

such as a Restricted Area or a Class B airspace

segment. Numerous pilots have ventured into

airspace they were trying to avoid by using an

outdated database. If you don’t have a current

database in the receiver, disregard the moving map

display for critical navigation decisions.

(3) In addition, waypoints are added,

removed, relocated, or re−named as required to meet

operational needs. When using GPS to navigate

relative to a named fix, a current database must be

used to properly locate a named waypoint. Without

the update, it is the pilot’s responsibility to verify the

waypoint location referencing to an official current

source, such as the Airport/Facility Directory,

Sectional Chart, or En Route Chart.

(c) Antenna Location

(1) In many VFR installations of GPS

receivers, antenna location is more a matter of

convenience than performance. In IFR installations,

care is exercised to ensure that an adequate clear view

is provided for the antenna to see satellites. If an

alternate location is used, some portion of the aircraft

may block the view of the antenna, causing a greater

opportunity to lose navigation signal.

(2) This is especially true in the case of

hand−helds. The use of hand−held receivers for VFR

operations is a growing trend, especially among

rental pilots. Typically, suction cups are used to place

the GPS antennas on the inside of cockpit windows.

While this method has great utility, the antenna

location is limited to the cockpit or cabin only and is

rarely optimized to provide a clear view of available

satellites. Consequently, signal losses may occur in

certain situations of aircraft−satellite geometry,

causing a loss of navigation signal. These losses,

coupled with a lack of RAIM capability, could

present erroneous position and navigation information with no warning to the pilot.

(3) While the use of a hand−held GPS for

VFR operations is not limited by regulation,

modification of the aircraft, such as installing a

panel− or yoke−mounted holder, is governed by

14 CFR Part 43. Consult with your mechanic to

ensure compliance with the regulation, and a safe

installation.

4. As a result of these and other concerns, here

are some tips for using GPS for VFR operations:

(a) Always check to see if your unit has

RAIM capability. If no RAIM capability exists, be

suspicious of your GPS position when any

disagreement exists with the position derived from

other radio navigation systems, pilotage, or dead

reckoning.

(b) Check the currency of the database, if any.

If expired, update the database using the current

revision. If an update of an expired database is not

possible, disregard any moving map display of

airspace for critical navigation decisions. Be aware

that named waypoints may no longer exist or may

have been relocated since the database expired. At a

minimum, the waypoints planned to be used should

be checked against a current official source, such as

the Airport/Facility Directory, or a Sectional

Aeronautical Chart.

(c) While hand−helds can provide excellent

navigation capability to VFR pilots, be prepared for

intermittent loss of navigation signal, possibly with

no RAIM warning to the pilot. If mounting the

receiver in the aircraft, be sure to comply with

14 CFR Part 43.

(d) Plan flights carefully before taking off. If

you wish to navigate to user−defined waypoints,

enter them before flight, not on−the−fly. Verify your

planned flight against a current source, such as a

current sectional chart. There have been cases in

which one pilot used waypoints created by another

pilot that were not where the pilot flying was

expecting. This generally resulted in a navigation

error. Minimize head−down time in the aircraft and

keep a sharp lookout for traffic, terrain, and obstacles.

Just a few minutes of preparation and planning on the

ground will make a great difference in the air.

(e) Another way to minimize head−down

time is to become very familiar with your receiver’s

operation. Most receivers are not intuitive. The pilot

must take the time to learn the various keystrokes,

knob functions, and displays that are used in the

operation of the receiver. Some manufacturers

provide computer−based tutorials or simulations of

their receivers. Take the time to learn about your

particular unit before you try to use it in flight.
7/26/12 AIM

Navigation Aids 1−1−21

5. In summary, be careful not to rely on GPS to

solve all your VFR navigational problems. Unless an

IFR receiver is installed in accordance with IFR

requirements, no standard of accuracy or integrity has

been assured. While the practicality of GPS is

compelling, the fact remains that only the pilot can

navigate the aircraft, and GPS is just one of the pilot’s

tools to do the job.

c. VFR Waypoints

1. VFR waypoints provide VFR pilots with a

supplementary tool to assist with position awareness

while navigating visually in aircraft equipped with

area navigation receivers. VFR waypoints should be

used as a tool to supplement current navigation

procedures. The uses of VFR waypoints include

providing navigational aids for pilots unfamiliar with

an area, waypoint definition of existing reporting

points, enhanced navigation in and around Class B

and Class C airspace, and enhanced navigation

around Special Use Airspace. VFR pilots should rely

on appropriate and current aeronautical charts

published specifically for visual navigation. If

operating in a terminal area, pilots should take

advantage of the Terminal Area Chart available for

that area, if published. The use of VFR waypoints

does not relieve the pilot of any responsibility to

comply with the operational requirements of 14 CFR

Part 91.

2. VFR waypoint names (for computer−entry

and flight plans) consist of five letters beginning with

the letters “VP” and are retrievable from navigation

databases. The VFR waypoint names are not intended

to be pronounceable, and they are not for use in ATC

communications. On VFR charts, stand−alone VFR

waypoints will be portrayed using the same

four−point star symbol used for IFR waypoints. VFR

waypoints collocated with visual check points on the

chart will be identified by small magenta flag

symbols. VFR waypoints collocated with visual

check points will be pronounceable based on the

name of the visual check point and may be used for

ATC communications. Each VFR waypoint name

will appear in parentheses adjacent to the geographic

location on the chart. Latitude/longitude data for all

established VFR waypoints may be found in the

appropriate regional Airport/Facility Directory

(A/FD).

3. VFR waypoints must not be used to plan

flights under IFR. VFR waypoints will not be

recognized by the IFR system and will be rejected for

IFR routing purposes.

4. When filing VFR flight plans, pilots may use

the five letter identifier as a waypoint in the route of

flight section if there is an intended course change at

that point or if used to describe the planned route of

flight. This VFR filing would be similar to how a

VOR would be used in a route of flight. Pilots must

use the VFR waypoints only when operating under

VFR conditions.

5. Any VFR waypoints intended for use during

a flight should be loaded into the receiver while on the

ground and prior to departure. Once airborne, pilots

should avoid programming routes or VFR waypoint

chains into their receivers.

6. Pilots should be especially vigilant for other

traffic while operating near VFR waypoints. The

same effort to see and avoid other aircraft near VFR

waypoints will be necessary, as was the case with

VORs and NDBs in the past. In fact, the increased

accuracy of navigation through the use of GPS will

demand even greater vigilance, as off−course

deviations among different pilots and receivers will

be less. When operating near a VFR waypoint, use

whatever ATC services are available, even if outside

a class of airspace where communications are

required. Regardless of the class of airspace, monitor

the available ATC frequency closely for information

on other aircraft operating in the vicinity. It is also a

good idea to turn on your landing light(s) when

operating near a VFR waypoint to make your aircraft

more conspicuous to other pilots, especially when

visibility is reduced. See paragraph 7−5−2, VFR in

Congested Areas, for more information.

d. General Requirements

1. Authorization to conduct any GPS operation

under IFR requires that:

(a) GPS navigation equipment used must be

approved in accordance with the requirements

specified in Technical Standard Order (TSO)

TSO−C129, or equivalent, and the installation must

be done in accordance with Advisory Circular

AC 20−138, Airworthiness Approval of Global

Positioning System (GPS) Navigation Equipment for

Use as a VFR and IFR Supplemental Navigation

System, or Advisory Circular AC 20−130A, Airworthiness Approval of Navigation or Flight

Management Systems Integrating Multiple Navigation Sensors, or equivalent. Equipment approved in
AIM 7/26/12

1−1−22 Navigation Aids

accordance with TSO−C115a does not meet the

requirements of TSO−C129. Visual flight rules

(VFR) and hand−held GPS systems are not

authorized for IFR navigation, instrument approaches, or as a principal instrument flight

reference. During IFR operations they may be

considered only an aid to situational awareness.

(b) Aircraft using GPS navigation equipment

under IFR must be equipped with an approved and

operational alternate means of navigation appropriate

to the flight. Active monitoring of alternative

navigation equipment is not required if the GPS

receiver uses RAIM for integrity monitoring. Active

monitoring of an alternate means of navigation is

required when the RAIM capability of the GPS

equipment is lost.

(c) Procedures must be established for use in

the event that the loss of RAIM capability is predicted

to occur. In situations where this is encountered, the

flight must rely on other approved equipment, delay

departure, or cancel the flight.

(d) The GPS operation must be conducted in

accordance with the FAA−approved aircraft flight

manual (AFM) or flight manual supplement. Flight

crew members must be thoroughly familiar with the

particular GPS equipment installed in the aircraft, the

receiver operation manual, and the AFM or flight

manual supplement. Unlike ILS and VOR, the basic

operation, receiver presentation to the pilot, and some

capabilities of the equipment can vary greatly. Due to

these differences, operation of different brands, or

even models of the same brand, of GPS receiver

under IFR should not be attempted without thorough

study of the operation of that particular receiver and

installation. Most receivers have a built−in simulator

mode which will allow the pilot to become familiar

with operation prior to attempting operation in the

aircraft. Using the equipment in flight under VFR

conditions prior to attempting IFR operation will

allow further familiarization.

(e) Aircraft navigating by IFR approved GPS

are considered to be area navigation (RNAV) aircraft

and have special equipment suffixes. File the

appropriate equipment suffix in accordance with

TBL 5−1−2, on the ATC flight plan. If GPS avionics

become inoperative, the pilot should advise ATC and

amend the equipment suffix.

(f) Prior to any GPS IFR operation, the pilot

must review appropriate NOTAMs and aeronautical

information. (See GPS NOTAMs/Aeronautical Information.)

(g) Air carrier and commercial operators

must meet the appropriate provisions of their

approved operations specifications.

e. Use of GPS for IFR Oceanic, Domestic

En Route, and Terminal Area Operations

1. GPS IFR operations in oceanic areas can be

conducted as soon as the proper avionics systems are

installed, provided all general requirements are met.

A GPS installation with TSO−C129 authorization in

class A1, A2, B1, B2, C1, or C2 may be used to

replace one of the other approved means of

long−range navigation, such as dual INS. (See

TBL 1−1−5 and TBL 1−1−6.) A single GPS installation with these classes of equipment which provide

RAIM for integrity monitoring may also be used on

short oceanic routes which have only required one

means of long−range navigation.

2. GPS domestic en route and terminal IFR

operations can be conducted as soon as proper

avionics systems are installed, provided all general

requirements are met. The avionics necessary to

receive all of the ground−based facilities appropriate

for the route to the destination airport and any

required alternate airport must be installed and

operational. Ground−based facilities necessary for

these routes must also be operational.

(a) GPS en route IFR RNAV operations may

be conducted in Alaska outside the operational

service volume of ground−based navigation aids

when a TSO−C145a or TSO−C146a GPS/WAAS

system is installed and operating. Ground−based

navigation equipment is not required to be installed

and operating for en route IFR RNAV operations

when using GPS WAAS navigation systems. All

operators should ensure that an alternate means of

navigation is available in the unlikely event the GPS

WAAS navigation system becomes inoperative.
7/26/12 AIM

Navigation Aids 1−1−23

TBL 1−1−5

GPS IFR Equipment Classes/Categories

TSO−C129

Equipment

Class RAIM

Int. Nav. Sys. to

Prov. RAIM

Equiv.

Oceanic En Route Terminal

Nonprecision

Approach

Capable

Class A − GPS sensor and navigation capability.

A1 yes yes yes yes yes

A2 yes yes yes yes no

Class B − GPS sensor data to an integrated navigation system (i.e., FMS, multi−sensor navigation system, etc.).

B1 yes yes yes yes yes

B2 yes yes yes yes no

B3 yes yes yes yes yes

B4 yes yes yes yes no

Class C − GPS sensor data to an integrated navigation system (as in Class B) which provides enhanced guidance to an autopilot, or

flight director, to reduce flight tech. errors. Limited to 14 CFR Part 121 or equivalent criteria.

C1 yes yes yes yes yes

C2 yes yes yes yes no

C3 yes yes yes yes yes

C4 yes yes yes yes no

TBL 1−1−6

GPS Approval Required/Authorized Use

Equipment

Type1

Installation

Approval

Required

Operational

Approval

Required

IFR 

En Route2

IFR

Terminal2

IFR 

Approach3

Oceanic 

Remote

In Lieu of

ADF and/or

DME3

Hand held4 X5

VFR Panel Mount4 X

IFR En Route

and Terminal

X X X X X

IFR Oceanic/

Remote

X X X X X X

IFR En Route,

Terminal, and

Approach

X X X X X X

NOTE− 1To determine equipment approvals and limitations, refer to the AFM, AFM supplements, or pilot guides.

2Requires verification of data for correctness if database is expired.

3Requires current database or verification that the procedure has not been amended since the expiration of the database.

4VFR and hand−held GPS systems are not authorized for IFR navigation, instrument approaches, or as a primary instrument

flight reference. During IFR operations they may be considered only an aid to situational awareness.

5Hand−held receivers require no approval. However, any aircraft modification to support the hand−held receiver;

i.e., installation of an external antenna or a permanent mounting bracket, does require approval.
AIM 7/26/12

1−1−24 Navigation Aids

3. The GPS Approach Overlay Program is an

authorization for pilots to use GPS avionics under

IFR for flying designated nonprecision instrument

approach procedures, except LOC, LDA, and

simplified directional facility (SDF) procedures.

These procedures are now identified by the name of

the procedure and “or GPS” (e.g., VOR/DME or GPS

RWY 15). Other previous types of overlays have

either been converted to this format or replaced with

stand−alone procedures. Only approaches contained

in the current onboard navigation database are

authorized. The navigation database may contain

information about nonoverlay approach procedures

that is intended to be used to enhance position

orientation, generally by providing a map, while

flying these approaches using conventional

NAVAIDs. This approach information should not be

confused with a GPS overlay approach (see the

receiver operating manual, AFM, or AFM Supplement for details on how to identify these approaches

in the navigation database).

NOTE−

Overlay approaches are predicated upon the design

criteria of the ground−based NAVAID used as the basis of

the approach. As such, they do not adhere to the design

criteria described in paragraph 5−4−5k, Area Navigation

(RNAV) Instrument Approach Charts, for stand−alone

GPS approaches.

4. GPS IFR approach operations can be

conducted as soon as proper avionics systems are

installed and the following requirements are met:

(a) The authorization to use GPS to fly

instrument approaches is limited to U.S. airspace.

(b) The use of GPS in any other airspace must

be expressly authorized by the FAA Administrator.

(c) GPS instrument approach operations

outside the U.S. must be authorized by the

appropriate sovereign authority.

f. Equipment and Database Requirements

1. Authorization to fly approaches under IFR

using GPS avionics systems requires that:

(a) A pilot use GPS avionics with TSO−

C129, or equivalent, authorization in class A1, B1,

B3, C1, or C3; and

(b) All approach procedures to be flown must

be retrievable from the current airborne navigation

database supplied by the TSO−C129 equipment

manufacturer or other FAA approved source. The

system must be able to retrieve the procedure by

name from the aircraft navigation database, not just

as a manually entered series of waypoints.

(c) Prior to using a procedure or waypoint

retrieved from the airborne navigation database, the

pilot should verify the validity of the database. This

verification should include the following preflight

and in−flight steps:

(1) Preflight:

[a] Determine the date of database

issuance, and verify that the date/time of proposed

use is before the expiration date/time.

[b] Verify that the database provider has

not published a notice limiting the use of the specific

waypoint or procedure.

(2) Inflight:

[a] Determine that the waypoints and

transition names coincide with names found on the

procedure chart. Do not use waypoints, which do not

exactly match the spelling shown on published

procedure charts.

[b] Determine that the waypoints are

generally logical in location, in the correct order, and

that their orientation to each other is as found on the

procedure chart, both laterally and vertically.

NOTE−

There is no specific requirement to check each waypoint

latitude and longitude, type of waypoint and/or altitude

constraint, only the general relationship of waypoints in

the procedure, or the logic of an individual waypoint’s

location.

[c] If the cursory check of procedure

logic or individual waypoint location, specified in [b]

above, indicates a potential error, do not use the

retrieved procedure or waypoint until a verification of

latitude and longitude, waypoint type, and altitude

constraints indicate full conformity with the

published data.

g. GPS Approach Procedures

As the production of stand−alone GPS approaches

has progressed, many of the original overlay

approaches have been replaced with stand−alone

procedures specifically designed for use by GPS

systems. The title of the remaining GPS overlay

procedures has been revised on the approach chart to

“or GPS” (e.g., VOR or GPS RWY 24). Therefore, all
7/26/12 AIM

Navigation Aids 1−1−25

the approaches that can be used by GPS now contain

“GPS” in the title (e.g., “VOR or GPS RWY 24,”

“GPS RWY 24,” or “RNAV (GPS) RWY 24”).

During these GPS approaches, underlying ground−

based NAVAIDs are not required to be operational

and associated aircraft avionics need not be installed,

operational, turned on or monitored (monitoring of

the underlying approach is suggested when equipment is available and functional). Existing overlay

approaches may be requested using the GPS title,

such as “GPS RWY 24” for the VOR or GPS

RWY 24.

NOTE−

Any required alternate airport must have an approved

instrument approach procedure other than GPS that is

anticipated to be operational and available at the

estimated time of arrival, and which the aircraft is

equipped to fly.

h. GPS NOTAMs/Aeronautical Information

1. GPS satellite outages are issued as GPS

NOTAMs both domestically and internationally.

However, the effect of an outage on the intended

operation cannot be determined unless the pilot has a

RAIM availability prediction program which allows

excluding a satellite which is predicted to be out of

service based on the NOTAM information.

2. The term UNRELIABLE is used in conjunction with GPS NOTAMs. The term UNRELIABLE

is an advisory to pilots indicating the expected level

of service may not be available. GPS operation may

be NOTAMed UNRELIABLE due to testing or

anomalies. Air Traffic Control will advise pilots

requesting a GPS or RNAV (GPS) approach of GPS

UNRELIABLE for:

(a) NOTAMs not contained in the ATIS

broadcast.

(b) Pilot reports of GPS anomalies received

within the preceding 15 minutes.

3. Civilian pilots may obtain GPS RAIM

availability information for nonprecision approach

procedures by specifically requesting GPS aeronautical information from a Flight Service Station during

preflight briefings. GPS RAIM aeronautical information can be obtained for a period of 3 hours (for

example, if you are scheduled to arrive at 1215 hours,

then the GPS RAIM information is available from

1100 to 1400 hours) or a 24 hour time frame at a

particular airport. FAA briefers will provide RAIM

information for a period of 1 hour before to 1 hour

after the ETA hour, unless a specific time frame is

requested by the pilot. If flying a published GPS

departure, a RAIM prediction should also be

requested for the departure airport.

4. The military provides airfield specific GPS

RAIM NOTAMs for nonprecision approach procedures at military airfields. The RAIM outages are

issued as M−series NOTAMs and may be obtained for

up to 24 hours from the time of request.

5. Receiver manufacturers and/or database

suppliers may supply “NOTAM” type information

concerning database errors. Pilots should check these

sources, when available, to ensure that they have the

most current information concerning their electronic

database.

i. Receiver Autonomous Integrity Monitoring

(RAIM)

1. RAIM outages may occur due to an

insufficient number of satellites or due to unsuitable

satellite geometry which causes the error in the

position solution to become too large. Loss of satellite

reception and RAIM warnings may occur due to

aircraft dynamics (changes in pitch or bank angle).

Antenna location on the aircraft, satellite position

relative to the horizon, and aircraft attitude may affect

reception of one or more satellites. Since the relative

positions of the satellites are constantly changing,

prior experience with the airport does not guarantee

reception at all times, and RAIM availability should

always be checked.

2. If RAIM is not available, another type of

navigation and approach system must be used,

another destination selected, or the trip delayed until

RAIM is predicted to be available on arrival. On

longer flights, pilots should consider rechecking the

RAIM prediction for the destination during the flight.

This may provide early indications that an

unscheduled satellite outage has occurred since

takeoff.

3. If a RAIM failure/status annunciation

occurs prior to the final approach waypoint

(FAWP), the approach should not be completed

since GPS may no longer provide the required

accuracy. The receiver performs a RAIM prediction

by 2 NM prior to the FAWP to ensure that RAIM is

available at the FAWP as a condition for entering the

approach mode. The pilot should ensure that the

receiver has sequenced from “Armed” to “Ap-
AIM 7/26/12

1−1−26 Navigation Aids

proach” prior to the FAWP (normally occurs 2 NM

prior). Failure to sequence may be an indication of the

detection of a satellite anomaly, failure to arm the

receiver (if required), or other problems which

preclude completing the approach.

4. If the receiver does not sequence into the

approach mode or a RAIM failure/status annunciation occurs prior to the FAWP, the pilot should not

descend to Minimum Descent Altitude (MDA), but

should proceed to the missed approach waypoint (MAWP) via the FAWP, perform a missed

approach, and contact ATC as soon as practical. Refer

to the receiver operating manual for specific

indications and instructions associated with loss of

RAIM prior to the FAF.

5. If a RAIM failure occurs after the FAWP, the

receiver is allowed to continue operating without an

annunciation for up to 5 minutes to allow completion

of the approach (see receiver operating manual). If

the RAIM flag/status annunciation appears after

the FAWP, the missed approach should be

executed immediately.

j. Waypoints

1. GPS approaches make use of both fly−over

and fly−by waypoints. Fly−by waypoints are used

when an aircraft should begin a turn to the next course

prior to reaching the waypoint separating the two

route segments. This is known as turn anticipation

and is compensated for in the airspace and terrain

clearances. Approach waypoints, except for the

MAWP and the missed approach holding waypoint

(MAHWP), are normally fly−by waypoints. Fly−

over waypoints are used when the aircraft must fly

over the point prior to starting a turn. New approach

charts depict fly−over waypoints as a circled

waypoint symbol. Overlay approach charts and some

early stand alone GPS approach charts may not

reflect this convention.

2. Since GPS receivers are basically “To−To”

navigators, they must always be navigating to a

defined point. On overlay approaches, if no

pronounceable five−character name is published for

an approach waypoint or fix, it was given a database

identifier consisting of letters and numbers. These

points will appear in the list of waypoints in the

approach procedure database, but may not appear on

the approach chart. A point used for the purpose of

defining the navigation track for an airborne

computer system (i.e., GPS or FMS) is called a

Computer Navigation Fix (CNF). CNFs include

unnamed DME fixes, beginning and ending points of

DME arcs and sensor final approach fixes (FAFs) on

some GPS overlay approaches. To aid in the approach

chart/database correlation process, the FAA has

begun a program to assign five−letter names to CNFs

and to chart CNFs on various FAA Aeronautical

Navigation Products (AeroNav Products). These

CNFs are not to be used for any air traffic control

(ATC) application, such as holding for which the fix

has not already been assessed. CNFs will be charted

to distinguish them from conventional reporting

points, fixes, intersections, and waypoints. The CNF

name will be enclosed in parenthesis, e.g., (CFBCD),

and the name will be placed next to the CNF it

defines. If the CNF is not at an existing point defined

by means such as crossing radials or radial/DME, the

point will be indicated by an “X.” The CNF name will

not be used in filing a flight plan or in aircraft/ATC

communications. Use current phraseology, e.g.,

facility name, radial, distance, to describe these fixes.

3. Unnamed waypoints in the database will be

uniquely identified for each airport but may be

repeated for another airport (e.g., RW36 will be used

at each airport with a runway 36 but will be at the

same location for all approaches at a given airport).

4. The runway threshold waypoint, which is

normally the MAWP, may have a five letter identifier

(e.g., SNEEZ) or be coded as RW## (e.g., RW36,

RW36L). Those thresholds which are coded as five

letter identifiers are being changed to the RW##

designation. This may cause the approach chart and

database to differ until all changes are complete. The

runway threshold waypoint is also used as the center

of the Minimum Safe Altitude (MSA) on most GPS

approaches. MAWPs not located at the threshold will

have a five letter identifier.

k. Position Orientation

As with most RNAV systems, pilots should pay

particular attention to position orientation while

using GPS. Distance and track information are

provided to the next active waypoint, not to a fixed

navigation aid. Receivers may sequence when the

pilot is not flying along an active route, such as when

being vectored or deviating for weather, due to the

proximity to another waypoint in the route. This can

be prevented by placing the receiver in the

nonsequencing mode. When the receiver is in the

nonsequencing mode, bearing and distance are
7/26/12 AIM

Navigation Aids 1−1−27

provided to the selected waypoint and the receiver

will not sequence to the next waypoint in the route

until placed back in the auto sequence mode or the

pilot selects a different waypoint. On overlay

approaches, the pilot may have to compute the

along−track distance to stepdown fixes and other

points due to the receiver showing along−track

distance to the next waypoint rather than DME to the

VOR or ILS ground station.

l. Conventional Versus GPS Navigation Data

There may be slight differences between the course

information portrayed on navigational charts and a

GPS navigation display when flying authorized GPS

instrument procedures or along an airway. All

magnetic tracks defined by any conventional

navigation aids are determined by the application of

the station magnetic variation. In contrast, GPS

RNAV systems may use an algorithm, which applies

the local magnetic variation and may produce small

differences in the displayed course. However, both

methods of navigation should produce the same

desired ground track when using approved, IFR

navigation system. Should significant differences

between the approach chart and the GPS avionics’

application of the navigation database arise, the

published approach chart, supplemented by NOTAMs, holds precedence.

Due to the GPS avionics’ computation of great circle

courses, and the variations in magnetic variation, the

bearing to the next waypoint and the course from the

last waypoint (if available) may not be exactly 180

apart when long distances are involved. Variations in

distances will occur since GPS distance−to−waypoint

values are along−track distances (ATD) computed to

the next waypoint and the DME values published on

underlying procedures are slant−range distances

measured to the station. This difference increases

with aircraft altitude and proximity to the NAVAID.

m. Departures and Instrument Departure

Procedures (DPs)

The GPS receiver must be set to terminal (±1 NM)

CDI sensitivity and the navigation routes contained in

the database in order to fly published IFR charted

departures and DPs. Terminal RAIM should be

automatically provided by the receiver. (Terminal

RAIM for departure may not be available unless the

waypoints are part of the active flight plan rather than

proceeding direct to the first destination.) Certain

segments of a DP may require some manual

intervention by the pilot, especially when radar

vectored to a course or required to intercept a specific

course to a waypoint. The database may not contain

all of the transitions or departures from all runways

and some GPS receivers do not contain DPs in the

database. It is necessary that helicopter procedures be

flown at 70 knots or less since helicopter departure

procedures and missed approaches use a

20:1 obstacle clearance surface (OCS), which is

double the fixed−wing OCS, and turning areas are

based on this speed as well.

n. Flying GPS Approaches

1. Determining which area of the TAA the

aircraft will enter when flying a “T” with a TAA must

be accomplished using the bearing and distance to the

IF(IAF). This is most critical when entering the TAA

in the vicinity of the extended runway centerline and

determining whether you will be entering the right or

left base area. Once inside the TAA, all sectors and

stepdowns are based on the bearing and distance to

the IAF for that area, which the aircraft should be

proceeding direct to at that time, unless on vectors.

(See FIG 5−4−3 and FIG 5−4−4.)

2. Pilots should fly the full approach from an

Initial Approach Waypoint (IAWP) or feeder fix

unless specifically cleared otherwise. Randomly

joining an approach at an intermediate fix does not

assure terrain clearance.

3. When an approach has been loaded in the

flight plan, GPS receivers will give an “arm”

annunciation 30 NM straight line distance from the

airport/heliport reference point. Pilots should arm the

approach mode at this time, if it has not already been

armed (some receivers arm automatically). Without

arming, the receiver will not change from en route

CDI and RAIM sensitivity of ±5 NM either side of

centerline to ±1 NM terminal sensitivity. Where the

IAWP is inside this 30 mile point, a CDI sensitivity

change will occur once the approach mode is armed

and the aircraft is inside 30 NM. Where the IAWP is

beyond 30 NM from the airport/heliport reference

point, CDI sensitivity will not change until the

aircraft is within 30 miles of the airport/heliport

reference point even if the approach is armed earlier.

Feeder route obstacle clearance is predicated on the

receiver being in terminal (±1 NM) CDI sensitivity

and RAIM within 30 NM of the airport/heliport

reference point, therefore, the receiver should always
AIM 7/26/12

1−1−28 Navigation Aids

be armed (if required) not later than the 30 NM

annunciation.

4. The pilot must be aware of what bank

angle/turn rate the particular receiver uses to compute

turn anticipation, and whether wind and airspeed are

included in the receiver’s calculations. This information should be in the receiver operating manual. Over

or under banking the turn onto the final approach

course may significantly delay getting on course and

may result in high descent rates to achieve the next

segment altitude.

5. When within 2 NM of the FAWP with the

approach mode armed, the approach mode will

switch to active, which results in RAIM changing to

approach sensitivity and a change in CDI sensitivity.

Beginning 2 NM prior to the FAWP, the full scale CDI

sensitivity will smoothly change from ±1 NM to

±0.3 NM at the FAWP. As sensitivity changes from

±1 NM to ±0.3 NM approaching the FAWP, with the

CDI not centered, the corresponding increase in CDI

displacement may give the impression that the

aircraft is moving further away from the intended

course even though it is on an acceptable intercept

heading. Referencing the digital track displacement

information (cross track error), if it is available in the

approach mode, may help the pilot remain position

oriented in this situation. Being established on the

final approach course prior to the beginning of the

sensitivity change at 2 NM will help prevent

problems in interpreting the CDI display during ramp

down. Therefore, requesting or accepting vectors

which will cause the aircraft to intercept the final

approach course within 2 NM of the FAWP is not

recommended.

6. When receiving vectors to final, most

receiver operating manuals suggest placing the

receiver in the nonsequencing mode on the FAWP

and manually setting the course. This provides an

extended final approach course in cases where the

aircraft is vectored onto the final approach course

outside of any existing segment which is aligned with

the runway. Assigned altitudes must be maintained

until established on a published segment of the

approach. Required altitudes at waypoints outside the

FAWP or stepdown fixes must be considered.

Calculating the distance to the FAWP may be

required in order to descend at the proper location.

7. Overriding an automatically selected sensitivity during an approach will cancel the approach

mode annunciation. If the approach mode is not

armed by 2 NM prior to the FAWP, the approach

mode will not become active at 2 NM prior to the

FAWP, and the equipment will flag. In these

conditions, the RAIM and CDI sensitivity will not

ramp down, and the pilot should not descend to MDA,

but fly to the MAWP and execute a missed approach.

The approach active annunciator and/or the receiver

should be checked to ensure the approach mode is

active prior to the FAWP.

8. Do not attempt to fly an approach unless the

procedure in the on−board database is current and

identified as “GPS” on the approach chart. The

navigation database may contain information about

nonoverlay approach procedures that is intended to

be used to enhance position orientation, generally by

providing a map, while flying these approaches using

conventional NAVAIDs. This approach information

should not be confused with a GPS overlay approach

(see the receiver operating manual, AFM, or AFM

Supplement for details on how to identify these

procedures in the navigation database). Flying point

to point on the approach does not assure compliance

with the published approach procedure. The proper

RAIM sensitivity will not be available and the CDI

sensitivity will not automatically change to

±0.3 NM. Manually setting CDI sensitivity does not

automatically change the RAIM sensitivity on some

receivers. Some existing nonprecision approach

procedures cannot be coded for use with GPS and will

not be available as overlays.

9. Pilots should pay particular attention to the

exact operation of their GPS receivers for performing

holding patterns and in the case of overlay

approaches, operations such as procedure turns.

These procedures may require manual intervention

by the pilot to stop the sequencing of waypoints by the

receiver and to resume automatic GPS navigation

sequencing once the maneuver is complete. The same

waypoint may appear in the route of flight more than

once consecutively (e.g., IAWP, FAWP, MAHWP on

a procedure turn). Care must be exercised to ensure

that the receiver is sequenced to the appropriate

waypoint for the segment of the procedure being

flown, especially if one or more fly−overs are skipped

(e.g., FAWP rather than IAWP if the procedure turn

is not flown). The pilot may have to sequence past one

or more fly−overs of the same waypoint in order to

start GPS automatic sequencing at the proper place in

the sequence of waypoints.
7/26/12 AIM

Navigation Aids 1−1−29

10. Incorrect inputs into the GPS receiver are

especially critical during approaches. In some cases,

an incorrect entry can cause the receiver to leave the

approach mode.

11. A fix on an overlay approach identified by a

DME fix will not be in the waypoint sequence on the

GPS receiver unless there is a published name

assigned to it. When a name is assigned, the along

track to the waypoint may be zero rather than the

DME stated on the approach chart. The pilot should

be alert for this on any overlay procedure where the

original approach used DME.

12. If a visual descent point (VDP) is published,

it will not be included in the sequence of waypoints.

Pilots are expected to use normal piloting techniques

for beginning the visual descent, such as ATD.

13. Unnamed stepdown fixes in the final

approach segment will not be coded in the waypoint

sequence of the aircraft’s navigation database and

must be identified using ATD. Stepdown fixes in the

final approach segment of RNAV (GPS) approaches

are being named, in addition to being identified by

ATD. However, since most GPS avionics do not

accommodate waypoints between the FAF and MAP,

even when the waypoint is named, the waypoints for

these stepdown fixes may not appear in the sequence

of waypoints in the navigation database. Pilots must

continue to identify these stepdown fixes using ATD.

o. Missed Approach

1. A GPS missed approach requires pilot

action to sequence the receiver past the MAWP to the

missed approach portion of the procedure. The pilot

must be thoroughly familiar with the activation

procedure for the particular GPS receiver installed in

the aircraft and must initiate appropriate action

after the MAWP. Activating the missed approach

prior to the MAWP will cause CDI sensitivity to

immediately change to terminal (±1NM) sensitivity

and the receiver will continue to navigate to the

MAWP. The receiver will not sequence past the

MAWP. Turns should not begin prior to the MAWP.

If the missed approach is not activated, the GPS

receiver will display an extension of the inbound final

approach course and the ATD will increase from the

MAWP until it is manually sequenced after crossing

the MAWP.

2. Missed approach routings in which the first

track is via a course rather than direct to the next

waypoint require additional action by the pilot to

set the course. Being familiar with all of the inputs

required is especially critical during this phase of

flight.

p. GPS Familiarization

Pilots should practice GPS approaches under visual

meteorological conditions (VMC) until thoroughly

proficient with all aspects of their equipment

(receiver and installation) prior to attempting flight

by IFR in instrument meteorological conditions

(IMC). Some of the areas which the pilot should

practice are:

1. Utilizing the receiver autonomous integrity

monitoring (RAIM) prediction function;

2. Inserting a DP into the flight plan, including

setting terminal CDI sensitivity, if required, and the

conditions under which terminal RAIM is available

for departure (some receivers are not DP or STAR

capable);

3. Programming the destination airport;

4. Programming and flying the overlay approaches (especially procedure turns and arcs);

5. Changing to another approach after selecting

an approach;

6. Programming and flying “direct” missed

approaches;

7. Programming and flying “routed” missed

approaches;

8. Entering, flying, and exiting holding patterns,

particularly on overlay approaches with a second

waypoint in the holding pattern;

9. Programming and flying a “route” from a

holding pattern;

10. Programming and flying an approach with

radar vectors to the intermediate segment;

11. Indication of the actions required for RAIM

failure both before and after the FAWP; and

12. Programming a radial and distance from a

VOR (often used in departure instructions).

1−1−20. Wide Area Augmentation System

(WAAS)

a. General

1. The FAA developed the Wide Area Augmentation System (WAAS) to improve the accuracy,
AIM 7/26/12

1−1−30 Navigation Aids

integrity and availability of GPS signals. WAAS will

allow GPS to be used, as the aviation navigation

system, from takeoff through Category I precision

approach when it is complete. WAAS is a critical

component of the FAA’s strategic objective for a

seamless satellite navigation system for civil

aviation, improving capacity and safety.

2. The International Civil Aviation Organization (ICAO) has defined Standards and

Recommended Practices (SARPs) for satellite−based

augmentation systems (SBAS) such as WAAS. Japan

and Europe are building similar systems that are

planned to be interoperable with WAAS: EGNOS,

the European Geostationary Navigation Overlay

System, and MSAS, the Japan Multifunctional

Transport Satellite (MTSAT) Satellite−based Augmentation System. The merging of these systems will

create a worldwide seamless navigation capability

similar to GPS but with greater accuracy, availability

and integrity.

3. Unlike traditional ground−based navigation

aids, WAAS will cover a more extensive service area.

Precisely surveyed wide−area ground reference

stations (WRS) are linked to form the U.S. WAAS

network. Signals from the GPS satellites are

monitored by these WRSs to determine satellite clock

and ephemeris corrections and to model the

propagation effects of the ionosphere. Each station in

the network relays the data to a wide−area master

station (WMS) where the correction information is

computed. A correction message is prepared and

uplinked to a geostationary satellite (GEO) via a

ground uplink station (GUS). The message is then

broadcast on the same frequency as GPS (L1,

1575.42 MHz) to WAAS receivers within the

broadcast coverage area of the WAAS GEO.

4. In addition to providing the correction signal,

the WAAS GEO provides an additional pseudorange

measurement to the aircraft receiver, improving the

availability of GPS by providing, in effect, an

additional GPS satellite in view. The integrity of GPS

is improved through real−time monitoring, and the

accuracy is improved by providing differential

corrections to reduce errors. The performance

improvement is sufficient to enable approach

procedures with GPS/WAAS glide paths (vertical

guidance).

5. The FAA has completed installation of

25 WRSs, 2 WMSs, 4 GUSs, and the required

terrestrial communications to support the WAAS

network. Prior to the commissioning of the WAAS for

public use, the FAA has been conducting a series of

test and validation activities. Enhancements to the

initial phase of WAAS will include additional master

and reference stations, communication satellites, and

transmission frequencies as needed.

6. GNSS navigation, including GPS and

WAAS, is referenced to the WGS−84 coordinate

system. It should only be used where the Aeronautical

Information Publications (including electronic data

and aeronautical charts) conform to WGS−84 or

equivalent. Other countries civil aviation authorities

may impose additional limitations on the use of their

SBAS systems.

b. Instrument Approach Capabilities

1. A new class of approach procedures which

provide vertical guidance, but which do not meet the

ICAO Annex 10 requirements for precision approaches has been developed to support satellite

navigation use for aviation applications worldwide.

These new procedures called Approach with Vertical

Guidance (APV), are defined in ICAO Annex 6, and

include approaches such as the LNAV/VNAV

procedures presently being flown with barometric

vertical navigation (Baro−VNAV). These approaches

provide vertical guidance, but do not meet the more

stringent standards of a precision approach. Properly

certified WAAS receivers will be able to fly these

LNAV/VNAV procedures using a WAAS electronic

glide path, which eliminates the errors that can be

introduced by using Barometric altimetery.

2. A new type of APV approach procedure, in

addition to LNAV/VNAV, is being implemented to

take advantage of the high accuracy guidance and

increased integrity provided by WAAS. This WAAS

generated angular guidance allows the use of the

same TERPS approach criteria used for ILS

approaches. The resulting approach procedure

minima, titled LPV (localizer performance with

vertical guidance), may have a decision altitude as

low as 200 feet height above touchdown with

visibility minimums as low as 1/2 mile, when the

terrain and airport infrastructure support the lowest

minima. LPV minima is published on the RNAV

(GPS) approach charts (see paragraph 5−4−5,

Instrument Approach Procedure Charts).

3. A new nonprecision WAAS approach, called

Localizer Performance (LP) is being added in
7/26/12 AIM

Navigation Aids 1−1−31

locations where the terrain or obstructions do not

allow publication of vertically guided LPV procedures. This new approach takes advantage of the

angular lateral guidance and smaller position errors

provided by WAAS to provide a lateral only

procedure similar to an ILS Localizer. LP procedures

may provide lower minima than a LNAV procedure

due to the narrower obstacle clearance surface.

NOTE−

WAAS receivers certified prior to TSO C−145b and TSO

C−146b, even if they have LPV capability, do not contain

LP capability unless the receiver has been upgraded.

Receivers capable of flying LP procedures must contain a

statement in the Flight Manual Supplement or Approved

Supplemental Flight Manual stating that the receiver has

LP capability, as well as the capability for the other WAAS

and GPS approach procedure types.

4. WAAS provides a level of service that

supports all phases of flight, including RNAV (GPS)

approaches to LNAV, LP, LNAV/VNAV and LPV

lines of minima, within system coverage. Some

locations close to the edge of the coverage may have

a lower availability of vertical guidance.

c. General Requirements

1. WAAS avionics must be certified in

accordance with Technical Standard Order (TSO)

TSO−C145A, Airborne Navigation Sensors Using

the (GPS) Augmented by the Wide Area Augmentation System (WAAS); or TSO−146A, Stand−Alone

Airborne Navigation Equipment Using the Global

Positioning System (GPS) Augmented by the Wide

Area Augmentation System (WAAS), and installed in

accordance with Advisory Circular (AC) 20−130A,

Airworthiness Approval of Navigation or Flight

Management Systems Integrating Multiple Navigation Sensors, or AC 20−138A, Airworthiness

Approval of Global Positioning System (GPS)

Navigation Equipment for Use as a VFR and IFR

Navigation System.

2. GPS/WAAS operation must be conducted in

accordance with the FAA−approved aircraft flight

manual (AFM) and flight manual supplements. Flight

manual supplements will state the level of approach

procedure that the receiver supports. IFR approved

WAAS receivers support all GPS only operations as

long as lateral capability at the appropriate level is

functional. WAAS monitors both GPS and WAAS

satellites and provides integrity.

3. GPS/WAAS equipment is inherently capable

of supporting oceanic and remote operations if the

operator obtains a fault detection and exclusion

(FDE) prediction program.

4. Air carrier and commercial operators must

meet the appropriate provisions of their approved

operations specifications.

5. Prior to GPS/WAAS IFR operation, the pilot

must review appropriate Notices to Airmen (NOTAMs) and aeronautical information. This

information is available on request from a Flight

Service Station. The FAA will provide NOTAMs to

advise pilots of the status of the WAAS and level of

service available.

(a) The term UNRELIABLE is used in

conjunction with GPS and WAAS NOTAMs. The

term UNRELIABLE is an advisory to pilots

indicating the expected level of WAAS service

(LNAV/VNAV, LPV) may not be available;

e.g., !BOS BOS WAAS LPV AND LNAV/VNAV

MNM UNREL WEF 0305231700 − 0305231815.

WAAS UNRELIABLE NOTAMs are predictive in

nature and published for flight planning purposes.

Upon commencing an approach at locations

NOTAMed WAAS UNRELIABLE, if the WAAS

avionics indicate LNAV/VNAV or LPV service is

available, then vertical guidance may be used to

complete the approach using the displayed level of

service. Should an outage occur during the approach,

reversion to LNAV minima may be required.

(1) Area−wide WAAS UNAVAILABLE

NOTAMs indicate loss or malfunction of the WAAS

system. In flight, Air Traffic Control will advise

pilots requesting a GPS or RNAV (GPS) approach of

WAAS UNAVAILABLE NOTAMs if not contained

in the ATIS broadcast.

(2) Site−specific WAAS UNRELIABLE

NOTAMs indicate an expected level of service,

e.g., LNAV/VNAV or LPV may not be available.

Pilots must request site−specific WAAS NOTAMs

during flight planning. In flight, Air Traffic Control

will not advise pilots of WAAS UNRELIABLE

NOTAMs.

(3) When the approach chart is annotated

with the symbol, site−specific WAAS UNRELIABLE NOTAMs or Air Traffic advisories are not

provided for outages in WAAS LNAV/VNAV and

LPV vertical service. Vertical outages may occur

daily at these locations due to being close to the edge
AIM 7/26/12

1−1−32 Navigation Aids

of WAAS system coverage. Use LNAV minima for

flight planning at these locations, whether as a

destination or alternate. For flight operations at these

locations, when the WAAS avionics indicate that

LNAV/VNAV or LPV service is available, then the

vertical guidance may be used to complete the

approach using the displayed level of service. Should

an outage occur during the procedure, reversion to

LNAV minima may be required.

NOTE−

Area−wide WAAS UNAVAILABLE NOTAMs apply to all

airports in the WAAS UNAVAILABLE area designated in

the NOTAM, including approaches at airports where an

approach chart is annotated with the symbol.

6. GPS/WAAS was developed to be used within

SBAS GEO coverage (WAAS or other interoperable

system) without the need for other radio navigation

equipment appropriate to the route of flight to be

flown. Outside the SBAS coverage or in the event of

a WAAS failure, GPS/WAAS equipment reverts to

GPS−only operation and satisfies the requirements

for basic GPS equipment.

7. Unlike TSO−C129 avionics, which were

certified as a supplement to other means of

navigation, WAAS avionics are evaluated without

reliance on other navigation systems. As such,

installation of WAAS avionics does not require the

aircraft to have other equipment appropriate to the

route to be flown.

(a) Pilots with WAAS receivers may flight

plan to use any instrument approach procedure

authorized for use with their WAAS avionics as

the planned approach at a required alternate, with

the following restrictions. When using WAAS at

an alternate airport, flight planning must be based

on flying the RNAV (GPS) LNAV minima line,

or minima on a GPS approach procedure, or

conventional approach procedure with “or GPS” in

the title. Code of Federal Regulation (CFR) Part 91

nonprecision weather requirements must be used for

planning. Upon arrival at an alternate, when the

WAAS navigation system indicates that LNAV/

VNAV or LPV service is available, then vertical

guidance may be used to complete the approach using

the displayed level of service. The FAA has begun

removing the NA (Alternate Minimums Not

Authorized) symbol from select RNAV (GPS) and

GPS approach procedures so they may be used by

approach approved WAAS receivers at alternate

airports. Some approach procedures will still require

the NA for other reasons, such as no weather

reporting, so it cannot be removed from all

procedures. Since every procedure must be individually evaluated, removal of the NA from RNAV

(GPS) and GPS procedures will take some time.

d. Flying Procedures with WAAS

1. WAAS receivers support all basic GPS

approach functions and provide additional capabilities. One of the major improvements is the ability to

generate glide path guidance, independent of ground

equipment or barometric aiding. This eliminates

several problems such as hot and cold temperature

effects, incorrect altimeter setting or lack of a local

altimeter source. It also allows approach procedures

to be built without the cost of installing ground

stations at each airport or runway. Some approach

certified receivers may only generate a glide path

with performance similar to Baro−VNAV and are

only approved to fly the LNAV/VNAV line of minima

on the RNAV (GPS) approach charts. Receivers with

additional capability (including faster update rates

and smaller integrity limits) are approved to fly the

LPV line of minima. The lateral integrity changes

dramatically from the 0.3 NM (556 meter) limit for

GPS, LNAV and LNAV/VNAV approach mode, to 40

meters for LPV. It also provides vertical integrity

monitoring, which bounds the vertical error to 50

meters for LNAV/VNAV and LPVs with minima of

250’ or above, and bounds the vertical error to 35

meters for LPVs with minima below 250’.

2. When an approach procedure is selected and

active, the receiver will notify the pilot of the most

accurate level of service supported by the combination of the WAAS signal, the receiver, and the

selected approach, using the naming conventions on

the minima lines of the selected approach procedure.

For example, if an approach is published with LPV

minima and the receiver is only certified for

LNAV/VNAV, the equipment would indicate

“LNAV/VNAV available,” even though the WAAS

signal would support LPV. If flying an existing

LNAV/VNAV procedure with no LPV minima, the

receiver will notify the pilot “LNAV/VNAV

available,” even if the receiver is certified for LPV

and the signal supports LPV. If the signal does not

support vertical guidance on procedures with LPV

and/or LNAV/VNAV minima, the receiver annunciation will read “LNAV available.” On lateral only
7/26/12 AIM

Navigation Aids 1−1−33

procedures with LP and LNAV minima the receiver

will indicate “LP available” or “LNAV available”

based on the level of lateral service available. Once

the level of service notification has been given, the

receiver will operate in this mode for the duration of

the approach procedure, unless that level of service

becomes unavailable. The receiver cannot change

back to a more accurate level of service until the next

time an approach is activated.

NOTE−

Receivers do not “fail down” to lower levels of service

once the approach has been activated. If only the

vertical off flag appears, the pilot may elect to use the

LNAV minima if the rules under which the flight is

operating allow changing the type of approach being flown

after commencing the procedure. If the lateral integrity

limit is exceeded on an LP approach, a missed approach

will be necessary since there is no way to reset the lateral

alarm limit while the approach is active.

3. Another additional feature of WAAS receivers is the ability to exclude a bad GPS signal and

continue operating normally. This is normally

accomplished by the WAAS correction information.

Outside WAAS coverage or when WAAS is not

available, it is accomplished through a receiver

algorithm called FDE. In most cases this operation

will be invisible to the pilot since the receiver will

continue to operate with other available satellites

after excluding the “bad” signal. This capability

increases the reliability of navigation.

4. Both lateral and vertical scaling for the

LNAV/VNAV and LPV approach procedures are

different than the linear scaling of basic GPS. When

the complete published procedure is flown, +/−1 NM

linear scaling is provided until two (2) NM prior to the

FAF, where the sensitivity increases to be similar to

the angular scaling of an ILS. There are two differences in the WAAS scaling and ILS: 1) on long final

approach segments, the initial scaling will be

+/−0.3 NM to achieve equivalent performance to

GPS (and better than ILS, which is less sensitive far

from the runway); 2) close to the runway threshold,

the scaling changes to linear instead of continuing to

become more sensitive. The width of the final

approach course is tailored so that the total width is

usually 700 feet at the runway threshold. Since the

origin point of the lateral splay for the angular portion

of the final is not fixed due to antenna placement like

localizer, the splay angle can remain fixed, making a

consistent width of final for aircraft being vectored

onto the final approach course on different length

runways. When the complete published procedure is

not flown, and instead the aircraft needs to capture the

extended final approach course similar to ILS, the

vector to final (VTF) mode is used. Under VTF the

scaling is linear at +/−1 NM until the point where the

ILS angular splay reaches a width of +/−1 NM

regardless of the distance from the FAWP.

5. The WAAS scaling is also different than GPS

TSO−C129 in the initial portion of the missed

approach. Two differences occur here. First, the

scaling abruptly changes from the approach scaling to

the missed approach scaling, at approximately the

departure end of the runway or when the pilot

requests missed approach guidance rather than

ramping as GPS does. Second, when the first leg of

the missed approach is a Track to Fix (TF) leg aligned

within 3 degrees of the inbound course, the receiver

will change to 0.3 NM linear sensitivity until the turn

initiation point for the first waypoint in the missed

approach procedure, at which time it will abruptly

change to terminal (+/−1 NM) sensitivity. This allows

the elimination of close in obstacles in the early part

of the missed approach that may cause the DA to be

raised.

6. A new method has been added for selecting

the final approach segment of an instrument

approach. Along with the current method used by

most receivers using menus where the pilot selects the

airport, the runway, the specific approach procedure

and finally the IAF, there is also a channel number

selection method. The pilot enters a unique 5−digit

number provided on the approach chart, and the

receiver recalls the matching final approach segment

from the aircraft database. A list of information

including the available IAFs is displayed and the pilot

selects the appropriate IAF. The pilot should confirm

that the correct final approach segment was loaded by

cross checking the Approach ID, which is also

provided on the approach chart.

7. The Along−Track Distance (ATD) during the

final approach segment of an LNAV procedure (with

a minimum descent altitude) will be to the MAWP. On

LNAV/VNAV and LPV approaches to a decision

altitude, there is no missed approach waypoint so the

along−track distance is displayed to a point normally

located at the runway threshold. In most cases the

MAWP for the LNAV approach is located on the

runway threshold at the centerline, so these distances

will be the same. This distance will always vary
AIM 7/26/12

1−1−34 Navigation Aids

slightly from any ILS DME that may be present, since

the ILS DME is located further down the runway.

Initiation of the missed approach on the LNAV/

VNAV and LPV approaches is still based on reaching

the decision altitude without any of the items listed in

14 CFR Section 91.175 being visible, and must not be

delayed until the ATD reaches zero. The WAAS

receiver, unlike a GPS receiver, will automatically

sequence past the MAWP if the missed approach

procedure has been designed for RNAV. The pilot

may also select missed approach prior to the MAWP,

however, navigation will continue to the MAWP prior

to waypoint sequencing taking place.

1−1−21. Ground Based Augmentation

System (GBAS) Landing System (GLS)

a. General

1. The GLS provides precision navigation

guidance for exact alignment and descent of aircraft

on approach to a runway. It provides differential

augmentation to the Global Navigation Satellite

System (GNSS).

NOTE−

GBAS is the ICAO term for Local Area Augmentation

System (LAAS).

2. LAAS was developed as an “ILS look−alike”

system from the pilot perspective. LAAS is based on

GPS signals augmented by ground equipment and has

been developed to provide GLS precision approaches

similar to ILS at airfields.

3. GLS provides guidance similar to ILS

approaches for the final approach segment; portions

of the GLS approach prior to and after the final

approach segment will be based on Area Navigation

(RNAV) or Required Navigation Performance

(RNP).

4. The equipment consists of a GBAS Ground

Facility (GGF), four reference stations, a VHF Data

Broadcast (VDB) uplink antenna, and an aircraft

GBAS receiver.

b. Procedure

1. Pilots will select the five digit GBAS channel

number of the associated approach within the Flight

Management System (FMS) menu or manually select

the five digits (system dependent). Selection of the

GBAS channel number also tunes the VDB.

2. Following procedure selection, confirmation

that the correct LAAS procedure is loaded can be

accomplished by cross checking the charted

Reference Path Indicator (RPI) or approach ID with

the cockpit displayed RPI or audio identification of

the RPI with Morse Code (for some systems).

3. The pilot will fly the GLS approach using the

same techniques as an ILS, once selected and

identified.

1−1−22. Precision Approach Systems other

than ILS, GLS, and MLS

a. General

Approval and use of precision approach systems

other than ILS, GLS and MLS require the issuance of

special instrument approach procedures.

b. Special Instrument Approach Procedure

1. Special instrument approach procedures

must be issued to the aircraft operator if pilot training,

aircraft equipment, and/or aircraft performance is

different than published procedures. Special instrument approach procedures are not distributed for

general public use. These procedures are issued to an

aircraft operator when the conditions for operations

approval are satisfied.

2. General aviation operators requesting approval for special procedures should contact the local

Flight Standards District Office to obtain a letter of

authorization. Air carrier operators requesting

approval for use of special procedures should contact

their Certificate Holding District Office for authorization through their Operations Specification.

c. Transponder Landing System (TLS)

1. The TLS is designed to provide approach

guidance utilizing existing airborne ILS localizer,

glide slope, and transponder equipment.

2. Ground equipment consists of a transponder

interrogator, sensor arrays to detect lateral and

vertical position, and ILS frequency transmitters. The

TLS detects the aircraft’s position by interrogating its

transponder. It then broadcasts ILS frequency signals

to guide the aircraft along the desired approach path.

3. TLS instrument approach procedures are

designated Special Instrument Approach Procedures.

Special aircrew training is required. TLS ground

equipment provides approach guidance for only one

aircraft at a time. Even though the TLS signal is
7/26/12 AIM

Navigation Aids 1−1−35

received using the ILS receiver, no fixed course or

glidepath is generated. The concept of operation is

very similar to an air traffic controller providing radar

vectors, and just as with radar vectors, the guidance

is valid only for the intended aircraft. The TLS

ground equipment tracks one aircraft, based on its

transponder code, and provides correction signals to

course and glidepath based on the position of the

tracked aircraft. Flying the TLS corrections computed for another aircraft will not provide guidance

relative to the approach; therefore, aircrews must not

use the TLS signal for navigation unless they have

received approach clearance and completed the

required coordination with the TLS ground equipment operator. Navigation fixes based on

conventional NAVAIDs or GPS are provided in the

special instrument approach procedure to allow

aircrews to verify the TLS guidance.

d. Special Category I Differential GPS (SCAT−

I DGPS)

1. The SCAT−I DGPS is designed to provide

approach guidance by broadcasting differential

correction to GPS.

2. SCAT−I DGPS procedures require aircraft

equipment and pilot training.

3. Ground equipment consists of GPS receivers

and a VHF digital radio transmitter. The SCAT−I

DGPS detects the position of GPS satellites relative

to GPS receiver equipment and broadcasts differential corrections over the VHF digital radio.

4. Category I Ground Based Augmentation

System (GBAS) will displace SCAT−I DGPS as the

public use service.

REFERENCE−

AIM, Para 5−4−7f, Instrument Approach Procedures.

7/26/12 AIM

Area Navigation (RNAV) and Required Navigation Performance (RNP) 1−2−1

Section 2. Area Navigation (RNAV) and Required

Navigation Performance (RNP)

1−2−1. Area Navigation (RNAV)

a. General. RNAV is a method of navigation that

permits aircraft operation on any desired flight path

within the coverage of ground or space based

navigation aids or within the limits of the capability

of self−contained aids, or a combination of these. In

the future, there will be an increased dependence on

the use of RNAV in lieu of routes defined by

ground−based navigation aids.

RNAV routes and terminal procedures, including

departure procedures (DPs) and standard terminal

arrivals (STARs), are designed with RNAV systems

in mind. There are several potential advantages of

RNAV routes and procedures:

1. Time and fuel savings,

2. Reduced dependence on radar vectoring,

altitude, and speed assignments allowing a reduction

in required ATC radio transmissions, and

3. More efficient use of airspace.

In addition to information found in this manual,

guidance for domestic RNAV DPs, STARs, and

routes may also be found in Advisory Circular 90−100A, U.S. Terminal and En Route Area

Navigation (RNAV) Operations.

b. RNAV Operations. RNAV procedures, such

as DPs and STARs, demand strict pilot awareness and

maintenance of the procedure centerline. Pilots

should possess a working knowledge of their aircraft

navigation system to ensure RNAV procedures are

flown in an appropriate manner. In addition, pilots

should have an understanding of the various

waypoint and leg types used in RNAV procedures;

these are discussed in more detail below.

1. Waypoints. A waypoint is a predetermined

geographical position that is defined in terms of

latitude/longitude coordinates. Waypoints may be a

simple named point in space or associated with

existing navaids, intersections, or fixes. A waypoint

is most often used to indicate a change in direction,

speed, or altitude along the desired path. RNAV

procedures make use of both fly−over and fly−by

waypoints.

(a) Fly−by waypoints. Fly−by waypoints

are used when an aircraft should begin a turn to the

next course prior to reaching the waypoint separating

the two route segments. This is known as turn

anticipation.

(b) Fly−over waypoints. Fly−over waypoints are used when the aircraft must fly over the

point prior to starting a turn.

NOTE−

FIG 1−2−1 illustrates several differences between a fly−by

and a fly−over waypoint.

FIG 1−2−1

Fly−by and Fly−over Waypoints

2. RNAV Leg Types. A leg type describes the

desired path proceeding, following, or between

waypoints on an RNAV procedure. Leg types are

identified by a two−letter code that describes the path

(e.g., heading, course, track, etc.) and the termination

point (e.g., the path terminates at an altitude, distance,

fix, etc.). Leg types used for procedure design are

included in the aircraft navigation database, but not

normally provided on the procedure chart. The

narrative depiction of the RNAV chart describes how

a procedure is flown. The “path and terminator

concept” defines that every leg of a procedure has a

termination point and some kind of path into that

termination point. Some of the available leg types are

described below.
AIM 7/26/12

1−2−2 Area Navigation (RNAV) and Required Navigation Performance (RNP)

(a) Track to Fix. A Track to Fix (TF) leg is

intercepted and acquired as the flight track to the

following waypoint. Track to a Fix legs are

sometimes called point−to−point legs for this reason.

Narrative: “on track 087 to CHEZZ WP.” See

FIG 1−2−2.

(b) Direct to Fix. A Direct to Fix (DF) leg is

a path described by an aircraft’s track from an initial

area direct to the next waypoint. Narrative: “left

turn direct BARGN WP.” See FIG 1−2−3.

FIG 1−2−2

Track to Fix Leg Type

FIG 1−2−3

Direct to Fix Leg Type
7/26/12 AIM

Area Navigation (RNAV) and Required Navigation Performance (RNP) 1−2−3

(c) Course to Fix. A Course to Fix (CF) leg

is a path that terminates at a fix with a specified course

at that fix. Narrative: “on course 078 to PRIMY

WP.” See FIG 1−2−4.

FIG 1−2−4

Course to Fix Leg Type

(d) Radius to Fix. A Radius to Fix (RF) leg

is defined as a constant radius circular path around a

defined turn center that terminates at a fix. See

FIG 1−2−5.

FIG 1−2−5

Radius to Fix Leg Type

(e) Heading. A Heading leg may be defined

as, but not limited to, a Heading to Altitude (VA),

Heading to DME range (VD), and Heading to Manual

Termination, i.e., Vector (VM). Narrative: “climb

heading 350 to 1500”, “heading 265, at 9 DME west

of PXR VORTAC, right turn heading 360”, “fly

heading 090, expect radar vectors to DRYHT INT.”

3. Navigation Issues. Pilots should be aware

of their navigation system inputs, alerts, and

annunciations in order to make better−informed

decisions. In addition, the availability and suitability

of particular sensors/systems should be considered.

(a) GPS. Operators using TSO−C129 systems should ensure departure and arrival airports are

entered to ensure proper RAIM availability and CDI

sensitivity.

(b) DME/DME. Operators should be aware

that DME/DME position updating is dependent on

FMS logic and DME facility proximity, availability,

geometry, and signal masking.

(c) VOR/DME. Unique VOR characteristics may result in less accurate values from

VOR/DME position updating than from GPS or

DME/DME position updating.

(d) Inertial Navigation. Inertial reference

units and inertial navigation systems are often

coupled with other types of navigation inputs,

e.g., DME/DME or GPS, to improve overall

navigation system performance.

NOTE−

Specific inertial position updating requirements may

apply.

4. Flight Management System (FMS). An

FMS is an integrated suite of sensors, receivers, and

computers, coupled with a navigation database.

These systems generally provide performance and

RNAV guidance to displays and automatic flight

control systems.

Inputs can be accepted from multiple sources such as

GPS, DME, VOR, LOC and IRU. These inputs may

be applied to a navigation solution one at a time or in

combination. Some FMSs provide for the detection

and isolation of faulty navigation information.

When appropriate navigation signals are available,

FMSs will normally rely on GPS and/or DME/DME

(that is, the use of distance information from two or

more DME stations) for position updates. Other

inputs may also be incorporated based on FMS

system architecture and navigation source geometry.

NOTE−

DME/DME inputs coupled with one or more IRU(s) are

often abbreviated as DME/DME/IRU or D/D/I.
AIM 7/26/12

1−2−4 Area Navigation (RNAV) and Required Navigation Performance (RNP)

1−2−2. Required Navigation Performance

(RNP)

a. General. RNP is RNAV with on−board

navigation monitoring and alerting, RNP is also a

statement of navigation performance necessary for

operation within a defined airspace. A critical

component of RNP is the ability of the aircraft

navigation system to monitor its achieved navigation

performance, and to identify for the pilot whether the

operational requirement is, or is not being met during

an operation. This on−board performance monitoring and alerting capability therefore allows a lessened

reliance on air traffic control intervention (via radar

monitoring, automatic dependent surveillance

(ADS), multilateration, communications), and/or

route separation to achieve the overall safety of the

operation. RNP capability of the aircraft is a major

component in determining the separation criteria to

ensure that the overall containment of the operation

is met.

The RNP capability of an aircraft will vary depending

upon the aircraft equipment and the navigation

infrastructure. For example, an aircraft may be

equipped and certified for RNP 1.0, but may not be

capable of RNP 1.0 operations due to limited navaid

coverage.

b. RNP Operations.

1. RNP Levels. An RNP “level” or “type” is

applicable to a selected airspace, route, or procedure.

As defined in the Pilot/Controller Glossary, the RNP

Level or Type is a value typically expressed as a

distance in nautical miles from the intended

centerline of a procedure, route, or path. RNP

applications also account for potential errors at some

multiple of RNP level (e.g., twice the RNP level).

(a) Standard RNP Levels. U.S. standard

values supporting typical RNP airspace are as

specified in TBL 1−2−1 below. Other RNP levels as

identified by ICAO, other states and the FAA may

also be used.

(b) Application of Standard RNP Levels.

U.S. standard levels of RNP typically used for

various routes and procedures supporting RNAV

operations may be based on use of a specific

navigational system or sensor such as GPS, or on

multi−sensor RNAV systems having suitable performance.

(c) Depiction of Standard RNP Levels. The

applicable RNP level will be depicted on affected

charts and procedures.

TBL 1−2−1

U.S. Standard RNP Levels

RNP Level Typical Application Primary Route Width (NM) −

Centerline to Boundary

0.1 to 1.0 RNP AR Approach Segments 0.1 to 1.0

0.3 to 1.0 RNP Approach Segments 0.3 to 1.0

1 Terminal and En Route 1.0

2 En Route 2.0

NOTE−

1. The “performance” of navigation in RNP refers not only to the level of accuracy of a particular sensor or aircraft

navigation system, but also to the degree of precision with which the aircraft will be flown.

2. Specific required flight procedures may vary for different RNP levels.
7/26/12 AIM

Area Navigation (RNAV) and Required Navigation Performance (RNP) 1−2−5

TBL 1−2−2

RNP Levels Supported for International Operations

RNP Level Typical Application

4 Projected for oceanic/remote areas where 30 NM horizontal separation is applied

10 Oceanic/remote areas where 50 NM lateral separation is applied

c. Other RNP Applications Outside the U.S.

The FAA and ICAO member states have led

initiatives in implementing the RNP concept to

oceanic operations. For example, RNP−10 routes

have been established in the northern Pacific

(NOPAC) which has increased capacity and

efficiency by reducing the distance between tracks

to 50 NM. (See TBL 1−2−2.)

d. Aircraft and Airborne Equipment Eligibility

for RNP Operations. Aircraft meeting RNP criteria

will have an appropriate entry including special

conditions and limitations in its Aircraft Flight

Manual (AFM), or supplement. Operators of aircraft

not having specific AFM−RNP certification may be

issued operational approval including special conditions and limitations for specific RNP levels.

NOTE−

Some airborne systems use Estimated Position Uncertainty (EPU) as a measure of the current estimated

navigational performance. EPU may also be referred to as

Actual Navigation Performance (ANP) or Estimated

Position Error (EPE).

1−2−3. Use of Suitable Area Navigation

(RNAV) Systems on Conventional

Procedures and Routes

a. Discussion. This paragraph sets forth policy,

while providing operational and airworthiness

guidance regarding the suitability and use of RNAV

systems when operating on, or transitioning to,

conventional, non−RNAV routes and procedures

within the U.S. National Airspace System (NAS):

1. Use of a suitable RNAV system as a

Substitute Means of Navigation when a Very−High

Frequency (VHF) Omni−directional Range (VOR),

Distance Measuring Equipment (DME), Tactical Air

Navigation (TACAN), VOR/TACAN (VORTAC),

VOR/DME, Non−directional Beacon (NDB), or

compass locator facility including locator outer

marker and locator middle marker is out−of−service

(that is, the navigation aid (NAVAID) information is

not available); an aircraft is not equipped with an

Automatic Direction Finder (ADF) or DME; or the

installed ADF or DME on an aircraft is not

operational. For example, if equipped with a suitable

RNAV system, a pilot may hold over an out−of−

service NDB.

2. Use of a suitable RNAV system as an

Alternate Means of Navigation when a VOR, DME,

VORTAC, VOR/DME, TACAN, NDB, or compass

locator facility including locator outer marker and

locator middle marker is operational and the

respective aircraft is equipped with operational

navigation equipment that is compatible with

conventional navaids. For example, if equipped with

a suitable RNAV system, a pilot may fly a procedure

or route based on operational VOR using that RNAV

system without monitoring the VOR.

NOTE−

1. Additional information and associated requirements

are available in Advisory Circular 90-108 titled “Use of

Suitable RNAV Systems on Conventional Routes and

Procedures.”

2. Good planning and knowledge of your RNAV system are

critical for safe and successful operations.

3. Pilots planning to use their RNAV system as a substitute

means of navigation guidance in lieu of an out−of−service

NAVAID may need to advise ATC of this intent and

capability.

4. The navigation database should be current for the

duration of the flight. If the AIRAC cycle will change

during flight, operators and pilots should establish

procedures to ensure the accuracy of navigation data,

including suitability of navigation facilities used to define

the routes and procedures for flight. To facilitate validating

database currency, the FAA has developed procedures for

publishing the amendment date that instrument approach

procedures were last revised. The amendment date follows

the amendment number, e.g., Amdt 4 14Jan10. Currency of

graphic departure procedures and STARs may be

ascertained by the numerical designation in the procedure

title. If an amended chart is published for the procedure, or

the procedure amendment date shown on the chart is on or
AIM 7/26/12

1−2−6 Area Navigation (RNAV) and Required Navigation Performance (RNP)

after the expiration date of the database, the operator must

not use the database to conduct the operation.

b. Types of RNAV Systems that Qualify as a

Suitable RNAV System. When installed in accordance with appropriate airworthiness installation

requirements and operated in accordance with

applicable operational guidance (e.g., aircraft flight

manual and Advisory Circular material), the

following systems qualify as a suitable RNAV

system:

1. An RNAV system with TSO−C129/

−C145/−C146 equipment, installed in accordance

with AC 20−138, Airworthiness Approval of Global

Positioning System (GPS) Navigation Equipment for

Use as a VFR and IFR Supplemental Navigation

System, or AC 20−130A, Airworthiness Approval of

Navigation or Flight Management Systems Integrating Multiple Navigation Sensors, and authorized for

instrument flight rules (IFR) en route and terminal

operations (including those systems previously

qualified for “GPS in lieu of ADF or DME”

operations), or

2. An RNAV system with DME/DME/IRU

inputs that is compliant with the equipment

provisions of AC 90−100A, U.S. Terminal and

En Route Area Navigation (RNAV) Operations, for

RNAV routes. A table of compliant equipment is

available at the following website:

http://www.faa.gov/about/office_org/

headquarters_offices/avs/offices/afs/afs400/afs47

0/policy_guidance/

NOTE−

Approved RNAV systems using DME/DME/IRU, without

GPS/WAAS position input, may only be used as a substitute

means of navigation when specifically authorized by a

Notice to Airmen (NOTAM) or other FAA guidance for a

specific procedure. The NOTAM or other FAA guidance

authorizing the use of DME/DME/IRU systems will also

identify any required DME facilities based on an FAA

assessment of the DME navigation infrastructure.

c. Uses of Suitable RNAV Systems. Subject to

the operating requirements, operators may use a

suitable RNAV system in the following ways.

1. Determine aircraft position relative to, or

distance from a VOR (see NOTE 5 below), TACAN,

NDB, compass locator, DME fix; or a named fix

defined by a VOR radial, TACAN course, NDB

bearing, or compass locator bearing intersecting a

VOR or localizer course.

2. Navigate to or from a VOR, TACAN, NDB,

or compass locator.

3. Hold over a VOR, TACAN, NDB, compass

locator, or DME fix.

4. Fly an arc based upon DME.

NOTE−

1. The allowances described in this section apply even

when a facility is identified as required on a procedure (for

example, “Note ADF required”).

2. These operations do not include lateral navigation on

localizer−based courses (including localizer back−course

guidance) without reference to raw localizer data.

3. Unless otherwise specified, a suitable RNAV system

cannot be used for navigation on procedures that are

identified as not authorized (“NA”) without exception by

a NOTAM. For example, an operator may not use a RNAV

system to navigate on a procedure affected by an expired or

unsatisfactory flight inspection, or a procedure that is

based upon a recently decommissioned NAVAID.

4. Pilots may not substitute for the NAVAID (for example,

a VOR or NDB) providing lateral guidance for the final

approach segment. This restriction does not refer to

instrument approach procedures with “or GPS” in the title

when using GPS or WAAS. These allowances do not apply

to procedures that are identified as not authorized (NA)

without exception by a NOTAM, as other conditions may

still exist and result in a procedure not being available. For

example, these allowances do not apply to a procedure

associated with an expired or unsatisfactory flight

inspection, or is based upon a recently decommissioned

NAVAID.

5. For the purpose of paragraph c, “VOR” includes VOR,

VOR/DME, and VORTAC facilities and “compass

locator” includes locator outer marker and locator middle

marker.
7/26/12 AIM

Area Navigation (RNAV) and Required Navigation Performance (RNP) 1−2−7

d. Alternate Airport Considerations. For the

purposes of flight planning, any required alternate

airport must have an available instrument approach

procedure that does not require the use of GPS. This

restriction includes conducting a conventional

approach at the alternate airport using a substitute

means of navigation that is based upon the use of

GPS. For example, these restrictions would apply

when planning to use GPS equipment as a substitute

means of navigation for an out−of−service VOR that

supports an ILS missed approach procedure at an

alternate airport. In this case, some other approach

not reliant upon the use of GPS must be available.

This restriction does not apply to RNAV systems

using TSO−C145/−C146 WAAS equipment. For

further WAAS guidance see AIM 1−1−20.

7/26/12 AIM

Airport Lighting Aids 2−1−1

Chapter 2. Aeronautical Lighting and 

Other Airport Visual Aids

Section 1. Airport Lighting Aids

2−1−1. Approach Light Systems (ALS)

a. ALS provide the basic means to transition from

instrument flight to visual flight for landing.

Operational requirements dictate the sophistication

and configuration of the approach light system for a

particular runway.

b. ALS are a configuration of signal lights starting

at the landing threshold and extending into the

approach area a distance of 2400−3000 feet for

precision instrument runways and 1400−1500 feet for

nonprecision instrument runways. Some systems

include sequenced flashing lights which appear to the

pilot as a ball of light traveling towards the runway at

high speed (twice a second). (See FIG 2−1−1.)

2−1−2. Visual Glideslope Indicators

a. Visual Approach Slope Indicator (VASI)

1. VASI installations may consist of either 2, 4,

6, 12, or 16 light units arranged in bars referred to as

near, middle, and far bars. Most VASI installations

consist of 2 bars, near and far, and may consist of 2,

4, or 12 light units. Some VASIs consist of three bars,

near, middle, and far, which provide an additional

visual glide path to accommodate high cockpit

aircraft. This installation may consist of either 6 or

16 light units. VASI installations consisting of 2, 4, or

6 light units are located on one side of the runway,

usually the left. Where the installation consists of

12 or 16 light units, the units are located on both sides

of the runway.

2. Two−bar VASI installations provide one

visual glide path which is normally set at 3 degrees.

Three−bar VASI installations provide two visual

glide paths. The lower glide path is provided by the

near and middle bars and is normally set at 3 degrees

while the upper glide path, provided by the middle

and far bars, is normally 1/4 degree higher. This

higher glide path is intended for use only by high

cockpit aircraft to provide a sufficient threshold

crossing height. Although normal glide path angles

are three degrees, angles at some locations may be as

high as 4.5 degrees to give proper obstacle clearance.

Pilots of high performance aircraft are cautioned that

use of VASI angles in excess of 3.5 degrees may cause

an increase in runway length required for landing and

rollout.

3. The basic principle of the VASI is that of color

differentiation between red and white. Each light unit

projects a beam of light having a white segment in the

upper part of the beam and red segment in the lower

part of the beam. The light units are arranged so that

the pilot using the VASIs during an approach will see

the combination of lights shown below.

4. The VASI is a system of lights so arranged to

provide visual descent guidance information during

the approach to a runway. These lights are visible

from 3−5 miles during the day and up to 20 miles or

more at night. The visual glide path of the VASI

provides safe obstruction clearance within plus or

minus 10 degrees of the extended runway centerline

and to 4 NM from the runway threshold. Descent,

using the VASI, should not be initiated until the

aircraft is visually aligned with the runway. Lateral

course guidance is provided by the runway or runway

lights. In certain circumstances, the safe obstruction

clearance area may be reduced due to local

limitations, or the VASI may be offset from the

extended runway centerline. This will be noted in the

Airport/ Facility Directory.
AIM 7/26/12

2−1−2 Airport Lighting Aids

FIG 2−1−1

Precision & Nonprecision Configurations

NOTE−

Civil ALSF−2 may be operated as SSALR during favorable weather conditions.
7/26/12 AIM

Airport Lighting Aids 2−1−3

5. For 2−bar VASI (4 light units) see FIG 2−1−2.

FIG 2−1−2

2−Bar VASI

Far Bar

= Red

= White Near Bar

Below Glide Path On Glide Path Above Glide Path

6. For 3−bar VASI (6 light units) see FIG 2−1−3.

FIG 2−1−3

3−Bar VASI

Far Bar

Middle Bar

Near Bar

Below Both

Glide Paths

On Lower

Glide Path

On Upper

Glide Path

Above Both

Glide Paths

7. For other VASI configurations see FIG 2−1−4.

FIG 2−1−4

VASI Variations

2 Bar

2 Light Units

On Glide Path

2 Bar

12 Light Units

On Glide Path

3 Bar

16 Light Units

on Lower Glide Path
AIM 7/26/12

2−1−4 Airport Lighting Aids

b. Precision Approach Path Indicator (PAPI).

The precision approach path indicator (PAPI) uses

light units similar to the VASI but are installed in a

single row of either two or four light units. These

lights are visible from about 5 miles during the day

and up to 20 miles at night. The visual glide path of

the PAPI typically provides safe obstruction

clearance within plus or minus 10 degrees of the

extended runway centerline and to 4 SM from the

runway threshold. Descent, using the PAPI, should

not be initiated until the aircraft is visually aligned

with the runway. The row of light units is normally

installed on the left side of the runway and the glide

path indications are as depicted. Lateral course

guidance is provided by the runway or runway lights.

In certain circumstances, the safe obstruction

clearance area may be reduced due to local

limitations, or the PAPI may be offset from the

extended runway centerline. This will be noted in the

Airport/ Facility Directory. (See FIG 2−1−5.)

FIG 2−1−5

Precision Approach Path Indicator (PAPI)

Slightly High

(3.2 Degrees)

White

Red

High

(More Than

3,5 Degrees)

On Glide Path

(3 Degrees)

Slightly Low

(2.8 Degrees)

Low

(Less Than

2.5 Degrees)

c. Tri−color Systems. Tri−color visual approach

slope indicators normally consist of a single light unit

projecting a three−color visual approach path into the

final approach area of the runway upon which the

indicator is installed. The below glide path indication

is red, the above glide path indication is amber, and

the on glide path indication is green. These types of

indicators have a useful range of approximately

one−half to one mile during the day and up to

five miles at night depending upon the visibility

conditions. (See FIG 2−1−6.)

FIG 2−1−6

Tri−Color Visual Approach Slope Indicator

Amber

Above Glide Path

On Glide Path

Below Glide Path

Amber

Green

Red

NOTE−

1. Since the tri−color VASI consists of a single light source which could possibly be confused with other light sources, pilots

should exercise care to properly locate and identify the light signal.

2. When the aircraft descends from green to red, the pilot may see a dark amber color during the transition from green to

red.
7/26/12 AIM

Airport Lighting Aids 2−1−5

FIG 2−1−7

Pulsating Visual Approach Slope Indicator

Above Glide Path

On Glide Path

Below Glide Path

Slightly Below Glide Path

Threshold

PULSATING WHITE

PULSATING RED

STEADY WHITE

STEADY RED

NOTE−

Since the PVASI consists of a single light source which could possibly be confused with other light sources, pilots should

exercise care to properly locate and identify the light signal.

FIG 2−1−8

Alignment of Elements

Above Glide Path On Glide Path Below Glide Path

d. Pulsating Systems. Pulsating visual approach slope indicators normally consist of a single

light unit projecting a two−color visual approach

path into the final approach area of the runway upon

which the indicator is installed. The on glide path

indication is a steady white light. The slightly below

glide path indication is a steady red light. If the

aircraft descends further below the glide path, the red

light starts to pulsate. The above glide path indication

is a pulsating white light. The pulsating rate increases

as the aircraft gets further above or below the desired

glide slope. The useful range of the system is about

four miles during the day and up to ten miles at night.

(See FIG 2−1−7.)

e. Alignment of Elements Systems. Alignment

of elements systems are installed on some small

general aviation airports and are a low−cost system

consisting of painted plywood panels, normally black

and white or fluorescent orange. Some of these

systems are lighted for night use. The useful range of

these systems is approximately three−quarter miles.

To use the system the pilot positions the aircraft so the
AIM 7/26/12

2−1−6 Airport Lighting Aids

elements are in alignment. The glide path indications

are shown in FIG 2−1−8.

2−1−3. Runway End Identifier Lights (REIL)

REILs are installed at many airfields to provide rapid

and positive identification of the approach end of a

particular runway. The system consists of a pair of

synchronized flashing lights located laterally on each

side of the runway threshold. REILs may be either

omnidirectional or unidirectional facing the approach

area. They are effective for:

a. Identification of a runway surrounded by a

preponderance of other lighting.

b. Identification of a runway which lacks contrast

with surrounding terrain.

c. Identification of a runway during reduced

visibility.

2−1−4. Runway Edge Light Systems

a. Runway edge lights are used to outline the

edges of runways during periods of darkness or

restricted visibility conditions. These light systems

are classified according to the intensity or brightness

they are capable of producing: they are the High

Intensity Runway Lights (HIRL), Medium Intensity

Runway Lights (MIRL), and the Low Intensity

Runway Lights (LIRL). The HIRL and MIRL

systems have variable intensity controls, whereas the

LIRLs normally have one intensity setting.

b. The runway edge lights are white, except on

instrument runways yellow replaces white on the last

2,000 feet or half the runway length, whichever is

less, to form a caution zone for landings.

c. The lights marking the ends of the runway emit

red light toward the runway to indicate the end of

runway to a departing aircraft and emit green outward

from the runway end to indicate the threshold to

landing aircraft.

2−1−5. In−runway Lighting

a. Runway Centerline Lighting System

(RCLS). Runway centerline lights are installed on

some precision approach runways to facilitate

landing under adverse visibility conditions. They are

located along the runway centerline and are spaced at

50−foot intervals. When viewed from the landing

threshold, the runway centerline lights are white until

the last 3,000 feet of the runway. The white lights

begin to alternate with red for the next 2,000 feet, and

for the last 1,000 feet of the runway, all centerline

lights are red.

b. Touchdown Zone Lights (TDZL). Touchdown zone lights are installed on some precision

approach runways to indicate the touchdown zone

when landing under adverse visibility conditions.

They consist of two rows of transverse light bars

disposed symmetrically about the runway centerline.

The system consists of steady−burning white lights

which start 100 feet beyond the landing threshold and

extend to 3,000 feet beyond the landing threshold or

to the midpoint of the runway, whichever is less.

c. Taxiway Centerline Lead−Off Lights. Taxiway centerline lead−off lights provide visual

guidance to persons exiting the runway. They are

color−coded to warn pilots and vehicle drivers that

they are within the runway environment or

instrument landing system/microwave landing system (ILS/MLS) critical area, whichever is more

restrictive. Alternate green and yellow lights are

installed, beginning with green, from the runway

centerline to one centerline light position beyond the

runway holding position or ILS/MLS critical area

holding position.

d. Taxiway Centerline Lead−On Lights. Taxiway centerline lead−on lights provide visual

guidance to persons entering the runway. These

“lead−on” lights are also color−coded with the same

color pattern as lead−off lights to warn pilots and

vehicle drivers that they are within the runway

environment or instrument landing system/microwave landing system (ILS/MLS) critical area,

whichever is more conservative. The fixtures used for

lead−on lights are bidirectional, i.e., one side emits

light for the lead−on function while the other side

emits light for the lead−off function. Any fixture that

emits yellow light for the lead−off function must also

emit yellow light for the lead−on function.

(See FIG 2−1−14.)

e. Land and Hold Short Lights. Land and hold

short lights are used to indicate the hold short point on

certain runways which are approved for Land and

Hold Short Operations (LAHSO). Land and hold

short lights consist of a row of pulsing white lights

installed across the runway at the hold short point.

Where installed, the lights will be on anytime
7/26/12 AIM

Airport Lighting Aids 2−1−7

LAHSO is in effect. These lights will be off when

LAHSO is not in effect.

REFERENCE−

AIM, Pilot Responsibilities When Conducting Land and Hold Short

Operations (LAHSO), Paragraph 4−3−11.

2−1−6. Runway Status Light (RWSL)

System

a. Introduction.

RWSL is a fully automated system that provides

runway status information to pilots and surface

vehicle operators to clearly indicate when it is unsafe

to enter, cross, takeoff from, or land on a runway. The

RWSL system processes information from surveillance systems and activates Runway Entrance Lights

(REL), Takeoff Hold Lights (THL), Runway

Intersection Lights (RIL), and Final Approach

Runway Occupancy Signal (FAROS) in accordance

with the position and velocity of the detected surface

traffic and approach traffic. REL, THL, and RIL are

in-pavement light fixtures that are directly visible to

pilots and surface vehicle operators. FAROS alerts

arriving pilots that the approaching runway is

occupied by flashing the Precision Approach Path

Indicator (PAPI). FAROS may be implemented as an

add-on to the RWSL system or implemented as a

stand-alone system at airports without a RWSL

system. RWSL is an independent safety enhancement

that does not substitute for or convey an ATC

clearance. Clearance to enter, cross, takeoff from,

land on, or operate on a runway must still be received

from ATC. Although ATC has limited control over

the system, personnel do not directly use and may not

be able to view light fixture activations and

deactivations during the conduct of daily ATC

operations.

b. Runway Entrance Lights (REL): The REL

system is composed of flush mounted, in-pavement,

unidirectional light fixtures that are parallel to and

focused along the taxiway centerline and directed

toward the pilot at the hold line. An array of REL

lights include the first light at the hold line followed

by a series of evenly spaced lights to the runway edge;

one additional light at the runway centerline is in line

with the last two lights before the runway edge (see

FIG 2−1−9 and FIG 2−1−12). When activated, the

red lights indicate that there is high speed traffic on

the runway or there is an aircraft on final approach

within the activation area.

1. REL Operating Characteristics − Departing

Aircraft:

When a departing aircraft reaches a site adaptable

speed of approximately 30 knots, all taxiway

intersections with REL arrays along the runway

ahead of the aircraft will illuminate (see FIG 2−1−9).

As the aircraft approaches an REL equipped taxiway

intersection, the lights at that intersection extinguish

approximately 3 to 4 seconds before the aircraft

reaches it. This allows controllers to apply

“anticipated separation” to permit ATC to move

traffic more expeditiously without compromising

safety. After the aircraft is declared “airborne” by the

system, all REL lights associated with this runway

will extinguish.

2. REL Operating Characteristics − Arriving

Aircraft:

When an aircraft on final approach is approximately

1 mile from the runway threshold, all sets of taxiway

REL light arrays that intersect the runway illuminate.

The distance is adjustable and can be configured for

specific operations at particular airports. Lights

extinguish at each equipped taxiway intersection

approximately 3 to 4 seconds before the aircraft

reaches it to apply anticipated separation until the

aircraft has slowed to approximately 80 knots (site

adjustable parameter). Below 80 knots, all arrays that

are not within 30 seconds of the aircraft’s forward

path are extinguished. Once the arriving aircraft

slows to approximately 34 knots (site adjustable

parameter), it is declared to be in a taxi state, and all

lights extinguish.

3. What a pilot would observe: A pilot at or

approaching the hold line to a runway will observe

RELs illuminate and extinguish in reaction to an

aircraft or vehicle operating on the runway, or an

arriving aircraft operating less than 1 mile from the

runway threshold.

4. When a pilot observes the red lights of the

REL, that pilot will stop at the hold line or remain

stopped. The pilot will then contact ATC for

resolution if the clearance is in conflict with the

lights. Should pilots note illuminated lights under

circumstances when remaining clear of the runway is

impractical for safety reasons (for example, aircraft

is already on the runway), the crew should proceed

according to their best judgment while understanding

the illuminated lights indicate the runway is unsafe to
AIM 7/26/12

2−1−8 Airport Lighting Aids

enter or cross. Contact ATC at the earliest possible

opportunity.

FIG 2−1−9

Runway Status Light System

c. Takeoff Hold Lights (THL) : The THL system

is composed of flush mounted, in-pavement,

unidirectional light fixtures in a double longitudinal

row aligned either side of the runway centerline

lighting. Fixtures are focused toward the arrival end

of the runway at the “line up and wait” point. THLs

extend for 1,500 feet in front of the holding aircraft

starting at a point 375 feet from the departure

threshold (see FIG 2−1−13). Illuminated red lights

provide a signal, to an aircraft in position for takeoff

or rolling, that it is unsafe to takeoff because the

runway is occupied or about to be occupied by

another aircraft or ground vehicle. Two aircraft, or a

surface vehicle and an aircraft, are required for the

lights to illuminate. The departing aircraft must be in

position for takeoff or beginning takeoff roll. Another

aircraft or a surface vehicle must be on or about to

cross the runway.

1. THL Operating Characteristics − Departing

Aircraft:

THLs will illuminate for an aircraft in position for

departure or departing when there is another aircraft

or vehicle on the runway or about to enter the runway

(see FIG 2−1−9.) Once that aircraft or vehicle exits

the runway, the THLs extinguish. A pilot may notice

lights extinguish prior to the downfield aircraft or

vehicle being completely clear of the runway but still

moving. Like RELs, THLs have an “anticipated

separation” feature.

NOTE−

When the THLs extinguish, this is not clearance to begin a

takeoff roll. All takeoff clearances will be issued by ATC.

2. What a pilot would observe: A pilot in

position to depart from a runway, or has begun takeoff

roll, will observe THLs illuminate in reaction to an

aircraft or vehicle on the runway or entering or

crossing it. Lights will extinguish when the runway is

clear. A pilot may observe several cycles of

illumination and extinguishing depending on the

amount of crossing traffic.

3. When a pilot observes the red light of the

THLs, the pilot should safely stop if it’s feasible or

remain stopped. The pilot must contact ATC for

resolution if any clearance is in conflict with the

lights. Should pilots note illuminated lights while in

takeoff roll and under circumstances when stopping

is impractical for safety reasons, the crew should
7/26/12 AIM

Airport Lighting Aids 2−1−9

proceed according to their best judgment while

understanding the illuminated lights indicate that

continuing the takeoff is unsafe. Contact ATC at the

earliest possible opportunity.

d. Runway Intersection Lights (RIL): The RIL

system is composed of flush mounted, in−pavement,

unidirectional light fixtures in a double longitudinal

row aligned either side of the runway centerline

lighting in the same manner as THLs. Their

appearance to a pilot is similar to that of THLs.

Fixtures are focused toward the arrival end of the

runway, and they extend for 3,000 feet in front of an

aircraft that is approaching an intersecting runway.

They end at the Land and Hold Short Operation

(LASHO) light bar or the hold short line for the

intersecting runway.

1. RIL Operating Characteristics − Departing

Aircraft:

RILs will illuminate for an aircraft departing or in

position to depart when there is high speed traffic

operating on the intersecting runway (see

FIG 2−1−9). Note that there must be an aircraft or

vehicle in a position to observe the RILs for them to

illuminate. Once the conflicting traffic passes

through the intersection, the RILs extinguish.

2. RIL Operating Characteristics − Arriving

Aircraft:

RILs will illuminate for an aircraft that has landed and

is rolling out when there is high speed traffic on the

intersecting runway that is 5 seconds of meeting at

the intersection. Once the conflicting traffic passes

through the intersection, the RILs extinguish.

3. What a pilot would observe: A pilot departing

or arriving will observe RILs illuminate in reaction to

the high speed traffic operation on the intersecting

runway. The lights will extinguish when that traffic

has passed through the runway intersection.

4. Whenever a pilot observes the red light of the

RIL array, the pilot will stop before the LAHSO stop

bar or the hold line for the intersecting runway. If a

departing aircraft is already at high speed in the

takeoff roll when the RILs illuminate, it may be

impractical to stop for safety reasons. The crew

should safely operate according to their best

judgment while understanding the illuminated lights

indicate that continuing the takeoff is unsafe. Contact

ATC at the earliest possible opportunity.

e. The Final Approach Runway Occupancy Signal

(FAROS) is communicated by flashing of the

Precision Approach Path Indicator (PAPI) (see FIG

2-1-9). When activated, the light fixtures of the PAPI

flash or pulse to indicate to the pilot on an approach

that the runway is occupied and that it may be unsafe

to land.

NOTE−

FAROS is an independent automatic alerting system that

does not rely on ATC control or input.

1. FAROS Operating Characteristics:

If an aircraft or surface vehicle occupies a FAROS

equipped runway, the PAPI(s) on that runway will

flash. The glide path indication will not be affected,

and the allotment of red and white PAPI lights

observed by the pilot on approach will not change.

The FAROS system will flash the PAPI when traffic

enters the runway and there is an aircraft on approach

and within 1.5 nautical miles of the landing threshold.

2. What a pilot would observe: A pilot on

approach to the runway will observe the PAPI flash if

there is traffic on the runway and will notice the PAPI

ceases to flash when the traffic moves outside the

hold short lines for the runway.

3. When a pilot observes a flashing PAPI at 500

feet above ground level (AGL), the contact height,

the pilot must look for and acquire the traffic on the

runway. At 300 feet AGL, the pilot must contact ATC

for resolution if the FAROS indication is in conflict

with the clearance. If the PAPI continues to flash, the

pilot must execute an immediate “go around” and

contact ATC at the earliest possible opportunity.

f. Pilot Actions:

1. When operating at airports with RWSL, pilots

will operate with the transponder “On” when

departing the gate or parking area until it is shutdown

upon arrival at the gate or parking area. This ensures

interaction with the FAA surveillance systems such

as ASDE-X which provide information to the RWSL

system.

2. Pilots must always inform the ATCT when

they have either stopped, are verifying a landing

clearance, or are executing a go-around due to RWSL

or FAROS indication that are in conflict with ATC

instructions. Pilots must request clarification of the

taxi, takeoff, or landing clearance.

3. Never cross over illuminated red lights.

Under normal circumstances, RWSL will confirm the
AIM 7/26/12

2−1−10 Airport Lighting Aids

pilot’s taxi or takeoff clearance previously issued by

ATC. If RWSL indicates that it is unsafe to takeoff

from, land on, cross, or enter a runway, immediately

notify ATC of the conflict and re-confirm the

clearance.

4. Do not proceed when lights have extinguished without an ATC clearance. RWSL verifies an

ATC clearance; it does not substitute for an ATC

clearance.

5. Never land if PAPI continues to flash.

Execute a go around and notify ATC.

g. ATC Control of RWSL System:

1. Controllers can set in−pavement lights to one

of five (5) brightness levels to assure maximum

conspicuity under all visibility and lighting conditions. REL, THL, and RIL subsystems may be

independently set.

2. System lights can be disabled should RWSL

operations impact the efficient movement of air

traffic or contribute, in the opinion of the assigned

ATC Manager, to unsafe operations. REL, THL, RIL,

and FAROS light fixtures may be disabled separately.

Disabling of the FAROS subsystem does not

extinguish PAPI lights or impact its glide path

function. Whenever the system or a component is

disabled, a NOTAM must be issued, and the

Automatic Terminal Information System (ATIS)

must be updated.

2−1−7. Stand-Alone Final Approach

Runway Occupancy Signal (FAROS)

a. Introduction:

The stand-alone FAROS system is a fully automated

system that provides runway occupancy status to

pilots on final approach to indicate whether it may be

unsafe to land. When an aircraft or vehicle is detected

on the runway, the Precision Approach Path Indicator

(PAPI) light fixtures flash as a signal to indicate that

the runway is occupied and that it may be unsafe to

land. The stand-alone FAROS system is activated by

localized or comprehensive sensors detecting aircraft

or ground vehicles occupying activation zones.

The stand-alone FAROS system monitors specific

areas of the runway, called activation zones, to

determine the presence of aircraft or ground vehicles

in the zone (see FIG 2−1−10). These activation zones

are defined as areas on the runway that are frequently

occupied by ground traffic during normal airport

operations and could present a hazard to landing

aircraft. Activation zones may include the full-length

departure position, the midfield departure position, a

frequently crossed intersection, or the entire runway.

Pilots can refer to the airport specific FAROS pilot

information sheet for activation zone configuration.

FIG 2−1−10

FAROS Activation Zones

Clearance to land on a runway must be issued by Air

Traffic Control (ATC). ATC personnel have limited

control over the system and may not be able to view

the FAROS signal.
7/26/12 AIM

Airport Lighting Aids 2−1−11

b. Operating Characteristics:

If an aircraft or ground vehicle occupies an activation

zone on the runway, the PAPI light fixtures on that

runway will flash. The glide path indication is not

affected, i.e. the configuration of red and white PAPI

lights observed by the pilot on approach does not

change. The stand-alone FAROS system flashes the

PAPI lights when traffic occupies an activation zone

whether or not there is an aircraft on approach.

c. Pilot Observations:

A pilot on approach to the runway observes the PAPI

lights flashing if there is traffic on the runway

activation zones and notices the PAPI lights cease to

flash when the traffic moves outside the activation

zones.

A pilot on departure from the runway should

disregard any observations of flashing PAPI lights.

d. Pilot Actions:

When a pilot observes a flashing PAPI at 500 feet

above ground level (AGL), the pilot must look for and

attempt to acquire the traffic on the runway. At 300

feet AGL, the pilot must contact ATC for resolution

if the FAROS indication is in conflict with the

clearance (see FIG 2−1−11). If the PAPI lights

continue to flash and the pilot cannot visually

determine that it is safe to land, the pilot must execute

an immediate “go around”. As with operations at

non-FAROS airports, it is always the pilot’s

responsibility to determine whether or not it is safe to

continue with the approach and to land on the runway.

FIG 2−1−11

FAROS Glide Slope Action Points

Pilots should inform the ATCT when they have

executed a go around due to a FAROS indication that

is in conflict with ATC instructions.

NOTE−

At this time, the stand-alone FAROS system is not widely

implemented and is used for evaluation purposes.

2−1−8. Control of Lighting Systems

a. Operation of approach light systems and

runway lighting is controlled by the control tower

(ATCT). At some locations the FSS may control the

lights where there is no control tower in operation.

b. Pilots may request that lights be turned on or off.

Runway edge lights, in−pavement lights and

approach lights also have intensity controls which

may be varied to meet the pilots request. Sequenced

flashing lights (SFL) may be turned on and off. Some

sequenced flashing light systems also have intensity

control.

2−1−9. Pilot Control of Airport Lighting

Radio control of lighting is available at selected

airports to provide airborne control of lights by

keying the aircraft’s microphone. Control of lighting

systems is often available at locations without

specified hours for lighting and where there is no

control tower or FSS or when the tower or FSS is

closed (locations with a part−time tower or FSS) or

specified hours. All lighting systems which are radio

controlled at an airport, whether on a single runway

or multiple runways, operate on the same radio

frequency. (See TBL 2−1−1 and TBL 2−1−2.)
AIM 7/26/12

2−1−12 Airport Lighting Aids

FIG 2−1−12

Runway Entrance Lights

FIG 2−1−13

Takeoff Hold Lights
7/26/12 AIM

Airport Lighting Aids 2−1−13

FIG 2−1−14

Taxiway Lead−On Light Configuration

TBL 2−1−1

Runways With Approach Lights

Lighting System No. of Int.

Steps

Status During 

Nonuse Period

Intensity Step Selected Per No. of Mike Clicks

3 Clicks 5 Clicks 7 Clicks

Approach Lights (Med. Int.) 2 Off Low Low High

Approach Lights (Med. Int.) 3 Off Low Med High

MIRL 3 Off or Low 

HIRL 5 Off or Low 

VASI 2 Off   

NOTES: Predetermined intensity step.

 Low intensity for night use. High intensity for day use as determined by photocell control.

TBL 2−1−2

Runways Without Approach Lights

Lighting System No. of Int.

Steps

Status During

Nonuse Period

Intensity Step Selected Per No. of Mike Clicks

3 Clicks 5 Clicks 7 Clicks

MIRL 3 Off or Low Low Med. High

HIRL 5 Off or Low Step 1 or 2 Step 3 Step 5

LIRL 1 Off On On On

VASI 2 Off 

REIL 1 Off Off On/Off On

REIL 3 Off Low Med. High

NOTES: Low intensity for night use. High intensity for day use as determined by photocell control.

 The control of VASI and/or REIL may be independent of other lighting systems.
AIM 7/26/12

2−1−14 Airport Lighting Aids

a. With FAA approved systems, various combinations of medium intensity approach lights, runway

lights, taxiway lights, VASI and/or REIL may be

activated by radio control. On runways with both

approach lighting and runway lighting (runway edge

lights, taxiway lights, etc.) systems, the approach

lighting system takes precedence for air−to−ground

radio control over the runway lighting system which

is set at a predetermined intensity step, based on

expected visibility conditions. Runways without

approach lighting may provide radio controlled

intensity adjustments of runway edge lights. Other

lighting systems, including VASI, REIL, and taxiway

lights may be either controlled with the runway edge

lights or controlled independently of the runway edge

lights.

b. The control system consists of a 3−step control

responsive to 7, 5, and/or 3 microphone clicks. This

3−step control will turn on lighting facilities capable

of either 3−step, 2−step or 1−step operation. The

3−step and 2−step lighting facilities can be altered in

intensity, while the 1−step cannot. All lighting is

illuminated for a period of 15 minutes from the most

recent time of activation and may not be extinguished

prior to end of the 15 minute period (except for 1−step

and 2−step REILs which may be turned off when

desired by keying the mike 5 or 3 times respectively).

c. Suggested use is to always initially key the mike

7 times; this assures that all controlled lights are

turned on to the maximum available intensity. If

desired, adjustment can then be made, where the

capability is provided, to a lower intensity (or the

REIL turned off) by keying 5 and/or 3 times. Due to

the close proximity of airports using the same

frequency, radio controlled lighting receivers may be

set at a low sensitivity requiring the aircraft to be

relatively close to activate the system. Consequently,

even when lights are on, always key mike as directed

when overflying an airport of intended landing or just

prior to entering the final segment of an approach.

This will assure the aircraft is close enough to activate

the system and a full 15 minutes lighting duration is

available. Approved lighting systems may be

activated by keying the mike (within 5 seconds) as

indicated in TBL 2−1−3.

TBL 2−1−3

Radio Control System

Key Mike Function

7 times within 5 seconds Highest intensity available

5 times within 5 seconds Medium or lower intensity

(Lower REIL or REIL−off)

3 times within 5 seconds Lowest intensity available

(Lower REIL or REIL−off)

d. For all public use airports with FAA standard

systems the Airport/Facility Directory contains the

types of lighting, runway and the frequency that is

used to activate the system. Airports with IAPs

include data on the approach chart identifying the

light system, the runway on which they are installed,

and the frequency that is used to activate the system.

NOTE−

Although the CTAF is used to activate the lights at many

airports, other frequencies may also be used. The

appropriate frequency for activating the lights on the

airport is provided in the Airport/Facility Directory and

the standard instrument approach procedures publications. It is not identified on the sectional charts.

e. Where the airport is not served by an IAP, it may

have either the standard FAA approved control

system or an independent type system of different

specification installed by the airport sponsor. The

Airport/Facility Directory contains descriptions of

pilot controlled lighting systems for each airport

having other than FAA approved systems, and

explains the type lights, method of control, and

operating frequency in clear text.

2−1−10. Airport/Heliport Beacons

a. Airport and heliport beacons have a vertical

light distribution to make them most effective from

one to ten degrees above the horizon; however, they

can be seen well above and below this peak spread.

The beacon may be an omnidirectional capacitor−discharge device, or it may rotate at a constant speed

which produces the visual effect of flashes at regular

intervals. Flashes may be one or two colors

alternately. The total number of flashes are:

1. 24 to 30 per minute for beacons marking

airports, landmarks, and points on Federal airways.

2. 30 to 45 per minute for beacons marking

heliports.
7/26/12 AIM

Airport Lighting Aids 2−1−15

b. The colors and color combinations of beacons

are:

1. White and Green− Lighted land airport.

2. *Green alone− Lighted land airport.

3. White and Yellow− Lighted water airport.

4. *Yellow alone− Lighted water airport.

5. Green, Yellow, and White− Lighted heliport.

NOTE−

*Green alone or yellow alone is used only in connection

with a white−and−green or white−and−yellow beacon

display, respectively.

c. Military airport beacons flash alternately white

and green, but are differentiated from civil beacons

by dualpeaked (two quick) white flashes between the

green flashes.

d. In Class B, Class C, Class D and Class E surface

areas, operation of the airport beacon during the hours

of daylight often indicates that the ground visibility

is less than 3 miles and/or the ceiling is less than

1,000 feet. ATC clearance in accordance with

14 CFR Part 91 is required for landing, takeoff and

flight in the traffic pattern. Pilots should not rely

solely on the operation of the airport beacon to

indicate if weather conditions are IFR or VFR. At

some locations with operating control towers, ATC

personnel turn the beacon on or off when controls are

in the tower. At many airports the airport beacon is

turned on by a photoelectric cell or time clocks and

ATC personnel cannot control them. There is no

regulatory requirement for daylight operation and it

is the pilot’s responsibility to comply with proper

preflight planning as required by 14 CFR

Section 91.103.

2−1−11. Taxiway Lights

a. Taxiway Edge Lights. Taxiway edge lights are

used to outline the edges of taxiways during periods

of darkness or restricted visibility conditions. These

fixtures emit blue light.

NOTE−

At most major airports these lights have variable intensity

settings and may be adjusted at pilot request or when

deemed necessary by the controller.

b. Taxiway Centerline Lights. Taxiway centerline lights are used to facilitate ground traffic under

low visibility conditions. They are located along the

taxiway centerline in a straight line on straight

portions, on the centerline of curved portions, and

along designated taxiing paths in portions of

runways, ramp, and apron areas. Taxiway centerline

lights are steady burning and emit green light.

c. Clearance Bar Lights. Clearance bar lights

are installed at holding positions on taxiways in order

to increase the conspicuity of the holding position in

low visibility conditions. They may also be installed

to indicate the location of an intersecting taxiway

during periods of darkness. Clearance bars consist of

three in−pavement steady−burning yellow lights.

d. Runway Guard Lights. Runway guard lights

are installed at taxiway/runway intersections. They

are primarily used to enhance the conspicuity of

taxiway/runway intersections during low visibility

conditions, but may be used in all weather conditions.

Runway guard lights consist of either a pair of

elevated flashing yellow lights installed on either side

of the taxiway, or a row of in−pavement yellow lights

installed across the entire taxiway, at the runway

holding position marking.

NOTE−

Some airports may have a row of three or five in−pavement

yellow lights installed at taxiway/runway intersections.

They should not be confused with clearance bar lights

described in paragraph 2−1−11 c, Clearance Bar Lights.

e. Stop Bar Lights. Stop bar lights, when

installed, are used to confirm the ATC clearance to

enter or cross the active runway in low visibility

conditions (below 1,200 ft Runway Visual Range). A

stop bar consists of a row of red, unidirectional,

steady−burning in−pavement lights installed across

the entire taxiway at the runway holding position, and

elevated steady−burning red lights on each side. A

controlled stop bar is operated in conjunction with the

taxiway centerline lead−on lights which extend from

the stop bar toward the runway. Following the ATC

clearance to proceed, the stop bar is turned off and the

lead−on lights are turned on. The stop bar and lead−on

lights are automatically reset by a sensor or backup

timer.

CAUTION−

Pilots should never cross a red illuminated stop bar, even

if an ATC clearance has been given to proceed onto or

across the runway.

NOTE−

If after crossing a stop bar, the taxiway centerline lead−on

lights inadvertently extinguish, pilots should hold their

position and contact ATC for further instructions.

7/26/12 AIM

Air Navigation and Obstruction Lighting 2−2−1

Section 2. Air Navigation and Obstruction Lighting

2−2−1. Aeronautical Light Beacons

a. An aeronautical light beacon is a visual

NAVAID displaying flashes of white and/or colored

light to indicate the location of an airport, a heliport,

a landmark, a certain point of a Federal airway in

mountainous terrain, or an obstruction. The light used

may be a rotating beacon or one or more flashing

lights. The flashing lights may be supplemented by

steady burning lights of lesser intensity.

b. The color or color combination displayed by a

particular beacon and/or its auxiliary lights tell

whether the beacon is indicating a landing place,

landmark, point of the Federal airways, or an

obstruction. Coded flashes of the auxiliary lights, if

employed, further identify the beacon site.

2−2−2. Code Beacons and Course Lights

a. Code Beacons. The code beacon, which can be

seen from all directions, is used to identify airports

and landmarks. The code beacon flashes the three or

four character airport identifier in International

Morse Code six to eight times per minute. Green

flashes are displayed for land airports while yellow

flashes indicate water airports.

b. Course Lights. The course light, which can be

seen clearly from only one direction, is used only with

rotating beacons of the Federal Airway System:

two course lights, back to back, direct coded flashing

beams of light in either direction along the course of

airway.

NOTE−

Airway beacons are remnants of the “lighted” airways

which antedated the present electronically equipped

federal airways system. Only a few of these beacons exist

today to mark airway segments in remote mountain areas.

Flashes in Morse code identify the beacon site.

2−2−3. Obstruction Lights

a. Obstructions are marked/lighted to warn airmen

of their presence during daytime and nighttime

conditions. They may be marked/lighted in any of the

following combinations:

1. Aviation Red Obstruction Lights. Flashing aviation red beacons (20 to 40 flashes per minute)

and steady burning aviation red lights during

nighttime operation. Aviation orange and white paint

is used for daytime marking.

2. Medium Intensity Flashing White

Obstruction Lights. Medium intensity flashing

white obstruction lights may be used during daytime

and twilight with automatically selected reduced

intensity for nighttime operation. When this system

is used on structures 500 feet (153m) AGL or less in

height, other methods of marking and lighting the

structure may be omitted. Aviation orange and white

paint is always required for daytime marking on

structures exceeding 500 feet (153m) AGL. This

system is not normally installed on structures less

than 200 feet (61m) AGL.

3. High Intensity White Obstruction Lights.

Flashing high intensity white lights during daytime

with reduced intensity for twilight and nighttime

operation. When this type system is used, the marking

of structures with red obstruction lights and aviation

orange and white paint may be omitted.

4. Dual Lighting. A combination of flashing

aviation red beacons and steady burning aviation red

lights for nighttime operation and flashing high

intensity white lights for daytime operation. Aviation

orange and white paint may be omitted.

5. Catenary Lighting. Lighted markers are

available for increased night conspicuity of high−

voltage (69KV or higher) transmission line catenary

wires. Lighted markers provide conspicuity both day

and night.

b. Medium intensity omnidirectional flashing

white lighting system provides conspicuity both day

and night on catenary support structures. The unique

sequential/simultaneous flashing light system alerts

pilots of the associated catenary wires.

c. High intensity flashing white lights are being

used to identify some supporting structures of

overhead transmission lines located across rivers,

chasms, gorges, etc. These lights flash in a middle,

top, lower light sequence at approximately 60 flashes

per minute. The top light is normally installed near

the top of the supporting structure, while the lower

light indicates the approximate lower portion of the
AIM 7/26/12

2−2−2 Air Navigation and Obstruction Lighting

wire span. The lights are beamed towards the

companion structure and identify the area of the wire

span.

d. High intensity flashing white lights are also

employed to identify tall structures, such as chimneys

and towers, as obstructions to air navigation. The

lights provide a 360 degree coverage about the

structure at 40 flashes per minute and consist of from

one to seven levels of lights depending upon the

height of the structure. Where more than one level is

used the vertical banks flash simultaneously.
7/26/12 AIM

Airport Marking Aids and Signs 2−3−1

Section 3. Airport Marking Aids and Signs

2−3−1. General

a. Airport pavement markings and signs provide

information that is useful to a pilot during takeoff,

landing, and taxiing.

b. Uniformity in airport markings and signs from

one airport to another enhances safety and improves

efficiency. Pilots are encouraged to work with the

operators of the airports they use to achieve the

marking and sign standards described in this section.

c. Pilots who encounter ineffective, incorrect, or

confusing markings or signs on an airport should

make the operator of the airport aware of the problem.

These situations may also be reported under the

Aviation Safety Reporting Program as described in

paragraph 7−6−1, Aviation Safety Reporting Program. Pilots may also report these situations to the

FAA regional airports division.

d. The markings and signs described in this

section of the AIM reflect the current FAA

recommended standards.

REFERENCE−

AC 150/5340−1, Standards for Airport Markings.

AC 150/5340−18, Standards for Airport Sign Systems.

2−3−2. Airport Pavement Markings

a. General. For the purpose of this presentation

the Airport Pavement Markings have been grouped

into four areas:

1. Runway Markings.

2. Taxiway Markings.

3. Holding Position Markings.

4. Other Markings.

b. Marking Colors. Markings for runways are

white. Markings defining the landing area on a

heliport are also white except for hospital heliports

which use a red “H” on a white cross. Markings for

taxiways, areas not intended for use by aircraft

(closed and hazardous areas), and holding positions

(even if they are on a runway) are yellow.

2−3−3. Runway Markings

a. General. There are three types of markings for

runways: visual, nonprecision instrument, and

precision instrument. TBL 2−3−1 identifies the

marking elements for each type of runway and

TBL 2−3−2 identifies runway threshold markings.

TBL 2−3−1

Runway Marking Elements

Marking Element Visual Runway

Nonprecision

Instrument

Runway

Precision

Instrument

Runway

Designation X X X

Centerline X X X

Threshold X1 X X

Aiming Point X2 X X

Touchdown Zone X

Side Stripes X

1 On runways used, or intended to be used, by international commercial transports.

2 On runways 4,000 feet (1200 m) or longer used by jet aircraft.
AIM 7/26/12

2−3−2 Airport Marking Aids and Signs

FIG 2−3−1

Precision Instrument Runway Markings

b. Runway Designators. Runway numbers and

letters are determined from the approach direction.

The runway number is the whole number nearest

one-tenth the magnetic azimuth of the centerline of

the runway, measured clockwise from the magnetic

north. The letters, differentiate between left (L),

right (R), or center (C), parallel runways, as

applicable:

1. For two parallel runways “L” “R.”

2. For three parallel runways “L” “C” “R.”

c. Runway Centerline Marking. The runway

centerline identifies the center of the runway and

provides alignment guidance during takeoff and

landings. The centerline consists of a line of

uniformly spaced stripes and gaps.

d. Runway Aiming Point Marking. The aiming

point marking serves as a visual aiming point for a

landing aircraft. These two rectangular markings

consist of a broad white stripe located on each side of

the runway centerline and approximately 1,000 feet

from the landing threshold, as shown in FIG 2−3−1,

Precision Instrument Runway Markings.

e. Runway Touchdown Zone Markers. The

touchdown zone markings identify the touchdown

zone for landing operations and are coded to provide

distance information in 500 feet (150m) increments.

These markings consist of groups of one, two, and

three rectangular bars symmetrically arranged in

pairs about the runway centerline, as shown in

FIG 2−3−1, Precision Instrument Runway Markings.

For runways having touchdown zone markings on

both ends, those pairs of markings which extend to

within 900 feet (270m) of the midpoint between the

thresholds are eliminated.
7/26/12 AIM

Airport Marking Aids and Signs 2−3−3

FIG 2−3−2

Nonprecision Instrument Runway and Visual Runway Markings 20

20

AIMING POINT

MARKING

THRESHOLD THRESHOLD

MARKINGS

DESIGNATION

MARKING

PAVEMENT EDGE

AIMING POINT

MARKING

PAVEMENT EDGE

DESIGNATION MARKING

THRESHOLD

NONPRECISION INSTRUMENT RUNWAY MARKINGS

VISUAL RUNWAY MARKINGS

f. Runway Side Stripe Marking. Runway side

stripes delineate the edges of the runway. They

provide a visual contrast between runway and the

abutting terrain or shoulders. Side stripes consist of

continuous white stripes located on each side of the

runway as shown in FIG 2−3−4.

g. Runway Shoulder Markings. Runway shoulder stripes may be used to supplement runway side

stripes to identify pavement areas contiguous to the

runway sides that are not intended for use by aircraft.

Runway Shoulder stripes are Yellow. 

(See FIG 2−3−5.)

h. Runway Threshold Markings. Runway

threshold markings come in two configurations. They

either consist of eight longitudinal stripes of uniform

dimensions disposed symmetrically about the

runway centerline, as shown in FIG 2−3−1, or the

number of stripes is related to the runway width as

indicated in TBL 2−3−2. A threshold marking helps

identify the beginning of the runway that is available

for landing. In some instances the landing threshold

may be relocated or displaced.

TBL 2−3−2

Number of Runway Threshold Stripes

Runway Width Number of Stripes

60 feet (18 m) 4

75 feet (23 m) 6

100 feet (30 m) 8

150 feet (45 m) 12

200 feet (60 m) 16
AIM 7/26/12

2−3−4 Airport Marking Aids and Signs

1. Relocation of a Threshold. Sometimes

construction, maintenance, or other activities require

the threshold to be relocated towards the rollout end

of the runway. (See FIG 2−3−3.) When a threshold is

relocated, it closes not only a set portion of the

approach end of a runway, but also shortens the length

of the opposite direction runway. In these cases, a

NOTAM should be issued by the airport operator

identifying the portion of the runway that is closed,

e.g., 10/28 W 900 CLSD. Because the duration of the

relocation can vary from a few hours to several

months, methods identifying the new threshold may

vary. One common practice is to use a ten feet wide

white threshold bar across the width of the runway.

Although the runway lights in the area between the

old threshold and new threshold will not be

illuminated, the runway markings in this area may or

may not be obliterated, removed, or covered.

2. Displaced Threshold. A displaced threshold is a threshold located at a point on the runway

other than the designated beginning of the runway.

Displacement of a threshold reduces the length of

runway available for landings. The portion of runway

behind a displaced threshold is available for takeoffs

in either direction and landings from the opposite

direction. A ten feet wide white threshold bar is

located across the width of the runway at the

displaced threshold. White arrows are located along

the centerline in the area between the beginning of the

runway and displaced threshold. White arrow heads

are located across the width of the runway just prior

to the threshold bar, as shown in FIG 2−3−4.

NOTE−

Airport operator. When reporting the relocation or

displacement of a threshold, the airport operator should

avoid language which confuses the two.

i. Demarcation Bar. A demarcation bar delineates a runway with a displaced threshold from a blast

pad, stopway or taxiway that precedes the runway. A

demarcation bar is 3 feet (1m) wide and yellow, since

it is not located on the runway as shown in

FIG 2−3−6.

1. Chevrons. These markings are used to show

pavement areas aligned with the runway that are

unusable for landing, takeoff, and taxiing. Chevrons

are yellow. (See FIG 2−3−7.)

j. Runway Threshold Bar. A threshold bar

delineates the beginning of the runway that is

available for landing when the threshold has been

relocated or displaced. A threshold bar is 10 feet (3m)

in width and extends across the width of the runway,

as shown in FIG 2−3−4.
7/26/12 AIM

Airport Marking Aids and Signs 2−3−5

FIG 2−3−3

Relocation of a Threshold with Markings for Taxiway Aligned with Runway
AIM 7/26/12

2−3−6 Airport Marking Aids and Signs

FIG 2−3−4

Displaced Threshold Markings
7/26/12 AIM

Airport Marking Aids and Signs 2−3−7

FIG 2−3−5

Runway Shoulder Markings

RUNWAY THRESHOLD

MIDPOINT OF

RUNWAY

SHOULDER RUNWAY SHOULDER

45° 45°

45° 45°

2−3−4. Taxiway Markings

a. General. All taxiways should have centerline

markings and runway holding position markings

whenever they intersect a runway. Taxiway edge

markings are present whenever there is a need to

separate the taxiway from a pavement that is not

intended for aircraft use or to delineate the edge of the

taxiway. Taxiways may also have shoulder markings

and holding position markings for Instrument

Landing System/Microwave Landing System (ILS/

MLS) critical areas, and taxiway/taxiway

intersection markings.

REFERENCE−

AIM, Holding Position Markings, Paragraph 2−3−5.

b. Taxiway Centerline.

1. Normal Centerline. The taxiway centerline

is a single continuous yellow line, 6 inches (15 cm) to

12 inches (30 cm) in width. This provides a visual cue

to permit taxiing along a designated path. Ideally, the

aircraft should be kept centered over this line during

taxi. However, being centered on the taxiway

centerline does not guarantee wingtip clearance with

other aircraft or other objects.

2. Enhanced Centerline. At some airports,

mostly the larger commercial service airports, an

enhanced taxiway centerline will be used. The

enhanced taxiway centerline marking consists of a

parallel line of yellow dashes on either side of the

normal taxiway centerline. The taxiway centerlines

are enhanced for a maximum of 150 feet prior to a

runway holding position marking. The purpose of

this enhancement is to warn the pilot that he/she is

approaching a runway holding position marking and

should prepare to stop unless he/she has been cleared

onto or across the runway by ATC. (See FIG 2−3−8.)

c. Taxiway Edge Markings. Taxiway edge

markings are used to define the edge of the taxiway.

They are primarily used when the taxiway edge does

not correspond with the edge of the pavement. There

are two types of markings depending upon whether

the aircraft is suppose to cross the taxiway edge:

1. Continuous Markings. These consist of a

continuous double yellow line, with each line being

at least 6 inches (15 cm) in width spaced 6 inches

(15 cm) apart. They are used to define the taxiway

edge from the shoulder or some other abutting paved

surface not intended for use by aircraft.

2. Dashed Markings. These markings are

used when there is an operational need to define the

edge of a taxiway or taxilane on a paved surface

where the adjoining pavement to the taxiway edge is

intended for use by aircraft, e.g., an apron. Dashed

taxiway edge markings consist of a broken double

yellow line, with each line being at least 6 inches

(15 cm) in width, spaced 6 inches (15 cm) apart (edge

to edge). These lines are 15 feet (4.5 m) in length with

25 foot (7.5 m) gaps. (See FIG 2−3−9.)

d. Taxi Shoulder Markings. Taxiways, holding

bays, and aprons are sometimes provided with paved

shoulders to prevent blast and water erosion.

Although shoulders may have the appearance of full

strength pavement they are not intended for use by

aircraft, and may be unable to support an aircraft.

Usually the taxiway edge marking will define this

area. Where conditions exist such as islands or

taxiway curves that may cause confusion as to which

side of the edge stripe is for use by aircraft, taxiway

shoulder markings may be used to indicate the

pavement is unusable. Taxiway shoulder markings

are yellow. (See FIG 2−3−10.)
AIM 7/26/12

2−3−8 Airport Marking Aids and Signs

FIG 2−3−6

Markings for Blast Pad or Stopway or Taxiway Preceding a Displaced Threshold
7/26/12 AIM

Airport Marking Aids and Signs 2−3−9

FIG 2−3−7

Markings for Blast Pads and Stopways
AIM 7/26/12

2−3−10 Airport Marking Aids and Signs

FIG 2−3−8

Enhanced Taxiway Centerline

FIG 2−3−9

Dashed Markings

DOUBLE

YELLOW

LINES

TAXIWAY EDGE

MARKINGS

CONTINUOUS

TAXIWAY EDGE

MARKINGS

DASHED

e. Surface Painted Taxiway Direction

Signs. Surface painted taxiway direction signs have

a yellow background with a black inscription, and are

provided when it is not possible to provide taxiway

direction signs at intersections, or when necessary to

supplement such signs. These markings are located

adjacent to the centerline with signs indicating turns

to the left being on the left side of the taxiway

centerline and signs indicating turns to the right being

on the right side of the centerline. (See FIG 2−3−11.)

FIG 2−3−10

Taxi Shoulder Markings

YELLOW STRIPES

PAVEMENT EDGE

TAXIWAY EDGE

MARKINGS

RUNWAY

f. Surface Painted Location Signs. Surface

painted location signs have a black background with

a yellow inscription. When necessary, these markings

are used to supplement location signs located along

side the taxiway and assist the pilot in confirming the

designation of the taxiway on which the aircraft is

located. These markings are located on the right side

of the centerline. (See FIG 2−3−11.)

g. Geographic Position Markings. These markings are located at points along low visibility taxi

routes designated in the airport’s Surface Movement

Guidance Control System (SMGCS) plan. They are

used to identify the location of taxiing aircraft during

low visibility operations. Low visibility operations

are those that occur when the runway visible

range (RVR) is below 1200 feet(360m). They are

positioned to the left of the taxiway centerline in the

direction of taxiing. (See FIG 2−3−12.) The

geographic position marking is a circle comprised of

an outer black ring contiguous to a white ring with a

pink circle in the middle. When installed on asphalt

or other dark-colored pavements, the white ring and

the black ring are reversed, i.e., the white ring

becomes the outer ring and the black ring becomes the

inner ring. It is designated with either a number or a

number and letter. The number corresponds to the

consecutive position of the marking on the route.
7/26/12 AIM

Airport Marking Aids and Signs 2−3−11

FIG 2−3−11

Surface Painted Signs
AIM 7/26/12

2−3−12 Airport Marking Aids and Signs

2−3−5. Holding Position Markings

a. Runway Holding Position Markings. For

runways, these markings indicate where an aircraft is

supposed to stop when approaching a runway. They

consist of four yellow lines, two solid and two dashed,

spaced six or twelve inches apart, and extending

across the width of the taxiway or runway. The solid

lines are always on the side where the aircraft is to

hold. There are three locations where runway holding

position markings are encountered.

1. Runway Holding Position Markings on

Taxiways. These markings identify the locations on

a taxiway where an aircraft is supposed to stop when

it does not have clearance to proceed onto the runway.

Generally, runway holding position markings also

identify the boundary of the runway safety area for

aircraft exiting the runway. The runway holding

position markings are shown in FIG 2−3−13 and

FIG 2−3−16. When instructed by ATC to, “Hold short

of (runway “xx”),” the pilot must stop so that no part

of the aircraft extends beyond the runway holding

position marking. When approaching the runway, a

pilot should not cross the runway holding position

marking without ATC clearance at a controlled

airport, or without making sure of adequate

separation from other aircraft at uncontrolled

airports. An aircraft exiting a runway is not clear of

the runway until all parts of the aircraft have crossed

the applicable holding position marking.

REFERENCE−

AIM, Exiting the Runway After Landing,. Paragraph 4−3−20.

2. Runway Holding Position Markings on

Runways. These markings are installed on runways

only if the runway is normally used by air traffic

control for “land, hold short” operations or taxiing

operations and have operational significance only for

those two types of operations. A sign with a white

inscription on a red background is installed adjacent

to these holding position markings. (See

FIG 2−3−14.) The holding position markings are

placed on runways prior to the intersection with

another runway, or some designated point. Pilots

receiving instructions “cleared to land, runway “xx””

from air traffic control are authorized to use the entire

landing length of the runway and should disregard

any holding position markings located on the runway.

Pilots receiving and accepting instructions “cleared

to land runway “xx,” hold short of runway “yy”” from

air traffic control must either exit runway “xx,” or

stop at the holding position prior to runway “yy.”

3. Taxiways Located in Runway Approach

Areas. These markings are used at some airports

where it is necessary to hold an aircraft on a taxiway

located in the approach or departure area of a runway

so that the aircraft does not interfere with the

operations on that runway. This marking is collocated

with the runway approach area holding position sign.

When specifically instructed by ATC “Hold short of

(runway xx approach area)” the pilot should stop so

no part of the aircraft extends beyond the holding

position marking. (See subparagraph 2−3−8b2,

Runway Approach Area Holding Position Sign, and

FIG 2−3−15.)

b. Holding Position Markings for Instrument

Landing System (ILS). Holding position markings

for ILS/MLS critical areas consist of two yellow solid

lines spaced two feet apart connected by pairs of solid

lines spaced ten feet apart extending across the width

of the taxiway as shown. (See FIG 2−3−16.) A sign

with an inscription in white on a red background is

installed adjacent to these hold position markings.

When the ILS critical area is being protected, the pilot

should stop so no part of the aircraft extends beyond

the holding position marking. When approaching the

holding position marking, a pilot should not cross the

marking without ATC clearance. ILS critical area is

not clear until all parts of the aircraft have crossed the

applicable holding position marking.

REFERENCE−

AIM, Instrument Landing System (ILS), Paragraph 1−1−9.

c. Holding Position Markings for Taxiway/

Taxiway Intersections. Holding position markings

for taxiway/taxiway intersections consist of a single

dashed line extending across the width of the taxiway

as shown. (See FIG 2−3−17.) They are installed on

taxiways where air traffic control normally holds

aircraft short of a taxiway intersection. When

instructed by ATC “hold short of (taxiway)” the pilot

should stop so no part of the aircraft extends beyond

the holding position marking. When the marking is

not present the pilot should stop the aircraft at a point

which provides adequate clearance from an aircraft

on the intersecting taxiway.

d. Surface Painted Holding Position Signs.

Surface painted holding position signs have a red

background with a white inscription and supplement

the signs located at the holding position. This type of

marking is normally used where the width of the

holding position on the taxiway is greater than 200

feet(60m). It is located to the left side of the taxiway

centerline on the holding side and prior to the holding

position marking. (See FIG 2−3−11.)
7/26/12 AIM

Airport Marking Aids and Signs 2−3−13

FIG 2−3−12

Geographic Position Markings

FIG 2−3−13

Runway Holding Position Markings on Taxiway

RUNWAY

TAXIWAY

EXAMPLE OF HOLDING POSITION MARKINGS

EXTENDED ACROSS HOLDING BAY

HOLDING

BAY

15

TAXIWAY/RUNWAY

HOLDING POSITION

MARKINGS
AIM 7/26/12

2−3−14 Airport Marking Aids and Signs

FIG 2−3−14

Runway Holding Position Markings on Runways
7/26/12 AIM

Airport Marking Aids and Signs 2−3−15

FIG 2−3−15

Taxiways Located in Runway Approach Area
AIM 7/26/12

2−3−16 Airport Marking Aids and Signs

FIG 2−3−16

Holding Position Markings: ILS Critical Area15

DETAIL 2

DETAIL 1 RUNWAY HOLDING

POSITION MARKINGS,

YELLOW, SEE

DETAIL 1

ILS HOLDING

POSITION MARKINGS,

YELLOW, SEE

DETAIL 2

ILS CRITICAL

AREA

2−3−6. Other Markings

a. Vehicle Roadway Markings. The vehicle

roadway markings are used when necessary to define

a pathway for vehicle operations on or crossing areas

that are also intended for aircraft. These markings

consist of a white solid line to delineate each edge of

the roadway and a dashed line to separate lanes within

the edges of the roadway. In lieu of the solid lines,

zipper markings may be used to delineate the edges

of the vehicle roadway. (See FIG 2−3−18.) Details of

the zipper markings are shown in FIG 2−3−19.

b. VOR Receiver Checkpoint Markings. The

VOR receiver checkpoint marking allows the pilot to

check aircraft instruments with navigational aid

signals. It consists of a painted circle with an arrow in

the middle; the arrow is aligned in the direction of the

checkpoint azimuth. This marking, and an associated

sign, is located on the airport apron or taxiway at a

point selected for easy access by aircraft but where

other airport traffic is not to be unduly obstructed.

(See FIG 2−3−20.)

NOTE−

The associated sign contains the VOR station identification

letter and course selected (published) for the check, the

words “VOR check course,” and DME data (when

applicable). The color of the letters and numerals are black

on a yellow background.

EXAMPLE−

DCA 176−356

VOR check course

DME XXX
7/26/12 AIM

Airport Marking Aids and Signs 2−3−17

FIG 2−3−17

Holding Position Markings: Taxiway/Taxiway Intersections

TAXIWAY HOLDING

POSITION MARKINGS,

YELLOW, SEE

DETAIL 1

DETAIL 1

FIG 2−3−18

Vehicle Roadway Markings
AIM 7/26/12

2−3−18 Airport Marking Aids and Signs

FIG 2−3−19

Roadway Edge Stripes, White, Zipper Style

c. Nonmovement Area Boundary Markings.

These markings delineate the movement area,

i.e., area under air traffic control. These markings are

yellow and located on the boundary between the

movement and nonmovement area. The nonmovement area boundary markings consist of two yellow

lines (one solid and one dashed) 6 inches (15cm) in

width. The solid line is located on the nonmovement

area side while the dashed yellow line is located on

the movement area side. The nonmovement

boundary marking area is shown in FIG 2−3−21.

FIG 2−3−20

Ground Receiver Checkpoint Markings

1

4

2

3

1. WHITE

2. YELLOW

3. YELLOW ARROW ALIGNED TOWARD THE FACILITY

4. INTERIOR OF CIRCLE BLACK (CONCRETE SURFACE ONLY)

5. CIRCLE MAY BE BORDERED ON INSIDE AND OUTSIDE WITH

6" BLACK BAND IF NECESSARY FOR CONTRAST

5

FIG 2−3−21

Nonmovement Area Boundary Markings

BOTH LINES

ARE YELLOW

SOLID LINE ON

NONMOVEMENT

SIDE

DASHED LINE ON

MOVEMENT SIDE

FIG 2−3−22

Closed or Temporarily Closed Runway

 and Taxiway Markings

2

X

d. Marking and Lighting of Permanently

Closed Runways and Taxiways. For runways and

taxiways which are permanently closed, the lighting

circuits will be disconnected. The runway threshold,

runway designation, and touchdown markings are

obliterated and yellow crosses are placed at each end

of the runway and at 1,000 foot intervals. 

(See FIG 2−3−22.)
7/26/12 AIM

Airport Marking Aids and Signs 2−3−19

FIG 2−3−23

Helicopter Landing Areas

e. Temporarily Closed Runways and Taxiways.

To provide a visual indication to pilots that a runway

is temporarily closed, crosses are placed on the

runway only at each end of the runway. The crosses

are yellow in color. (See FIG 2−3−22.)

1. A raised lighted yellow cross may be placed

on each runway end in lieu of the markings described

in subparagraph e,Temporarily Closed Runways and

Taxiways, to indicate the runway is closed.

2. A visual indication may not be present

depending on the reason for the closure, duration of

the closure, airfield configuration and the existence

and the hours of operation of an airport traffic control

tower. Pilots should check NOTAMs and the

Automated Terminal Information System (ATIS) for

local runway and taxiway closure information.

3. Temporarily closed taxiways are usually

treated as hazardous areas, in which no part of an

aircraft may enter, and are blocked with barricades.

However, as an alternative a yellow cross may be

installed at each entrance to the taxiway.

f. Helicopter Landing Areas. The markings

illustrated in FIG 2−3−23 are used to identify the

landing and takeoff area at a public use heliport and

hospital heliport. The letter “H” in the markings is

oriented to align with the intended direction of

approach. FIG 2−3−23 also depicts the markings for

a closed airport.

2−3−7. Airport Signs

There are six types of signs installed on airfields:

mandatory instruction signs, location signs, direction

signs, destination signs, information signs, and

runway distance remaining signs. The characteristics

and use of these signs are discussed in paragraph 2−3−8, Mandatory Instruction Signs, through

paragraph 2−3−13, Runway Distance Remaining

Signs.

REFERENCE−

AC150/5340−18, Standards for Airport Sign Systems for Detailed

Information on Airport Signs.
AIM 7/26/12

2−3−20 Airport Marking Aids and Signs

FIG 2−3−24

Runway Holding Position Sign

FIG 2−3−25

Holding Position Sign at Beginning of Takeoff Runway

2−3−8. Mandatory Instruction Signs

a. These signs have a red background with a white

inscription and are used to denote:

1. An entrance to a runway or critical area and;

2. Areas where an aircraft is prohibited from

entering.

b. Typical mandatory signs and applications

are:

1. Runway Holding Position Sign. This sign

is located at the holding position on taxiways that

intersect a runway or on runways that intersect other

runways. The inscription on the sign contains the

designation of the intersecting runway as shown in

FIG 2−3−24. The runway numbers on the sign are

arranged to correspond to the respective runway

threshold. For example, “15−33” indicates that the

threshold for Runway 15 is to the left and the

threshold for Runway 33 is to the right.

(a) On taxiways that intersect the beginning

of the takeoff runway, only the designation of the

takeoff runway may appear on the sign as shown in

FIG 2−3−25, while all other signs will have the

designation of both runway directions.
7/26/12 AIM

Airport Marking Aids and Signs 2−3−21

FIG 2−3−26

Holding Position Sign for a Taxiway that Intersects the Intersection of Two Runways

FIG 2−3−27

Holding Position Sign for a Runway Approach Area

(b) If the sign is located on a taxiway that

intersects the intersection of two runways, the

designations for both runways will be shown on the

sign along with arrows showing the approximate

alignment of each runway as shown in FIG 2−3−26.

In addition to showing the approximate runway

alignment, the arrow indicates the direction to the

threshold of the runway whose designation is

immediately next to the arrow.

(c) A runway holding position sign on a

taxiway will be installed adjacent to holding position

markings on the taxiway pavement. On runways,

holding position markings will be located only on the

runway pavement adjacent to the sign, if the runway

is normally used by air traffic control for “Land, Hold

Short” operations or as a taxiway. The holding

position markings are described in paragraph 2−3−5,

Holding Position Markings.

2. Runway Approach Area Holding Position

Sign. At some airports, it is necessary to hold an

aircraft on a taxiway located in the approach or

departure area for a runway so that the aircraft does

not interfere with operations on that runway. In these

situations, a sign with the designation of the approach

end of the runway followed by a “dash” (−) and letters

“APCH” will be located at the holding position on the

taxiway. Holding position markings in accordance

with paragraph 2−3−5, Holding Position Markings,

will be located on the taxiway pavement. An example

of this sign is shown in FIG 2−3−27. In this example,

the sign may protect the approach to Runway 15

and/or the departure for Runway 33.
AIM 7/26/12

2−3−22 Airport Marking Aids and Signs

FIG 2−3−28

Holding Position Sign for ILS Critical Area

FIG 2−3−29

Sign Prohibiting Aircraft Entry into an Area

3. ILS Critical Area Holding Position

Sign. At some airports, when the instrument landing

system is being used, it is necessary to hold an aircraft

on a taxiway at a location other than the holding

position described in paragraph 2−3−5, Holding

Position Markings. In these situations the holding

position sign for these operations will have the

inscription “ILS” and be located adjacent to the

holding position marking on the taxiway described in

paragraph 2−3−5. An example of this sign is shown

in FIG 2−3−28.

4. No Entry Sign. This sign, shown in

FIG 2−3−29, prohibits an aircraft from entering an

area. Typically, this sign would be located on a

taxiway intended to be used in only one direction or

at the intersection of vehicle roadways with runways,

taxiways or aprons where the roadway may be

mistaken as a taxiway or other aircraft movement

surface.

NOTE−

The holding position sign provides the pilot with a visual

cue as to the location of the holding position marking. The

operational significance of holding position markings are

described in the notes for paragraph 2−3−5, Holding

Position Markings.
7/26/12 AIM

Airport Marking Aids and Signs 2−3−23

FIG 2−3−30

Taxiway Location Sign

FIG 2−3−31

Taxiway Location Sign Collocated with Runway Holding Position Sign

2−3−9. Location Signs

a. Location signs are used to identify either a

taxiway or runway on which the aircraft is located.

Other location signs provide a visual cue to pilots to

assist them in determining when they have exited an

area. The various location signs are described below.

1. Taxiway Location Sign. This sign has a

black background with a yellow inscription and

yellow border as shown in FIG 2−3−30. The

inscription is the designation of the taxiway on which

the aircraft is located. These signs are installed along

taxiways either by themselves or in conjunction with

direction signs or runway holding position signs. 

(See FIG 2−3−35 and FIG 2−3−31.)
AIM 7/26/12

2−3−24 Airport Marking Aids and Signs

FIG 2−3−32

Runway Location Sign

FIG 2−3−33

Runway Boundary Sign

2. Runway Location Sign. This sign has a

black background with a yellow inscription and

yellow border as shown in FIG 2−3−32. The

inscription is the designation of the runway on which

the aircraft is located. These signs are intended to

complement the information available to pilots

through their magnetic compass and typically are

installed where the proximity of two or more runways

to one another could cause pilots to be confused as to

which runway they are on.

3. Runway Boundary Sign. This sign has a

yellow background with a black inscription with a

graphic depicting the pavement holding position

marking as shown in FIG 2−3−33. This sign, which

faces the runway and is visible to the pilot exiting the

runway, is located adjacent to the holding position

marking on the pavement. The sign is intended to

provide pilots with another visual cue which they can

use as a guide in deciding when they are “clear of the

runway.”
7/26/12 AIM

Airport Marking Aids and Signs 2−3−25

FIG 2−3−34

ILS Critical Area Boundary Sign

4. ILS Critical Area Boundary Sign. This

sign has a yellow background with a black inscription

with a graphic depicting the ILS pavement holding

position marking as shown in FIG 2−3−34. This sign

is located adjacent to the ILS holding position

marking on the pavement and can be seen by pilots

leaving the critical area. The sign is intended to

provide pilots with another visual cue which they can

use as a guide in deciding when they are “clear of the

ILS critical area.”

2−3−10. Direction Signs

a. Direction signs have a yellow background with

a black inscription. The inscription identifies the

designation(s) of the intersecting taxiway(s) leading

out of the intersection that a pilot would normally be

expected to turn onto or hold short of. Each

designation is accompanied by an arrow indicating

the direction of the turn.

b. Except as noted in subparagraph e, each

taxiway designation shown on the sign is accompanied by only one arrow. When more than one taxiway

designation is shown on the sign each designation and

its associated arrow is separated from the other

taxiway designations by either a vertical message

divider or a taxiway location sign as shown in

FIG 2−3−35.

c. Direction signs are normally located on the left

prior to the intersection. When used on a runway to

indicate an exit, the sign is located on the same side

of the runway as the exit. FIG 2−3−36 shows a

direction sign used to indicate a runway exit.

d. The taxiway designations and their associated

arrows on the sign are arranged clockwise starting

from the first taxiway on the pilot’s left. 

(See FIG 2−3−35.)

e. If a location sign is located with the direction

signs, it is placed so that the designations for all turns

to the left will be to the left of the location sign; the

designations for continuing straight ahead or for all

turns to the right would be located to the right of the

location sign. (See FIG 2−3−35.)

f. When the intersection is comprised of only one

crossing taxiway, it is permissible to have two arrows

associated with the crossing taxiway as shown in

FIG 2−3−37. In this case, the location sign is located

to the left of the direction sign.
AIM 7/26/12

2−3−26 Airport Marking Aids and Signs

FIG 2−3−35

Direction Sign Array with Location Sign on Far Side of Intersection

FIG 2−3−36

Direction Sign for Runway Exit
7/26/12 AIM

Airport Marking Aids and Signs 2−3−27

FIG 2−3−37

Direction Sign Array for Simple Intersection
AIM 7/26/12

2−3−28 Airport Marking Aids and Signs

FIG 2−3−38

Destination Sign for Military Area

FIG 2−3−39

Destination Sign for Common Taxiing Route to Two Runways

2−3−11. Destination Signs

a. Destination signs also have a yellow background with a black inscription indicating a

destination on the airport. These signs always have an

arrow showing the direction of the taxiing route to

that destination. FIG 2−3−38 is an example of a

typical destination sign. When the arrow on the

destination sign indicates a turn, the sign is located

prior to the intersection.

b. Destinations commonly shown on these types

of signs include runways, aprons, terminals, military

areas, civil aviation areas, cargo areas, international

areas, and fixed base operators. An abbreviation may

be used as the inscription on the sign for some of these

destinations.

c. When the inscription for two or more

destinations having a common taxiing route are

placed on a sign, the destinations are separated by a

“dot” () and one arrow would be used as shown in

FIG 2−3−39. When the inscription on a sign contains

two or more destinations having different taxiing

routes, each destination will be accompanied by an

arrow and will be separated from the other

destinations on the sign with a vertical black message

divider as shown in FIG 2−3−40.
7/26/12 AIM

Airport Marking Aids and Signs 2−3−29

FIG 2−3−40

Destination Sign for Different Taxiing Routes to Two Runways

2−3−12. Information Signs

Information signs have a yellow background with a

black inscription. They are used to provide the pilot

with information on such things as areas that cannot

be seen from the control tower, applicable radio

frequencies, and noise abatement procedures. The

airport operator determines the need, size, and

location for these signs.

2−3−13. Runway Distance Remaining Signs

Runway distance remaining signs have a black

background with a white numeral inscription and

may be installed along one or both side(s) of the

runway. The number on the signs indicates the

distance (in thousands of feet) of landing runway

remaining. The last sign, i.e., the sign with the

numeral “1,” will be located at least 950 feet from the

runway end. FIG 2−3−41 shows an example of a

runway distance remaining sign.

FIG 2−3−41

Runway Distance Remaining Sign Indicating 

3,000 feet of Runway Remaining

3
AIM 7/26/12

2−3−30 Airport Marking Aids and Signs

2−3−14. Aircraft Arresting Systems

a. Certain airports are equipped with a means of

rapidly stopping military aircraft on a runway. This

equipment, normally referred to as EMERGENCY

ARRESTING GEAR, generally consists of pendant

cables supported over the runway surface by rubber

“donuts.” Although most devices are located in the

overrun areas, a few of these arresting systems have

cables stretched over the operational areas near the

ends of a runway.

b. Arresting cables which cross over a runway

require special markings on the runway to identify

the cable location. These markings consist of 10 feet

diameter solid circles painted “identification yellow,” 30 feet on center, perpendicular to the runway

centerline across the entire runway width. Additional

details are contained in AC 150/5220−9, Aircraft

Arresting Systems for Joint Civil/Military Airports.

NOTE−

Aircraft operations on the runway are not restricted by the

installation of aircraft arresting devices.

c. Engineered materials arresting systems

(EMAS). EMAS, which are constructed of high

energy−absorbing materials of selected strength, are

located in the safety area beyond the end of the

runway. They are designed to crush under the weight

of commercial aircraft and they exert deceleration

forces on the landing gear. These systems do not

affect the normal landing and takeoff of airplanes.

More information concerning EMAS is in FAA

Advisory Circular AC 150/5220−22, Engineered

Materials Arresting Systems (EMAS) for Aircraft

Overruns.

NOTE−

EMAS may be located as close as 35 feet beyond the end of

the runway. Aircraft should never taxi or drive across the

runway.

FIG 2−3−42

Engineered Materials Arresting System (EMAS)
7/26/12 AIM

Airport Marking Aids and Signs 2−3−31

2−3−15. Security Identifications Display

Area (Airport Ramp Area)

a. Security Identification Display Areas (SIDA)

are limited access areas that require a badge issued in

accordance with procedures in CFR 49 Part 1542.

Movement through or into these areas is prohibited

without proper identification being displayed. If you

are unsure of the location of a SIDA, contact the

airport authority for additional information. Airports

that have a SIDA must have the following

information available:

1. A description and map detailing boundaries

and pertinent features;

2. Measures used to perform the access control

functions required under CFR 49 Part

1542.201(b)(1);

3. Procedures to control movement within the

secured area, including identification media required

under CFR 49 Part 1542.201(b)(3); and

4. A description of the notification signs

required under CFR 49 Part 1542.201(b)(6).

b. Pilots or passengers without proper identification that are observed entering a SIDA (ramp area)

may be reported to TSA or airport security. Pilots are

advised to brief passengers accordingly.

7/26/12 AIM

General 3−1−1

Chapter 3. Airspace

Section 1. General

3−1−1. General

a. There are two categories of airspace or airspace

areas:

1. Regulatory (Class A, B, C, D and E airspace

areas, restricted and prohibited areas); and

2. Nonregulatory (military operations areas

(MOAs), warning areas, alert areas, and controlled

firing areas).

NOTE−

Additional information on special use airspace (prohibited

areas, restricted areas, warning areas, MOAs, alert areas

and controlled firing areas) may be found in Chapter 3,

Airspace, Section 4, Special Use Airspace, paragraphs 3−4−1 through 3−4−7.

b. Within these two categories, there are four

types:

1. Controlled,

2. Uncontrolled,

3. Special use, and

4. Other airspace.

c. The categories and types of airspace are dictated

by:

1. The complexity or density of aircraft

movements,

2. The nature of the operations conducted

within the airspace,

3. The level of safety required, and

4. The national and public interest.

d. It is important that pilots be familiar with the

operational requirements for each of the various types

or classes of airspace. Subsequent sections will cover

each class in sufficient detail to facilitate

understanding.

3−1−2. General Dimensions of Airspace

Segments

Refer to Code of Federal Regulations (CFRs) for

specific dimensions, exceptions, geographical areas

covered, exclusions, specific transponder or equipment requirements, and flight operations.

3−1−3. Hierarchy of Overlapping Airspace

Designations

a. When overlapping airspace designations apply

to the same airspace, the operating rules associated

with the more restrictive airspace designation apply.

b. For the purpose of clarification:

1. Class A airspace is more restrictive than

Class B, Class C, Class D, Class E, or Class G

airspace;

2. Class B airspace is more restrictive than

Class C, Class D, Class E, or Class G airspace;

3. Class C airspace is more restrictive than

Class D, Class E, or Class G airspace;

4. Class D airspace is more restrictive than

Class E or Class G airspace; and

5. Class E is more restrictive than Class G

airspace.

3−1−4. Basic VFR Weather Minimums

a. No person may operate an aircraft under basic

VFR when the flight visibility is less, or at a distance

from clouds that is less, than that prescribed for the

corresponding altitude and class of airspace. 

(See TBL 3−1−1.)

NOTE−

Student pilots must comply with 14 CFR Section 61.89(a)

(6) and (7).

b. Except as provided in 14 CFR Section 91.157,

Special VFR Weather Minimums, no person may

operate an aircraft beneath the ceiling under VFR

within the lateral boundaries of controlled airspace

designated to the surface for an airport when the

ceiling is less than 1,000 feet. (See 14 CFR

Section 91.155(c).)
AIM 7/26/12

3−1−2 General

TBL 3−1−1

Basic VFR Weather Minimums

Airspace Flight Visibility Distance from Clouds

Class A ........................................ Not Applicable Not Applicable

Class B ........................................ 3 statute miles Clear of Clouds

Class C ........................................ 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal

Class D ........................................ 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal

Class E

Less than 10,000 feet MSL ........................ 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal

At or above 10,000 feet MSL ...................... 5 statute miles 1,000 feet below

1,000 feet above

1 statute mile horizontal

Class G

1,200 feet or less above the surface (regardless of MSL

altitude).

Day, except as provided in section 91.155(b) .......... 1 statute mile Clear of clouds

Night, except as provided in section 91.155(b) ......... 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal

More than 1,200 feet above the surface but less than

10,000 feet MSL.

Day . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 statute mile 500 feet below

1,000 feet above

2,000 feet horizontal

Night ......................................... 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal

More than 1,200 feet above the surface and at or above

10,000 feet MSL. ................................

5 statute miles 1,000 feet below

1,000 feet above

1 statute mile horizontal

3−1−5. VFR Cruising Altitudes and Flight Levels

(See TBL 3−1−2.)

TBL 3−1−2

VFR Cruising Altitudes and Flight Levels

If your magnetic course 

(ground track) is:

And you are more than 3,000 feet above the

surface but below 18,000 feet MSL, fly:

And you are above 18,000 feet

MSL to FL 290, fly:

0to 179................ Odd thousands MSL, plus 500 feet 

(3,500; 5,500; 7,500, etc.)

Odd Flight Levels plus 500 feet

(FL 195; FL 215; FL 235, etc.)

180to 359.............. Even thousands MSL, plus 500 feet 

(4,500; 6,500; 8,500, etc.)

Even Flight Levels plus 500 feet

(FL 185; FL 205; FL 225, etc.)
7/26/12 AIM

Controlled Airspace 3−2−1

Section 2. Controlled Airspace

3−2−1. General

a. Controlled Airspace. A generic term that

covers the different classification of airspace

(Class A, Class B, Class C, Class D, and Class E

airspace) and defined dimensions within which air

traffic control service is provided to IFR flights and

to VFR flights in accordance with the airspace

classification. (See FIG 3−2−1.)

b. IFR Requirements. IFR operations in any

class of controlled airspace requires that a pilot must

file an IFR flight plan and receive an appropriate ATC

clearance.

c. IFR Separation. Standard IFR separation is

provided to all aircraft operating under IFR in

controlled airspace.

d. VFR Requirements. It is the responsibility of

the pilot to ensure that ATC clearance or radio

communication requirements are met prior to entry

into Class B, Class C, or Class D airspace. The pilot

retains this responsibility when receiving ATC radar

advisories. (See 14 CFR Part 91.)

e. Traffic Advisories. Traffic advisories will be

provided to all aircraft as the controller’s work

situation permits.

f. Safety Alerts. Safety Alerts are mandatory

services and are provided to ALL aircraft. There are

two types of Safety Alerts:

1. Terrain/Obstruction Alert. A Terrain/

Obstruction Alert is issued when, in the controller’s

judgment, an aircraft’s altitude places it in unsafe

proximity to terrain and/or obstructions; and

2. Aircraft Conflict/Mode C Intruder Alert.

 An Aircraft Conflict/Mode C Intruder Alert is issued

if the controller observes another aircraft which

places it in an unsafe proximity. When feasible, the

controller will offer the pilot an alternative course of

action.

FIG 3−2−1

Airspace Classes

MSL - mean sea level

AGL - above ground level

FL - flight level

CLASS B CLASS B

CLASS C CLASS C

CLASS E CLASS E

CLASS D CLASS D

CLASS G CLASS G CLASS G CLASS G CLASS G CLASS G

Nontowered

Airport

Nontowered

Airport

FL 600

18,000 MSL

FL 600

18,000 MSL

14,500 MSL 14,500 MSL

700 AGL 1,200 AGL

CLASS A CLASS A
AIM 7/26/12

3−2−2 Controlled Airspace

g. Ultralight Vehicles. No person may operate an

ultralight vehicle within Class A, Class B, Class C, or

Class D airspace or within the lateral boundaries of

the surface area of Class E airspace designated for an

airport unless that person has prior authorization from

the ATC facility having jurisdiction over that

airspace. (See 14 CFR Part 103.)

h. Unmanned Free Balloons. Unless otherwise

authorized by ATC, no person may operate an

unmanned free balloon below 2,000 feet above the

surface within the lateral boundaries of Class B,

Class C, Class D, or Class E airspace designated for

an airport. (See 14 CFR Part 101.)

i. Parachute Jumps. No person may make a

parachute jump, and no pilot−in−command may

allow a parachute jump to be made from that aircraft,

in or into Class A, Class B, Class C, or Class D

airspace without, or in violation of, the terms of an

ATC authorization issued by the ATC facility having

jurisdiction over the airspace. (See 14 CFR Part 105.)

3−2−2. Class A Airspace

a. Definition. Generally, that airspace from

18,000 feet MSL up to and including FL 600,

including the airspace overlying the waters within

12 nautical miles of the coast of the 48 contiguous

States and Alaska; and designated international

airspace beyond 12 nautical miles of the coast of the

48 contiguous States and Alaska within areas of

domestic radio navigational signal or ATC radar

coverage, and within which domestic procedures are

applied.

b. Operating Rules and Pilot/Equipment

Requirements. Unless otherwise authorized, all

persons must operate their aircraft under IFR. (See

14 CFR Section 71.33 and 14 CFR Section 91.167

through 14 CFR Section 91.193.)

c. Charts. Class A airspace is not specifically

charted.

3−2−3. Class B Airspace

a. Definition. Generally, that airspace from the

surface to 10,000 feet MSL surrounding the nation’s

busiest airports in terms of IFR operations or

passenger enplanements. The configuration of each

Class B airspace area is individually tailored and

consists of a surface area and two or more layers

(some Class B airspace areas resemble upside-down

wedding cakes), and is designed to contain all

published instrument procedures once an aircraft

enters the airspace. An ATC clearance is required for

all aircraft to operate in the area, and all aircraft that

are so cleared receive separation services within the

airspace. The cloud clearance requirement for VFR

operations is “clear of clouds.”

b. Operating Rules and Pilot/Equipment

Requirements for VFR Operations. Regardless of

weather conditions, an ATC clearance is required

prior to operating within Class B airspace. Pilots

should not request a clearance to operate within

Class B airspace unless the requirements of 14 CFR

Section 91.215 and 14 CFR Section 91.131 are met.

Included among these requirements are:

1. Unless otherwise authorized by ATC, aircraft

must be equipped with an operable two-way radio

capable of communicating with ATC on appropriate

frequencies for that Class B airspace.

2. No person may take off or land a civil aircraft

at the following primary airports within Class B

airspace unless the pilot−in−command holds at least

a private pilot certificate:

(a) Andrews Air Force Base, MD

(b) Atlanta Hartsfield Airport, GA

(c) Boston Logan Airport, MA

(d) Chicago O’Hare Intl. Airport, IL

(e) Dallas/Fort Worth Intl. Airport, TX

(f) Los Angeles Intl. Airport, CA

(g) Miami Intl. Airport, FL

(h) Newark Intl. Airport, NJ

(i) New York Kennedy Airport, NY

(j) New York La Guardia Airport, NY

(k) Ronald Reagan Washington National

Airport, DC

(l) San Francisco Intl. Airport, CA

3. No person may take off or land a civil aircraft

at an airport within Class B airspace or operate a civil

aircraft within Class B airspace unless:

(a) The pilot−in−command holds at least a

private pilot certificate; or
7/26/12 AIM

Controlled Airspace 3−2−3

(b) The aircraft is operated by a student pilot

or recreational pilot who seeks private pilot

certification and has met the requirements of 14 CFR

Section 61.95.

4. Unless otherwise authorized by ATC, each

person operating a large turbine engine-powered

airplane to or from a primary airport must operate at

or above the designated floors while within the lateral

limits of Class B airspace.

5. Unless otherwise authorized by ATC, each

aircraft must be equipped as follows:

(a) For IFR operations, an operable VOR or

TACAN receiver; and

(b) For all operations, a two-way radio

capable of communications with ATC on appropriate

frequencies for that area; and

(c) Unless otherwise authorized by ATC, an

operable radar beacon transponder with automatic

altitude reporting equipment.

NOTE−

ATC may, upon notification, immediately authorize a

deviation from the altitude reporting equipment requirement; however, a request for a deviation from the 4096

transponder equipment requirement must be submitted to

the controlling ATC facility at least one hour before the

proposed operation.

REFERENCE−

AIM, Transponder Operation, Paragraph 4−1−20.

6. Mode C Veil. The airspace within 30 nautical miles of an airport listed in Appendix D, Section 1

of 14 CFR Part 91 (generally primary airports within

Class B airspace areas), from the surface upward to

10,000 feet MSL. Unless otherwise authorized by

ATC, aircraft operating within this airspace must be

equipped with automatic pressure altitude reporting

equipment having Mode C capability.

However, an aircraft that was not originally

certificated with an engine−driven electrical system

or which has not subsequently been certified with a

system installed may conduct operations within a

Mode C veil provided the aircraft remains outside

Class A, B or C airspace; and below the altitude of the

ceiling of a Class B or Class C airspace area

designated for an airport or 10,000 feet MSL,

whichever is lower.

c. Charts. Class B airspace is charted on

Sectional Charts, IFR En Route Low Altitude, and

Terminal Area Charts.

d. Flight Procedures.

1. Flights. Aircraft within Class B airspace are

required to operate in accordance with current IFR

procedures. A clearance for a visual approach to a

primary airport is not authorization for turbine−

powered airplanes to operate below the designated

floors of the Class B airspace.

2. VFR Flights.

(a) Arriving aircraft must obtain an ATC

clearance prior to entering Class B airspace and must

contact ATC on the appropriate frequency, and in

relation to geographical fixes shown on local charts.

Although a pilot may be operating beneath the floor

of the Class B airspace on initial contact,

communications with ATC should be established in

relation to the points indicated for spacing and

sequencing purposes.

(b) Departing aircraft require a clearance to

depart Class B airspace and should advise the

clearance delivery position of their intended altitude

and route of flight. ATC will normally advise VFR

aircraft when leaving the geographical limits of the

Class B airspace. Radar service is not automatically

terminated with this advisory unless specifically

stated by the controller.

(c) Aircraft not landing or departing the

primary airport may obtain an ATC clearance to

transit the Class B airspace when traffic conditions

permit and provided the requirements of 14 CFR

Section 91.131 are met. Such VFR aircraft are

encouraged, to the extent possible, to operate at

altitudes above or below the Class B airspace or

transit through established VFR corridors. Pilots

operating in VFR corridors are urged to use frequency

122.750 MHz for the exchange of aircraft position

information.

e. ATC Clearances and Separation. An ATC

clearance is required to enter and operate within

Class B airspace. VFR pilots are provided sequencing and separation from other aircraft while operating

within Class B airspace.

REFERENCE−

AIM, Terminal Radar Services for VFR Aircraft, Paragraph 4−1−18.
AIM 7/26/12

3−2−4 Controlled Airspace

NOTE−

1. Separation and sequencing of VFR aircraft will be

suspended in the event of a radar outage as this service is

dependent on radar. The pilot will be advised that the

service is not available and issued wind, runway

information and the time or place to contact the tower.

2. Separation of VFR aircraft will be suspended during

CENRAP operations. Traffic advisories and sequencing to

the primary airport will be provided on a workload

permitting basis. The pilot will be advised when center

radar presentation (CENRAP) is in use.

1. VFR aircraft are separated from all VFR/IFR

aircraft which weigh 19,000 pounds or less by a

minimum of:

(a) Target resolution, or

(b) 500 feet vertical separation, or

(c) Visual separation.

2. VFR aircraft are separated from all VFR/IFR

aircraft which weigh more than 19,000 and turbojets

by no less than:

(a) 1 1/2 miles lateral separation, or

(b) 500 feet vertical separation, or

(c) Visual separation.

3. This program is not to be interpreted as

relieving pilots of their responsibilities to see and

avoid other traffic operating in basic VFR weather

conditions, to adjust their operations and flight path

as necessary to preclude serious wake encounters, to

maintain appropriate terrain and obstruction clearance or to remain in weather conditions equal to or

better than the minimums required by 14 CFR

Section 91.155. Approach control should be advised

and a revised clearance or instruction obtained when

compliance with an assigned route, heading and/or

altitude is likely to compromise pilot responsibility

with respect to terrain and obstruction clearance,

vortex exposure, and weather minimums.

4. ATC may assign altitudes to VFR aircraft that

do not conform to 14 CFR Section 91.159.

“RESUME APPROPRIATE VFR ALTITUDES”

will be broadcast when the altitude assignment is no

longer needed for separation or when leaving Class B

airspace. Pilots must return to an altitude that

conforms to 14 CFR Section 91.159.

f. Proximity operations. VFR aircraft operating

in proximity to Class B airspace are cautioned against

operating too closely to the boundaries, especially

where the floor of the Class B airspace is 3,000 feet

or less above the surface or where VFR cruise

altitudes are at or near the floor of higher levels.

Observance of this precaution will reduce the

potential for encountering an aircraft operating at the

altitudes of Class B floors. Additionally, VFR aircraft

are encouraged to utilize the VFR Planning Chart as

a tool for planning flight in proximity to Class B

airspace. Charted VFR Flyway Planning Charts are

published on the back of the existing VFR Terminal

Area Charts.

3−2−4. Class C Airspace

a. Definition. Generally, that airspace from the

surface to 4,000 feet above the airport elevation

(charted in MSL) surrounding those airports that have

an operational control tower, are serviced by a radar

approach control, and that have a certain number of

IFR operations or passenger enplanements. Although

the configuration of each Class C airspace area is

individually tailored, the airspace usually consists of

a 5 NM radius core surface area that extends from the

surface up to 4,000 feet above the airport elevation,

and a 10 NM radius shelf area that extends no lower

than 1,200 feet up to 4,000 feet above the airport

elevation.

b. Charts. Class C airspace is charted on

Sectional Charts, IFR En Route Low Altitude, and

Terminal Area Charts where appropriate.

c. Operating Rules and Pilot/Equipment

Requirements:

1. Pilot Certification. No specific certification required.

2. Equipment.

(a) Two-way radio; and

(b) Unless otherwise authorized by ATC, an

operable radar beacon transponder with automatic

altitude reporting equipment.

NOTE−

See paragraph 4−1−20, Transponder Operation, subparagraph f2(c) for Mode C transponder requirements for

operating above Class C airspace.

3. Arrival or Through Flight Entry Requirements. Two-way radio communication must be

established with the ATC facility providing ATC

services prior to entry and thereafter maintain those

communications while in Class C airspace. Pilots of
7/26/12 AIM

Controlled Airspace 3−2−5

arriving aircraft should contact the Class C airspace

ATC facility on the publicized frequency and give

their position, altitude, radar beacon code, destination, and request Class C service. Radio contact

should be initiated far enough from the Class C

airspace boundary to preclude entering Class C

airspace before two-way radio communications are

established.

NOTE−

1. If the controller responds to a radio call with, “(aircraft

callsign) standby,” radio communications have been

established and the pilot can enter the Class C airspace.

2. If workload or traffic conditions prevent immediate

provision of Class C services, the controller will inform the

pilot to remain outside the Class C airspace until

conditions permit the services to be provided.

3. It is important to understand that if the controller

responds to the initial radio call without using the aircraft

identification, radio communications have not been

established and the pilot may not enter the Class C

airspace.

4. Though not requiring regulatory action, Class C

airspace areas have a procedural Outer Area. Normally

this area is 20 NM from the primary Class C airspace

airport. Its vertical limit extends from the lower limits of

radio/radar coverage up to the ceiling of the approach

control’s delegated airspace, excluding the Class C

airspace itself, and other airspace as appropriate. (This

outer area is not charted.)

5. Pilots approaching an airport with Class C service

should be aware that if they descend below the base altitude

of the 5 to 10 mile shelf during an instrument or visual

approach, they may encounter nontransponder, VFR

aircraft.

EXAMPLE−

1. [Aircraft callsign] “remain outside the Class Charlie

airspace and standby.”

2. “Aircraft calling Dulles approach control, standby.”

4. Departures from:

(a) A primary or satellite airport with an

operating control tower. Two-way radio communications must be established and maintained with the

control tower, and thereafter as instructed by ATC

while operating in Class C airspace.

(b) A satellite airport without an operating

control tower. Two-way radio communications must

be established as soon as practicable after departing

with the ATC facility having jurisdiction over the

Class C airspace.

5. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an

aircraft at or below 2,500 feet above the surface

within 4 nautical miles of the primary airport of a

Class C airspace area at an indicated airspeed of more

than 200 knots (230 mph).

d. Air Traffic Services. When two-way radio

communications and radar contact are established, all

participating VFR aircraft are:

1. Sequenced to the primary airport.

2. Provided Class C services within the Class C

airspace and the outer area.

3. Provided basic radar services beyond the

outer area on a workload permitting basis. This can be

terminated by the controller if workload dictates.

e. Aircraft Separation. Separation is provided

within the Class C airspace and the outer area after

two-way radio communications and radar contact are

established. VFR aircraft are separated from IFR

aircraft within the Class C airspace by any of the

following:

1. Visual separation.

2. 500 feet vertical; except when operating

beneath a heavy jet.

3. Target resolution.

NOTE−

1. Separation and sequencing of VFR aircraft will be

suspended in the event of a radar outage as this service is

dependent on radar. The pilot will be advised that the

service is not available and issued wind, runway

information and the time or place to contact the tower.

2. Separation of VFR aircraft will be suspended during

CENRAP operations. Traffic advisories and sequencing to

the primary airport will be provided on a workload

permitting basis. The pilot will be advised when CENRAP

is in use.

3. Pilot participation is voluntary within the outer area

and can be discontinued, within the outer area, at the pilot’s

request. Class C services will be provided in the outer area

unless the pilot requests termination of the service.

4. Some facilities provide Class C services only during

published hours. At other times, terminal IFR radar service

will be provided. It is important to note that the

communications and transponder requirements are

dependent of the class of airspace established outside of the

published hours.
AIM 7/26/12

3−2−6 Controlled Airspace

f. Secondary Airports

1. In some locations Class C airspace may

overlie the Class D surface area of a secondary

airport. In order to allow that control tower to provide

service to aircraft, portions of the overlapping

Class C airspace may be procedurally excluded when

the secondary airport tower is in operation. Aircraft

operating in these procedurally excluded areas will

only be provided airport traffic control services when

in communication with the secondary airport tower.

2. Aircraft proceeding inbound to a satellite

airport will be terminated at a sufficient distance to

allow time to change to the appropriate tower or

advisory frequency. Class C services to these aircraft

will be discontinued when the aircraft is instructed to

contact the tower or change to advisory frequency.

3. Aircraft departing secondary controlled

airports will not receive Class C services until they

have been radar identified and two-way communications have been established with the Class C airspace

facility.

4. This program is not to be interpreted as

relieving pilots of their responsibilities to see and

avoid other traffic operating in basic VFR weather

conditions, to adjust their operations and flight path

as necessary to preclude serious wake encounters, to

maintain appropriate terrain and obstruction clearance or to remain in weather conditions equal to or

better than the minimums required by 14 CFR

Section 91.155. Approach control should be advised

and a revised clearance or instruction obtained when

compliance with an assigned route, heading and/or

altitude is likely to compromise pilot responsibility

with respect to terrain and obstruction clearance,

vortex exposure, and weather minimums.

g. Class C Airspace Areas by State

These states currently have designated Class C

airspace areas that are depicted on sectional charts.

Pilots should consult current sectional charts and

NOTAMs for the latest information on services

available. Pilots should be aware that some Class C

airspace underlies or is adjacent to Class B airspace.

(See TBL 3−2−1.)

TBL 3−2−1

Class C Airspace Areas by State

State/City Airport

ALABAMA

Birmingham ......... Birmingham−Shuttlesworth 

International

Huntsville ........... International−Carl T Jones Fld

Mobile .............. Regional

ALASKA

Anchorage ........... Ted Stevens International

ARIZONA

Davis−Monthan ....... AFB

Tucson .............. International

ARKANSAS

Fayetteville (Springdale) Northwest Arkansas Regional

Little Rock .......... Adams Field

CALIFORNIA

Beale ............... AFB

Burbank ............ Bob Hope

Fresno .............. Yosemite International

Monterey ............ Peninsula

Oakland ............. Metropolitan Oakland 

International

Ontario ............. International

Riverside ............ March AFB

Sacramento .......... International

San Jose ............ Norman Y. Mineta International

Santa Ana ........... John Wayne/Orange County

Santa Barbara ........ Municipal

COLORADO

Colorado Springs ..... Municipal

CONNECTICUT

Windsor Locks ....... Bradley International

FLORIDA

Daytona Beach ....... International

Fort Lauderdale ....... Hollywood International

Fort Myers .......... SW Florida Regional

Jacksonville .......... International

Orlando ............. Sanford International

Palm Beach .......... International

Pensacola ........... NAS

Pensacola ........... Regional

Sarasota ............. Bradenton International

Tallahassee .......... Regional

Whiting ............. NAS

GEORGIA

Columbus ........... Metropolitan

Savannah ............ Hilton Head International

HAWAII

Kahului ............. Kahului

IDAHO

Boise ............... Air Terminal

ILLINOIS

Champaign .......... Urbana U of Illinois−Willard

Chicago ............. Midway International
7/26/12 AIM

Controlled Airspace 3−2−7

State/City Airport

Moline .............. Quad City International

Peoria .............. Greater Peoria Regional

Springfield .......... Abraham Lincoln Capital

INDIANA

Evansville ........... Regional

Fort Wayne .......... International

Indianapolis .......... International

South Bend .......... Regional

IOWA

Cedar Rapids ......... The Eastern Iowa

Des Moines .......... International

KANSAS

Wichita ............. Mid−Continent

KENTUCKY

Lexington ........... Blue Grass

Louisville ........... International−Standiford Field

LOUISIANA

Baton Rouge ......... Metropolitan, Ryan Field

Lafayette ............ Regional

Shreveport ........... Barksdale AFB

Shreveport ........... Regional

MAINE

Bangor ............. International

Portland ............. International Jetport

MICHIGAN

Flint ................ Bishop International

Grand Rapids ........ Gerald R. Ford International

Lansing ............. Capital City

MISSISSIPPI

Columbus ........... AFB

Jackson ............. Jackson−Evers International

MISSOURI

Springfield .......... Springfield−Branson National

MONTANA

Billings ............. Logan International

NEBRASKA

Lincoln ............. Lincoln

Omaha .............. Eppley Airfield

Offutt ............... AFB

NEVADA

Reno ............... Reno/Tahoe International

NEW HAMPSHIRE

Manchester .......... Manchester

NEW JERSEY

Atlantic City ......... International

NEW MEXICO

Albuquerque ......... International Sunport

NEW YORK

Albany ............. International

Buffalo ............. Niagara International

Islip ................ Long Island MacArthur

Rochester ........... Greater Rochester International

Syracuse ............ Hancock International

State/City Airport

NORTH CAROLINA

Asheville ........... Regional

Fayetteville .......... Regional/Grannis Field

Greensboro .......... Piedmont Triad International

Pope ............... AFB

Raleigh ............. Raleigh−Durham International

OHIO

Akron .............. Akron−Canton Regional

Columbus ........... Port Columbus International

Dayton ............. James M. Cox International

Toledo .............. Express

OKLAHOMA

Oklahoma City ....... Will Rogers World

Tinker .............. AFB

Tulsa ............... International

OREGON

Portland ............. International

PENNSYLVANIA

Allentown ........... Lehigh Valley International

PUERTO RICO

San Juan ............ Luis Munoz Marin International

RHODE ISLAND

Providence .......... Theodore Francis Green State

SOUTH CAROLINA

Charleston ........... AFB/International

Columbia ............ Metropolitan

Greer ............... Greenville−Spartanburg 

International

Myrtle Beach ........ Myrtle Beach International

Shaw ............... AFB

TENNESSEE

Chattanooga ......... Lovell Field

Knoxville ........... McGhee Tyson

Nashville ............ International

TEXAS

Abilene ............. Regional

Amarillo ............ Rick Husband International

Austin .............. Austin−Bergstrom International

Corpus Christi ........ International

Dyess .............. AFB

El Paso ............. International

Harlingen ........... Valley International

Laughlin ............ AFB

Lubbock ............ Preston Smith International

Midland ............. International

San Antonio ......... International

VERMONT

Burlington ........... International

VIRGIN ISLANDS

St. Thomas .......... Charlotte Amalie Cyril E. King
AIM 7/26/12

3−2−8 Controlled Airspace

State/City Airport

VIRGINIA

Richmond ........... International

Norfolk ............. International

Roanoke ............ Regional/Woodrum Field

WASHINGTON

Point Roberts ........ Vancouver International

Spokane ............ Fairchild AFB

Spokane ............ International

Whidbey Island ....... NAS, Ault Field

WEST VIRGINIA

Charleston ........... Yeager

WISCONSIN

Green Bay ........... Austin Straubel International

Madison ............ Dane County Regional−Traux

Field

Milwaukee .......... General Mitchell International

3−2−5. Class D Airspace

a. Definition. Generally, that airspace from the

surface to 2,500 feet above the airport elevation

(charted in MSL) surrounding those airports that have

an operational control tower. The configuration of

each Class D airspace area is individually tailored and

when instrument procedures are published, the

airspace will normally be designed to contain the

procedures.

b. Operating Rules and Pilot/Equipment

Requirements:

1. Pilot Certification. No specific certification required.

2. Equipment. Unless otherwise authorized

by ATC, an operable two−way radio is required.

3. Arrival or Through Flight Entry

Requirements. Two−way radio communication

must be established with the ATC facility providing

ATC services prior to entry and thereafter maintain

those communications while in the Class D airspace.

Pilots of arriving aircraft should contact the control

tower on the publicized frequency and give their

position, altitude, destination, and any request(s).

Radio contact should be initiated far enough from the

Class D airspace boundary to preclude entering the

Class D airspace before two−way radio communications are established.

NOTE−

1. If the controller responds to a radio call with, “[aircraft

callsign] standby,” radio communications have been

established and the pilot can enter the Class D airspace.

2. If workload or traffic conditions prevent immediate

entry into Class D airspace, the controller will inform the

pilot to remain outside the Class D airspace until

conditions permit entry.

EXAMPLE−

1. “[Aircraft callsign] remain outside the Class Delta

airspace and standby.”

It is important to understand that if the controller responds

to the initial radio call without using the aircraft callsign,

radio communications have not been established and the

pilot may not enter the Class D airspace.

2. “Aircraft calling Manassas tower standby.”

At those airports where the control tower does not operate

24 hours a day, the operating hours of the tower will be

listed on the appropriate charts and in the A/FD. During

the hours the tower is not in operation, the Class E surface

area rules or a combination of Class E rules to 700 feet

above ground level and Class G rules to the surface will

become applicable. Check the A/FD for specifics.

4. Departures from:

(a) A primary or satellite airport with an

operating control tower. Two-way radio communications must be established and maintained with the

control tower, and thereafter as instructed by ATC

while operating in the Class D airspace.

(b) A satellite airport without an operating

control tower. Two-way radio communications must

be established as soon as practicable after departing

with the ATC facility having jurisdiction over the

Class D airspace as soon as practicable after

departing.

5. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an

aircraft at or below 2,500 feet above the surface

within 4 nautical miles of the primary airport of a

Class D airspace area at an indicated airspeed of more

than 200 knots (230 mph).

c. Class D airspace areas are depicted on Sectional

and Terminal charts with blue segmented lines, and

on IFR En Route Lows with a boxed [D].

d. Arrival extensions for instrument approach

procedures may be Class D or Class E airspace. As a

general rule, if all extensions are 2 miles or less, they

remain part of the Class D surface area. However, if

any one extension is greater than 2 miles, then all

extensions become Class E.

e. Separation for VFR Aircraft. No separation

services are provided to VFR aircraft.
7/26/12 AIM

Controlled Airspace 3−2−9

3−2−6. Class E Airspace

a. Definition. Generally, if the airspace is not

Class A, Class B, Class C, or Class D, and it is

controlled airspace, it is Class E airspace.

b. Operating Rules and Pilot/Equipment

Requirements:

1. Pilot Certification. No specific certification required.

2. Equipment. No specific equipment

required by the airspace.

3. Arrival or Through Flight Entry Requirements. No specific requirements.

c. Charts. Class E airspace below 14,500 feet

MSL is charted on Sectional, Terminal, and IFR

Enroute Low Altitude charts.

d. Vertical limits. Except for 18,000 feet MSL,

Class E airspace has no defined vertical limit but

rather it extends upward from either the surface or a

designated altitude to the overlying or adjacent

controlled airspace.

e. Types of Class E Airspace:

1. Surface area designated for an airport. When designated as a surface area for an

airport, the airspace will be configured to contain all

instrument procedures.

2. Extension to a surface area. There are

Class E airspace areas that serve as extensions to

Class B, Class C, and Class D surface areas

designated for an airport. Such airspace provides

controlled airspace to contain standard instrument

approach procedures without imposing a communications requirement on pilots operating under VFR.

3. Airspace used for transition. There are

Class E airspace areas beginning at either 700 or

1,200 feet AGL used to transition to/from the

terminal or en route environment.

4. En Route Domestic Areas. There are

Class E airspace areas that extend upward from a

specified altitude and are en route domestic airspace

areas that provide controlled airspace in those areas

where there is a requirement to provide IFR en route

ATC services but the Federal airway system is

inadequate.

5. Federal Airways. The Federal airways are

Class E airspace areas and, unless otherwise

specified, extend upward from 1,200 feet to, but not

including, 18,000 feet MSL. The colored airways are

green, red, amber, and blue. The VOR airways are

classified as Domestic, Alaskan, and Hawaiian.

6. Offshore Airspace Areas. There are

Class E airspace areas that extend upward from a

specified altitude to, but not including, 18,000 feet

MSL and are designated as offshore airspace areas.

These areas provide controlled airspace beyond

12 miles from the coast of the U.S. in those areas

where there is a requirement to provide IFR en route

ATC services and within which the U.S. is applying

domestic procedures.

7. Unless designated at a lower altitude, Class E

airspace begins at 14,500 feet MSL to, but not

including, 18,000 feet MSL overlying: the 48 contiguous States including the waters within 12 miles from

the coast of the 48 contiguous States; the District of

Columbia; Alaska, including the waters within

12 miles from the coast of Alaska, and that airspace

above FL 600; excluding the Alaska peninsula west

of long. 160 00’00’’W, and the airspace below

1,500 feet above the surface of the earth unless

specifically so designated.

f. Separation for VFR Aircraft. No separation

services are provided to VFR aircraft.

7/26/12 AIM

Class G Airspace 3−3−1

Section 3. Class G Airspace

3−3−1. General

Class G airspace (uncontrolled) is that portion of

airspace that has not been designated as Class A,

Class B, Class C, Class D, or Class E airspace.

3−3−2. VFR Requirements

Rules governing VFR flight have been adopted to

assist the pilot in meeting the responsibility to see and

avoid other aircraft. Minimum flight visibility and

distance from clouds required for VFR flight are

contained in 14 CFR Section 91.155.

(See TBL 3−1−1.)

3−3−3. IFR Requirements

a. Title 14 CFR specifies the pilot and aircraft

equipment requirements for IFR flight. Pilots are

reminded that in addition to altitude or flight level

requirements, 14 CFR Section 91.177 includes a

requirement to remain at least 1,000 feet (2,000 feet

in designated mountainous terrain) above the highest

obstacle within a horizontal distance of 4 nautical

miles from the course to be flown.

b. IFR Altitudes. 

(See TBL 3−3−1.)

TBL 3−3−1

IFR Altitudes

Class G Airspace

If your magnetic course 

(ground track) is:

And you are below 

18,000 feet MSL, fly:

0 to 179 Odd thousands MSL, (3,000; 5,000; 7,000, etc.)

180 to 359 Even thousands MSL, (2,000; 4,000; 6,000, etc.)

7/26/12 AIM

Special Use Airspace 3−4−1

Section 4. Special Use Airspace

3−4−1. General

a. Special use airspace consists of that airspace

wherein activities must be confined because of their

nature, or wherein limitations are imposed upon

aircraft operations that are not a part of those

activities, or both. Except for controlled firing areas,

special use airspace areas are depicted on aeronautical charts.

b. Prohibited and restricted areas are regulatory

special use airspace and are established in 14 CFR

Part 73 through the rulemaking process.

c. Warning areas, military operations areas

(MOAs), alert areas, and controlled firing areas

(CFAs) are nonregulatory special use airspace.

d. Special use airspace descriptions (except CFAs)

are contained in FAA Order JO 7400.8, Special Use

Airspace.

e. Special use airspace (except CFAs) are charted

on IFR or visual charts and include the hours of

operation, altitudes, and the controlling agency.

3−4−2. Prohibited Areas

Prohibited areas contain airspace of defined

dimensions identified by an area on the surface of the

earth within which the flight of aircraft is prohibited.

Such areas are established for security or other

reasons associated with the national welfare. These

areas are published in the Federal Register and are

depicted on aeronautical charts.

3−4−3. Restricted Areas

a. Restricted areas contain airspace identified by

an area on the surface of the earth within which the

flight of aircraft, while not wholly prohibited, is

subject to restrictions. Activities within these areas

must be confined because of their nature or

limitations imposed upon aircraft operations that are

not a part of those activities or both. Restricted areas

denote the existence of unusual, often invisible,

hazards to aircraft such as artillery firing, aerial

gunnery, or guided missiles. Penetration of restricted

areas without authorization from the using or

controlling agency may be extremely hazardous to

the aircraft and its occupants. Restricted areas are

published in the Federal Register and constitute

14 CFR Part 73.

b. ATC facilities apply the following procedures

when aircraft are operating on an IFR clearance

(including those cleared by ATC to maintain

VFR-on-top) via a route which lies within joint-use

restricted airspace.

1. If the restricted area is not active and has been

released to the controlling agency (FAA), the ATC

facility will allow the aircraft to operate in the

restricted airspace without issuing specific clearance

for it to do so.

2. If the restricted area is active and has not been

released to the controlling agency (FAA), the ATC

facility will issue a clearance which will ensure the

aircraft avoids the restricted airspace unless it is on an

approved altitude reservation mission or has obtained

its own permission to operate in the airspace and so

informs the controlling facility.

NOTE−

The above apply only to joint-use restricted airspace and

not to prohibited and nonjoint-use airspace. For the latter

categories, the ATC facility will issue a clearance so the

aircraft will avoid the restricted airspace unless it is on an

approved altitude reservation mission or has obtained its

own permission to operate in the airspace and so informs

the controlling facility.

c. Restricted airspace is depicted on the en route

chart appropriate for use at the altitude or flight level

being flown. For joint-use restricted areas, the name

of the controlling agency is shown on these charts.

For all prohibited areas and nonjoint-use restricted

areas, unless otherwise requested by the using

agency, the phrase “NO A/G” is shown.

3−4−4. Warning Areas

A warning area is airspace of defined dimensions,

extending from three nautical miles outward from the

coast of the U.S., that contains activity that may be

hazardous to nonparticipating aircraft. The purpose

of such warning areas is to warn nonparticipating

pilots of the potential danger. A warning area may be

located over domestic or international waters or both.
AIM 7/26/12

3−4−2 Special Use Airspace

3−4−5. Military Operations Areas

a. MOAs consist of airspace of defined vertical

and lateral limits established for the purpose of

separating certain military training activities from

IFR traffic. Whenever a MOA is being used,

nonparticipating IFR traffic may be cleared through

a MOA if IFR separation can be provided by ATC.

Otherwise, ATC will reroute or restrict nonparticipating IFR traffic.

b. Examples of activities conducted in MOAs

include, but are not limited to: air combat tactics, air

intercepts, aerobatics, formation training, and

low−altitude tactics. Military pilots flying in an active

MOA are exempted from the provisions of 14 CFR

Section 91.303(c) and (d) which prohibits aerobatic

flight within Class D and Class E surface areas, and

within Federal airways. Additionally, the Department

of Defense has been issued an authorization to

operate aircraft at indicated airspeeds in excess of

250 knots below 10,000 feet MSL within active

MOAs.

c. Pilots operating under VFR should exercise

extreme caution while flying within a MOA when

military activity is being conducted. The activity

status (active/inactive) of MOAs may change

frequently. Therefore, pilots should contact any FSS

within 100 miles of the area to obtain accurate

real-time information concerning the MOA hours of

operation. Prior to entering an active MOA, pilots

should contact the controlling agency for traffic

advisories.

d. MOAs are depicted on sectional, VFR Terminal

Area, and Enroute Low Altitude charts.

3−4−6. Alert Areas

Alert areas are depicted on aeronautical charts to

inform nonparticipating pilots of areas that may

contain a high volume of pilot training or an unusual

type of aerial activity. Pilots should be particularly

alert when flying in these areas. All activity within an

alert area must be conducted in accordance with

CFRs, without waiver, and pilots of participating

aircraft as well as pilots transiting the area must be

equally responsible for collision avoidance.

3−4−7. Controlled Firing Areas

CFAs contain activities which, if not conducted in a

controlled environment, could be hazardous to

nonparticipating aircraft. The distinguishing feature

of the CFA, as compared to other special use airspace,

is that its activities are suspended immediately when

spotter aircraft, radar, or ground lookout positions

indicate an aircraft might be approaching the area.

There is no need to chart CFAs since they do not cause

a nonparticipating aircraft to change its flight path.
7/26/12 AIM

Other Airspace Areas 3−5−1

Section 5. Other Airspace Areas

3−5−1. Airport Advisory/Information

Services

a. There are three advisory type services available

at selected airports.

1. Local Airport Advisory (LAA) service is

operated within 10 statute miles of an airport where

a control tower is not operating but where a FSS is

located on the airport. At such locations, the FSS

provides a complete local airport advisory service to

arriving and departing aircraft. During periods of fast

changing weather the FSS will automatically provide

Final Guard as part of the service from the time the

aircraft reports “on−final” or “taking−the−active−

runway” until the aircraft reports “on−the−ground” or

“airborne.”

NOTE−

Current policy, when requesting remote ATC services,

requires that a pilot monitor the automated weather

broadcast at the landing airport prior to requesting ATC

services. The FSS automatically provides Final Guard,

when appropriate, during LAA/Remote Airport Advisory

(RAA) operations. Final Guard is a value added

wind/altimeter monitoring service, which provides an

automatic wind and altimeter check during active weather

situations when the pilot reports on−final or taking the

active runway. During the landing or take−off operation

when the winds or altimeter are actively changing the FSS

will blind broadcast significant changes when the

specialist believes the change might affect the operation.

Pilots should acknowledge the first wind/altimeter check

but due to cockpit activity no acknowledgement is expected

for the blind broadcasts. It is prudent for a pilot to report

on−the−ground or airborne to end the service.

2. RAA service is operated within 10 statute

miles of specified high activity GA airports where a

control tower is not operating. Airports offering this

service are listed in the A/FD and the published

service hours may be changed by NOTAM D. Final

Guard is automatically provided with RAA.

3. Remote Airport Information Service (RAIS)

is provided in support of short term special events like

small to medium fly−ins. The service is advertised by

NOTAM D only. The FSS will not have access to a

continuous readout of the current winds and

altimeter; therefore, RAIS does not include weather

and/or Final Guard service. However, known traffic,

special event instructions, and all other services are

provided.

NOTE−

The airport authority and/or manager should request RAIS

support on official letterhead directly with the manager of

the FSS that will provide the service at least 60 days in

advance. Approval authority rests with the FSS manager

and is based on workload and resource availability.

REFERENCE−

AIM, Traffic Advisory Practices at Airports Without Operating Control

Towers, Paragraph 4−1−9.

b. It is not mandatory that pilots participate in the

Airport Advisory programs. Participation enhances

safety for everyone operating around busy GA

airports; therefore, everyone is encouraged to

participate and provide feedback that will help

improve the program.

3−5−2. Military Training Routes

a. National security depends largely on the

deterrent effect of our airborne military forces. To be

proficient, the military services must train in a wide

range of airborne tactics. One phase of this training

involves “low level” combat tactics. The required

maneuvers and high speeds are such that they may

occasionally make the see-and-avoid aspect of VFR

flight more difficult without increased vigilance in

areas containing such operations. In an effort to

ensure the greatest practical level of safety for all

flight operations, the Military Training Route (MTR)

program was conceived.

b. The MTR program is a joint venture by the FAA

and the Department of Defense (DOD). MTRs are

mutually developed for use by the military for the

purpose of conducting low-altitude, high-speed

training. The routes above 1,500 feet AGL are

developed to be flown, to the maximum extent

possible, under IFR. The routes at 1,500 feet AGL

and below are generally developed to be flown under

VFR.
AIM 7/26/12

3−5−2 Other Airspace Areas

c. Generally, MTRs are established below

10,000 feet MSL for operations at speeds in excess of

250 knots. However, route segments may be defined

at higher altitudes for purposes of route continuity.

For example, route segments may be defined for

descent, climbout, and mountainous terrain. There

are IFR and VFR routes as follows:

1. IFR Military Training Routes−(IR).

Operations on these routes are conducted in

accordance with IFR regardless of weather

conditions.

2. VFR Military Training Routes−(VR).

Operations on these routes are conducted in

accordance with VFR except flight visibility must be

5 miles or more; and flights must not be conducted

below a ceiling of less than 3,000 feet AGL.

d. Military training routes will be identified and

charted as follows:

1. Route identification.

(a) MTRs with no segment above 1,500 feet

AGL must be identified by four number characters;

e.g., IR1206, VR1207.

(b) MTRs that include one or more segments

above 1,500 feet AGL must be identified by three

number characters; e.g., IR206, VR207.

(c) Alternate IR/VR routes or route segments

are identified by using the basic/principal route

designation followed by a letter suffix, e.g., IR008A,

VR1007B, etc.

2. Route charting.

(a) IFR Low Altitude En Route Chart. This

chart will depict all IR routes and all VR routes that

accommodate operations above 1,500 feet AGL.

(b) VFR Sectional Charts. These charts

will depict military training activities such as IR, VR,

MOA, Restricted Area, Warning Area, and Alert

Area information.

(c) Area Planning (AP/1B) Chart (DOD

Flight Information Publication−FLIP). This chart

is published by the DOD primarily for military users

and contains detailed information on both IR and VR

routes.

REFERENCE−

AIM, National Geospatial−Intelligence Agency (NGA) Products,

Paragraph 9−1−5, Subparagraph a.

e. The FLIP contains charts and narrative

descriptions of these routes. This publication is

available to the general public by single copy or

annual subscription from:

Aeronautical Navigation Products (AeroNav)

Logistics Group

Federal Aviation Administration

10201 Good Luck Road

Glenn Dale, MD 20769−9700

Toll free phone: 1−800−638−8972

Commercial: 301−436−8301

This DOD FLIP is available for pilot briefings at FSS

and many airports.

f. Nonparticipating aircraft are not prohibited

from flying within an MTR; however, extreme

vigilance should be exercised when conducting flight

through or near these routes. Pilots should contact

FSSs within 100 NM of a particular MTR to obtain

current information or route usage in their vicinity.

Information available includes times of scheduled

activity, altitudes in use on each route segment, and

actual route width. Route width varies for each MTR

and can extend several miles on either side of the

charted MTR centerline. Route width information for

IR and VR MTRs is also available in the FLIP AP/1B

along with additional MTR (slow routes/air refueling

routes) information. When requesting MTR information, pilots should give the FSS their position, route

of flight, and destination in order to reduce frequency

congestion and permit the FSS specialist to identify

the MTR which could be a factor.

3−5−3. Temporary Flight Restrictions

a. General. This paragraph describes the types of

conditions under which the FAA may impose

temporary flight restrictions. It also explains which

FAA elements have been delegated authority to issue

a temporary flight restrictions NOTAM and lists the

types of responsible agencies/offices from which the

FAA will accept requests to establish temporary

flight restrictions. The 14 CFR is explicit as to what

operations are prohibited, restricted, or allowed in a

temporary flight restrictions area. Pilots are responsible to comply with 14 CFR Sections 91.137, 91.138,

91.141 and 91.143 when conducting flight in an area

where a temporary flight restrictions area is in effect,

and should check appropriate NOTAMs during flight

planning.
7/26/12 AIM

Other Airspace Areas 3−5−3

b. The purpose for establishing a temporary

flight restrictions area is to:

1. Protect persons and property in the air or on

the surface from an existing or imminent hazard

associated with an incident on the surface when the

presence of low flying aircraft would magnify, alter,

spread, or compound that hazard (14 CFR

Section 91.137(a)(1));

2. Provide a safe environment for the operation

of disaster relief aircraft (14 CFR Section 91.137(a)(2)); or

3. Prevent an unsafe congestion of sightseeing

aircraft above an incident or event which may

generate a high degree of public interest (14 CFR

Section 91.137(a)(3)).

4. Protect declared national disasters for

humanitarian reasons in the State of Hawaii (14 CFR

Section 91.138).

5. Protect the President, Vice President, or other

public figures (14 CFR Section 91.141).

6. Provide a safe environment for space agency

operations (14 CFR Section 91.143).

c. Except for hijacking situations, when the

provisions of 14 CFR Section 91.137(a)(1) or (a)(2)

are necessary, a temporary flight restrictions area will

only be established by or through the area manager at

the Air Route Traffic Control Center (ARTCC)

having jurisdiction over the area concerned. A

temporary flight restrictions NOTAM involving the

conditions of 14 CFR Section 91.137(a)(3) will be

issued at the direction of the service area office

director having oversight of the airspace concerned.

When hijacking situations are involved, a temporary

flight restrictions area will be implemented through

the TSA Aviation Command Center. The appropriate

FAA air traffic element, upon receipt of such a

request, will establish a temporary flight restrictions

area under 14 CFR Section 91.137(a)(1).

d. The FAA accepts recommendations for the

establishment of a temporary flight restrictions area

under 14 CFR Section 91.137(a)(1) from military

major command headquarters, regional directors of

the Office of Emergency Planning, Civil Defense

State Directors, State Governors, or other similar

authority. For the situations involving 14 CFR

Section 91.137(a)(2), the FAA accepts recommendations from military commanders serving as regional,

subregional, or Search and Rescue (SAR) coordinators; by military commanders directing or

coordinating air operations associated with disaster

relief; or by civil authorities directing or coordinating

organized relief air operations (includes representatives of the Office of Emergency Planning, U.S.

Forest Service, and State aeronautical agencies).

Appropriate authorities for a temporary flight

restrictions establishment under 14 CFR

Section 91.137(a)(3) are any of those listed above or

by State, county, or city government entities.

e. The type of restrictions issued will be kept to a

minimum by the FAA consistent with achievement of

the necessary objective. Situations which warrant the

extreme restrictions of 14 CFR Section 91.137(a)(1)

include, but are not limited to: toxic gas leaks or

spills, flammable agents, or fumes which if fanned by

rotor or propeller wash could endanger persons or

property on the surface, or if entered by an aircraft

could endanger persons or property in the air;

imminent volcano eruptions which could endanger

airborne aircraft and occupants; nuclear accident or

incident; and hijackings. Situations which warrant

the restrictions associated with 14 CFR Section 91.137(a)(2) include: forest fires which are

being fought by releasing fire retardants from

aircraft; and aircraft relief activities following a

disaster (earthquake, tidal wave, flood, etc.). 14 CFR

Section 91.137(a)(3) restrictions are established for

events and incidents that would attract an unsafe

congestion of sightseeing aircraft.

f. The amount of airspace needed to protect

persons and property or provide a safe environment

for rescue/relief aircraft operations is normally

limited to within 2,000 feet above the surface and

within a 3−nautical−mile radius. Incidents occurring

within Class B, Class C, or Class D airspace will

normally be handled through existing procedures and

should not require the issuance of a temporary flight

restrictions NOTAM. Temporary flight restrictions

affecting airspace outside of the U.S. and its

territories and possessions are issued with verbiage

excluding that airspace outside of the 12−mile coastal

limits.
AIM 7/26/12

3−5−4 Other Airspace Areas

g. The FSS nearest the incident site is normally the

“coordination facility.” When FAA communications

assistance is required, the designated FSS will

function as the primary communications facility for

coordination between emergency control authorities

and affected aircraft. The ARTCC may act as liaison

for the emergency control authorities if adequate

communications cannot be established between the

designated FSS and the relief organization. For

example, the coordination facility may relay

authorizations from the on-scene emergency response official in cases where news media aircraft

operations are approved at the altitudes used by relief

aircraft.

h. ATC may authorize operations in a temporary

flight restrictions area under its own authority only

when flight restrictions are established under 14 CFR

Section 91.137(a)(2) and (a)(3). The appropriate

ARTCC/airport traffic control tower manager will,

however, ensure that such authorized flights do not

hamper activities or interfere with the event for which

restrictions were implemented. However, ATC will

not authorize local IFR flights into the temporary

flight restrictions area.

i. To preclude misunderstanding, the implementing NOTAM will contain specific and formatted

information. The facility establishing a temporary

flight restrictions area will format a NOTAM

beginning with the phrase “FLIGHT RESTRICTIONS” followed by: the location of the temporary

flight restrictions area; the effective period; the area

defined in statute miles; the altitudes affected; the

FAA coordination facility and commercial telephone

number; the reason for the temporary flight

restrictions; the agency directing any relief activities

and its commercial telephone number; and other

information considered appropriate by the issuing

authority.

EXAMPLE−

1. 14 CFR Section 91.137(a)(1):

The following NOTAM prohibits all aircraft operations

except those specified in the NOTAM.

Flight restrictions Matthews, Virginia, effective immediately until 9610211200. Pursuant to 14 CFR

Section 91.137(a)(1) temporary flight restrictions are in

effect. Rescue operations in progress. Only relief aircraft

operations under the direction of the Department of

Defense are authorized in the airspace at and below

5,000 feet MSL within a 2−nautical−mile radius of Laser

AFB, Matthews, Virginia. Commander, Laser AFB, in

charge (897) 946−5543 (122.4). Steenson FSS

(792) 555−6141 (123.1) is the FAA coordination facility.

2. 14 CFR Section 91.137(a)(2):

The following NOTAM permits flight operations in

accordance with 14 CFR Section 91.137(a)(2). The on-site

emergency response official to authorize media aircraft

operations below the altitudes used by the relief aircraft.

Flight restrictions 25 miles east of Bransome, Idaho,

effective immediately until 9601202359 UTC. Pursuant to

14 CFR Section 91.137(a)(2) temporary flight restrictions

are in effect within a 4−nautical−mile radius of the

intersection of county roads 564 and 315 at and below

3,500 feet MSL to provide a safe environment for fire

fighting aircraft operations. Davis County sheriff ’s

department (792) 555−8122 (122.9) is in charge of

on-scene emergency response activities. Glivings FSS

(792) 555−1618 (122.2) is the FAA coordination facility.

3. 14 CFR Section 91.137(a)(3):

The following NOTAM prohibits sightseeing aircraft

operations.

Flight restrictions Brown, Tennessee, due to olympic

activity. Effective 9606181100 UTC until 9607190200

UTC. Pursuant to 14 CFR Section 91.137(a)(3) temporary

flight restrictions are in effect within a 3−nautical−mile

radius of N355783/W835242 and Volunteer VORTAC 019

degree radial 3.7 DME fix at and below 2,500 feet MSL.

Norton FSS (423) 555−6742 (126.6) is the FAA

coordination facility.

4. 14 CFR Section 91.138:

The following NOTAM prohibits all aircraft except those

operating under the authorization of the official in charge

of associated emergency or disaster relief response

activities, aircraft carrying law enforcement officials,

aircraft carrying personnel involved in an emergency or

legitimate scientific purposes, carrying properly accredited news media, and aircraft operating in accordance with

an ATC clearance or instruction.

Flight restrictions Kapalua, Hawaii, effective 9605101200

UTC until 9605151500 UTC. Pursuant to 14 CFR

Section 91.138 temporary flight restrictions are in effect

within a 3−nautical−mile radius of N205778/W1564038

and Maui/OGG/VORTAC 275 degree radial at 14.1

nautical miles. John Doe 808−757−4469 or 122.4 is in

charge of the operation. Honolulu/HNL 808−757−4470

(123.6) FSS is the FAA coordination facility.

5. 14 CFR Section 91.141:

The following NOTAM prohibits all aircraft.

Flight restrictions Stillwater, Oklahoma, June 21, 1996.

Pursuant to 14 CFR Section 91.141 aircraft flight

operations are prohibited within a 3−nautical−mile radius,
7/26/12 AIM

Other Airspace Areas 3−5−5

below 2000 feet AGL of N360962/W970515 and the

Stillwater/SWO/VOR/DME 176 degree radial 3.8−nautical−mile fix from 1400 local time to 1700 local time

June 21, 1996, unless otherwise authorized by ATC.

6. 14 CFR Section 91.143:

The following NOTAM prohibits any aircraft of U.S.

registry, or pilot any aircraft under the authority of an

airman certificate issued by the FAA.

Kennedy space center space operations area effective

immediately until 9610152100 UTC. Pursuant to 14 CFR

Section 91.143, flight operations conducted by FAA

certificated pilots or conducted in aircraft of U.S. registry

are prohibited at any altitude from surface to unlimited,

within the following area 30−nautical−mile radius of the

Melbourne/MLB/VORTAC 010 degree radial 21−nautical−mile fix. St. Petersburg, Florida/PIE/FSS

813−545−1645 (122.2) is the FAA coordination facility and

should be contacted for the current status of any airspace

associated with the space shuttle operations. This airspace

encompasses R2933, R2932, R2931, R2934, R2935,

W497A and W158A. Additional warning and restricted

areas will be active in conjunction with the operations.

Pilots must consult all NOTAMs regarding this operation.

3−5−4. Parachute Jump Aircraft Operations

a. Procedures relating to parachute jump areas are

contained in 14 CFR Part 105. Tabulations of

parachute jump areas in the U.S. are contained in the

A/FD.

b. Pilots of aircraft engaged in parachute jump

operations are reminded that all reported altitudes

must be with reference to mean sea level, or flight

level, as appropriate, to enable ATC to provide

meaningful traffic information.

c. Parachute operations in the vicinity of an airport

without an operating control tower − there is no

substitute for alertness while in the vicinity of an

airport. It is essential that pilots conducting parachute

operations be alert, look for other traffic, and

exchange traffic information as recommended in

paragraph 4−1−9, Traffic Advisory Practices at

Airports Without Operating Control Towers. In

addition, pilots should avoid releasing parachutes

while in an airport traffic pattern when there are other

aircraft in that pattern. Pilots should make

appropriate broadcasts on the designated Common

Traffic Advisory Frequency (CTAF), and monitor

that CTAF until all parachute activity has terminated

or the aircraft has left the area. Prior to commencing

a jump operation, the pilot should broadcast the

aircraft’s altitude and position in relation to the

airport, the approximate relative time when the jump

will commence and terminate, and listen to the

position reports of other aircraft in the area.

3−5−5. Published VFR Routes

Published VFR routes for transitioning around, under

and through complex airspace such as Class B

airspace were developed through a number of FAA

and industry initiatives. All of the following terms,

i.e., “VFR Flyway” “VFR Corridor” and “Class B

Airspace VFR Transition Route” have been used

when referring to the same or different types of routes

or airspace. The following paragraphs identify and

clarify the functionality of each type of route, and

specify where and when an ATC clearance is

required.

a. VFR Flyways.

1. VFR Flyways and their associated Flyway

Planning Charts were developed from the recommendations of a National Airspace Review Task Group.

A VFR Flyway is defined as a general flight path not

defined as a specific course, for use by pilots in

planning flights into, out of, through or near complex

terminal airspace to avoid Class B airspace. An ATC

clearance is NOT required to fly these routes.
AIM 7/26/12

3−5−6 Other Airspace Areas

FIG 3−5−1

VFR Flyway Planning Chart
7/26/12 AIM

Other Airspace Areas 3−5−7

2. VFR Flyways are depicted on the reverse side

of some of the VFR Terminal Area Charts (TAC),

commonly referred to as Class B airspace charts. (See

FIG 3−5−1.) Eventually all TACs will include a VFR

Flyway Planning Chart. These charts identify VFR

flyways designed to help VFR pilots avoid major

controlled traffic flows. They may further depict

multiple VFR routings throughout the area which

may be used as an alternative to flight within Class B

airspace. The ground references provide a guide for

improved visual navigation. These routes are not

intended to discourage requests for VFR operations

within Class B airspace but are designed solely to

assist pilots in planning for flights under and around

busy Class B airspace without actually entering

Class B airspace.

3. It is very important to remember that these

suggested routes are not sterile of other traffic. The

entire Class B airspace, and the airspace underneath

it, may be heavily congested with many different

types of aircraft. Pilot adherence to VFR rules must

be exercised at all times. Further, when operating

beneath Class B airspace, communications must be

established and maintained between your aircraft and

any control tower while transiting the Class B,

Class C, and Class D surface areas of those airports

under Class B airspace.

b. VFR Corridors.

1. The design of a few of the first Class B

airspace areas provided a corridor for the passage of

uncontrolled traffic. A VFR corridor is defined as

airspace through Class B airspace, with defined

vertical and lateral boundaries, in which aircraft may

operate without an ATC clearance or communication

with air traffic control.

2. These corridors are, in effect, a “hole”

through Class B airspace. (See FIG 3−5−2.) A classic

example would be the corridor through the Los

Angeles Class B airspace, which has been subsequently changed to Special Flight Rules airspace

(SFR). A corridor is surrounded on all sides by

Class B airspace and does not extend down to the

surface like a VFR Flyway. Because of their finite

lateral and vertical limits, and the volume of VFR

traffic using a corridor, extreme caution and vigilance

must be exercised.

FIG 3−5−2

Class B Airspace

3. Because of the heavy traffic volume and the

procedures necessary to efficiently manage the flow

of traffic, it has not been possible to incorporate VFR

corridors in the development or modifications of

Class B airspace in recent years.

c. Class B Airspace VFR Transition Routes.

1. To accommodate VFR traffic through certain

Class B airspace, such as Seattle, Phoenix and

Los Angeles, Class B Airspace VFR Transition

Routes were developed. A Class B Airspace VFR

Transition Route is defined as a specific flight course

depicted on a TAC for transiting a specific Class B

airspace. These routes include specific ATC-assigned

altitudes, and pilots must obtain an ATC clearance

prior to entering Class B airspace on the route.

2. These routes, as depicted in FIG 3−5−3, are

designed to show the pilot where to position the

aircraft outside of, or clear of, the Class B airspace

where an ATC clearance can normally be expected

with minimal or no delay. Until ATC authorization is

received, pilots must remain clear of Class B

airspace. On initial contact, pilots should advise ATC

of their position, altitude, route name desired, and

direction of flight. After a clearance is received, pilots

must fly the route as depicted and, most importantly,

adhere to ATC instructions.
AIM 7/26/12

3−5−8 Other Airspace Areas

FIG 3−5−3

VFR Transition Route
7/26/12 AIM

Other Airspace Areas 3−5−9

3−5−6. Terminal Radar Service Area (TRSA)

a. Background. TRSAs were originally established as part of the Terminal Radar Program at

selected airports. TRSAs were never controlled

airspace from a regulatory standpoint because the

establishment of TRSAs was never subject to the

rulemaking process; consequently, TRSAs are not

contained in 14 CFR Part 71 nor are there any TRSA

operating rules in 14 CFR Part 91. Part of the Airport

Radar Service Area (ARSA) program was to

eventually replace all TRSAs. However, the ARSA

requirements became relatively stringent and it was

subsequently decided that TRSAs would have to

meet ARSA criteria before they would be converted.

TRSAs do not fit into any of the U.S. airspace classes;

therefore, they will continue to be non−Part 71

airspace areas where participating pilots can receive

additional radar services which have been redefined

as TRSA Service.

b. TRSAs. The primary airport(s) within the

TRSA become(s) Class D airspace. The remaining

portion of the TRSA overlies other controlled

airspace which is normally Class E airspace

beginning at 700 or 1,200 feet and established to

transition to/from the en route/terminal environment.

c. Participation. Pilots operating under VFR are

encouraged to contact the radar approach control and

avail themselves of the TRSA Services. However,

participation is voluntary on the part of the pilot. See

Chapter 4, Air Traffic Control, for details and

procedures.

d. Charts. TRSAs are depicted on VFR sectional

and terminal area charts with a solid black line and

altitudes for each segment. The Class D portion is

charted with a blue segmented line.

3−5−7. National Security Areas

National Security Areas consist of airspace of defined

vertical and lateral dimensions established at

locations where there is a requirement for increased

security and safety of ground facilities. Pilots are

requested to voluntarily avoid flying through the

depicted NSA. When it is necessary to provide a

greater level of security and safety, flight in NSAs

may be temporarily prohibited by regulation under

the provisions of 14 CFR Section 99.7. Regulatory

prohibitions will be issued by System Operations,

System Operations Airspace and AIM Office,

Airspace and Rules, and disseminated via NOTAM.

Inquiries about NSAs should be directed to Airspace

and Rules.

7/26/12 AIM

Services Available to Pilots 4−1−1

Chapter 4. Air Traffic Control

Section 1. Services Available to Pilots

4−1−1. Air Route Traffic Control Centers

Centers are established primarily to provide air traffic

service to aircraft operating on IFR flight plans within

controlled airspace, and principally during the

en route phase of flight.

4−1−2. Control Towers

Towers have been established to provide for a safe,

orderly and expeditious flow of traffic on and in the

vicinity of an airport. When the responsibility has

been so delegated, towers also provide for the

separation of IFR aircraft in the terminal areas.

REFERENCE−

AIM, Approach Control, Paragraph 5−4−3.

4−1−3. Flight Service Stations

Flight Service Stations (FSSs) are air traffic

facilities which provide pilot briefings, flight plan

processing, en route radio communications, search

and rescue services, and assistance to lost aircraft

and aircraft in emergency situations. FSSs also

relay ATC clearances, process Notices to Airmen,

broadcast aviation weather and aeronautical

information, and notify Customs and Border

Protection of transborder flights. In addition, at

selected locations FSSs provide En Route Flight

Advisory Service (Flight Watch) and Airport

Advisory Service (AAS). In Alaska, designated FSSs

also provide TWEB recordings and take weather

observations.

4−1−4. Recording and Monitoring

a. Calls to air traffic control (ATC) facilities

(ARTCCs, Towers, FSSs, Central Flow, and

Operations Centers) over radio and ATC operational

telephone lines (lines used for operational purposes

such as controller instructions, briefings, opening and

closing flight plans, issuance of IFR clearances and

amendments, counter hijacking activities, etc.) may

be monitored and recorded for operational uses such

as accident investigations, accident prevention,

search and rescue purposes, specialist training and

evaluation, and technical evaluation and repair of

control and communications systems.

b. Where the public access telephone is recorded,

a beeper tone is not required. In place of the “beep”

tone the FCC has substituted a mandatory requirement that persons to be recorded be given notice they

are to be recorded and give consent. Notice is given

by this entry, consent to record is assumed by the

individual placing a call to the operational facility.

4−1−5. Communications Release of IFR

Aircraft Landing at an Airport Without an

Operating Control Tower

Aircraft operating on an IFR flight plan, landing at an

airport without an operating control tower will be

advised to change to the airport advisory frequency

when direct communications with ATC are no longer

required. Towers and centers do not have nontower

airport traffic and runway in use information. The

instrument approach may not be aligned with the

runway in use; therefore, if the information has not

already been obtained, pilots should make an

expeditious change to the airport advisory frequency

when authorized.

REFERENCE−

AIM, Advance Information on Instrument Approach, Paragraph 5−4−4.

4−1−6. Pilot Visits to Air Traffic Facilities

Pilots are encouraged to visit air traffic facilities

(Towers, Centers and FSSs) and familiarize themselves with the ATC system. On rare occasions,

facilities may not be able to approve a visit because

of ATC workload or other reasons. It is, therefore,

requested that pilots contact the facility prior to the

visit and advise of the number of persons in the group,

the time and date of the proposed visit and the primary

interest of the group. With this information available,

the facility can prepare an itinerary and have someone

available to guide the group through the facility.
AIM 7/26/12

4−1−2 Services Available to Pilots

4−1−7. Operation Take-off and Operation

Raincheck

Operation Take-off is a program that educates pilots

in how best to utilize the FSS modernization efforts

and services available in Flight Service Stations

(FSS), as stated in FAA Order 7230.17, Pilot

Education Program − Operation Takeoff. Operation

Raincheck is a program designed to familiarize pilots

with the ATC system, its functions, responsibilities

and benefits.

4−1−8. Approach Control Service for VFR

Arriving Aircraft

a. Numerous approach control facilities have

established programs for arriving VFR aircraft to

contact approach control for landing information.

This information includes: wind, runway, and

altimeter setting at the airport of intended landing.

This information may be omitted if contained in the

Automatic Terminal Information Service (ATIS)

broadcast and the pilot states the appropriate ATIS

code.

NOTE−

Pilot use of “have numbers” does not indicate receipt of the

ATIS broadcast. In addition, the controller will provide

traffic advisories on a workload permitting basis.

b. Such information will be furnished upon initial

contact with concerned approach control facility. The

pilot will be requested to change to the tower

frequency at a predetermined time or point, to receive

further landing information.

c. Where available, use of this procedure will not

hinder the operation of VFR flights by requiring

excessive spacing between aircraft or devious

routing.

d. Compliance with this procedure is not

mandatory but pilot participation is encouraged.

REFERENCE−

AIM, Terminal Radar Services for VFR Aircraft, Paragraph 4−1−18.

NOTE−

Approach control services for VFR aircraft are normally

dependent on ATC radar. These services are not available

during periods of a radar outage. Approach control

services for VFR aircraft are limited when CENRAP is in

use.

4−1−9. Traffic Advisory Practices at

Airports Without Operating Control Towers

(See TBL 4−1−1.)

a. Airport Operations Without Operating

Control Tower

1. There is no substitute for alertness while in

the vicinity of an airport. It is essential that pilots be

alert and look for other traffic and exchange traffic

information when approaching or departing an

airport without an operating control tower. This is of

particular importance since other aircraft may not

have communication capability or, in some cases,

pilots may not communicate their presence or

intentions when operating into or out of such airports.

To achieve the greatest degree of safety, it is essential

that all radio-equipped aircraft transmit/receive on a

common frequency identified for the purpose of

airport advisories.

2. An airport may have a full or part-time tower

or FSS located on the airport, a full or part-time

UNICOM station or no aeronautical station at all.

There are three ways for pilots to communicate their

intention and obtain airport/traffic information when

operating at an airport that does not have an operating

tower: by communicating with an FSS, a UNICOM

operator, or by making a self-announce broadcast.

3. Many airports are now providing completely

automated weather, radio check capability and airport

advisory information on an automated UNICOM

system. These systems offer a variety of features,

typically selectable by microphone clicks, on the

UNICOM frequency. Availability of the automated

UNICOM will be published in the Airport/Facility

Directory and approach charts.

b. Communicating on a Common Frequency

1. The key to communicating at an airport

without an operating control tower is selection of the

correct common frequency. The acronym CTAF

which stands for Common Traffic Advisory

Frequency, is synonymous with this program. A

CTAF is a frequency designated for the purpose of

carrying out airport advisory practices while

operating to or from an airport without an operating

control tower. The CTAF may be a UNICOM,

MULTICOM, FSS, or tower frequency and is

identified in appropriate aeronautical publications.
7/26/12 AIM

Services Available to Pilots 4−1−3

TBL 4−1−1

Summary of Recommended Communication Procedures

Communication/Broadcast Procedures

Facility at Airport Frequency Use Outbound Inbound

Practice

Instrument

Approach

1. UNICOM (No Tower or

FSS)

Communicate with UNICOM

station on published CTAF

frequency (122.7; 122.8; 122.725;

122.975; or 123.0). If unable to

contact UNICOM station, use

self-announce procedures on

CTAF.

Before taxiing and

before taxiing on

the runway for

departure.

10 miles out.

Entering

downwind, base,

and final. Leaving

the runway.

2. No Tower, FSS, or

UNICOM

Self-announce on MULTICOM

frequency 122.9.

Before taxiing and

before taxiing on

the runway for

departure.

10 miles out.

Entering

downwind, base,

and final. Leaving

the runway.

Departing final

approach fix

(name) or on final

approach segment

inbound.

3. No Tower in operation,

FSS open

Communicate with FSS on CTAF

frequency.

Before taxiing and

before taxiing on

the runway for

departure.

10 miles out.

Entering

downwind, base,

and final. Leaving

the runway.

Approach completed/terminated.

4. FSS Closed (No Tower) Self-announce on CTAF. Before taxiing and

before taxiing on

the runway for

departure.

10 miles out.

Entering

downwind, base,

and final. Leaving

the runway.

5. Tower or FSS not in

operation

Self-announce on CTAF. Before taxiing and

before taxiing on

the runway for

departure.

10 miles out.

Entering

downwind, base,

and final. Leaving

the runway.

2. The CTAF frequency for a particular airport

is contained in the A/FD, Alaska Supplement, Alaska

Terminal Publication, Instrument Approach Procedure Charts, and Instrument Departure

Procedure (DP) Charts. Also, the CTAF frequency

can be obtained by contacting any FSS. Use of the

appropriate CTAF, combined with a visual alertness

and application of the following recommended good

operating practices, will enhance safety of flight into

and out of all uncontrolled airports.

c. Recommended Traffic Advisory Practices

1. Pilots of inbound traffic should monitor and

communicate as appropriate on the designated CTAF

from 10 miles to landing. Pilots of departing aircraft

should monitor/communicate on the appropriate

frequency from start-up, during taxi, and until

10 miles from the airport unless the CFRs or local

procedures require otherwise.

2. Pilots of aircraft conducting other than

arriving or departing operations at altitudes normally

used by arriving and departing aircraft should

monitor/communicate on the appropriate frequency

while within 10 miles of the airport unless required to

do otherwise by the CFRs or local procedures. Such

operations include parachute jumping/dropping, en

route, practicing maneuvers, etc.

REFERENCE−

AIM, Parachute Jump Aircraft Operations, Paragraph 3−5−4.

d. Airport Advisory/Information Services

Provided by a FSS

1. There are three advisory type services

provided at selected airports.

(a) Local Airport Advisory (LAA) is provided at airports that have a FSS physically located on

the airport, which does not have a control tower or

where the tower is operated on a part−time basis. The

CTAF for LAA airports is disseminated in the

appropriate aeronautical publications.
AIM 7/26/12

4−1−4 Services Available to Pilots

(b) Remote Airport Advisory (RAA) is

provided at selected very busy GA airports, which do

not have an operating control tower. The CTAF for

RAA airports is disseminated in the appropriate

aeronautical publications.

(c) Remote Airport Information Service (RAIS) is provided in support of special events

at nontowered airports by request from the airport

authority.

2. In communicating with a CTAF FSS, check

the airport’s automated weather and establish

two−way communications before transmitting outbound/inbound intentions or information. An

inbound aircraft should initiate contact approximately 10 miles from the airport, reporting aircraft

identification and type, altitude, location relative to

the airport, intentions (landing or over flight),

possession of the automated weather, and request

airport advisory or airport information service. A

departing aircraft should initiate contact before

taxiing, reporting aircraft identification and type,

VFR or IFR, location on the airport, intentions,

direction of take−off, possession of the automated

weather, and request airport advisory or information

service. Also, report intentions before taxiing onto

the active runway for departure. If you must change

frequencies for other service after initial report to

FSS, return to FSS frequency for traffic update.

(a) Inbound

EXAMPLE−

Vero Beach radio, Centurion Six Niner Delta Delta is

ten miles south, two thousand, landing Vero Beach. I have

the automated weather, request airport advisory.

(b) Outbound

EXAMPLE−

Vero Beach radio, Centurion Six Niner Delta Delta, ready

to taxi to runway 22, VFR, departing to the southwest. I

have the automated weather, request airport advisory.

3. Airport advisory service includes wind

direction and velocity, favored or designated runway,

altimeter setting, known airborne and ground traffic,

NOTAMs, airport taxi routes, airport traffic pattern

information, and instrument approach procedures.

These elements are varied so as to best serve the

current traffic situation. Some airport managers have

specified that under certain wind or other conditions

designated runways be used. Pilots should advise the

FSS of the runway they intend to use.

CAUTION−

All aircraft in the vicinity of an airport may not be in

communication with the FSS.

e. Information Provided by Aeronautical

Advisory Stations (UNICOM)

1. UNICOM is a nongovernment air/ground

radio communication station which may provide

airport information at public use airports where there

is no tower or FSS.

2. On pilot request, UNICOM stations may

provide pilots with weather information, wind

direction, the recommended runway, or other

necessary information. If the UNICOM frequency is

designated as the CTAF, it will be identified in

appropriate aeronautical publications.

f. Unavailability of Information from FSS or

UNICOM

Should LAA by an FSS or Aeronautical Advisory

Station UNICOM be unavailable, wind and weather

information may be obtainable from nearby

controlled airports via Automatic Terminal Information Service (ATIS) or Automated Weather

Observing System (AWOS) frequency.

g. Self-Announce Position and/or Intentions

1. General. Self-announce is a procedure

whereby pilots broadcast their position or intended

flight activity or ground operation on the designated

CTAF. This procedure is used primarily at airports

which do not have an FSS on the airport. The

self-announce procedure should also be used if a pilot

is unable to communicate with the FSS on the

designated CTAF. Pilots stating, “Traffic in the area,

please advise” is not a recognized Self−Announce

Position and/or Intention phrase and should not be

used under any condition.

2. If an airport has a tower and it is temporarily

closed, or operated on a part-time basis and there is no

FSS on the airport or the FSS is closed, use the CTAF

to self-announce your position or intentions.

3. Where there is no tower, FSS, or UNICOM

station on the airport, use MULTICOM frequency

122.9 for self-announce procedures. Such airports

will be identified in appropriate aeronautical

information publications.

4. Practice Approaches. Pilots conducting

practice instrument approaches should be particularly alert for other aircraft that may be departing in the
7/26/12 AIM

Services Available to Pilots 4−1−5

opposite direction. When conducting any practice

approach, regardless of its direction relative to other

airport operations, pilots should make announcements on the CTAF as follows:

(a) Departing the final approach fix, inbound

(nonprecision approach) or departing the outer

marker or fix used in lieu of the outer marker, inbound

(precision approach);

(b) Established on the final approach segment

or immediately upon being released by ATC;

(c) Upon completion or termination of the

approach; and

(d) Upon executing the missed approach

procedure.

5. Departing aircraft should always be alert for

arrival aircraft coming from the opposite direction.

6. Recommended self-announce phraseologies:

It should be noted that aircraft operating to or from

another nearby airport may be making self-announce

broadcasts on the same UNICOM or MULTICOM

frequency. To help identify one airport from another,

the airport name should be spoken at the beginning

and end of each self-announce transmission.

(a) Inbound

EXAMPLE−

Strawn traffic, Apache Two Two Five Zulu, (position),

(altitude), (descending) or entering downwind/base/final

(as appropriate) runway one seven full stop, touch−and−

go, Strawn.

Strawn traffic Apache Two Two Five Zulu clear of runway

one seven Strawn.

(b) Outbound

EXAMPLE−

Strawn traffic, Queen Air Seven One Five Five Bravo

(location on airport) taxiing to runway two six Strawn.

Strawn traffic, Queen Air Seven One Five Five Bravo

departing runway two six. Departing the pattern to the

(direction), climbing to (altitude) Strawn.

(c) Practice Instrument Approach

EXAMPLE−

Strawn traffic, Cessna Two One Four Three Quebec

(position from airport) inbound descending through

(altitude) practice (name of approach) approach runway

three five Strawn.

Strawn traffic, Cessna Two One Four Three Quebec

practice (type) approach completed or terminated runway

three five Strawn.

h. UNICOM Communications Procedures

1. In communicating with a UNICOM station,

the following practices will help reduce frequency

congestion, facilitate a better understanding of pilot

intentions, help identify the location of aircraft in the

traffic pattern, and enhance safety of flight:

(a) Select the correct UNICOM frequency.

(b) State the identification of the UNICOM

station you are calling in each transmission.

(c) Speak slowly and distinctly.

(d) Report approximately 10 miles from the

airport, reporting altitude, and state your aircraft type,

aircraft identification, location relative to the airport,

state whether landing or overflight, and request wind

information and runway in use.

(e) Report on downwind, base, and final

approach.

(f) Report leaving the runway.

2. Recommended UNICOM phraseologies:

(a) Inbound

PHRASEOLOGY−

FREDERICK UNICOM CESSNA EIGHT ZERO ONE

TANGO FOXTROT 10 MILES SOUTHEAST

DESCENDING THROUGH (altitude) LANDING

FREDERICK, REQUEST WIND AND RUNWAY

INFORMATION FREDERICK.

FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE

TANGO FOXTROT ENTERING DOWNWIND/BASE/

FINAL (as appropriate) FOR RUNWAY ONE NINER (full

stop/touch−and−go) FREDERICK.

FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE

TANGO FOXTROT CLEAR OF RUNWAY ONE NINER

FREDERICK.

(b) Outbound

PHRASEOLOGY−

FREDERICK UNICOM CESSNA EIGHT ZERO ONE

TANGO FOXTROT (location on airport) TAXIING TO

RUNWAY ONE NINER, REQUEST WIND AND TRAFFIC

INFORMATION FREDERICK. 

FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE

TANGO FOXTROT DEPARTING RUNWAY ONE NINER.

“REMAINING IN THE PATTERN” OR “DEPARTING

THE PATTERN TO THE (direction) (as appropriate)”

FREDERICK.
AIM 7/26/12

4−1−6 Services Available to Pilots

4−1−10. IFR Approaches/Ground Vehicle

Operations

a. IFR Approaches. When operating in accordance with an IFR clearance and ATC approves a

change to the advisory frequency, make an

expeditious change to the CTAF and employ the

recommended traffic advisory procedures.

b. Ground Vehicle Operation. Airport ground

vehicles equipped with radios should monitor the

CTAF frequency when operating on the airport

movement area and remain clear of runways/taxiways being used by aircraft. Radio transmissions

from ground vehicles should be confined to

safety-related matters.

c. Radio Control of Airport Lighting Systems.

Whenever possible, the CTAF will be used to control

airport lighting systems at airports without operating

control towers. This eliminates the need for pilots to

change frequencies to turn the lights on and allows a

continuous listening watch on a single frequency. The

CTAF is published on the instrument approach chart

and in other appropriate aeronautical information

publications. For further details concerning radio

controlled lights, see AC 150/5340−27, Air−to−

Ground Radio Control of Airport Lighting Systems.

4−1−11. Designated UNICOM/MULTICOM

Frequencies

Frequency use

a. The following listing depicts UNICOM and

MULTICOM frequency uses as designated by the

Federal Communications Commission (FCC). 

(See TBL 4−1−2.)

TBL 4−1−2

Unicom/Multicom Frequency Usage

Use Frequency

Airports without an operating

control tower.

122.700

122.725

122.800

122.975

123.000

123.050

123.075

(MULTICOM FREQUENCY)

Activities of a temporary, seasonal,

emergency nature or search and

rescue, as well as, airports with no

tower, FSS, or UNICOM.

122.900

(MULTICOM FREQUENCY)

Forestry management and fire

suppression, fish and game

management and protection, and

environmental monitoring and

protection.

122.925

Airports with a control tower or

FSS on airport.

122.950

NOTE−

1. In some areas of the country, frequency interference

may be encountered from nearby airports using the same

UNICOM frequency. Where there is a problem, UNICOM

operators are encouraged to develop a “least interference” frequency assignment plan for airports concerned

using the frequencies designated for airports without

operating control towers. UNICOM licensees are

encouraged to apply for UNICOM 25 kHz spaced channel

frequencies. Due to the extremely limited number of

frequencies with 50 kHz channel spacing, 25 kHz channel

spacing should be implemented. UNICOM licensees may

then request FCC to assign frequencies in accordance with

the plan, which FCC will review and consider for approval.

2. Wind direction and runway information may not be

available on UNICOM frequency 122.950.

b. The following listing depicts other frequency

uses as designated by the Federal Communications

Commission (FCC). (See TBL 4−1−3.)
7/26/12 AIM

Services Available to Pilots 4−1−7

TBL 4−1−3

Other Frequency Usage Designated by FCC

Use Frequency

Air-to-air communication 

(private fixed wing aircraft).

122.750

Air-to-air communications

(general aviation helicopters).

123.025

Aviation instruction, Glider, Hot Air

Balloon (not to be used for

advisory service).

123.300

123.500

4−1−12. Use of UNICOM for ATC Purposes

UNICOM service may be used for ATC purposes,

only under the following circumstances:

a. Revision to proposed departure time.

b. Takeoff, arrival, or flight plan cancellation

time.

c. ATC clearance, provided arrangements are

made between the ATC facility and the UNICOM

licensee to handle such messages.

4−1−13. Automatic Terminal Information

Service (ATIS)

a. ATIS is the continuous broadcast of recorded

noncontrol information in selected high activity

terminal areas. Its purpose is to improve controller

effectiveness and to relieve frequency congestion by

automating the repetitive transmission of essential

but routine information. The information is continuously broadcast over a discrete VHF radio frequency

or the voice portion of a local NAVAID. ATIS

transmissions on a discrete VHF radio frequency are

engineered to be receivable to a maximum of 60 NM

from the ATIS site and a maximum altitude of

25,000 feet AGL. At most locations, ATIS signals

may be received on the surface of the airport, but local

conditions may limit the maximum ATIS reception

distance and/or altitude. Pilots are urged to cooperate

in the ATIS program as it relieves frequency

congestion on approach control, ground control, and

local control frequencies. The A/FD indicates

airports for which ATIS is provided.

b. ATIS information includes the time of the latest

weather sequence, ceiling, visibility, obstructions to

visibility, temperature, dew point (if available), wind

direction (magnetic), and velocity, altimeter, other

pertinent remarks, instrument approach and runway

in use. The ceiling/sky condition, visibility, and

obstructions to vision may be omitted from the ATIS

broadcast if the ceiling is above 5,000 feet and the

visibility is more than 5 miles. The departure runway

will only be given if different from the landing

runway except at locations having a separate ATIS for

departure. The broadcast may include the appropriate

frequency and instructions for VFR arrivals to make

initial contact with approach control. Pilots of aircraft

arriving or departing the terminal area can receive the

continuous ATIS broadcast at times when cockpit

duties are least pressing and listen to as many repeats

as desired. ATIS broadcast must be updated upon the

receipt of any official hourly and special weather. A

new recording will also be made when there is a

change in other pertinent data such as runway change,

instrument approach in use, etc.

EXAMPLE−

Dulles International information Sierra. 1300 zulu

weather. Measured ceiling three thousand overcast.

Visibility three, smoke. Temperature six eight. Wind

three five zero at eight. Altimeter two niner niner two. ILS

runway one right approach in use. Landing runway one

right and left. Departure runway three zero. Armel

VORTAC out of service. Advise you have Sierra.

c. Pilots should listen to ATIS broadcasts

whenever ATIS is in operation.

d. Pilots should notify controllers on initial

contact that they have received the ATIS broadcast by

repeating the alphabetical code word appended to the

broadcast.

EXAMPLE−

“Information Sierra received.”

e. When a pilot acknowledges receipt of the ATIS

broadcast, controllers may omit those items contained in the broadcast if they are current. Rapidly

changing conditions will be issued by ATC and the

ATIS will contain words as follows:

EXAMPLE−

“Latest ceiling/visibility/altimeter/wind/(other conditions) will be issued by approach control/tower.”

NOTE−

The absence of a sky condition or ceiling and/or visibility

on ATIS indicates a sky condition or ceiling of 5,000 feet or

above and visibility of 5 miles or more. A remark may be

made on the broadcast, “the weather is better than

5000 and 5,” or the existing weather may be broadcast.

f. Controllers will issue pertinent information to

pilots who do not acknowledge receipt of a broadcast
AIM 7/26/12

4−1−8 Services Available to Pilots

or who acknowledge receipt of a broadcast which is

not current.

g. To serve frequency limited aircraft, FSSs are

equipped to transmit on the omnirange frequency at

most en route VORs used as ATIS voice outlets. Such

communication interrupts the ATIS broadcast. Pilots

of aircraft equipped to receive on other FSS

frequencies are encouraged to do so in order that these

override transmissions may be kept to an absolute

minimum.

h. While it is a good operating practice for pilots

to make use of the ATIS broadcast where it is

available, some pilots use the phrase “have numbers”

in communications with the control tower. Use of this

phrase means that the pilot has received wind,

runway, and altimeter information ONLY and the

tower does not have to repeat this information. It does

not indicate receipt of the ATIS broadcast and should

never be used for this purpose.

4−1−14. Automatic Flight Information

Service (AFIS) − Alaska FSSs Only

a. Alaska FSSs AFIS is the continuous broadcast

of recorded noncontrol information at airports in

Alaska where a Flight Service Station (FSS) provides

local airport advisory service. Its purpose is to

improve FSS Specialist efficiency by reducing

frequency congestion on the local airport advisory

frequency. The AFIS broadcast will automate the

repetitive transmission of essential but routine

information (weather, favored runway, breaking

action, airport NOTAMs, other applicable information). The information is continuously broadcast over

a discrete VHF radio frequency (usually the ASOS

frequency). Use of AFIS is not mandatory, but pilots

who choose to utilize two−way radio communications with the FSS are urged to listen to AFIS, as it

relieves frequency congestion on the local airport

advisory frequency. AFIS broadcasts are updated

upon the receipt of any official hourly and special

weather, worsening braking action reports, and

changes in other pertinent data. When a pilot

acknowledges receipt of the AFIS broadcast, FSS

Specialists may omit those items contained in the

broadcast if they are current. When rapidly changing

conditions exist, the latest ceiling, visibility,

altimeter, wind or other conditions may be omitted

from the AFIS and will be issued by the Flight Service

Specialist on the appropriate radio frequency.

EXAMPLE−

“Kotzebue information ALPHA. One six five five zulu.

Wind, two one zero at five; visibility two, fog; ceiling one

hundred overcast; temperature minus one two, dew point

minus one four; altimeter three one zero five. Altimeter in

excess of three one zero zero, high pressure altimeter

setting procedures are in effect. Favored runway two six.

Weather in Kotzebue surface area is below V−F−R

minima − an ATC clearance is required. Contact

Kotzebue Radio on 123.6 for traffic advisories and advise

intentions. Notice to Airmen, Hotham NDB out of service.

Transcribed Weather Broadcast out of service. Advise on

initial contact you have ALPHA.”

NOTE−

The absence of a sky condition or ceiling and/or visibility

on Alaska FSS AFIS indicates a sky condition or ceiling of

5,000 feet or above and visibility of 5 miles or more. A

remark may be made on the broadcast, “the weather is

better than 5000 and 5.”

b. Pilots should listen to Alaska FSSs AFIS

broadcasts whenever Alaska FSSs AFIS is in

operation.

NOTE−

Some Alaska FSSs are open part time and/or seasonally.

c. Pilots should notify controllers on initial

contact that they have received the Alaska FSSs

AFIS broadcast by repeating the phonetic alphabetic

letter appended to the broadcast.

EXAMPLE−

“Information Alpha received.”

d. While it is a good operating practice for pilots

to make use of the Alaska FSS AFIS broadcast where

it is available, some pilots use the phrase “have

numbers” in communications with the FSS. Use of

this phrase means that the pilot has received wind,

runway, and altimeter information ONLY and the

Alaska FSS does not have to repeat this information.

It does not indicate receipt of the AFIS broadcast and

should never be used for this purpose.

4−1−15. Radar Traffic Information Service

This is a service provided by radar ATC facilities.

Pilots receiving this service are advised of any radar

target observed on the radar display which may be in

such proximity to the position of their aircraft or its

intended route of flight that it warrants their attention.

This service is not intended to relieve the pilot of the

responsibility for continual vigilance to see and avoid

other aircraft.
7/26/12 AIM

Services Available to Pilots 4−1−9

a. Purpose of the Service

1. The issuance of traffic information as

observed on a radar display is based on the principle

of assisting and advising a pilot that a particular radar

target’s position and track indicates it may intersect or

pass in such proximity to that pilot’s intended flight

path that it warrants attention. This is to alert the pilot

to the traffic, to be on the lookout for it, and thereby

be in a better position to take appropriate action

should the need arise.

2. Pilots are reminded that the surveillance radar

used by ATC does not provide altitude information

unless the aircraft is equipped with Mode C and the

radar facility is capable of displaying altitude

information.

b. Provisions of the Service

1. Many factors, such as limitations of the radar,

volume of traffic, controller workload and communications frequency congestion, could prevent the

controller from providing this service. Controllers

possess complete discretion for determining whether

they are able to provide or continue to provide this

service in a specific case. The controller’s reason

against providing or continuing to provide the service

in a particular case is not subject to question nor need

it be communicated to the pilot. In other words, the

provision of this service is entirely dependent upon

whether controllers believe they are in a position to

provide it. Traffic information is routinely provided

to all aircraft operating on IFR flight plans except

when the pilot declines the service, or the pilot is

operating within Class A airspace. Traffic information may be provided to flights not operating on IFR

flight plans when requested by pilots of such flights.

NOTE−

Radar ATC facilities normally display and monitor both

primary and secondary radar when it is available, except

that secondary radar may be used as the sole display

source in Class A airspace, and under some circumstances

outside of Class A airspace (beyond primary coverage and

in en route areas where only secondary is available).

Secondary radar may also be used outside Class A

airspace as the sole display source when the primary radar

is temporarily unusable or out of service. Pilots in contact

with the affected ATC facility are normally advised when

a temporary outage occurs; i.e., “primary radar out of

service; traffic advisories available on transponder

aircraft only.” This means simply that only the aircraft

which have transponders installed and in use will be

depicted on ATC radar indicators when the primary radar

is temporarily out of service.

2. When receiving VFR radar advisory service,

pilots should monitor the assigned frequency at all

times. This is to preclude controllers’ concern for

radio failure or emergency assistance to aircraft under

the controller’s jurisdiction. VFR radar advisory

service does not include vectors away from

conflicting traffic unless requested by the pilot. When

advisory service is no longer desired, advise the

controller before changing frequencies and then

change your transponder code to 1200, if applicable.

Pilots should also inform the controller when

changing VFR cruising altitude. Except in programs

where radar service is automatically terminated, the

controller will advise the aircraft when radar is

terminated.

NOTE−

Participation by VFR pilots in formal programs

implemented at certain terminal locations constitutes pilot

request. This also applies to participating pilots at those

locations where arriving VFR flights are encouraged to

make their first contact with the tower on the approach

control frequency.

c. Issuance of Traffic Information. Traffic

information will include the following concerning a

target which may constitute traffic for an aircraft that

is:

1. Radar identified

(a) Azimuth from the aircraft in terms of the

12 hour clock, or

(b) When rapidly maneuvering civil test or

military aircraft prevent accurate issuance of traffic

as in (a) above, specify the direction from an aircraft’s

position in terms of the eight cardinal compass points

(N, NE, E, SE, S, SW, W, NW). This method must be

terminated at the pilot’s request.

(c) Distance from the aircraft in nautical

miles;

(d) Direction in which the target is proceeding; and

(e) Type of aircraft and altitude if known.

EXAMPLE−

Traffic 10 o’clock, 3 miles, west-bound (type aircraft and

altitude, if known, of the observed traffic). The altitude may

be known, by means of Mode C, but not verified with the

pilot for accuracy. (To be valid for separation purposes by

ATC, the accuracy of Mode C readouts must be verified.

This is usually accomplished upon initial entry into the
AIM 7/26/12

4−1−10 Services Available to Pilots

radar system by a comparison of the readout to pilot stated

altitude, or the field elevation in the case of continuous

readout being received from an aircraft on the airport.)

When necessary to issue traffic advisories containing

unverified altitude information, the controller will issue the

advisory in the same manner as if it were verified due to the

accuracy of these readouts. The pilot may upon receipt of

traffic information, request a vector (heading) to avoid

such traffic. The vector will be provided to the extent

possible as determined by the controller provided the

aircraft to be vectored is within the airspace under the

jurisdiction of the controller.

2. Not radar identified

(a) Distance and direction with respect to a

fix;

(b) Direction in which the target is proceeding; and

(c) Type of aircraft and altitude if known.

EXAMPLE−

Traffic 8 miles south of the airport northeastbound, (type

aircraft and altitude if known).

d. The examples depicted in the following figures

point out the possible error in the position of this

traffic when it is necessary for a pilot to apply drift

correction to maintain this track. This error could also

occur in the event a change in course is made at the

time radar traffic information is issued.

FIG 4−1−1

Induced Error in Position of Traffic

TRACK

(A) (B)

WIND

TRACK

EXAMPLE−

In FIG 4−1−1 traffic information would be issued to the

pilot of aircraft “A” as 12 o’clock. The actual position of

the traffic as seen by the pilot of aircraft “A” would be

2 o’clock. Traffic information issued to aircraft “B” would

also be given as 12 o’clock, but in this case, the pilot of “B”

would see the traffic at 10 o’clock.

FIG 4−1−2

Induced Error in Position of Traffic

TRACK

(C)

(D)

WIND TRACK

EXAMPLE−

In FIG 4−1−2 traffic information would be issued to the

pilot of aircraft “C” as 2 o’clock. The actual position of the

traffic as seen by the pilot of aircraft “C” would be

3 o’clock. Traffic information issued to aircraft “D” would

be at an 11 o’clock position. Since it is not necessary for the

pilot of aircraft “D” to apply wind correction (crab) to

remain on track, the actual position of the traffic issued

would be correct. Since the radar controller can only

observe aircraft track (course) on the radar display, traffic

advisories are issued accordingly, and pilots should give

due consideration to this fact when looking for reported

traffic.

4−1−16. Safety Alert

A safety alert will be issued to pilots of aircraft being

controlled by ATC if the controller is aware the

aircraft is at an altitude which, in the controller’s

judgment, places the aircraft in unsafe proximity to

terrain, obstructions or other aircraft. The provision

of this service is contingent upon the capability of the

controller to have an awareness of a situation

involving unsafe proximity to terrain, obstructions

and uncontrolled aircraft. The issuance of a safety

alert cannot be mandated, but it can be expected on a

reasonable, though intermittent basis. Once the alert

is issued, it is solely the pilot’s prerogative to

determine what course of action, if any, to take. This

procedure is intended for use in time critical

situations where aircraft safety is in question.

Noncritical situations should be handled via the

normal traffic alert procedures.

a. Terrain or Obstruction Alert

1. Controllers will immediately issue an alert to

the pilot of an aircraft under their control when they

recognize that the aircraft is at an altitude which, in

their judgment, may be in an unsafe proximity to

terrain/obstructions. The primary method of detecting unsafe proximity is through Mode C automatic

altitude reports.
7/26/12 AIM

Services Available to Pilots 4−1−11

EXAMPLE−

Low altitude alert, check your altitude immediately. The, as

appropriate, MEA/MVA/MOCA in your area is (altitude)

or, if past the final approach fix (nonprecision approach) or

the outer marker or fix used in lieu of the outer marker

(precision approach), the, as appropriate, MDA/DH (if

known) is (altitude).

2. Terminal Automated Radar Terminal System

(ARTS) IIIA, Common ARTS (to include ARTS IIIE

and ARTS IIE) (CARTS), Micro En Route

Automated Radar Tracking System (MEARTS), and

Standard Terminal Automation Replacement System

(STARS) facilities have an automated function

which, if operating, alerts controllers when a tracked

Mode C equipped aircraft under their control is below

or is predicted to be below a predetermined minimum

safe altitude. This function, called Minimum Safe

Altitude Warning (MSAW), is designed solely as a

controller aid in detecting potentially unsafe aircraft

proximity to terrain/obstructions. The ARTS IIIA,

CARTS, MEARTS, and STARS facility will, when

MSAW is operating, provide MSAW monitoring for

all aircraft with an operating Mode C altitude

encoding transponder that are tracked by the system

and are:

(a) Operating on an IFR flight plan; or

(b) Operating VFR and have requested

MSAW monitoring.

3. Terminal AN/TPX−42A (number beacon

decoder system) facilities have an automated

function called Low Altitude Alert System (LAAS).

Although not as sophisticated as MSAW, LAAS

alerts the controller when a Mode C transponder

equipped aircraft operating on an IFR flight plan is

below a predetermined minimum safe altitude.

NOTE−

Pilots operating VFR may request MSAW or LAAS

monitoring if their aircraft are equipped with Mode C

transponders.

EXAMPLE−

Apache Three Three Papa request MSAW/LAAS.

b. Aircraft Conflict Alert.

1. Controllers will immediately issue an alert to

the pilot of an aircraft under their control if they are

aware of another aircraft which is not under their

control, at an altitude which, in the controller’s

judgment, places both aircraft in unsafe proximity to

each other. With the alert, when feasible, the

controller will offer the pilot the position of the traffic

if time permits and an alternate course(s) of action.

Any alternate course(s) of action the controller may

recommend to the pilot will be predicated only on

other traffic being worked by the controller.

EXAMPLE−

American Three, traffic alert, (position of traffic, if time

permits), advise you turn right/left heading (degrees)

and/or climb/descend to (altitude) immediately.

4−1−17. Radar Assistance to VFR Aircraft

a. Radar equipped FAA ATC facilities provide

radar assistance and navigation service (vectors) to

VFR aircraft provided the aircraft can communicate

with the facility, are within radar coverage, and can be

radar identified.

b. Pilots should clearly understand that authorization to proceed in accordance with such radar

navigational assistance does not constitute authorization for the pilot to violate CFRs. In effect, assistance

provided is on the basis that navigational guidance

information issued is advisory in nature and the job of

flying the aircraft safely, remains with the pilot.

c. In many cases, controllers will be unable to

determine if flight into instrument conditions will

result from their instructions. To avoid possible

hazards resulting from being vectored into IFR

conditions, pilots should keep controllers advised of

the weather conditions in which they are operating

and along the course ahead.

d. Radar navigation assistance (vectors) may be

initiated by the controller when one of the following

conditions exist:

1. The controller suggests the vector and the

pilot concurs.

2. A special program has been established and

vectoring service has been advertised.

3. In the controller’s judgment the vector is

necessary for air safety.

e. Radar navigation assistance (vectors) and other

radar derived information may be provided in

response to pilot requests. Many factors, such as

limitations of radar, volume of traffic, communications frequency, congestion, and controller workload

could prevent the controller from providing it.

Controllers have complete discretion for determining

if they are able to provide the service in a particular

case. Their decision not to provide the service in a

particular case is not subject to question.
AIM 7/26/12

4−1−12 Services Available to Pilots

4−1−18. Terminal Radar Services for VFR

Aircraft

a. Basic Radar Service:

1. In addition to the use of radar for the control

of IFR aircraft, all commissioned radar facilities

provide the following basic radar services for VFR

aircraft:

(a) Safety alerts.

(b) Traffic advisories.

(c) Limited radar vectoring (on a workload

permitting basis).

(d) Sequencing at locations where procedures have been established for this purpose and/or

when covered by a Letter of Agreement.

NOTE−

When the stage services were developed, two basic radar

services (traffic advisories and limited vectoring) were

identified as “Stage I.” This definition became unnecessary and the term “Stage I” was eliminated from use. The

term “Stage II” has been eliminated in conjunction with

the airspace reclassification, and sequencing services to

locations with local procedures and/or letters of agreement

to provide this service have been included in basic services

to VFR aircraft. These basic services will still be provided

by all terminal radar facilities whether they include

Class B, Class C, Class D or Class E airspace. “Stage III”

services have been replaced with “Class B” and “TRSA”

service where applicable.

2. Vectoring service may be provided when

requested by the pilot or with pilot concurrence when

suggested by ATC.

3. Pilots of arriving aircraft should contact

approach control on the publicized frequency and

give their position, altitude, aircraft call sign, type

aircraft, radar beacon code (if transponder equipped),

destination, and request traffic information.

4. Approach control will issue wind and

runway, except when the pilot states “have numbers”

or this information is contained in the ATIS broadcast

and the pilot states that the current ATIS information

has been received. Traffic information is provided on

a workload permitting basis. Approach control will

specify the time or place at which the pilot is to

contact the tower on local control frequency for

further landing information. Radar service is

automatically terminated and the aircraft need not be

advised of termination when an arriving VFR aircraft

receiving radar services to a tower−controlled airport

where basic radar service is provided has landed, or

to all other airports, is instructed to change to tower

or advisory frequency. (See FAA Order JO 7110.65,

Air Traffic Control, paragraph 5−1−13, Radar

Service Termination.)

5. Sequencing for VFR aircraft is available at

certain terminal locations (see locations listed in the

Airport/Facility Directory). The purpose of the

service is to adjust the flow of arriving VFR and IFR

aircraft into the traffic pattern in a safe and orderly

manner and to provide radar traffic information to

departing VFR aircraft. Pilot participation is urged

but is not mandatory. Traffic information is provided

on a workload permitting basis. Standard radar

separation between VFR or between VFR and IFR

aircraft is not provided.

(a) Pilots of arriving VFR aircraft should

initiate radio contact on the publicized frequency

with approach control when approximately 25 miles

from the airport at which sequencing services are

being provided. On initial contact by VFR aircraft,

approach control will assume that sequencing service

is requested. After radar contact is established, the

pilot may use pilot navigation to enter the traffic

pattern or, depending on traffic conditions, approach

control may provide the pilot with routings or vectors

necessary for proper sequencing with other participating VFR and IFR traffic en route to the airport.

When a flight is positioned behind a preceding

aircraft and the pilot reports having that aircraft in

sight, the pilot will be instructed to follow the

preceding aircraft. THE ATC INSTRUCTION TO

FOLLOW THE PRECEDING AIRCRAFT DOES

NOT AUTHORIZE THE PILOT TO COMPLY

WITH ANY ATC CLEARANCE OR INSTRUCTION ISSUED TO THE PRECEDING AIRCRAFT.

If other “nonparticipating” or “local” aircraft are in

the traffic pattern, the tower will issue a landing

sequence. If an arriving aircraft does not want radar

service, the pilot should state “NEGATIVE RADAR

SERVICE” or make a similar comment, on initial

contact with approach control.

(b) Pilots of departing VFR aircraft are

encouraged to request radar traffic information by

notifying ground control on initial contact with their

request and proposed direction of flight.
7/26/12 AIM

Services Available to Pilots 4−1−13

EXAMPLE−

Xray ground control, November One Eight Six, Cessna One

Seventy Two, ready to taxi, VFR southbound at 2,500, have

information bravo and request radar traffic information.

NOTE−

Following takeoff, the tower will advise when to contact

departure control.

(c) Pilots of aircraft transiting the area and in

radar contact/communication with approach control

will receive traffic information on a controller

workload permitting basis. Pilots of such aircraft

should give their position, altitude, aircraft call sign,

aircraft type, radar beacon code (if transponder

equipped), destination, and/or route of flight.

b. TRSA Service (Radar Sequencing and

Separation Service for VFR Aircraft in a TRSA).

1. This service has been implemented at certain

terminal locations. The service is advertised in the

Airport/Facility Directory. The purpose of this

service is to provide separation between all

participating VFR aircraft and all IFR aircraft

operating within the airspace defined as the Terminal

Radar Service Area (TRSA). Pilot participation is

urged but is not mandatory.

2. If any aircraft does not want the service, the

pilot should state “NEGATIVE TRSA SERVICE” or

make a similar comment, on initial contact with

approach control or ground control, as appropriate.

3. TRSAs are depicted on sectional aeronautical

charts and listed in the Airport/Facility Directory.

4. While operating within a TRSA, pilots are

provided TRSA service and separation as prescribed

in this paragraph. In the event of a radar outage,

separation and sequencing of VFR aircraft will be

suspended as this service is dependent on radar. The

pilot will be advised that the service is not available

and issued wind, runway information, and the time or

place to contact the tower. Traffic information will be

provided on a workload permitting basis.

5. Visual separation is used when prevailing

conditions permit and it will be applied as follows:

(a) When a VFR flight is positioned behind a

preceding aircraft and the pilot reports having that

aircraft in sight, the pilot will be instructed by ATC to

follow the preceding aircraft. Radar service will be

continued to the runway. THE ATC INSTRUCTION

TO FOLLOW THE PRECEDING AIRCRAFT

DOES NOT AUTHORIZE THE PILOT TO

COMPLY WITH ANY ATC CLEARANCE OR

INSTRUCTION ISSUED TO THE PRECEDING

AIRCRAFT.

(b) If other “nonparticipating” or “local”

aircraft are in the traffic pattern, the tower will issue

a landing sequence.

(c) Departing VFR aircraft may be asked if

they can visually follow a preceding departure out of

the TRSA. The pilot will be instructed to follow the

other aircraft provided that the pilot can maintain

visual contact with that aircraft.

6. VFR aircraft will be separated from VFR/IFR

aircraft by one of the following:

(a) 500 feet vertical separation.

(b) Visual separation.

(c) Target resolution (a process to ensure that

correlated radar targets do not touch).

7. Participating pilots operating VFR in a

TRSA:

(a) Must maintain an altitude when assigned

by ATC unless the altitude assignment is to maintain

at or below a specified altitude. ATC may assign

altitudes for separation that do not conform to

14 CFR Section 91.159. When the altitude assignment is no longer needed for separation or when

leaving the TRSA, the instruction will be broadcast,

“RESUME APPROPRIATE VFR ALTITUDES.”

Pilots must then return to an altitude that conforms to

14 CFR Section 91.159 as soon as practicable.

(b) When not assigned an altitude, the pilot

should coordinate with ATC prior to any altitude

change.

8. Within the TRSA, traffic information on

observed but unidentified targets will, to the extent

possible, be provided to all IFR and participating

VFR aircraft. The pilot will be vectored upon request

to avoid the observed traffic, provided the aircraft to

be vectored is within the airspace under the

jurisdiction of the controller.

9. Departing aircraft should inform ATC of their

intended destination and/or route of flight and

proposed cruising altitude.

10. ATC will normally advise participating

VFR aircraft when leaving the geographical limits of

the TRSA. Radar service is not automatically
AIM 7/26/12

4−1−14 Services Available to Pilots

terminated with this advisory unless specifically

stated by the controller.

c. Class C Service. This service provides, in

addition to basic radar service, approved separation

between IFR and VFR aircraft, and sequencing of

VFR arrivals to the primary airport.

d. Class B Service. This service provides, in

addition to basic radar service, approved separation

of aircraft based on IFR, VFR, and/or weight, and

sequencing of VFR arrivals to the primary airport(s).

e. PILOT RESPONSIBILITY. THESE SERVICES ARE NOT TO BE INTERPRETED AS

RELIEVING PILOTS OF THEIR RESPONSIBILITIES TO SEE AND AVOID OTHER TRAFFIC

OPERATING IN BASIC VFR WEATHER CONDITIONS, TO ADJUST THEIR OPERATIONS AND

FLIGHT PATH AS NECESSARY TO PRECLUDE

SERIOUS WAKE ENCOUNTERS, TO MAINTAIN

APPROPRIATE TERRAIN AND OBSTRUCTION

CLEARANCE, OR TO REMAIN IN WEATHER

CONDITIONS EQUAL TO OR BETTER THAN

THE MINIMUMS REQUIRED BY 14 CFR

SECTION 91.155. WHENEVER COMPLIANCE

WITH AN ASSIGNED ROUTE, HEADING

AND/OR ALTITUDE IS LIKELY TO COMPROMISE PILOT RESPONSIBILITY RESPECTING

TERRAIN AND OBSTRUCTION CLEARANCE,

VORTEX EXPOSURE, AND WEATHER MINIMUMS, APPROACH CONTROL SHOULD BE SO

ADVISED AND A REVISED CLEARANCE OR

INSTRUCTION OBTAINED.

f. ATC services for VFR aircraft participating in

terminal radar services are dependent on ATC radar.

Services for VFR aircraft are not available during

periods of a radar outage and are limited during

CENRAP operations. The pilot will be advised when

VFR services are limited or not available.

NOTE−

Class B and Class C airspace are areas of regulated

airspace. The absence of ATC radar does not negate the

requirement of an ATC clearance to enter Class B airspace

or two way radio contact with ATC to enter Class C

airspace.

4−1−19. Tower En Route Control (TEC)

a. TEC is an ATC program to provide a service to

aircraft proceeding to and from metropolitan areas. It

links designated Approach Control Areas by a

network of identified routes made up of the existing

airway structure of the National Airspace System.

The FAA initiated an expanded TEC program to

include as many facilities as possible. The program’s

intent is to provide an overflow resource in the low

altitude system which would enhance ATC services.

A few facilities have historically allowed turbojets to

proceed between certain city pairs, such as

Milwaukee and Chicago, via tower en route and these

locations may continue this service. However, the

expanded TEC program will be applied, generally,

for nonturbojet aircraft operating at and below

10,000 feet. The program is entirely within the

approach control airspace of multiple terminal

facilities. Essentially, it is for relatively short flights.

Participating pilots are encouraged to use TEC for

flights of two hours duration or less. If longer flights

are planned, extensive coordination may be required

within the multiple complex which could result in

unanticipated delays.

b. Pilots requesting TEC are subject to the same

delay factor at the destination airport as other aircraft

in the ATC system. In addition, departure and en route

delays may occur depending upon individual facility

workload. When a major metropolitan airport is

incurring significant delays, pilots in the TEC

program may want to consider an alternative airport

experiencing no delay.

c. There are no unique requirements upon pilots to

use the TEC program. Normal flight plan filing

procedures will ensure proper flight plan processing.

Pilots should include the acronym “TEC” in the

remarks section of the flight plan when requesting

tower en route control.

d. All approach controls in the system may not

operate up to the maximum TEC altitude of

10,000 feet. IFR flight may be planned to any

satellite airport in proximity to the major primary

airport via the same routing.
7/26/12 AIM

Services Available to Pilots 4−1−15

4−1−20. Transponder Operation

a. General

1. Pilots should be aware that proper application

of transponder operating procedures will provide

both VFR and IFR aircraft with a higher degree of

safety in the environment where high-speed closure

rates are possible. Transponders substantially increase the capability of radar to see an aircraft and the

Mode C feature enables the controller to quickly

determine where potential traffic conflicts may exist.

Even VFR pilots who are not in contact with ATC will

be afforded greater protection from IFR aircraft and

VFR aircraft which are receiving traffic advisories.

Nevertheless, pilots should never relax their visual

scanning vigilance for other aircraft.

2. Air Traffic Control Radar Beacon System

(ATCRBS) is similar to and compatible with military

coded radar beacon equipment. Civil Mode A is

identical to military Mode 3.

3. Civil and military transponders should be

turned to the “on” or normal altitude reporting

position prior to moving on the airport surface to

ensure the aircraft is visible to ATC surveillance

systems. IN ALL CASES, WHILE IN CONTROLLED AIRSPACE EACH PILOT

OPERATING AN AIRCRAFT EQUIPPED WITH

AN OPERABLE ATC TRANSPONDER MAINTAINED IN ACCORDANCE WITH 14 CFR

SECTION 91.413 MUST OPERATE THE TRANSPONDER, INCLUDING MODE C IF INSTALLED,

ON THE APPROPRIATE CODE OR AS ASSIGNED BY ATC. IN CLASS G AIRSPACE, THE

TRANSPONDER SHOULD BE OPERATING

WHILE AIRBORNE UNLESS OTHERWISE REQUESTED BY ATC.

4. A pilot on an IFR flight who elects to cancel

the IFR flight plan prior to reaching destination,

should adjust the transponder according to VFR

operations.

5. If entering a U.S. OFFSHORE AIRSPACE

AREA from outside the U.S., the pilot should advise

on first radio contact with a U.S. radar ATC facility

that such equipment is available by adding

“transponder” to the aircraft identification.

6. It should be noted by all users of ATC

transponders that the coverage they can expect is

limited to “line of sight.” Low altitude or aircraft

antenna shielding by the aircraft itself may result in

reduced range. Range can be improved by climbing

to a higher altitude. It may be possible to minimize

antenna shielding by locating the antenna where dead

spots are only noticed during abnormal flight

attitudes.

7. Aircraft equipped with ADS−B (1090 ES or

UAT) must operate the equipment in the transmit

mode (on position) at all times while on any airport

surface.

NOTE−

Pilots of aircraft equipped with ADS−B should refer to

AIM, Automatic Dependant Surveillance − Broadcast

Services, Paragraph 4−5−7, for a complete description of

operating limitations and procedures.

b. Transponder Code Designation

1. For ATC to utilize one or a combination of the

4096 discrete codes FOUR DIGIT CODE DESIGNATION will be used, e.g., code 2100 will be

expressed as TWO ONE ZERO ZERO. Due to the

operational characteristics of the rapidly expanding

automated ATC system, THE LAST TWO DIGITS

OF THE SELECTED TRANSPONDER CODE

SHOULD ALWAYS READ “00” UNLESS SPECIFICALLY REQUESTED BY ATC TO BE

OTHERWISE.

c. Automatic Altitude Reporting (Mode C)

1. Some transponders are equipped with a

Mode C automatic altitude reporting capability. This

system converts aircraft altitude in 100 foot

increments to coded digital information which is

transmitted together with Mode C framing pulses to

the interrogating radar facility. The manner in which

transponder panels are designed differs, therefore, a

pilot should be thoroughly familiar with the operation

of the transponder so that ATC may realize its full

capabilities.

2. Adjust transponder to reply on the Mode A/3

code specified by ATC and, if equipped, to reply on

Mode C with altitude reporting capability activated

unless deactivation is directed by ATC or unless the

installed aircraft equipment has not been tested and

calibrated as required by 14 CFR Section 91.217. If

deactivation is required by ATC, turn off the altitude

reporting feature of your transponder. An instruction

by ATC to “STOP ALTITUDE SQUAWK, ALTITUDE DIFFERS (number of feet) FEET,” may be an

indication that your transponder is transmitting

incorrect altitude information or that you have an
AIM 7/26/12

4−1−16 Services Available to Pilots

incorrect altimeter setting. While an incorrect

altimeter setting has no effect on the Mode C altitude

information transmitted by your transponder (transponders are preset at 29.92), it would cause you to fly

at an actual altitude different from your assigned

altitude. When a controller indicates that an altitude

readout is invalid, the pilot should initiate a check to

verify that the aircraft altimeter is set correctly.

3. Pilots of aircraft with operating Mode C

altitude reporting transponders should report exact

altitude or flight level to the nearest hundred foot

increment when establishing initial contact with an

ATC facility. Exact altitude or flight level reports on

initial contact provide ATC with information that is

required prior to using Mode C altitude information

for separation purposes. This will significantly

reduce altitude verification requests.

d. Transponder IDENT Feature

1. The transponder must be operated only as

specified by ATC. Activate the “IDENT” feature only

upon request of the ATC controller.

e. Code Changes

1. When making routine code changes, pilots

should avoid inadvertent selection of Codes 7500,

7600 or 7700 thereby causing momentary false

alarms at automated ground facilities. For example,

when switching from Code 2700 to Code 7200,

switch first to 2200 then to 7200, NOT to 7700 and

then 7200. This procedure applies to nondiscrete

Code 7500 and all discrete codes in the 7600 and 7700

series (i.e., 7600−7677, 7700−7777) which will

trigger special indicators in automated facilities.

Only nondiscrete Code 7500 will be decoded as the

hijack code.

2. Under no circumstances should a pilot of a

civil aircraft operate the transponder on Code 7777.

This code is reserved for military interceptor

operations.

3. Military pilots operating VFR or IFR within

restricted/warning areas should adjust their transponders to Code 4000 unless another code has been

assigned by ATC.

f. Mode C Transponder Requirements

1. Specific details concerning requirements to

carry and operate Mode C transponders, as well as

exceptions and ATC authorized deviations from the

requirements are found in 14 CFR Section 91.215 and

14 CFR Section 99.12.

2. In general, the CFRs require aircraft to be

equipped with Mode C transponders when operating:

(a) At or above 10,000 feet MSL over the

48 contiguous states or the District of Columbia,

excluding that airspace below 2,500 feet AGL;

(b) Within 30 miles of a Class B airspace

primary airport, below 10,000 feet MSL. Balloons,

gliders, and aircraft not equipped with an engine

driven electrical system are excepted from the above

requirements when operating below the floor of

Class A airspace and/or; outside of a Class B airspace

and below the ceiling of the Class B airspace (or

10,000 feet MSL, whichever is lower);

(c) Within and above all Class C airspace, up

to 10,000 feet MSL;

(d) Within 10 miles of certain designated

airports, excluding that airspace which is both outside

the Class D surface area and below 1,200 feet AGL.

Balloons, gliders and aircraft not equipped with an

engine driven electrical system are excepted from this

requirement.

3. 14 CFR Section 99.12 requires all aircraft

flying into, within, or across the contiguous U.S.

ADIZ be equipped with a Mode C or Mode S

transponder. Balloons, gliders and aircraft not

equipped with an engine driven electrical system are

excepted from this requirement.

4. Pilots must ensure that their aircraft transponder is operating on an appropriate ATC assigned

VFR/IFR code and Mode C when operating in such

airspace. If in doubt about the operational status of

either feature of your transponder while airborne,

contact the nearest ATC facility or FSS and they will

advise you what facility you should contact for

determining the status of your equipment.

5. In-flight requests for “immediate” deviation

from the transponder requirement may be approved

by controllers only when the flight will continue IFR

or when weather conditions prevent VFR descent and

continued VFR flight in airspace not affected by the

CFRs. All other requests for deviation should be

made by contacting the nearest Flight Service or

Air Traffic facility in person or by telephone. The

nearest ARTCC will normally be the controlling

agency and is responsible for coordinating requests

involving deviations in other ARTCC areas.
7/26/12 AIM

Services Available to Pilots 4−1−17

g. Transponder Operation Under Visual Flight

Rules (VFR)

1. Unless otherwise instructed by an ATC

facility, adjust transponder to reply on Mode 3/A

Code 1200 regardless of altitude.

NOTE−

1. Aircraft not in contact with an ATC facility may squawk

1255 in lieu of 1200 while en route to, from, or within the

designated fire fighting area(s).

2. VFR aircraft which fly authorized SAR missions for the

USAF or USCG may be advised to squawk 1277 in lieu of

1200 while en route to, from, or within the designated

search area.

3. Gliders not in contact with an ATC facility should

squawk 1202 in lieu of 1200.

REFERENCE−

FAAO 7110.66, National Beacon Code Allocation Plan.

2. Adjust transponder to reply on Mode C, with

altitude reporting capability activated if the aircraft is

so equipped, unless deactivation is directed by ATC

or unless the installed equipment has not been tested

and calibrated as required by 14 CFR Section 91.217.

If deactivation is required and your transponder is so

designed, turn off the altitude reporting switch and

continue to transmit Mode C framing pulses. If this

capability does not exist, turn off Mode C.

h. Radar Beacon Phraseology

Air traffic controllers, both civil and military, will use

the following phraseology when referring to

operation of the Air Traffic Control Radar Beacon

System (ATCRBS). Instructions by ATC refer only to

Mode A/3 or Mode C operation and do not affect the

operation of the transponder on other Modes.

1. SQUAWK (number). Operate radar beacon

transponder on designated code in Mode A/3.

2. IDENT. Engage the “IDENT” feature (military I/P) of the transponder.

3. SQUAWK (number) and IDENT. Operate

transponder on specified code in Mode A/3 and

engage the “IDENT” (military I/P) feature.

4. SQUAWK STANDBY. Switch transponder

to standby position.

5. SQUAWK LOW/NORMAL. Operate

transponder on low or normal sensitivity as specified.

Transponder is operated in “NORMAL” position

unless ATC specifies “LOW” (“ON” is used instead

of “NORMAL” as a master control label on some

types of transponders.)

6. SQUAWK ALTITUDE. Activate Mode C

with automatic altitude reporting.

7. STOP ALTITUDE SQUAWK. Turn off

altitude reporting switch and continue transmitting

Mode C framing pulses. If your equipment does not

have this capability, turn off Mode C.

8. STOP SQUAWK (mode in use). Switch off

specified mode. (Used for military aircraft when the

controller is unaware of military service requirements for the aircraft to continue operation on another

Mode.)

9. STOP SQUAWK. Switch off transponder.

10. SQUAWK MAYDAY. Operate transponder in the emergency position (Mode A Code 7700 for

civil transponder. Mode 3 Code 7700 and emergency

feature for military transponder.)

11. SQUAWK VFR. Operate radar beacon

transponder on Code 1200 in the Mode A/3, or other

appropriate VFR code.
AIM 7/26/12

4−1−18 Services Available to Pilots

FIG 4−1−3

Hazardous Area Reporting Service

4−1−21. Hazardous Area Reporting Service

a. Selected FSSs provide flight monitoring where

regularly traveled VFR routes cross large bodies of

water, swamps, and mountains. This service is

provided for the purpose of expeditiously alerting

Search and Rescue facilities when required. 

(See FIG 4−1−3.)

1. When requesting the service either in person,

by telephone or by radio, pilots should be prepared to

give the following information: type of aircraft,

altitude, indicated airspeed, present position, route of

flight, heading.

2. Radio contacts are desired at least every

10 minutes. If contact is lost for more than

15 minutes, Search and Rescue will be alerted. Pilots

are responsible for canceling their request for service

when they are outside the service area boundary.

Pilots experiencing two-way radio failure are

expected to land as soon as practicable and cancel

their request for the service. FIG 4−1−3 depicts the

areas and the FSS facilities involved in this program.

b. Long Island Sound Reporting Service.

New York and Bridgeport FSS Radio Sectors

provide Long Island Sound Reporting service on

request for aircraft traversing Long Island Sound.

1. When requesting the service, pilots should

ask for SOUND REPORTING SERVICE and should

be prepared to provide the following appropriate

information:

(a) Type and color of aircraft;

(b) The specific route and altitude across the

sound including the shore crossing point;

(c) The overwater crossing time;

(d) Number of persons on board; and

(e) True air speed.
7/26/12 AIM

Services Available to Pilots 4−1−19

2. Radio contacts are desired at least every

10 minutes; however, for flights of shorter duration a

midsound report is requested. If contact is lost for

more than 15 minutes Search and Rescue will be

alerted. Pilots are responsible for canceling their

request for the Long Island Sound Reporting Service

when outside the service area boundary. Aircraft

experiencing radio failure will be expected to land as

soon as practicable and cancel their request for the

service.

3. Communications. Primary communications − pilots are to transmit on 122.1 MHz and listen

on one of the following VOR frequencies:

(a) New York FSS Radio Sector Controls:

(1) Hampton RCO (FSS transmits and

receives on 122.6 MHz).

(2) Calverton VOR (FSS transmits on

117.2 and receives on standard FSS frequencies).

(3) Kennedy VORTAC (FSS transmits on

115.9 and receives on 122.1 MHz).

(b) Bridgeport FSS Radio Sector Controls:

(1) Madison VORTAC (FSS transmits on

110.4 and receives on 122.1 MHz).

(2) Groton VOR (FSS transmits on 110.85

and receives on 122.1 MHz).

(3) Bridgeport VOR (FSS transmits on

108.8 and receives on 122.1 MHz).

c. Block Island Reporting Service.

Within the Long Island Sound Reporting Service,

the New York FSS Radio Sector also provides an

additional service for aircraft operating between

Montauk Point and Block Island. When requesting

this service, pilots should ask for BLOCK ISLAND

REPORTING SERVICE and should be prepared to

provide the same flight information as required for

the Long Island Sound Reporting Service.

1. A minimum of three position reports are

mandatory for this service; these are:

(a) Reporting leaving either Montauk Point

or Block Island.

(b) Midway report.

(c) Report when over either Montauk Point or

Block Island. At this time, the overwater service is

canceled.

2. Communications. Pilots are to transmit and

receive on 122.6 MHz.

NOTE−

Pilots are advised that 122.6 MHz is a remote receiver

located at the Hampton VORTAC site and designed to

provide radio coverage between Hampton and Block Island. Flights proceeding beyond Block Island may contact

the Bridgeport FSS Radio Sector by transmitting on

122.1 MHz and listening on Groton VOR frequency

110.85 MHz.

d. Cape Cod and Islands Radar Overwater

Flight Following.

In addition to normal VFR radar advisory services,

traffic permitting, Cape Approach Control provides

a radar overwater flight following service for aircraft

traversing the Cape Cod and adjacent Island area.

Pilots desiring this service may contact Cape

TRACON on 118.2 MHz.

1. Pilots requesting this service should be

prepared to give the following information:

(a) Type and color of aircraft;

(b) Altitude;

(c) Position and heading;

(d) Route of flight; and

(e) True airspeed.

2. For best radar coverage, pilots are encouraged to fly at 1,500 feet MSL or above.

3. Pilots are responsible for canceling their

request for overwater flight following when they are

over the mainland and/or outside the service area

boundary.

e. Lake Reporting Service.

Cleveland and Lansing FSS Radio Sectors provide

Lake Reporting Service on request for aircraft

traversing the western half of Lake Erie; Green Bay,

Kankakee, Lansing, and Terre Haute FSS Radio

Sectors provide Lake Reporting Service on request

for aircraft traversing Lake Michigan.

1. When requesting the service, pilots should

ask for LAKE REPORTING SERVICE.

2. Pilots not on a VFR flight plan should be

prepared to provide all information that is normally

provided for a complete VFR flight plan.
AIM 7/26/12

4−1−20 Services Available to Pilots

3. Pilots already on a VFR flight plan should be

prepared to provide the following information:

(a) Aircraft or flight identification.

(b) Type of aircraft.

(c) Near−shore crossing point or last fix

before crossing.

(d) Proposed time over near−shore crossing

point or last fix before crossing.

(e) Proposed altitude.

(f) Proposed route of flight.

(g) Estimated time over water.

(h) Next landing point.

(i) FSS having complete VFR flight plan

information.

4. Radio contacts must not exceed 10 minutes

when pilots fly at an altitude that affords continuous

communications. If radio contact is lost for more than

15 minutes (5 minutes after a scheduled reporting

time), Search and Rescue (SAR) will be alerted.

5. The estimated time for crossing the far shore

will be the scheduled reporting time for aircraft that

fly at an altitude that does not afford continuous

communication coverage while crossing the lake. If

radio contact is not established within 5 minutes of

that time, SAR will be alerted.

6. Pilots are responsible for canceling their

request for Lake Reporting Service when outside the

service area boundary. Aircraft experiencing radio

failure will be expected to land as soon as practicable

and cancel their Lake Reporting Service flight plan.

7. Communications. Primary communications − Pilots should communicate with the following

facilities on the indicated frequencies:

(a) Cleveland FSS Radio Sector Controls:

(1) Cleveland RCO (FSS transmits and

receives on 122.35 or 122.55 MHz).

(2) Sandusky VOR (FSS transmits on

109.2 and receives on 122.1 MHz).

(b) Green Bay FSS Radio Sector Controls:

(1) Escanaba VORTAC (FSS transmits on

110.8 and receives on 122.1 MHz).

(2) Green Bay RCO (FSS transmits and

receives on 122.55 MHz).

(3) Manistique RCO (FSS transmits and

receives on 122.25 MHz).

(4) Manitowoc VOR (FSS transmits on

111.0 and receives on 122.1 MHz).

(5) Menominee VOR (FSS transmits on

109.6 and receives on 122.1 MHz).

(6) Milwaukee RCO (FSS transmits and

receives on 122.65 MHz).

(7) Falls VOR (FSS transmits on 110.0 and

receives on 122.1 MHz).

(c) Kankakee FSS Radio Sector Controls:

(1) Chicago Heights VORTAC (FSS transmits on 114.2 and receives on 122.1 MHz).

(2) Meigs RCO (FSS transmits and receives on 122.15 MHz).

(3) Waukegan RCO (FSS transmits and

receives on 122.55 MHz).

(d) Lansing FSS Radio Sector Controls:

(1) Lake Erie. Detroit City RCO (FSS

transmits and receives on 122.55 MHz).

(2) Lake Michigan:

[a] Keeler VORTAC (FSS transmits on

116.6 and receives on 122.1 MHz).

[b] Ludington RCO (FSS transmits and

receives on 122.45 MHz).

[c] Manistee VORTAC (FSS transmits

on 111.4 and receives on 122.1 MHz).

[d] Muskegon RCO (FSS transmits and

receives on 122.5 MHz).

[e] Pellston RCO (FSS transmits and

receives on 122.3 MHz).

[f] Pullman VORTAC (FSS transmits on

112.1 and receives on 122.1 MHz).

[g] Traverse City RCO (FSS transmits

and receives on 122.65 MHz).

(e) Terre Haute FSS Radio Sector Controls. South Bend RCO (FSS transmits and receives

on 122.6 MHz).
7/26/12 AIM

Services Available to Pilots 4−1−21

f. Everglades Reporting Service.

This service is offered by Miami Automated

International Flight Service Station (MIA AIFSS), in

extreme southern Florida. The service is provided to

aircraft crossing the Florida Everglades, between Lee

County (Ft. Myers, FL) VORTAC (RSW) on the

northwest side, and Dolphin (Miami, FL) VOR

(DHP) on the southeast side.

1. The pilot must request the service from

Miami AIFSS.

2. MIA AIFSS frequency information, 122.2,

122.3, and 122.65.

3. The pilot must file a VFR flight plan with the

remark: ERS.

4. The pilot must maintain 2000 feet of altitude.

5. The pilot must make position reports every

ten (10) minutes. SAR begins fifteen (15) minutes

after position report is not made on time.

6. The pilot is expected to land as soon as is

practical, in the event of two−way radio failure, and

advise MIA AIFSS that the service is terminated.

7. The pilot must notify Miami AIFSS when the

flight plan is cancelled or the service is suspended.

4−1−22. Airport Reservation Operations

and Special Traffic Management Programs

This section describes procedures for obtaining

required airport reservations at airports designated by

the FAA and for airports operating under Special

Traffic Management Programs.

a. Slot Controlled Airports.

1. The FAA may adopt rules to require advance

operations for unscheduled operations at certain

airports. In addition to the information in the rules

adopted by the FAA, a listing of the airports and

relevant information will be maintained on the FAA

Web site listed below.

2. The FAA has established an Airport

Reservation Office (ARO) to receive and process

reservations for unscheduled flights at the slot

controlled airports. The ARO uses the Enhanced

Computer Voice Reservation System (e−CVRS) to

allocate reservations. Reservations will be available

beginning 72 hours in advance of the operation at the

slot controlled airport. Refer to the Web site or

touch−tone phone interface for the current listing of

slot controlled airports, limitations, and reservation

procedures.

NOTE−

The web interface/telephone numbers to obtain a

reservation for unscheduled operations at a slot controlled

airport are:

1. http://www.fly.faa.gov/ecvrs.

2. Touch−tone: 1−800−875−9694 or 703−707−0568.

(e−CVRS interface).

3. Trouble number: 703−904−4452.

3. For more detailed information on operations

and reservation procedures at a Slot Controlled

Airport, please see Advisory Circular 93−1A,

Reservations for Unscheduled Operations at slot

controlled airports. A copy of the Advisory

Circular may be obtained via the Internet at:

http://www.faa.gov.

b. Special Traffic Management Programs

(STMP).

1. Special procedures may be established when

a location requires special traffic handling to

accommodate above normal traffic demand (e.g., the

Indianapolis 500, Super Bowl) or reduced airport

capacity (e.g., airport runway/taxiway closures for

airport construction). The special procedures may

remain in effect until the problem has been resolved

or until local traffic management procedures can

handle the situation and a need for special handling no

longer exists.

2. There will be two methods available for

obtaining slot reservations through the

ATCSCC: the web interface and the touch−tone

interface. If these methods are used, a NOTAM will

be issued relaying the web site address and toll free

telephone number. Be sure to check current

NOTAMs to determine: what airports are included

in the STMP; the dates and times reservations are

required; the time limits for reservation requests; the

point of contact for reservations; and any other

instructions.

c. Users may contact the ARO at 703−904−4452

if they have a problem making a reservation or have

a question concerning the slot controlled airport/

STMP regulations or procedures.
AIM 7/26/12

4−1−22 Services Available to Pilots

d. Making Reservations.

1. Internet Users. Detailed information and

User Instruction Guides for using the Web interface

to the reservation systems are available on the

websites for the slot controlled airports (e−CVRS),

http://www.fly.faa.gov/ecvrs; and STMPs

(e−STMP), http://www.fly.faa.gov/estmp.

2. Telephone users. When using the telephone

to make a reservation, you are prompted for input of

information about what you wish to do. All input is

accomplished using the keypad on the telephone. The

only problem with a telephone is that most keys have

a letter and number associated with them. When the

system asks for a date or time, it is expecting an input

of numbers. A problem arises when entering an

aircraft call sign or tail number. The system does not

detect if you are entering a letter (alpha character) or

a number. Therefore, when entering an aircraft call

sign or tail number two keys are used to represent

each letter or number. When entering a number,

precede the number you wish by the number 0 (zero)

i.e., 01, 02, 03, 04, . . .. If you wish to enter a letter, first

press the key on which the letter appears and then

press 1, 2, or 3, depending upon whether the letter you

desire is the first, second, or third letter on that key.

For example to enter the letter “N” first press the

“6” key because “N” is on that key, then press the

“2” key because the letter “N” is the second letter on

the “6” key. Since there are no keys for the letters “Q”

and “Z” e−CVRS pretends they are on the number

“1” key. Therefore, to enter the letter “Q”, press 11,

and to enter the letter “Z” press 12.

NOTE−

Users are reminded to enter the “N” character with their

tail numbers. (See TBL 4−1−4.)

TBL 4−1−4

Codes for Call Sign/Tail Number Input

Codes for Call Sign/Tail Number Input Only

A−21 J−51 S−73 1-01

B−22 K−52 T−81 2−02

C−23 L−53 U−82 3−03

D−31 M−61 V−83 4−04

E−32 N−62 W−91 5−05

F−33 O−63 X−92 6−06

G−41 P−71 Y−93 7−07

H−42 Q−11 Z−12 8−08

I−43 R−72 0−00 9−09
7/26/12 AIM

Services Available to Pilots 4−1−23

3. Additional helpful key entries: (See TBL 4−1−5.)

TBL 4−1−5

Helpful Key Entries

# After entering a call sign/tail number, depressing the “pound key” (#) twice will indicate the end of the

entry.

*2 Will take the user back to the start of the process.

*3 Will repeat the call sign/tail number used in a previous reservation.

*5 Will repeat the previous question.

*8 Tutorial Mode: In the tutorial mode each prompt for input includes a more detailed description of what

is expected as input. *8 is a toggle on/off switch. If you are in tutorial mode and enter *8, you will return

to the normal mode.

*0 Expert Mode: In the expert mode each prompt for input is brief with little or no explanation. Expert

mode is also on/off toggle.

4−1−23. Requests for Waivers and

Authorizations from Title 14, Code of

Federal Regulations (14 CFR)

a. Requests for a Certificate of Waiver or

Authorization (FAA Form 7711−2), or requests for

renewal of a waiver or authorization, may be accepted

by any FAA facility and will be forwarded, if

necessary, to the appropriate office having waiver

authority.

b. The grant of a Certificate of Waiver or

Authorization from 14 CFR constitutes relief from

specific regulations, to the degree and for the period

of time specified in the certificate, and does not waive

any state law or local ordinance. Should the proposed

operations conflict with any state law or local

ordinance, or require permission of local authorities

or property owners, it is the applicant’s responsibility

to resolve the matter. The holder of a waiver is

responsible for compliance with the terms of the

waiver and its provisions.

c. A waiver may be canceled at any time by the

Administrator, the person authorized to grant the

waiver, or the representative designated to monitor a

specific operation. In such case either written notice

of cancellation, or written confirmation of a verbal

cancellation will be provided to the holder.

4−1−24. Weather System Processor

The Weather System Processor (WSP) was developed for use in the National Airspace System to

provide weather processor enhancements to selected

Airport Surveillance Radar (ASR)−9 facilities. The

WSP provides Air Traffic with warnings of

hazardous wind shear and microbursts. The WSP also

provides users with terminal area 6−level weather,

storm cell locations and movement, as well as the

location and predicted future position and intensity of

wind shifts that may affect airport operations.

7/26/12 AIM

Radio Communications Phraseology 4−2−1

Section 2. Radio Communications Phraseology 

and Techniques

4−2−1. General

a. Radio communications are a critical link in the

ATC system. The link can be a strong bond between

pilot and controller or it can be broken with surprising

speed and disastrous results. Discussion herein

provides basic procedures for new pilots and also

highlights safe operating concepts for all pilots.

b. The single, most important thought in pilotcontroller communications is understanding. It is

essential, therefore, that pilots acknowledge each

radio communication with ATC by using the

appropriate aircraft call sign. Brevity is important,

and contacts should be kept as brief as possible, but

controllers must know what you want to do before

they can properly carry out their control duties. And

you, the pilot, must know exactly what the controller

wants you to do. Since concise phraseology may not

always be adequate, use whatever words are

necessary to get your message across. Pilots are to

maintain vigilance in monitoring air traffic control

radio communications frequencies for potential

traffic conflicts with their aircraft especially when

operating on an active runway and/or when

conducting a final approach to landing.

c. All pilots will find the Pilot/Controller Glossary

very helpful in learning what certain words or phrases

mean. Good phraseology enhances safety and is the

mark of a professional pilot. Jargon, chatter, and

“CB” slang have no place in ATC communications.

The Pilot/Controller Glossary is the same glossary

used in FAA Order JO 7110.65, Air Traffic Control.

We recommend that it be studied and reviewed from

time to time to sharpen your communication skills.

4−2−2. Radio Technique

a. Listen before you transmit. Many times you can

get the information you want through ATIS or by

monitoring the frequency. Except for a few situations

where some frequency overlap occurs, if you hear

someone else talking, the keying of your transmitter

will be futile and you will probably jam their

receivers causing them to repeat their call. If you have

just changed frequencies, pause, listen, and make sure

the frequency is clear.

b. Think before keying your transmitter. Know

what you want to say and if it is lengthy; e.g., a flight

plan or IFR position report, jot it down.

c. The microphone should be very close to your

lips and after pressing the mike button, a slight pause

may be necessary to be sure the first word is

transmitted. Speak in a normal, conversational tone.

d. When you release the button, wait a few

seconds before calling again. The controller or FSS

specialist may be jotting down your number, looking

for your flight plan, transmitting on a different

frequency, or selecting the transmitter for your

frequency.

e. Be alert to the sounds or the lack of sounds in

your receiver. Check your volume, recheck your

frequency, and make sure that your microphone is not

stuck in the transmit position. Frequency blockage

can, and has, occurred for extended periods of time

due to unintentional transmitter operation. This type

of interference is commonly referred to as a “stuck

mike,” and controllers may refer to it in this manner

when attempting to assign an alternate frequency. If

the assigned frequency is completely blocked by this

type of interference, use the procedures described for

en route IFR radio frequency outage to establish or

reestablish communications with ATC.

f. Be sure that you are within the performance

range of your radio equipment and the ground station

equipment. Remote radio sites do not always transmit

and receive on all of a facility’s available frequencies,

particularly with regard to VOR sites where you can

hear but not reach a ground station’s receiver.

Remember that higher altitudes increase the range of

VHF “line of sight” communications.

4−2−3. Contact Procedures

a. Initial Contact.

1. The terms initial contact or initial callup

means the first radio call you make to a given facility

or the first call to a different controller or FSS

specialist within a facility. Use the following format:
AIM 7/26/12

4−2−2 Radio Communications Phraseology

(a) Name of the facility being called;

(b) Your full aircraft identification as filed in

the flight plan or as discussed in paragraph 4−2−4,

Aircraft Call Signs;

(c) When operating on an airport surface,

state your position.

(d) The type of message to follow or your

request if it is short; and

(e) The word “Over” if required.

EXAMPLE−

1. “New York Radio, Mooney Three One One Echo.”

2. “Columbia Ground, Cessna Three One Six Zero

Foxtrot, south ramp, I−F−R Memphis.”

3. “Miami Center, Baron Five Six Three Hotel, request

V−F−R traffic advisories.”

2. Many FSSs are equipped with Remote

Communications Outlets (RCOs) and can transmit on

the same frequency at more than one location. The

frequencies available at specific locations are

indicated on charts above FSS communications

boxes. To enable the specialist to utilize the correct

transmitter, advise the location and the frequency on

which you expect a reply.

EXAMPLE−

St. Louis FSS can transmit on frequency 122.3 at either

Farmington, Missouri, or Decatur, Illinois, if you are in the

vicinity of Decatur, your callup should be “Saint Louis

radio, Piper Six Niner Six Yankee, receiving Decatur One

Two Two Point Three.”

3. If radio reception is reasonably assured,

inclusion of your request, your position or altitude,

and the phrase “(ATIS) Information Charlie

received” in the initial contact helps decrease radio

frequency congestion. Use discretion; do not

overload the controller with information unneeded or

superfluous. If you do not get a response from the

ground station, recheck your radios or use another

transmitter, but keep the next contact short.

EXAMPLE−

“Atlanta Center, Duke Four One Romeo, request V−F−R

traffic advisories, Twenty Northwest Rome, seven thousand

five hundred, over.”

b. Initial Contact When Your Transmitting and

Receiving Frequencies are Different.

1. If you are attempting to establish contact with

a ground station and you are receiving on a different

frequency than that transmitted, indicate the VOR

name or the frequency on which you expect a reply.

Most FSSs and control facilities can transmit on

several VOR stations in the area. Use the appropriate

FSS call sign as indicated on charts.

EXAMPLE−

New York FSS transmits on the Kennedy, the Hampton, and

the Calverton VORTACs. If you are in the Calverton area,

your callup should be “New York radio, Cessna Three One

Six Zero Foxtrot, receiving Calverton V−O−R, over.”

2. If the chart indicates FSS frequencies above

the VORTAC or in the FSS communications boxes,

transmit or receive on those frequencies nearest your

location.

3. When unable to establish contact and you

wish to call any ground station, use the phrase “ANY

RADIO (tower) (station), GIVE CESSNA THREE

ONE SIX ZERO FOXTROT A CALL ON

(frequency) OR (V−O−R).” If an emergency exists or

you need assistance, so state.

c. Subsequent Contacts and Responses to

Callup from a Ground Facility.

Use the same format as used for the initial contact

except you should state your message or request with

the callup in one transmission. The ground station

name and the word “Over” may be omitted if the

message requires an obvious reply and there is no

possibility for misunderstandings. You should

acknowledge all callups or clearances unless the

controller or FSS specialist advises otherwise. There

are some occasions when controllers must issue

time-critical instructions to other aircraft, and they

may be in a position to observe your response, either

visually or on radar. If the situation demands your

response, take appropriate action or immediately

advise the facility of any problem. Acknowledge with

your aircraft identification, either at the beginning or

at the end of your transmission, and one of the words

“Wilco,” “Roger,” “Affirmative,” “Negative,” or

other appropriate remarks; e.g., “PIPER TWO ONE

FOUR LIMA, ROGER.” If you have been receiving

services; e.g., VFR traffic advisories and you are

leaving the area or changing frequencies, advise the

ATC facility and terminate contact.

d. Acknowledgement of Frequency Changes.

1. When advised by ATC to change frequencies,

acknowledge the instruction. If you select the new

frequency without an acknowledgement, the controller’s workload is increased because there is no way of

knowing whether you received the instruction or have

had radio communications failure.
7/26/12 AIM

Radio Communications Phraseology 4−2−3

2. At times, a controller/specialist may be

working a sector with multiple frequency assignments. In order to eliminate unnecessary verbiage

and to free the controller/specialist for higher priority

transmissions, the controller/specialist may request

the pilot “(Identification), change to my frequency

123.4.” This phrase should alert the pilot that the

controller/specialist is only changing frequencies, not

controller/specialist, and that initial callup phraseology may be abbreviated.

EXAMPLE−

“United Two Twenty−Two on one two three point four” or

“one two three point four, United Two Twenty−Two.”

e. Compliance with Frequency Changes.

When instructed by ATC to change frequencies,

select the new frequency as soon as possible unless

instructed to make the change at a specific time, fix,

or altitude. A delay in making the change could result

in an untimely receipt of important information. If

you are instructed to make the frequency change at a

specific time, fix, or altitude, monitor the frequency

you are on until reaching the specified time, fix, or

altitudes unless instructed otherwise by ATC.

REFERENCE−

AIM, ARTCC Communications, Paragraph 5−3−1.

4−2−4. Aircraft Call Signs

a. Precautions in the Use of Call Signs.

1. Improper use of call signs can result in pilots

executing a clearance intended for another aircraft.

Call signs should never be abbreviated on an initial

contact or at any time when other aircraft call signs

have similar numbers/sounds or identical letters/

number; e.g., Cessna 6132F, Cessna 1622F,

Baron 123F, Cherokee 7732F, etc.

EXAMPLE−

Assume that a controller issues an approach clearance to

an aircraft at the bottom of a holding stack and an aircraft

with a similar call sign (at the top of the stack)

acknowledges the clearance with the last two or three

numbers of the aircraft’s call sign. If the aircraft at the

bottom of the stack did not hear the clearance and

intervene, flight safety would be affected, and there would

be no reason for either the controller or pilot to suspect that

anything is wrong. This kind of “human factors” error can

strike swiftly and is extremely difficult to rectify.

2. Pilots, therefore, must be certain that aircraft

identification is complete and clearly identified

before taking action on an ATC clearance. ATC

specialists will not abbreviate call signs of air carrier

or other civil aircraft having authorized call signs.

ATC specialists may initiate abbreviated call signs of

other aircraft by using the prefix and the last three

digits/letters of the aircraft identification after

communications are established. The pilot may use

the abbreviated call sign in subsequent contacts with

the ATC specialist. When aware of similar/identical

call signs, ATC specialists will take action to

minimize errors by emphasizing certain numbers/letters, by repeating the entire call sign, by repeating the

prefix, or by asking pilots to use a different call sign

temporarily. Pilots should use the phrase “VERIFY

CLEARANCE FOR (your complete call sign)” if

doubt exists concerning proper identity.

3. Civil aircraft pilots should state the aircraft

type, model or manufacturer’s name, followed by the

digits/letters of the registration number. When the

aircraft manufacturer’s name or model is stated, the

prefix “N” is dropped; e.g., Aztec Two Four Six Four

Alpha.

EXAMPLE−

1. Bonanza Six Five Five Golf.

2. Breezy Six One Three Romeo Experimental (omit

“Experimental” after initial contact).

4. Air Taxi or other commercial operators not

having FAA authorized call signs should prefix their

normal identification with the phonetic word

“Tango.”

EXAMPLE−

Tango Aztec Two Four Six Four Alpha.

5. Air carriers and commuter air carriers having

FAA authorized call signs should identify themselves

by stating the complete call sign (using group form

for the numbers) and the word “heavy” if appropriate.

EXAMPLE−

1. United Twenty−Five Heavy.

2. Midwest Commuter Seven Eleven.

6. Military aircraft use a variety of systems

including serial numbers, word call signs, and

combinations of letters/numbers. Examples include

Army Copter 48931; Air Force 61782; REACH

31792; Pat 157; Air Evac 17652; Navy Golf Alfa

Kilo 21; Marine 4 Charlie 36, etc.
AIM 7/26/12

4−2−4 Radio Communications Phraseology

b. Air Ambulance Flights.

Because of the priority afforded air ambulance flights

in the ATC system, extreme discretion is necessary

when using the term “LIFEGUARD.” It is only

intended for those missions of an urgent medical

nature and to be utilized only for that portion of the

flight requiring expeditious handling. When requested by the pilot, necessary notification to

expedite ground handling of patients, etc., is provided

by ATC; however, when possible, this information

should be passed in advance through non−ATC

communications systems.

1. Civilian air ambulance flights responding to

medical emergencies (first call to an accident scene,

carrying patients, organ donors, organs, or other

urgently needed lifesaving medical material) will be

expedited by ATC when necessary. When expeditious handling is necessary, add the word

“LIFEGUARD” in the remarks section of the flight

plan. In radio communications, use the call sign

“LIFEGUARD” followed by the aircraft registration

letters/numbers.

2. Similar provisions have been made for the use

of “AIR EVAC” and “MED EVAC” by military air

ambulance flights, except that these military flights

will receive priority handling only when specifically

requested.

EXAMPLE−

Lifeguard Two Six Four Six.

3. Air carrier and Air Taxi flights responding to

medical emergencies will also be expedited by ATC

when necessary. The nature of these medical

emergency flights usually concerns the transportation of urgently needed lifesaving medical materials

or vital organs. IT IS IMPERATIVE THAT THE

COMPANY/PILOT DETERMINE, BY THE NATURE/URGENCY OF THE SPECIFIC MEDICAL

CARGO, IF PRIORITY ATC ASSISTANCE IS

REQUIRED. Pilots must ensure that the word

“LIFEGUARD” is included in the remarks section of

the flight plan and use the call sign “LIFEGUARD”

followed by the company name and flight number for

all transmissions when expeditious handling is

required. It is important for ATC to be aware of

“LIFEGUARD” status, and it is the pilot’s

responsibility to ensure that this information is

provided to ATC.

EXAMPLE−

Lifeguard Delta Thirty−Seven.

c. Student Pilots Radio Identification.

1. The FAA desires to help student pilots in

acquiring sufficient practical experience in the

environment in which they will be required to

operate. To receive additional assistance while

operating in areas of concentrated air traffic, student

pilots need only identify themselves as a student pilot

during their initial call to an FAA radio facility.

EXAMPLE−

Dayton tower, Fleetwing One Two Three Four, student

pilot.

2. This special identification will alert FAA

ATC personnel and enable them to provide student

pilots with such extra assistance and consideration as

they may need. It is recommended that student pilots

identify themselves as such, on initial contact with

each clearance delivery prior to taxiing, ground

control, tower, approach and departure control

frequency, or FSS contact.

4−2−5. Description of Interchange or

Leased Aircraft

a. Controllers issue traffic information based on

familiarity with airline equipment and color/

markings. When an air carrier dispatches a flight

using another company’s equipment and the pilot

does not advise the terminal ATC facility, the possible

confusion in aircraft identification can compromise

safety.

b. Pilots flying an “interchange” or “leased”

aircraft not bearing the colors/markings of the

company operating the aircraft should inform the

terminal ATC facility on first contact the name of the

operating company and trip number, followed by the

company name as displayed on the aircraft, and

aircraft type.

EXAMPLE−

Air Cal Three Eleven, United (interchange/lease),

Boeing Seven Two Seven.

4−2−6. Ground Station Call Signs

Pilots, when calling a ground station, should begin

with the name of the facility being called followed by

the type of the facility being called as indicated in

TBL 4−2−1.
7/26/12 AIM

Radio Communications Phraseology 4−2−5

TBL 4−2−1

Calling a Ground Station

Facility Call Sign

Airport UNICOM “Shannon UNICOM”

FAA Flight Service Station “Chicago Radio”

FAA Flight Service Station

(En Route Flight Advisory

Service (Weather))

“Seattle Flight Watch”

Airport Traffic Control

Tower

“Augusta Tower”

Clearance Delivery Position

(IFR)

“Dallas Clearance

Delivery”

Ground Control Position in

Tower

“Miami Ground”

Radar or Nonradar

Approach Control Position

“Oklahoma City

Approach”

Radar Departure Control

Position

“St. Louis Departure”

FAA Air Route Traffic

Control Center

“Washington Center”

4−2−7. Phonetic Alphabet

The International Civil Aviation Organization

(ICAO) phonetic alphabet is used by FAA personnel

when communications conditions are such that the

information cannot be readily received without their

use. ATC facilities may also request pilots to use

phonetic letter equivalents when aircraft with similar

sounding identifications are receiving communications on the same frequency. Pilots should use the

phonetic alphabet when identifying their aircraft

during initial contact with air traffic control facilities.

Additionally, use the phonetic equivalents for single

letters and to spell out groups of letters or difficult

words during adverse communications conditions.

(See TBL 4−2−2.)

TBL 4−2−2

Phonetic Alphabet/Morse Code

Character Morse Code Telephony Phonic

(Pronunciation)

A   Alfa (AL−FAH)

B     Bravo (BRAH−VOH)

C     Charlie (CHAR−LEE) or

(SHAR−LEE)

D    Delta (DELL−TAH)

E  Echo (ECK−OH)

F     Foxtrot (FOKS−TROT)

G    Golf (GOLF)

H     Hotel (HOH−TEL)

I   India (IN−DEE−AH)

J     Juliett (JEW−LEE−ETT)

K    Kilo (KEY−LOH)

L     Lima (LEE−MAH)

M   Mike (MIKE)

N   November (NO−VEM−BER)

O    Oscar (OSS−CAH)

P     Papa (PAH−PAH)

Q     Quebec (KEH−BECK)

R    Romeo (ROW−ME−OH)

S    Sierra (SEE−AIR−RAH)

T  Tango (TANG−GO)

U    Uniform (YOU−NEE−FORM) or

(OO−NEE−FORM)

V     Victor (VIK−TAH)

W    Whiskey (WISS−KEY)

X     Xray (ECKS−RAY)

Y     Yankee (YANG−KEY)

Z     Zulu (ZOO−LOO)

1      One (WUN)

2      Two (TOO)

3      Three (TREE)

4      Four (FOW−ER)

5      Five (FIFE)

6      Six (SIX)

7      Seven (SEV−EN)

8      Eight (AIT)

9      Nine (NIN−ER)

0      Zero (ZEE−RO)
AIM 7/26/12

4−2−6 Radio Communications Phraseology

4−2−8. Figures

a. Figures indicating hundreds and thousands in

round number, as for ceiling heights, and upper wind

levels up to 9,900 must be spoken in accordance with

the following.

EXAMPLE−

1. 500 five hundred ........

2. 4,500 four thousand five hundred ......

b. Numbers above 9,900 must be spoken by

separating the digits preceding the word “thousand.”

EXAMPLE−

1. 10,000 one zero thousand .....

2. 13,500 one three thousand five hundred .....

c. Transmit airway or jet route numbers as follows.

EXAMPLE−

1. V12 Victor Twelve .......

2. J533 J ....... Five Thirty−Three

d. All other numbers must be transmitted by

pronouncing each digit.

EXAMPLE−

10 one zero ...........

e. When a radio frequency contains a decimal

point, the decimal point is spoken as “POINT.”

EXAMPLE−

122.1 one two two point one .........

NOTE−

ICAO procedures require the decimal point be spoken as

“DECIMAL.” The FAA will honor such usage by military

aircraft and all other aircraft required to use ICAO

procedures.

4−2−9. Altitudes and Flight Levels

a. Up to but not including 18,000 feet MSL, state

the separate digits of the thousands plus the hundreds

if appropriate.

EXAMPLE−

1. 12,000 one two thousand .....

2. 12,500 one two thousand five hundred .....

b. At and above 18,000 feet MSL (FL 180), state

the words “flight level” followed by the separate

digits of the flight level.

EXAMPLE−

1. 190 Flight Level One Niner Zero ........

2. 275 Flight Level Two Seven Five ........

4−2−10. Directions

The three digits of bearing, course, heading, or wind

direction should always be magnetic. The word

“true” must be added when it applies.

EXAMPLE−

1. (Magnetic course) 005 zero zero five ......

2. (True course) 050 .......... zero five zero true

3. (Magnetic bearing) 360 three six zero .....

4. (Magnetic heading) 100 heading one zero .....

zero

5. (Wind direction) 220 wind two two zero ........

4−2−11. Speeds

The separate digits of the speed followed by the word

“KNOTS.” Except, controllers may omit the word

“KNOTS” when using speed adjustment procedures;

e.g., “REDUCE/INCREASE SPEED TO TWO

FIVE ZERO.”

EXAMPLE−

(Speed) 250 two five zero knots .................

(Speed) 190 one niner zero knots .................

The separate digits of the Mach Number preceded by

“Mach.”

EXAMPLE−

(Mach number) 1.5 Mach one point five ...........

(Mach number) 0.64 Mach point six four ..........

(Mach number) 0.7 Mach point seven ...........

4−2−12. Time

a. FAA uses Coordinated Universal Time (UTC)

for all operations. The word “local” or the time zone

equivalent must be used to denote local when local

time is given during radio and telephone communications. The term “Zulu” may be used to denote UTC.

EXAMPLE−

0920 UTC zero niner two zero, .....

 zero one two zero pacific or local,

 or one twenty AM
7/26/12 AIM

Radio Communications Phraseology 4−2−7

b. To convert from Standard Time to Coordinated

Universal Time:

TBL 4−2−3

Standard Time to Coordinated Universal Time

Eastern Standard Time .........

Central Standard Time .........

Mountain Standard Time .......

Pacific Standard Time .........

Alaska Standard Time .........

Hawaii Standard Time .........

Add 5 hours

Add 6 hours

Add 7 hours

Add 8 hours

Add 9 hours

Add 10 hours

NOTE−

For daylight time, subtract 1 hour.

c. A reference may be made to local daylight or

standard time utilizing the 24−hour clock system. The

hour is indicated by the first two figures and the

minutes by the last two figures.

EXAMPLE−

0000 zero zero zero zero .......................

0920 zero niner two zero .......................

d. Time may be stated in minutes only

(two figures) in radiotelephone communications

when no misunderstanding is likely to occur.

e. Current time in use at a station is stated in the

nearest quarter minute in order that pilots may use this

information for time checks. Fractions of a quarter

minute less than 8 seconds are stated as the preceding

quarter minute; fractions of a quarter minute of

8 seconds or more are stated as the succeeding quarter

minute.

EXAMPLE−

0929:05 time, zero niner two niner ......

0929:10 time, zero niner two niner and ......

one−quarter

4−2−13. Communications with Tower when

Aircraft Transmitter or Receiver or Both are

Inoperative

a. Arriving Aircraft.

1. Receiver inoperative.

(a) If you have reason to believe your receiver

is inoperative, remain outside or above the Class D

surface area until the direction and flow of traffic has

been determined; then, advise the tower of your type

aircraft, position, altitude, intention to land, and

request that you be controlled with light signals.

REFERENCE−

AIM, Traffic Control Light Signals, Paragraph 4−3−13.

(b) When you are approximately 3 to 5 miles

from the airport, advise the tower of your position and

join the airport traffic pattern. From this point on,

watch the tower for light signals. Thereafter, if a

complete pattern is made, transmit your position

downwind and/or turning base leg.

2. Transmitter inoperative. Remain outside

or above the Class D surface area until the direction

and flow of traffic has been determined; then, join the

airport traffic pattern. Monitor the primary local

control frequency as depicted on Sectional Charts for

landing or traffic information, and look for a light

signal which may be addressed to your aircraft.

During hours of daylight, acknowledge tower

transmissions or light signals by rocking your wings.

At night, acknowledge by blinking the landing or

navigation lights. To acknowledge tower transmissions during daylight hours, hovering helicopters will

turn in the direction of the controlling facility and

flash the landing light. While in flight, helicopters

should show their acknowledgement of receiving a

transmission by making shallow banks in opposite

directions. At night, helicopters will acknowledge

receipt of transmissions by flashing either the landing

or the search light.

3. Transmitter and receiver inoperative.

Remain outside or above the Class D surface area

until the direction and flow of traffic has been

determined; then, join the airport traffic pattern and

maintain visual contact with the tower to receive light

signals. Acknowledge light signals as noted above.

b. Departing Aircraft. If you experience radio

failure prior to leaving the parking area, make every

effort to have the equipment repaired. If you are

unable to have the malfunction repaired, call the

tower by telephone and request authorization to

depart without two-way radio communications. If

tower authorization is granted, you will be given

departure information and requested to monitor the

tower frequency or watch for light signals as

appropriate. During daylight hours, acknowledge

tower transmissions or light signals by moving the

ailerons or rudder. At night, acknowledge by blinking

the landing or navigation lights. If radio malfunction
AIM 7/26/12

4−2−8 Radio Communications Phraseology

occurs after departing the parking area, watch the

tower for light signals or monitor tower frequency.

REFERENCE−

14 CFR Section 91.125 and 14 CFR Section 91.129.

4−2−14. Communications for VFR Flights

a. FSSs and Supplemental Weather Service

Locations (SWSLs) are allocated frequencies for

different functions; for example, 122.0 MHz is

assigned as the En Route Flight Advisory Service

frequency at selected FSSs. In addition, certain FSSs

provide Local Airport Advisory on 123.6 MHz or

other frequencies which can be found in the A/FD. If

you are in doubt as to what frequency to use,

122.2 MHz is assigned to the majority of FSSs as a

common en route simplex frequency.

NOTE−

In order to expedite communications, state the frequency

being used and the aircraft location during initial callup.

EXAMPLE−

Dayton radio, November One Two Three Four Five on one

two two point two, over Springfield V−O−R, over.

b. Certain VOR voice channels are being utilized

for recorded broadcasts; i.e., ATIS, HIWAS, etc.

These services and appropriate frequencies are listed

in the A/FD. On VFR flights, pilots are urged to

monitor these frequencies. When in contact with a

control facility, notify the controller if you plan to

leave the frequency to monitor these broadcasts.
7/26/12 AIM

Airport Operations 4−3−1

Section 3. Airport Operations

4−3−1. General

Increased traffic congestion, aircraft in climb and

descent attitudes, and pilot preoccupation with

cockpit duties are some factors that increase the

hazardous accident potential near the airport. The

situation is further compounded when the weather is

marginal, that is, just meeting VFR requirements.

Pilots must be particularly alert when operating in the

vicinity of an airport. This section defines some rules,

practices, and procedures that pilots should be

familiar with and adhere to for safe airport operations.

4−3−2. Airports with an Operating Control

Tower

a. When operating at an airport where traffic

control is being exercised by a control tower, pilots

are required to maintain two−way radio contact with

the tower while operating within the Class B, Class C,

and Class D surface area unless the tower authorizes

otherwise. Initial callup should be made about

15 miles from the airport. Unless there is a good

reason to leave the tower frequency before exiting the

Class B, Class C, and Class D surface areas, it is a

good operating practice to remain on the tower

frequency for the purpose of receiving traffic

information. In the interest of reducing tower

frequency congestion, pilots are reminded that it is

not necessary to request permission to leave the tower

frequency once outside of Class B, Class C, and

Class D surface areas. Not all airports with an

operating control tower will have Class D airspace.

These airports do not have weather reporting which

is a requirement for surface based controlled

airspace, previously known as a control zone. The

controlled airspace over these airports will normally

begin at 700 feet or 1,200 feet above ground level and

can be determined from the visual aeronautical

charts. Pilots are expected to use good operating

practices and communicate with the control tower as

described in this section.

b. When necessary, the tower controller will issue

clearances or other information for aircraft to

generally follow the desired flight path (traffic

patterns) when flying in Class B, Class C, and Class D

surface areas and the proper taxi routes when

operating on the ground. If not otherwise authorized

or directed by the tower, pilots of fixed−wing aircraft

approaching to land must circle the airport to the left.

Pilots approaching to land in a helicopter must avoid

the flow of fixed−wing traffic. However, in all

instances, an appropriate clearance must be received

from the tower before landing.

FIG 4−3−1

Components of a Traffic Pattern

NOTE−

This diagram is intended only to illustrate terminology

used in identifying various components of a traffic pattern.

It should not be used as a reference or guide on how to enter

a traffic pattern.

c. The following terminology for the various

components of a traffic pattern has been adopted as

standard for use by control towers and pilots (See

FIG 4−3−1):

1. Upwind leg. A flight path parallel to the

landing runway in the direction of landing.

2. Crosswind leg. A flight path at right angles

to the landing runway off its takeoff end.

3. Downwind leg. A flight path parallel to the

landing runway in the opposite direction of landing.

4. Base leg. A flight path at right angles to the

landing runway off its approach end and extending

from the downwind leg to the intersection of the

extended runway centerline.

5. Final approach. A flight path in the

direction of landing along the extended runway

centerline from the base leg to the runway.

6. Departure leg. The flight path which begins

after takeoff and continues straight ahead along the

extended runway centerline. The departure climb

continues until reaching a point at least 1/2 mile
AIM 7/26/12

4−3−2 Airport Operations

beyond the departure end of the runway and within

300 feet of the traffic pattern altitude.

d. Many towers are equipped with a tower radar

display. The radar uses are intended to enhance the

effectiveness and efficiency of the local control, or

tower, position. They are not intended to provide

radar services or benefits to pilots except as they may

accrue through a more efficient tower operation. The

four basic uses are:

1. To determine an aircraft’s exact location.

This is accomplished by radar identifying the VFR

aircraft through any of the techniques available to a

radar position, such as having the aircraft squawk

ident. Once identified, the aircraft’s position and

spatial relationship to other aircraft can be quickly

determined, and standard instructions regarding VFR

operation in Class B, Class C, and Class D surface

areas will be issued. Once initial radar identification

of a VFR aircraft has been established and the

appropriate instructions have been issued, radar

monitoring may be discontinued; the reason being

that the local controller’s primary means of

surveillance in VFR conditions is visually scanning

the airport and local area.

2. To provide radar traffic advisories. Radar

traffic advisories may be provided to the extent that

the local controller is able to monitor the radar

display. Local control has primary control responsibilities to the aircraft operating on the runways, which

will normally supersede radar monitoring duties.

3. To provide a direction or suggested

heading. The local controller may provide pilots

flying VFR with generalized instructions which will

facilitate operations; e.g., “PROCEED SOUTHWESTBOUND, ENTER A RIGHT DOWNWIND

RUNWAY THREE ZERO,” or provide a suggested

heading to establish radar identification or as an

advisory aid to navigation; e.g., “SUGGESTED

HEADING TWO TWO ZERO, FOR RADAR

IDENTIFICATION.” In both cases, the instructions

are advisory aids to the pilot flying VFR and are not

radar vectors.

NOTE−

Pilots have complete discretion regarding acceptance of

the suggested headings or directions and have sole

responsibility for seeing and avoiding other aircraft.

4. To provide information and instructions to

aircraft operating within Class B, Class C, and

Class D surface areas. In an example of this

situation, the local controller would use the radar to

advise a pilot on an extended downwind when to turn

base leg.

NOTE−

The above tower radar applications are intended to

augment the standard functions of the local control

position. There is no controller requirement to maintain

constant radar identification. In fact, such a requirement

could compromise the local controller’s ability to visually

scan the airport and local area to meet FAA responsibilities

to the aircraft operating on the runways and within the

Class B, Class C, and Class D surface areas. Normally,

pilots will not be advised of being in radar contact since

that continued status cannot be guaranteed and since the

purpose of the radar identification is not to establish a link

for the provision of radar services.

e. A few of the radar equipped towers are

authorized to use the radar to ensure separation

between aircraft in specific situations, while still

others may function as limited radar approach

controls. The various radar uses are strictly a function

of FAA operational need. The facilities may be

indistinguishable to pilots since they are all referred

to as tower and no publication lists the degree of radar

use. Therefore, when in communication with a

tower controller who may have radar available, do

not assume that constant radar monitoring and

complete ATC radar services are being provided.

4−3−3. Traffic Patterns

At most airports and military air bases, traffic pattern

altitudes for propeller−driven aircraft generally

extend from 600 feet to as high as 1,500 feet above the

ground. Also, traffic pattern altitudes for military

turbojet aircraft sometimes extend up to 2,500 feet

above the ground. Therefore, pilots of en route

aircraft should be constantly on the alert for other

aircraft in traffic patterns and avoid these areas

whenever possible. Traffic pattern altitudes should be

maintained unless otherwise required by the

applicable distance from cloud criteria (14 CFR

Section 91.155). (See FIG 4−3−2 and FIG 4−3−3.)
7/26/12 AIM

Airport Operations 4−3−3

FIG 4−3−2

Traffic Pattern Operations

Single Runway

EXAMPLE−

Key to traffic pattern operations

1. Enter pattern in level flight, abeam the midpoint of the

runway, at pattern altitude. (1,000’ AGL is recommended

pattern altitude unless established otherwise. . .)

2. Maintain pattern altitude until abeam approach end of

the landing runway on downwind leg.

3. Complete turn to final at least 1/4 mile from the runway.

4. Continue straight ahead until beyond departure end of

runway.

5. If remaining in the traffic pattern, commence turn to

crosswind leg beyond the departure end of the runway

within 300 feet of pattern altitude.

6. If departing the traffic pattern, continue straight out, or

exit with a 45 degree turn (to the left when in a left−hand

traffic pattern; to the right when in a right−hand traffic

pattern) beyond the departure end of the runway, after

reaching pattern altitude.
AIM 7/26/12

4−3−4 Airport Operations

FIG 4−3−3

Traffic Pattern Operations

Parallel Runways

EXAMPLE−

Key to traffic pattern operations

1. Enter pattern in level flight, abeam the midpoint of the

runway, at pattern altitude. (1,000’ AGL is recommended

pattern altitude unless established otherwise. . .)

2. Maintain pattern altitude until abeam approach end of

the landing runway on downwind leg.

3. Complete turn to final at least 1/4 mile from the runway.

4. Continue straight ahead until beyond departure end of

runway.

5. If remaining in the traffic pattern, commence turn to

crosswind leg beyond the departure end of the runway

within 300 feet of pattern altitude.

6. If departing the traffic pattern, continue straight out, or

exit with a 45 degree turn (to the left when in a left−hand

traffic pattern; to the right when in a right−hand traffic

pattern) beyond the departure end of the runway, after

reaching pattern altitude.

7. Do not overshoot final or continue on a track which will

penetrate the final approach of the parallel runway.

8. Do not continue on a track which will penetrate the

departure path of the parallel runway.
7/26/12 AIM

Airport Operations 4−3−5

4−3−4. Visual Indicators at Airports

Without an Operating Control Tower

a. At those airports without an operating control

tower, a segmented circle visual indicator system, if

installed, is designed to provide traffic pattern

information.

REFERENCE−

AIM, Traffic Advisory Practices at Airports Without Operating Control

Towers, Paragraph 4−1−9.

b. The segmented circle system consists of the

following components:

1. The segmented circle. Located in a position

affording maximum visibility to pilots in the air and

on the ground and providing a centralized location for

other elements of the system.

2. The wind direction indicator. A wind cone,

wind sock, or wind tee installed near the operational

runway to indicate wind direction. The large end of

the wind cone/wind sock points into the wind as does

the large end (cross bar) of the wind tee. In lieu of a

tetrahedron and where a wind sock or wind cone is

collocated with a wind tee, the wind tee may be

manually aligned with the runway in use to indicate

landing direction. These signaling devices may be

located in the center of the segmented circle and may

be lighted for night use. Pilots are cautioned against

using a tetrahedron to indicate wind direction.

3. The landing direction indicator. A tetrahedron is installed when conditions at the airport

warrant its use. It may be used to indicate the direction

of landings and takeoffs. A tetrahedron may be

located at the center of a segmented circle and may be

lighted for night operations. The small end of the

tetrahedron points in the direction of landing. Pilots

are cautioned against using a tetrahedron for any

purpose other than as an indicator of landing

direction. Further, pilots should use extreme caution

when making runway selection by use of a

tetrahedron in very light or calm wind conditions as

the tetrahedron may not be aligned with the

designated calm−wind runway. At airports with

control towers, the tetrahedron should only be

referenced when the control tower is not in operation.

Tower instructions supersede tetrahedron indications.

4. Landing strip indicators. Installed in pairs

as shown in the segmented circle diagram and used to

show the alignment of landing strips.

5. Traffic pattern indicators. Arranged in

pairs in conjunction with landing strip indicators and

used to indicate the direction of turns when there is a

variation from the normal left traffic pattern. (If there

is no segmented circle installed at the airport, traffic

pattern indicators may be installed on or near the end

of the runway.)

c. Preparatory to landing at an airport without a

control tower, or when the control tower is not in

operation, pilots should concern themselves with the

indicator for the approach end of the runway to be

used. When approaching for landing, all turns must

be made to the left unless a traffic pattern indicator

indicates that turns should be made to the right. If the

pilot will mentally enlarge the indicator for the

runway to be used, the base and final approach legs

of the traffic pattern to be flown immediately become

apparent. Similar treatment of the indicator at the

departure end of the runway will clearly indicate the

direction of turn after takeoff.

d. When two or more aircraft are approaching an

airport for the purpose of landing, the pilot of the

aircraft at the lower altitude has the right−of−way

over the pilot of the aircraft at the higher altitude.

However, the pilot operating at the lower altitude

should not take advantage of another aircraft, which

is on final approach to land, by cutting in front of, or

overtaking that aircraft.
AIM 7/26/12

4−3−6 Airport Operations

4−3−5. Unexpected Maneuvers in the

Airport Traffic Pattern

There have been several incidents in the vicinity of

controlled airports that were caused primarily by

aircraft executing unexpected maneuvers. ATC

service is based upon observed or known traffic and

airport conditions. Controllers establish the sequence

of arriving and departing aircraft by requiring them to

adjust flight as necessary to achieve proper spacing.

These adjustments can only be based on observed

traffic, accurate pilot reports, and anticipated aircraft

maneuvers. Pilots are expected to cooperate so as to

preclude disrupting traffic flows or creating

conflicting patterns. The pilot−in−command of an

aircraft is directly responsible for and is the final

authority as to the operation of the aircraft. On

occasion it may be necessary for pilots to maneuver

their aircraft to maintain spacing with the traffic they

have been sequenced to follow. The controller can

anticipate minor maneuvering such as shallow “S”

turns. The controller cannot, however, anticipate a

major maneuver such as a 360 degree turn. If a pilot

makes a 360 degree turn after obtaining a landing

sequence, the result is usually a gap in the landing

interval and, more importantly, it causes a chain

reaction which may result in a conflict with following

traffic and an interruption of the sequence established

by the tower or approach controller. Should a pilot

decide to make maneuvering turns to maintain

spacing behind a preceding aircraft, the pilot should

always advise the controller if at all possible. Except

when requested by the controller or in emergency

situations, a 360 degree turn should never be executed

in the traffic pattern or when receiving radar service

without first advising the controller.

4−3−6. Use of Runways/Declared Distances

a. Runways are identified by numbers which

indicate the nearest 10−degree increment of the

azimuth of the runway centerline. For example,

where the magnetic azimuth is 183 degrees, the

runway designation would be 18; for a magnetic

azimuth of 87 degrees, the runway designation would

be 9. For a magnetic azimuth ending in the number 5,

such as 185, the runway designation could be either

18 or 19. Wind direction issued by the tower is also

magnetic and wind velocity is in knots.

b. Airport proprietors are responsible for taking

the lead in local aviation noise control. Accordingly,

they may propose specific noise abatement plans to

the FAA. If approved, these plans are applied in the

form of Formal or Informal Runway Use Programs

for noise abatement purposes.

REFERENCE−

Pilot/Controller Glossary Term− “Runway Use Program”

1. At airports where no runway use program is

established, ATC clearances may specify:

(a) The runway most nearly aligned with the

wind when it is 5 knots or more;

(b) The “calm wind” runway when wind is

less than 5 knots; or

(c) Another runway if operationally advantageous.

NOTE−

It is not necessary for a controller to specifically inquire if

the pilot will use a specific runway or to offer a choice of

runways. If a pilot prefers to use a different runway from

that specified, or the one most nearly aligned with the wind,

the pilot is expected to inform ATC accordingly.

2. At airports where a runway use program is

established, ATC will assign runways deemed to have

the least noise impact. If in the interest of safety a

runway different from that specified is preferred, the

pilot is expected to advise ATC accordingly. ATC will

honor such requests and advise pilots when the

requested runway is noise sensitive. When use of a

runway other than the one assigned is requested, pilot

cooperation is encouraged to preclude disruption of

traffic flows or the creation of conflicting patterns.

c. Declared Distances.

1. Declared distances for a runway represent

the maximum distances available and suitable for

meeting takeoff and landing distance performance

requirements. These distances are determined in

accordance with FAA runway design standards by

adding to the physical length of paved runway any

clearway or stopway and subtracting from that sum

any lengths necessary to obtain the standard runway

safety areas, runway object free areas, or runway

protection zones. As a result of these additions and

subtractions, the declared distances for a runway may

be more or less than the physical length of the runway

as depicted on aeronautical charts and related

publications, or available in electronic navigation

databases provided by either the U.S. Government or

commercial companies.

2. All 14 CFR Part 139 airports report declared

distances for each runway. Other airports may also
7/26/12 AIM

Airport Operations 4−3−7

report declared distances for a runway if necessary

to meet runway design standards or to indicate the

presence of a clearway or stopway. Where reported,

declared distances for each runway end are

published in the Airport/Facility Directory (A/FD).

For runways without published declared distances,

the declared distances may be assumed to be equal to

the physical length of the runway unless there is a

displaced landing threshold, in which case the

Landing Distance Available (LDA) is shortened by

the amount of the threshold displacement.

NOTE−

A symbol is shown on U.S. Government charts to

indicate that runway declared distance information is

available (See appropriate A/FD, Alaska, or Pacific

Supplement).

(a) The FAA uses the following definitions

for runway declared distances (See FIG 4−3−4):

REFERENCE−

Pilot/Controller Glossary Terms: “Accelerate−Stop Distance

Available,” “Landing Distance Available,” “Takeoff Distance

Available,” “Takeoff Run Available,” ” Stopway,” and “Clearway.”

(1) Takeoff Run Available (TORA) – The

runway length declared available and suitable for

the ground run of an airplane taking off.

The TORA is typically the physical length of the

runway, but it may be shorter than the runway length

if necessary to satisfy runway design standards. For

example, the TORA may be shorter than the runway

length if a portion of the runway must be used to

satisfy runway protection zone requirements.

(2) Takeoff Distance Available (TODA) –

The takeoff run available plus the length of any

remaining runway or clearway beyond the far end of

the takeoff run available.

The TODA is the distance declared available for

satisfying takeoff distance requirements for airplanes

where the certification and operating rules and

available performance data allow for the consideration of a clearway in takeoff performance

computations.

NOTE−

The length of any available clearway will be included in the

TODA published in the A/FD’s entry for that runway end.

(3) Accelerate−Stop Distance Available

(ASDA) – The runway plus stopway length declared

available and suitable for the acceleration and

deceleration of an airplane aborting a takeoff.

The ASDA may be longer than the physical length of

the runway when a stopway has been designated

available by the airport operator, or it may be shorter

than the physical length of the runway if necessary to

use a portion of the runway to satisfy runway design

standards; for example, where the airport operator

uses a portion of the runway to achieve the runway

safety area requirement. ASDA is the distance used

to satisfy the airplane accelerate−stop distance

performance requirements where the certification

and operating rules require accelerate−stop distance

computations.

NOTE−

The length of any available stopway will be included in the

ASDA published in the A/FD’s entry for that runway end.

(4) Landing Distance Available (LDA) −

The runway length declared available and suitable

for a landing airplane.

The LDA may be less than the physical length of the

runway or the length of the runway remaining beyond

a displaced threshold if necessary to satisfy runway

design standards;for example, where the airport

operator uses a portion of the runway to achieve the

runway safety area requirement.

Although some runway elements (such as stopway

length and clearway length) may be available

information, pilots must use the declared distances

determined by the airport operator and not attempt to

independently calculate declared distances by

adding those elements to the reported physical

length of the runway.

(b) The airplane operating rules and/or the

airplane operating limitations establish minimum

distance requirements for takeoff and landing and

are based on performance data supplied in the

Airplane Flight Manual or Pilot’s Operating

Handbook. The minimum distances required for

takeoff and landing obtained either in planning

prior to takeoff or in performance assessments

conducted at the time of landing must fall within the

applicable declared distances before the pilot can

accept that runway for takeoff or landing.

(c) Runway design standards may impose

restrictions on the amount of runway available for

use in takeoff and landing that are not apparent

from the reported physical length of the runway or

from runway markings and lighting. The runway

elements of Runway Safety Area (RSA), Runway

Object Free Area (ROFA), and Runway Protection
AIM 7/26/12

4−3−8 Airport Operations

Zone (RPZ) may reduce a runway’s declared

distances to less than the physical length of the

runway at geographically constrained airports (See

FIG 4−3−5). When considering the amount of

runway available for use in takeoff or landing

performance calculations, the declared distances

published for a runway must always be used in lieu

of the runway’s physical length.

REFERENCE−

AC 150/5300−13, Airport Design.

(d) While some runway elements associated

with declared distances may be identifiable through

runway markings or lighting (for example, a

displaced threshold or a stopway), the individual

declared distance limits are not marked or otherwise

identified on the runway. An aircraft is not

prohibited from operating beyond a declared

distance limit during the takeoff, landing, or taxi

operation provided the runway surface is appropriately marked as usable runway (See FIG 4−3−5). The

following examples clarify the intent of this

paragraph.

REFERENCE−

AIM, Runway Markings, Paragraph 2−3−3.

AC 150/5340−1, Standards for Airport Markings.

EXAMPLE−

1. The declared LDA for runway 9 must be used when

showing compliance with the landing distance requirements of the applicable airplane operating rules and/or

airplane operating limitations or when making a before

landing performance assessment. The LDA is less than the

physical runway length, not only because of the displaced

threshold, but also because of the subtractions necessary

to meet the RSA beyond the far end of the runway. However,

during the actual landing operation, it is permissible for

the airplane to roll beyond the unmarked end of the LDA.

2. The declared ASDA for runway 9 must be used when

showing compliance with the accelerate−stop distance

requirements of the applicable airplane operating rules

and/or airplane operating limitations. The ASDA is less

than the physical length of the runway due to subtractions

necessary to achieve the full RSA requirement. However, in

the event of an aborted takeoff, it is permissible for the

airplane to roll beyond the unmarked end of the ASDA as

it is brought to a full−stop on the remaining usable runway.
7/26/12 AIM

Airport Operations 4−3−9

FIG 4−3−4

Declared Distances with Full−Standard Runway Safety Areas, Runway Object Free Areas, and Runway

Protection Zones
AIM 7/26/12

4−3−10 Airport Operations

FIG 4−3−5

Effects of a Geographical Constraint on a Runway’s Declared Distances

NOTE−

A runway’s RSA begins a set distance prior to the threshold and will extend a set distance beyond the end of the runway

depending on the runway’s design criteria. If these required lengths cannot be achieved, the ASDA and/or LDA will be

reduced as necessary to obtain the required lengths to the extent practicable.
7/26/12 AIM

Airport Operations 4−3−11

4−3−7. Low Level Wind Shear/Microburst

Detection Systems

Low Level Wind Shear Alert System (LLWAS),

Terminal Doppler Weather Radar (TDWR), Weather

System Processor (WSP), and Integrated Terminal

Weather System (ITWS) display information on

hazardous wind shear and microburst activity in the

vicinity of an airport to air traffic controllers who

relay this information to pilots.

a. LLWAS provides wind shear alert and gust front

information but does not provide microburst alerts.

The LLWAS is designed to detect low level wind

shear conditions around the periphery of an airport. It

does not detect wind shear beyond that limitation.

Controllers will provide this information to pilots by

giving the pilot the airport wind followed by the

boundary wind.

EXAMPLE−

Wind shear alert, airport wind 230 at 8, south boundary

wind 170 at 20.

b. LLWAS “network expansion,” (LLWAS NE)

and LLWAS Relocation/Sustainment (LLWAS−RS)

are systems integrated with TDWR. These systems

provide the capability of detecting microburst alerts

and wind shear alerts. Controllers will issue the

appropriate wind shear alerts or microburst alerts. In

some of these systems controllers also have the ability

to issue wind information oriented to the threshold or

departure end of the runway.

EXAMPLE−

Runway 17 arrival microburst alert, 40 knot loss 3 mile

final.

REFERENCE−

AIM, Microbursts, Paragraph 7−1−26.

c. More advanced systems are in the field or being

developed such as ITWS. ITWS provides alerts for

microbursts, wind shear, and significant thunderstorm activity. ITWS displays wind information

oriented to the threshold or departure end of the

runway.

d. The WSP provides weather processor enhancements to selected Airport Surveillance Radar

(ASR)−9 facilities. The WSP provides Air Traffic

with detection and alerting of hazardous weather such

as wind shear, microbursts, and significant thunderstorm activity. The WSP displays terminal area

6 level weather, storm cell locations and movement,

as well as the location and predicted future position

and intensity of wind shifts that may affect airport

operations. Controllers will receive and issue alerts

based on Areas Noted for Attention (ARENA). An

ARENA extends on the runway center line from a

3 mile final to the runway to a 2 mile departure.

e. An airport equipped with the LLWAS, ITWS, or

WSP is so indicated in the Airport/Facility Directory

under Weather Data Sources for that particular

airport.

4−3−8. Braking Action Reports and

Advisories

a. When available, ATC furnishes pilots the

quality of braking action received from pilots or

airport management. The quality of braking action is

described by the terms “good,” “fair,” “poor,” and

“nil,” or a combination of these terms. When pilots

report the quality of braking action by using the terms

noted above, they should use descriptive terms that

are easily understood, such as, “braking action poor

the first/last half of the runway,” together with the

particular type of aircraft.

b. For NOTAM purposes, braking action reports

are classified according to the most critical term

(“fair,” “poor,” or “nil”) used and issued as a

NOTAM(D).

c. When tower controllers have received runway

braking action reports which include the terms poor

or nil, or whenever weather conditions are conducive

to deteriorating or rapidly changing runway braking

conditions, the tower will include on the ATIS

broadcast the statement, “BRAKING ACTION

ADVISORIES ARE IN EFFECT.”

d. During the time that braking action advisories

are in effect, ATC will issue the latest braking action

report for the runway in use to each arriving and

departing aircraft. Pilots should be prepared for

deteriorating braking conditions and should request

current runway condition information if not

volunteered by controllers. Pilots should also be

prepared to provide a descriptive runway condition

report to controllers after landing.

4−3−9. Runway Friction Reports and

Advisories

a. Friction is defined as the ratio of the tangential

force needed to maintain uniform relative motion

between two contacting surfaces (aircraft tires to the
AIM 7/26/12

4−3−12 Airport Operations

pavement surface) to the perpendicular force holding

them in contact (distributed aircraft weight to the

aircraft tire area). Simply stated, friction quantifies

slipperiness of pavement surfaces.

b. The greek letter MU (pronounced “myew”), is

used to designate a friction value representing

runway surface conditions.

c. MU (friction) values range from 0 to 100 where

zero is the lowest friction value and 100 is the

maximum friction value obtainable. For frozen

contaminants on runway surfaces, a MU value of

40 or less is the level when the aircraft braking

performance starts to deteriorate and directional

control begins to be less responsive. The lower the

MU value, the less effective braking performance

becomes and the more difficult directional control

becomes.

d. At airports with friction measuring devices,

airport management should conduct friction measurements on runways covered with compacted snow

and/or ice.

1. Numerical readings may be obtained by using

any FAA approved friction measuring device. As

these devices do not provide equal numerical

readings on contaminated surfaces, it is necessary to

designate the type of friction measuring device used.

2. When the MU value for any one−third zone of

an active runway is 40 or less, a report should be given

to ATC by airport management for dissemination to

pilots. The report will identify the runway, the time of

measurement, the type of friction measuring device

used, MU values for each zone, and the contaminant

conditions, e.g., wet snow, dry snow, slush, deicing

chemicals, etc. Measurements for each one−third

zone will be given in the direction of takeoff and

landing on the runway. A report should also be given

when MU values rise above 40 in all zones of a

runway previously reporting a MU below 40.

3. Airport management should initiate a

NOTAM(D) when the friction measuring device is

out of service.

e. When MU reports are provided by airport

management, the ATC facility providing approach

control or local airport advisory will provide the

report to any pilot upon request.

f. Pilots should use MU information with other

knowledge including aircraft performance characteristics, type, and weight, previous experience, wind

conditions, and aircraft tire type (i.e., bias ply vs.

radial constructed) to determine runway suitability.

g. No correlation has been established between

MU values and the descriptive terms “good,” “fair,”

“poor,” and “nil” used in braking action reports.

4−3−10. Intersection Takeoffs

a. In order to enhance airport capacities, reduce

taxiing distances, minimize departure delays, and

provide for more efficient movement of air traffic,

controllers may initiate intersection takeoffs as well

as approve them when the pilot requests. If for ANY

reason a pilot prefers to use a different intersection or

the full length of the runway or desires to obtain the

distance between the intersection and the runway end,

THE PILOT IS EXPECTED TO INFORM ATC

ACCORDINGLY.

b. Pilots are expected to assess the suitability of an

intersection for use at takeoff during their preflight

planning. They must consider the resultant length

reduction to the published runway length and to the

published declared distances from the intersection

intended to be used for takeoff. The minimum runway

required for takeoff must fall within the reduced

runway length and the reduced declared distances

before the intersection can be accepted for takeoff.

REFERENCE−

AIM, Use of Runways/Declared Distances, Paragraph 4−3−6.

c. Controllers will issue the measured distance

from the intersection to the runway end rounded

“down” to the nearest 50 feet to any pilot who

requests and to all military aircraft, unless use of the

intersection is covered in appropriate directives.

Controllers, however, will not be able to inform pilots

of the distance from the intersection to the end of any

of the published declared distances.

REFERENCE−

FAAO JO 7110.65, Ground Traffic Movement, Paragraph 3−7−1.

d. An aircraft is expected to taxi to (but not onto)

the end of the assigned runway unless prior approval

for an intersection departure is received from ground

control.

e. Pilots should state their position on the airport

when calling the tower for takeoff from a runway

intersection.

EXAMPLE−

Cleveland Tower, Apache Three Seven Two Two Papa, at

the intersection of taxiway Oscar and runway two three

right, ready for departure.
7/26/12 AIM

Airport Operations 4−3−13

f. Controllers are required to separate small

aircraft (12,500 pounds or less, maximum certificated takeoff weight) departing (same or opposite

direction) from an intersection behind a large

nonheavy aircraft on the same runway, by ensuring

that at least a 3−minute interval exists between the

time the preceding large aircraft has taken off and the

succeeding small aircraft begins takeoff roll. To

inform the pilot of the required 3−minute hold, the

controller will state, “Hold for wake turbulence.” If

after considering wake turbulence hazards, the pilot

feels that a lesser time interval is appropriate, the pilot

may request a waiver to the 3−minute interval. To

initiate such a request, simply say “Request waiver to

3−minute interval,” or a similar statement. Controllers may then issue a takeoff clearance if other traffic

permits, since the pilot has accepted the responsibility

for wake turbulence separation.

g. The 3−minute interval is not required when the

intersection is 500 feet or less from the departure

point of the preceding aircraft and both aircraft are

taking off in the same direction. Controllers may

permit the small aircraft to alter course after takeoff

to avoid the flight path of the preceding departure.

h. The 3−minute interval is mandatory behind a

heavy aircraft in all cases.

4−3−11. Pilot Responsibilities When

Conducting Land and Hold Short

Operations (LAHSO)

a. LAHSO is an acronym for “Land and Hold

Short Operations.” These operations include landing

and holding short of an intersecting runway, an

intersecting taxiway, or some other designated

point on a runway other than an intersecting runway

or taxiway. (See FIG 4−3−6, FIG 4−3−7,

FIG 4−3−8.)

b. Pilot Responsibilities and Basic Procedures.

1. LAHSO is an air traffic control procedure that

requires pilot participation to balance the needs for

increased airport capacity and system efficiency,

consistent with safety. This procedure can be done

safely provided pilots and controllers are knowledgeable and understand their responsibilities. The

following paragraphs outline specific pilot/operator

responsibilities when conducting LAHSO.

2. At controlled airports, air traffic may clear a

pilot to land and hold short. Pilots may accept such a

clearance provided that the pilot−in−command

determines that the aircraft can safely land and stop

within the Available Landing Distance (ALD). ALD

data are published in the special notices section of the

Airport/Facility Directory (A/FD) and in the U.S.

Terminal Procedures Publications. Controllers will

also provide ALD data upon request. Student pilots or

pilots not familiar with LAHSO should not

participate in the program.

3. The pilot−in−command has the final

authority to accept or decline any land and hold

short clearance. The safety and operation of the

aircraft remain the responsibility of the pilot.

Pilots are expected to decline a LAHSO clearance

if they determine it will compromise safety.

4. To conduct LAHSO, pilots should become

familiar with all available information concerning

LAHSO at their destination airport. Pilots should

have, readily available, the published ALD and

runway slope information for all LAHSO runway

combinations at each airport of intended landing.

Additionally, knowledge about landing performance

data permits the pilot to readily determine that the

ALD for the assigned runway is sufficient for safe

LAHSO. As part of a pilot’s preflight planning

process, pilots should determine if their destination

airport has LAHSO. If so, their preflight planning

process should include an assessment of which

LAHSO combinations would work for them given

their aircraft’s required landing distance. Good pilot

decision making is knowing in advance whether one

can accept a LAHSO clearance if offered.
AIM 7/26/12

4−3−14 Airport Operations

FIG 4−3−6

Land and Hold Short of an Intersecting Runway

EXAMPLE−

FIG 4−3−8 − holding short at a designated point may be

required to avoid conflicts with the runway safety

area/flight path of a nearby runway.

NOTE−

Each figure shows the approximate location of LAHSO

markings, signage, and in−pavement lighting when

installed.

REFERENCE−

AIM, Chapter 2, Aeronautical Lighting and Other Airport Visual Aids.

FIG 4−3−7

Land and Hold Short of an Intersecting Taxiway

FIG 4−3−8

Land and Hold Short of a Designated Point

on a Runway Other Than an Intersecting

Runway or Taxiway

5. If, for any reason, such as difficulty in

discerning the location of a LAHSO intersection,

wind conditions, aircraft condition, etc., the pilot

elects to request to land on the full length of the

runway, to land on another runway, or to decline

LAHSO, a pilot is expected to promptly inform air

traffic, ideally even before the clearance is issued. A

LAHSO clearance, once accepted, must be

adhered to, just as any other ATC clearance,

unless an amended clearance is obtained or an

emergency occurs. A LAHSO clearance does not

preclude a rejected landing.

6. A pilot who accepts a LAHSO clearance

should land and exit the runway at the first convenient

taxiway (unless directed otherwise) before reaching

the hold short point. Otherwise, the pilot must stop

and hold at the hold short point. If a rejected landing

becomes necessary after accepting a LAHSO

clearance, the pilot should maintain safe separation from other aircraft or vehicles, and should

promptly notify the controller.

7. Controllers need a full read back of all

LAHSO clearances. Pilots should read back their

LAHSO clearance and include the words, “HOLD

SHORT OF (RUNWAY/TAXIWAY/OR POINT)” in

their acknowledgment of all LAHSO clearances. In

order to reduce frequency congestion, pilots are

encouraged to read back the LAHSO clearance
7/26/12 AIM

Airport Operations 4−3−15

without prompting. Don’t make the controller have to

ask for a read back!

c. LAHSO Situational Awareness

1. Situational awareness is vital to the success

of LAHSO. Situational awareness starts with having

current airport information in the cockpit, readily

accessible to the pilot. (An airport diagram assists

pilots in identifying their location on the airport, thus

reducing requests for “progressive taxi instructions”

from controllers.)

2. Situational awareness includes effective

pilot−controller radio communication. ATC expects

pilots to specifically acknowledge and read back all

LAHSO clearances as follows:

EXAMPLE−

ATC: “(Aircraft ID) cleared to land runway six right, hold

short of taxiway bravo for crossing traffic (type aircraft).”

Aircraft: “(Aircraft ID), wilco, cleared to land runway six

right to hold short of taxiway bravo.”

ATC: “(Aircraft ID) cross runway six right at taxiway

bravo, landing aircraft will hold short.”

Aircraft: “(Aircraft ID), wilco, cross runway six right at

bravo, landing traffic (type aircraft) to hold.”

3. For those airplanes flown with two crewmembers, effective intra−cockpit communication

between cockpit crewmembers is also critical. There

have been several instances where the pilot working

the radios accepted a LAHSO clearance but then

simply forgot to tell the pilot flying the aircraft.

4. Situational awareness also includes a thorough understanding of the airport markings, signage,

and lighting associated with LAHSO. These visual

aids consist of a three−part system of yellow

hold−short markings, red and white signage and,

in certain cases, in−pavement lighting. Visual aids

assist the pilot in determining where to hold short.

FIG 4−3−6, FIG 4−3−7, FIG 4−3−8 depict how these

markings, signage, and lighting combinations will

appear once installed. Pilots are cautioned that not all

airports conducting LAHSO have installed any or all

of the above markings, signage, or lighting.

5. Pilots should only receive a LAHSO

clearance when there is a minimum ceiling of

1,000 feet and 3 statute miles visibility. The intent of

having “basic” VFR weather conditions is to allow

pilots to maintain visual contact with other aircraft

and ground vehicle operations. Pilots should consider

the effects of prevailing inflight visibility (such as

landing into the sun) and how it may affect overall

situational awareness. Additionally, surface vehicles

and aircraft being taxied by maintenance personnel

may also be participating in LAHSO, especially in

those operations that involve crossing an active

runway.

4−3−12. Low Approach

a. A low approach (sometimes referred to as a low

pass) is the go−around maneuver following an

approach. Instead of landing or making a touch−and−

go, a pilot may wish to go around (low approach) in

order to expedite a particular operation (a series of

practice instrument approaches is an example of such

an operation). Unless otherwise authorized by ATC,

the low approach should be made straight ahead, with

no turns or climb made until the pilot has made a

thorough visual check for other aircraft in the area.

b. When operating within a Class B, Class C, and

Class D surface area, a pilot intending to make a low

approach should contact the tower for approval. This

request should be made prior to starting the final

approach.

c. When operating to an airport, not within a

Class B, Class C, and Class D surface area, a pilot

intending to make a low approach should, prior to

leaving the final approach fix inbound (nonprecision

approach) or the outer marker or fix used in lieu of the

outer marker inbound (precision approach), so advise

the FSS, UNICOM, or make a broadcast as

appropriate.

REFERENCE−

AIM, Traffic Advisory Practices at Airports Without Operating Control

Towers, Paragraph 4−1−9.

4−3−13. Traffic Control Light Signals

a. The following procedures are used by ATCTs in

the control of aircraft, ground vehicles, equipment,

and personnel not equipped with radio. These same

procedures will be used to control aircraft, ground

vehicles, equipment, and personnel equipped with

radio if radio contact cannot be established. ATC

personnel use a directive traffic control signal which

emits an intense narrow light beam of a selected color

(either red, white, or green) when controlling traffic

by light signals.
AIM 7/26/12

4−3−16 Airport Operations

b. Although the traffic signal light offers the

advantage that some control may be exercised over

nonradio equipped aircraft, pilots should be cognizant of the disadvantages which are:

1. Pilots may not be looking at the control tower

at the time a signal is directed toward their aircraft.

2. The directions transmitted by a light signal

are very limited since only approval or disapproval of

a pilot’s anticipated actions may be transmitted. No

supplement or explanatory information may be

transmitted except by the use of the “General

Warning Signal” which advises the pilot to be on the

alert.

c. Between sunset and sunrise, a pilot wishing to

attract the attention of the control tower should turn

on a landing light and taxi the aircraft into a position,

clear of the active runway, so that light is visible to the

tower. The landing light should remain on until

appropriate signals are received from the tower.

d. Air Traffic Control Tower Light Gun Signals.

(See TBL 4−3−1.)

e. During daylight hours, acknowledge tower

transmissions or light signals by moving the ailerons

or rudder. At night, acknowledge by blinking the

landing or navigation lights. If radio malfunction

occurs after departing the parking area, watch the

tower for light signals or monitor tower frequency.

TBL 4−3−1

Air Traffic Control Tower Light Gun Signals

Meaning

Color and Type of Signal

Movement of Vehicles,

Equipment and Personnel Aircraft on the Ground Aircraft in Flight

Steady green Cleared to cross, proceed or go Cleared for takeoff Cleared to land

Flashing green Not applicable Cleared for taxi Return for landing (to be

followed by steady green at the

proper time)

Steady red STOP STOP Give way to other aircraft and

continue circling

Flashing red Clear the taxiway/runway Taxi clear of the runway in use Airport unsafe, do not land

Flashing white Return to starting point on airport Return to starting point on airport Not applicable

Alternating red and green Exercise extreme caution Exercise extreme caution Exercise extreme caution

4−3−14. Communications

a. Pilots of departing aircraft should communicate

with the control tower on the appropriate ground

control/clearance delivery frequency prior to starting

engines to receive engine start time, taxi and/or

clearance information. Unless otherwise advised by

the tower, remain on that frequency during taxiing

and runup, then change to local control frequency

when ready to request takeoff clearance.

NOTE−

Pilots are encouraged to monitor the local tower frequency

as soon as practical consistent with other ATC

requirements.

REFERENCE−

AIM, Automatic Terminal Information Service (ATIS),

Paragraph 4−1−13.

b. The tower controller will consider that pilots of

turbine−powered aircraft are ready for takeoff when

they reach the runway or warm−up block unless

advised otherwise.

c. The majority of ground control frequencies are

in the 121.6−121.9 MHz bandwidth. Ground control

frequencies are provided to eliminate frequency

congestion on the tower (local control) frequency and

are limited to communications between the tower and

aircraft on the ground and between the tower and

utility vehicles on the airport, provide a clear VHF

channel for arriving and departing aircraft. They are

used for issuance of taxi information, clearances, and

other necessary contacts between the tower and

aircraft or other vehicles operated on the airport. A

pilot who has just landed should not change from the

tower frequency to the ground control frequency until

directed to do so by the controller. Normally, only one

ground control frequency is assigned at an airport;

however, at locations where the amount of traffic so

warrants, a second ground control frequency and/or

another frequency designated as a clearance delivery

frequency, may be assigned.
7/26/12 AIM

Airport Operations 4−3−17

d. A controller may omit the ground or local

control frequency if the controller believes the pilot

knows which frequency is in use. If the ground

control frequency is in the 121 MHz bandwidth the

controller may omit the numbers preceding the

decimal point; e.g., 121.7, “CONTACT GROUND

POINT SEVEN.” However, if any doubt exists as to

what frequency is in use, the pilot should promptly

request the controller to provide that information.

e. Controllers will normally avoid issuing a radio

frequency change to helicopters, known to be

single−piloted, which are hovering, air taxiing, or

flying near the ground. At times, it may be necessary

for pilots to alert ATC regarding single pilot

operations to minimize delay of essential ATC

communications. Whenever possible, ATC instructions will be relayed through the frequency being

monitored until a frequency change can be

accomplished. You must promptly advise ATC if you

are unable to comply with a frequency change. Also,

you should advise ATC if you must land to

accomplish the frequency change unless it is clear the

landing will have no impact on other air traffic;

e.g., on a taxiway or in a helicopter operating area.

4−3−15. Gate Holding Due to Departure

Delays

a. Pilots should contact ground control or

clearance delivery prior to starting engines as gate

hold procedures will be in effect whenever departure

delays exceed or are anticipated to exceed

15 minutes. The sequence for departure will be

maintained in accordance with initial call up unless

modified by flow control restrictions. Pilots should

monitor the ground control or clearance delivery

frequency for engine startup advisories or new

proposed start time if the delay changes.

b. The tower controller will consider that pilots of

turbine−powered aircraft are ready for takeoff when

they reach the runway or warm−up block unless

advised otherwise.

4−3−16. VFR Flights in Terminal Areas

Use reasonable restraint in exercising the prerogative

of VFR flight, especially in terminal areas. The

weather minimums and distances from clouds are

minimums. Giving yourself a greater margin in

specific instances is just good judgment.

a. Approach Area. Conducting a VFR operation

in a Class B, Class C, Class D, and Class E surface

area when the official visibility is 3 or 4 miles is not

prohibited, but good judgment would dictate that you

keep out of the approach area.

b. Reduced Visibility. It has always been recognized that precipitation reduces forward visibility.

Consequently, although again it may be perfectly

legal to cancel your IFR flight plan at any time you

can proceed VFR, it is good practice, when

precipitation is occurring, to continue IFR operation

into a terminal area until you are reasonably close to

your destination.

c. Simulated Instrument Flights. In conducting

simulated instrument flights, be sure that the weather

is good enough to compensate for the restricted

visibility of the safety pilot and your greater

concentration on your flight instruments. Give

yourself a little greater margin when your flight plan

lies in or near a busy airway or close to an airport.

4−3−17. VFR Helicopter Operations at

Controlled Airports

a. General.

1. The following ATC procedures and phraseologies recognize the unique capabilities of helicopters

and were developed to improve service to all users.

Helicopter design characteristics and user needs often

require operations from movement areas and

nonmovement areas within the airport boundary. In

order for ATC to properly apply these procedures, it

is essential that pilots familiarize themselves with the

local operations and make it known to controllers

when additional instructions are necessary.

2. Insofar as possible, helicopter operations will

be instructed to avoid the flow of fixed−wing aircraft

to minimize overall delays; however, there will be

many situations where faster/larger helicopters may

be integrated with fixed−wing aircraft for the benefit

of all concerned. Examples would include IFR

flights, avoidance of noise sensitive areas, or use of

runways/taxiways to minimize the hazardous effects

of rotor downwash in congested areas.

3. Because helicopter pilots are intimately

familiar with the effects of rotor downwash, they are

best qualified to determine if a given operation can be

conducted safely. Accordingly, the pilot has the final

authority with respect to the specific airspeed/altitude
AIM 7/26/12

4−3−18 Airport Operations

combinations. ATC clearances are in no way intended

to place the helicopter in a hazardous position. It is

expected that pilots will advise ATC if a specific

clearance will cause undue hazards to persons or

property.

b. Controllers normally limit ATC ground service

and instruction to movement areas; therefore,

operations from nonmovement areas are conducted at

pilot discretion and should be based on local policies,

procedures, or letters of agreement. In order to

maximize the flexibility of helicopter operations, it is

necessary to rely heavily on sound pilot judgment.

For example, hazards such as debris, obstructions,

vehicles, or personnel must be recognized by the

pilot, and action should be taken as necessary to avoid

such hazards. Taxi, hover taxi, and air taxi operations

are considered to be ground movements. Helicopters

conducting such operations are expected to adhere to

the same conditions, requirements, and practices as

apply to other ground taxiing and ATC procedures in

the AIM.

1. The phraseology taxi is used when it is

intended or expected that the helicopter will taxi on

the airport surface, either via taxiways or other

prescribed routes. Taxi is used primarily for

helicopters equipped with wheels or in response to a

pilot request. Preference should be given to this

procedure whenever it is necessary to minimize

effects of rotor downwash.

2. Pilots may request a hover taxi when slow

forward movement is desired or when it may be

appropriate to move very short distances. Pilots

should avoid this procedure if rotor downwash is

likely to cause damage to parked aircraft or if blowing

dust/snow could obscure visibility. If it is necessary

to operate above 25 feet AGL when hover taxiing, the

pilot should initiate a request to ATC.

3. Air taxi is the preferred method for helicopter

ground movements on airports provided ground

operations and conditions permit. Unless otherwise

requested or instructed, pilots are expected to remain

below 100 feet AGL. However, if a higher than

normal airspeed or altitude is desired, the request

should be made prior to lift−off. The pilot is solely

responsible for selecting a safe airspeed for the

altitude/operation being conducted. Use of air taxi

enables the pilot to proceed at an optimum

airspeed/altitude, minimize downwash effect, conserve fuel, and expedite movement from one point to

another. Helicopters should avoid overflight of other

aircraft, vehicles, and personnel during air−taxi

operations. Caution must be exercised concerning

active runways and pilots must be certain that air taxi

instructions are understood. Special precautions may

be necessary at unfamiliar airports or airports with

multiple/intersecting active runways. The taxi

procedures given in Paragraph 4−3−18, Taxiing,

Paragraph 4−3−19, Taxi During Low Visibility, and

Paragraph 4−3−20, Exiting the Runway After

Landing, also apply.

REFERENCE−

Pilot/Controller Glossary Term− Taxi.

Pilot/Controller Glossary Term− Hover Taxi.

Pilot/Controller Glossary Term− Air Taxi.

c. Takeoff and Landing Procedures.

1. Helicopter operations may be conducted

from a runway, taxiway, portion of a landing strip, or

any clear area which could be used as a landing site

such as the scene of an accident, a construction site,

or the roof of a building. The terms used to describe

designated areas from which helicopters operate are:

movement area, landing/takeoff area, apron/ramp,

heliport and helipad (See Pilot/Controller Glossary).

These areas may be improved or unimproved and

may be separate from or located on an airport/

heliport. ATC will issue takeoff clearances from

movement areas other than active runways, or in

diverse directions from active runways, with

additional instructions as necessary. Whenever

possible, takeoff clearance will be issued in lieu of

extended hover/air taxi operations. Phraseology will

be “CLEARED FOR TAKEOFF FROM (taxiway,

helipad, runway number, etc.), MAKE RIGHT/

LEFT TURN FOR (direction, heading, NAVAID

radial) DEPARTURE/DEPARTURE ROUTE (number, name, etc.).” Unless requested by the pilot,

downwind takeoffs will not be issued if the tailwind

exceeds 5 knots.

2. Pilots should be alert to wind information as

well as to wind indications in the vicinity of the

helicopter. ATC should be advised of the intended

method of departing. A pilot request to takeoff in a

given direction indicates that the pilot is willing to

accept the wind condition and controllers will honor

the request if traffic permits. Departure points could

be a significant distance from the control tower and

it may be difficult or impossible for the controller to

determine the helicopter’s relative position to the

wind.
7/26/12 AIM

Airport Operations 4−3−19

3. If takeoff is requested from nonmovement

areas, an area not authorized for helicopter use, an

area not visible from the tower, an unlighted area at

night, or an area off the airport, the phraseology

“DEPARTURE FROM (requested location) WILL

BE AT YOUR OWN RISK (additional instructions,

as necessary). USE CAUTION (if applicable).” The

pilot is responsible for operating in a safe manner and

should exercise due caution.

4. Similar phraseology is used for helicopter

landing operations. Every effort will be made to

permit helicopters to proceed direct and land as near

as possible to their final destination on the airport.

Traffic density, the need for detailed taxiing

instructions, frequency congestion, or other factors

may affect the extent to which service can be

expedited. As with ground movement operations, a

high degree of pilot/controller cooperation and

communication is necessary to achieve safe and

efficient operations.

4−3−18. Taxiing

a. General. Approval must be obtained prior to

moving an aircraft or vehicle onto the movement area

during the hours an Airport Traffic Control Tower is

in operation.

1. Always state your position on the airport

when calling the tower for taxi instructions.

2. The movement area is normally described in

local bulletins issued by the airport manager or

control tower. These bulletins may be found in FSSs,

fixed base operators offices, air carrier offices, and

operations offices.

3. The control tower also issues bulletins

describing areas where they cannot provide ATC

service due to nonvisibility or other reasons.

4. A clearance must be obtained prior to taxiing

on a runway, taking off, or landing during the hours

an Airport Traffic Control Tower is in operation.

5. A clearance must be obtained prior to

crossing any runway. ATC will issue an explicit

clearance for all runway crossings.

6. When assigned a takeoff runway, ATC will

first specify the runway, issue taxi instructions, and

state any hold short instructions or runway crossing

clearances if the taxi route will cross a runway. This

does not authorize the aircraft to “enter” or “cross”

the assigned departure runway at any point. In order

to preclude misunderstandings in radio communications, ATC will not use the word “cleared” in

conjunction with authorization for aircraft to taxi.

7. When issuing taxi instructions to any point

other than an assigned takeoff runway, ATC will

specify the point to taxi to, issue taxi instructions, and

state any hold short instructions or runway crossing

clearances if the taxi route will cross a runway.

NOTE−

ATC is required to obtain a readback from the pilot of all

runway hold short instructions.

8. If a pilot is expected to hold short of a runway

approach (“APPCH”) area or ILS holding position

(see FIG 2−3−15, Taxiways Located in Runway

Approach Area), ATC will issue instructions.

9. When taxi instructions are received from the

controller, pilots should always read back:

(a) The runway assignment.

(b) Any clearance to enter a specific runway.

(c) Any instruction to hold short of a specific

runway or line up and wait.

Controllers are required to request a readback of

runway hold short assignment when it is not received

from the pilot/vehicle.

b. ATC clearances or instructions pertaining to

taxiing are predicated on known traffic and known

physical airport conditions. Therefore, it is important

that pilots clearly understand the clearance or

instruction. Although an ATC clearance is issued for

taxiing purposes, when operating in accordance with

the CFRs, it is the responsibility of the pilot to avoid

collision with other aircraft. Since “the pilot−in−command of an aircraft is directly responsible for, and is

the final authority as to, the operation of that aircraft”

the pilot should obtain clarification of any clearance

or instruction which is not understood.

REFERENCE−

AIM, General, Paragraph 7−3−1.

1. Good operating practice dictates that pilots

acknowledge all runway crossing, hold short, or

takeoff clearances unless there is some misunderstanding, at which time the pilot should query the

controller until the clearance is understood.
AIM 7/26/12

4−3−20 Airport Operations

NOTE−

Air traffic controllers are required to obtain from the pilot

a readback of all runway hold short instructions.

2. Pilots operating a single pilot aircraft should

monitor only assigned ATC communications after

being cleared onto the active runway for departure.

Single pilot aircraft should not monitor other than

ATC communications until flight from Class B,

Class C, or Class D surface area is completed. This

same procedure should be practiced from after receipt

of the clearance for landing until the landing and taxi

activities are complete. Proper effective scanning for

other aircraft, surface vehicles, or other objects

should be continuously exercised in all cases.

3. If the pilot is unfamiliar with the airport or for

any reason confusion exists as to the correct taxi

routing, a request may be made for progressive taxi

instructions which include step−by−step routing

directions. Progressive instructions may also be

issued if the controller deems it necessary due to

traffic or field conditions (for example, construction

or closed taxiways).

c. At those airports where the U.S. Government

operates the control tower and ATC has authorized

noncompliance with the requirement for two−way

radio communications while operating within the

Class B, Class C, or Class D surface area, or at those

airports where the U.S. Government does not operate

the control tower and radio communications cannot

be established, pilots must obtain a clearance by

visual light signal prior to taxiing on a runway and

prior to takeoff and landing.

d. The following phraseologies and procedures

are used in radiotelephone communications with

aeronautical ground stations.

1. Request for taxi instructions prior to

departure. State your aircraft identification, location, type of operation planned (VFR or IFR), and the

point of first intended landing.

EXAMPLE−

Aircraft: “Washington ground, Beechcraft One Three One

Five Niner at hangar eight, ready to taxi, I−F−R to

Chicago.”

Tower: “Beechcraft one three one five niner, Washington

ground, runway two seven, taxi via taxiways Charlie and

Delta, hold short of runway three three left.”

Aircraft: “Beechcraft One Three One Five Niner, hold

short of runway three three left.”

2. Receipt of ATC clearance. ARTCC clearances are relayed to pilots by airport traffic

controllers in the following manner.

EXAMPLE−

Tower: “Beechcraft One Three One Five Niner, cleared to

the Chicago Midway Airport via Victor Eight, maintain

eight thousand.”

Aircraft: “Beechcraft One Three One Five Niner, cleared

to the Chicago Midway Airport via Victor Eight, maintain

eight thousand.”

NOTE−

Normally, an ATC IFR clearance is relayed to a pilot by the

ground controller. At busy locations, however, pilots may

be instructed by the ground controller to “contact

clearance delivery” on a frequency designated for this

purpose. No surveillance or control over the movement of

traffic is exercised by this position of operation.

3. Request for taxi instructions after landing.

State your aircraft identification, location, and that

you request taxi instructions.

EXAMPLE−

Aircraft: “Dulles ground, Beechcraft One Four Two Six

One clearing runway one right on taxiway echo three,

request clearance to Page.”

Tower: “Beechcraft One Four Two Six One, Dulles

ground, taxi to Page via taxiways echo three, echo one, and

echo niner.”

or

Aircraft: “Orlando ground, Beechcraft One Four Two Six

One clearing runway one eight left at taxiway bravo three,

request clearance to Page.”

Tower: “Beechcraft One Four Two Six One, Orlando

ground, hold short of runway one eight right.”

Aircraft: “Beechcraft One Four Two Six One, hold short

of runway one eight right.”

4−3−19. Taxi During Low Visibility

a. Pilots and aircraft operators should be constantly aware that during certain low visibility conditions

the movement of aircraft and vehicles on airports may

not be visible to the tower controller. This may

prevent visual confirmation of an aircraft’s adherence

to taxi instructions.
7/26/12 AIM

Airport Operations 4−3−21

b. Of vital importance is the need for pilots to

notify the controller when difficulties are encountered or at the first indication of becoming

disoriented. Pilots should proceed with extreme

caution when taxiing toward the sun. When vision

difficulties are encountered pilots should

immediately inform the controller.

c. Advisory Circular 120−57, Surface Movement

Guidance and Control System, commonly known as

SMGCS (pronounced “SMIGS”) requires a low

visibility taxi plan for any airport which has takeoff

or landing operations in less than 1,200 feet runway

visual range (RVR) visibility conditions. These plans,

which affect aircrew and vehicle operators, may

incorporate additional lighting, markings, and

procedures to control airport surface traffic. They

will be addressed at two levels; operations less than

1,200 feet RVR to 600 feet RVR and operations less

than 600 feet RVR.

NOTE−

Specific lighting systems and surface markings may be

found in paragraph 2−1−11, Taxiway Lights, and

paragraph 2−3−4, Taxiway Markings.

d. When low visibility conditions exist, pilots

should focus their entire attention on the safe

operation of the aircraft while it is moving. Checklists

and nonessential communication should be withheld

until the aircraft is stopped and the brakes set.

4−3−20. Exiting the Runway After Landing

The following procedures must be followed after

landing and reaching taxi speed.

a. Exit the runway without delay at the first

available taxiway or on a taxiway as instructed by

ATC. Pilots must not exit the landing runway onto

another runway unless authorized by ATC. At

airports with an operating control tower, pilots should

not stop or reverse course on the runway without first

obtaining ATC approval.

b. Taxi clear of the runway unless otherwise

directed by ATC. An aircraft is considered clear of the

runway when all parts of the aircraft are past the

runway edge and there are no restrictions to its

continued movement beyond the runway holding

position markings. In the absence of ATC instructions, the pilot is expected to taxi clear of the landing

runway by taxiing beyond the runway holding

position markings associated with the landing

runway, even if that requires the aircraft to protrude

into or cross another taxiway or ramp area. Once all

parts of the aircraft have crossed the runway holding

position markings, the pilot must hold unless further

instructions have been issued by ATC.

NOTE−

1. The tower will issue the pilot instructions which will

permit the aircraft to enter another taxiway, runway, or

ramp area when required.

2. Guidance contained in subparagraphs a and b above is

considered an integral part of the landing clearance and

satisfies the requirement of 14 CFR Section 91.129.

c. Immediately change to ground control frequency when advised by the tower and obtain a taxi

clearance.

NOTE−

1. The tower will issue instructions required to resolve any

potential conflictions with other ground traffic prior to

advising the pilot to contact ground control.

2. A clearance from ATC to taxi to the ramp authorizes the

aircraft to cross all runways and taxiway intersections.

Pilots not familiar with the taxi route should request

specific taxi instructions from ATC.

4−3−21. Practice Instrument Approaches

a. Various air traffic incidents have indicated the

necessity for adoption of measures to achieve more

organized and controlled operations where practice

instrument approaches are conducted. Practice

instrument approaches are considered to be instrument approaches made by either a VFR aircraft not on

an IFR flight plan or an aircraft on an IFR flight plan.

To achieve this and thereby enhance air safety, it is

Air Traffic’s policy to provide for separation of such

operations at locations where approach control

facilities are located and, as resources permit, at

certain other locations served by ARTCCs or parent

approach control facilities. Pilot requests to practice

instrument approaches may be approved by ATC

subject to traffic and workload conditions. Pilots

should anticipate that in some instances the controller

may find it necessary to deny approval or withdraw

previous approval when traffic conditions warrant. It

must be clearly understood, however, that even

though the controller may be providing separation,

pilots on VFR flight plans are required to comply with

basic VFR weather minimums (14 CFR Section 91.155). Application of ATC procedures or any

action taken by the controller to avoid traffic

conflictions does not relieve IFR and VFR pilots of
AIM 7/26/12

4−3−22 Airport Operations

their responsibility to see−and−avoid other traffic

while operating in VFR conditions (14 CFR

Section 91.113). In addition to the normal IFR

separation minimums (which includes visual separation) during VFR conditions, 500 feet vertical

separation may be applied between VFR aircraft and

between a VFR aircraft and the IFR aircraft. Pilots not

on IFR flight plans desiring practice instrument

approaches should always state ‘practice’ when

making requests to ATC. Controllers will instruct

VFR aircraft requesting an instrument approach to

maintain VFR. This is to preclude misunderstandings

between the pilot and controller as to the status of the

aircraft. If pilots wish to proceed in accordance with

instrument flight rules, they must specifically request

and obtain, an IFR clearance.

b. Before practicing an instrument approach,

pilots should inform the approach control facility or

the tower of the type of practice approach they desire

to make and how they intend to terminate it,

i.e., full−stop landing, touch−and−go, or missed or

low approach maneuver. This information may be

furnished progressively when conducting a series of

approaches. Pilots on an IFR flight plan, who have

made a series of instrument approaches to full stop

landings should inform ATC when they make their

final landing. The controller will control flights

practicing instrument approaches so as to ensure that

they do not disrupt the flow of arriving and departing

itinerant IFR or VFR aircraft. The priority afforded

itinerant aircraft over practice instrument approaches

is not intended to be so rigidly applied that it causes

grossly inefficient application of services. A

minimum delay to itinerant traffic may be appropriate

to allow an aircraft practicing an approach to

complete that approach.

NOTE−

A clearance to land means that appropriate separation on

the landing runway will be ensured. A landing clearance

does not relieve the pilot from compliance with any

previously issued restriction.

c. At airports without a tower, pilots wishing to

make practice instrument approaches should notify

the facility having control jurisdiction of the desired

approach as indicated on the approach chart. All

approach control facilities and ARTCCs are required

to publish a Letter to Airmen depicting those airports

where they provide standard separation to both VFR

and IFR aircraft conducting practice instrument

approaches.

d. The controller will provide approved separation

between both VFR and IFR aircraft when authorization is granted to make practice approaches to airports

where an approach control facility is located and to

certain other airports served by approach control or

an ARTCC. Controller responsibility for separation

of VFR aircraft begins at the point where the

approach clearance becomes effective, or when the

aircraft enters Class B or Class C airspace, or a TRSA,

whichever comes first.

e. VFR aircraft practicing instrument approaches

are not automatically authorized to execute the

missed approach procedure. This authorization must

be specifically requested by the pilot and approved by

the controller. Separation will not be provided unless

the missed approach has been approved by ATC.

f. Except in an emergency, aircraft cleared to

practice instrument approaches must not deviate from

the approved procedure until cleared to do so by the

controller.

g. At radar approach control locations when a full

approach procedure (procedure turn, etc.,) cannot be

approved, pilots should expect to be vectored to a

final approach course for a practice instrument

approach which is compatible with the general

direction of traffic at that airport.

h. When granting approval for a practice

instrument approach, the controller will usually ask

the pilot to report to the tower prior to or over the final

approach fix inbound (nonprecision approaches) or

over the outer marker or fix used in lieu of the outer

marker inbound (precision approaches).

i. When authorization is granted to conduct

practice instrument approaches to an airport with a

tower, but where approved standard separation is not

provided to aircraft conducting practice instrument

approaches, the tower will approve the practice

approach, instruct the aircraft to maintain VFR and

issue traffic information, as required.

j. When an aircraft notifies a FSS providing Local

Airport Advisory to the airport concerned of the

intent to conduct a practice instrument approach and

whether or not separation is to be provided, the pilot

will be instructed to contact the appropriate facility

on a specified frequency prior to initiating the

approach. At airports where separation is not

provided, the FSS will acknowledge the message and

issue known traffic information but will neither

approve or disapprove the approach.
7/26/12 AIM

Airport Operations 4−3−23

k. Pilots conducting practice instrument

approaches should be particularly alert for other

aircraft operating in the local traffic pattern or in

proximity to the airport.

4−3−22. Option Approach

The “Cleared for the Option” procedure will permit

an instructor, flight examiner or pilot the option to

make a touch−and−go, low approach, missed

approach, stop−and−go, or full stop landing. This

procedure can be very beneficial in a training

situation in that neither the student pilot nor examinee

would know what maneuver would be accomplished.

The pilot should make a request for this procedure

passing the final approach fix inbound on an

instrument approach or entering downwind for a VFR

traffic pattern. The advantages of this procedure as a

training aid are that it enables an instructor or

examiner to obtain the reaction of a trainee or

examinee under changing conditions, the pilot would

not have to discontinue an approach in the middle of

the procedure due to student error or pilot proficiency

requirements, and finally it allows more flexibility

and economy in training programs. This procedure

will only be used at those locations with an

operational control tower and will be subject to ATC

approval.

4−3−23. Use of Aircraft Lights

a. Aircraft position lights are required to be lighted

on aircraft operated on the surface and in flight from

sunset to sunrise. In addition, aircraft equipped with

an anti−collision light system are required to operate

that light system during all types of operations (day

and night). However, during any adverse meteorological conditions, the pilot−in−command may

determine that the anti−collision lights should be

turned off when their light output would constitute a

hazard to safety (14 CFR Section 91.209).

Supplementary strobe lights should be turned off on

the ground when they adversely affect ground

personnel or other pilots, and in flight when there are

adverse reflection from clouds.

b. An aircraft anti−collision light system can use

one or more rotating beacons and/or strobe lights, be

colored either red or white, and have different (higher

than minimum) intensities when compared to other

aircraft. Many aircraft have both a rotating beacon

and a strobe light system.

c. The FAA has a voluntary pilot safety program,

Operation Lights On, to enhance the see−and−avoid

concept. Pilots are encouraged to turn on their landing

lights during takeoff; i.e., either after takeoff

clearance has been received or when beginning

takeoff roll. Pilots are further encouraged to turn on

their landing lights when operating below

10,000 feet, day or night, especially when operating

within 10 miles of any airport, or in conditions of

reduced visibility and in areas where flocks of birds

may be expected, i.e., coastal areas, lake areas,

around refuse dumps, etc. Although turning on

aircraft lights does enhance the see−and−avoid

concept, pilots should not become complacent about

keeping a sharp lookout for other aircraft. Not all

aircraft are equipped with lights and some pilots may

not have their lights turned on. Aircraft manufacturer’s recommendations for operation of landing lights

and electrical systems should be observed.

d. Prop and jet blast forces generated by large

aircraft have overturned or damaged several smaller

aircraft taxiing behind them. To avoid similar results,

and in the interest of preventing upsets and injuries to

ground personnel from such forces, the FAA

recommends that air carriers and commercial

operators turn on their rotating beacons anytime their

aircraft engines are in operation. General aviation

pilots using rotating beacon equipped aircraft are also

encouraged to participate in this program which is

designed to alert others to the potential hazard. Since

this is a voluntary program, exercise caution and do

not rely solely on the rotating beacon as an indication

that aircraft engines are in operation.

e. Prior to commencing taxi, it is recommended to

turn on navigation, position, anti-collision, and logo

lights (if equipped). To signal intent to other pilots,

consider turning on the taxi light when the aircraft is

moving or intending to move on the ground, and

turning it off when stopped or yielding to other

ground traffic. Strobe lights should not be illuminated

during taxi if they will adversely affect the vision of

other pilots or ground personnel.

f. At the discretion of the pilot-in-command, all

exterior lights should be illuminated when taxiing on

or across any runway. This increases the conspicuousness of the aircraft to controllers and other pilots

approaching to land, taxiing, or crossing the runway.

Pilots should comply with any equipment operating

limitations and consider the effects of landing and

strobe lights on other aircraft in their vicinity.
AIM 7/26/12

4−3−24 Airport Operations

g. When entering the departure runway for takeoff

or to “line up and wait,” all lights, except for landing

lights, should be illuminated to make the aircraft

conspicuous to ATC and other aircraft on approach.

Landing lights should be turned on when takeoff

clearance is received or when commencing takeoff

roll at an airport without an operating control tower.

4−3−24. Flight Inspection/‘Flight Check’

Aircraft in Terminal Areas

a. Flight check is a call sign used to alert pilots and

air traffic controllers when a FAA aircraft is engaged

in flight inspection/certification of NAVAIDs and

flight procedures. Flight check aircraft fly preplanned

high/low altitude flight patterns such as grids, orbits,

DME arcs, and tracks, including low passes along the

full length of the runway to verify NAVAID

performance.

b. Pilots should be especially watchful and avoid

the flight paths of any aircraft using the call sign

“Flight Check.” These flights will normally receive

special handling from ATC. Pilot patience and

cooperation in allowing uninterrupted recordings can

significantly help expedite flight inspections, minimize costly, repetitive runs, and reduce the burden on

the U.S. taxpayer.

4−3−25. Hand Signals

FIG 4−3−9

Signalman Directs Towing

SIGNALMAN SIGNALMAN
7/26/12 AIM

Airport Operations 4−3−25

FIG 4−3−10

Signalman’s Position

SIGNALMAN SIGNALMAN

FIG 4−3−11

All Clear

(O.K.)

FIG 4−3−12

Start Engine

POINT

TO

ENGINE

TO BE

STARTED

FIG 4−3−13

Pull Chocks
AIM 7/26/12

4−3−26 Airport Operations

FIG 4−3−14

Proceed Straight Ahead

FIG 4−3−15

Left Turn

FIG 4−3−16

Right Turn

FIG 4−3−17

Slow Down
7/26/12 AIM

Airport Operations 4−3−27

FIG 4−3−18

Flagman Directs Pilot

FIG 4−3−19

Insert Chocks

FIG 4−3−20

Cut Engines

FIG 4−3−21

Night Operation

Use same hand movements

as day operation
AIM 7/26/12

4−3−28 Airport Operations

FIG 4−3−22

Stop

4−3−26. Operations at Uncontrolled

Airports With Automated Surface

Observing System (ASOS)/Automated

Weather Sensor System(AWSS)/Automated

Weather Observing System (AWOS)

a. Many airports throughout the National Airspace System are equipped with either ASOS,

AWSS, or AWOS. At most airports with an operating

control tower or human observer, the weather will be

available to you in an Aviation Routine Weather

Report (METAR) hourly or special observation

format on the Automatic Terminal Information

Service (ATIS) or directly transmitted from the

controller/observer.

b. At uncontrolled airports that are equipped with

ASOS/AWSS/AWOS with ground−to−air broadcast

capability, the one−minute updated airport weather

should be available to you within approximately 25

NM of the airport below 10,000 feet. The frequency

for the weather broadcast will be published on

sectional charts and in the Airport/Facility Directory.

Some part−time towered airports may also broadcast

the automated weather on their ATIS frequency

during the hours that the tower is closed.

c. Controllers issue SVFR or IFR clearances

based on pilot request, known traffic and reported

weather, i.e., METAR/Nonroutine (Special) Aviation

Weather Report (SPECI) observations, when they are

available. Pilots have access to more current weather

at uncontrolled ASOS/AWSS/AWOS airports than

do the controllers who may be located several miles

away. Controllers will rely on the pilot to determine

the current airport weather from the ASOS/AWSS/

AWOS. All aircraft arriving or departing an

ASOS/AWSS/AWOS equipped uncontrolled airport

should monitor the airport weather frequency to

ascertain the status of the airspace. Pilots in Class E

airspace must be alert for changing weather

conditions which may effect the status of the airspace

from IFR/VFR. If ATC service is required for

IFR/SVFR approach/departure or requested for VFR

service, the pilot should advise the controller that

he/she has received the one−minute weather and state

his/her intentions.

EXAMPLE−

“I have the (airport) one−minute weather, request an ILS

Runway 14 approach.”

REFERENCE−

AIM, Weather Observing Programs, Paragraph 7−1−12.
7/26/12 AIM

ATC Clearances and Aircraft Separation 4−4−1

Section 4. ATC Clearances and Aircraft Separation

4−4−1. Clearance

a. A clearance issued by ATC is predicated on

known traffic and known physical airport conditions.

An ATC clearance means an authorization by ATC,

for the purpose of preventing collision between

known aircraft, for an aircraft to proceed under

specified conditions within controlled airspace. IT IS

NOT AUTHORIZATION FOR A PILOT TO

DEVIATE FROM ANY RULE, REGULATION, OR

MINIMUM ALTITUDE NOR TO CONDUCT

UNSAFE OPERATION OF THE AIRCRAFT.

b. 14 CFR Section 91.3(a) states: “The pilot−in−

command of an aircraft is directly responsible for,

and is the final authority as to, the operation of that

aircraft.” If ATC issues a clearance that would cause

a pilot to deviate from a rule or regulation, or in the

pilot’s opinion, would place the aircraft in jeopardy,

IT IS THE PILOT’S RESPONSIBILITY TO

REQUEST AN AMENDED CLEARANCE. Similarly, if a pilot prefers to follow a different course of

action, such as make a 360 degree turn for spacing to

follow traffic when established in a landing or

approach sequence, land on a different runway,

takeoff from a different intersection, takeoff from the

threshold instead of an intersection, or delay

operation, THE PILOT IS EXPECTED TO

INFORM ATC ACCORDINGLY. When the pilot

requests a different course of action, however, the

pilot is expected to cooperate so as to preclude

disruption of traffic flow or creation of conflicting

patterns. The pilot is also expected to use

the appropriate aircraft call sign to acknowledge all

ATC clearances, frequency changes, or advisory

information.

c. Each pilot who deviates from an ATC clearance

in response to a Traffic Alert and Collision Avoidance

System resolution advisory must notify ATC of that

deviation as soon as possible.

REFERENCE−

Pilot/Controller Glossary Term− Traffic Alert and Collision Avoidance

System.

d. When weather conditions permit, during the

time an IFR flight is operating, it is the direct

responsibility of the pilot to avoid other aircraft since

VFR flights may be operating in the same area

without the knowledge of ATC. Traffic clearances

provide standard separation only between IFR

flights.

4−4−2. Clearance Prefix

A clearance, control information, or a response to a

request for information originated by an ATC facility

and relayed to the pilot through an air−to−ground

communication station will be prefixed by “ATC

clears,” “ATC advises,” or “ATC requests.”

4−4−3. Clearance Items

ATC clearances normally contain the following:

a. Clearance Limit. The traffic clearance issued

prior to departure will normally authorize flight to the

airport of intended landing. Many airports and

associated NAVAIDs are collocated with the same

name and/or identifier, so care should be exercised to

ensure a clear understanding of the clearance limit.

When the clearance limit is the airport of intended

landing, the clearance should contain the airport

name followed by the word “airport.” Under certain

conditions, a clearance limit may be a NAVAID or

other fix. When the clearance limit is a NAVAID,

intersection, or waypoint and the type is known, the

clearance should contain type. Under certain

conditions, at some locations a short−range clearance

procedure is utilized whereby a clearance is issued to

a fix within or just outside of the terminal area and

pilots are advised of the frequency on which they will

receive the long−range clearance direct from the

center controller.

b. Departure Procedure. Headings to fly and

altitude restrictions may be issued to separate a

departure from other air traffic in the terminal area.

Where the volume of traffic warrants, DPs have been

developed.

REFERENCE−

AIM, Abbreviated IFR Departure Clearance (Cleared. . .as Filed)

Procedures, Paragraph 5−2−5.

AIM, Instrument Departure Procedures (DP) − Obstacle Departure

Procedures (ODP) and Standard Instrument Departures (SID),

Paragraph 5−2−8.

c. Route of Flight.

1. Clearances are normally issued for the

altitude or flight level and route filed by the pilot.

However, due to traffic conditions, it is frequently

necessary for ATC to specify an altitude or flight level
AIM 7/26/12

4−4−2 ATC Clearances and Aircraft Separation

or route different from that requested by the pilot. In

addition, flow patterns have been established in

certain congested areas or between congested areas

whereby traffic capacity is increased by routing all

traffic on preferred routes. Information on these flow

patterns is available in offices where preflight

briefing is furnished or where flight plans are

accepted.

2. When required, air traffic clearances include

data to assist pilots in identifying radio reporting

points. It is the responsibility of pilots to notify ATC

immediately if their radio equipment cannot receive

the type of signals they must utilize to comply with

their clearance.

d. Altitude Data.

1. The altitude or flight level instructions in an

ATC clearance normally require that a pilot

“MAINTAIN” the altitude or flight level at which the

flight will operate when in controlled airspace.

Altitude or flight level changes while en route should

be requested prior to the time the change is desired.

2. When possible, if the altitude assigned is

different from the altitude requested by the pilot, ATC

will inform the pilot when to expect climb or descent

clearance or to request altitude change from another

facility. If this has not been received prior to crossing

the boundary of the ATC facility’s area and

assignment at a different altitude is still desired, the

pilot should reinitiate the request with the next

facility.

3. The term “cruise” may be used instead of

“MAINTAIN” to assign a block of airspace to a pilot

from the minimum IFR altitude up to and including

the altitude specified in the cruise clearance. The pilot

may level off at any intermediate altitude within this

block of airspace. Climb/descent within the block is

to be made at the discretion of the pilot. However,

once the pilot starts descent and verbally reports

leaving an altitude in the block, the pilot may not

return to that altitude without additional ATC

clearance.

REFERENCE−

Pilot/Controller Glossary Term− Cruise.

e. Holding Instructions.

1. Whenever an aircraft has been cleared to a fix

other than the destination airport and delay is

expected, it is the responsibility of the ATC controller

to issue complete holding instructions (unless the

pattern is charted), an EFC time, and a best estimate

of any additional en route/terminal delay.

2. If the holding pattern is charted and the

controller doesn’t issue complete holding instructions, the pilot is expected to hold as depicted on the

appropriate chart. When the pattern is charted, the

controller may omit all holding instructions except

the charted holding direction and the statement

AS PUBLISHED, e.g., “HOLD EAST AS

PUBLISHED.” Controllers must always issue

complete holding instructions when pilots request

them.

NOTE−

Only those holding patterns depicted on U.S. government

or commercially produced charts which meet FAA

requirements should be used.

3. If no holding pattern is charted and holding

instructions have not been issued, the pilot should ask

ATC for holding instructions prior to reaching the fix.

This procedure will eliminate the possibility of an

aircraft entering a holding pattern other than that

desired by ATC. If unable to obtain holding

instructions prior to reaching the fix (due to

frequency congestion, stuck microphone, etc.), hold

in a standard pattern on the course on which you

approached the fix and request further clearance as

soon as possible. In this event, the altitude/flight level

of the aircraft at the clearance limit will be protected

so that separation will be provided as required.

4. When an aircraft is 3 minutes or less from a

clearance limit and a clearance beyond the fix has not

been received, the pilot is expected to start a speed

reduction so that the aircraft will cross the fix,

initially, at or below the maximum holding airspeed.

5. When no delay is expected, the controller

should issue a clearance beyond the fix as soon as

possible and, whenever possible, at least 5 minutes

before the aircraft reaches the clearance limit.

6. Pilots should report to ATC the time and

altitude/flight level at which the aircraft reaches the

clearance limit and report leaving the clearance limit.

NOTE−

In the event of two−way communications failure, pilots are

required to comply with 14 CFR Section 91.185.

4−4−4. Amended Clearances

a. Amendments to the initial clearance will be

issued at any time an air traffic controller deems such
7/26/12 AIM

ATC Clearances and Aircraft Separation 4−4−3

action necessary to avoid possible confliction

between aircraft. Clearances will require that a flight

“hold” or change altitude prior to reaching the point

where standard separation from other IFR traffic

would no longer exist.

NOTE−

Some pilots have questioned this action and requested

“traffic information” and were at a loss when the reply

indicated “no traffic report.” In such cases the controller

has taken action to prevent a traffic confliction which

would have occurred at a distant point.

b. A pilot may wish an explanation of the handling

of the flight at the time of occurrence; however,

controllers are not able to take time from their

immediate control duties nor can they afford to

overload the ATC communications channels to

furnish explanations. Pilots may obtain an explanation by directing a letter or telephone call to the chief

controller of the facility involved.

c. Pilots have the privilege of requesting a

different clearance from that which has been issued

by ATC if they feel that they have information which

would make another course of action more

practicable or if aircraft equipment limitations or

company procedures forbid compliance with the

clearance issued.

4−4−5. Coded Departure Route (CDR)

a. CDRs provide air traffic control a rapid means

to reroute departing aircraft when the filed route is

constrained by either weather or congestion.

b. CDRs consist of an eight−character designator

that represents a route of flight. The first three

alphanumeric characters represent the departure

airport, characters four through six represent the

arrival airport, and the last two characters are chosen

by the overlying ARTCC. For example, PITORDN1

is an alternate route from Pittsburgh to Chicago.

Participating aircrews may then be re−cleared by air

traffic control via the CDR abbreviated clearance,

PITORDN1.

c. CDRs are updated on the 56 day charting cycle.

Participating aircrews must ensure that their CDR is

current.

d. Traditionally, CDRs have been used by air

transport companies that have signed a Memorandum

of Agreement with the local air traffic control facility.

General aviation customers who wish to participate in

the program may now enter “CDR Capable” in the

remarks section of their flight plan.

e. When “CDR Capable” is entered into the

remarks section of the flight plan the general aviation

customer communicates to ATC the ability to decode

the current CDR into a flight plan route and the

willingness to fly a different route than that which

was filed.

4−4−6. Special VFR Clearances

a. An ATC clearance must be obtained prior to

operating within a Class B, Class C, Class D, or

Class E surface area when the weather is less than that

required for VFR flight. A VFR pilot may request and

be given a clearance to enter, leave, or operate within

most Class D and Class E surface areas and some

Class B and Class C surface areas in special VFR

conditions, traffic permitting, and providing such

flight will not delay IFR operations. All special VFR

flights must remain clear of clouds. The visibility

requirements for special VFR aircraft (other than

helicopters) are:

1. At least 1 statute mile flight visibility for

operations within Class B, Class C, Class D, and

Class E surface areas.

2. At least 1 statute mile ground visibility if

taking off or landing. If ground visibility is not

reported at that airport, the flight visibility must be at

least 1 statute mile.

3. The restrictions in subparagraphs 1 and 2 do

not apply to helicopters. Helicopters must remain

clear of clouds and may operate in Class B, Class C,

Class D, and Class E surface areas with less than

1 statute mile visibility.

b. When a control tower is located within the

Class B, Class C, or Class D surface area, requests for

clearances should be to the tower. In a Class E surface

area, a clearance may be obtained from the nearest

tower, FSS, or center.

c. It is not necessary to file a complete flight plan

with the request for clearance, but pilots should state

their intentions in sufficient detail to permit ATC to

fit their flight into the traffic flow. The clearance will

not contain a specific altitude as the pilot must remain

clear of clouds. The controller may require the pilot

to fly at or below a certain altitude due to other traffic,

but the altitude specified will permit flight at or above

the minimum safe altitude. In addition, at radar
AIM 7/26/12

4−4−4 ATC Clearances and Aircraft Separation

locations, flights may be vectored if necessary for

control purposes or on pilot request.

NOTE−

The pilot is responsible for obstacle or terrain clearance.

REFERENCE−

14 CFR Section 91.119, Minimum safe altitudes: General.

d. Special VFR clearances are effective within

Class B, Class C, Class D, and Class E surface areas

only. ATC does not provide separation after an

aircraft leaves the Class B, Class C, Class D, or

Class E surface area on a special VFR clearance.

e. Special VFR operations by fixed−wing aircraft

are prohibited in some Class B and Class C surface

areas due to the volume of IFR traffic. A list of these

Class B and Class C surface areas is contained in

14 CFR Part 91, Appendix D, Section 3. They are

also depicted on sectional aeronautical charts.

f. ATC provides separation between Special VFR

flights and between these flights and other IFR

flights.

g. Special VFR operations by fixed−wing aircraft

are prohibited between sunset and sunrise unless the

pilot is instrument rated and the aircraft is equipped

for IFR flight.

h. Pilots arriving or departing an uncontrolled

airport that has automated weather broadcast

capability (ASOS/AWSS/AWOS) should monitor

the broadcast frequency, advise the controller that

they have the “one−minute weather” and state

intentions prior to operating within the Class B, Class

C, Class D, or Class E surface areas.

REFERENCE−

Pilot/Controller Glossary Term− One−minute Weather.

4−4−7. Pilot Responsibility upon Clearance

Issuance

a. Record ATC clearance. When conducting an

IFR operation, make a written record of your

clearance. The specified conditions which are a part

of your air traffic clearance may be somewhat

different from those included in your flight plan.

Additionally, ATC may find it necessary to ADD

conditions, such as particular departure route. The

very fact that ATC specifies different or additional

conditions means that other aircraft are involved in

the traffic situation.

b. ATC Clearance/Instruction Readback.

Pilots of airborne aircraft should read back

those parts of ATC clearances and instructions

containing altitude assignments, vectors, or runway

assignments as a means of mutual verification. The

read back of the “numbers” serves as a double check

between pilots and controllers and reduces the kinds

of communications errors that occur when a number

is either “misheard” or is incorrect.

1. Include the aircraft identification in all

readbacks and acknowledgments. This aids controllers in determining that the correct aircraft received

the clearance or instruction. The requirement to

include aircraft identification in all readbacks and

acknowledgements becomes more important as

frequency congestion increases and when aircraft

with similar call signs are on the same frequency.

EXAMPLE−

“Climbing to Flight Level three three zero, United Twelve”

or “November Five Charlie Tango, roger, cleared to land

runway nine left.”

2. Read back altitudes, altitude restrictions, and

vectors in the same sequence as they are given in the

clearance or instruction.

3. Altitudes contained in charted procedures,

such as DPs, instrument approaches, etc., should not

be read back unless they are specifically stated by the

controller.

4. Initial read back of a taxi, departure or landing

clearance should include the runway assignment,

including left, right, center, etc. if applicable.

c. It is the responsibility of the pilot to accept or

refuse the clearance issued.

4−4−8. IFR Clearance VFR−on−top

a. A pilot on an IFR flight plan operating in VFR

weather conditions, may request VFR−on−top in lieu

of an assigned altitude. This permits a pilot to select

an altitude or flight level of their choice (subject to

any ATC restrictions.)

b. Pilots desiring to climb through a cloud, haze,

smoke, or other meteorological formation and then

either cancel their IFR flight plan or operate

VFR-on-top may request a climb to VFR-on-top. The

ATC authorization must contain either a top report or

a statement that no top report is available, and a

request to report reaching VFR-on-top. Additionally,

the ATC authorization may contain a clearance limit,
7/26/12 AIM

ATC Clearances and Aircraft Separation 4−4−5

routing and an alternative clearance if VFR−on−top

is not reached by a specified altitude.

c. A pilot on an IFR flight plan, operating in VFR

conditions, may request to climb/descend in VFR

conditions.

d. ATC may not authorize VFR−on−top/VFR

conditions operations unless the pilot requests the

VFR operation or a clearance to operate in VFR

conditions will result in noise abatement benefits

where part of the IFR departure route does not

conform to an FAA approved noise abatement route

or altitude.

e. When operating in VFR conditions with an ATC

authorization to “maintain VFR−on−top/maintain

VFR conditions” pilots on IFR flight plans must:

1. Fly at the appropriate VFR altitude as

prescribed in 14 CFR Section 91.159.

2. Comply with the VFR visibility and distance

from cloud criteria in 14 CFR Section 91.155 (Basic

VFR Weather Minimums).

3. Comply with instrument flight rules that are

applicable to this flight; i.e., minimum IFR altitudes,

position reporting, radio communications, course to

be flown, adherence to ATC clearance, etc.

NOTE−

Pilots should advise ATC prior to any altitude change to

ensure the exchange of accurate traffic information.

f. ATC authorization to “maintain VFR−on−top”

is not intended to restrict pilots so that they must

operate only above an obscuring meteorological

formation (layer). Instead, it permits operation above,

below, between layers, or in areas where there is no

meteorological obscuration. It is imperative, however, that pilots understand that clearance to operate

“VFR−on−top/VFR conditions” does not imply

cancellation of the IFR flight plan.

g. Pilots operating VFR−on−top/VFR conditions

may receive traffic information from ATC on other

pertinent IFR or VFR aircraft. However, aircraft

operating in Class B airspace/TRSAs must be

separated as required by FAA Order JO 7110.65,

Air Traffic Control.

NOTE−

When operating in VFR weather conditions, it is the pilot’s

responsibility to be vigilant so as to see−and−avoid other

aircraft.

h. ATC will not authorize VFR or VFR−on−top

operations in Class A airspace.

REFERENCE−

AIM, Class A Airspace, Paragraph 3−2−2.

4−4−9. VFR/IFR Flights

A pilot departing VFR, either intending to or needing

to obtain an IFR clearance en route, must be aware of

the position of the aircraft and the relative

terrain/obstructions. When accepting a clearance

below the MEA/MIA/MVA/OROCA, pilots are

responsible for their own terrain/obstruction clearance until reaching the MEA/MIA/MVA/OROCA. If

pilots are unable to maintain terrain/obstruction

clearance, the controller should be advised and pilots

should state their intentions.

NOTE−

OROCA is an off−route altitude which provides obstruction clearance with a 1,000 foot buffer in nonmountainous

terrain areas and a 2,000 foot buffer in designated

mountainous areas within the U.S. This altitude may not

provide signal coverage from ground−based navigational

aids, air traffic control radar, or communications

coverage.

4−4−10. Adherence to Clearance

a. When air traffic clearance has been obtained

under either visual or instrument flight rules, the

pilot−in−command of the aircraft must not deviate

from the provisions thereof unless an amended

clearance is obtained. When ATC issues a clearance

or instruction, pilots are expected to execute its

provisions upon receipt. ATC, in certain situations,

will include the word “IMMEDIATELY” in a

clearance or instruction to impress urgency of an

imminent situation and expeditious compliance by

the pilot is expected and necessary for safety. The

addition of a VFR or other restriction; i.e., climb or

descent point or time, crossing altitude, etc., does not

authorize a pilot to deviate from the route of flight or

any other provision of the ATC clearance.

b. When a heading is assigned or a turn is

requested by ATC, pilots are expected to promptly

initiate the turn, to complete the turn, and maintain the

new heading unless issued additional instructions.

c. The term “AT PILOT’S DISCRETION”

included in the altitude information of an ATC

clearance means that ATC has offered the pilot the

option to start climb or descent when the pilot wishes,
AIM 7/26/12

4−4−6 ATC Clearances and Aircraft Separation

is authorized to conduct the climb or descent at any

rate, and to temporarily level off at any intermediate

altitude as desired. However, once the aircraft has

vacated an altitude, it may not return to that altitude.

d. When ATC has not used the term “AT PILOT’S

DISCRETION” nor imposed any climb or descent

restrictions, pilots should initiate climb or descent

promptly on acknowledgement of the clearance.

Descend or climb at an optimum rate consistent with

the operating characteristics of the aircraft to

1,000 feet above or below the assigned altitude, and

then attempt to descend or climb at a rate of between

500 and 1,500 fpm until the assigned altitude is

reached. If at anytime the pilot is unable to climb or

descend at a rate of at least 500 feet a minute, advise

ATC. If it is necessary to level off at an intermediate

altitude during climb or descent, advise ATC, except

when leveling off at 10,000 feet MSL on descent, or

2,500 feet above airport elevation (prior to entering a

Class C or Class D surface area), when required for

speed reduction.

REFERENCE−

14 CFR Section 91.117.

NOTE−

Leveling off at 10,000 feet MSL on descent or 2,500 feet

above airport elevation (prior to entering a Class C or

Class D surface area) to comply with 14 CFR

Section 91.117 airspeed restrictions is commonplace.

Controllers anticipate this action and plan accordingly.

Leveling off at any other time on climb or descent may

seriously affect air traffic handling by ATC. Consequently,

it is imperative that pilots make every effort to fulfill the

above expected actions to aid ATC in safely handling and

expediting traffic.

e. If the altitude information of an ATC

DESCENT clearance includes a provision to

“CROSS (fix) AT” or “AT OR ABOVE/BELOW

(altitude),” the manner in which the descent is

executed to comply with the crossing altitude is at the

pilot’s discretion. This authorization to descend at

pilot’s discretion is only applicable to that portion of

the flight to which the crossing altitude restriction

applies, and the pilot is expected to comply with the

crossing altitude as a provision of the clearance. Any

other clearance in which pilot execution is optional

will so state “AT PILOT’S DISCRETION.”

EXAMPLE−

1. “United Four Seventeen, descend and maintain

six thousand.”

NOTE−

1. The pilot is expected to commence descent upon receipt

of the clearance and to descend at the suggested rates until

reaching the assigned altitude of 6,000 feet.

EXAMPLE−

2. “United Four Seventeen, descend at pilot’s discretion,

maintain six thousand.”

NOTE−

2. The pilot is authorized to conduct descent within the

context of the term at pilot’s discretion as described above.

EXAMPLE−

3. “United Four Seventeen, cross Lakeview V−O−R at or

above Flight Level two zero zero, descend and maintain

six thousand.”

NOTE−

3. The pilot is authorized to conduct descent at pilot’s

discretion until reaching Lakeview VOR and must comply

with the clearance provision to cross the Lakeview VOR at

or above FL 200. After passing Lakeview VOR, the pilot is

expected to descend at the suggested rates until reaching

the assigned altitude of 6,000 feet.

EXAMPLE−

4. “United Four Seventeen, cross Lakeview V−O−R at

six thousand, maintain six thousand.”

NOTE−

4. The pilot is authorized to conduct descent at pilot’s

discretion, however, must comply with the clearance

provision to cross the Lakeview VOR at 6,000 feet.

EXAMPLE−

5. “United Four Seventeen, descend now to Flight

Level two seven zero, cross Lakeview V−O−R at or below

one zero thousand, descend and maintain six thousand.”

NOTE−

5. The pilot is expected to promptly execute and complete

descent to FL 270 upon receipt of the clearance. After

reaching FL 270 the pilot is authorized to descend “at

pilot’s discretion” until reaching Lakeview VOR. The pilot

must comply with the clearance provision to cross

Lakeview VOR at or below 10,000 feet. After Lakeview

VOR the pilot is expected to descend at the suggested rates

until reaching 6,000 feet.

EXAMPLE−

6. “United Three Ten, descend now and maintain Flight

Level two four zero, pilot’s discretion after reaching Flight

Level two eight zero.”

NOTE−

6. The pilot is expected to commence descent upon receipt

of the clearance and to descend at the suggested rates until

reaching FL 280. At that point, the pilot is authorized to

continue descent to FL 240 within the context of the term

“at pilot’s discretion” as described above.

f. In case emergency authority is used to deviate

from provisions of an ATC clearance, the pilot−in−
7/26/12 AIM

ATC Clearances and Aircraft Separation 4−4−7

command must notify ATC as soon as possible and

obtain an amended clearance. In an emergency

situation which does not result in a deviation from the

rules prescribed in 14 CFR Part 91 but which requires

ATC to give priority to an aircraft, the pilot of such

aircraft must, when requested by ATC, make a report

within 48 hours of such emergency situation to the

manager of that ATC facility.

g. The guiding principle is that the last ATC

clearance has precedence over the previous ATC

clearance. When the route or altitude in a previously

issued clearance is amended, the controller will

restate applicable altitude restrictions. If altitude to

maintain is changed or restated, whether prior to

departure or while airborne, and previously issued

altitude restrictions are omitted, those altitude

restrictions are canceled, including departure procedures and STAR altitude restrictions.

EXAMPLE−

1. A departure flight receives a clearance to destination

airport to maintain FL 290. The clearance incorporates a

DP which has certain altitude crossing restrictions. Shortly

after takeoff, the flight receives a new clearance changing

the maintaining FL from 290 to 250. If the altitude

restrictions are still applicable, the controller restates

them.

2. A departing aircraft is cleared to cross Fluky

Intersection at or above 3,000 feet, Gordonville VOR at or

above 12,000 feet, maintain FL 200. Shortly after

departure, the altitude to be maintained is changed to

FL 240. If the altitude restrictions are still applicable, the

controller issues an amended clearance as follows: “cross

Fluky Intersection at or above three thousand, cross

Gordonville V−O−R at or above one two thousand,

maintain Flight Level two four zero.”

3. An arriving aircraft is cleared to the destination airport

via V45 Delta VOR direct; the aircraft is cleared to cross

Delta VOR at 10,000 feet, and then to maintain 6,000 feet.

Prior to Delta VOR, the controller issues an amended

clearance as follows: “turn right heading one eight zero

for vector to runway three six I−L−S approach, maintain

six thousand.”

NOTE−

Because the altitude restriction “cross Delta V−O−R at

10,000 feet” was omitted from the amended clearance, it is

no longer in effect.

h. Pilots of turbojet aircraft equipped with

afterburner engines should advise ATC prior to

takeoff if they intend to use afterburning during their

climb to the en route altitude. Often, the controller

may be able to plan traffic to accommodate a high

performance climb and allow the aircraft to climb to

the planned altitude without restriction.

i. If an “expedite” climb or descent clearance is

issued by ATC, and the altitude to maintain is

subsequently changed or restated without an expedite

instruction, the expedite instruction is canceled.

Expedite climb/descent normally indicates to the

pilot that the approximate best rate of climb/descent

should be used without requiring an exceptional

change in aircraft handling characteristics. Normally

controllers will inform pilots of the reason for an

instruction to expedite.

4−4−11. IFR Separation Standards

a. ATC effects separation of aircraft vertically by

assigning different altitudes; longitudinally by

providing an interval expressed in time or distance

between aircraft on the same, converging, or crossing

courses, and laterally by assigning different flight

paths.

b. Separation will be provided between all aircraft

operating on IFR flight plans except during that part

of the flight (outside Class B airspace or a TRSA)

being conducted on a VFR−on−top/VFR conditions

clearance. Under these conditions, ATC may issue

traffic advisories, but it is the sole responsibility of the

pilot to be vigilant so as to see and avoid other aircraft.

c. When radar is employed in the separation of

aircraft at the same altitude, a minimum of 3 miles

separation is provided between aircraft operating

within 40 miles of the radar antenna site, and 5 miles

between aircraft operating beyond 40 miles from the

antenna site. These minima may be increased or

decreased in certain specific situations.

NOTE−

Certain separation standards are increased in the terminal

environment when CENRAP is being utilized.

4−4−12. Speed Adjustments

a. ATC will issue speed adjustments to pilots of

radar−controlled aircraft to achieve or maintain

required or desire spacing.

b. ATC will express all speed adjustments in

terms of knots based on indicated airspeed (IAS) in

10 knot increments except that at or above FL 240

speeds may be expressed in terms of Mach numbers

in 0.01 increments. The use of Mach numbers is

restricted to turbojet aircraft with Mach meters.
AIM 7/26/12

4−4−8 ATC Clearances and Aircraft Separation

c. Pilots complying with speed adjustments are

expected to maintain a speed within plus or minus

10 knots or 0.02 Mach number of the specified speed.

d. When ATC assigns speed adjustments, it will

be in accordance with the following recommended

minimums:

1. To aircraft operating between FL 280 and

10,000 feet, a speed not less than 250 knots or the

equivalent Mach number.

NOTE−

1. On a standard day the Mach numbers equivalent to

250 knots CAS (subject to minor variations) are:

FL 240−0.6

FL 250−0.61

FL 260−0.62

FL 270−0.64

FL 280−0.65

FL 290−0.66.

2. When an operational advantage will be realized, speeds

lower than the recommended minima may be applied.

2. To arriving turbojet aircraft operating below

10,000 feet:

(a) A speed not less than 210 knots, except;

(b) Within 20 flying miles of the airport of

intended landing, a speed not less than 170 knots.

3. To arriving reciprocating engine or turboprop

aircraft within 20 flying miles of the runway

threshold of the airport of intended landing, a speed

not less than 150 knots.

4. To departing aircraft:

(a) Turbojet aircraft, a speed not less than

230 knots.

(b) Reciprocating engine aircraft, a speed not

less than 150 knots.

e. When ATC combines a speed adjustment with

a descent clearance, the sequence of delivery, with the

word “then” between, indicates the expected order of

execution.

EXAMPLE−

1. Descend and maintain (altitude); then, reduce speed to

(speed).

2. Reduce speed to (speed); then, descend and maintain

(altitude).

NOTE−

The maximum speeds below 10,000 feet as established in

14 CFR Section 91.117 still apply. If there is any doubt

concerning the manner in which such a clearance is to be

executed, request clarification from ATC.

f. If ATC determines (before an approach

clearance is issued) that it is no longer necessary to

apply speed adjustment procedures, they will inform

the pilot to resume normal speed. Approach

clearances supersede any prior speed adjustment

assignments, and pilots are expected to make their

own speed adjustments, as necessary, to complete the

approach. Under certain circumstances, however, it

may be necessary for ATC to issue further speed

adjustments after approach clearance is issued to

maintain separation between successive arrivals.

Under such circumstances, previously issued speed

adjustments will be restated if that speed is to be

maintained or additional speed adjustments are

requested. ATC must obtain pilot concurrence for

speed adjustments after approach clearances are

issued. Speed adjustments should not be assigned

inside the final approach fix on final or a point 5 miles

from the runway, whichever is closer to the runway.

NOTE−

An instruction to “resume normal speed” does not delete

speed restrictions that are contained in a published

procedure, unless specifically stated by ATC, nor does it

relieve the pilot of those speed restrictions which are

applicable to 14 CFR Section 91.117.

g. The pilots retain the prerogative of rejecting the

application of speed adjustment by ATC if the

minimum safe airspeed for any particular operation is

greater than the speed adjustment.

NOTE−

In such cases, pilots are expected to advise ATC of the

speed that will be used.

h. Pilots are reminded that they are responsible for

rejecting the application of speed adjustment by ATC

if, in their opinion, it will cause them to exceed the

maximum indicated airspeed prescribed by 14 CFR

Section 91.117(a), (c) and (d). IN SUCH CASES,

THE PILOT IS EXPECTED TO SO INFORM ATC.

Pilots operating at or above 10,000 feet MSL who are

issued speed adjustments which exceed 250 knots

IAS and are subsequently cleared below 10,000 feet

MSL are expected to comply with 14 CFR

Section 91.117(a).

i. Speed restrictions of 250 knots do not apply to

U.S. registered aircraft operating beyond 12 nautical

miles from the coastline within the U.S. Flight

Information Region, in Class E airspace below

10,000 feet MSL. However, in airspace underlying a
7/26/12 AIM

ATC Clearances and Aircraft Separation 4−4−9

Class B airspace area designated for an airport, or in

a VFR corridor designated through such as a Class B

airspace area, pilots are expected to comply with the

200 knot speed limit specified in 14 CFR

Section 91.117(c).

j. For operations in a Class C and Class D surface

area, ATC is authorized to request or approve a speed

greater than the maximum indicated airspeeds

prescribed for operation within that airspace (14 CFR

Section 91.117(b)).

NOTE−

Pilots are expected to comply with the maximum speed of

200 knots when operating beneath Class B airspace or in

a Class B VFR corridor (14 CFR Section 91.117(c)

and (d)).

k. When in communications with the ARTCC or

approach control facility, pilots should, as a good

operating practice, state any ATC assigned speed

restriction on initial radio contact associated with an

ATC communications frequency change.

4−4−13. Runway Separation

Tower controllers establish the sequence of arriving

and departing aircraft by requiring them to adjust

flight or ground operation as necessary to achieve

proper spacing. They may “HOLD” an aircraft short

of the runway to achieve spacing between it and an

arriving aircraft; the controller may instruct a pilot to

“EXTEND DOWNWIND” in order to establish

spacing from an arriving or departing aircraft. At

times a clearance may include the word “IMMEDIATE.” For example: “CLEARED FOR

IMMEDIATE TAKEOFF.” In such cases “IMMEDIATE” is used for purposes of air traffic separation. It

is up to the pilot to refuse the clearance if, in the pilot’s

opinion, compliance would adversely affect the

operation.

REFERENCE−

AIM, Gate Holding due to Departure Delays, Paragraph 4−3−15.

4−4−14. Visual Separation

a. Visual separation is a means employed by ATC

to separate aircraft in terminal areas and en route

airspace in the NAS. There are two methods

employed to effect this separation:

1. The tower controller sees the aircraft

involved and issues instructions, as necessary, to

ensure that the aircraft avoid each other.

2. A pilot sees the other aircraft involved and

upon instructions from the controller provides

separation by maneuvering the aircraft to avoid it.

When pilots accept responsibility to maintain visual

separation, they must maintain constant visual

surveillance and not pass the other aircraft until it is

no longer a factor.

NOTE−

Traffic is no longer a factor when during approach phase

the other aircraft is in the landing phase of flight or

executes a missed approach; and during departure or

en route, when the other aircraft turns away or is on a

diverging course.

b. A pilot’s acceptance of instructions to follow

another aircraft or provide visual separation from it is

an acknowledgment that the pilot will maneuver the

aircraft as necessary to avoid the other aircraft or to

maintain in−trail separation. In operations conducted

behind heavy jet aircraft, it is also an acknowledgment that the pilot accepts the responsibility for wake

turbulence separation.

NOTE−

When a pilot has been told to follow another aircraft or to

provide visual separation from it, the pilot should promptly

notify the controller if visual contact with the other aircraft

is lost or cannot be maintained or if the pilot cannot accept

the responsibility for the separation for any reason.

c. Scanning the sky for other aircraft is a key factor

in collision avoidance. Pilots and copilots (or the right

seat passenger) should continuously scan to cover all

areas of the sky visible from the cockpit. Pilots must

develop an effective scanning technique which

maximizes one’s visual capabilities. Spotting a

potential collision threat increases directly as more

time is spent looking outside the aircraft. One must

use timesharing techniques to effectively scan the

surrounding airspace while monitoring instruments

as well.

d. Since the eye can focus only on a narrow

viewing area, effective scanning is accomplished

with a series of short, regularly spaced eye

movements that bring successive areas of the sky into

the central visual field. Each movement should not

exceed ten degrees, and each area should be observed

for at least one second to enable collision detection.

Although many pilots seem to prefer the method of

horizontal back−and−forth scanning every pilot

should develop a scanning pattern that is not only

comfortable but assures optimum effectiveness.

Pilots should remember, however, that they have a
AIM 7/26/12

4−4−10 ATC Clearances and Aircraft Separation

regulatory responsibility (14 CFR Section 91.113(a))

to see and avoid other aircraft when weather

conditions permit.

4−4−15. Use of Visual Clearing Procedures

a. Before Takeoff. Prior to taxiing onto a runway

or landing area in preparation for takeoff, pilots

should scan the approach areas for possible landing

traffic and execute the appropriate clearing maneuvers to provide them a clear view of the approach

areas.

b. Climbs and Descents. During climbs and

descents in flight conditions which permit visual

detection of other traffic, pilots should execute gentle

banks, left and right at a frequency which permits

continuous visual scanning of the airspace about

them.

c. Straight and Level. Sustained periods of

straight and level flight in conditions which permit

visual detection of other traffic should be broken at

intervals with appropriate clearing procedures to

provide effective visual scanning.

d. Traffic Pattern. Entries into traffic patterns

while descending create specific collision hazards

and should be avoided.

e. Traffic at VOR Sites. All operators should

emphasize the need for sustained vigilance in the

vicinity of VORs and airway intersections due to the

convergence of traffic.

f. Training Operations. Operators of pilot training programs are urged to adopt the following

practices:

1. Pilots undergoing flight instruction at all

levels should be requested to verbalize clearing

procedures (call out “clear” left, right, above, or

below) to instill and sustain the habit of vigilance

during maneuvering.

2. High−wing airplane. Momentarily raise the

wing in the direction of the intended turn and look.

3. Low−wing airplane. Momentarily lower

the wing in the direction of the intended turn and look.

4. Appropriate clearing procedures should

precede the execution of all turns including

chandelles, lazy eights, stalls, slow flight, climbs,

straight and level, spins, and other combination

maneuvers.

4−4−16. Traffic Alert and Collision

Avoidance System (TCAS I & II)

a. TCAS I provides proximity warning only, to

assist the pilot in the visual acquisition of intruder

aircraft. No recommended avoidance maneuvers are

provided nor authorized as a direct result of a TCAS I

warning. It is intended for use by smaller commuter

aircraft holding 10 to 30 passenger seats, and general

aviation aircraft.

b. TCAS II provides traffic advisories (TAs) and

resolution advisories (RAs). Resolution advisories

provide recommended maneuvers in a vertical

direction (climb or descend only) to avoid conflicting

traffic. Airline aircraft, and larger commuter and

business aircraft holding 31 passenger seats or more,

use TCAS II equipment.

1. Each pilot who deviates from an ATC

clearance in response to a TCAS II RA must notify

ATC of that deviation as soon as practicable and

expeditiously return to the current ATC clearance

when the traffic conflict is resolved.

2. Deviations from rules, policies, or clearances

should be kept to the minimum necessary to satisfy a

TCAS II RA.

3. The serving IFR air traffic facility is not

responsible to provide approved standard IFR

separation to an aircraft after a TCAS II RA maneuver

until one of the following conditions exists:

(a) The aircraft has returned to its assigned

altitude and course.

(b) Alternate ATC instructions have been

issued.

c. TCAS does not alter or diminish the pilot’s basic

authority and responsibility to ensure safe flight.

Since TCAS does not respond to aircraft which are

not transponder equipped or aircraft with a

transponder failure, TCAS alone does not ensure safe

separation in every case.

d. At this time, no air traffic service nor handling

is predicated on the availability of TCAS equipment

in the aircraft.

4−4−17. Traffic Information Service (TIS)

a. TIS provides proximity warning only, to assist

the pilot in the visual acquisition of intruder aircraft.

No recommended avoidance maneuvers are provided

nor authorized as a direct result of a TIS intruder
7/26/12 AIM

ATC Clearances and Aircraft Separation 4−4−11

display or TIS alert. It is intended for use by aircraft

in which TCAS is not required.

b. TIS does not alter or diminish the pilot’s basic

authority and responsibility to ensure safe flight.

Since TIS does not respond to aircraft which are not

transponder equipped, aircraft with a transponder

failure, or aircraft out of radar coverage, TIS alone

does not ensure safe separation in every case.

c. At this time, no air traffic service nor handling

is predicated on the availability of TIS equipment in

the aircraft.

d. Presently, no air traffic services or handling is

predicated on the availability of an ADS−B cockpit

display. A “traffic−in−sight” reply to ATC must be

based on seeing an aircraft out−the−window, NOT on

the cockpit display.

7/26/12 AIM

Surveillance Systems 4−5−1

Section 5. Surveillance Systems

4−5−1. Radar

a. Capabilities

1. Radar is a method whereby radio waves are

transmitted into the air and are then received when

they have been reflected by an object in the path of the

beam. Range is determined by measuring the time it

takes (at the speed of light) for the radio wave to go

out to the object and then return to the receiving

antenna. The direction of a detected object from a

radar site is determined by the position of the rotating

antenna when the reflected portion of the radio wave

is received.

2. More reliable maintenance and improved

equipment have reduced radar system failures to a

negligible factor. Most facilities actually have some

components duplicated, one operating and another

which immediately takes over when a malfunction

occurs to the primary component.

b. Limitations

1. It is very important for the aviation

community to recognize the fact that there are

limitations to radar service and that ATC controllers

may not always be able to issue traffic advisories

concerning aircraft which are not under ATC control

and cannot be seen on radar. (See FIG 4−5−1.)

FIG 4−5−1

Limitations to Radar Service

Precipitation Attenuation

The nearby target absorbs and scatters so much of the out-going and returning

energy that the radar does not detect the distant target.

AREA BLACKED OUT

BY ATTENUATION

NOT OBSERVED

OBSERVED

ECHO

(a) The characteristics of radio waves are

such that they normally travel in a continuous straight

line unless they are:

(1) “Bent” by abnormal atmospheric phenomena such as temperature inversions;

(2) Reflected or attenuated by dense

objects such as heavy clouds, precipitation, ground

obstacles, mountains, etc.; or

(3) Screened by high terrain features.

(b) The bending of radar pulses, often called

anomalous propagation or ducting, may cause many

extraneous blips to appear on the radar operator’s

display if the beam has been bent toward the ground

or may decrease the detection range if the wave is

bent upward. It is difficult to solve the effects of

anomalous propagation, but using beacon radar and

electronically eliminating stationary and slow

moving targets by a method called moving target

indicator (MTI) usually negate the problem.

(c) Radar energy that strikes dense objects

will be reflected and displayed on the operator’s

scope thereby blocking out aircraft at the same range

and greatly weakening or completely eliminating the

display of targets at a greater range. Again, radar

beacon and MTI are very effectively used to combat

ground clutter and weather phenomena, and a method

of circularly polarizing the radar beam will eliminate

some weather returns. A negative characteristic of

MTI is that an aircraft flying a speed that coincides

with the canceling signal of the MTI (tangential or

“blind” speed) may not be displayed to the radar

controller.

(d) Relatively low altitude aircraft will not be

seen if they are screened by mountains or are below

the radar beam due to earth curvature. The only

solution to screening is the installation of strategically placed multiple radars which has been done in

some areas.

(e) There are several other factors which

affect radar control. The amount of reflective surface

of an aircraft will determine the size of the radar

return. Therefore, a small light airplane or a sleek jet

fighter will be more difficult to see on radar than a

large commercial jet or military bomber. Here again,

the use of radar beacon is invaluable if the aircraft is
AIM 7/26/12

4−5−2 Surveillance Systems

equipped with an airborne transponder. All ARTCCs’

radars in the conterminous U.S. and many airport

surveillance radars have the capability to interrogate

Mode C and display altitude information to the

controller from appropriately equipped aircraft.

However, there are a number of airport surveillance

radars that don’t have Mode C display capability and;

therefore, altitude information must be obtained from

the pilot.

(f) At some locations within the ATC en route

environment, secondary−radar−only (no primary

radar) gap filler radar systems are used to give lower

altitude radar coverage between two larger radar

systems, each of which provides both primary and

secondary radar coverage. In those geographical

areas served by secondary−radar only, aircraft

without transponders cannot be provided with radar

service. Additionally, transponder equipped aircraft

cannot be provided with radar advisories concerning

primary targets and weather.

REFERENCE−

Pilot/Controller Glossary Term− Radar.

(g) The controller’s ability to advise a pilot

flying on instruments or in visual conditions of the

aircraft’s proximity to another aircraft will be limited

if the unknown aircraft is not observed on radar, if no

flight plan information is available, or if the volume

of traffic and workload prevent issuing traffic

information. The controller’s first priority is given to

establishing vertical, lateral, or longitudinal separation between aircraft flying IFR under the control of

ATC.

c. FAA radar units operate continuously at the

locations shown in the Airport/Facility Directory, and

their services are available to all pilots, both civil and

military. Contact the associated FAA control tower or

ARTCC on any frequency guarded for initial

instructions, or in an emergency, any FAA facility for

information on the nearest radar service.

4−5−2. Air Traffic Control Radar Beacon

System (ATCRBS)

a. The ATCRBS, sometimes referred to as

secondary surveillance radar, consists of three main

components:

1. Interrogator. Primary radar relies on a

signal being transmitted from the radar antenna site

and for this signal to be reflected or “bounced back”

from an object (such as an aircraft). This reflected

signal is then displayed as a “target” on the

controller’s radarscope. In the ATCRBS, the

Interrogator, a ground based radar beacon transmitter−receiver, scans in synchronism with the primary

radar and transmits discrete radio signals which

repetitiously request all transponders, on the mode

being used, to reply. The replies received are then

mixed with the primary returns and both are

displayed on the same radarscope.

2. Transponder. This airborne radar beacon

transmitter−receiver automatically receives the signals from the interrogator and selectively replies with

a specific pulse group (code) only to those

interrogations being received on the mode to which

it is set. These replies are independent of, and much

stronger than a primary radar return.

3. Radarscope. The radarscope used by the

controller displays returns from both the primary

radar system and the ATCRBS. These returns, called

targets, are what the controller refers to in the control

and separation of traffic.

b. The job of identifying and maintaining

identification of primary radar targets is a long and

tedious task for the controller. Some of the

advantages of ATCRBS over primary radar are:

1. Reinforcement of radar targets.

2. Rapid target identification.

3. Unique display of selected codes.

c. A part of the ATCRBS ground equipment is the

decoder. This equipment enables a controller to

assign discrete transponder codes to each aircraft

under his/her control. Normally only one code will be

assigned for the entire flight. Assignments are made

by the ARTCC computer on the basis of the National

Beacon Code Allocation Plan. The equipment is also

designed to receive Mode C altitude information

from the aircraft.

NOTE−

Refer to figures with explanatory legends for an illustration

of the target symbology depicted on radar scopes in the

NAS Stage A (en route), the ARTS III (terminal) Systems,

and other nonautomated (broadband) radar systems. (See

FIG 4−5−2 and FIG 4−5−3.)

d. It should be emphasized that aircraft transponders greatly improve the effectiveness of radar

systems.

REFERENCE−

AIM, Transponder Operation, Paragraph 4−1−20.
7/26/12 AIM

Surveillance Systems 4−5−3

FIG 4−5−2

ARTS III Radar Scope With Alphanumeric Data

NOTE−

A number of radar terminals do not have ARTS equipment. Those facilities and certain ARTCCs outside the contiguous U.S.

would have radar displays similar to the lower right hand subset. ARTS facilities and NAS Stage A ARTCCs, when operating

in the nonautomation mode, would also have similar displays and certain services based on automation may not be

available.
AIM 7/26/12

4−5−4 Surveillance Systems

EXAMPLE−

1. Areas of precipitation (can be reduced by CP)

2. Arrival/departure tabular list

3. Trackball (control) position symbol (A)

4. Airway (lines are sometimes deleted in part)

5. Radar limit line for control

6. Obstruction (video map)

7. Primary radar returns of obstacles or terrain (can be

removed by MTI)

8. Satellite airports

9. Runway centerlines (marks and spaces indicate

miles)

10. Primary airport with parallel runways

11. Approach gates

12. Tracked target (primary and beacon target)

13. Control position symbol

14. Untracked target select code (monitored) with

Mode C readout of 5,000’

15. Untracked target without Mode C

16. Primary target

17. Beacon target only (secondary radar) (transponder)

18. Primary and beacon target

19. Leader line

20. Altitude Mode C readout is 6,000’ 

(Note: readouts may not be displayed because of

nonreceipt of beacon information, garbled beacon

signals, and flight plan data which is displayed

alternately with the altitude readout)

21. Ground speed readout is 240 knots 

(Note: readouts may not be displayed because of a loss

of beacon signal, a controller alert that a pilot was

squawking emergency, radio failure, etc.)

22. Aircraft ID

23. Asterisk indicates a controller entry in Mode C

block. In this case 5,000’ is entered and “05” would

alternate with Mode C readout.

24. Indicates heavy

25. “Low ALT” flashes to indicate when an aircraft’s

predicted descent places the aircraft in an unsafe

proximity to terrain. 

(Note: this feature does not function if the aircraft is not

squawking Mode C. When a helicopter or aircraft is

known to be operating below the lower safe limit, the

“low ALT” can be changed to “inhibit” and flashing

ceases.)

26. NAVAIDs

27. Airways

28. Primary target only

29. Nonmonitored. No Mode C (an asterisk would

indicate nonmonitored with Mode C)

30. Beacon target only (secondary radar based on

aircraft transponder)

31. Tracked target (primary and beacon target) control

position A

32. Aircraft is squawking emergency Code 7700 and is

nonmonitored, untracked, Mode C

33. Controller assigned runway 36 right alternates with

Mode C readout 

(Note: a three letter identifier could also indicate the

arrival is at specific airport)

34. Ident flashes

35. Identing target blossoms

36. Untracked target identing on a selected code

37. Range marks (10 and 15 miles) (can be

changed/offset)

38. Aircraft controlled by center

39. Targets in suspend status

40. Coast/suspend list (aircraft holding, temporary loss

of beacon/target, etc.)

41. Radio failure (emergency information)

42. Select beacon codes (being monitored)

43. General information (ATIS, runway, approach in

use)

44. Altimeter setting

45. Time

46. System data area
7/26/12 AIM

Surveillance Systems 4−5−5

FIG 4−5−3

NAS Stage A Controllers View Plan Display

This figure illustrates the controller’s radar scope (PVD) when operating in the full automation (RDP) mode, which is

normally 20 hours per day.

(When not in automation mode, the display is similar to the broadband mode shown in the ARTS III radar scope figure.

Certain ARTCCs outside the contiguous U.S. also operate in “broadband” mode.)

25 26

X

X

X

X

X

X

X

X

X

#

X

X

X

AAL373

280C

191H-33

VIG123

310N

095

NWA258

170 143

AAL353

70 231

2734

R15909

290 170C

2103

N1467F

140 + 143

460

UAL33

100A

296

7700

EMRG

7600

RDOF

1200

1200

85

+++

+ UAL712

310N

228CST

1

22 23

24 27

28

29

29

30

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17 18

19

20

21

H

H

H

H

H

H

H

H

H H

H

H

H

RADAR SERVICES AND PROCEDURES
AIM 7/26/12

4−5−6 Surveillance Systems

EXAMPLE−

Target symbols:

1. Uncorrelated primary radar target [] [+]

2. Correlated primary radar target []

See note below.

3. Uncorrelated beacon target [ / ]

4. Correlated beacon target [ \ ]

5. Identing beacon target []

Note: in Number 2 correlated means the association of

radar data with the computer projected track of an

identified aircraft.

Position symbols:

6. Free track (no flight plan tracking) []

7. Flat track (flight plan tracking) []

8. Coast (beacon target lost) [#]

9. Present position hold [  ]

Data block information:

10. Aircraft ident 

See note below.

11. Assigned altitude FL 280, Mode C altitude same or

within  200’ of assigned altitude. 

See note below.

12. Computer ID #191, handoff is to sector 33

 (0−33 would mean handoff accepted) 

See note below.

13. Assigned altitude 17,000’, aircraft is climbing,

Mode C readout was 14,300 when last beacon interrogation was received.

14. Leader line connecting target symbol and data block

15. Track velocity and direction vector line (projected

ahead of target)

16. Assigned altitude 7,000, aircraft is descending, last

Mode C readout (or last reported altitude) was 100’ above

FL 230

17. Transponder code shows in full data block only when

different than assigned code

18. Aircraft is 300’ above assigned altitude

19. Reported altitude (no Mode C readout) same as

assigned. (An “n” would indicate no reported altitude.)

20. Transponder set on emergency Code 7700 (EMRG

flashes to attract attention)

21. Transponder Code 1200 (VFR) with no Mode C

22. Code 1200 (VFR) with Mode C and last altitude

readout

23. Transponder set on radio failure Code 7600 (RDOF

flashes)

24. Computer ID #228, CST indicates target is in coast

status

25. Assigned altitude FL 290, transponder code (these two

items constitute a “limited data block”)

Note: numbers 10, 11, and 12 constitute a “full data

block”

Other symbols: 

26. Navigational aid

27. Airway or jet route

28. Outline of weather returns based on primary radar.

“H” represents areas of high density precipitation which

might be thunderstorms. Radial lines indicated lower

density precipitation.

29. Obstruction

30. Airports

 Major:

Small:
7/26/12 AIM

Surveillance Systems 4−5−7

4−5−3. Surveillance Radar

a. Surveillance radars are divided into two general

categories: Airport Surveillance Radar (ASR) and

Air Route Surveillance Radar (ARSR).

1. ASR is designed to provide relatively

short−range coverage in the general vicinity of an

airport and to serve as an expeditious means of

handling terminal area traffic through observation of

precise aircraft locations on a radarscope. The ASR

can also be used as an instrument approach aid.

2. ARSR is a long−range radar system designed

primarily to provide a display of aircraft locations

over large areas.

3. Center Radar Automated Radar Terminal

Systems (ARTS) Processing (CENRAP) was developed to provide an alternative to a nonradar

environment at terminal facilities should an ASR fail

or malfunction. CENRAP sends aircraft radar beacon

target information to the ASR terminal facility

equipped with ARTS. Procedures used for the

separation of aircraft may increase under certain

conditions when a facility is utilizing CENRAP

because radar target information updates at a slower

rate than the normal ASR radar. Radar services for

VFR aircraft are also limited during CENRAP

operations because of the additional workload

required to provide services to IFR aircraft.

b. Surveillance radars scan through 360 degrees of

azimuth and present target information on a radar

display located in a tower or center. This information

is used independently or in conjunction with other

navigational aids in the control of air traffic.

4−5−4. Precision Approach Radar (PAR)

a. PAR is designed for use as a landing aid rather

than an aid for sequencing and spacing aircraft. PAR

equipment may be used as a primary landing aid (See

Chapter 5, Air Traffic Procedures, for additional

information), or it may be used to monitor other types

of approaches. It is designed to display range,

azimuth, and elevation information.

b. Two antennas are used in the PAR array, one

scanning a vertical plane, and the other scanning

horizontally. Since the range is limited to 10 miles,

azimuth to 20 degrees, and elevation to 7 degrees,

only the final approach area is covered. Each scope is

divided into two parts. The upper half presents

altitude and distance information, and the lower half

presents azimuth and distance.

4−5−5. Airport Surface Detection

Equipment − Model X (ASDE−X)

a. The Airport Surface Detection Equipment −

Model X (ASDE−X) is a multi−sensor surface

surveillance system the FAA is acquiring for airports

in the United States. This system will provide high

resolution, short−range, clutter free surveillance

information about aircraft and vehicles, both moving

and fixed, located on or near the surface of the

airport’s runways and taxiways under all weather and

visibility conditions. The system consists of:

1. A Primary Radar System. ASDE−X system coverage includes the airport surface and the

airspace up to 200 feet above the surface. Typically

located on the control tower or other strategic

location on the airport, the Primary Radar antenna is

able to detect and display aircraft that are not

equipped with or have malfunctioning transponders.

2. Interfaces. ASDE−X contains an automation interface for flight identification via all

automation platforms and interfaces with the

terminal radar for position information.

3. ASDE−X Automation. A Multi−sensor

Data Processor (MSDP) combines all sensor reports

into a single target which is displayed to the air traffic

controller.

4. Air Traffic Control Tower Display. A high

resolution, color monitor in the control tower cab

provides controllers with a seamless picture of airport

operations on the airport surface.

b. The combination of data collected from the

multiple sensors ensures that the most accurate

information about aircraft location is received in the

tower, thereby increasing surface safety and

efficiency.
AIM 7/26/12

4−5−8 Surveillance Systems

c. The following facilities have been projected to

receive ASDE−X:

TBL 4−5−1

STL Lambert−St. Louis International

CLT Charlotte Douglas International

SDF Louisville International Standiford

DFW Dallas/Ft. Worth International

ORD Chicago O’Hare International

LAX Los Angeles International

ATL Hartsfield Atlanta International

IAD Washington Dulles International

SEA Seattle−Tacoma International

MKE General Mitchell International

MCO Orlando International

PVD Theodore Francis Green State

PHX Phoenix Sky Harbor International

MEM Memphis International

RDU Raleigh−Durham International

HOU William P. Hobby (Houston, TX)

BDL Bradley International

SJC San Jose International

SAT San Antonio International

SMF Sacramento International

FLL Ft. Lauderdale/Hollywood

HNL Honolulu International − Hickam AFB

OAK Metropolitan Oakland International

IND Indianapolis International

TPA Tampa International

BUR Burbank−Glendale−Pasadena

CMH Port Columbus International

MDW Chicago Midway

COS Colorado Springs Municipal

SNA John Wayne − Orange County

ONT Ontario International

AUS Austin−Bergstrom International

RNO Reno/Tahoe International

ABQ Albuquerque International Sunport

SJU San Juan International

4−5−6. Traffic Information Service (TIS)

a. Introduction

The Traffic Information Service (TIS) provides

information to the cockpit via data link, that is similar

to VFR radar traffic advisories normally received

over voice radio. Among the first FAA−provided data

services, TIS is intended to improve the safety and

efficiency of “see and avoid” flight through an

automatic display that informs the pilot of nearby

traffic and potential conflict situations. This traffic

display is intended to assist the pilot in visual

acquisition of these aircraft. TIS employs an

enhanced capability of the terminal Mode S radar

system, which contains the surveillance data, as well

as the data link required to “uplink” this information

to suitably−equipped aircraft (known as a TIS

“client”). TIS provides estimated position, altitude,

altitude trend, and ground track information for up to

8 intruder aircraft within 7 NM horizontally,

+3,500 and −3,000 feet vertically of the client aircraft

(see FIG 4−5−4, TIS Proximity Coverage Volume).

The range of a target reported at a distance greater

than 7 NM only indicates that this target will be a

threat within 34 seconds and does not display an

precise distance. TIS will alert the pilot to aircraft

(under surveillance of the Mode S radar) that are

estimated to be within 34 seconds of potential

collision, regardless of distance of altitude. TIS

surveillance data is derived from the same radar used

by ATC; this data is uplinked to the client aircraft on

each radar scan (nominally every 5 seconds).

b. Requirements

1. In order to use TIS, the client and any intruder

aircraft must be equipped with the appropriate

cockpit equipment and fly within the radar coverage

of a Mode S radar capable of providing TIS.

Typically, this will be within 55 NM of the sites

depicted in FIG 4−5−5, Terminal Mode S Radar Sites.

ATC communication is not a requirement to receive

TIS, although it may be required by the particular

airspace or flight operations in which TIS is being

used.
7/26/12 AIM

Surveillance Systems 4−5−9

FIG 4−5−4

TIS Proximity Coverage Volume

FIG 4−5−5

Terminal Mode S Radar Sites
AIM 7/26/12

4−5−10 Surveillance Systems

FIG 4−5−6

Traffic Information Service (TIS)

Avionics Block Diagram
7/26/12 AIM

Surveillance Systems 4−5−11

2. The cockpit equipment functionality required

by a TIS client aircraft to receive the service consists

of the following (refer to FIG 4−5−6):

(a) Mode S data link transponder with

altitude encoder.

(b) Data link applications processor with TIS

software installed.

(c) Control−display unit.

(d) Optional equipment includes a digital

heading source to correct display errors caused by

“crab angle” and turning maneuvers.

NOTE−

Some of the above functions will likely be combined into

single pieces of avionics, such as (a) and (b).

3. To be visible to the TIS client, the intruder

aircraft must, at a minimum, have an operating

transponder (Mode A, C or S). All altitude

information provided by TIS from intruder aircraft is

derived from Mode C reports, if appropriately

equipped.

4. TIS will initially be provided by the terminal

Mode S systems that are paired with ASR−9 digital

primary radars. These systems are in locations with

the greatest traffic densities, thus will provide the

greatest initial benefit. The remaining terminal

Mode S sensors, which are paired with ASR−7 or

ASR−8 analog primary radars, will provide TIS

pending modification or relocation of these sites. See

FIG 4−5−5, Terminal Mode S Radar Sites, for site

locations. There is no mechanism in place, such as

NOTAMs, to provide status update on individual

radar sites since TIS is a nonessential, supplemental

information service.

The FAA also operates en route Mode S radars (not

illustrated) that rotate once every 12 seconds. These

sites will require additional development of TIS

before any possible implementation. There are no

plans to implement TIS in the en route Mode S radars

at the present time.

c. Capabilities

1. TIS provides ground−based surveillance

information over the Mode S data link to properly

equipped client aircraft to aid in visual acquisition of

proximate air traffic. The actual avionics capability of

each installation will vary and the supplemental

handbook material must be consulted prior to using

TIS. A maximum of eight (8) intruder aircraft may be

displayed; if more than eight aircraft match intruder

parameters, the eight “most significant” intruders are

uplinked. These “most significant” intruders are

usually the ones in closest proximity and/or the

greatest threat to the TIS client.

2. TIS, through the Mode S ground sensor,

provides the following data on each intruder aircraft:

(a) Relative bearing information in 6−degree

increments.

(b) Relative range information in 1/8 NM to

1 NM increments (depending on range).

(c) Relative altitude in 100−foot increments

(within 1,000 feet) or 500−foot increments (from

1,000−3,500 feet) if the intruder aircraft has operating

altitude reporting capability.

(d) Estimated intruder ground track in

45−degree increments.

(e) Altitude trend data (level within 500 fpm

or climbing/descending >500 fpm) if the intruder

aircraft has operating altitude reporting capability.

(f) Intruder priority as either an “traffic

advisory” or “proximate” intruder.

3. When flying from surveillance coverage of

one Mode S sensor to another, the transfer of TIS is

an automatic function of the avionics system and

requires no action from the pilot.

4. There are a variety of status messages that are

provided by either the airborne system or ground

equipment to alert the pilot of high priority intruders

and data link system status. These messages include

the following:

(a) Alert. Identifies a potential collision

hazard within 34 seconds. This alert may be visual

and/or audible, such as a flashing display symbol or

a headset tone. A target is a threat if the time to the

closest approach in vertical and horizontal coordinates is less than 30 seconds and the closest approach

is expected to be within 500 feet vertically and

0.5 nautical miles laterally.

(b) TIS Traffic. TIS traffic data is displayed.

(c) Coasting. The TIS display is more than

6 seconds old. This indicates a missing uplink from

the ground system. When the TIS display information

is more than 12 seconds old, the “No Traffic” status

will be indicated.
AIM 7/26/12

4−5−12 Surveillance Systems

(d) No Traffic. No intruders meet proximate

or alert criteria. This condition may exist when the

TIS system is fully functional or may indicate

“coasting” between 12 and 59 seconds old (see (c)

above).

(e) TIS Unavailable. The pilot has requested TIS, but no ground system is available. This

condition will also be displayed when TIS uplinks are

missing for 60 seconds or more.

(f) TIS Disabled. The pilot has not requested

TIS or has disconnected from TIS.

(g) Good−bye. The client aircraft has flown

outside of TIS coverage.

NOTE−

Depending on the avionics manufacturer implementation,

it is possible that some of these messages will not be directly

available to the pilot.

5. Depending on avionics system design, TIS

may be presented to the pilot in a variety of different

displays, including text and/or graphics. Voice

annunciation may also be used, either alone or in

combination with a visual display. FIG 4−5−6,

Traffic Information Service (TIS), Avionics Block

Diagram, shows an example of a TIS display using

symbology similar to the Traffic Alert and Collision

Avoidance System (TCAS) installed on most

passenger air carrier/commuter aircraft in the U.S.

The small symbol in the center represents the client

aircraft and the display is oriented “track up,” with the

12 o’clock position at the top. The range rings

indicate 2 and 5 NM. Each intruder is depicted by a

symbol positioned at the approximate relative

bearing and range from the client aircraft. The

circular symbol near the center indicates an “alert”

intruder and the diamond symbols indicate “proximate” intruders.

6. The inset in the lower right corner of

FIG 4−5−6, Traffic Information Service (TIS),

Avionics Block Diagram, shows a possible TIS data

block display. The following information is contained in this data block:

(a) The intruder, located approximately

four o’clock, three miles, is a “proximate” aircraft

and currently not a collision threat to the client

aircraft. This is indicated by the diamond symbol

used in this example.

(b) The intruder ground track diverges to the

right of the client aircraft, indicated by the small

arrow.

(c) The intruder altitude is 700 feet less than

or below the client aircraft, indicated by the “−07”

located under the symbol.

(d) The intruder is descending >500 fpm,

indicated by the downward arrow next to the “−07”

relative altitude information. The absence of this

arrow when an altitude tag is present indicates level

flight or a climb/descent rate less than 500 fpm.

NOTE−

If the intruder did not have an operating altitude encoder

(Mode C), the altitude and altitude trend “tags” would

have been omitted.

d. Limitations

1. TIS is NOT intended to be used as a collision

avoidance system and does not relieve the pilot

responsibility to “see and avoid” other aircraft (see

paragraph 5−5−8, See and Avoid). TIS must not be for

avoidance maneuvers during IMC or other times

when there is no visual contact with the intruder

aircraft. TIS is intended only to assist in visual

acquisition of other aircraft in VMC. No recommended avoidance maneuvers are provided for,

nor authorized, as a direct result of a TIS intruder

display or TIS alert.

2. While TIS is a useful aid to visual traffic

avoidance, it has some system limitations that must

be fully understood to ensure proper use. Many of

these limitations are inherent in secondary radar

surveillance. In other words, the information

provided by TIS will be no better than that provided

to ATC. Other limitations and anomalies are

associated with the TIS predictive algorithm.

(a) Intruder Display Limitations. TIS will

only display aircraft with operating transponders

installed. TIS relies on surveillance of the Mode S

radar, which is a “secondary surveillance” radar

similar to the ATCRBS described in paragraph 4−5−2.

(b) TIS Client Altitude Reporting Requirement. Altitude reporting is required by the TIS client

aircraft in order to receive TIS. If the altitude encoder

is inoperative or disabled, TIS will be unavailable, as

TIS requests will not be honored by the ground

system. As such, TIS requires altitude reporting to

determine the Proximity Coverage Volume as
7/26/12 AIM

Surveillance Systems 4−5−13

indicated in FIG 4−5−4. TIS users must be alert to

altitude encoder malfunctions, as TIS has no

mechanism to determine if client altitude reporting is

correct. A failure of this nature will cause erroneous

and possibly unpredictable TIS operation. If this

malfunction is suspected, confirmation of altitude

reporting with ATC is suggested.

(c) Intruder Altitude Reporting. Intruders

without altitude reporting capability will be displayed without the accompanying altitude tag.

Additionally, nonaltitude reporting intruders are

assumed to be at the same altitude as the TIS client for

alert computations. This helps to ensure that the pilot

will be alerted to all traffic under radar coverage, but

the actual altitude difference may be substantial.

Therefore, visual acquisition may be difficult in this

instance.

(d) Coverage Limitations. Since TIS is

provided by ground−based, secondary surveillance

radar, it is subject to all limitations of that radar. If an

aircraft is not detected by the radar, it cannot be

displayed on TIS. Examples of these limitations are

as follows:

(1) TIS will typically be provided within

55 NM of the radars depicted in FIG 4−5−5, Terminal

Mode S Radar Sites. This maximum range can vary

by radar site and is always subject to “line of sight”

limitations; the radar and data link signals will be

blocked by obstructions, terrain, and curvature of the

earth.

(2) TIS will be unavailable at low altitudes

in many areas of the country, particularly in

mountainous regions. Also, when flying near the

“floor” of radar coverage in a particular area,

intruders below the client aircraft may not be detected

by TIS.

(3) TIS will be temporarily disrupted when

flying directly over the radar site providing coverage

if no adjacent site assumes the service. A

ground−based radar, like a VOR or NDB, has a zenith

cone, sometimes referred to as the cone of confusion

or cone of silence. This is the area of ambiguity

directly above the station where bearing information

is unreliable. The zenith cone setting for TIS is

34 degrees: Any aircraft above that angle with

respect to the radar horizon will lose TIS coverage

from that radar until it is below this 34 degree angle.

The aircraft may not actually lose service in areas of

multiple radar coverage since an adjacent radar will

provide TIS. If no other TIS−capable radar is

available, the “Good−bye” message will be received

and TIS terminated until coverage is resumed.

(e) Intermittent Operations. TIS operation

may be intermittent during turns or other maneuvering, particularly if the transponder system does not

include antenna diversity (antenna mounted on the

top and bottom of the aircraft). As in (d) above, TIS

is dependent on two−way, “line of sight” communications between the aircraft and the Mode S radar.

Whenever the structure of the client aircraft comes

between the transponder antenna (usually located on

the underside of the aircraft) and the ground−based

radar antenna, the signal may be temporarily

interrupted.

(f) TIS Predictive Algorithm. TIS information is collected one radar scan prior to the scan

during which the uplink occurs. Therefore, the

surveillance information is approximately 5 seconds

old. In order to present the intruders in a “real time”

position, TIS uses a “predictive algorithm” in its

tracking software. This algorithm uses track history

data to extrapolate intruders to their expected

positions consistent with the time of display in the

cockpit. Occasionally, aircraft maneuvering will

cause this algorithm to induce errors in the TIS

display. These errors primarily affect relative bearing

information; intruder distance and altitude will

remain relatively accurate and may be used to assist

in “see and avoid.” Some of the more common

examples of these errors are as follows:

(1) When client or intruder aircraft maneuver excessively or abruptly, the tracking algorithm

will report incorrect horizontal position until the

maneuvering aircraft stabilizes.

(2) When a rapidly closing intruder is on a

course that crosses the client at a shallow angle (either

overtaking or head on) and either aircraft abruptly

changes course within 1⁄4 NM, TIS will display the

intruder on the opposite side of the client than it

actually is.

These are relatively rare occurrences and will be

corrected in a few radar scans once the course has

stabilized.

(g) Heading/Course Reference. Not all TIS

aircraft installations will have onboard heading

reference information. In these installations, aircraft

course reference to the TIS display is provided by the
AIM 7/26/12

4−5−14 Surveillance Systems

Mode S radar. The radar only determines ground

track information and has no indication of the client

aircraft heading. In these installations, all intruder

bearing information is referenced to ground track and

does not account for wind correction. Additionally,

since ground−based radar will require several scans

to determine aircraft course following a course

change, a lag in TIS display orientation (intruder

aircraft bearing) will occur. As in (f) above, intruder

distance and altitude are still usable.

(h) Closely−Spaced Intruder Errors.

When operating more than 30 NM from the Mode S

sensor, TIS forces any intruder within 3/8 NM of the

TIS client to appear at the same horizontal position as

the client aircraft. Without this feature, TIS could

display intruders in a manner confusing to the pilot in

critical situations (e.g., a closely−spaced intruder that

is actually to the right of the client may appear on the

TIS display to the left). At longer distances from the

radar, TIS cannot accurately determine relative

bearing/distance information on intruder aircraft that

are in close proximity to the client.

Because TIS uses a ground−based, rotating radar for

surveillance information, the accuracy of TIS data is

dependent on the distance from the sensor (radar)

providing the service. This is much the same

phenomenon as experienced with ground−based

navigational aids, such as VOR or NDB. As distance

from the radar increases, the accuracy of surveillance

decreases. Since TIS does not inform the pilot of

distance from the Mode S radar, the pilot must assume

that any intruder appearing at the same position as the

client aircraft may actually be up to 3/8 NM away in

any direction. Consistent with the operation of TIS,

an alert on the display (regardless of distance from the

radar) should stimulate an outside visual scan,

intruder acquisition, and traffic avoidance based on

outside reference.

e. Reports of TIS Malfunctions

1. Users of TIS can render valuable assistance in

the early correction of malfunctions by reporting their

observations of undesirable performance. Reporters

should identify the time of observation, location, type

and identity of aircraft, and describe the condition

observed; the type of transponder processor, and

software in use can also be useful information. Since

TIS performance is monitored by maintenance

personnel rather than ATC, it is suggested that

malfunctions be reported in the following ways:

(a) By radio or telephone to the nearest Flight

Service Station (FSS) facility.

(b) By FAA Form 8740−5, Safety Improvement Report, a postage−paid card designed for this

purpose. These cards may be obtained at FAA FSSs,

General Aviation District Offices, Flight Standards

District Offices, and General Aviation Fixed Based

Operations.

4−5−7. Automatic Dependent

Surveillance−Broadcast (ADS−B) Services

a. Introduction

1. Automatic Dependent Surveillance−Broadcast (ADS−B) is a surveillance technology being

deployed throughout the NAS (see FIG 4−5−7). The

ADS−B system is composed of aircraft avionics and

a ground infrastructure. Onboard avionics determine

the position of the aircraft by using the GNSS and

transmit its position along with additional information about the aircraft to ground stations for use by

ATC and other ADS−B services. This information is

transmitted at a rate of approximately once per

second.

2. In the United States, ADS−B equipped

aircraft exchange information is on one of two

frequencies: 978 or 1090 MHz. The 1090 MHz

frequency is associated with Mode A, C, and S

transponder operations. 1090 MHz transponders

with integrated ADS−B functionality extend the

transponder message sets with additional ADS−B

information. This additional information is known

as an “extended squitter” message and referred to as

1090ES. ADS−B equipment operating on 978 MHz

is known as the Universal Access Transceiver (UAT).
7/26/12 AIM

Surveillance Systems 4−5−15

FIG 4−5−7

ADS−B, TIS−B, and FIS−B:

Broadcast Services Architecture

3. ADS B avionics can have the ability to both

transmit and receive information. The transmission

of ADS−B information from an aircraft is known as

ADS−B Out. The receipt of ADS−B information by

an aircraft is known as ADS−B In. On January 1,

2020, all aircraft operating within the airspace

defined in 14 CFR part 91, § 91.225 will be required

to transmit the information defined in § 91.227

using ADS−B Out avionics.

4. In general, operators flying at 18,000 feet and

above will require equipment which uses 1090 ES.

Those that do not fly above 18,000 may use either

UAT or 1090ES equipment. (Refer to 14 CFR 91.225

and 91.227.) While the regulation will not require it,

operators equipped with ADS−B In will realize

additional benefits from ADS−B broadcast services:

Traffic Information Service – Broadcast (TIS−B)

(paragraph 4−5−8) and Flight Information Service −

Broadcast (FIS−B) (paragraph 4−5−9).

b. ADS−B Certification and Performance

Requirements

ADS−B equipment may be certified as a surveillance

source for air traffic separation services using

ADS−B Out. ADS−B equipment may also be

certified for use with ADS−B In advisory services

that enable appropriately equipped aircraft to

display traffic and flight information. Refer to the

aircraft’s flight manual supplement or Pilot

Operating Handbook for the capabilities of a specific

aircraft installation.

c. ADS−B Capabilities

1. ADS−B enables improved surveillance services, both air−to−air and air−to−ground, especially

in areas where radar is ineffective due to terrain or

where it is impractical or cost prohibitive. Initial NAS

applications of air−to−air ADS−B are for “advisory”

use only, enhancing a pilot’s visual acquisition of

other nearby equipped aircraft either when airborne

or on the airport surface. Additionally, ADS−B will

enable ATC and fleet operators to monitor aircraft

throughout the available ground station coverage

area.

2. ADS−B avionics typically allow pilots to

enter the aircraft’s call sign and Air Traffic Control

(ATC)−assigned transponder code, which will be

transmitted to other aircraft and ground receivers.

Pilots are cautioned to use care when selecting and
AIM 7/26/12

4−5−16 Surveillance Systems

entering the aircraft’s identification and transponder

codes. Some installations may require separate

entries of this information into both the ADS−B

system and the transponder. Therefore, it is

extremely important to ensure that the

transponder and ADS−B codes being transmitted

are identical to avoid false conflict alerts within

the ATC system.

3. ADS B systems integrated with the transponder will automatically set the applicable emergency

status when 7500, 7600, or 7700 are entered into the

transponder. ADS B systems not integrated with the

transponder, or systems with optional emergency

codes, will require that the appropriate emergency

code is entered through a pilot interface. ADS−B is

intended for in−flight and airport surface use.

ADS−B systems should be turned “on” −− and

remain “on” −− whenever operating in the air and

moving on the airport surface. Civil and military

Mode A/C transponders and ADS−B systems

should be adjusted to the “on” or normal

operating position as soon as practical, unless the

change to “standby” has been accomplished

previously at the request of ATC. Mode S transponders should be left on whenever power is applied to

the aircraft.

d. ATC Surveillance Services using ADS−B −

Procedures and Recommended Phraseology −

For Use In Alaska Only

Radar procedures, with the exceptions found in this

paragraph, are identical to those procedures prescribed for radar in AIM Chapter 4 and Chapter 5.

1. Preflight:

If a request for ATC services is predicated on ADS−B

and such services are anticipated when either a VFR

or IFR flight plan is filed, the aircraft’s “N” number

or call−sign as filed in “Block 2” of the Flight Plan

must be entered in the ADS−B avionics as the

aircraft’s flight ID.

2. Inflight:

When requesting ADS−B services while airborne,

pilots should ensure that their ADS−B equipment is

transmitting their aircraft’s “N” number or call sign

prior to contacting ATC. To accomplish this, the pilot

must select the ADS−B “broadcast flight ID”

function.

NOTE−

The broadcast “VFR” or “Standby” mode built into some

ADS−B systems will not provide ATC with the appropriate

aircraft identification information. This function should

first be disabled before contacting ATC.

3. Aircraft with an Inoperative/Malfunctioning

ADS−B Transmitter or in the Event of an Inoperative

Ground Broadcast Transceiver (GBT).

(a) ATC will inform the flight crew when the

aircraft’s ADS−B transmitter appears to be inoperative or malfunctioning:

PHRASEOLOGY−

YOUR ADS−B TRANSMITTER APPEARS TO BE

INOPERATIVE/MALFUNCTIONING. STOP ADS−B

TRANSMISSIONS.

(b) ATC will inform the flight crew when the

GBT transceiver becomes inoperative or malfunctioning, as follows:

PHRASEOLOGY−

(Name of facility) GROUND BASED TRANSCEIVER

INOPERATIVE/MALFUNCTIONING.

(And if appropriate) RADAR CONTACT LOST.

NOTE−

An inoperative or malfunctioning GBT may also cause a

loss of ATC surveillance services.

(c) ATC will inform the flight crew if it

becomes necessary to turn off the aircraft’s ADS−B

transmitter.

PHRASEOLOGY−

STOP ADS−B TRANSMISSIONS.

(d) Other malfunctions and considerations:

Loss of automatic altitude reporting capabilities

(encoder failure) will result in loss of ATC altitude

advisory services.

e. ADS−B Limitations

1. The ADS−B cockpit display of traffic is NOT

intended to be used as a collision avoidance system

and does not relieve the pilot’s responsibility to “see

and avoid” other aircraft. (See paragraph 5−5−8, See

and Avoid). ADS−B must not be used for avoidance

maneuvers during IMC or other times when there is

no visual contact with the intruder aircraft. ADS−B is

intended only to assist in visual acquisition of other

aircraft. No avoidance maneuvers are provided nor

authorized, as a direct result of an ADS−B target

being displayed in the cockpit.
7/26/12 AIM

Surveillance Systems 4−5−17

2. Use of ADS−B radar services is limited to the

service volume of the GBT.

NOTE−

The coverage volume of GBTs are limited to line−of−sight.

f. Reports of ADS−B Malfunctions

Users of ADS−B can provide valuable assistance in

the correction of malfunctions by reporting instances

of undesirable system performance. Reports should

identify the time of observation, location, type and

identity of aircraft, and describe the condition

observed; the type of avionics system and its software

version in use should also be included. Since ADS−B

performance is monitored by maintenance personnel

rather than ATC, it is suggested that malfunctions be

reported in any one of the following ways:

1. By radio or telephone to the nearest Flight

Service Station (FSS) facility.

2. By FAA Form 8740−5, Safety Improvement

Report, a postage−paid card is designed for this

purpose. These cards may be obtained from FAA

FSSs, Flight Standards District Offices, and general

aviation fixed−based operators.

3. By reporting the failure directly to the FAA

Safe Flight 21 program at 1−877−FLYADSB or

http://www.adsb.gov.

4−5−8. Traffic Information Service−

Broadcast (TIS−B)

TIS−B is the broadcast of ATC derived traffic

information to ADS−B equipped (1090ES or UAT)

aircraft from ground radio stations. The source of this

traffic information is derived from ground−based air

traffic surveillance radar sensors. TIS−B service

will be available throughout the NAS where there are

both adequate surveillance coverage (radar) from

ground sensors and adequate broadcast coverage

from ADS−B ground radio stations. The quality level

of traffic information provided by TIS−B is

dependent upon the number and type of ground

sensors available as TIS−B sources and the

timeliness of the reported data.

a. TIS−B Requirements.

In order to receive TIS−B service, the following

conditions must exist:

1. Aircraft must be equipped with an ADS−B

transmitter/receiver or transceiver, and a cockpit

display of traffic information (CDTI).

2. Aircraft must fly within the coverage volume

of a compatible ground radio station that is

configured for TIS−B uplinks. (Not all ground radio

stations provide TIS−B due to a lack of radar

coverage or because a radar feed is not available).

3. Aircraft must be within the coverage of and

detected by at least one ATC radar serving the ground

radio station in use.

b. TIS−B Capabilities.

1. TIS−B is intended to provide ADS−B

equipped aircraft with a more complete traffic picture

in situations where not all nearby aircraft are

equipped with ADS−B Out. This advisory−only

application is intended to enhance a pilot’s visual

acquisition of other traffic.

2. Only transponder−equipped targets

(i.e., Mode A/C or Mode S transponders) are

transmitted through the ATC ground system

architecture. Current radar siting may result in

limited radar surveillance coverage at lower

altitudes near some airports, with subsequently

limited TIS−B service volume coverage. If there is

no radar coverage in a given area, then there will be

no TIS−B coverage in that area.

c. TIS−B Limitations.

1. TIS−B is NOT intended to be used as a

collision avoidance system and does not relieve the

pilot’s responsibility to “see and avoid” other aircraft,

in accordance with 14CFR §91.113b. TIS−B must

not be used for avoidance maneuvers during times

when there is no visual contact with the intruder

aircraft. TIS−B is intended only to assist in the visual

acquisition of other aircraft.

NOTE−

No aircraft avoidance maneuvers are authorized as a

direct result of a TIS−B target being displayed in the

cockpit.

2. While TIS−B is a useful aid to visual traffic

avoidance, its inherent system limitations must be

understood to ensure proper use.

(a) A pilot may receive an intermittent TIS−B

target of themselves, typically when maneuvering

(e.g., climbing turns) due to the radar not tracking

the aircraft as quickly as ADS−B.
AIM 7/26/12

4−5−18 Surveillance Systems

(b) The ADS−B−to−radar association process within the ground system may at times have

difficulty correlating an ADS−B report with

corresponding radar returns from the same aircraft.

When this happens the pilot may see duplicate traffic

symbols (i.e., “TIS−B shadows”) on the cockpit

display.

(c) Updates of TIS−B traffic reports will

occur less often than ADS−B traffic updates. TIS−B

position updates will occur approximately once

every 3−13 seconds depending on the type of radar

system in use within the coverage area. In

comparison, the update rate for ADS−B is nominally

once per second.

(d) The TIS−B system only uplinks data

pertaining to transponder−equipped aircraft. Aircraft

without a transponder will not be displayed as TIS−B

traffic.

(e) There is no indication provided when any

aircraft is operating inside or outside the TIS−B

service volume, therefore it is difficult to know if one

is receiving uplinked TIS−B traffic information.

3. Pilots and operators are reminded that the

airborne equipment that displays TIS−B targets is for

pilot situational awareness only and is not approved

as a collision avoidance tool. Unless there is an

imminent emergency requiring immediate action,

any deviation from an air traffic control clearance in

response to perceived converging traffic appearing

on a TIS−B display must be approved by the

controlling ATC facility before commencing the

maneuver, except as permitted under certain

conditions in 14CFR §91.123. Uncoordinated

deviations may place an aircraft in close proximity to

other aircraft under ATC control not seen on the

airborne equipment and may result in a pilot

deviation or other incident.

d. Reports of TIS−B Malfunctions

Users of TIS−B can provide valuable assistance in the

correction of malfunctions by reporting instances of

undesirable system performance. Reporters should

identify the time of observation, location, type and

identity of the aircraft, and describe the condition

observed; the type of avionics system and its software

version used. Since TIS−B performance is monitored

by maintenance personnel rather than ATC, it is

suggested that malfunctions be reported in anyone of

the following ways:

1. By radio or telephone to the nearest Flight

Service Station (FSS) facility.

2. By FAA Form 8740−5, Safety Improvement

Report, a postage−paid card is designed for this

purpose. These cards may be obtained from FAA

FSSs, Flight Standards District Offices, and general

aviation fixed−based operators.

3. By reporting the failure directly to the FAA

Surveillance and Broadcast Services Program Office

at 1−877−FLYADSB or http://www.adsb.gov.

4−5−9. Flight Information Service−

Broadcast (FIS−B)

a. FIS−B is a ground broadcast service provided

through the ADS−B Services network over the

978 MHz UAT data link. The FAA FIS−B system

provides pilots and flight crews of properly equipped

aircraft with a cockpit display of certain aviation

weather and aeronautical information. FIS−B service

availability is expected across the NAS in 2013 and

is currently available within certain regions.

b. The weather products provided by FIS−B are

for information only. Therefore, these products do

not meet the safety and regulatory requirements of

official weather products. The weather products

displayed on FIS−B should not be used as primary

weather products, i.e., aviation weather to meet

operational and safety requirements. Official

weather products (primary products) can be obtained

from a variety of sources including ATC, FSSs, and,

if applicable, AOCC VHF/HF voice, which can

transmit aviation weather, NOTAMS, and other

operational aeronautical information to aircraft in

flight. FIS−B augments the traditional ATC/FSS/

AOCC services by providing additional information

and, for some products, offers the advantage of being

displayed graphically. By using FIS−B for orientation

and information, the usefulness of information

received from official sources may be enhanced, but

the user should be alert and understand any

limitations associated with individual products.

FIS−B provides the initial basic products listed below

at no−charge to the user. Additional products are

envisioned, but may incur subscription charges to the

user. FIS−B reception is line−of−sight within the

service volume of the ground infrastructure.
7/26/12 AIM

Surveillance Systems 4−5−19

1. Airmen’s Meteorological Conditions

(AIRMET) − Text/graphical report − A concise

description of expected occurrence of specified

en route weather phenomena.

REFERENCE−

Advisory Circular AC−00−45, “Aviation Weather Services.”

2. Convective Significant Meteorological

Conditions (SIGMET) − Text report/graphical

−Convective SIGMETs (also known internationally

as SIGMET for Convection) are issued for the

contiguous U.S. Each bulletin includes one or more

Convective SIGMETs for a specific region of the

CONUS. Convective SIGMETs issued for thunderstorms and related phenomena do not include

references to all weather associated with thunderstorms such as turbulence, icing, low−level wind

shear and IFR conditions.

REFERENCE−

Advisory Circular AC−00−45, “Aviation Weather Services.”

3. Aviation Routine Weather Reports (METAR)

− Text reports − Surface meteorological data. The

body of the report includes airport identifier, time of

observation, wind, visibility, runway visual range,

present weather phenomena, sky conditions, temperature, dew point, and altimeter setting. Remarks may

be appended to the end.

REFERENCE−

Advisory Circular AC−00−45, “Aviation Weather Services.”

4. Special Aviation Reports (SPECI) − Text

reports − Non− routine, unscheduled report when any

of SPECI criteria have been met.Contains all data

elements found in METAR plus additional information which elaborates on data.

REFERENCE−

Reference Advisory Circular AC−00−45, “Aviation Weather Services.”

5. Next Generation Radar (NEXRAD)

(CONUS and Regional) − Derived from Next

Generation Weather Radar (WSR−88D). Radar

mosaic consists of multiple single site radar images

combined to produce a graphical image on a regional

or national scale. Regional and national radar

mosaics can be found at the National Weather Service

(NWS) Doppler Radar Images web site:

http://radar.weather.gov/ridge/.

REFERENCE−

Advisory Circular AC−00−45, “AviationWeather Services.”

6. Notice to Airmen (NOTAM) Distant and

Flight Data Center (D/FDC) − Text/graphical reports

− includes Temporary Flight Restrictions (TFRs) −

TFR text and graphic reports, prescribes procedures

used to obtain, format, and disseminate information

on unanticipated or temporary changes to components of or hazards in the NAS until the associated

aeronautical charts and related publications have

been amended.

REFERENCE−

FAA Order JO 7930.2, Notices to Airmen (NOTAM).

7. Pilot Weather Reports (PIREP) − Text report

− Pilots report observations to assist other pilots with

flight planning and preparation, help NWS verify

forecast products, and create more accurate products

for aviation community.

REFERENCE−

Advisory Circular AC−00−45, “Aviation Weather Services.”

8. Significant Meteorological Information

(SIGMET) − Text/graphical report − Potentially

hazardous en route phenomena such as thunderstorms and hail, turbulence, icing, sand and dust

storms, tropical cyclones, and volcanic ash in an area

affecting 3,000 square miles or an area deemed to

have a significant effect on safety of aircraft

operations.

REFERENCE−

Advisory Circular AC−00−45, “AviationWeather Services.”

9. Special Use Airspace (SUA) Status −

Text/graphical report − Establishes/designates

airspace in the interest of National Defense, security

and/or welfare. Charted SUA identifies to other

airspace users where these activities occur. SUA is

airspace of defined dimensions wherein activities

must be confined because of their nature, or wherein

limitations may be imposed upon aircraft operations

that are not a part of those activities.

REFERENCE−

FAA Order JO 7400.2G, Procedures for Handling Airspace Matters.

10. Terminal Aerodrome Forecast (TAF) and

their amendments (AMEND) − Text report − Routine

forecast that gives a concise statement of expected

meteorological conditions for a specified time period

within five statute miles (SM) of the center of the

airport’s runway complex (terminal). TAFs are

amended whenever they become, in the forecaster’s

judgment, unrepresentative of existing or expected

conditions, particularly regarding those elements and

events significant to aircraft and airports. An

amended forecast is identified by TAF AMD (in place

of TAF) on the first line of the forecast text.

REFERENCE−

Advisory Circular AC−00−45, “Aviation Weather Services.”
AIM 7/26/12

4−5−20 Surveillance Systems

11. Temperature Aloft − Text report − Computer

prepared forecasts, based on North American

Mesoscale (NAM) forecast model run, of temperature at specified times, altitudes, and locations.

REFERENCE−

 Advisory Circular AC−00−45, “Aviation Weather Services.”

12. Winds Aloft − Text report − Computerprepared forecasts, based on North American

Mesoscale (NAM) forecast model run, of wind

direction and wind speed at specified times, altitudes,

and locations.

REFERENCE−

Advisory Circular AC−00−45, “Aviation Weather Services.”

TBL 4−5−2

FIS−B Basic Product Update and Transmission Intervals

Product

FIS−B Service

Update Interval1

FIS−B Service

Transmission Interval2

AIRMET As available 5 minutes

Convective SIGMET As available 5 minutes

METAR/SPECI Hourly/as available 5 minutes

NEXRAD Reflectivity (CONUS) 5 minutes 15 minutes

NEXRAD Reflectivity (Regional) 5 minutes 2.5 minutes

NOTAM−D/FDC As available 10 minutes

PIREP As available 10 minutes

SIGMET As available 5 minutes

SUA Status As available 10 minutes

TAF/AMEND 8 hours/as available 10 minutes

Temperature Aloft 6 hours 10 minutes

Winds Aloft 6 hours 10 minutes

1 The Update Interval is the rate at which the product data is available from the source.

2 The Transmission Interval is the amount of time within which a new or updated product transmission must be

completed and the rate or repetition interval at which the product is rebroadcast.

NOTE−

Details concerning the content, format, and symbols of the various data link products provided should be obtained from

the specific avionics manufacturer.

4−5−10. Automatic Dependent

Surveillance−Rebroadcast (ADS−R)

ADS−R is a datalink translation function of the ADS−B

ground system required to accommodate the two separate

operating frequencies (978 MHz and 1090 ES). The

ADS−B system receives the ADS−B messages transmitted

on one frequency and ADS−R translates and reformats the

information for rebroadcast and use on the other frequency.

This allows ADS−B In equipped aircraft to see nearby

ADS−B Out traffic regardless of the operating link of the

other aircraft. Aircraft operating on the same ADS−B

frequency exchange information directly and do not

require the ADS−R translation function.
7/26/12 AIM

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the 4−6−1

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

Section 6. Operational Policy/Procedures for Reduced

Vertical Separation Minimum (RVSM) in the Domestic

U.S., Alaska, Offshore Airspace and the San Juan FIR

4−6−1. Applicability and RVSM Mandate

(Date/Time and Area)

a. Applicability. The policies, guidance and

direction in this section apply to RVSM operations in

the airspace over the lower 48 states, Alaska, Atlantic

and Gulf of Mexico High Offshore Airspace and

airspace in the San Juan FIR where VHF or UHF

voice direct controller−pilot communication (DCPC)

is normally available. Policies, guidance and

direction for RVSM operations in oceanic airspace

where VHF or UHF voice DCPC is not available and

the airspace of other countries are posted on the FAA

“RVSM Documentation” Webpage described in

paragraph 4−6−3, Aircraft and Operator Approval

Policy/Procedures, RVSM Monitoring and Databases for Aircraft and Operator Approval.

b. Mandate. At 0901 UTC on January 20, 2005,

the FAA implemented RVSM between flight

level (FL) 290−410 (inclusive) in the following

airspace: the airspace of the lower 48 states of the

United States, Alaska, Atlantic and Gulf of Mexico

High Offshore Airspace and the San Juan FIR. (A

chart showing the location of offshore airspace is

posted on the Domestic U.S. RVSM (DRVSM)

Webpage. See paragraph 4−6−3.) On the same time

and date, RVSM was also introduced into the

adjoining airspace of Canada and Mexico to provide

a seamless environment for aircraft traversing those

borders. In addition, RVSM was implemented on the

same date in the Caribbean and South American

regions.

c. RVSM Authorization. In accordance with

14 CFR Section 91.180, with only limited exceptions, prior to operating in RVSM airspace, operators

and aircraft must have received RVSM authorization

from the responsible civil aviation authority. (See

paragraph 4−6−10, Procedures for Accommodation

of Non−RVSM Aircraft.) If the operator or aircraft or

both have not been authorized for RVSM operations,

the aircraft will be referred to as a “non−RVSM”

aircraft. Paragraph 4−6−10 discusses ATC policies

for accommodation of non−RVSM aircraft flown by

the Department of Defense, Air Ambulance

(Lifeguard) operators, foreign State governments and

aircraft flown for certification and development.

Paragraph 4−6−11, Non−RVSM Aircraft Requesting

Climb to and Descent from Flight Levels Above

RVSM Airspace Without Intermediate Level Off,

contains policies for non−RVSM aircraft climbing

and descending through RVSM airspace to/from

flight levels above RVSM airspace.

d. Benefits. RVSM enhances ATC flexibility,

mitigates conflict points, enhances sector throughput,

reduces controller workload and enables crossing

traffic. Operators gain fuel savings and operating

efficiency benefits by flying at more fuel efficient

flight levels and on more user preferred routings.

4−6−2. Flight Level Orientation Scheme

Altitude assignments for direction of flight follow a

scheme of odd altitude assignment for magnetic

courses 000−179 degrees and even altitudes for

magnetic courses 180−359 degrees for flights up to

and including FL 410, as indicated in FIG 4−6−1.

FIG 4−6−1

Flight Level Orientation Scheme

NOTE−

Odd Flight Levels: Magnetic Course 000−179 Degrees

Even Flight Levels: Magnetic Course 180−359 Degrees.
AIM 7/26/12

4−6−2 Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

4−6−3. Aircraft and Operator Approval

Policy/Procedures, RVSM Monitoring and

Databases for Aircraft and Operator

Approval

a. RVSM Authority. 14 CFR Section 91.180

applies to RVSM operations within the U.S. 14 CFR

Section 91.706 applies to RVSM operations outside

the U.S. Both sections require that the operator obtain

authorization prior to operating in RVSM airspace.

14 CFR Section 91.180 requires that, prior to

conducting RVSM operations within the U.S., the

operator obtain authorization from the FAA or from

the responsible authority, as appropriate. In addition,

it requires that the operator and the operator’s aircraft

comply with the standards of 14 CFR Part 91

Appendix G (Operations in RVSM Airspace).

b. Sources of Information. The FAA

RVSM Website Homepage can be accessed at:

http://www.faa.gov/about/office_org/

headquarters_offices/ato/service_units/enroute/

rvsm/. The “RVSM Documentation” and “Domestic

RVSM” webpages are linked to the RVSM

Homepage. “RVSM Documentation” contains guidance and direction for an operator to obtain aircraft

and operator approval to conduct RVSM operations.

It provides information for DRVSM and oceanic and

international RVSM airspace. It is recommended that

operators planning to operate in Domestic U.S.

RVSM airspace first review the following documents

to orient themselves to the approval process.

1. Under “Area of Operations Specific Information,” the document, “Basic Operator Information on

DRVSM Programs,” provides an overview of the

DRVSM program and the related aircraft and

operator approval programs.

2. In the “Getting Started” section, review the

“RVSM Approval Checklist − U.S. Operators” or

“RVSM Approval Checklist − Non−U.S. Operators”

(as applicable). These are job aids or checklists that

show aircraft/operator approval process events with

references to related RVSM documents published on

the website.

3. Under “Documents Applicable to All RVSM

Approvals,” review “RVSM Area New to the

Operator.” This document provides a guide for

operators that are conducting RVSM operations in

one or more areas of operation, but are planning to

conduct RVSM operations in an area where they have

not previously conducted RVSM operations, such as

the U.S.

c. TCAS Equipage. TCAS equipage requirements are contained in 14 CFR Sections 121.356,

125.224, 129.18 and 135.189. Part 91 Appendix G

does not contain TCAS equipage requirements

specific to RVSM, however, Appendix G does

require that aircraft equipped with TCAS II and flown

in RVSM airspace be modified to incorporate

TCAS II Version 7.0 or a later version.

d. Aircraft Monitoring. Operators are required

to participate in the RVSM aircraft monitoring

program. The “Monitoring Requirements and

Procedures” section of the RVSM Documentation

Webpage contains policies and procedures for

participation in the monitoring program. Ground−

based and GPS−based monitoring systems are

available for the Domestic RVSM program.

Monitoring is a quality control program that enables

the FAA and other civil aviation authorities to assess

the in−service altitude−keeping performance of

aircraft and operators.

e. Registration on RVSM Approvals Databases. The “Registration on RVSM Approvals

Database” section of the RVSM Documentation

Webpage provides policies/procedures for operator

and aircraft registration on RVSM approvals

databases.

1. Purpose of RVSM Approvals Databases.

ATC does not use RVSM approvals databases to

determine whether or not a clearance can be issued

into RVSM airspace. RVSM program managers do

regularly review the operators and aircraft that

operate in RVSM airspace to identify and investigate

those aircraft and operators flying in RVSM airspace,

but not listed on the RVSM approvals databases.

2. Registration of U.S. Operators. When U.S.

operators and aircraft are granted RVSM authority,

the FAA Flight Standards office makes an input to the

FAA Program Tracking and Reporting Subsystem

(PTRS). The Separation Standards Group at the FAA

Technical Center obtains PTRS operator and aircraft

information to update the FAA maintained U.S.

Operator/Aircraft RVSM Approvals Database. Basic

database operator and aircraft information can be

viewed on the RVSM Documentation Webpage by

clicking on the appropriate database icon.
7/26/12 AIM

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the 4−6−3

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

3. Registration of Non−U.S. Operators.

Non−U.S. operators can find policy/procedures for

registration on the North American Approvals

Registry and Monitoring Organization (NAARMO)

database in the “Registration on RVSM Approvals

Database” section of RVSM Documentation.

4−6−4. Flight Planning into RVSM Airspace

a. Operators that do not file the correct aircraft

equipment suffix on the FAA or ICAO Flight Plan

may be denied clearance into RVSM airspace.

Policies for the FAA Flight Plan are detailed in

subparagraph c below. Policies for the ICAO Flight

Plan are detailed in subparagraph d.

b. The operator will annotate the equipment block

of the FAA or ICAO Flight Plan with an aircraft

equipment suffix indicating RVSM capability only

after the responsible civil aviation authority has

determined that both the operator and its aircraft are

RVSM−compliant and has issued RVSM authorization to the operator.

c. General Policies for FAA Flight Plan Equipment Suffix. TBL 5−1−2, Aircraft Suffixes, allows

operators to indicate that the aircraft has both RVSM

and Advanced Area Navigation (RNAV) capabilities

or has only RVSM capability.

1. The operator will annotate the equipment

block of the FAA Flight Plan with the appropriate

aircraft equipment suffix from TBL 5−1−2.

2. Operators can only file one equipment suffix

in block 3 of the FAA Flight Plan. Only this

equipment suffix is displayed directly to the

controller.

3. Aircraft with RNAV Capability. For flight in

RVSM airspace, aircraft with RNAV capability, but

not Advanced RNAV capability, will file “/W”. Filing

“/W” will not preclude such aircraft from filing and

flying direct routes in en route airspace.

d. Policy for ICAO Flight Plan Equipment

Suffixes.

1. Operators/aircraft that are RVSM−compliant

and that file ICAO flight plans will file “/W” in

block 10 (Equipment) to indicate RVSM authorization and will also file the appropriate ICAO Flight

Plan suffixes to indicate navigation and communication capabilities. The equipment suffixes in

TBL 5−1−2 are for use only in an FAA Flight Plan

(FAA Form 7233−1).

2. Operators/aircraft that file ICAO flight plans

that include flight in Domestic U.S. RVSM airspace

must file “/W” in block 10 to indicate RVSM

authorization.

e. Importance of Flight Plan Equipment Suffixes.

The operator must file the appropriate equipment

suffix in the equipment block of the FAA Flight Plan

(FAA Form 7233−1) or the ICAO Flight Plan. The

equipment suffix informs ATC:

1. Whether or not the operator and aircraft are

authorized to fly in RVSM airspace.

2. The navigation and/or transponder capability

of the aircraft (e.g., advanced RNAV, transponder

with Mode C).

f. Significant ATC uses of the flight plan

equipment suffix information are:

1. To issue or deny clearance into RVSM

airspace.

2. To apply a 2,000 foot vertical separation

minimum in RVSM airspace to aircraft that are not

authorized for RVSM, but are in one of the limited

categories that the FAA has agreed to accommodate.

(See paragraphs 4−6−10, Procedures for Accommodation of Non−RVSM Aircraft, and 4−6−11,

Non−RVSM Aircraft Requesting Climb to and

Descent from Flight Levels Above RVSM Airspace

Without Intermediate Level Off, for policy on limited

operation of unapproved aircraft in RVSM airspace).

3. To determine if the aircraft has “Advanced

RNAV” capabilities and can be cleared to fly

procedures for which that capability is required.

4−6−5. Pilot RVSM Operating Practices and

Procedures

a. RVSM Mandate. If either the operator or the

aircraft or both have not received RVSM authorization (non−RVSM aircraft), the pilot will neither

request nor accept a clearance into RVSM airspace

unless:

1. The flight is conducted by a non−RVSM

DOD, Lifeguard, certification/development or foreign State (government) aircraft in accordance with

paragraph 4−6−10, Procedures for Accommodation

of Non−RVSM Aircraft.
AIM 7/26/12

4−6−4 Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

2. The pilot intends to climb to or descend from

FL 430 or above in accordance with paragraph 4−6−11, Non−RVSM Aircraft Requesting

Climb to and Descent from Flight Levels Above

RVSM Airspace Without Intermediate Level Off.

3. An emergency situation exists.

b. Basic RVSM Operating Practices and

Procedures. Appendix 4 of AC 91−85, Authorization of Aircraft and Operators for Flight in Reduced

Vertical Separation Minimum Airspace contains pilot

practices and procedures for RVSM. Operators must

incorporate Appendix 4 practices and procedures, as

supplemented by the applicable paragraphs of this

section, into operator training or pilot knowledge

programs and operator documents containing RVSM

operational policies.

c. Appendix 4 contains practices and procedures

for flight planning, preflight procedures at the

aircraft, procedures prior to RVSM airspace entry,

inflight (en route) procedures, contingency procedures and post flight.

d. The following paragraphs either clarify or

supplement Appendix 4 practices and procedures.

4−6−6. Guidance on Severe Turbulence

and Mountain Wave Activity (MWA)

a. Introduction/Explanation

1. The information and practices in this

paragraph are provided to emphasize to pilots and

controllers the importance of taking appropriate

action in RVSM airspace when aircraft experience

severe turbulence and/or MWA that is of sufficient

magnitude to significantly affect altitude−keeping.

2. Severe Turbulence. Severe turbulence

causes large, abrupt changes in altitude and/or

attitude usually accompanied by large variations in

indicated airspeed. Aircraft may be momentarily out

of control. Encounters with severe turbulence must

be remedied immediately in any phase of flight.

Severe turbulence may be associated with MWA.

3. Mountain Wave Activity (MWA)

(a) Significant MWA occurs both below and

above the floor of RVSM airspace, FL 290. MWA

often occurs in western states in the vicinity of

mountain ranges. It may occur when strong winds

blow perpendicular to mountain ranges resulting in

up and down or wave motions in the atmosphere.

Wave action can produce altitude excursions and

airspeed fluctuations accompanied by only light

turbulence. With sufficient amplitude, however,

wave action can induce altitude and airspeed

fluctuations accompanied by severe turbulence.

MWA is difficult to forecast and can be highly

localized and short lived.

(b) Wave activity is not necessarily limited to

the vicinity of mountain ranges. Pilots experiencing

wave activity anywhere that significantly affects

altitude−keeping can follow the guidance provided

below.

(c) Inflight MWA Indicators (Including Turbulence). Indicators that the aircraft is being

subjected to MWA are:

(1) Altitude excursions and/or airspeed

fluctuations with or without associated turbulence.

(2) Pitch and trim changes required to

maintain altitude with accompanying airspeed

fluctuations.

(3) Light to severe turbulence depending

on the magnitude of the MWA.

4. Priority for Controller Application of

Merging Target Procedures

(a) Explanation of Merging Target Procedures. As described in subparagraph c3 below, ATC

will use “merging target procedures” to mitigate the

effects of both severe turbulence and MWA. The

procedures in subparagraph c3 have been adapted

from existing procedures published in FAA

Order JO 7110.65, Air Traffic Control, paragraph 5−1−8, Merging Target Procedures.

Paragraph 5−1−8 calls for en route controllers to

advise pilots of potential traffic that they perceive

may fly directly above or below his/her aircraft at

minimum vertical separation. In response, pilots are

given the option of requesting a radar vector to ensure

their radar target will not merge or overlap with the

traffic’s radar target.

(b) The provision of “merging target procedures” to mitigate the effects of severe turbulence

and/or MWA is not optional for the controller, but

rather is a priority responsibility. Pilot requests for

vectors for traffic avoidance when encountering

MWA or pilot reports of “Unable RVSM due

turbulence or MWA” are considered first priority

aircraft separation and sequencing responsibilities.
7/26/12 AIM

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the 4−6−5

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

(FAA Order JO 7110.65, paragraph 2−1−2, Duty

Priority, states that the controller’s first priority is to

separate aircraft and issue safety alerts).

(c) Explanation of the term “traffic permitting.” The contingency actions for MWA and severe

turbulence detailed in paragraph 4−6−9, Contingency

Actions: Weather Encounters and Aircraft System

Failures, state that the controller will “vector aircraft

to avoid merging targets with traffic at adjacent flight

levels, traffic permitting.” The term “traffic permitting” is not intended to imply that merging target

procedures are not a priority duty. The term is

intended to recognize that, as stated in FAA

Order JO 7110.65, paragraph 2−1−2, Duty Priority,

there are circumstances when the controller is

required to perform more than one action and must

“exercise their best judgment based on the facts and

circumstances known to them” to prioritize their

actions. Further direction given is: “That action

which is most critical from a safety standpoint is

performed first.”

5. TCAS Sensitivity. For both MWA and

severe turbulence encounters in RVSM airspace, an

additional concern is the sensitivity of collision

avoidance systems when one or both aircraft

operating in close proximity receive TCAS advisories in response to disruptions in altitude hold

capability.

b. Pre−flight tools. Sources of observed and

forecast information that can help the pilot ascertain

the possibility of MWA or severe turbulence are:

Forecast Winds and Temperatures Aloft (FD), Area

Forecast (FA), SIGMETs and PIREPs.

c. Pilot Actions When Encountering Weather

(e.g., Severe Turbulence or MWA)

1. Weather Encounters Inducing Altitude

Deviations of Approximately 200 feet. When the

pilot experiences weather induced altitude deviations

of approximately 200 feet, the pilot will contact ATC

and state “Unable RVSM Due (state reason)”

(e.g., turbulence, mountain wave). See contingency

actions in paragraph 4−6−9.

2. Severe Turbulence (including that associated with MWA). When pilots encounter severe

turbulence, they should contact ATC and report the

situation. Until the pilot reports clear of severe

turbulence, the controller will apply merging target

vectors to one or both passing aircraft to prevent their

targets from merging:

EXAMPLE−

“Yankee 123, FL 310, unable RVSM due severe

turbulence.”

“Yankee 123, fly heading 290; traffic twelve o’clock,

10 miles, opposite direction; eastbound MD−80 at

FL 320” (or the controller may issue a vector to the

MD−80 traffic to avoid Yankee 123).

3. MWA. When pilots encounter MWA, they

should contact ATC and report the magnitude and

location of the wave activity. When a controller

makes a merging targets traffic call, the pilot may

request a vector to avoid flying directly over or under

the traffic. In situations where the pilot is

experiencing altitude deviations of 200 feet or

greater, the pilot will request a vector to avoid traffic.

Until the pilot reports clear of MWA, the controller

will apply merging target vectors to one or both

passing aircraft to prevent their targets from merging:

EXAMPLE−

“Yankee 123, FL 310, unable RVSM due mountain wave.”

“Yankee 123, fly heading 290; traffic twelve o’clock,

10 miles, opposite direction; eastbound MD−80 at

FL 320” (or the controller may issue a vector to the

MD−80 traffic to avoid Yankee 123).

4. FL Change or Re−route. To leave airspace

where MWA or severe turbulence is being

encountered, the pilot may request a FL change

and/or re−route, if necessary.

4−6−7. Guidance on Wake Turbulence

a. Pilots should be aware of the potential for wake

turbulence encounters in RVSM airspace. Experience

gained since 1997 has shown that such encounters in

RVSM airspace are generally moderate or less in

magnitude.

b. Prior to DRVSM implementation, the FAA

established provisions for pilots to report wake

turbulence events in RVSM airspace using the NASA

Aviation Safety Reporting System (ASRS). A

“Safety Reporting” section established on the FAA

RVSM Documentation webpage provides contacts,

forms, and reporting procedures.

c. To date, wake turbulence has not been reported

as a significant factor in DRVSM operations.

European authorities also found that reports of wake

turbulence encounters did not increase significantly
AIM 7/26/12

4−6−6 Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

after RVSM implementation (eight versus seven

reports in a ten−month period). In addition, they

found that reported wake turbulence was generally

similar to moderate clear air turbulence.

d. Pilot Action to Mitigate Wake Turbulence

Encounters

1. Pilots should be alert for wake turbulence

when operating:

(a) In the vicinity of aircraft climbing or

descending through their altitude.

(b) Approximately 10−30 miles after passing

1,000 feet below opposite−direction traffic.

(c) Approximately 10−30 miles behind and

1,000 feet below same−direction traffic.

2. Pilots encountering or anticipating wake

turbulence in DRVSM airspace have the option of

requesting a vector, FL change, or if capable, a lateral

offset.

NOTE−

1. Offsets of approximately a wing span upwind generally

can move the aircraft out of the immediate vicinity of

another aircraft’s wake vortex.

2. In domestic U.S. airspace, pilots must request clearance

to fly a lateral offset. Strategic lateral offsets flown in

oceanic airspace do not apply.

e. The FAA will track wake turbulence events as

an element of its post implementation program. The

FAA will advertise wake turbulence reporting

procedures to the operator community and publish

reporting procedures on the RVSM Documentation

Webpage (See address in paragraph 4−6−3, Aircraft

and Operator Approval Policy/Procedures, RVSM

Monitoring and Databases for Aircraft and Operator

Approval.

4−6−8. Pilot/Controller Phraseology

TBL 4−6−1 shows standard phraseology that pilots

and controllers will use to communicate in DRVSM

operations.
7/26/12 AIM

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the 4−6−7

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

TBL 4−6−1

Pilot/Controller Phraseology

Message Phraseology

For a controller to ascertain the RVSM approval status of

an aircraft:

(call sign) confirm RVSM approved

Pilot indication that flight is RVSM approved Affirm RVSM

Pilot report of lack of RVSM approval (non−RVSM status).

Pilot will report non−RVSM status, as follows:

Negative RVSM, (supplementary information,

e.g., “Certification flight”).

a. On the initial call on any frequency in the RVSM

airspace and . . ..

b. In all requests for flight level changes pertaining to

flight levels within the RVSM airspace and . . ..

c. In all read backs to flight level clearances pertaining

to flight levels within the RVSM airspace and . . ..

d. In read back of flight level clearances involving

climb and descent through RVSM airspace 

(FL 290 − 410).

Pilot report of one of the following after entry into RVSM

airspace: all primary altimeters, automatic altitude control

systems or altitude alerters have failed. 

(See paragraph 4−6−9, Contingency Actions: Weather

Encounters and Aircraft System Failures.) 

NOTE−

This phrase is to be used to convey both the initial indication of

RVSM aircraft system failure and on initial contact on all

frequencies in RVSM airspace until the problem ceases to exist

or the aircraft has exited RVSM airspace.

Unable RVSM Due Equipment

ATC denial of clearance into RVSM airspace Unable issue clearance into RVSM airspace, maintain FL

*Pilot reporting inability to maintain cleared flight level

due to weather encounter. 

(See paragraph 4−6−9, Contingency Actions: Weather

Encounters and Aircraft System Failures).

*Unable RVSM due (state reason) (e.g., turbulence,

mountain wave)

ATC requesting pilot to confirm that an aircraft has

regained RVSM−approved status or a pilot is ready to

resume RVSM

Confirm able to resume RVSM

Pilot ready to resume RVSM after aircraft system or

weather contingency

Ready to resume RVSM
AIM 7/26/12

4−6−8 Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

4−6−9. Contingency Actions: Weather

Encounters and Aircraft System Failures

TBL 4−6−2 provides pilot guidance on actions to

take under certain conditions of aircraft system

failure and weather encounters. It also describes the

expected ATC controller actions in these situations. It

is recognized that the pilot and controller will use

judgment to determine the action most appropriate to

any given situation.

TBL 4−6−2

Contingency Actions: Weather Encounters and Aircraft System Failures

Initial Pilot Actions in Contingency Situations

Initial pilot actions when unable to maintain flight level (FL) or unsure of aircraft altitude−keeping

capability: 

Notify ATC and request assistance as detailed below. 

Maintain cleared flight level, to the extent possible, while evaluating the situation.

Watch for conflicting traffic both visually and by reference to TCAS, if equipped.

Alert nearby aircraft by illuminating exterior lights (commensurate with aircraft limitations).

Severe Turbulence and/or Mountain Wave Activity (MWA) Induced 

Altitude Deviations of Approximately 200 feet

Pilot will: Controller will:

When experiencing severe turbulence and/or

MWA induced altitude deviations of

approximately 200 feet or greater, pilot will

contact ATC and state “Unable RVSM Due (state

reason)” (e.g., turbulence, mountain wave)

If not issued by the controller, request vector

clear of traffic at adjacent FLs

If desired, request FL change or re−route

Report location and magnitude of turbulence or

MWA to ATC

Vector aircraft to avoid merging target with

traffic at adjacent flight levels, traffic permitting

Advise pilot of conflicting traffic

Issue FL change or re−route, traffic permitting

Issue PIREP to other aircraft

See paragraph 4−6−6, Guidance on Severe

Turbulence and Mountain Wave Activity (MWA) for

detailed guidance.

Paragraph 4−6−6 explains “traffic permitting.”
7/26/12 AIM

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the 4−6−9

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

Mountain Wave Activity (MWA) Encounters − General

Pilot actions: Controller actions:

Contact ATC and report experiencing MWA

If so desired, pilot may request a FL change or

re−route 

Report location and magnitude of MWA to ATC

Advise pilot of conflicting traffic at adjacent FL

If pilot requests, vector aircraft to avoid merging

target with traffic at adjacent RVSM flight levels,

traffic permitting

Issue FL change or re−route, traffic permitting

Issue PIREP to other aircraft

See paragraph 4−6−6 for guidance on MWA. Paragraph 4−6−6 explains “traffic permitting.”

NOTE−

MWA encounters do not necessarily result in altitude deviations on the order of 200 feet. The guidance below is

intended to address less significant MWA encounters.

Wake Turbulence Encounters

Pilot should: Controller should:

Contact ATC and request vector, FL change or,

if capable, a lateral offset

Issue vector, FL change or lateral offset

clearance, traffic permitting

See paragraph 4−6−7, Guidance on Wake

Turbulence.

Paragraph 4−6−6 explains “traffic permitting.”

“Unable RVSM Due Equipment”

Failure of Automatic Altitude Control System, Altitude Alerter or All Primary Altimeters

Pilot will: Controller will:

Contact ATC and state “Unable RVSM Due

Equipment”

Request clearance out of RVSM airspace unless

operational situation dictates otherwise

Provide 2,000 feet vertical separation or

appropriate horizontal separation

Clear aircraft out of RVSM airspace unless

operational situation dictates otherwise

One Primary Altimeter Remains Operational

Pilot will: Controller will:

Cross check stand−by altimeter

Notify ATC of operation with single primary

altimeter

If unable to confirm primary altimeter accuracy,

follow actions for failure of all primary altimeters

Acknowledge operation with single primary

altimeter
AIM 7/26/12

4−6−10 Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

Transponder Failure

Pilot will: Controller will:

Contact ATC and request authority to continue

to operate at cleared flight level

Comply with revised ATC clearance, if issued

Consider request to continue to operate at

cleared flight level

Issue revised clearance, if necessary

NOTE−

14 CFR Section 91.215 (ATC transponder and altitude

reporting equipment and use) regulates operation with the

transponder inoperative.

4−6−10. Procedures for Accommodation of

Non−RVSM Aircraft

a. General Policies for Accommodation of

Non−RVSM Aircraft

1. The RVSM mandate calls for only RVSM

authorized aircraft/operators to fly in designated

RVSM airspace with limited exceptions. The policies

detailed below are intended exclusively for use by

aircraft that the FAA has agreed to accommodate.

They are not intended to provide other operators a

means to circumvent the normal RVSM approval

process.

2. If either the operator or aircraft or both have

not been authorized to conduct RVSM operations, the

aircraft will be referred to as a “non−RVSM” aircraft.

14 CFR Section 91.180 and Part 91 Appendix G

enable the FAA to authorize a deviation to operate a

non−RVSM aircraft in RVSM airspace.

3. Non−RVSM aircraft flights will be handled

on a workload permitting basis. The vertical

separation standard applied between aircraft not

approved for RVSM and all other aircraft must be

2,000 feet.

4. Required Pilot Calls. The pilot of non−

RVSM aircraft will inform the controller of the lack

of RVSM approval in accordance with the direction

provided in paragraph 4−6−8, Pilot/Controller

Phraseology.

b. Categories of Non−RVSM Aircraft that may

be Accommodated

Subject to FAA approval and clearance, the following

categories of non−RVSM aircraft may operate in

domestic U.S. RVSM airspace provided they have an

operational transponder.

1. Department of Defense (DOD) aircraft.

2. Flights conducted for aircraft certification

and development purposes.

3. Active air ambulance flights utilizing a

“Lifeguard” call sign.

4. Aircraft climbing/descending through

RVSM flight levels (without intermediate level off)

to/from FLs above RVSM airspace (Policies for these

flights are detailed in paragraph 4−6−11, Non−RVSM

Aircraft Requesting Climb to and Descent from

Flight Levels Above RVSM Airspace Without

Intermediate Level Off.

5. Foreign State (government) aircraft.

c. Methods for operators of non−RVSM aircraft to

request access to RVSM Airspace. Operators may:

1. LOA/MOU. Enter into a Letter of Agreement (LOA)/Memorandum of Understanding

(MOU) with the RVSM facility (the Air Traffic

facility that provides air traffic services in RVSM

airspace). Operators must comply with LOA/MOU.
7/26/12 AIM

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the 4−6−11

Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

2. File−and−Fly. File a flight plan to notify the

FAA of their intention to request access to RVSM

airspace.

NOTE−

Priority for access to RVSM airspace will be afforded to

RVSM compliant aircraft, then File−and−Fly flights.

d. Center Phone Numbers. Center phone numbers are posted on the RVSM Documentation

Webpage, North American RVSM, Domestic U.S.

RVSM section. This address provides direct access to

the phone number listing:

http://www.faa.gov/ats/ato/150_docs/

Center_Phone_No._Non−RVSM_Acft.doc

4−6−11. Non−RVSM Aircraft Requesting

Climb to and Descent from Flight Levels

Above RVSM Airspace Without

Intermediate Level Off

a. File−and−Fly. Operators of Non−RVSM aircraft climbing to and descending from RVSM flight

levels should just file a flight plan.

b. Non−RVSM aircraft climbing to and descending from flight levels above RVSM airspace will be

handled on a workload permitting basis. The vertical

separation standard applied in RVSM airspace

between non−RVSM aircraft and all other aircraft

must be 2,000 feet.

c. Non−RVSM aircraft climbing to/descending

from RVSM airspace can only be considered for

accommodation provided:

1. Aircraft is capable of a continuous climb/

descent and does not need to level off at an

intermediate altitude for any operational considerations and

2. Aircraft is capable of climb/descent at the

normal rate for the aircraft.

d. Required Pilot Calls. The pilot of non−RVSM

aircraft will inform the controller of the lack of

RVSM approval in accordance with the direction

provided in paragraph 4−6−8, Pilot/Controller

Phraseology.

7/26/12 AIM

Operational Policy/Procedures for the Gulf of Mexico 50 NM Lateral Separation Initiative 4−7−1

Section 7. Operational Policy/Procedures for the Gulf of

Mexico 50 NM Lateral Separation Initiative

4−7−1. Introduction and Background

a. Introduction. On 20 October 2011 at 0900

UTC, the Federal Aviation Administration (FAA),

Serviciós a la Navegacion en el Espacio Aéreo

Mexicano (SENEAM) and the Direccion General de

Aeronautica Civil (DGAC) Mexico implemented 50

Nautical Mile (NM) lateral separation between

aircraft authorized Required Navigation Performance 10 (RNP 10) or RNP 4 operating in the Gulf of

Mexico (GoMex) Oceanic Control Areas (CTA).

Existing Air Traffic Services (ATS) routes and route

operating policies did not change for this implementation.

b. RNP 10 Versus RNAV 10 Terminology. “RNP

10” has the same meaning and application as “RNAV

10”. The ICAO Performance-based Navigation

(PBN) Manual (ICAO Doc 9613), Volume II, Part B,

Chapter 1 (Implementing RNAV 10, Designated and

Authorized as RNP 10) explains that the term “RNP

10” was in use before the publication of the ICAO

PBN Manual and the manual has “grandfathered in”

its continued use when implementing an “RNAV 10”

navigation specification.

c. Background. 50 NM lateral separation was

first applied between aircraft authorized for RNP 10

operations on the North Pacific Route System in

April 1998. Since that time, 50 NM lateral separation

has been expanded throughout the Pacific Flight

Information Regions (FIRs) and is currently applied

in other airspaces, including, starting in June 2008,

the West Atlantic Route System. GoMex 50 NM

lateral separation implementation will apply the

experience gained in those operations.

d. Project Objectives. The project objectives

were to:

1. Reduce lateral separation to 50 NM between

aircraft authorized RNP 10 or RNP 4.

2. Leave existing ATS routes and operating

policies in place.

3. Have approximately 90% of flights conducted by operators/aircraft over the Gulf of Mexico

authorized for RNP 10 or RNP 4 operations by the

appropriate State authority.

4. Accommodate the operation of the small

percentage of flights not authorized RNP 10.

5. Establish a policy that aircraft equipped with

a Single Long-Range Navigation System (S-LRNS)

can qualify for RNP 10 operations in the Gulf of

Mexico in accordance with the ICAO PBN Manual

and the appropriate FAA and DGAC documents. (See

paragraph 4−7−7e.)

e. Control Areas (CTA) Affected. 50 NM lateral

separation is implemented in the following CTAs/

FIRs/Upper Control Areas (UTA).

1 The Houston Oceanic CTA/FIR and the

Gulf of Mexico portion of the Miami Oceanic

CTA/FIR.

(a) The Monterrey CTA and Merida High

CTA within the Mexico FIR/UTA

f. Policy and Procedures Coordination with

SENEAM and the DGAC. The policies and

procedures were coordinated with SENEAM and the

Mexico DGAC. They are applied in the GoMex

CTA’s where the FAA and SENEAM provide Air

Traffic Control.

4−7−2. Gulf of Mexico 50 NM Lateral

Separation Initiative Web Page: Policy,

Procedures and Guidance for Operators

and Regulators

Information on plans, policies and procedures for 50

NM lateral separation is posted on the “Gulf of

Mexico 50 NM Lateral Separation Web Page”:

http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/enroute/oceanic/gome

x/

The web page contains detailed guidance on operator

and aircraft authorization for RNP 10 or RNP 4 and

includes Job Aids with FAA and ICAO document

references.

4−7−3. Lateral Separation Minima Applied

a. 50 NM lateral separation is applied in the

GoMex CTA’s between aircraft authorized RNP 10 or

RNP 4 at all altitudes above the floor of controlled

airspace.
AIM 7/26/12

4−7−2 Operational Policy/Procedures for the Gulf of Mexico 50 NM Lateral Separation Initiative

b. The current lateral separation minima of 100

NM in the Houston, Monterrey and Merida CTAs,

and 90 NM in the Miami Oceanic CTA will continues

to be applied between aircraft not authorized RNP 10

or RNP 4.

4−7−4. Operation on Routes on the

periphery of the Gulf of Mexico CTAs

Operations on certain routes that fall within the

boundaries of affected CTAs are not affected by the

introduction of 50 NM lateral separation. Operation

on the following routes is not affected:

a. Routes that are flown by reference to ICAO

standard ground-based navigation aids (VOR,

VOR/DME, NDB).

b. Special Area Navigation (RNAV) routes Q100,

Q102 and Q105 in the Houston, Jacksonville and

Miami CTAs.

4−7−5. Provisions for Accommodation of

NonRNP10 Aircraft (Aircraft Not Authorized

RNP 10 or RNP 4)

a. Operators of NonRNP10 aircraft must annotate

ICAO flight plan Item 18 as follows:

“STS/NONRNP10” (no space between letters and

numbers).

b. Pilots of NonRNP10 aircraft that operate in

GoMex CTA’s must report the lack of authorization

by stating “Negative RNP 10”:

1. On initial call to ATC in a GoMex CTA:

2. In read back of a clearance to climb to or

descend from cruise altitude. (See paragraph

4−7−5e.); and

3. When approval status is requested by the

controller. (See paragraph 4−7−9e.)

c. Operators of NonRNP10 aircraft must not

annotate ICAO flight plan Item 18 (Other

Information) with “NAV/RNP10” or “NAV/RNP4”,

as shown in paragraph 7, if they have not obtained

RNP 10 or RNP 4 authorization.

d. NonRNP10 operators/aircraft may file any

route at any altitude in a GoMex CTA. They will be

cleared to operate on their preferred routes and

altitudes as traffic permits. 50 NM lateral separation

will not be applied to NonRNP10 aircraft.

e. NonRNP10 aircraft are encouraged to operate at

altitudes above those where traffic is most dense (i.e.,

at/above FL 380), if possible. NonRNP10 aircraft

should plan on completing their climb to or descent

from higher FLs within radar coverage, if possible.

4−7−6. Operator Action

In order to maximize operational flexibility provided

by 50 NM lateral separation, operators capable of

meeting RNP 10 or RNP 4 that operate on oceanic

routes or areas in the GoMex CTA’s should obtain

authorization for RNP 10 or RNP 4 and annotate the

ICAO flight plan accordingly.

NOTE−

1. RNP 10 is the minimum “Navigation Specification

(NavSpec)” required for the application of 50 NM lateral

separation. RNP 4 is an operator option. Operators/aircraft authorized RNP 4 are not required to also obtain

RNP 10 authorization.

2. “RNP navigation specification” (e.g., RNP 10) is the

term adopted in the ICAO Performance-based Navigation

(PBN) Manual (Doc 9613). It replaces the term “RNP

type”.

4−7−7. RNP 10 or RNP 4 Authorization:

Policy and Procedures for Aircraft and

Operators

a. RNP NavSpecs Applicable To Oceanic Operations. In accordance with ICAO guidance, RNP 10

and RNP 4 are the only NavSpecs applicable to

oceanic and remote area operations. Other RNAV and

RNP NavSpecs are applicable to continental en route,

terminal area and approach operations.

b. FAA Documents. The guidance and direction

of FAA Order 8400.12 (as amended) (RNP 10

Operational Authorization) is used to grant RNP 10

authorization to operators and aircraft for which the

FAA is responsible. FAA Order 8400.33 (as

amended) (Procedures for Obtaining Authorization

for RNP 4 Oceanic/Remote Area Operations) is used

to authorize RNP 4. The FAA RNP 10 and RNP 4

orders are consistent with the ICAO PBN Manual

guidance discussed below. FAA and ICAO documents are posted on the FAA Gulf of Mexico 50 NM

Lateral Separation Initiative Web Page.

c. ICAO Performance-based Navigation (PBN)

Manual (ICAO Doc 9613). Guidance for authorization of RNP 10 and RNP 4 is provided in ICAO Doc

9613. RNP 10 is addressed in Volume II, Part B;
7/26/12 AIM

Operational Policy/Procedures for the Gulf of Mexico 50 NM Lateral Separation Initiative 4−7−3

Chapter 1. RNP 4 is addressed in Volume II, Part C;

Chapter 1.

d. RNP 10 and RNP 4 Job Aids. Operators and

authorities are encouraged to use the RNP 10 or RNP

4 Job Aids posted on the FAA Gulf of Mexico 50 NM

Lateral Separation Initiative Web Page. For U.S.

operators, one set of RNP 10 and RNP 4 Job Aids

provides references to FAA documents. For

international operators, a second set of Job Aids

provide references to the ICAO PBN Manual. These

Job Aids address the operational and airworthiness

elements of aircraft and operator authorization and

provide references to appropriate document paragraphs. The Job Aids provide a method for operators

to develop and authorities to track the operator/aircraft program elements required for RNP 10 or RNP

4 authorization.

e. Qualification of Aircraft Equipped With a

Single Long-Range Navigation System (S-LRNS)

For RNP 10 Operations In GoMex CTA’s.

1. Background. S-LRNS operations in the Gulf

of Mexico, the Caribbean Sea and the other

designated areas have been conducted for at least 25

years. Provisions allowing aircraft equipage with a

S-LRNS for operations in specified oceanic and

off-shore areas are contained in the following

sections of 14 Code Of Federal Regulations (CFR):

91.511, 121.351, 125.203 and 135.165.

2. ICAO PBN Manual Reference. In reference

to RNP 10 authorization, the ICAO PBN Manual,

Volume II, Part B, Chapter 1, paragraph 1.3.6.2 states

that: “A State authority may approve the use of a

single LRNS in specific circumstances (e.g., North

Atlantic MNPS and 14 CFR 121.351 (c) refer). An

RNP 10 approval is still required.”

3. Policy Development. The FAA worked with

the ICAO NACC Office (North American, Central

American and Caribbean), State regulators and ATS

providers in the GoMex and Caribbean areas to

implement a policy for S-LRNS equipped aircraft to

qualify for RNP 10 for GoMex operations. Allowing

S-LRNS equipped aircraft to qualify for RNP 10

enables more operator aircraft to be authorized RNP

10, thereby creating a more uniform operating

environment for the application of 50 NM lateral

separation. The factors considered were: the

shortness of the legs outside the range of ground

navigation aids, the availability of radar and VHF

coverage in a large portion of GoMex airspace and the

absence of events attributed to S-LRNS in GoMex

operations.

4. Document Revision. The following documents were revised or created to enable

implementation of the S-LRNS/RNP 10 qualification policy:

(a) FAA Order (FAAO) 8400.12

(b) FAA Order 8900.1 (Flight Standards

Information Management System (FSIMS))

(c) Paragraph B054 of FAA Operations

Specifications and Management Specifications

(Class II Navigation Using Single Long-Range

Navigation System)

(d) LOA B054 (Class II Navigation Using

Single Long-Range Navigation System (S-LRNS)

Equipped Airplane Authorized RNP 10) (LOA’s are

applicable to International General Aviation operators.)

(e) FAA RNP 10 Job Aid with FAAO

8400.12 references

(f) RNP 10 Job Aid with ICAO PBN Manual

references

5. S-LRNS/RNP 10 Authorization Limited To

GoMex. At this time, S-LRNS qualification for RNP

10 only applies to GoMex operations. Any expansion

of this provision will require assessment and

agreement by the appropriate State authorities.

f. RNP 10 Time Limit for INS or IRU Only

Equipped Aircraft. Operators should review their

Airplane Flight Manual (AFM), AFM Supplement or

other appropriate documents and/or contact the

airplane or avionics manufacturer to determine the

RNP 10 time limit applicable to their aircraft. They

will then need to determine its effect, if any, on their

operation. Unless otherwise approved, the basic RNP

10 time limit is 6.2 hours between position updates

for aircraft on which Inertial Navigation Systems

(INS) or Inertial Reference Units (IRU) provide the

only source of long range navigation. Extended RNP

10 time limits of 10 hours and greater are already

approved for many IRU systems. FAA Order 8400.12

contains provisions for extending RNP 10 time

limits.
AIM 7/26/12

4−7−4 Operational Policy/Procedures for the Gulf of Mexico 50 NM Lateral Separation Initiative

4−7−8. Flight Planning Requirements

Operators must make ICAO flight plan annotations

in accordance with this paragraph and, if applicable,

paragraph 4−7−5, Provisions for Accommodation of

NonRNP10 Aircraft (Aircraft Not Authorized RNP

10 or RNP 4).

a. ICAO Flight Plan Requirement. ICAO flight

plans must be filed for operation on oceanic routes

and areas in the Houston Oceanic CTA/FIR, the Gulf

of Mexico portion of the Miami CTA/FIR, the

Monterrey CTA and Merida High CTA.

b. To inform ATC that they have obtained RNP 10

or RNP 4 authorization and are eligible for 50 NM

lateral separation, operators must:

1. Annotate ICAO Flight Plan Item 10

(Equipment) with the letters “R” and “Z”, and

2. Annotate Item 18 (Other Information) with,

as appropriate, “NAV/RNP10” or “NAV/RNP4” (no

space between letters and numbers).

NOTE−

1. See paragraph 4−7−8e. It provides recommended

filing practices for domestic U.S. RNAV operations and

filing with EUROCONTROL.

2. On the ICAO Flight Plan, the letter “R” in Item 10

indicates that the aircraft will maintain the appropriate

RNP navigation specification for the entire flight through

airspace where RNP is prescribed. Letter “Z” in Item 10

indicates that information explaining aircraft navigation

and/or communication capability is found in Item 18.

c. 50 NM lateral separation will only be applied to

operators/aircraft that annotate the ICAO flight plan

in accordance with this policy. (See 4−7−8b.)

d. Operators that have not obtained RNP 10 or

RNP 4 authorization must not annotate ICAO flight

plan Item 18 (Other information) with “NAV/

RNP10” or “NAV/RNP4”, but must follow the

practices detailed in paragraph 4−7−5.

e. Recommendation for Filing to Show Domestic

U.S. RNAV and Oceanic RNP Capabilities.

1. Explanation. The FAA program to enhance

operators’ capability to communicate their domestic

U.S. RNAV capabilities to ATC has been in place for

over three years. It requires an entry following the

NAV/ indicator in Item 18 of the ICAO flight plan.

The initiative has provisions for including RNAV

capabilities for departure (“D”), enroute (“E”) and

arrival (“A”) with RNAV accuracy values. Detailed

instructions are available on the following web page:

http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/enroute/flight_plan_fi

ling/

EXAMPLE−

An example Item 18 entry is: NAV/RNVD1E2A1. The

characters in the example indicate RNAV 1 and RNAV 2

accuracy.

2. Recommendation. It is recommended that

operators provide their RNAV capability for

domestic U.S. and capabilities for oceanic operations

(RNP 10 or RNP 4) by filing: “NAV/”, then the

domestic U.S. alphanumeric sequence, then a

mandatory space and then “RNP10” or “RNP4”, as

appropriate.

EXAMPLE−

“NAV/RNVD1E2A1 RNP10”

3. Multiple NAV/ Entries. Operators should be

aware that if they make multiple “NAV/” entries in a

flight plan filed with EUROCONTROL, only the last

“NAV/” entry will be forwarded to the next ATC

facility. For example, if “NAV/RNVD1E2A1” and

“NAV/RNP10” are entered, only “NAV/RNP10” will

be forwarded. Multiple “NAV/” entries should,

therefore, be consolidated following a single “NAV/”

indicator.

4. Recommendation. Item 18 entries made in

accordance with paragraph 4-7-8 e. 2. above will

limit the number of characters needed to show

domestic U.S. RNAV and oceanic RNP capabilities

and mitigate the chance that one or the other will not

be forwarded for use by FAA domestic and oceanic

automation systems.

f. Implementation of ICAO Doc 4444, Revised

Appendix 2 (Flight Plan). ICAO Doc 4444,

Amendment 1 revises Appendix 2 (Flight Plan).

Specifically, Amendment 1 revises the flight plan

annotations in Item 10 (Equipment) and Item 18

(Other Information) that show aircraft communications, navigation and surveillance capabilities. The

new Appendix 2 flight plan annotations will be

required on 15 November 2012. The following

Websites provide information on implementation

planning:

1. FAA Website: http://www.faa.gov/go/

fpl2012.
7/26/12 AIM

Operational Policy/Procedures for the Gulf of Mexico 50 NM Lateral Separation Initiative 4−7−5

2. ICAO Flight Plan Implementation Tracking

System (FITS): http://www2.icao.int/en/FITS/

Pages/home.aspx.

4−7−9. Pilot and Dispatcher Procedures:

Basic and In-flight Contingency

Procedures

a. Basic Pilot Procedures. The RNP 10 and RNP

4 Job Aids contain references to pilot and, if

applicable, dispatcher procedures contained in:

1. FAA Order 8400.12C (RNP 10), Appendix D

(Training Programs and Operating Practices and

Procedures)

2. FAA Order 8400.33 (RNP 4): paragraph 9

(Operational Requirements) and paragraph 10

(Training Programs, Operating Practices and Procedures)

3. ICAO PBN Manual, Volume II, Part B,

Chapter 1 (RNP 10)

4. ICAO PBN Manual, Volume II, Part C,

Chapter 1 (RNP 4)

b. ICAO Doc 4444, Chapter 15, In-flight

Contingency Procedures. Doc 4444 Chapter 15

contains important guidance for pilot training

programs. For ease of reference, significant Chapter

15 paragraphs are posted on the Gulf of Mexico 50

NM Lateral Separation Web Page. Chapter 15

paragraphs posted on the website include:

1. Paragraph 15.2 (Special Procedures for

In-Flight Contingencies in Oceanic Airspace).

Paragraph 15.2.2 (General Procedures) provides

guidance for in-flight diversions, turn-backs and for

loss of, or significant reduction in, required

navigation capability when operating in an airspace

where the navigation performance accuracy is a

prerequisite to the safe conduct of flight operations.

2. Paragraph 15.2.3 (Weather Deviation Procedures). Paragraph 15.2.3 provides guidance for

events where the pilot is able to obtain a clearance

prior to deviating from track to avoid convective

weather and for events where the pilot is unable to

obtain clearance prior to deviating.

c. Strategic Lateral Offset Procedures (SLOP).

Pilots should use SLOP procedures in the course of

regular oceanic operations. SLOP procedures are

published in ICAO Document 4444, 15th Edition,

Amendment 2, paragraph 16.5 and FAA Notices.

They are posted on the Gulf of Mexico 50 NM Lateral

Separation Web Page and are addressed in the RNP

10 and RNP 4 Job Aids.

d. Pilot Report of NonRNP10 Status. The pilot

must report the lack of RNP 10 or RNP 4 status in

accordance with the following:

1. When the operator/aircraft is not authorized

RNP 10 or RNP 4. See paragraph 4−7−5.

2. If approval status is requested by the

controller in accordance with paragraph 4−7−9e.

e. Pilot Statement of RNP 10 or RNP 4

Approval Status, If Requested. If requested by the

controller, the pilot must communicate approval

status using the following phraseology:

Controller Request:

(Call sign) confirm RNP 10 or 4 approved

Pilot Response:

“Affirm RNP 10 approved” or “Affirm RNP 4

approved,” as appropriate, or

“Negative RNP 10” (See paragraph 4−7−5 for

NonRNP10 aircraft procedures.)

f. Pilot action when navigation system malfunctions. In addition to the actions suggested in

ICAO Doc. 4444, Chapter 15, when pilots suspect a

navigation system malfunction, the following actions

should be taken:

1. Immediately inform ATC of navigation

system malfunction or failure.

2. Accounting for wind drift, fly magnetic

compass heading to maintain track.

3. Request radar vectors from ATC, when

available

7/26/12 AIM

Preflight 5−1−1

Chapter 5. Air Traffic Procedures

Section 1. Preflight

5−1−1. Preflight Preparation

a. Every pilot is urged to receive a preflight

briefing and to file a flight plan. This briefing should

consist of the latest or most current weather, airport,

and en route NAVAID information. Briefing service

may be obtained from an FSS either by telephone or

interphone, by radio when airborne, or by a personal

visit to the station. Pilots with a current medical

certificate in the 48 contiguous States may access

toll-free the Direct User Access Terminal System

(DUATS) through a personal computer. DUATS will

provide alpha-numeric preflight weather data and

allow pilots to file domestic VFR or IFR flight plans.

REFERENCE−

AIM, FAA Weather Services, Paragraph 7−1−2, lists DUATS vendors.

NOTE−

Pilots filing flight plans via “fast file” who desire to have

their briefing recorded, should include a statement at the

end of the recording as to the source of their weather

briefing.

b. The information required by the FAA to process

flight plans is contained on FAA Form 7233−1, Flight

Plan, or FAA Form 7233−4, International Flight Plan.

The forms are available at all flight service stations.

Additional copies will be provided on request.

REFERENCE−

AIM, Flight Plan− VFR Flights, Paragraph 5−1−4

AIM, Flight Plan− IFR Flights, Paragraph 5−1−8

AIM, International Flight Plan− IFR Flights, Paragraph 5−1−9

c. Consult an FSS or a Weather Service Office

(WSO) for preflight weather briefing. Supplemental

Weather Service Locations (SWSLs) do not provide

weather briefings.

d. FSSs are required to advise of pertinent

NOTAMs if a standard briefing is requested, but if

they are overlooked, don’t hesitate to remind the

specialist that you have not received NOTAM

information.

NOTE−

NOTAMs which are known in sufficient time for

publication and are of 7 days duration or longer are

normally incorporated into the Notices to Airmen

Publication and carried there until cancellation time. FDC

NOTAMs, which apply to instrument flight procedures, are

also included in the Notices to Airmen Publication up to

and including the number indicated in the FDC NOTAM

legend. Printed NOTAMs are not provided during a

briefing unless specifically requested by the pilot since the

FSS specialist has no way of knowing whether the pilot has

already checked the Notices to Airmen Publication prior to

calling. Remember to ask for NOTAMs in the Notices to

Airmen Publication. This information is not normally

furnished during your briefing.

REFERENCE−

AIM, Notice to Airmen (NOTAM) System, Paragraph 5−1−3.

e. Pilots are urged to use only the latest issue of

aeronautical charts in planning and conducting flight

operations. Aeronautical charts are revised and

reissued on a regular scheduled basis to ensure that

depicted data are current and reliable. In the

conterminous U.S., Sectional Charts are updated

every 6 months, IFR En Route Charts every 56 days,

and amendments to civil IFR Approach Charts are

accomplished on a 56−day cycle with a change notice

volume issued on the 28−day midcycle. Charts that

have been superseded by those of a more recent date

may contain obsolete or incomplete flight

information.

REFERENCE−

AIM, General Description of Each Chart Series, Paragraph 9−1−4.

f. When requesting a preflight briefing, identify

yourself as a pilot and provide the following:

1. Type of flight planned; e.g., VFR or IFR.

2. Aircraft’s number or pilot’s name.

3. Aircraft type.

4. Departure Airport.

5. Route of flight.

6. Destination.

7. Flight altitude(s).

8. ETD and ETE.

g. Prior to conducting a briefing, briefers are

required to have the background information listed

above so that they may tailor the briefing to the needs

of the proposed flight. The objective is to

communicate a “picture” of meteorological and

aeronautical information necessary for the conduct of
AIM 7/26/12

5−1−2 Preflight

a safe and efficient flight. Briefers use all available

weather and aeronautical information to summarize

data applicable to the proposed flight. They do not

read weather reports and forecasts verbatim unless

specifically requested by the pilot. FSS briefers do

not provide FDC NOTAM information for special

instrument approach procedures unless specifically

asked. Pilots authorized by the FAA to use special

instrument approach procedures must specifically

request FDC NOTAM information for these

procedures. Pilots who receive the information

electronically will receive NOTAMs for special IAPs

automatically.

REFERENCE−

AIM, Preflight Briefings, Paragraph 7−1−4, contains those items of a

weather briefing that should be expected or requested.

h. FAA by 14 CFR Part 93, Subpart K, has

designated High Density Traffic Airports (HDTAs)

and has prescribed air traffic rules and requirements

for operating aircraft (excluding helicopter operations) to and from these airports.

REFERENCE−

Airport/Facility Directory, Special Notices Section.

AIM, Airport Reservation Operations and Special Traffic Management

Programs, Paragraph 4−1−22.

i. In addition to the filing of a flight plan, if the

flight will traverse or land in one or more foreign

countries, it is particularly important that pilots leave

a complete itinerary with someone directly concerned

and keep that person advised of the flight’s progress.

If serious doubt arises as to the safety of the flight, that

person should first contact the FSS.

REFERENCE−

AIM, Flights Outside the U.S. and U.S. Territories, Paragraph 5−1−11

j. Pilots operating under provisions of 14 CFR

Part 135 on a domestic flight and not having an FAA

assigned 3−letter designator, are urged to prefix the

normal registration (N) number with the letter “T” on

flight plan filing; e.g., TN1234B.

REFERENCE−

AIM, Aircraft Call Signs, Paragraph 4−2−4

5−1−2. Follow IFR Procedures Even When

Operating VFR

a. To maintain IFR proficiency, pilots are urged to

practice IFR procedures whenever possible, even

when operating VFR. Some suggested practices

include:

1. Obtain a complete preflight and weather

briefing. Check the NOTAMs.

2. File a flight plan. This is an excellent low cost

insurance policy. The cost is the time it takes to fill it

out. The insurance includes the knowledge that

someone will be looking for you if you become

overdue at your destination.

3. Use current charts.

4. Use the navigation aids. Practice maintaining

a good course−keep the needle centered.

5. Maintain a constant altitude which is

appropriate for the direction of flight.

6. Estimate en route position times.

7. Make accurate and frequent position reports

to the FSSs along your route of flight.

b. Simulated IFR flight is recommended (under

the hood); however, pilots are cautioned to review

and adhere to the requirements specified in 14 CFR

Section 91.109 before and during such flight.

c. When flying VFR at night, in addition to the

altitude appropriate for the direction of flight, pilots

should maintain an altitude which is at or above the

minimum en route altitude as shown on charts. This

is especially true in mountainous terrain, where there

is usually very little ground reference. Do not depend

on your eyes alone to avoid rising unlighted terrain,

or even lighted obstructions such as TV towers.

5−1−3. Notice to Airmen (NOTAM) System

a. Time-critical aeronautical information which

is of either a temporary nature or not sufficiently

known in advance to permit publication on

aeronautical charts or in other operational publications receives immediate dissemination via the

National NOTAM System.

NOTE−

1. NOTAM information is that aeronautical information

that could affect a pilot’s decision to make a flight. It

includes such information as airport or aerodrome

primary runway closures, taxiways, ramps, obstructions,

communications, airspace, changes in the status of

navigational aids, ILSs, radar service availability, and

other information essential to planned en route, terminal,

or landing operations.

2. NOTAM information is transmitted using standard

contractions to reduce transmission time. See TBL 5−1−1

for a listing of the most commonly used contractions. For

a complete listing, see FAA Order JO 7340.2,

Contractions.

b. NOTAM information is classified into four

categories. These are NOTAM (D) or distant, Flight
7/26/12 AIM

Preflight 5−1−3

Data Center (FDC) NOTAMs, Pointer NOTAMs, and

Military NOTAMs.

1. NOTAM (D) information is disseminated for

all navigational facilities that are part of the National

Airspace System (NAS), all public use airports,

seaplane bases, and heliports listed in the Airport/

Facility Directory (A/FD). The complete file of all

NOTAM (D) information is maintained in a computer

database at the Weather Message Switching Center

(WMSC), located in Atlanta, Georgia. This category

of information is distributed automatically via

Service A telecommunications system. Air traffic

facilities, primarily FSSs, with Service A capability

have access to the entire WMSC database of

NOTAMs. These NOTAMs remain available via

Service A for the duration of their validity or until

published. Once published, the NOTAM data is

deleted from the system. NOTAM (D) information

includes such data as taxiway closures, personnel

and equipment near or crossing runways, and airport

lighting aids that do not affect instrument approach

criteria, such as VASI.

All NOTAM Ds must have one of the following

keywords as the first part of the text after the location

identifier:

Keyword Definition

RWY .......

 Example

Runway

ABC XX/XXX ABC RWY 3/21 CLSD

TWY .......

 Example

Taxiway

ABC XX/XXX ABC TWY F LGTS OTS

RAMP ......

 Example

Ramp

ABC XX/XXX ABC RAMP TERMINAL

EAST SIDE CONSTRUCTION

APRON .....

 Example

Apron

ABC XX/XXX ABC APRON SW TWY

C NEAR HANGARS CLSD

AD .........

 Example

Aerodrome

ABC XX/XXX ABC AD ABN OTS

OBST .......

 Example

Obstruction

ABC XX/XXX ABC OBST TOWER 283

(246 AGL) 2.2 S LGTS OTS (ASR

1065881) TIL 1003282300

NAV ........

 Example

Navigation

ABC XX/XXX ABC NAV VOR OTS

COM .......

 Example

Communications

ABC XX/XXX ABC COM ATIS OTS

SVC ........

 Example

Services

XX/XXX ABC SVC JET FUEL

UNAVBL TIL 1003291600

Keyword Definition

AIRSPACE . .

 Example

Airspace

ABC XX/XXX ABC AIRSPACE

AIRSHOW ACFT 5000/BLW 5 NMR

AIRPORT AVOIDANCE ADZD TIL

1003152200

U ........... Unverified Aeronautical Information

(for use only where authorized by Letter

of Agreement)*

O .......... Other Aeronautical Information**

* Unverified Aeronauticatical Information can be

movement area or other information received that

meets NOTAM criteria and has not been confirmed

by the Airport Manager (AMGR) or their designee. If

Flight Service is unable to contact airport management, Flight Service must forward (U) NOTAM

information to the United States NOTAM System

(USNS). Subsequent to USNS distribution of a (U)

NOTAM, Flight Service will inform airport management of the action taken as soon as practical. Any

such NOTAM will be prefaced with “(U)” as the

keyword and followed by the appropriate keyword

contraction, following the location identifier.

** Other Aeronautical Information is that which

is received from any authorized source that may be

beneficial to aircraft operations and does not meet

defined NOTAM criteria. Any such NOTAM will be

prefaced with “(O)” as the keyword following the

location identifier.

2. FDC NOTAMs

(a) On those occasions when it becomes

necessary to disseminate information which is

regulatory in nature, the National Flight Data Center

(NFDC), in Washington, DC, will issue an FDC

NOTAM. FDC NOTAMs contain such things as

amendments to published IAPs and other current

aeronautical charts. They are also used to advertise

temporary flight restrictions caused by such things as

natural disasters or large-scale public events that may

generate a congestion of air traffic over a site.

(b) FDC NOTAMs are transmitted via

Service A only once and are kept on file at the FSS

until published or canceled. FSSs are responsible for

maintaining a file of current, unpublished FDC

NOTAMs concerning conditions within 400 miles of

their facilities. FDC information concerning conditions that are more than 400 miles from the FSS, or

that is already published, is given to a pilot only on

request.
AIM 7/26/12

5−1−4 Preflight

NOTE−

1. DUATS vendors will provide FDC NOTAMs only upon

site-specific requests using a location identifier.

2. NOTAM data may not always be current due to the

changeable nature of national airspace system components, delays inherent in processing information, and

occasional temporary outages of the U.S. NOTAM system.

While en route, pilots should contact FSSs and obtain

updated information for their route of flight and

destination.

3. Pointer NOTAMs. NOTAMs issued by a

flight service station to highlight or point out another

NOTAM, such as an FDC or NOTAM (D) NOTAM.

This type of NOTAM will assist users in

cross−referencing important information that may

not be found under an airport or NAVAID identifier.

Keywords in pointer NOTAMs must match the

keywords in the NOTAM that is being pointed out.

The keyword in pointer NOTAMs related to

Temporary Flight Restrictions (TFR) must be

AIRSPACE.

4. Special Use Airspace (SUA) NOTAMs.

SUA NOTAMs are issued when Special Use

Airspace will be active outside the published

schedule times and when required by the published

schedule. Pilots and other users are still responsible

to check published schedule times for Special Use

Airspace as well as any NOTAMs for that airspace.

5. Military NOTAMs. NOTAMs pertaining

to U.S. Air Force, Army, Marine, and Navy

navigational aids/airports that are part of the NAS.

c. An integral part of the NOTAM System is the

Notices to Airmen Publication (NTAP) published

every four weeks. Data is included in this publication

to reduce congestion on the telecommunications

circuits and, therefore, is not available via Service A.

Once published, the information is not provided

during pilot weather briefings unless specifically

requested by the pilot. This publication contains two

sections.

1. The first section consists of notices that meet

the criteria for NOTAM (D) and are expected to

remain in effect for an extended period and FDC

NOTAMs that are current at the time of publication.

Occasionally, unique information is included in this

section when it will contribute to flight safety.

2. The second section contains special notices

that are either too long or concern a wide or

unspecified geographic area and are not suitable for

inclusion in the first section. The content of these

notices vary widely and there are no specific criteria

for their inclusion, other than their enhancement of

flight safety.

3. The number of the last FDC NOTAM

included in the publication is noted on the first page

to aid the user in updating the listing with any FDC

NOTAMs which may have been issued between the

cut-off date and the date the publication is received.

All information contained will be carried until the

information expires, is canceled, or in the case of

permanent conditions, is published in other publications, such as the A/FD.

4. All new notices entered, excluding FDC

NOTAMs, will be published only if the information

is expected to remain in effect for at least 7 days after

the effective date of the publication.

d. NOTAM information is not available from a

Supplemental Weather Service Locations (SWSL).

TBL 5−1−1

NOTAM CONTRACTIONS

A

AADC ........ Approach and Departure Control

ABV . . . . . . . . . . Above

A/C . . . . . . . . . . . Approach Control

ACCUM ....... Accumulate

ACFT ......... Aircraft

ACR . . . . . . . . . . Air Carrier

ACTV/ACTVT . Active/Activate

ADF . . . . . . . . . . Automatic Direction Finder

ADJ . . . . . . . . . . Adjacent

ADZ/ADZD .... Advise/Advised

AFD . . . . . . . . . . Airport/Facility Directory

ALS . . . . . . . . . . Approach Light System

ALTM . . . . . . . . . Altimeter

ALTN/ALTNLY . Alternate/Alternately

ALSTG ........ Altimeter Setting

AMDT ........ Amendment

APCH ......... Approach

APL . . . . . . . . . . Airport Lights

ARFF ......... Aircraft Rescue & Fire Fighting

ARPT ......... Airport

ARSR ......... Air Route Surveillance Radar

ASDE ......... Airport Surface Detection Equipment

ASOS ......... Automated Surface Observing System

ASPH ......... Asphalt

ASR . . . . . . . . . . Airport Surveillance Radar

ATC . . . . . . . . . . Air Traffic Control

ATCT . . . . . . . . . Airport Traffic Control Tower

ATIS . . . . . . . . . . Automated Terminal Information

Service

AVBL . . . . . . . . . Available
7/26/12 AIM

Preflight 5−1−5

AWOS . . . . . . . . Automatic Weather Observing System

AWSS . . . . . . . . . Automated Weather Sensor System

AZM . . . . . . . . . . Azimuth

B

BC . . . . . . . . . . . Back Course

BCN . . . . . . . . . . Beacon

BERM ........ Snowbank/s Containing Earth/Gravel

BLO . . . . . . . . . . Below

BND . . . . . . . . . . Bound

BRAF ......... Braking Action Fair

BRAG ........ Braking Action Good

BRAN ........ Braking Action Nil

BRAP ......... Braking Action Poor

BYD . . . . . . . . . . Beyond

C

CAAS ......... Class A Airspace

CAT . . . . . . . . . . Category

CBAS ......... Class B Airspace

CBSA ......... Class B Surface Area

CCAS ......... Class C Airspace

CCLKWS ...... Counterclockwise

CCSA ......... Class C Surface Area

CD . . . . . . . . . . . Clearance Delivery

CDAS ......... Class D Airspace

CDSA ......... Class D Surface Area

CEAS ......... Class E Airspace

CESA ......... Class E Surface Area

CFA . . . . . . . . . . Controlled Firing Area

CGAS ......... Class G Airspace

CHG . . . . . . . . . . Change

CLKWS ....... Clockwise

CLNC ......... Clearance

CLSD ......... Closed

CMSN/CMSND . Commission/Commissioned

CNCL/CNCLD/

CNL . . . . . . . . . .

Cancel/Canceled/Cancel

CNTRLN ...... Centerline

CONC ........ Concrete

CONT ......... Continue/Continuously

CRS . . . . . . . . . . Course

CTAF . . . . . . . . . Common Traffic Advisory Frequency

CTLZ ......... Control Zone

D

DALGT ....... Daylight

DCMS/DCMSND Decommission/Decommissioned

DCT . . . . . . . . . . Direct

DEP . . . . . . . . . . Depart/Departure

DEPT ......... Department

DH . . . . . . . . . . . Decision Height

DISABLD ..... Disabled

DLA/DLAD .... Delay/Delayed

DLT/DLTD ..... Delete/Deleted

DLY . . . . . . . . . . Daily

DME . . . . . . . . . . Distance Measuring Equipment

DMSTN ....... Demonstration

DP . . . . . . . . . . . Instrument Departure Procedure

DPCR ......... Departure Procedure

DRCT ......... Direct

DRFT/DRFTD . . Drift/Drifted Snowbank/s Caused By

Wind Action

DSPLCD ...... Displaced

DSTC ......... Distance

DWPNT ....... Dew Point

E

E ............. East

EBND ......... Eastbound

EFAS . . . . . . . . . En Route Flight Advisory Service

EFF . . . . . . . . . . . Effective

ELEV ......... Elevate/Elevation

ENG . . . . . . . . . . Engine

ENTR ......... Entire

EXCP ......... Except

F

FA . . . . . . . . . . . . Final Approach

FAC . . . . . . . . . . Facility

FAF . . . . . . . . . . . Final Approach Fix

FDC . . . . . . . . . . Flight Data Center

FM . . . . . . . . . . . Fan Marker

FREQ ......... Frequency

FRH . . . . . . . . . . Fly Runway Heading

FRZN ......... Frozen

FRNZ SLR ..... Frozen Slush on Runway/s

FSS . . . . . . . . . . . Flight Service Station

G

GC . . . . . . . . . . . Ground Control

GCA . . . . . . . . . . Ground Controlled Approach

GOVT ........ Government

GP . . . . . . . . . . . Glide Path

GPS . . . . . . . . . . Global Positioning System

GRVL . . . . . . . . . Gravel

GS . . . . . . . . . . . Glide Slope

H

HAA . . . . . . . . . . Height Above Airport

HAT . . . . . . . . . . Height Above Touchdown

HAZ . . . . . . . . . . Hazard

HEL . . . . . . . . . . Helicopter

HELI ......... Heliport

HF . . . . . . . . . . . High Frequency

HIRL ......... High Intensity Runway Lights

HIWAS . . . . . . . . Hazardous Inflight Weather Advisory

Service

HOL . . . . . . . . . . Holiday

HP . . . . . . . . . . . Holding Pattern

I

IAP . . . . . . . . . . . Instrument Approach Procedure

IBND ......... Inbound

ID . . . . . . . . . . . . Identification

IDENT ........ Identify/Identifier/Identification

IFR . . . . . . . . . . . Instrument Flight Rules

ILS . . . . . . . . . . . Instrument Landing System

IM . . . . . . . . . . . . Inner Marker

IN . . . . . . . . . . . . Inch/Inches

INDEFLY ...... Indefinitely
AIM 7/26/12

5−1−6 Preflight

INOP ......... Inoperative

INST .......... Instrument

INT . . . . . . . . . . . Intersection

INTST ........ Intensity

IR . . . . . . . . . . . . Ice On Runway/s

L

L ............. Left

LAA . . . . . . . . . . Local Airport Advisory

LAT . . . . . . . . . . Latitude

LAWRS . . . . . . . Limited Aviation Weather Reporting

Station

LB . . . . . . . . . . . Pound/Pounds

LC . . . . . . . . . . . Local Control

LCL . . . . . . . . . . Local

LCTD ......... Located

LDA . . . . . . . . . . Localizer Type Directional Aid

LGT/LGTD/

LGTS . .

Light/Lighted/Lights

LIRL .......... Low Intensity Runway Edge Lights

LLWAS . . . . . . . . Low Level Wind Shear Alert System

LMM . . . . . . . . . Compass Locator at ILS Middle Marker

LNDG ........ Landing

LOC . . . . . . . . . . Localizer

LOM . . . . . . . . . . Compass Locator at ILS Outer Marker

LONG ........ Longitude

LSR . . . . . . . . . . Loose Snow on Runway/s

LT . . . . . . . . . . . . Left Turn After Take-off

M

MALS ........ Medium Intensity Approach Lighting

System

MALSF ....... Medium Intensity Approach Lighting

System with Sequenced Flashers

MALSR ....... Medium Intensity Approach Lighting

System with Runway Alignment

Indicator Lights

MAP . . . . . . . . . . Missed Approach Point

MCA . . . . . . . . . Minimum Crossing Altitude

MDA . . . . . . . . . Minimum Descent Altitude

MEA . . . . . . . . . . Minimum En Route Altitude

MED . . . . . . . . . . Medium

MIN . . . . . . . . . . Minute

MIRL ......... Medium Intensity Runway Edge Lights

MLS . . . . . . . . . . Microwave Landing System

MM . . . . . . . . . . Middle Marker

MNM . . . . . . . . . Minimum

MOCA ........ Minimum Obstruction Clearance

Altitude

MONTR ....... Monitor

MSA . . . . . . . . . . Minimum Safe Altitude/Minimum

Sector Altitude

MSAW . . . . . . . . Minimum Safe Altitude Warning

MSL . . . . . . . . . . Mean Sea Level

MU . . . . . . . . . . . Designate a Friction Value Representing

Runway Surface Conditions

MUD . . . . . . . . . Mud

MUNI ......... Municipal

N

N............. North

NA . . . . . . . . . . . Not Authorized

NBND ........ Northbound

NDB . . . . . . . . . . Nondirectional Radio Beacon

NE . . . . . . . . . . . Northeast

NGT . . . . . . . . . . Night

NM . . . . . . . . . . . Nautical Mile/s

NMR . . . . . . . . . Nautical Mile Radius

NOPT ......... No Procedure Turn Required

NTAP . . . . . . . . . Notice To Airmen Publication

NW . . . . . . . . . . . Northwest

O

OBSC ......... Obscured

OBSTN ....... Obstruction

OM . . . . . . . . . . . Outer Marker

OPER ......... Operate

OPN . . . . . . . . . . Operation

ORIG ......... Original

OTS . . . . . . . . . . Out of Service

OVR . . . . . . . . . . Over

P

PAEW . . . . . . . . . Personnel and Equipment Working

PAJA . . . . . . . . . Parachute Jumping Activities

PAPI . . . . . . . . . . Precision Approach Path Indicator

PAR . . . . . . . . . . Precision Approach Radar

PARL . . . . . . . . . Parallel

PAT . . . . . . . . . . . Pattern

PCL . . . . . . . . . . Pilot Controlled Lighting

PERM/PERMLY Permanent/Permanently

PLA . . . . . . . . . . Practice Low Approach

PLW . . . . . . . . . . Plow/Plowed

PN . . . . . . . . . . . Prior Notice Required

PPR . . . . . . . . . . Prior Permission Required

PREV ......... Previous

PRIRA ........ Primary Radar

PROC ......... Procedure

PROP ......... Propeller

PSGR ......... Passenger/s

PSR . . . . . . . . . . Packed Snow on Runway/s

PT/PTN ....... Procedure Turn

PVT . . . . . . . . . . Private

R

RAIL ......... Runway Alignment Indicator Lights

RCAG ........ Remote Communication Air/Ground

Facility

RCL . . . . . . . . . . Runway Centerline

RCLS ......... Runway Centerline Light System

RCO . . . . . . . . . . Remote Communication Outlet

RCV/RCVR .... Receive/Receiver

REF . . . . . . . . . . Reference

REIL .......... Runway End Identifier Lights

RELCTD ...... Relocated

RLLS ......... Runway Lead−in Light System

RMDR ........ Remainder

RNAV . . . . . . . . . Area Navigation

RPRT . . . . . . . . . Report

RQRD ........ Required

RRL . . . . . . . . . . Runway Remaining Lights
7/26/12 AIM

Preflight 5−1−7

RSVN ......... Reservation

RT . . . . . . . . . . . . Right Turn after Take-off

RTE . . . . . . . . . . Route

RTR . . . . . . . . . . Remote Transmitter/Receiver

RTS . . . . . . . . . . Return to Service

RUF . . . . . . . . . . Rough

RVR . . . . . . . . . . Runway Visual Range

RVRM . . . . . . . . RVR Midpoint

RVRR . . . . . . . . . RVR Rollout

RVRT . . . . . . . . . RVR Touchdown

RVV . . . . . . . . . . Runway Visibility Value

RY/RWY . . . . . . Runway

S

S ............. South

SAA . . . . . . . . . . Special Activity Airspace

SBND ......... Southbound

SDF . . . . . . . . . . Simplified Directional Facility

SE . . . . . . . . . . . . Southeast

SECRA ........ Secondary Radar

SFL . . . . . . . . . . . Sequenced Flashing Lights

SI . . . . . . . . . . . . Straight-In Approach

SIR . . . . . . . . . . . Packed or Compacted Snow and Ice on

Runway/s

SKED ......... Scheduled

SLR . . . . . . . . . . Slush on Runway/s

SNBNK ....... Snowbank/s Caused by Plowing

SND . . . . . . . . . . Sand/Sanded

SNGL ......... Single

SNW . . . . . . . . . . Snow

SPD . . . . . . . . . . Speed

SR . . . . . . . . . . . . Sunrise

SS . . . . . . . . . . . . Sunset

SSALF ........ Simplified Short Approach Lighting

System with Sequenced Flashers

SSALR ........ Simplified Short Approach Lighting

System with Runway Alignment

Indicator Lights

SSALS ........ Simplified Short Approach Lighting

System

STAR . . . . . . . . . Standard Terminal Arrival

SUA . . . . . . . . . . Special Use Airspace

SVC . . . . . . . . . . Service

SW . . . . . . . . . . . Southwest

SWEPT ........ Swept or Broom/Broomed

T

TACAN ....... Tactical Air Navigational Aid

TDZ/TDZL ..... Touchdown Zone/Touchdown Zone

Lights

TFC . . . . . . . . . . Traffic

TFR . . . . . . . . . . Temporary Flight Restriction

TGL . . . . . . . . . . Touch and Go Landings

THN . . . . . . . . . . Thin

THR . . . . . . . . . . Threshold

THRU ......... Through

TIL . . . . . . . . . . . Until

TKOF ......... Takeoff

TMPRY ....... Temporary

TRML ........ Terminal

TRNG ......... Training

TRSA ......... Terminal Radar Service Area

TRSN ......... Transition

TSNT ......... Transient

TWEB ........ Transcribed Weather Broadcast

TWR . . . . . . . . . . Tower

TWY . . . . . . . . . Taxiway

U

UNAVBL . . . . . . Unavailable

UNLGTD ...... Unlighted

UNMKD ...... Unmarked

UNMON ...... Unmonitored

UNRELBL ..... Unreliable

UNUSBL ...... Unusable

V

VASI . . . . . . . . . . Visual Approach Slope Indicator

VDP . . . . . . . . . . Visual Descent Point

VFR . . . . . . . . . . Visual Flight Rules

VIA . . . . . . . . . . By Way Of

VICE ......... Instead/Versus

VIS/VSBY ..... Visibility

VMC . . . . . . . . . Visual Meteorological Conditions

VOL . . . . . . . . . . Volume

VOLMET ...... Meteorlogical Information for Aircraft

in Flight

VOR . . . . . . . . . . VHF Omni-Directional Radio Range

VORTAC . . . . . . VOR and TACAN (collocated)

VOT . . . . . . . . . . VOR Test Signal

W

W ............ West

WBND ........ Westbound

WEA/WX ...... Weather

WI . . . . . . . . . . . Within

WKDAYS ..... Monday through Friday

WKEND ....... Saturday and Sunday

WND . . . . . . . . . Wind

WP . . . . . . . . . . . Waypoint

WSR . . . . . . . . . . Wet Snow on Runway/s

WTR . . . . . . . . . . Water on Runway/s

WX . . . . . . . . . . . Weather

/ ............. And

+ ............. In Addition/Also
AIM 7/26/12

5−1−8 Preflight

5−1−4. Flight Plan − VFR Flights

a. Except for operations in or penetrating a Coastal

or Domestic ADIZ or DEWIZ a flight plan is not

required for VFR flight.

REFERENCE−

AIM, National Security, Paragraph 5−6−1.

b. It is strongly recommended that a flight plan

(for a VFR flight) be filed with an FAA FSS. This will

ensure that you receive VFR Search and Rescue

Protection.

REFERENCE−

AIM, Search and Rescue, Paragraph 6−2−7 gives the proper method of

filing a VFR flight plan.

c. To obtain maximum benefits from the flight

plan program, flight plans should be filed directly

with the nearest FSS. For your convenience, FSSs

provide aeronautical and meteorological briefings

while accepting flight plans. Radio may be used to

file if no other means are available.

NOTE−

Some states operate aeronautical communications facilities which will accept and forward flight plans to the FSS

for further handling.

d. When a “stopover” flight is anticipated, it is

recommended that a separate flight plan be filed for

each “leg” when the stop is expected to be more than

1 hour duration.

e. Pilots are encouraged to give their departure

times directly to the FSS serving the departure airport

or as otherwise indicated by the FSS when the flight

plan is filed. This will ensure more efficient flight

plan service and permit the FSS to advise you of

significant changes in aeronautical facilities or

meteorological conditions. When a VFR flight plan

is filed, it will be held by the FSS until 1 hour after the

proposed departure time unless:

1. The actual departure time is received.

2. A revised proposed departure time is

received.

3. At a time of filing, the FSS is informed that

the proposed departure time will be met, but actual

time cannot be given because of inadequate

communications (assumed departures).

f. On pilot’s request, at a location having an active

tower, the aircraft identification will be forwarded by

the tower to the FSS for reporting the actual departure

time. This procedure should be avoided at busy

airports.

g. Although position reports are not required for

VFR flight plans, periodic reports to FAA FSSs along

the route are good practice. Such contacts permit

significant information to be passed to the transiting

aircraft and also serve to check the progress of the

flight should it be necessary for any reason to locate

the aircraft.

EXAMPLE−

1. Bonanza 314K, over Kingfisher at (time), VFR flight

plan, Tulsa to Amarillo.

2. Cherokee 5133J, over Oklahoma City at (time),

Shreveport to Denver, no flight plan.

h. Pilots not operating on an IFR flight plan and

when in level cruising flight, are cautioned to

conform with VFR cruising altitudes appropriate to

the direction of flight.

i. When filing VFR flight plans, indicate aircraft

equipment capabilities by appending the appropriate

suffix to aircraft type in the same manner as that

prescribed for IFR flight.

REFERENCE−

AIM, Flight Plan− Domestic IFR Flights, Paragraph 5−1−8.

j. Under some circumstances, ATC computer

tapes can be useful in constructing the radar history

of a downed or crashed aircraft. In each case,

knowledge of the aircraft’s transponder equipment is

necessary in determining whether or not such

computer tapes might prove effective.
7/26/12 AIM

Preflight 5−1−9

FIG 5−1−1

FAA Flight Plan

Form 7233−1 (8−82)

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION (FAA USE ONLY) (FAA USE ONLY) PILOT BRIEFING PILOT BRIEFING VNR

STOPOVER STOPOVER

TIME STARTED TIME STARTED SPECIALIST

INITIALS

SPECIALIST

INITIALS

1. TYPE 1. TYPE

VFR

IFR

DVFR

3. AIRCRAFT TYPE/

SPECIAL EQUIPMENT

3. AIRCRAFT TYPE/

SPECIAL EQUIPMENT

5. DEPARTURE POINT 5. DEPARTURE POINT 6. DEPARTURE TIME 6. DEPARTURE TIME

PROPOSED (Z) PROPOSED (Z) ACTUAL (Z) ACTUAL (Z)

7. CRUISING

ALTITUDE

7. CRUISING

ALTITUDE

8. ROUTE OF FLIGHT 8. ROUTE OF FLIGHT

KTS

9. DESTINATION (Name of airport

and city)

9. DESTINATION (Name of airport

and city)

10. EST. TIME ENROUTE 10. EST. TIME ENROUTE

HOURS

HOURS

MINUTES MINUTES

MINUTES MINUTES

11. REMARKS 11. REMARKS

12. FUEL ON BOARD 12. FUEL ON BOARD 13. ALTERNATE AIRPORT(S) 13. ALTERNATE AIRPORT(S) 14. PILOT’S NAME, ADDRESS & TELEPHONE NUMBER & AIRCRAFT HOME BASE 14. PILOT’S NAME, ADDRESS & TELEPHONE NUMBER & AIRCRAFT HOME BASE 15. NUMBER

ABOARD

15. NUMBER

ABOARD

17. DESTINATION CONTACT/TELEPHONE (OPTIONAL) 17. DESTINATION CONTACT/TELEPHONE (OPTIONAL)

16. COLOR OF AIRCRAFT 16. COLOR OF AIRCRAFT

FAA Form 7233-1 FAA Form 7233-1 (8-82) CLOSE VFR FLIGHT PLAN WITH _________________ FSS ON ARRIVAL CLOSE VFR FLIGHT PLAN WITH _________________ FSS ON ARRIVAL

FLIGHT PLAN FLIGHT PLAN

CIVIL AIRCRAFT PILOTS, FAR 91 requires you file an IFR flight plan to operate under instrument flight rules in

controlled airspace. Failure to file could result in a civil penalty not to exceed $1,000 for each violation (Section 901 of the Federal Aviation Act of 1958, as amended). Filing of a VFR flight plan is recommended as a good operating practice. See also

Part 99 for requirements concerning DVFR flight plans.

2. AIRCRAFT

IDENTIFICATION

2. AIRCRAFT

IDENTIFICATION

4. TRUE

AIRSPEED

4. TRUE

AIRSPEED

k. Flight Plan Form − (See FIG 5−1−1).

l. Explanation of VFR Flight Plan Items.

1. Block 1. Check the type flight plan. Check

both the VFR and IFR blocks if composite VFR/IFR.

2. Block 2. Enter your complete aircraft

identification including the prefix “N” if applicable.

3. Block 3. Enter the designator for the aircraft,

or if unknown, consult an FSS briefer.

4. Block 4. Enter your true airspeed (TAS).

5. Block 5. Enter the departure airport identifier code, or if unknown, the name of the airport.

6. Block 6. Enter the proposed departure time

in Coordinated Universal Time (UTC) (Z). If

airborne, specify the actual or proposed departure

time as appropriate.

7. Block 7. Enter the appropriate VFR altitude

(to assist the briefer in providing weather and wind

information).

8. Block 8. Define the route of flight by using

NAVAID identifier codes and airways.

9. Block 9. Enter the destination airport

identifier code, or if unknown, the airport name.

NOTE−

Include the city name (or even the state name) if needed for

clarity.

10. Block 10. Enter your estimated time

en route in hours and minutes.

11. Block 11. Enter only those remarks that

may aid in VFR search and rescue, such as planned

stops en route or student cross country, or remarks

pertinent to the clarification of other flight plan

information, such as the radiotelephony (call sign)

associated with a designator filed in Block 2, if the

radiotelephony is new, has changed within the last 60

days, or is a special FAA-assigned temporary

radiotelephony. Items of a personal nature are not

accepted.
AIM 7/26/12

5−1−10 Preflight

12. Block 12. Specify the fuel on board in

hours and minutes.

13. Block 13. Specify an alternate airport if

desired.

14. Block 14. Enter your complete name,

address, and telephone number. Enter sufficient

information to identify home base, airport, or

operator.

NOTE−

This information is essential in the event of search and

rescue operations.

15. Block 15. Enter total number of persons on

board (POB) including crew.

16. Block 16. Enter the predominant colors.

17. Block 17. Record the FSS name for closing

the flight plan. If the flight plan is closed with a

different FSS or facility, state the recorded FSS name

that would normally have closed your flight plan.

NOTE−

1. Optional− record a destination telephone number to

assist search and rescue contact should you fail to report

or cancel your flight plan within 1/2 hour after your

estimated time of arrival (ETA).

2. The information transmitted to the destination FSS will

consist only of flight plan blocks 2, 3, 9, and 10. Estimated

time en route (ETE) will be converted to the correct ETA.

5−1−5. Operational Information System

(OIS)

a. The FAA’s Air Traffic Control System

Command Center (ATCSCC) maintains a web site

with near real−time National Airspace System (NAS)

status information. NAS operators are encouraged to

access the web site at http://www.fly.faa.gov prior to

filing their flight plan.

b. The web site consolidates information from

advisories. An advisory is a message that is

disseminated electronically by the ATCSCC that

contains information pertinent to the NAS.

1. Advisories are normally issued for the

following items:

(a) Ground Stops.

(b) Ground Delay Programs.

(c) Route Information.

(d) Plan of Operations.

(e) Facility Outages and Scheduled Facility

Outages.

(f) Volcanic Ash Activity Bulletins.

(g) Special Traffic Management Programs.

2. This list is not all−inclusive. Any time there

is information that may be beneficial to a large

number of people, an advisory may be sent.

Additionally, there may be times when an advisory is

not sent due to workload or the short length of time of

the activity.

3. Route information is available on the web site

and in specific advisories. Some route information,

subject to the 56−day publishing cycle, is located on

the “OIS” under “Products,” Route Management

Tool (RMT), and “What’s New” Playbook. The RMT

and Playbook contain routings for use by Air Traffic

and NAS operators when they are coordinated

“real−time” and are then published in an ATCSCC

advisory.

4. Route advisories are identified by the word

“Route” in the header; the associated action is

required (RQD), recommended (RMD), planned

(PLN), or for your information (FYI). Operators are

expected to file flight plans consistent with the Route

RQD advisories.

5. Electronic System Impact Reports are on the

intranet at http://www.atcscc.faa.gov/ois/ under

“System Impact Reports.” This page lists scheduled

outages/events/projects that significantly impact

the NAS; for example, runway closures, air shows,

and construction projects. Information includes

anticipated delays and traffic management initiatives (TMI) that may be implemented.

5−1−6. Flight Plan− Defense VFR (DVFR)

Flights

VFR flights into a Coastal or Domestic ADIZ/

DEWIZ are required to file DVFR flight plans for

security purposes. Detailed ADIZ procedures are

found in Section 6, National Security and Interception Procedures, of this chapter. (See 14 CFR

Part 99.)
7/26/12 AIM

Preflight 5−1−11

5−1−7. Composite Flight Plan (VFR/IFR

Flights)

a. Flight plans which specify VFR operation for

one portion of a flight, and IFR for another portion,

will be accepted by the FSS at the point of departure.

If VFR flight is conducted for the first portion of the

flight, pilots should report their departure time to the

FSS with whom the VFR/IFR flight plan was filed;

and, subsequently, close the VFR portion and request

ATC clearance from the FSS nearest the point at

which change from VFR to IFR is proposed.

Regardless of the type facility you are communicating with (FSS, center, or tower), it is the pilot’s

responsibility to request that facility to “CLOSE VFR

FLIGHT PLAN.” The pilot must remain in VFR

weather conditions until operating in accordance with

the IFR clearance.

b. When a flight plan indicates IFR for the first

portion of flight and VFR for the latter portion, the

pilot will normally be cleared to the point at which the

change is proposed. After reporting over the

clearance limit and not desiring further IFR

clearance, the pilot should advise ATC to cancel the

IFR portion of the flight plan. Then, the pilot should

contact the nearest FSS to activate the VFR portion of

the flight plan. If the pilot desires to continue the IFR

flight plan beyond the clearance limit, the pilot should

contact ATC at least 5 minutes prior to the clearance

limit and request further IFR clearance. If the

requested clearance is not received prior to reaching

the clearance limit fix, the pilot will be expected to

enter into a standard holding pattern on the radial or

course to the fix unless a holding pattern for the

clearance limit fix is depicted on a U.S. Government

or commercially produced (meeting FAA requirements) low or high altitude enroute, area or STAR

chart. In this case the pilot will hold according to the

depicted pattern.

5−1−8. Flight Plan (FAA Form 7233−1)−

Domestic IFR Flights

NOTE−

1. Procedures outlined in this section apply to operators

filing FAA Form 7233−1 (Flight Plan) and to flights that

will be conducted entirely within U.S. domestic airspace.

2. Filers utilizing FAA Form 7233−1 may not be eligible

for assignment of RNAV SIDs and STARs. Filers desiring

assignment of these procedures should file using FAA Form

7233−4 (International Flight Plan), as described in

paragraph 5−1−9.

a. General

1. Prior to departure from within, or prior to

entering controlled airspace, a pilot must submit a

complete flight plan and receive an air traffic

clearance, if weather conditions are below VFR

minimums. Instrument flight plans may be submitted

to the nearest FSS or ATCT either in person or by

telephone (or by radio if no other means are

available). Pilots should file IFR flight plans at least

30 minutes prior to estimated time of departure to

preclude possible delay in receiving a departure

clearance from ATC. In order to provide FAA traffic

management units strategic route planning capabilities, nonscheduled operators conducting IFR

operations above FL 230 are requested to voluntarily

file IFR flight plans at least 4 hours prior to estimated

time of departure (ETD). To minimize your delay in

entering Class B, Class C, Class D, and Class E

surface areas at destination when IFR weather

conditions exist or are forecast at that airport, an IFR

flight plan should be filed before departure.

Otherwise, a 30 minute delay is not unusual in

receiving an ATC clearance because of time spent in

processing flight plan data. Traffic saturation

frequently prevents control personnel from accepting

flight plans by radio. In such cases, the pilot is advised

to contact the nearest FSS for the purpose of filing the

flight plan.

NOTE−

1. There are several methods of obtaining IFR clearances

at nontower, non−FSS, and outlying airports. The

procedure may vary due to geographical features, weather

conditions, and the complexity of the ATC system. To

determine the most effective means of receiving an IFR

clearance, pilots should ask the nearest FSS the most

appropriate means of obtaining the IFR clearance.

2. When requesting an IFR clearance, it is highly

recommended that the departure airport be identified by

stating the city name and state and/or the airport location

identifier in order to clarify to ATC the exact location of the

intended airport of departure.

2. When filing an IFR flight plan, include as a

prefix to the aircraft type, the number of aircraft when

more than one and/or heavy aircraft indicator “H/” if

appropriate.

EXAMPLE−

H/DC10/A

2/F15/A
AIM 7/26/12

5−1−12 Preflight

3. When filing an IFR flight plan, identify the

equipment capability by adding a suffix, preceded by

a slant, to the AIRCRAFT TYPE, as shown in

TBL 5−1−2, Aircraft Suffixes.

NOTE−

1. ATC issues clearances based on filed suffixes. Pilots

should determine the appropriate suffix based upon

desired services and/or routing. For example, if a desired

route/procedure requires GPS, a pilot should file /G even

if the aircraft also qualifies for other suffixes.

2. For procedures requiring GPS, if the navigation system

does not automatically alert the flight crew of a loss of GPS,

the operator must develop procedures to verify correct GPS

operation.

3. The suffix is not to be added to the aircraft identification

or be transmitted by radio as part of the aircraft

identification.

4. It is recommended that pilots file the

maximum transponder or navigation capability of

their aircraft in the equipment suffix. This will

provide ATC with the necessary information to utilize

all facets of navigational equipment and transponder

capabilities available.

5. When filing an IFR flight plan via telephone

or radio, it is highly recommended that the departure

airport be clearly identified by stating the city name

and state and/or airport location identifier. With cell

phone use and flight service specialists covering

larger areas of the country, clearly identifying the

departure airport can prevent confusing your airport

of departure with those of identical or similar names

in other states.
7/26/12 AIM

Preflight 5−1−13

TBL 5−1−2

Aircraft Suffixes

Suffix Equipment Capability

NO DME

/X No transponder

/T Transponder with no Mode C

/U Transponder with Mode C

DME

/D No transponder

/B Transponder with no Mode C

/A Transponder with Mode C

TACAN ONLY

/M No transponder

/N Transponder with no Mode C

/P Transponder with Mode C

AREA NAVIGATION (RNAV)

/Y VOR/DME, or INS with no transponder

/C VOR/DME, or INS, transponder with no Mode C

/I VOR/DME, or INS, transponder with Mode C

ADVANCED RNAV WITH TRANSPONDER AND MODE C (If an aircraft is unable to operate with a

transponder and/or Mode C, it will revert to the appropriate code listed above under Area Navigation.)

/E Flight Management System (FMS) with DME/DME and IRU position updating

/F FMS with DME/DME position updating

/G Global Navigation Satellite System (GNSS), including GPS or Wide Area Augmentation System (WAAS), with

en route and terminal capability.

/R Required Navigational Performance (RNP). The aircraft meets the RNP type prescribed for the route segment(s),

route(s) and/or area concerned.

REDUCED VERTICAL SEPARATION MINIMUM (RVSM). Prior to conducting RVSM operations within the

U.S., the operator must obtain authorization from the FAA or from the responsible authority, as appropriate.

/J /E with RVSM

/K /F with RVSM

/L /G with RVSM

/Q /R with RVSM

/W RVSM
AIM 7/26/12

5−1−14 Preflight

b. Airways and Jet Routes Depiction on Flight

Plan

1. It is vitally important that the route of flight

be accurately and completely described in the flight

plan. To simplify definition of the proposed route,

and to facilitate ATC, pilots are requested to file via

airways or jet routes established for use at the altitude

or flight level planned.

2. If flight is to be conducted via designated

airways or jet routes, describe the route by indicating

the type and number designators of the airway(s) or

jet route(s) requested. If more than one airway or jet

route is to be used, clearly indicate points of

transition. If the transition is made at an unnamed

intersection, show the next succeeding NAVAID or

named intersection on the intended route and the

complete route from that point. Reporting points may

be identified by using authorized name/code as

depicted on appropriate aeronautical charts. The

following two examples illustrate the need to specify

the transition point when two routes share more than

one transition fix.

EXAMPLE−

1. ALB J37 BUMPY J14 BHM

Spelled out: from Albany, New York, via Jet Route 37

transitioning to Jet Route 14 at BUMPY intersection,

thence via Jet Route 14 to Birmingham, Alabama.

2. ALB J37 ENO J14 BHM

Spelled out: from Albany, New York, via Jet Route 37

transitioning to Jet Route 14 at Smyrna VORTAC (ENO)

thence via Jet Route 14 to Birmingham, Alabama.

3. The route of flight may also be described by

naming the reporting points or NAVAIDs over which

the flight will pass, provided the points named are

established for use at the altitude or flight level

planned.

EXAMPLE−

BWI V44 SWANN V433 DQO

Spelled out: from Baltimore-Washington International, via

Victor 44 to Swann intersection, transitioning to Victor 433

at Swann, thence via Victor 433 to Dupont.

4. When the route of flight is defined by named

reporting points, whether alone or in combination

with airways or jet routes, and the navigational aids

(VOR, VORTAC, TACAN, NDB) to be used for the

flight are a combination of different types of aids,

enough information should be included to clearly

indicate the route requested.

EXAMPLE−

LAX J5 LKV J3 GEG YXC FL 330 J500 VLR J515 YWG

Spelled out: from Los Angeles International via Jet Route 5

Lakeview, Jet Route 3 Spokane, direct Cranbrook, British

Columbia VOR/DME, Flight Level 330 Jet Route 500 to

Langruth, Manitoba VORTAC, Jet Route 515 to Winnepeg,

Manitoba.

5. When filing IFR, it is to the pilot’s advantage

to file a preferred route.

REFERENCE−

Preferred IFR Routes are described and tabulated in the Airport/Facility

Directory.

6. ATC may issue a SID or a STAR, as

appropriate.

REFERENCE−

AIM, Instrument Departure Procedures (DP) − Obstacle Departure

Procedures (ODP) and Standard Instrument Departures (SID),

Paragraph 5−2−8.

AIM, Standard Terminal Arrival (STAR), Area Navigation (RNAV) STAR,

and Flight Management System Procedures (FMSP) for Arrivals,

Paragraph 5−4−1.

NOTE−

Pilots not desiring a SID or STAR should so indicate in the

remarks section of the flight plan as “no SID” or “no

STAR.”

c. Direct Flights

1. All or any portions of the route which will not

be flown on the radials or courses of established

airways or routes, such as direct route flights, must be

defined by indicating the radio fixes over which the

flight will pass. Fixes selected to define the route

must be those over which the position of the aircraft

can be accurately determined. Such fixes automatically become compulsory reporting points for the

flight, unless advised otherwise by ATC. Only those

navigational aids established for use in a particular

structure; i.e., in the low or high structures, may be

used to define the en route phase of a direct flight

within that altitude structure.

2. The azimuth feature of VOR aids and that

azimuth and distance (DME) features of VORTAC

and TACAN aids are assigned certain frequency

protected areas of airspace which are intended for

application to established airway and route use, and

to provide guidance for planning flights outside of

established airways or routes. These areas of airspace

are expressed in terms of cylindrical service volumes

of specified dimensions called “class limits” or

“categories.”

REFERENCE−

AIM, Navigational Aid (NAVAID) Service Volumes, Paragraph 1−1−8.
7/26/12 AIM

Preflight 5−1−15

3. An operational service volume has been

established for each class in which adequate signal

coverage and frequency protection can be assured. To

facilitate use of VOR, VORTAC, or TACAN aids,

consistent with their operational service volume

limits, pilot use of such aids for defining a direct route

of flight in controlled airspace should not exceed the

following:

(a) Operations above FL 450 − Use aids not

more than 200 NM apart. These aids are depicted on

enroute high altitude charts.

(b) Operation off established routes from

18,000 feet MSL to FL 450 − Use aids not more than

260 NM apart. These aids are depicted on enroute

high altitude charts.

(c) Operation off established airways below

18,000 feet MSL − Use aids not more than 80 NM

apart. These aids are depicted on enroute low altitude

charts.

(d) Operation off established airways between 14,500 feet MSL and 17,999 feet MSL in the

conterminous U.S. − (H) facilities not more than

200 NM apart may be used.

4. Increasing use of self-contained airborne

navigational systems which do not rely on the

VOR/VORTAC/TACAN system has resulted in pilot

requests for direct routes which exceed NAVAID

service volume limits. These direct route requests

will be approved only in a radar environment, with

approval based on pilot responsibility for navigation

on the authorized direct route. Radar flight following

will be provided by ATC for ATC purposes.

5. At times, ATC will initiate a direct route in a

radar environment which exceeds NAVAID service

volume limits. In such cases ATC will provide radar

monitoring and navigational assistance as necessary.

6. Airway or jet route numbers, appropriate to

the stratum in which operation will be conducted,

may also be included to describe portions of the route

to be flown.

EXAMPLE−

MDW V262 BDF V10 BRL STJ SLN GCK

Spelled out: from Chicago Midway Airport via Victor 262

to Bradford, Victor 10 to Burlington, Iowa, direct

St. Joseph, Missouri, direct Salina, Kansas, direct

Garden City, Kansas.

NOTE−

When route of flight is described by radio fixes, the pilot

will be expected to fly a direct course between the points

named.

7. Pilots are reminded that they are responsible

for adhering to obstruction clearance requirements on

those segments of direct routes that are outside of

controlled airspace. The MEAs and other altitudes

shown on low altitude IFR enroute charts pertain to

those route segments within controlled airspace, and

those altitudes may not meet obstruction clearance

criteria when operating off those routes.

d. Area Navigation (RNAV)

1. Random RNAV routes can only be approved

in a radar environment. Factors that will be

considered by ATC in approving random RNAV

routes include the capability to provide radar

monitoring and compatibility with traffic volume and

flow. ATC will radar monitor each flight, however,

navigation on the random RNAV route is the

responsibility of the pilot.

2. Pilots of aircraft equipped with approved area

navigation equipment may file for RNAV routes

throughout the National Airspace System and may be

filed for in accordance with the following procedures.

(a) File airport-to-airport flight plans.

(b) File the appropriate RNAV capability

certification suffix in the flight plan.

(c) Plan the random route portion of the flight

plan to begin and end over appropriate arrival and

departure transition fixes or appropriate navigation

aids for the altitude stratum within which the flight

will be conducted. The use of normal preferred

departure and arrival routes (DP/STAR), where

established, is recommended.

(d) File route structure transitions to and from

the random route portion of the flight.

(e) Define the random route by waypoints.

File route description waypoints by using degreedistance fixes based on navigational aids which are

appropriate for the altitude stratum.

(f) File a minimum of one route description

waypoint for each ARTCC through whose area the

random route will be flown. These waypoints must be

located within 200 NM of the preceding center’s

boundary.

(g) File an additional route description

waypoint for each turnpoint in the route.
AIM 7/26/12

5−1−16 Preflight

(h) Plan additional route description waypoints as required to ensure accurate navigation via

the filed route of flight. Navigation is the pilot’s

responsibility unless ATC assistance is requested.

(i) Plan the route of flight so as to avoid

prohibited and restricted airspace by 3 NM unless

permission has been obtained to operate in that

airspace and the appropriate ATC facilities are

advised.

NOTE−

To be approved for use in the National Airspace System,

RNAV equipment must meet the appropriate system

availability, accuracy, and airworthiness standards. For

additional guidance on equipment requirements see

AC 20−130, Airworthiness Approval of Vertical Navigation (VNAV) Systems for use in the U.S. NAS and Alaska,

or AC 20−138, Airworthiness Approval of Global

Positioning System (GPS) Navigation Equipment for Use

as a VFR and IFR Supplemental Navigation System. For

airborne navigation database, see AC 90−94, Guidelines

for Using GPS Equipment for IFR En Route and Terminal

Operations and for Nonprecision Instrument Approaches

in the U.S. National Airspace System, Section 2.

3. Pilots of aircraft equipped with latitude/

longitude coordinate navigation capability,

independent of VOR/TACAN references, may file

for random RNAV routes at and above FL 390 within

the conterminous U.S. using the following

procedures.

(a) File airport-to-airport flight plans prior to

departure.

(b) File the appropriate RNAV capability

certification suffix in the flight plan.

(c) Plan the random route portion of the flight

to begin and end over published departure/arrival

transition fixes or appropriate navigation aids for

airports without published transition procedures. The

use of preferred departure and arrival routes, such as

DP and STAR where established, is recommended.

(d) Plan the route of flight so as to avoid

prohibited and restricted airspace by 3 NM unless

permission has been obtained to operate in that

airspace and the appropriate ATC facility is advised.

(e) Define the route of flight after the

departure fix, including each intermediate fix

(turnpoint) and the arrival fix for the destination

airport in terms of latitude/longitude coordinates

plotted to the nearest minute or in terms of Navigation

Reference System (NRS) waypoints. For latitude/

longitude filing the arrival fix must be identified by

both the latitude/longitude coordinates and a fix

identifier.

EXAMPLE−

MIA1 SRQ2 3407/106153 3407/11546 TNP4 LAX 5

1Departure airport.

2Departure fix.

3 Intermediate fix (turning point).

4Arrival fix.

5Destination airport.

 or

ORD1 IOW2 KP49G3 KD34U4 KL16O5 OAL6 MOD27

SFO8

1 Departure airport.

2 Transition fix (pitch point).

3 Minneapolis ARTCC waypoint.

4 Denver ARTCC Waypoint.

5 Los Angeles ARTCC waypoint (catch point).

6 Transition fix.

7 Arrival. 

8 Destination airport.

(f) Record latitude/longitude coordinates by

four figures describing latitude in degrees and

minutes followed by a solidus and five figures

describing longitude in degrees and minutes.

(g) File at FL 390 or above for the random

RNAV portion of the flight.

(h) Fly all routes/route segments on Great

Circle tracks.

(i) Make any inflight requests for random

RNAV clearances or route amendments to an en route

ATC facility.

e. Flight Plan Form− See FIG 5−1−2.

f. Explanation of IFR Flight Plan Items.

1. Block 1. Check the type flight plan. Check

both the VFR and IFR blocks if composite VFR/IFR.

2. Block 2. Enter your complete aircraft

identification including the prefix “N” if applicable.

3. Block 3. Enter the designator for the aircraft,

followed by a slant(/), and the transponder or DME

equipment code letter; e.g., C−182/U. Heavy aircraft,

add prefix “H” to aircraft type; example: H/DC10/U.

Consult an FSS briefer for any unknown elements.
7/26/12 AIM

Preflight 5−1−17

FIG 5−1−2

FAA Flight Plan

Form 7233−1 (8−82)

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION (FAA USE ONLY) (FAA USE ONLY) PILOT BRIEFING PILOT BRIEFING VNR

STOPOVER STOPOVER

TIME STARTED TIME STARTED SPECIALIST

INITIALS

SPECIALIST

INITIALS

1. TYPE 1. TYPE

VFR

IFR

DVFR

3. AIRCRAFT TYPE/

SPECIAL EQUIPMENT

3. AIRCRAFT TYPE/

SPECIAL EQUIPMENT

5. DEPARTURE POINT 5. DEPARTURE POINT 6. DEPARTURE TIME 6. DEPARTURE TIME

PROPOSED (Z) PROPOSED (Z) ACTUAL (Z) ACTUAL (Z)

7. CRUISING

ALTITUDE

7. CRUISING

ALTITUDE

8. ROUTE OF FLIGHT 8. ROUTE OF FLIGHT

KTS

9. DESTINATION (Name of airport

and city)

9. DESTINATION (Name of airport

and city)

10. EST. TIME ENROUTE 10. EST. TIME ENROUTE

HOURS

HOURS

MINUTES MINUTES

MINUTES MINUTES

11. REMARKS 11. REMARKS

12. FUEL ON BOARD 12. FUEL ON BOARD 13. ALTERNATE AIRPORT(S) 13. ALTERNATE AIRPORT(S) 14. PILOT’S NAME, ADDRESS & TELEPHONE NUMBER & AIRCRAFT HOME BASE 14. PILOT’S NAME, ADDRESS & TELEPHONE NUMBER & AIRCRAFT HOME BASE 15. NUMBER

ABOARD

15. NUMBER

ABOARD

17. DESTINATION CONTACT/TELEPHONE (OPTIONAL) 17. DESTINATION CONTACT/TELEPHONE (OPTIONAL)

16. COLOR OF AIRCRAFT 16. COLOR OF AIRCRAFT

FAA Form 7233-1 FAA Form 7233-1 (8-82) CLOSE VFR FLIGHT PLAN WITH _________________ FSS ON ARRIVAL CLOSE VFR FLIGHT PLAN WITH _________________ FSS ON ARRIVAL

FLIGHT PLAN FLIGHT PLAN

CIVIL AIRCRAFT PILOTS, FAR 91 requires you file an IFR flight plan to operate under instrument flight rules in

controlled airspace. Failure to file could result in a civil penalty not to exceed $1,000 for each violation (Section 901 of the

Federal Aviation Act of 1958, as amended). Filing of a VFR flight plan is recommended as a good operating practice. See also

Part 99 for requirements concerning DVFR flight plans.

2. AIRCRAFT

IDENTIFICATION

2. AIRCRAFT

IDENTIFICATION

4. TRUE

AIRSPEED

4. TRUE

AIRSPEED

4. Block 4. Enter your computed true airspeed

(TAS).

NOTE−

If the average TAS changes plus or minus 5 percent or

10 knots, whichever is greater, advise ATC.

5. Block 5. Enter the departure airport identifier code (or the airport name, city and state, if the

identifier is unknown).

NOTE−

Use of identifier codes will expedite the processing of your

flight plan.

6. Block 6. Enter the proposed departure time in

Coordinated Universal Time (UTC) (Z). If airborne,

specify the actual or proposed departure time as

appropriate.

7. Block 7. Enter the requested en route altitude

or flight level.

NOTE−

Enter only the initial requested altitude in this block. When

more than one IFR altitude or flight level is desired along

the route of flight, it is best to make a subsequent request

direct to the controller.

8. Block 8. Define the route of flight by using

NAVAID identifier codes (or names if the code is

unknown), airways, jet routes, and waypoints (for

RNAV).

NOTE−

Use NAVAIDs or waypoints to define direct routes and

radials/bearings to define other unpublished routes.

9. Block 9. Enter the destination airport

identifier code (or name if the identifier is unknown).

10. Block 10. Enter your estimated time en

route based on latest forecast winds.
AIM 7/26/12

5−1−18 Preflight

11. Block 11. Enter only those remarks pertinent to ATC or to the clarification of other flight plan

information, such as the appropriate radiotelephony

(call sign) associated with the FAA-assigned

three-letter company designator filed in Block 2, if

the radiotelephony is new or has changed within the

last 60 days. In cases where there is no three-letter

designator but only an assigned radiotelephony or an

assigned three-letter designator is used in a medical

emergency, the radiotelephony must be included in

the remarks field. Items of a personal nature are not

accepted.

NOTE−

1. The pilot is responsible for knowing when it is

appropriate to file the radiotelephony in remarks under the

60-day rule or when using FAA special radiotelephony

assignments.

2. “DVRSN” should be placed in Block 11 only if the

pilot/company is requesting priority handling to their

original destination from ATC as a result of a diversion as

defined in the Pilot/Controller Glossary.

3. Do not assume that remarks will be automatically

transmitted to every controller. Specific ATC or en route

requests should be made directly to the appropriate

controller.

12. Block 12. Specify the fuel on board,

computed from the departure point.

13. Block 13. Specify an alternate airport if

desired or required, but do not include routing to the

alternate airport.

14. Block 14. Enter the complete name,

address, and telephone number of pilot-in-command,

or in the case of a formation flight, the formation

commander. Enter sufficient information to identify

home base, airport, or operator.

NOTE−

This information would be essential in the event of search

and rescue operation.

15. Block 15. Enter the total number of persons

on board including crew.

16. Block 16. Enter the predominant colors.

NOTE−

Close IFR flight plans with tower, approach control, or

ARTCC, or if unable, with FSS. When landing at an airport

with a functioning control tower, IFR flight plans are

automatically canceled.

g. The information transmitted to the ARTCC for

IFR flight plans will consist of only flight plan

blocks 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

h. A description of the International Flight Plan

Form is contained in the International Flight

Information Manual (IFIM).

5−1−9. International Flight Plan (FAA Form

7233−4)− IFR Flights (For Domestic or

International Flights)

a. General

Use of FAA Form 7233−4 is recommended for

domestic IFR flights and is mandatory for all IFR

flights that will depart U.S. domestic airspace.

NOTE−

1. An abbreviated description of FAA Form 7233−4

(International Flight Plan) may be found in this section. A

detailed description of FAA Form 7233−4 may be found on

the FAA website at:

http://www.faa.gov/about/office_org/

headquarters_offices/ato/service_units/enroute/flight_pl

an_filing/

2. Filers utilizing FAA Form 7233−1 (Flight Plan) may not

be eligible for assignment of RNAV SIDs and STARs. Filers

desiring assignment of these procedures should file using

FAA Form 7233−4, as described in this section.

3. When filing an IFR flight plan using FAA Form 7233−4,

it is recommended that filers include all operable

navigation, communication, and surveillance equipment

capabilities by adding appropriate equipment qualifiers as

shown in Tables 5−1−3 and 5−1−4. These equipment

qualifiers should be filed in Item 10 of FAA Form 7233−4.

4. ATC issues clearances based on equipment qualifiers

filed in Items 10 and aircraft capabilities filed in Item 18

(NAV/) of FAA Form 7233−4. Operators should file all

equipment qualifiers for which the aircraft is certified and

capable. They should also file aircraft capabilities,

following the NAV/ indicator in Item 18.

b. Explanation of Items Filed in FAA Form

7233−4

Procedures and other information provided in this

section are designed to assist operators using FAA

Form 7233−4 to file IFR flight plans for flights that

will be conducted entirely within U.S. domestic

airspace. Requirements and procedures for operating

outside U.S. domestic airspace may vary significantly from country to country. It is, therefore,

recommended that operators planning flights outside U.S. domestic airspace become familiar with
7/26/12 AIM

Preflight 5−1−19

applicable international documents, including

Aeronautical Information Publications (AIP); International Flight Information Manuals (IFIM); and

ICAO Document 4444, Procedures for Air Navigation Services/Air Traffic Management, Appendix 2.

NOTE−

FAA Form 7233−4 is shown in FIG 5−1−3. The filer is

normally responsible for providing the information

required in Items 3 through 19.
AIM 7/26/12

5−1−20 Preflight

FIG 5−1−3

FAA International Flight Plan Form 7233−4 (9−06)
7/26/12 AIM

Preflight 5−1−21
AIM 7/26/12

5−1−22 Preflight

1. Item 7. Aircraft Identification. Insert the

full registration number of the aircraft, or the

approved FAA/ICAO company or organizational

designator, followed by the flight number.

EXAMPLE−

N235RA, AAL3342, BONGO33

NOTE−

Callsigns filed in this item must begin with a letter followed

by 1−6 additional alphanumeric characters.

2. Item 8. Flight Rules and Type of Flight.

(a) Flight Rules. Insert the character “I” to

indicate IFR

(b) Type of Flight. Insert one of the

following letters to denote the type of flight:

(1) S if scheduled air service

(2) N if non−scheduled air transport

operation

(3) G if general aviation

(4) M if military

(5) X if other than any of the defined

categories above.

NOTE−

Type of flight is optional for flights that will be conducted

entirely within U.S. domestic airspace.

3. Item 9. Number, Type of Aircraft, and

Wake Turbulence Category.

(a) Number. Insert the number of aircraft, if

more than 1 (maximum 99).

(b) Type of Aircraft.

(1) Insert the appropriate designator as

specified in ICAO Doc 8643, Aircraft Type

Designators;

(2) Or, if no such designator has been

assigned, or in the case of formation flights consisting

of more than one type;

(3) Insert ZZZZ, and specify in Item 18, the

(numbers and) type(s) of aircraft preceded by TYP/.

(c) Wake Turbulence Category. Insert an

oblique stroke followed by one of the following

letters to indicate the wake turbulence category of

the aircraft:

(1) H — HEAVY, to indicate an aircraft

type with a maximum certificated takeoff weight of

300,000 pounds (136 000 kg), or more;

(2) M — MEDIUM, to indicate an aircraft

type with a maximum certificated takeoff weight of

less than 300,000 pounds (136,000 kg), but more than

15,500 pounds (7,000 kg);

(3) L — LIGHT, to indicate an aircraft type

with a maximum certificated takeoff weight of

15,500 pounds (7,000 kg) or less.

4. Item 10. Equipment
7/26/12 AIM

Preflight 5−1−23

TBL 5−1−3

Aircraft COM, NAV, and Approach Equipment Qualifiers

INSERT one letter as follows:

N if no COM/NAV/approach aid equipment for the route to be flown is carried, or the equipment 

is unserviceable,

(OR) 

S if standard COM/NAV/approach aid equipment for the route to be flown is carried and 

serviceable (see Note 1),

(AND/OR)

INSERT one or more of the following letters to indicate the COM/NAV/approach aid equipment available 

and serviceable:

A (Not allocated) O VOR

B (Not allocated) P (Not allocated)

D DME Q (Not allocated)

E (Not allocated) R RNP type certification − see Note 5

F ADF T TACAN

G (GNSS) U UHF RTF

H HF RTF V VHF RTF

I Inertial navigation W RVSM Certififed

J (Data link) − see Note 3 X When prescribed by ATS

K (MLS) Y When prescribed by ATS

L ILS Z Other equipment carried − see Note 2

NOTE−

1. Standard equipment is considered to be VHF RTF, ADF, VOR, and ILS within U.S. domestic airspace.

2. If the letter Z is used, specify in Item 18 the other equipment carried, preceded by COM/ and/or NAV/, as appropriate.

3. If the letter J is used, specify in Item 18 the equipment carried, preceded by DAT/ followed by one or more letters as

appropriate.

4. Information on navigation capability is provided to ATC for clearance and routing purposes.

5. Inclusion of letter R indicates that an aircraft meets the RNP type prescribed for the route segment(s), route(s), and/or

area concerned.
AIM 7/26/12

5−1−24 Preflight

TBL 5−1−4

Aircraft Surveillance Equipment

INSERT one or two of the following letters to describe the serviceable surveillance equipment carried:

N Nil

A Transponder — Mode A (4 digits — 4 096 codes)

C Transponder — Mode A (4 digits — 4 096 codes) and Mode C

X Transponder — Mode S without both aircraft identification and pressure−altitude transmission

P Transponder — Mode S, including pressure−altitude transmission, but no aircraft identification transmission

I Transponder — Mode S, including aircraft identification transmission, but no pressure−altitude transmission

S Transponder — Mode S, including both pressure−altitude and aircraft identification transmission

ADS equipment

D ADS capability

EXAMPLE−

1. OFLV/C {VOR, ADF, ILS, VHF, Transponder, Mode C}

2. S/C {VOR, ADF, ILS, VHF, Transponder, Mode C}

3. OLVDGWZ/S {VOR, ILS, VHF, DME, GPS, RVSM,

Other, Mode S w/ altitude reporting}

NOTE−

The equipment qualifier Z indicates that additional

equipment or capability information can be found in Item

18, following the NAV/ indicator. Operators requesting

assignment of RNAV SIDs and/or STARs are required to

include a Z in Item 10 and associated RNAV capabilities in

Item 18 following the NAV/ indicator.

5. Item 13. Departure Aerodrome/Time

(a) Insert the ICAO four−letter location

indicator of the departure aerodrome, or

NOTE−

ICAO location indicators must consist of 4 letters. Airport

identifiers such as 5IA7, 39LL and Z40 are not in ICAO

standard format.

(b) If no four−letter location indicator has

been assigned to the departure aerodrome, insert

ZZZZ and specify the non−ICAO location identifier,

or fix/radial/distance from a nearby navaid, followed

by the name of the aerodrome, in Item 18, following

characters DEP/,

(c) Then, without a space, insert the estimated

off−block time.

EXAMPLE−

1. KSMF2215

2. ZZZZ0330

6. Item 15. Cruise Speed, Level and Route

(a) Cruise Speed (maximum 5 characters).

Insert the true airspeed for the first or the whole

cruising portion of the flight, in terms of knots,

expressed as N followed by 4 digits (e.g. N0485), or

Mach number to the nearest hundredth of unit Mach,

expressed as M followed by 3 digits (for example,

M082).

(b) Cruising level (maximum 5 characters).

Insert the planned cruising level for the first or the

whole portion of the route to be flown, in terms of

flight level, expressed as F followed by 3 figures (for

example, F180; F330), or altitude in hundreds of feet,

expressed as A followed by 3 figures (for example,

A040; A170).

(c) Route. Insert the requested route of flight

in accordance with guidance below.

NOTE−

Speed and/or altitude changes en route will be accepted by

FAA computer systems, but will not be processed or

forwarded to controllers. Pilots are expected to maintain

the last assigned altitude and request revised altitude

clearances directly from ATC.

(d) Insert the desired route of flight using a

combination of published routes and/or fixes in the

following formats:
7/26/12 AIM

Preflight 5−1−25

(1) Consecutive fixes, navaids and waypoints should be separated by the characters “DCT”,

meaning direct.

EXAMPLE−

FLACK DCT IRW DCT IRW125023

NOTE−

IRW125023 identifies the fix located on the Will Rogers

VORTAC 125 radial at 23 DME.

(2) Combinations of published routes, and

fixes, navaids or waypoints should be separated by a

single space.

EXAMPLE−

WORTH5 MQP V66 ABI V385

(3) Although it is recommended that filed

airway junctions be identified using a named junction

fix when possible, there may be cases where it is

necessary to file junctioning airways without a named

fix. In these cases, separate consecutive airways with

a space.

EXAMPLE−

V325 V49

NOTE−

This method of filing an airway junction may result in a

processing ambiguity. This might cause the flight plan to be

rejected in some cases.

7. Item 16. Destination Aerodrome, Total

EET, Alternate and 2nd Alternate Aerodrome

(a) Destination Aerodrome and Total Estimated Elapsed Time (EET).

(1) Insert the ICAO four−letter location

identifier for the destination aerodrome; or, if no

ICAO location identifier has been assigned,

(Location identifiers, such as WY66, A08, and 5B1,

are not an ICAO standard format),

(2) Insert ZZZZ and specify the non−ICAO

location identifier, or fix/radial/distance from a

nearby navaid, followed the name of the aerodrome,

in Item 18, following characters DEST/,

(3) Then, without a space, insert the total

estimated time en route to the destination.

EXAMPLE−

1. KOKC0200

2. ZZZZ0330

(b) Alternate and 2nd Alternate Aerodrome

(Optional).

(1) Following the intended destination,

insert the ICAO four−letter location identifier(s) of

alternate aerodromes; or, if no location identifier(s)

have been assigned;

(2) Insert ZZZZ and specify the name of the

aerodrome in Item 18, following the characters

ALTN/.

EXAMPLE−

1. KDFW0234 KPWA

2. KBOS0304 ZZZZ

NOTE−

Although alternate airport information filed in an FPL will

be accepted by air traffic computer systems, it will not be

presented to controllers. If diversion to an alternate airport

becomes necessary, pilots are expected to notify ATC and

request an amended clearance.

8. Item 18. Other Information

(a) Insert 0 (zero) if no other information; or,

any other necessary information in the preferred

sequence shown hereunder, in the form of the

appropriate indicator followed by an oblique stroke

and the information to be recorded:

(1) EET/ Significant points or FIR boundary designators and accumulated estimated elapsed

times to such points or FIR boundaries.

EXAMPLE−

EET/KZLA0745 KZAB0830

(2) REG/ The registration markings of the

aircraft, if different from the aircraft identification in

Item 7.

(3) CODE/ Aircraft address (expressed in

the form of an alphanumerical code of six

hexadecimal characters) when required by the

appropriate ATS authority.

EXAMPLE−

“F00001” is the lowest aircraft address contained in the

specific block administered by ICAO.

(4) SEL/ SELCAL code.

(5) OPR/ Name of the operator, if not

obvious from the aircraft identification in Item 7.

(6) STS/ Reason for special handling by

ATS.

EXAMPLE−

STS/HOSP

(7) TYP/ Insert the type of aircraft if ZZZZ

was entered in Item 9. If necessary, insert the number

and type(s) of aircraft in a formation.
AIM 7/26/12

5−1−26 Preflight

EXAMPLE−

1. TYP/Homebuilt

2. TYP/2 P51 B17 B24

(8) COM/ Significant data related to communication.

(9) NAV/ Significant data related to navigation equipment.

(b) In addition to filing appropriate equipment qualifiers in Item10, operators requesting

assignment of RNAV departure and/or arrival

procedures should file appropriate RNAV capabilities for each segment of flight, following the NAV/

indicator.

NOTE−

Aircraft certification requirements for RNAV operations

within U.S. airspace are defined in Advisory Circular AC

90−45A, Approval of Area Navigation Systems for Use in

the U.S. National Airspace System, and AC 90−100A, U.S.

Terminal and En Route Area Navigation (RNAV)

Operations, as amended.

(c) Operators should file their maximum

capabilities in order to qualify for the most advanced

procedures.

EXAMPLE−

1. NAV/RNVD1E2A1, or

2. NAV/RNVE99

(d) Explanation:

(1) NAV/ = Indicates the beginning of

additional navigation information.

(2) RNV = Precedes RNAV capability for

each phase of flight.

(3) D# = Departure segment RNAV

capability.

(4) E# = En route segment RNAV capability.

(5) A# = Arrival segment RNAV capability.

NOTE−

In the examples above, “#” indicates the numeric RNAV

accuracy values, based on aircraft certification and

capabilities.

(e) Follow each flight segment indicator with

appropriate numeric RNAV accuracy values as

defined in the Advisory Circulars below.

(f) Operators equipped for advanced RNAV

procedures in accordance with AC 90−100A, may

file any or all of the following, as appropriate:

EXAMPLE−

NAV/RNVD1E2A1

(g) Operators equipped for Point−to−Point

(PTP) RNAV only, in accordance with AC 90−45A,

should file the en route segment only, with a value of

“E99”.

EXAMPLE−

NAV/RNVE99

NOTE−

Operators filing FAA Form 7233−4 may suppress

application of RNAV procedures by omitting, or filing a 0

(zero) value in Item 18 data for any or all segments of flight.

(h) DEP/ Insert the non−ICAO identifier, or

fix/radial/distance from navaid, followed by the

name of the departure aerodrome, if ZZZZ is inserted

in Item 13.

EXAMPLE−

1. DEP/T23 ALBANY MUNI

2. DEP/UKW197011 TICK HOLLR RANCH

(i) DEST/ Name of destination aerodrome, if

ZZZZ is inserted in Item 16.

EXAMPLE−

1. DEST/T23 ALBANY MUNI

2. DEST/PIE335033 LEXI DUNES

(j) ALTN/ Name of destination alternate

aerodrome(s), if ZZZZ is inserted in Item 16.

EXAMPLE−

1. ALTN/F35 POSSUM KINGDOM

2. ALTN/TCC233016 LAZY S RANCH

(k) RMK/ Any other plain−language remarks when required by the ATC or deemed

necessary.

EXAMPLE−

1. RMK/LIFEGUARD

2. RMK/DRVSN
7/26/12 AIM

Preflight 5−1−27

9. Item 19. Supplementary Information

NOTE−

Item 19 data must be included when completing FAA Form

7233−4. This information will be retained by the

facility/organization that transmits the flight plan to Air

Traffic Control (ATC), for Search and Rescue purposes, but

it will not be transmitted to ATC as part of the FPL.

(a) E/ (ENDURANCE). Insert 4−digits group

giving the fuel endurance in hours and minutes.

(b) P/ (PERSONS ON BOARD). Insert the

total number of persons (passengers and crew) on

board.

(c) Emergency and survival equipment

(1) R/ (RADIO).

[a] Cross out “UHF” if frequency 243.0

MHz is not available.

[b] Cross out “VHF” frequency 121.5

MHz is not available.

[c] Cross out “ELBA” if emergency

locator transmitter (ELT) is not available.

(2) S/ (SURVIVAL EQUIPMENT).

[a] Cross out “POLAR” if polar survival

equipment is not carried.

[b] Cross out “DESERT” if desert

survival equipment is not carried.

[c] Cross out “MARITIME” if maritime

survival equipment is not carried.

[d] Cross out J if “JUNGLE” survival

equipment is not carried.

(3) J/ (JACKETS).

[a] Cross out “LIGHT” if life jackets are

not equipped with lights.

[b] Cross out “FLUORES” if life jackets

are not equipped with fluorescein.

[c] Cross out “UHF” or “VHF” or both as

in R/ above to indicate radio capability of jackets, if

any.

(4) D/ (DINGHIES).

[a] NUMBER. Cross out indicators

“NUMBER” and “CAPACITY” if no dinghies are

carried, or insert number of dinghies carried; and

[b] CAPACITY. Insert total capacity, in

persons, of all dinghies carried; and

[c] COVER. Cross out indicator

“COVER” if dinghies are not covered; and

[d] COLOR. Insert color of dinghies if

carried.

(5) A/ (AIRCRAFT COLOR AND

MARKINGS). Insert color of aircraft and significant

markings.

(6) N/ (REMARKS). Cross out indicator N

if no remarks, or indicate any other survival

equipment carried and any other remarks regarding

survival equipment.

(7) C/ (PILOT). Insert name of pilot−in−

command.

5−1−10. IFR Operations to High Altitude

Destinations

a. Pilots planning IFR flights to airports located in

mountainous terrain are cautioned to consider the

necessity for an alternate airport even when the

forecast weather conditions would technically relieve

them from the requirement to file one.

REFERENCE−

14 CFR Section 91.167.

AIM, Tower En Route Control (TEC), Paragraph 4−1−19. 

b. The FAA has identified three possible situations

where the failure to plan for an alternate airport when

flying IFR to such a destination airport could result in

a critical situation if the weather is less than forecast

and sufficient fuel is not available to proceed to a

suitable airport.

1. An IFR flight to an airport where the

Minimum Descent Altitudes (MDAs) or landing

visibility minimums for all instrument approaches

are higher than the forecast weather minimums

specified in 14 CFR Section 91.167(b). For example,

there are 3 high altitude airports in the U.S. with

approved instrument approach procedures where all

of the MDAs are greater than 2,000 feet and/or the

landing visibility minimums are greater than 3 miles

(Bishop, California; South Lake Tahoe, California;

and Aspen−Pitkin Co./Sardy Field, Colorado). In the

case of these airports, it is possible for a pilot to elect,

on the basis of forecasts, not to carry sufficient fuel to

get to an alternate when the ceiling and/or visibility

is actually lower than that necessary to complete the

approach.
AIM 7/26/12

5−1−28 Preflight

2. A small number of other airports in

mountainous terrain have MDAs which are slightly

(100 to 300 feet) below 2,000 feet AGL. In situations

where there is an option as to whether to plan for an

alternate, pilots should bear in mind that just a slight

worsening of the weather conditions from those

forecast could place the airport below the published

IFR landing minimums.

3. An IFR flight to an airport which requires

special equipment; i.e., DME, glide slope, etc., in

order to make the available approaches to the lowest

minimums. Pilots should be aware that all other

minimums on the approach charts may require

weather conditions better than those specified in

14 CFR Section 91.167(b). An inflight equipment

malfunction could result in the inability to comply

with the published approach procedures or, again, in

the position of having the airport below the published

IFR landing minimums for all remaining instrument

approach alternatives.

5−1−11. Flights Outside the U.S. and U.S.

Territories

a. When conducting flights, particularly extended

flights, outside the U.S. and its territories, full

account should be taken of the amount and quality of

air navigation services available in the airspace to be

traversed. Every effort should be made to secure

information on the location and range of navigational

aids, availability of communications and meteorological services, the provision of air traffic services,

including alerting service, and the existence of search

and rescue services.

b. Pilots should remember that there is a need to

continuously guard the VHF emergency frequency

121.5 MHz when on long over-water flights, except

when communications on other VHF channels,

equipment limitations, or cockpit duties prevent

simultaneous guarding of two channels. Guarding of

121.5 MHz is particularly critical when operating in

proximity to Flight Information Region (FIR)

boundaries, for example, operations on Route R220

between Anchorage and Tokyo, since it serves to

facilitate communications with regard to aircraft

which may experience in-flight emergencies, communications, or navigational difficulties.

REFERENCE−

ICAO Annex 10, Vol II, Paras 5.2.2.1.1.1 and 5.2.2.1.1.2.

c. The filing of a flight plan, always good practice,

takes on added significance for extended flights

outside U.S. airspace and is, in fact, usually required

by the laws of the countries being visited or

overflown. It is also particularly important in the case

of such flights that pilots leave a complete itinerary

and schedule of the flight with someone directly

concerned and keep that person advised of the flight’s

progress. If serious doubt arises as to the safety of the

flight, that person should first contact the appropriate

FSS. Round Robin Flight Plans to Mexico are not

accepted.

d. All pilots should review the foreign airspace

and entry restrictions published in the IFIM during

the flight planning process. Foreign airspace

penetration without official authorization can involve

both danger to the aircraft and the imposition of

severe penalties and inconvenience to both passengers and crew. A flight plan on file with ATC

authorities does not necessarily constitute the prior

permission required by certain other authorities. The

possibility of fatal consequences cannot be ignored in

some areas of the world.

e. Current NOTAMs for foreign locations must

also be reviewed. The publication Notices to Airmen,

Domestic/International, published biweekly, contains considerable information pertinent to foreign

flight. Current foreign NOTAMs are also available

from the U.S. International NOTAM Office in

Washington, D.C., through any local FSS.

f. When customs notification is required, it is the

responsibility of the pilot to arrange for customs

notification in a timely manner. The following

guidelines are applicable:

1. When customs notification is required on

flights to Canada and Mexico and a predeparture

flight plan cannot be filed or an advise customs

message (ADCUS) cannot be included in a

predeparture flight plan, call the nearest en route

domestic or International FSS as soon as radio

communication can be established and file a VFR or

DVFR flight plan, as required, and include as the last

item the advise customs information. The station with

which such a flight plan is filed will forward it to the

appropriate FSS who will notify the customs office

responsible for the destination airport.

2. If the pilot fails to include ADCUS in the

radioed flight plan, it will be assumed that other
7/26/12 AIM

Preflight 5−1−29

arrangements have been made and FAA will not

advise customs.

3. The FAA assumes no responsibility for any

delays in advising customs if the flight plan is given

too late for delivery to customs before arrival of the

aircraft. It is still the pilot’s responsibility to give

timely notice even though a flight plan is given to

FAA.

4. Air Commerce Regulations of the Treasury

Department’s Customs Service require all private

aircraft arriving in the U.S. via:

(a) The U.S./Mexican border or the Pacific

Coast from a foreign place in the Western

Hemisphere south of 33 degrees north latitude and

between 97 degrees and 120 degrees west longitude;

or

(b) The Gulf of Mexico and Atlantic Coasts

from a foreign place in the Western Hemisphere south

of 30 degrees north latitude, must furnish a notice of

arrival to the Customs service at the nearest

designated airport. This notice may be furnished

directly to Customs by:

(1) Radio through the appropriate FAA

Flight Service Station.

(2) Normal FAA flight plan notification

procedures (a flight plan filed in Mexico does not

meet this requirement due to unreliable relay of data);

or

(3) Directly to the district Director of

Customs or other Customs officer at place of first

intended landing but must be furnished at least 1 hour

prior to crossing the U.S./Mexican border or the U.S.

coastline.

(c) This notice will be valid as long as actual

arrival is within 15 minutes of the original ETA,

otherwise a new notice must be given to Customs.

Notices will be accepted up to 23 hours in advance.

Unless an exemption has been granted by Customs,

private aircraft are required to make first landing in

the U.S. at one of the following designated airports

nearest to the point of border of coastline crossing:

Designated Airports

ARIZONA

Bisbee Douglas Intl Airport

Douglas Municipal Airport

Nogales Intl Airport

Tucson Intl Airport

Yuma MCAS−Yuma Intl Airport

CALIFORNIA

Calexico Intl Airport

Brown Field Municipal Airport (San Diego)

FLORIDA

Fort Lauderdale Executive Airport

Fort Lauderdale/Hollywood Intl Airport

Key West Intl Airport (Miami Intl Airport)

Opa Locka Airport (Miami)

Kendall−Tamiami Executive Airport (Miami)

St. Lucie County Intl Airport (Fort Pierce)

Tampa Intl Airport

Palm Beach Intl Airport (West Palm Beach)

LOUISANA

New Orleans Intl Airport (Moisant Field)

New Orleans Lakefront Airport

NEW MEXICO

Las Cruces Intl Airport

NORTH CAROLINA

New Hanover Intl Airport (Wilmington)

TEXAS

Brownsville/South Padre Island Intl Airport

Corpus Christi Intl Airport

Del Rio Intl Airport

Eagle Pass Municipal Airport

El Paso Intl Airport

William P. Hobby Airport (Houston)

Laredo Intl Airport

McAllen Miller Intl Airport

Presidio Lely Intl Airport

5−1−12. Change in Flight Plan

In addition to altitude or flight level, destination

and/or route changes, increasing or decreasing the

speed of an aircraft constitutes a change in a flight

plan. Therefore, at any time the average true airspeed

at cruising altitude between reporting points varies or

is expected to vary from that given in the flight plan

by plus or minus 5 percent, or 10 knots, whichever is

greater, ATC should be advised.
AIM 7/26/12

5−1−30 Preflight

5−1−13. Change in Proposed Departure

Time

a. To prevent computer saturation in the en route

environment, parameters have been established to

delete proposed departure flight plans which have not

been activated. Most centers have this parameter set

so as to delete these flight plans a minimum of 1 hour

after the proposed departure time. To ensure that a

flight plan remains active, pilots whose actual

departure time will be delayed 1 hour or more beyond

their filed departure time, are requested to notify ATC

of their departure time.

b. Due to traffic saturation, control personnel

frequently will be unable to accept these revisions via

radio. It is recommended that you forward these

revisions to the nearest FSS.

5−1−14. Closing VFR/DVFR Flight Plans

A pilot is responsible for ensuring that his/her VFR or

DVFR flight plan is canceled. You should close your

flight plan with the nearest FSS, or if one is not

available, you may request any ATC facility to relay

your cancellation to the FSS. Control towers do not

automatically close VFR or DVFR flight plans since

they do not know if a particular VFR aircraft is on a

flight plan. If you fail to report or cancel your flight

plan within 1/2 hour after your ETA, search and rescue

procedures are started.

REFERENCE−

14 CFR Section 91.153.

14 CFR Section 91.169.

5−1−15. Canceling IFR Flight Plan

a. 14 CFR Sections 91.153 and 91.169 include the

statement “When a flight plan has been activated, the

pilot-in-command, upon canceling or completing the

flight under the flight plan, must notify an FAA Flight

Service Station or ATC facility.”

b. An IFR flight plan may be canceled at any time

the flight is operating in VFR conditions outside

Class A airspace by pilots stating “CANCEL MY IFR

FLIGHT PLAN” to the controller or air/ground

station with which they are communicating.

Immediately after canceling an IFR flight plan, a pilot

should take the necessary action to change to the

appropriate air/ground frequency, VFR radar beacon

code and VFR altitude or flight level.

c. ATC separation and information services will

be discontinued, including radar services (where

applicable). Consequently, if the canceling flight

desires VFR radar advisory service, the pilot must

specifically request it.

NOTE−

Pilots must be aware that other procedures may be

applicable to a flight that cancels an IFR flight plan within

an area where a special program, such as a designated

TRSA, Class C airspace, or Class B airspace, has been

established.

d. If a DVFR flight plan requirement exists, the

pilot is responsible for filing this flight plan to replace

the canceled IFR flight plan. If a subsequent IFR

operation becomes necessary, a new IFR flight plan

must be filed and an ATC clearance obtained before

operating in IFR conditions.

e. If operating on an IFR flight plan to an airport

with a functioning control tower, the flight plan is

automatically closed upon landing.

f. If operating on an IFR flight plan to an airport

where there is no functioning control tower, the pilot

must initiate cancellation of the IFR flight plan. This

can be done after landing if there is a functioning FSS

or other means of direct communications with ATC.

In the event there is no FSS and/or air/ground

communications with ATC is not possible below a

certain altitude, the pilot should, weather conditions

permitting, cancel the IFR flight plan while still

airborne and able to communicate with ATC by radio.

This will not only save the time and expense of

canceling the flight plan by telephone but will quickly

release the airspace for use by other aircraft.

5−1−16. RNAV and RNP Operations

a. During the pre−flight planning phase the

availability of the navigation infrastructure required

for the intended operation, including any non−RNAV

contingencies, must be confirmed for the period of

intended operation. Availability of the onboard

navigation equipment necessary for the route to be

flown must be confirmed.

b. If a pilot determines a specified RNP level

cannot be achieved, revise the route or delay the

operation until appropriate RNP level can be ensured.

c. The onboard navigation database must be

current and appropriate for the region of intended

operation and must include the navigation aids,
7/26/12 AIM

Preflight 5−1−31

waypoints, and coded terminal airspace procedures

for the departure, arrival and alternate airfields.

d. During system initialization, pilots of aircraft

equipped with a Flight Management System or other

RNAV−certified system, must confirm that the

navigation database is current, and verify that the

aircraft position has been entered correctly. Flight

crews should crosscheck the cleared flight plan

against charts or other applicable resources, as well as

the navigation system textual display and the aircraft

map display. This process includes confirmation of

the waypoints sequence, reasonableness of track

angles and distances, any altitude or speed

constraints, and identification of fly−by or fly−over

waypoints. A procedure must not be used if validity

of the navigation database is in doubt.

e. Prior to commencing takeoff, the flight crew

must verify that the RNAV system is operating

correctly and the correct airport and runway data have

been loaded.

f. During the pre−flight planning phase RAIM

prediction must be performed if TSO−C129()

equipment is used to solely satisfy the RNAV and

RNP requirement. GPS RAIM availability must be

confirmed for the intended route of flight (route and

time) using current GPS satellite information. In the

event of a predicted, continuous loss of RAIM of

more than five (5) minutes for any part of the intended

flight, the flight should be delayed, canceled, or

re−routed where RAIM requirements can be met.

Operators may satisfy the predictive RAIM requirement through any one of the following methods:

1. Operators may monitor the status of each

satellite in its plane/slot position, by accounting for

the latest GPS constellation status (e.g., NOTAMs or

NANUs), and compute RAIM availability using

model−specific RAIM prediction software;

2. Operators may use the FAA en route and

terminal RAIM prediction website:

www.raimprediction.net;

3. Operators may contact a Flight Service

Station (not DUATS) to obtain non−precision

approach RAIM;

4. Operators may use a third party interface,

incorporating FAA/VOLPE RAIM prediction data

without altering performance values, to predict

RAIM outages for the aircraft’s predicted flight path

and times;

5. Operators may use the receiver’s installed

RAIM prediction capability (for TSO−C129a/Class

A1/B1/C1 equipment) to provide non−precision

approach RAIM, accounting for the latest GPS

constellation status (e.g., NOTAMs or NANUs).

Receiver non−precision approach RAIM should be

checked at airports spaced at intervals not to exceed

60 NM along the RNAV 1 procedure’s flight track.

“Terminal” or “Approach” RAIM must be available

at the ETA over each airport checked; or,

6. Operators not using model−specific software

or FAA/VOLPE RAIM data will need FAA

operational approval.

NOTE−

If TSO−C145/C146 equipment is used to satisfy the RNAV

and RNP requirement, the pilot/operator need not perform

the prediction if WAAS coverage is confirmed to be

available along the entire route of flight. Outside the U.S.

or in areas where WAAS coverage is not available,

operators using TSO−C145/C146 receivers are required to

check GPS RAIM availability.

7/26/12 AIM

Departure Procedures 5−2−1

Section 2. Departure Procedures

5−2−1. Pre-taxi Clearance Procedures

a. Certain airports have established pre-taxi clearance programs whereby pilots of departing

instrument flight rules (IFR) aircraft may elect to receive their IFR clearances before they start taxiing for

takeoff. The following provisions are included in

such procedures:

1. Pilot participation is not mandatory.

2. Participating pilots call clearance delivery or

ground control not more than 10 minutes before proposed taxi time.

3. IFR clearance (or delay information, if clearance cannot be obtained) is issued at the time of this

initial call-up.

4. When the IFR clearance is received on clearance delivery frequency, pilots call ground control

when ready to taxi.

5. Normally, pilots need not inform ground control that they have received IFR clearance on

clearance delivery frequency. Certain locations may,

however, require that the pilot inform ground control

of a portion of the routing or that the IFR clearance

has been received.

6. If a pilot cannot establish contact on clearance

delivery frequency or has not received an IFR clearance before ready to taxi, the pilot should contact

ground control and inform the controller accordingly.

b. Locations where these procedures are in effect

are indicated in the Airport/Facility Directory.

5−2−2. Pre−departure Clearance Procedures

a. Many airports in the National Airspace System

are equipped with the Tower Data Link System

(TDLS) that includes the Pre−departure Clearance

(PDC) function. The PDC function automates the

Clearance Delivery operations in the ATCT for participating users. The PDC function displays IFR

clearances from the ARTCC to the ATCT. The Clearance Delivery controller in the ATCT can append

local departure information and transmit the clearance via data link to participating airline/service

provider computers. The airline/service provider will

then deliver the clearance via the Aircraft Communications Addressing and Reporting System

(ACARS) or a similar data link system or, for nondata

link equipped aircraft, via a printer located at the departure gate. PDC reduces frequency congestion,

controller workload and is intended to mitigate delivery/readback errors. Also, information from

participating users indicates a reduction in pilot

workload.

b. PDC is available only to participating aircraft

that have subscribed to the service through an approved service provider.

c. Due to technical reasons, the following limitations currently exist in the PDC program:

1. Aircraft filing multiple flight plans are limited to one PDC clearance per departure airport within

a 24−hour period. Additional clearances will be delivered verbally.

2. If the clearance is revised or modified prior to

delivery, it will be rejected from PDC and the clearance will need to be delivered verbally.

d. No acknowledgment of receipt or readback is

required for a PDC.

e. In all situations, the pilot is encouraged to contact clearance delivery if a question or concern exists

regarding an automated clearance.

5−2−3. Taxi Clearance

Pilots on IFR flight plans should communicate with

the control tower on the appropriate ground control or

clearance delivery frequency, prior to starting engines, to receive engine start time, taxi and/or

clearance information.

5−2−4. Line Up and Wait (LUAW)

a. Line up and wait is an air traffic control (ATC)

procedure designed to position an aircraft onto the

runway for an imminent departure. The ATC

instruction “LINE UP AND WAIT” is used to instruct

a pilot to taxi onto the departure runway and line up

and wait.

EXAMPLE−

Tower: “N234AR Runway 24L, line up and wait.”

b. This ATC instruction is not an authorization to

takeoff. In instances where the pilot has been
AIM 7/26/12

5−2−2 Departure Procedures

instructed to line up and wait and has been advised of

a reason/condition (wake turbulence, traffic on an

intersecting runway, etc.) or the reason/condition is

clearly visible (another aircraft that has landed on or

is taking off on the same runway), and the reason/

condition is satisfied, the pilot should expect an

imminent takeoff clearance, unless advised of a

delay. If you are uncertain about any ATC instruction

or clearance, contact ATC immediately.

c. If a takeoff clearance is not received within a

reasonable amount of time after clearance to line up

and wait, ATC should be contacted.

EXAMPLE−

Aircraft: Cessna 234AR holding in position Runway 24L.

Aircraft: Cessna 234AR holding in position Runway 24L

at Bravo.

NOTE−

FAA analysis of accidents and incidents involving aircraft

holding in position indicate that two minutes or more

elapsed between the time the instruction was issued to line

up and wait and the resulting event (for example, land−over

or go−around). Pilots should consider the length of time

that they have been holding in position whenever they

HAVE NOT been advised of any expected delay to

determine when it is appropriate to query the controller.

REFERENCE−

Advisory Circulars 91−73A, Part 91 and Part 135 Single−Pilot Procedures during Taxi Operations, and 120−74A, Parts 91, 121, 125, and 135

Flightcrew Procedures during Taxi Operations

d. Situational awareness during line up and wait

operations is enhanced by monitoring ATC

instructions/clearances issued to other aircraft. Pilots

should listen carefully if another aircraft is on

frequency that has a similar call sign and pay close

attention to communications between ATC and other

aircraft. If you are uncertain of an ATC instruction or

clearance, query ATC immediately. Care should be

taken to not inadvertently execute a clearance/

instruction for another aircraft.

e. Pilots should be especially vigilant when

conducting line up and wait operations at night or

during reduced visibility conditions. They should

scan the full length of the runway and look for aircraft

on final approach or landing roll out when taxiing

onto a runway. ATC should be contacted anytime

there is a concern about a potential conflict.

f. When two or more runways are active, aircraft

may be instructed to “LINE UP AND WAIT” on two

or more runways. When multiple runway operations

are being conducted, it is important to listen closely

for your call sign and runway. Be alert for similar

sounding call signs and acknowledge all instructions

with your call sign. When you are holding in position

and are not sure if the takeoff clearance was for you,

ask ATC before you begin takeoff roll. ATC prefers

that you confirm a takeoff clearance rather than

mistake another aircraft’s clearance for your own.

g. When ATC issues intersection “line up and

wait” and takeoff clearances, the intersection

designator will be used. If ATC omits the intersection

designator, call ATC for clarification.

EXAMPLE−

Aircraft: “Cherokee 234AR, Runway 24L at November 4,

line up and wait.”

h. If landing traffic is a factor during line up and

wait operations, ATC will inform the aircraft in

position of the closest traffic that has requested a full−

stop, touch−and−go, stop−and−go, or an unrestricted

low approach to the same runway. Pilots should take

care to note the position of landing traffic. ATC will

also advise the landing traffic when an aircraft is

authorized to “line up and wait” on the same runway.

EXAMPLE−

Tower: “Cessna 234AR, Runway 24L, line up and wait.

Traffic a Boeing 737, six mile final.”

Tower: “Delta 1011, continue, traffic a Cessna 210

holding in position Runway 24L.”

NOTE−

ATC will normally withhold landing clearance to arrival

aircraft when another aircraft is in position and holding on

the runway.

i. Never land on a runway that is occupied by

another aircraft, even if a landing clearance was

issued. Do not hesitate to ask the controller about the

traffic on the runway and be prepared to execute a go−

around.

NOTE−

Always clarify any misunderstanding or confusion

concerning ATC instructions or clearances. ATC should be

advised immediately if there is any uncertainty about the

ability to comply with any of their instructions.

5−2−5. Abbreviated IFR Departure Clearance (Cleared. . .as Filed) Procedures

a. ATC facilities will issue an abbreviated IFR departure clearance based on the ROUTE of flight filed

in the IFR flight plan, provided the filed route can be

approved with little or no revision. These abbreviated

clearance procedures are based on the following

conditions:
7/26/12 AIM

Departure Procedures 5−2−3

1. The aircraft is on the ground or it has departed

visual flight rules (VFR) and the pilot is requesting

IFR clearance while airborne.

2. That a pilot will not accept an abbreviated

clearance if the route or destination of a flight plan

filed with ATC has been changed by the pilot or the

company or the operations officer before departure.

3. That it is the responsibility of the company or

operations office to inform the pilot when they make

a change to the filed flight plan.

4. That it is the responsibility of the pilot to inform ATC in the initial call-up (for clearance) when

the filed flight plan has been either:

(a) Amended, or

(b) Canceled and replaced with a new filed

flight plan.

NOTE−

The facility issuing a clearance may not have received the

revised route or the revised flight plan by the time a pilot requests clearance.

b. Controllers will issue a detailed clearance when

they know that the original filed flight plan has been

changed or when the pilot requests a full route clearance.

c. The clearance as issued will include the destination airport filed in the flight plan.

d. ATC procedures now require the controller to

state the DP name, the current number and the DP

transition name after the phrase “Cleared to (destination) airport” and prior to the phrase, “then as filed,”

for ALL departure clearances when the DP or DP

transition is to be flown. The procedures apply whether or not the DP is filed in the flight plan.

e. STARs, when filed in a flight plan, are considered a part of the filed route of flight and will not

normally be stated in an initial departure clearance. If

the ARTCC’s jurisdictional airspace includes both

the departure airport and the fix where a STAR or

STAR transition begins, the STAR name, the current

number and the STAR transition name MAY be stated

in the initial clearance.

f. “Cleared to (destination) airport as filed” does

NOT include the en route altitude filed in a flight plan.

An en route altitude will be stated in the clearance or

the pilot will be advised to expect an assigned or filed

altitude within a given time frame or at a certain point

after departure. This may be done verbally in the departure instructions or stated in the DP.

g. In both radar and nonradar environments, the

controller will state “Cleared to (destination) airport

as filed” or:

1. If a DP or DP transition is to be flown, specify

the DP name, the current DP number, the DP transition name, the assigned altitude/flight level, and any

additional instructions (departure control frequency,

beacon code assignment, etc.) necessary to clear a departing aircraft via the DP or DP transition and the

route filed.

EXAMPLE−

National Seven Twenty cleared to Miami Airport Intercontinental one departure, Lake Charles transition then as

filed, maintain Flight Level two seven zero.

2. When there is no DP or when the pilot cannot

accept a DP, the controller will specify the assigned

altitude or flight level, and any additional instructions

necessary to clear a departing aircraft via an appropriate departure routing and the route filed.

NOTE−

A detailed departure route description or a radar vector

may be used to achieve the desired departure routing.

3. If it is necessary to make a minor revision to

the filed route, the controller will specify the assigned

DP or DP transition (or departure routing), the revision to the filed route, the assigned altitude or flight

level and any additional instructions necessary to

clear a departing aircraft.

EXAMPLE−

Jet Star One Four Two Four cleared to Atlanta Airport,

South Boston two departure then as filed except change

route to read South Boston Victor 20 Greensboro, maintain

one seven thousand.

4. Additionally, in a nonradar environment, the

controller will specify one or more fixes, as necessary, to identify the initial route of flight.

EXAMPLE−

Cessna Three One Six Zero Foxtrot cleared to Charlotte

Airport as filed via Brooke, maintain seven thousand.
AIM 7/26/12

5−2−4 Departure Procedures

h. To ensure success of the program, pilots should:

1. Avoid making changes to a filed flight plan

just prior to departure.

2. State the following information in the initial

call-up to the facility when no change has been made

to the filed flight plan: Aircraft call sign, location,

type operation (IFR) and the name of the airport (or

fix) to which you expect clearance.

EXAMPLE−

“Washington clearance delivery (or ground control if appropriate) American Seventy Six at gate one, IFR

Los Angeles.”

3. If the flight plan has been changed, state the

change and request a full route clearance.

EXAMPLE−

“Washington clearance delivery, American Seventy Six at

gate one. IFR San Francisco. My flight plan route has been

amended (or destination changed). Request full route

clearance.”

4. Request verification or clarification from

ATC if ANY portion of the clearance is not clearly understood.

5. When requesting clearance for the IFR portion of a VFR/IFR flight, request such clearance prior

to the fix where IFR operation is proposed to commence in sufficient time to avoid delay. Use the

following phraseology:

EXAMPLE−

“Los Angeles center, Apache Six One Papa, VFR estimating Paso Robles VOR at three two, one thousand five

hundred, request IFR to Bakersfield.”

5−2−6. Departure Restrictions, Clearance

Void Times, Hold for Release, and Release

Times

a. ATC may assign departure restrictions, clearance void times, hold for release, and release times,

when necessary, to separate departures from other

traffic or to restrict or regulate the departure flow.

1. Clearance Void Times. A pilot may receive

a clearance, when operating from an airport without

a control tower, which contains a provision for the

clearance to be void if not airborne by a specific time.

A pilot who does not depart prior to the clearance void

time must advise ATC as soon as possible of their

intentions. ATC will normally advise the pilot of the

time allotted to notify ATC that the aircraft did not depart prior to the clearance void time. This time cannot

exceed 30 minutes. Failure of an aircraft to contact

ATC within 30 minutes after the clearance void time

will result in the aircraft being considered overdue

and search and rescue procedures initiated.

NOTE−

1. Other IFR traffic for the airport where the clearance is

issued is suspended until the aircraft has contacted ATC or

until 30 minutes after the clearance void time or 30 minutes

after the clearance release time if no clearance void time

is issued.

2. Pilots who depart at or after their clearance void time

are not afforded IFR separation and may be in violation of

14 CFR Section 91.173 which requires that pilots receive

an appropriate ATC clearance before operating IFR in

controlled airspace.

EXAMPLE−

Clearance void if not off by (clearance void time) and, if required, if not off by (clearance void time) advise (facility)

not later than (time) of intentions.

2. Hold for Release. ATC may issue “hold for

release” instructions in a clearance to delay an aircraft’s departure for traffic management reasons (i.e.,

weather, traffic volume, etc.). When ATC states in the

clearance, “hold for release,” the pilot may not depart

utilizing that IFR clearance until a release time or

additional instructions are issued by ATC. In addition, ATC will include departure delay information in

conjunction with “hold for release” instructions. The

ATC instruction, “hold for release,” applies to the IFR

clearance and does not prevent the pilot from departing under VFR. However, prior to takeoff the pilot

should cancel the IFR flight plan and operate the

transponder on the appropriate VFR code. An IFR

clearance may not be available after departure.

EXAMPLE−

(Aircraft identification) cleared to (destination) airport as

filed, maintain (altitude), and, if required (additional instructions or information), hold for release, expect (time in

hours and/or minutes) departure delay.

3. Release Times. A “release time” is a departure restriction issued to a pilot by ATC, specifying

the earliest time an aircraft may depart. ATC will use

“release times” in conjunction with traffic management procedures and/or to separate a departing

aircraft from other traffic.

EXAMPLE−

(Aircraft identification) released for departure at (time in

hours and/or minutes).
7/26/12 AIM

Departure Procedures 5−2−5

4. Expect Departure Clearance Time

(EDCT). The EDCT is the runway release time

assigned to an aircraft included in traffic management

programs. Aircraft are expected to depart no earlier

than 5 minutes before, and no later than 5 minutes after the EDCT.

b. If practical, pilots departing uncontrolled airports should obtain IFR clearances prior to becoming

airborne when two-way communications with the

controlling ATC facility is available.

5−2−7. Departure Control

a. Departure Control is an approach control function responsible for ensuring separation between

departures. So as to expedite the handling of departures, Departure Control may suggest a takeoff

direction other than that which may normally have

been used under VFR handling. Many times it is preferred to offer the pilot a runway that will require the

fewest turns after takeoff to place the pilot on course

or selected departure route as quickly as possible. At

many locations particular attention is paid to the use

of preferential runways for local noise abatement programs, and route departures away from congested

areas.

b. Departure Control utilizing radar will normally

clear aircraft out of the terminal area using DPs via radio navigation aids. When a departure is to be

vectored immediately following takeoff, the pilot

will be advised prior to takeoff of the initial heading

to be flown but may not be advised of the purpose of

the heading. Pilots operating in a radar environment

are expected to associate departure headings with

vectors to their planned route or flight. When given

a vector taking the aircraft off a previously assigned

nonradar route, the pilot will be advised briefly what

the vector is to achieve. Thereafter, radar service will

be provided until the aircraft has been reestablished

“on-course” using an appropriate navigation aid and

the pilot has been advised of the aircraft’s position or

a handoff is made to another radar controller with further surveillance capabilities.

c. Controllers will inform pilots of the departure

control frequencies and, if appropriate, the transponder code before takeoff. Pilots must ensure their

transponder is adjusted to the “on” or normal operating position as soon as practical and remain on during

all operations unless otherwise requested to change to

“standby” by ATC. Pilots should not change to the departure control frequency until requested. Controllers

may omit the departure control frequency if a DP has

or will be assigned and the departure control frequency is published on the DP.

5−2−8. Instrument Departure Procedures

(DP) − Obstacle Departure Procedures

(ODP) and Standard Instrument Departures

(SID)

Instrument departure procedures are preplanned instrument flight rule (IFR) procedures which provide

obstruction clearance from the terminal area to the

appropriate en route structure. There are two types of

DPs, Obstacle Departure Procedures (ODPs), printed

either textually or graphically, and Standard Instrument Departures (SIDs), always printed graphically.

All DPs, either textual or graphic may be designed using either conventional or RNAV criteria. RNAV

procedures will have RNAV printed in the title,

e.g., SHEAD TWO DEPARTURE (RNAV). ODPs

provide obstruction clearance via the least onerous

route from the terminal area to the appropriate en

route structure. ODPs are recommended for obstruction clearance and may be flown without ATC

clearance unless an alternate departure procedure

(SID or radar vector) has been specifically assigned

by ATC. Graphic ODPs will have (OBSTACLE)

printed in the procedure title, e.g., GEYSR THREE

DEPARTURE (OBSTACLE), or, CROWN ONE

DEPARTURE (RNAV) (OBSTACLE). Standard Instrument Departures are air traffic control (ATC)

procedures printed for pilot/controller use in graphic

form to provide obstruction clearance and a transition

from the terminal area to the appropriate en route

structure. SIDs are primarily designed for system enhancement and to reduce pilot/controller workload.

ATC clearance must be received prior to flying a SID.

All DPs provide the pilot with a way to depart the airport and transition to the en route structure safely.

Pilots operating under 14 CFR Part 91 are strongly

encouraged to file and fly a DP at night, during marginal Visual Meteorological Conditions (VMC) and

Instrument Meteorological Conditions (IMC), when

one is available. The following paragraphs will provide an overview of the DP program, why DPs are

developed, what criteria are used, where to find them,
AIM 7/26/12

5−2−6 Departure Procedures

how they are to be flown, and finally pilot and ATC

responsibilities.

a. Why are DPs necessary? The primary reason is

to provide obstacle clearance protection information

to pilots. A secondary reason, at busier airports, is to

increase efficiency and reduce communications and

departure delays through the use of SIDs. When an instrument approach is initially developed for an

airport, the need for DPs is assessed. The procedure

designer conducts an obstacle analysis to support departure operations. If an aircraft may turn in any

direction from a runway within the limits of the assessment area (see paragraph 5−2−8b3) and remain

clear of obstacles, that runway passes what is called

a diverse departure assessment and no ODP will be

published. A SID may be published if needed for air

traffic control purposes. However, if an obstacle penetrates what is called the 40:1 obstacle identification

surface, then the procedure designer chooses whether

to:

1. Establish a steeper than normal climb gradient; or

2. Establish a steeper than normal climb gradient with an alternative that increases takeoff minima

to allow the pilot to visually remain clear of the obstacle(s); or

3. Design and publish a specific departure route;

or

4. A combination or all of the above.

b. What criteria is used to provide obstruction

clearance during departure?

1. Unless specified otherwise, required obstacle

clearance for all departures, including diverse, is

based on the pilot crossing the departure end of the

runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the

departure end of runway elevation before making the

initial turn, and maintaining a minimum climb gradient of 200 feet per nautical mile (FPNM), unless

required to level off by a crossing restriction, until the

minimum IFR altitude. A greater climb gradient may

be specified in the DP to clear obstacles or to achieve

an ATC crossing restriction. If an initial turn higher

than 400 feet above the departure end of runway

elevation is specified in the DP, the turn should be

commenced at the higher altitude. If a turn is specified at a fix, the turn must be made at that fix. Fixes

may have minimum and/or maximum crossing altitudes that must be adhered to prior to passing the fix.

In rare instances, obstacles that exist on the extended

runway centerline may make an “early turn” more desirable than proceeding straight ahead. In these cases,

the published departure instructions will include the

language “turn left(right) as soon as practicable.”

These departures will also include a ceiling and visibility minimum of at least 300 and 1. Pilots

encountering one of these DPs should preplan the

climb out to gain altitude and begin the turn as quickly

as possible within the bounds of safe operating practices and operating limitations. This type of departure

procedure is being phased out.

NOTE−

“Practical” or “feasible” may exist in some existing departure text instead of “practicable.”

2. ODPs and SIDs assume normal aircraft performance, and that all engines are operating.

Development of contingency procedures, required

to cover the case of an engine failure or other

emergency in flight that may occur after liftoff, is

the responsibility of the operator. (More detailed

information on this subject is available in Advisory

Circular AC 120−91, Airport Obstacle Analysis, and

in the “Departure Procedures” section of chapter 2 in

the Instrument Procedures Handbook,

FAA−H−8261−1.)

3. The 40:1 obstacle identification surface

(OIS) begins at the departure end of runway (DER)

and slopes upward at 152 FPNM until reaching the

minimum IFR altitude or entering the en route structure. This assessment area is limited to 25 NM from

the airport in nonmountainous areas and 46 NM in

designated mountainous areas. Beyond this distance,

the pilot is responsible for obstacle clearance if not

operating on a published route, if below (having not

reached) the MEA or MOCA of a published route, or

an ATC assigned altitude. See FIG 5−2−1. (Ref 14

CFR 91.177 for further information on en route altitudes.)

NOTE−

ODPs are normally designed to terminate within these distance limitations, however, some ODPs will contain routes

that may exceed 25/46 NM; these routes will ensure

obstacle protection until reaching the end of the ODP.
7/26/12 AIM

Departure Procedures 5−2−7

FIG 5−2−1

Diverse Departure Obstacle Assessment to 25/46 NM

4. Obstacles that are located within 1 NM of the

DER and penetrate the 40:1 OCS are referred to as

“low, close−in obstacles.” The standard required

obstacle clearance (ROC) of 48 feet per NM to clear

these obstacles would require a climb gradient greater

than 200 feet per NM for a very short distance, only

until the aircraft was 200 feet above the DER. To

eliminate publishing an excessive climb gradient, the

obstacle AGL/MSL height and location relative to the

DER is noted in the “Take−off Minimums and

(OBSTACLE) Departure Procedures” section of a

given Terminal Procedures Publication (TPP) booklet. The purpose of this note is to identify the

obstacle(s) and alert the pilot to the height and location of the obstacle(s) so they can be avoided. This

can be accomplished in a variety of ways, e.g., the

pilot may be able to see the obstruction and maneuver

around the obstacle(s) if necessary; early liftoff/climb

performance may allow the aircraft to cross well

above the obstacle(s); or if the obstacle(s) cannot be

visually acquired during departure, preflight planning should take into account what turns or other

maneuver may be necessary immediately after

takeoff to avoid the obstruction(s).

5. Climb gradients greater than 200 FPNM are

specified when required to support procedure design

constraints, obstacle clearance, and/or airspace restrictions. Compliance with a climb gradient for these

purposes is mandatory when the procedure is part of

the ATC clearance, unless increased takeoff minimums are provided and weather conditions allow

compliance with these minimums. Additionally, ATC

required crossing restrictions may also require climb

gradients greater than 200 FPNM. These climb gradients may be amended or canceled at ATC’s discretion.

Multiple ATC climb gradients are permitted. An ATC

climb gradient will not be used on an ODP.

EXAMPLE−

“Cross ALPHA intersection at or below 4000; maintain

6000.” The pilot climbs at least 200 FPNM to 6000. If 4000

is reached before ALPHA, the pilot levels off at 4000 until

passing ALPHA; then immediately resumes at least 200

FPNM climb.

EXAMPLE−

“TAKEOFF MINIMUMS: RWY 27, Standard with a minimum climb of 280’ per NM to 2500, ATC climb of 310’ per

NM to 4000 ft.” A climb of at least 280 FPNM is required

to 2500 and is mandatory when the departure procedure is

included in the ATC clearance. ATC requires a climb gradient of 310 FPNM to 4000, however, this ATC climb

gradient may be amended or canceled.

6. Climb gradients may be specified only to an

altitude/fix, above which the normal gradient applies.

EXAMPLE−

“Minimum climb 340 FPNM to ALPHA.” The pilot climbs

at least 340 FPNM to ALPHA, then at least 200 FPNM to

MIA.
AIM 7/26/12

5−2−8 Departure Procedures

7. Some DPs established solely for obstacle

avoidance require a climb in visual conditions to

cross the airport or an on−airport NAVAID in a specified direction, at or above a specified altitude. These

procedures are called Visual Climb Over the Airport

(VCOA).

EXAMPLE−

“Climb in visual conditions so as to cross the McElory Airport southbound, at or above 6000, then climb via

Keemmling radial zero three three to Keemmling VORTAC.”

c. Who is responsible for obstacle clearance? DPs

are designed so that adherence to the procedure by the

pilot will ensure obstacle protection. Additionally:

1. Obstacle clearance responsibility also rests

with the pilot when he/she chooses to climb in visual

conditions in lieu of flying a DP and/or depart under

increased takeoff minima rather than fly the climb

gradient. Standard takeoff minima are one statute

mile for aircraft having two engines or less and one−

half statute mile for aircraft having more than two

engines. Specified ceiling and visibility minima

(VCOA or increased takeoff minima) will allow visual avoidance of obstacles until the pilot enters the

standard obstacle protection area. Obstacle avoidance is not guaranteed if the pilot maneuvers farther

from the airport than the specified visibility minimum

prior to reaching the specified altitude. DPs may also

contain what are called Low Close in Obstacles.

These obstacles are less than 200 feet above the departure end of runway elevation and within one NM

of the runway end, and do not require increased takeoff minimums. These obstacles are identified on the

SID chart or in the Take−off Minimums and (Obstacle) Departure Procedures section of the U. S.

Terminal Procedure booklet. These obstacles are especially critical to aircraft that do not lift off until

close to the departure end of the runway or which

climb at the minimum rate. Pilots should also consider drift following lift−off to ensure sufficient

clearance from these obstacles. That segment of the

procedure that requires the pilot to see and avoid obstacles ends when the aircraft crosses the specified

point at the required altitude. In all cases continued

obstacle clearance is based on having climbed a minimum of 200 feet per nautical mile to the specified

point and then continuing to climb at least 200 foot

per nautical mile during the departure until reaching

the minimum enroute altitude, unless specified otherwise.

2. ATC may assume responsibility for obstacle

clearance by vectoring the aircraft prior to reaching

the minimum vectoring altitude by using a Diverse

Vector Area (DVA). The DVA has been assessed for

departures which do not follow a specific ground

track. ATC may also vector an aircraft off a previously assigned DP. In all cases, the 200 FPNM climb

gradient is assumed and obstacle clearance is not provided by ATC until the controller begins to provide

navigational guidance in the form of radar vectors.

NOTE−

When used by the controller during departure, the term

“radar contact” should not be interpreted as relieving pilots of their responsibility to maintain appropriate terrain

and obstruction clearance which may include flying the obstacle DP.

3. Pilots must preplan to determine if the aircraft

can meet the climb gradient (expressed in feet per

nautical mile) required by the departure procedure,

and be aware that flying at a higher than anticipated

ground speed increases the climb rate requirement in

feet per minute. Higher than standard climb gradients

are specified by a note on the departure procedure

chart for graphic DPs, or in the Take−Off Minimums

and (Obstacle) Departure Procedures section of the

U.S. Terminal Procedures booklet for textual ODPs.

The required climb gradient, or higher, must be maintained to the specified altitude or fix, then the

standard climb gradient of 200 ft/NM can be resumed. A table for the conversion of climb gradient

(feet per nautical mile) to climb rate (feet per minute),

at a given ground speed, is included on page D1 of the

U.S. Terminal Procedures booklets.

d. Where are DPs located? DPs will be listed by

airport in the IFR Takeoff Minimums and (Obstacle)

Departure Procedures Section, Section C, of the Terminal Procedures Publications (TPPs). If the DP is

textual, it will be described in TPP Section C. SIDs

and complex ODPs will be published graphically and

named. The name will be listed by airport name and

runway in Section C. Graphic ODPs will also have

the term “(OBSTACLE)” printed in the charted procedure title, differentiating them from SIDs.

1. An ODP that has been developed solely for

obstacle avoidance will be indicated with the symbol

“T” on appropriate Instrument Approach Procedure

(IAP) charts and DP charts for that airport. The “T”

symbol will continue to refer users to TPP Section C.

In the case of a graphic ODP, the TPP Section C will

only contain the name of the ODP. Since there may be
7/26/12 AIM

Departure Procedures 5−2−9

both a textual and a graphic DP, Section C should still

be checked for additional information. The nonstandard takeoff minimums and minimum climb

gradients found in TPP Section C also apply to

charted DPs and radar vector departures unless different minimums are specified on the charted DP.

Takeoff minimums and departure procedures apply to

all runways unless otherwise specified. New graphic

DPs will have all the information printed on the

graphic depiction. As a general rule, ATC will only

assign an ODP from a nontowered airport when compliance with the ODP is necessary for aircraft to

aircraft separation. Pilots may use the ODP to help

ensure separation from terrain and obstacles.

e. Responsibilities

1. Each pilot, prior to departing an airport on an

IFR flight should:

(a) Consider the type of terrain and other obstacles on or in the vicinity of the departure airport;

(b) Determine whether an ODP is available;

(c) Determine if obstacle avoidance can be

maintained visually or if the ODP should be flown;

and

(d) Consider the effect of degraded climb performance and the actions to take in the event of an

engine loss during the departure. Pilots should notify

ATC as soon as possible of reduced climb capability

in that circumstance.

NOTE−

Guidance concerning contingency procedures that

address an engine failure on takeoff after V1 speed on a

large or turbine−powered transport category airplane

may be found in AC 120−91, Airport Obstacle Analysis.

2. After an aircraft is established on an SID and

subsequently vectored or cleared off of the SID or

SID transition, pilots must consider the SID canceled,

unless the controller adds “expect to resume SID.”

Aircraft may not be vectored off of an ODP until at or

above the MVA/MIA, at which time the ODP is canceled.

3. Aircraft instructed to resume a SID that contains ATC altitude restrictions, shall be

issued/reissued all applicable restrictions or shall be

advised to comply with those restrictions.

4. If prior to or after takeoff an altitude restriction is issued by ATC, all previously issued “ATC”

altitude restrictions are cancelled including those

published on a SID.

5. ATC crossing altitude restrictions published

on SIDs are identified on the chart with “(ATC)” following the altitude restriction. This will indicate to

the pilot and the controller that this restriction is for

ATC purposes and may be deleted by ATC. When an

ATC crossing altitude has been established prior to

the beginning of a transition route, a minimum altitude for obstruction clearance or other design

constraints will also be published at the same fix adjacent/below the “(ATC)” altitude. The absence of

“(ATC)” at a “minimum altitude” indicates the restriction is there to support obstacle clearance,

airspace restrictions, Navaid reception, and/or other

reason(s) that mandate compliance. These altitudes

CANNOT be lowered or cancelled by ATC. A standalone “(ATC)” altitude restriction may also be

located on a transition route; however, it must never

be lower than the published Minimum Enroute Altitude (MEA).

6. Altitude restrictions published on an ODP are

necessary for obstacle clearance and/or design constraints. Compliance with these restrictions is

mandatory and CANNOT be lowered or cancelled by

ATC.

f. RNAV Departure Procedures

All public RNAV SIDs and graphic ODPs are

RNAV 1. These procedures generally start with an

initial RNAV or heading leg near the departure runway end. In addition, these procedures require system

performance currently met by GPS or DME/DME/

IRU RNAV systems that satisfy the criteria discussed

in AC 90−100A, U.S. Terminal and En Route Area

Navigation (RNAV) Operations. RNAV 1 procedures require the aircraft’s total system error remain

bounded by 1 NM for 95% of the total flight time.

7/26/12 AIM

En Route Procedures 5−3−1

Section 3. En Route Procedures

5−3−1. ARTCC Communications

a. Direct Communications, Controllers and

Pilots.

1. ARTCCs are capable of direct communications with IFR air traffic on certain frequencies.

Maximum communications coverage is possible

through the use of Remote Center Air/Ground

(RCAG) sites comprised of both VHF and UHF

transmitters and receivers. These sites are located

throughout the U.S. Although they may be several

hundred miles away from the ARTCC, they are

remoted to the various ARTCCs by land lines or

microwave links. Since IFR operations are expedited

through the use of direct communications, pilots are

requested to use these frequencies strictly for

communications pertinent to the control of IFR

aircraft. Flight plan filing, en route weather, weather

forecasts, and similar data should be requested

through FSSs, company radio, or appropriate military

facilities capable of performing these services.

2. An ARTCC is divided into sectors. Each

sector is handled by one or a team of controllers and

has its own sector discrete frequency. As a flight

progresses from one sector to another, the pilot is

requested to change to the appropriate sector discrete

frequency.

3. Controller Pilot Data Link Communications

(CPDLC) is a system that supplements air/ground

voice communications. As a result, it expands

two−way air traffic control air/ground communications capabilities. Consequently, the air traffic

system’s operational capacity is increased and any

associated air traffic delays become minimized. A

related safety benefit is that pilot/controller read−

back and hear−back errors will be significantly

reduced. The CPDLC’s principal operating criteria

are:

(a) Voice remains the primary and controlling

air/ground communications means.

(b) Participating aircraft will need to have the

appropriate CPDLC avionics equipment in order to

receive uplink or transmit downlink messages.

(c) CPDLC Build 1 offers four ATC data link

services. These are altimeter setting (AS), transfer of

communications (TC), initial contact (IC), and menu

text messages (MT).

(1) Altimeter settings are usually transmitted automatically when a CPDLC session and

eligibility has been established with an aircraft. A

controller may also manually send an altimeter

setting message.

NOTE−

When conducting instrument approach procedures, pilots

are responsible to obtain and use the appropriate altimeter

setting in accordance with 14 CFR Section 97.20. CPDLC

issued altimeter settings are excluded for this purpose.

(2) Initial contact is a safety validation

transaction that compares a pilot’s initiated altitude

downlink message with an aircraft’s ATC host

computer stored altitude. If an altitude mismatch is

detected, the controller will verbally provide

corrective action.

(3) Transfer of communications automatically establishes data link contact with a succeeding

sector.

(4) Menu text transmissions are scripted

nontrajectory altering uplink messages.

NOTE−

Initial use of CPDLC will be at the Miami Air Route Traffic

Control Center (ARTCC). Air carriers will be the first

users. Subsequently, CPDLC will be made available to all

NAS users. Later versions will include trajectory altering

services and expanded clearance and advisory message

capabilities.

b. ATC Frequency Change Procedures.

1. The following phraseology will be used by

controllers to effect a frequency change:

EXAMPLE−

(Aircraft identification) contact (facility name or location

name and terminal function) (frequency) at (time, fix, or

altitude).

NOTE−

Pilots are expected to maintain a listening watch on the

transferring controller’s frequency until the time, fix, or

altitude specified. ATC will omit frequency change

restrictions whenever pilot compliance is expected upon

receipt.
AIM 7/26/12

5−3−2 En Route Procedures

2. The following phraseology should be utilized

by pilots for establishing contact with the designated

facility:

(a) When operating in a radar environment:

On initial contact, the pilot should inform the

controller of the aircraft’s assigned altitude preceded

by the words “level,” or “climbing to,” or

“descending to,” as appropriate; and the aircraft’s

present vacating altitude, if applicable.

EXAMPLE−

1. (Name) CENTER, (aircraft identification), LEVEL

(altitude or flight level).

2. (Name) CENTER, (aircraft identification), LEAVING

(exact altitude or flight level), CLIMBING TO OR

DESCENDING TO (altitude of flight level).

NOTE−

Exact altitude or flight level means to the nearest 100 foot

increment. Exact altitude or flight level reports on initial

contact provide ATC with information required prior to

using Mode C altitude information for separation

purposes.

(b) When operating in a nonradar environment:

(1) On initial contact, the pilot should

inform the controller of the aircraft’s present position,

altitude and time estimate for the next reporting point.

EXAMPLE−

(Name) CENTER, (aircraft identification), (position),

(altitude), ESTIMATING (reporting point) AT (time).

(2) After initial contact, when a position

report will be made, the pilot should give the

controller a complete position report.

EXAMPLE−

(Name) CENTER, (aircraft identification), (position),

(time), (altitude), (type of flight plan), (ETA and name of

next reporting point), (the name of the next succeeding

reporting point), AND (remarks).

REFERENCE−

AIM, Position Reporting, Paragraph 5−3−2.

3. At times controllers will ask pilots to verify

that they are at a particular altitude. The phraseology

used will be: “VERIFY AT (altitude).” In climbing or

descending situations, controllers may ask pilots to

“VERIFY ASSIGNED ALTITUDE AS (altitude).”

Pilots should confirm that they are at the altitude

stated by the controller or that the assigned altitude is

correct as stated. If this is not the case, they should

inform the controller of the actual altitude being

maintained or the different assigned altitude.

CAUTION−

Pilots should not take action to change their actual

altitude or different assigned altitude to the altitude stated

in the controllers verification request unless the

controller specifically authorizes a change.

c. ARTCC Radio Frequency Outage. ARTCCs

normally have at least one back-up radio receiver and

transmitter system for each frequency, which can

usually be placed into service quickly with little or no

disruption of ATC service. Occasionally, technical

problems may cause a delay but switchover seldom

takes more than 60 seconds. When it appears that the

outage will not be quickly remedied, the ARTCC will

usually request a nearby aircraft, if there is one, to

switch to the affected frequency to broadcast

communications instructions. It is important, therefore, that the pilot wait at least 1 minute before

deciding that the ARTCC has actually experienced a

radio frequency failure. When such an outage does

occur, the pilot should, if workload and equipment

capability permit, maintain a listening watch on the

affected frequency while attempting to comply with

the following recommended communications

procedures:

1. If two-way communications cannot be

established with the ARTCC after changing frequencies, a pilot should attempt to recontact the

transferring controller for the assignment of an

alternative frequency or other instructions.

2. When an ARTCC radio frequency failure

occurs after two-way communications have been

established, the pilot should attempt to reestablish

contact with the center on any other known ARTCC

frequency, preferably that of the next responsible

sector when practicable, and ask for instructions.

However, when the next normal frequency change

along the route is known to involve another ATC

facility, the pilot should contact that facility, if

feasible, for instructions. If communications cannot

be reestablished by either method, the pilot is

expected to request communications instructions

from the FSS appropriate to the route of flight.
7/26/12 AIM

En Route Procedures 5−3−3

NOTE−

The exchange of information between an aircraft and an

ARTCC through an FSS is quicker than relay via company

radio because the FSS has direct interphone lines to the

responsible ARTCC sector. Accordingly, when circumstances dictate a choice between the two, during an

ARTCC frequency outage, relay via FSS radio is

recommended.

5−3−2. Position Reporting

The safety and effectiveness of traffic control

depends to a large extent on accurate position

reporting. In order to provide the proper separation

and expedite aircraft movements, ATC must be able

to make accurate estimates of the progress of every

aircraft operating on an IFR flight plan.

a. Position Identification.

1. When a position report is to be made passing

a VOR radio facility, the time reported should be the

time at which the first complete reversal of the

“to/from” indicator is accomplished.

2. When a position report is made passing a

facility by means of an airborne ADF, the time

reported should be the time at which the indicator

makes a complete reversal.

3. When an aural or a light panel indication is

used to determine the time passing a reporting point,

such as a fan marker, Z marker, cone of silence or

intersection of range courses, the time should be

noted when the signal is first received and again when

it ceases. The mean of these two times should then be

taken as the actual time over the fix.

4. If a position is given with respect to distance

and direction from a reporting point, the distance and

direction should be computed as accurately as

possible.

5. Except for terminal area transition purposes,

position reports or navigation with reference to aids

not established for use in the structure in which flight

is being conducted will not normally be required by

ATC.

b. Position Reporting Points. CFRs require

pilots to maintain a listening watch on the appropriate

frequency and, unless operating under the provisions

of subparagraph c, to furnish position reports passing

certain reporting points. Reporting points are

indicated by symbols on en route charts. The

designated compulsory reporting point symbol is a

solid triangle and the “on request” reporting

point symbol is the open triangle . Reports

passing an “on request” reporting point are only

necessary when requested by ATC.

c. Position Reporting Requirements.

1. Flights along airways or routes. A position

report is required by all flights regardless of altitude,

including those operating in accordance with an ATC

clearance specifying “VFR−on−top,” over each

designated compulsory reporting point along the

route being flown.

2. Flights Along a Direct Route. Regardless

of the altitude or flight level being flown, including

flights operating in accordance with an ATC

clearance specifying “VFR−on−top,” pilots must

report over each reporting point used in the flight plan

to define the route of flight.

3. Flights in a Radar Environment. When

informed by ATC that their aircraft are in “Radar

Contact,” pilots should discontinue position reports

over designated reporting points. They should

resume normal position reporting when ATC advises

“RADAR CONTACT LOST” or “RADAR SERVICE

TERMINATED.”

NOTE−

ATC will inform pilots that they are in “radar contact”:

(a) when their aircraft is initially identified in the ATC

system; and

(b) when radar identification is reestablished after

radar service has been terminated or radar contact lost.

Subsequent to being advised that the controller has

established radar contact, this fact will not be repeated to

the pilot when handed off to another controller. At times,

the aircraft identity will be confirmed by the receiving

controller; however, this should not be construed to mean

that radar contact has been lost. The identity of

transponder equipped aircraft will be confirmed by asking

the pilot to “ident,” “squawk standby,” or to change codes.

Aircraft without transponders will be advised of their

position to confirm identity. In this case, the pilot is

expected to advise the controller if in disagreement with the

position given. Any pilot who cannot confirm the accuracy

of the position given because of not being tuned to the

NAVAID referenced by the controller, should ask for

another radar position relative to the tuned in NAVAID.
AIM 7/26/12

5−3−4 En Route Procedures

d. Position Report Items:

1. Position reports should include the following items:

(a) Identification;

(b) Position;

(c) Time;

(d) Altitude or flight level (include actual

altitude or flight level when operating on a clearance

specifying VFR−on−top);

(e) Type of flight plan (not required in IFR

position reports made directly to ARTCCs or

approach control);

(f) ETA and name of next reporting point;

(g) The name only of the next succeeding

reporting point along the route of flight; and

(h) Pertinent remarks.

5−3−3. Additional Reports

a. The following reports should be made to

ATC or FSS facilities without a specific ATC

request:

1. At all times.

(a) When vacating any previously assigned

altitude or flight level for a newly assigned altitude or

flight level.

(b) When an altitude change will be made if

operating on a clearance specifying VFR−on−top.

(c) When unable to climb/descend at a rate of

a least 500 feet per minute.

(d) When approach has been missed.

(Request clearance for specific action; i.e., to

alternative airport, another approach, etc.)

(e) Change in the average true airspeed (at

cruising altitude) when it varies by 5 percent or

10 knots (whichever is greater) from that filed in the

flight plan.

(f) The time and altitude or flight level upon

reaching a holding fix or point to which cleared.

(g) When leaving any assigned holding fix or

point.

NOTE−

The reports in subparagraphs (f) and (g) may be omitted by

pilots of aircraft involved in instrument training at military

terminal area facilities when radar service is being

provided.

(h) Any loss, in controlled airspace, of VOR,

TACAN, ADF, low frequency navigation receiver

capability, GPS anomalies while using installed

IFR−certified GPS/GNSS receivers, complete or

partial loss of ILS receiver capability or impairment

of air/ground communications capability. Reports

should include aircraft identification, equipment

affected, degree to which the capability to operate

under IFR in the ATC system is impaired, and the

nature and extent of assistance desired from ATC.

NOTE−

1. Other equipment installed in an aircraft may effectively

impair safety and/or the ability to operate under IFR. If

such equipment (e.g., airborne weather radar) malfunctions and in the pilot’s judgment either safety or IFR

capabilities are affected, reports should be made as above.

2. When reporting GPS anomalies, include the location

and altitude of the anomaly. Be specific when describing

the location and include duration of the anomaly if

necessary.

(i) Any information relating to the safety of

flight.

2. When not in radar contact.

(a) When leaving final approach fix inbound

on final approach (nonprecision approach) or when

leaving the outer marker or fix used in lieu of the outer

marker inbound on final approach (precision

approach).

(b) A corrected estimate at anytime it

becomes apparent that an estimate as previously

submitted is in error in excess of 3 minutes. For

flights in the North Atlantic (NAT), a revised

estimate is required if the error is 3 minutes or more.

b. Pilots encountering weather conditions which

have not been forecast, or hazardous conditions

which have been forecast, are expected to forward a

report of such weather to ATC.

REFERENCE−

AIM, Pilot Weather Reports (PIREPs), Paragraph 7−1−20.

14 CFR Section 91.183(B) and (C).
7/26/12 AIM

En Route Procedures 5−3−5

5−3−4. Airways and Route Systems

a. Three fixed route systems are established for air

navigation purposes. They are the Federal airway

system (consisting of VOR and L/MF routes), the jet

route system, and the RNAV route system. To the

extent possible, these route systems are aligned in an

overlying manner to facilitate transition between

each.

1. The VOR and L/MF (nondirectional radio

beacons) Airway System consists of airways

designated from 1,200 feet above the surface (or in

some instances higher) up to but not including 18,000

feet MSL. These airways are depicted on IFR Enroute

Low Altitude Charts.

NOTE−

The altitude limits of a victor airway should not be

exceeded except to effect transition within or between route

structures.

(a) Except in Alaska, the VOR airways are:

predicated solely on VOR or VORTAC navigation

aids; depicted in black on aeronautical charts; and

identified by a “V” (Victor) followed by the airway

number (for example, V12).

NOTE−

Segments of VOR airways in Alaska are based on L/MF

navigation aids and charted in brown instead of black on

en route charts.

(1) A segment of an airway which is

common to two or more routes carries the numbers of

all the airways which coincide for that segment.

When such is the case, pilots filing a flight plan need

to indicate only that airway number for the route filed.

NOTE−

A pilot who intends to make an airway flight, using VOR

facilities, will simply specify the appropriate “victor”

airway(s) in the flight plan. For example, if a flight is to be

made from Chicago to New Orleans at 8,000 feet, using

omniranges only, the route may be indicated as “departing

from Chicago−Midway, cruising 8,000 feet via Victor 9 to

Moisant International.” If flight is to be conducted in part

by means of L/MF navigation aids and in part on

omniranges, specifications of the appropriate airways in

the flight plan will indicate which types of facilities will be

used along the described routes, and, for IFR flight, permit

ATC to issue a traffic clearance accordingly. A route may

also be described by specifying the station over which the

flight will pass, but in this case since many VORs and L/MF

aids have the same name, the pilot must be careful to

indicate which aid will be used at a particular location.

This will be indicated in the route of flight portion of the

flight plan by specifying the type of facility to be used after

the location name in the following manner: Newark L/MF,

Allentown VOR.

(2) With respect to position reporting,

reporting points are designated for VOR Airway

Systems. Flights using Victor Airways will report

over these points unless advised otherwise by ATC.

(b) The L/MF airways (colored airways) are

predicated solely on L/MF navigation aids and are

depicted in brown on aeronautical charts and are

identified by color name and number (e.g., Amber

One). Green and Red airways are plotted east and

west. Amber and Blue airways are plotted north and

south.

NOTE−

Except for G13 in North Carolina, the colored airway

system exists only in the state of Alaska. All other such

airways formerly so designated in the conterminous U.S.

have been rescinded.

(c) The use of TSO−C145a or TSO−C146a

GPS/WAAS navigation systems is allowed in Alaska

as the only means of navigation on published air

traffic routes including those Victor and colored

airway segments designated with a second minimum

en route altitude (MEA) depicted in blue and

followed by the letter G at those lower altitudes. The

altitudes so depicted are below the minimum

reception altitude (MRA) of the land−based

navigation facility defining the route segment, and

guarantee standard en route obstacle clearance and

two−way communications. Air carrier operators

requiring operations specifications are authorized to

conduct operations on those routes in accordance

with FAA operations specifications.

2. The jet route system consists of jet routes

established from 18,000 feet MSL to FL 450

inclusive.

(a) These routes are depicted on Enroute

High Altitude Charts. Jet routes are depicted in black

on aeronautical charts and are identified by a “J” (Jet)

followed by the airway number (e.g., J12). Jet routes,

as VOR airways, are predicated solely on VOR or

VORTAC navigation facilities (except in Alaska).

NOTE−

Segments of jet routes in Alaska are based on L/MF

navigation aids and are charted in brown color instead of

black on en route charts.

(b) With respect to position reporting,

reporting points are designated for jet route systems.
AIM 7/26/12

5−3−6 En Route Procedures

Flights using jet routes will report over these points

unless otherwise advised by ATC.

3. Area Navigation (RNAV) Routes.

(a) Published RNAV routes, including

Q−Routes and T−Routes, can be flight planned for

use by aircraft with RNAV capability, subject to any

limitations or requirements noted on en route charts,

in applicable Advisory Circulars, or by NOTAM.

RNAV routes are depicted in blue on aeronautical

charts and are identified by the letter “Q” or “T”

followed by the airway number (e.g., Q−13, T−205).

Published RNAV routes are RNAV−2 except when

specifically charted as RNAV−1. These routes

require system performance currently met by GPS or

DME/DME/IRU RNAV systems that satisfy the

criteria discussed in AC 90−100A, U.S. Terminal and

En Route Area Navigation (RNAV) Operations.

NOTE−

AC 90−100A does not apply to over water RNAV routes

(reference 14 CFR 91.511, including the Q−routes in the

Gulf of Mexico and the Atlantic routes) or Alaska

VOR/DME RNAV routes (“JxxxR”). The AC does not apply

to off−route RNAV operations, Alaska GPS routes or

Caribbean routes.

(1) Q−routes are available for use by RNAV

equipped aircraft between 18,000 feet MSL and

FL 450 inclusive. Q−routes are depicted on Enroute

High Altitude Charts.

(2) T−routes are available for use by RNAV

equipped aircraft from 1,200 feet above the surface

(or in some instances higher) up to but not including

18,000 feet MSL. T−routes are depicted on Enroute

Low Altitude Charts.

(b) Unpublished RNAV routes are direct

routes, based on area navigation capability, between

waypoints defined in terms of latitude/longitude

coordinates, degree−distance fixes, or offsets from

established routes/airways at a specified distance and

direction. Radar monitoring by ATC is required on all

unpublished RNAV routes.

(c) Magnetic Reference Bearing (MRB) is the

published bearing between two waypoints on an

RNAV/GPS/GNSS route. The MRB is calculated by

applying magnetic variation at the waypoint to the

calculated true course between two waypoints. The

MRB enhances situational awareness by indicating a

reference bearing (no−wind heading) that a pilot

should see on the compass/HSI/RMI etc., when

turning prior to/over a waypoint en route to another

waypoint. Pilots should use this bearing as a reference

only, because their RNAV/GPS/GNSS navigation

system will fly the true course between the

waypoints.

b. Operation above FL 450 may be conducted on

a point-to-point basis. Navigational guidance is

provided on an area basis utilizing those facilities

depicted on the enroute high altitude charts.

c. Radar Vectors. Controllers may vector aircraft within controlled airspace for separation

purposes, noise abatement considerations, when an

operational advantage will be realized by the pilot or

the controller, or when requested by the pilot. Vectors

outside of controlled airspace will be provided only

on pilot request. Pilots will be advised as to what the

vector is to achieve when the vector is controller

initiated and will take the aircraft off a previously

assigned nonradar route. To the extent possible,

aircraft operating on RNAV routes will be allowed to

remain on their own navigation.

d. When flying in Canadian airspace, pilots are

cautioned to review Canadian Air Regulations.

1. Special attention should be given to the parts

which differ from U.S. CFRs.

(a) The Canadian Airways Class B airspace

restriction is an example. Class B airspace is all

controlled low level airspace above 12,500 feet MSL

or the MEA, whichever is higher, within which only

IFR and controlled VFR flights are permitted. (Low

level airspace means an airspace designated and

defined as such in the Designated Airspace

Handbook.)

(b) Regardless of the weather conditions or

the height of the terrain, no person must operate an

aircraft under VFR conditions within Class B

airspace except in accordance with a clearance for

VFR flight issued by ATC.

(c) The requirement for entry into Class B

airspace is a student pilot permit (under the guidance

or control of a flight instructor).

(d) VFR flight requires visual contact with

the ground or water at all times.

2. Segments of VOR airways and high level

routes in Canada are based on L/MF navigation aids

and are charted in brown color instead of blue on

en route charts.
7/26/12 AIM

En Route Procedures 5−3−7

FIG 5−3−1

Adhering to Airways or Routes

5−3−5. Airway or Route Course Changes

a. Pilots of aircraft are required to adhere to

airways or routes being flown. Special attention must

be given to this requirement during course changes.

Each course change consists of variables that make

the technique applicable in each case a matter only the

pilot can resolve. Some variables which must be

considered are turn radius, wind effect, airspeed,

degree of turn, and cockpit instrumentation. An early

turn, as illustrated below, is one method of adhering

to airways or routes. The use of any available cockpit

instrumentation, such as Distance Measuring Equipment, may be used by the pilot to lead the turn when

making course changes. This is consistent with the

intent of 14 CFR Section 91.181, which requires

pilots to operate along the centerline of an airway and

along the direct course between navigational aids or

fixes.

b. Turns which begin at or after fix passage may

exceed airway or route boundaries. FIG 5−3−1

contains an example flight track depicting this,

together with an example of an early turn.
AIM 7/26/12

5−3−8 En Route Procedures

c. Without such actions as leading a turn, aircraft

operating in excess of 290 knots true air speed (TAS)

can exceed the normal airway or route boundaries

depending on the amount of course change required,

wind direction and velocity, the character of the turn

fix (DME, overhead navigation aid, or intersection),

and the pilot’s technique in making a course change.

For example, a flight operating at 17,000 feet MSL

with a TAS of 400 knots, a 25 degree bank, and a

course change of more than 40 degrees would exceed

the width of the airway or route; i.e., 4 nautical miles

each side of centerline. However, in the airspace

below 18,000 feet MSL, operations in excess of

290 knots TAS are not prevalent and the provision of

additional IFR separation in all course change

situations for the occasional aircraft making a turn in

excess of 290 knots TAS creates an unacceptable

waste of airspace and imposes a penalty upon the

preponderance of traffic which operate at low speeds.

Consequently, the FAA expects pilots to lead turns

and take other actions they consider necessary during

course changes to adhere as closely as possible to the

airways or route being flown.

5−3−6. Changeover Points (COPs)

a. COPs are prescribed for Federal airways, jet

routes, area navigation routes, or other direct routes

for which an MEA is designated under 14 CFR

Part 95. The COP is a point along the route or airway

segment between two adjacent navigation facilities or

waypoints where changeover in navigation guidance

should occur. At this point, the pilot should change

navigation receiver frequency from the station

behind the aircraft to the station ahead.

b. The COP is normally located midway between

the navigation facilities for straight route segments,

or at the intersection of radials or courses forming a

dogleg in the case of dogleg route segments. When

the COP is NOT located at the midway point,

aeronautical charts will depict the COP location and

give the mileage to the radio aids.

c. COPs are established for the purpose of

preventing loss of navigation guidance, to prevent

frequency interference from other facilities, and to

prevent use of different facilities by different aircraft

in the same airspace. Pilots are urged to observe COPs

to the fullest extent.

5−3−7. Minimum Turning Altitude (MTA)

Due to increased airspeeds at 10,000 ft MSL or above,

the published minimum enroute altitude (MEA) may

not be sufficient for obstacle clearance when a turn is

required over a fix, NAVAID, or waypoint. In these

instances, an expanded area in the vicinity of the turn

point is examined to determine whether the published

MEA is sufficient for obstacle clearance. In some

locations (normally mountainous), terrain/obstacles

in the expanded search area may necessitate a higher

minimum altitude while conducting the turning

maneuver. Turning fixes requiring a higher minimum

turning altitude (MTA) will be denoted on

government charts by the minimum crossing altitude

(MCA) icon (“x” flag) and an accompanying note

describing the MTA restriction. An MTA restriction

will normally consist of the air traffic service (ATS)

route leading to the turn point, the ATS route leading

from the turn point, and the required altitude; e.g.,

MTA V330 E TO V520 W 16000. When an MTA is

applicable for the intended route of flight, pilots must

ensure they are at or above the charted MTA not later

than the turn point and maintain at or above the MTA

until joining the centerline of the ATS route following

the turn point. Once established on the centerline

following the turning fix, the MEA/MOCA determines the minimum altitude available for assignment.

An MTA may also preclude the use of a specific

altitude or a range of altitudes during a turn. For

example, the MTA may restrict the use of 10,000

through 11,000 ft MSL. In this case, any altitude

greater than 11,000 ft MSL is unrestricted, as are

altitudes less than 10,000 ft MSL provided

MEA/MOCA requirements are satisfied.

5−3−8. Holding

a. Whenever an aircraft is cleared to a fix other

than the destination airport and delay is expected, it

is the responsibility of the ATC controller to issue

complete holding instructions (unless the pattern is

charted), an EFC time and best estimate of any

additional en route/terminal delay.

NOTE−

Only those holding patterns depicted on U.S. government

or commercially produced (meeting FAA requirements)

low/high altitude enroute, and area or STAR charts should

be used.

b. If the holding pattern is charted and the

controller doesn’t issue complete holding instructions, the pilot is expected to hold as depicted on the
7/26/12 AIM

En Route Procedures 5−3−9

appropriate chart. When the pattern is charted, the

controller may omit all holding instructions except

the charted holding direction and the statement AS

PUBLISHED; e.g., HOLD EAST AS PUBLISHED.

Controllers must always issue complete holding

instructions when pilots request them.

c. If no holding pattern is charted and holding

instructions have not been issued, the pilot should ask

ATC for holding instructions prior to reaching the fix.

This procedure will eliminate the possibility of an

aircraft entering a holding pattern other than that

desired by ATC. If unable to obtain holding

instructions prior to reaching the fix (due to

frequency congestion, stuck microphone, etc.), then

enter a standard pattern on the course on which the

aircraft approached the fix and request further

clearance as soon as possible. In this event, the

altitude/flight level of the aircraft at the clearance

limit will be protected so that separation will be

provided as required.

d. When an aircraft is 3 minutes or less from a

clearance limit and a clearance beyond the fix has not

been received, the pilot is expected to start a speed

reduction so that the aircraft will cross the fix,

initially, at or below the maximum holding airspeed.

e. When no delay is expected, the controller

should issue a clearance beyond the fix as soon as

possible and, whenever possible, at least 5 minutes

before the aircraft reaches the clearance limit.

f. Pilots should report to ATC the time and

altitude/flight level at which the aircraft reaches the

clearance limit and report leaving the clearance limit.

NOTE−

In the event of two-way communications failure, pilots are

required to comply with 14 CFR Section 91.185.

g. When holding at a VOR station, pilots should

begin the turn to the outbound leg at the time of the

first complete reversal of the to/from indicator.

h. Patterns at the most generally used holding

fixes are depicted (charted) on U.S. Government or

commercially produced (meeting FAA requirements)

Low or High Altitude Enroute, Area and STAR

Charts. Pilots are expected to hold in the pattern

depicted unless specifically advised otherwise by

ATC.

NOTE−

Holding patterns that protect for a maximum holding

airspeed other than the standard may be depicted by an

icon, unless otherwise depicted. The icon is a standard

holding pattern symbol (racetrack) with the airspeed

restriction shown in the center. In other cases, the airspeed

restriction will be depicted next to the standard holding

pattern symbol.

REFERENCE−

AIM, Holding, Paragraph 5−3−8j2.

i. An ATC clearance requiring an aircraft to hold

at a fix where the pattern is not charted will include

the following information: (See FIG 5−3−2.)

1. Direction of holding from the fix in terms of

the eight cardinal compass points (i.e., N, NE, E, SE,

etc.).

2. Holding fix (the fix may be omitted if

included at the beginning of the transmission as the

clearance limit).

3. Radial, course, bearing, airway or route on

which the aircraft is to hold.

4. Leg length in miles if DME or RNAV is to be

used (leg length will be specified in minutes on pilot

request or if the controller considers it necessary).

5. Direction of turn if left turns are to be made,

the pilot requests, or the controller considers it

necessary.

6. Time to expect further clearance and any

pertinent additional delay information.
AIM 7/26/12

5−3−10 En Route Procedures

FIG 5−3−2

Holding Patterns

TYPICAL PROCEDURE ON AN ILS OUTER MARKER TYPICAL PROCEDURE ON AN ILS OUTER MARKER

EXAMPLES OF HOLDING EXAMPLES OF HOLDING

L OM M M MM

RUNWAY RUN

VORR

VORR

TYPICAL PROCEDURE AT INTERSECTION TYPICAL PROCEDURE AT INTERSECTION

OF VOR RADIALS OF VOR RADIALS

HOLDING COURSE

AWAY FROM NAVAID

HOLDING COURSE

AWAY FROM NAVAID

HOLDING COURSE

TOWARD NAVAID

HOLDING COURSE

TOWARD NAVAID

VORTAC

15 NM DME FIX 15 NM DME FIX 10 NM DME FIX 10 NM DME FIX

TYPICAL PROCEDURE AT DME FIX TYPICAL PROCEDURE AT DME FIX
7/26/12 AIM

En Route Procedures 5−3−11

FIG 5−3−3

Holding Pattern Descriptive Terms

ABEAM

HOLDING SIDE HOLDING SIDE

OUTBOUND

END

OUTBOUND

HOLDING

COURSE

HOLDING

COURSE

OUTBOUND OUTBOUND

INBOUND INBOUND

NONHOLDING SIDE NONHOLDING SIDE

FIX END FIX END

RECIPROCAL RECIPROCAL

FIX

j. Holding pattern airspace protection is based on

the following procedures.

1. Descriptive Terms.

(a) Standard Pattern. Right turns 

(See FIG 5−3−3.)

(b) Nonstandard Pattern. Left turns

2. Airspeeds.

(a) All aircraft may hold at the following

altitudes and maximum holding airspeeds:

TBL 5−3−1

Altitude (MSL) Airspeed (KIAS)

MHA − 6,000’ 200

6,001’ − 14,000’ 230

14,001’ and above 265

(b) The following are exceptions to the

maximum holding airspeeds:

(1) Holding patterns from 6,001’ to

14,000’ may be restricted to a maximum airspeed of

210 KIAS. This nonstandard pattern will be depicted

by an icon.

(2) Holding patterns may be restricted to a

maximum speed. The speed restriction is depicted in

parenthesis inside the holding pattern on the chart:

e.g., (175). The aircraft should be at or below the

maximum speed prior to initially crossing the holding

fix to avoid exiting the protected airspace. Pilots

unable to comply with the maximum airspeed

restriction should notify ATC.

(3) Holding patterns at USAF airfields

only − 310 KIAS maximum, unless otherwise

depicted.

(4) Holding patterns at Navy fields only −

230 KIAS maximum, unless otherwise depicted.

(5) When a climb−in hold is specified by a

published procedure (e.g., “Climb−in holding

pattern to depart XYZ VORTAC at or above 10,000.”

or “All aircraft climb−in TRUCK holding pattern to

cross TRUCK Int at or above 11,500 before

proceeding on course.”), additional obstacle protection area has been provided to allow for greater

airspeeds in the climb for those aircraft requiring

them. The holding pattern template for a maximum

airspeed of 310 KIAS has been used for the holding

pattern if there are no airspeed restrictions on the

holding pattern as specified in subparagraph j2(b)(2)

of this paragraph. Where the holding pattern is

restricted to a maximum airspeed of 175 KIAS, the

200 KIAS holding pattern template has been applied

for published climb−in hold procedures for altitudes

6,000 feet and below and the 230 KIAS holding

pattern template has been applied for altitudes above

6,000 feet. The airspeed limitations in 14 CFR

Section 91.117, Aircraft Speed, still apply.

(c) The following phraseology may be used

by an ATCS to advise a pilot of the maximum holding

airspeed for a holding pattern airspace area.

PHRASEOLOGY−

(AIRCRAFT IDENTIFICATION) (holding instructions,

when needed) MAXIMUM HOLDING AIRSPEED IS

(speed in knots).
AIM 7/26/12

5−3−12 En Route Procedures

FIG 5−3−4

Holding Pattern Entry Procedures

3. Entry Procedures. (See FIG 5−3−4.)

(a) Parallel Procedure. When approaching

the holding fix from anywhere in sector (a), the

parallel entry procedure would be to turn to a heading

to parallel the holding course outbound on the

nonholding side for one minute, turn in the direction

of the holding pattern through more than 180 degrees,

and return to the holding fix or intercept the holding

course inbound.

(b) Teardrop Procedure. When approaching the holding fix from anywhere in sector (b), the

teardrop entry procedure would be to fly to the fix,

turn outbound to a heading for a 30 degree teardrop

entry within the pattern (on the holding side) for a

period of one minute, then turn in the direction of the

holding pattern to intercept the inbound holding

course.

(c) Direct Entry Procedure. When approaching the holding fix from anywhere in

sector (c), the direct entry procedure would be to fly

directly to the fix and turn to follow the holding

pattern.

(d) While other entry procedures may enable

the aircraft to enter the holding pattern and remain

within protected airspace, the parallel, teardrop and

direct entries are the procedures for entry and holding

recommended by the FAA.

4. Timing.

(a) Inbound Leg.

(1) At or below 14,000 feet MSL: 1 minute.

(2) Above 14,000 feet MSL: 11/2 minutes.

NOTE−

The initial outbound leg should be flown for 1 minute or

1 1/2 minutes (appropriate to altitude). Timing for

subsequent outbound legs should be adjusted, as

necessary, to achieve proper inbound leg time. Pilots may

use any navigational means available; i.e., DME, RNAV,

etc., to ensure the appropriate inbound leg times.

(b) Outbound leg timing begins over/abeam

the fix, whichever occurs later. If the abeam position

cannot be determined, start timing when turn to

outbound is completed.

5. Distance Measuring Equipment (DME)/

GPS Along−Track Distance (ATD). DME/GPS

holding is subject to the same entry and holding

procedures except that distances (nautical miles) are

used in lieu of time values. The outbound course of

the DME/GPS holding pattern is called the outbound

leg of the pattern. The controller or the instrument

approach procedure chart will specify the length of

the outbound leg. The end of the outbound leg is

determined by the DME or ATD readout. The holding

fix on conventional procedures, or controller defined

holding based on a conventional navigation aid with

DME, is a specified course or radial and distances are

from the DME station for both the inbound and
7/26/12 AIM

En Route Procedures 5−3−13

outbound ends of the holding pattern. When flying

published GPS overlay or stand alone procedures

with distance specified, the holding fix will be a

waypoint in the database and the end of the outbound

leg will be determined by the ATD. Some GPS

overlay and early stand alone procedures may have

timing specified. (See FIG 5−3−5, FIG 5−3−6 and

FIG 5−3−7.) See paragraph 1−1−19, Global Positioning System (GPS), for requirements and restriction

on using GPS for IFR operations.

FIG 5−3−5

Inbound Toward NAVAID

NOTE−

When the inbound course is toward the NAVAID, the fix distance is 10 NM, and the leg length is 5 NM, then the end of the

outbound leg will be reached when the DME/ATD reads 15 NM.

FIG 5−3−6

Inbound Leg Away from NAVAID

NOTE−

When the inbound course is away from the NAVAID and the fix distance is 28 NM, and the leg length is 8 NM, then the end

of the outbound leg will be reached when the DME/ATD reads 20 NM.

FIG 5−3−7

GPS/RNAV Holding

NOTE−

The inbound course is always toward the waypoint and the ATD is zero at the waypoint. The end of the outbound leg of the

holding pattern is reached when the ATD reads the specified distance.
AIM 7/26/12

5−3−14 En Route Procedures

6. Pilot Action.

(a) Start speed reduction when 3 minutes or

less from the holding fix. Cross the holding fix,

initially, at or below the maximum holding airspeed.

(b) Make all turns during entry and while

holding at:

(1) 3 degrees per second; or

(2) 30 degree bank angle; or

(3) 25 degree bank provided a flight

director system is used.

NOTE−

Use whichever requires the least bank angle.

(c) Compensate for wind effect primarily by

drift correction on the inbound and outbound legs.

When outbound, triple the inbound drift correction to

avoid major turning adjustments; e.g., if correcting

left by 8 degrees when inbound, correct right by

24 degrees when outbound.

(d) Determine entry turn from aircraft

heading upon arrival at the holding fix; +/−5 degrees

in heading is considered to be within allowable good

operating limits for determining entry.

(e) Advise ATC immediately what increased

airspeed is necessary, if any, due to turbulence, icing,

etc., or if unable to accomplish any part of the holding

procedures. When such higher speeds become no

longer necessary, operate according to the appropriate published holding speed and notify ATC.

7. Nonstandard Holding Pattern. Fix end

and outbound end turns are made to the left. Entry

procedures to a nonstandard pattern are oriented in

relation to the 70 degree line on the holding side just

as in the standard pattern.

k. When holding at a fix and instructions are

received specifying the time of departure from the fix,

the pilot should adjust the aircraft’s flight path within

the limits of the established holding pattern in order

to leave the fix at the exact time specified. After

departing the holding fix, normal speed is to be

resumed with respect to other governing speed

requirements, such as terminal area speed limits,

specific ATC requests, etc. Where the fix is associated

with an instrument approach and timed approaches

are in effect, a procedure turn must not be executed

unless the pilot advises ATC, since aircraft holding

are expected to proceed inbound on final approach

directly from the holding pattern when approach

clearance is received.

l. Radar surveillance of outer fix holding pattern

airspace areas.

1. Whenever aircraft are holding at an outer fix,

ATC will usually provide radar surveillance of the

outer fix holding pattern airspace area, or any portion

of it, if it is shown on the controller’s radar scope.

2. The controller will attempt to detect any

holding aircraft that stray outside the holding pattern

airspace area and will assist any detected aircraft to

return to the assigned airspace area.

NOTE−

Many factors could prevent ATC from providing this

additional service, such as workload, number of targets,

precipitation, ground clutter, and radar system capability.

These circumstances may make it unfeasible to maintain

radar identification of aircraft to detect aircraft straying

from the holding pattern. The provision of this service

depends entirely upon whether controllers believe they are

in a position to provide it and does not relieve a pilot of their

responsibility to adhere to an accepted ATC clearance.

3. If an aircraft is established in a published

holding pattern at an assigned altitude above the

published minimum holding altitude and subsequently cleared for the approach, the pilot may descend to

the published minimum holding altitude. The holding

pattern would only be a segment of the IAP if it is

published on the instrument procedure chart and is

used in lieu of a procedure turn.

m. For those holding patterns where there are no

published minimum holding altitudes, the pilot, upon

receiving an approach clearance, must maintain the

last assigned altitude until leaving the holding pattern

and established on the inbound course. Thereafter, the

published minimum altitude of the route segment

being flown will apply. It is expected that the pilot

will be assigned a holding altitude that will permit a

normal descent on the inbound course.
7/26/12 AIM

Arrival Procedures 5−4−1

Section 4. Arrival Procedures

5−4−1. Standard Terminal Arrival (STAR),

Area Navigation (RNAV) STAR, and Flight

Management System Procedures (FMSP)

for Arrivals

a. A STAR is an ATC coded IFR arrival route

established for application to arriving IFR aircraft

destined for certain airports. RNAV STAR/FMSP

procedures for arrivals serve the same purpose but are

only used by aircraft equipped with FMS or GPS. The

purpose of both is to simplify clearance delivery

procedures and facilitate transition between en route

and instrument approach procedures.

1. STAR/RNAV STAR/FMSP procedures may

have mandatory speeds and/or crossing altitudes

published. Other STARs may have planning

information depicted to inform pilots what clearances

or restrictions to “expect.” “Expect” altitudes/speeds

are not considered STAR/RNAV STAR/FMSP

procedures crossing restrictions unless verbally

issued by ATC.

NOTE−

The “expect” altitudes/speeds are published so that pilots

may have the information for planning purposes. These

altitudes/speeds must not be used in the event of lost

communications unless ATC has specifically advised the

pilot to expect these altitudes/speeds as part of a further

clearance.

REFERENCE−

14 CFR Section 91.185(c)(2)(iii).

2. Pilots navigating on STAR/RNAV STAR/

FMSP procedures must maintain last assigned

altitude until receiving authorization to descend so as

to comply with all published/issued restrictions. This

authorization will contain the phraseology

“DESCEND VIA.”

(a) Clearance to “descend via” authorizes

pilots to:

(1) Vertically and laterally navigate on a

STAR/RNAV STAR/FMSP.

(2) When cleared to a waypoint depicted on

a STAR/RNAV STAR/FMSP, to descend from a

previously assigned altitude at pilot’s discretion to the

altitude depicted for that waypoint, and once

established on the depicted arrival, to navigate

laterally and vertically to meet all published restrictions.

NOTE−

1. Air traffic is responsible for obstacle clearance when issuing a “descend via” instruction to the pilot. The descend

via is used in conjunction with STARs/RNAV STARs/

FMSPs to reduce phraseology by not requiring the

controller to restate the altitude at the next waypoint/fix to

which the pilot has been cleared.

2. Air traffic will assign an altitude to cross the waypoint/

fix, if no altitude is depicted at the waypoint/fix, for aircraft

on a direct routing to a STAR/RNAV STAR/FMSP.

3. Minimum en route altitudes (MEA) are not considered

restrictions; however, pilots are expected to remain above

MEAs.

EXAMPLE−

1. Lateral/routing clearance only.

“Cleared Hadly One arrival.”

2. Routing with assigned altitude.

“Cleared Hadly One arrival, descend and maintain

Flight Level two four zero.”

“Cleared Hadly One arrival, descend at pilot’s discretion, maintain Flight Level two four zero.”

3. Lateral/routing and vertical navigation clearance.

“Descend via the Civit One arrival.”

“Descend via the Civit One arrival, except, cross

Arnes at or above one one thousand.”

4. Lateral/routing and vertical navigation clearance

when assigning altitude not published on procedure.

“Descend via the Haris One arrival, except after Bruno, maintain one zero thousand.”

“Descend via the Haris One arrival, except cross Bruno at one three thousand then maintain one zero

thousand.”

5. Direct routing to intercept a STAR/RNAV STAR/

FMSP and vertical navigation clearance.

“Proceed direct Mahem, descend via Mahem One arrival.”

“Proceed direct Luxor, cross Luxor at or above flight

level two zero zero, then descend via the Ksino One Arrival.”

NOTE−

1. In Example 2, pilots are expected to descend to FL 240

as directed, and maintain FL 240 until cleared for further

vertical navigation with a newly assigned altitude or a “descend via” clearance.

2. In Example 4, the aircraft should track laterally and

vertically on the Haris One arrival and should descend so
AIM 7/26/12

5−4−2 Arrival Procedures

as to comply with all speed and altitude restrictions until

reaching Bruno and then maintain 10,000. Upon reaching

10,000, aircraft should maintain 10,000 until cleared by

ATC to continue to descend.

(b) Pilots cleared for vertical navigation

using the phraseology “descend via” must inform

ATC upon initial contact with a new frequency.

EXAMPLE−

“Delta One Twenty One leaving FL 240, descending via

the Civit One arrival.”

b. Pilots of IFR aircraft destined to locations for

which STARs have been published may be issued a

clearance containing a STAR whenever ATC deems

it appropriate.

c. Use of STARs requires pilot possession of at

least the approved chart. RNAV STARs must be

retrievable by the procedure name from the aircraft

database and conform to charted procedure. As with

any ATC clearance or portion thereof, it is the

responsibility of each pilot to accept or refuse an

issued STAR. Pilots should notify ATC if they do not

wish to use a STAR by placing “NO STAR” in the

remarks section of the flight plan or by the less

desirable method of verbally stating the same to ATC.

d. STAR charts are published in the Terminal

Procedures Publications (TPP) and are available on

subscription from the National Aeronautical

Charting Office.

e. RNAV STAR.

1. All public RNAV STARs are RNAV1. These

procedures require system performance currently

met by GPS or DME/DME/IRU RNAV systems that

satisfy the criteria discussed in AC 90−100A, U.S.

Terminal and En Route Area Navigation (RNAV)

Operations. RNAV1 procedures require the aircraft’s

total system error remain bounded by +1 NM for 95%

of the total flight time.

2. For procedures requiring GPS, if the

navigation system does not automatically alert the

flight crew of a loss of GPS, the operator must

develop procedures to verify correct GPS operation.

5−4−2. Local Flow Traffic Management Program

a. This program is a continuing effort by the FAA

to enhance safety, minimize the impact of aircraft

noise and conserve aviation fuel. The enhancement of

safety and reduction of noise is achieved in this

program by minimizing low altitude maneuvering of

arriving turbojet and turboprop aircraft weighing

more than 12,500 pounds and, by permitting

departure aircraft to climb to higher altitudes sooner,

as arrivals are operating at higher altitudes at the

points where their flight paths cross. The application

of these procedures also reduces exposure time

between controlled aircraft and uncontrolled aircraft

at the lower altitudes in and around the terminal

environment. Fuel conservation is accomplished by

absorbing any necessary arrival delays for aircraft

included in this program operating at the higher and

more fuel efficient altitudes.

b. A fuel efficient descent is basically an

uninterrupted descent (except where level flight is

required for speed adjustment) from cruising altitude

to the point when level flight is necessary for the pilot

to stabilize the aircraft on final approach. The

procedure for a fuel efficient descent is based on an

altitude loss which is most efficient for the majority

of aircraft being served. This will generally result in

a descent gradient window of 250−350 feet per

nautical mile.

c. When crossing altitudes and speed restrictions

are issued verbally or are depicted on a chart, ATC

will expect the pilot to descend first to the crossing

altitude and then reduce speed. Verbal clearances for

descent will normally permit an uninterrupted

descent in accordance with the procedure as

described in paragraph b above. Acceptance of a

charted fuel efficient descent (Runway Profile

Descent) clearance requires the pilot to adhere to the

altitudes, speeds, and headings depicted on the charts

unless otherwise instructed by ATC. PILOTS

RECEIVING A CLEARANCE FOR A FUEL

EFFICIENT DESCENT ARE EXPECTED TO

ADVISE ATC IF THEY DO NOT HAVE RUNWAY

PROFILE DESCENT CHARTS PUBLISHED FOR

THAT AIRPORT OR ARE UNABLE TO COMPLY

WITH THE CLEARANCE.

5−4−3. Approach Control

a. Approach control is responsible for controlling

all instrument flight operating within its area of

responsibility. Approach control may serve one or

more airfields, and control is exercised primarily by

direct pilot and controller communications. Prior to

arriving at the destination radio facility, instructions
7/26/12 AIM

Arrival Procedures 5−4−3

will be received from ARTCC to contact approach

control on a specified frequency.

b. Radar Approach Control.

1. Where radar is approved for approach control

service, it is used not only for radar approaches

(Airport Surveillance Radar [ASR] and Precision

Approach Radar [PAR]) but is also used to provide

vectors in conjunction with published nonradar

approaches based on radio NAVAIDs (ILS, MLS,

VOR, NDB, TACAN). Radar vectors can provide

course guidance and expedite traffic to the final

approach course of any established IAP or to the

traffic pattern for a visual approach. Approach

control facilities that provide this radar service will

operate in the following manner:

(a) Arriving aircraft are either cleared to an

outer fix most appropriate to the route being flown

with vertical separation and, if required, given

holding information or, when radar handoffs are

effected between the ARTCC and approach control,

or between two approach control facilities, aircraft

are cleared to the airport or to a fix so located that the

handoff will be completed prior to the time the

aircraft reaches the fix. When radar handoffs are

utilized, successive arriving flights may be handed

off to approach control with radar separation in lieu

of vertical separation.

(b) After release to approach control, aircraft

are vectored to the final approach course (ILS, MLS,

VOR, ADF, etc.). Radar vectors and altitude or flight

levels will be issued as required for spacing and

separating aircraft. Therefore, pilots must not deviate

from the headings issued by approach control.

Aircraft will normally be informed when it is

necessary to vector across the final approach course

for spacing or other reasons. If approach course

crossing is imminent and the pilot has not been

informed that the aircraft will be vectored across the

final approach course, the pilot should query the

controller.

(c) The pilot is not expected to turn inbound

on the final approach course unless an approach

clearance has been issued. This clearance will

normally be issued with the final vector for

interception of the final approach course, and the

vector will be such as to enable the pilot to establish

the aircraft on the final approach course prior to

reaching the final approach fix.

(d) In the case of aircraft already inbound on

the final approach course, approach clearance will be

issued prior to the aircraft reaching the final approach

fix. When established inbound on the final approach

course, radar separation will be maintained and the

pilot will be expected to complete the approach

utilizing the approach aid designated in the clearance

(ILS, MLS, VOR, radio beacons, etc.) as the primary

means of navigation. Therefore, once established on

the final approach course, pilots must not deviate

from it unless a clearance to do so is received from

ATC.

(e) After passing the final approach fix on

final approach, aircraft are expected to continue

inbound on the final approach course and complete

the approach or effect the missed approach procedure

published for that airport.

2. ARTCCs are approved for and may provide

approach control services to specific airports. The

radar systems used by these centers do not provide the

same precision as an ASR/PAR used by approach

control facilities and towers, and the update rate is not

as fast. Therefore, pilots may be requested to report

established on the final approach course.

3. Whether aircraft are vectored to the appropriate final approach course or provide their own

navigation on published routes to it, radar service is

automatically terminated when the landing is

completed or when instructed to change to advisory

frequency at uncontrolled airports, whichever occurs

first.

5−4−4. Advance Information on Instrument

Approach

a. When landing at airports with approach control

services and where two or more IAPs are published,

pilots will be provided in advance of their arrival with

the type of approach to expect or that they may be

vectored for a visual approach. This information will

be broadcast either by a controller or on ATIS. It will

not be furnished when the visibility is three miles or

better and the ceiling is at or above the highest initial

approach altitude established for any low altitude IAP

for the airport.

b. The purpose of this information is to aid the

pilot in planning arrival actions; however, it is not an

ATC clearance or commitment and is subject to

change. Pilots should bear in mind that fluctuating

weather, shifting winds, blocked runway, etc., are
AIM 7/26/12

5−4−4 Arrival Procedures

conditions which may result in changes to approach

information previously received. It is important that

pilots advise ATC immediately they are unable to

execute the approach ATC advised will be used, or if

they prefer another type of approach.

c. Aircraft destined to uncontrolled airports,

which have automated weather data with broadcast

capability, should monitor the ASOS/AWSS/AWOS

frequency to ascertain the current weather for the airport. The pilot must advise ATC when he/she has

received the broadcast weather and state his/her

intentions.

NOTE−

1. ASOS/AWSS/AWOS should be set to provide one−

minute broadcast weather updates at uncontrolled airports

that are without weather broadcast capability by a human

observer.

2. Controllers will consider the long line disseminated

weather from an automated weather system at an

uncontrolled airport as trend and planning information

only and will rely on the pilot for current weather

information for the airport. If the pilot is unable to receive

the current broadcast weather, the last long line

disseminated weather will be issued to the pilot. When

receiving IFR services, the pilot/aircraft operator is

responsible for determining if weather/visibility is

adequate for approach/landing.

d. When making an IFR approach to an airport not

served by a tower or FSS, after ATC advises

“CHANGE TO ADVISORY FREQUENCY APPROVED” you should broadcast your intentions,

including the type of approach being executed, your

position, and when over the final approach fix

inbound (nonprecision approach) or when over the

outer marker or fix used in lieu of the outer marker

inbound (precision approach). Continue to monitor

the appropriate frequency (UNICOM, etc.) for

reports from other pilots.

5−4−5. Instrument Approach Procedure

Charts

a. 14 CFR Section 91.175(a), Instrument approaches to civil airports, requires the use of SIAPs

prescribed for the airport in 14 CFR Part 97 unless

otherwise authorized by the Administrator (including

ATC). If there are military procedures published at a

civil airport, aircraft operating under 14 CFR Part 91

must use the civil procedure(s). Civil procedures are

defined with “FAA” in parenthesis; e.g., (FAA), at the

top, center of the procedure chart. DOD procedures

are defined using the abbreviation of the applicable

military service in parenthesis; e.g., (USAF), (USN),

(USA). 14 CFR Section 91.175(g), Military airports,

requires civil pilots flying into or out of military

airports to comply with the IAPs and takeoff and

landing minimums prescribed by the authority

having jurisdiction at those airports. Unless an

emergency exists, civil aircraft operating at military

airports normally require advance authorization,

commonly referred to as “Prior Permission

Required” or “PPR.” Information on obtaining a PPR

for a particular military airport can be found in the

Airport/Facility Directory.

NOTE−

Civil aircraft may conduct practice VFR approaches using

DOD instrument approach procedures when approved by

the air traffic controller.

1. IAPs (standard and special, civil and military)

are based on joint civil and military criteria contained

in the U.S. Standard for TERPS. The design of IAPs

based on criteria contained in TERPS, takes into

account the interrelationship between airports,

facilities, and the surrounding environment, terrain,

obstacles, noise sensitivity, etc. Appropriate

altitudes, courses, headings, distances, and other

limitations are specified and, once approved, the

procedures are published and distributed by

government and commercial cartographers as

instrument approach charts.

2. Not all IAPs are published in chart form.

Radar IAPs are established where requirements and

facilities exist but they are printed in tabular form in

appropriate U.S. Government Flight Information

Publications.

3. The navigation equipment required to join

and fly an instrument approach procedure is indicated

by the title of the procedure and notes on the chart.

(a) Straight−in IAPs are identified by the

navigational system providing the final approach

guidance and the runway to which the approach is

aligned (e.g., VOR RWY 13). Circling only

approaches are identified by the navigational system

providing final approach guidance and a letter

(e.g., VOR A). More than one navigational system

separated by a slash indicates that more than one type

of equipment must be used to execute the final

approach (e.g., VOR/DME RWY 31). More than

one navigational system separated by the word “or”

indicates either type of equipment may be used to
7/26/12 AIM

Arrival Procedures 5−4−5

execute the final approach (e.g., VOR or GPS

RWY 15).

(b) In some cases, other types of navigation

systems including radar may be required to execute

other portions of the approach or to navigate to the

IAF (e.g., an NDB procedure turn to an ILS, an NDB

in the missed approach, or radar required to join the

procedure or identify a fix). When radar or other

equipment is required for procedure entry from the

en route environment, a note will be charted in the

planview of the approach procedure chart

(e.g., RADAR REQUIRED or ADF REQUIRED).

When radar or other equipment is required on

portions of the procedure outside the final approach

segment, including the missed approach, a note will

be charted in the notes box of the pilot briefing

portion of the approach chart (e.g., RADAR

REQUIRED or DME REQUIRED). Notes are not

charted when VOR is required outside the final

approach segment. Pilots should ensure that the

aircraft is equipped with the required NAVAID(s) in

order to execute the approach, including the missed

approach.

NOTE−

Some military (i.e., U.S. Air Force and U.S. Navy)

IAPs have these “additional equipment required”

notes charted only in the planview of the approach

procedure and do not conform to the same application

standards used by the FAA.

(c) The FAA has initiated a program to

provide a new notation for LOC approaches when

charted on an ILS approach requiring other

navigational aids to fly the final approach course. The

LOC minimums will be annotated with the NAVAID

required (e.g., “DME Required” or “RADAR

Required”). During the transition period, ILS

approaches will still exist without the annotation.

(d) Many ILS approaches having minima

based on RVR are eligible for a landing minimum of

RVR 1800. Some of these approaches are to runways

that have touchdown zone and centerline lights. For

many runways that do not have touchdown and

centerline lights, it is still possible to allow a landing

minimum of RVR 1800. For these runways, the

normal ILS minimum of RVR 2400 can be annotated

with a single or double asterisk or the dagger symbol

“†”; for example “** 696/24 200 (200/1/2).” A note

is included on the chart stating “**RVR 1800

authorized with use of FD or AP or HUD to DA.” The

pilot must use the flight director, or autopilot with an

approved approach coupler, or head up display to

decision altitude or to the initiation of a missed

approach. In the interest of safety, single pilot

operators should not fly approaches to 1800 RVR

minimums on runways without touchdown and

centerline lights using only a flight director, unless

accompanied by the use of an autopilot with an

approach coupler.

(e) The naming of multiple approaches of the

same type to the same runway is also changing.

Multiple approaches with the same guidance will be

annotated with an alphabetical suffix beginning at the

end of the alphabet and working backwards for

subsequent procedures (e.g., ILS Z RWY 28, ILS Y

RWY 28, etc.). The existing annotations such as

ILS 2 RWY 28 or Silver ILS RWY 28 will be phased

out and replaced with the new designation. The Cat II

and Cat III designations are used to differentiate

between multiple ILSs to the same runway unless

there are multiples of the same type.

(f) RNAV (GPS) approaches to LNAV, LP,

LNAV/VNAV and LPV lines of minima using WAAS

and RNAV (GPS) approaches to LNAV and

LNAV/VNAV lines of minima using GPS are charted

as RNAV (GPS) RWY (Number) (e.g., RNAV (GPS)

RWY 21). VOR/DME RNAV approaches will

continue to be identified as VOR/DME RNAV RWY

(Number) (e.g., VOR/DME RNAV RWY 21).

VOR/DME RNAV procedures which can be flown by

GPS will be annotated with “or GPS”

(e.g., VOR/DME RNAV or GPS RWY 31).

4. Approach minimums are based on the local

altimeter setting for that airport, unless annotated

otherwise; e.g., Oklahoma City/Will Rogers World

approaches are based on having a Will Rogers World

altimeter setting. When a different altimeter source is

required, or more than one source is authorized, it will

be annotated on the approach chart; e.g., use Sidney

altimeter setting, if not received, use Scottsbluff

altimeter setting. Approach minimums may be raised

when a nonlocal altimeter source is authorized. When

more than one altimeter source is authorized, and the

minima are different, they will be shown by separate

lines in the approach minima box or a note; e.g., use

Manhattan altimeter setting; when not available use

Salina altimeter setting and increase all MDAs

40 feet. When the altimeter must be obtained from a

source other than air traffic a note will indicate the

source; e.g., Obtain local altimeter setting on CTAF.
AIM 7/26/12

5−4−6 Arrival Procedures

When the altimeter setting(s) on which the approach

is based is not available, the approach is not

authorized. Baro−VNAV must be flown using the

local altimeter setting only. Where no local altimeter

is available, the LNAV/VNAV line will still be

published for use by WAAS receivers with a note that

Baro−VNAV is not authorized. When a local and at

least one other altimeter setting source is authorized

and the local altimeter is not available Baro−VNAV

is not authorized; however, the LNAV/VNAV

minima can still be used by WAAS receivers using the

alternate altimeter setting source.

NOTE−

Barometric Vertical Navigation (baro−VNAV). An RNAV

system function which uses barometric altitude information from the aircraft’s altimeter to compute and present

a vertical guidance path to the pilot. The specified vertical

path is computed as a geometric path, typically computed

between two waypoints or an angle based computation

from a single waypoint. Further guidance may be found in

Advisory Circular 90−105.

5. A pilot adhering to the altitudes, flight paths,

and weather minimums depicted on the IAP chart or

vectors and altitudes issued by the radar controller, is

assured of terrain and obstruction clearance and

runway or airport alignment during approach for

landing.

6. IAPs are designed to provide an IFR descent

from the en route environment to a point where a safe

landing can be made. They are prescribed and

approved by appropriate civil or military authority to

ensure a safe descent during instrument flight

conditions at a specific airport. It is important that

pilots understand these procedures and their use prior

to attempting to fly instrument approaches.

7. TERPS criteria are provided for the following

types of instrument approach procedures:

(a) Precision Approach (PA). An instrument

approach based on a navigation system that provides

course and glidepath deviation information meeting

the precision standards of ICAO Annex 10. For

example, PAR, ILS, and GLS are precision

approaches.

(b) Approach with Vertical Guidance (APV).

An instrument approach based on a navigation

system that is not required to meet the precision

approach standards of ICAO Annex 10 but provides

course and glidepath deviation information. For

example, Baro−VNAV, LDA with glidepath,

LNAV/VNAV and LPV are APV approaches.

(c) Nonprecision Approach (NPA). An instrument approach based on a navigation system

which provides course deviation information, but no

glidepath deviation information. For example, VOR,

NDB and LNAV. As noted in subparagraph i, Vertical

Descent Angle (VDA) on Nonprecision Approaches,

some approach procedures may provide a Vertical

Descent Angle as an aid in flying a stabilized

approach, without requiring its use in order to fly the

procedure. This does not make the approach an APV

procedure, since it must still be flown to an MDA and

has not been evaluated with a glidepath.

b. The method used to depict prescribed altitudes

on instrument approach charts differs according to

techniques employed by different chart publishers.

Prescribed altitudes may be depicted in four different

configurations: minimum, maximum, mandatory,

and recommended. The U.S. Government distributes

charts produced by National Geospatial−Intelligence

Agency (NGA) and FAA. Altitudes are depicted on

these charts in the profile view with underscore,

overscore, both or none to identify them as minimum,

maximum, mandatory or recommended.

1. Minimum altitude will be depicted with the

altitude value underscored. Aircraft are required to

maintain altitude at or above the depicted value,

e.g., 3000.

2. Maximum altitude will be depicted with the

altitude value overscored. Aircraft are required to

maintain altitude at or below the depicted value,

e.g., 4000.

3. Mandatory altitude will be depicted with the

altitude value both underscored and overscored.

Aircraft are required to maintain altitude at the

depicted value, e.g., 5000.

4. Recommended altitude will be depicted with

no overscore or underscore. These altitudes are

depicted for descent planning, e.g., 6000.

NOTE−

1. Pilots are cautioned to adhere to altitudes as prescribed

because, in certain instances, they may be used as the basis

for vertical separation of aircraft by ATC. When a depicted

altitude is specified in the ATC clearance, that altitude becomes mandatory as defined above.

2. The ILS glide slope is intended to be intercepted at the

published glide slope intercept altitude. This point marks

the PFAF and is depicted by the ”lightning bolt” symbol
7/26/12 AIM

Arrival Procedures 5−4−7

on U.S. Government charts. Intercepting the glide slope

at this altitude marks the beginning of the final

approach segment and ensures required obstacle

clearance during descent from the glide slope intercept

altitude to the lowest published decision altitude for

the approach. Interception and tracking of the glide slope

prior to the published glide slope interception altitude

does not necessarily ensure that minimum, maximum,

and/or mandatory altitudes published for any preceding

fixes will be complied with during the descent. If the pilot

chooses to track the glide slope prior to the glide slope

interception altitude, they remain responsible for

complying with published altitudes for any preceding

stepdown fixes encountered during the subsequent

descent.

c. Minimum Safe/Sector Altitudes (MSA) are

published for emergency use on IAP charts. For

conventional navigation systems, the MSA is

normally based on the primary omnidirectional

facility on which the IAP is predicated. The MSA

depiction on the approach chart contains the facility

identifier of the NAVAID used to determine the MSA

altitudes. For RNAV approaches, the MSA is based

on the runway waypoint (RWY WP) for straight−in

approaches, or the airport waypoint (APT WP) for

circling approaches. For GPS approaches, the MSA

center will be the missed approach waypoint

(MAWP). MSAs are expressed in feet above mean

sea level and normally have a 25 NM radius;

however, this radius may be expanded to 30 NM if

necessary to encompass the airport landing surfaces.

Ideally, a single sector altitude is established and

depicted on the plan view of approach charts;

however, when necessary to obtain relief from

obstructions, the area may be further sectored and as

many as four MSAs established. When established,

sectors may be no less than 90 in spread. MSAs

provide 1,000 feet clearance over all obstructions but

do not necessarily assure acceptable navigation

signal coverage.

d. Terminal Arrival Area (TAA)

1. The objective of the TAA is to provide a

seamless transition from the en route structure to the

terminal environment for arriving aircraft equipped

with Flight Management System (FMS) and/or

Global Positioning System (GPS) navigational

equipment. The underlying instrument approach

procedure is an area navigation (RNAV) procedure

described in this section. The TAA provides the pilot

and air traffic controller with a very efficient method

for routing traffic into the terminal environment with

little required air traffic control interface, and with

minimum altitudes depicted that provide standard

obstacle clearance compatible with the instrument

procedure associated with it. The TAA will not be

found on all RNAV procedures, particularly in areas

of heavy concentration of air traffic. When the TAA

is published, it replaces the MSA for that approach

procedure. See FIG 5−4−9 for a depiction of a RNAV

approach chart with a TAA.

2. The RNAV procedure underlying the TAA

will be the “T” design (also called the “Basic T”), or

a modification of the “T.” The “T” design

incorporates from one to three IAFs; an intermediate

fix (IF) that serves as a dual purpose IF (IAF); a final

approach fix (FAF), and a missed approach point

(MAP) usually located at the runway threshold. The

three IAFs are normally aligned in a straight line

perpendicular to the intermediate course, which is an

extension of the final course leading to the runway,

forming a “T.” The initial segment is normally from

3−6 NM in length; the intermediate 5−7 NM, and the

final segment 5 NM. Specific segment length may be

varied to accommodate specific aircraft categories

for which the procedure is designed. However, the

published segment lengths will reflect the highest

category of aircraft normally expected to use the

procedure.

(a) A standard racetrack holding pattern may

be provided at the center IAF, and if present may be

necessary for course reversal and for altitude

adjustment for entry into the procedure. In the latter

case, the pattern provides an extended distance for the

descent required by the procedure. Depiction of this

pattern in U.S. Government publications will utilize

the “hold−in−lieu−of−PT” holding pattern symbol.

(b) The published procedure will be annotated to indicate when the course reversal is not

necessary when flying within a particular TAA area;

e.g., “NoPT.” Otherwise, the pilot is expected to

execute the course reversal under the provisions of

14 CFR Section 91.175. The pilot may elect to use

the course reversal pattern when it is not required by

the procedure, but must inform air traffic control and

receive clearance to do so. (See FIG 5−4−1,

FIG 5−4−2, FIG 5−4−9, and paragraph 5−4−9,

Procedure Turn and Hold−in−lieu of Procedure

Turn).
AIM 7/26/12

5−4−8 Arrival Procedures

3. The “T” design may be modified by the

procedure designers where required by terrain or air

traffic control considerations. For instance, the “T”

design may appear more like a regularly or irregularly

shaped “Y”, or may even have one or both outboard

IAFs eliminated resulting in an upside down “L” or

an “I” configuration. (See FIG 5−4−3 and

FIG 5−4−10). Further, the leg lengths associated with

the outboard IAFs may differ. (See FIG 5−4−5 and

FIG 5−4−6).

4. Another modification of the “T” design may

be found at airports with parallel runway configurations. Each parallel runway may be served by its own

“T” IAF, IF (IAF), and FAF combination, resulting in

parallel final approach courses. (See FIG 5−4−4).

Common IAFs may serve both runways; however,

only the intermediate and final approach segments for

the landing runway will be shown on the approach

chart. (See FIG 5−4−5 and FIG 5−4−6).
7/26/12 AIM

Arrival Procedures 5−4−9

FIG 5−4−1

Basic “T” Design

FIG 5−4−2

Basic “T” Design
AIM 7/26/12

5−4−10 Arrival Procedures

FIG 5−4−3

Modified Basic “T”

FIG 5−4−4

Modified “T” Approach to Parallel Runways
7/26/12 AIM

Arrival Procedures 5−4−11

FIG 5−4−5

“T” Approach with Common IAFs to Parallel Runways

FIG 5−4−6

“T” Approach with Common IAFs to Parallel Runways
AIM 7/26/12

5−4−12 Arrival Procedures

FIG 5−4−7

TAA Area

5. The standard TAA consists of three areas

defined by the extension of the IAF legs and the

intermediate segment course. These areas are called

the straight−in, left−base, and right−base areas. (See

FIG 5−4−7). TAA area lateral boundaries are

identified by magnetic courses TO the IF (IAF). The

straight−in area can be further divided into

pie−shaped sectors with the boundaries identified by

magnetic courses TO the IF (IAF), and may contain

stepdown sections defined by arcs based on RNAV

distances (DME or ATD) from the IF (IAF). The

right/left−base areas can only be subdivided using

arcs based on RNAV distances from the IAFs for

those areas. Minimum MSL altitudes are charted

within each of these defined areas/subdivisions that

provide at least 1,000 feet of obstacle clearance, or

more as necessary in mountainous areas.

(a) Prior to arriving at the TAA boundary, the

pilot can determine which area of the TAA the aircraft

will enter by selecting the IF (IAF) to determine the

magnetic bearing TO the center IF (IAF). That

bearing should then be compared with the published

bearings that define the lateral boundaries of the TAA

areas. Using the end IAFs may give a false indication

of which area the aircraft will enter. This is critical

when approaching the TAA near the extended

boundary between the left and right−base areas,

especially where these areas contain different

minimum altitude requirements.

(b) Pilots entering the TAA and cleared by air

traffic control, are expected to proceed directly to the

IAF associated with that area of the TAA at the

altitude depicted, unless otherwise cleared by air

traffic control. Cleared direct to an Initial Approach

Fix (IAF) without a clearance for the procedure does

not authorize a pilot to descend to a lower TAA

altitude. If a pilot desires a lower altitude without an

approach clearance, request the lower TAA altitude.

If a pilot is not sure of what they are authorized or

expected to do by air traffic, they should ask air traffic

or request a specific clearance. Pilots entering the

TAA with two−way radio communications failure

(14 CFR Section 91.185, IFR Operations: Two−way

Radio Communications Failure), must maintain the

highest altitude prescribed by Section 91.185(c)(2)

until arriving at the appropriate IAF.
7/26/12 AIM

Arrival Procedures 5−4−13

FIG 5−4−8

Sectored TAA Areas

(c) Depiction of the TAA on U.S. Government charts will be through the use of icons located

in the plan view outside the depiction of the actual

approach procedure. (See FIG 5−4−9). Use of icons

is necessary to avoid obscuring any portion of the “T”

procedure (altitudes, courses, minimum altitudes,

etc.). The icon for each TAA area will be located and

oriented on the plan view with respect to the direction

of arrival to the approach procedure, and will show all

TAA minimum altitudes and sector/radius subdivisions for that area. The IAF for each area of the TAA

is included on the icon where it appears on the approach, to help the pilot orient the icon to the

approach procedure. The IAF name and the distance

of the TAA area boundary from the IAF are included

on the outside arc of the TAA area icon. Examples

here are shown with the TAA around the approach to

aid pilots in visualizing how the TAA corresponds to

the approach and should not be confused with the

actual approach chart depiction.

(d) Each waypoint on the “T”, except the

missed approach waypoint, is assigned a pronounceable 5−character name used in air traffic control

communications, and which is found in the RNAV

databases for the procedure. The missed approach

waypoint is assigned a pronounceable name when it

is not located at the runway threshold.

6. Once cleared to fly the TAA, pilots are

expected to obey minimum altitudes depicted within

the TAA icons, unless instructed otherwise by air

traffic control. In FIG 5−4−8, pilots within the left or

right−base areas are expected to maintain a minimum

altitude of 6,000 feet until within 17 NM of the

associated IAF. After crossing the 17 NM arc, descent

is authorized to the lower charted altitudes. Pilots

approaching from the northwest are expected to

maintain a minimum altitude of 6,000 feet, and when

within 22 NM of the IF (IAF), descend to a minimum

altitude of 2,000 feet MSL until reaching the IF

(IAF).
AIM 7/26/12

5−4−14 Arrival Procedures

FIG 5−4−9

RNAV (GPS) Approach Chart

NOTE−

This chart has been modified to depict new concepts and may not reflect actual approach minima.
7/26/12 AIM

Arrival Procedures 5−4−15

FIG 5−4−10

TAA with Left and Right Base Areas Eliminated

7. Just as the underlying “T” approach procedure may be modified in shape, the TAA may contain

modifications to the defined area shapes and sizes.

Some areas may even be eliminated, with other areas

expanded as needed. FIG 5−4−10 is an example of a

design limitation where a course reversal is necessary

when approaching the IF (IAF) from certain

directions due to the amount of turn required at the IF

(IAF). Design criteria require a course reversal

whenever this turn exceeds 120 degrees. In this

generalized example, pilots approaching on a bearing

TO the IF (IAF) from 300 clockwise through 060

are expected to execute a course reversal. The term

“NoPT” will be annotated on the boundary of the

TAA icon for the other portion of the TAA.
AIM 7/26/12

5−4−16 Arrival Procedures

FIG 5−4−11

TAA with Right Base Eliminated

8. FIG 5−4−11 depicts another TAA modification that pilots may encounter. In this generalized

example, the right−base area has been eliminated.

Pilots operating within the TAA between 360clockwise to 060 bearing TO the IF (IAF) are expected to

execute the course reversal in order to properly align

the aircraft for entry onto the intermediate segment.

Aircraft operating in all other areas from 060 

clockwise to 360 bearing TO the IF (IAF) need not

perform the course reversal, and the term “NoPT”

will be annotated on the TAA boundary of the icon in

these areas. TAAs are no longer being produced with

sections removed; however, some may still exist on

previously published procedures.
7/26/12 AIM

Arrival Procedures 5−4−17

FIG 5−4−12

Examples of a TAA with Feeders from an Airway

9. When an airway does not cross the lateral

TAA boundaries, a feeder route will be established to

provide a transition from the en route structure to the

appropriate IAF. Each feeder route will terminate at

the TAA boundary, and will be aligned along a path

pointing to the associated IAF. Pilots should descend

to the TAA altitude after crossing the TAA boundary

and cleared by air traffic control. (See FIG 5−4−12).
AIM 7/26/12

5−4−18 Arrival Procedures

FIG 5−4−13

Minimum Vectoring Altitude Charts

1500

2000

3000

3000

3000

3500

2500

5000

5500

5

10

15

20

25

30

348 013

057

102

160

250

277

289

N

e. Minimum Vectoring Altitudes (MVAs) are

established for use by ATC when radar ATC is

exercised. MVA charts are prepared by air traffic

facilities at locations where there are numerous

different minimum IFR altitudes. Each MVA chart

has sectors large enough to accommodate vectoring

of aircraft within the sector at the MVA. Each sector

boundary is at least 3 miles from the obstruction

determining the MVA. To avoid a large sector with an

excessively high MVA due to an isolated prominent

obstruction, the obstruction may be enclosed in a

buffer area whose boundaries are at least 3 miles from

the obstruction. This is done to facilitate vectoring

around the obstruction. (See FIG 5−4−13.)

1. The minimum vectoring altitude in each

sector provides 1,000 feet above the highest obstacle

in nonmountainous areas and 2,000 feet above the

highest obstacle in designated mountainous areas.

Where lower MVAs are required in designated

mountainous areas to achieve compatibility with

terminal routes or to permit vectoring to an IAP,

1,000 feet of obstacle clearance may be authorized

with the use of Airport Surveillance Radar (ASR).

The minimum vectoring altitude will provide at least

300 feet above the floor of controlled airspace.

NOTE−

OROCA is an off−route altitude which provides obstruction clearance with a 1,000 foot buffer in nonmountainous

terrain areas and a 2,000 foot buffer in designated

mountainous areas within the U.S. This altitude may not

provide signal coverage from ground−based navigational

aids, air traffic control radar, or communications

coverage.

2. Because of differences in the areas considered for MVA, and those applied to other minimum

altitudes, and the ability to isolate specific obstacles,

some MVAs may be lower than the nonradar

Minimum En Route Altitudes (MEAs), Minimum

Obstruction Clearance Altitudes (MOCAs) or other

minimum altitudes depicted on charts for a given

location. While being radar vectored, IFR altitude

assignments by ATC will be at or above MVA.

f. Visual Descent Points (VDPs) are being

incorporated in nonprecision approach procedures.

The VDP is a defined point on the final approach

course of a nonprecision straight−in approach

procedure from which normal descent from the MDA

to the runway touchdown point may be commenced,

provided visual reference required by 14 CFR

Section 91.175(c)(3) is established. The VDP will

normally be identified by DME on VOR and LOC
7/26/12 AIM

Arrival Procedures 5−4−19

procedures and by along−track distance to the next

waypoint for RNAV procedures. The VDP is

identified on the profile view of the approach chart by

the symbol: V.

1. VDPs are intended to provide additional

guidance where they are implemented. No special

technique is required to fly a procedure with a VDP.

The pilot should not descend below the MDA prior to

reaching the VDP and acquiring the necessary visual

reference.

2. Pilots not equipped to receive the VDP should

fly the approach procedure as though no VDP had

been provided.

g. Visual Segment of a Published Instrument

Approach Procedure. Instrument procedures designers perform a visual area obstruction evaluation

off the approach end of each runway authorized for

instrument landing, straight−in, or circling. Restrictions to instrument operations are imposed if

penetrations of the obstruction clearance surfaces

exist. These restrictions vary based on the severity of

the penetrations, and may include increasing required

visibility, denying VDPs, prohibiting night instrument operations to the runway, and/or provide a “Fly

Visual” option to the landing surface.

1. In isolated cases, due to procedure design

peculiarities, an IAP may contain a published visual

flight path. These procedures are annotated “Fly

Visual to Airport” or “Fly Visual.” A dashed arrow

indicating the visual flight path will be included in the

profile and plan views with an approximate heading

and distance to the end of the runway. The depicted

ground track associated with the visual segment

should be flown as a “DR” course. When executing

the visual segment, the flight visibility must not be

less than that prescribed in the IAP, the pilot must remain clear of clouds and proceed to the airport

maintaining visual contact with the ground. Altitude

on the visual flight path is at the discretion of the pilot.

2. Since missed approach obstacle clearance is

assured only if the missed approach is commenced at

the published MAP or above the DA/MDA, the pilot

should have preplanned climb out options based on

aircraft performance and terrain features. Obstacle

clearance is the sole responsibility of the pilot when

the approach is continued beyond the MAP.

NOTE−

The FAA Administrator retains the authority to approve

instrument approach procedures where the pilot may not

necessarily have one of the visual references specified in

CFR 14, part 91.175 and related rules. It is not a function

of procedure design to ensure compliance with part

91.175. The annotation “Fly Visual to Airport” provides

relief from part 91.175 requirements that the pilot have distinctly visible and identifiable visual references prior to

descent below MDA/DA.

h. Charting of Close in Obstacles on Instrument Procedure Charts. Obstacles that are close to

the airport may be depicted in either the planview of

the instrument approach chart or the airport sketch.

Obstacles are charted in only one of the areas, based

on space available and distance from the runway.

These obstacles could be in the visual segment of the

instrument approach procedure. On nonprecision

approaches, these obstacles should be considered

when determining where to begin descent from the

MDA (see “Pilot Operational Considerations When

Flying Nonprecision Approaches” in this paragraph).

i. Vertical Descent Angle (VDA) on Nonprecision Approaches. FAA policy is to publish VDAs on

all nonprecision approaches. Published along with

VDA is the threshold crossing height (TCH) that was

used to compute the angle. The descent angle may be

computed from either the final approach fix (FAF), or

a stepdown fix, to the runway threshold at the

published TCH. A stepdown fix is only used as the

start point when an angle computed from the FAF

would place the aircraft below the stepdown fix

altitude. The descent angle and TCH information are

charted on the profile view of the instrument

approach chart following the fix the angle was based

on. The optimum descent angle is 3.00 degrees; and

whenever possible the approach will be designed

using this angle.

1. The VDA provides the pilot with information

not previously available on nonprecision approaches.

It provides a means for the pilot to establish a

stabilized descent from the FAF or stepdown fix to the

MDA. Stabilized descent is a key factor in the

reduction of controlled flight into terrain (CFIT)

incidents. However, pilots should be aware that the

published angle is for information only − it is

strictly advisory in nature. There is no implicit

additional obstacle protection below the MDA. Pilots

must still respect the published minimum descent

altitude (MDA) unless the visual cues stated 14 CFR

Section 91.175 are present and they can visually
AIM 7/26/12

5−4−20 Arrival Procedures

acquire and avoid obstacles once below the MDA.

The presence of a VDA does not guarantee obstacle

protection in the visual segment and does not change

any of the requirements for flying a nonprecision

approach.

2. Additional protection for the visual segment

below the MDA is provided if a VDP is published and

descent below the MDA is started at or after the VDP.

Protection is also provided, if a Visual Glide Slope

Indicator (VGSI); e.g., VASI or PAPI, is installed and

the aircraft remains on the VGSI glide path angle

from the MDA. In either case, a chart note will

indicate if the VDP or VGSI are not coincident with

the VDA. On RNAV approach charts, a small shaded

arrowhead shaped symbol (see the legend of the U.S.

Terminal Procedures books, page H1) from the end of

the VDA to the runway indicates that the 34:1 visual

surface is clear.

3. Pilots may use the published angle and

estimated/actual groundspeed to find a target rate of

descent from the rate of descent table published in the

back of the U.S. Terminal Procedures Publication.

This rate of descent can be flown with the Vertical

Velocity Indicator (VVI) in order to use the VDA as

an aid to flying a stabilized descent. No special

equipment is required.

4. Since one of the reasons for publishing a circling only instrument landing procedure is that the

descent rate required exceeds the maximum allowed

for a straight in approach, circling only procedures

may have VDAs which are considerably steeper than

the standard 3 degree angle on final. In this case, the

VDA provides the crew with information about the

descent rate required to land straight in from the FAF

or step down fix to the threshold. This is not intended

to imply that landing straight ahead is recommended,

or even possible, since the descent rate may exceed

the capabilities of many aircraft. The pilot must

determine how to best maneuver the aircraft within

the circling obstacle clearance area in order to land.

5. In rare cases the LNAV minima may have a

lower HAT than minima with a glide path due to the

location of the obstacles. This should be a clear indication to the pilot that obstacles exist below the MDA

which the pilot must see in order to ensure adequate

clearance. In those cases, the glide path may be

treated as a VDA and used to descend to the LNAV

MDA as long as all the rules for a nonprecision

approach are applied at the MDA. However, the pilot

must keep in mind the information in this paragraph

and in paragraph 5−4−5j.

j. Pilot Operational Considerations When

Flying Nonprecision Approaches. The missed

approach point (MAP) on a nonprecision approach

is not designed with any consideration to where

the aircraft must begin descent to execute a safe

landing. It is developed based on terrain, obstructions, NAVAID location and possibly air traffic

considerations. Because the MAP may be located

anywhere from well prior to the runway threshold to

past the opposite end of the runway, the descent from

the Minimum Descent Altitude (MDA) to the runway

threshold cannot be determined based on the MAP

location. Descent from MDA at the MAP when the

MAP is located close to the threshold would require

an excessively steep descent gradient to land in the

normal touchdown zone. Any turn from the final

approach course to the runway heading may also be

a factor in when to begin the descent.

1. Pilots are cautioned that descent to a

straight−in landing from the MDA at the MAP may

be inadvisable or impossible, on a nonprecision

approach, even if current weather conditions meet the

published ceiling and visibility. Aircraft speed, height

above the runway, descent rate, amount of turn and

runway length are some of the factors which must be

considered by the pilot to determine if a landing can

be accomplished. 

2. Visual descent points (VDPs) provide pilots

with a reference for the optimal location to begin

descent from the MDA, based on the designed

vertical descent angle (VDA) for the approach

procedure, assuming required visual references are

available. Approaches without VDPs have not been

assessed for terrain clearance below the MDA, and

may not provide a clear vertical path to the runway at

the normally expected descent angle. Therefore,

pilots must be especially vigilant when descending

below the MDA at locations without VDPs. This does

not necessarily prevent flying the normal angle; it

only means that obstacle clearance in the visual

segment could be less and greater care should be

exercised in looking for obstacles in the visual

segment. Use of visual glide slope indicator (VGSI)

systems can aid the pilot in determining if the aircraft

is in a position to make the descent from the MDA.

However, when the visibility is close to minimums,

the VGSI may not be visible at the start descent point
7/26/12 AIM

Arrival Procedures 5−4−21

for a “normal” glidepath, due to its location down the

runway.

3. Accordingly, pilots are advised to carefully

review approach procedures, prior to initiating the

approach, to identify the optimum position(s), and

any unacceptable positions, from which a descent to

landing can be initiated (in accordance with 14 CFR

Section 91.175(c)).

k. Area Navigation (RNAV) Instrument

Approach Charts. Reliance on RNAV systems for

instrument operations is becoming more commonplace as new systems such as GPS and augmented

GPS such as the Wide Area Augmentation System

(WAAS) are developed and deployed. In order to

support full integration of RNAV procedures into the

National Airspace System (NAS), the FAA

developed a new charting format for IAPs (See

FIG 5−4−9). This format avoids unnecessary

duplication and proliferation of instrument approach

charts. The original stand alone GPS charts, titled

simply “GPS,” are being converted to the newer

format as the procedures are revised. One reason for

the revision is the addition of WAAS based minima

to the approach chart. The reformatted approach chart

is titled “RNAV (GPS) RWY XX.” Up to four lines

of minima are included on these charts. Ground

Based Augmentation System (GBAS) Landing System (GLS) was a placeholder for future WAAS and

LAAS minima, and the minima was always listed as

N/A. The GLS minima line has now been replaced by

the WAAS LPV (Localizer Performance with

Vertical Guidance) minima on most RNAV (GPS)

charts. LNAV/VNAV (lateral navigation/vertical

navigation) was added to support both WAAS

electronic vertical guidance and Barometric VNAV.

LPV and LNAV/VNAV are both APV procedures as

described in paragraph 5−4−5a7. The original GPS

minima, titled “S−XX,” for straight in runway XX, is

retitled LNAV (lateral navigation). Circling minima

may also be published. A new type of nonprecision

WAAS minima will also be published on this chart

and titled LP (localizer performance). LP will be

published in locations where vertically guided

minima cannot be provided due to terrain and

obstacles and therefore, no LPV or LNAV/VNAV

minima will be published. Current plans call for

LAAS based procedures to be published on a separate

chart and for the GLS minima line to be used only for

LAAS. ATC clearance for the RNAV procedure

authorizes a properly certified pilot to utilize any

minimums for which the aircraft is certified: e.g. a

WAAS equipped aircraft utilize the LPV or LP

minima but a GPS only aircraft may not. The RNAV

chart includes information formatted for quick

reference by the pilot or flight crew at the top of the

chart. This portion of the chart, developed based on

a study by the Department of Transportation, Volpe

National Transportation System Center, is commonly

referred to as the pilot briefing.

1. The minima lines are:

(a) GLS. “GLS” is the acronym for Ground

Based Augmentation System (GBAS) Landing

System. GBAS is the ICAO term for Local Area

Augmentation System (LAAS). This line was

originally published as a placeholder for both WAAS

and LAAS minima and marked as N/A since no

minima was published. As the concepts for LAAS

and WAAS procedure publication have evolved, GLS

will now be used only for LAAS minima, which will

be on a separate approach chart. Most RNAV(GPS)

approach charts have had the GLS minima line

replaced by a WAAS LPV line of minima.

(b) LPV. “LPV” is the acronym for localizer

performance with vertical guidance. RNAV (GPS)

approaches to LPV lines of minima take advantage of

the improved accuracy of WAAS lateral and vertical

guidance to provide an approach that is very similar

to a Category I Instrument Landing System (ILS).

The approach to LPV line of minima is designed for

angular guidance with increasing sensitivity as the

aircraft gets closer to the runway. The sensitivities are

nearly identical to those of the ILS at similar

distances. This was done intentionally to allow the

skills required to proficiently fly an ILS to readily

transfer to flying RNAV (GPS) approaches to the

LPV line of minima. Just as with an ILS, the LPV has

vertical guidance and is flown to a DA. Aircraft can

fly this minima line with a statement in the Aircraft

Flight Manual that the installed equipment supports

LPV approaches. This includes Class 3 and 4

TSO−C146 WAAS equipment.

(c) LNAV/VNAV. LNAV/VNAV identifies

APV minimums developed to accommodate an

RNAV IAP with vertical guidance, usually provided

by approach certified Baro−VNAV, but with lateral

and vertical integrity limits larger than a precision

approach or LPV. LNAV stands for Lateral

Navigation; VNAV stands for Vertical Navigation.

This minima line can be flown by aircraft with a

statement in the Aircraft Flight Manual that the
AIM 7/26/12

5−4−22 Arrival Procedures

installed equipment supports GPS approaches and

has an approach−approved barometric VNAV, or if

the aircraft has been demonstrated to support

LNAV/VNAV approaches. This includes Class 2, 3

and 4 TSO−C146 WAAS equipment. Aircraft using

LNAV/VNAV minimums will descend to landing via

an internally generated descent path based on satellite

or other approach approved VNAV systems. Since

electronic vertical guidance is provided, the minima

will be published as a DA. Other navigation systems

may be specifically authorized to use this line of

minima, see Section A, Terms/Landing Minima Data,

of the U.S. Terminal Procedures books.

(d) LP. “LP” is the acronym for localizer

performance. Approaches to LP lines of minima take

advantage of the improved accuracy of WAAS to

provide approaches, with lateral guidance and

angular guidance. Angular guidance does not refer to

a glideslope angle but rather to the increased lateral

sensitivity as the aircraft gets closer to the runway,

similar to localizer approaches. However, the LP line

of minima is a Minimum Descent Altitude (MDA)

rather than a DA (H). Procedures with LP lines of

minima will not be published with another approach

that contains approved vertical guidance

(LNAV/VNAV or LPV). It is possible to have LP and

LNAV published on the same approach chart but LP

will only be published if it provides lower minima

than an LNAV line of minima. LP is not a fail−down

mode for LPV. LP will only be published if terrain,

obstructions, or some other reason prevent publishing

a vertically guided procedure. WAAS avionics may

provide GNSS−based advisory vertical guidance

during an approach to an LP line of minima (reference

section 9.b for further information on advisory

vertical guidance). Barometric altimeter information

remains the primary altitude reference for complying

with any altitude restrictions. WAAS equipment may

not support LP, even if it supports LPV, if it was

approved before TSO C−145B and TSO C−146B.

Receivers approved under previous TSOs may

require an upgrade by the manufacturer in order to be

used to fly to LP minima. Receivers approved for LP

must have a statement in the approved Flight Manual

or Supplemental Flight Manual including LP as one

of the approved approach types.

(e) LNAV. This minima is for lateral

navigation only, and the approach minimum altitude

will be published as a minimum descent altitude

(MDA). LNAV provides the same level of service as

the present GPS stand alone approaches. LNAV

minimums support the following navigation systems:

WAAS, when the navigation solution will not support

vertical navigation; and, GPS navigation systems

which are presently authorized to conduct GPS

approaches. Existing GPS approaches continue to be

converted to the RNAV (GPS) format as they are

revised or reviewed.

NOTE−

GPS receivers approved for approach operations in

accordance with: AC 20−138, Airworthiness Approval of

Global Positioning System (GPS) Navigation Equipment

for Use as a VFR and IFR Supplemental Navigation

System, for stand−alone Technical Standard Order (TSO)

TSO−C129 Class A(1) systems; or AC 20−130A,

Airworthiness Approval of Navigation or Flight

Management Systems Integrating Multiple Navigation

Sensors, for GPS as part of a multi−sensor system, qualify

for this minima. WAAS navigation equipment must be

approved in accordance with the requirements specified in

TSO−C145 or TSO−C146 and installed in accordance with

Advisory Circular AC 20−138A, Airworthiness Approval

of Global Navigation Satellite System (GNSS) Equipment.

2. Other systems may be authorized to utilize

these approaches. See the description in Section A of

the U.S. Terminal Procedures books for details.

Operational approval must also be obtained for

Baro−VNAV systems to operate to the LNAV/VNAV

minimums. Baro−VNAV may not be authorized on

some approaches due to other factors, such as no local

altimeter source being available. Baro−VNAV is not

authorized on LPV procedures. Pilots are directed to

their local Flight Standards District Office (FSDO)

for additional information.

NOTE−

RNAV and Baro−VNAV systems must have a manufacturer

supplied electronic database which must include the

waypoints, altitudes, and vertical data for the procedure to

be flown. The system must be able to retrieve the procedure

by name from the aircraft navigation database, not just as

a manually entered series of waypoints.

3. ILS or RNAV (GPS) charts.

(a) Some RNAV (GPS) charts will also contain an ILS line of minima to make use of the ILS

precision final in conjunction with the RNAV GPS

capabilities for the portions of the procedure prior to

the final approach segment and for the missed approach. Obstacle clearance for the portions of the

procedure other than the final approach segment is

still based on GPS criteria.
7/26/12 AIM

Arrival Procedures 5−4−23

NOTE−

Some GPS receiver installations inhibit GPS navigation

whenever ANY ILS frequency is tuned. Pilots flying

aircraft with receivers installed in this manner must wait

until they are on the intermediate segment of the procedure

prior to the PFAF (PFAF is the active waypoint) to tune the

ILS frequency and must tune the ILS back to a VOR frequency in order to fly the GPS based missed approach.

(b) Charting. There are charting differences

between ILS, RNAV (GPS), and GLS approaches.

(1) The LAAS procedure is titled “GLS

RWY XX” on the approach chart.

(2) The VDB provides information to the

airborne receiver where the guidance is synthesized.

(3) The LAAS procedure is identified by a

four alpha−numeric character field referred to as the

RPI or approach ID and is similar to the IDENT feature of the ILS.

(4) The RPI is charted.

(5) Most RNAV(GPS) approach charts

have had the GLS (NA) minima line replaced by an

LPV line of minima.

(6) Since the concepts for LAAS and

WAAS procedure publication have evolved, GLS

will now be used only for LAAS minima, which will

be on a separate approach chart.

4. Required Navigation Performance (RNP)

(a) Pilots are advised to refer to the

“TERMS/LANDING MINIMUMS DATA”

(Section A) of the U.S. Government Terminal

Procedures books for aircraft approach eligibility

requirements by specific RNP level requirements.

(b) Some aircraft have RNP approval in their

AFM without a GPS sensor. The lowest level of

sensors that the FAA will support for RNP service is

DME/DME. However, necessary DME signal may

not be available at the airport of intended operations.

For those locations having an RNAV chart published

with LNAV/VNAV minimums, a procedure note may

be provided such as “DME/DME RNP−0.3 NA.”

This means that RNP aircraft dependent on

DME/DME to achieve RNP−0.3 are not authorized to

conduct this approach. Where DME facility

availability is a factor, the note may read “DME/DME

RNP−0.3 Authorized; ABC and XYZ Required.”

This means that ABC and XYZ facilities have been

determined by flight inspection to be required in the

navigation solution to assure RNP−0.3. VOR/DME

updating must not be used for approach procedures.

5. Chart Terminology

(a) Decision Altitude (DA) replaces the

familiar term Decision Height (DH). DA conforms to

the international convention where altitudes relate to

MSL and heights relate to AGL. DA will eventually

be published for other types of instrument approach

procedures with vertical guidance, as well. DA

indicates to the pilot that the published descent profile

is flown to the DA (MSL), where a missed approach

will be initiated if visual references for landing are not

established. Obstacle clearance is provided to allow

a momentary descent below DA while transitioning

from the final approach to the missed approach. The

aircraft is expected to follow the missed instructions

while continuing along the published final approach

course to at least the published runway threshold

waypoint or MAP (if not at the threshold) before

executing any turns.

(b) Minimum Descent Altitude (MDA) has

been in use for many years, and will continue to be

used for the LNAV only and circling procedures.

(c) Threshold Crossing Height (TCH) has

been traditionally used in “precision” approaches as

the height of the glide slope above threshold. With

publication of LNAV/VNAV minimums and RNAV

descent angles, including graphically depicted

descent profiles, TCH also applies to the height of the

“descent angle,” or glidepath, at the threshold. Unless

otherwise required for larger type aircraft which may

be using the IAP, the typical TCH is 30 to 50 feet.

6. The MINIMA FORMAT will also change

slightly.

(a) Each line of minima on the RNAV IAP is

titled to reflect the level of service available; e.g.,

GLS, LPV, LNAV/VNAV, LP, and LNAV.

CIRCLING minima will also be provided.

(b) The minima title box indicates the nature

of the minimum altitude for the IAP. For example:

(1) DA will be published next to the

minima line title for minimums supporting vertical

guidance such as for GLS, LPV or LNAV/VNAV.

(2) MDA will be published where the

minima line was designed to support aircraft with

only lateral guidance available, such as LNAV or LP.

Descent below the MDA, including during the missed
AIM 7/26/12

5−4−24 Arrival Procedures

approach, is not authorized unless the visual

conditions stated in 14 CFR Section 91.175 exist.

(3) Where two or more systems, such as

LPV and LNAV/VNAV, share the same minima, each

line of minima will be displayed separately.

7. Chart Symbology changed slightly to

include:

(a) Descent Profile. The published descent

profile and a graphical depiction of the vertical path

to the runway will be shown. Graphical depiction of

the RNAV vertical guidance will differ from the

traditional depiction of an ILS glide slope (feather)

through the use of a shorter vertical track beginning

at the decision altitude.

(1) It is FAA policy to design IAPs with

minimum altitudes established at fixes/waypoints to

achieve optimum stabilized (constant rate) descents

within each procedure segment. This design can

enhance the safety of the operations and contribute

toward reduction in the occurrence of controlled

flight into terrain (CFIT) accidents. Additionally, the

National Transportation Safety Board (NTSB)

recently emphasized that pilots could benefit from

publication of the appropriate IAP descent angle for

a stabilized descent on final approach. The RNAV

IAP format includes the descent angle to the

hundredth of a degree; e.g., 3.00 degrees. The angle

will be provided in the graphically depicted descent

profile.

(2) The stabilized approach may be

performed by reference to vertical navigation

information provided by WAAS or LNAV/VNAV

systems; or for LNAV−only systems, by the pilot

determining the appropriate aircraft

attitude/groundspeed combination to attain a

constant rate descent which best emulates the

published angle. To aid the pilot, U.S. Government

Terminal Procedures Publication charts publish an

expanded Rate of Descent Table on the inside of the

back hard cover for use in planning and executing

precision descents under known or approximate

groundspeed conditions.

(b) Visual Descent Point (VDP). A VDP

will be published on most RNAV IAPs. VDPs apply

only to aircraft utilizing LP or LNAV minima, not

LPV or LNAV/VNAV minimums.

(c) Missed Approach Symbology. In order

to make missed approach guidance more readily

understood, a method has been developed to display

missed approach guidance in the profile view through

the use of quick reference icons. Due to limited space

in the profile area, only four or fewer icons can be

shown. However, the icons may not provide

representation of the entire missed approach

procedure. The entire set of textual missed approach

instructions are provided at the top of the approach

chart in the pilot briefing. (See FIG 5−4−9).

(d) Waypoints. All RNAV or GPS

stand−alone IAPs are flown using data pertaining to

the particular IAP obtained from an onboard

database, including the sequence of all WPs used for

the approach and missed approach, except that step

down waypoints may not be included in some

TSO−C129 receiver databases. Included in the

database, in most receivers, is coding that informs the

navigation system of which WPs are fly−over (FO) or

fly−by (FB). The navigation system may provide

guidance appropriately − including leading the turn

prior to a fly−by WP; or causing overflight of a

fly−over WP. Where the navigation system does not

provide such guidance, the pilot must accomplish the

turn lead or waypoint overflight manually. Chart

symbology for the FB WP provides pilot awareness

of expected actions. Refer to the legend of the U.S.

Terminal Procedures books.

(e) TAAs are described in paragraph 5−4−5d,

Terminal Arrival Area (TAA). When published, the

RNAV chart depicts the TAA areas through the use of

“icons” representing each TAA area associated with

the RNAV procedure (See FIG 5−4−9). These icons

are depicted in the plan view of the approach chart,

generally arranged on the chart in accordance with

their position relative to the aircraft’s arrival from the

en route structure. The WP, to which navigation is

appropriate and expected within each specific TAA

area, will be named and depicted on the associated

TAA icon. Each depicted named WP is the IAF for

arrivals from within that area. TAAs may not be used

on all RNAV procedures because of airspace

congestion or other reasons.

(f) Hot and Cold Temperature Limitations.

A minimum and maximum temperature limitation

is published on procedures which authorize

Baro−VNAV operation. These temperatures

represent the airport temperature above or below

which Baro−VNAV is not authorized to
7/26/12 AIM

Arrival Procedures 5−4−25

LNAV/VNAV minimums. As an example, the

limitation will read: “Uncompensated Baro−VNAV

NA below −8C (+18F) or above 47C (117F).”

This information will be found in the upper left hand

box of the pilot briefing. When the temperature is

above the high temperature or below the low

temperature limit, Baro−VNAV may be used to

provide a stabilized descent to the LNAV MDA;

however, extra caution should be used in the visual

segment to ensure a vertical correction is not

required. If the VGSI is aligned with the published

glidepath, and the aircraft instruments indicate on

glidepath, an above or below glidepath indication on

the VGSI may indicate that temperature error is

causing deviations to the glidepath. These deviations

should be considered if the approach is continued

below the MDA.

NOTE−

Many systems which apply Baro−VNAV temperature

compensation only correct for cold temperature. In this

case, the high temperature limitation still applies. Also,

temperature compensation may require activation by

maintenance personnel during installation in order to be

functional, even though the system has the feature. Some

systems may have a temperature correction capability, but

correct the Baro−altimeter all the time, rather than just on

the final, which would create conflicts with other aircraft

if the feature were activated. Pilots should be aware of

compensation capabilities of the system prior to

disregarding the temperature limitations.

NOTE−

Temperature limitations do not apply to flying the LNAV/

VNAV line of minima using approach certified WAAS

receivers when LPV or LNAV/VNAV are annunciated to be

available.

(g) WAAS Channel Number/Approach ID.

The WAAS Channel Number is an optional

equipment capability that allows the use of a 5−digit

number to select a specific final approach segment

without using the menu method. The Approach ID is

an airport unique 4−character combination for

verifying the selection and extraction of the correct

final approach segment information from the aircraft

database. It is similar to the ILS ident, but displayed

visually rather than aurally. The Approach ID

consists of the letter W for WAAS, the runway

number, and a letter other than L, C or R, which could

be confused with Left, Center and Right, e.g., W35A.

Approach IDs are assigned in the order that WAAS

approaches are built to that runway number at that

airport. The WAAS Channel Number and Approach

ID are displayed in the upper left corner of the

approach procedure pilot briefing.

(h) At locations where outages of WAAS

vertical guidance may occur daily due to initial

system limitations, a negative W symbol ( ) will be

placed on RNAV (GPS) approach charts. Many of

these outages will be very short in duration, but may

result in the disruption of the vertical portion of the

approach. The symbol indicates that NOTAMs or

Air Traffic advisories are not provided for outages

which occur in the WAAS LNAV/VNAV or LPV

vertical service. Use LNAV minima for flight

planning at these locations, whether as a destination

or alternate. For flight operations at these locations,

when the WAAS avionics indicate that LNAV/VNAV

or LPV service is available, then vertical guidance

may be used to complete the approach using the

displayed level of service. Should an outage occur

during the procedure, reversion to LNAV minima

may be required. As the WAAS coverage is

expanded, the will be removed.

5−4−6. Approach Clearance

a. An aircraft which has been cleared to a holding

fix and subsequently “cleared . . . approach” has not

received new routing. Even though clearance for the

approach may have been issued prior to the aircraft

reaching the holding fix, ATC would expect the pilot

to proceed via the holding fix (his/her last assigned

route), and the feeder route associated with that fix (if

a feeder route is published on the approach chart) to

the initial approach fix (IAF) to commence the

approach. WHEN CLEARED FOR THE

APPROACH, THE PUBLISHED OFF AIRWAY

(FEEDER) ROUTES THAT LEAD FROM THE

EN ROUTE STRUCTURE TO THE IAF ARE PART

OF THE APPROACH CLEARANCE.

b. If a feeder route to an IAF begins at a fix located

along the route of flight prior to reaching the holding

fix, and clearance for an approach is issued, a pilot

should commence the approach via the published

feeder route; i.e., the aircraft would not be expected

to overfly the feeder route and return to it. The pilot

is expected to commence the approach in a similar

manner at the IAF, if the IAF for the procedure is

located along the route of flight to the holding fix.

c. If a route of flight directly to the initial approach

fix is desired, it should be so stated by the controller

with phraseology to include the words “direct . . . ,”
AIM 7/26/12

5−4−26 Arrival Procedures

“proceed direct” or a similar phrase which the pilot

can interpret without question. When uncertain of the

clearance, immediately query ATC as to what route of

flight is desired.

d. The name of an instrument approach, as

published, is used to identify the approach, even

though a component of the approach aid, such as the

glideslope on an Instrument Landing System, is

inoperative or unreliable. The controller will use the

name of the approach as published, but must advise

the aircraft at the time an approach clearance is issued

that the inoperative or unreliable approach aid

component is unusable.

e. The following applies to aircraft on radar

vectors and/or cleared “direct to” in conjunction with

an approach clearance:

1. Maintain the last altitude assigned by ATC

until the aircraft is established on a published segment of a transition route, or approach procedure

segment, or other published route, for which a lower

altitude is published on the chart. If already on an established route, or approach or arrival segment, you

may descend to whatever minimum altitude is listed

for that route or segment.

2. Continue on the vector heading until intercepting the next published ground track applicable to

the approach clearance.

3. Once reaching the final approach fix via the

published segments, the pilot may continue on approach to a landing.

4. If proceeding to an IAF with a published

course reversal (procedure turn or hold-in-lieu of PT

pattern), except when cleared for a straight in approach by ATC, the pilot must execute the procedure

turn/hold-in-lieu of PT, and complete the approach.

5. If cleared to an IAF/IF via a NoPT route, or

no procedure turn/hold-in-lieu of PT is published,

continue with the published approach.

6. In addition to the above, RNAV aircraft may

be issued a clearance direct to an Intermediate Fix followed by a straight-in approach clearance.

NOTE−

Refer to 14 CFR 91.175 (i).

5−4−7. Instrument Approach Procedures

a. Aircraft approach category means a grouping of

aircraft based on a speed of VREF, if specified, or if

VREF is not specified, 1.3 VSO at the maximum

certified landing weight. VREF, VSO, and the

maximum certified landing weight are those values as

established for the aircraft by the certification

authority of the country of registry. A pilot must use

the minima corresponding to the category determined

during certification or higher. Helicopters may use

Category A minima. If it is necessary to operate at a

speed in excess of the upper limit of the speed range

for an aircraft’s category, the minimums for the

higher category must be used. For example, an

airplane which fits into Category B, but is circling to

land at a speed of 145 knots, must use the approach

Category D minimums. As an additional example, a

Category A airplane (or helicopter) which is

operating at 130 knots on a straight−in approach must

use the approach Category C minimums. See the

following category limits:

1. Category A: Speed less than 91 knots.

2. Category B: Speed 91 knots or more but less

than 121 knots.

3. Category C: Speed 121 knots or more but

less than 141 knots.

4. Category D: Speed 141 knots or more but

less than 166 knots.

5. Category E: Speed 166 knots or more.

NOTE−

VREF in the above definition refers to the speed used in

establishing the approved landing distance under the

airworthiness regulations constituting the type

certification basis of the airplane, regardless of whether

that speed for a particular airplane is 1.3 VSO, 1.23 VSR, or

some higher speed required for airplane controllability.

This speed, at the maximum certificated landing weight,

determines the lowest applicable approach category for

all approaches regardless of actual landing weight.

b. When operating on an unpublished route or

while being radar vectored, the pilot, when an

approach clearance is received, must, in addition to

complying with the minimum altitudes for IFR

operations (14 CFR Section 91.177), maintain the

last assigned altitude unless a different altitude is

assigned by ATC, or until the aircraft is established on

a segment of a published route or IAP. After the

aircraft is so established, published altitudes apply to

descent within each succeeding route or approach
7/26/12 AIM

Arrival Procedures 5−4−27

segment unless a different altitude is assigned by

ATC. Notwithstanding this pilot responsibility, for

aircraft operating on unpublished routes or while

being radar vectored, ATC will, except when

conducting a radar approach, issue an IFR approach

clearance only after the aircraft is established on a

segment of a published route or IAP, or assign an

altitude to maintain until the aircraft is established on

a segment of a published route or instrument

approach procedure. For this purpose, the procedure

turn of a published IAP must not be considered a

segment of that IAP until the aircraft reaches the

initial fix or navigation facility upon which the

procedure turn is predicated.

EXAMPLE−

Cross Redding VOR at or above five thousand, cleared

VOR runway three four approach. 

 or

Five miles from outer marker, turn right heading three three

zero, maintain two thousand until established on the

localizer, cleared ILS runway three six approach.

NOTE−

The altitude assigned will assure IFR obstruction

clearance from the point at which the approach clearance

is issued until established on a segment of a published route

or IAP. If uncertain of the meaning of the clearance,

immediately request clarification from ATC.

c. Several IAPs, using various navigation and

approach aids may be authorized for an airport. ATC

may advise that a particular approach procedure is

being used, primarily to expedite traffic. If issued a

clearance that specifies a particular approach

procedure, notify ATC immediately if a different one

is desired. In this event it may be necessary for ATC

to withhold clearance for the different approach until

such time as traffic conditions permit. However, a

pilot involved in an emergency situation will be given

priority. If the pilot is not familiar with the specific

approach procedure, ATC should be advised and they

will provide detailed information on the execution of

the procedure.

REFERENCE−

AIM, Advance Information on Instrument Approach, Paragraph 5−4−4.

d. The name of an instrument approach, as

published, is used to identify the approach, even

though a component of the approach aid, such as the

glideslope on an Instrument Landing System, is

inoperative or unreliable. The controller will use the

name of the approach as published, but must advise

the aircraft at the time an approach clearance is issued

that the inoperative or unreliable approach aid

component is unusable, except when the title of the

published approach procedures otherwise allows, for

example, ILS or LOC.

e. Except when being radar vectored to the final

approach course, when cleared for a specifically

prescribed IAP; i.e., “cleared ILS runway one niner

approach” or when “cleared approach” i.e., execution

of any procedure prescribed for the airport, pilots

must execute the entire procedure commencing at an

IAF or an associated feeder route as described on the

IAP chart unless an appropriate new or revised ATC

clearance is received, or the IFR flight plan is

canceled.

f. Pilots planning flights to locations which are

private airfields or which have instrument approach

procedures based on private navigation aids should

obtain approval from the owner. In addition, the pilot

must be authorized by the FAA to fly special

instrument approach procedures associated with

private navigation aids (see paragraph 5−4−8).

Owners of navigation aids that are not for public use

may elect to turn off the signal for whatever reason

they may have; e.g., maintenance, energy

conservation, etc. Air traffic controllers are not

required to question pilots to determine if they have

permission to land at a private airfield or to use

procedures based on privately owned navigation aids,

and they may not know the status of the navigation

aid. Controllers presume a pilot has obtained

approval from the owner and the FAA for use of

special instrument approach procedures and is aware

of any details of the procedure if an IFR flight plan

was filed to that airport.

g. Pilots should not rely on radar to identify a fix

unless the fix is indicated as “RADAR” on the IAP.

Pilots may request radar identification of an OM, but

the controller may not be able to provide the service

due either to workload or not having the fix on the

video map.

h. If a missed approach is required, advise ATC

and include the reason (unless initiated by ATC).

Comply with the missed approach instructions for the

instrument approach procedure being executed,

unless otherwise directed by ATC.

REFERENCE−

AIM, Missed Approach, Paragraph 5−4−21.

AIM, Missed Approach, Paragraph 5−5−5.

i. ATC may clear aircraft that have filed an

Advanced RNAV equipment suffix to the

intermediate fix when clearing aircraft for an
AIM 7/26/12

5−4−28 Arrival Procedures

instrument approach procedure. ATC will take the

following actions when clearing Advanced RNAV

aircraft to the intermediate fix:

1. Provide radar monitoring to the intermediate

fix.

2. Advise the pilot to expect clearance direct to

the intermediate fix at least 5 miles from the fix.

NOTE−

This is to allow the pilot to program the RNAV equipment

to allow the aircraft to fly to the intermediate fix when

cleared by ATC.

3. Assign an altitude to maintain until the

intermediate fix.

4. ensure the aircraft is on a course that will

intercept the intermediate segment at an angle not

greater than 90 degrees and is at an altitude that will

permit normal descent from the intermediate fix to

the final approach fix.

5−4−8. Special Instrument Approach

Procedures

Instrument Approach Procedure (IAP) charts reflect

the criteria associated with the U.S. Standard for

Terminal Instrument [Approach] Procedures

(TERPs), which prescribes standardized methods for

use in developing IAPs. Standard IAPs are published

in the Federal Register (FR) in accordance with

Title 14 of the Code of Federal Regulations, Part 97,

and are available for use by appropriately qualified

pilots operating properly equipped and airworthy

aircraft in accordance with operating rules and

procedures acceptable to the FAA. Special IAPs are

also developed using TERPS but are not given public

notice in the FR. The FAA authorizes only certain

individual pilots and/or pilots in individual

organizations to use special IAPs, and may require

additional crew training and/or aircraft equipment or

performance, and may also require the use of landing

aids, communications, or weather services not

available for public use. Additionally, IAPs that

service private use airports or heliports are generally

special IAPs.

5−4−9. Procedure Turn and Hold−in−lieu of

Procedure Turn

a. A procedure turn is the maneuver prescribed

when it is necessary to reverse direction to establish

the aircraft inbound on an intermediate or final

approach course. The procedure turn or

hold−in−lieu−of−PT is a required maneuver when it

is depicted on the approach chart, unless cleared by

ATC for a straight−in approach. Additionally, the

procedure turn or hold−in−lieu−of−PT is not

permitted when the symbol “No PT” is depicted on

the initial segment being used, when a RADAR

VECTOR to the final approach course is provided,

or when conducting a timed approach from a holding

fix. The altitude prescribed for the procedure turn is

a minimum altitude until the aircraft is established on

the inbound course. The maneuver must be

completed within the distance specified in the

profile view. For a hold−in−lieu−of−PT, the holding

pattern direction must be flown as depicted and the

specified leg length/timing must not be exceeded.

NOTE−

The pilot may elect to use the procedure turn or

hold−in−lieu−of−PT when it is not required by the

procedure, but must first receive an amended clearance

from ATC. If the pilot is uncertain whether the ATC

clearance intends for a procedure turn to be conducted or

to allow for a straight−in approach, the pilot must

immediately request clarification from ATC (14 CFR

Section 91.123).

1. On U.S. Government charts, a barbed arrow

indicates the maneuvering side of the outbound

course on which the procedure turn is made.

Headings are provided for course reversal using the

45 degree type procedure turn. However, the point at

which the turn may be commenced and the type and

rate of turn is left to the discretion of the pilot (limited

by the charted remain within xx NM distance). Some

of the options are the 45 degree procedure turn, the

racetrack pattern, the teardrop procedure turn, or the

80 degree  260 degree course reversal. Racetrack

entries should be conducted on the maneuvering side

where the majority of protected airspace resides. If an

entry places the pilot on the non−maneuvering side of

the PT, correction to intercept the outbound course

ensures remaining within protected airspace. Some

procedure turns are specified by procedural track.

These turns must be flown exactly as depicted.

2. Descent to the procedure turn (PT)

completion altitude from the PT fix altitude (when

one has been published or assigned by ATC) must not

begin until crossing over the PT fix or abeam and

proceeding outbound. Some procedures contain a

note in the chart profile view that says “Maintain

(altitude) or above until established outbound for
7/26/12 AIM

Arrival Procedures 5−4−29

procedure turn” (See FIG 5−4−14). Newer

procedures will simply depict an “at or above”

altitude at the PT fix without a chart note (See

FIG 5−4−15). Both are there to ensure required

obstacle clearance is provided in the procedure turn

entry zone (See FIG 5−4−16). Absence of a chart note

or specified minimum altitude adjacent to the PT fix

is an indication that descent to the procedure turn

altitude can commence immediately upon crossing

over the PT fix, regardless of the direction of flight.

This is because the minimum altitudes in the PT entry

zone and the PT maneuvering zone are the same.

FIG 5−4−14

FIG 5−4−15
AIM 7/26/12

5−4−30 Arrival Procedures

FIG 5−4−16

3. When the approach procedure involves a

procedure turn, a maximum speed of not greater than

200 knots (IAS) should be observed from first

overheading the course reversal IAF through the

procedure turn maneuver to ensure containment

within the obstruction clearance area. Pilots should

begin the outbound turn immediately after passing

the procedure turn fix. The procedure turn maneuver

must be executed within the distance specified in the

profile view. The normal procedure turn distance is

10 miles. This may be reduced to a minimum of

5 miles where only Category A or helicopter aircraft

are to be operated or increased to as much as 15 miles

to accommodate high performance aircraft.

4. A teardrop procedure or penetration turn may

be specified in some procedures for a required course

reversal. The teardrop procedure consists of

departure from an initial approach fix on an outbound

course followed by a turn toward and intercepting the

inbound course at or prior to the intermediate fix or

point. Its purpose is to permit an aircraft to reverse

direction and lose considerable altitude within

reasonably limited airspace. Where no fix is available

to mark the beginning of the intermediate segment, it

must be assumed to commence at a point 10 miles

prior to the final approach fix. When the facility is

located on the airport, an aircraft is considered to be

on final approach upon completion of the penetration

turn. However, the final approach segment begins on

the final approach course 10 miles from the facility.
7/26/12 AIM

Arrival Procedures 5−4−31

5. A holding pattern in lieu of procedure turn

may be specified for course reversal in some

procedures. In such cases, the holding pattern is

established over an intermediate fix or a final

approach fix. The holding pattern distance or time

specified in the profile view must be observed. For a

hold−in−lieu−of−PT, the holding pattern direction

must be flown as depicted and the specified leg

length/timing must not be exceeded. Maximum

holding airspeed limitations as set forth for all

holding patterns apply. The holding pattern maneuver

is completed when the aircraft is established on the

inbound course after executing the appropriate entry.

If cleared for the approach prior to returning to the

holding fix, and the aircraft is at the prescribed

altitude, additional circuits of the holding pattern are

not necessary nor expected by ATC. If pilots elect to

make additional circuits to lose excessive altitude or

to become better established on course, it is their

responsibility to so advise ATC upon receipt of their

approach clearance.

NOTE−

Some approach charts have an arrival holding pattern

depicted at the IAF using a “thin line” holding symbol. It

is charted where holding is frequently required prior to

starting the approach procedure so that detailed holding

instructions are not required. The arrival holding pattern

is not authorized unless assigned by Air Traffic Control.

Holding at the same fix may also be depicted on the enroute

chart. A hold−in−lieu of procedure turn is depicted by a

“thick line” symbol, and is part of the instrument approach

procedure as described in paragraph 5−4−9. (See U. S.

Terminal Procedures booklets page G1 for both examples.)

6. A procedure turn is not required when an

approach can be made directly from a specified

intermediate fix to the final approach fix. In such

cases, the term “NoPT” is used with the appropriate

course and altitude to denote that the procedure turn

is not required. If a procedure turn is desired, and

when cleared to do so by ATC, descent below the

procedure turn altitude should not be made until the

aircraft is established on the inbound course, since

some NoPT altitudes may be lower than the

procedure turn altitudes.

b. Limitations on Procedure Turns

1. In the case of a radar initial approach to a final

approach fix or position, or a timed approach from a

holding fix, or where the procedure specifies NoPT,

no pilot may make a procedure turn unless, when final

approach clearance is received, the pilot so advises

ATC and a clearance is received to execute a

procedure turn.

2. When a teardrop procedure turn is depicted

and a course reversal is required, this type turn must

be executed.

3. When a holding pattern replaces a procedure

turn, the holding pattern must be followed, except

when RADAR VECTORING is provided or when

NoPT is shown on the approach course. The

recommended entry procedures will ensure the

aircraft remains within the holding pattern’s

protected airspace. As in the procedure turn, the

descent from the minimum holding pattern altitude to

the final approach fix altitude (when lower) may not

commence until the aircraft is established on the

inbound course. Where a holding pattern is

established in−lieu−of a procedure turn, the

maximum holding pattern airspeeds apply.

REFERENCE−

AIM, Holding, Paragraph 5−3−8j2.

4. The absence of the procedure turn barb in the

plan view indicates that a procedure turn is not

authorized for that procedure.

5−4−10. Timed Approaches from a Holding

Fix

a. TIMED APPROACHES may be conducted

when the following conditions are met:

1. A control tower is in operation at the airport

where the approaches are conducted.

2. Direct communications are maintained

between the pilot and the center or approach

controller until the pilot is instructed to contact the

tower.

3. If more than one missed approach procedure

is available, none require a course reversal.

4. If only one missed approach procedure is

available, the following conditions are met:

(a) Course reversal is not required; and,

(b) Reported ceiling and visibility are equal

to or greater than the highest prescribed circling

minimums for the IAP.

5. When cleared for the approach, pilots must

not execute a procedure turn. (14 CFR

Section 91.175.)
AIM 7/26/12

5−4−32 Arrival Procedures

b. Although the controller will not specifically

state that “timed approaches are in progress,” the

assigning of a time to depart the final approach fix

inbound (nonprecision approach) or the outer marker

or fix used in lieu of the outer marker inbound

(precision approach) is indicative that timed

approach procedures are being utilized, or in lieu of

holding, the controller may use radar vectors to the

Final Approach Course to establish a mileage interval

between aircraft that will ensure the appropriate time

sequence between the final approach fix/outer marker

or fix used in lieu of the outer marker and the airport.

c. Each pilot in an approach sequence will be given

advance notice as to the time they should leave the

holding point on approach to the airport. When a time

to leave the holding point has been received, the pilot

should adjust the flight path to leave the fix as closely

as possible to the designated time. (See FIG 5−4−17.)
7/26/12 AIM

Arrival Procedures 5−4−33

FIG 5−4−17

Timed Approaches from a Holding Fix

ONE MINUTE

FLYING TIME

APPROXIMATELY 5 MILES

12:03 CLEARANCE RECEIVED

:04 INITIAL TIME

OVER FIX

1000 FT.

1000 FT.

1000 FT.

1000 FT.

:06 1/2

:07 REPORT

LEAVING FINAL

APPROACH TIME

:05 1/2

:05

30 SEC.

REPORT LEAVING

PREVIOUS ALTITUDE FOR

NEW ASSIGNED ALTITUDE

LOM LMM

AIRPORT

EXAMPLE−

At 12:03 local time, in the example shown, a pilot holding, receives instructions to leave the fix inbound at 12:07. These

instructions are received just as the pilot has completed turn at the outbound end of the holding pattern and is proceeding

inbound towards the fix. Arriving back over the fix, the pilot notes that the time is 12:04 and that there are 3 minutes to lose

in order to leave the fix at the assigned time. Since the time remaining is more than two minutes, the pilot plans to fly a race

track pattern rather than a 360 degree turn, which would use up 2 minutes. The turns at the ends of the race track pattern

will consume approximately 2 minutes. Three minutes to go, minus 2 minutes required for the turns, leaves 1 minute for level

flight. Since two portions of level flight will be required to get back to the fix inbound, the pilot halves the 1 minute remaining
AIM 7/26/12

5−4−34 Arrival Procedures

and plans to fly level for 30 seconds outbound before starting the turn back to the fix on final approach. If the winds were

negligible at flight altitude, this procedure would bring the pilot inbound across the fix precisely at the specified time of

12:07. However, if expecting headwind on final approach, the pilot should shorten the 30 second outbound course somewhat,

knowing that the wind will carry the aircraft away from the fix faster while outbound and decrease the ground speed while

returning to the fix. On the other hand, compensating for a tailwind on final approach, the pilot should lengthen the

calculated 30 second outbound heading somewhat, knowing that the wind would tend to hold the aircraft closer to the fix

while outbound and increase the ground speed while returning to the fix.

5−4−11. Radar Approaches

a. The only airborne radio equipment required for

radar approaches is a functioning radio transmitter

and receiver. The radar controller vectors the aircraft

to align it with the runway centerline. The controller

continues the vectors to keep the aircraft on course

until the pilot can complete the approach and landing

by visual reference to the surface. There are two types

of radar approaches: Precision (PAR) and

Surveillance (ASR).

b. A radar approach may be given to any aircraft

upon request and may be offered to pilots of aircraft

in distress or to expedite traffic, however, an ASR

might not be approved unless there is an ATC

operational requirement, or in an unusual or

emergency situation. Acceptance of a PAR or ASR by

a pilot does not waive the prescribed weather

minimums for the airport or for the particular aircraft

operator concerned. The decision to make a radar

approach when the reported weather is below the

established minimums rests with the pilot.

c. PAR and ASR minimums are published on

separate pages in the FAA Terminal Procedures

Publication (TPP).

1. A PRECISION APPROACH (PAR) is one

in which a controller provides highly accurate

navigational guidance in azimuth and elevation to a

pilot. Pilots are given headings to fly, to direct them

to, and keep their aircraft aligned with the extended

centerline of the landing runway. They are told to

anticipate glidepath interception approximately 10 to

30 seconds before it occurs and when to start descent.

The published Decision Height will be given only if

the pilot requests it. If the aircraft is observed to

deviate above or below the glidepath, the pilot is

given the relative amount of deviation by use of terms

“slightly” or “well” and is expected to adjust the

aircraft’s rate of descent/ascent to return to the

glidepath. Trend information is also issued with

respect to the elevation of the aircraft and may be

modified by the terms “rapidly” and “slowly”;

e.g., “well above glidepath, coming down rapidly.”

Range from touchdown is given at least once each

mile. If an aircraft is observed by the controller to

proceed outside of specified safety zone limits in

azimuth and/or elevation and continue to operate

outside these prescribed limits, the pilot will be

directed to execute a missed approach or to fly a

specified course unless the pilot has the runway

environment (runway, approach lights, etc.) in sight.

Navigational guidance in azimuth and elevation is

provided the pilot until the aircraft reaches the

published Decision Height (DH). Advisory course

and glidepath information is furnished by the

controller until the aircraft passes over the landing

threshold, at which point the pilot is advised of any

deviation from the runway centerline. Radar service

is automatically terminated upon completion of the

approach.

2. A SURVEILLANCE APPROACH (ASR)

is one in which a controller provides navigational

guidance in azimuth only. The pilot is furnished

headings to fly to align the aircraft with the extended

centerline of the landing runway. Since the radar

information used for a surveillance approach is

considerably less precise than that used for a

precision approach, the accuracy of the approach will

not be as great and higher minimums will apply.

Guidance in elevation is not possible but the pilot will

be advised when to commence descent to the

Minimum Descent Altitude (MDA) or, if appropriate,

to an intermediate step−down fix Minimum Crossing

Altitude and subsequently to the prescribed MDA. In

addition, the pilot will be advised of the location of

the Missed Approach Point (MAP) prescribed for the

procedure and the aircraft’s position each mile on

final from the runway, airport or heliport or MAP, as

appropriate. If requested by the pilot, recommended

altitudes will be issued at each mile, based on the

descent gradient established for the procedure, down

to the last mile that is at or above the MDA. Normally,

navigational guidance will be provided until the

aircraft reaches the MAP. Controllers will terminate

guidance and instruct the pilot to execute a missed

approach unless at the MAP the pilot has the runway,
7/26/12 AIM

Arrival Procedures 5−4−35

airport or heliport in sight or, for a helicopter

point−in−space approach, the prescribed visual

reference with the surface is established. Also, if, at

any time during the approach the controller considers

that safe guidance for the remainder of the approach

cannot be provided, the controller will terminate

guidance and instruct the pilot to execute a missed

approach. Similarly, guidance termination and

missed approach will be effected upon pilot request

and, for civil aircraft only, controllers may terminate

guidance when the pilot reports the runway,

airport/heliport or visual surface route

(point−in−space approach) in sight or otherwise

indicates that continued guidance is not required.

Radar service is automatically terminated at the

completion of a radar approach.

NOTE−

1. The published MDA for straight−in approaches will be

issued to the pilot before beginning descent. When a

surveillance approach will terminate in a circle−to−land

maneuver, the pilot must furnish the aircraft approach

category to the controller. The controller will then provide

the pilot with the appropriate MDA.

2. ASR APPROACHES ARE NOT AVAILABLE WHEN

AN ATC FACILITY IS USING CENRAP.

3. A NO−GYRO APPROACH is available to

a pilot under radar control who experiences

circumstances wherein the directional gyro or other

stabilized compass is inoperative or inaccurate.

When this occurs, the pilot should so advise ATC and

request a No−Gyro vector or approach. Pilots of

aircraft not equipped with a directional gyro or other

stabilized compass who desire radar handling may

also request a No−Gyro vector or approach. The pilot

should make all turns at standard rate and should

execute the turn immediately upon receipt of

instructions. For example, “TURN RIGHT,” “STOP

TURN.” When a surveillance or precision approach

is made, the pilot will be advised after the aircraft has

been turned onto final approach to make turns at half

standard rate.

5−4−12. Radar Monitoring of Instrument

Approaches

a. PAR facilities operated by the FAA and the

military services at some joint−use (civil and

military) and military installations monitor aircraft

on instrument approaches and issue radar advisories

to the pilot when weather is below VFR minimums

(1,000 and 3), at night, or when requested by a pilot.

This service is provided only when the PAR Final

Approach Course coincides with the final approach

of the navigational aid and only during the

operational hours of the PAR. The radar advisories

serve only as a secondary aid since the pilot has

selected the navigational aid as the primary aid for the

approach.

b. Prior to starting final approach, the pilot will be

advised of the frequency on which the advisories will

be transmitted. If, for any reason, radar advisories

cannot be furnished, the pilot will be so advised.

c. Advisory information, derived from radar

observations, includes information on:

1. Passing the final approach fix inbound

(nonprecision approach) or passing the outer marker

or fix used in lieu of the outer marker inbound

(precision approach).

NOTE−

At this point, the pilot may be requested to report sighting

the approach lights or the runway.

2. Trend advisories with respect to elevation

and/or azimuth radar position and movement will be

provided.

NOTE−

Whenever the aircraft nears the PAR safety limit, the pilot

will be advised that the aircraft is well above or below the

glidepath or well left or right of course. Glidepath

information is given only to those aircraft executing a

precision approach, such as ILS or MLS. Altitude

information is not transmitted to aircraft executing other

than precision approaches because the descent portions of

these approaches generally do not coincide with the

depicted PAR glidepath. At locations where the MLS

glidepath and PAR glidepath are not coincidental, only

azimuth monitoring will be provided.
AIM 7/26/12

5−4−36 Arrival Procedures

3. If, after repeated advisories, the aircraft

proceeds outside the PAR safety limit or if a radical

deviation is observed, the pilot will be advised to

execute a missed approach unless the prescribed

visual reference with the surface is established.

d. Radar service is automatically terminated upon

completion of the approach.

5−4−13. ILS/MLS Approaches to Parallel

Runways

a. ATC procedures permit ILS instrument

approach operations to dual or triple parallel runway

configurations. ILS/MLS approaches to parallel

runways are grouped into three classes: Parallel

(dependent) ILS/MLS Approaches; Simultaneous

Parallel (independent) ILS/MLS Approaches; and

Simultaneous Close Parallel (independent) ILS

Precision Runway Monitor (PRM) Approaches. (See

FIG 5−4−18.) The classification of a parallel runway

approach procedure is dependent on adjacent parallel

runway centerline separation, ATC procedures, and

airport ATC radar monitoring and communications

capabilities. At some airports one or more parallel

localizer courses may be offset up to 3 degrees. Offset

localizer configurations result in loss of Category II

capabilities and an increase in decision height (50’).

b. Parallel approach operations demand

heightened pilot situational awareness. A thorough

Approach Procedure Chart review should be

conducted with, as a minimum, emphasis on the

following approach chart information: name and

number of the approach, localizer frequency, inbound

localizer/azimuth course, glide slope intercept

altitude, decision height, missed approach

instructions, special notes/procedures, and the

assigned runway location/proximity to adjacent

runways. Pilots will be advised that simultaneous

ILS/MLS or simultaneous close parallel ILS PRM

approaches are in use. This information may be

provided through the ATIS.

c. The close proximity of adjacent aircraft

conducting simultaneous parallel ILS/MLS and

simultaneous close parallel ILS PRM approaches

mandates strict pilot compliance with all ATC

clearances. ATC assigned airspeeds, altitudes, and

headings must be complied with in a timely manner.

Autopilot coupled ILS/MLS approaches require pilot

knowledge of procedures necessary to comply with

ATC instructions. Simultaneous parallel ILS/MLS

and simultaneous close parallel ILS PRM approaches

necessitate precise localizer tracking to minimize

final monitor controller intervention, and unwanted

No Transgression Zone (NTZ) penetration. In the

unlikely event of a breakout, ATC will not assign

altitudes lower than the minimum vectoring altitude.

Pilots should notify ATC immediately if there is a

degradation of aircraft or navigation systems.

d. Strict radio discipline is mandatory during

parallel ILS/MLS approach operations. This includes

an alert listening watch and the avoidance of lengthy,

unnecessary radio transmissions. Attention must be

given to proper call sign usage to prevent the

inadvertent execution of clearances intended for

another aircraft. Use of abbreviated call signs must be

avoided to preclude confusion of aircraft with similar

sounding call signs. Pilots must be alert to unusually

long periods of silence or any unusual background

sounds in their radio receiver. A stuck microphone

may block the issuance of ATC instructions by the

final monitor controller during simultaneous parallel

ILS/MLS and simultaneous close parallel ILS PRM

approaches.

REFERENCE−

AIM, Chapter 4, Section 2, Radio Communications Phraseology and

Techniques, gives additional communications information.

e. Use of Traffic Collision Avoidance Systems

(TCAS) provides an additional element of safety to

parallel approach operations. Pilots should follow

recommended TCAS operating procedures presented

in approved flight manuals, original equipment

manufacturer recommendations, professional

newsletters, and FAA publications.
7/26/12 AIM

Arrival Procedures 5−4−37

FIG 5−4−18

Parallel ILS Approaches
AIM 7/26/12

5−4−38 Arrival Procedures

5−4−14. Parallel ILS/MLS Approaches (Dependent)

(See FIG 5−4−19.)

FIG 5−4−19

Staggered ILS Approaches

a. Parallel approaches are an ATC procedure

permitting parallel ILS/MLS approaches to airports

having parallel runways separated by at least

2,500 feet between centerlines. Integral parts of a

total system are ILS/MLS, radar, communications,

ATC procedures, and required airborne equipment.

b. A parallel (dependent) approach differs from a

simultaneous (independent) approach in that, the

minimum distance between parallel runway

centerlines is reduced; there is no requirement for

radar monitoring or advisories; and a staggered

separation of aircraft on the adjacent

localizer/azimuth course is required.

c. Aircraft are afforded a minimum of 1.5 miles

radar separation diagonally between successive

aircraft on the adjacent localizer/azimuth course

when runway centerlines are at least 2,500 feet but no

more than 4,300 feet apart. When runway centerlines

are more than 4,300 feet but no more than 9,000 feet

apart a minimum of 2 miles diagonal radar separation

is provided. Aircraft on the same localizer/azimuth

course within 10 miles of the runway end are

provided a minimum of 2.5 miles radar separation. In

addition, a minimum of 1,000 feet vertical or a

minimum of three miles radar separation is provided

between aircraft during turn on to the parallel final

approach course.

d. Whenever parallel ILS/MLS approaches are in

progress, pilots are informed that approaches to both

runways are in use. In addition, the radar controller

will have the interphone capability of communicating

with the tower controller where separation

responsibility has not been delegated to the tower.
7/26/12 AIM

Arrival Procedures 5−4−39

5−4−15. Simultaneous Parallel ILS/MLS Approaches (Independent)

(See FIG 5−4−20.)

FIG 5−4−20

Simultaneous Parallel ILS Approaches

NO TRANSGRESSION ZONE

2200’

2200’

2200’

2200’

OM

OM INTERCEPT GLIDE

SLOPE AT 2200’

3200’

3200’

EXTEND RADAR MONITORING AND NTZ TO 7NM BEYOND RUNWAY

DEPARTURE END FOR QUADRUPLE SIMULTANEOUS ILS APPROACHES.

7NM

14L

14R

RADAR MONITORING

PROVIDED TO

ENSURE SEPARATION

BETWEEN AIRCRAFT ON

PARALLEL LOCALIZERS.

AIRCRAFT MAY BE

VECTORED TO EITHER

14L OR 14R ILS

FROM OUTER FIX.

MEADOWVIEW INT (NW COURSE OHA ILS &

OBK VOR R-227) ESTABLISHED WHERE

3200’ ALTITUDE INTERCEPTS GLIDE SLOPE.

RADAR MONITORING PROVIDED TO ENSURE SEPARATION

BETWEEN AIRCRAFT ON PARALLEL LOCALIZERS. WHEN GLIDE

SLOPE INOPERATIVE BEGIN DESCENT AT MEADOW INTERSECTION.

(RUNWAY CENTERLINES SPACED 4300’ OR MORE [DUAL RUNWAYS]

OR 5000’ OR MORE, [TRIPLE OR QUADRUPLE RUNWAYS] - RADAR MONITORING REQUIRED)

a. System. An approach system permitting

simultaneous ILS/MLS approaches to parallel

runways with centerlines separated by 4,300 to

9,000 feet, and equipped with final monitor

controllers. Simultaneous parallel ILS/MLS

approaches require radar monitoring to ensure

separation between aircraft on the adjacent parallel

approach course. Aircraft position is tracked by final

monitor controllers who will issue instructions to

aircraft observed deviating from the assigned

localizer course. Staggered radar separation

procedures are not utilized. Integral parts of a total

system are ILS/MLS, radar, communications, ATC

procedures, and required airborne equipment. The

Approach Procedure Chart permitting simultaneous

parallel ILS/MLS approaches will contain the note

“simultaneous approaches authorized RWYS 14L

and 14R,” identifying the appropriate runways as the

case may be. When advised that simultaneous parallel

ILS/MLS approaches are in progress, pilots must

advise approach control immediately of

malfunctioning or inoperative receivers, or if a

simultaneous parallel ILS/MLS approach is not

desired.

b. Radar Monitoring. This service is provided

for each simultaneous parallel ILS/MLS approach to

ensure aircraft do not deviate from the final approach

course. Radar monitoring includes instructions if an

aircraft nears or penetrates the prescribed NTZ (an
AIM 7/26/12

5−4−40 Arrival Procedures

area 2,000 feet wide located equidistant between

parallel final approach courses). This service will be

provided as follows:

1. During turn on to parallel final approach,

aircraft will be provided 3 miles radar separation or

a minimum or 1,000 feet vertical separation. The

assigned altitude must be maintained until

intercepting the glide path, unless cleared otherwise

by ATC. Aircraft will not be vectored to intercept the

final approach course at an angle greater than thirty

degrees.

2. The final monitor controller will have the

capability of overriding the tower controller on the

tower frequency.

3. Pilots will be instructed to monitor the tower

frequency to receive advisories and instructions.

4. Aircraft observed to overshoot the turn−on or

to continue on a track which will penetrate the NTZ

will be instructed to return to the correct final

approach course immediately. The final monitor

controller may also issue missed approach or

breakout instructions to the deviating aircraft.

PHRASEOLOGY−

“(Aircraft call sign) YOU HAVE CROSSED THE FINAL

APPROACH COURSE. TURN (left/right)

IMMEDIATELY AND RETURN TO THE

LOCALIZER/AZIMUTH COURSE,”

or

“(aircraft call sign) TURN (left/right) AND RETURN TO

THE LOCALIZER/AZIMUTH COURSE.”

5. If a deviating aircraft fails to respond to such

instructions or is observed penetrating the NTZ, the

aircraft on the adjacent final approach course may be

instructed to alter course.

PHRASEOLOGY−

“TRAFFIC ALERT (aircraft call sign) TURN (left/right)

IMMEDIATELY HEADING (degrees), (climb/descend)

AND MAINTAIN (altitude).”

6. Radar monitoring will automatically be

terminated when visual separation is applied, the

aircraft reports the approach lights or runway in sight,

or the aircraft is 1 mile or less from the runway

threshold (for runway centerlines spaced 4,300 feet

or greater). Final monitor controllers will not advise

pilots when radar monitoring is terminated.
7/26/12 AIM

Arrival Procedures 5−4−41

5−4−16. Simultaneous Close Parallel ILS PRM Approaches (Independent) and 

Simultaneous Offset Instrument Approaches (SOIA) (See FIG 5−4−21.)

FIG 5−4−21

ILS PRM Approaches

(Simultaneous Close Parallel)

a. System

1. ILS/PRM is an acronym for Instrument

Landing System/Precision Runway Monitor.

(a) An approach system that permits

simultaneous ILS/PRM approaches to dual runways

with centerlines separated by less than 4,300 feet but

at least 3,400 feet for parallel approach courses, and

at least 3,000 feet if one ILS if offset by 2.5 to

3.0 degrees. The airspace between the final approach

courses contains a No Transgression Zone (NTZ)

with surveillance provided by two PRM monitor

controllers, one for each approach course. To qualify

for reduced lateral runway separation, monitor

controllers must be equipped with high update radar

and high resolution ATC radar displays, collectively

called a PRM system. The PRM system displays

almost instantaneous radar information. Automated

tracking software provides PRM monitor controllers

with aircraft identification, position, speed and a

ten−second projected position, as well as visual and

aural controller alerts. The PRM system is a

supplemental requirement for simultaneous close

parallel approaches in addition to the system
AIM 7/26/12

5−4−42 Arrival Procedures

requirements for simultaneous parallel ILS/MLS

approaches described in paragraph 5−4−15,

Simultaneous Parallel ILS/MLS Approaches

(Independent).

(b) Simultaneous close parallel ILS/PRM

approaches are depicted on a separate Approach

Procedure Chart titled ILS/PRM Rwy XXX

(Simultaneous Close Parallel).

2. SOIA is an acronym for Simultaneous Offset

Instrument Approach, a procedure used to conduct

simultaneous approaches to runways spaced less than

3,000 feet, but at least 750 feet apart. The SOIA

procedure utilizes an ILS/PRM approach to one

runway and an offset Localizer Type Directional Aid

(LDA)/PRM approach with glide slope to the

adjacent runway.

(a) The ILS/PRM approach plates used in

SOIA operations are identical to other ILS/PRM

approach plates, with an additional note, which

provides the separation between the two runways

used for simultaneous approaches. The LDA/PRM

approach plate displays the required notations for

closely spaced approaches as well as depicting the

visual segment of the approach, and a note that

provides the separation between the two runways

used for simultaneous operations.

(b) Controllers monitor the SOIA ILS/PRM

and LDA/PRM approaches with a PRM system using

high update radar and high−resolution ATC radar

displays in exactly the same manner as is done for

ILS/PRM approaches. The procedures and system

requirements for SOIA ILS/PRM and LDA/PRM

approaches are identical with those used for

simultaneous close parallel ILS/PRM approaches

until near the LDA/PRM approach missed approach

point (MAP)−−−where visual acquisition of the ILS

aircraft by the LDA aircraft must be accomplished.

Since the ILS/PRM and LDA/PRM approaches are

identical except for the visual segment in the SOIA

concept, an understanding of the procedures for

conducting ILS/PRM approaches is essential before

conducting a SOIA ILS/PRM or LDA/PRM

operation.

(c) In SOIA, the approach course separation

(instead of the runway separation) meets established

close parallel approach criteria. Refer to FIG 5−4−22

for the generic SOIA approach geometry. A visual

segment of the LDA/PRM approach is established

between the LDA MAP and the runway threshold.

Aircraft transition in visual conditions from the LDA

course, beginning at the LDA MAP, to align with the

runway and can be stabilized by 500 feet above

ground level (AGL) on the extended runway

centerline. Aircraft will be “paired” in SOIA

operations, with the ILS aircraft ahead of the LDA

aircraft prior to the LDA aircraft reaching the LDA

MAP. A cloud ceiling for the approach is established

so that the LDA aircraft has nominally 30 seconds to

acquire the leading ILS aircraft prior to the LDA

aircraft reaching the LDA MAP. If visual acquisition

is not accomplished, a missed approach must be

executed.

b. Requirements

Besides system requirements as identified in

subpara a above all pilots must have completed

special training before accepting a clearance to

conduct ILS/PRM or LDA/PRM Simultaneous Close

Parallel Approaches.

1. Pilot Training Requirement. Pilots must

complete special pilot training, as outlined below,

before accepting a clearance for a simultaneous close

parallel ILS/PRM or LDA/PRM approach.

(a) For operations under 14 CFR Parts 121,

129, and 135 pilots must comply with FAA approved

company training as identified in their Operations

Specifications. Training, at a minimum, must require

pilots to view the FAA video “ILS PRM AND SOIA

APPROACHES: INFORMATION FOR AIR

CARRIER PILOTS.” Refer to http://www.faa.gov

for additional information and to view or download

the video.

(b) For operations under Part 91:

(1) Pilots operating transport category

aircraft must be familiar with PRM operations as

contained in this section of the Aeronautical

Information Manual (AIM). In addition, pilots

operating transport category aircraft must view the

FAA video “ILS PRM AND SOIA APPROACHES:

INFORMATION FOR AIR CARRIER PILOTS.”

Refer to http://www.faa.gov for additional

information and to view or download the video.
7/26/12 AIM

Arrival Procedures 5−4−43

FIG 5−4−22

SOIA Approach Geometry

NOTE−

SAP The SAP is a design point along the extended centerline of the intended landing runway on the

glide slope at 500 feet above the landing threshold. It is used to verify a sufficient distance is provided for the visual maneuver after the missed approach point (MAP) to permit the pilots to conform to approved, stabilized approach criteria.

MAP The point along the LDA where the course separation with the adjacent ILS reaches 3,000 feet.

The altitude of the glide slope at that point determines the approach minimum descent altitude

and is where the NTZ terminates. Maneuvering inside the MAP is done in visual conditions.

Angle Angle formed at the intersection of the extended LDA runway centerline and a line drawn between

the LDA MAP and the SAP. The size of the angle is determined by the FAA SOIA computer design

program, and is dependent on whether Heavy aircraft use the LDA and the spacing between the

runways.

Visibility Distance from MAP to runway threshold in statute miles (light credit applies).

Procedure LDA aircraft must see the runway landing environment and, if less than standard radar separation exists between the aircraft on the adjacent ILS course, the LDA aircraft must visually acquire

the ILS aircraft and report it in sight to ATC prior to the LDA MAP.

CC Clear Clouds.

(2) Pilots not operating transport category

aircraft must be familiar with PRM and SOIA

operations as contained in this section of the AIM.

The FAA strongly recommends that pilots not

involved in transport category aircraft operations

view the FAA video, “ILS PRM AND SOIA

APPROACHES: INFORMATION FOR GENERAL

AVIATION PILOTS.” Refer to http://www.faa.gov

for additional information and to view or download

the video.

2. ATC Directed Breakout. An ATC directed

“breakout” is defined as a vector off the ILS or LDA

approach course in response to another aircraft

penetrating the NTZ, the 2,000 foot wide area located

equidistance between the two approach courses that

is monitored by the PRM monitor controllers.

3. Dual Communications. The aircraft flying

the ILS/PRM or LDA/PRM approach must have the

capability of enabling the pilot/s to listen to two

communications frequencies simultaneously.
AIM 7/26/12

5−4−44 Arrival Procedures

c. Radar Monitoring. Simultaneous close

parallel ILS/PRM and LDA/PRM approaches require

that final monitor controllers utilize the PRM system

to ensure prescribed separation standards are met.

Procedures and communications phraseology are

also described in paragraph 5−4−15, Simultaneous

Parallel ILS/MLS Approaches (Independent). A

minimum of 3 miles radar separation or 1,000 feet

vertical separation will be provided during the

turn−on to close parallel final approach courses. To

ensure separation is maintained, and in order to avoid

an imminent situation during simultaneous close

parallel ILS/PRM or SOIA ILS/PRM and LDA/PRM

approaches, pilots must immediately comply with

PRM monitor controller instructions. In the event of

a missed approach, radar monitoring is provided to

one−half mile beyond the most distant of the two

runway departure ends for ILS/RPM approaches. In

SOIA, PRM radar monitoring terminates at the LDA

MAP. Final monitor controllers will not notify pilots

when radar monitoring is terminated.

d. Attention All Users Page (AAUP). ILS/PRM

and LDA/PRM approach charts have an AAUP

associated with them that must be referred to in

preparation for conducting the approach. This page

contains the following instructions that must be

followed if the pilot is unable to accept an ILS/PRM

or LDA/PRM approach.

1. At airports that conduct PRM operations,

(ILS/PRM or, in the case of airports where SOIAs are

conducted, ILS/PRM and LDA/PRM approaches)

pilots not qualified to except PRM approaches must

follow notification procedures found on the Attention

All Users Page (AAUP) of the Standard Instrument

Approach Procedures (SIAP) for the specific airport

PRM approach.

2. The AAUP covers the following operational

topics:

(a) ATIS. When the ATIS broadcast advises

ILS/PRM approaches are in progress (or ILS PRM

and LDA PRM approaches in the case of SOIA),

pilots should brief to fly the ILS/PRM or LDA/PRM

approach. If later advised to expect the ILS or LDA

approach (should one be published), the ILS/PRM or

LDA/PRM chart may be used after completing the

following briefing items:

(1) Minimums and missed approach

procedures are unchanged.

(2) PRM Monitor frequency no longer

required.

(3) ATC may assign a lower altitude for

glide slope intercept.

NOTE−

In the case of the LDA/PRM approach, this briefing

procedure only applies if an LDA approach is also

published.

In the case of the SOIA ILS/PRM and LDA/PRM

procedure, the AAUP describes the weather

conditions in which simultaneous approaches are

authorized:

Simultaneous approach weather minimums are

X,XXX feet (ceiling), x miles (visibility).

(b) Dual VHF Communications Required.

To avoid blocked transmissions, each runway will

have two frequencies, a primary and a monitor

frequency. The tower controller will transmit on both

frequencies. The monitor controller’s transmissions,

if needed, will override both frequencies. Pilots will

ONLY transmit on the tower controller’s frequency,

but will listen to both frequencies. Begin to monitor

the PRM monitor controller when instructed by ATC

to contact the tower. The volume levels should be set

about the same on both radios so that the pilots will

be able to hear transmissions on at least one frequency

if the other is blocked. Site specific procedures take

precedence over the general information presented in

this paragraph. Refer to the AAUP for applicable

procedures at specific airports.
7/26/12 AIM

Arrival Procedures 5−4−45

(c) Breakouts. Breakouts differ from other

types of abandoned approaches in that they can

happen anywhere and unexpectedly. Pilots directed

by ATC to break off an approach must assume that an

aircraft is blundering toward them and a breakout

must be initiated immediately.

(1) Hand−fly breakouts. All breakouts

are to be hand−flown to ensure the maneuver is

accomplished in the shortest amount of time.

(2) ATC Directed “Breakouts.” ATC

directed breakouts will consist of a turn and a climb

or descent. Pilots must always initiate the breakout in

response to an air traffic controller’s instruction.

Controllers will give a descending breakout only

when there are no other reasonable options available,

but in no case will the descent be below the minimum

vectoring altitude (MVA) which provides at least

1,000 feet required obstruction clearance. The AAUP

provides the MVA in the final approach segment as

X,XXX feet at (Name) Airport.

NOTE−

“TRAFFIC ALERT.” If an aircraft enters the “NO

TRANSGRESSION ZONE” (NTZ), the controller will

breakout the threatened aircraft on the adjacent approach.

The phraseology for the breakout will be:

PHRASEOLOGY−

TRAFFIC ALERT, (aircraft call sign) TURN (left/right)

IMMEDIATELY, HEADING (degrees),

CLIMB/DESCEND AND MAINTAIN (altitude).

(d) ILS/PRM Navigation. The pilot may

find crossing altitudes along the final approach

course. The pilot is advised that descending on the

ILS glideslope ensures complying with any charted

crossing restrictions.

SOIA AAUP differences from ILS PRM AAUP

(e) ILS/PRM LDA Traffic (only published

on ILS/PRM AAUP when the ILS PRM approach

is used in conjunctions with an LDA/PRM

approach to the adjacent runway). To provide

better situational awareness, and because traffic on

the LDA may be visible on the ILS aircraft’s TCAS,

pilots are reminded of the fact that aircraft will be

maneuvering behind them to align with the adjacent

runway. While conducting the ILS/PRM approach to

Runway XXX, other aircraft may be conducting the

offset LDA/PRM approach to Runway XXX. These

aircraft will approach from the (left/right)−rear and

will realign with runway XXX after making visual

contact with the ILS traffic. Under normal

circumstances these aircraft will not pass the ILS

traffic.

SOIA LDA/PRM AAUP Items. The AAUP for the

SOIA LDA/PRM approach contains most

information found on ILS/PRM AAUPs. It replaces

certain information as seen below and provides pilots

with the procedures to be used in the visual segment

of the LDA/PRM approach, from the time the ILS

aircraft is visually acquired until landing.

(f) SOIA LDA/PRM Navigation (replaces

ILS/PRM (d) and (e) above). The pilot may find

crossing altitudes along the final approach course.

The pilot is advised that descending on the LDA

glideslope ensures complying with any charted

crossing restrictions. Remain on the LDA course

until passing XXXXX (LDA MAP name)

intersection prior to maneuvering to align with the

centerline of runway XXX.

(g) SOIA (Name) Airport Visual Segment

(replaces ILS/PRM (e) above). Pilot procedures for

navigating beyond the LDA MAP are spelled out. If

ATC advises that there is traffic on the adjacent ILS,

pilots are authorized to continue past the LDA MAP

to align with runway centerline when:

(1) the ILS traffic is in sight and is expected

to remain in sight,

(2) ATC has been advised that “traffic is in

sight.”

(3) the runway environment is in sight.

Otherwise, a missed approach must be executed.

Between the LDA MAP and the runway threshold,

pilots of the LDA aircraft are responsible for

separating themselves visually from traffic on the ILS

approach, which means maneuvering the aircraft as

necessary to avoid the ILS traffic until landing, and

providing wake turbulence avoidance, if applicable.

Pilots should advise ATC, as soon as practical, if

visual contact with the ILS traffic is lost and execute

a missed approach unless otherwise instructed by

ATC.

e. SOIA LDA Approach Wake Turbulence.

Pilots are responsible for wake turbulence avoidance

when maneuvering between the LDA missed

approach point and the runway threshold.
AIM 7/26/12

5−4−46 Arrival Procedures

f. Differences between ILS and ILS/PRM

approaches of importance to the pilot.

1. Runway Spacing. Prior to ILS/PRM and

LDA/PRM approaches, most ATC directed breakouts

were the result of two aircraft in−trail on the same

final approach course getting too close together.

Two aircraft going in the same direction did not

mandate quick reaction times. With PRM

approaches, two aircraft could be along side each

other, navigating on courses that are separated by less

than 4,300 feet. In the unlikely event that an aircraft

“blunders” off its course and makes a worst case turn

of 30 degrees toward the adjacent final approach

course, closing speeds of 135 feet per second could

occur that constitute the need for quick reaction. A

blunder has to be recognized by the monitor

controller, and breakout instructions issued to the

endangered aircraft. The pilot will not have any

warning that a breakout is imminent because the

blundering aircraft will be on another frequency. It is

important that, when a pilot receives breakout

instructions, he/she assumes that a blundering aircraft

is about to or has penetrated the NTZ and is heading

toward his/her approach course. The pilot must

initiate a breakout as soon as safety allows. While

conducting PRM approaches, pilots must maintain an

increased sense of awareness in order to immediately

react to an ATC instruction (breakout) and maneuver

as instructed by ATC, away from a blundering

aircraft.

2. Communications. To help in avoiding

communication problems caused by stuck

microphones and two parties talking at the same time,

two frequencies for each runway will be in use during

ILS/PRM and LDA/PRM approach operations, the

primary tower frequency and the PRM monitor

frequency. The tower controller transmits and

receives in a normal fashion on the primary frequency

and also transmits on the PRM monitor frequency.

The monitor controller’s transmissions override on

both frequencies. The pilots flying the approach will

listen to both frequencies but only transmit on the

primary tower frequency. If the PRM monitor

controller initiates a breakout and the primary

frequency is blocked by another transmission, the

breakout instruction will still be heard on the PRM

monitor frequency.

3. Hand−flown Breakouts. The use of the

autopilot is encouraged while flying an ILS/PRM or

LDA/PRM approach, but the autopilot must be

disengaged in the rare event that a breakout is issued.

Simulation studies of breakouts have shown that a

hand−flown breakout can be initiated consistently

faster than a breakout performed using the autopilot.

4. TCAS. The ATC breakout instruction is the

primary means of conflict resolution. TCAS, if

installed, provides another form of conflict resolution

in the unlikely event other separation standards

would fail. TCAS is not required to conduct a closely

spaced approach.

The TCAS provides only vertical resolution of

aircraft conflicts, while the ATC breakout instruction

provides both vertical and horizontal guidance for

conflict resolutions. Pilots should always

immediately follow the TCAS Resolution Advisory

(RA), whenever it is received. Should a TCAS RA be

received before, during, or after an ATC breakout

instruction is issued, the pilot should follow the RA,

even if it conflicts with the climb/descent portion of

the breakout maneuver. If following an RA requires

deviating from an ATC clearance, the pilot must

advise ATC as soon as practical. While following an

RA, it is extremely important that the pilot also

comply with the turn portion of the ATC breakout

instruction unless the pilot determines safety to be

factor. Adhering to these procedures assures the pilot

that acceptable “breakout” separation margins will

always be provided, even in the face of a normal

procedural or system failure.

5. Breakouts. The probability is extremely

low that an aircraft will “blunder” from its assigned

approach course and enter the NTZ, causing ATC to

“breakout” the aircraft approaching on the adjacent

ILS course. However, because of the close proximity

of the final approach courses, it is essential that pilots

follow the ATC breakout instructions precisely and

expeditiously. The controller’s “breakout”

instructions provide conflict resolution for the

threatened aircraft, with the turn portion of the

“breakout” being the single most important element

in achieving maximum protection. A descending

breakout will only be issued when it is the only

controller option. In no case will the controller

descend an aircraft below the MVA, which will

provide at least 1,000 feet clearance above obstacles.
7/26/12 AIM

Arrival Procedures 5−4−47

The pilot is not expected to exceed 1,000 feet per

minute rate of descent in the event a descending

breakout is issued.

5−4−17. Simultaneous Converging

Instrument Approaches

a. ATC may conduct instrument approaches

simultaneously to converging runways; i.e., runways

having an included angle from 15 to 100 degrees, at

airports where a program has been specifically

approved to do so.

b. The basic concept requires that dedicated,

separate standard instrument approach procedures be

developed for each converging runway included.

Missed Approach Points must be at least 3 miles apart

and missed approach procedures ensure that missed

approach protected airspace does not overlap.

c. Other requirements are: radar availability,

nonintersecting final approach courses, precision

(ILS/MLS) approach systems on each runway and, if

runways intersect, controllers must be able to apply

visual separation as well as intersecting runway

separation criteria. Intersecting runways also require

minimums of at least 700 foot ceilings and 2 miles

visibility. Straight in approaches and landings must

be made.

d. Whenever simultaneous converging

approaches are in progress, aircraft will be informed

by the controller as soon as feasible after initial

contact or via ATIS. Additionally, the radar controller

will have direct communications capability with the

tower controller where separation responsibility has

not been delegated to the tower.

5−4−18. RNP AR Instrument Approach

Procedures

These procedures require authorization analogous to

the special authorization required for Category II or

III ILS procedures. Authorization required (AR)

procedures are to be conducted by aircrews meeting

special training requirements in aircraft that meet the

specified performance and functional requirements.

a. Unique characteristics of RNP AR

Approaches

1. RNP value. Each published line of minima

has an associated RNP value. The indicated value

defines the lateral and vertical performance

requirements. A minimum RNP type is documented

as part of the RNP AR authorization for each operator

and may vary depending on aircraft configuration or

operational procedures (e.g., GPS inoperative, use of

flight director vice autopilot).

2. Curved path procedures. Some RNP

approaches have a curved path, also called a

radius−to−a−fix (RF) leg. Since not all aircraft have

the capability to fly these arcs, pilots are responsible

for knowing if they can conduct an RNP approach

with an arc or not. Aircraft speeds, winds and bank

angles have been taken into consideration in the

development of the procedures.

3. RNP required for extraction or not.

Where required, the missed approach procedure may

use RNP values less than RNP−1. The reliability of

the navigation system has to be very high in order to

conduct these approaches. Operation on these

procedures generally requires redundant equipment,

as no single point of failure can cause loss of both

approach and missed approach navigation.

4. Non−standard speeds or climb gradients.

RNP AR approaches are developed based on standard

approach speeds and a 200 ft/NM climb gradient in

the missed approach. Any exceptions to these

standards will be indicated on the approach

procedure, and the operator should ensure they can

comply with any published restrictions before

conducting the operation.

5. Temperature Limits. For aircraft using

barometric vertical navigation (without temperature

compensation) to conduct the approach, low and

high−temperature limits are identified on the

procedure. Cold temperatures reduce the glidepath

angle while high temperatures increase the glidepath

angle. Aircraft using baro VNAV with temperature

compensation or aircraft using an alternate means for

vertical guidance (e.g., SBAS) may disregard the

temperature restrictions. The charted temperature

limits are evaluated for the final approach segment

only. Regardless of charted temperature limits or

temperature compensation by the FMS, the pilot may

need to manually compensate for cold temperature on

minimum altitudes and the decision altitude.

6. Aircraft size. The achieved minimums may

be dependent on aircraft size. Large aircraft may

require higher minimums due to gear height and/or

wingspan. Approach procedure charts will be

annotated with applicable aircraft size restrictions.
AIM 7/26/12

5−4−48 Arrival Procedures

b. Types of RNP AR Approach Operations

1. RNP Stand−alone Approach Operations.

RNP AR procedures can provide access to runways

regardless of the ground−based NAVAID

infrastructure, and can be designed to avoid

obstacles, terrain, airspace, or resolve environmental

constraints.

2. RNP Parallel Approach (RPA)

Operations. RNP AR procedures can be used for

parallel approaches where the runway separation is

adequate (See FIG 5−4−23). Parallel approach

procedures can be used either simultaneously or as

stand−alone operations. They may be part of either

independent or dependent operations depending on

the ATC ability to provide radar monitoring.

FIG 5−4−23

3. RNP Parallel Approach Runway

Transitions (RPAT) Operations. RPAT

approaches begin as a parallel IFR approach

operation using simultaneous independent or

dependent procedures. (See FIG 5−4−24). Visual

separation standards are used in the final segment of

the approach after the final approach fix, to permit the

RPAT aircraft to transition in visual conditions along

a predefined lateral and vertical path to align with the

runway centerline.

FIG 5−4−24

4. RNP Converging Runway Operations. At

airports where runways converge, but may or may not

intersect, an RNP AR approach can provide a precise

curved missed approach path that conforms to aircraft

separation minimums for simultaneous operations

(See FIG 5−4−25). By flying this curved missed

approach path with high accuracy and containment

provided by RNP, dual runway operations may

continue to be used to lower ceiling and visibility

values than currently available. This type of

operation allows greater capacity at airports where it

can be applied.

FIG 5−4−25
7/26/12 AIM

Arrival Procedures 5−4−49

5−4−19. Side−step Maneuver

a. ATC may authorize a standard instrument

approach procedure which serves either one of

parallel runways that are separated by 1,200 feet or

less followed by a straight−in landing on the adjacent

runway.

b. Aircraft that will execute a side−step maneuver

will be cleared for a specified approach procedure

and landing on the adjacent parallel runway.

Example, “cleared ILS runway 7 left approach,

side−step to runway 7 right.” Pilots are expected to

commence the side−step maneuver as soon as

possible after the runway or runway environment is

in sight. Compliance with minimum altitudes

associated with stepdown fixes is expected even after

the side−step maneuver is initiated.

NOTE−

Side−step minima are flown to a Minimum Descent

Altitude (MDA) regardless of the approach authorized.

c. Landing minimums to the adjacent runway will

be based on nonprecision criteria and therefore higher

than the precision minimums to the primary runway,

but will normally be lower than the published circling

minimums.

5−4−20. Approach and Landing Minimums

a. Landing Minimums. The rules applicable to

landing minimums are contained in 14 CFR

Section 91.175. TBL 5−4−1 may be used to convert

RVR to ground or flight visibility. For converting

RVR values that fall between listed values, use the

next higher RVR value; do not interpolate. For

example, when converting 1800 RVR, use 2400 RVR

with the resultant visibility of 1/2 mile.

TBL 5−4−1

RVR Value Conversions

RVR Visibility

(statute miles)

1600 1/4

2400 1/2

3200 5/8

4000 3/4

4500 7/8

5000 1

6000 1 1/4

b. Obstacle Clearance. Final approach obstacle

clearance is provided from the start of the final

segment to the runway or missed approach point,

whichever occurs last. Side−step obstacle protection

is provided by increasing the width of the final

approach obstacle clearance area.

1. Circling approach protected areas are defined

by the tangential connection of arcs drawn from each

runway end. The arc radii distance differs by aircraft

approach category (see FIG 5−4−26). Because of

obstacles near the airport, a portion of the circling

area may be restricted by a procedural note: e.g.,

“Circling NA E of RWY 17−35.” Obstacle clearance

is provided at the published minimums (MDA) for

the pilot who makes a straight−in approach,

side−steps, or circles. Once below the MDA the pilot

must see and avoid obstacles. Executing the missed

approach after starting to maneuver usually places the

aircraft beyond the MAP. The aircraft is clear of

obstacles when at or above the MDA while inside the

circling area, but simply joining the missed approach

ground track from the circling maneuver may not

provide vertical obstacle clearance once the aircraft

exits the circling area. Additional climb inside the

circling area may be required before joining the

missed approach track. See paragraph 5−4−21,
AIM 7/26/12

5−4−50 Arrival Procedures

Missed Approach, for additional considerations

when starting a missed approach at other than the

MAP.

FIG 5−4−26

Final Approach Obstacle Clearance

CIRCLING APPROACH AREA RADII

CIRCLING APPROACH AREA

RADI (r) DEFINING SIZE

OF AREAS, VARY WITH THE

APPROACH CATEGORY

r

r

r

r

r

A

B

C

D

E

1.3

1.5

1.7

2.3

4.5

Approach Category Radius (Miles)

2. Precision Obstacle Free Zone (POFZ). A

volume of airspace above an area beginning at the

runway threshold, at the threshold elevation, and

centered on the extended runway centerline. The

POFZ is 200 feet (60m) long and 800 feet (240m)

wide. The POFZ must be clear when an aircraft on a

vertically guided final approach is within 2 nautical

miles of the runway threshold and the reported ceiling

is below 250 feet or visibility less than 3/4 statute mile

(SM) (or runway visual range below 4,000 feet). If the

POFZ is not clear, the MINIMUM authorized height

above touchdown (HAT) and visibility is 250 feet and 3/4SM. The POFZ is considered clear even if the wing

of the aircraft holding on a taxiway waiting for

runway clearance penetrates the POFZ; however,

neither the fuselage nor the tail may infringe on the

POFZ. The POFZ is applicable at all runway ends

including displaced thresholds.
7/26/12 AIM

Arrival Procedures 5−4−51

FIG 5−4−27

c. Straight−in Minimums are shown on the IAP

when the final approach course is within 30 degrees

of the runway alignment (15 degrees for GPS IAPs)

and a normal descent can be made from the IFR

altitude shown on the IAP to the runway surface.

When either the normal rate of descent or the runway

alignment factor of 30 degrees (15 degrees for GPS

IAPs) is exceeded, a straight−in minimum is not

published and a circling minimum applies. The fact

that a straight−in minimum is not published does not

preclude pilots from landing straight−in if they have

the active runway in sight and have sufficient time to

make a normal approach for landing. Under such

conditions and when ATC has cleared them for

landing on that runway, pilots are not expected to

circle even though only circling minimums are

published. If they desire to circle, they should advise

ATC.

d. Side−Step Maneuver Minimums. Landing

minimums for a side−step maneuver to the adjacent

runway will normally be higher than the minimums

to the primary runway.

e. Published Approach Minimums. Approach

minimums are published for different aircraft

categories and consist of a minimum altitude (DA,

DH, MDA) and required visibility. These minimums

are determined by applying the appropriate TERPS

criteria. When a fix is incorporated in a nonprecision

final segment, two sets of minimums may be

published: one for the pilot that is able to identify the

fix, and a second for the pilot that cannot. Two sets of

minimums may also be published when a second

altimeter source is used in the procedure. When a

nonprecision procedure incorporates both a

stepdown fix in the final segment and a second
AIM 7/26/12

5−4−52 Arrival Procedures

altimeter source, two sets of minimums are published

to account for the stepdown fix and a note addresses

minimums for the second altimeter source.

f. Circling Minimums. In some busy terminal

areas, ATC may not allow circling and circling

minimums will not be published. Published circling

minimums provide obstacle clearance when pilots

remain within the appropriate area of protection.

Pilots should remain at or above the circling altitude

until the aircraft is continuously in a position from

which a descent to a landing on the intended runway

can be made at a normal rate of descent using normal

maneuvers. Circling may require maneuvers at low

altitude, at low airspeed, and in marginal weather

conditions. Pilots must use sound judgment, have an

indepth knowledge of their capabilities, and fully

understand the aircraft performance to determine the

exact circling maneuver since weather, unique airport

design, and the aircraft position, altitude, and

airspeed must all be considered. The following basic

rules apply:

1. Maneuver the shortest path to the base or

downwind leg, as appropriate, considering existing

weather conditions. There is no restriction from

passing over the airport or other runways.

2. It should be recognized that circling

maneuvers may be made while VFR or other flying

is in progress at the airport. Standard left turns or

specific instruction from the controller for

maneuvering must be considered when circling to

land.

3. At airports without a control tower, it may be

desirable to fly over the airport to observe wind and

turn indicators and other traffic which may be on the

runway or flying in the vicinity of the airport.

REFERENCE−

AC 90−66A, Recommended Standards Traffic patterns for Aeronautical

Operations at Airports without Operating Control Towers.

4. The missed approach point (MAP) varies

depending upon the approach flown. For vertically

guided approaches, the MAP is at the decision

altitude/decision height. Non−vertically guided and

circling procedures share the same MAP and the pilot

determines this MAP by timing from the final

approach fix, by a fix, a NAVAID, or a waypoint.

Circling from a GLS, an ILS without a localizer line

of minima or an RNAV (GPS) approach without an

LNAV line of minima is prohibited.

g. Instrument Approach at a Military Field.

When instrument approaches are conducted by civil

aircraft at military airports, they must be conducted in

accordance with the procedures and minimums

approved by the military agency having jurisdiction

over the airport.

5−4−21. Missed Approach

a. When a landing cannot be accomplished, advise

ATC and, upon reaching the missed approach point

defined on the approach procedure chart, the pilot

must comply with the missed approach instructions

for the procedure being used or with an alternate

missed approach procedure specified by ATC.

b. Obstacle protection for missed approach is

predicated on the missed approach being initiated at

the decision altitude/height (DA/H) or at the missed

approach point and not lower than minimum descent

altitude (MDA). A climb gradient of at least 200 feet

per nautical mile is required, (except for Copter

approaches, where a climb of at least 400 feet per

nautical mile is required), unless a higher climb

gradient is published in the notes section of the

approach procedure chart. When higher than standard

climb gradients are specified, the end point of the

non−standard climb will be specified at either an

altitude or a fix. Pilots must preplan to ensure that the

aircraft can meet the climb gradient (expressed in feet

per nautical mile) required by the procedure in the

event of a missed approach, and be aware that flying

at a higher than anticipated ground speed increases

the climb rate requirement (feet per minute). Tables

for the conversion of climb gradients (feet per

nautical mile) to climb rate (feet per minute), based

on ground speed, are included on page D1 of the U.S.

Terminal Procedures booklets. Reasonable buffers

are provided for normal maneuvers. However, no

consideration is given to an abnormally early turn.

Therefore, when an early missed approach is

executed, pilots should, unless otherwise cleared by

ATC, fly the IAP as specified on the approach plate

to the missed approach point at or above the MDA or

DH before executing a turning maneuver.

c. If visual reference is lost while circling−to−land

from an instrument approach, the missed approach

specified for that particular procedure must be

followed (unless an alternate missed approach

procedure is specified by ATC). To become

established on the prescribed missed approach

course, the pilot should make an initial climbing turn
7/26/12 AIM

Arrival Procedures 5−4−53

toward the landing runway and continue the turn until

established on the missed approach course. Inasmuch

as the circling maneuver may be accomplished in

more than one direction, different patterns will be

required to become established on the prescribed

missed approach course, depending on the aircraft

position at the time visual reference is lost.

Adherence to the procedure will help assure that an

aircraft will remain laterally within the circling and

missed approach obstruction clearance areas. Refer

to paragraph h concerning vertical obstruction

clearance when starting a missed approach at other

than the MAP. (See FIG 5−4−28.)

d. At locations where ATC radar service is

provided, the pilot should conform to radar vectors

when provided by ATC in lieu of the published

missed approach procedure. (See FIG 5−4−29.)

e. Some locations may have a preplanned alternate

missed approach procedure for use in the event the

primary NAVAID used for the missed approach

procedure is unavailable. To avoid confusion, the

alternate missed approach instructions are not

published on the chart. However, the alternate missed

approach holding pattern will be depicted on the

instrument approach chart for pilot situational

awareness and to assist ATC by not having to issue

detailed holding instructions. The alternate missed

approach may be based on NAVAIDs not used in the

approach procedure or the primary missed approach.

When the alternate missed approach procedure is

implemented by NOTAM, it becomes a mandatory

part of the procedure. The NOTAM will specify both

the textual instructions and any additional equipment

requirements necessary to complete the procedure.

Air traffic may also issue instructions for the alternate

missed approach when necessary, such as when the

primary missed approach NAVAID fails during the

approach. Pilots may reject an ATC clearance for an

alternate missed approach that requires equipment

not necessary for the published approach procedure

when the alternate missed approach is issued after

beginning the approach. However, when the alternate

missed approach is issued prior to beginning the

approach the pilot must either accept the entire

procedure (including the alternate missed approach),

request a different approach procedure, or coordinate

with ATC for alternative action to be taken, i.e.,

proceed to an alternate airport, etc.

f. When approach has been missed, request

clearance for specific action; i.e., to alternative

airport, another approach, etc.

g. Pilots must ensure that they have climbed to a

safe altitude prior to proceeding off the published

missed approach, especially in nonradar

environments. Abandoning the missed approach

prior to reaching the published altitude may not

provide adequate terrain clearance. Additional climb

may be required after reaching the holding pattern

before proceeding back to the IAF or to an alternate.
AIM 7/26/12

5−4−54 Arrival Procedures

FIG 5−4−28

Circling and Missed Approach Obstruction

Clearance Areas

X

X

CLIMBING TURN

CLIMBING TURN

DECISION TO MISS

HERE

DECISION

TO MISS HERE

VOR

VOR

CIRCLING

MANEUVER

(WHEN

CLEARED IN

RIGHT HAND

TRAFFIC

PATTERN)

FIG 5−4−29

Missed Approach

x

CHANUTE

109.2 CNU

090°

1450 1265

1581

1180

1172

Portion of a Published Procedure

Remain within

10 NM

VOR

MISSED APPROACH

Climbing right turn to

2600 2600 direct to VOR

236°

056°

2500

5.7 NM

R236

056°

011°

191°

h. A clearance for an instrument approach

procedure includes a clearance to fly the published

missed approach procedure, unless otherwise

instructed by ATC. The published missed approach

procedure provides obstacle clearance only when the

missed approach is conducted on the missed

approach segment from or above the missed approach

point, and assumes a climb rate of 200 feet/NM or

higher, as published. If the aircraft initiates a missed

approach at a point other than the missed approach

point (see paragraph 5−4−5b), from below MDA or

DA (H), or on a circling approach, obstacle clearance

is not necessarily provided by following the

published missed approach procedure, nor is

separation assured from other air traffic in the

vicinity.

In the event a balked (rejected) landing occurs at a position other than the published missed approach

point, the pilot should contact ATC as soon as possible to obtain an amended clearance. If unable to

contact ATC for any reason, the pilot should attempt

to re−intercept a published segment of the missed approach and comply with route and altitude

instructions. If unable to contact ATC, and in the pilot’s judgment it is no longer appropriate to fly the

published missed approach procedure, then consider

either maintaining visual conditions if practicable

and reattempt a landing, or a circle−climb over the

airport. Should a missed approach become necessary

when operating to an airport that is not served by an

operating control tower, continuous contact with an

air traffic facility may not be possible. In this case, the

pilot should execute the appropriate go−around/

missed approach procedure without delay and contact

ATC when able to do so.

Prior to initiating an instrument approach procedure,

the pilot should assess the actions to be taken in the

event of a balked (rejected) landing beyond the

missed approach point or below the MDA or DA (H)

considering the anticipated weather conditions and

available aircraft performance. 14 CFR 91.175(e)

authorizes the pilot to fly an appropriate missed

approach procedure that ensures obstruction clearance, but it does not necessarily consider separation

from other air traffic. The pilot must consider other

factors such as the aircraft’s geographical location

with respect to the prescribed missed approach point,

direction of flight, and/or minimum turning altitudes

in the prescribed missed approach procedure. The

pilot must also consider aircraft performance, visual
7/26/12 AIM

Arrival Procedures 5−4−55

climb restrictions, charted obstacles, published

obstacle departure procedure, takeoff visual climb

requirements as expressed by nonstandard takeoff

minima, other traffic expected to be in the vicinity, or

other factors not specifically expressed by the approach procedures.

5−4−22. Use of Enhanced Flight Vision

Systems (EFVS) on Instrument Approaches

An EFVS is an installed airborne system which uses

an electronic means to provide a display of the

forward external scene topography (the applicable

natural or manmade features of a place or region

especially in a way to show their relative positions

and elevation) through the use of imaging sensors,

such as forward looking infrared, millimeter wave

radiometry, millimeter wave radar, and/or low light

level image intensifying. The EFVS imagery is

displayed along with the additional flight information

and aircraft flight symbology required by 14 CFR

91.175 (m) on a head−up display (HUD), or an

equivalent display, in the same scale and alignment as

the external view and includes the display element,

sensors, computers and power supplies, indications,

and controls. The display is typically presented to the

pilot by means of an approved HUD.

a. Basic Strategy Using EFVS. When flying an

instrument approach procedure (IAP), if the runway

environment cannot be visually acquired at decision

altitude (DA) or minimum descent altitude (MDA)

using natural vision, then a pilot may use an EFVS to

continue descending down to 100 feet above the

Touchdown Zone Elevation (TDZE), provided all of

the visibility requirements of 14 CFR part 91.175 (l)

are met. The primary reference for maneuvering the

aircraft is based on what the pilot sees through the

EFVS. At 100 feet above the TDZE, a pilot can continue to descend only when the visual reference

requirements for descent below 100 feet can be seen

using natural vision (without the aid of the EFVS). In

other words, a pilot may not continue to rely on the

EFVS sensor image to identify the required visual

references below 100 feet above the TDZE. Supporting information is provided by the flight path vector

(FPV), flight path angle (FPA) reference cue, onboard navigation system, and other imagery and

flight symbology displayed on the EFVS. The FPV

and FPA reference cue, along with the EFVS imagery

of the Touchdown Zone (TDZ), provide the primary

vertical path reference for the pilot when vertical

guidance from a precision approach or approach with

vertical guidance is not available.

1. Straight−In Instrument Approach

Procedures. An EFVS may be used to descend

below DA or MDA from any straight−in IAP, other

than Category II or Category III approaches,

provided all of the requirements of 14 CFR part

91.175 (l) are met. This includes straight−in precision

approaches, approaches with vertical guidance (for

example, LPV or LNAV/VNAV), and non−precision

approaches (for example, VOR, NDB, LOC, RNAV,

GPS, LDA, SDF, etc.).

2. Circling Approach Procedure. An IAP

with a circle−to−land maneuver or circle−to−land

minimums does not meet criteria for straight−in

landing minimums. While the regulations do not

prohibit EFVS from being used during any phase of

flight, they do prohibit it from being used for

operational credit on anything but a straight−in IAP

with straight−in landing minima. EFVS must only be

used during a circle−to−land maneuver provided the

visual references required throughout the circling

maneuver are distinctly visible using natural vision.

An EFVS cannot be used to satisfy the requirement

that an identifiable part of the airport be distinctly

visible to the pilot during a circling maneuver at or

above MDA or while descending below MDA from

a circling maneuver.

3. Enhanced Flight Visibility. Flight visibility

is determined by using natural vision, and enhanced

flight visibility (EFV) is determined by using an

EFVS. 14 CFR part 91.175 (l) requires that the EFV

observed by using an EFVS cannot be less than the

visibility prescribed in the IAP to be used in order to

continue to descend below the DA or MDA.

b. EFVS Operations At or Below DA or MDA

Down to 100 Feet Above the TDZE. The visual

segment of an IAP begins at DA or MDA and continues to the runway. There are two means of operating

in the visual segment−−one is by using natural vision

and the other is by using an EFVS. If the pilot determines that the EFV observed by using the EFVS is not

less than the minimum visibility prescribed in the IAP

being flown, and the pilot acquires the required visual

references prescribed in 14 CFR part 91.175 (l)(3) using the EFVS, then the pilot can continue the

approach to 100 feet above the TDZE. To continue

the approach, the pilot uses the EFVS image to visually acquire the runway environment (the approach
AIM 7/26/12

5−4−56 Arrival Procedures

light system (ALS), if installed, or both the runway

threshold and the TDZ), confirm lateral alignment,

maneuver to the extended runway centerline earlier

than would otherwise be possible, and continue a normal descent from the DA or MDA to 100 feet above

the TDZE.

1. Required Visual References. In order to

descend below DA or MDA, the following visual

references (specified in 14 CFR part 91.175 (l)(3)) for

the runway of intended landing must be distinctly

visible and identifiable to the pilot using the EFVS:

(a) The ALS (if installed), or

(b) The following visual references in both

(b)(1) and (b)(2) below:

(1) The runway threshold, identified by at

least one of the following: the beginning of the runway landing surface, the threshold lights, or the

runway end identifier lights (REIL).

(2) The TDZ, identified by at least one of

the following: the runway TDZ landing surface, the

TDZ lights, the TDZ markings, or the runway lights.

2. Comparison of Visual Reference Requirements for EFVS and Natural Vision. The EFVS

visual reference requirements of 14 CFR part 91.175

(l)(3) comprise a more stringent standard than the

visual reference requirements prescribed under 14

CFR part 91.175 (c)(3) when using natural vision.

The more stringent standard is needed because an

EFVS might not display the color of the lights used

to identify specific portions of the runway or might

not be able to consistently display the runway markings. The main differences for EFVS operations are

that the visual glide slope indicator (VGSI) lights

cannot be used as a visual reference, and specific

visual references from both the threshold and TDZ

must be distinctly visible and identifiable. However,

when using natural vision, only one of the specified

visual references must be visible and identifiable.

3. Visual References and Offset

Approaches. Pilots must be especially knowledgeable of the approach conditions and approach course

alignment when considering whether to rely on EFVS

during a non−precision approach with an offset final

approach course. Depending upon the combination of

crosswind correction and the lateral field of view

provided by a particular EFVS, the required visual

references may or may not be within the pilot’s view

looking through the EFVS display. Pilots conducting

any non−precision approach must verify lateral alignment with the runway centerline when determining

when to descend from MDA.

4. When to Go Around. Any pilot operating

an aircraft with an EFVS installed should be aware

that the requirements of 14 CFR part 91.175 (c) for

using natural vision and the requirements of 14 CFR

part 91.175 (l) for using an EFVS are different. A

pilot would, therefore, first have to determine

whether an approach will be commenced using

natural vision or using an EFVS. While these two sets

of requirements provide a parallel decisionmaking

process, the requirements for when a missed

approach must be executed differ. Using EFVS, a

missed approach must be initiated at or below DA or

MDA down to 100 feet above TDZE whenever the

pilot determines that:

(a) The EFV is less than the visibility minima

prescribed for the IAP being used;

(b) The required visual references for the runway of intended landing are no longer distinctly

visible and identifiable to the pilot using the EFVS

imagery;

(c) The aircraft is not continuously in a position from which a descent to a landing can be made

on the intended runway, at a normal rate of descent,

using normal maneuvers; or

(d) For operations under 14 CFR parts 121

and 135, the descent rate of the aircraft would not

allow touchdown to occur within the TDZ of the

runway of intended landing.

5. Missed Approach Considerations. It

should be noted that a missed approach after passing

the DA, or beyond the missed approach point (MAP),

involves additional risk until established on the published missed approach segment. Initiating a

go−around after passing the published MAP may result in loss of obstacle clearance. As with any

approach, pilot planning should include contingencies between the published MAP and touchdown with

reference to obstacle clearance, aircraft performance,

and alternate escape plans.

c. EFVS Operations At and Below 100 Feet

Above the TDZE. At and below 100 feet above the

TDZE, the regulations do not require the EFVS to be

turned off or the display to be stowed in order to continue to a landing. A pilot may continue the approach
7/26/12 AIM

Arrival Procedures 5−4−57

below this altitude using an EFVS as long as the required visual references can be seen through the

display using natural vision. An operator may not

continue to descend beyond this point by relying

solely on the sensor image displayed on the EFVS.

1. Required Visual References. In order to

descend below 100 feet above the TDZE, the flight

visibility−−assessed using natural vision−−must be

sufficient for the following visual references to be

distinctly visible and identifiable to the pilot without

reliance on the EFVS to continue to a landing:

(a) The lights or markings of the threshold, or

(b) The lights or markings of the TDZ.

It is important to note that from 100 feet above the

TDZE and below, the flight visibility does not have

to be equal to or greater than the visibility prescribed

for the IAP in order to continue descending. It only

has to be sufficient for the visual references required

by 14 CFR part 91.175 (l)(4) to be distinctly visible

and identifiable to the pilot without reliance on the

EFVS.

2. Comparison of Visual Reference Requirements for EFVS and Natural Vision. Again, the

visual reference requirements for EFVS in 14 CFR

part 91.175 (l)(4) are more stringent than those required for natural vision in 14 CFR part 91.175 (c)(3).

The main differences for EFVS operations are that

the ALS and red terminating bars or red side row bars,

the REIL, and the VASI cannot be used as visual references. Only very specific visual references from the

threshold or the TDZ can be used (that is, the lights

or markings of the threshold or the lights or markings

of the TDZ).

3. When to Go Around. A missed approach

must be initiated when the pilot determines that:

(a) The flight visibility is no longer sufficient

to distinctly see and identify the required visual references listed in 14 CFR part 91.175 (l)(4) using natural

vision;

(b) The aircraft is not continuously in a position from which a descent to a landing can be made

on the intended runway, at a normal rate of descent,

using normal maneuvers; or

(c) For operations under 14 CFR parts 121

and 135, the descent rate of the aircraft would not allow touchdown to occur within the TDZ of the

runway of intended landing.

While touchdown within the TDZ is not specifically

addressed in the regulations for operators other than

14 CFR parts 121 and 135 operators, continued operations below DA or MDA where touchdown in the

TDZ is not assured, where a high sink rate occurs, or

where the decision to conduct a missed approach procedure is not executed in a timely manner, all create

a significant risk to the operation.

4. Missed Approach Considerations. As

noted earlier, a missed approach initiated after the DA

or MAP involves additional risk. At 100 feet or less

above the runway, it is likely that an aircraft is significantly below the TERPS missed approach obstacle

clearance surface. Prior planning is recommended

and should include contingencies between the published MAP and touchdown with reference to

obstacle clearance, aircraft performance, and alternate escape plans.

d. Light Emitting Diode (LED) Airport Lighting Impact on EFVS Operations. The FAA has

recently begun to replace incandescent lamps with

LEDs at some airports in threshold lights, taxiway

edge lights, taxiway centerline lights, low intensity

runway edge lights, windcone lights, beacons, and

some obstruction lighting. Pilots should be aware that

LED lights cannot be sensed by current EFVS systems.

5−4−23. Visual Approach

a. A visual approach is conducted on an IFR flight

plan and authorizes a pilot to proceed visually and

clear of clouds to the airport. The pilot must have

either the airport or the preceding identified aircraft

in sight. This approach must be authorized and

controlled by the appropriate air traffic control

facility. Reported weather at the airport must have a

ceiling at or above 1,000 feet and visibility 3 miles or

greater. ATC may authorize this type approach when

it will be operationally beneficial. Visual approaches

are an IFR procedure conducted under IFR in visual

meteorological conditions. Cloud clearance

requirements of 14 CFR Section 91.155 are not

applicable, unless required by operation

specifications.

b. Operating to an Airport Without Weather

Reporting Service. ATC will advise the pilot when

weather is not available at the destination airport.

ATC may initiate a visual approach provided there is

a reasonable assurance that weather at the airport is a
AIM 7/26/12

5−4−58 Arrival Procedures

ceiling at or above 1,000 feet and visibility 3 miles or

greater (e.g., area weather reports, PIREPs, etc.).

c. Operating to an Airport With an Operating

Control Tower. Aircraft may be authorized to

conduct a visual approach to one runway while other

aircraft are conducting IFR or VFR approaches to

another parallel, intersecting, or converging runway.

When operating to airports with parallel runways

separated by less than 2,500 feet, the succeeding

aircraft must report sighting the preceding aircraft

unless standard separation is being provided by ATC.

When operating to parallel runways separated by at

least 2,500 feet but less than 4,300 feet, controllers

will clear/vector aircraft to the final at an angle not

greater than 30 degrees unless radar, vertical, or

visual separation is provided during the turn−on. The

purpose of the 30 degree intercept angle is to reduce

the potential for overshoots of the final and to

preclude side−by−side operations with one or both

aircraft in a belly−up configuration during the

turn−on. Once the aircraft are established within

30 degrees of final, or on the final, these operations

may be conducted simultaneously. When the parallel

runways are separated by 4,300 feet or more, or

intersecting/converging runways are in use, ATC

may authorize a visual approach after advising all

aircraft involved that other aircraft are conducting

operations to the other runway. This may be

accomplished through use of the ATIS.

d. Separation Responsibilities. If the pilot has

the airport in sight but cannot see the aircraft to be

followed, ATC may clear the aircraft for a visual

approach; however, ATC retains both separation and

wake vortex separation responsibility. When visually

following a preceding aircraft, acceptance of the

visual approach clearance constitutes acceptance of

pilot responsibility for maintaining a safe approach

interval and adequate wake turbulence separation.

e. A visual approach is not an IAP and therefore

has no missed approach segment. If a go around is

necessary for any reason, aircraft operating at

controlled airports will be issued an appropriate

advisory/clearance/instruction by the tower. At

uncontrolled airports, aircraft are expected to remain

clear of clouds and complete a landing as soon as

possible. If a landing cannot be accomplished, the

aircraft is expected to remain clear of clouds and

contact ATC as soon as possible for further clearance.

Separation from other IFR aircraft will be maintained

under these circumstances.

f. Visual approaches reduce pilot/controller

workload and expedite traffic by shortening flight

paths to the airport. It is the pilot’s responsibility to

advise ATC as soon as possible if a visual approach

is not desired.

g. Authorization to conduct a visual approach is an

IFR authorization and does not alter IFR flight plan

cancellation responsibility.

REFERENCE−

AIM, Canceling IFR Flight Plan, Paragraph 5−1−15.

h. Radar service is automatically terminated,

without advising the pilot, when the aircraft is

instructed to change to advisory frequency.

5−4−24. Charted Visual Flight Procedure

(CVFP)

a. CVFPs are charted visual approaches

established for environmental/noise considerations,

and/or when necessary for the safety and efficiency of

air traffic operations. The approach charts depict

prominent landmarks, courses, and recommended

altitudes to specific runways. CVFPs are designed to

be used primarily for turbojet aircraft.

b. These procedures will be used only at airports

with an operating control tower.

c. Most approach charts will depict some

NAVAID information which is for supplemental

navigational guidance only.

d. Unless indicating a Class B airspace floor, all

depicted altitudes are for noise abatement purposes

and are recommended only. Pilots are not prohibited

from flying other than recommended altitudes if

operational requirements dictate.

e. When landmarks used for navigation are not

visible at night, the approach will be annotated

“PROCEDURE NOT AUTHORIZED AT NIGHT.”

f. CVFPs usually begin within 20 flying miles

from the airport.

g. Published weather minimums for CVFPs are

based on minimum vectoring altitudes rather than the

recommended altitudes depicted on charts.

h. CVFPs are not instrument approaches and do

not have missed approach segments.

i. ATC will not issue clearances for CVFPs when

the weather is less than the published minimum.
7/26/12 AIM

Arrival Procedures 5−4−59

j. ATC will clear aircraft for a CVFP after the pilot

reports siting a charted landmark or a preceding

aircraft. If instructed to follow a preceding aircraft,

pilots are responsible for maintaining a safe approach

interval and wake turbulence separation.

k. Pilots should advise ATC if at any point they are

unable to continue an approach or lose sight of a

preceding aircraft. Missed approaches will be

handled as a go−around.

5−4−25. Contact Approach

a. Pilots operating in accordance with an IFR

flight plan, provided they are clear of clouds and have

at least 1 mile flight visibility and can reasonably

expect to continue to the destination airport in those

conditions, may request ATC authorization for a

contact approach.

b. Controllers may authorize a contact approach

provided:

1. The contact approach is specifically

requested by the pilot. ATC cannot initiate this

approach.

EXAMPLE−

Request contact approach.

2. The reported ground visibility at the

destination airport is at least 1 statute mile.

3. The contact approach will be made to an

airport having a standard or special instrument

approach procedure.

4. Approved separation is applied between

aircraft so cleared and between these aircraft and

other IFR or special VFR aircraft.

EXAMPLE−

Cleared contact approach (and, if required) at or below

(altitude) (routing) if not possible (alternative procedures)

and advise.

c. A contact approach is an approach procedure

that may be used by a pilot (with prior authorization

from ATC) in lieu of conducting a standard or special

IAP to an airport. It is not intended for use by a pilot

on an IFR flight clearance to operate to an airport not

having a published and functioning IAP. Nor is it

intended for an aircraft to conduct an instrument

approach to one airport and then, when “in the clear,”

discontinue that approach and proceed to another

airport. In the execution of a contact approach, the

pilot assumes the responsibility for obstruction

clearance. If radar service is being received, it will

automatically terminate when the pilot is instructed to

change to advisory frequency.

5−4−26. Landing Priority

A clearance for a specific type of approach (ILS,

MLS, ADF, VOR or Straight−in Approach) to an

aircraft operating on an IFR flight plan does not mean

that landing priority will be given over other traffic.

ATCTs handle all aircraft, regardless of the type of

flight plan, on a “first−come, first−served” basis.

Therefore, because of local traffic or runway in use,

it may be necessary for the controller in the interest

of safety, to provide a different landing sequence. In

any case, a landing sequence will be issued to each

aircraft as soon as possible to enable the pilot to

properly adjust the aircraft’s flight path.

5−4−27. Overhead Approach Maneuver

a. Pilots operating in accordance with an

IFR flight plan in Visual Meteorological

Conditions (VMC) may request ATC authorization

for an overhead maneuver. An overhead maneuver is

not an instrument approach procedure. Overhead

maneuver patterns are developed at airports where

aircraft have an operational need to conduct the

maneuver. An aircraft conducting an overhead

maneuver is considered to be VFR and the IFR flight

plan is cancelled when the aircraft reaches the initial

point on the initial approach portion of the maneuver.

(See FIG 5−4−30.) The existence of a standard

overhead maneuver pattern does not eliminate the

possible requirement for an aircraft to conform to

conventional rectangular patterns if an overhead

maneuver cannot be approved. Aircraft operating to

an airport without a functioning control tower must

initiate cancellation of an IFR flight plan prior to

executing the overhead maneuver. Cancellation of

the IFR flight plan must be accomplished after

crossing the landing threshold on the initial portion of

the maneuver or after landing. Controllers may

authorize an overhead maneuver and issue the

following to arriving aircraft:

1. Pattern altitude and direction of traffic. This

information may be omitted if either is standard.

PHRASEOLOGY−

PATTERN ALTITUDE (altitude). RIGHT TURNS.
AIM 7/26/12

5−4−60 Arrival Procedures

2. Request for a report on initial approach.

PHRASEOLOGY−

REPORT INITIAL.

3. “Break” information and a request for the

pilot to report. The “Break Point” will be specified if

nonstandard. Pilots may be requested to report

“break” if required for traffic or other reasons.

PHRASEOLOGY−

BREAK AT (specified point).

REPORT BREAK.

FIG 5−4−30

Overhead Maneuver

3 - 5 NM

X X

INITIAL POINT INITIAL POINT

INITIAL APPROACH INITIAL APPROACH

X

ROLL OUT ROLL OUT

BREAK POINT BREAK POINT

180° TURN

180° TURN
7/26/12 AIM

Pilot/Controller Roles and Responsibilities 5−5−1

Section 5. Pilot/Controller Roles and Responsibilities

5−5−1. General

a. The roles and responsibilities of the pilot and

controller for effective participation in the ATC

system are contained in several documents. Pilot

responsibilities are in the CFRs and the air traffic

controllers’ are in the FAA Order JO 7110.65,

Air Traffic Control, and supplemental FAA directives. Additional and supplemental information for

pilots can be found in the current Aeronautical

Information Manual (AIM), Notices to Airmen,

Advisory Circulars and aeronautical charts. Since

there are many other excellent publications produced

by nongovernment organizations, as well as other

government organizations, with various updating

cycles, questions concerning the latest or most

current material can be resolved by cross-checking

with the above mentioned documents.

b. The pilot−in−command of an aircraft is directly

responsible for, and is the final authority as to the safe

operation of that aircraft. In an emergency requiring

immediate action, the pilot−in−command may

deviate from any rule in the General Subpart A and

Flight Rules Subpart B in accordance with 14 CFR

Section 91.3.

c. The air traffic controller is responsible to give

first priority to the separation of aircraft and to the

issuance of radar safety alerts, second priority to other

services that are required, but do not involve

separation of aircraft and third priority to additional

services to the extent possible.

d. In order to maintain a safe and efficient air

traffic system, it is necessary that each party fulfill

their responsibilities to the fullest.

e. The responsibilities of the pilot and the

controller intentionally overlap in many areas

providing a degree of redundancy. Should one or the

other fail in any manner, this overlapping responsibility is expected to compensate, in many cases, for

failures that may affect safety.

f. The following, while not intended to be all

inclusive, is a brief listing of pilot and controller

responsibilities for some commonly used procedures

or phases of flight. More detailed explanations are

contained in other portions of this publication, the

appropriate CFRs, ACs and similar publications. The

information provided is an overview of the principles

involved and is not meant as an interpretation of the

rules nor is it intended to extend or diminish

responsibilities.

5−5−2. Air Traffic Clearance

a. Pilot.

1. Acknowledges receipt and understanding of

an ATC clearance.

2. Reads back any hold short of runway

instructions issued by ATC.

3. Requests clarification or amendment, as

appropriate, any time a clearance is not fully

understood or considered unacceptable from a safety

standpoint.

4. Promptly complies with an air traffic

clearance upon receipt except as necessary to cope

with an emergency. Advises ATC as soon as possible

and obtains an amended clearance, if deviation is

necessary.

NOTE−

A clearance to land means that appropriate separation on

the landing runway will be ensured. A landing clearance

does not relieve the pilot from compliance with any

previously issued altitude crossing restriction.

b. Controller.

1. Issues appropriate clearances for the operation to be conducted, or being conducted, in

accordance with established criteria.

2. Assigns altitudes in IFR clearances that are at

or above the minimum IFR altitudes in controlled

airspace.

3. Ensures acknowledgement by the pilot for

issued information, clearances, or instructions.

4. Ensures that readbacks by the pilot of

altitude, heading, or other items are correct. If

incorrect, distorted, or incomplete, makes corrections

as appropriate.
AIM 7/26/12

5−5−2 Pilot/Controller Roles and Responsibilities

5−5−3. Contact Approach

a. Pilot.

1. Must request a contact approach and makes it

in lieu of a standard or special instrument approach.

2. By requesting the contact approach, indicates

that the flight is operating clear of clouds, has at least

one mile flight visibility, and reasonably expects to

continue to the destination airport in those conditions.

3. Assumes responsibility for obstruction clearance while conducting a contact approach.

4. Advises ATC immediately if unable to

continue the contact approach or if encounters less

than 1 mile flight visibility.

5. Is aware that if radar service is being received,

it may be automatically terminated when told to

contact the tower.

REFERENCE−

Pilot/Controller Glossary Term− Radar Service Terminated.

b. Controller.

1. Issues clearance for a contact approach only

when requested by the pilot. Does not solicit the use

of this procedure.

2. Before issuing the clearance, ascertains that

reported ground visibility at destination airport is at

least 1 mile.

3. Provides approved separation between the

aircraft cleared for a contact approach and other IFR

or special VFR aircraft. When using vertical

separation, does not assign a fixed altitude, but clears

the aircraft at or below an altitude which is at least

1,000 feet below any IFR traffic but not below

Minimum Safe Altitudes prescribed in 14 CFR

Section 91.119.

4. Issues alternative instructions if, in their

judgment, weather conditions may make completion

of the approach impracticable.

5−5−4. Instrument Approach

a. Pilot.

1. Be aware that the controller issues clearance

for approach based only on known traffic.

2. Follows the procedure as shown on the IAP,

including all restrictive notations, such as:

(a) Procedure not authorized at night;

(b) Approach not authorized when local area

altimeter not available;

(c) Procedure not authorized when control

tower not in operation;

(d) Procedure not authorized when glide

slope not used;

(e) Straight-in minimums not authorized at

night; etc.

(f) Radar required; or

(g) The circling minimums published on the

instrument approach chart provide adequate obstruction clearance and pilots should not descend below

the circling altitude until the aircraft is in a position

to make final descent for landing. Sound judgment

and knowledge of the pilot’s and the aircraft’s

capabilities are the criteria for determining the exact

maneuver in each instance since airport design and

the aircraft position, altitude and airspeed must all be

considered.

REFERENCE−

AIM, Approach and Landing Minimums, Paragraph 5−4−20.

3. Upon receipt of an approach clearance while

on an unpublished route or being radar vectored:

(a) Complies with the minimum altitude for

IFR; and

(b) Maintains the last assigned altitude until

established on a segment of a published route or IAP,

at which time published altitudes apply.

b. Controller.

1. Issues an approach clearance based on known

traffic.

2. Issues an IFR approach clearance only after

the aircraft is established on a segment of published

route or IAP, or assigns an appropriate altitude for the

aircraft to maintain until so established.

5−5−5. Missed Approach

a. Pilot.

1. Executes a missed approach when one of the

following conditions exist:

(a) Arrival at the Missed Approach

Point (MAP) or the Decision Height (DH) and visual

reference to the runway environment is insufficient to

complete the landing.

(b) Determines that a safe approach or

landing is not possible (see subparagraph 5−4−21h).
7/26/12 AIM

Pilot/Controller Roles and Responsibilities 5−5−3

(c) Instructed to do so by ATC.

2. Advises ATC that a missed approach will be

made. Include the reason for the missed approach

unless the missed approach is initiated by ATC.

3. Complies with the missed approach instructions for the IAP being executed from the MAP,

unless other missed approach instructions are

specified by ATC.

4. If executing a missed approach prior to

reaching the MAP, fly the lateral navigation path of

the instrument procedure to the MAP. Climb to the

altitude specified in the missed approach procedure,

except when a maximum altitude is specified

between the final approach fix (FAF) and the MAP. In

that case, comply with the maximum altitude

restriction. Note, this may require a continued

descent on the final approach.

5. Following a missed approach, requests

clearance for specific action; i.e., another approach,

hold for improved conditions, proceed to an alternate

airport, etc.

b. Controller.

1. Issues an approved alternate missed approach

procedure if it is desired that the pilot execute a

procedure other than as depicted on the instrument

approach chart.

2. May vector a radar identified aircraft

executing a missed approach when operationally

advantageous to the pilot or the controller.

3. In response to the pilot’s stated intentions,

issues a clearance to an alternate airport, to a holding

fix, or for reentry into the approach sequence, as

traffic conditions permit.

5−5−6. Radar Vectors

a. Pilot.

1. Promptly complies with headings and

altitudes assigned to you by the controller.

2. Questions any assigned heading or altitude

believed to be incorrect.

3. If operating VFR and compliance with any

radar vector or altitude would cause a violation of any

CFR, advises ATC and obtains a revised clearance or

instructions.

b. Controller.

1. Vectors aircraft in Class A, Class B, Class C,

Class D, and Class E airspace:

(a) For separation.

(b) For noise abatement.

(c) To obtain an operational advantage for the

pilot or controller.

2. Vectors aircraft in Class A, Class B, Class C,

Class D, Class E, and Class G airspace when

requested by the pilot.

3. Vectors IFR aircraft at or above minimum

vectoring altitudes.

4. May vector VFR aircraft, not at an ATC

assigned altitude, at any altitude. In these cases,

terrain separation is the pilot’s responsibility.

5−5−7. Safety Alert

a. Pilot.

1. Initiates appropriate action if a safety alert is

received from ATC.

2. Be aware that this service is not always

available and that many factors affect the ability of

the controller to be aware of a situation in which

unsafe proximity to terrain, obstructions, or another

aircraft may be developing.

b. Controller.

1. Issues a safety alert if aware an aircraft under

their control is at an altitude which, in the controller’s

judgment, places the aircraft in unsafe proximity to

terrain, obstructions or another aircraft. Types of

safety alerts are:

(a) Terrain or Obstruction Alert. Immediately issued to an aircraft under their control if aware

the aircraft is at an altitude believed to place the

aircraft in unsafe proximity to terrain or obstructions.

(b) Aircraft Conflict Alert. Immediately

issued to an aircraft under their control if aware of an

aircraft not under their control at an altitude believed

to place the aircraft in unsafe proximity to each other.

With the alert, they offer the pilot an alternative, if

feasible.

2. Discontinue further alerts if informed by the

pilot action is being taken to correct the situation or

that the other aircraft is in sight.
AIM 7/26/12

5−5−4 Pilot/Controller Roles and Responsibilities

5−5−8. See and Avoid

a. Pilot. When meteorological conditions permit,

regardless of type of flight plan or whether or not

under control of a radar facility, the pilot is

responsible to see and avoid other traffic, terrain, or

obstacles.

b. Controller.

1. Provides radar traffic information to radar

identified aircraft operating outside positive control

airspace on a workload permitting basis.

2. Issues safety alerts to aircraft under their

control if aware the aircraft is at an altitude believed

to place the aircraft in unsafe proximity to terrain,

obstructions, or other aircraft.

5−5−9. Speed Adjustments

a. Pilot.

1. Advises ATC any time cruising airspeed

varies plus or minus 5 percent or 10 knots, whichever

is greater, from that given in the flight plan.

2. Complies with speed adjustments from ATC

unless:

(a) The minimum or maximum safe airspeed

for any particular operation is greater or less than the

requested airspeed. In such cases, advises ATC.

NOTE−

It is the pilot’s responsibility and prerogative to refuse

speed adjustments considered excessive or contrary to the

aircraft’s operating specifications.

(b) Operating at or above 10,000 feet MSL on

an ATC assigned SPEED ADJUSTMENT of more

than 250 knots IAS and subsequent clearance is

received for descent below 10,000 feet MSL. In such

cases, pilots are expected to comply with 14 CFR

Section 91.117(a).

3. When complying with speed adjustment

assignments, maintains an indicated airspeed within

plus or minus 10 knots or 0.02 Mach number of the

specified speed.

b. Controller.

1. Assigns speed adjustments to aircraft when

necessary but not as a substitute for good vectoring

technique.

2. Adheres to the restrictions published in the

FAAO JO 7110.65, Air Traffic Control, as to when

speed adjustment procedures may be applied.

3. Avoids speed adjustments requiring alternate

decreases and increases.

4. Assigns speed adjustments to a specified IAS

(KNOTS)/Mach number or to increase or decrease

speed using increments of 10 knots or multiples

thereof.

5. Advises pilots to resume normal speed when

speed adjustments are no longer required.

6. Gives due consideration to aircraft capabilities to reduce speed while descending.

7. Does not assign speed adjustments to aircraft

at or above FL 390 without pilot consent.

5−5−10. Traffic Advisories (Traffic

Information)

a. Pilot.

1. Acknowledges receipt of traffic advisories.

2. Informs controller if traffic in sight.

3. Advises ATC if a vector to avoid traffic is

desired.

4. Does not expect to receive radar traffic

advisories on all traffic. Some aircraft may not appear

on the radar display. Be aware that the controller may

be occupied with higher priority duties and unable to

issue traffic information for a variety of reasons.

5. Advises controller if service is not desired.

b. Controller.

1. Issues radar traffic to the maximum extent

consistent with higher priority duties except in

Class A airspace.

2. Provides vectors to assist aircraft to avoid

observed traffic when requested by the pilot.

3. Issues traffic information to aircraft in the

Class B, Class C, and Class D surface areas for

sequencing purposes.

4. Controllers are required to issue to each

aircraft operating on intersecting or nonintersecting

converging runways where projected flight paths

will cross.
7/26/12 AIM

Pilot/Controller Roles and Responsibilities 5−5−5

5−5−11. Visual Approach

a. Pilot.

1. If a visual approach is not desired, advises

ATC.

2. Complies with controller’s instructions for

vectors toward the airport of intended landing or to a

visual position behind a preceding aircraft.

3. The pilot must, at all times, have either the

airport or the preceding aircraft in sight. After being

cleared for a visual approach, proceed to the airport

in a normal manner or follow the preceding aircraft.

Remain clear of clouds while conducting a visual

approach.

4. If the pilot accepts a visual approach

clearance to visually follow a preceding aircraft, you

are required to establish a safe landing interval behind

the aircraft you were instructed to follow. You are

responsible for wake turbulence separation.

5. Advise ATC immediately if the pilot is unable

to continue following the preceding aircraft, cannot

remain clear of clouds, needs to climb, or loses sight

of the airport.

6. Be aware that radar service is automatically

terminated, without being advised by ATC, when the

pilot is instructed to change to advisory frequency.

7. Be aware that there may be other traffic in the

traffic pattern and the landing sequence may differ

from the traffic sequence assigned by approach

control or ARTCC.

b. Controller.

1. Do not clear an aircraft for a visual approach

unless reported weather at the airport is ceiling at or

above 1,000 feet and visibility is 3 miles or greater.

When weather is not available for the destination

airport, inform the pilot and do not initiate a visual

approach to that airport unless there is reasonable

assurance that descent and flight to the airport can be

made visually.

2. Issue visual approach clearance when the

pilot reports sighting either the airport or a preceding

aircraft which is to be followed.

3. Provide separation except when visual

separation is being applied by the pilot.

4. Continue flight following and traffic information until the aircraft has landed or has been

instructed to change to advisory frequency.

5. Inform the pilot when the preceding aircraft

is a heavy.

6. When weather is available for the destination

airport, do not initiate a vector for a visual approach

unless the reported ceiling at the airport is 500 feet or

more above the MVA and visibility is 3 miles or more.

If vectoring weather minima are not available but

weather at the airport is ceiling at or above 1,000 feet

and visibility of 3 miles or greater, visual approaches

may still be conducted.

7. Informs the pilot conducting the visual

approach of the aircraft class when pertinent traffic is

known to be a heavy aircraft.

5−5−12. Visual Separation

a. Pilot.

1. Acceptance of instructions to follow another

aircraft or to provide visual separation from it is an

acknowledgment that the pilot will maneuver the

aircraft as necessary to avoid the other aircraft or to

maintain in-trail separation. Pilots are responsible to

maintain visual separation until flight paths (altitudes

and/or courses) diverge.

2. If instructed by ATC to follow another aircraft

or to provide visual separation from it, promptly

notify the controller if you lose sight of that aircraft,

are unable to maintain continued visual contact with

it, or cannot accept the responsibility for your own

separation for any reason.

3. The pilot also accepts responsibility for wake

turbulence separation under these conditions.

b. Controller. Applies visual separation only:

1. Within the terminal area when a controller

has both aircraft in sight or by instructing a pilot who

sees the other aircraft to maintain visual separation

from it.

2. Pilots are responsible to maintain visual

separation until flight paths (altitudes and/or courses)

diverge.

3. Within en route airspace when aircraft are on

opposite courses and one pilot reports having seen the

other aircraft and that the aircraft have passed each

other.
AIM 7/26/12

5−5−6 Pilot/Controller Roles and Responsibilities

5−5−13. VFR-on-top

a. Pilot.

1. This clearance must be requested by the pilot

on an IFR flight plan, and if approved, allows the pilot

the choice (subject to any ATC restrictions) to select

an altitude or flight level in lieu of an assigned

altitude.

NOTE−

VFR−on−top is not permitted in certain airspace areas,

such as Class A airspace, certain restricted areas, etc.

Consequently, IFR flights operating VFR−on−top will

avoid such airspace.

REFERENCE−

AIM, IFR Clearance VFR−on−top, Paragraph 4−4−8.

AIM, IFR Separation Standards, Paragraph 4−4−11.

AIM, Position Reporting, Paragraph 5−3−2.

AIM, Additional Reports, Paragraph 5−3−3.

2. By requesting a VFR-on-top clearance, the

pilot assumes the sole responsibility to be vigilant so

as to see and avoid other aircraft and to:

(a) Fly at the appropriate VFR altitude as

prescribed in 14 CFR Section 91.159.

(b) Comply with the VFR visibility and

distance from clouds criteria in 14 CFR Section 91.155, Basic VFR weather minimums.

(c) Comply with instrument flight rules that

are applicable to this flight; i.e., minimum IFR

altitudes, position reporting, radio communications,

course to be flown, adherence to ATC clearance, etc.

3. Should advise ATC prior to any altitude

change to ensure the exchange of accurate traffic

information.

b. Controller.

1. May clear an aircraft to maintain VFR-on-top

if the pilot of an aircraft on an IFR flight plan requests

the clearance.

2. Informs the pilot of an aircraft cleared to

climb to VFR-on-top the reported height of the tops

or that no top report is available; issues an alternate

clearance if necessary; and once the aircraft reports

reaching VFR-on-top, reclears the aircraft to

maintain VFR-on-top.

3. Before issuing clearance, ascertain that the

aircraft is not in or will not enter Class A airspace.

5−5−14. Instrument Departures

a. Pilot.

1. Prior to departure considers the type of terrain

and other obstructions on or in the vicinity of the

departure airport.

2. Determines if obstruction avoidance can be

maintained visually or that the departure procedure

should be followed.

3. Determines whether a departure procedure

and/or DP is available for obstruction avoidance.

4. At airports where IAPs have not been

published, hence no published departure procedure,

determines what action will be necessary and takes

such action that will assure a safe departure.

b. Controller.

1. At locations with airport traffic control

service, when necessary, specifies direction of

takeoff, turn, or initial heading to be flown after

takeoff.

2. At locations without airport traffic control

service but within Class E surface area when

necessary to specify direction of takeoff, turn, or

initial heading to be flown, obtains pilot’s concurrence that the procedure will allow the pilot to comply

with local traffic patterns, terrain, and obstruction

avoidance.

3. Includes established departure procedures as

part of the ATC clearance when pilot compliance is

necessary to ensure separation.

5−5−15. Minimum Fuel Advisory

a. Pilot.

1. Advise ATC of your minimum fuel status

when your fuel supply has reached a state where,

upon reaching destination, you cannot accept any

undue delay.

2. Be aware this is not an emergency situation,

but merely an advisory that indicates an emergency

situation is possible should any undue delay occur.

3. On initial contact the term “minimum fuel”

should be used after stating call sign.

EXAMPLE−

Salt Lake Approach, United 621, “minimum fuel.”

4. Be aware a minimum fuel advisory does not

imply a need for traffic priority.
7/26/12 AIM

Pilot/Controller Roles and Responsibilities 5−5−7

5. If the remaining usable fuel supply suggests

the need for traffic priority to ensure a safe landing,

you should declare an emergency due to low fuel and

report fuel remaining in minutes.

REFERENCE−

Pilot/Controller Glossary Item− Fuel Remaining.

b. Controller.

1. When an aircraft declares a state of minimum

fuel, relay this information to the facility to whom

control jurisdiction is transferred.

2. Be alert for any occurrence which might

delay the aircraft.

5−5−16. RNAV and RNP Operations

a. Pilot.

1. If unable to comply with the requirements of

an RNAV or RNP procedure, pilots must advise air

traffic control as soon as possible. For example,

“N1234, failure of GPS system, unable RNAV,

request amended clearance.”

2. Pilots are not authorized to fly a published

RNAV or RNP procedure (instrument approach,

departure, or arrival procedure) unless it is retrievable

by the procedure name from the current aircraft

navigation database and conforms to the charted

procedure. The system must be able to retrieve the

procedure by name from the aircraft navigation

database, not just as a manually entered series of

waypoints.

3. Whenever possible, RNAV routes (Q− or

T−route) should be extracted from the database in

their entirety, rather than loading RNAV route

waypoints from the database into the flight plan

individually. However, selecting and inserting

individual, named fixes from the database is

permitted, provided all fixes along the published

route to be flown are inserted.

4. Pilots must not change any database

waypoint type from a fly−by to fly−over, or vice

versa. No other modification of database waypoints

or the creation of user−defined waypoints on

published RNAV or RNP procedures is permitted,

except to:

(a) Change altitude and/or airspeed waypoint

constraints to comply with an ATC clearance/

instruction.

(b) Insert a waypoint along the published

route to assist in complying with ATC instruction,

example, “Descend via the WILMS arrival except

cross 30 north of BRUCE at/or below FL 210.” This

is limited only to systems that allow along−track

waypoint construction.

5. Pilots of FMS−equipped aircraft, who are

assigned an RNAV DP or STAR procedure and

subsequently receive a change of runway, transition

or procedure, must verify that the appropriate

changes are loaded and available for navigation.

6. For RNAV 1 DPs and STARs, pilots must use

a CDI, flight director and/or autopilot, in lateral

navigation mode. Other methods providing an

equivalent level of performance may also be

acceptable.

7. For RNAV 1 DPs and STARs, pilots of

aircraft without GPS, using DME/DME/IRU, must

ensure the aircraft navigation system position is

confirmed, within 1,000 feet, at the start point of

take−off roll. The use of an automatic or manual

runway update is an acceptable means of compliance

with this requirement. Other methods providing an

equivalent level of performance may also be

acceptable.

8. For procedures or routes requiring the use of

GPS, if the navigation system does not automatically

alert the flight crew of a loss of GPS, the operator

must develop procedures to verify correct GPS

operation.

9. RNAV terminal procedures (DP and STAR)

may be amended by ATC issuing radar vectors and/or

clearances direct to a waypoint. Pilots should avoid

premature manual deletion of waypoints from their

active “legs” page to allow for rejoining procedures.

10. RAIM Prediction: If TSO−C129 equipment

is used to solely satisfy the RNAV and RNP

requirement, GPS RAIM availability must be

confirmed for the intended route of flight (route and

time). If RAIM is not available, pilots need an

approved alternate means of navigation.

REFERENCE−

AIM, RNAV and RNP Operations, Paragraph 5−1−16

11. Definition of “established” for RNAV and

RNP operations. An aircraft is considered to be

established on-course during RNAV and RNP

operations anytime it is within 1 times the required

accuracy for the segment being flown. For example,
AIM 7/26/12

5−5−8 Pilot/Controller Roles and Responsibilities

while operating on a Q-Route (RNAV 2), the aircraft

is considered to be established on-course when it is

within 2 nm of the course centerline.

NOTE−

Pilots must be aware of how their navigation system

operates, along with any AFM limitations, and confirm

that the aircraft’s lateral deviation display (or map display

if being used as an allowed alternate means) is suitable for

the accuracy of the segment being flown. Automatic scaling

and alerting changes are appropriate for some operations.

For example, TSO-C129 systems change within 30 miles of

destination and within 2 miles of FAF to support approach

operations. For some navigation systems and operations,

manual selection of scaling will be necessary.

(a) Pilots flying FMS equipped aircraft with barometric

vertical navigation (Baro-VNAV) may descend when the

aircraft is established on-course following FMS leg

transition to the next segment. Leg transition normally

occurs at the turn bisector for a fly-by waypoint (reference

paragraph 1-2-1 for more on waypoints). When using full

automation, pilots should monitor the aircraft to ensure the

aircraft is turning at appropriate lead times and

descending once established on-course.

(b) Pilots flying TSO-C129 navigation system equipped

aircraft without full automation should use normal lead

points to begin the turn. Pilots may descend when

established on-course on the next segment of the approach.
7/26/12 AIM

National Security and Interception Procedures 5−6−1

Section 6. National Security and Interception Procedures

5−6−1. National Security

a. National security in the control of air traffic is

governed by 14 CFR Part 99.

b. All aircraft entering domestic U.S. airspace

from points outside must provide for identification

prior to entry. To facilitate early aircraft identification

of all aircraft in the vicinity of U.S. and international

airspace boundaries, Air Defense Identification

Zones (ADIZ) have been established.

REFERENCE−

AIM, ADIZ Boundaries and Designated Mountainous Areas, 

Paragraph 5−6−5.

c. Operational requirements for aircraft operations associated with an ADIZ are as follows:

1. Flight Plan. Except as specified in subparagraphs d and e below, an IFR or DVFR flight plan

must be filed with an appropriate aeronautical facility

as follows:

(a) Generally, for all operations that enter an

ADIZ.

(b) For operations that will enter or exit the

U.S. and which will operate into, within or across the

Contiguous U.S. ADIZ regardless of true airspeed.

(c) The flight plan must be filed before

departure except for operations associated with the

Alaskan ADIZ when the airport of departure has no

facility for filing a flight plan, in which case the flight

plan may be filed immediately after takeoff or when

within range of the aeronautical facility.

2. Two-way Radio. For the majority of operations associated with an ADIZ, an operating two-way

radio is required. See 14 CFR Section 99.1 for

exceptions.

3. Transponder Requirements. Unless otherwise authorized by ATC, each aircraft conducting

operations into, within, or across the Contiguous U.S.

ADIZ must be equipped with an operable radar

beacon transponder having altitude reporting capability (Mode C), and that transponder must be turned

on and set to reply on the appropriate code or as

assigned by ATC.

4. Position Reporting.

(a) For IFR flight. Normal IFR position

reporting.

(b) For DVFR flights. The estimated time

of ADIZ penetration must be filed with the

aeronautical facility at least 15 minutes prior to

penetration except for flight in the Alaskan ADIZ, in

which case report prior to penetration.

(c) For inbound aircraft of foreign registry. The pilot must report to the aeronautical facility

at least one hour prior to ADIZ penetration.

5. Aircraft Position Tolerances.

(a) Over land, the tolerance is within plus or

minus five minutes from the estimated time over a

reporting point or point of penetration and within

10 NM from the centerline of an intended track over

an estimated reporting point or penetration point.

(b) Over water, the tolerance is plus or minus

five minutes from the estimated time over a reporting

point or point of penetration and within 20 NM from

the centerline of the intended track over an estimated

reporting point or point of penetration (to include the

Aleutian Islands).

6. Land−Based ADIZ. Land−Based ADIZ are

activated and deactivated over U.S. metropolitan

areas as needed, with dimensions, activation dates

and other relevant information disseminated via

NOTAM.

(a) In addition to requirements outlined in

subparagraphs c1 through c3, pilots operating within

a Land−Based ADIZ must report landing or leaving

the Land−Based ADIZ if flying too low for radar

coverage.

(b) Pilots unable to comply with all requirements must remain clear of Land−Based ADIZ. Pilots

entering a Land−Based ADIZ without authorization

or who fail to follow all requirements risk

interception by military fighter aircraft.

d. Except when applicable under 14 CFR

Section 99.7, 14 CFR Part 99 does not apply to

aircraft operations:
AIM 7/26/12

5−6−2 National Security and Interception Procedures

1. Within the 48 contiguous states and the

District of Columbia, or within the State of Alaska,

and remains within 10 miles of the point of departure;

2. Over any island, or within three nautical

miles of the coastline of any island, in the Hawaii

ADIZ; or

3. Associated with any ADIZ other than the

Contiguous U.S. ADIZ, when the aircraft true

airspeed is less than 180 knots.

e. Authorizations to deviate from the requirements

of Part 99 may also be granted by the ARTCC, on a

local basis, for some operations associated with an

ADIZ.

f. An airfiled VFR Flight Plan makes an aircraft

subject to interception for positive identification

when entering an ADIZ. Pilots are, therefore, urged

to file the required DVFR flight plan either in person

or by telephone prior to departure.

g. Special Security Instructions.

1. During defense emergency or air defense

emergency conditions, additional special security

instructions may be issued in accordance with the

Emergency Security Control of Air Traffic (ESCAT)

Plan.

2. Under the provisions of the ESCAT Plan, the

military will direct the action to be taken in regard

to landing, grounding, diversion, or dispersal of

aircraft and the control of air navigation aids in the

defense of the U.S. during emergency conditions.

3. At the time a portion or all of ESCAT is

implemented, ATC facilities will broadcast

appropriate instructions received from the Air Traffic

Control System Command Center (ATCSCC) over

available ATC frequencies. Depending on

instructions received from the ATCSCC, VFR flights

may be directed to land at the nearest available

airport, and IFR flights will be expected to proceed as

directed by ATC.

4. Pilots on the ground may be required to file a

flight plan and obtain an approval (through FAA)

prior to conducting flight operation.

5. In view of the above, all pilots should guard

an ATC or FSS frequency at all times while

conducting flight operations.

5−6−2. Interception Procedures

a. General.

1. In conjunction with the FAA, Air Defense

Sectors monitor air traffic and could order an

intercept in the interest of national security or

defense. Intercepts during peacetime operations are

vastly different than those conducted under increased

states of readiness. The interceptors may be fighters

or rotary wing aircraft. The reasons for aircraft

intercept include, but are not limited to:

(a) Identify an aircraft;

(b) Track an aircraft;

(c) Inspect an aircraft;

(d) Divert an aircraft;

(e) Establish communications with an aircraft.

2. When specific information is required (i.e.,

markings, serial numbers, etc.) the interceptor

pilot(s) will respond only if, in their judgment, the

request can be conducted in a safe manner. Intercept

procedures are described in some detail in the

paragraphs below. In all situations, the interceptor

pilot will consider safety of flight for all concerned

throughout the intercept procedure. The interceptor

pilot(s) will use caution to avoid startling the

intercepted crew or passengers and understand that

maneuvers considered normal for interceptor aircraft

may be considered hazardous to other aircraft.

3. All aircraft operating in US national airspace

are highly encouraged to maintain a listening watch

on VHF/UHF guard frequencies (121.5 or 243.0

MHz). If subjected to a military intercept, it is

incumbent on civilian aviators to understand their

responsibilities and to comply with ICAO standard

signals relayed from the intercepting aircraft.

Specifically, aviators are expected to contact air

traffic control without delay (if able) on the local

operating frequency or on VHF/UHF guard.

Noncompliance may result in the use of force.

b. Fighter intercept phases (See FIG 5−6−1).

1. Approach Phase.

As standard procedure, intercepted aircraft are

approached from behind. Typically, interceptor

aircraft will be employed in pairs, however, it is not

uncommon for a single aircraft to perform the

intercept operation. Safe separation between inter-
7/26/12 AIM

National Security and Interception Procedures 5−6−3

ceptors and intercepted aircraft is the responsibility of

the intercepting aircraft and will be maintained at all

times.

2. Identification Phase.

Interceptor aircraft will initiate a controlled closure

toward the aircraft of interest, holding at a distance no

closer than deemed necessary to establish positive

identification and to gather the necessary information. The interceptor may also fly past the intercepted

aircraft while gathering data at a distance considered

safe based on aircraft performance characteristics.

3. Post Intercept Phase.

An interceptor may attempt to establish communications via standard ICAO signals. In time-critical

situations where the interceptor is seeking an

immediate response from the intercepted aircraft or if

the intercepted aircraft remains non-compliant to

instruction, the interceptor pilot may initiate a divert

maneuver. In this maneuver, the interceptor flies

across the intercepted aircraft’s flight path (minimum

500 feet separation and commencing from slightly

below the intercepted aircraft altitude) in the general

direction the intercepted aircraft is expected to turn.

The interceptor will rock its wings (daytime) or flash

external lights/select afterburners (night) while

crossing the intercepted aircraft’s flight path. The

interceptor will roll out in the direction the

intercepted aircraft is expected to turn before

returning to verify the aircraft of interest is

complying. The intercepted aircraft is expected to

execute an immediate turn to the direction of the

intercepting aircraft. If the aircraft of interest does not

comply, the interceptor may conduct a second

climbing turn across the intercepted aircraft’s flight

path (minimum 500 feet separation and commencing

from slightly below the intercepted aircraft altitude)

while expending flares as a warning signal to the

intercepted aircraft to comply immediately and to

turn in the direction indicated and to leave the area.

The interceptor is responsible to maintain safe

separation during these and all intercept maneuvers.

Flight safety is paramount.

NOTE−

1. NORAD interceptors will take every precaution to

preclude the possibility of the intercepted aircraft

experiencing jet wash/wake turbulence; however, there is

a potential that this condition could be encountered.

2. During Night/IMC, the intercept will be from below

flight path.

FIG 5−6−1

Intercept Procedures
AIM 7/26/12

5−6−4 National Security and Interception Procedures

c. Helicopter Intercept phases (See FIG 5−6−2)

1. Approach Phase.

Aircraft intercepted by helicopter may be approached

from any direction, although the helicopter should

close for identification and signaling from behind.

Generally, the helicopter will approach off the left

side of the intercepted aircraft. Safe separation

between the helicopter and the unidentified aircraft

will be maintained at all times.

2. Identification Phase.

The helicopter will initiate a controlled closure

toward the aircraft of interest, holding at a distance no

closer than deemed necessary to establish positive

identification and gather the necessary information.

The intercepted pilot should expect the interceptor

helicopter to take a position off his left wing slightly

forward of abeam.

3. Post Intercept Phase.

Visual signaling devices may be used in an attempt to

communicate with the intercepted aircraft. Visual

signaling devices may include, but are not limited to,

LED scrolling signboards or blue flashing lights. If

compliance is not attained through the use of radios

or signaling devices, standard ICAO intercept signals

(Table 5-6-1) may be employed. In order to maintain

safe aircraft separation, it is incumbent upon the pilot

of the intercepted aircraft not to fall into a trail

position (directly behind the helicopter) if instructed

to follow the helicopter. This is because the helicopter

pilot may lose visual contact with the intercepted

aircraft.

NOTE−

Intercepted aircraft must not follow directly behind the

helicopter thereby allowing the helicopter pilot to maintain

visual contact with the intercepted aircraft and ensuring

safe separation is maintained.

FIG 5−6−2

Helicopter Intercept Procedures
7/26/12 AIM

National Security and Interception Procedures 5−6−5

d. Summary of Intercepted Aircraft Actions. An

intercepted aircraft must, without delay:

1. Adhere to instructions relayed through the

use of visual devices, visual signals, and radio

communications from the intercepting aircraft.

2. Attempt to establish radio communications

with the intercepting aircraft or with the appropriate

air traffic control facility by making a general call on

guard frequencies (121.5 or 243.0 MHz), giving the

identity, position, and nature of the flight.

3. If transponder equipped, select Mode 3/A

Code 7700 unless otherwise instructed by air traffic

control.

NOTE−

If instruction received from any agency conflicts with that

given by the intercepting aircraft through visual or radio

communications, the intercepted aircraft must seek

immediate clarification.

4. The crew of the intercepted aircraft must

continue to comply with interceptor aircraft signals

and instructions until positively released.

5−6−3. Law Enforcement Operations by

Civil and Military Organizations

a. Special law enforcement operations.

1. Special law enforcement operations include

in-flight identification, surveillance, interdiction, and

pursuit activities performed in accordance with

official civil and/or military mission responsibilities.

2. To facilitate accomplishment of these special

missions, exemptions from specified sections of the

CFRs have been granted to designated departments

and agencies. However, it is each organization’s

responsibility to apprise ATC of their intent to operate

under an authorized exemption before initiating

actual operations.

3. Additionally, some departments and agencies

that perform special missions have been assigned

coded identifiers to permit them to apprise ATC of

ongoing mission activities and solicit special

air traffic assistance.
AIM 7/26/12

5−6−6 National Security and Interception Procedures

5−6−4. Interception Signals

TBL 5−6−1 and TBL 5−6−2.

TBL 5−6−1

Intercepting Signals

INTERCEPTING SIGNALS

Signals initiated by intercepting aircraft and responses by intercepted aircraft

(as set forth in ICAO Annex 2-Appendix 1, 2.1)

Series INTERCEPTING Aircraft Signals Meaning INTERCEPTED Aircraft Responds Meaning

1 DAY−Rocking wings from a position

slightly above and ahead of, and normally

to the left of, the intercepted aircraft and,

after acknowledgement, a slow level turn,

normally to the left, on to the desired

heading.

NIGHT-Same and, in addition, flashing

navigational lights at irregular intervals.

NOTE 1−Meteorological conditions or

terrain may require the intercepting

aircraft to take up a position slightly above

and ahead of, and to the right of, the

intercepted aircraft and to make the

subsequent turn to the right.

NOTE 2−If the intercepted aircraft is not

able to keep pace with the intercepting

aircraft, the latter is expected to fly a series

of race−track patterns and to rock its wings

each time it passes the intercepted aircraft.

You have

been

intercepted.

Follow me.

AEROPLANES:

DAY−Rocking wings and following.

NIGHT−Same and, in addition, flashing

navigational lights at irregular intervals.

HELICOPTERS:

DAY or NIGHT−Rocking aircraft, flashing

navigational lights at irregular intervals and

following.

Understood,

will comply.

2 DAY or NIGHT−An abrupt break−away

maneuver from the intercepted aircraft

consisting of a climbing turn of 90 degrees

or more without crossing the line of flight

of the intercepted aircraft.

You may

proceed.

AEROPLANES:

DAY or NIGHT-Rocking wings.

HELICOPTERS:

DAY or NIGHT−Rocking aircraft.

Understood,

will comply.

3 DAY−Circling aerodrome, lowering landing gear and overflying runway in direction

of landing or, if the intercepted aircraft is a

helicopter, overflying the helicopter landing area.

NIGHT−Same and, in addition, showing

steady landing lights.

Land at this

aerodrome.

AEROPLANES:

DAY−Lowering landing gear, following

the intercepting aircraft and, if after

overflying the runway landing is considered safe, proceeding to land.

NIGHT−Same and, in addition, showing

steady landing lights (if carried).

HELICOPTERS:

DAY or NIGHT-Following the intercepting

aircraft and proceeding to land, showing a

steady landing light (if carried).

Understood,

will comply.
7/26/12 AIM

National Security and Interception Procedures 5−6−7

TBL 5−6−2

Intercepting Signals

INTERCEPTING SIGNALS

Signals and Responses During Aircraft Intercept

Signals initiated by intercepted aircraft and responses by intercepting aircraft

(as set forth in ICAO Annex 2-Appendix 1, 2.2)

Series INTERCEPTED Aircraft Signals Meaning INTERCEPTING Aircraft Responds Meaning

4 DAY or NIGHT−Raising landing gear (if

fitted) and flashing landing lights while

passing over runway in use or helicopter

landing area at a height exceeding 300m

(1,000 ft) but not exceeding 600m

(2,000 ft) (in the case of a helicopter, at a

height exceeding 50m (170 ft) but not

exceeding 100m (330 ft) above the

aerodrome level, and continuing to circle

runway in use or helicopter landing area. If

unable to flash landing lights, flash any

other lights available.

Aerodrome

you have

designated is

inadequate.

DAY or NIGHT−If it is desired that the

intercepted aircraft follow the intercepting

aircraft to an alternate aerodrome, the

intercepting aircraft raises its landing gear

(if fitted) and uses the Series 1 signals

prescribed for intercepting aircraft.

If it is decided to release the intercepted

aircraft, the intercepting aircraft uses the

Series 2 signals prescribed for intercepting

aircraft.

Understood,

follow me.

Understood,

you may

proceed.

5 DAY or NIGHT−Regular switching on and

off of all available lights but in such a

manner as to be distinct from flashing

lights.

Cannot

comply.

DAY or NIGHT-Use Series 2 signals

prescribed for intercepting aircraft.

Understood.

6 DAY or NIGHT−Irregular flashing of all

available lights.

In distress. DAY or NIGHT-Use Series 2 signals

prescribed for intercepting aircraft.

Understood.
AIM 7/26/12

5−6−8 National Security and Interception Procedures

5−6−5. ADIZ Boundaries and Designated Mountainous Areas (See FIG 5−6−3.)

FIG 5−6−3

Air Defense Identification Zone Boundaries

Designated Mountainous Areas



  

 

   

 

  

 

 

  

 

   

 

  

 

 











































































































































 











































































































































 











































































































































 











































































































































 











































































































































 











































































































































 











































































































































 











































































































































 











































































































































 











































































































































          



  

 

   

 

  

 

 

  

 

   

 

  

 

 

  

 

   

 

 











































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































 

 



 

 

 

 



 

 

 



 

 

 

 



 

 

 

 



 

 

 



 

 

 

 



 

 

 

 



 

 



  

 

   

 

  





























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































 





















 















   











  


7/26/12 AIM

National Security and Interception Procedures 5−6−9

5−6−6. Visual Warning System (VWS)

The VWS signal consists of highly-focused red and

green colored laser lights designed to illuminate in an

alternating red and green signal pattern. These lasers

may be directed at specific aircraft suspected of

making unauthorized entry into the Washington, DC

Special Flight Rules Area (DC SFRA) proceeding on

a heading or flight path that may be interpreted as a

threat or that operate contrary to the operating rules

for the DC SFRA. The beam is neither hazardous to

the eyes of pilots/aircrew or passengers, regardless of

altitude or distance from the source nor will the beam

affect aircraft systems.

a. If you are communicating with ATC, and this

signal is directed at your aircraft, you are required to

contact ATC and advise that you are being

illuminated by a visual warning system.

b. If this signal is directed at you, and you are not

communicating with ATC, you are advised to turn to

the most direct heading away from the center of the

DC SFRA as soon as possible. Immediately contact

ATC on an appropriate frequency, VHF Guard 121.5

or UHF Guard 243.0, and provide your aircraft

identification, position, and nature of the flight.

Failure to follow these procedures may result in

interception by military aircraft. Further noncompliance with interceptor aircraft or ATC may result in the

use of force.

c. Pilots planning to operate aircraft in or near the

DC SFRA are to familiarize themselves with aircraft

intercept procedures. This information applies to all

aircraft operating within the DC SFRA including

DOD, Law Enforcement, and aircraft engaged in

aeromedical operations and does not change

procedures established for reporting unauthorized

laser illumination as published in FAA Advisory

Circulars and Notices.

REFERENCE−

CFR 91.161

d. More details including a video demonstration of

the VWS are available from the following FAA web

site: www.faasafety.gov/VisualWarningSystem/

VisualWarning.htm.

7/26/12 AIM

General 6−1−1

Chapter 6. Emergency Procedures

Section 1. General

6−1−1. Pilot Responsibility and Authority

a. The pilot−in−command of an aircraft is directly

responsible for and is the final authority as to the

operation of that aircraft. In an emergency requiring

immediate action, the pilot−in−command may

deviate from any rule in 14 CFR Part 91, Subpart A,

General, and Subpart B, Flight Rules, to the extent

required to meet that emergency.

REFERENCE−

14 CFR Section 91.3(b).

b. If the emergency authority of 14 CFR

Section 91.3(b) is used to deviate from the provisions

of an ATC clearance, the pilot−in−command must

notify ATC as soon as possible and obtain an

amended clearance.

c. Unless deviation is necessary under the

emergency authority of 14 CFR Section 91.3, pilots

of IFR flights experiencing two-way radio communications failure are expected to adhere to the

procedures prescribed under “IFR operations,

two-way radio communications failure.”

REFERENCE−

14 CFR Section 91.185.

6−1−2. Emergency Condition− Request

Assistance Immediately

a. An emergency can be either a distress or

urgency condition as defined in the Pilot/Controller

Glossary. Pilots do not hesitate to declare an

emergency when they are faced with distress

conditions such as fire, mechanical failure, or

structural damage. However, some are reluctant to

report an urgency condition when they encounter

situations which may not be immediately perilous,

but are potentially catastrophic. An aircraft is in at

least an urgency condition the moment the pilot

becomes doubtful about position, fuel endurance,

weather, or any other condition that could adversely

affect flight safety. This is the time to ask for help, not

after the situation has developed into a distress

condition.

b. Pilots who become apprehensive for their safety

for any reason should request assistance immediately.

Ready and willing help is available in the form of

radio, radar, direction finding stations and other

aircraft. Delay has caused accidents and cost lives.

Safety is not a luxury! Take action!

7/26/12 AIM

Emergency Services Available to Pilots 6−2−1

Section 2. Emergency Services Available to Pilots

6−2−1. Radar Service for VFR Aircraft in

Difficulty

a. Radar equipped ATC facilities can provide

radar assistance and navigation service (vectors) to

VFR aircraft in difficulty when the pilot can talk with

the controller, and the aircraft is within radar

coverage. Pilots should clearly understand that

authorization to proceed in accordance with such

radar navigational assistance does not constitute

authorization for the pilot to violate CFRs. In effect,

assistance is provided on the basis that navigational

guidance information is advisory in nature, and the

responsibility for flying the aircraft safely remains

with the pilot.

b. Experience has shown that many pilots who are

not qualified for instrument flight cannot maintain

control of their aircraft when they encounter clouds

or other reduced visibility conditions. In many cases,

the controller will not know whether flight into

instrument conditions will result from ATC instructions. To avoid possible hazards resulting from being

vectored into IFR conditions, a pilot in difficulty

should keep the controller advised of the current

weather conditions being encountered and the

weather along the course ahead and observe the

following:

1. If a course of action is available which will

permit flight and a safe landing in VFR weather

conditions, noninstrument rated pilots should choose

the VFR condition rather than requesting a vector or

approach that will take them into IFR weather

conditions; or

2. If continued flight in VFR conditions is not

possible, the noninstrument rated pilot should so

advise the controller and indicating the lack of an

instrument rating, declare a distress condition; or

3. If the pilot is instrument rated and current, and

the aircraft is instrument equipped, the pilot should so

indicate by requesting an IFR flight clearance.

Assistance will then be provided on the basis that the

aircraft can operate safely in IFR weather conditions.

6−2−2. Transponder Emergency Operation

a. When a distress or urgency condition is

encountered, the pilot of an aircraft with a coded radar

beacon transponder, who desires to alert a ground

radar facility, should squawk Mode 3/A,

Code 7700/Emergency and Mode C altitude reporting and then immediately establish communications

with the ATC facility.

b. Radar facilities are equipped so that Code 7700

normally triggers an alarm or special indicator at all

control positions. Pilots should understand that they

might not be within a radar coverage area. Therefore,

they should continue squawking Code 7700 and

establish radio communications as soon as possible.

6−2−3. Direction Finding Instrument

Approach Procedure

a. Direction Finder (DF) equipment has long been

used to locate lost aircraft and to guide aircraft to

areas of good weather or to airports. Now at most DF

equipped airports, DF instrument approaches may be

given to aircraft in a distress or urgency condition.

b. Experience has shown that most emergencies

requiring DF assistance involve pilots with little

flight experience. With this in mind, DF approach

procedures provide maximum flight stability in the

approach by using small turns, and wings-level

descents. The DF specialist will give the pilot

headings to fly and tell the pilot when to begin

descent.

c. DF IAPs are for emergency use only and will not

be used in IFR weather conditions unless the pilot has

declared a distress or urgency condition.

d. To become familiar with the procedures and

other benefits of DF, pilots are urged to request

practice DF guidance and approaches in VFR

weather conditions. DF specialists welcome the

practice and will honor such requests, workload

permitting.
AIM 7/26/12

6−2−2 Emergency Services Available to Pilots

6−2−4. Intercept and Escort

a. The concept of airborne intercept and escort is

based on the Search and Rescue (SAR) aircraft

establishing visual and/or electronic contact with an

aircraft in difficulty, providing in-flight assistance,

and escorting it to a safe landing. If bailout, crash

landing or ditching becomes necessary, SAR

operations can be conducted without delay. For most

incidents, particularly those occurring at night and/or

during instrument flight conditions, the availability

of intercept and escort services will depend on the

proximity of SAR units with suitable aircraft on alert

for immediate dispatch. In limited circumstances,

other aircraft flying in the vicinity of an aircraft in

difficulty can provide these services.

b. If specifically requested by a pilot in difficulty

or if a distress condition is declared, SAR

coordinators will take steps to intercept and escort an

aircraft. Steps may be initiated for intercept and

escort if an urgency condition is declared and unusual

circumstances make such action advisable.

c. It is the pilot’s prerogative to refuse intercept

and escort services. Escort services will normally be

provided to the nearest adequate airport. Should the

pilot receiving escort services continue onto another

location after reaching a safe airport, or decide not to

divert to the nearest safe airport, the escort aircraft is

not obligated to continue and further escort is

discretionary. The decision will depend on the

circumstances of the individual incident.

6−2−5. Emergency Locator Transmitter

(ELT)

a. General.

1. ELTs are required for most General Aviation

airplanes.

REFERENCE−

14 CFR SECTION 91.207.

2. ELTs of various types were developed as a

means of locating downed aircraft. These electronic,

battery operated transmitters operate on one of three

frequencies. These operating frequencies are

121.5 MHz, 243.0 MHz, and the newer 406 MHz.

ELTs operating on 121.5 MHz and 243.0 MHz are

analog devices. The newer 406 MHz ELT is a digital

transmitter that can be encoded with the owner’s

contact information or aircraft data. The latest

406 MHz ELT models can also be encoded with the

aircraft’s position data which can help SAR forces

locate the aircraft much more quickly after a crash.

The 406 MHz ELTs also transmits a stronger signal

when activated than the older 121.5 MHz ELTs.

(a) The Federal Communications Commission (FCC) requires 406 MHz ELTs be registered

with the National Oceanic and Atmospheric

Administration (NOAA) as outlined in the ELTs

documentation. The FAA’s 406 MHz ELT Technical

Standard Order (TSO) TSO−C126 also requires that

each 406 MHz ELT be registered with NOAA. The

reason is NOAA maintains the owner registration

database for U.S. registered 406 MHz alerting

devices, which includes ELTs. NOAA also operates

the United States’ portion of the Cospas−Sarsat

satellite distress alerting system designed to detect

activated ELTs and other distress alerting devices.

(b) In the event that a properly registered

406 MHz ELT activates, the Cospas−Sarsat satellite

system can decode the owner’s information and

provide that data to the appropriate search and

rescue (SAR) center. In the United States, NOAA

provides the alert data to the appropriate U.S. Air

Force Rescue Coordination Center (RCC) or U.S.

Coast Guard Rescue Coordination Center. That RCC

can then telephone or contact the owner to verify the

status of the aircraft. If the aircraft is safely secured

in a hangar, a costly ground or airborne search is

avoided. In the case of an inadvertent 406 MHz ELT

activation, the owner can deactivate the 406 MHz

ELT. If the 406 MHz ELT equipped aircraft is being

flown, the RCC can quickly activate a search.

406 MHz ELTs permit the Cospas−Sarsat satellite

system to narrow the search area to a more confined

area compared to that of a 121.5 MHz or 243.0 MHz

ELT. 406 MHz ELTs also include a low−power

121.5 MHz homing transmitter to aid searchers in

finding the aircraft in the terminal search phase.

(c) Each analog ELT emits a distinctive

downward swept audio tone on 121.5 MHz and

243.0 MHz.

(d) If “armed” and when subject to crash−

generated forces, ELTs are designed to automatically

activate and continuously emit their respective

signals, analog or digital. The transmitters will

operate continuously for at least 48 hours over a wide

temperature range. A properly installed, maintained,

and functioning ELT can expedite search and rescue
7/26/12 AIM

Emergency Services Available to Pilots 6−2−3

operations and save lives if it survives the crash and

is activated.

(e) Pilots and their passengers should know

how to activate the aircraft’s ELT if manual activation

is required. They should also be able to verify the

aircraft’s ELT is functioning and transmitting an alert

after a crash or manual activation.

(f) Because of the large number of 121.5 MHz

ELT false alerts and the lack of a quick means of

verifying the actual status of an activated 121.5 MHz

or 243.0 MHz analog ELT through an owner

registration database, U.S. SAR forces do not

respond as quickly to initial 121.5/243.0 MHz ELT

alerts as the SAR forces do to 406 MHz ELT alerts.

Compared to the almost instantaneous detection of a

406 MHz ELT, SAR forces’ normal practice is to wait

for either a confirmation of a 121.5/243.0 MHz alert

by additional satellite passes or through confirmation

of an overdue aircraft or similar notification. In some

cases, this confirmation process can take hours. SAR

forces can initiate a response to 406 MHz alerts in

minutes compared to the potential delay of hours for

a 121.5/243.0 MHz ELT.

3. The Cospas−Sarsat system has announced the

termination of satellite monitoring and reception of

the 121.5 MHz and 243.0 MHz frequencies in 2009.

The Cospas−Sarsat system will continue to monitor

the 406 MHz frequency. What this means for pilots is

that after the termination date, those aircraft with only

121.5 MHz or 243.0 MHz ELT’s onboard will have

to depend upon either a nearby Air Traffic Control

facility receiving the alert signal or an overflying

aircraft monitoring 121.5 MHz or 243.0 MHz

detecting the alert. To ensure adequate monitoring of

these frequencies and timely alerts after 2009, all

airborne pilots should periodically monitor these

frequencies to try and detect an activated

121.5/243.0 MHz ELT.

b. Testing.

1. ELTs should be tested in accordance with the

manufacturer’s instructions, preferably in a shielded

or screened room or specially designed test container

to prevent the broadcast of signals which could

trigger a false alert.

2. When this cannot be done, aircraft operational testing is authorized as follows:

(a) Analog 121.5/243 MHz ELTs should only

be tested during the first 5 minutes after any hour. If

operational tests must be made outside of this period,

they should be coordinated with the nearest FAA

Control Tower or FSS. Tests should be no longer than

three audible sweeps. If the antenna is removable, a

dummy load should be substituted during test

procedures.

(b) Digital 406 MHz ELTs should only be

tested in accordance with the unit’s manufacturer’s

instructions.

(c) Airborne tests are not authorized.

c. False Alarms.

1. Caution should be exercised to prevent the

inadvertent activation of ELTs in the air or while they

are being handled on the ground. Accidental or

unauthorized activation will generate an emergency

signal that cannot be distinguished from the real

thing, leading to expensive and frustrating searches.

A false ELT signal could also interfere with genuine

emergency transmissions and hinder or prevent the

timely location of crash sites. Frequent false alarms

could also result in complacency and decrease the

vigorous reaction that must be attached to all ELT

signals.

2. Numerous cases of inadvertent activation

have occurred as a result of aerobatics, hard landings,

movement by ground crews and aircraft maintenance. These false alarms can be minimized by

monitoring 121.5 MHz and/or 243.0 MHz as follows:

(a) In flight when a receiver is available.

(b) Before engine shut down at the end of

each flight.

(c) When the ELT is handled during installation or maintenance.

(d) When maintenance is being performed

near the ELT.

(e) When a ground crew moves the aircraft.

(f) If an ELT signal is heard, turn off the

aircraft’s ELT to determine if it is transmitting. If it

has been activated, maintenance might be required

before the unit is returned to the “ARMED” position.

You should contact the nearest Air Traffic facility and

notify it of the inadvertent activation.
AIM 7/26/12

6−2−4 Emergency Services Available to Pilots

d. Inflight Monitoring and Reporting.

1. Pilots are encouraged to monitor 121.5 MHz

and/or 243.0 MHz while inflight to assist in

identifying possible emergency ELT transmissions.

On receiving a signal, report the following

information to the nearest air traffic facility:

(a) Your position at the time the signal was

first heard.

(b) Your position at the time the signal was

last heard.

(c) Your position at maximum signal

strength.

(d) Your flight altitudes and frequency on

which the emergency signal was heard: 121.5 MHz or

243.0 MHz. If possible, positions should be given

relative to a navigation aid. If the aircraft has homing

equipment, provide the bearing to the emergency

signal with each reported position.

6−2−6. FAA K−9 Explosives Detection

Team Program

a. The FAA’s Office of Civil Aviation Security

Operations manages the FAA K−9 Explosives

Detection Team Program which was established in

1972. Through a unique agreement with law

enforcement agencies and airport authorities, the

FAA has strategically placed FAA−certified K−9

teams (a team is one handler and one dog) at airports

throughout the country. If a bomb threat is received

while an aircraft is in flight, the aircraft can be

directed to an airport with this capability. The FAA

provides initial and refresher training for all handlers,

provides single purpose explosive detector dogs, and

requires that each team is annually evaluated in five

areas for FAA certification: aircraft (widebody and

narrowbody), vehicles, terminal, freight (cargo), and

luggage. If you desire this service, notify your

company or an FAA air traffic control facility.

b. The following list shows the locations of

current FAA K−9 teams:

TBL 6−2−1

FAA Sponsored Explosives Detection 

Dog/Handler Team Locations

Airport Symbol Location

ATL Atlanta, Georgia

BHM Birmingham, Alabama

BOS Boston, Massachusetts

BUF Buffalo, New York

CLT Charlotte, North Carolina

ORD Chicago, Illinois

CVG Cincinnati, Ohio

DFW Dallas, Texas

DEN Denver, Colorado

DTW Detroit, Michigan

IAH Houston, Texas

JAX Jacksonville, Florida

MCI Kansas City, Missouri

LAX Los Angeles, California

MEM Memphis, Tennessee

MIA Miami, Florida

MKE Milwaukee, Wisconsin

MSY New Orleans, Louisiana

 MCO Orlando, Florida

PHX Phoenix, Arizona

PIT Pittsburgh, Pennsylvania

PDX Portland, Oregon

SLC Salt Lake City, Utah

SFO San Francisco, California

SJU San Juan, Puerto Rico

SEA Seattle, Washington

STL St. Louis, Missouri

TUS Tucson, Arizona

TUL Tulsa, Oklahoma

c. If due to weather or other considerations an

aircraft with a suspected hidden explosive problem

were to land or intended to land at an airport other

than those listed in b above, it is recommended that

they call the FAA’s Washington Operations Center

(telephone 202−267−3333, if appropriate) or have an

air traffic facility with which you can communicate

contact the above center requesting assistance.
7/26/12 AIM

Emergency Services Available to Pilots 6−2−5

6−2−7. Search and Rescue

a. General. SAR is a lifesaving service provided

through the combined efforts of the federal agencies

signatory to the National SAR Plan, and the agencies

responsible for SAR within each state. Operational

resources are provided by the U.S. Coast Guard,

DOD components, the Civil Air Patrol, the Coast

Guard Auxiliary, state, county and local law

enforcement and other public safety agencies, and

private volunteer organizations. Services include

search for missing aircraft, survival aid, rescue, and

emergency medical help for the occupants after an

accident site is located.

b. National Search and Rescue Plan. By federal

interagency agreement, the National Search and

Rescue Plan provides for the effective use of all

available facilities in all types of SAR missions.

These facilities include aircraft, vessels, pararescue

and ground rescue teams, and emergency radio

fixing. Under the plan, the U.S. Coast Guard is

responsible for the coordination of SAR in the

Maritime Region, and the USAF is responsible in the

Inland Region. To carry out these responsibilities, the

Coast Guard and the Air Force have established

Rescue Coordination Centers (RCCs) to direct SAR

activities within their regions. For aircraft emergencies, distress, and urgency, information normally will

be passed to the appropriate RCC through an ARTCC

or FSS.

c. Coast Guard Rescue Coordination Centers.

(See TBL 6−2−2.)

TBL 6−2−2

Coast Guard Rescue Coordination Centers

Coast Guard Rescue Coordination Centers

Alameda, CA

510−437−3701

Miami, FL

305−415−6800

Boston, MA

617−223−8555

New Orleans, LA

504−589−6225

Cleveland, OH

216−902−6117

Portsmouth, VA

757−398−6390

Honolulu, HI

808−541−2500

Seattle, WA

206−220−7001

Juneau, AK

907−463−2000

San Juan, PR

787−289−2042

d. Air Force Rescue Coordination Centers. 

(See TBL 6−2−3 and TBL 6−2−4.)

TBL 6−2−3

Air Force Rescue Coordination Center

48 Contiguous States

Air Force Rescue Coordination Center

Tyndall AFB, Florida Phone

Commercial 850−283−5955

WATS 800−851−3051

DSN 523−5955

TBL 6−2−4

Air Command Rescue Coordination Center

Alaska

Alaskan Air Command Rescue

Coordination Center

Elmendorf AFB, Alaska Phone

Commercial 907−428−7230

800−420−7230 

(outside Anchorage)

DSN 317−551−7230

e. Joint Rescue Coordination Center. 

(See TBL 6−2−5.)

TBL 6−2−5

Joint Rescue Coordination Center

Hawaii

Honolulu Joint Rescue Coordination Center

HQ 14th CG District

Honolulu Phone

Commercial 808−541−2500

DSN 448−0301

f. Emergency and Overdue Aircraft.

1. ARTCCs and FSSs will alert the SAR system

when information is received from any source that an

aircraft is in difficulty, overdue, or missing.

(a) Radar facilities providing radar flight

following or advisories consider the loss of radar and

radios, without service termination notice, to be a

possible emergency. Pilots receiving VFR services

from radar facilities should be aware that SAR may

be initiated under these circumstances.

(b) A filed flight plan is the most timely and

effective indicator that an aircraft is overdue. Flight

plan information is invaluable to SAR forces for

search planning and executing search efforts.
AIM 7/26/12

6−2−6 Emergency Services Available to Pilots

2. Prior to departure on every flight, local or

otherwise, someone at the departure point should be

advised of your destination and route of flight if other

than direct. Search efforts are often wasted and rescue

is often delayed because of pilots who thoughtlessly

takeoff without telling anyone where they are going.

File a flight plan for your safety.

3. According to the National Search and Rescue

Plan, “The life expectancy of an injured survivor

decreases as much as 80 percent during the first

24 hours, while the chances of survival of uninjured

survivors rapidly diminishes after the first 3 days.”

4. An Air Force Review of 325 SAR missions

conducted during a 23−month period revealed that

“Time works against people who experience a

distress but are not on a flight plan, since 36 hours

normally pass before family concern initiates an

(alert).”

g. VFR Search and Rescue Protection.

1. To receive this valuable protection, file a VFR

or DVFR Flight Plan with an FAA FSS. For

maximum protection, file only to the point of first

intended landing, and refile for each leg to final

destination. When a lengthy flight plan is filed, with

several stops en route and an ETE to final destination,

a mishap could occur on any leg, and unless other

information is received, it is probable that no one

would start looking for you until 30 minutes after

your ETA at your final destination.

2. If you land at a location other than the

intended destination, report the landing to the nearest

FAA FSS and advise them of your original

destination.

3. If you land en route and are delayed more than

30 minutes, report this information to the nearest FSS

and give them your original destination.

4. If your ETE changes by 30 minutes or more,

report a new ETA to the nearest FSS and give them

your original destination. Remember that if you fail

to respond within one-half hour after your ETA at

final destination, a search will be started to locate you.

5. It is important that you close your flight plan

IMMEDIATELY AFTER ARRIVAL AT YOUR FINAL

DESTINATION WITH THE FSS DESIGNATED

WHEN YOUR FLIGHT PLAN WAS FILED. The pilot

is responsible for closure of a VFR or DVFR flight

plan; they are not closed automatically. This will

prevent needless search efforts.

6. The rapidity of rescue on land or water will

depend on how accurately your position may be

determined. If a flight plan has been followed and

your position is on course, rescue will be expedited.

h. Survival Equipment.

1. For flight over uninhabited land areas, it is

wise to take and know how to use survival equipment

for the type of climate and terrain.

2. If a forced landing occurs at sea, chances for

survival are governed by the degree of crew

proficiency in emergency procedures and by the

availability and effectiveness of water survival

equipment.

i. Body Signal Illustrations.

1. If you are forced down and are able to attract

the attention of the pilot of a rescue airplane, the body

signals illustrated on these pages can be used to

transmit messages to the pilot circling over your

location.

2. Stand in the open when you make the signals.

3. Be sure the background, as seen from the air,

is not confusing.

4. Go through the motions slowly and repeat

each signal until you are positive that the pilot

understands you.
7/26/12 AIM

Emergency Services Available to Pilots 6−2−7

j. Observance of Downed Aircraft.

1. Determine if crash is marked with a yellow

cross; if so, the crash has already been reported and

identified.

2. If possible, determine type and number of

aircraft and whether there is evidence of survivors.

3. Fix the position of the crash as accurately as

possible with reference to a navigational aid. If

possible, provide geographic or physical description

of the area to aid ground search parties.

4. Transmit the information to the nearest FAA

or other appropriate radio facility.

5. If circumstances permit, orbit the scene to

guide in other assisting units until their arrival or until

you are relieved by another aircraft.

6. Immediately after landing, make a complete

report to the nearest FAA facility, or Air Force or

Coast Guard Rescue Coordination Center. The report

can be made by a long distance collect telephone call.
AIM 7/26/12

6−2−8 Emergency Services Available to Pilots

FIG 6−2−1

Ground−Air Visual Code for Use by Survivors

V

X

N

Y

NO. MESSAGE MESSAGE CODE SYMBOL CODE SYMBOL

1 Require assistance Require assistance

Require medical assistance Require medical assistance

No or Negative No or Negative

Yes or Affirmative Yes or Affirmative

Proceeding in this direction Proceeding in this direction

IF IN DOUBT, USE INTERNATIONAL SYMBOL IF IN DOUBT, USE INTERNATIONAL SYMBOL

INSTRUCTIONS INSTRUCTIONS

2

3

4

5

S O S

1. Lay out symbols by using strips of fabric or parachutes, pieces of wood, stones, or any available material.

2. Provide as much color contrast as possible between material used for symbols and background against which symbols are exposed. 3. Symbols should be at least 10 feet high or larger. Care should be taken to lay out symbols exactly as shown.

4. In addition to using symbols, every effort is to be made to attract attention by means of radio, flares, smoke, or other available means.

5. On snow covered ground, signals can be made by dragging, shoveling or tramping. Depressed areas forming symbols will

appear black from the air.

6. Pilot should acknowledge message by rocking wings from side to side.

FIG 6−2−2

Ground−Air Visual Code for use by Ground Search Parties

L L L

L L

X X

N N

NO. MESSAGE MESSAGE CODE SYMBOL CODE SYMBOL

1

2

3

4

5

6

7

Operation completed. Operation completed.

We have found all personnel. We have found all personnel.

We have found only some personnel. We have found only some personnel.

We are not able to continue.

Returning to base.

We are not able to continue.

Returning to base.

Have divided into two groups.

Each proceeding in direction indicated.

Have divided into two groups.

Each proceeding in direction indicated.

Information received that aircraft is in this direction. Information received that aircraft is in this direction.

Nothing found. Will continue search. Nothing found. Will continue search.

Note: These visual signals have been accepted for international use and appear in Annex 12 to the Convention on International

Civil Aviation.
7/26/12 AIM

Emergency Services Available to Pilots 6−2−9

FIG 6−2−3

Urgent Medical Assistance

NEED MEDICAL

ASSISTANCE-URGENT

Used only when life is at stake

NEED MEDICAL

ASSISTANCE-URGENT

Used only when life is at stake

FIG 6−2−4

All OK

ALL OK-DO NOT WAIT

Wave one arm overhead

ALL OK-DO NOT WAIT

Wave one arm overhead

FIG 6−2−5

Short Delay

CAN PROCEED SHORTLY

WAIT IF PRACTICABLE

One arm horizontal

CAN PROCEED SHORTLY

WAIT IF PRACTICABLE

One arm horizontal

FIG 6−2−6

Long Delay

NEED MECHANICAL HELP

OR PARTS - LONG DELAY

Both arms horizontal

NEED MECHANICAL HELP

OR PARTS - LONG DELAY

Both arms horizontal
AIM 7/26/12

6−2−10 Emergency Services Available to Pilots

FIG 6−2−7

Drop Message

Make throwing motion

FIG 6−2−8

Receiver Operates

OUR RECEIVER IS

OPERATING

Cup hands over ears

OUR RECEIVER IS

OPERATING

Cup hands over ears

FIG 6−2−9

Do Not Land Here

DO NOT ATTEMPT

TO LAND HERE

Both arms waved across face

DO NOT ATTEMPT

TO LAND HERE

Both arms waved across face

FIG 6−2−10

Land Here

LAND HERE

Both arms forward horizontally,

squatting and point in direction

of landing - Repeat

LAND HERE

Both arms forward horizontally,

squatting and point in direction

of landing - Repeat
7/26/12 AIM

Emergency Services Available to Pilots 6−2−11

FIG 6−2−11

Negative (Ground)

NEGATIVE (NO)

White cloth waved horizontally

NEGATIVE (NO)

White cloth waved horizontally

FIG 6−2−12

Affirmative (Ground)

AFFIRMATIVE (YES)

White cloth waved vertically

AFFIRMATIVE (YES)

White cloth waved vertically

FIG 6−2−13

Pick Us Up

PICK US UPPLANE ABANDONED

Both arms vertical

PICK US UPPLANE ABANDONED

Both arms vertical

FIG 6−2−14

Affirmative (Aircraft)

Affirmative reply from aircraft:

AFFIRMATIVE (YES)

Dip nose of plane several times
AIM 7/26/12

6−2−12 Emergency Services Available to Pilots

FIG 6−2−15

Negative (Aircraft)

NEGATIVE (NO)

Fishtail plane

NEGATIVE (NO)

Fishtail plane

Negative reply from aircraft: Negative reply from aircraft:

FIG 6−2−16

Message received and understood (Aircraft)

Message received and understood by aircraft:

Day or moonlight - Rocking wings

Night - Green flashed from signal lamp

Message received and understood by aircraft:

Day or moonlight - Rocking wings

Night - Green flashed from signal lamp

FIG 6−2−17

Message received and NOT understood (Aircraft)

Message received and NOT understood by aircraft:

Day or moonlight - Making a complete right-hand circle

Night-Red flashes from signal lamp.

Message received and NOT understood by aircraft:

Day or moonlight - Making a complete right-hand circle

Night-Red flashes from signal lamp.
7/26/12 AIM

Distress and Urgency Procedures 6−3−1

Section 3. Distress and Urgency Procedures

6−3−1. Distress and Urgency

Communications

a. A pilot who encounters a distress or urgency

condition can obtain assistance simply by contacting

the air traffic facility or other agency in whose area of

responsibility the aircraft is operating, stating the

nature of the difficulty, pilot’s intentions and

assistance desired. Distress and urgency communications procedures are prescribed by the International

Civil Aviation Organization (ICAO), however, and

have decided advantages over the informal procedure

described above.

b. Distress and urgency communications procedures discussed in the following paragraphs relate to

the use of air ground voice communications.

c. The initial communication, and if considered

necessary, any subsequent transmissions by an

aircraft in distress should begin with the signal

MAYDAY, preferably repeated three times. The

signal PAN−PAN should be used in the same manner

for an urgency condition.

d. Distress communications have absolute priority

over all other communications, and the word

MAYDAY commands radio silence on the frequency

in use. Urgency communications have priority over

all other communications except distress, and the

word PAN−PAN warns other stations not to interfere

with urgency transmissions.

e. Normally, the station addressed will be the

air traffic facility or other agency providing air traffic

services, on the frequency in use at the time. If the

pilot is not communicating and receiving services,

the station to be called will normally be the air traffic

facility or other agency in whose area of responsibility the aircraft is operating, on the appropriate

assigned frequency. If the station addressed does not

respond, or if time or the situation dictates, the

distress or urgency message may be broadcast, or a

collect call may be used, addressing “Any Station

(Tower)(Radio)(Radar).”

f. The station addressed should immediately

acknowledge a distress or urgency message, provide

assistance, coordinate and direct the activities of

assisting facilities, and alert the appropriate search

and rescue coordinator if warranted. Responsibility

will be transferred to another station only if better

handling will result.

g. All other stations, aircraft and ground, will

continue to listen until it is evident that assistance is

being provided. If any station becomes aware that the

station being called either has not received a distress

or urgency message, or cannot communicate with the

aircraft in difficulty, it will attempt to contact the

aircraft and provide assistance.

h. Although the frequency in use or other

frequencies assigned by ATC are preferable, the

following emergency frequencies can be used for

distress or urgency communications, if necessary or

desirable:

1. 121.5 MHz and 243.0 MHz. Both have a

range generally limited to line of sight. 121.5 MHz is

guarded by direction finding stations and some

military and civil aircraft. 243.0 MHz is guarded by

military aircraft. Both 121.5 MHz and 243.0 MHz are

guarded by military towers, most civil towers, FSSs,

and radar facilities. Normally ARTCC emergency

frequency capability does not extend to radar

coverage limits. If an ARTCC does not respond when

called on 121.5 MHz or 243.0 MHz, call the nearest

tower or FSS.

2. 2182 kHz. The range is generally less than

300 miles for the average aircraft installation. It can

be used to request assistance from stations in the

maritime service. 2182 kHz is guarded by major radio

stations serving Coast Guard Rescue Coordination

Centers, and Coast Guard units along the sea coasts

of the U.S. and shores of the Great Lakes. The call

“Coast Guard” will alert all Coast Guard Radio

Stations within range. 2182 kHz is also guarded by

most commercial coast stations and some ships and

boats.
AIM 7/26/12

6−3−2 Distress and Urgency Procedures

6−3−2. Obtaining Emergency Assistance

a. A pilot in any distress or urgency condition

should immediately take the following action, not

necessarily in the order listed, to obtain assistance:

1. Climb, if possible, for improved communications, and better radar and direction finding detection.

However, it must be understood that unauthorized

climb or descent under IFR conditions within

controlled airspace is prohibited, except as permitted

by 14 CFR Section 91.3(b).

2. If equipped with a radar beacon transponder

(civil) or IFF/SIF (military):

(a) Continue squawking assigned Mode A/3

discrete code/VFR code and Mode C altitude

encoding when in radio contact with an air traffic

facility or other agency providing air traffic services,

unless instructed to do otherwise.

(b) If unable to immediately establish communications with an air traffic facility/agency,

squawk Mode A/3, Code 7700/Emergency and

Mode C.

3. Transmit a distress or urgency message

consisting of as many as necessary of the following

elements, preferably in the order listed:

(a) If distress, MAYDAY, MAYDAY, MAY−

DAY; if urgency, PAN−PAN, PAN−PAN, PAN−PAN.

(b) Name of station addressed.

(c) Aircraft identification and type.

(d) Nature of distress or urgency.

(e) Weather.

(f) Pilots intentions and request.

(g) Present position, and heading; or if lost,

last known position, time, and heading since that

position.

(h) Altitude or flight level.

(i) Fuel remaining in minutes.

(j) Number of people on board.

(k) Any other useful information.

REFERENCE−

Pilot/Controller Glossary Term− Fuel Remaining.

b. After establishing radio contact, comply with

advice and instructions received. Cooperate. Do not

hesitate to ask questions or clarify instructions when

you do not understand or if you cannot comply with

clearance. Assist the ground station to control

communications on the frequency in use. Silence

interfering radio stations. Do not change frequency or

change to another ground station unless absolutely

necessary. If you do, advise the ground station of the

new frequency and station name prior to the change,

transmitting in the blind if necessary. If two−way

communications cannot be established on the new

frequency, return immediately to the frequency or

station where two−way communications last existed.

c. When in a distress condition with bailout, crash

landing or ditching imminent, take the following

additional actions to assist search and rescue units:

1. Time and circumstances permitting, transmit

as many as necessary of the message elements in

subparagraph a3 above, and any of the following that

you think might be helpful:

(a) ELT status.

(b) Visible landmarks.

(c) Aircraft color.

(d) Number of persons on board.

(e) Emergency equipment on board.

2. Actuate your ELT if the installation permits.

3. For bailout, and for crash landing or ditching

if risk of fire is not a consideration, set your radio for

continuous transmission.

4. If it becomes necessary to ditch, make every

effort to ditch near a surface vessel. If time permits,

an FAA facility should be able to get the position of

the nearest commercial or Coast Guard vessel from a

Coast Guard Rescue Coordination Center.

5. After a crash landing, unless you have good

reason to believe that you will not be located by

search aircraft or ground teams, it is best to remain

with your aircraft and prepare means for signaling

search aircraft.
7/26/12 AIM

Distress and Urgency Procedures 6−3−3

6−3−3. Ditching Procedures

FIG 6−3−1

Single Swell (15 knot wind)

SWELL

DITCHING

HEADING

WIND

FIG 6−3−2

Double Swell (15 knot wind)

PRIMARY

SWELL

PRIMARY

SWELL

SECONDARY

SWELL

SECONDARY

SWELL

HEADING

WIND

DITCHING

FIG 6−3−3

Double Swell (30 knot wind)

PRIMARY

SWELL

PRIMARY

SWELL

SECONDARY

SWELL

SECONDARY

SWELL

WIND

DITCHING

HEADING

FIG 6−3−4

(50 knot wind)

SWELL

WIND

Aircraft with low landing speeds - land into the wind.

Aircraft with high landing speeds - choose compromise

heading between wind and swell.

Both - land on back side of swell.
AIM 7/26/12

6−3−4 Distress and Urgency Procedures

FIG 6−3−5

Wind−Swell−Ditch Heading

GOOD

GOOD !!

BACK SIDE

POOR!!!

FACE

GOOD

FAIR

BESTE

DIRECTION OF

SWELL MOVEMENT

Landing parallel to the major swell

Landing on the face and back of swell

a. A successful aircraft ditching is dependent on

three primary factors. In order of importance they are:

1. Sea conditions and wind.

2. Type of aircraft.

3. Skill and technique of pilot.

b. Common oceanographic terminology.

1. Sea. The condition of the surface that is the

result of both waves and swells.

2. Wave (or Chop). The condition of the

surface caused by the local winds.

3. Swell. The condition of the surface which

has been caused by a distance disturbance.

4. Swell Face. The side of the swell toward the

observer. The backside is the side away from the

observer. These definitions apply regardless of the

direction of swell movement.

5. Primary Swell. The swell system having the

greatest height from trough to crest.

6. Secondary Swells. Those swell systems of

less height than the primary swell.

7. Fetch. The distance the waves have been

driven by a wind blowing in a constant direction,

without obstruction.

8. Swell Period. The time interval between the

passage of two successive crests at the same spot in

the water, measured in seconds.

9. Swell Velocity. The speed and direction of

the swell with relation to a fixed reference point,

measured in knots. There is little movement of water

in the horizontal direction. Swells move primarily in

a vertical motion, similar to the motion observed

when shaking out a carpet.

10. Swell Direction. The direction from which

a swell is moving. This direction is not necessarily the

result of the wind present at the scene. The swell may

be moving into or across the local wind. Swells, once

set in motion, tend to maintain their original direction

for as long as they continue in deep water, regardless

of changes in wind direction.
7/26/12 AIM

Distress and Urgency Procedures 6−3−5

11. Swell Height. The height between crest

and trough, measured in feet. The vast majority of

ocean swells are lower than 12 to 15 feet, and swells

over 25 feet are not common at any spot on the

oceans. Successive swells may differ considerably in

height.

c. In order to select a good heading when ditching

an aircraft, a basic evaluation of the sea is required.

Selection of a good ditching heading may well

minimize damage and could save your life. It can be

extremely dangerous to land into the wind without

regard to sea conditions; the swell system, or systems,

must be taken into consideration. Remember one

axiom− AVOID THE FACE OF A SWELL.

1. In ditching parallel to the swell, it makes little

difference whether touchdown is on the top of the

crest or in the trough. It is preferable, however, to land

on the top or back side of the swell, if possible. After

determining which heading (and its reciprocal) will

parallel the swell, select the heading with the most

into the wind component.

2. If only one swell system exists, the problem

is relatively simple−even with a high, fast system.

Unfortunately, most cases involve two or more swell

systems running in different directions. With more

than one system present, the sea presents a confused

appearance. One of the most difficult situations

occurs when two swell systems are at right angles.

For example, if one system is eight feet high, and the

other three feet, plan to land parallel to the primary

system, and on the down swell of the secondary

system. If both systems are of equal height, a

compromise may be advisable−select an intermediate

heading at 45 degrees down swell to both systems.

When landing down a secondary swell, attempt to

touch down on the back side, not on the face of the

swell.

3. If the swell system is formidable, it is

considered advisable, in landplanes, to accept more

crosswind in order to avoid landing directly into the

swell.

4. The secondary swell system is often from the

same direction as the wind. Here, the landing may be

made parallel to the primary system, with the wind

and secondary system at an angle. There is a choice

to two directions paralleling the primary system. One

direction is downwind and down the secondary swell,

and the other is into the wind and into the secondary

swell, the choice will depend on the velocity of the

wind versus the velocity and height of the secondary

swell.

d. The simplest method of estimating the wind

direction and velocity is to examine the windstreaks

on the water. These appear as long streaks up and

down wind. Some persons may have difficulty

determining wind direction after seeing the streaks on

the water. Whitecaps fall forward with the wind but

are overrun by the waves thus producing the illusion

that the foam is sliding backward. Knowing this, and

by observing the direction of the streaks, the wind

direction is easily determined. Wind velocity can be

estimated by noting the appearance of the whitecaps,

foam and wind streaks.

1. The behavior of the aircraft on making

contact with the water will vary within wide limits

according to the state of the sea. If landed parallel to

a single swell system, the behavior of the aircraft may

approximate that to be expected on a smooth sea. If

landed into a heavy swell or into a confused sea, the

deceleration forces may be extremely great−resulting

in breaking up of the aircraft. Within certain limits,

the pilot is able to minimize these forces by proper sea

evaluation and selection of ditching heading.

2. When on final approach the pilot should look

ahead and observe the surface of the sea. There may

be shadows and whitecaps−signs of large seas.

Shadows and whitecaps close together indicate short

and rough seas. Touchdown in these areas is to be

avoided. Select and touchdown in any area (only

about 500 feet is needed) where the shadows and

whitecaps are not so numerous.

3. Touchdown should be at the lowest speed and

rate of descent which permit safe handling and

optimum nose up attitude on impact. Once first

impact has been made, there is often little the pilot can

do to control a landplane.

e. Once preditching preparations are completed,

the pilot should turn to the ditching heading and

commence let−down. The aircraft should be flown

low over the water, and slowed down until ten knots

or so above stall. At this point, additional power

should be used to overcome the increased drag caused

by the nose up attitude. When a smooth stretch of

water appears ahead, cut power, and touchdown at the

best recommended speed as fully stalled as possible.

By cutting power when approaching a relatively

smooth area, the pilot will prevent overshooting and
AIM 7/26/12

6−3−6 Distress and Urgency Procedures

will touchdown with less chance of planing off into

a second uncontrolled landing. Most experienced

seaplane pilots prefer to make contact with the water

in a semi−stalled attitude, cutting power as the tail

makes contact. This technique eliminates the chance

of misjudging altitude with a resultant heavy drop in

a fully stalled condition. Care must be taken not to

drop the aircraft from too high altitude or to balloon

due to excessive speed. The altitude above water

depends on the aircraft. Over glassy smooth water, or

at night without sufficient light, it is very easy, for

even the most experienced pilots to misjudge altitude

by 50 feet or more. Under such conditions, carry

enough power to maintain nine to twelve degrees

nose up attitude, and 10 to 20 percent over stalling

speed until contact is made with the water. The proper

use of power on the approach is of great importance.

If power is available on one side only, a little power

should be used to flatten the approach; however, the

engine should not be used to such an extent that the

aircraft cannot be turned against the good engines

right down to the stall with a margin of rudder

movement available. When near the stall, sudden

application of excessive unbalanced power may

result in loss of directional control. If power is

available on one side only, a slightly higher than

normal glide approach speed should be used. This

will ensure good control and some margin of speed

after leveling off without excessive use of power. The

use of power in ditching is so important that when it

is certain that the coast cannot be reached, the pilot

should, if possible, ditch before fuel is exhausted. The

use of power in a night or instrument ditching is far

more essential than under daylight contact

conditions.

1. If no power is available, a greater than normal

approach speed should be used down to the flare−out.

This speed margin will allow the glide to be broken

early and more gradually, thereby giving the pilot

time and distance to feel for the surface − decreasing

the possibility of stalling high or flying into the water.

When landing parallel to a swell system, little

difference is noted between landing on top of a crest

or in the trough. If the wings of aircraft are trimmed

to the surface of the sea rather than the horizon, there

is little need to worry about a wing hitting a swell

crest. The actual slope of a swell is very gradual. If

forced to land into a swell, touchdown should be

made just after passage of the crest. If contact is made

on the face of the swell, the aircraft may be swamped

or thrown violently into the air, dropping heavily into

the next swell. If control surfaces remain intact, the

pilot should attempt to maintain the proper nose

above the horizon attitude by rapid and positive use

of the controls.

f. After Touchdown. In most cases drift, caused

by crosswind can be ignored; the forces acting on the

aircraft after touchdown are of such magnitude that

drift will be only a secondary consideration. If the

aircraft is under good control, the “crab” may be

kicked out with rudder just prior to touchdown. This

is more important with high wing aircraft, for they are

laterally unstable on the water in a crosswind and may

roll to the side in ditching.

REFERENCE−

This information has been extracted from Appendix H of the “National

Search and Rescue Manual.”

6−3−4. Special Emergency (Air Piracy)

a. A special emergency is a condition of air piracy,

or other hostile act by a person(s) aboard an aircraft,

which threatens the safety of the aircraft or its

passengers.

b. The pilot of an aircraft reporting a special

emergency condition should:

1. If circumstances permit, apply distress or

urgency radio−telephony procedures. Include the

details of the special emergency.

REFERENCE−

AIM, Distress and Urgency Communications, Paragraph 6−3−1.

2. If circumstances do not permit the use of

prescribed distress or urgency procedures, transmit:

(a) On the air/ground frequency in use at the

time.

(b) As many as possible of the following

elements spoken distinctly and in the following order:

(1) Name of the station addressed (time and

circumstances permitting).

(2) The identification of the aircraft and

present position.

(3) The nature of the special emergency

condition and pilot intentions (circumstances

permitting).
7/26/12 AIM

Distress and Urgency Procedures 6−3−7

(4) If unable to provide this information,

use code words and/or transponder as follows:

Spoken Words

TRANSPONDER SEVEN FIVE ZERO ZERO

Meaning

I am being hijacked/forced to a new destination

Transponder Setting

Mode 3/A, Code 7500

NOTE−

Code 7500 will never be assigned by ATC without prior

notification from the pilot that the aircraft is being

subjected to unlawful interference. The pilot should refuse

the assignment of Code 7500 in any other situation and

inform the controller accordingly. Code 7500 will trigger

the special emergency indicator in all radar ATC facilities.

c. Air traffic controllers will acknowledge and

confirm receipt of transponder Code 7500 by asking

the pilot to verify it. If the aircraft is not being

subjected to unlawful interference, the pilot should

respond to the query by broadcasting in the clear that

the aircraft is not being subjected to unlawful

interference. Upon receipt of this information, the

controller will request the pilot to verify the code

selection depicted in the code selector windows in the

transponder control panel and change the code to the

appropriate setting. If the pilot replies in the

affirmative or does not reply, the controller will not

ask further questions but will flight follow, respond to

pilot requests and notify appropriate authorities.

d. If it is possible to do so without jeopardizing the

safety of the flight, the pilot of a hijacked passenger

aircraft, after departing from the cleared routing over

which the aircraft was operating, will attempt to do

one or more of the following things, insofar as

circumstances may permit:

1. Maintain a true airspeed of no more than

400 knots, and preferably an altitude of between

10,000 and 25,000 feet.

2. Fly a course toward the destination which the

hijacker has announced.

e. If these procedures result in either radio contact

or air intercept, the pilot will attempt to comply with

any instructions received which may direct the

aircraft to an appropriate landing field or alter the

aircraft’s flight path off its current course, away from

protected airspace.

6−3−5. Fuel Dumping

a. Should it become necessary to dump fuel, the

pilot should immediately advise ATC. Upon receipt

of information that an aircraft will dump fuel, ATC

will broadcast or cause to be broadcast immediately

and every 3 minutes thereafter the following on

appropriate ATC and FSS radio frequencies:

EXAMPLE−

Attention all aircraft − fuel dumping in progress over −

(location) at (altitude) by (type aircraft) (flight direction).

b. Upon receipt of such a broadcast, pilots of

aircraft affected, which are not on IFR flight plans or

special VFR clearances, should clear the area

specified in the advisory. Aircraft on IFR flight plans

or special VFR clearances will be provided specific

separation by ATC. At the termination of the fuel

dumping operation, pilots should advise ATC. Upon

receipt of such information, ATC will issue, on the

appropriate frequencies, the following:

EXAMPLE−

ATTENTION ALL AIRCRAFT − FUEL DUMPING BY −

(type aircraft) − TERMINATED.

7/26/12 AIM

Two-way Radio Communications Failure 6−4−1

Section 4. Two-way Radio Communications Failure

6−4−1. Two-way Radio Communications

Failure

a. It is virtually impossible to provide regulations

and procedures applicable to all possible situations

associated with two-way radio communications

failure. During two-way radio communications

failure, when confronted by a situation not covered in

the regulation, pilots are expected to exercise good

judgment in whatever action they elect to take.

Should the situation so dictate they should not be

reluctant to use the emergency action contained in

14 CFR Section 91.3(b).

b. Whether two-way communications failure

constitutes an emergency depends on the circumstances, and in any event, it is a determination made

by the pilot. 14 CFR Section 91.3(b) authorizes a

pilot to deviate from any rule in Subparts A and B to

the extent required to meet an emergency.

c. In the event of two-way radio communications

failure, ATC service will be provided on the basis that

the pilot is operating in accordance with 14 CFR

Section 91.185. A pilot experiencing two-way

communications failure should (unless emergency

authority is exercised) comply with 14 CFR

Section 91.185 quoted below:

1. General. Unless otherwise authorized by

ATC, each pilot who has two-way radio communications failure when operating under IFR must comply

with the rules of this section.

2. VFR conditions. If the failure occurs in

VFR conditions, or if VFR conditions are encountered after the failure, each pilot must continue the

flight under VFR and land as soon as practicable.

NOTE−

This procedure also applies when two-way radio failure

occurs while operating in Class A airspace. The primary

objective of this provision in 14 CFR Section 91.185 is to

preclude extended IFR operation by these aircraft within

the ATC system. Pilots should recognize that operation

under these conditions may unnecessarily as well as

adversely affect other users of the airspace, since ATC may

be required to reroute or delay other users in order to

protect the failure aircraft. However, it is not intended that

the requirement to “land as soon as practicable” be

construed to mean “as soon as possible.” Pilots retain the

prerogative of exercising their best judgment and are not

required to land at an unauthorized airport, at an airport

unsuitable for the type of aircraft flown, or to land only

minutes short of their intended destination.

3. IFR conditions. If the failure occurs in IFR

conditions, or if subparagraph 2 above cannot be

complied with, each pilot must continue the flight

according to the following:

(a) Route.

(1) By the route assigned in the last ATC

clearance received;

(2) If being radar vectored, by the direct

route from the point of radio failure to the fix, route,

or airway specified in the vector clearance;

(3) In the absence of an assigned route, by

the route that ATC has advised may be expected in a

further clearance; or

(4) In the absence of an assigned route or a

route that ATC has advised may be expected in a

further clearance by the route filed in the flight plan.

(b) Altitude. At the HIGHEST of the

following altitudes or flight levels FOR THE ROUTE

SEGMENT BEING FLOWN:

(1) The altitude or flight level assigned in

the last ATC clearance received;

(2) The minimum altitude (converted, if

appropriate, to minimum flight level as prescribed in

14 CFR Section 91.121(c)) for IFR operations; or

(3) The altitude or flight level ATC has

advised may be expected in a further clearance.

NOTE−

The intent of the rule is that a pilot who has experienced

two-way radio failure should select the appropriate

altitude for the particular route segment being flown and

make the necessary altitude adjustments for subsequent

route segments. If the pilot received an “expect further

clearance” containing a higher altitude to expect at a

specified time or fix, maintain the highest of the following

altitudes until that time/fix:

(1) the last assigned altitude; or 

(2) the minimum altitude/flight level for IFR

operations.

Upon reaching the time/fix specified, the pilot should

commence climbing to the altitude advised to expect. If the
AIM 7/26/12

6−4−2 Two-way Radio Communications Failure

radio failure occurs after the time/fix specified, the altitude

to be expected is not applicable and the pilot should

maintain an altitude consistent with 1 or 2 above. If the

pilot receives an “expect further clearance” containing a

lower altitude, the pilot should maintain the highest of 1 or

2 above until that time/fix specified in subparagraph (c)

Leave clearance limit, below.

EXAMPLE−

1. A pilot experiencing two-way radio failure at an

assigned altitude of 7,000 feet is cleared along a direct

route which will require a climb to a minimum IFR altitude

of 9,000 feet, should climb to reach 9,000 feet at the time

or place where it becomes necessary (see 14 CFR

Section 91.177(b)). Later while proceeding along an

airway with an MEA of 5,000 feet, the pilot would descend

to 7,000 feet (the last assigned altitude), because that

altitude is higher than the MEA.

2. A pilot experiencing two-way radio failure while being

progressively descended to lower altitudes to begin an

approach is assigned 2,700 feet until crossing the VOR and

then cleared for the approach. The MOCA along the airway

is 2,700 feet and MEA is 4,000 feet. The aircraft is within

22 NM of the VOR. The pilot should remain at 2,700 feet

until crossing the VOR because that altitude is the

minimum IFR altitude for the route segment being flown.

3. The MEA between a and b: 5,000 feet. The MEA

between b and c: 5,000 feet. The MEA between c and d:

11,000 feet. The MEA between d and e: 7,000 feet. A pilot

had been cleared via a, b, c, d, to e. While flying between

a and b the assigned altitude was 6,000 feet and the pilot

was told to expect a clearance to 8,000 feet at b. Prior to

receiving the higher altitude assignment, the pilot

experienced two-way failure. The pilot would maintain

6,000 to b, then climb to 8,000 feet (the altitude advised to

expect). The pilot would maintain 8,000 feet, then climb to

11,000 at c, or prior to c if necessary to comply with an

MCA at c. (14 CFR Section 91.177(b).) Upon reaching d,

the pilot would descend to 8,000 feet (even though the MEA

was 7,000 feet), as 8,000 was the highest of the altitude

situations stated in the rule (14 CFR Section 91.185).

(c) Leave clearance limit.

(1) When the clearance limit is a fix from

which an approach begins, commence descent or

descent and approach as close as possible to the

expect further clearance time if one has been

received, or if one has not been received, as close as

possible to the Estimated Time of Arrival (ETA) as

calculated from the filed or amended (with ATC)

Estimated Time En Route (ETE).

(2) If the clearance limit is not a fix from

which an approach begins, leave the clearance limit

at the expect further clearance time if one has been

received, or if none has been received, upon arrival

over the clearance limit, and proceed to a fix from

which an approach begins and commence descent or

descent and approach as close as possible to the

estimated time of arrival as calculated from the filed

or amended (with ATC) estimated time en route.

6−4−2. Transponder Operation During

Two-way Communications Failure

a. If an aircraft with a coded radar beacon

transponder experiences a loss of two-way radio

capability, the pilot should adjust the transponder to

reply on Mode A/3, Code 7600.

b. The pilot should understand that the aircraft

may not be in an area of radar coverage.

6−4−3. Reestablishing Radio Contact

a. In addition to monitoring the NAVAID voice

feature, the pilot should attempt to reestablish

communications by attempting contact:

1. On the previously assigned frequency; or

2. With an FSS or *ARINC.

b. If communications are established with an FSS

or ARINC, the pilot should advise that radio

communications on the previously assigned frequency has been lost giving the aircraft’s position, altitude,

last assigned frequency and then request further

clearance from the controlling facility. The preceding

does not preclude the use of 121.5 MHz. There is no

priority on which action should be attempted first. If

the capability exists, do all at the same time.

NOTE−

*Aeronautical Radio/Incorporated (ARINC) is a commercial communications corporation which designs,

constructs, operates, leases or otherwise engages in radio

activities serving the aviation community. ARINC has the

capability of relaying information to/from ATC facilities

throughout the country.
7/26/12 AIM

Aircraft Rescue and Fire Fighting Communications 6−5−1

Section 5. Aircraft Rescue and

Fire Fighting Communications

6−5−1. Discrete Emergency Frequency

a. Direct contact between an emergency aircraft

flight crew, Aircraft Rescue and Fire Fighting

Incident Commander (ARFF IC), and the Airport

Traffic Control Tower (ATCT), is possible on an

aeronautical radio frequency (Discrete Emergency

Frequency [DEF]), designated by Air Traffic

Control (ATC) from the operational frequencies

assigned to that facility.

b. Emergency aircraft at airports without an

ATCT, (or when the ATCT is closed), may contact the

ARFF IC (if ARFF service is provided), on the

Common Traffic Advisory Frequency (CTAF)

published for the airport or the civil emergency

frequency 121.5 MHz.

6−5−2. Radio Call Signs

Preferred radio call sign for the ARFF IC is

“(location/facility) Command” when communicating with the flight crew and the FAA ATCT.

EXAMPLE−

LAX Command.

Washington Command.

6−5−3. ARFF Emergency Hand Signals

In the event that electronic communications cannot

be maintained between the ARFF IC and the flight

crew, standard emergency hand signals as depicted in

FIG 6−5−1 through FIG 6−5−3 should be used. These

hand signals should be known and understood by all

cockpit and cabin aircrew, and all ARFF firefighters.

FIG 6−5−1

Recommend Evacuation

FIG 6−5−2

Recommend Stop
AIM 7/26/12

6−5−2 Aircraft Rescue and Fire Fighting Communications

FIG 6−5−3

Emergency Contained
7/26/12 AIM

Meteorology 7−1−1

Chapter 7. Safety of Flight

Section 1. Meteorology

7−1−1. National Weather Service Aviation

Products

a. Weather service to aviation is a joint effort of the

National Weather Service (NWS), the Federal

Aviation Administration (FAA), the military weather

services, and other aviation oriented groups and

individuals. The NWS maintains an extensive

surface, upper air, and radar weather observing

program; a nationwide aviation weather forecasting

service; and provides limited pilot briefing service

(interpretational). Pilot weather briefings are provided by personnel at Flight Service Stations

operated by FAA (in Alaska) or by federal contract

facilities (elsewhere in the U.S.). Aviation routine

weather reports (METAR) are taken manually by

NWS, FAA, contractors, or supplemental observers.

METAR reports are also provided by Automated

Weather Observing System (AWOS), Automated

Surface Observing System (ASOS), and Automated

Weather Sensor System (AWSS).

REFERENCE−

AIM, Para 7−1−12, Weather Observing Programs.

b. Aerodrome forecasts are prepared by approximately 100 Weather Forecast Offices (WFOs). These

offices prepare and distribute approximately

525 aerodrome forecasts 4 times daily for specific

airports in the 50 States, Puerto Rico, the Caribbean

and Pacific Islands. These forecasts are valid for

24 hours and amended as required. WFOs prepare

over 300 route forecasts and 39 synopses for

Transcribed Weather Broadcasts (TWEB) outside the

continental United States (OCONUS) only and

briefing purposes. The route forecasts are issued

4 times daily; each forecast is valid for 12 hours. A

centralized aviation forecast program originating

from the Aviation Weather Center (AWC) in Kansas

City was implemented in October 1995. In the

conterminous U.S., all inflight advisories, Significant

Meteorological Information (SIGMETs), Convective

SIGMETs, and Airmen’s Meteorological Information (AIRMET−text bulletins [WA] and graphics

[G−AIRMETs]), and all Area Forecasts (FAs) (6

areas) are now issued by AWC. FAs are prepared 3

times a day in the conterminous U.S. and Alaska (4

times in Hawaii), and amended as required. Inflight

advisories are issued only when conditions warrant.

Winds aloft forecasts are provided for 176 locations

in the 48 contiguous States and 21 locations in

Alaska for flight planning purposes. (Winds aloft

forecasts for Hawaii are prepared locally.) All the

aviation weather forecasts are given wide distribution

through the Weather Message Switching Center

Replacement (WMSCR) in Atlanta, Georgia, and

Salt Lake City, Utah.

REFERENCE−

AIM, Para 7−1−6, Inflight Aviation Weather Advisories.

c. Weather element values may be expressed by

using different measurement systems depending on

several factors, such as whether the weather products

will be used by the general public, aviation interests,

international services, or a combination of these

users. FIG 7−1−1 provides conversion tables for the

most used weather elements that will be encountered

by pilots.

7−1−2. FAA Weather Services

a. The FAA maintains a nationwide network of

Flight Service Stations (FSSs) to serve the weather

needs of pilots. In addition, NWS meteorologists are

assigned to most ARTCCs as part of the Center

Weather Service Unit (CWSU). They provide Center

Weather Advisories (CWAs) and gather weather

information to support the needs of the FAA and other

users of the system.

b. The primary source of preflight weather

briefings is an individual briefing obtained from a

briefer at the FSS. These briefings, which are tailored

to your specific flight, are available 24 hours a day

through the use of the toll free number (1−800−WX

BRIEF). Numbers for these services can be found in

the Airport/Facility Directory (A/FD) under “FAA

and NWS Telephone Numbers” section. They may

also be listed in the U.S. Government section of your

local telephone directory under Department of

Transportation, Federal Aviation Administration.

REFERENCE−

AIM, Para 7−1−4, Preflight Briefing, explains the types of preflight

briefings available and the information contained in each.
AIM 7/26/12

7−1−2 Meteorology

FIG 7−1−1

Weather Elements Conversion Tables
7/26/12 AIM

Meteorology 7−1−3

c. Other Sources of Weather Information

1. Telephone Information Briefing Service

(TIBS) (FSS); and in Alaska, Transcribed Weather

Broadcast (TWEB) locations, and telephone access

to the TWEB (TEL−TWEB) provide continuously

updated recorded weather information for short or

local flights. Separate paragraphs in this section give

additional information regarding these services.

REFERENCE−

AIM, Telephone Information Briefing Service (TIBS), Paragraph 7−1−8.

AIM, Transcribed Weather Broadcast (TWEB) (Alaska Only),

Paragraph 7−1−9.

2. Weather and aeronautical information are

also available from numerous private industry

sources on an individual or contract pay basis.

Information on how to obtain this service should be

available from local pilot organizations.

3. The Direct User Access Terminal System (DUATS) can be accessed by pilots with a

current medical certificate toll-free in the 48 contiguous States via personal computer. Pilots can receive

alpha-numeric preflight weather data and file

domestic VFR and IFR flight plans. The following

are the contract DUATS vendors:

Computer Sciences Corporation (CSC) 

15000 Conference Center Drive

Chantilly, VA 22021−3808

Internet Access: http://www.duats.com

Telnet Access (modem terminal−style): 

(800) 767−9989 or 

telnet://direct.duats.com

For customer service: (800) 345−3828

Data Transformation Corporation (DTC)

108−D Greentree Road

Turnersville, NJ 08012

Internet Access: http://www.duat.com

For customer service: (800)243−3828

d. Inflight weather information is available from

any FSS within radio range. The common frequency

for all FSSs is 122.2. Discrete frequencies for

individual stations are listed in the A/FD.

1. Information on In-Flight Weather broadcasts.

REFERENCE−

AIM, Inflight Weather Broadcasts, Paragraph 7−1−10.

2. En Route Flight Advisory Service (EFAS) is

provided to serve the nonroutine weather needs of

pilots in flight.

REFERENCE−

AIM, En Route Flight Advisory Service (EFAS), Paragraph 7−1−5, gives

details on this service.

7−1−3. Use of Aviation Weather Products

a. Air carriers and operators certificated under the

provisions of 14 CFR Part 119 are required to use the

aeronautical weather information systems defined in

the Operations Specifications issued to that certificate holder by the FAA. These systems may utilize

basic FAA/National Weather Service (NWS) weather

services, contractor− or operator−proprietary weather services and/or Enhanced Weather Information

System (EWINS) when approved in the Operations

Specifications. As an integral part of this system

approval, the procedures for collecting, producing

and disseminating aeronautical weather information,

as well as the crew member and dispatcher training to

support the use of system weather products, must be

accepted or approved.

b. Operators not certificated under the provisions

of 14 CFR Part 119 are encouraged to use FAA/NWS

products through Flight Service Stations, Direct User

Access Terminal System (DUATS), and/or Flight

Information Services Data Link (FISDL).

c. The suite of available aviation weather product

types is expanding, with the development of new

sensor systems, algorithms and forecast models. The

FAA and NWS, supported by the National Center for

Atmospheric Research and the Forecast Systems

Laboratory, develop and implement new aviation

weather product types through a comprehensive

process known as the Aviation Weather Technology

Transfer process. This process ensures that user needs

and technical readiness requirements are met before

experimental products mature to operational

application.

d. The FAA, in conjunction with the NWS,

established the Aviation Weather Technology

Transfer (AWTT) Board so that newly developed

aviation weather products meet regulatory

requirements and enhance safety. The AWTT is

charged with managing and accelerating the transfer

of these products into operational use. Members of

the AWTT Board include mid−level managers from

the FAA and NWS who are responsible for various
AIM 7/26/12

7−1−4 Meteorology

aspects of the development and use of aviation

weather products (e.g., aviation weather R & D,

transition of weather products from R & D to

operational use, etc.).

e. The AWTT is a management−review and

decision−making process that applies criteria to

weather products at various development stages

(decision stages, i.e., “D−stages”). The D−stages are

composed of the following:

1. (D1) Sponsorship of user needs.

2. (D2) R & D and controlled testing.

3. (D3) Experimental application.

4. (D4) Operational application.

f. Weather products maturing into the D3

experimental stage of the AWTT process are often

made available to the public on the Aviation Weather

Center’s Experimental Aviation Digital Data Service

(ADDS) website at: http://weather.aero/. The intent

is to allow public access to this information in order

to obtain feedback for product development and

improvement. However, it is important to note that

weather products displayed on this site are

experimental, and although they may appear to be

fully operational products, they are subject to change

without notification and may not be used for any

flight related decisions. At the D4 stage, the FAA

approves a weather product for operational use by

end users (with restrictions, if necessary), and the

product is made available to the public via long−line

circuit, satellite, and/or other means of

communication.

g. Pilots and operators should be aware that

weather services provided by entities other than FAA,

NWS or their contractors (such as the DUATS and

FISDL providers) may not meet FAA/NWS quality

control standards. Hence, operators and pilots

contemplating using such services should request

and/or review an appropriate description of services

and provider disclosure. This should include, but is

not limited to, the type of weather product (e.g.,

current weather or forecast weather), the currency of

the product (i.e., product issue and valid times), and

the relevance of the product. Pilots and operators

should be cautious when using unfamiliar products,

or products not supported by FAA/NWS technical

specifications.

NOTE−

When in doubt, consult with a FAA Flight Service Station

Specialist.

h. In addition, pilots and operators should be

aware there are weather services and products

available from government organizations beyond the

scope of the AWTT process mentioned earlier in this

section. For example, governmental agencies such as

the NWS, the Aviation Weather Center (AWC), and

the National Center for Atmospheric Research

(NCAR) display weather “model data” and

“experimental” products which require training

and/or expertise to properly interpret and use. These

products are developmental prototypes that are

subject to ongoing research and can change without

notice. Therefore, some data on display by

government organizations, or government data on

display by independent organizations may be

unsuitable for flight planning purposes. Operators

and pilots contemplating using such services should

request and/or review an appropriate description of

services and provider disclosure. This should include,

but is not limited to, the type of weather product (e.g.,

current weather or forecast weather), the currency of

the product (i.e., product issue and valid times), and

the relevance of the product. Pilots and operators

should be cautious when using unfamiliar weather

products.

NOTE−

When in doubt, consult with a FAA Flight Service Station

Specialist.

i. The development of new weather products

coupled with increased access to these products via

the public Internet, created confusion within the

aviation community regarding the relationship

between regulatory requirements and new weather

products. Consequently, FAA differentiates between

those weather products that may be utilized to comply

with regulatory requirements and those that may only

be used to improve situational awareness. To clarify

the proper use of aviation weather products to meet

the requirements of 14 CFR, FAA defines weather

products as follows:

1. Primary Weather Product. An aviation

weather product that meets all the regulatory

requirements and safety needs for use in making

flight related, aviation weather decisions.

2. Supplementary Weather Product. An

aviation weather product that may be used for

enhanced situational awareness. If utilized, a
7/26/12 AIM

Meteorology 7−1−5

supplementary weather product must only be used in

conjunction with one or more primary weather

product. In addition, the FAA may further restrict the

use of supplementary aviation weather products

through limitations described in the product label.

NOTE−

An aviation weather product produced by the Federal

Government and managed by the AWTT is classified a

primary weather product unless designated a

supplementary weather product by the FAA.

j. In developing the definitions of primary and

supplementary weather products, it is not the intent of

FAA to change or increase the regulatory burden on

the user. Rather, the definitions are meant to eliminate

confusion by differentiating between weather

products that may be utilized to meet regulatory

requirements and other weather products that may

only be used to improve situational awareness.

k. All flight−related, aviation weather decisions

must be based on primary weather products.

Supplementary weather products augment the

primary products by providing additional weather

information but may not be used as stand−alone

weather products to meet aviation weather regulatory

requirements or without the relevant primary

products. When discrepancies exist between primary

and supplementary weather products describing the

same weather phenomena, users must base flight−

related decisions on the primary weather product.

Furthermore, multiple primary products may be

necessary to meet all aviation weather regulatory

requirements.

l. The development of enhanced communications

capabilities, most notably the Internet, has allowed

pilots access to an ever−increasing range of weather

service providers and proprietary products. The FAA

has identified three distinct types of weather

information available to pilots and operators.

1. Observations. Raw weather data collected

by some type of sensor suite including surface and

airborne observations, radar, lightning, satellite

imagery, and profilers.

2. Analysis. Enhanced depiction and/or

interpretation of observed weather data.

3. Forecasts. Predictions of the development

and/or movement of weather phenomena based on

meteorological observations and various

mathematical models.

m. Not all sources of aviation weather information

are able to provide all three types of weather

information. The FAA has determined that operators

and pilots may utilize the following approved sources

of aviation weather information:

1. Federal Government. The FAA and NWS

collect raw weather data, analyze the observations,

and produce forecasts. The FAA and NWS

disseminate meteorological observations, analyses,

and forecasts through a variety of systems. In

addition, the Federal Government is the only

approval authority for sources of weather

observations; for example, contract towers and

airport operators may be approved by the Federal

Government to provide weather observations.

2. Enhanced Weather Information System

(EWINS). An EWINS is an FAA approved,

proprietary system for tracking, evaluating,

reporting, and forecasting the presence or lack of

adverse weather phenomena. An EWINS is

authorized to produce flight movement forecasts,

adverse weather phenomena forecasts, and other

meteorological advisories. For more detailed

information regarding EWINS, see the Aviation

Weather Services Advisory Circular 00−45 and the

Air Transportation Operations Inspector’s

Handbook 8400.10.

3. Commercial Weather Information

Providers. In general, commercial providers

produce proprietary weather products based on

NWS/FAA products with formatting and layout

modifications but no material changes to the weather

information itself. This is also referred to as

“repackaging.” In addition, commercial providers

may produce analyses, forecasts, and other

proprietary weather products that substantially alter

the information contained in government−produced

products. However, those proprietary weather

products that substantially alter government−

produced weather products or information, may only

be approved for use by 14 CFR Part 121 and Part 135

certificate holders if the commercial provider is

EWINS qualified.

NOTE−

Commercial weather information providers contracted by

FAA to provide weather observations, analyses, and

forecasts (e.g., contract towers) are included in the Federal
AIM 7/26/12

7−1−6 Meteorology

Government category of approved sources by virtue of

maintaining required technical and quality assurance

standards under Federal Government oversight.

n. As a point of clarification, Advisory

Circular 00−62, Internet Communications of

Aviation Weather and NOTAMS, describes the

process for a weather information provider to become

a Qualified Internet Communications Provider

(QICP) and only applies to 14 CFR Part 121 and

Part 135 certificate holders. Therefore, pilots

conducting operations under 14 CFR Part 91 may

access weather products via the public Internet.

7−1−4. Preflight Briefing

a. Flight Service Stations (FSSs) are the primary

source for obtaining preflight briefings and inflight

weather information. Flight Service Specialists are

qualified and certificated by the NWS as Pilot

Weather Briefers. They are not authorized to make

original forecasts, but are authorized to translate and

interpret available forecasts and reports directly into

terms describing the weather conditions which you

can expect along your flight route and at your

destination. Available aviation weather reports,

forecasts and aviation weather charts are displayed at

each FSS, for pilot use. Pilots should feel free to use

these self briefing displays where available, or to ask

for a briefing or assistance from the specialist on duty.

Three basic types of preflight briefings are available

to serve your specific needs. These are: Standard

Briefing, Abbreviated Briefing, and Outlook Briefing. You should specify to the briefer the type of

briefing you want, along with your appropriate

background information. This will enable the briefer

to tailor the information to your intended flight. The

following paragraphs describe the types of briefings

available and the information provided in each

briefing.

REFERENCE−

AIM, Preflight Preparation, Paragraph 5−1−1, for items that are

required.

b. Standard Briefing. You should request a

Standard Briefing any time you are planning a flight

and you have not received a previous briefing or have

not received preliminary information through mass

dissemination media; e.g., TIBS, TWEB (Alaska

only), etc. International data may be inaccurate or

incomplete. If you are planning a flight outside of

U.S. controlled airspace, the briefer will advise you

to check data as soon as practical after entering

foreign airspace, unless you advise that you have the

international cautionary advisory. The briefer will

automatically provide the following information in

the sequence listed, except as noted, when it is

applicable to your proposed flight.

1. Adverse Conditions. Significant meteorological and/or aeronautical information that might

influence the pilot to alter or cancel the proposed

flight; for example, hazardous weather conditions,

airport closures, air traffic delays, etc. Pilots should

be especially alert for current or forecast weather

that could reduce flight minimums below VFR or

IFR conditions. Pilots should also be alert for any

reported or forecast icing if the aircraft is not certified

for operating in icing conditions. Flying into areas

of icing or weather below minimums could have

disastrous results.

2. VFR Flight Not Recommended. When

VFR flight is proposed and sky conditions or

visibilities are present or forecast, surface or aloft,

that, in the briefer’s judgment, would make flight

under VFR doubtful, the briefer will describe the

conditions, describe the affected locations, and use

the phrase “VFR flight not recommended.” This

recommendation is advisory in nature. The final

decision as to whether the flight can be conducted

safely rests solely with the pilot. Upon receiving a

“VFR flight not recommended” statement, the

non−IFR rated pilot will need to make a “go or no go”

decision. This decision should be based on weighing

the current and forecast weather conditions against

the pilot’s experience and ratings. The aircraft’s

equipment, capabilities and limitations should also

be considered.

NOTE−

Pilots flying into areas of minimal VFR weather could

encounter unforecasted lowering conditions that place the

aircraft outside the pilot’s ratings and experience level.

This could result in spatial disorientation and/or loss of

control of the aircraft.

3. Synopsis. A brief statement describing the

type, location and movement of weather systems

and/or air masses which might affect the proposed

flight.

NOTE−

These first 3 elements of a briefing may be combined in any

order when the briefer believes it will help to more clearly

describe conditions.
7/26/12 AIM

Meteorology 7−1−7

4. Current Conditions. Reported weather

conditions applicable to the flight will be summarized

from all available sources; e.g., METARs/ SPECIs,

PIREPs, RAREPs. This element will be omitted if the

proposed time of departure is beyond 2 hours, unless

the information is specifically requested by the pilot.

5. En Route Forecast. Forecast en route

conditions for the proposed route are summarized in

logical order; i.e., departure/climbout, en route, and

descent. (Heights are MSL, unless the contractions

“AGL” or “CIG” are denoted indicating that heights

are above ground.)

6. Destination Forecast. The destination forecast for the planned ETA. Any significant changes

within 1 hour before and after the planned arrival are

included.

7. Winds Aloft. Forecast winds aloft will be

provided using degrees of the compass. The briefer

will interpolate wind directions and speeds between

levels and stations as necessary to provide expected

conditions at planned altitudes. (Heights are MSL.)

Temperature information will be provided on request.

8. Notices to Airmen (NOTAMs).

(a) Available NOTAM (D) information pertinent to the proposed flight, including special use

airspace (SUA) NOTAMs for restricted areas, aerial

refueling, and night vision goggles (NVG).

NOTE−

Other SUA NOTAMs (D), such as military operations

area (MOA), military training route (MTR), and warning

area NOTAMs, are considered “upon request” briefing

items as indicated in paragraph 7−1−4b10(a).

(b) Prohibited Areas P−40, P−49, P−56,

and the special flight rules area (SFRA) for

Washington, DC.

(c) FSS briefers do not provide FDC NOTAM

information for special instrument approach procedures unless specifically asked. Pilots authorized by

the FAA to use special instrument approach

procedures must specifically request FDC NOTAM

information for these procedures.

NOTE−

NOTAM information may be combined with current

conditions when the briefer believes it is logical to do so.

NOTE−

NOTAM (D) information and FDC NOTAMs which have

been published in the Notices to Airmen Publication are

not included in pilot briefings unless a review of this

publication is specifically requested by the pilot. For

complete flight information you are urged to review the

printed NOTAMs in the Notices to Airmen Publication and

the A/FD in addition to obtaining a briefing.

9. ATC Delays. Any known ATC delays and

flow control advisories which might affect the

proposed flight.

10. Pilots may obtain the following from

flight service station briefers upon request:

(a) Information on SUA and SUA−related

airspace, except those listed in paragraph 7−1−4b8.

NOTE−

1. For the purpose of this paragraph, SUA and related

airspace includes the following types of airspace: alert

area, military operations area (MOA), warning area, and

air traffic control assigned airspace (ATCAA). MTR data

includes the following types of airspace: IFR training

routes (IR), VFR training routes (VR), and slow training

routes (SR).

2. Pilots are encouraged to request updated information

from ATC facilities while in flight.

(b) A review of the Notices to Airmen

Publication for pertinent NOTAMs and Special

Notices.

(c) Approximate density altitude data.

(d) Information regarding such items as air

traffic services and rules, customs/immigration

procedures, ADIZ rules, search and rescue, etc.

(e) GPS RAIM availability for 1 hour before

to 1 hour after ETA or a time specified by the pilot.

(f) Other assistance as required.

c. Abbreviated Briefing. Request an Abbreviated Briefing when you need information to

supplement mass disseminated data, update a

previous briefing, or when you need only one or two

specific items. Provide the briefer with appropriate

background information, the time you received the

previous information, and/or the specific items

needed. You should indicate the source of the

information already received so that the briefer can

limit the briefing to the information that you have not

received, and/or appreciable changes in meteorological/aeronautical conditions since your previous

briefing. To the extent possible, the briefer will

provide the information in the sequence shown for a

Standard Briefing. If you request only one or two

specific items, the briefer will advise you if adverse

conditions are present or forecast. (Adverse condi-
AIM 7/26/12

7−1−8 Meteorology

tions contain both meteorological and/or aeronautical

information.) Details on these conditions will be

provided at your request. International data may be

inaccurate or incomplete. If you are planning a flight

outside of U.S. controlled airspace, the briefer will

advise you to check data as soon as practical after

entering foreign airspace, unless you advise that you

have the international cautionary advisory.

d. Outlook Briefing. You should request an

Outlook Briefing whenever your proposed time of

departure is six or more hours from the time of the

briefing. The briefer will provide available forecast

data applicable to the proposed flight. This type of

briefing is provided for planning purposes only. You

should obtain a Standard or Abbreviated Briefing

prior to departure in order to obtain such items as

adverse conditions, current conditions, updated

forecasts, winds aloft and NOTAMs, etc.

e. When filing a flight plan only, you will be asked

if you require the latest information on adverse

conditions pertinent to the route of flight.

f. Inflight Briefing. You are encouraged to

obtain your preflight briefing by telephone or in

person before departure. In those cases where you

need to obtain a preflight briefing or an update to a

previous briefing by radio, you should contact the

nearest FSS to obtain this information. After

communications have been established, advise the

specialist of the type briefing you require and provide

appropriate background information. You will be

provided information as specified in the above

paragraphs, depending on the type of briefing

requested. In addition, the specialist will recommend

shifting to the Flight Watch frequency when

conditions along the intended route indicate that it

would be advantageous to do so. Remember that

weather conditions can change rapidly and that a “go

or no go” decision, as mentioned in paragraph

7−1−4b2, should be assessed at all phases of flight.

g. Following any briefing, feel free to ask for any

information that you or the briefer may have missed

or are not understood. This way, the briefer is able to

present the information in a logical sequence, and

lessens the chance of important items being

overlooked.

7−1−5. En Route Flight Advisory Service

(EFAS)

a. EFAS (radio call “Flight Watch”) is a service

specifically designed to provide en route aircraft with

timely and meaningful weather advisories pertinent

to the type of flight intended, route of flight, and

altitude. In conjunction with this service, EFAS is

also a central collection and distribution point for

pilot reported weather information. EFAS is provided

by specially trained FSS specialists controlling

multiple Remote Communications Outlets covering

a large geographical area and is normally available

throughout the conterminous U.S. and Puerto Rico

from 6 a.m. to 10 p.m. EFAS provides communications capabilities for aircraft flying at 5,000 feet

above ground level to 17,500 feet MSL on a common

frequency of 122.0 MHz. Discrete EFAS frequencies

have been established to ensure communications

coverage from 18,000 through 45,000 MSL serving

in each specific ARTCC area. These discrete

frequencies may be used below 18,000 feet when

coverage permits reliable communication.

NOTE−

When an EFAS outlet is located in a time zone different from

the zone in which the flight watch control station is located,

the availability of service may be plus or minus one hour

from the normal operating hours.

b. In some regions of the contiguous U.S.,

especially those that are mountainous, it is necessary

to be above 5000 feet AGL in order to be at an altitude

where the EFAS frequency, 122.0 MHz, is available.

Pilots should take this into account when flight

planning. Other FSS communication frequencies

may be available at lower altitudes. See FIG 7−1−2.

c. Contact flight watch by using the name of the

ARTCC facility identification serving the area of

your location, followed by your aircraft identification, and the name of the nearest VOR to your

position. The specialist needs to know this

approximate location to select the most appropriate

transmitter/receiver outlet for communications

coverage.

EXAMPLE−

Cleveland Flight Watch, Cessna One Two Three Four Kilo,

Mansfield V−O−R, over.
7/26/12 AIM

Meteorology 7−1−9

d. Charts depicting the location of the flight watch

control stations (parent facility) and the outlets they

use are contained in the A/FD. If you do not know in

which flight watch area you are flying, initiate contact

by using the words “Flight Watch,” your aircraft

identification, and the name of the nearest VOR. The

facility will respond using the name of the flight

watch facility.

EXAMPLE−

Flight Watch, Cessna One Two Three Four Kilo,

Mansfield V−O−R, over.

e. Radio outlets that provide En Route Flight

Advisory Service are listed regionally in the A/FDs.

f. EFAS is not intended to be used for filing or

closing flight plans, position reporting, getting

complete preflight briefings, or obtaining random

weather reports and forecasts. En route flight

advisories are tailored to the phase of flight that

begins after climb-out and ends with descent to land.

Immediate destination weather and terminal aerodrome forecasts will be provided on request. Pilots

requesting information not within the scope of flight

watch will be advised of the appropriate FSS

frequency to obtain the information. Pilot participation is essential to the success of EFAS by providing

a continuous exchange of information on weather,

winds, turbulence, flight visibility, icing, etc.,

between pilots and flight watch specialists. Pilots are

encouraged to report good weather as well as bad, and

to confirm expected conditions as well as unexpected

to EFAS facilities.

7−1−6. Inflight Aviation Weather Advisories

a. Background

1. Inflight Aviation Weather Advisories are

forecasts to advise en route aircraft of development of

potentially hazardous weather. All inflight aviation

weather advisories in the conterminous U.S. are

issued by the Aviation Weather Center (AWC) in

Kansas City, Missouri. The Weather Forecast

Office (WFO) in Honolulu issues advisories for the

Hawaiian Islands. In Alaska, the Alaska Aviation

Weather Unit (AAWU) issues inflight aviation

weather advisories. All heights are referenced MSL,

except in the case of ceilings (CIG) which indicate

AGL.

2. There are three types of inflight aviation

weather advisories: the SIGMET, the Convective

SIGMET, and the AIRMET (text or graphical

product). All of these advisories use the same location

identifiers (either VORs, airports, or well−known

geographic areas) to describe the hazardous weather

areas. See FIG 7−1−3 and FIG 7−1−4. Graphics with

improved clarity can be found in the latest version of

Advisory Circular AC 00−45 series, Aviation Weather Services, which is available on the following Web

site: http://www.faa.gov.

3. Two other weather products supplement

these Inflight Aviation Weather Advisories:

(a) The Severe Weather Watch Bulletins (WWs), (with associated Alert Messages)

(AWW), and

(b) The Center Weather Advisories (CWAs).
AIM 7/26/12

7−1−10 Meteorology

FIG 7−1−2

EFAS Radio Coverage Areas

NOTE−

EFAS radio coverage at 5000 feet AGL. The shaded areas depict limited coverage areas in which altitudes above 5000 feet

AGL would be required to contact EFAS.
7/26/12 AIM

Meteorology 7−1−11

FIG 7−1−3

Inflight Advisory Plotting Chart
AIM 7/26/12

7−1−12 Meteorology

FIG 7−1−4

Geographical Areas and Terrain Features
7/26/12 AIM

Meteorology 7−1−13

FIG 7−1−5

Aviation Area Forecasts

FA Locations − Contiguous United States

b. SIGMET (WS)/AIRMET (WA or

G−AIRMET)

SIGMETs/AIRMET text (WA) products are issued

corresponding to the Area Forecast (FA) areas

described in FIG 7−1−5, FIG 7−1−6 and FIG 7−1−7.

The maximum forecast period is 4 hours for

SIGMETs and 6 hours for AIRMETs. The

G−AIRMET is issued over the CONUS every 6

hours, valid at 3−hour increments through 12 hours

with optional forecasts possible during the first

6 hours. The first 6 hours of the G−AIRMET

correspond to the 6−hour period of the AIRMET.

SIGMETs and AIRMETs are considered “widespread” because they must be either affecting or be

forecasted to affect an area of at least 3,000 square

miles at any one time. However, if the total area to be

affected during the forecast period is very large, it

could be that in actuality only a small portion of this

total area would be affected at any one time.
AIM 7/26/12

7−1−14 Meteorology

FIG 7−1−6

Alaska Area Forecast Sectors

FIG 7−1−7

Hawaii Area Forecast Locations
7/26/12 AIM

Meteorology 7−1−15

c. SIGMET (WS)

1. A SIGMET advises of nonconvective

weather that is potentially hazardous to all aircraft.

SIGMETs are unscheduled products that are valid for

4 hours. However, conditions that are associated with

hurricanes are valid for 6 hours. Unscheduled updates

and corrections are issued as necessary. In the

conterminous U.S., SIGMETs are issued when the

following phenomena occur or are expected to occur:

(a) Severe icing not associated with thunderstorms.

(b) Severe or extreme turbulence or clear air

turbulence (CAT) not associated with thunderstorms.

(c) Dust storms or sandstorms lowering

surface or inflight visibilities to below 3 miles.

(d) Volcanic ash.

2. In Alaska and Hawaii, SIGMETs are also

issued for:

(a) Tornadoes.

(b) Lines of thunderstorms.

(c) Embedded thunderstorms.

(d) Hail greater than or equal to 3/4 inch in

diameter.

3. SIGMETs are identified by an alphabetic

designator from November through Yankee excluding Sierra and Tango. (Sierra, Tango, and Zulu are

reserved for AIRMET text [WA] products;

G−AIRMETS do not use the Sierra, Tango, or Zulu

designators.) The first issuance of a SIGMET will be

labeled as UWS (Urgent Weather SIGMET).

Subsequent issuances are at the forecaster’s discretion. Issuance for the same phenomenon will be

sequentially numbered, using the original designator

until the phenomenon ends. For example, the first

issuance in the Chicago (CHI) FA area for

phenomenon moving from the Salt Lake City (SLC)

FA area will be SIGMET Papa 3, if the previous two

issuances, Papa 1 and Papa 2, had been in the SLC FA

area. Note that no two different phenomena across the

country can have the same alphabetic designator at

the same time.

EXAMPLE−

Example of a SIGMET:

BOSR WS 050600

SIGMET ROMEO 2 VALID UNTIL 051000

ME NH VT

FROM CAR TO YSJ TO CON TO MPV TO CAR

MOD TO OCNL SEV TURB BLW 080 EXP DUE TO STG

NWLY FLOW. CONDS CONTG BYD

1000Z.

d. Convective SIGMET (WST)

1. Convective SIGMETs are issued in the

conterminous U.S. for any of the following:

(a) Severe thunderstorm due to:

(1) Surface winds greater than or equal to

50 knots.

(2) Hail at the surface greater than or equal

to 3/4 inches in diameter.

(3) Tornadoes.

(b) Embedded thunderstorms.

(c) A line of thunderstorms.

(d) Thunderstorms producing precipitation

greater than or equal to heavy precipitation affecting

40 percent or more of an area at least 3,000 square

miles.

2. Any convective SIGMET implies severe or

greater turbulence, severe icing, and low−level wind

shear. A convective SIGMET may be issued for any

convective situation that the forecaster feels is

hazardous to all categories of aircraft.

3. Convective SIGMET bulletins are issued for

the western (W), central (C), and eastern (E) United

States. (Convective SIGMETs are not issued for

Alaska or Hawaii.) The areas are separated at 87 and

107 degrees west longitude with sufficient overlap to

cover most cases when the phenomenon crosses the

boundaries. Bulletins are issued hourly at H+55.

Special bulletins are issued at any time as required

and updated at H+55. If no criteria meeting

convective SIGMET requirements are observed or

forecasted, the message “CONVECTIVE SIGMET...

NONE” will be issued for each area at H+55.

Individual convective SIGMETs for each area (W, C,

E) are numbered sequentially from number one each

day, beginning at 00Z. A convective SIGMET for a

continuing phenomenon will be reissued every hour

at H+55 with a new number. The text of the bulletin

consists of either an observation and a forecast or just

a forecast. The forecast is valid for up to 2 hours.
AIM 7/26/12

7−1−16 Meteorology

EXAMPLE−

Example of a Convective SIGMET:

MKCC WST 251655

CONVECTIVE SIGMET 54C

VALID UNTIL 1855Z

WI IL

FROM 30E MSN−40ESE DBQ

DMSHG LINE TS 15 NM WIDE MOV FROM 30025KT.

TOPS TO FL450. WIND GUSTS TO 50 KT POSS.

CONVECTIVE SIGMET 55C

VALID UNTIL 1855Z

WI IA

FROM 30NNW MSN−30SSE MCW

DVLPG LINE TS 10 NM WIDE MOV FROM 30015KT.

TOPS TO FL300.

CONVECTIVE SIGMET 56C

VALID UNTIL 1855Z

MT ND SD MN IA MI

LINE TS 15 NM WIDE MOV FROM 27020KT. TOPS TO

FL380.

OUTLOOK VALID 151855−252255

FROM 60NW ISN−INL−TVC−SBN−BRL−FSD−

BIL−60NW ISN

IR STLT IMGRY SHOWS CNVTV CLD TOP TEMPS

OVER SRN WI HAVE BEEN WARMING STEADILY

INDCG A WKNG TREND. THIS ALSO REFLECTED BY

LTST RADAR AND LTNG DATA. WKNG TREND OF

PRESENT LN MAY CONT...HWVR NEW DVLPMT IS

PSBL ALG OUTFLOW BDRY AND/OR OVR NE IA/SW

WI BHD CURRENT ACT.

A SCND TS IS CONTG TO MOV EWD THRU ERN MT

WITH NEW DVLPMT OCRG OVR CNTRL ND. MT ACT

IS MOVG TWD MORE FVRBL AMS OVR THE WRN

DAKS WHERE DWPTS ARE IN THE UPR 60S WITH

LIFTED INDEX VALUES TO MS 6. TS EXPD TO INCR IN

COVERAGE AND INTSTY DURG AFTN HRS.

WST ISSUANCES EXPD TO BE RQRD THRUT AFTN

HRS WITH INCRG PTNTL FOR STGR CELLS TO

CONTAIN LRG HAIL AND PSBLY DMGG SFC WNDS.

e. International SIGMET

1. Some NWS offices have been designated by

the ICAO as Meteorological Watch Offices (MWOs).

These offices are responsible for issuing International

SIGMETs for designated areas that include Alaska,

Hawaii, portions of the Atlantic and Pacific Oceans,

and the Gulf of Mexico.

2. The offices which issue international

SIGMETs are:

(a) The AWC in Kansas City, Missouri.

(b) The AAWU in Anchorage, Alaska.

(c) The WFO in Honolulu, Hawaii.

3. These SIGMETs are considered “widespread” because they must be either affecting or be

forecasted to affect an area of at least 3,000 square

miles at any one time. The International SIGMET is

issued for 6 hours for volcanic ash events, 6 hours for

hurricanes and tropical storms, and 4 hours for all

other events. Like the domestic SIGMETs, international SIGMETs are also identified by an alphabetic

designator from Alpha through Mike and are

numbered sequentially until that weather phenomenon ends. The criteria for an international SIGMET

are:

(a) Thunderstorms occurring in lines, embedded in clouds, or in large areas producing

tornadoes or large hail.

(b) Tropical cyclones.

(c) Severe icing.

(d) Severe or extreme turbulence.

(e) Dust storms and sandstorms lowering

visibilities to less than 3 miles.

(f) Volcanic ash.

EXAMPLE−

Example of an International SIGMET:

WSNT06 KKCI 022014

SIGA0F

KZMA KZNY TJZS SIGMET FOXTROT 3 VALID

022015/030015 KKCI− MIAMI OCEANIC FIR NEW

YORK OCEANIC FIR SAN JUAN FIR FRQ TS WI AREA

BOUNDED BY 2711N6807W 2156N6654W 2220N7040W

2602N7208W 2711N6807W. TOPS TO FL470. MOV NE

15KT. WKN. BASED ON SAT AND LTG OBS.

MOSHER

f. AIRMET

1. AIRMETs (WAs) are advisories of significant weather phenomena but describe conditions at

intensities lower than those which require the

issuance of SIGMETs. AIRMETs are intended for

dissemination to all pilots in the preflight and en route

phase of flight to enhance safety. AIRMET

information is available in two formats: text bulletins

(WA) and graphics (G−AIRMET). Both formats meet

the criteria of paragraph 7−1−3i1 and are issued on a

scheduled basis every 6 hours beginning at

0245 UTC. Unscheduled updates and corrections are

issued as necessary. AIRMETs contain details about
7/26/12 AIM

Meteorology 7−1−17

IFR, extensive mountain obscuration, turbulence,

strong surface winds, icing, and freezing levels.

2. There are three AIRMETs: Sierra, Tango,

and Zulu. After the first issuance each day, scheduled

or unscheduled bulletins are numbered sequentially

for easier identification.

(a) AIRMET Sierra describes IFR conditions

and/or extensive mountain obscurations.

(b) AIRMET Tango describes moderate

turbulence, sustained surface winds of 30 knots or

greater, and/or nonconvective low−level wind shear.

(c) AIRMET Zulu describes moderate icing

and provides freezing level heights.

EXAMPLE−

Example of AIRMET Sierra issued for the Chicago FA

area:

CHIS WA 131445

AIRMET SIERRA UPDT 2 FOR IFR AND MTN OBSCN

VALID UNTIL 132100.

AIRMET IFR...KY 

FROM 20SSW HNN TO HMV TO 50ENE DYR TO20SSW

HNN 

CIG BLW 010/VIS BLW 3SM PCPN/BR/FG. CONDS

ENDG BY 18Z. 

.

AIRMET IFR....MN LS

FROM INL TO 70W YQT TO 40ENE DLH TO 

30WNW DLH TO 50SE GFK TO 20 ENE GFK TO

INL 

CIG BLW 010/VIS BLW 3SM BR. CONDS ENDG 15−

18Z. 

.

AIRMET IFR....KS

FROM 30N SLN TO 60E ICT TO 40S ICT TO 50W

LBL TO 30SSW GLD TO 30N SLN

CIG BLW 010/VIS BLW 3SM PCPN/BR/FG. CONDS

ENDG 15−18Z.

.

AIRMET MTN OBSCN...KY TN

FROM HNN TO HMV TO GQO TO LOZ TO HNN

MTN OBSC BY CLDS/PCPN/BR. CONDS CONTG

BYD 21Z THRU 03Z.

.....

EXAMPLE−

Example of AIRMET Tango issued for the Salt Lake City

FA area:

SLCT WA 131445

AIRMET TANGO UPDT 2 FOR TURB VALID UNTIL

132100.

AIRMET TURB...MT 

FROM 40NW HVR TO 50SE BIL TO 60E DLN TO

60SW YQL TO 40NW HVR

MOD TURB BLW 150. CONDS DVLPG 18−21Z.

CONDS CONTG BYD 21Z THRU 03Z.

.

AIRMET TURB....ID MT WY NV UT CO

FROM 100SE MLS TO 50SSW BFF TO 20SW BTY

TO 40SW BAM TO 100SE MLS

MOD TURB BTN FL310 AND FL410. CONDS

CONTG BYD 21Z ENDG 21−00Z.

.

AIRMET TURB...NV AZ NM CA AND CSTL WTRS

FROM 100WSW ENI TO 40W BTY TO 40S LAS TO

30ESE TBE TO INK TO ELP TO 50S TUS TO BZA

TO 20S MZB TO 150SW PYE TO 100WSW ENI

MOD TURB BTWN FL210 AND FL380. CONDS

CONTG BYD 21Z THRU 03Z.

....

EXAMPLE−

Example of AIRMET Zulu issued for the San Francisco

FA area:

SFOZ WA 131445

AIRMET ZULU UPDT 2 FOR ICE AND FRZLVL VALID

UNTIL 132100.

NO SGFNT ICE EXP OUTSIDE OF CNVTV ACT.

.

FRZLVL....RANGING FROM SFC−105 ACRS AREA

 MULT FRZLVL BLW 080 BOUNDED BY 40SE

 YDC−60NNW GEG−60SW MLP−30WSW BKE−

 20SW BAM−70W BAM−40SW YKM−40E HUH−

 40SE YDC

 SFC ALG 20NNW HUH−30SSE HUH−60S SEA

 50NW LKV−60WNWOAL−30SW OAL

 040 ALG 40W HUH−30W HUH−30NNW SEA−40N

 PDX−20NNW DSD

 080 ALG 160NW FOT−80SW ONP−50SSW EUG

 40SSE OED−50SSE CZQ−60E EHF−40WSW LAS

....

3. Graphical AIRMETs (G−AIRMETs),

found on the Aviation Weather Center webpage at

http://aviationweather.gov, are graphical forecasts of

en−route weather hazards valid at discrete times no

more than 3 hours apart for a period of up to 12 hours

into the future (for example, 00, 03, 06, 09, and 12

hours). Additional forecasts may be inserted during

the first 6 hours (for example, 01, 02, 04, and 05). 00

hour represents the initial conditions, and the

subsequent graphics depict the area affected by the

particular hazard at that valid time. Forecasts valid at

00 through 06 hours correspond to the text AIRMET

bulletin. Forecasts valid at 06 through 12 hours

correspond to the text bulletin outlook. G−AIRMET

depicts the following en route aviation weather

hazards:
AIM 7/26/12

7−1−18 Meteorology

(a) Instrument flight rule conditions (ceiling

< 1000’ and/or surface visibility <3 miles)

(b) Mountain obscuration

(c) Icing

(d) Freezing level

(e) Turbulence

(f) Low level wind shear (LLWS)

(g) Strong surface winds

G−AIRMETs are snap shots at discrete time intervals

as defined above. The text AIRMET is the result of

the production of the G−AIRMET but provided in a

time smear for a 6hr valid period. G−AIRMETs

provide a higher forecast resolution than text

AIRMET products. Since G−AIRMETs and text

AIRMETs are created from the same forecast

“production” process, there exists perfect consistency between the two. Using the two together will

provide clarity of the area impacted by the weather

hazard and improve situational awareness and

decision making.

Interpolation of time periods between G−AIRMET

valid times: Users must keep in mind when using the

G−AIRMET that if a 00 hour forecast shows no

significant weather and a 03 hour forecast shows

hazardous weather, they must assume a change is

occurring during the period between the two

forecasts. It should be taken into consideration that

the hazardous weather starts immediately after the 00

hour forecast unless there is a defined initiation or

ending time for the hazardous weather. The same

would apply after the 03 hour forecast. The user

should assume the hazardous weather condition

is occurring between the snap shots unless informed

otherwise. For example, if a 00 hour forecast shows

no hazard, a 03 hour forecast shows the presence of

hazardous weather, and a 06 hour forecast shows no

hazard, the user should assume the hazard exists from

the 0001 hour to the 0559 hour time period.

EXAMPLE−

See FIG 7−1−8 for an example of the G−AIRMET

graphical product.

g. Severe Weather Watch Bulletins (WWs) and

Alert Messages (AWWs)

1. WWs define areas of possible severe

thunderstorms or tornado activity. The bulletins are

issued by the Storm Prediction Center (SPC) in

Norman, OK. WWs are unscheduled and are issued

as required.

2. A severe thunderstorm watch describes areas

of expected severe thunderstorms. (Severe thunderstorm criteria are 3/4−inch hail or larger and/or wind

gusts of 50 knots [58 mph] or greater.)

3. A tornado watch describes areas where the

threat of tornadoes exists.

4. In order to alert the WFOs, CWSUs, FSSs,

and other users, a preliminary notification of a watch

called the Alert Severe Weather Watch bulletin

(AWW) is sent before the WW. (WFOs know this

product as a SAW).

EXAMPLE−

Example of an AWW:

MKC AWW 011734

WW 75 TORNADO TX OK AR 011800Z−020000Z

AXIS..80 STATUTE MILES EAST AND WEST OF A

LINE..60ESE DAL/DALLAS TX/ − 30 NW ARG/ WALNUT

RIDGE AR/

..AVIATION COORDS.. 70NM E/W /58W GGG − 25NW

ARG/

HAIL SURFACE AND ALOFT..1 3/4 INCHES. WIND

GUSTS..70 KNOTS. MAX TOPS TO 450. MEAN WIND

VECTOR 24045.

5. Soon after the AWW goes out, the actual

watch bulletin itself is issued. A WW is in the

following format:

(a) Type of severe weather watch, watch area,

valid time period, type of severe weather possible,

watch axis, meaning of a watch, and a statement that

persons should be on the lookout for severe weather.

(b) Other watch information; i.e., references

to previous watches.

(c) Phenomena, intensities, hail size, wind

speed (knots), maximum cumulonimbus (CB) tops,

and estimated cell movement (mean wind vector).

(d) Cause of severe weather.

(e) Information on updating Convective

Outlook (AC) products.

EXAMPLE−

Example of a WW:

BULLETIN − IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 381

STORM PREDICTION CENTER NORMAN OK

556 PM CDT MON JUN 2 1997

THE STORM PREDICTON CENTER HAS ISSUED A
7/26/12 AIM

Meteorology 7−1−19

TORNADO WATCH FOR PORTIONS OF NORTHEAST

NEW MEXICO TEXAS PANHANDLE

EFFECTIVE THIS MONDAY NIGHT AND TUESDAY

MORNING FROM 630 PM UNTIL MIDNIGHT CDT.

TORNADOES...HAIL TO 2 3/4 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE

IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 60

STATUTE MILES NORTH AND SOUTH OF A LINE

FROM 50 MILES SOUTHWEST OF RATON NEW

MEXICO TO 50 MILES EAST OF AMARILLO TEXAS.

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES AND

SEVERE THUNDERSTORMS IN AND CLOSE TO THE

WATCH AREA. PERSONS IN THESE AREAS SHOULD

BE ON THE LOOKOUT FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER

STATEMENTS AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...

WW 378...WW 379...WW 380

DISCUSSION...THUNDERSTORMS ARE INCREASING

OVER NE NM IN MOIST SOUTHEASTERLY UPSLOPE

FLOW. OUTFLOW BOUNDARY EXTENDS EASTWARD

INTO THE TEXAS PANHANDLE AND EXPECT STORMS

TO MOVE ESE ALONG AND NORTH OF THE

BOUNDARY ON THE N EDGE OF THE CAP. VEERING

WINDS WITH HEIGHT ALONG WITH INCREASGING

MID LVL FLOW INDICATE A THREAT FOR SUPERCELLS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 2

3/4 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI

WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 28025.

6. Status reports are issued as needed to show

progress of storms and to delineate areas no longer

under the threat of severe storm activity. Cancellation

bulletins are issued when it becomes evident that no

severe weather will develop or that storms have

subsided and are no longer severe.

7. When tornadoes or severe thunderstorms

have developed, the local WFO office will issue the

warnings covering those areas.

h. Center Weather Advisories (CWAs)

1. CWAs are unscheduled inflight, flow control,

air traffic, and air crew advisory. By nature of its short

lead time, the CWA is not a flight planning product.

It is generally a nowcast for conditions beginning

within the next two hours. CWAs will be issued:

(a) As a supplement to an existing SIGMET,

Convective SIGMET or AIRMET.

(b) When an Inflight Advisory has not been

issued but observed or expected weather conditions

meet SIGMET/AIRMET criteria based on current

pilot reports and reinforced by other sources

of information about existing meteorological

conditions.

(c) When observed or developing weather

conditions do not meet SIGMET, Convective

SIGMET, or AIRMET criteria; e.g., in terms of

intensity or area coverage, but current pilot reports or

other weather information sources indicate that

existing or anticipated meteorological phenomena

will adversely affect the safe flow of air traffic within

the ARTCC area of responsibility.

2. The following example is a CWA issued from

the Kansas City, Missouri, ARTCC. The “3” after

ZKC in the first line denotes this CWA has been

issued for the third weather phenomena to occur for

the day. The “301” in the second line denotes the

phenomena number again (3) and the issuance

number (01) for this phenomena. The CWA was

issued at 2140Z and is valid until 2340Z.

EXAMPLE−

ZKC3 CWA 032140

ZKC CWA 301 VALID UNTIL 032340

ISOLD SVR TSTM over KCOU MOVG SWWD

10 KTS ETC.

7−1−7. Categorical Outlooks

a. Categorical outlook terms, describing general

ceiling and visibility conditions for advanced

planning purposes are used only in area forecasts and

are defined as follows:

1. LIFR (Low IFR). Ceiling less than 500 feet

and/or visibility less than 1 mile.

2. IFR. Ceiling 500 to less than 1,000 feet

and/or visibility 1 to less than 3 miles.

3. MVFR (Marginal VFR). Ceiling 1,000 to

3,000 feet and/or visibility 3 to 5 miles inclusive.

4. VFR. Ceiling greater than 3,000 feet and

visibility greater than 5 miles; includes sky clear.

b. The cause of LIFR, IFR, or MVFR is indicated

by either ceiling or visibility restrictions or both. The
AIM 7/26/12

7−1−20 Meteorology

contraction “CIG” and/or weather and obstruction to

vision symbols are used. If winds or gusts of 25 knots

or greater are forecast for the outlook period, the word

“WIND” is also included for all categories including

VFR.

EXAMPLE−

1. LIFR CIG−low IFR due to low ceiling.

2. IFR FG−IFR due to visibility restricted by fog.

3. MVFR CIG HZ FU−marginal VFR due to both ceiling

and visibility restricted by haze and smoke.

4. IFR CIG RA WIND−IFR due to both low ceiling and

visibility restricted by rain; wind expected to be 25 knots or

greater.

7−1−8. Telephone Information Briefing

Service (TIBS)

a. TIBS, provided by FSS, is a system of

automated telephone recordings of meteorological

and aeronautical information available throughout

the United States. Based on the specific needs of each

area, TIBS provides route and/or area briefings in

addition to airspace procedures and special announcements concerning aviation interests that may

be available. Depending on user demand, other items

may be provided; for example, surface weather

observations, terminal forecasts, wind and temperatures aloft forecasts, etc.

b. TIBS is not intended to be a substitute for

specialist−provided preflight briefings from FSS.

TIBS is recommended as a preliminary briefing and

often will be valuable in helping you to make a “go”

or “no go” decision.

c. Pilots are encouraged to utilize TIBS, which can

be accessed by dialing the FSS toll−free telephone

number, 1−800−WX−BRIEF (992−7433) or specific

published TIBS telephone numbers in certain areas.

Consult the “FSS Telephone Numbers” section of the

A/FD or the Alaska or Pacific Chart Supplement

book.

NOTE−

A touch−tone telephone is necessary to fully utilize TIBS.

7−1−9. Transcribed Weather Broadcast

(TWEB) (Alaska Only)

Equipment is provided in Alaska by which

meteorological and aeronautical data are recorded on

tapes and broadcast continuously over selected L/MF

and VOR facilities. Broadcasts are made from a series

of individual tape recordings, and changes, as they

occur, are transcribed onto the tapes. The information

provided varies depending on the type equipment

available. Generally, the broadcast contains a

summary of adverse conditions, surface weather

observations, pilot weather reports, and a density

altitude statement (if applicable). At the discretion of

the broadcast facility, recordings may also include a

synopsis, winds aloft forecast, en route and terminal

forecast data, and radar reports. At selected locations,

telephone access to the TWEB has been provided

(TEL−TWEB). Telephone numbers for this service

are found in the Supplement Alaska A/FD. These

broadcasts are made available primarily for preflight

and inflight planning, and as such, should not be

considered as a substitute for specialist−provided

preflight briefings.

7−1−10. Inflight Weather Broadcasts

a. Weather Advisory Broadcasts. ARTCCs

broadcast a Severe Weather Forecast Alert (AWW),

Convective SIGMET, SIGMET, or CWA alert once

on all frequencies, except emergency, when any part

of the area described is within 150 miles of the

airspace under their jurisdiction. These broadcasts

contain SIGMET or CWA (identification) and a brief

description of the weather activity and general area

affected.

EXAMPLE−

1. Attention all aircraft, SIGMET Delta Three, from Myton

to Tuba City to Milford, severe turbulence and severe clear

icing below one zero thousand feet. Expected to continue

beyond zero three zero zero zulu.

2. Attention all aircraft, convective SIGMET Two Seven

Eastern. From the vicinity of Elmira to Phillipsburg.

Scattered embedded thunderstorms moving east at one

zero knots. A few intense level five cells, maximum tops four

five zero.

3. Attention all aircraft, Kansas City Center weather

advisory one zero three. Numerous reports of moderate to

severe icing from eight to niner thousand feet in a three zero

mile radius of St. Louis. Light or negative icing reported

from four thousand to one two thousand feet remainder of

Kansas City Center area.

NOTE−

1. Terminal control facilities have the option to limit the

AWW, convective SIGMET, SIGMET, or CWA broadcast as

follows: local control and approach control positions may

opt to broadcast SIGMET or CWA alerts only when any
7/26/12 AIM

Meteorology 7−1−21

part of the area described is within 50 miles of the airspace

under their jurisdiction.

2. In areas where HIWAS is available, ARTCC, Terminal

ATC, and FSS facilities no longer broadcast Inflight

Weather Advisories as described above in paragraph a. See

paragraphs b1 and b2 below.

b. Hazardous Inflight Weather Advisory Service (HIWAS). HIWAS is an automated, continuous

broadcast of inflight weather advisories, provided by

FSS over select VOR outlets, which include the

following weather products: AWW, SIGMET,

Convective SIGMET, CWA, AIRMET (text [WA] or

graphical [G−AIRMET] products), and urgent

PIREP. HIWAS is available throughout the conterminous United States as an additional source of

hazardous weather information. HIWAS does not

replace preflight or inflight weather briefings from

FSS or real−time weather updates from Enroute

Flight Advisory Service (EFAS), radio call “Flight

Watch.” Pilots should call FSS or Flight Watch if

there are any questions about weather that is different

than forecasted or if the HIWAS broadcast appears to

be in error.

1. Where HIWAS is available, ARTCC and

terminal ATC facilities will broadcast, upon receipt,

a HIWAS alert once on all frequencies, except

emergency frequencies. Included in the broadcast

will be an alert announcement, frequency instruction,

number, and type of advisory updated; for example,

AWW, SIGMET, Convective SIGMET, or CWA.

EXAMPLE−

Attention all aircraft. Hazardous weather information

(SIGMET, Convective SIGMET, AIRMET (text [WA] or

graphical [G−AIRMET] product), Urgent Pilot

Weather Report [UUA], or Center Weather Advisory

[CWA], Number or Numbers) for (geographical area)

available on HIWAS, Flight Watch, or Flight Service

frequencies.

2. Upon notification of an update to HIWAS,

FSS will broadcast a HIWAS update announcement

once on all frequencies except emergency frequencies. Included in the broadcast will be the type of

advisory updated; for example, AWW, SIGMET,

Convective SIGMET, CWA, etc.

EXAMPLE−

Attention all aircraft. Hazardous weather information for

(geographical area) available from Flight Watch or Flight

Service.

3. HIWAS availability is notated with VOR

listings in the Airport/Facility Directory (A/FD), and

is shown by symbols on IFR Enroute Low Altitude

Charts and VFR Sectional Charts. The symbol

depiction is identified in the chart legend.
AIM 7/26/12

7−1−22 Meteorology

FIG 7−1−8

G−AIRMET Graphical Product
7/26/12 AIM

Meteorology 7−1−23

7−1−11. Flight Information Services (FIS)

a. FIS. Aviation weather and other operational

information may be displayed in the cockpit through

the use of FIS. FIS systems are of two basic types:

Broadcast only systems (called FIS−B) and two−way

request/reply systems. Broadcast system components

include a ground− or space−based transmitter, an

aircraft receiver, and a portable or installed cockpit

display device. Two−way systems utilize transmitter/

receivers at both the ground− or space−based site and

the aircraft.

1. Broadcast FIS (i.e., FIS−B) allows the pilot to

passively collect weather and other operational data

and to display that data at the appropriate time. In

addition to textual weather products such as Aviation

Routine Weather Reports (METARs)/ Aviation

Selected Special Weather Reports (SPECIs) and

Terminal Area Forecasts (TAFs), graphical weather

products such as radar composite/mosaic images,

temporary flight restricted airspace and other

NOTAMs may be provided to the cockpit. Two−way

FIS services permit the pilot to make specific weather

and other operational information requests for

cockpit display. A FIS service provider will then

prepare a reply in response to that specific request and

transmit the product to that specific aircraft.

2. FIS services are available from four types of

service providers:

(a) A private sector FIS provider operating

under service agreement with the FAA using

broadcast data link over VHF aeronautical spectrum

and whose products have been reviewed and accepted

by the FAA prior to transmission. (Products and

services are defined under subparagraph c.)

(b) Through an FAA operated service using a

broadcast data link on the ADS−B UAT network.

(Products and services are defined under subparagraph d.)

(c) Private sector FIS providers operating

under customer contracts using aeronautical spectrum.

(d) Private sector FIS providers operating

under customer contract using methods other than

aeronautical spectrum, including Internet data−to−

the−cockpit service providers.

3. FIS is a method of receiving aviation weather

and other operational data in the cockpit that

augments traditional pilot voice communication with

FAA’s Flight Service Stations (FSSs), ATC facilities,

or Airline Operations Control Centers (AOCCs). FIS

is not intended to replace traditional pilot and

controller/flight service specialist/aircraft dispatcher

pre−flight briefings or inflight voice communications. FIS; however, can provide textual and

graphical background information that can help

abbreviate and improve the usefulness of such

communications. FIS enhances pilot situational

awareness and improves safety.

4. To ensure airman compliance with Federal

Aviation Regulations, manufacturer’s operating

manuals should remind airmen to contact ATC

controllers, FSS specialists, operator dispatchers, or

airline operations control centers for general and

mission critical aviation weather information and/or

NAS status conditions (such as NOTAMs, Special

Use Airspace status, and other government flight

information). If FIS products are systemically

modified (for example, are displayed as abbreviated

plain text and/or graphical depictions), the modification process and limitations of the resultant product

should be clearly described in the vendor’s user

guidance.

b. Operational Use of FIS. Regardless of the

type of FIS system being used, several factors must

be considered when using FIS:

1. Before using FIS for inflight operations,

pilots and other flight crewmembers should become

familiar with the operation of the FIS system to be

used, the airborne equipment to be used, including its

system architecture, airborne system components,

coverage service volume and other limitations of the

particular system, modes of operation and indications

of various system failures. Users should also be

familiar with the specific content and format of the

services available from the FIS provider(s). Sources

of information that may provide this specific

guidance include manufacturer’s manuals, training

programs and reference guides.

2. FIS should not serve as the sole source of

aviation weather and other operational information.

ATC, FSSs and, if applicable, AOCC VHF/HF voice

remain as a redundant method of communicating

aviation weather, NOTAMs, and other operational

information to aircraft in flight. FIS augments these

traditional ATC/FSS/AOCC services and, for some

products, offers the advantage of being displayed as

graphical information. By using FIS for orientation,
AIM 7/26/12

7−1−24 Meteorology

the usefulness of information received from

conventional means may be enhanced. For example,

FIS may alert the pilot to specific areas of concern

that will more accurately focus requests made to FSS

or AOCC for inflight updates or similar queries made

to ATC.

3. The airspace and aeronautical environment is

constantly changing. These changes occur quickly

and without warning. Critical operational decisions

should be based on use of the most current and

appropriate data available. When differences exist

between FIS and information obtained by voice

communication with ATC, FSS, and/or AOCC (if

applicable), pilots are cautioned to use the most

recent data from the most authoritative source.

4. FIS aviation weather products (e.g., graphical

ground−based radar precipitation depictions) are not

appropriate for tactical avoidance of severe weather

such as negotiating a path through a weather hazard

area. FIS supports strategic weather decision making

such as route selection to avoid a weather hazard area

in its entirety. The misuse of information beyond its

applicability may place the pilot and aircraft in

jeopardy. In addition, FIS should never be used in lieu

of an individual pre−flight weather and flight

planning briefing.

5. FIS NOTAM products, including Temporary

Flight Restriction (TFR) information, are advisory−

use information and are intended for situational

awareness purposes only. Cockpit displays of this

information are not appropriate for tactical navigation − pilots should stay clear of any geographic area

displayed as a TFR NOTAM. Pilots should contact

FSSs and/or ATC while en route to obtain updated

information and to verify the cockpit display of

NOTAM information.

6. FIS supports better pilot decision making by

increasing situational awareness. Better decision−

making is based on using information from a variety

of sources. In addition to FIS, pilots should take

advantage of other weather/NAS status sources,

including, briefings from Flight Service Stations,

FAA’s en route “Flight Watch” service, data from

other air traffic control facilities, airline operation

control centers, pilot reports, as well as their own

observations.

c. FAA FISDL (VHF) Service. The FAA’s

FISDL (VHF datalink) system is a VHF Data Link

(VDL) Mode 2 implementation that provides pilots

and flight crews of properly equipped aircraft with a

cockpit display of certain aviation weather and flight

operational information. This information may be

displayed in both textual and graphical formats. The

system is operated under a service agreement with the

FAA, using broadcast data link on VHF aeronautical

spectrum on two 25 KHz spaced frequencies

(136.450 and 136.475 MHz). The FAA FISDL

(VHF) service is designed to provide coverage

throughout the continental U.S. from 5,000 feet AGL

to 17,500 feet MSL, except in areas where this is not

feasible due to mountainous terrain. Aircraft

operating near transmitter sites may receive useable

FISDL signals at altitudes lower than 5,000 feet

AGL, including on the surface in some locations,

depending on transmitter/aircraft line of sight

geometry. Aircraft operating above 17,500 feet MSL

may also receive useable FISDL signals under certain

circumstances.

1. FAA FISDL (VHF) service provides, free of

charge, the following basic text products:

(a) Aviation Routine Weather Reports

(METARs).

(b) Aviation Selected Special Weather

Reports (SPECIs).

(c) Terminal Area Forecasts (TAFs), and their

amendments.

(d) Significant Meteorological Information

(SIGMETs).

(e) Convective SIGMETs.

(f) AIRMET text bulletins (WA).

(g) Pilot Reports (both urgent and routine)

(PIREPs); and,

(h) Severe Weather Forecast Alerts and

Warnings (AWWs/WW) issued by the NOAA Storm

Prediction Center (SPC).

2. The format and coding of these text products

are described in Advisory Circular AC−00−45,

Aviation Weather Services, and paragraph 7−1−30,

Key to Aerodrome Forecast (TAF) and Aviation

Routine Weather Report (METAR).
7/26/12 AIM

Meteorology 7−1−25

3. Additional products, called “Value−Added

Products,” are also available from the vendor on a

paid subscription basis. Details concerning the

content, format, symbology and cost of these

products may be obtained from the vendor.

d. FAA’s Flight Information Service−Broadcast (FIS−B).

1. FIS−B is a ground−based broadcast service

provided through the FAA’s Automatic Dependent

Surveillance – Broadcast (ADS−B) Services Universal Access Transceiver (UAT) network. The service

provides users with a 978 MHz data link capability

when operating within range and line−of−sight of a

transmitting ground station. FIS−B enables users of

properly equipped aircraft to receive and display a

suite of broadcast weather and aeronautical information products. Services are currently available in

specific geographic regions of the U.S. with

NAS−wide service availability planned for 2013.

2. The following list represents the initial suite

of text and graphical products available through

FIS−B and provided free−of−charge. Detailed

information concerning FIS−B meteorological

products can be found in Advisory Circular 00−45,

Aviation Weather Services. Information on Special

Use Airspace (SUA), Temporary Flight Restriction

(TFR) and Notice to Airmen (NOTAM) products can

be found in Chapters 3, 4 and 5 of this manual.

(a) Text: Aviation Routine Weather Report

(METAR) and Special Aviation Report (SPECI);

(b) Text: Pilot Weather Report (PIREP);

(c) Text: Winds and Temperatures Aloft;

(d) Text: Terminal Area Forecast (TAF) and

amendments;

(e) Text: Notice to Airmen (NOTAM)

Distant and Flight Data Center;

(f) Text/Graphic: Airmen’s Meteorological

Conditions (AIRMET);

(g) Text/Graphic: Significant Meteorological Conditions (SIGMET);

(h) Text/Graphic: Convective SIGMET;

(i) Text/Graphic: Special Use Airspace

(SUA);

(j) Text/Graphic: Temporary Flight Restriction (TFR) NOTAM; and

(k) Graphic: NEXRAD Composite Reflectivity Products (Regional and National).

3. Users of FIS−B should familiarize themselves with the operational characteristics and

limitations of the system, including: system architecture; service environment; product lifecycles; modes

of operation; and indications of system failure.

4. FIS−B products are updated and transmitted

at specific intervals based primarily on product

issuance criteria. Update intervals are defined as the

rate at which the product data is available from the

source for transmission. Transmission intervals are

defined as the amount of time within which a new or

updated product transmission must be completed

and/or the rate or repetition interval at which the

product is rebroadcast. Update and transmission

intervals for each product are provided in

TBL 7−1−1.

5. Where applicable, FIS−B products include a

look−ahead range expressed in nautical miles (NM)

for three service domains: Airport Surface; Terminal

Airspace; and En−route/Gulf−of−Mexico

(GOMEX). TBL 7−1−1 provides service domain

availability and look−ahead ranging for each FIS−B

product.

6. Prior to using this capability, users should

familiarize themselves with the operation of FIS−B

avionics by referencing the applicable User’s Guides.

Guidance concerning the interpretation of information displayed should be obtained from the

appropriate avionics manufacturer.

7. FIS−B malfunctions not attributed to aircraft

system failures or covered by active NOTAM should

be reported by radio or telephone to the nearest FSS

facility. Malfunctions may also be reported by

submitting FAA Form 8740−5, Safety Improvement

Report via mail, fax, or email to your local Flight

District Standards Office, Safety Program Manager.
AIM 7/26/12

7−1−26 Meteorology

TBL 7−1−1

Product Update Interval Transmission

Interval

Service Domain and

Look-ahead Range (NM)

AIRMET As Available 5 minutes 100 (Airport Surface),

500 (Terminal, Enroute/

GOMEX)

SIGMET & Convective

SIGMET

As Available, then at 15

minute intervals for 1 hour

5 minutes 100 (Airport Surface),

500 (Terminal, Enroute/

GOMEX)

METAR/SPECI 1 minute (where available), As Available otherwise5 minute 100 (Airport Surface),

500 (Terminal, Enroute/

GOMEX)

NEXRAD Composite

Reflectivity (National)

~5 minutes precipitation

mode

10 minutes for clear air

mode

15 minutes CONUS

NEXRAD Composite

Reflectivity (Regional)

~5 minutes precipitation

mode

10 minutes for clear air

mode

2.5 minutes 250

NOTAM (D) / FDC

(including TFR)

As Available 10 minutes 100

PIREP As Available 10 minutes N/A (Airport Surface),

500 (Terminal, Enroute/

GOMEX)

SUA As Available 10 minutes N/A (Airport Surface),

500 (Terminal, Enroute/

GOMEX)

TAF/AMEND 8 Hours 10 minutes 100 (Airport Surface),

500 (Terminal, Enroute/

GOMEX)

Winds & Temperatures

Aloft

12 Hours 10 minutes 1,000

e. Non−FAA FISDL Systems. Several commercial vendors also provide customers with FIS data

over both the aeronautical spectrum and on other

frequencies using a variety of data link protocols. In

some cases, the vendors provide only the communications system that carries customer messages,

such as the Aircraft Communications Addressing and

Reporting System (ACARS) used by many air carrier

and other operators.

1. Operators using non−FAA FIS data for

inflight weather and other operational information

should ensure that the products used conform to

FAA/NWS standards. Specifically, aviation weather

and NAS status information should meet the

following criteria:
7/26/12 AIM

Meteorology 7−1−27

(a) The products should be either FAA/NWS

“accepted” aviation weather reports or products, or

based on FAA/NWS accepted aviation weather

reports or products. If products are used which do not

meet this criteria, they should be so identified. The

operator must determine the applicability of such

products to their particular flight operations.

(b) In the case of a weather product which is

the result of the application of a process which alters

the form, function or content of the base FAA/NWS

accepted weather product(s), that process, and any

limitations to the application of the resultant product,

should be described in the vendor’s user guidance

material.

2. An example would be a NEXRAD radar

composite/mosaic map, which has been modified by

changing the scaling resolution. The methodology of

assigning reflectivity values to the resultant image

components should be described in the vendor’s

guidance material to ensure that the user can

accurately interpret the displayed data.

7−1−12. Weather Observing Programs

a. Manual Observations. With only a few

exceptions, these reports are from airport locations

staffed by FAA or NWS personnel who manually

observe, perform calculations, and enter these

observations into the (WMSCR) communication

system. The format and coding of these observations

are contained in paragraph 7−1−30, Key to Aviation

Routine Weather Report (METAR) and Aerodrome

Forecasts (TAF).

b. Automated Weather Observing System

(AWOS).

1. Automated weather reporting systems are

increasingly being installed at airports. These

systems consist of various sensors, a processor, a

computer-generated voice subsystem, and a transmitter to broadcast local, minute-by-minute weather data

directly to the pilot.

NOTE−

When the barometric pressure exceeds 31.00 inches Hg.,

see paragraph 7−2−2, Procedures, for the altimeter setting

procedures.

2. The AWOS observations will include the

prefix “AUTO” to indicate that the data are derived

from an automated system. Some AWOS locations

will be augmented by certified observers who will

provide weather and obstruction to vision information in the remarks of the report when the reported

visibility is less than 7 miles. These sites, along with

the hours of augmentation, are to be published in the

A/FD. Augmentation is identified in the observation

as “OBSERVER WEATHER.” The AWOS wind

speed, direction and gusts, temperature, dew point,

and altimeter setting are exactly the same as for

manual observations. The AWOS will also report

density altitude when it exceeds the field elevation by

more than 1,000 feet. The reported visibility is

derived from a sensor near the touchdown of the

primary instrument runway. The visibility sensor

output is converted to a visibility value using a

10−minute harmonic average. The reported sky

condition/ceiling is derived from the ceilometer

located next to the visibility sensor. The AWOS

algorithm integrates the last 30 minutes of ceilometer

data to derive cloud layers and heights. This output

may also differ from the observer sky condition in

that the AWOS is totally dependent upon the cloud

advection over the sensor site.

3. These real-time systems are operationally

classified into nine basic levels:

(a) AWOS−A only reports altimeter setting;

NOTE−

Any other information is advisory only.

(b) AWOS−AV reports altimeter and

visibility;

NOTE−

Any other information is advisory only.

(c) AWOS−l usually reports altimeter setting,

wind data, temperature, dew point, and density

altitude;

(d) AWOS−2 provides the information provided by AWOS−l plus visibility; and

(e) AWOS−3 provides the information provided by AWOS−2 plus cloud/ceiling data.

(f) AWOS− 3P provides reports the same as

the AWOS 3 system, plus a precipitation identification sensor.

(g) AWOS− 3PT reports the same as the

AWOS 3P System, plus thunderstorm/lightning

reporting capability.
AIM 7/26/12

7−1−28 Meteorology

(h) AWOS− 3T reports the same as AWOS 3

system and includes a thunderstorm/lightning

reporting capability.

(i) AWOS− 4 reports the same as the AWOS

3 system, plus precipitation occurrence, type and

accumulation, freezing rain, thunderstorm, and

runway surface sensors.

4. The information is transmitted over a discrete

VHF radio frequency or the voice portion of a local

NAVAID. AWOS transmissions on a discrete VHF

radio frequency are engineered to be receivable to a

maximum of 25 NM from the AWOS site and a

maximum altitude of 10,000 feet AGL. At many

locations, AWOS signals may be received on the

surface of the airport, but local conditions may limit

the maximum AWOS reception distance and/or

altitude. The system transmits a 20 to 30 second

weather message updated each minute. Pilots should

monitor the designated frequency for the automated

weather broadcast. A description of the broadcast is

contained in subparagraph c. There is no two-way

communication capability. Most AWOS sites also

have a dial-up capability so that the minute-by-minute weather messages can be accessed via telephone.

5. AWOS information (system level, frequency,

phone number, etc.) concerning specific locations is

published, as the systems become operational, in the

A/FD, and where applicable, on published Instrument Approach Procedures. Selected individual

systems may be incorporated into nationwide data

collection and dissemination networks in the future.

c. AWOS Broadcasts. Computer-generated

voice is used in AWOS to automate the broadcast of

the minute-by-minute weather observations. In

addition, some systems are configured to permit the

addition of an operator-generated voice message;

e.g., weather remarks following the automated

parameters. The phraseology used generally follows

that used for other weather broadcasts. Following are

explanations and examples of the exceptions.

1. Location and Time. The location/name and

the phrase “AUTOMATED WEATHER OBSERVATION,” followed by the time are announced.

(a) If the airport’s specific location is

included in the airport’s name, the airport’s name is

announced.

EXAMPLE−

“Bremerton National Airport automated weather observation, one four five six zulu;”

“Ravenswood Jackson County Airport automated weather

observation, one four five six zulu.”

(b) If the airport’s specific location is not

included in the airport’s name, the location is

announced followed by the airport’s name.

EXAMPLE−

“Sault Ste. Marie, Chippewa County International Airport

automated weather observation;”

“Sandusky, Cowley Field automated weather

observation.”

(c) The word “TEST” is added following

“OBSERVATION” when the system is not in

commissioned status.

EXAMPLE−

“Bremerton National Airport automated weather observation test, one four five six zulu.”

(d) The phrase “TEMPORARILY INOPERATIVE” is added when the system is inoperative.

EXAMPLE−

“Bremerton National Airport automated weather observing system temporarily inoperative.”

2. Visibility.

(a) The lowest reportable visibility value in

AWOS is “less than 1/4.” It is announced as

“VISIBILITY LESS THAN ONE QUARTER.”

(b) A sensor for determining visibility is not

included in some AWOS. In these systems, visibility

is not announced. “VISIBILITY MISSING” is

announced only if the system is configured with a

visibility sensor and visibility information is not

available.

3. Weather. In the future, some AWOSs are to

be configured to determine the occurrence of

precipitation. However, the type and intensity may

not always be determined. In these systems, the word

“PRECIPITATION” will be announced if precipitation is occurring, but the type and intensity are not

determined.

4. Ceiling and Sky Cover.

(a) Ceiling is announced as either “CEILING” or “INDEFINITE CEILING.” With the

exception of indefinite ceilings, all automated ceiling

heights are measured.
7/26/12 AIM

Meteorology 7−1−29

EXAMPLE−

“Bremerton National Airport automated weather observation, one four five six zulu. Ceiling two thousand overcast;”

“Bremerton National Airport automated weather observation, one four five six zulu. Indefinite ceiling two hundred,

sky obscured.”

(b) The word “Clear” is not used in AWOS

due to limitations in the height ranges of the sensors.

No clouds detected is announced as “NO CLOUDS

BELOW XXX” or, in newer systems as “CLEAR

BELOW XXX” (where XXX is the range limit of the

sensor).

EXAMPLE−

“No clouds below one two thousand.”

“Clear below one two thousand.”

(c) A sensor for determining ceiling and sky

cover is not included in some AWOS. In these

systems, ceiling and sky cover are not announced.

“SKY CONDITION MISSING” is announced only if

the system is configured with a ceilometer and the

ceiling and sky cover information is not available.

5. Remarks. If remarks are included in the

observation, the word “REMARKS” is announced

following the altimeter setting.

(a) Automated “Remarks.”

(1) Density Altitude.

(2) Variable Visibility.

(3) Variable Wind Direction.

(b) Manual Input Remarks. Manual input

remarks are prefaced with the phrase “OBSERVER

WEATHER.” As a general rule the manual remarks

are limited to:

(1) Type and intensity of precipitation.

(2) Thunderstorms and direction; and

(3) Obstructions to vision when the visibility is 3 miles or less.

EXAMPLE−

“Remarks ... density altitude, two thousand five hundred ...

visibility variable between one and two ... wind direction

variable between two four zero and three one zero

...observed weather ... thunderstorm moderate rain

showers and fog ... thunderstorm overhead.”

(c) If an automated parameter is “missing”

and no manual input for that parameter is available,

the parameter is announced as “MISSING.” For

example, a report with the dew point “missing” and

no manual input available, would be announced as

follows:

EXAMPLE−

“Ceiling one thousand overcast ... visibility three ...

precipitation ... temperature three zero, dew point missing

... wind calm ... altimeter three zero zero one.”

(d) “REMARKS” are announced in the

following order of priority:

(1) Automated “REMARKS.”

[a] Density Altitude.

[b] Variable Visibility.

[c] Variable Wind Direction.

(2) Manual Input “REMARKS.”

[a] Sky Condition.

[b] Visibility.

[c] Weather and Obstructions to Vision.

[d] Temperature.

[e] Dew Point.

[f] Wind; and

[g] Altimeter Setting.

EXAMPLE−

“Remarks ... density altitude, two thousand five hundred ...

visibility variable between one and two ... wind direction

variable between two four zero and three one zero ...

observer ceiling estimated two thousand broken ...

observer temperature two, dew point minus five.”

d. Automated Surface Observing System

(ASOS)/Automated Weather Sensor System

(AWSS). The ASOS/AWSS is the primary surface

weather observing system of the U.S. (See Key to

Decode an ASOS/AWSS (METAR) Observation,

FIG 7−1−9 and FIG 7−1−10.) The program to install

and operate these systems throughout the U.S. is a

joint effort of the NWS, the FAA and the Department

of Defense. AWSS is a follow−on program that

provides identical data as ASOS. ASOS/AWSS is

designed to support aviation operations and weather

forecast activities. The ASOS/AWSS will provide

continuous minute-by-minute observations and

perform the basic observing functions necessary to

generate an aviation routine weather report (METAR) and other aviation weather information. The

information may be transmitted over a discrete VHF

radio frequency or the voice portion of a local
AIM 7/26/12

7−1−30 Meteorology

NAVAID. ASOS/AWSS transmissions on a discrete

VHF radio frequency are engineered to be receivable

to a maximum of 25 NM from the ASOS/AWSS site

and a maximum altitude of 10,000 feet AGL. At many

locations, ASOS/AWSS signals may be received on

the surface of the airport, but local conditions may

limit the maximum reception distance and/or altitude.

While the automated system and the human may

differ in their methods of data collection and

interpretation, both produce an observation quite

similar in form and content. For the “objective”

elements such as pressure, ambient temperature, dew

point temperature, wind, and precipitation accumulation, both the automated system and the observer use

a fixed location and time-averaging technique. The

quantitative differences between the observer and the

automated observation of these elements are

negligible. For the “subjective” elements, however,

observers use a fixed time, spatial averaging

technique to describe the visual elements (sky

condition, visibility and present weather), while the

automated systems use a fixed location, time

averaging technique. Although this is a fundamental

change, the manual and automated techniques yield

remarkably similar results within the limits of their

respective capabilities.

1. System Description.

(a) The ASOS/AWSS at each airport location

consists of four main components:

(1) Individual weather sensors.

(2) Data collection and processing units.

(3) Peripherals and displays.

(b) The ASOS/AWSS sensors perform the

basic function of data acquisition. They continuously

sample and measure the ambient environment, derive

raw sensor data and make them available to the

collection and processing units.

2. Every ASOS/AWSS will contain the

following basic set of sensors:

(a) Cloud height indicator (one or possibly

three).

(b) Visibility sensor (one or possibly three).

(c) Precipitation identification sensor.

(d) Freezing rain sensor (at select sites).

(e) Pressure sensors (two sensors at small

airports; three sensors at large airports).

(f) Ambient temperature/Dew point temperature sensor.

(g) Anemometer (wind direction and speed

sensor).

(h) Rainfall accumulation sensor.

3. The ASOS/AWSS data outlets include:

(a) Those necessary for on-site airport users.

(b) National communications networks.

(c) Computer-generated voice (available

through FAA radio broadcast to pilots, and dial-in

telephone line).

NOTE−

Wind direction broadcast over FAA radios is in reference

to magnetic north.

4. An ASOS/AWOS/AWSS report without

human intervention will contain only that weather

data capable of being reported automatically. The

modifier for this METAR report is “AUTO.” When

an observer augments or backs−up an ASOS/AWOS/

AWSS site, the “AUTO” modifier disappears.

5. There are two types of automated stations,

AO1 for automated weather reporting stations

without a precipitation discriminator, and AO2 for

automated stations with a precipitation discriminator.

As appropriate, “AO1” and “AO2” must appear in

remarks. (A precipitation discriminator can determine the difference between liquid and

frozen/freezing precipitation).

NOTE−

To decode an ASOS/AWSS report, refer to FIG 7−1−9 and

FIG 7−1−10.

REFERENCE−

A complete explanation of METAR terminology is located in AIM,

Paragraph 7−1−30, Key to Aerodrome Forecast (TAF) and Aviation

Routine Weather Report (METAR).
7/26/12 AIM

Meteorology 7−1−31

FIG 7−1−9

Key to Decode an ASOS/AWSS (METAR) Observation (Front)
AIM 7/26/12

7−1−32 Meteorology

FIG 7−1−10

Key to Decode an ASOS/AWSS (METAR) Observation (Back)
7/26/12 AIM

Meteorology 7−1−33

e. TBL 7−1−2 contains a comparison of weather

observing programs and the elements reported.

f. Service Standards. During 1995, a government/industry team worked to comprehensively

reassess the requirements for surface observations at

the nation’s airports. That work resulted in agreement

on a set of service standards, and the FAA and NWS

ASOS sites to which the standards would apply. The

term “Service Standards” refers to the level of detail

in weather observation. The service standards consist

of four different levels of service (A, B, C, and D) as

described below. Specific observational elements

included in each service level are listed in

TBL 7−1−3.

1. Service Level D defines the minimum

acceptable level of service. It is a completely

automated service in which the ASOS/AWSS

observation will constitute the entire observation,

i.e., no additional weather information is added by a

human observer. This service is referred to as a stand

alone D site.

2. Service Level C is a service in which the

human observer, usually an air traffic controller,

augments or adds information to the automated

observation. Service Level C also includes backup of

ASOS/AWSS elements in the event of an ASOS/

AWSS malfunction or an unrepresentative

ASOS/AWSS report. In backup, the human observer

inserts the correct or missing value for the automated

ASOS/AWSS elements. This service is provided by

air traffic controllers under the Limited Aviation

Weather Reporting Station (LAWRS) process, FSS

and NWS observers, and, at selected sites,

Non−Federal Observation Program observers.

Two categories of airports require detail beyond

Service Level C in order to enhance air traffic control

efficiency and increase system capacity. Services at

these airports are typically provided by contract

weather observers, NWS observers, and, at some

locations, FSS observers.

3. Service Level B is a service in which weather

observations consist of all elements provided under

Service Level C, plus augmentation of additional data

beyond the capability of the ASOS/AWSS. This

category of airports includes smaller hubs or special

airports in other ways that have worse than average

bad weather operations for thunderstorms and/or

freezing/frozen precipitation, and/or that are remote

airports.

4. Service Level A, the highest and most

demanding category, includes all the data reported in

Service Standard B, plus additional requirements as

specified. Service Level A covers major aviation

hubs and/or high volume traffic airports with average

or worse weather.

TBL 7−1−2

Weather Observing Programs

ElementReportedWind

Visibility

TemperatureDew Point

Altimeter

Density 

Altimeter

Cloud/Ceiling

PrecipitationIdentification

Thunderstorm/

Lightning

PrecipitationOccurrence

Rainfall

Accumulation

Runway Surface

Condition

Freezing Rain

Occurrence

Remarks

Type

AWSS X X X X X X X X X X

ASOS X X X X X X X X X X

AWOS−A X

AWOS−A/V X X

AWOS−1 X X X X

AWOS−2 X X X X X

AWOS−3 X X X X X X

AWOS−3P X X X X X X X

AWOS−3T X X X X X X X

AWOS−3P/T X X X X X X X X

AWOS−4 X X X X X X X X X X X X

Manual X X X X X X X

REFERENCE− FAA Order 7900.5B, Surface Weather Observing, for element reporting.
AIM 7/26/12

7−1−34 Meteorology

TBL 7−1−3

SERVICE LEVEL A

Service Level A consists of all the elements of

Service Levels B, C and D plus the elements

listed to the right, if observed.

10 minute longline RVR at precedented sites or

additional visibility increments of 1/8, 1/16 and 0

Sector visibility

Variable sky condition

Cloud layers above 12,000 feet and cloud types

Widespread dust, sand and other obscurations

Volcanic eruptions

SERVICE LEVEL B

Service Level B consists of all the elements of

Service Levels C and D plus the elements listed to

the right, if observed.

Longline RVR at precedented sites

(may be instantaneous readout)

Freezing drizzle versus freezing rain

Ice pellets

Snow depth & snow increasing rapidly remarks

Thunderstorm and lightning location remarks

Observed significant weather not at the station

remarks

SERVICE LEVEL C

Service Level C consists of all the elements of Service

Level D plus augmentation and backup by a human

observer or an air traffic control specialist on location

nearby. Backup consists of inserting the correct value if

the system malfunctions or is unrepresentative.

Augmentation consists of adding the elements listed to

the right, if observed. During hours that the observing

facility is closed, the site reverts to Service Level D.

Thunderstorms

Tornadoes

Hail

Virga

Volcanic ash

Tower visibility

Operationally significant remarks as deemed

appropriate by the observer

SERVICE LEVEL D

This level of service consists of an ASOS or AWSS

continually measuring the atmosphere at a point near the

runway. The ASOS or AWSS senses and measures the

weather parameters listed to the right.

Wind

Visibility

Precipitation/Obstruction to vision

Cloud height

Sky cover

Temperature

Dew point

Altimeter

7−1−13. Weather Radar Services

a. The National Weather Service operates a

network of radar sites for detecting coverage,

intensity, and movement of precipitation. The

network is supplemented by FAA and DOD radar

sites in the western sections of the country. Local

warning radar sites augment the network by operating

on an as needed basis to support warning and forecast

programs.

b. Scheduled radar observations are taken hourly

and transmitted in alpha-numeric format on weather

telecommunications circuits for flight planning

purposes. Under certain conditions, special radar

reports are issued in addition to the hourly

transmittals. Data contained in the reports are also

collected by the National Center for Environmental

Prediction and used to prepare national radar

summary charts for dissemination on facsimile

circuits.

c. A clear radar display (no echoes) does not mean

that there is no significant weather within the

coverage of the radar site. Clouds and fog are not

detected by the radar. However, when echoes are

present, turbulence can be implied by the intensity of

the precipitation, and icing is implied by the presence

of the precipitation at temperatures at or below zero

degrees Celsius. Used in conjunction with other

weather products, radar provides invaluable information for weather avoidance and flight planning.
7/26/12 AIM

Meteorology 7−1−35

FIG 7−1−11

NEXRAD Coverage
AIM 7/26/12

7−1−36 Meteorology

FIG 7−1−12

NEXRAD Coverage
7/26/12 AIM

Meteorology 7−1−37

FIG 7−1−13

NEXRAD Coverage
AIM 7/26/12

7−1−38 Meteorology

d. All En Route Flight Advisory Service facilities

and FSSs have equipment to directly access the radar

displays from the individual weather radar sites.

Specialists at these locations are trained to interpret

the display for pilot briefing and inflight advisory

services. The Center Weather Service Units located in

ARTCCs also have access to weather radar displays

and provide support to all air traffic facilities within

their center’s area.

e. Additional information on weather radar

products and services can be found in AC 00−45,

Aviation Weather Services.

REFERENCE−

Pilot/Controller Glossary Term− Precipitation Radar Weather

Descriptions.

AIM, Thunderstorms, Paragraph 7−1−28.

A/FD, Charts, NWS Upper Air Observing Stations and Weather Network

for the location of specific radar sites.

7−1−14. ATC Inflight Weather Avoidance

Assistance

a. ATC Radar Weather Display.

1. ATC radars are able to display areas of

precipitation by sending out a beam of radio energy

that is reflected back to the radar antenna when it

strikes an object or moisture which may be in the form

of rain drops, hail, or snow. The larger the object is,

or the more dense its reflective surface, the stronger

the return will be presented. Radar weather

processors indicate the intensity of reflective returns

in terms of decibels (dBZ). ATC systems cannot

detect the presence or absence of clouds. The ATC

systems can often determine the intensity of a

precipitation area, but the specific character of that

area (snow, rain, hail, VIRGA, etc.) cannot be

determined. For this reason, ATC refers to all

weather areas displayed on ATC radar scopes as

“precipitation.”

2. All ATC facilities using radar weather

processors with the ability to determine precipitation

intensity, will describe the intensity to pilots as:

(a) “LIGHT” (< 30 dBZ)

(b) “MODERATE” (30 to 40 dBZ)

(c) “HEAVY” (> 40 to 50 dBZ)

(d) “EXTREME” (> 50 dBZ)

3. ATC facilities that, due to equipment

limitations, cannot display the intensity levels of

precipitation, will describe the location of the

precipitation area by geographic position, or position

relative to the aircraft. Since the intensity level is not

available, the controller will state “INTENSITY

UNKNOWN.”

4. ARTCC facilities normally use a Weather and

Radar Processor (WARP) to display a mosaic of data

obtained from multiple NEXRAD sites. There is a

time delay between actual conditions and those

displayed to the controller. For example, the

precipitation data on the ARTCC controller’s display

could be up to 6 minutes old. When the WARP is not

available, a second system, the narrowband Air Route

Surveillance Radar (ARSR) can display two distinct

levels of precipitation intensity that will be described

to pilots as “MODERATE” (30 to 40 dBZ) and

“HEAVY TO EXTREME” ( > 40 dBZ ). The WARP

processor is only used in ARTCC facilities.

5. ATC radar is not able to detect turbulence.

Generally, turbulence can be expected to occur as the

rate of rainfall or intensity of precipitation increases.

Turbulence associated with greater rates of rainfall/

precipitation will normally be more severe than any

associated with lesser rates of rainfall/precipitation.

Turbulence should be expected to occur near

convective activity, even in clear air. Thunderstorms

are a form of convective activity that imply severe or

greater turbulence. Operation within 20 miles of

thunderstorms should be approached with great

caution, as the severity of turbulence can be markedly

greater than the precipitation intensity might indicate.

b. Weather Avoidance Assistance.

1. To the extent possible, controllers will issue

pertinent information on weather or chaff areas and

assist pilots in avoiding such areas when requested.

Pilots should respond to a weather advisory by either

acknowledging the advisory or by acknowledging the

advisory and requesting an alternative course of

action as follows:

(a) Request to deviate off course by stating

the number of miles and the direction of the requested

deviation. In this case, when the requested deviation

is approved, navigation is at the pilot’s prerogative,

but must maintain the altitude assigned by ATC and

to remain within the specified mileage of the original

course.

(b) Request a new route to avoid the affected

area.

(c) Request a change of altitude.
7/26/12 AIM

Meteorology 7−1−39

(d) Request radar vectors around the affected

areas.

2. For obvious reasons of safety, an IFR pilot

must not deviate from the course or altitude or flight

level without a proper ATC clearance. When weather

conditions encountered are so severe that an

immediate deviation is determined to be necessary

and time will not permit approval by ATC, the pilot’s

emergency authority may be exercised.

3. When the pilot requests clearance for a route

deviation or for an ATC radar vector, the controller

must evaluate the air traffic picture in the affected

area, and coordinate with other controllers (if ATC

jurisdictional boundaries may be crossed) before

replying to the request.

4. It should be remembered that the controller’s

primary function is to provide safe separation

between aircraft. Any additional service, such as

weather avoidance assistance, can only be provided

to the extent that it does not derogate the primary

function. It’s also worth noting that the separation

workload is generally greater than normal when

weather disrupts the usual flow of traffic. ATC radar

limitations and frequency congestion may also be a

factor in limiting the controller’s capability to

provide additional service.

5. It is very important, therefore, that the request

for deviation or radar vector be forwarded to ATC as

far in advance as possible. Delay in submitting it may

delay or even preclude ATC approval or require that

additional restrictions be placed on the clearance.

Insofar as possible the following information should

be furnished to ATC when requesting clearance to

detour around weather activity:

(a) Proposed point where detour will

commence.

(b) Proposed route and extent of detour

(direction and distance).

(c) Point where original route will be

resumed.

(d) Flight conditions (IFR or VFR).

(e) Any further deviation that may become

necessary as the flight progresses.

(f) Advise if the aircraft is equipped with

functioning airborne radar.

6. To a large degree, the assistance that might be

rendered by ATC will depend upon the weather

information available to controllers. Due to the

extremely transitory nature of severe weather

situations, the controller’s weather information may

be of only limited value if based on weather observed

on radar only. Frequent updates by pilots giving

specific information as to the area affected, altitudes,

intensity and nature of the severe weather can be of

considerable value. Such reports are relayed by radio

or phone to other pilots and controllers and also

receive widespread teletypewriter dissemination.

7. Obtaining IFR clearance or an ATC radar

vector to circumnavigate severe weather can often be

accommodated more readily in the en route areas

away from terminals because there is usually less

congestion and, therefore, offer greater freedom of

action. In terminal areas, the problem is more acute

because of traffic density, ATC coordination

requirements, complex departure and arrival routes,

adjacent airports, etc. As a consequence, controllers

are less likely to be able to accommodate all requests

for weather detours in a terminal area or be in a

position to volunteer such routing to the pilot.

Nevertheless, pilots should not hesitate to advise

controllers of any observed severe weather and

should specifically advise controllers if they desire

circumnavigation of observed weather.

c. Procedures for Weather Deviations and

Other Contingencies in Oceanic Controlled

Airspace.

1. When the pilot initiates communications with

ATC, rapid response may be obtained by stating

“WEATHER DEVIATION REQUIRED” to indicate

priority is desired on the frequency and for ATC

response.

2. The pilot still retains the option of initiating

the communications using the urgency call “PAN−

PAN” 3 times to alert all listening parties of a special

handling condition which will receive ATC priority

for issuance of a clearance or assistance.

3. ATC will:

(a) Approve the deviation.

(b) Provide vertical separation and then

approve the deviation; or

(c) If ATC is unable to establish vertical

separation, ATC must advise the pilot that standard

separation cannot be applied; provide essential traffic
AIM 7/26/12

7−1−40 Meteorology

information for all affected aircraft, to the extent

practicable; and if possible, suggest a course of

action. ATC may suggest that the pilot climb or

descend to a contingency altitude (1,000 feet above or

below that assigned if operating above FL 290;

500 feet above or below that assigned if operating at

or below FL 290).

PHRASEOLOGY−

STANDARD SEPARATION NOT AVAILABLE, DEVIATE

AT PILOT’S DISCRETION; SUGGEST CLIMB (or

descent) TO (appropriate altitude); TRAFFIC (position

and altitude); REPORT DEVIATION COMPLETE.

4. The pilot will follow the ATC advisory

altitude when approximately 10 NM from track as

well as execute the procedures detailed in paragraph 7−1−14c5.

5. If contact cannot be established or revised

ATC clearance or advisory is not available and

deviation from track is required, the pilot must take

the following actions:

(a) If possible, deviate away from an

organized track or route system.

(b) Broadcast aircraft position and intentions

on the frequency in use, as well as on frequency

121.5 MHz at suitable intervals stating: flight

identification (operator call sign), flight level, track

code or ATS route designator, and extent of deviation

expected.

(c) Watch for conflicting traffic both visually

and by reference to TCAS (if equipped).

(d) Turn on aircraft exterior lights.

(e) Deviations of less than 10 NM or

operations within COMPOSITE (NOPAC and

CEPAC) Airspace, should REMAIN at ASSIGNED

altitude. Otherwise, when the aircraft is approximately 10 NM from track, initiate an altitude change based

on the following criteria:

TBL 7−1−4

Route

 Centerline/Track

Deviations

>10 NM

Altitude Change

East

000 − 179M

Left

Right

Descend 300 Feet

Climb 300 Feet

West

180−359M

Left

Right

Climb 300 Feet

Descend 300 Feet

Pilot Memory Slogan: “East right up, 

West right down.”

(f) When returning to track, be at assigned

flight level when the aircraft is within approximately

10 NM of centerline.

(g) If contact was not established prior to

deviating, continue to attempt to contact ATC to

obtain a clearance. If contact was established,

continue to keep ATC advised of intentions and

obtain essential traffic information.

7−1−15. Runway Visual Range (RVR)

There are currently two configurations of RVR in the

NAS commonly identified as Taskers and New

Generation RVR. The Taskers are the existing

configuration which uses transmissometer technology. The New Generation RVRs were deployed in

November 1994 and use forward scatter technology.

The New Generation RVRs are currently being

deployed in the NAS to replace the existing Taskers.

a. RVR values are measured by transmissometers

mounted on 14−foot towers along the runway. A full

RVR system consists of:

1. Transmissometer projector and related items.

2. Transmissometer receiver (detector) and

related items.

3. Analog

4. recorder.

5. Signal data converter and related items.

6. Remote digital or remote display programmer.

b. The transmissometer projector and receiver are

mounted on towers 250 feet apart. A known intensity

of light is emitted from the projector and is measured
7/26/12 AIM

Meteorology 7−1−41

by the receiver. Any obscuring matter such as rain,

snow, dust, fog, haze or smoke reduces the light

intensity arriving at the receiver. The resultant

intensity measurement is then converted to an RVR

value by the signal data converter. These values are

displayed by readout equipment in the associated air

traffic facility and updated approximately once every

minute for controller issuance to pilots.

c. The signal data converter receives information

on the high intensity runway edge light setting in use

(step 3, 4, or 5); transmission values from the

transmissometer and the sensing of day or night

conditions. From the three data sources, the system

will compute appropriate RVR values.

d. An RVR transmissometer established on a

250 foot baseline provides digital readouts to a

minimum of 600 feet, which are displayed in 200 foot

increments to 3,000 feet and in 500 foot increments

from 3,000 feet to a maximum value of 6,000 feet.

e. RVR values for Category IIIa operations extend

down to 700 feet RVR; however, only 600 and

800 feet are reportable RVR increments. The

800 RVR reportable value covers a range of 701 feet

to 900 feet and is therefore a valid minimum

indication of Category IIIa operations.

f. Approach categories with the corresponding

minimum RVR values. (See TBL 7−1−5.)

TBL 7−1−5

Approach Category/Minimum RVR Table

Category Visibility (RVR)

Nonprecision 2,400 feet

Category I 1,800 feet*

Category II 1,000 feet

Category IIIa 700 feet

Category IIIb 150 feet

Category IIIc 0 feet

* 1,400 feet with special equipment and authorization

g. Ten minute maximum and minimum RVR

values for the designated RVR runway are reported in

the body of the aviation weather report when the

prevailing visibility is less than one mile and/or the

RVR is 6,000 feet or less. ATCTs report RVR when

the prevailing visibility is 1 mile or less and/or the

RVR is 6,000 feet or less.

h. Details on the requirements for the operational

use of RVR are contained in FAA AC 97−1, “Runway

Visual Range (RVR).” Pilots are responsible for

compliance with minimums prescribed for their class

of operations in the appropriate CFRs and/or

operations specifications.

i. RVR values are also measured by forward

scatter meters mounted on 14−foot frangible

fiberglass poles. A full RVR system consists of:

1. Forward scatter meter with a transmitter,

receiver and associated items.

2. A runway light intensity monitor (RLIM).

3. An ambient light sensor (ALS).

4. A data processor unit (DPU).

5. Controller display (CD).

j. The forward scatter meter is mounted on a

14−foot frangible pole. Infrared light is emitted from

the transmitter and received by the receiver. Any

obscuring matter such as rain, snow, dust, fog, haze

or smoke increases the amount of scattered light

reaching the receiver. The resulting measurement

along with inputs from the runway light intensity

monitor and the ambient light sensor are forwarded to

the DPU which calculates the proper RVR value. The

RVR values are displayed locally and remotely on

controller displays.

k. The runway light intensity monitors both the

runway edge and centerline light step settings (steps 1

through 5). Centerline light step settings are used for

CAT IIIb operations. Edge Light step settings are

used for CAT I, II, and IIIa operations.

l. New Generation RVRs can measure and display

RVR values down to the lowest limits of

Category IIIb operations (150 feet RVR). RVR

values are displayed in 100 feet increments and are

reported as follows:

1. 100−feet increments for products below

800 feet.

2. 200−feet increments for products between

800 feet and 3,000 feet.

3. 500−feet increments for products between

3,000 feet and 6,500 feet.

4. 25−meter increments for products below

150 meters.

5. 50−meter increments for products between

150 meters and 800 meters.
AIM 7/26/12

7−1−42 Meteorology

6. 100−meter increments for products between

800 meters and 1,200 meters.

7. 200−meter increments for products between

1,200 meters and 2,000 meters.

7−1−16. Reporting of Cloud Heights

a. Ceiling, by definition in the CFRs and as used

in aviation weather reports and forecasts, is the height

above ground (or water) level of the lowest layer of

clouds or obscuring phenomenon that is reported as

“broken,” “overcast,” or “obscuration,” e.g., an

aerodrome forecast (TAF) which reads “BKN030”

refers to height above ground level. An area forecast

which reads “BKN030” indicates that the height is

above mean sea level.

REFERENCE−

AIM, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather

Report (METAR), Paragraph 7−1−30, defines “broken,” “overcast,” and

“obscuration.”

b. Pilots usually report height values above MSL,

since they determine heights by the altimeter. This is

taken in account when disseminating and otherwise

applying information received from pilots. (“Ceiling” heights are always above ground level.) In

reports disseminated as PIREPs, height references

are given the same as received from pilots, that is,

above MSL.

c. In area forecasts or inflight advisories, ceilings

are denoted by the contraction “CIG” when used with

sky cover symbols as in “LWRG TO CIG OVC005,”

or the contraction “AGL” after, the forecast cloud

height value. When the cloud base is given in height

above MSL, it is so indicated by the contraction

“MSL” or “ASL” following the height value. The

heights of clouds tops, freezing level, icing, and

turbulence are always given in heights above ASL or

MSL.

7−1−17. Reporting Prevailing Visibility

a. Surface (horizontal) visibility is reported in

METAR reports in terms of statute miles and

increments thereof; e.g., 1/16, 1/8, 3/16, 1/4, 5/16, 3/8, 1/2, 5/8, 3/4, 7/8, 1, 1 1/8, etc. (Visibility reported by an

unaugmented automated site is reported differently

than in a manual report, i.e., ASOS/AWSS: 0, 1/16, 1/8, 1/4, 1/2, 3/4, 1, 1 1/4, 1 1/2, 1 3/4, 2, 2 1/2, 3, 4, 5, etc., AWOS:

M1/4, 1/4, 1/2, 3/4, 1, 1 1/4, 1 1/2, 1 3/4, 2, 2 1/2, 3, 4, 5, etc.)

Visibility is determined through the ability to see and

identify preselected and prominent objects at a

known distance from the usual point of observation.

Visibilities which are determined to be less than

7 miles, identify the obscuring atmospheric condition; e.g., fog, haze, smoke, etc., or combinations

thereof.

b. Prevailing visibility is the greatest visibility

equalled or exceeded throughout at least one half of

the horizon circle, not necessarily contiguous.

Segments of the horizon circle which may have a

significantly different visibility may be reported in

the remarks section of the weather report; i.e., the

southeastern quadrant of the horizon circle may be

determined to be 2 miles in mist while the remaining

quadrants are determined to be 3 miles in mist.

c. When the prevailing visibility at the usual point

of observation, or at the tower level, is less than

4 miles, certificated tower personnel will take

visibility observations in addition to those taken at the

usual point of observation. The lower of these two

values will be used as the prevailing visibility for

aircraft operations.

7−1−18. Estimating Intensity of Rain and

Ice Pellets

a. Rain

1. Light. From scattered drops that, regardless

of duration, do not completely wet an exposed surface

up to a condition where individual drops are easily

seen.

2. Moderate. Individual drops are not clearly

identifiable; spray is observable just above pavements and other hard surfaces.

3. Heavy. Rain seemingly falls in sheets;

individual drops are not identifiable; heavy spray to

height of several inches is observed over hard

surfaces.

b. Ice Pellets

1. Light. Scattered pellets that do not completely cover an exposed surface regardless of

duration. Visibility is not affected.

2. Moderate. Slow accumulation on ground.

Visibility reduced by ice pellets to less than 7 statute

miles.

3. Heavy. Rapid accumulation on ground.

Visibility reduced by ice pellets to less than 3 statute

miles.
7/26/12 AIM

Meteorology 7−1−43

7−1−19. Estimating Intensity of Snow or

Drizzle (Based on Visibility)

a. Light. Visibility more than 1/2 statute mile.

b. Moderate. Visibility from more than 1/4 statute mile to 1/2 statute mile.

c. Heavy. Visibility 1/4 statute mile or less.

7−1−20. Pilot Weather Reports (PIREPs)

a. FAA air traffic facilities are required to solicit

PIREPs when the following conditions are reported

or forecast: ceilings at or below 5,000 feet; visibility

at or below 5 miles (surface or aloft); thunderstorms

and related phenomena; icing of light degree or

greater; turbulence of moderate degree or greater;

wind shear and reported or forecast volcanic ash

clouds.

b. Pilots are urged to cooperate and promptly

volunteer reports of these conditions and other

atmospheric data such as: cloud bases, tops and

layers; flight visibility; precipitation; visibility

restrictions such as haze, smoke and dust; wind at

altitude; and temperature aloft.

c. PIREPs should be given to the ground facility

with which communications are established;

i.e., EFAS, FSS, ARTCC, or terminal ATC. One of

the primary duties of EFAS facilities, radio call

“FLIGHT WATCH,” is to serve as a collection point

for the exchange of PIREPs with en route aircraft.

d. If pilots are not able to make PIREPs by radio,

reporting upon landing of the inflight conditions

encountered to the nearest FSS or Weather Forecast

Office will be helpful. Some of the uses made of the

reports are:

1. The ATCT uses the reports to expedite the

flow of air traffic in the vicinity of the field and for

hazardous weather avoidance procedures.

2. The FSS uses the reports to brief other pilots,

to provide inflight advisories, and weather avoidance

information to en route aircraft.

3. The ARTCC uses the reports to expedite the

flow of en route traffic, to determine most favorable

altitudes, and to issue hazardous weather information

within the center’s area.

4. The NWS uses the reports to verify or amend

conditions contained in aviation forecast and

advisories. In some cases, pilot reports of hazardous

conditions are the triggering mechanism for the

issuance of advisories. They also use the reports for

pilot weather briefings.

5. The NWS, other government organizations,

the military, and private industry groups use PIREPs

for research activities in the study of meteorological

phenomena.

6. All air traffic facilities and the NWS forward

the reports received from pilots into the weather

distribution system to assure the information is made

available to all pilots and other interested parties.

e. The FAA, NWS, and other organizations that

enter PIREPs into the weather reporting system use

the format listed in TBL 7−1−6. Items 1 through 6 are

included in all transmitted PIREPs along with one or

more of items 7 through 13. Although the PIREP

should be as complete and concise as possible, pilots

should not be overly concerned with strict format or

phraseology. The important thing is that the

information is relayed so other pilots may benefit

from your observation. If a portion of the report needs

clarification, the ground station will request the

information. Completed PIREPs will be transmitted

to weather circuits as in the following examples:
AIM 7/26/12

7−1−44 Meteorology

TBL 7−1−6

PIREP Element Code Chart

PIREP ELEMENT PIREP CODE CONTENTS

1. 3−letter station identifier XXX Nearest weather reporting location to the reported phenomenon

2. Report type UA or UUA Routine or Urgent PIREP

3. Location /OV In relation to a VOR

4. Time /TM Coordinated Universal Time

5. Altitude /FL Essential for turbulence and icing reports

6. Type Aircraft /TP Essential for turbulence and icing reports

7. Sky cover /SK Cloud height and coverage (sky clear, few, scattered, broken, or

overcast)

8. Weather /WX Flight visibility, precipitation, restrictions to visibility, etc.

9. Temperature /TA Degrees Celsius

10. Wind /WV Direction in degrees magnetic north and speed in knots

11. Turbulence /TB See AIM paragraph 7−1−23

12. Icing /IC See AIM paragraph NO TAG

13. Remarks /RM For reporting elements not included or to clarify previously

reported items

EXAMPLE−

1. KCMH UA /OV APE 230010/TM 1516/FL085/TP

BE20/SK BKN065/WX FV03SM HZ FU/TA 20/TB LGT

NOTE−

1. One zero miles southwest of Appleton VOR; time

1516 UTC; altitude eight thousand five hundred; aircraft

type BE200; bases of the broken cloud layer is six thousand

five hundred; flight visibility 3 miles with haze and smoke;

air temperature 20 degrees Celsius; light turbulence.

EXAMPLE−

2. KCRW UV /OV KBKW 360015−KCRW/TM

1815/FL120//TP BE99/SK IMC/WX RA/TA M08 /WV

290030/TB LGT−MDT/IC LGT RIME/RM MDT MXD

ICG DURC KROA NWBND FL080−100 1750Z

NOTE−

2. From 15 miles north of Beckley VOR to Charleston VOR; time 1815 UTC; altitude 12,000 feet; type

aircraft, BE−99; in clouds; rain; temperature minus

8 Celsius; wind 290 degrees magnetic at 30 knots; light to

moderate turbulence; light rime icing during climb

northwestbound from Roanoke, VA, between 8,000 and

10,000 feet at 1750 UTC.

7−1−21. PIREPs Relating to Airframe Icing

a. The effects of ice on aircraft are cumulativethrust is reduced, drag increases, lift lessens, and

weight increases. The results are an increase in stall

speed and a deterioration of aircraft performance. In

extreme cases, 2 to 3 inches of ice can form on the

leading edge of the airfoil in less than 5 minutes. It

takes but 1/2 inch of ice to reduce the lifting power of

some aircraft by 50 percent and increases the

frictional drag by an equal percentage.

b. A pilot can expect icing when flying in visible

precipitation, such as rain or cloud droplets, and the

temperature is between +02 and −10 degrees Celsius.

When icing is detected, a pilot should do one of two

things, particularly if the aircraft is not equipped with

deicing equipment; get out of the area of

precipitation; or go to an altitude where the

temperature is above freezing. This “warmer”

altitude may not always be a lower altitude. Proper

preflight action includes obtaining information on the

freezing level and the above freezing levels in

precipitation areas. Report icing to ATC, and if

operating IFR, request new routing or altitude if icing

will be a hazard. Be sure to give the type of aircraft to

ATC when reporting icing. The following describes

how to report icing conditions.

1. Trace. Ice becomes perceptible. Rate of

accumulation slightly greater than sublimation.

Deicing/anti-icing equipment is not utilized unless

encountered for an extended period of time (over

1 hour).
7/26/12 AIM

Meteorology 7−1−45

2. Light. The rate of accumulation may create

a problem if flight is prolonged in this environment

(over 1 hour). Occasional use of deicing/anti-icing

equipment removes/prevents accumulation. It does

not present a problem if the deicing/anti-icing

equipment is used.

3. Moderate. The rate of accumulation is such

that even short encounters become potentially

hazardous and use of deicing/anti-icing equipment or

flight diversion is necessary.

4. Severe. The rate of accumulation is such that

deicing/anti-icing equipment fails to reduce or

control the hazard. Immediate flight diversion is

necessary.

EXAMPLE−

Pilot report: give aircraft identification, location,

time (UTC), intensity of type, altitude/FL, aircraft

type, indicated air speed (IAS), and outside air

temperature (OAT).

NOTE−

1. Rime ice. Rough, milky, opaque ice formed by the

instantaneous freezing of small supercooled water

droplets.

2. Clear ice. A glossy, clear, or translucent ice formed by

the relatively slow freezing of large supercooled water

droplets.

3. The OAT should be requested by the FSS or ATC if not

included in the PIREP.

7−1−22. Definitions of Inflight Icing Terms

See TBL 7−1−7, Icing Types, and TBL 7−1−8, Icing

Conditions.
AIM 7/26/12

7−1−46 Meteorology

TBL 7−1−7

Icing Types

Clear Ice See Glaze Ice.

Glaze Ice Ice, sometimes clear and smooth, but usually containing some air pockets, which results in a

lumpy translucent appearance. Glaze ice results from supercooled drops/droplets striking a

surface but not freezing rapidly on contact. Glaze ice is denser, harder, and sometimes more

transparent than rime ice. Factors, which favor glaze formation, are those that favor slow

dissipation of the heat of fusion (i.e., slight supercooling and rapid accretion). With larger

accretions, the ice shape typically includes “horns” protruding from unprotected leading edge

surfaces. It is the ice shape, rather than the clarity or color of the ice, which is most likely to

be accurately assessed from the cockpit. The terms “clear” and “glaze” have been used for

essentially the same type of ice accretion, although some reserve “clear” for thinner accretions

which lack horns and conform to the airfoil.

Intercycle Ice Ice which accumulates on a protected surface between actuation cycles of a deicing system.

Known or Observed or

Detected Ice Accretion

Actual ice observed visually to be on the aircraft by the flight crew or identified by on−board

sensors.

Mixed Ice Simultaneous appearance or a combination of rime and glaze ice characteristics. Since the

clarity, color, and shape of the ice will be a mixture of rime and glaze characteristics, accurate

identification of mixed ice from the cockpit may be difficult.

Residual Ice Ice which remains on a protected surface immediately after the actuation of a deicing system.

Rime Ice A rough, milky, opaque ice formed by the rapid freezing of supercooled drops/droplets after

they strike the aircraft. The rapid freezing results in air being trapped, giving the ice its opaque

appearance and making it porous and brittle. Rime ice typically accretes along the stagnation

line of an airfoil and is more regular in shape and conformal to the airfoil than glaze ice. It is

the ice shape, rather than the clarity or color of the ice, which is most likely to be accurately

assessed from the cockpit.

Runback Ice Ice which forms from the freezing or refreezing of water leaving protected surfaces and

running back to unprotected surfaces.

Note−

Ice types are difficult for the pilot to discern and have uncertain effects on an airplane in flight. Ice type definitions will

be included in the AIM for use in the “Remarks” section of the PIREP and for use in forecasting.
7/26/12 AIM

Meteorology 7−1−47

TBL 7−1−8

Icing Conditions

Appendix C Icing Conditions Appendix C (14 CFR, Part 25 and 29) is the certification icing condition standard

for approving ice protection provisions on aircraft. The conditions are specified in

terms of altitude, temperature, liquid water content (LWC), representative droplet

size (mean effective drop diameter [MED]), and cloud horizontal extent.

Forecast Icing Conditions Environmental conditions expected by a National Weather Service or an

FAA−approved weather provider to be conducive to the formation of inflight icing

on aircraft.

Freezing Drizzle (FZDZ) Drizzle is precipitation at ground level or aloft in the form of liquid water drops

which have diameters less than 0.5 mm and greater than 0.05 mm. Freezing drizzle

is drizzle that exists at air temperatures less than 0C (supercooled), remains in

liquid form, and freezes upon contact with objects on the surface or airborne.

Freezing Precipitation Freezing precipitation is freezing rain or freezing drizzle falling through or outside

of visible cloud.

Freezing Rain (FZRA) Rain is precipitation at ground level or aloft in the form of liquid water drops which

have diameters greater than 0.5 mm. Freezing rain is rain that exists at air

temperatures less than 0C (supercooled), remains in liquid form, and freezes upon

contact with objects on the ground or in the air.

Icing in Cloud Icing occurring within visible cloud. Cloud droplets (diameter < 0.05 mm) will be

present; freezing drizzle and/or freezing rain may or may not be present.

Icing in Precipitation Icing occurring from an encounter with freezing precipitation, that is, supercooled

drops with diameters exceeding 0.05 mm, within or outside of visible cloud.

Known Icing Conditions Atmospheric conditions in which the formation of ice is observed or detected in

flight.

Note−

Because of the variability in space and time of atmospheric conditions, the existence

of a report of observed icing does not assure the presence or intensity of icing

conditions at a later time, nor can a report of no icing assure the absence of icing

conditions at a later time.

Potential Icing Conditions Atmospheric icing conditions that are typically defined by airframe manufacturers

relative to temperature and visible moisture that may result in aircraft ice accretion

on the ground or in flight. The potential icing conditions are typically defined in the

Airplane Flight Manual or in the Airplane Operation Manual.

Supercooled Drizzle Drops

(SCDD)

Synonymous with freezing drizzle aloft.

Supercooled Drops or /Droplets Water drops/droplets which remain unfrozen at temperatures below 0 C.

Supercooled drops are found in clouds, freezing drizzle, and freezing rain in the

atmosphere. These drops may impinge and freeze after contact on aircraft surfaces.

Supercooled Large Drops (SLD) Liquid droplets with diameters greater than 0.05 mm at temperatures less than

0C, i.e., freezing rain or freezing drizzle.
AIM 7/26/12

7−1−48 Meteorology

7−1−23. PIREPs Relating to Turbulence

a. When encountering turbulence, pilots are

urgently requested to report such conditions to ATC

as soon as practicable. PIREPs relating to turbulence

should state:

1. Aircraft location.

2. Time of occurrence in UTC.

3. Turbulence intensity.

4. Whether the turbulence occurred in or

near clouds.

5. Aircraft altitude or flight level.

6. Type of aircraft.

7. Duration of turbulence.

EXAMPLE−

1. Over Omaha, 1232Z, moderate turbulence in clouds at

Flight Level three one zero, Boeing 707.

2. From five zero miles south of Albuquerque to three zero

miles north of Phoenix, 1250Z, occasional moderate chop

at Flight Level three three zero, DC8.

b. Duration and classification of intensity should

be made using TBL 7−1−9.

TBL 7−1−9

Turbulence Reporting Criteria Table

Intensity Aircraft Reaction Reaction Inside Aircraft Reporting Term−Definition

Light Turbulence that momentarily causes

slight, erratic changes in altitude and/or

attitude (pitch, roll, yaw). Report as

Light Turbulence; 1

or

Turbulence that causes slight, rapid and

somewhat rhythmic bumpiness without

appreciable changes in altitude or

attitude. Report as Light Chop.

Occupants may feel a slight strain

against seat belts or shoulder straps.

Unsecured objects may be displaced

slightly. Food service may be conducted and little or no difficulty is

encountered in walking.

Occasional−Less than 1/3 of the time.

Intermittent−1/3 to 2/3.

Continuous−More than 2/3.

Moderate Turbulence that is similar to Light

Turbulence but of greater intensity.

Changes in altitude and/or attitude occur

but the aircraft remains in positive

control at all times. It usually causes

variations in indicated airspeed. Report

as Moderate Turbulence; 1

or

Turbulence that is similar to Light Chop

but of greater intensity. It causes rapid

bumps or jolts without appreciable

changes in aircraft altitude or attitude.

Report as Moderate Chop.1

Occupants feel definite strains against

seat belts or shoulder straps. Unsecured objects are dislodged. Food

service and walking are difficult.

NOTE

1. Pilots should report location(s),

time (UTC), intensity, whether in or

near clouds, altitude, type of aircraft

and, when applicable, duration of

turbulence.

2. Duration may be based on time

between two locations or over a single

location. All locations should be

readily identifiable.

Severe Turbulence that causes large, abrupt

changes in altitude and/or attitude. It

usually causes large variations in

indicated airspeed. Aircraft may be

momentarily out of control. Report as

Severe Turbulence. 1

Occupants are forced violently against

seat belts or shoulder straps. Unsecured objects are tossed about. Food

Service and walking are impossible.

EXAMPLES:

a. Over Omaha. 1232Z, Moderate

Turbulence, in cloud, Flight

Level 310, B707.

Extreme Turbulence in which the aircraft is

violently tossed about and is practically

impossible to control. It may cause

structural damage. Report as Extreme

Turbulence. 1

b. From 50 miles south of Albuquerque to 30 miles north of Phoenix,

1210Z to 1250Z, occasional Moderate

Chop, Flight Level 330, DC8.

1 High level turbulence (normally above 15,000 feet ASL) not associated with cumuliform cloudiness, including thunderstorms,

should be reported as CAT (clear air turbulence) preceded by the appropriate intensity, or light or moderate chop.
7/26/12 AIM

Meteorology 7−1−49

7−1−24. Wind Shear PIREPs

a. Because unexpected changes in wind speed and

direction can be hazardous to aircraft operations at

low altitudes on approach to and departing from

airports, pilots are urged to promptly volunteer

reports to controllers of wind shear conditions they

encounter. An advance warning of this information

will assist other pilots in avoiding or coping with a

wind shear on approach or departure.

b. When describing conditions, use of the terms

“negative” or “positive” wind shear should be

avoided. PIREPs of “negative wind shear on final,”

intended to describe loss of airspeed and lift, have

been interpreted to mean that no wind shear was

encountered. The recommended method for wind

shear reporting is to state the loss or gain of airspeed

and the altitudes at which it was encountered.

EXAMPLE−

1. Denver Tower, Cessna 1234 encountered wind shear,

loss of 20 knots at 400.

2. Tulsa Tower, American 721 encountered wind shear on

final, gained 25 knots between 600 and 400 feet followed

by loss of 40 knots between 400 feet and surface.

1. Pilots who are not able to report wind shear in

these specific terms are encouraged to make reports

in terms of the effect upon their aircraft.

EXAMPLE−

Miami Tower, Gulfstream 403 Charlie encountered an

abrupt wind shear at 800 feet on final, max thrust required.

2. Pilots using Inertial Navigation Systems

(INSs) should report the wind and altitude both above

and below the shear level.

7−1−25. Clear Air Turbulence (CAT) PIREPs

CAT has become a very serious operational factor to

flight operations at all levels and especially to jet

traffic flying in excess of 15,000 feet. The best

available information on this phenomenon must

come from pilots via the PIREP reporting procedures.

All pilots encountering CAT conditions are urgently

requested to report time, location, and intensity (light,

moderate, severe, or extreme) of the element to the

FAA facility with which they are maintaining radio

contact. If time and conditions permit, elements

should be reported according to the standards for

other PIREPs and position reports.

REFERENCE−

AIM, PIREPs Relating to Turbulence, Paragraph 7−1−23.

7−1−26. Microbursts

a. Relatively recent meteorological studies have

confirmed the existence of microburst phenomenon.

Microbursts are small scale intense downdrafts

which, on reaching the surface, spread outward in all

directions from the downdraft center. This causes the

presence of both vertical and horizontal wind shears

that can be extremely hazardous to all types and

categories of aircraft, especially at low altitudes. Due

to their small size, short life span, and the fact that

they can occur over areas without surface precipitation, microbursts are not easily detectable using

conventional weather radar or wind shear alert

systems.

b. Parent clouds producing microburst activity

can be any of the low or middle layer convective

cloud types. Note, however, that microbursts

commonly occur within the heavy rain portion of

thunderstorms, and in much weaker, benign

appearing convective cells that have little or no

precipitation reaching the ground.
AIM 7/26/12

7−1−50 Meteorology

FIG 7−1−14

Evolution of a Microburst

T-5 Min T-5 Min T-2 Min T-2 Min T T + 5 Min T + 5 Min T + 10 Min T + 10 Min

HEIGHT (feet) HEIGHT (feet) 10,000

5,000

WIND SPEED WIND SPEED

10-20 knots 10-20 knots

> 20 knots > 20 knots

SCALE (miles) SCALE (miles)

0 1 2 3

Vertical cross section of the evolution of a microburst wind field. T is the time of initial divergence at

the surface. The shading refers to the vector wind speeds. Figure adapted from Wilson et al., 1984,

Microburst Wind Structure and Evaluation of Doppler Radar for Wind Shear Detection, DOT/FAA

Report No. DOT/FAA/PM-84/29, National Technical Information Service, Springfield, VA 37 pp.

c. The life cycle of a microburst as it descends in

a convective rain shaft is seen in FIG 7−1−14. An

important consideration for pilots is the fact that the

microburst intensifies for about 5 minutes after it

strikes the ground.

d. Characteristics of microbursts include:

1. Size. The microburst downdraft is typically

less than 1 mile in diameter as it descends from the

cloud base to about 1,000−3,000 feet above the

ground. In the transition zone near the ground, the

downdraft changes to a horizontal outflow that can

extend to approximately 2 1/2 miles in diameter.

2. Intensity. The downdrafts can be as strong

as 6,000 feet per minute. Horizontal winds near the

surface can be as strong as 45 knots resulting in a

90 knot shear (headwind to tailwind change for a

traversing aircraft) across the microburst. These

strong horizontal winds occur within a few hundred

feet of the ground.

3. Visual Signs. Microbursts can be found

almost anywhere that there is convective activity.

They may be embedded in heavy rain associated with

a thunderstorm or in light rain in benign appearing

virga. When there is little or no precipitation at the

surface accompanying the microburst, a ring of

blowing dust may be the only visual clue of its

existence.

4. Duration. An individual microburst will

seldom last longer than 15 minutes from the time it

strikes the ground until dissipation. The horizontal

winds continue to increase during the first 5 minutes

with the maximum intensity winds lasting approximately 2−4 minutes. Sometimes microbursts are

concentrated into a line structure, and under these

conditions, activity may continue for as long as an

hour. Once microburst activity starts, multiple

microbursts in the same general area are not

uncommon and should be expected.
7/26/12 AIM

Meteorology 7−1−51

FIG 7−1−15

Microburst Encounter During Takeoff

A microburst encounter during takeoff. The airplane first encounters a headwind and experiences increasing

performance (1), this is followed in short succession by a decreasing headwind component (2), a downdraft

(3), and finally a strong tailwind (4), where 2 through 5 all result in decreasing performance of the airplane.

Position (5) represents an extreme situation just prior to impact. Figure courtesy of Walter Frost, FWG

Associates, Inc., Tullahoma, Tennessee.

e. Microburst wind shear may create a severe

hazard for aircraft within 1,000 feet of the ground,

particularly during the approach to landing and

landing and take-off phases. The impact of a

microburst on aircraft which have the unfortunate

experience of penetrating one is characterized in

FIG 7−1−15. The aircraft may encounter a headwind

(performance increasing) followed by a downdraft

and tailwind (both performance decreasing), possibly

resulting in terrain impact.
AIM 7/26/12

7−1−52 Meteorology

FIG 7−1−16

NAS Wind Shear Product Systems

(33)

(39)

(36)

(9)

f. Detection of Microbursts, Wind Shear and

Gust Fronts.

1. FAA’s Integrated Wind Shear Detection

Plan.

(a) The FAA currently employs an integrated

plan for wind shear detection that will significantly

improve both the safety and capacity of the majority

of the airports currently served by the air carriers.

This plan integrates several programs, such as the

Integrated Terminal Weather System (ITWS),

Terminal Doppler Weather Radar (TDWR), Weather

System Processor (WSP), and Low Level Wind Shear

Alert Systems (LLWAS) into a single strategic

concept that significantly improves the aviation

weather information in the terminal area. (See

FIG 7−1−16.)

(b) The wind shear/microburst information

and warnings are displayed on the ribbon display

terminals (RBDT) located in the tower cabs. They are

identical (and standardized) in the LLWAS, TDWR

and WSP systems, and so designed that the controller

does not need to interpret the data, but simply read the

displayed information to the pilot. The RBDTs are

constantly monitored by the controller to ensure the

rapid and timely dissemination of any hazardous

event(s) to the pilot.
7/26/12 AIM

Meteorology 7−1−53

FIG 7−1−17

LLWAS Siting Criteria

(c) The early detection of a wind shear/

micro−burst event, and the subsequent warning(s)

issued to an aircraft on approach or departure, will

alert the pilot/crew to the potential of, and to be

prepared for, a situation that could become very

dangerous! Without these warnings, the aircraft may

NOT be able to climb out of, or safely transition, the

event, resulting in a catastrophe. The air carriers,

working with the FAA, have developed specialized

training programs using their simulators to train and

prepare their pilots on the demanding aircraft

procedures required to escape these very dangerous

wind shear and/or microburst encounters.

2. Low Level Wind Shear Alert System

(LLWAS).

(a) The LLWAS provides wind data and

software processes to detect the presence of

hazardous wind shear and microbursts in the vicinity

of an airport. Wind sensors, mounted on poles

sometimes as high as 150 feet, are (ideally) located

2,000 − 3,500 feet, but not more than 5,000 feet, from

the centerline of the runway. (See FIG 7−1−17.)
AIM 7/26/12

7−1−54 Meteorology

FIG 7−1−18

Warning Boxes

(b) LLWAS was fielded in 1988 at 110 airports across the nation. Many of these systems have

been replaced by new TDWR and WSP technology.

Eventually all LLWAS systems will be phased out;

however, 39 airports will be upgraded to the

LLWAS−NE (Network Expansion) system, which

employs the very latest software and sensor

technology. The new LLWAS−NE systems will not

only provide the controller with wind shear warnings

and alerts, including wind shear/microburst detection

at the airport wind sensor location, but will also

provide the location of the hazards relative to the

airport runway(s). It will also have the flexibility and

capability to grow with the airport as new runways are

built. As many as 32 sensors, strategically located

around the airport and in relationship to its runway

configuration, can be accommodated by the

LLWAS−NE network.

3. Terminal Doppler Weather Radar

(TDWR).

(a) TDWRs are being deployed at 45 locations across the U.S. Optimum locations for TDWRs

are 8 to 12 miles off of the airport proper, and

designed to look at the airspace around and over the

airport to detect microbursts, gust fronts, wind shifts

and precipitation intensities. TDWR products advise

the controller of wind shear and microburst events

impacting all runways and the areas 1/2 mile on either

side of the extended centerline of the runways out to

3 miles on final approach and 2 miles out on

departure.

(FIG 7−1−18 is a theoretical view of the warning

boxes, including the runway, that the software uses in

determining the location(s) of wind shear or

microbursts). These warnings are displayed (as

depicted in the examples in subparagraph 5) on the

RBDT.

(b) It is very important to understand what

TDWR does NOT DO:

(1) It DOES NOT warn of wind shear

outside of the alert boxes (on the arrival and departure

ends of the runways);

(2) It DOES NOT detect wind shear that is

NOT a microburst or a gust front;

(3) It DOES NOT detect gusty or cross

wind conditions; and

(4) It DOES NOT detect turbulence.

However, research and development is continuing on

these systems. Future improvements may include

such areas as storm motion (movement), improved
7/26/12 AIM

Meteorology 7−1−55

gust front detection, storm growth and decay,

microburst prediction, and turbulence detection.

(c) TDWR also provides a geographical

situation display (GSD) for supervisors and traffic

management specialists for planning purposes. The

GSD displays (in color) 6 levels of weather

(precipitation), gust fronts and predicted storm

movement(s). This data is used by the tower

supervisor(s), traffic management specialists and

controllers to plan for runway changes and

arrival/departure route changes in order to both

reduce aircraft delays and increase airport capacity.

4. Weather System Processor (WSP).

(a) The WSP provides the controller, supervisor, traffic management specialist, and ultimately the

pilot, with the same products as the terminal doppler

weather radar (TDWR) at a fraction of the cost of a

TDWR. This is accomplished by utilizing new

technologies to access the weather channel capabilities of the existing ASR−9 radar located on or near the

airport, thus eliminating the requirements for a

separate radar location, land acquisition, support

facilities and the associated communication landlines

and expenses.

(b) The WSP utilizes the same RBDT display

as the TDWR and LLWAS, and, just like TDWR, also

has a GSD for planning purposes by supervisors,

traffic management specialists and controllers. The

WSP GSD emulates the TDWR display, i.e., it also

depicts 6 levels of precipitation, gust fronts and

predicted storm movement, and like the TDWR GSD,

is used to plan for runway changes and arrival/departure route changes in order to reduce aircraft delays

and to increase airport capacity.

(c) This system is currently under development and is operating in a developmental test status

at the Albuquerque, New Mexico, airport. When

fielded, the WSP is expected to be installed at

34 airports across the nation, substantially increasing

the safety of the American flying public.

5. Operational aspects of LLWAS, TDWR

and WSP.

To demonstrate how this data is used by both the

controller and the pilot, 3 ribbon display examples

and their explanations are presented:

(a) MICROBURST ALERTS

EXAMPLE−

This is what the controller sees on his/her ribbon display

in the tower cab.

27A MBA 35K− 2MF 250 20

NOTE−

(See FIG 7−1−19 to see how the TDWR/WSP determines

the microburst location).

This is what the controller will say when issuing the

alert.

PHRASEOLOGY−

RUNWAY 27 ARRIVAL, MICROBURST ALERT, 35 KT

LOSS 2 MILE FINAL, THRESHOLD WIND 250 AT 20.

In plain language, the controller is telling the pilot

that on approach to runway 27, there is a microburst

alert on the approach lane to the runway, and to

anticipate or expect a 35 knot loss of airspeed at

approximately 2 miles out on final approach (where

it will first encounter the phenomena). With that

information, the aircrew is forewarned, and should be

prepared to apply wind shear/microburst escape

procedures should they decide to continue the

approach. Additionally, the surface winds at the

airport for landing runway 27 are reported as

250 degrees at 20 knots.

NOTE−

Threshold wind is at pilot’s request or as deemed

appropriate by the controller.

REFERENCE−

FAA Order JO 7110.65, Air Traffic Control, Low Level Wind

Shear/Microburst Advisories, Paragraph 3−1−8b2(a).
AIM 7/26/12

7−1−56 Meteorology

FIG 7−1−19

Microburst Alert

(b) WIND SHEAR ALERTS

EXAMPLE−

This is what the controller sees on his/her ribbon display

in the tower cab.

 27A WSA 20K− 3MF 200 15

NOTE−

(See FIG 7−1−20 to see how the TDWR/WSP determines

the wind shear location).

This is what the controller will say when issuing the

alert.

PHRASEOLOGY−

RUNWAY 27 ARRIVAL, WIND SHEAR ALERT, 20 KT

LOSS 3 MILE FINAL, THRESHOLD WIND 200 AT 15.

In plain language, the controller is advising the

aircraft arriving on runway 27 that at about 3 miles

out they can expect to encounter a wind shear

condition that will decrease their airspeed by 20 knots

and possibly encounter turbulence. Additionally, the

airport surface winds for landing runway 27 are

reported as 200 degrees at 15 knots.

NOTE−

Threshold wind is at pilot’s request or as deemed

appropriate by the controller.

REFERENCE−

FAA Order JO 7110.65, Air Traffic Control, Low Level Wind

Shear/Microburst Advisories, Paragraph 3−1−8b2(a).
7/26/12 AIM

Meteorology 7−1−57

FIG 7−1−20

Weak Microburst Alert
AIM 7/26/12

7−1−58 Meteorology

FIG 7−1−21

Gust Front Alert

(c) MULTIPLE WIND SHEAR ALERTS

EXAMPLE−

This is what the controller sees on his/her ribbon display

in the tower cab.

27A WSA 20K+ RWY 250 20

27D WSA 20K+ RWY 250 20

NOTE−

(See FIG 7−1−21 to see how the TDWR/WSP determines

the gust front/wind shear location.)

This is what the controller will say when issuing the

alert.

PHRASEOLOGY−

MULTIPLE WIND SHEAR ALERTS. RUNWAY 27

ARRIVAL, WIND SHEAR ALERT, 20 KT GAIN ON

RUNWAY; RUNWAY 27 DEPARTURE, WIND SHEAR

ALERT, 20 KT GAIN ON RUNWAY, WIND 250 AT 20.

EXAMPLE−

In this example, the controller is advising arriving and

departing aircraft that they could encounter a wind shear

condition right on the runway due to a gust front

(significant change of wind direction) with the possibility

of a 20 knot gain in airspeed associated with the gust front.

Additionally, the airport surface winds (for the runway in

use) are reported as 250 degrees at 20 knots.

REFERENCE−

FAA Order JO 7110.65, Air Traffic Control, Low Level Wind

Shear/Microburst Advisories, Paragraph 3−1−8b2(d).
7/26/12 AIM

Meteorology 7−1−59

6. The Terminal Weather Information for

Pilots System (TWIP).

(a) With the increase in the quantity and

quality of terminal weather information available

through TDWR, the next step is to provide this

information directly to pilots rather than relying on

voice communications from ATC. The National

Airspace System has long been in need of a means of

delivering terminal weather information to the

cockpit more efficiently in terms of both speed and

accuracy to enhance pilot awareness of weather

hazards and reduce air traffic controller workload.

With the TWIP capability, terminal weather

information, both alphanumerically and graphically,

is now available directly to the cockpit on a test basis

at 9 locations.

(b) TWIP products are generated using

weather data from the TDWR or the Integrated

Terminal Weather System (ITWS) testbed. TWIP

products are generated and stored in the form of text

and character graphic messages. Software has been

developed to allow TDWR or ITWS to format the

data and send the TWIP products to a database

resident at Aeronautical Radio, Inc. (ARINC). These

products can then be accessed by pilots using the

ARINC Aircraft Communications Addressing and

Reporting System (ACARS) data link services.

Airline dispatchers can also access this database and

send messages to specific aircraft whenever wind

shear activity begins or ends at an airport.

(c) TWIP products include descriptions and

character graphics of microburst alerts, wind shear

alerts, significant precipitation, convective activity

within 30 NM surrounding the terminal area, and

expected weather that will impact airport operations.

During inclement weather, i.e., whenever a predetermined level of precipitation or wind shear is detected

within 15 miles of the terminal area, TWIP products

are updated once each minute for text messages and

once every five minutes for character graphic

messages. During good weather (below the predetermined precipitation or wind shear parameters) each

message is updated every 10 minutes. These products

are intended to improve the situational awareness of

the pilot/flight crew, and to aid in flight planning prior

to arriving or departing the terminal area. It is

important to understand that, in the context of TWIP,

the predetermined levels for inclement versus good

weather has nothing to do with the criteria for

VFR/MVFR/IFR/LIFR; it only deals with precipitation, wind shears and microbursts.

7−1−27. PIREPs Relating to Volcanic Ash

Activity

a. Volcanic eruptions which send ash into the

upper atmosphere occur somewhere around the world

several times each year. Flying into a volcanic ash

cloud can be extremely dangerous. At least two

B747s have lost all power in all four engines after

such an encounter. Regardless of the type aircraft,

some damage is almost certain to ensue after an

encounter with a volcanic ash cloud.

b. While some volcanoes in the U.S. are

monitored, many in remote areas are not. These

unmonitored volcanoes may erupt without prior

warning to the aviation community. A pilot observing

a volcanic eruption who has not had previous

notification of it may be the only witness to the

eruption. Pilots are strongly encouraged to transmit a

PIREP regarding volcanic eruptions and any

observed volcanic ash clouds.

c. Pilots should submit PIREPs regarding volcanic

activity using the Volcanic Activity Reporting (VAR)

form as illustrated in Appendix 2. If a VAR form is

not immediately available, relay enough information

to identify the position and type of volcanic activity.

d. Pilots should verbally transmit the data required

in items 1 through 8 of the VAR as soon as possible.

The data required in items 9 through 16 of the VAR

should be relayed after landing if possible.

7−1−28. Thunderstorms

a. Turbulence, hail, rain, snow, lightning, sustained updrafts and downdrafts, icing conditions−all

are present in thunderstorms. While there is some

evidence that maximum turbulence exists at the

middle level of a thunderstorm, recent studies show

little variation of turbulence intensity with altitude.

b. There is no useful correlation between the

external visual appearance of thunderstorms and the

severity or amount of turbulence or hail within them.

The visible thunderstorm cloud is only a portion of a

turbulent system whose updrafts and downdrafts

often extend far beyond the visible storm cloud.

Severe turbulence can be expected up to 20 miles

from severe thunderstorms. This distance decreases

to about 10 miles in less severe storms.
AIM 7/26/12

7−1−60 Meteorology

c. Weather radar, airborne or ground based, will

normally reflect the areas of moderate to heavy

precipitation (radar does not detect turbulence). The

frequency and severity of turbulence generally

increases with the radar reflectivity which is closely

associated with the areas of highest liquid water

content of the storm. NO FLIGHT PATH THROUGH

AN AREA OF STRONG OR VERY STRONG

RADAR ECHOES SEPARATED BY 20−30 MILES

OR LESS MAY BE CONSIDERED FREE OF

SEVERE TURBULENCE.

d. Turbulence beneath a thunderstorm should not

be minimized. This is especially true when the

relative humidity is low in any layer between the

surface and 15,000 feet. Then the lower altitudes may

be characterized by strong out flowing winds and

severe turbulence.

e. The probability of lightning strikes occurring to

aircraft is greatest when operating at altitudes where

temperatures are between minus 5 degrees Celsius

and plus 5 degrees Celsius. Lightning can strike

aircraft flying in the clear in the vicinity of a

thunderstorm.

f. METAR reports do not include a descriptor for

severe thunderstorms. However, by understanding

severe thunderstorm criteria, i.e., 50 knot winds or

3/4 inch hail, the information is available in the report

to know that one is occurring.

g. Current weather radar systems are able to

objectively determine precipitation intensity. These

precipitation intensity areas are described as “light,”

“moderate,” “heavy,” and “extreme.”

REFERENCE−

Pilot/Controller Glossary, Precipitation Radar Weather Descriptions.

EXAMPLE−

1. Alert provided by an ATC facility to an aircraft:

(aircraft identification) EXTREME precipitation between

ten o’clock and two o’clock, one five miles. Precipitation

area is two five miles in diameter.

2. Alert provided by an FSS:

(aircraft identification) EXTREME precipitation two zero

miles west of Atlanta V−O−R, two five miles wide, moving

east at two zero knots, tops flight level three niner zero.

7−1−29. Thunderstorm Flying

a. Above all, remember this: never regard any

thunderstorm “lightly” even when radar observers

report the echoes are of light intensity. Avoiding

thunderstorms is the best policy. Following are some

Do’s and Don’ts of thunderstorm avoidance:

1. Don’t land or takeoff in the face of an

approaching thunderstorm. A sudden gust front of

low level turbulence could cause loss of control.

2. Don’t attempt to fly under a thunderstorm

even if you can see through to the other side.

Turbulence and wind shear under the storm could be

disastrous.

3. Don’t fly without airborne radar into a cloud

mass containing scattered embedded thunderstorms.

Scattered thunderstorms not embedded usually can

be visually circumnavigated.

4. Don’t trust the visual appearance to be a

reliable indicator of the turbulence inside a

thunderstorm.

5. Do avoid by at least 20 miles any

thunderstorm identified as severe or giving an intense

radar echo. This is especially true under the anvil of

a large cumulonimbus.

6. Do clear the top of a known or suspected

severe thunderstorm by at least 1,000 feet altitude for

each 10 knots of wind speed at the cloud top. This

should exceed the altitude capability of most aircraft.

7. Do circumnavigate the entire area if the area

has 6/10 thunderstorm coverage.

8. Do remember that vivid and frequent

lightning indicates the probability of a strong

thunderstorm.

9. Do regard as extremely hazardous any

thunderstorm with tops 35,000 feet or higher whether

the top is visually sighted or determined by radar.

b. If you cannot avoid penetrating a thunderstorm,

following are some Do’s before entering the storm:

1. Tighten your safety belt, put on your shoulder

harness if you have one and secure all loose objects.

2. Plan and hold your course to take you through

the storm in a minimum time.
7/26/12 AIM

Meteorology 7−1−61

3. To avoid the most critical icing, establish a

penetration altitude below the freezing level or above

the level of minus 15 degrees Celsius.

4. Verify that pitot heat is on and turn on

carburetor heat or jet engine anti-ice. Icing can be

rapid at any altitude and cause almost instantaneous

power failure and/or loss of airspeed indication.

5. Establish power settings for turbulence

penetration airspeed recommended in your aircraft

manual.

6. Turn up cockpit lights to highest intensity to

lessen temporary blindness from lightning.

7. If using automatic pilot, disengage altitude

hold mode and speed hold mode. The automatic

altitude and speed controls will increase maneuvers

of the aircraft thus increasing structural stress.

8. If using airborne radar, tilt the antenna up and

down occasionally. This will permit you to detect

other thunderstorm activity at altitudes other than the

one being flown.

c. Following are some Do’s and Don’ts during the

thunderstorm penetration:

1. Do keep your eyes on your instruments.

Looking outside the cockpit can increase danger of

temporary blindness from lightning.

2. Don’t change power settings; maintain

settings for the recommended turbulence penetration

airspeed.

3. Don’t attempt to maintain constant altitude;

let the aircraft “ride the waves.”

4. Don’t turn back once you are in the

thunderstorm. A straight course through the storm

most likely will get you out of the hazards most

quickly. In addition, turning maneuvers increase

stress on the aircraft.
AIM 7/26/12

7−1−62 Meteorology

7−1−30. Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR)

FIG 7−1−22

Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Front)

Key to Aerodrome Forecast (TAF) and Aviation

Routine Weather Report (METAR) (Front)

TAF KPIT 091730Z 0918/1024 15005KT 5SM HZ FEW020 WS010/31022KT

FM091930 30015G25KT 3SM SHRA OVC015

TEMPO 0920/0922 1/2SM +TSRA OVC008CB

FM100100 27008KT 5SM SHRA BKN020 OVC040

PROB30 1004/1007 1SM -RA BR

FM101015 18005KT 6SM -SHRA OVC020

BECMG 1013/1015 P6SM NSW SKC

NOTE: Users are cautioned to confirm DATE and TIME of the TAF. For example FM100000 is

0000Z on the 10th. Do not confuse with 1000Z!

METAR KPIT 091955Z COR 22015G25KT 3/4SM R28L/2600FT TSRA OVC010CB 18/16 A2992 RMK

SLP045 T01820159

Forecast Explanation Report

TAF Message type: TAF-routine or TAF AMD-amended forecast, METARhourly, SPECI-special or TESTM-non-commissioned ASOS reportMETAR

KPIT ICAO location indicator KPIT

091730Z Issuance time: ALL times in UTC “Z”, 2-digit date, 4-digit time 091955Z

0918/1024 Valid period, either 24 hours or 30 hours. The first two digits of EACH

four digit number indicate the date of the valid period, the final two digits indicate the time (valid from 18Z on the 9th to 24Z on the 10th).

In U.S. METAR: CORrected ob; or AUTOmated ob for automated report with no human intervention; omitted when observer logs on.COR

15005KT Wind: 3 digit true-north direction, nearest 10 degrees (or VaRiaBle);

next 2-3 digits for speed and unit, KT (KMH or MPS); as needed, Gust

and maximum speed; 00000KT for calm; for METAR, if direction varies

60 degrees or more, Variability appended, e.g., 180V260

22015G25KT

5SM Prevailing visibility; in U.S., Statute Miles & fractions; above 6 miles in

TAF Plus6SM. (Or, 4-digit minimum visibility in meters and as required, lowest value with direction)

3⁄4SM

Runway Visual Range: R; 2-digit runway designator Left, Center, or

Right as needed; “/”, Minus or Plus in U.S., 4-digit value, FeeT in U.S.,

(usually meters elsewhere); 4-digit value Variability 4-digit value (and

tendency Down, Up or No change)

R28L/2600FT

HZ Significant present, forecast and recent weather: see table (on back) TSRA

FEW020 Cloud amount, height and type: Sky Clear 0/8, FEW >0/8-2/8, ScaTtered

3/8-4/8, BroKeN 5/8-7/8, OverCast 8/8; 3-digit height in hundreds of ft;

Towering Cumulus or CumulonimBus in METAR; in TAF, only CB.

Vertical Visibility for obscured sky and height “VV004”. More than 1

layer may be reported or forecast. In automated METAR reports only,

CleaR for “clear below 12,000 feet”

OVC 010CB

Temperature: degrees Celsius; first 2 digits, temperature “/” last 2 digits,

dew-point temperature; Minus for below zero, e.g., M06

18/16

Altimeter setting: indicator and 4 digits; in U.S., A-inches and hundredths; (Q-hectoPascals, e.g., Q1013)A2992

WS010/31022KT In U.S. TAF, non-convective low-level (≤2,000 ft) W  ind Shear; 3-digit

height (hundreds of ft); “/”; 3-digit wind direction and 2-3 digit wind

speed above the indicated height, and unit, KT
7/26/12 AIM

Meteorology 7−1−63

FIG 7−1−23

Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Back)

Key to Aerodrome Forecast (TAF) and Aviation

Routine Weather Report (METAR) (Back)

In METAR, ReMarK indicator & remarks. For example: Sea- Level

Pressure in hectoPascals & tenths, as shown: 1004.5 hPa; Temp/dewpoint in tenths °C, as shown: temp. 18.2°C, dew-point 15.9°C

RMK SLP045

T01820159

FM091930 FroM: changes are expected at: 2-digit date, 2-digit hour, and 2-digit

minute beginning time: indicates significant change. Each FM starts on a

new line, indented 5 spaces

TEMPO

0920/0922

TEMPOrary: changes expected for <1 hour and in total, < half of the

period between the 2-digit date and 2-digit hour beginning, and 2-digit

date and 2-digit hour ending time

PROB30

1004/1007

PROBability and 2-digit percent (30 or 40): probable condition in the

period between the 2-digit date & 2-digit hour beginning time, and the

2-digit date and 2-digit hour ending time

BECMG

1013/1015

BECoMinG: change expected in the period between the 2-digit date and

2-digit hour beginning time, and the 2-digit date and 2-digit hour ending

time

Table of Significant Present, Forecast and Recent Weather - Grouped in categories and

used in the order listed below; or as needed in TAF, No Significant Weather.

Qualifiers

Intensity or Proximity

“-” = Light No sign = Moderate “+” = Heavy

“VC” = Vicinity, but not at aerodrome. In the US METAR, 5 to 10 SM from the point of observation. In the US

TAF, 5 to 10 SM from the center of the runway complex. Elsewhere, within 8000m.

Descriptor

BC – Patches BL – Blowing DR – Drifting FZ – Freezing

MI – Shallow PR – Partial SH – Showers TS – Thunderstorm

Weather Phenomena

Precipitation

DZ – Drizzle GR – Hail GS – Small Hail/Snow Pellets

IC – Ice Crystals PL – Ice Pellets RA – Rain SG – Snow Grains

SN – Snow UP – Unknown Precipitation in automated observations

Obscuration

BR – Mist (≥5/8SM) DU – Widespread Dust FG – Fog (<5/8SM) FU – Smoke

HZ – Haze PY – Spray SA – Sand VA – Volcanic Ash

Other

DS – Dust Storm FC – Funnel Cloud +FC – Tornado or Waterspout

PO – Well developed dust or sand whirls SQ – Squall SS – Sandstorm

- Explanations in parentheses “()” indicate different worldwide practices.

- Ceiling is not specified; defined as the lowest broken or overcast layer, or the vertical visibility.

- NWS TAFs exclude BECMG groups and temperature forecasts, NWS TAFS do not use PROB in the first 9

hours of a TAF; NWS METARs exclude trend forecasts. US Military TAFs include Turbulence and Icing groups.
AIM 7/26/12

7−1−64 Meteorology

7−1−31. International Civil Aviation

Organization (ICAO) Weather Formats

The U.S. uses the ICAO world standard for aviation

weather reporting and forecasting. The utilization of

terminal forecasts affirms our commitment to a single

global format for aviation weather. The World

Meteorological Organization’s (WMO) publication

No. 782 “Aerodrome Reports and Forecasts”

contains the base METAR and TAF code as adopted

by the WMO member countries.

a. Although the METAR code is adopted

worldwide, each country is allowed to make

modifications or exceptions to the code for use in

their particular country, e.g., the U.S. will continue to

use statute miles for visibility, feet for RVR values,

knots for wind speed, and inches of mercury for

altimetry. However, temperature and dew point will

be reported in degrees Celsius. The U.S. will continue

reporting prevailing visibility rather than lowest

sector visibility. Most of the current U.S. observing

procedures and policies will continue after the

METAR conversion date, with the information

disseminated in the METAR code and format. The

elements in the body of a METAR report are

separated with a space. The only exceptions are RVR,

temperature and dew point, which are separated with

a solidus (/). When an element does not occur, or

cannot be observed, the preceding space and that

element are omitted from that particular report. A

METAR report contains the following sequence of

elements in the following order:

1. Type of report.

2. ICAO Station Identifier.

3. Date and time of report.

4. Modifier (as required).

5. Wind.

6. Visibility.

7. Runway Visual Range (RVR).

8. Weather phenomena.

9. Sky conditions.

10. Temperature/dew point group.

11. Altimeter.

12. Remarks (RMK).

b. The following paragraphs describe the elements in a METAR report.

1. Type of report. There are two types of

report:

(a) Aviation Routine Weather Report

(METAR); and

(b) Nonroutine (Special) Aviation Weather

Report (SPECI).

The type of report (METAR or SPECI) will always

appear as the lead element of the report.

2. ICAO Station Identifier. The METAR

code uses ICAO 4−letter station identifiers. In the

contiguous 48 States, the 3−letter domestic station

identifier is prefixed with a “K;” i.e., the domestic

identifier for Seattle is SEA while the ICAO identifier

is KSEA. Elsewhere, the first two letters of the ICAO

identifier indicate what region of the world and

country (or state) the station is in. For Alaska, all

station identifiers start with “PA;” for Hawaii, all

station identifiers start with “PH.” Canadian station

identifiers start with “CU,” “CW,” “CY,” and “CZ.”

Mexican station identifiers start with “MM.” The

identifier for the western Caribbean is “M” followed

by the individual country’s letter; i.e., Cuba is “MU;”

Dominican Republic “MD;” the Bahamas “MY.” The

identifier for the eastern Caribbean is “T” followed

by the individual country’s letter; i.e., Puerto Rico is

“TJ.” For a complete worldwide listing see ICAO

Document 7910, Location Indicators.

3. Date and Time of Report. The date and

time the observation is taken are transmitted as a

six−digit date/time group appended with Z to denote

Coordinated Universal Time (UTC). The first two

digits are the date followed with two digits for hour

and two digits for minutes.

EXAMPLE−

172345Z (the 17th day of the month at 2345Z)

4. Modifier (As Required). “AUTO” identifies a METAR/SPECI report as an automated weather

report with no human intervention. If “AUTO” is

shown in the body of the report, the type of sensor

equipment used at the station will be encoded in the

remarks section of the report. The absence of

“AUTO” indicates that a report was made manually

by an observer or that an automated report had human

augmentation/backup. The modifier “COR” indicates a corrected report that is sent out to replace an

earlier report with an error.
7/26/12 AIM

Meteorology 7−1−65

NOTE−

There are two types of automated stations, AO1 for

automated weather reporting stations without a precipitation discriminator, and AO2 for automated stations with a

precipitation discriminator. (A precipitation discriminator

can determine the difference between liquid and

frozen/freezing precipitation). This information appears in

the remarks section of an automated report.

5. Wind. The wind is reported as a five digit

group (six digits if speed is over 99 knots). The first

three digits are the direction the wind is blowing

from, in tens of degrees referenced to true north, or

“VRB” if the direction is variable. The next two digits

is the wind speed in knots, or if over 99 knots, the next

three digits. If the wind is gusty, it is reported as a “G”

after the speed followed by the highest gust reported.

The abbreviation “KT” is appended to denote the use

of knots for wind speed.

EXAMPLE−

13008KT − wind from 130 degrees at 8 knots

08032G45KT − wind from 080 degrees at 32 knots with

gusts to 45 knots

VRB04KT − wind variable in direction at 4 knots

00000KT − wind calm

210103G130KT − wind from 210 degrees at 103 knots with

gusts to 130 knots

If the wind direction is variable by 60 degrees or more and

the speed is greater than 6 knots, a variable group

consisting of the extremes of the wind direction separated

by a “v” will follow the prevailing wind group.

32012G22KT 280V350

(a) Peak Wind. Whenever the peak wind

exceeds 25 knots “PK WND” will be included in

Remarks, e.g., PK WND 28045/1955 “Peak wind two

eight zero at four five occurred at one niner five five.”

If the hour can be inferred from the report time, only

the minutes will be appended, e.g., PK WND

34050/38 “Peak wind three four zero at five zero

occurred at three eight past the hour.”

(b) Wind shift. Whenever a wind shift

occurs, “WSHFT” will be included in remarks

followed by the time the wind shift began, e.g.,

WSHFT 30 FROPA “Wind shift at three zero due to

frontal passage.”

6. Visibility. Prevailing visibility is reported in

statute miles with “SM” appended to it.

EXAMPLE−

7SM − seven statute miles

15SM − fifteen statute miles

1/2SM − one−half statute mile

(a) Tower/surface visibility. If either visibility (tower or surface) is below four statute miles,

the lesser of the two will be reported in the body of the

report; the greater will be reported in remarks.

(b) Automated visibility. ASOS/AWSS

visibility stations will show visibility 10 or greater

than 10 miles as “10SM.” AWOS visibility stations

will show visibility less than 1/4 statute mile as

“M1/4SM” and visibility 10 or greater than 10 miles

as “10SM.”

(c) Variable visibility. Variable visibility is

shown in remarks (when rapid increase or decrease

by 1/2 statute mile or more and the average prevailing

visibility is less than three miles) e.g., VIS 1V2

“visibility variable between one and two.”

(d) Sector visibility. Sector visibility is

shown in remarks when it differs from the prevailing

visibility, and either the prevailing or sector visibility

is less than three miles.

EXAMPLE−

VIS N2 − visibility north two

7. Runway Visual Range (When Reported).

“R” identifies the group followed by the runway

heading (and parallel runway designator, if needed)

“/” and the visual range in feet (meters in other

countries) followed with “FT” (feet is not spoken).

(a) Variability Values. When RVR varies

(by more than on reportable value), the lowest and

highest values are shown with “V” between them.

(b) Maximum/Minimum Range. “P” indicates an observed RVR is above the maximum value

for this system (spoken as “more than”). “M”

indicates an observed RVR is below the minimum

value which can be determined by the system (spoken

as “less than”).

EXAMPLE−

R32L/1200FT − runway three two left R−V−R one thousand

two hundred.

R27R/M1000V4000FT − runway two seven right R−V−R

variable from less than one thousand to four thousand.
AIM 7/26/12

7−1−66 Meteorology

8. Weather Phenomena. The weather as

reported in the METAR code represents a significant

change in the way weather is currently reported. In

METAR, weather is reported in the format:

Intensity/Proximity/Descriptor/Precipitation/

Obstruction to visibility/Other

NOTE−

The “/” above and in the following descriptions (except as

the separator between the temperature and dew point) are

for separation purposes in this publication and do not

appear in the actual METARs.

(a) Intensity applies only to the first type of

precipitation reported. A “−” denotes light, no symbol

denotes moderate, and a “+” denotes heavy.

(b) Proximity applies to and reported only

for weather occurring in the vicinity of the airport

(between 5 and 10 miles of the point(s) of

observation). It is denoted by the letters “VC.”

(Intensity and “VC” will not appear together in the

weather group).

(c) Descriptor. These eight descriptors apply to the precipitation or obstructions to visibility:

TS ........... thunderstorm

DR ........... low drifting

SH ........... showers

MI ........... shallow

FZ ........... freezing

BC ........... patches

BL ........... blowing

PR ........... partial

NOTE−

Although “TS” and “SH” are used with precipitation and

may be preceded with an intensity symbol, the intensity still

applies to the precipitation, not the descriptor.

(d) Precipitation. There are nine types of

precipitation in the METAR code:

RA .......... rain

DZ .......... drizzle

SN .......... snow

GR hail (1 .......... /4” or greater)

GS .......... small hail/snow pellets

PL .......... ice pellets

SG .......... snow grains

IC ........... ice crystals (diamond dust)

UP .......... unknown precipitation

(automated stations only)

(e) Obstructions to visibility. There are

eight types of obscuration phenomena in the METAR

code (obscurations are any phenomena in the

atmosphere, other than precipitation, that reduce

horizontal visibility):

FG fog (vsby less than 5 .......... /8 mile)

HZ haze ..........

FU .......... smoke

PY .......... spray

BR mist (vsby 5 .......... /8 − 6 miles)

SA .......... sand

DU .......... dust

VA .......... volcanic ash

NOTE−

Fog (FG) is observed or forecast only when the visibility is

less than five−eighths of mile, otherwise mist (BR) is

observed or forecast.

(f) Other. There are five categories of other

weather phenomena which are reported when they

occur:

SQ ........... squall

SS ........... sandstorm

DS ........... duststorm

PO .......... dust/sand whirls

FC ........... funnel cloud

+FC ......... tornado/waterspout

Examples:

TSRA ......... thunderstorm with moderate

 rain

+SN .......... heavy snow

−RA FG ....... light rain and fog

BRHZ ........ mist and haze 

(visibility 5/8 mile or greater)

FZDZ ......... freezing drizzle

VCSH ........ rain shower in the vicinity

+SHRASNPL . . heavy rain showers, snow,

ice pellets (intensity

indicator refers to the 

predominant rain)

9. Sky Condition. The sky condition as

reported in METAR represents a significant change

from the way sky condition is currently reported. In

METAR, sky condition is reported in the format:

Amount/Height/(Type) or Indefinite Ceiling/Height
7/26/12 AIM

Meteorology 7−1−67

(a) Amount. The amount of sky cover is

reported in eighths of sky cover, using the

contractions:

SKC ......... clear (no clouds)

FEW >0 to 2 ........ /8

SCT scattered (3/8s to 4/8s ......... of

clouds)

BKN broken (5/8s to 7 ......... /8s of clouds)

OVC overcast (8/8s ......... clouds)

CB .......... Cumulonimbus when present

TCU ......... Towering cumulus when

present

NOTE−

1. “SKC” will be reported at manual stations. “CLR” will

be used at automated stations when no clouds below

12,000 feet are reported.

2. A ceiling layer is not designated in the METAR code.

For aviation purposes, the ceiling is the lowest broken or

overcast layer, or vertical visibility into an obscuration.

Also there is no provision for reporting thin layers in the

METAR code. When clouds are thin, that layer must be

reported as if it were opaque.

(b) Height. Cloud bases are reported with

three digits in hundreds of feet. (Clouds above

12,000 feet cannot be reported by an automated

station).

(c) (Type). If Towering Cumulus Clouds

(TCU) or Cumulonimbus Clouds (CB) are present,

they are reported after the height which represents

their base.

EXAMPLE−

(Reported as) SCT025TCU BKN080 BKN250 (spoken as)

“TWO THOUSAND FIVE HUNDRED SCATTERED

TOWERING CUMULUS, CEILING EIGHT THOUSAND

BROKEN, TWO FIVE THOUSAND BROKEN.”

(Reported as) SCT008 OVC012CB (spoken as) “EIGHT

HUNDRED SCATTERED CEILING ONE THOUSAND

TWO HUNDRED OVERCAST CUMULONIMBUS

CLOUDS.”

(d) Vertical Visibility (indefinite ceiling

height). The height into an indefinite ceiling is

preceded by “VV” and followed by three digits

indicating the vertical visibility in hundreds of feet.

This layer indicates total obscuration.

EXAMPLE− 1/8 SM FG VV006 − visibility one eighth, fog, indefinite

ceiling six hundred.

(e) Obscurations are reported when the sky

is partially obscured by a ground−based phenomena

by indicating the amount of obscuration as FEW,

SCT, BKN followed by three zeros (000). In remarks,

the obscuring phenomenon precedes the amount of

obscuration and three zeros.

EXAMPLE−

BKN000 (in body) “sky partially obscured” ........

FU BKN000 (in remarks) ... “smoke obscuring five−

to seven−eighths of the

sky”

(f) When sky conditions include a layer aloft,

other than clouds, such as smoke or haze the type of

phenomena, sky cover and height are shown in

remarks.

EXAMPLE−

BKN020 (in body) “ceiling two thousand ........

broken”

RMK FU BKN020 “broken layer of smoke ........

aloft, based at 

two thousand”

(g) Variable ceiling. When a ceiling is

below three thousand and is variable, the remark

“CIG” will be shown followed with the lowest and

highest ceiling heights separated by a “V.”

EXAMPLE−

CIG 005V010 “ceiling variable ............

between five hundred and

one thousand”

(h) Second site sensor. When an automated

station uses meteorological discontinuity sensors,

remarks will be shown to identify site specific sky

conditions which differ and are lower than conditions

reported in the body.

EXAMPLE−

CIG 020 RY11 “ceiling two thousand at ...........

runway one one”

(i) Variable cloud layer. When a layer is

varying in sky cover, remarks will show the

variability range. If there is more than one cloud

layer, the variable layer will be identified by

including the layer height.

EXAMPLE−

SCT V BKN “scattered ............. layer variable to

broken”

BKN025 V OVC “broken layer at .........

two thousand five hundred

variable to overcast”
AIM 7/26/12

7−1−68 Meteorology

(j) Significant clouds. When significant

clouds are observed, they are shown in remarks,

along with the specified information as shown below:

(1) Cumulonimbus (CB), or Cumulonimbus Mammatus (CBMAM), distance (if known),

direction from the station, and direction of

movement, if known. If the clouds are beyond

10 miles from the airport, DSNT will indicate

distance.

EXAMPLE−

CB W MOV E “cumulonimbus west moving .......

east”

CBMAM DSNT S “cumulonimbus mammatus ....

distant south”

(2) Towering Cumulus (TCU), location, (if

known), or direction from the station.

EXAMPLE−

TCU OHD “towering cumulus overhead” .........

TCU W “towering cumulus west” ............

(3) Altocumulus Castellanus (ACC), Stratocumulus Standing Lenticular (SCSL),

Altocumulus Standing Lenticular (ACSL), Cirrocumulus Standing Lenticular (CCSL) or rotor clouds,

describing the clouds (if needed) and the direction

from the station.

EXAMPLE−

ACC W “altocumulus ............. castellanus west”

ACSL SW−S “standing lenticular .........

altocumulus southwest

through south”

APRNT ROTOR CLD S “apparent rotor cloud south”

CCSL OVR MT E “standing lenticular .....

cirrocumulus over the 

mountains east”

10. Temperature/Dew Point. Temperature

and dew point are reported in two, two-digit groups

in degrees Celsius, separated by a solidus (“/”).

Temperatures below zero are prefixed with an “M.”

If the temperature is available but the dew point is

missing, the temperature is shown followed by a

solidus. If the temperature is missing, the group is

omitted from the report.

EXAMPLE−

15/08 “temperature one five, ..............

dew point 8”

00/M02 “temperature zero, ............

dew point minus 2”

M05/ “temperature minus five, ...............

dew point missing”

11. Altimeter. Altimeter settings are reported

in a four-digit format in inches of mercury prefixed

with an “A” to denote the units of pressure.

EXAMPLE−

A2995 − “Altimeter two niner niner five”

12. Remarks. Remarks will be included in all

observations, when appropriate. The contraction

“RMK” denotes the start of the remarks section of a

METAR report.

Except for precipitation, phenomena located within

5 statute miles of the point of observation will be

reported as at the station. Phenomena between 5 and

10 statute miles will be reported in the vicinity, “VC.”

Precipitation not occurring at the point of observation

but within 10 statute miles is also reported as in the

vicinity, “VC.” Phenomena beyond 10 statute miles

will be shown as distant, “DSNT.” Distances are in

statute miles except for automated lightning remarks

which are in nautical miles. Movement of clouds or

weather will be indicated by the direction toward

which the phenomena is moving.

(a) There are two categories of remarks:

(1) Automated, manual, and plain

language.

(2) Additive and automated maintenance

data.

(b) Automated, Manual, and Plain Language. This group of remarks may be generated

from either manual or automated weather reporting

stations and generally elaborate on parameters

reported in the body of the report. (Plain language

remarks are only provided by manual stations).

(1) Volcanic eruptions.

(2) Tornado, Funnel Cloud, Waterspout.

(3) Station Type (AO1 or AO2).

(4) PK WND.

(5) WSHFT (FROPA).

(6) TWR VIS or SFC VIS.

(7) VRB VIS.

(8) Sector VIS.

(9) VIS @ 2nd Site.

(10) (freq) LTG (type) (loc).
7/26/12 AIM

Meteorology 7−1−69

(11) Beginning/Ending of Precipitation/

TSTMS.

(12) TSTM Location MVMT.

(13) Hailstone Size (GR).

(14) Virga.

(15) VRB CIG (height).

(16) Obscuration.

(17) VRB Sky Condition.

(18) Significant Cloud Types.

(19) Ceiling Height 2nd Location.

(20) PRESFR PRESRR.

(21) Sea−Level Pressure.

(22) ACFT Mishap (not transmitted).

(23) NOSPECI.

(24) SNINCR.

(25) Other SIG Info.

(c) Additive and Automated Maintenance

Data.

(1) Hourly Precipitation.

(2) 3− and 6−Hour Precipitation Amount.

(3) 24−Hour Precipitation.

(4) Snow Depth on Ground.

(5) Water Equivalent of Snow.

(6) Cloud Type.

(7) Duration of Sunshine.

(8) Hourly Temperature/Dew Point

(Tenths).

(9) 6−Hour Maximum Temperature.

(10) 6−Hour Minimum Temperature.

(11) 24−Hour Maximum/Minimum

Temperature.

(12) Pressure Tendency.

(13) Sensor Status.

PWINO

FZRANO

TSNO

RVRNO

PNO

VISNO

Examples of METAR reports and explanation:

METAR KBNA 281250Z 33018KT 290V360

1/2SM R31/2700FT SN BLSN FG VV008 00/M03

A2991 RMK RAE42SNB42

METAR ...... aviation routine weather 

report

KBNA ........ Nashville, TN

281250Z date 28th ...... , time 1250 UTC

(no modifier) . . This is a manually generated

report, due to the absence of

“AUTO” and “AO1 or AO2”

in remarks

33018KT ..... wind three three zero at one

eight

290V360 ...... wind variable between

two nine zero and three six

zero

1/2SM ........ visibility one half

R31/2700FT ... Runway three one RVR two

thousand seven hundred

SN ........... moderate snow

BLSN FG ..... visibility obscured by 

blowing snow and fog

VV008 ....... indefinite ceiling eight

hundred

00/M03 ....... temperature zero, dew point

 minus three

A2991 ........ altimeter two niner niner one

RMK ........ remarks

RAE42 ....... rain ended at four two

SNB42 ....... snow began at four two

METAR KSFO 041453Z AUTO VRB02KT 3SM

BR CLR 15/12 A3012 RMK AO2

METAR ...... aviation routine weather 

report

KSFO ........ San Francisco, CA

041453Z date 4th ...... , time 1453 UTC

AUTO ....... fully automated; no human

intervention

VRB02KT .... wind variable at two

3SM ......... visibility three

BR .......... visibility obscured by mist

CLR ......... no clouds below one two

thousand

15/12 ......... temperature one five, dew

point one two
AIM 7/26/12

7−1−70 Meteorology

A3012 ........ altimeter three zero one two

RMK ........ remarks

AO2 ......... this automated station has a

weather discriminator (for

precipitation)

SPECI KCVG 152224Z 28024G36KT 3/4SM

+TSRA BKN008 OVC020CB 28/23 A3000 RMK

TSRAB24 TS W MOV E

SPECI ....... (nonroutine) aviation special

weather report

KCVG ....... Cincinnati, OH

152228Z date 15th ...... , time 2228 UTC

(no modifier) . . This is a manually generated

report due to the absence of

“AUTO” and “AO1 or AO2”

in remarks

28024G36KT . . wind two eight zero at 

two four gusts three six

3/4SM ........ visibility three fourths

+TSRA ....... thunderstorms, heavy rain

BKN008 ceiling eight hundred broken

OVC020CB ... two thousand overcast

cumulonimbus clouds

28/23 ......... temperature two eight, 

dew point two three

A3000 ........ altimeter three zero zero zero

RMK ........ remarks 

TSRAB24 ..... thunderstorm and rain began

at two four

TS W MOV E thunderstorm west moving

east

c. Aerodrome Forecast (TAF). A concise statement of the expected meteorological conditions at an

airport during a specified period. At most locations,

TAFs have a 24 hour forecast period. However, TAFs

for some locations have a 30 hour forecast period.

These forecast periods may be shorter in the case of

an amended TAF. TAFs use the same codes as

METAR weather reports. They are scheduled four

times daily for 24−hour periods beginning at 0000Z,

0600Z, 1200Z, and 1800Z.

Forecast times in the TAF are depicted in two ways.

The first is a 6−digit number to indicate a specific

point in time, consisting of a two−digit date,

two−digit hour, and two−digit minute (such as

issuance time or FM). The second is a pair of

four−digit numbers separated by a “/” to indicate a

beginning and end for a period of time. In this case,

each four−digit pair consists of a two−digit date and

a two−digit hour.

TAFs are issued in the following format:

TYPE OF REPORT/ICAO STATION IDENTIFIER/

DATE AND TIME OF ORIGIN/VALID PERIOD

DATE AND TIME/FORECAST METEOROLOGICAL CONDITIONS

NOTE−

The “/” above and in the following descriptions are for

separation purposes in this publication and do not appear

in the actual TAFs.

TAF KORD 051130Z 0512/0618 14008KT 5SM BR

BKN030 

TEMPO 0513/0516 1 1/2SM BR

FM051600 16010KT P6SM SKC

FM052300 20013G20KT 4SM SHRA OVC020

PROB40 0600/0606 2SM TSRA OVC008CB 

BECMG 0606/0608 21015KT P6SM NSW

SCT040

TAF format observed in the above example:

TAF = type of report

KORD = ICAO station identifier

051130Z = date and time of origin (issuance time)

0512/0618 = valid period date and times

14008KT 5SM BR BKN030 = forecast meteorological conditions

Explanation of TAF elements:

1. Type of Report. There are two types of TAF

issuances, a routine forecast issuance (TAF) and an

amended forecast (TAF AMD). An amended TAF is

issued when the current TAF no longer adequately

describes the on-going weather or the forecaster feels

the TAF is not representative of the current or

expected weather. Corrected (COR) or delayed

(RTD) TAFs are identified only in the communications header which precedes the actual forecasts.

2. ICAO Station Identifier. The TAF code

uses ICAO 4−letter location identifiers as described

in the METAR section.

3. Date and Time of Origin. This element is

the date and time the forecast is actually prepared.

The format is a two−digit date and four−digit time

followed, without a space, by the letter “Z.”

4. Valid Period Date and Time. The UTC

valid period of the forecast consists of two four−digit
7/26/12 AIM

Meteorology 7−1−71

sets, separated by a “/”. The first four−digit set is a

two−digit date followed by the two−digit beginning

hour, and the second four−digit set is a two−digit date

followed by the two−digit ending hour. Although

most airports have a 24−hour TAF, a select number of

airports have a 30−hour TAF. In the case of an

amended forecast, or a forecast which is corrected or

delayed, the valid period may be for less than 24

hours. Where an airport or terminal operates on a

part−time basis (less than 24 hours/day), the TAFs

issued for those locations will have the abbreviated

statement “NIL AMD SKED AFT (closing time) Z”

added to the end of the forecasts. For the TAFs issued

while these locations are closed, the word “NIL” will

appear in place of the forecast text. A delayed (RTD)

forecast will then be issued for these locations after

two complete observations are received.

5. Forecast Meteorological Conditions. This

is the body of the TAF. The basic format is:

WIND/VISIBILITY/WEATHER/SKY

CONDITION/OPTIONAL DATA (WIND SHEAR)

The wind, visibility, and sky condition elements are

always included in the initial time group of the

forecast. Weather is included only if significant to

aviation. If a significant, lasting change in any of the

elements is expected during the valid period, a new

time period with the changes is included. It should be

noted that with the exception of a “FM” group the

new time period will include only those elements

which are expected to change, i.e., if a lowering of the

visibility is expected but the wind is expected to

remain the same, the new time period reflecting the

lower visibility would not include a forecast wind.

The forecast wind would remain the same as in the

previous time period. Any temporary conditions

expected during a specific time period are included

with that time period. The following describes the

elements in the above format.

(a) Wind. This five (or six) digit group

includes the expected wind direction (first 3 digits)

and speed (last 2 digits or 3 digits if 100 knots or

greater). The contraction “KT” follows to denote the

units of wind speed. Wind gusts are noted by the letter

“G” appended to the wind speed followed by the

highest expected gust. A variable wind direction is

noted by “VRB” where the three digit direction

usually appears. A calm wind (3 knots or less) is

forecast as “00000KT.”

EXAMPLE−

18010KT wind one ..... eight zero at one zero (wind is

blowing from 180).

35012G20KT wind three five zer . . o at one two gust two

zero.

(b) Visibility. The expected prevailing visibility up to and including 6 miles is forecast in statute

miles, including fractions of miles, followed by “SM”

to note the units of measure. Expected visibilities

greater than 6 miles are forecast as P6SM (plus

six statute miles).

EXAMPLE− 1/2SM − visibility one−half

4SM − visibility four

P6SM − visibility more than six

(c) Weather Phenomena. The expected

weather phenomena is coded in TAF reports using the

same format, qualifiers, and phenomena contractions

as METAR reports (except UP). Obscurations to

vision will be forecast whenever the prevailing

visibility is forecast to be 6 statute miles or less. If no

significant weather is expected to occur during a

specific time period in the forecast, the weather

phenomena group is omitted for that time period. If,

after a time period in which significant weather

phenomena has been forecast, a change to a forecast

of no significant weather phenomena occurs, the

contraction NSW (No Significant Weather) will

appear as the weather group in the new time period.

(NSW is included only in BECMG or TEMPO

groups).

NOTE−

It is very important that pilots understand that NSW only

refers to weather phenomena, i.e., rain, snow, drizzle, etc.

Omitted conditions, such as sky conditions, visibility,

winds, etc., are carried over from the previous time group.

(d) Sky Condition. TAF sky condition

forecasts use the METAR format described in the

METAR section. Cumulonimbus clouds (CB) are the

only cloud type forecast in TAFs. When clear skies

are forecast, the contraction “SKC” will always be

used. The contraction “CLR” is never used in the

TAF. When the sky is obscured due to a

surface−based phenomenon, vertical visibility (VV)

into the obscuration is forecast. The format for

vertical visibility is “VV” followed by a three−digit

height in hundreds of feet.

NOTE−

As in METAR, ceiling layers are not designated in the TAF

code. For aviation purposes, the ceiling is the lowest
AIM 7/26/12

7−1−72 Meteorology

broken or overcast layer or vertical visibility into a

complete obscuration.

SKC .............. “sky clear”

SCT005 BKN025CB “five hundred scattered,

ceiling two thousand

five hundred broken 

cumulonimbus clouds”

VV008 ............ “indefinite ceiling

eight hundred”

(e) Optional Data (Wind Shear). Wind

shear is the forecast of nonconvective low level winds

(up to 2,000 feet). The forecast includes the letters

“WS” followed by the height of the wind shear, the

wind direction and wind speed at the indicated height

and the ending letters “KT” (knots). Height is given

in hundreds of feet (AGL) up to and including

2,000 feet. Wind shear is encoded with the

contraction “WS,” followed by a three−digit height,

slant character “/,” and winds at the height indicated

in the same format as surface winds. The wind shear

element is omitted if not expected to occur.

WS010/18040KT − “LOW LEVEL WIND SHEAR

AT ONE THOUSAND, WIND ONE EIGHT ZERO

AT FOUR ZERO”

d. Probability Forecast. The probability or

chance of thunderstorms or other precipitation events

occurring, along with associated weather conditions

(wind, visibility, and sky conditions). The PROB30

group is used when the occurrence of thunderstorms

or precipitation is 30−39% and the PROB40 group is

used when the occurrence of thunderstorms or

precipitation is 40−49%. This is followed by two

four−digit groups separated by a “/”, giving the

beginning date and hour, and the ending date and hour

of the time period during which the thunderstorms or

precipitation are expected.

NOTE−

Neither PROB30 nor PROB40 will be shown during the

first six hours of a forecast.

EXAMPLE−

PROB40 2221/2302 1/2SM +TSRA “chance between

2100Z and 0200Z of

visibility one−half 

statute mile in 

thunderstorms and

heavy rain.”

PROB30 3010/3014 1SM RASN “chance between .

1000Z and 1400Z of

visibility one statute

mile in mixed rain

and snow.”

e. Forecast Change Indicators. The following

change indicators are used when either a rapid,

gradual, or temporary change is expected in some or

all of the forecast meteorological conditions. Each

change indicator marks a time group within the TAF

report.

1. From (FM) group. The FM group is used

when a rapid change, usually occurring in less than

one hour, in prevailing conditions is expected.

Typically, a rapid change of prevailing conditions to

more or less a completely new set of prevailing

conditions is associated with a synoptic feature

passing through the terminal area (cold or warm

frontal passage). Appended to the “FM” indicator is

the six−digit date, hour, and minute the change is

expected to begin and continues until the next change

group or until the end of the current forecast. A “FM”

group will mark the beginning of a new line in a TAF

report (indented 5 spaces). Each “FM” group

contains all the required elements−wind, visibility,

weather, and sky condition. Weather will be omitted

in “FM” groups when it is not significant to aviation.

FM groups will not include the contraction NSW.

EXAMPLE−

FM210100 14010KT P6SM SKC − “after 0100Z on the

21st, wind one four zero at one zero, visibility more than six,

sky clear.”

2. Becoming (BECMG) group. The BECMG

group is used when a gradual change in conditions is

expected over a longer time period, usually two

hours. The time period when the change is expected

is two four−digit groups separated by a “/”, with the

beginning date and hour, and ending date and hour of

the change period which follows the BECMG

indicator. The gradual change will occur at an

unspecified time within this time period. Only the

changing forecast meteorological conditions are

included in BECMG groups. The omitted conditions

are carried over from the previous time group.

EXAMPLE−

OVC012 BECMG 0114/0116 BKN020 − “ceiling one

thousand two hundred overcast. Then a gradual change

to ceiling two thousand broken between 1400Z on the 1st

and 1600Z on the 1st.”
7/26/12 AIM

Meteorology 7−1−73

3. Temporary (TEMPO) group. The TEMPO

group is used for any conditions in wind, visibility,

weather, or sky condition which are expected to last

for generally less than an hour at a time (occasional),

and are expected to occur during less than half the

time period. The TEMPO indicator is followed by

two four−digit groups separated by a “/”. The first

four digit group gives the beginning date and hour,

and the second four digit group gives the ending date

and hour of the time period during which the

temporary conditions are expected. Only the

changing forecast meteorological conditions are

included in TEMPO groups. The omitted conditions

are carried over from the previous time group.

EXAMPLE−

1. SCT030 TEMPO 0519/0523 BKN030 − “three

thousand scattered with occasional ceilings three thousand

broken between 1900Z on the 5th and 2300Z on the 5th.”

2. 4SM HZ TEMPO 1900/1906 2SM BR HZ − “visibility

four in haze with occasional visibility two in mist and haze

between 0000Z on the 19th and 0600Z on the 19th.”

7/26/12 AIM

Altimeter Setting Procedures 7−2−1

Section 2. Altimeter Setting Procedures

7−2−1. General

a. The accuracy of aircraft altimeters is subject to

the following factors:

1. Nonstandard temperatures of the atmosphere.

2. Nonstandard atmospheric pressure.

3. Aircraft static pressure systems (position

error); and

4. Instrument error.

b. EXTREME CAUTION SHOULD BE EXERCISED WHEN FLYING IN PROXIMITY TO

OBSTRUCTIONS OR TERRAIN IN LOW TEMPERATURES AND PRESSURES. This is especially

true in extremely cold temperatures that cause a large

differential between the Standard Day temperature

and actual temperature. This circumstance can cause

serious errors that result in the aircraft being

significantly lower than the indicated altitude.

NOTE−

Standard temperature at sea level is 15 degrees Celsius

(59 degrees Fahrenheit). The temperature gradient from

sea level is minus 2 degrees Celsius (3.6 degrees

Fahrenheit) per 1,000 feet. Pilots should apply corrections

for static pressure systems and/or instruments, if

appreciable errors exist.

c. The adoption of a standard altimeter setting at

the higher altitudes eliminates station barometer

errors, some altimeter instrument errors, and errors

caused by altimeter settings derived from different

geographical sources.

7−2−2. Procedures

The cruising altitude or flight level of aircraft must be

maintained by reference to an altimeter which must

be set, when operating:

a. Below 18,000 feet MSL.

1. When the barometric pressure is

31.00 inches Hg. or less. To the current reported

altimeter setting of a station along the route and

within 100 NM of the aircraft, or if there is no station

within this area, the current reported altimeter setting

of an appropriate available station. When an aircraft

is en route on an instrument flight plan, air traffic

controllers will furnish this information to the pilot at

least once while the aircraft is in the controllers area

of jurisdiction. In the case of an aircraft not equipped

with a radio, set to the elevation of the departure

airport or use an appropriate altimeter setting

available prior to departure.

2. When the barometric pressure exceeds

31.00 inches Hg. The following procedures will be

placed in effect by NOTAM defining the geographic

area affected:

(a) For all aircraft. Set 31.00 inches for en

route operations below 18,000 feet MSL. Maintain

this setting until beyond the affected area or until

reaching final approach segment. At the beginning of

the final approach segment, the current altimeter

setting will be set, if possible. If not possible,

31.00 inches will remain set throughout the approach. Aircraft on departure or missed approach will

set 31.00 inches prior to reaching any mandatory/

crossing altitude or 1,500 feet AGL, whichever is

lower. (Air traffic control will issue actual altimeter

settings and advise pilots to set 31.00 inches in their

altimeters for en route operations below 18,000 feet

MSL in affected areas.)

(b) During preflight, barometric altimeters

must be checked for normal operation to the extent

possible.

(c) For aircraft with the capability of setting

the current altimeter setting and operating into

airports with the capability of measuring the current

altimeter setting, no additional restrictions apply.

(d) For aircraft operating VFR, there are no

additional restrictions, however, extra diligence in

flight planning and in operating in these conditions is

essential.

(e) Airports unable to accurately measure

barometric pressures above 31.00 inches of Hg. will

report the barometric pressure as “missing” or “in

excess of 31.00 inches of Hg.” Flight operations to

and from those airports are restricted to VFR weather

conditions.
AIM 7/26/12

7−2−2 Altimeter Setting Procedures

(f) For aircraft operating IFR and unable to set

the current altimeter setting, the following restrictions apply:

(1) To determine the suitability of departure alternate airports, destination airports, and

destination alternate airports, increase ceiling

requirements by 100 feet and visibility requirements

by 1/4 statute mile for each 1/10 of an inch of Hg., or

any portion thereof, over 31.00 inches. These

adjusted values are then applied in accordance with

the requirements of the applicable operating

regulations and operations specifications.

EXAMPLE−

Destination altimeter is 31.28 inches, ILS DH 250 feet

(200−1/2 ). When flight planning, add 300−3/4 to the

weather requirements which would become 500−11/4.

(2) On approach, 31.00 inches will remain

set. Decision height (DH) or minimum descent

altitude must be deemed to have been reached when

the published altitude is displayed on the altimeter.

NOTE−

Although visibility is normally the limiting factor on an

approach, pilots should be aware that when reaching DH

the aircraft will be higher than indicated. Using the

example above the aircraft would be approximately

300 feet higher.

(3) These restrictions do not apply to

authorized Category II and III ILS operations nor do

they apply to certificate holders using approved QFE

altimetry systems.

(g) The FAA Regional Flight Standards

Division Manager of the affected area is authorized to

approve temporary waivers to permit emergency

resupply or emergency medical service operation.

b. At or above 18,000 feet MSL. To 29.92 inches of mercury (standard setting). The lowest usable

flight level is determined by the atmospheric pressure

in the area of operation as shown in TBL 7−2−1.

TBL 7−2−1

Lowest Usable Flight Level

Altimeter Setting

(Current Reported)

Lowest Usable

Flight Level

29.92 or higher 180

29.91 to 29.42 185

29.41 to 28.92 190

28.91 to 28.42 195

28.41 to 27.92 200

c. Where the minimum altitude, as prescribed in

14 CFR Section 91.159 and 14 CFR Section 91.177,

is above 18,000 feet MSL, the lowest usable flight

level must be the flight level equivalent of the

minimum altitude plus the number of feet specified in

TBL 7−2−2.

TBL 7−2−2

Lowest Flight Level Correction Factor

Altimeter Setting Correction Factor

29.92 or higher none

29.91 to 29.42 500 feet

29.41 to 28.92 1000 feet

28.91 to 28.42 1500 feet

28.41 to 27.92 2000 feet

27.91 to 27.42 2500 feet

EXAMPLE−

The minimum safe altitude of a route is 19,000 feet MSL

and the altimeter setting is reported between 29.92 and

29.42 inches of mercury, the lowest usable flight level will

be 195, which is the flight level equivalent of 19,500 feet

MSL (minimum altitude plus 500 feet).
7/26/12 AIM

Altimeter Setting Procedures 7−2−3

7−2−3. Altimeter Errors

a. Most pressure altimeters are subject to

mechanical, elastic, temperature, and installation

errors. (Detailed information regarding the use of

pressure altimeters is found in the Instrument Flying

Handbook, Chapter IV.) Although manufacturing

and installation specifications, as well as the periodic

test and inspections required by regulations (14 CFR

Part 43, Appendix E), act to reduce these errors, any

scale error may be observed in the following manner:

1. Set the current reported altimeter setting on

the altimeter setting scale.

2. Altimeter should now read field elevation if

you are located on the same reference level used to

establish the altimeter setting.

3. Note the variation between the known field

elevation and the altimeter indication. If this variation

is in the order of plus or minus 75 feet, the accuracy

of the altimeter is questionable and the problem

should be referred to an appropriately rated repair

station for evaluation and possible correction.

b. Once in flight, it is very important to obtain

frequently current altimeter settings en route. If you

do not reset your altimeter when flying from an area

of high pressure into an area of low pressure, your

aircraft will be closer to the surface than your

altimeter indicates. An inch error in the altimeter

setting equals 1,000 feet of altitude. To quote an old

saying: “GOING FROM A HIGH TO A LOW,

LOOK OUT BELOW.”

c. Temperature also has an effect on the accuracy

of altimeters and your altitude. The crucial values to

consider are standard temperature versus the ambient

(at altitude) temperature. It is this “difference” that

causes the error in indicated altitude. When the air is

warmer than standard, you are higher than your

altimeter indicates. Subsequently, when the air is

colder than standard you are lower than indicated. It

is the magnitude of this “difference” that determines

the magnitude of the error. When flying into a cooler

air mass while maintaining a constant indicated

altitude, you are losing true altitude. However, flying

into a cooler air mass does not necessarily mean you

will be lower than indicated if the difference is still on

the plus side. For example, while flying at 10,000 feet

(where STANDARD temperature is −5 degrees

Celsius (C)), the outside air temperature cools from

+5 degrees C to 0 degrees C, the temperature error

will nevertheless cause the aircraft to be HIGHER

than indicated. It is the extreme “cold” difference that

normally would be of concern to the pilot. Also, when

flying in cold conditions over mountainous country,

the pilot should exercise caution in flight planning

both in regard to route and altitude to ensure adequate

en route and terminal area terrain clearance.

d. TBL 7−2−3, derived from ICAO formulas,

indicates how much error can exist when the

temperature is extremely cold. To use the table, find

the reported temperature in the left column, then read

across the top row to locate the height above the

airport/reporting station (i.e., subtract the airport/

reporting elevation from the intended flight altitude).

The intersection of the column and row is how much

lower the aircraft may actually be as a result of the

possible cold temperature induced error.

e. The possible result of the above example should

be obvious, particularly if operating at the minimum

altitude or when conducting an instrument approach.

When operating in extreme cold temperatures, pilots

may wish to compensate for the reduction in terrain

clearance by adding a cold temperature correction.
AIM 7/26/12

7−2−4 Altimeter Setting Procedures

TBL 7−2−3

ICAO Cold Temperature Error Table

Reported Temp C

Height Above Airport in Feet

200 300 400 500 600 700 800 900 1000 1500 2000 3000 4000 5000

+10 10 10 10 10 20 20 20 20 20 30 40 60 80 90

 0 20 20 30 30 40 40 50 50 60 90 120 170 230 280

−10 20 30 40 50 60 70 80 90 100 150 200 290 390 490

−20 30 50 60 70 90 100 120 130 140 210 280 420 570 710

−30 40 60 80 100 120 140 150 170 190 280 380 570 760 950

−40 50 80 100 120 150 170 190 220 240 360 480 720 970 1210

−50 60 90 120 150 180 210 240 270 300 450 590 890 1190 1500

EXAMPLE−

Temperature−10 degrees Celsius, and the aircraft altitude is 1,000 feet above the airport elevation. The chart shows that

the reported current altimeter setting may place the aircraft as much as 100 feet below the altitude indicated by the altimeter.

7−2−4. High Barometric Pressure

a. Cold, dry air masses may produce barometric

pressures in excess of 31.00 inches of Mercury, and

many altimeters do not have an accurate means of

being adjusted for settings of these levels. When the

altimeter cannot be set to the higher pressure setting,

the aircraft actual altitude will be higher than the

altimeter indicates.

REFERENCE−

AIM, Paragraph 7−2−3, Altimeter Errors.

b. When the barometric pressure exceeds

31.00 inches, air traffic controllers will issue the

actual altimeter setting, and:

1. En Route/Arrivals. Advise pilots to remain

set on 31.00 inches until reaching the final approach

segment.

2. Departures. Advise pilots to set 31.00 inches prior to reaching any mandatory/crossing altitude

or 1,500 feet, whichever is lower.

c. The altimeter error caused by the high pressure

will be in the opposite direction to the error caused by

the cold temperature.

7−2−5. Low Barometric Pressure

When abnormally low barometric pressure conditions occur (below 28.00), flight operations by

aircraft unable to set the actual altimeter setting are

not recommended.

NOTE−

The true altitude of the aircraft is lower than the indicated

altitude if the pilot is unable to set the actual altimeter

setting.
7/26/12 AIM

Wake Turbulence 7−3−1

Section 3. Wake Turbulence

7−3−1. General

a. Every aircraft generates a wake while in flight.

Initially, when pilots encountered this wake in flight,

the disturbance was attributed to “prop wash.” It is

known, however, that this disturbance is caused by a

pair of counter−rotating vortices trailing from the

wing tips. The vortices from larger aircraft pose

problems to encountering aircraft. For instance, the

wake of these aircraft can impose rolling moments

exceeding the roll−control authority of the encountering aircraft. Further, turbulence generated within the

vortices can damage aircraft components and

equipment if encountered at close range. The pilot

must learn to envision the location of the vortex wake

generated by larger (transport category) aircraft and

adjust the flight path accordingly.

b. During ground operations and during takeoff,

jet engine blast (thrust stream turbulence) can cause

damage and upsets if encountered at close range.

Exhaust velocity versus distance studies at various

thrust levels have shown a need for light aircraft to

maintain an adequate separation behind large turbojet

aircraft. Pilots of larger aircraft should be particularly

careful to consider the effects of their “jet blast” on

other aircraft, vehicles, and maintenance equipment

during ground operations.

7−3−2. Vortex Generation

Lift is generated by the creation of a pressure

differential over the wing surface. The lowest

pressure occurs over the upper wing surface and the

highest pressure under the wing. This pressure

differential triggers the roll up of the airflow aft of the

wing resulting in swirling air masses trailing

downstream of the wing tips. After the roll up is

completed, the wake consists of two counter−rotating

cylindrical vortices. (See FIG 7−3−1.) Most of the

energy is within a few feet of the center of each

vortex, but pilots should avoid a region within about

100 feet of the vortex core.

FIG 7−3−1

Wake Vortex Generation

7−3−3. Vortex Strength

a. The strength of the vortex is governed by the

weight, speed, and shape of the wing of the generating

aircraft. The vortex characteristics of any given

aircraft can also be changed by extension of flaps or

other wing configuring devices as well as by change

in speed. However, as the basic factor is weight, the

vortex strength increases proportionately. Peak

vortex tangential speeds exceeding 300 feet per

second have been recorded. The greatest vortex

strength occurs when the generating aircraft is

HEAVY, CLEAN, and SLOW.

b. Induced Roll

1. In rare instances a wake encounter could

cause inflight structural damage of catastrophic

proportions. However, the usual hazard is associated

with induced rolling moments which can exceed the

roll−control authority of the encountering aircraft. In

flight experiments, aircraft have been intentionally

flown directly up trailing vortex cores of larger

aircraft. It was shown that the capability of an aircraft

to counteract the roll imposed by the wake vortex

primarily depends on the wingspan and counter−

control responsiveness of the encountering aircraft.
AIM 7/26/12

7−3−2 Wake Turbulence

2. Counter control is usually effective and

induced roll minimal in cases where the wingspan

and ailerons of the encountering aircraft extend

beyond the rotational flow field of the vortex. It is

more difficult for aircraft with short wingspan

(relative to the generating aircraft) to counter the

imposed roll induced by vortex flow. Pilots of short

span aircraft, even of the high performance type, must

be especially alert to vortex encounters. 

(See FIG 7−3−2.)

FIG 7−3−2

Wake Encounter Counter Control

COUNTER

CONTROL

3. The wake of larger aircraft requires the

respect of all pilots.

7−3−4. Vortex Behavior

a. Trailing vortices have certain behavioral

characteristics which can help a pilot visualize the

wake location and thereby take avoidance precautions.

1. Vortices are generated from the moment

aircraft leave the ground, since trailing vortices are a

by−product of wing lift. Prior to takeoff or touchdown

pilots should note the rotation or touchdown point of

the preceding aircraft. (See FIG 7−3−3.)

2. The vortex circulation is outward, upward

and around the wing tips when viewed from either

ahead or behind the aircraft. Tests with large aircraft

have shown that the vortices remain spaced a bit less

than a wingspan apart, drifting with the wind, at

altitudes greater than a wingspan from the ground. In

view of this, if persistent vortex turbulence is

encountered, a slight change of altitude and lateral

position (preferably upwind) will provide a flight

path clear of the turbulence.

3. Flight tests have shown that the vortices from

larger (transport category) aircraft sink at a rate of

several hundred feet per minute, slowing their

descent and diminishing in strength with time and

distance behind the generating aircraft. Atmospheric

turbulence hastens breakup. Pilots should fly at or

above the preceding aircraft’s flight path, altering

course as necessary to avoid the area behind and

below the generating aircraft. (See FIG 7−3−4.)

However, vertical separation of 1,000 feet may be

considered safe.

4. When the vortices of larger aircraft sink close

to the ground (within 100 to 200 feet), they tend to

move laterally over the ground at a speed of 2 or

3 knots. (See FIG 7−3−5.)

FIG 7−3−3

Wake Ends/Wake Begins

Touchdown Rotation

Wake Ends Wake Begins
7/26/12 AIM

Wake Turbulence 7−3−3

FIG 7−3−4

Vortex Flow Field

AVOID Nominally 500-1000 Ft. Nominally 500-1000 Ft.

Sink Rate

Several Hundred Ft.,/Min.

Sink Rate

Several Hundred Ft.,/Min.

FIG 7−3−5

Vortex Movement Near Ground − No Wind

No Wind No Wind

3K 3K

FIG 7−3−6

Vortex Movement Near Ground − with Cross Winds

6K

(3K + 3K) (3K + 3K)

3K Wind 3K Wind

0 (3K - 3K) 0 (3K - 3K)
AIM 7/26/12

7−3−4 Wake Turbulence

5. There is a small segment of the aviation

community that have become convinced that wake

vortices may “bounce” up to twice their nominal

steady state height. With a 200−foot span aircraft, the

“bounce” height could reach approximately 200 feet

AGL. This conviction is based on a single

unsubstantiated report of an apparent coherent

vortical flow that was seen in the volume scan of a

research sensor. No one can say what conditions

cause vortex bouncing, how high they bounce, at

what angle they bounce, or how many times a vortex

may bounce. On the other hand, no one can say for

certain that vortices never “bounce.” Test data have

shown that vortices can rise with the air mass in which

they are embedded. Wind shear, particularly, can

cause vortex flow field “tilting.” Also, ambient

thermal lifting and orographic effects (rising terrain

or tree lines) can cause a vortex flow field to rise.

Notwithstanding the foregoing, pilots are reminded

that they should be alert at all times for possible wake

vortex encounters when conducting approach and

landing operations. The pilot has the ultimate

responsibility for ensuring appropriate separations

and positioning of the aircraft in the terminal area to

avoid the wake turbulence created by a preceding

aircraft.

b. A crosswind will decrease the lateral movement

of the upwind vortex and increase the movement of

the downwind vortex. Thus a light wind with a cross

runway component of 1 to 5 knots could result in the

upwind vortex remaining in the touchdown zone for

a period of time and hasten the drift of the downwind

vortex toward another runway. (See FIG 7−3−6.)

Similarly, a tailwind condition can move the vortices

of the preceding aircraft forward into the touchdown

zone. THE LIGHT QUARTERING TAILWIND

REQUIRES MAXIMUM CAUTION. Pilots should

be alert to large aircraft upwind from their approach

and takeoff flight paths. (See FIG 7−3−7.)

FIG 7−3−7

Vortex Movement in Ground Effect − Tailwind

Light Quartering

Tailwind

Light Quartering Tailwind

x

Tail Wind Tail Wind

Touchdown Point Touchdown Point
7/26/12 AIM

Wake Turbulence 7−3−5

7−3−5. Operations Problem Areas

a. A wake encounter can be catastrophic. In 1972

at Fort Worth a DC−9 got too close to a DC−10

(two miles back), rolled, caught a wingtip, and

cartwheeled coming to rest in an inverted position on

the runway. All aboard were killed. Serious and even

fatal GA accidents induced by wake vortices are not

uncommon. However, a wake encounter is not

necessarily hazardous. It can be one or more jolts with

varying severity depending upon the direction of the

encounter, weight of the generating aircraft, size of

the encountering aircraft, distance from the generating aircraft, and point of vortex encounter. The

probability of induced roll increases when the

encountering aircraft’s heading is generally aligned

with the flight path of the generating aircraft.

b. AVOID THE AREA BELOW AND BEHIND

THE GENERATING AIRCRAFT, ESPECIALLY

AT LOW ALTITUDE WHERE EVEN A

MOMENTARY WAKE ENCOUNTER COULD BE

HAZARDOUS. This is not easy to do. Some

accidents have occurred even though the pilot of the

trailing aircraft had carefully noted that the aircraft in

front was at a considerably lower altitude. Unfortunately, this does not ensure that the flight path of the

lead aircraft will be below that of the trailing aircraft.

c. Pilots should be particularly alert in calm wind

conditions and situations where the vortices could:

1. Remain in the touchdown area.

2. Drift from aircraft operating on a nearby

runway.

3. Sink into the takeoff or landing path from a

crossing runway.

4. Sink into the traffic pattern from other airport

operations.

5. Sink into the flight path of VFR aircraft

operating on the hemispheric altitude 500 feet below.

d. Pilots of all aircraft should visualize the

location of the vortex trail behind larger aircraft and

use proper vortex avoidance procedures to achieve

safe operation. It is equally important that pilots of

larger aircraft plan or adjust their flight paths to

minimize vortex exposure to other aircraft.

7−3−6. Vortex Avoidance Procedures

a. Under certain conditions, airport traffic controllers apply procedures for separating IFR aircraft. If a

pilot accepts a clearance to visually follow a

preceding aircraft, the pilot accepts responsibility for

separation and wake turbulence avoidance. The

controllers will also provide to VFR aircraft, with

whom they are in communication and which in the

tower’s opinion may be adversely affected by wake

turbulence from a larger aircraft, the position, altitude

and direction of flight of larger aircraft followed by

the phrase “CAUTION − WAKE TURBULENCE.”

After issuing the caution for wake turbulence, the

airport traffic controllers generally do not provide

additional information to the following aircraft

unless the airport traffic controllers know the

following aircraft is overtaking the preceding

aircraft. WHETHER OR NOT A WARNING OR

INFORMATION HAS BEEN GIVEN, HOWEVER,

THE PILOT IS EXPECTED TO ADJUST AIRCRAFT OPERATIONS AND FLIGHT PATH AS

NECESSARY TO PRECLUDE SERIOUS WAKE

ENCOUNTERS. When any doubt exists about

maintaining safe separation distances between

aircraft during approaches, pilots should ask the

control tower for updates on separation distance and

aircraft groundspeed.

b. The following vortex avoidance procedures are

recommended for the various situations:

1. Landing behind a larger aircraft− same

runway. Stay at or above the larger aircraft’s final

approach flight path−note its touchdown point−land

beyond it.

2. Landing behind a larger aircraft− when

parallel runway is closer than 2,500 feet. Consider

possible drift to your runway. Stay at or above the

larger aircraft’s final approach flight path− note its

touchdown point.

3. Landing behind a larger aircraft− crossing

runway. Cross above the larger aircraft’s flight path.

4. Landing behind a departing larger aircraft− same runway. Note the larger aircraft’s

rotation point− land well prior to rotation point.

5. Landing behind a departing larger aircraft− crossing runway. Note the larger aircraft’s

rotation point− if past the intersection− continue the

approach− land prior to the intersection. If larger

aircraft rotates prior to the intersection, avoid flight
AIM 7/26/12

7−3−6 Wake Turbulence

below the larger aircraft’s flight path. Abandon the

approach unless a landing is ensured well before

reaching the intersection.

6. Departing behind a larger aircraft. Note

the larger aircraft’s rotation point and rotate prior to

the larger aircraft’s rotation point. Continue climbing

above the larger aircraft’s climb path until turning

clear of the larger aircraft’s wake. Avoid subsequent

headings which will cross below and behind a larger

aircraft. Be alert for any critical takeoff situation

which could lead to a vortex encounter.

7. Intersection takeoffs− same runway. Be

alert to adjacent larger aircraft operations, particularly upwind of your runway. If intersection takeoff

clearance is received, avoid subsequent heading

which will cross below a larger aircraft’s path.

8. Departing or landing after a larger

aircraft executing a low approach, missed

approach, or touch−and−go landing. Because

vortices settle and move laterally near the ground, the

vortex hazard may exist along the runway and in your

flight path after a larger aircraft has executed a low

approach, missed approach, or a touch−and−go

landing, particular in light quartering wind conditions. You should ensure that an interval of at least

2 minutes has elapsed before your takeoff or landing.

9. En route VFR (thousand−foot altitude plus

500 feet). Avoid flight below and behind a large

aircraft’s path. If a larger aircraft is observed above on

the same track (meeting or overtaking) adjust your

position laterally, preferably upwind.

7−3−7. Helicopters

In a slow hover taxi or stationary hover near the

surface, helicopter main rotor(s) generate downwash

producing high velocity outwash vortices to a

distance approximately three times the diameter of

the rotor. When rotor downwash hits the surface, the

resulting outwash vortices have behavioral characteristics similar to wing tip vortices produced by fixed

wing aircraft. However, the vortex circulation is

outward, upward, around, and away from the main

rotor(s) in all directions. Pilots of small aircraft

should avoid operating within three rotor diameters

of any helicopter in a slow hover taxi or stationary

hover. In forward flight, departing or landing

helicopters produce a pair of strong, high−speed

trailing vortices similar to wing tip vortices of larger

fixed wing aircraft. Pilots of small aircraft should use

caution when operating behind or crossing behind

landing and departing helicopters.

7−3−8. Pilot Responsibility

a. Government and industry groups are making

concerted efforts to minimize or eliminate the

hazards of trailing vortices. However, the flight

disciplines necessary to ensure vortex avoidance

during VFR operations must be exercised by the pilot.

Vortex visualization and avoidance procedures

should be exercised by the pilot using the same degree

of concern as in collision avoidance.

b. Wake turbulence may be encountered by

aircraft in flight as well as when operating on the

airport movement area.

REFERENCE−

Pilot/Controller Glossary Term− Wake Turbulence.

c. Pilots are reminded that in operations conducted

behind all aircraft, acceptance of instructions from

ATC in the following situations is an acknowledgment that the pilot will ensure safe takeoff and

landing intervals and accepts the responsibility for

providing wake turbulence separation.

1. Traffic information.

2. Instructions to follow an aircraft; and

3. The acceptance of a visual approach

clearance.

d. For operations conducted behind heavy aircraft, ATC will specify the word “heavy” when this

information is known. Pilots of heavy aircraft should

always use the word “heavy” in radio communications.

e. Heavy and large jet aircraft operators should use

the following procedures during an approach to

landing. These procedures establish a dependable

baseline from which pilots of in−trail, lighter aircraft

may reasonably expect to make effective flight path

adjustments to avoid serious wake vortex turbulence.

1. Pilots of aircraft that produce strong wake

vortices should make every attempt to fly on the

established glidepath, not above it; or, if glidepath

guidance is not available, to fly as closely as possible

to a “3−1” glidepath, not above it.

EXAMPLE−

Fly 3,000 feet at 10 miles from touchdown, 1,500 feet at 5

miles, 1,200 feet at 4 miles, and so on to touchdown.
7/26/12 AIM

Wake Turbulence 7−3−7

2. Pilots of aircraft that produce strong wake

vortices should fly as closely as possible to the

approach course centerline or to the extended

centerline of the runway of intended landing as

appropriate to conditions.

f. Pilots operating lighter aircraft on visual

approaches in−trail to aircraft producing strong wake

vortices should use the following procedures to assist

in avoiding wake turbulence. These procedures apply

only to those aircraft that are on visual approaches.

1. Pilots of lighter aircraft should fly on or

above the glidepath. Glidepath reference may be

furnished by an ILS, by a visual approach slope

system, by other ground−based approach slope

guidance systems, or by other means. In the absence

of visible glidepath guidance, pilots may very nearly

duplicate a 3−degree glideslope by adhering to the

“3 to 1” glidepath principle.

EXAMPLE−

Fly 3,000 feet at 10 miles from touchdown, 1,500 feet at

5 miles, 1,200 feet at 4 miles, and so on to touchdown.

2. If the pilot of the lighter following aircraft has

visual contact with the preceding heavier aircraft and

also with the runway, the pilot may further adjust for

possible wake vortex turbulence by the following

practices:

(a) Pick a point of landing no less than

1,000 feet from the arrival end of the runway.

(b) Establish a line−of−sight to that landing

point that is above and in front of the heavier

preceding aircraft.

(c) When possible, note the point of landing

of the heavier preceding aircraft and adjust point of

intended landing as necessary.

EXAMPLE−

A puff of smoke may appear at the 1,000−foot markings of

the runway, showing that touchdown was that point;

therefore, adjust point of intended landing to the

1,500−foot markings.

(d) Maintain the line−of−sight to the point of

intended landing above and ahead of the heavier

preceding aircraft; maintain it to touchdown.

(e) Land beyond the point of landing of the

preceding heavier aircraft.

3. During visual approaches pilots may ask ATC

for updates on separation and groundspeed with

respect to heavier preceding aircraft, especially when

there is any question of safe separation from wake

turbulence.

7−3−9. Air Traffic Wake Turbulence

Separations

a. Because of the possible effects of wake

turbulence, controllers are required to apply no less

than specified minimum separation for aircraft

operating behind a heavy jet and, in certain instances,

behind large nonheavy aircraft (i.e., B757 aircraft).

1. Separation is applied to aircraft operating

directly behind a heavy/B757 jet at the same altitude

or less than 1,000 feet below:

(a) Heavy jet behind heavy jet−4 miles.

(b) Large/heavy behind B757 − 4 miles.

(c) Small behind B757 − 5 miles.

(d) Small/large aircraft behind heavy jet −

5 miles.

2. Also, separation, measured at the time the

preceding aircraft is over the landing threshold, is

provided to small aircraft:

(a) Small aircraft landing behind heavy jet −

6 miles.

(b) Small aircraft landing behind B757 −

5 miles.

(c) Small aircraft landing behind large

aircraft− 4 miles.

REFERENCE−

Pilot/Controller Glossary Term− Aircraft Classes.

3. Additionally, appropriate time or distance

intervals are provided to departing aircraft:

(a) Two minutes or the appropriate 4 or 5 mile

radar separation when takeoff behind a heavy/B757

jet will be:

(1) From the same threshold.

(2) On a crossing runway and projected

flight paths will cross.

(3) From the threshold of a parallel runway

when staggered ahead of that of the adjacent runway

by less than 500 feet and when the runways are

separated by less than 2,500 feet.

NOTE−

Controllers may not reduce or waive these intervals.
AIM 7/26/12

7−3−8 Wake Turbulence

b. A 3−minute interval will be provided when a

small aircraft will takeoff:

1. From an intersection on the same runway

(same or opposite direction) behind a departing large

aircraft,

2. In the opposite direction on the same runway

behind a large aircraft takeoff or low/missed

approach.

NOTE−

This 3−minute interval may be waived upon specific pilot

request.

c. A 3−minute interval will be provided for all

aircraft taking off when the operations are as

described in subparagraph b1 and 2 above, the

preceding aircraft is a heavy/B757 jet, and the

operations are on either the same runway or parallel

runways separated by less than 2,500 feet.

Controllers may not reduce or waive this interval.

d. Pilots may request additional separation i.e.,

2 minutes instead of 4 or 5 miles for wake turbulence

avoidance. This request should be made as soon as

practical on ground control and at least before taxiing

onto the runway.

NOTE−

14 CFR Section 91.3(a) states: “The pilot−in−command of

an aircraft is directly responsible for and is the final

authority as to the operation of that aircraft.”

e. Controllers may anticipate separation and need

not withhold a takeoff clearance for an aircraft

departing behind a large/heavy aircraft if there is

reasonable assurance the required separation will

exist when the departing aircraft starts takeoff roll.
7/26/12 AIM

Bird Hazards and Flight Over National Refuges, Parks, and Forests 7−4−1

Section 4. Bird Hazards and Flight Over National

Refuges, Parks, and Forests

7−4−1. Migratory Bird Activity

a. Bird strike risk increases because of bird

migration during the months of March through April,

and August through November.

b. The altitudes of migrating birds vary with winds

aloft, weather fronts, terrain elevations, cloud

conditions, and other environmental variables. While

over 90 percent of the reported bird strikes occur at or

below 3,000 feet AGL, strikes at higher altitudes are

common during migration. Ducks and geese are

frequently observed up to 7,000 feet AGL and pilots

are cautioned to minimize en route flying at lower

altitudes during migration.

c. Considered the greatest potential hazard to

aircraft because of their size, abundance, or habit of

flying in dense flocks are gulls, waterfowl, vultures,

hawks, owls, egrets, blackbirds, and starlings.

Four major migratory flyways exist in the U.S. The

Atlantic flyway parallels the Atlantic Coast. The

Mississippi Flyway stretches from Canada through

the Great Lakes and follows the Mississippi River.

The Central Flyway represents a broad area east of the

Rockies, stretching from Canada through Central

America. The Pacific Flyway follows the west coast

and overflies major parts of Washington, Oregon, and

California. There are also numerous smaller flyways

which cross these major north-south migratory

routes.

7−4−2. Reducing Bird Strike Risks

a. The most serious strikes are those involving

ingestion into an engine (turboprops and turbine jet

engines) or windshield strikes. These strikes can

result in emergency situations requiring prompt

action by the pilot.

b. Engine ingestions may result in sudden loss of

power or engine failure. Review engine out

procedures, especially when operating from airports

with known bird hazards or when operating near high

bird concentrations.

c. Windshield strikes have resulted in pilots

experiencing confusion, disorientation, loss of

communications, and aircraft control problems.

Pilots are encouraged to review their emergency

procedures before flying in these areas.

d. When encountering birds en route, climb to

avoid collision, because birds in flocks generally

distribute themselves downward, with lead birds

being at the highest altitude.

e. Avoid overflight of known areas of bird

concentration and flying at low altitudes during bird

migration. Charted wildlife refuges and other natural

areas contain unusually high local concentration of

birds which may create a hazard to aircraft.

7−4−3. Reporting Bird Strikes

Pilots are urged to report any bird or other wildlife

strike using FAA Form 5200−7, Bird/Other Wildlife

Strike Report (Appendix 1). Additional forms are

available at any FSS; at any FAA Regional Office or

at http://wildlife−mitigation.tc.faa.gov. The data

derived from these reports are used to develop

standards to cope with this potential hazard to aircraft

and for documentation of necessary habitat control on

airports.

7−4−4. Reporting Bird and Other Wildlife

Activities

If you observe birds or other animals on or near the

runway, request airport management to disperse the

wildlife before taking off. Also contact the nearest

FAA ARTCC, FSS, or tower (including non−Federal

towers) regarding large flocks of birds and report the:

a. Geographic location.

b. Bird type (geese, ducks, gulls, etc.).

c. Approximate numbers.

d. Altitude.

e. Direction of bird flight path.
AIM 7/26/12

7−4−2 Bird Hazards and Flight Over National Refuges, Parks, and Forests

7−4−5. Pilot Advisories on Bird and Other

Wildlife Hazards

Many airports advise pilots of other wildlife hazards

caused by large animals on the runway through the

A/FD and the NOTAM system. Collisions of landing

and departing aircraft and animals on the runway are

increasing and are not limited to rural airports. These

accidents have also occurred at several major

airports. Pilots should exercise extreme caution when

warned of the presence of wildlife on and in the

vicinity of airports. If you observe deer or other large

animals in close proximity to movement areas, advise

the FSS, tower, or airport management.

7−4−6. Flights Over Charted U.S. Wildlife

Refuges, Parks, and Forest Service Areas

a. The landing of aircraft is prohibited on lands or

waters administered by the National Park Service,

U.S. Fish and Wildlife Service, or U.S. Forest Service

without authorization from the respective agency.

Exceptions include:

1. When forced to land due to an emergency

beyond the control of the operator;

2. At officially designated landing sites; or

3. An approved official business of the Federal

Government.

b. Pilots are requested to maintain a minimum

altitude of 2,000 feet above the surface of the

following: National Parks, Monuments, Seashores,

Lakeshores, Recreation Areas and Scenic Riverways

administered by the National Park Service, National

Wildlife Refuges, Big Game Refuges, Game Ranges

and Wildlife Ranges administered by the U.S. Fish

and Wildlife Service, and Wilderness and Primitive

areas administered by the U.S. Forest Service.

NOTE−

FAA Advisory Circular AC 91−36, Visual Flight

Rules (VFR) Flight Near Noise-Sensitive Areas, defines

the surface of a national park area (including parks,

forests, primitive areas, wilderness areas, recreational

areas, national seashores, national monuments, national

lakeshores, and national wildlife refuge and range areas)

as: the highest terrain within 2,000 feet laterally of the

route of flight, or the upper-most rim of a canyon or valley.

c. Federal statutes prohibit certain types of flight

activity and/or provide altitude restrictions over

designated U.S. Wildlife Refuges, Parks, and Forest

Service Areas. These designated areas, for example:

Boundary Waters Canoe Wilderness Areas,

Minnesota; Haleakala National Park, Hawaii;

Yosemite National Park, California; and Grand

Canyon National Park, Arizona, are charted on

Sectional Charts.

d. Federal regulations also prohibit airdrops by

parachute or other means of persons, cargo, or objects

from aircraft on lands administered by the three

agencies without authorization from the respective

agency. Exceptions include:

1. Emergencies involving the safety of human

life; or

2. Threat of serious property loss.
7/26/12 AIM

Potential Flight Hazards 7−5−1

Section 5. Potential Flight Hazards

7−5−1. Accident Cause Factors

a. The 10 most frequent cause factors for general

aviation accidents that involve the pilot-in-command

are:

1. Inadequate preflight preparation and/or

planning.

2. Failure to obtain and/or maintain flying

speed.

3. Failure to maintain direction control.

4. Improper level off.

5. Failure to see and avoid objects or

obstructions.

6. Mismanagement of fuel.

7. Improper inflight decisions or planning.

8. Misjudgment of distance and speed.

9. Selection of unsuitable terrain.

10. Improper operation of flight controls.

b. This list remains relatively stable and points out

the need for continued refresher training to establish

a higher level of flight proficiency for all pilots. A

part of the FAA’s continuing effort to promote

increased aviation safety is the Aviation Safety

Program. For information on Aviation Safety

Program activities contact your nearest Flight

Standards District Office.

c. Alertness. Be alert at all times, especially

when the weather is good. Most pilots pay attention

to business when they are operating in full IFR

weather conditions, but strangely, air collisions

almost invariably have occurred under ideal weather

conditions. Unlimited visibility appears to encourage

a sense of security which is not at all justified.

Considerable information of value may be obtained

by listening to advisories being issued in the terminal

area, even though controller workload may prevent a

pilot from obtaining individual service.

d. Giving Way. If you think another aircraft is too

close to you, give way instead of waiting for the other

pilot to respect the right-of-way to which you may be

entitled. It is a lot safer to pursue the right-of-way

angle after you have completed your flight.

7−5−2. VFR in Congested Areas

A high percentage of near midair collisions occur

below 8,000 feet AGL and within 30 miles of an

airport. When operating VFR in these highly

congested areas, whether you intend to land at an

airport within the area or are just flying through, it is

recommended that extra vigilance be maintained and

that you monitor an appropriate control frequency.

Normally the appropriate frequency is an approach

control frequency. By such monitoring action you can

“get the picture” of the traffic in your area. When the

approach controller has radar, radar traffic advisories

may be given to VFR pilots upon request.

REFERENCE−

AIM, Paragraph 4−1−14, Radar Traffic Information Service.

7−5−3. Obstructions To Flight

a. General. Many structures exist that could

significantly affect the safety of your flight when

operating below 500 feet AGL, and particularly

below 200 feet AGL. While 14 CFR Part 91.119

allows flight below 500 AGL when over sparsely

populated areas or open water, such operations are

very dangerous. At and below 200 feet AGL there are

numerous power lines, antenna towers, etc., that are

not marked and lighted as obstructions and; therefore,

may not be seen in time to avoid a collision. Notices

to Airmen (NOTAMs) are issued on those lighted

structures experiencing temporary light outages.

However, some time may pass before the FAA is

notified of these outages, and the NOTAM issued,

thus pilot vigilance is imperative.

b. Antenna Towers. Extreme caution should be

exercised when flying less than 2,000 feet AGL

because of numerous skeletal structures, such as radio

and television antenna towers, that exceed 1,000 feet

AGL with some extending higher than 2,000 feet

AGL. Most skeletal structures are supported by guy

wires which are very difficult to see in good weather

and can be invisible at dusk or during periods of

reduced visibility. These wires can extend about

1,500 feet horizontally from a structure; therefore, all

skeletal structures should be avoided horizontally by
AIM 7/26/12

7−5−2 Potential Flight Hazards

at least 2,000 feet. Additionally, new towers may not

be on your current chart because the information was

not received prior to the printing of the chart.

c. Overhead Wires. Overhead transmission and

utility lines often span approaches to runways,

natural flyways such as lakes, rivers, gorges, and

canyons, and cross other landmarks pilots frequently

follow such as highways, railroad tracks, etc. As with

antenna towers, these high voltage/power lines or the

supporting structures of these lines may not always be

readily visible and the wires may be virtually

impossible to see under certain conditions. In some

locations, the supporting structures of overhead

transmission lines are equipped with unique sequence

flashing white strobe light systems to indicate that

there are wires between the structures. However,

many power lines do not require notice to the FAA

and, therefore, are not marked and/or lighted. Many

of those that do require notice do not exceed 200 feet

AGL or meet the Obstruction Standard of 14 CFR

Part 77 and, therefore, are not marked and/or lighted.

All pilots are cautioned to remain extremely vigilant

for these power lines or their supporting structures

when following natural flyways or during the

approach and landing phase. This is particularly

important for seaplane and/or float equipped aircraft

when landing on, or departing from, unfamiliar lakes

or rivers.

d. Other Objects/Structures. There are other

objects or structures that could adversely affect your

flight such as construction cranes near an airport,

newly constructed buildings, new towers, etc. Many

of these structures do not meet charting requirements

or may not yet be charted because of the charting

cycle. Some structures do not require obstruction

marking and/or lighting and some may not be marked

and lighted even though the FAA recommended it.

7−5−4. Avoid Flight Beneath Unmanned

Balloons

a. The majority of unmanned free balloons

currently being operated have, extending below

them, either a suspension device to which the payload

or instrument package is attached, or a trailing wire

antenna, or both. In many instances these balloon

subsystems may be invisible to the pilot until the

aircraft is close to the balloon, thereby creating a

potentially dangerous situation. Therefore, good

judgment on the part of the pilot dictates that aircraft

should remain well clear of all unmanned free

balloons and flight below them should be avoided at

all times.

b. Pilots are urged to report any unmanned free

balloons sighted to the nearest FAA ground facility

with which communication is established. Such

information will assist FAA ATC facilities to identify

and flight follow unmanned free balloons operating

in the airspace.

7−5−5. Unmanned Aircraft Systems

a. Unmanned Aircraft Systems (UAS), formerly

referred to as “Unmanned Aerial Vehicles” (UAVs)

or “drones,” are having an increasing operational

presence in the NAS. Once the exclusive domain of

the military, UAS are now being operated by various

entities. Although these aircraft are “unmanned,”

UAS are flown by a remotely located pilot and crew.

Physical and performance characteristics of unmanned aircraft (UA) vary greatly and unlike model

aircraft that typically operate lower than 400 feet

AGL, UA may be found operating at virtually any

altitude and any speed. Sizes of UA can be as small

as several pounds to as large as a commercial

transport aircraft. UAS come in various categories

including airplane, rotorcraft, powered−lift (tilt−

rotor), and lighter−than−air. Propulsion systems of

UAS include a broad range of alternatives from

piston powered and turbojet engines to battery and

solar−powered electric motors.

b. To ensure segregation of UAS operations from

other aircraft, the military typically conducts UAS

operations within restricted or other special use

airspace. However, UAS operations are now being

approved in the NAS outside of special use airspace

through the use of FAA−issued Certificates of Waiver

or Authorization (COA) or through the issuance of a

special airworthiness certificate. COA and special

airworthiness approvals authorize UAS flight

operations to be contained within specific geographic

boundaries and altitudes, usually require coordination with an ATC facility, and typically require the

issuance of a NOTAM describing the operation to be

conducted. UAS approvals also require observers to

provide “see−and−avoid” capability to the UAS crew

and to provide the necessary compliance with 14 CFR

Section 91.113. For UAS operations approved at or

above FL180, UAS operate under the same

requirements as that of manned aircraft (i.e., flights
7/26/12 AIM

Potential Flight Hazards 7−5−3

are operated under instrument flight rules, are in

communication with ATC, and are appropriately

equipped).

c. UAS operations may be approved at either

controlled or uncontrolled airports and are typically

disseminated by NOTAM. In all cases, approved

UAS operations must comply with all applicable

regulations and/or special provisions specified in the

COA or in the operating limitations of the special

airworthiness certificate. At uncontrolled airports,

UAS operations are advised to operate well clear of

all known manned aircraft operations. Pilots of

manned aircraft are advised to follow normal

operating procedures and are urged to monitor the

CTAF for any potential UAS activity. At controlled

airports, local ATC procedures may be in place to

handle UAS operations and should not require any

special procedures from manned aircraft entering or

departing the traffic pattern or operating in the

vicinity of the airport.

d. In addition to approved UAS operations

described above, a recently approved agreement

between the FAA and the Department of Defense

authorizes small UAS operations wholly contained

within Class G airspace, and in no instance, greater

than 1200 feet AGL over military owned or leased

property. These operations do not require any special

authorization as long as the UA remains within the

lateral boundaries of the military installation as well

as other provisions including the issuance of a

NOTAM. Unlike special use airspace, these areas

may not be depicted on an aeronautical chart.

e. There are several factors a pilot should consider

regarding UAS activity in an effort to reduce

potential flight hazards. Pilots are urged to exercise

increased vigilance when operating in the vicinity of

restricted or other special use airspace, military

operations areas, and any military installation. Areas

with a preponderance of UAS activity are typically

noted on sectional charts advising pilots of this

activity. Since the size of a UA can be very small, they

may be difficult to see and track. If a UA is

encountered during flight, as with manned aircraft,

never assume that the pilot or crew of the UAS can see

you, maintain increased vigilance with the UA and

always be prepared for evasive action if necessary.

Always check NOTAMs for potential UAS activity

along the intended route of flight and exercise

increased vigilance in areas specified in the NOTAM.

7−5−6. Mountain Flying

a. Your first experience of flying over mountainous terrain (particularly if most of your flight time has

been over the flatlands of the midwest) could be a

never-to-be-forgotten nightmare if proper planning is

not done and if you are not aware of the potential

hazards awaiting. Those familiar section lines are not

present in the mountains; those flat, level fields for

forced landings are practically nonexistent; abrupt

changes in wind direction and velocity occur; severe

updrafts and downdrafts are common, particularly

near or above abrupt changes of terrain such as cliffs

or rugged areas; even the clouds look different and

can build up with startling rapidity. Mountain flying

need not be hazardous if you follow the recommendations below.

b. File a Flight Plan. Plan your route to avoid

topography which would prevent a safe forced

landing. The route should be over populated areas and

well known mountain passes. Sufficient altitude

should be maintained to permit gliding to a safe

landing in the event of engine failure.

c. Don’t fly a light aircraft when the winds aloft, at

your proposed altitude, exceed 35 miles per hour.

Expect the winds to be of much greater velocity over

mountain passes than reported a few miles from them.

Approach mountain passes with as much altitude as

possible. Downdrafts of from 1,500 to 2,000 feet per

minute are not uncommon on the leeward side.

d. Don’t fly near or above abrupt changes in

terrain. Severe turbulence can be expected, especially

in high wind conditions.

e. Understand Mountain Obscuration. The

term Mountain Obscuration (MTOS) is used to

describe a visibility condition that is distinguished

from IFR because ceilings, by definition, are

described as “above ground level” (AGL). In

mountainous terrain clouds can form at altitudes

significantly higher than the weather reporting

station and at the same time nearby mountaintops

may be obscured by low visibility. In these areas the

ground level can also vary greatly over a small area.

Beware if operating VFR−on−top. You could be

operating closer to the terrain than you think because

the tops of mountains are hidden in a cloud deck

below. MTOS areas are identified daily on The

Aviation Weather Center located at:

http://www.aviationweather.gov.
AIM 7/26/12

7−5−4 Potential Flight Hazards

f. Some canyons run into a dead end. Don’t fly so

far up a canyon that you get trapped. ALWAYS BE

ABLE TO MAKE A 180 DEGREE TURN!

g. VFR flight operations may be conducted at

night in mountainous terrain with the application of

sound judgment and common sense. Proper pre-flight

planning, giving ample consideration to winds and

weather, knowledge of the terrain and pilot

experience in mountain flying are prerequisites for

safety of flight. Continuous visual contact with the

surface and obstructions is a major concern and flight

operations under an overcast or in the vicinity of

clouds should be approached with extreme caution.

h. When landing at a high altitude field, the same

indicated airspeed should be used as at low elevation

fields. Remember: that due to the less dense air at

altitude, this same indicated airspeed actually results

in higher true airspeed, a faster landing speed, and

more important, a longer landing distance. During

gusty wind conditions which often prevail at high

altitude fields, a power approach and power landing

is recommended. Additionally, due to the faster

groundspeed, your takeoff distance will increase

considerably over that required at low altitudes.

i. Effects of Density Altitude. Performance

figures in the aircraft owner’s handbook for length of

takeoff run, horsepower, rate of climb, etc., are

generally based on standard atmosphere conditions

(59 degrees Fahrenheit (15 degrees Celsius), pressure

29.92 inches of mercury) at sea level. However,

inexperienced pilots, as well as experienced pilots,

may run into trouble when they encounter an

altogether different set of conditions. This is

particularly true in hot weather and at higher

elevations. Aircraft operations at altitudes above sea

level and at higher than standard temperatures are

commonplace in mountainous areas. Such operations

quite often result in a drastic reduction of aircraft

performance capabilities because of the changing air

density. Density altitude is a measure of air density.

It is not to be confused with pressure altitude, true

altitude or absolute altitude. It is not to be used as a

height reference, but as a determining criteria in the

performance capability of an aircraft. Air density

decreases with altitude. As air density decreases,

density altitude increases. The further effects of high

temperature and high humidity are cumulative,

resulting in an increasing high density altitude

condition. High density altitude reduces all aircraft

performance parameters. To the pilot, this means that

the normal horsepower output is reduced, propeller

efficiency is reduced and a higher true airspeed is

required to sustain the aircraft throughout its

operating parameters. It means an increase in runway

length requirements for takeoff and landings, and

decreased rate of climb. An average small airplane,

for example, requiring 1,000 feet for takeoff at sea

level under standard atmospheric conditions will

require a takeoff run of approximately 2,000 feet at an

operational altitude of 5,000 feet.

NOTE−

A turbo-charged aircraft engine provides some slight

advantage in that it provides sea level horsepower up to a

specified altitude above sea level.

1. Density Altitude Advisories. At airports

with elevations of 2,000 feet and higher, control

towers and FSSs will broadcast the advisory “Check

Density Altitude” when the temperature reaches a

predetermined level. These advisories will be

broadcast on appropriate tower frequencies or, where

available, ATIS. FSSs will broadcast these advisories

as a part of Local Airport Advisory, and on TWEB.

2. These advisories are provided by air traffic

facilities, as a reminder to pilots that high

temperatures and high field elevations will cause

significant changes in aircraft characteristics. The

pilot retains the responsibility to compute density

altitude, when appropriate, as a part of preflight

duties.

NOTE−

All FSSs will compute the current density altitude upon

request.

j. Mountain Wave. Many pilots go all their lives

without understanding what a mountain wave is.

Quite a few have lost their lives because of this lack

of understanding. One need not be a licensed

meteorologist to understand the mountain wave

phenomenon.
7/26/12 AIM

Potential Flight Hazards 7−5−5

1. Mountain waves occur when air is being

blown over a mountain range or even the ridge of a

sharp bluff area. As the air hits the upwind side of the

range, it starts to climb, thus creating what is

generally a smooth updraft which turns into a

turbulent downdraft as the air passes the crest of the

ridge. From this point, for many miles downwind,

there will be a series of downdrafts and updrafts.

Satellite photos of the Rockies have shown mountain

waves extending as far as 700 miles downwind of the

range. Along the east coast area, such photos of the

Appalachian chain have picked up the mountain

wave phenomenon over a hundred miles eastward.

All it takes to form a mountain wave is wind blowing

across the range at 15 knots or better at an intersection

angle of not less than 30 degrees.

2. Pilots from flatland areas should understand

a few things about mountain waves in order to stay

out of trouble. When approaching a mountain range

from the upwind side (generally the west), there will

usually be a smooth updraft; therefore, it is not quite

as dangerous an area as the lee of the range. From the

leeward side, it is always a good idea to add an extra

thousand feet or so of altitude because downdrafts

can exceed the climb capability of the aircraft. Never

expect an updraft when approaching a mountain

chain from the leeward. Always be prepared to cope

with a downdraft and turbulence.

3. When approaching a mountain ridge from the

downwind side, it is recommended that the ridge be

approached at approximately a 45 degree angle to the

horizontal direction of the ridge. This permits a safer

retreat from the ridge with less stress on the aircraft

should severe turbulence and downdraft be experienced. If severe turbulence is encountered,

simultaneously reduce power and adjust pitch until

aircraft approaches maneuvering speed, then adjust

power and trim to maintain maneuvering speed and

fly away from the turbulent area.

7−5−7. Use of Runway Half−way Signs at

Unimproved Airports

When installed, runway half−way signs provide the

pilot with a reference point to judge takeoff

acceleration trends. Assuming that the runway length

is appropriate for takeoff (considering runway

condition and slope, elevation, aircraft weight, wind,

and temperature), typical takeoff acceleration should

allow the airplane to reach 70 percent of lift−off

airspeed by the midpoint of the runway. The “rule of

thumb” is that should airplane acceleration not allow

the airspeed to reach this value by the midpoint, the

takeoff should be aborted, as it may not be possible to

liftoff in the remaining runway.

Several points are important when considering using

this “rule of thumb”:

a. Airspeed indicators in small airplanes are not

required to be evaluated at speeds below stalling, and

may not be usable at 70 percent of liftoff airspeed.

b. This “rule of thumb” is based on a uniform

surface condition. Puddles, soft spots, areas of tall

and/or wet grass, loose gravel, etc., may impede

acceleration or even cause deceleration. Even if the

airplane achieves 70 percent of liftoff airspeed by the

midpoint, the condition of the remainder of the runway

may not allow further acceleration. The entire length

of the runway should be inspected prior to takeoff to

ensure a usable surface.

c. This “rule of thumb” applies only to runway

required for actual liftoff. In the event that obstacles

affect the takeoff climb path, appropriate distance

must be available after liftoff to accelerate to best angle

of climb speed and to clear the obstacles. This will, in

effect, require the airplane to accelerate to a higher

speed by midpoint, particularly if the obstacles are

close to the end of the runway. In addition, this

technique does not take into account the effects of

upslope or tailwinds on takeoff performance. These

factors will also require greater acceleration than

normal and, under some circumstances, prevent

takeoff entirely.

d. Use of this “rule of thumb” does not alleviate the

pilot’s responsibility to comply with applicable

Federal Aviation Regulations, the limitations and

performance data provided in the FAA approved

Airplane Flight Manual (AFM), or, in the absence of

an FAA approved AFM, other data provided by the

aircraft manufacturer.

In addition to their use during takeoff, runway

half−way signs offer the pilot increased awareness of

his or her position along the runway during landing

operations.
AIM 7/26/12

7−5−6 Potential Flight Hazards

NOTE−

No FAA standard exists for the appearance of the runway

half−way sign. FIG 7−5−1 shows a graphical depiction of

a typical runway half−way sign.

7−5−8. Seaplane Safety

a. Acquiring a seaplane class rating affords access

to many areas not available to landplane pilots.

Adding a seaplane class rating to your pilot certificate

can be relatively uncomplicated and inexpensive.

However, more effort is required to become a safe,

efficient, competent “bush” pilot. The natural hazards

of the backwoods have given way to modern

man-made hazards. Except for the far north, the

available bodies of water are no longer the exclusive

domain of the airman. Seaplane pilots must be

vigilant for hazards such as electric power lines,

power, sail and rowboats, rafts, mooring lines, water

skiers, swimmers, etc.

FIG 7−5−1

Typical Runway Half−way Sign

b. Seaplane pilots must have a thorough understanding of the right-of-way rules as they apply to

aircraft versus other vessels. Seaplane pilots are

expected to know and adhere to both the U.S. Coast

Guard’s (USCG) Navigation Rules, International−Inland, and 14 CFR Section 91.115, Right−of−Way

Rules; Water Operations. The navigation rules of the

road are a set of collision avoidance rules as they

apply to aircraft on the water. A seaplane is

considered a vessel when on the water for the

purposes of these collision avoidance rules. In

general, a seaplane on the water must keep well clear

of all vessels and avoid impeding their navigation.

The CFR requires, in part, that aircraft operating on

the water “. . . shall, insofar as possible, keep clear of

all vessels and avoid impeding their navigation, and

shall give way to any vessel or other aircraft that is

given the right−of−way . . . .” This means that a

seaplane should avoid boats and commercial

shipping when on the water. If on a collision course,

the seaplane should slow, stop, or maneuver to the

right, away from the bow of the oncoming vessel.

Also, while on the surface with an engine running, an

aircraft must give way to all nonpowered vessels.

Since a seaplane in the water may not be as

maneuverable as one in the air, the aircraft on the

water has right-of-way over one in the air, and one

taking off has right-of-way over one landing. A

seaplane is exempt from the USCG safety equipment

requirements, including the requirements for Personal Flotation Devices (PFD). Requiring seaplanes on

the water to comply with USCG equipment

requirements in addition to the FAA equipment

requirements would be an unnecessary burden on

seaplane owners and operators.

c. Unless they are under Federal jurisdiction,

navigable bodies of water are under the jurisdiction

of the state, or in a few cases, privately owned. Unless

they are specifically restricted, aircraft have as much

right to operate on these bodies of water as other

vessels. To avoid problems, check with Federal or

local officials in advance of operating on unfamiliar

waters. In addition to the agencies listed in

TBL 7−5−1, the nearest Flight Standards District

Office can usually offer some practical suggestions as

well as regulatory information. If you land on a

restricted body of water because of an inflight

emergency, or in ignorance of the restrictions you

have violated, report as quickly as practical to the

nearest local official having jurisdiction and explain

your situation.

d. When operating a seaplane over or into remote

areas, appropriate attention should be given to

survival gear. Minimum kits are recommended for

summer and winter, and are required by law for flight

into sparsely settled areas of Canada and Alaska.

Alaska State Department of Transportation and

Canadian Ministry of Transport officials can provide

specific information on survival gear requirements.

The kit should be assembled in one container and be

easily reachable and preferably floatable.
7/26/12 AIM

Potential Flight Hazards 7−5−7

TBL 7−5−1

Jurisdictions Controlling Navigable Bodies of Water

Authority to Consult For Use of a Body of Water

Location Authority Contact

Wilderness Area U.S. Department

of Agriculture,

Forest Service

Local forest ranger

National Forest USDA Forest

Service

Local forest ranger

National Park U.S. Department

of the Interior,

National Park

Service

Local park ranger

Indian Reservation USDI, Bureau of

Indian Affairs

Local Bureau

office

State Park State government

or state forestry or

park service

Local state

aviation office for

further

information

Canadian National

and Provincial

Parks

Supervised and

restricted on an

individual basis

from province to

province and by

different

departments of the

Canadian

government;

consult Canadian

Flight Information

Manual and/or

Water Aerodrome

Supplement

Park

Superintendent in

an emergency

e. The FAA recommends that each seaplane owner

or operator provide flotation gear for occupants any

time a seaplane operates on or near water. 14 CFR

Section 91.205(b)(12) requires approved flotation

gear for aircraft operated for hire over water and

beyond power-off gliding distance from shore.

FAA-approved gear differs from that required for

navigable waterways under USCG rules. FAA-approved life vests are inflatable designs as compared

to the USCG’s noninflatable PFD’s that may consist

of solid, bulky material. Such USCG PFDs are

impractical for seaplanes and other aircraft because

they may block passage through the relatively narrow

exits available to pilots and passengers. Life vests

approved under Technical Standard Order (TSO)

TSO−C13E contain fully inflatable compartments.

The wearer inflates the compartments (AFTER

exiting the aircraft) primarily by independent CO2

cartridges, with an oral inflation tube as a backup. The

flotation gear also contains a water-activated,

self-illuminating signal light. The fact that pilots and

passengers can easily don and wear inflatable life

vests (when not inflated) provides maximum

effectiveness and allows for unrestricted movement.

It is imperative that passengers are briefed on the

location and proper use of available PFDs prior to

leaving the dock.

f. The FAA recommends that seaplane owners and

operators obtain Advisory Circular (AC) 91−69,

Seaplane Safety for 14 CFR Part 91 Operations, free

from the U.S. Department of Transportation,

Subsequent Distribution Office, SVC−121.23, Ardmore East Business Center, 3341 Q 75th Avenue,

Landover, MD 20785; fax: (301) 386−5394. The

USCG Navigation Rules International−Inland

(COMDTINSTM 16672.2B) is available for a fee

from the Government Printing Office by facsimile

request to (202) 512−2250, and can be ordered using

Mastercard or Visa.

7−5−9. Flight Operations in Volcanic Ash

a. Severe volcanic eruptions which send ash into

the upper atmosphere occur somewhere around the

world several times each year. Flying into a volcanic

ash cloud can be exceedingly dangerous. A

B747−200 lost all four engines after such an

encounter and a B747−400 had the same nearly

catastrophic experience. Piston−powered aircraft are

less likely to lose power but severe damage is almost

certain to ensue after an encounter with a volcanic ash

cloud which is only a few hours old.

b. Most important is to avoid any encounter with

volcanic ash. The ash plume may not be visible,

especially in instrument conditions or at night; and

even if visible, it is difficult to distinguish visually

between an ash cloud and an ordinary weather cloud.

Volcanic ash clouds are not displayed on airborne or

ATC radar. The pilot must rely on reports from air

traffic controllers and other pilots to determine the

location of the ash cloud and use that information to

remain well clear of the area. Every attempt should be

made to remain on the upwind side of the volcano.

c. It is recommended that pilots encountering an

ash cloud should immediately reduce thrust to idle

(altitude permitting), and reverse course in order to

escape from the cloud. Ash clouds may extend for

hundreds of miles and pilots should not attempt to fly

through or climb out of the cloud. In addition, the

following procedures are recommended:
AIM 7/26/12

7−5−8 Potential Flight Hazards

1. Disengage the autothrottle if engaged. This

will prevent the autothrottle from increasing engine

thrust;

2. Turn on continuous ignition;

3. Turn on all accessory airbleeds including all

air conditioning packs, nacelles, and wing anti-ice.

This will provide an additional engine stall margin by

reducing engine pressure.

d. The following has been reported by flightcrews

who have experienced encounters with volcanic dust

clouds:

1. Smoke or dust appearing in the cockpit.

2. An acrid odor similar to electrical smoke.

3. Multiple engine malfunctions, such as

compressor stalls, increasing EGT, torching from

tailpipe, and flameouts.

4. At night, St. Elmo’s fire or other static

discharges accompanied by a bright orange glow in

the engine inlets.

5. A fire warning in the forward cargo area.

e. It may become necessary to shut down and then

restart engines to prevent exceeding EGT limits.

Volcanic ash may block the pitot system and result in

unreliable airspeed indications.

f. If you see a volcanic eruption and have not been

previously notified of it, you may have been the first

person to observe it. In this case, immediately contact

ATC and alert them to the existence of the eruption.

If possible, use the Volcanic Activity Reporting form

(VAR) depicted in Appendix 2 of this manual.

Items 1 through 8 of the VAR should be transmitted

immediately. The information requested in

items 9 through 16 should be passed after landing. If

a VAR form is not immediately available, relay

enough information to identify the position and

nature of the volcanic activity. Do not become

unnecessarily alarmed if there is merely steam or very

low-level eruptions of ash.

g. When landing at airports where volcanic ash has

been deposited on the runway, be aware that even a

thin layer of dry ash can be detrimental to braking

action. Wet ash on the runway may also reduce

effectiveness of braking. It is recommended that

reverse thrust be limited to minimum practical to

reduce the possibility of reduced visibility and engine

ingestion of airborne ash.

h. When departing from airports where volcanic

ash has been deposited, it is recommended that pilots

avoid operating in visible airborne ash. Allow ash to

settle before initiating takeoff roll. It is also

recommended that flap extension be delayed until

initiating the before takeoff checklist and that a

rolling takeoff be executed to avoid blowing ash back

into the air.

7−5−10. Emergency Airborne Inspection of

Other Aircraft

a. Providing airborne assistance to another aircraft

may involve flying in very close proximity to that

aircraft. Most pilots receive little, if any, formal

training or instruction in this type of flying activity.

Close proximity flying without sufficient time to plan

(i.e., in an emergency situation), coupled with the

stress involved in a perceived emergency can be

hazardous.

b. The pilot in the best position to assess the

situation should take the responsibility of coordinating the airborne intercept and inspection, and take

into account the unique flight characteristics and

differences of the category(s) of aircraft involved.

c. Some of the safety considerations are:

1. Area, direction and speed of the intercept;

2. Aerodynamic effects (i.e., rotorcraft downwash);

3. Minimum safe separation distances;

4. Communications requirements, lost communications procedures, coordination with ATC;

5. Suitability of diverting the distressed aircraft

to the nearest safe airport; and

6. Emergency actions to terminate the intercept.

d. Close proximity, inflight inspection of another

aircraft is uniquely hazardous. The pilot−in−

command of the aircraft experiencing the

problem/emergency must not relinquish control of

the situation and/or jeopardize the safety of their

aircraft. The maneuver must be accomplished with

minimum risk to both aircraft.
7/26/12 AIM

Potential Flight Hazards 7−5−9

7−5−11. Precipitation Static

a. Precipitation static is caused by aircraft in flight

coming in contact with uncharged particles. These

particles can be rain, snow, fog, sleet, hail, volcanic

ash, dust; any solid or liquid particles. When the

aircraft strikes these neutral particles the positive

element of the particle is reflected away from the

aircraft and the negative particle adheres to the skin

of the aircraft. In a very short period of time a

substantial negative charge will develop on the skin

of the aircraft. If the aircraft is not equipped with

static dischargers, or has an ineffective static

discharger system, when a sufficient negative voltage

level is reached, the aircraft may go into

“CORONA.” That is, it will discharge the static

electricity from the extremities of the aircraft, such as

the wing tips, horizontal stabilizer, vertical stabilizer,

antenna, propeller tips, etc. This discharge of static

electricity is what you will hear in your headphones

and is what we call P−static.

b. A review of pilot reports often shows different

symptoms with each problem that is encountered.

The following list of problems is a summary of many

pilot reports from many different aircraft. Each

problem was caused by P−static:

1. Complete loss of VHF communications.

2. Erroneous magnetic compass readings

(30 percent in error).

3. High pitched squeal on audio.

4. Motor boat sound on audio.

5. Loss of all avionics in clouds.

6. VLF navigation system inoperative most of

the time.

7. Erratic instrument readouts.

8. Weak transmissions and poor receptivity of

radios.

9. “St. Elmo’s Fire” on windshield.

c. Each of these symptoms is caused by one

general problem on the airframe. This problem is the

inability of the accumulated charge to flow easily to

the wing tips and tail of the airframe, and properly

discharge to the airstream.

d. Static dischargers work on the principal of

creating a relatively easy path for discharging

negative charges that develop on the aircraft by using

a discharger with fine metal points, carbon coated

rods, or carbon wicks rather than wait until a large

charge is developed and discharged off the trailing

edges of the aircraft that will interfere with avionics

equipment. This process offers approximately

50 decibels (dB) static noise reduction which is

adequate in most cases to be below the threshold of

noise that would cause interference in avionics

equipment.

e. It is important to remember that precipitation

static problems can only be corrected with the proper

number of quality static dischargers, properly

installed on a properly bonded aircraft. P−static is

indeed a problem in the all weather operation of the

aircraft, but there are effective ways to combat it. All

possible methods of reducing the effects of P−static

should be considered so as to provide the best

possible performance in the flight environment.

f. A wide variety of discharger designs is available

on the commercial market. The inclusion of

well−designed dischargers may be expected to

improve airframe noise in P−static conditions by as

much as 50 dB. Essentially, the discharger provides

a path by which accumulated charge may leave the

airframe quietly. This is generally accomplished by

providing a group of tiny corona points to permit

onset of corona−current flow at a low aircraft

potential. Additionally, aerodynamic design of

dischargers to permit corona to occur at the lowest

possible atmospheric pressure also lowers the corona

threshold. In addition to permitting a low−potential

discharge, the discharger will minimize the radiation

of radio frequency (RF) energy which accompanies

the corona discharge, in order to minimize effects of

RF components at communications and navigation

frequencies on avionics performance. These effects

are reduced through resistive attachment of the

corona point(s) to the airframe, preserving direct

current connection but attenuating the higher−frequency components of the discharge.

g. Each manufacturer of static dischargers offers

information concerning appropriate discharger location on specific airframes. Such locations emphasize

the trailing outboard surfaces of wings and horizontal

tail surfaces, plus the tip of the vertical stabilizer,

where charge tends to accumulate on the airframe.
AIM 7/26/12

7−5−10 Potential Flight Hazards

Sufficient dischargers must be provided to allow for

current−carrying capacity which will maintain

airframe potential below the corona threshold of the

trailing edges.

h. In order to achieve full performance of avionic

equipment, the static discharge system will require

periodic maintenance. A pilot knowledgeable of

P−static causes and effects is an important element in

assuring optimum performance by early recognition

of these types of problems.

7−5−12. Light Amplification by Stimulated

Emission of Radiation (Laser) Operations

and Reporting Illumination of Aircraft

a. Lasers have many applications. Of concern to

users of the National Airspace System are those laser

events that may affect pilots, e.g., outdoor laser light

shows or demonstrations for entertainment and

advertisements at special events and theme parks.

Generally, the beams from these events appear as

bright blue−green in color; however, they may be red,

yellow, or white. However, some laser systems

produce light which is invisible to the human eye.

b. FAA regulations prohibit the disruption of

aviation activity by any person on the ground or in the

air. The FAA and the Food and Drug Administration

(the Federal agency that has the responsibility to

enforce compliance with Federal requirements for

laser systems and laser light show products) are

working together to ensure that operators of these

devices do not pose a hazard to aircraft operators.

c. Pilots should be aware that illumination from

these laser operations are able to create temporary

vision impairment miles from the actual location. In

addition, these operations can produce permanent eye

damage. Pilots should make themselves aware of

where these activities are being conducted and avoid

these areas if possible.

d. Recent and increasing incidents of unauthorized illumination of aircraft by lasers, as well as the

proliferation and increasing sophistication of laser

devices available to the general public, dictates that

the FAA, in coordination with other government

agencies, take action to safeguard flights from these

unauthorized illuminations.

e. Pilots should report laser illumination activity to

the controlling Air Traffic Control facilities, Federal

Contract Towers or Flight Service Stations as soon as

possible after the event. The following information

should be included:

1. UTC Date and Time of Event.

2. Call Sign or Aircraft Registration Number.

3. Type Aircraft.

4. Nearest Major City.

5. Altitude.

6. Location of Event (Latitude/Longitude and/

or Fixed Radial Distance (FRD)).

7. Brief Description of the Event and any other

Pertinent Information.

f. Pilots are also encouraged to complete the Laser

Beam Exposure Questionnaire (See Appendix 3), and

fax or email it, per the directions on the questionnaire,

as soon as possible after landing.

g. When a laser event is reported to an air traffic

facility, a general caution warning will be broadcasted on all appropriate frequencies every

five minutes for 20 minutes and broadcasted on the

ATIS for one hour following the report.

PHRASEOLOGY−

UNAUTHORIZED LASER ILLUMINATION EVENT,

(UTC time), (location), (altitude), (color), (direction).

EXAMPLE−

“Unauthorized laser illumination event, at 0100z, 8 mile

final runway 18R at 3,000 feet, green laser from the

southwest.”

REFERENCE−

FAAO 7110.65, Unauthorized Laser Illumination of Aircraft,

Para 10−2−14.

FAAO 7210.3, Reporting Laser Illumination of Aircraft, Para 2−1−27.

h. When these activities become known to the

FAA, Notices to Airmen (NOTAMs) are issued to

inform the aviation community of the events. Pilots

should consult NOTAMs or the Special Notices

section of the Airport/Facility Directory for information regarding these activities.

7−5−13. Flying in Flat Light and White Out

Conditions

a. Flat Light. Flat light is an optical illusion, also

known as “sector or partial white out.” It is not as

severe as “white out” but the condition causes pilots

to lose their depth−of−field and contrast in vision.
7/26/12 AIM

Potential Flight Hazards 7−5−11

Flat light conditions are usually accompanied by

overcast skies inhibiting any visual clues. Such

conditions can occur anywhere in the world,

primarily in snow covered areas but can occur in dust,

sand, mud flats, or on glassy water. Flat light can

completely obscure features of the terrain, creating an

inability to distinguish distances and closure rates.

As a result of this reflected light, it can give pilots the

illusion that they are ascending or descending when

they may actually be flying level. However, with

good judgment and proper training and planning, it is

possible to safely operate an aircraft in flat light

conditions.

b. White Out. As defined in meteorological

terms, white out occurs when a person becomes

engulfed in a uniformly white glow. The glow is a

result of being surrounded by blowing snow, dust,

sand, mud or water. There are no shadows, no horizon

or clouds and all depth−of−field and orientation are

lost. A white out situation is severe in that there are

no visual references. Flying is not recommended in

any white out situation. Flat light conditions can lead

to a white out environment quite rapidly, and both

atmospheric conditions are insidious; they sneak up

on you as your visual references slowly begin to

disappear. White out has been the cause of several

aviation accidents.

c. Self Induced White Out. This effect typically

occurs when a helicopter takes off or lands on a

snow−covered area. The rotor down wash picks up

particles and re−circulates them through the rotor

down wash. The effect can vary in intensity

depending upon the amount of light on the surface.

This can happen on the sunniest, brightest day with

good contrast everywhere. However, when it

happens, there can be a complete loss of visual clues.

If the pilot has not prepared for this immediate loss of

visibility, the results can be disastrous. Good

planning does not prevent one from encountering flat

light or white out conditions.

d. Never take off in a white out situation.

1. Realize that in flat light conditions it may be

possible to depart but not to return to that site. During

takeoff, make sure you have a reference point. Do not

lose sight of it until you have a departure reference

point in view. Be prepared to return to the takeoff

reference if the departure reference does not come

into view.

2. Flat light is common to snow skiers. One way

to compensate for the lack of visual contrast and

depth−of−field loss is by wearing amber tinted lenses

(also known as blue blockers). Special note of

caution: Eyewear is not ideal for every pilot. Take

into consideration personal factors − age, light

sensitivity, and ambient lighting conditions.

3. So what should a pilot do when all visual

references are lost?

(a) Trust the cockpit instruments.

(b) Execute a 180 degree turnaround and start

looking for outside references.

(c) Above all − fly the aircraft.

e. Landing in Low Light Conditions. When

landing in a low light condition − use extreme

caution. Look for intermediate reference points, in

addition to checkpoints along each leg of the route for

course confirmation and timing. The lower the

ambient light becomes, the more reference points a

pilot should use.

f. Airport Landings.

1. Look for features around the airport or

approach path that can be used in determining depth

perception. Buildings, towers, vehicles or other

aircraft serve well for this measurement. Use

something that will provide you with a sense of height

above the ground, in addition to orienting you to the

runway.

2. Be cautious of snowdrifts and snow banks −

anything that can distinguish the edge of the runway.

Look for subtle changes in snow texture or shading to

identify ridges or changes in snow depth.

g. Off−Airport Landings.

1. In the event of an off−airport landing, pilots

have used a number of different visual cues to gain

reference. Use whatever you must to create the

contrast you need. Natural references seem to work

best (trees, rocks, snow ribs, etc.)

(a) Over flight.

(b) Use of markers.

(c) Weighted flags.

(d) Smoke bombs.

(e) Any colored rags.
AIM 7/26/12

7−5−12 Potential Flight Hazards

(f) Dye markers.

(g) Kool−aid.

(h) Trees or tree branches.

2. It is difficult to determine the depth of snow

in areas that are level. Dropping items from the

aircraft to use as reference points should be used as a

visual aid only and not as a primary landing reference.

Unless your marker is biodegradable, be sure to

retrieve it after landing. Never put yourself in a

position where no visual references exist.

3. Abort landing if blowing snow obscures your

reference. Make your decisions early. Don’t assume

you can pick up a lost reference point when you get

closer.

4. Exercise extreme caution when flying from

sunlight into shade. Physical awareness may tell you

that you are flying straight but you may actually be in

a spiral dive with centrifugal force pressing against

you. Having no visual references enhances this

illusion. Just because you have a good visual

reference does not mean that it’s safe to continue.

There may be snow−covered terrain not visible in the

direction that you are traveling. Getting caught in a no

visual reference situation can be fatal.

h. Flying Around a Lake.

1. When flying along lakeshores, use them as a

reference point. Even if you can see the other side,

realize that your depth perception may be poor. It is

easy to fly into the surface. If you must cross the lake,

check the altimeter frequently and maintain a safe

altitude while you still have a good reference. Don’t

descend below that altitude.

2. The same rules apply to seemingly flat areas

of snow. If you don’t have good references, avoid

going there.

i. Other Traffic. Be on the look out for other

traffic in the area. Other aircraft may be using your

same reference point. Chances are greater of

colliding with someone traveling in the same

direction as you, than someone flying in the opposite

direction.

j. Ceilings. Low ceilings have caught many pilots

off guard. Clouds do not always form parallel to the

surface, or at the same altitude. Pilots may try to

compensate for this by flying with a slight bank and

thus creating a descending turn.

k. Glaciers. Be conscious of your altitude when

flying over glaciers. The glaciers may be rising faster

than you are climbing.

7−5−14. Operations in Ground Icing

Conditions

a. The presence of aircraft airframe icing during

takeoff, typically caused by improper or no deicing of

the aircraft being accomplished prior to flight has

contributed to many recent accidents in turbine

aircraft. The General Aviation Joint Steering

Committee (GAJSC) is the primary vehicle for

government−industry cooperation, communication,

and coordination on GA accident mitigation. The

Turbine Aircraft Operations Subgroup (TAOS)

works to mitigate accidents in turbine accident

aviation. While there is sufficient information and

guidance currently available regarding the effects of

icing on aircraft and methods for deicing, the TAOS

has developed a list of recommended actions to

further assist pilots and operators in this area.

While the efforts of the TAOS specifically focus on

turbine aircraft, it is recognized that their recommendations are applicable to and can be adapted for the

pilot of a small, piston powered aircraft too.

b. The following recommendations are offered:

1. Ensure that your aircraft’s lift−generating

surfaces are COMPLETELY free of contamination

before flight through a tactile (hands on) check of the

critical surfaces when feasible. Even when otherwise

permitted, operators should avoid smooth or polished

frost on lift−generating surfaces as an acceptable

preflight condition.

2. Review and refresh your cold weather

standard operating procedures.

3. Review and be familiar with the Airplane

Flight Manual (AFM) limitations and procedures

necessary to deal with icing conditions prior to flight,

as well as in flight.

4. Protect your aircraft while on the ground, if

possible, from sleet and freezing rain by taking

advantage of aircraft hangars.

5. Take full advantage of the opportunities

available at airports for deicing. Do not refuse deicing

services simply because of cost.
7/26/12 AIM

Potential Flight Hazards 7−5−13

6. Always consider canceling or delaying a

flight if weather conditions do not support a safe

operation.

c. If you haven’t already developed a set of

Standard Operating Procedures for cold weather

operations, they should include:

1. Procedures based on information that is

applicable to the aircraft operated, such as AFM

limitations and procedures;

2. Concise and easy to understand guidance that

outlines best operational practices;

3. A systematic procedure for recognizing,

evaluating and addressing the associated icing risk,

and offer clear guidance to mitigate this risk;

4. An aid (such as a checklist or reference cards)

that is readily available during normal day−to−day

aircraft operations.

d. There are several sources for guidance relating

to airframe icing, including:

1. http://aircrafticing.grc.nasa.gov/index.html

2. http://www.ibac.org/is−bao/isbao.htm

3. http://www.natasafety1st.org/bus_deice.htm

4. Advisory Circular (AC) 91−74, Pilot Guide,

Flight in Icing Conditions.

5. AC 135−17, Pilot Guide Small Aircraft

Ground Deicing.

6. AC 135−9, FAR Part 135 Icing Limitations.

7. AC 120−60, Ground Deicing and Anti−icing

Program.

8. AC 135−16, Ground Deicing and Anti−icing

Training and Checking.

The FAA Approved Deicing Program Updates is

published annually as a Flight Standards Information

Bulletin for Air Transportation and contains detailed

information on deicing and anti−icing procedures and

holdover times. It may be accessed at the following

web site by selecting the current year’s information

bulletins:

http://www.faa.gov/library/manuals/examiners_inspe

ctors/8400/fsat

7−5−15. Avoid Flight in the Vicinity of

Thermal Plumes (Smoke Stacks and

Cooling Towers)

a. Flight Hazards Exist Around Thermal

Plumes. Thermal plumes are defined as visible or

invisible emissions from power plants, industrial

production facilities, or other industrial systems that

release large amounts of vertically directed unstable

gases. High temperature exhaust plumes may cause

significant air disturbances such as turbulence and

vertical shear. Other identified potential hazards

include, but are not necessarily limited to, reduced

visibility, oxygen depletion, engine particulate

contamination, exposure to gaseous oxides, and/or

icing. Results of encountering a plume may include

airframe damage, aircraft upset, and/or engine

damage/failure. These hazards are most critical

during low altitude flight, especially during takeoff

and landing.

b. When able, a pilot should fly upwind of

possible thermal plumes. When a plume is visible

via smoke or a condensation cloud, remain clear and

realize a plume may have both visible and invisible

characteristics. Exhaust stacks without visible

plumes may still be in full operation, and airspace in

the vicinity should be treated with caution. As with

mountain wave turbulence or clear air turbulence, an

invisible plume may be encountered unexpectedly.

Cooling towers, power plant stacks, exhaust fans, and

other similar structures are depicted in FIG 7−5−2.

Whether plumes are visible or invisible, the total

extent of their unstable air is difficult to ascertain.

FAA studies are underway to further characterize the

effects of thermal plumes as exhaust effluents. Until

the results of these studies are known and possible

changes to rules and policy are identified and/or

published, pilots are encouraged to exercise caution

when flying in the vicinity of thermal plumes. Pilots

are encouraged to reference the Airport/Facility

Directory where amplifying notes may caution pilots

and identify the location of structure(s) emitting

thermal plumes.
AIM 7/26/12

7−5−14 Potential Flight Hazards

FIG 7−5−2

Plumes
7/26/12 AIM

Safety, Accident, and Hazard Reports 7−6−1

Section 6. Safety, Accident, and Hazard Reports

7−6−1. Aviation Safety Reporting Program

a. The FAA has established a voluntary Aviation

Safety Reporting Program designed to stimulate the

free and unrestricted flow of information concerning

deficiencies and discrepancies in the aviation system.

This is a positive program intended to ensure the

safest possible system by identifying and correcting

unsafe conditions before they lead to accidents. The

primary objective of the program is to obtain

information to evaluate and enhance the safety and

efficiency of the present system.

b. This cooperative safety reporting program

invites pilots, controllers, flight attendants, maintenance personnel and other users of the airspace

system, or any other person, to file written reports of

actual or potential discrepancies and deficiencies

involving the safety of aviation operations. The

operations covered by the program include departure,

en route, approach, and landing operations and

procedures, air traffic control procedures and

equipment, crew and air traffic control communications, aircraft cabin operations, aircraft movement on

the airport, near midair collisions, aircraft maintenance and record keeping and airport conditions or

services.

c. The report should give the date, time, location,

persons and aircraft involved (if applicable), nature

of the event, and all pertinent details.

d. To ensure receipt of this information, the

program provides for the waiver of certain

disciplinary actions against persons, including pilots

and air traffic controllers, who file timely written

reports concerning potentially unsafe incidents. To be

considered timely, reports must be delivered or

postmarked within 10 days of the incident unless that

period is extended for good cause. Reports should be

submitted on NASA ARC Forms 277, which are

available free of charge, postage prepaid, at FAA

Flight Standards District Offices and Flight Service

Stations, and from NASA, ASRS, PO Box 189,

Moffet Field, CA 94035.

e. The FAA utilizes the National Aeronautics and

Space Administration (NASA) to act as an

independent third party to receive and analyze reports

submitted under the program. This program is

described in AC 00−46, Aviation Safety Reporting

Program.

7−6−2. Aircraft Accident and Incident

Reporting

a. Occurrences Requiring Notification. The

operator of an aircraft must immediately, and by the

most expeditious means available, notify the nearest

National Transportation Safety Board (NTSB) Field

Office when:

1. An aircraft accident or any of the following

listed incidents occur:

(a) Flight control system malfunction or

failure.

(b) Inability of any required flight crew

member to perform their normal flight duties as a

result of injury or illness.

(c) Failure of structural components of a

turbine engine excluding compressor and turbine

blades and vanes.

(d) Inflight fire.

(e) Aircraft collide in flight.

(f) Damage to property, other than the

aircraft, estimated to exceed $25,000 for repair

(including materials and labor) or fair market value in

the event of total loss, whichever is less.

(g) For large multi-engine aircraft (more than

12,500 pounds maximum certificated takeoff

weight):

(1) Inflight failure of electrical systems

which requires the sustained use of an emergency bus

powered by a back-up source such as a battery,

auxiliary power unit, or air-driven generator to retain

flight control or essential instruments;

(2) Inflight failure of hydraulic systems

that results in sustained reliance on the sole remaining

hydraulic or mechanical system for movement of

flight control surfaces;

(3) Sustained loss of the power or thrust

produced by two or more engines; and

(4) An evacuation of aircraft in which an

emergency egress system is utilized.
AIM 7/26/12

7−6−2 Safety, Accident, and Hazard Reports

2. An aircraft is overdue and is believed to have

been involved in an accident.

b. Manner of Notification.

1. The most expeditious method of notification

to the NTSB by the operator will be determined by the

circumstances existing at that time. The NTSB has

advised that any of the following would be

considered examples of the type of notification that

would be acceptable:

(a) Direct telephone notification.

(b) Telegraphic notification.

(c) Notification to the FAA who would in turn

notify the NTSB by direct communication; i.e., dispatch or telephone.

c. Items to be Included in Notification. The

notification required above must contain the

following information, if available:

1. Type, nationality, and registration marks of

the aircraft.

2. Name of owner and operator of the aircraft.

3. Name of the pilot-in-command.

4. Date and time of the accident, or incident.

5. Last point of departure, and point of intended

landing of the aircraft.

6. Position of the aircraft with reference to some

easily defined geographical point.

7. Number of persons aboard, number killed,

and number seriously injured.

8. Nature of the accident, or incident, the

weather, and the extent of damage to the aircraft so far

as is known; and

9. A description of any explosives, radioactive

materials, or other dangerous articles carried.

d. Follow−up Reports.

1. The operator must file a report on NTSB

Form 6120.1 or 6120.2, available from NTSB Field

Offices or from the NTSB, Washington, DC, 20594:

(a) Within 10 days after an accident;

(b) When, after 7 days, an overdue aircraft is

still missing;

(c) A report on an incident for which

notification is required as described in subparagraph a(1) must be filed only as requested by an

authorized representative of the NTSB.

2. Each crewmember, if physically able at the

time the report is submitted, must attach a statement

setting forth the facts, conditions, and circumstances

relating to the accident or incident as they appeared.

If the crewmember is incapacitated, a statement must

be submitted as soon as physically possible.

e. Where to File the Reports.

1. The operator of an aircraft must file with the

NTSB Field Office nearest the accident or incident

any report required by this section.

2. The NTSB Field Offices are listed under U.S.

Government in the telephone directories in the

following cities: Anchorage, AK; Atlanta, GA;

Chicago, IL; Denver, CO; Fort Worth, TX;

Los Angeles, CA; Miami, FL; Parsippany, NJ;

Seattle, WA.

7−6−3. Near Midair Collision Reporting

a. Purpose and Data Uses. The primary purpose

of the Near Midair Collision (NMAC) Reporting

Program is to provide information for use in

enhancing the safety and efficiency of the National

Airspace System. Data obtained from NMAC reports

are used by the FAA to improve the quality of FAA

services to users and to develop programs, policies,

and procedures aimed at the reduction of NMAC

occurrences. All NMAC reports are thoroughly

investigated by Flight Standards Facilities in

coordination with Air Traffic Facilities. Data from

these investigations are transmitted to FAA Headquarters in Washington, DC, where they are compiled

and analyzed, and where safety programs and

recommendations are developed.

b. Definition. A near midair collision is defined

as an incident associated with the operation of an

aircraft in which a possibility of collision occurs as a

result of proximity of less than 500 feet to another

aircraft, or a report is received from a pilot or a flight

crew member stating that a collision hazard existed

between two or more aircraft.

c. Reporting Responsibility. It is the responsibility of the pilot and/or flight crew to determine

whether a near midair collision did actually occur

and, if so, to initiate a NMAC report. Be specific, as
7/26/12 AIM

Safety, Accident, and Hazard Reports 7−6−3

ATC will not interpret a casual remark to mean that

a NMAC is being reported. The pilot should state “I

wish to report a near midair collision.”

d. Where to File Reports. Pilots and/or flight

crew members involved in NMAC occurrences are

urged to report each incident immediately:

1. By radio or telephone to the nearest FAA ATC

facility or FSS.

2. In writing, in lieu of the above, to the nearest

Flight Standards District Office (FSDO).

e. Items to be Reported.

1. Date and time (UTC) of incident.

2. Location of incident and altitude.

3. Identification and type of reporting aircraft,

aircrew destination, name and home base of pilot.

4. Identification and type of other aircraft,

aircrew destination, name and home base of pilot.

5. Type of flight plans; station altimeter setting

used.

6. Detailed weather conditions at altitude or

flight level.

7. Approximate courses of both aircraft:

indicate if one or both aircraft were climbing or

descending.

8. Reported separation in distance at first

sighting, proximity at closest point horizontally and

vertically, and length of time in sight prior to evasive

action.

9. Degree of evasive action taken, if any (from

both aircraft, if possible).

10. Injuries, if any.

f. Investigation. The FSDO in whose area the

incident occurred is responsible for the investigation

and reporting of NMACs.

g. Existing radar, communication, and weather

data will be examined in the conduct of the

investigation. When possible, all cockpit crew

members will be interviewed regarding factors

involving the NMAC incident. Air traffic controllers

will be interviewed in cases where one or more of the

involved aircraft was provided ATC service. Both

flight and ATC procedures will be evaluated. When

the investigation reveals a violation of an FAA

regulation, enforcement action will be pursued.

7−6−4. Unidentified Flying Object (UFO)

Reports

a. Persons wanting to report UFO/unexplained

phenomena activity should contact a UFO/unexplained phenomena reporting data collection center,

such as Bigelow Aerospace Advanced Space Studies

(BAASS) (voice: 1−877−979−7444 or e−mail:

Reporting@baass.org), the National UFO Reporting

Center, etc.

b. If concern is expressed that life or property

might be endangered, report the activity to the local

law enforcement department.

7−6−5. Safety Alerts For Operators (SAFO)

and Information For Operators (InFO)

a. SAFOs contain important safety information

that is often time-critical. A SAFO may contain

information and/or recommended (non-regulatory)

action to be taken by the respective operators or

parties identified in the SAFO. The audience for

SAFOs varies with each subject and may include: Air

carrier certificate holders, air operator certificate

holders, general aviation operators, directors of

safety, directors of operations, directors of maintenance, fractional ownership program managers,

training center managers, accountable managers at

repair stations, and other parties as applicable.

b. InFOs are similar to SAFOs, but contain

valuable information for operators that should help

them meet administrative requirements or certain

regulatory requirements with relatively low urgency

or impact in safety.

c. The SAFO and InFO system provides a means

to rapidly distribute this information to operators and

can be found at:

http://www.faa.gov/other_visit/aviation_industry/

airline_operators/airline_safety/safo and

http://www.faa.gov/other_visit/aviation_industry/

airline_operators/airline_safety/info

or search keyword FAA SAFO or FAA INFO. Free

electronic subscription is available on the “ALL

SAFOs” or “ALL InFOs” page of the website.

7/26/12 AIM

Fitness for Flight 8−1−1

Chapter 8. Medical Facts for Pilots

Section 1. Fitness for Flight

8−1−1. Fitness For Flight

a. Medical Certification.

1. All pilots except those flying gliders and free

air balloons must possess valid medical certificates in

order to exercise the privileges of their airman

certificates. The periodic medical examinations

required for medical certification are conducted by

designated Aviation Medical Examiners, who are

physicians with a special interest in aviation safety

and training in aviation medicine.

2. The standards for medical certification are

contained in 14 CFR Part 67. Pilots who have a

history of certain medical conditions described in

these standards are mandatorily disqualified from

flying. These medical conditions include a

personality disorder manifested by overt acts, a

psychosis, alcoholism, drug dependence, epilepsy,

an unexplained disturbance of consciousness,

myocardial infarction, angina pectoris and diabetes

requiring medication for its control. Other medical

conditions may be temporarily disqualifying, such as

acute infections, anemia, and peptic ulcer. Pilots who

do not meet medical standards may still be qualified

under special issuance provisions or the exemption

process. This may require that either additional

medical information be provided or practical flight

tests be conducted.

3. Student pilots should visit an Aviation

Medical Examiner as soon as possible in their flight

training in order to avoid unnecessary training

expenses should they not meet the medical standards.

For the same reason, the student pilot who plans to

enter commercial aviation should apply for the

highest class of medical certificate that might be

necessary in the pilot’s career.

CAUTION−

The CFRs prohibit a pilot who possesses a current

medical certificate from performing crewmember duties

while the pilot has a known medical condition or increase

of a known medical condition that would make the pilot

unable to meet the standards for the medical certificate.

b. Illness.

1. Even a minor illness suffered in day-to-day

living can seriously degrade performance of many

piloting tasks vital to safe flight. Illness can produce

fever and distracting symptoms that can impair

judgment, memory, alertness, and the ability to make

calculations. Although symptoms from an illness

may be under adequate control with a medication, the

medication itself may decrease pilot performance.

2. The safest rule is not to fly while suffering

from any illness. If this rule is considered too

stringent for a particular illness, the pilot should

contact an Aviation Medical Examiner for advice.

c. Medication.

1. Pilot performance can be seriously degraded

by both prescribed and over-the-counter medications,

as well as by the medical conditions for which they

are taken. Many medications, such as tranquilizers,

sedatives, strong pain relievers, and cough-suppressant preparations, have primary effects that may

impair judgment, memory, alertness, coordination,

vision, and the ability to make calculations. Others,

such as antihistamines, blood pressure drugs, muscle

relaxants, and agents to control diarrhea and motion

sickness, have side effects that may impair the same

critical functions. Any medication that depresses the

nervous system, such as a sedative, tranquilizer or

antihistamine, can make a pilot much more

susceptible to hypoxia.

2. The CFRs prohibit pilots from performing

crewmember duties while using any medication that

affects the faculties in any way contrary to safety. The

safest rule is not to fly as a crewmember while taking

any medication, unless approved to do so by the FAA.

d. Alcohol.

1. Extensive research has provided a number of

facts about the hazards of alcohol consumption and

flying. As little as one ounce of liquor, one bottle of

beer or four ounces of wine can impair flying skills,

with the alcohol consumed in these drinks being

detectable in the breath and blood for at least 3 hours.

Even after the body completely destroys a moderate

amount of alcohol, a pilot can still be severely
AIM 7/26/12

8−1−2 Fitness for Flight

impaired for many hours by hangover. There is

simply no way of increasing the destruction of

alcohol or alleviating a hangover. Alcohol also

renders a pilot much more susceptible to disorientation and hypoxia.

2. A consistently high alcohol related fatal

aircraft accident rate serves to emphasize that alcohol

and flying are a potentially lethal combination. The

CFRs prohibit pilots from performing crewmember

duties within 8 hours after drinking any alcoholic

beverage or while under the influence of alcohol.

However, due to the slow destruction of alcohol, a

pilot may still be under influence 8 hours after

drinking a moderate amount of alcohol. Therefore, an

excellent rule is to allow at least 12 to 24 hours

between “bottle and throttle,” depending on the

amount of alcoholic beverage consumed.

e. Fatigue.

1. Fatigue continues to be one of the most

treacherous hazards to flight safety, as it may not be

apparent to a pilot until serious errors are made.

Fatigue is best described as either acute (short-term)

or chronic (long-term).

2. A normal occurrence of everyday living,

acute fatigue is the tiredness felt after long periods of

physical and mental strain, including strenuous

muscular effort, immobility, heavy mental workload,

strong emotional pressure, monotony, and lack of

sleep. Consequently, coordination and alertness, so

vital to safe pilot performance, can be reduced. Acute

fatigue is prevented by adequate rest and sleep, as

well as by regular exercise and proper nutrition.

3. Chronic fatigue occurs when there is not

enough time for full recovery between episodes of

acute fatigue. Performance continues to fall off, and

judgment becomes impaired so that unwarranted

risks may be taken. Recovery from chronic fatigue

requires a prolonged period of rest.

4. OBSTRUCTIVE SLEEP APNEA (OSA).

OSA is now recognized as an important preventable

factor identified in transportation accidents. OSA

interrupts the normal restorative sleep necessary for

normal functioning and is associated with chronic

illnesses such as hypertension, heart attack, stroke,

obesity, and diabetes. Symptoms include snoring,

excessive daytime sleepiness, intermittent prolonged

breathing pauses while sleeping, memory impairment and lack of concentration. There are many

available treatments which can reverse the day time

symptoms and reduce the chance of an accident. OSA

can be easily treated. Most treatments are acceptable

for medical certification upon demonstrating effective treatment. If you have any symptoms described

above, or neck size over 17 inches in men or 16 inches

in women, or a body mass index greater than 30 you

should be evaluated for sleep apnea by a sleep

medicine specialist.

(http://www.cdc.gov/healthyweight/assessing/

bmi/adult_bmi/english_bmi_calculator/bmi_calc

ulator.html) With treatment you can avoid or delay

the onset of these chronic illnesses and prolong a

quality life.

f. Stress.

1. Stress from the pressures of everyday living

can impair pilot performance, often in very subtle

ways. Difficulties, particularly at work, can occupy

thought processes enough to markedly decrease

alertness. Distraction can so interfere with judgment

that unwarranted risks are taken, such as flying into

deteriorating weather conditions to keep on schedule.

Stress and fatigue (see above) can be an extremely

hazardous combination.

2. Most pilots do not leave stress “on the

ground.” Therefore, when more than usual difficulties are being experienced, a pilot should consider

delaying flight until these difficulties are satisfactorily resolved.

g. Emotion.

Certain emotionally upsetting events, including a

serious argument, death of a family member,

separation or divorce, loss of job, and financial

catastrophe, can render a pilot unable to fly an aircraft

safely. The emotions of anger, depression, and

anxiety from such events not only decrease alertness

but also may lead to taking risks that border on

self-destruction. Any pilot who experiences an

emotionally upsetting event should not fly until

satisfactorily recovered from it.

h. Personal Checklist. Aircraft accident statistics show that pilots should be conducting preflight

checklists on themselves as well as their aircraft for

pilot impairment contributes to many more accidents

than failures of aircraft systems. A personal checklist,

which includes all of the categories of pilot

impairment as discussed in this section, that can be
7/26/12 AIM

Fitness for Flight 8−1−3

easily committed to memory is being distributed by

the FAA in the form of a wallet-sized card.

i. PERSONAL CHECKLIST. I’m physically

and mentally safe to fly; not being impaired by:

Illness

Medication

Stress

Alcohol

Fatigue

Emotion

8−1−2. Effects of Altitude

a. Hypoxia.

1. Hypoxia is a state of oxygen deficiency in the

body sufficient to impair functions of the brain and

other organs. Hypoxia from exposure to altitude is

due only to the reduced barometric pressures

encountered at altitude, for the concentration of

oxygen in the atmosphere remains about 21 percent

from the ground out to space.

2. Although a deterioration in night vision

occurs at a cabin pressure altitude as low as

5,000 feet, other significant effects of altitude

hypoxia usually do not occur in the normal healthy

pilot below 12,000 feet. From 12,000 to 15,000 feet

of altitude, judgment, memory, alertness, coordination and ability to make calculations are impaired,

and headache, drowsiness, dizziness and either a

sense of well-being (euphoria) or belligerence occur.

The effects appear following increasingly shorter

periods of exposure to increasing altitude. In fact,

pilot performance can seriously deteriorate within

15 minutes at 15,000 feet.

3. At cabin pressure altitudes above 15,000 feet,

the periphery of the visual field grays out to a point

where only central vision remains (tunnel vision). A

blue coloration (cyanosis) of the fingernails and lips

develops. The ability to take corrective and protective

action is lost in 20 to 30 minutes at 18,000 feet and

5 to 12 minutes at 20,000 feet, followed soon

thereafter by unconsciousness.

4. The altitude at which significant effects of

hypoxia occur can be lowered by a number of factors.

Carbon monoxide inhaled in smoking or from

exhaust fumes, lowered hemoglobin (anemia), and

certain medications can reduce the oxygen-carrying

capacity of the blood to the degree that the amount of

oxygen provided to body tissues will already be

equivalent to the oxygen provided to the tissues when

exposed to a cabin pressure altitude of several

thousand feet. Small amounts of alcohol and low

doses of certain drugs, such as antihistamines,

tranquilizers, sedatives and analgesics can, through

their depressant action, render the brain much more

susceptible to hypoxia. Extreme heat and cold, fever,

and anxiety increase the body’s demand for oxygen,

and hence its susceptibility to hypoxia.

5. The effects of hypoxia are usually quite

difficult to recognize, especially when they occur

gradually. Since symptoms of hypoxia do not vary in

an individual, the ability to recognize hypoxia can be

greatly improved by experiencing and witnessing the

effects of hypoxia during an altitude chamber

“flight.” The FAA provides this opportunity through

aviation physiology training, which is conducted at

the FAA Civil Aeromedical Institute and at many

military facilities across the U.S. To attend the

Physiological Training Program at the Civil

Aeromedical Institute, Mike Monroney Aeronautical

Center, Oklahoma City, OK, contact by telephone

(405) 954−6212, or by writing Aerospace Medical

Education Division, AAM−400, CAMI, Mike

Monroney Aeronautical Center, P.O. Box 25082,

Oklahoma City, OK 73125.

NOTE−

To attend the physiological training program at one of the

military installations having the training capability, an

application form and a fee must be submitted. Full

particulars about location, fees, scheduling procedures,

course content, individual requirements, etc., are contained in the Physiological Training Application, Form

Number AC 3150−7, which is obtained by contacting the

accident prevention specialist or the office forms manager

in the nearest FAA office.

6. Hypoxia is prevented by heeding factors that

reduce tolerance to altitude, by enriching the inspired

air with oxygen from an appropriate oxygen system,

and by maintaining a comfortable, safe cabin

pressure altitude. For optimum protection, pilots are

encouraged to use supplemental oxygen above
AIM 7/26/12

8−1−4 Fitness for Flight

10,000 feet during the day, and above 5,000 feet at

night. The CFRs require that at the minimum, flight

crew be provided with and use supplemental oxygen

after 30 minutes of exposure to cabin pressure

altitudes between 12,500 and 14,000 feet and

immediately on exposure to cabin pressure altitudes

above 14,000 feet. Every occupant of the aircraft

must be provided with supplemental oxygen at cabin

pressure altitudes above 15,000 feet.

b. Ear Block.

1. As the aircraft cabin pressure decreases

during ascent, the expanding air in the middle ear

pushes the eustachian tube open, and by escaping

down it to the nasal passages, equalizes in pressure

with the cabin pressure. But during descent, the pilot

must periodically open the eustachian tube to

equalize pressure. This can be accomplished by

swallowing, yawning, tensing muscles in the throat,

or if these do not work, by a combination of closing

the mouth, pinching the nose closed, and attempting

to blow through the nostrils (Valsalva maneuver).

2. Either an upper respiratory infection, such as

a cold or sore throat, or a nasal allergic condition can

produce enough congestion around the eustachian

tube to make equalization difficult. Consequently, the

difference in pressure between the middle ear and

aircraft cabin can build up to a level that will hold the

eustachian tube closed, making equalization difficult

if not impossible. The problem is commonly referred

to as an “ear block.”

3. An ear block produces severe ear pain and

loss of hearing that can last from several hours to

several days. Rupture of the ear drum can occur in

flight or after landing. Fluid can accumulate in the

middle ear and become infected.

4. An ear block is prevented by not flying with

an upper respiratory infection or nasal allergic

condition. Adequate protection is usually not

provided by decongestant sprays or drops to reduce

congestion around the eustachian tubes. Oral

decongestants have side effects that can significantly

impair pilot performance.

5. If an ear block does not clear shortly after

landing, a physician should be consulted.

c. Sinus Block.

1. During ascent and descent, air pressure in the

sinuses equalizes with the aircraft cabin pressure

through small openings that connect the sinuses to the

nasal passages. Either an upper respiratory infection,

such as a cold or sinusitis, or a nasal allergic condition

can produce enough congestion around an opening to

slow equalization, and as the difference in pressure

between the sinus and cabin mounts, eventually plug

the opening. This “sinus block” occurs most

frequently during descent.

2. A sinus block can occur in the frontal sinuses,

located above each eyebrow, or in the maxillary

sinuses, located in each upper cheek. It will usually

produce excruciating pain over the sinus area. A

maxillary sinus block can also make the upper teeth

ache. Bloody mucus may discharge from the nasal

passages.

3. A sinus block is prevented by not flying with

an upper respiratory infection or nasal allergic

condition. Adequate protection is usually not

provided by decongestant sprays or drops to reduce

congestion around the sinus openings. Oral decongestants have side effects that can impair pilot

performance.

4. If a sinus block does not clear shortly after

landing, a physician should be consulted.

d. Decompression Sickness After Scuba

Diving.

1. A pilot or passenger who intends to fly after

scuba diving should allow the body sufficient time to

rid itself of excess nitrogen absorbed during diving.

If not, decompression sickness due to evolved gas can

occur during exposure to low altitude and create a

serious inflight emergency.

2. The recommended waiting time before going

to flight altitudes of up to 8,000 feet is at least

12 hours after diving which has not required

controlled ascent (nondecompression stop diving),

and at least 24 hours after diving which has required

controlled ascent (decompression stop diving). The

waiting time before going to flight altitudes above

8,000 feet should be at least 24 hours after any

SCUBA dive. These recommended altitudes are

actual flight altitudes above mean sea level (AMSL)

and not pressurized cabin altitudes. This takes into

consideration the risk of decompression of the

aircraft during flight.
7/26/12 AIM

Fitness for Flight 8−1−5

8−1−3. Hyperventilation in Flight

a. Hyperventilation, or an abnormal increase in

the volume of air breathed in and out of the lungs, can

occur subconsciously when a stressful situation is

encountered in flight. As hyperventilation “blows

off” excessive carbon dioxide from the body, a pilot

can experience symptoms of lightheadedness,

suffocation, drowsiness, tingling in the extremities,

and coolness and react to them with even greater

hyperventilation. Incapacitation can eventually result

from incoordination, disorientation, and painful

muscle spasms. Finally, unconsciousness can occur.

b. The symptoms of hyperventilation subside

within a few minutes after the rate and depth of

breathing are consciously brought back under

control. The buildup of carbon dioxide in the body

can be hastened by controlled breathing in and out of

a paper bag held over the nose and mouth.

c. Early symptoms of hyperventilation and

hypoxia are similar. Moreover, hyperventilation and

hypoxia can occur at the same time. Therefore, if a

pilot is using an oxygen system when symptoms are

experienced, the oxygen regulator should immediately be set to deliver 100 percent oxygen, and then the

system checked to assure that it has been functioning

effectively before giving attention to rate and depth of

breathing.

8−1−4. Carbon Monoxide Poisoning in

Flight

a. Carbon monoxide is a colorless, odorless, and

tasteless gas contained in exhaust fumes. When

breathed even in minute quantities over a period of

time, it can significantly reduce the ability of the

blood to carry oxygen. Consequently, effects of

hypoxia occur.

b. Most heaters in light aircraft work by air

flowing over the manifold. Use of these heaters while

exhaust fumes are escaping through manifold cracks

and seals is responsible every year for several

nonfatal and fatal aircraft accidents from carbon

monoxide poisoning.

c. A pilot who detects the odor of exhaust or

experiences symptoms of headache, drowsiness, or

dizziness while using the heater should suspect

carbon monoxide poisoning, and immediately shut

off the heater and open air vents. If symptoms are

severe or continue after landing, medical treatment

should be sought.

8−1−5. Illusions in Flight

a. Introduction. Many different illusions can be

experienced in flight. Some can lead to spatial

disorientation. Others can lead to landing errors.

Illusions rank among the most common factors cited

as contributing to fatal aircraft accidents.

b. Illusions Leading to Spatial Disorientation.

1. Various complex motions and forces and

certain visual scenes encountered in flight can create

illusions of motion and position. Spatial disorientation from these illusions can be prevented only by

visual reference to reliable, fixed points on the ground

or to flight instruments.

2. The leans. An abrupt correction of a banked

attitude, which has been entered too slowly to

stimulate the motion sensing system in the inner ear,

can create the illusion of banking in the opposite

direction. The disoriented pilot will roll the aircraft

back into its original dangerous attitude, or if level

flight is maintained, will feel compelled to lean in the

perceived vertical plane until this illusion subsides.

(a) Coriolis illusion. An abrupt head movement in a prolonged constant-rate turn that has ceased

stimulating the motion sensing system can create the

illusion of rotation or movement in an entirely

different axis. The disoriented pilot will maneuver the

aircraft into a dangerous attitude in an attempt to stop

rotation. This most overwhelming of all illusions in

flight may be prevented by not making sudden,

extreme head movements, particularly while making

prolonged constant-rate turns under IFR conditions.

(b) Graveyard spin. A proper recovery

from a spin that has ceased stimulating the motion

sensing system can create the illusion of spinning in

the opposite direction. The disoriented pilot will

return the aircraft to its original spin.

(c) Graveyard spiral. An observed loss of

altitude during a coordinated constant-rate turn that

has ceased stimulating the motion sensing system can

create the illusion of being in a descent with the wings

level. The disoriented pilot will pull back on the

controls, tightening the spiral and increasing the loss

of altitude.

(d) Somatogravic illusion. A rapid acceleration during takeoff can create the illusion of being
AIM 7/26/12

8−1−6 Fitness for Flight

in a nose up attitude. The disoriented pilot will push

the aircraft into a nose low, or dive attitude. A rapid

deceleration by a quick reduction of the throttles can

have the opposite effect, with the disoriented pilot

pulling the aircraft into a nose up, or stall attitude.

(e) Inversion illusion. An abrupt change

from climb to straight and level flight can create the

illusion of tumbling backwards. The disoriented pilot

will push the aircraft abruptly into a nose low attitude,

possibly intensifying this illusion.

(f) Elevator illusion. An abrupt upward

vertical acceleration, usually by an updraft, can create

the illusion of being in a climb. The disoriented pilot

will push the aircraft into a nose low attitude. An

abrupt downward vertical acceleration, usually by a

downdraft, has the opposite effect, with the

disoriented pilot pulling the aircraft into a nose up

attitude.

(g) False horizon. Sloping cloud formations, an obscured horizon, a dark scene spread with

ground lights and stars, and certain geometric

patterns of ground light can create illusions of not

being aligned correctly with the actual horizon. The

disoriented pilot will place the aircraft in a dangerous

attitude.

(h) Autokinesis. In the dark, a static light

will appear to move about when stared at for many

seconds. The disoriented pilot will lose control of the

aircraft in attempting to align it with the light.

3. Illusions Leading to Landing Errors.

(a) Various surface features and atmospheric

conditions encountered in landing can create illusions

of incorrect height above and distance from the

runway threshold. Landing errors from these

illusions can be prevented by anticipating them

during approaches, aerial visual inspection of

unfamiliar airports before landing, using electronic

glide slope or VASI systems when available, and

maintaining optimum proficiency in landing

procedures.

(b) Runway width illusion. A narrowerthan-usual runway can create the illusion that the

aircraft is at a higher altitude than it actually is. The

pilot who does not recognize this illusion will fly a

lower approach, with the risk of striking objects along

the approach path or landing short. A wider-thanusual runway can have the opposite effect, with the

risk of leveling out high and landing hard or

overshooting the runway.

(c) Runway and terrain slopes illusion. An

upsloping runway, upsloping terrain, or both, can

create the illusion that the aircraft is at a higher

altitude than it actually is. The pilot who does not

recognize this illusion will fly a lower approach. A

downsloping runway, downsloping approach terrain,

or both, can have the opposite effect.

(d) Featureless terrain illusion. An

absence of ground features, as when landing over

water, darkened areas, and terrain made featureless

by snow, can create the illusion that the aircraft is at

a higher altitude than it actually is. The pilot who does

not recognize this illusion will fly a lower approach.

(e) Atmospheric illusions. Rain on the

windscreen can create the illusion of greater height,

and atmospheric haze the illusion of being at a greater

distance from the runway. The pilot who does not

recognize these illusions will fly a lower approach.

Penetration of fog can create the illusion of pitching

up. The pilot who does not recognize this illusion will

steepen the approach, often quite abruptly.

(f) Ground lighting illusions. Lights along

a straight path, such as a road, and even lights on

moving trains can be mistaken for runway and

approach lights. Bright runway and approach lighting

systems, especially where few lights illuminate the

surrounding terrain, may create the illusion of less

distance to the runway. The pilot who does not

recognize this illusion will fly a higher approach.

Conversely, the pilot overflying terrain which has few

lights to provide height cues may make a lower than

normal approach.

8−1−6. Vision in Flight

a. Introduction. Of the body senses, vision is the

most important for safe flight. Major factors that

determine how effectively vision can be used are the

level of illumination and the technique of scanning

the sky for other aircraft.

b. Vision Under Dim and Bright Illumination.

1. Under conditions of dim illumination, small

print and colors on aeronautical charts and aircraft

instruments become unreadable unless adequate

cockpit lighting is available. Moreover, another

aircraft must be much closer to be seen unless its

navigation lights are on.
7/26/12 AIM

Fitness for Flight 8−1−7

2. In darkness, vision becomes more sensitive to

light, a process called dark adaptation. Although

exposure to total darkness for at least 30 minutes is

required for complete dark adaptation, a pilot can

achieve a moderate degree of dark adaptation within

20 minutes under dim red cockpit lighting. Since red

light severely distorts colors, especially on aeronautical charts, and can cause serious difficulty in focusing

the eyes on objects inside the aircraft, its use is

advisable only where optimum outside night vision

capability is necessary. Even so, white cockpit

lighting must be available when needed for map and

instrument reading, especially under IFR conditions.

Dark adaptation is impaired by exposure to cabin

pressure altitudes above 5,000 feet, carbon monoxide

inhaled in smoking and from exhaust fumes,

deficiency of Vitamin A in the diet, and by prolonged

exposure to bright sunlight. Since any degree of dark

adaptation is lost within a few seconds of viewing a

bright light, a pilot should close one eye when using

a light to preserve some degree of night vision.

3. Excessive illumination, especially from light

reflected off the canopy, surfaces inside the aircraft,

clouds, water, snow, and desert terrain, can produce

glare, with uncomfortable squinting, watering of the

eyes, and even temporary blindness. Sunglasses for

protection from glare should absorb at least

85 percent of visible light (15 percent transmittance)

and all colors equally (neutral transmittance), with

negligible image distortion from refractive and

prismatic errors.

c. Scanning for Other Aircraft.

1. Scanning the sky for other aircraft is a key

factor in collision avoidance. It should be used

continuously by the pilot and copilot (or right seat

passenger) to cover all areas of the sky visible from

the cockpit. Although pilots must meet specific visual

acuity requirements, the ability to read an eye chart

does not ensure that one will be able to efficiently spot

other aircraft. Pilots must develop an effective

scanning technique which maximizes one’s visual

capabilities. The probability of spotting a potential

collision threat obviously increases with the time

spent looking outside the cockpit. Thus, one must use

timesharing techniques to efficiently scan the

surrounding airspace while monitoring instruments

as well.

2. While the eyes can observe an approximate

200 degree arc of the horizon at one glance, only a

very small center area called the fovea, in the rear of

the eye, has the ability to send clear, sharply focused

messages to the brain. All other visual information

that is not processed directly through the fovea will be

of less detail. An aircraft at a distance of 7 miles

which appears in sharp focus within the foveal center

of vision would have to be as close as 7/10 of a mile

in order to be recognized if it were outside of foveal

vision. Because the eyes can focus only on this

narrow viewing area, effective scanning is accomplished with a series of short, regularly spaced eye

movements that bring successive areas of the sky into

the central visual field. Each movement should not

exceed 10 degrees, and each area should be observed

for at least 1 second to enable detection. Although

horizontal back-and-forth eye movements seem

preferred by most pilots, each pilot should develop a

scanning pattern that is most comfortable and then

adhere to it to assure optimum scanning.

3. Studies show that the time a pilot spends on

visual tasks inside the cabin should represent no more

that 1/4 to 1/3 of the scan time outside, or no more than

4 to 5 seconds on the instrument panel for every

16 seconds outside. Since the brain is already trained

to process sight information that is presented from

left to right, one may find it easier to start scanning

over the left shoulder and proceed across the

windshield to the right.

4. Pilots should realize that their eyes may

require several seconds to refocus when switching

views between items in the cockpit and distant

objects. The eyes will also tire more quickly when

forced to adjust to distances immediately after

close-up focus, as required for scanning the

instrument panel. Eye fatigue can be reduced by

looking from the instrument panel to the left wing

past the wing tip to the center of the first scan quadrant

when beginning the exterior scan. After having

scanned from left to right, allow the eyes to return to

the cabin along the right wing from its tip inward.

Once back inside, one should automatically commence the panel scan.

5. Effective scanning also helps avoid “emptyfield myopia.” This condition usually occurs when

flying above the clouds or in a haze layer that

provides nothing specific to focus on outside the

aircraft. This causes the eyes to relax and seek a
AIM 7/26/12

8−1−8 Fitness for Flight

comfortable focal distance which may range from

10 to 30 feet. For the pilot, this means looking

without seeing, which is dangerous.

8−1−7. Aerobatic Flight

a. Pilots planning to engage in aerobatics should

be aware of the physiological stresses associated with

accelerative forces during aerobatic maneuvers.

Many prospective aerobatic trainees enthusiastically

enter aerobatic instruction but find their first

experiences with G forces to be unanticipated and

very uncomfortable. To minimize or avoid potential

adverse effects, the aerobatic instructor and trainee

must have a basic understanding of the physiology of

G force adaptation.

b. Forces experienced with a rapid push-over

maneuver result in the blood and body organs being

displaced toward the head. Depending on forces

involved and individual tolerance, a pilot may

experience discomfort, headache, “red-out,” and

even unconsciousness.

c. Forces experienced with a rapid pull-up

maneuver result in the blood and body organ

displacement toward the lower part of the body away

from the head. Since the brain requires continuous

blood circulation for an adequate oxygen supply,

there is a physiologic limit to the time the pilot can

tolerate higher forces before losing consciousness.

As the blood circulation to the brain decreases as a

result of forces involved, a pilot will experience

“narrowing” of visual fields, “gray-out,” “blackout,” and unconsciousness. Even a brief loss of

consciousness in a maneuver can lead to improper

control movement causing structural failure of the

aircraft or collision with another object or terrain.

d. In steep turns, the centrifugal forces tend to

push the pilot into the seat, thereby resulting in blood

and body organ displacement toward the lower part of

the body as in the case of rapid pull-up maneuvers and

with the same physiologic effects and symptoms.

e. Physiologically, humans progressively adapt to

imposed strains and stress, and with practice, any

maneuver will have decreasing effect. Tolerance to

G forces is dependent on human physiology and the

individual pilot. These factors include the skeletal

anatomy, the cardiovascular architecture, the nervous

system, the quality of the blood, the general physical

state, and experience and recency of exposure. The

pilot should consult an Aviation Medical Examiner

prior to aerobatic training and be aware that poor

physical condition can reduce tolerance to accelerative forces.

f. The above information provides pilots with a

brief summary of the physiologic effects of G forces.

It does not address methods of “counteracting” these

effects. There are numerous references on the subject

of G forces during aerobatics available to pilots.

Among these are “G Effects on the Pilot During

Aerobatics,” FAA−AM−72−28, and “G Incapacitation in Aerobatic Pilots: A Flight Hazard”

FAA−AM−82−13. These are available from the

National Technical Information Service, Springfield,

Virginia 22161.

REFERENCE−

FAA AC 91−61, A Hazard in Aerobatics: Effects of G−forces on Pilots.

8−1−8. Judgment Aspects of Collision

Avoidance

a. Introduction. The most important aspects of

vision and the techniques to scan for other aircraft are

described in paragraph 8−1−6, Vision in Flight. Pilots

should also be familiar with the following information to reduce the possibility of mid-air collisions.

b. Determining Relative Altitude. Use the

horizon as a reference point. If the other aircraft is

above the horizon, it is probably on a higher flight

path. If the aircraft appears to be below the horizon,

it is probably flying at a lower altitude.

c. Taking Appropriate Action. Pilots should be

familiar with rules on right-of-way, so if an aircraft is

on an obvious collision course, one can take

immediate evasive action, preferably in compliance

with applicable Federal Aviation Regulations.

d. Consider Multiple Threats. The decision to

climb, descend, or turn is a matter of personal

judgment, but one should anticipate that the other

pilot may also be making a quick maneuver. Watch

the other aircraft during the maneuver and begin your

scanning again immediately since there may be other

aircraft in the area.

e. Collision Course Targets. Any aircraft that

appears to have no relative motion and stays in one

scan quadrant is likely to be on a collision course.

Also, if a target shows no lateral or vertical motion,

but increases in size, take evasive action.

f. Recognize High Hazard Areas.
7/26/12 AIM

Fitness for Flight 8−1−9

1. Airways, especially near VORs, and Class B,

Class C, Class D, and Class E surface areas are places

where aircraft tend to cluster.

2. Remember, most collisions occur during days

when the weather is good. Being in a “radar

environment” still requires vigilance to avoid

collisions.

g. Cockpit Management. Studying maps,

checklists, and manuals before flight, with other

proper preflight planning; e.g., noting necessary

radio frequencies and organizing cockpit materials,

can reduce the amount of time required to look at

these items during flight, permitting more scan time.

h. Windshield Conditions. Dirty or bugsmeared windshields can greatly reduce the ability of

pilots to see other aircraft. Keep a clean windshield.

i. Visibility Conditions. Smoke, haze, dust, rain,

and flying towards the sun can also greatly reduce the

ability to detect targets.

j. Visual Obstructions in the Cockpit.

1. Pilots need to move their heads to see around

blind spots caused by fixed aircraft structures, such as

door posts, wings, etc. It will be necessary at times to

maneuver the aircraft; e.g., lift a wing, to facilitate

seeing.

2. Pilots must ensure curtains and other cockpit

objects; e.g., maps on glare shield, are removed and

stowed during flight.

k. Lights On.

1. Day or night, use of exterior lights can greatly

increase the conspicuity of any aircraft.

2. Keep interior lights low at night.

l. ATC Support. ATC facilities often provide

radar traffic advisories on a workload-permitting

basis. Flight through Class C and Class D airspace

requires communication with ATC. Use this support

whenever possible or when required.

7/26/12 AIM

Types of Charts Available 9−1−1

Chapter 9. Aeronautical Charts and 

Related Publications

Section 1. Types of Charts Available

9−1−1. General

Civil aeronautical charts for the U.S. and its

territories, and possessions are produced by Aeronautical Navigation Products (AeroNav),

http://www.faa.gov/air_traffic/flight_info/

aeronav which is part of FAA’s Air Traffic

Organization, Mission Support Services.

9−1−2. Obtaining Aeronautical Charts

a. Most charts and publications described in this

Chapter can be obtained by subscription or one−time

sales from:

Aeronautical Navigation Products (AeroNav)

Logistics Group, AJV−372

Federal Aviation Administration

10201 Good Luck Road

Glenn Dale, MD 20769−9700

Telephone: 1−800−638−8972 (Toll free within U.S.)

 301−436−8301

 301−436−6829 (FAX)

e−mail: 9−AMC−Chartsales@faa.gov

b. Public sales of charts and publications are also

available through a network of FAA chart agents

primarily located at or near major civil airports. A

listing of products, dates of latest editions and agents

is available at the AeroNav Web site:

http://www.faa.gov/air_traffic/flight_info/

aeronav.

9−1−3. Selected Charts and Products

Available

VFR Navigation Charts

IFR Navigation Charts

Planning Charts

Supplementary Charts and Publications

Digital Products

9−1−4. General Description of each Chart

Series

a. VFR Navigation Charts.

1. Sectional Aeronautical Charts. Sectional

Charts are designed for visual navigation of slow to

medium speed aircraft. The topographic information

consists of contour lines, shaded relief, drainage

patterns, and an extensive selection of visual

checkpoints and landmarks used for flight under

VFR. Cultural features include cities and towns,

roads, railroads, and other distinct landmarks. The

aeronautical information includes visual and radio

aids to navigation, airports, controlled airspace,

special−use airspace, obstructions, and related data.

Scale 1 inch = 6.86nm/1:500,000. 60 x 20 inches

folded to 5 x 10 inches. Revised semiannually, except

most Alaskan charts are revised annually. 

(See FIG 9−1−1 and FIG 9−1−11.)

2. VFR Terminal Area Charts (TAC). TACs

depict the airspace designated as Class B airspace.

While similar to sectional charts, TACs have more

detail because the scale is larger. The TAC should be

used by pilots intending to operate to or from airfields

within or near Class B or Class C airspace. Areas with

TAC coverage are indicated by a • on the Sectional

Chart indexes. Scale 1 inch = 3.43nm/1:250,000.

Charts are revised semiannually, except Puerto

Rico−Virgin Islands revised annually.

(See FIG 9−1−1 and FIG 9−1−11.)

3. World Aeronautical Chart (WAC). WACs

cover land areas for navigation by moderate speed

aircraft operating at high altitudes. Included are city

tints, principal roads, railroads, distinctive landmarks, drainage patterns, and relief. Aeronautical

information includes visual and radio aids to

navigation, airports, airways, special−use airspace,

and obstructions. Because of a smaller scale, WACs

do not show as much detail as sectional or TACs, and;

therefore, are not recommended for exclusive use by

pilots of low speed, low altitude aircraft. Scale

1 inch = 13.7nm/1:1,000,000. 60 x 20 inches folded

to 5 x 10 inches. WACs are revised annually, except

for a few in Alaska and the Caribbean, which are

revised biennially. 

(See FIG 9−1−12 and FIG 9−1−13.)
AIM 7/26/12

9−1−2 Types of Charts Available

FIG 9−1−1

Sectional and VFR Terminal Area Charts for the Conterminous U.S., 

Hawaii, Puerto Rico, and Virgin Islands

4. U.S. Gulf Coast VFR Aeronautical Chart.

The Gulf Coast Chart is designed primarily for

helicopter operation in the Gulf of Mexico area.

Information depicted includes offshore mineral

leasing areas and blocks, oil drilling platforms, and

high density helicopter activity areas. Scale 1 inch =

13.7nm/1:1,000,000. 55 x 27 inches folded to

5 x 10 inches. Revised annually.

5. Grand Canyon VFR Aeronautical Chart.

Covers the Grand Canyon National Park area and is

designed to promote aviation safety, flight free zones,

and facilitate VFR navigation in this popular area.

The chart contains aeronautical information for

general aviation VFR pilots on one side and

commercial VFR air tour operators on the other side.

6. Helicopter Route Charts. A three−color

chart series which shows current aeronautical

information useful to helicopter pilots navigating in

areas with high concentrations of helicopter activity.

Information depicted includes helicopter routes, four

classes of heliports with associated frequency and

lighting capabilities, NAVAIDs, and obstructions. In

addition, pictorial symbols, roads, and easily

identified geographical features are portrayed.

Helicopter charts have a longer life span than other

chart products and may be current for several years.

All new editions of these charts are printed on a

durable plastic material. Helicopter Route Charts are

updated as requested by the FAA. Scale 1 inch =

1.71nm/1:125,000. 34 x 30 inches folded to

5 x 10 inches.

b. IFR Navigation Charts.

1. IFR Enroute Low Altitude Charts

(Conterminous U.S. and Alaska). Enroute low

altitude charts provide aeronautical information for

navigation under IFR conditions below 18,000 feet

MSL. This four−color chart series includes airways;

limits of controlled airspace; VHF NAVAIDs with

frequency, identification, channel, geographic coordinates; airports with terminal air/ground

communications; minimum en route and obstruction

clearance altitudes; airway distances; reporting

points; special use airspace; and military training

routes. Scales vary from 1 inch = 5nm to 1 inch =

20nm. 50 x 20 inches folded to 5 x 10 inches. Charts

revised every 56 days. Area charts show congested

terminal areas at a large scale. They are included with

subscriptions to any conterminous U.S. Set Low (Full

set, East or West sets).

(See FIG 9−1−2 and FIG 9−1−4.)
7/26/12 AIM

Types of Charts Available 9−1−3

FIG 9−1−2

Enroute Low Altitude Instrument Charts for the Conterminous U.S. (Includes Area Charts)

FIG 9−1−3

Enroute High Altitude Charts for the Conterminous U.S.
AIM 7/26/12

9−1−4 Types of Charts Available

2. IFR Enroute High Altitude Charts

(Conterminous U.S. and Alaska). Enroute high

altitude charts are designed for navigation at or above

18,000 feet MSL. This four−color chart series

includes the jet route structure; VHF NAVAIDs with

frequency, identification, channel, geographic coordinates; selected airports; reporting points. Scales

vary from 1 inch = 45nm to 1 inch = 18nm. 55 x 20

inches folded to 5 x 10 inches. Revised every 56 days.

(See FIG 9−1−3 and FIG 9−1−5.)

FIG 9−1−4

Alaska Enroute Low Altitude Chart

FIG 9−1−5

Alaskan Enroute High Altitude Chart
7/26/12 AIM

Types of Charts Available 9−1−5

3. U.S. Terminal Procedures Publication

(TPP). TPPs are published in 24 loose−leaf or

perfect bound volumes covering the conterminous

U.S., Puerto Rico and the Virgin Islands. A Change

Notice is published at the midpoint between revisions

in bound volume format and is available on the

internet for free download at the AeroNav web site.

(See FIG 9−1−9.) The TPPs include:

(a) Instrument Approach Procedure (IAP)

Charts. IAP charts portray the aeronautical data that

is required to execute instrument approaches to

airports. Each chart depicts the IAP, all related

navigation data, communications information, and an

airport sketch. Each procedure is designated for use

with a specific electronic navigational aid, such as

ILS, VOR, NDB, RNAV, etc.

(b) Instrument Departure Procedure (DP)

Charts. DP charts are designed to expedite

clearance delivery and to facilitate transition between

takeoff and en route operations. They furnish pilots’

departure routing clearance information in graphic

and textual form.

(c) Standard Terminal Arrival (STAR)

Charts. STAR charts are designed to expedite ATC

arrival procedures and to facilitate transition between

en route and instrument approach operations. They

depict preplanned IFR ATC arrival procedures in

graphic and textual form. Each STAR procedure is

presented as a separate chart and may serve either a

single airport or more than one airport in a given

geographic area.

(d) Airport Diagrams. Full page airport

diagrams are designed to assist in the movement of

ground traffic at locations with complex runway/taxiway configurations and provide information for

updating geodetic position navigational systems

aboard aircraft. Airport diagrams are available for

free download at the AeroNav website.

4. Alaska Terminal Procedures Publication.

This publication contains all terminal flight procedures for civil and military aviation in Alaska.

Included are IAP charts, DP charts, STAR charts,

airport diagrams, radar minimums, and supplementary support data such as IFR alternate minimums,

take−off minimums, rate of descent tables, rate of

climb tables and inoperative components tables.

Volume is 5−3/8 x 8−1/4 inch top bound. Publication

revised every 56 days with provisions for a Terminal

Change Notice, as required.

c. Planning Charts.

1. U.S. IFR/VFR Low Altitude Planning

Chart. This chart is designed for prefight and

en route flight planning for IFR/VFR flights.

Depiction includes low altitude airways and mileage,

NAVAIDs, airports, special use airspace, cities, times

zones, major drainage, a directory of airports with

their airspace classification, and a mileage table

showing great circle distances between major

airports. Scale 1 inch = 47nm/1:3,400,000. Chart

revised annually, and is available either folded or

unfolded for wall mounting. (See FIG 9−1−6.)

2. Gulf of Mexico and Caribbean Planning

Chart. This is a VFR planning chart on the reverse

side of the Puerto Rico − Virgin Islands VFR Terminal

Area Chart. Information shown includes mileage

between airports of entry, a selection of special use

airspace and a directory of airports with their

available services. Scale 1 inch = 85nm/1:6,192,178.

60 x 20 inches folded to 5 x 10 inches. Chart revised

annually. (See FIG 9−1−6.)

FIG 9−1−6

Planning Charts

3. Charted VFR Flyway Planning Charts.

This chart is printed on the reverse side of selected

TAC charts. The coverage is the same as the

associated TAC. Flyway planning charts depict flight

paths and altitudes recommended for use to bypass

high traffic areas. Ground references are provided as
AIM 7/26/12

9−1−6 Types of Charts Available

a guide for visual orientation. Flyway planning charts

are designed for use in conjunction with TACs and

sectional charts and are not to be used for navigation.

Chart scale 1 inch = 3.43nm/1:250,000.

d. Supplementary Charts and Publications.

1. Airport/Facility Directory (A/FD). This

7−volume booklet series contains data on airports,

seaplane bases, heliports, NAVAIDs, communications data, weather data sources, airspace, special

notices, and operational procedures. Coverage

includes the conterminous U.S., Puerto Rico, and the

Virgin Islands. The A/FD shows data that cannot be

readily depicted in graphic form; e.g., airport hours of

operations, types of fuel available, runway widths,

lighting codes, etc. The A/FD also provides a means

for pilots to update visual charts between edition

dates (A/FD is published every 56 days while

sectional and Terminal Area Charts are generally

revised every six months). The VFR Chart Update

Bulletins are available for free download from the

AeroNav web site. Volumes are side−bound 5−3/8 x

8−1/4 inches. (See FIG 9−1−10.)

2. Supplement Alaska. This is a civil/military

flight information publication issued by FAA every

56 days. It is a single volume booklet designed for use

with appropriate IFR or VFR charts. The Supplement

Alaska contains an A/FD, airport sketches, communications data, weather data sources, airspace, listing

of navigational facilities, and special notices and

procedures. Volume is side−bound 5−3/8 x

8−1/4 inches.

3. Chart Supplement Pacific. This supplement is designed for use with appropriate VFR or IFR

enroute charts. Included in this one−volume booklet

are the A/FD, communications data, weather data

sources, airspace, navigational facilities, special

notices, and Pacific area procedures. IAP charts, DP

charts, STAR charts, airport diagrams, radar

minimums, and supporting data for the Hawaiian and

Pacific Islands are included. The manual is published

every 56 days. Volume is side−bound 5−3/8 x

8−1/4 inches.

4. North Pacific Route Charts. These charts

are designed for FAA controllers to monitor

transoceanic flights. They show established intercontinental air routes, including reporting points with

geographic positions. Composite Chart: Scale

1 inch = 164nm/1:12,000,000. 48 x 41−1/2 inches.

Area Charts: Scale 1 inch = 95.9nm/1:7,000,000.

52 x 40−1/2 inches. All charts shipped unfolded.

Charts revised every 56 days. (See FIG 9−1−8.)

5. North Atlantic Route Chart. Designed for

FAA controllers to monitor transatlantic flights, this

5−color chart shows oceanic control areas, coastal

navigation aids, oceanic reporting points, and

NAVAID geographic coordinates. Full Size Chart:

Scale 1 inch = 113.1nm/1:8,250,000. Chart is shipped

flat only. Half Size Chart: Scale 1 inch =

150.8nm/1:11,000,000. Chart is 29−3/4 x

20−1/2 inches, shipped folded to 5 x 10 inches only.

Chart revised every 56 weeks. (See FIG 9−1−7.)

FIG 9−1−7

North Atlantic Route Charts
7/26/12 AIM

Types of Charts Available 9−1−7

FIG 9−1−8

North Pacific Oceanic Route Charts

6. Airport Obstruction Charts (OC). The

OC is a 1:12,000 scale graphic depicting 14 CFR

Part 77, Objects Affecting Navigable Airspace,

surfaces, a representation of objects that penetrate

these surfaces, aircraft movement and apron areas,

navigational aids, prominent airport buildings, and a

selection of roads and other planimetric detail in the

airport vicinity. Also included are tabulations of

runway and other operational data.

7. FAA Aeronautical Chart User’s Guide.

A booklet designed to be used as a teaching aid and

reference document. It describes the substantial

amount of information provided on FAA’s aeronautical charts and publications. It includes explanations

and illustrations of chart terms and symbols

organized by chart type. The users guide is available

for free download at the AeroNav web site.

e. Digital Products.

1. The Digital Aeronautical Information CD

(DAICD). The DAICD is a combination of the

NAVAID Digital Data File, the Digital Chart

Supplement, and the Digital Obstacle File on one

Compact Disk. These three digital products are no

longer sold separately. The files are updated every

56 days and are available by subscription only.

(a) The NAVAID Digital Data File. This

file contains a current listing of NAVAIDs that are

compatible with the National Airspace System. This

file contains all NAVAIDs including ILS and its

components, in the U.S., Puerto Rico, and the Virgin

Islands plus bordering facilities in Canada, Mexico,

and the Atlantic and Pacific areas.

(b) The Digital Obstacle File. This file

describes all obstacles of interest to aviation users in

the U.S., with limited coverage of the Pacific,

Caribbean, Canada, and Mexico. The obstacles are

assigned unique numerical identifiers, accuracy

codes, and listed in order of ascending latitude within

each state or area.

(c) The Digital Aeronautical Chart Supplement (DACS). The DACS is specifically designed

to provide digital airspace data not otherwise readily

available. The supplement includes a Change Notice

for IAPFIX.dat at the mid−point between revisions.

The Change Notice is available only by free

download from the AeroNav website.

The DACS individual data files are:

ENHIGH.DAT: High altitude airways (conterminous U.S.)

ENLOW.DAT: Low altitude airways (conterminous

U.S.)

IAPFIX.DAT: Selected instrument approach procedure NAVAID and fix data.

MTRFIX.DAT: Military training routes data.

ALHIGH.DAT: Alaska high altitude airways data.

ALLOW.DAT: Alaska low altitude airways data.

PR.DAT: Puerto Rico airways data.

HAWAII.DAT: Hawaii airways data.

BAHAMA.DAT: Bahamas routes data.

OCEANIC.DAT: Oceanic routes data.

STARS.DAT: Standard terminal arrivals data.

DP.DAT: Instrument departure procedures data.

LOPREF.DAT: Preferred low altitude IFR routes

data.

HIPREF.DAT: Preferred high altitude IFR routes

data.

ARF.DAT: Air route radar facilities data.

ASR.DAT: Airport surveillance radar facilities data.
AIM 7/26/12

9−1−8 Types of Charts Available

2. The National Flight Database (NFD)

(ARINC 424 [Ver 13 & 15]). The NFD is a basic

digital dataset, modeled to an international standard,

which can be used as a basis to support GPS

navigation. Initial data elements included are: Airport

and Helicopter Records, VHF and NDB Navigation

aids, en route waypoints and airways. Additional data

elements will be added in subsequent releases to

include: departure procedures, standard terminal

arrivals, and GPS/RNAV instrument approach

procedures. The database is updated every 28 days.

The data is available by subscription only and is

distributed on CD−ROM or by ftp download.

3. Sectional Raster Aeronautical Charts

(SRAC). These digital VFR charts are geo−

referenced scanned images of FAA sectional charts.

Additional digital data may easily be overlaid on the

raster image using commonly available Geographic

Information System software. Data such as weather,

temporary flight restrictions, obstacles, or other

geospatial data can be combined with SRAC data to

support a variety of needs. Most SRACs are provided

in two halves, a north side and a south side. The file

resolution is 200 dots per inch and the data is 8−bit

color. The data is provided as a GeoTIFF and

distributed on DVD−R media. The root mean square

error of the transformation will not exceed two pixels.

SRACs DVDs are updated every 28 days and are

available by subscription only.
7/26/12 AIM

Types of Charts Available 9−1−9

FIG 9−1−9

U.S. Terminal Publication Volumes
AIM 7/26/12

9−1−10 Types of Charts Available

FIG 9−1−10

Airport/Facility Directory Geographic Areas

FIG 9−1−11

Sectional and VFR Terminal Area Charts for Alaska
7/26/12 AIM

Types of Charts Available 9−1−11

FIG 9−1−12

World Aeronautical Charts for Alaska
AIM 7/26/12

9−1−12 Types of Charts Available

FIG 9−1−13

World Aeronautical Charts for the Conterminous U.S.

Mexico, and the Caribbean Areas

9−1−5. Where and How to Get Charts of

Foreign Areas

a. National Geospatial−Intelligence Agency

(NGA) Products. For the latest information regarding publication availability visit the NGA Web site:

https://www.nga.mil/ProductsServices/

Aeronautical/Pages/default.aspx

1. Flight Information Publication (FLIP)

Planning Documents.

General Planning (GP)

Area Planning

Area Planning − Special Use Airspace −

Planning Charts

2. FLIP Enroute Charts and Chart Supplements.

Pacific, Australasia, and Antarctica

U.S. − IFR and VFR Supplements

Flight Information Handbook

Caribbean and South America − Low Altitude

Caribbean and South America − High Altitude

Europe, North Africa, and Middle East −

Low Altitude

Europe, North Africa, and Middle East −

High Altitude

Africa

Eastern Europe and Asia

Area Arrival Charts
7/26/12 AIM

Types of Charts Available 9−1−13

3. FLIP Instrument Approach Procedures

(IAPs).

Africa

Canada and North Atlantic

Caribbean and South America

Eastern Europe and Asia

Europe, North Africa, and Middle East

Pacific, Australasia, and Antarctica

VFR Arrival/Departure Routes − Europe and Korea

U.S.

4. Miscellaneous DOD Charts and Products.

Aeronautical Chart Updating Manual (CHUM)

DOD Weather Plotting Charts (WPC)

Tactical Pilotage Charts (TPC)

Operational Navigation Charts (ONC)

Global Navigation and Planning Charts (GNC)

Jet Navigation Charts (JNC) and Universal Jet

Navigation Charts (JNU)

Jet Navigation Charts (JNCA)

Aerospace Planning Charts (ASC)

Oceanic Planning Charts (OPC)

Joint Operations Graphics − Air (JOG−A)

Standard Index Charts (SIC)

Universal Plotting Sheet (VP−OS)

Sight Reduction Tables for Air Navigation (PUB249)

Plotting Sheets (VP−30)

Dial−Up Electronic CHUM

b. Canadian Charts. Information on available

Canadian charts and publications may be obtained

from designated FAA chart agents or by contacting

the:

NAV CANADA

Aeronautical Publications

Sales and Distribution Unit

P.O. Box 9840, Station T 

Ottawa, Ontario K1G 6S8 Canada

Telephone: 613−744−6393 or 1−866−731−7827

Fax: 613−744−7120 or 1−866−740−9992

c. Mexican Charts. Information on available

Mexican charts and publications may be obtained by

contacting:

Dirección de Navigacion Aereo

Blvd. Puerto Aereo 485

Zona Federal Del Aeropuerto Int’l

15620 Mexico D.F.

Mexico

d. International Civil Aviation Organization

(ICAO). A free ICAO Publications and Audio−

Visual Training Aids Catalogue is available from:

International Civil Aviation Organization

ATTN: Document Sales Unit

999 University Street

Montreal, Quebec

H3C 5H7, Canada

Telephone: (514) 954−8022

Fax: (514) 954−6769

E−mail: sales_unit@icao.org

Internet: http://www.icao.org/cgi/goto.pl?icao/en/

sales.htm

Sitatex: YULCAYA

Telex: 05−24513

7/26/12 AIM

Helicopter IFR Operations 10−1−1

Chapter 10. Helicopter Operations

Section 1. Helicopter IFR Operations

10−1−1. Helicopter Flight Control Systems

a. The certification requirements for helicopters to

operate under Instrument Flight Rules (IFR) are

contained in 14 CFR Part 27, Airworthiness

Standards: Normal Category Rotorcraft, and 14 CFR

Part 29, Airworthiness Standards: Transport

Category Rotorcraft. To meet these requirements,

helicopter manufacturers usually utilize a set of

stabilization and/or Automatic Flight Control

Systems (AFCSs).

b. Typically, these systems fall into the following

categories:

1. Aerodynamic surfaces, which impart some

stability or control capability not found in the basic

VFR configuration.

2. Trim systems, which provide a cyclic

centering effect. These systems typically involve a

magnetic brake/spring device, and may also be

controlled by a four−way switch on the cyclic. This

is a system that supports “hands on” flying of the

helicopter by the pilot.

3. Stability Augmentation Systems (SASs),

which provide short−term rate damping control

inputs to increase helicopter stability. Like trim

systems, SAS supports “hands on” flying.

4. Attitude Retention Systems (ATTs), which

return the helicopter to a selected attitude after a

disturbance. Changes in desired attitude can be

accomplished usually through a four−way “beep”

switch, or by actuating a “force trim” switch on the

cyclic, setting the attitude manually, and releasing.

Attitude retention may be a SAS function, or may be

the basic “hands off” autopilot function.

5. Autopilot Systems (APs), which provide for

“hands off” flight along specified lateral and vertical

paths, including heading, altitude, vertical speed,

navigation tracking, and approach. These systems

typically have a control panel for mode selection, and

system for indication of mode status. Autopilots may

or may not be installed with an associated Flight

Director System (FD). Autopilots typically control

the helicopter about the roll and pitch axes (cyclic

control) but may also include yaw axis (pedal control)

and collective control servos.

6. FDs, which provide visual guidance to the

pilot to fly specific selected lateral and vertical modes

of operation. The visual guidance is typically

provided as either a “dual cue” (commonly known as

a “cross−pointer”) or “single cue” (commonly known

as a “vee−bar”) presentation superimposed over the

attitude indicator. Some FDs also include a collective

cue. The pilot manipulates the helicopter’s controls to

satisfy these commands, yielding the desired flight

path, or may couple the flight director to the autopilot

to perform automatic flight along the desired flight

path. Typically, flight director mode control and

indication is shared with the autopilot.

c. In order to be certificated for IFR operation, a

specific helicopter may require the use of one or more

of these systems, in any combination.

d. In many cases, helicopters are certificated for

IFR operations with either one or two pilots. Certain

equipment is required to be installed and functional

for two pilot operations, and typically, additional

equipment is required for single pilot operation.

These requirements are usually described in the

limitations section of the Rotorcraft Flight Manual

(RFM).

e. In addition, the RFM also typically defines

systems and functions that are required to be in

operation or engaged for IFR flight in either the single

or two pilot configuration. Often, particularly in two

pilot operation, this level of augmentation is less than

the full capability of the installed systems. Likewise,

single pilot operation may require a higher level of

augmentation.
AIM 7/26/12

10−1−2 Helicopter IFR Operations

f. The RFM also identifies other specific limitations associated with IFR flight. Typically, these

limitations include, but are not limited to:

1. Minimum equipment required for IFR flight

(in some cases, for both single pilot and two pilot

operations).

2. Vmini (minimum speed − IFR).

NOTE−

The manufacturer may also recommend a minimum IFR

airspeed during instrument approach.

3. Vnei (never exceed speed − IFR).

4. Maximum approach angle.

5. Weight and center of gravity limits.

6. Aircraft configuration limitations (such as

aircraft door positions and external loads).

7. Aircraft system limitations (generators,

inverters, etc.).

8. System testing requirements (many avionics

and AFCS/AP/FD systems incorporate a self−test

feature).

9. Pilot action requirements (such as the pilot

must have his/her hands and feet on the controls

during certain operations, such as during instrument

approach below certain altitudes).

g. It is very important that pilots be familiar with

the IFR requirements for their particular helicopter.

Within the same make, model and series of helicopter,

variations in the installed avionics may change the

required equipment or the level of augmentation for

a particular operation.

h. During flight operations, pilots must be aware

of the mode of operation of the augmentation

systems, and the control logic and functions

employed. For example, during an ILS approach

using a particular system in the three−cue mode

(lateral, vertical and collective cues), the flight

director collective cue responds to glideslope

deviation, while the horizontal bar of the “cross−

pointer” responds to airspeed deviations. The same

system, while flying an ILS in the two−cue mode,

provides for the horizontal bar to respond to

glideslope deviations. This concern is particularly

significant when operating using two pilots. Pilots

should have an established set of procedures and

responsibilities for the control of flight director/autopilot modes for the various phases of flight. Not only

does a full understanding of the system modes

provide for a higher degree of accuracy in control of

the helicopter, it is the basis for crew identification of

a faulty system.

i. Relief from the prohibition to takeoff with any

inoperative instruments or equipment may be

provided through a Minimum Equipment List (see

14 CFR Section 91.213 and 14 CFR Section 135.179,

Inoperative Instruments and Equipment). In many

cases, a helicopter configured for single pilot IFR

may depart IFR with certain equipment inoperative,

provided a crew of two pilots is used. Pilots are

cautioned to ensure the pilot−in−command and

second−in−command meet the requirements of

14 CFR Section 61.58, Pilot−in−Command Proficiency Check: Operation of Aircraft Requiring More

Than One Pilot Flight Crewmember, and 14 CFR

Section 61.55, Second−in−Command Qualifications,

or 14 CFR Part 135, Operating Requirements:

Commuter and On−Demand Operations, Subpart E,

Flight Crewmember Requirements, and Subpart G,

Crewmember Testing Requirements, as appropriate.

j. Experience has shown that modern AFCS/AP/

FD equipment installed in IFR helicopters can, in

some cases, be very complex. This complexity

requires the pilot(s) to obtain and maintain a high

level of knowledge of system operation, limitations,

failure indications and reversionary modes. In some

cases, this may only be reliably accomplished

through formal training.
7/26/12 AIM

Helicopter IFR Operations 10−1−3

10−1−2. Helicopter Instrument Approaches

a. Helicopters are capable of flying any published

14 CFR Part 97, Standard Instrument Approach

Procedures (SIAPs), for which they are properly

equipped, subject to the following limitations and

conditions:

1. Helicopters flying conventional (non−

Copter) SIAPs may reduce the visibility minima to

not less than one half the published Category A

landing visibility minima, or 1/4 statute mile

visibility/1200 RVR, whichever is greater unless the

procedure is annotated with “Visibility Reduction

by Helicopters NA.” This annotation means that

there are penetrations of the final approach obstacle

identification surface (OIS) and that the 14 CFR

Section 97.3 visibility reduction rule does not apply

and you must take precaution to avoid any obstacles

in the visual segment. No reduction in MDA/DA is

permitted. The helicopter may initiate the final

approach segment at speeds up to the upper limit of

the highest approach category authorized by the

procedure, but must be slowed to no more than

90 KIAS at the missed approach point (MAP) in

order to apply the visibility reduction. Pilots are

cautioned that such a decelerating approach may

make early identification of wind shear on the

approach path difficult or impossible. If required, use

the Inoperative Components and Visual Aids Table

provided in the front cover of the U.S. Terminal

Procedures Volume to derive the Category A minima

before applying the 14 CFR Section 97.3(d−1) rule.

2. Helicopters flying Copter SIAPs may use the

published minima, with no reductions allowed. The

maximum airspeed is 90 KIAS on any segment of the

approach or missed approach.

3. Helicopters flying GPS Copter SIAPs must

limit airspeed to 90 KIAS or less when flying any

segment of the procedure, except speeds must be

limited to no more than 70 KIAS on the final and

missed approach segments. Military GPS Copter

SIAPs are limited to no more than 90 KIAS

throughout the procedure. If annotated, holding may

also be limited to no more than 70 KIAS. Use the

published minima, no reductions allowed.

NOTE−

Obstruction clearance surfaces are based on the aircraft

speed and have been designed on these approaches for

70 knots. If the helicopter is flown at higher speeds, it may

fly outside of protected airspace. Some helicopters have a

VMINI greater than 70 knots; therefore, they cannot meet

the 70 knot limitation to conduct this type of procedure.

Some helicopter autopilots, when used in the “go−around”

mode, are programmed with a VYI greater than 70 knots,

therefore when using the autopilot “go−around” mode,

they cannot meet the 70 knot limitation to conduct this type

of approach. It may be possible to use the autopilot for the

missed approach in the other than the “go−around” mode

and meet the 70 knot limitation to conduct this type of

approach. When operating at speeds other than VYI or VY,

performance data may not be available in the RFM to

predict compliance with climb gradient requirements.

Pilots may use observed performance in similar

weight/altitude/temperature/speed conditions to evaluate

the suitability of performance. Pilots are cautioned to

monitor climb performance to ensure compliance with

procedure requirements.

4. TBL 10−1−1 summarizes these requirements.

5. Even with weather conditions reported at or

above landing minima, some combinations of

reduced cockpit cutoff angle, minimal approach/

runway lighting, and high MDA/DH coupled with a

low visibility minima, the pilot may not be able to

identify the required visual reference(s) during the

approach, or those references may only be visible in

a very small portion of the pilot’s available field of

view. Even if identified by the pilot, these visual

references may not support normal maneuvering and

normal rates of descent to landing. The effect of such

a combination may be exacerbated by other

conditions such as rain on the windshield, or

incomplete windshield defogging coverage.

6. Pilots are cautioned to be prepared to execute

a missed approach even though weather conditions

may be reported at or above landing minima.

NOTE−

See paragraph 5−4−21, Missed Approach, for additional

information on missed approach procedures.
AIM 7/26/12

10−1−4 Helicopter IFR Operations

TBL 10−1−1

Helicopter Use of Standard Instrument Approach Procedures

Procedure Helicopter Visibility

Minima

Helicopter MDA/DA Maximum Speed Limitations

Conventional

(non−Copter)

The greater of: one half

the Category A visibility

minima, 1/4 statute mile

visibility, or 1200 RVR

As published for

Category A

The helicopter may initiate the final

approach segment at speeds up to

the upper limit of the highest

Approach Category authorized by

the procedure, but must be slowed

to no more than 90 KIAS at the

MAP in order to apply the visibility

reduction.

Copter Procedure As published As published 90 KIAS when on a published

route/track.

GPS Copter Procedure As published As published 90 KIAS when on a published route

or track, EXCEPT 70 KIAS when

on the final approach or missed

approach segment and, if annotated,

in holding. Military procedures are

limited to 90 KIAS for all segments.

NOTE−

Several factors effect the ability of the pilot to acquire and

maintain the visual references specified in 14 CFR

Section 91.175(c), even in cases where the flight visibility

may be at the minimum derived by TBL 10−1−1. These

factors include, but are not limited to:

1. Cockpit cutoff angle (the angle at which the cockpit or

other airframe structure limits downward visibility below

the horizon).

2. Combinations of high MDA/DH and low visibility

minimum, such as a conventional nonprecision approach

with a reduced helicopter visibility minima (per 14 CFR

Section 97.3).

3. Type, configuration, and intensity of approach and

runway lighting systems.

4. Type of obscuring phenomenon and/or windshield

contamination.
7/26/12 AIM

Helicopter IFR Operations 10−1−5

10−1−3. Helicopter Approach Procedures

to VFR Heliports

a. Helicopter approaches may be developed for

heliports that do not meet the design standards for an

IFR heliport. The majority of IFR approaches to VFR

heliports are developed in support of helicopter

emergency medical services (HEMS) operators.

These approaches can be developed from conventional NAVAIDs or a RNAV system (including GPS).

They are developed either as a Special Approach

(pilot training is required for special procedures due

to their unique characteristics) or a public approach

(no special training required). These instrument

procedures are developed as either an approach

designed to a specific landing site, or an approach

designed to a point−in−space.

1. Approach to a specific landing site. The

approach is aligned to a missed approach point from

which a landing can be accomplished with a

maximum course change of 30 degrees. The visual

segment from the MAP to the landing site is evaluated

for obstacle hazards. These procedures are annotated:

“PROCEED VISUALLY FROM (NAMED MAP)

OR CONDUCT THE SPECIFIED MISSED

APPROACH.”

(a) This phrase requires the pilot to either

acquire and maintain visual contact with the landing

site at or prior to the MAP, or execute a missed

approach. The visibility minimum is based on the

distance from the MAP to the landing site, among

other factors.

(b) The pilot is required to maintain the

published minimum visibility throughout the visual

segment.

(c) Similar to an approach to a runway, the

missed approach segment protection is not provided

between the MAP and the landing site, and obstacle

or terrain avoidance from the MAP to the landing site

is the responsibility of the pilot.

(d) Upon reaching the MAP defined on the

approach procedure, or as soon as practicable after

reaching the MAP, the pilot advises ATC whether

proceeding visually and canceling IFR or complying

with the missed approach instructions. See paragraph 5−1−15, Canceling IFR Flight Plan.

(e) At least one of the following visual

references must be visible or identifiable before the

pilot may proceed visually:

(1) FATO or FATO lights.

(2) TLOF or TLOF lights.

(3) Heliport Instrument Lighting System

(HILS).

(4) Heliport Approach Lighting System

(HALS) or lead−in lights.

(5) Visual Glideslope Indicator (VGSI).

(6) Windsock or windsock light(s). See

note below.

(7) Heliport beacon. See note below.

(8) Other facilities or systems approved by

the Flight Technologies and Procedures Division

(AFS−400).

NOTE−

Windsock lights and heliport beacons should be located

within 500 ft of the TLOF.

2. Approach to a Point−in−Space (PinS). At

locations where the MAP is located more than 2 SM

from the landing site, or the path from the MAP to the

landing site is populated with obstructions which

require avoidance actions or requires turns greater

than 30 degrees, a PinS procedure may be developed.

These approaches are annotated “PROCEED VFR

FROM (NAMED MAP) OR CONDUCT THE

SPECIFIED MISSED APPROACH.”

(a) These procedures require the pilot, at or

prior to the MAP, to determine if the published

minimum visibility, or the weather minimums

required by the operating rule, or operations

specifications (whichever is higher) is available to

safely transition from IFR to VFR flight. If not, the

pilot must execute a missed approach. For Part 135

operations, pilots may not begin the instrument

approach unless the latest weather report indicates

that the weather conditions are at or above the

authorized IFR minimums or the VFR weather

minimums (as required by the class of airspace,

operating rule and/or Operations Specifications)

whichever is higher.

(b) Visual contact with the landing site is not

required; however, the pilot must maintain the

appropriate VFR weather minimums throughout the

visual segment. The visibility is limited to no lower
AIM 7/26/12

10−1−6 Helicopter IFR Operations

than that published in the procedure, until canceling

IFR.

(c) IFR obstruction clearance areas are not

applied to the VFR segment between the MAP and

the landing site. Obstacle or terrain avoidance from

the MAP to the landing site is the responsibility of the

pilot.

(d) Upon reaching the MAP defined on the

approach procedure, or as soon as practicable after

reaching the MAP, the pilot advises ATC whether

proceeding VFR and canceling IFR, or complying

with the missed approach instructions. See paragraph 5−1−15, Canceling IFR Flight Plan.

(e) If the visual segment penetrates Class B,

C, or D airspace, pilots are responsible for obtaining

a Special VFR clearance, when required.

10−1−4. The Gulf of Mexico Grid System

a. On October 8, 1998, the Southwest Regional

Office of the FAA, with assistance from the

Helicopter Safety Advisory Conference (HSAC),

implemented the world’s first Instrument Flight

Rules (IFR) Grid System in the Gulf of Mexico. This

navigational route structure is completely independent of ground−based navigation aids (NAVAIDs)

and was designed to facilitate helicopter IFR

operations to offshore destinations. The Grid System

is defined by over 300 offshore waypoints located 20

minutes apart (latitude and longitude). Flight plan

routes are routinely defined by just 4 segments:

departure point (lat/long), first en route grid

waypoint, last en route grid waypoint prior to

approach procedure, and destination point (lat/long).

There are over 4,000 possible offshore landing sites.

Upon reaching the waypoint prior to the destination,

the pilot may execute an Offshore Standard Approach

Procedure (OSAP), a Helicopter En Route Descent

Areas (HEDA) approach, or an Airborne Radar

Approach (ARA). For more information on these

helicopter instrument procedures, refer to FAA AC

90−80B, Approval of Offshore Standard Approach

Procedures, Airborne Radar Approaches, and

Helicopter En Route Descent Areas, on the FAA web

site http://www.faa.gov under Advisory Circulars.

The return flight plan is just the reverse with the

requested stand−alone GPS approach contained in the

remarks section.

1. The large number (over 300) of waypoints in

the grid system makes it difficult to assign

phonetically pronounceable names to the waypoints

that would be meaningful to pilots and controllers. A

unique naming system was adopted that enables

pilots and controllers to derive the fix position from

the name. The five−letter names are derived as

follows:

(a) The waypoints are divided into sets of

3 columns each. A three−letter identifier, identifying

a geographical area or a NAVAID to the north,

represents each set.

(b) Each column in a set is named after its

position, i.e., left (L), center (C), and right (R).

(c) The rows of the grid are named

alphabetically from north to south, starting with A for

the northern most row.

EXAMPLE−

LCHRC would be pronounced “Lake Charles Romeo

Charlie.” The waypoint is in the right−hand column of the

Lake Charles VOR set, in row C (third south from the

northern most row).

2. In December 2009, significant improvements

to the Gulf of Mexico grid system were realized with

the introduction of ATC separation services using

ADS−B. In cooperation with the oil and gas services

industry, HSAC and Helicopter Association International (HAI), the FAA installed an infrastructure of

ADS−B ground stations, weather stations (AWOS)

and VHF remote communication outlets (RCO)

throughout a large area of the Gulf of Mexico. This

infrastructure allows the FAA’s Houston ARTCC to

provide “domestic−like” air traffic control service in

the offshore area beyond 12nm from the coastline to

hundreds of miles offshore to aircraft equipped with

ADS−B. Properly equipped aircraft can now be

authorized to receive more direct routing, domestic

en route separation minima and real time flight

following. Operators who do not have authorization

to receive ATC separation services using ADS−B,

will continue to use the low altitude grid system and

receive procedural separation from Houston ARTCC.

Non−ADS−B equipped aircraft also benefit from

improved VHF communication and expanded

weather information coverage.

3. Three requirements must be met for operators

to file IFR flight plans utilizing the grid:
7/26/12 AIM

Helicopter IFR Operations 10−1−7

(a) The helicopter must be equipped for IFR

operations and equipped with IFR approved GPS

navigational units.

(b) The operator must obtain prior written

approval from the appropriate Flight Standards

District Office through a Letter of Authorization or

Operations Specification, as appropriate.

(c) The operator must be a signatory to the

Houston ARTCC Letter of Agreement.

4. Operators who wish to benefit from ADS−B

based ATC separation services must meet the

following additional requirements:

(a) The Operator’s installed ADS−B Out

equipment must meet the performance requirements

of one of the following FAA Technical Standard

Orders (TSO), or later revisions: TSO−C154c,

Universal Access Transceiver (UAT) Automatic

Dependent Surveillance−Broadcast (ADS−B) Equipment, or TSO−C166b, Extended Squitter Automatic

Dependent Surveillance−Broadcast (ADS−B) and

Traffic Information.

(b) Flight crews must comply with the

procedures prescribed in the Houston ARTCC Letter

of Agreement dated December 17, 2009, or later.

NOTE−

The unique ADS−B architecture in the Gulf of Mexico

depends upon reception of an aircraft’s Mode C in addition

to the other message elements described in 14 CFR 91.227.

Flight crews must be made aware that loss of Mode C also

means that ATC will not receive the aircraft’s ADS−B

signal.

5. FAA/AeroNav publishes the grid system

waypoints on the IFR Gulf of Mexico Vertical Flight

Reference Chart. A commercial equivalent is also

available. The chart is updated annually and is

available from a FAA chart agent or FAA directly,

web site address:

http://www.faa.gov/air_traffic/flight_info/aerona

v.

7/26/12 AIM

Special Operations 10−2−1

Section 2. Special Operations

10−2−1. Offshore Helicopter Operations

a. Introduction

The offshore environment offers unique applications

and challenges for helicopter pilots. The mission

demands, the nature of oil and gas exploration and

production facilities, and the flight environment

(weather, terrain, obstacles, traffic), demand special

practices, techniques and procedures not found in

other flight operations. Several industry

organizations have risen to the task of reducing

risks in offshore operations, including the Helicopter Safety Advisory Conference (HSAC)

(http://www.hsac.org), and the Offshore Committee

of the Helicopter Association International (HAI)

(http://www.rotor.com). The following recommended

practices for offshore helicopter operations are based

on guidance developed by HSAC for use in the Gulf

of Mexico, and provided here with their permission.

While not regulatory, these recommended practices

provide aviation and oil and gas industry operators

with useful information in developing procedures to

avoid certain hazards of offshore helicopter operations.

NOTE−

Like all aviation practices, these recommended practices

are under constant review. In addition to normal

procedures for comments, suggested changes, or corrections to the AIM (contained in the Preface), any questions

or feedback concerning these recommended procedures

may also be directed to the HSAC through the feedback

feature of the HSAC web site (http://www.hsac.org).

b. Passenger Management on and about

Heliport Facilities

1. Background. Several incidents involving

offshore helicopter passengers have highlighted the

potential for incidents and accidents on and about the

heliport area. The following practices will minimize

risks to passengers and others involved in heliport

operations.

2. Recommended Practices

(a) Heliport facilities should have a designated and posted passenger waiting area which is

clear of the heliport, heliport access points, and

stairways.

(b) Arriving passengers and cargo should be

unloaded and cleared from the heliport and access

route prior to loading departing passengers and cargo.

(c) Where a flight crew consists of more than

one pilot, one crewmember should supervise the

unloading/loading process from outside the aircraft.

(d) Where practical, a designated facility

employee should assist with loading/unloading, etc.

c. Crane−Helicopter Operational Procedures

1. Background. Historical experience has

shown that catastrophic consequences can occur

when industry safe practices for crane/helicopter

operations are not observed. The following recommended practices are designed to minimize risks

during crane and helicopter operations.

2. Recommended Practices

(a) Personnel awareness

(1) Crane operators and pilots should

develop a mutual understanding and respect of the

others’ operational limitations and cooperate in the

spirit of safety;

(2) Pilots need to be aware that crane

operators sometimes cannot release the load to cradle

the crane boom, such as when attached to wire line

lubricators or supporting diving bells; and

(3) Crane operators need to be aware that

helicopters require warm up before takeoff, a

two−minute cool down before shutdown, and cannot

circle for extended lengths of time because of fuel

consumption.

(b) It is recommended that when helicopters

are approaching, maneuvering, taking off, or running

on the heliport, cranes be shutdown and the operator

leave the cab. Cranes not in use must have their

booms cradled, if feasible. If in use, the crane’s

boom(s) are to be pointed away from the heliport and

the crane shutdown for helicopter operations.

(c) Pilots will not approach, land on, takeoff,

or have rotor blades turning on heliports of structures

not complying with the above practice.
AIM 7/26/12

10−2−2 Special Operations

(d) It is recommended that cranes on offshore

platforms, rigs, vessels, or any other facility, which

could interfere with helicopter operations (including

approach/departure paths):

(1) Be equipped with a red rotating beacon

or red high intensity strobe light connected to the

system powering the crane, indicating the crane is

under power;

(2) Be designed to allow the operator a

maximum view of the helideck area and should be

equipped with wide−angle mirrors to eliminate blind

spots; and

(3) Have their boom tips, headache balls,

and hooks painted with high visibility international

orange.

d. Helicopter/Tanker Operations

1. Background. The interface of helicopters

and tankers during shipboard helicopter operations is

complex and may be hazardous unless appropriate

procedures are coordinated among all parties. The

following recommended practices are designed to

minimize risks during helicopter/tanker operations:

2. Recommended Practices

(a) Management, flight operations personnel,

and pilots should be familiar with and apply the

operating safety standards set forth in “Guide to

Helicopter/Ship Operations”, International Chamber

of Shipping, Third Edition, 5−89 (as amended),

establishing operational guidelines/standards and

safe practices sufficient to safeguard helicopter/tanker operations.

(b) Appropriate plans, approvals, and communications must be accomplished prior to reaching

the vessel, allowing tanker crews sufficient time to

perform required safety preparations and position

crew members to receive or dispatch a helicopter

safely.

(c) Appropriate approvals and direct communications with the bridge of the tanker must be

maintained throughout all helicopter/tanker operations.

(d) Helicopter/tanker operations, including

landings/departures, must not be conducted until the

helicopter pilot−in−command has received and

acknowledged permission from the bridge of the

tanker.

(e) Helicopter/tanker operations must not be

conducted during product/cargo transfer.

(f) Generally, permission will not be granted

to land on tankers during mooring operations or while

maneuvering alongside another tanker.

e. Helideck/Heliport Operational Hazard

Warning(s) Procedures

1. Background

(a) A number of operational hazards can

develop on or near offshore helidecks or onshore

heliports that can be minimized through procedures

for proper notification or visual warning to pilots.

Examples of hazards include but are not limited to:

(1) Perforating operations: subparagraph f.

(2) H2S gas presence: subparagraph g.

(3) Gas venting: subparagraph h; or,

(4) Closed helidecks or heliports: sub−

paragraph i (unspecified cause).

(b) These and other operational hazards are

currently minimized through timely dissemination of

a written Notice to Airmen (NOTAM) for pilots by

helicopter companies and operators. A NOTAM

provides a written description of the hazard, time and

duration of occurrence, and other pertinent information. ANY POTENTIAL HAZARD should be

communicated to helicopter operators or company

aviation departments as early as possible to allow the

NOTAM to be activated.

(c) To supplement the existing NOTAM

procedure and further assist in reducing these

hazards, a standardized visual signal(s) on the

helideck/heliport will provide a positive indication to

an approaching helicopter of the status of the landing

area. Recommended Practice(s) have been developed

to reinforce the NOTAM procedures and standardize

visual signals.

f. Drilling Rig Perforating Operations:

Helideck/Heliport Operational Hazard

Warning(s)/Procedure(s)

1. Background. A critical step in the oil well

completion process is perforation, which involves the

use of explosive charges in the drill pipe to open the

pipe to oil or gas deposits. Explosive charges used in

conjunction with perforation operations offshore can

potentially be prematurely detonated by radio
7/26/12 AIM

Special Operations 10−2−3

transmissions, including those from helicopters. The

following practices are recommended.

2. Recommended Practices

(a) Personnel Conducting Perforating

Operations. Whenever perforating operations are

scheduled and operators are concerned that radio

transmissions from helicopters in the vicinity may

jeopardize the operation, personnel conducting

perforating operations should take the following

precautionary measures:

(1) Notify company aviation departments,

helicopter operators or bases, and nearby manned

platforms of the pending perforation operation so the

Notice to Airmen (NOTAM) system can be activated

for the perforation operation and the temporary

helideck closure.

(2) Close the deck and make the radio

warning clearly visible to passing pilots, install a

temporary marking (described in subparagraph 10−2−1i1(b)) with the words “NO RADIO”

stenciled in red on the legs of the diagonals. The

letters should be 24 inches high and 12 inches wide.

(See FIG 10−2−1.)

(3) The marker should be installed during

the time that charges may be affected by radio

transmissions.

(b) Pilots

(1) Pilots when operating within 1,000 feet

of a known perforation operation or observing the

white X with red “NO RADIO” warning indicating

perforation operations are underway will avoid radio

transmissions from or near the helideck (within

1,000 feet) and will not land on the deck if the X is

present. In addition to communications radios, radio

transmissions are also emitted by aircraft radar,

transponders, radar altimeters, and DME equipment,

and ELTs.

(2) Whenever possible, make radio calls to

the platform being approached or to the Flight

Following Communications Center at least one mile

out on approach. Ensure all communications are

complete outside the 1,000 foot hazard distance. If no

response is received, or if the platform is not radio

equipped, further radio transmissions should not be

made until visual contact with the deck indicates it is

open for operation (no white “X”).

g. Hydrogen Sulfide Gas Helideck/Heliport

Operational Hazard Warning(s)/Procedures

1. Background. Hydrogen sulfide (H2S) gas:

Hydrogen sulfide gas in higher concentrations

(300−500 ppm) can cause loss of consciousness

within a few seconds and presents a hazard to pilots

on/near offshore helidecks. When operating in

offshore areas that have been identified to have

concentrations of hydrogen sulfide gas, the following

practices are recommended.

2. Recommended Practices

(a) Pilots

(1) Ensure approved protective air packs

are available for emergency use by the crew on the

helicopter.

(2) If shutdown on a helideck, request the

supervisor in charge provide a briefing on location of

protective equipment and safety procedures.

(3) If while flying near a helideck and the

visual red beacon alarm is observed or an unusually

strong odor of “rotten eggs” is detected, immediately

don the protective air pack, exit to an area upwind,

and notify the suspected source field of the hazard.

FIG 10−2−1

Closed Helideck Marking − No Radio
AIM 7/26/12

10−2−4 Special Operations

(b) Oil Field Supervisors

(1) If presence of hydrogen sulfide is

detected, a red rotating beacon or red high intensity

strobe light adjacent to the primary helideck stairwell

or wind indicator on the structure should be turned on

to provide visual warning of hazard. If the beacon is

to be located near the stairwell, the State of Louisiana

“Offshore Heliport Design Guide” and FAA

Advisory Circular AC 150/5390−2A, “Heliport

Design Guide,” should be reviewed to ensure proper

clearance on the helideck.

(2) Notify nearby helicopter operators and

bases of the hazard and advise when hazard is cleared.

(3) Provide a safety briefing to include

location of protective equipment to all arriving

personnel.

(4) Wind socks or indicator should be

clearly visible to provide upwind indication for the

pilot.

h. Gas Venting Helideck/Heliport Operational

Hazard Warning(s)/Procedures − Operations

Near Gas Vent Booms

1. Background. Ignited flare booms can release a large volume of natural gas and create a hot

fire and intense heat with little time for the pilot to

react. Likewise, unignited gas vents can release

reasonably large volumes of methane gas under

certain conditions. Thus, operations conducted very

near unignited gas vents require precautions to

prevent inadvertent ingestion of combustible gases

by the helicopter engine(s). The following practices

are recommended.

2. Pilots

(a) Gas will drift upwards and downwind of

the vent. Plan the approach and takeoff to observe and

avoid the area downwind of the vent, remaining as far

away as practicable from the open end of the vent

boom.

(b) Do not attempt to start or land on an

offshore helideck when the deck is downwind of a gas

vent unless properly trained personnel verify

conditions are safe.

3. Oil Field Supervisors

(a) During venting of large amounts of

unignited raw gas, a red rotating beacon or red high

intensity strobe light adjacent to the primary helideck

stairwell or wind indicator should be turned on to

provide visible warning of hazard. If the beacon is to

be located near the stairwell, the State of Louisiana

“Offshore Heliport Design Guide” and FAA

Advisory Circular AC 150/5390−2A, Heliport

Design Guide, should be reviewed to ensure proper

clearance from the helideck.

(b) Notify nearby helicopter operators and

bases of the hazard for planned operations.

(c) Wind socks or indicator should be clearly

visible to provide upward indication for the pilot.

i. Helideck/Heliport Operational Warning(s)/Procedure(s) − Closed Helidecks or

Heliports

1. Background. A white “X” marked diagonally from corner to corner across a helideck or

heliport touchdown area is the universally accepted

visual indicator that the landing area is closed for

safety of other reasons and that helicopter operations

are not permitted. The following practices are

recommended.

(a) Permanent Closing. If a helideck or

heliport is to be permanently closed, X diagonals of

the same size and location as indicated above should

be used, but the markings should be painted on the

landing area.

NOTE−

White Decks: If a helideck is painted white, then

international orange or yellow markings can be used for

the temporary or permanent diagonals.

(b) Temporary Closing. A temporary

marker can be used for hazards of an interim nature.

This marker could be made from vinyl or other

durable material in the shape of a diagonal “X.” The

marker should be white with legs at least 20 feet long

and 3 feet in width. This marker is designed to be

quickly secured and removed from the deck using

grommets and rope ties. The duration, time, location,

and nature of these temporary closings should be

provided to and coordinated with company aviation

departments, nearby helicopter bases, and helicopter

operators supporting the area. These markers MUST

be removed when the hazard no longer exists. 

(See FIG 10−2−2.)
7/26/12 AIM

Special Operations 10−2−5

FIG 10−2−2

Closed Helideck Marking

j. Offshore (VFR) Operating Altitudes for

Helicopters

1. Background. Mid−air collisions constitute

a significant percentage of total fatal offshore

helicopter accidents. A method of reducing this risk

is the use of coordinated VFR cruising altitudes. To

enhance safety through standardized vertical separation of helicopters when flying in the offshore

environment, it is recommended that helicopter

operators flying in a particular area establish a

cooperatively developed Standard Operating Procedure (SOP) for VFR operating altitudes. An example

of such an SOP is contained in this example.

2. Recommended Practice Example

(a) Field Operations. Without compromising minimum safe operating altitudes, helicopters

working within an offshore field “constituting a

cluster” should use altitudes not to exceed 500 feet.

(b) En Route Operations

(1) Helicopters operating below 750’ AGL

should avoid transitioning through offshore fields.

(2) Helicopters en route to and from

offshore locations, below 3,000 feet, weather

permitting, should use en route altitudes as outlined

in TBL 10−2−1.

TBL 10−2−1

Magnetic Heading Altitude

0 to 179 750’

1750’

2750’

180 359 1250’

2250’

(c) Area Agreements. See HSAC Area

Agreement Maps for operating procedures for

onshore high density traffic locations.

NOTE−

Pilots of helicopters operating VFR above 3,000 feet above

the surface should refer to the current Federal Aviation

Regulations (14 CFR Part 91), and paragraph 3−1−4,

Basic VFR Weather Minimums, of the AIM.

(d) Landing Lights. Aircraft landing lights

should be on to enhance aircraft identification:

(1) During takeoff and landings;

(2) In congested helicopter or fixed wing

traffic areas;

(3) During reduced visibility; or,

(4) Anytime safety could be enhanced.

k. Offshore Helidecks/Landing Communications

1. Background. To enhance safety, and provide appropriate time to prepare for helicopter

operations, the following is recommended when

anticipating a landing on an offshore helideck.

2. Recommended Practices

(a) Before landing on an offshore helideck,

pilots are encouraged to establish communications

with the company owning or operating the helideck

if frequencies exist for that purpose.

(b) When impracticable, or if frequencies do

not exist, pilots or operations personnel should

attempt to contact the company owning or operating

the helideck by telephone. Contact should be made

before the pilot departs home base/point of departure

to advise of intentions and obtain landing permission

if necessary.
AIM 7/26/12

10−2−6 Special Operations

NOTE−

It is recommended that communications be established a

minimum of 10 minutes prior to planned arrival time. This

practice may be a requirement of some offshore

owner/operators.

NOTE−

1. See subparagraph 10−2−1d for Tanker Operations.

2. Private use Heliport. Offshore heliports are privately

owned/operated facilities and their use is limited to

persons having prior authorization to utilize the facility.

l. Two (2) Helicopter Operations on Offshore

Helidecks

1. Background. Standardized procedures can

enhance the safety of operating a second helicopter

on an offshore helideck, enabling pilots to

determine/maintain minimum operational parameters. Orientation of the parked helicopter on the

helideck, wind and other factors may prohibit

multi−helicopter operations. More conservative

Rotor Diameter (RD) clearances may be required

under differing condition, i.e., temperature, wet deck,

wind (velocity/direction/gusts), obstacles, approach/

departure angles, etc. Operations are at the pilot’s

discretion.

2. Recommended Practice. Helideck size,

structural weight capability, and type of main rotor on

the parked and operating helicopter will aid in

determining accessibility by a second helicopter.

Pilots should determine that multi−helicopter deck

operations are permitted by the helideck owner/

operator.

3. Recommended Criteria

(a) Minimum one−third rotor diameter

clearance (1/3 RD). The landing helicopter maintains a minimum 1/3 RD clearance between the tips of

its turning rotor and the closest part of a parked and

secured helicopter (rotors stopped and tied down).

(b) Three foot parking distance from deck

edge (3’). Helicopters operating on an offshore

helideck land or park the helicopter with a skid/wheel

assembly no closer than 3 feet from helideck edge.

(c) Tiedowns. Main rotors on all helicopters

that are shut down be properly secured (tied down) to

prevent the rotor blades from turning.

(d) Medium (transport) and larger helicopters

should not land on any offshore helideck where a light

helicopter is parked unless the light helicopter is

property secured to the helideck and has main rotor

tied down.

(e) Helideck owners/operators should ensure

that the helideck has a serviceable anti−skid surface.

4. Weight and limitations markings on

helideck. The helideck weight limitations should be

displayed by markings visible to the pilot (see State

of Louisiana “Offshore Heliport Design Guide” and

FAA Advisory Circular AC 150/5390−2A, Heliport

Design Guide).

NOTE−

Some offshore helideck owners/operators have restrictions

on the number of helicopters allowed on a helideck. When

helideck size permits, multiple (more than two) helicopter

operations are permitted by some operators.

m. Helicopter Rapid Refueling Procedures

(HRR)

1. Background. Helicopter Rapid Refueling

(HRR), engine(s)/rotors operating, can be conducted

safely when utilizing trained personnel and observing

safe practices. This recommended practice provides

minimum guidance for HRR as outlined in National

Fire Protection Association (NFPA) and industry

practices. For detailed guidance, please refer to

National Fire Protection Association (NFPA) Document 407, “Standard for Aircraft Fuel Servicing,”

1990 edition, including 1993 HRR Amendment.

NOTE−

Certain operators prohibit HRR, or “hot refueling,” or

may have specific procedures for certain aircraft or

refueling locations. See the General Operations Manual

and/or Operations Specifications to determine the

applicable procedures or limitations.

2. Recommended Practices

(a) Only turbine−engine helicopters fueled

with JET A or JET A−1 with fueling ports located

below any engine exhausts may be fueled while an

onboard engine(s) is (are) operating.

(b) Helicopter fueling while an onboard

engine(s) is (are) operating should only be conducted

under the following conditions:

(1) A properly certificated and current pilot

is at the controls and a trained refueler attending the

fuel nozzle during the entire fuel servicing process.

The pilot monitors the fuel quantity and signals the

refueler when quantity is reached.
7/26/12 AIM

Special Operations 10−2−7

(2) No electrical storms (thunderstorms)

are present within 10 nautical miles. Lightning can

travel great distances beyond the actual thunderstorm.

(3) Passengers disembark the helicopter

and move to a safe location prior to HRR operations.

When the pilot−in−command deems it necessary for

passenger safety that they remain onboard, passengers should be briefed on the evacuation route to

follow to clear the area.

(4) Passengers not board or disembark

during HRR operations nor should cargo be loaded or

unloaded.

(5) Only designated personnel, trained in

HRR operations should conduct HRR written

authorization to include safe handling of the fuel and

equipment. (See your Company Operations/Safety

Manual for detailed instructions.)

(6) All doors, windows, and access points

allowing entry to the interior of the helicopter that are

adjacent to or in the immediate vicinity of the fuel

inlet ports kept closed during HRR operations.

(7) Pilots ensure that appropriate electrical/

electronic equipment is placed in standby−off

position, to preclude the possibility of electrical

discharge or other fire hazard, such as [i.e., weather

radar is on standby and no radio transmissions are

made (keying of the microphone/transmitter)].

Remember, in addition to communications radios,

radio transmissions are also emitted by aircraft radar,

transponders, radar altimeters, DME equipment, and

ELTs.

(8) Smoking be prohibited in and around

the helicopter during all HRR operations.

The HRR procedures are critical and present

associated hazards requiring attention to detail

regarding quality control, weather conditions, static

electricity, bonding, and spill/fires potential.

Any activity associated with rotors turning

(i.e.; refueling embarking/disembarking, loading/

unloading baggage/freight; etc.) personnel should

only approach the aircraft when authorized to do so.

Approach should be made via safe approach

path/walkway or “arc”− remain clear of all rotors.

NOTE−

1. Marine vessels, barges etc.: Vessel motion presents

additional potential hazards to helicopter operations

(blade flex, aircraft movement).

2. See National Fire Protection Association (NFPA)

Document 407, “Standard for Aircraft Fuel Servicing” for specifics regarding non−HRR (routine refueling

operations).

10−2−2. Helicopter Night VFR Operations

a. Effect of Lighting on Seeing Conditions in

Night VFR Helicopter Operations

NOTE−

This guidance was developed to support safe night VFR

helicopter emergency medical services (HEMS) operations. The principles of lighting and seeing conditions are

useful in any night VFR operation.

While ceiling and visibility significantly affect safety

in night VFR operations, lighting conditions also

have a profound effect on safety. Even in conditions

in which visibility and ceiling are determined to be

visual meteorological conditions, the ability to

discern unlighted or low contrast objects and terrain

at night may be compromised. The ability to discern

these objects and terrain is the seeing condition, and

is related to the amount of natural and man made

lighting available, and the contrast, reflectivity, and

texture of surface terrain and obstruction features. In

order to conduct operations safely, seeing conditions

must be accounted for in the planning and execution

of night VFR operations.

Night VFR seeing conditions can be described by

identifying “high lighting conditions” and “low

lighting conditions.”

1. High lighting conditions exist when one of

two sets of conditions are present:

(a) The sky cover is less than broken (less

than 5/8 cloud cover), the time is between the local

Moon rise and Moon set, and the lunar disk is at least

50% illuminated; or

(b) The aircraft is operated over surface

lighting which, at least, provides for the lighting of

prominent obstacles, the identification of terrain

features (shorelines, valleys, hills, mountains, slopes)

and a horizontal reference by which the pilot may

control the helicopter. For example, this surface

lighting may be the result of:

(1) Extensive cultural lighting (man−made,

such as a built−up area of a city),
AIM 7/26/12

10−2−8 Special Operations

(2) Significant reflected cultural lighting

(such as the illumination caused by the reflection of

a major metropolitan area’s lighting reflecting off a

cloud ceiling), or

(3) Limited cultural lighting combined

with a high level of natural reflectivity of celestial

illumination, such as that provided by a surface

covered by snow or a desert surface.

2. Low lighting conditions are those that do not

meet the high lighting conditions requirements.

3. Some areas may be considered a high lighting

environment only in specific circumstances. For

example, some surfaces, such as a forest with limited

cultural lighting, normally have little reflectivity,

requiring dependence on significant moonlight to

achieve a high lighting condition. However, when

that same forest is covered with snow, its reflectivity

may support a high lighting condition based only on

starlight. Similarly, a desolate area, with little cultural

lighting, such as a desert, may have such inherent

natural reflectivity that it may be considered a high

lighting conditions area regardless of season,

provided the cloud cover does not prevent starlight

from being reflected from the surface. Other surfaces,

such as areas of open water, may never have enough

reflectivity or cultural lighting to ever be characterized as a high lighting area.

4. Through the accumulation of night flying

experience in a particular area, the operator will

develop the ability to determine, prior to departure,

which areas can be considered supporting high or low

lighting conditions. Without that operational experience, low lighting considerations should be applied

by operators for both pre−flight planning and

operations until high lighting conditions are observed

or determined to be regularly available.

b. Astronomical Definitions and Background

Information for Night Operations

1. Definitions

(a) Horizon. Wherever one is located on or

near the Earth’s surface, the Earth is perceived as

essentially flat and, therefore, as a plane. If there are

no visual obstructions, the apparent intersection of

the sky with the Earth’s (plane) surface is the horizon,

which appears as a circle centered at the observer. For

rise/set computations, the observer’s eye is considered to be on the surface of the Earth, so that the

horizon is geometrically exactly 90 degrees from the

local vertical direction.

(b) Rise, Set. During the course of a day the

Earth rotates once on its axis causing the phenomena

of rising and setting. All celestial bodies, the Sun,

Moon, stars and planets, seem to appear in the sky at

the horizon to the East of any particular place, then to

cross the sky and again disappear at the horizon to the

West. Because the Sun and Moon appear as circular

disks and not as points of light, a definition of rise or

set must be very specific, because not all of either

body is seen to rise or set at once.

(c) Sunrise and sunset refer to the times when

the upper edge of the disk of the Sun is on the horizon,

considered unobstructed relative to the location of

interest. Atmospheric conditions are assumed to be

average, and the location is in a level region on the

Earth’s surface.

(d) Moonrise and moonset times are computed for exactly the same circumstances as for

sunrise and sunset. However, moonrise and moonset

may occur at any time during a 24 hour period and,

consequently, it is often possible for the Moon to be

seen during daylight, and to have moonless nights. It

is also possible that a moonrise or moonset does not

occur relative to a specific place on a given date.

(e) Transit. The transit time of a celestial

body refers to the instant that its center crosses an

imaginary line in the sky − the observer’s meridian −

running from north to south.

(f) Twilight. Before sunrise and again after

sunset there are intervals of time, known as

“twilight,” during which there is natural light

provided by the upper atmosphere, which does

receive direct sunlight and reflects part of it toward

the Earth’s surface.

(g) Civil twilight is defined to begin in the

morning, and to end in the evening when the center of

the Sun is geometrically 6 degrees below the horizon.

This is the limit at which twilight illumination is

sufficient, under good weather conditions, for

terrestrial objects to be clearly distinguished.

2. Title 14 of the Code of Federal Regulations

applies these concepts and definitions in addressing

the definition of night (Section 1.1), the requirement

for aircraft lighting (Section 91.209) and pilot

recency of night experience (Section 61.67).
7/26/12 AIM

Special Operations 10−2−9

c. Information on Moon Phases and Changes in

the Percentage of the Moon Illuminated

From any location on the Earth, the Moon appears to

be a circular disk which, at any specific time, is

illuminated to some degree by direct sunlight. During

each lunar orbit (a lunar month), we see the Moon’s

appearance change from not visibly illuminated

through partially illuminated to fully illuminated,

then back through partially illuminated to not

illuminated again. There are eight distinct, traditionally recognized stages, called phases. The phases

designate both the degree to which the Moon is

illuminated and the geometric appearance of the

illuminated part. These phases of the Moon, in the

sequence of their occurrence (starting from New

Moon), are listed in FIG 10−2−3.

FIG 10−2−3

Phases of the Moon

New Moon − The Moon’s unilluminated side is facing the Earth. The Moon is not visible

(except during a solar eclipse).

Waxing Crescent − The Moon appears to be partly but less than one−half illuminated by

direct sunlight. The fraction of the Moon’s disk that is illuminated is increasing.

First Quarter − One−half of the Moon appears to be illuminated by direct sunlight. The

fraction of the Moon’s disk that is illuminated is increasing.

Waxing Gibbous − The Moon appears to be more than one−half but not fully illuminated by

direct sunlight. The fraction of the Moon’s disk that is illuminated is increasing.

Full Moon − The Moon’s illuminated side is facing the Earth. The Moon appears to be

completely illuminated by direct sunlight.

Waning Gibbous − The Moon appears to be more than one−half but not fully

illuminated by direct sunlight. The fraction of the Moon’s disk that is illuminated is

decreasing.

Last Quarter − One−half of the Moon appears to be illuminated by direct sunlight. The

fraction of the Moon’s disk that is illuminated is decreasing.

Waning Crescent − The Moon appears to be partly but less than one−half illuminated by

direct sunlight. The fraction of the Moon’s disk that is illuminated is decreasing.
AIM 7/26/12

10−2−10 Special Operations

1. The percent of the Moon’s surface illuminated is a more refined, quantitative description of the

Moon’s appearance than is the phase. Considering the

Moon as a circular disk, at New Moon the percent

illuminated is 0; at First and Last Quarters it is 50%;

and at Full Moon it is 100%. During the crescent

phases the percent illuminated is between 0 and 50%

and during gibbous phases it is between 50% and

100%.

2. For practical purposes, phases of the Moon

and the percent of the Moon illuminated are

independent of the location on the Earth from where

the Moon is observed. That is, all the phases occur at

the same time regardless of the observer’s position.

3. For more detailed information, refer to the

United States Naval Observatory site referenced

below.

d. Access to Astronomical Data for Determination of Moon Rise, Moon Set, and Percentage of

Lunar Disk Illuminated

1. Astronomical data for the determination of

Moon rise and set and Moon phase may be obtained

from the United States Naval Observatory using an

interactive query available at:

http://aa.usno.navy.mil/

2. Click on “Data Services,” and then on

“Complete Sun and Moon Data for One Day.”

3. You can obtain the times of sunrise, sunset,

moonrise, moonset, transits of the Sun and Moon, and

the beginning and end of civil twilight, along with

information on the Moon’s phase by specifying the

date and location in one of the two forms on this web

page and clicking on the “Get data” button at the end

of the form. Form “A” is used for cities or towns in the

U.S. or its territories. Form “B” for all other locations.

An example of the data available from this site is

shown in TBL 10−2−2.

4. Additionally, a yearly table may be

constructed for a particular location by using the

“Table of Sunrise/Sunset, Moonrise/Moonset, or

Twilight Times for an Entire Year” selection.

TBL 10−2−2

Sample of Astronomical Data Available 

from the Naval Observatory

The following information is provided for

New Orleans, Orleans Parish, Louisiana 

(longitude W90.1, latitude N30.0)

Tuesday

29 May 2007

Central Daylight Time

SUN

Begin civil twilight 5:34 a.m.

Sunrise 6:01 a.m.

Sun transit 12:58 p.m.

Sunset 7:55 p.m.

End civil twilight 8:22 p.m.

MOON

Moonrise 5:10 p.m. on preceding day

Moonset 4:07 a.m.

Moonrise 6:06 p.m.

Moon transit 11:26 p.m.

Moonset 4:41 a.m. on following day

Phase of the Moon on 29 May: waxing gibbous with

95% of the Moon’s visible disk illuminated.

Full Moon on 31 May 2007 at 8:04 p.m. Central

Daylight Time.

10−2−3. Landing Zone Safety

a. This information is provided for use by

helicopter emergency medical services (HEMS)

pilots, program managers, medical personnel, law

enforcement, fire, and rescue personnel to further

their understanding of the safety issues concerning

Landing Zones (LZs). It is recommended that HEMS

operators establish working relationships with the

ground responder organizations they may come in

contact with in their flight operations and share this

information in order to establish a common frame of

reference for LZ selection, operations, and safety.
7/26/12 AIM

Special Operations 10−2−11

b. The information provided is largely based on

the booklet, LZ − Preparing the Landing Zone, issued

by National Emergency Medical Services Pilots

Association (NEMSPA), and the guidance developed

by the University of Tennessee Medical Center’s

LIFESTAR program, and is used with their

permission. For additional information, go to

http://www.nemspa.org/.

c. Information concerning the estimation of wind

velocity is based on the Beaufort Scale. See

http://www.spc.noaa.gov/faq/tornado/beaufort.html

for more information.

d. Selecting a Scene LZ

1. If the situation requires the use of a helicopter,

first check to see if there is an area large enough to

land a helicopter safely.

FIG 10−2−4

Recommended Minimum Landing Zone Dimensions

2. For the purposes of FIG 10−2−4 the following are provided as examples of relative helicopter

size:

(a) Small Helicopter: Bell 206/407, Eurocopter AS−350/355, BO−105, BK−117.

(b) Medium Helicopter: Bell UH−1 (Huey)

and derivatives (Bell 212/412), Bell 222/230/430

Sikorsky S−76, Eurocopter SA−365.

(c) Large Helicopter: Boeing Chinook,

Eurocopter Puma, Sikorsky H−60 series

(Blackhawk), SK−92.

3. The LZ should be level, firm and free of loose

debris that could possibly blow up into the rotor

system.

4. The LZ should be clear of people, vehicles

and obstructions such as trees, poles and wires.

Remember that wires are difficult to see from the air.

The LZ must also be free of stumps, brush, post and

large rocks. See FIG 10−2−5.

FIG 10−2−5

Landing Zone Hazards

5. Keep spectators back at least 200 feet. Keep

emergency vehicles 100 feet away and have fire

equipment (if available) standing by. Ground

personnel should wear eye protection, if available,

during landing and takeoff operations. To avoid loose

objects being blown around in the LZ, hats should be

removed; if helmets are worn, chin straps must be

securely fastened.

6. Fire fighters (if available) should wet down

the LZ if it is extremely dusty.
AIM 7/26/12

10−2−12 Special Operations

e. Helping the Flightcrew Locate the Scene

1. If the LZ coordinator has access to a GPS unit,

the exact latitude and longitude of the LZ should be

relayed to the HEMS pilot. If unable to contact the

pilot directly, relay the information to the HEMS

ground communications specialist for relaying to the

pilot, so that they may locate your scene more

efficiently. Recognize that the aircraft may approach

from a direction different than the direct path from the

takeoff point to the scene, as the pilot may have to

detour around terrain, obstructions or weather

en route.

2. Especially in daylight hours, mountainous

and densely populated areas can make sighting a

scene from the air difficult. Often, the LZ coordinator

on the ground will be asked if she or he can see or hear

the helicopter.

3. Flightcrews use a clock reference method for

directing one another’s attention to a certain direction

from the aircraft. The nose of the aircraft is always

12 o’clock, the right side is 3 o’clock, etc. When the

LZ coordinator sees the aircraft, he/she should use

this method to assist the flightcrew by indicating the

scene’s clock reference position from the nose of the

aircraft. For example, “Accident scene is located at

your 2 o’clock position.” See FIG 10−2−6.

FIG 10−2−6

“Clock” System for Identifying Positions

Relative to the Nose of the Aircraft

4. When the helicopter approaches the scene, it

will normally orbit at least one time as the flight crew

observes the wind direction and obstacles that could

interfere with the landing. This is often referred to as

the “high reconnaissance” maneuver.

f. Wind Direction and Touchdown Area

1. Determine from which direction the wind is

blowing. Helicopters normally land and takeoff into

the wind.

2. If contact can be established with the pilot,

either directly or indirectly through the HEMS

ground communications specialist, describe the wind

in terms of the direction the wind is from and the

speed.

3. Common natural sources of wind direction

information are smoke, dust, vegetation movement,

water streaks and waves. Flags, pennants, streamers

can also be used. When describing the direction, use

the compass direction from which the wind is

blowing (example: from the North−West).

4. Wind speed can be measured by small

hand−held measurement devices, or an observer’s

estimate can be used to provide velocity information.

The wind value should be reported in knots (nautical

miles per hour). If unable to numerically measure

wind speed, use TBL 10−2−3 to estimate velocity.

Also, report if the wind conditions are gusty, or if the

wind direction or velocity is variable or has changed

recently.

5. If any obstacle(s) exist, ensure their description, position and approximate height are

communicated to the pilot on the initial radio call.
7/26/12 AIM

Special Operations 10−2−13

TBL 10−2−3

Table of Common References for Estimating Wind Velocity

Wind

(Knots)

Wind

Classification

Appearance of Wind Effects

On the Water On Land

Less than 1 Calm Sea surface smooth and mirror−like Calm, smoke rises vertically

1−3 Light Air Scaly ripples, no foam crests Smoke drift indicates wind direction,

wind vanes are still

4−6 Light Breeze Small wavelets, crests glassy, no

breaking

Wind felt on face, leaves rustle, vanes

begin to move

7−10 Gentle Breeze Large wavelets, crests begin to break,

scattered whitecaps

Leaves and small twigs constantly

moving, light flags extended

11−16 Moderate Breeze Small waves 1−4 ft. becoming longer,

numerous whitecaps

Dust, leaves, and loose paper lifted,

small tree branches move

17−21 Fresh Breeze Moderate waves 4−8 ft. taking longer

form, many whitecaps, some spray

Small trees in leaf begin to sway

22−27 Strong Breeze Larger waves 8−13 ft., whitecaps

common, more spray

Larger tree branches moving, whistling

in wires

28−33 Near Gale Sea heaps up, waves 13−20 ft., white

foam streaks off breakers

Whole trees moving, resistance felt

walking against wind

34−40 Gale Moderately high (13−20 ft.) waves of

greater length, edges of crests begin to

break into spindrift, foam blown in

streaks

Whole trees in motion, resistance felt

walking against wind

41−47 Strong Gale High waves (20 ft.), sea begins to roll,

dense streaks of foam, spray may reduce

visibility

Slight structural damage occurs, slate

blows off roofs

48−55 Storm Very high waves (20−30 ft.) with

overhanging crests, sea white with

densely blown foam, heavy rolling,

lowered visibility

Seldom experienced on land, trees

broken or uprooted, “considerable

structural damage”

56−63 Violent Storm Exceptionally high (30−45 ft.) waves,

foam patches cover sea, visibility more

reduced

64+ Hurricane Air filled with foam, waves over 45 ft.,

sea completely white with driving spray,

visibility greatly reduced

EXAMPLE−

Wind from the South−East, estimated speed 15 knots. Wind shifted from North−East about fifteen minutes ago, and is gusty.
AIM 7/26/12

10−2−14 Special Operations

g. Night LZs

1. There are several ways to light a night LZ:

(a) Mark the touchdown area with five lights

or road flares, one in each corner and one indicating

the direction of the wind. See FIG 10−2−7.

FIG 10−2−7

Recommended Lighting for 

Landing Zone Operations at Night

NOTE−

Road flares are an intense source of ignition and may be

unsuitable or dangerous in certain conditions. In any case,

they must be closely managed and firefighting equipment

should be present when used. Other light sources are

preferred, if available.

(b) If chemical light sticks may be used, care

should be taken to assure they are adequately secured

against being dislodged by the helicopter’s rotor

wash.

(c) Another method of marking a LZ uses four

emergency vehicles with their low beam headlights

aimed toward the intended landing area.

(d) A third method for marking a LZ uses two

vehicles. Have the vehicles direct their headlight

beams into the wind, crossing at the center of the LZ.

(If fire/rescue personnel are available, the reflective

stripes on their bunker gear will assist the pilot

greatly.)

2. At night, spotlights, flood lights and hand

lights used to define the LZ are not to be pointed at the

helicopter. However, they are helpful when pointed

toward utility poles, trees or other hazards to the

landing aircraft. White lights such as spotlights,

flashbulbs and hi−beam headlights ruin the pilot’s

night vision and temporarily blind him. Red lights,

however, are very helpful in finding accident

locations and do not affect the pilot’s night vision as

significantly.

3. As in Day LZ operations, ensure radio contact

is accomplished between ground and air, if possible.

h. Ground Guide

1. When the helicopter is in sight, one person

should assist the LZ Coordinator by guiding the

helicopter into a safe landing area. In selecting an LZ

Coordinator, recognize that medical personnel

usually are very busy with the patient at this time. It

is recommended that the LZ Coordinator be someone

other than a medical responder, if possible. Eye

protection should be worn. The ground guide should

stand with his/her back to the wind and his/her arms

raised over his/her head (flashlights in each hand for

night operations.)

2. The pilot will confirm the LZ sighting by

radio. If possible, once the pilot has identified the LZ,

the ground guide should move out of the LZ.

3. As the helicopter turns into the wind and

begins a descent, the LZ coordinator should provide

assistance by means of radio contact, or utilize the

“unsafe signal” to wave off the helicopter if the LZ is

not safe (see FIG 10−2−8). The LZ Coordinator

should be far enough from the touchdown area that

he/she can still maintain visual contact with the pilot.

i. Assisting the Crew

1. After the helicopter has landed, do not

approach the helicopter. The crew will approach you.

2. Be prepared to assist the crew by providing

security for the helicopter. If asked to provide

security, allow no one but the crew to approach the

aircraft.

3. Once the patient is prepared and ready to load,

allow the crew to open the doors to the helicopter and

guide the loading of the patient.

4. When approaching or departing the helicopter, always be aware of the tail rotor and always

follow the directions of the crew. Working around a

running helicopter can be potentially dangerous. The

environment is very noisy and, with exhaust gases

and rotor wash, often windy. In scene operations, the

surface may be uneven, soft, or slippery which can

lead to tripping. Be very careful of your footing in this

environment.
7/26/12 AIM

Special Operations 10−2−15

5. The tail rotor poses a special threat to

working around a running helicopter. The tail rotor

turns many times faster than the main rotor, and is

often invisible even at idle engine power. Avoid

walking towards the tail of a helicopter beyond the

end of the cabin, unless specifically directed by the

crew.

NOTE−

Helicopters typically have doors on the sides of the cabin,

but many use aft mounted “clamshell” type doors for

loading and unloading patients on litters or stretchers.

When using these doors, it is important to avoid moving any

further aft than necessary to operate the doors and

load/unload the patient. Again, always comply with the

crew’s instructions.

j. General Rules

1. When working around helicopters, always

approach and depart from the front, never from the

rear. Approaching from the rear can increase your risk

of being struck by the tail rotor, which, when at

operating engine speed, is nearly invisible.

2. To prevent injury or damage from the main

rotor, never raise anything over your head.

3. If the helicopter landed on a slope, approach

and depart from the down slope side only.

4. When the helicopter is loaded and ready for

take off, keep the departure path free of vehicles and

spectators. In an emergency, this area is needed to

execute a landing.

k. Hazardous Chemicals and Gases

1. Responding to accidents involving hazardous

materials requires special handling by fire/rescue

units on the ground. Equally important are the

preparations and considerations for helicopter

operations in these areas.

2. Hazardous materials of concern are those

which are toxic, poisonous, flammable, explosive,

irritating, or radioactive in nature. Helicopter

ambulance crews normally don’t carry protective

suits or breathing apparatuses to protect them from

hazardous materials.

3. The helicopter ambulance crew must be told

of hazardous materials on the scene in order to avoid

the contamination of the crew. Patients/victims

contaminated by hazardous materials may require

special precautions in packaging before loading on

the aircraft for the medical crew’s protection, or may

be transported by other means.

4. Hazardous chemicals and gases may be fatal

to the unprotected person if inhaled or absorbed

through the skin.

5. Upon initial radio contact, the helicopter crew

must be made aware of any hazardous gases in the

area. Never assume that the crew has already been

informed. If the aircraft were to fly through the

hazardous gases, the crew could be poisoned and/or

the engines could develop mechanical problems.

6. Poisonous or irritating gases may cling to a

victim’s clothing and go unnoticed until the patient is

loaded and the doors of the helicopter are closed. To

avoid possible compromise of the crew, all of these

patients must be decontaminated prior to loading.

l. Hand Signals

1. If unable to make radio contact with the

HEMS pilot, use the following signals:

FIG 10−2−8

Recommended Landing Zone Ground Signals
AIM 7/26/12

10−2−16 Special Operations

m. Emergency Situations

1. In the event of a helicopter accident in the

vicinity of the LZ, consider the following:

(a) Emergency Exits:

(1) Doors and emergency exits are typically prominently marked. If possible, operators should

familiarize ground responders with the door system

on their helicopter in preparation for an emergency

event.

(2) In the event of an accident during the LZ

operation, be cautious of hazards such as sharp and

jagged metal, plastic windows, glass, any rotating

components, such as the rotors, and fire sources, such

as the fuel tank(s) and the engine.

(b) Fire Suppression:

Helicopters used in HEMS operations are usually

powered by turboshaft engines, which use jet fuel.

Civil HEMS aircraft typically carry between 50 and

250 gallons of fuel, depending upon the size of the

helicopter, and planned flight duration, and the fuel

remaining after flying to the scene. Use water to

control heat and use foam over fuel to keep vapors

from ignition sources.

10−2−4. Emergency Medical Service (EMS)

Multiple Helicopter Operations

a. Background. EMS helicopter operators often

overlap other EMS operator areas. Standardized

procedures can enhance the safety of operating

multiple helicopters to landing zones (LZs) and to

hospital heliports. Communication is the key to

successful operations and in maintaining organization between helicopters, ground units and

communication centers. EMS helicopter operators

which operate in the same areas should establish joint

operating procedures and provide them to related

agencies.

b. Recommended Procedures.

1. Landing Zone Operations. The first helicopter to arrive on−scene should establish

communications with the ground unit at least 10 NMs

from the LZ to receive a LZ briefing and to provide

ground control the number of helicopters that can be

expected. An attempt should be made to contact other

helicopters on 123.025 to pass on to them pertinent

LZ information and the ground unit’s frequency.

Subsequent helicopters arriving on scene should

establish communications on 123.025 at least 10

NMs from the LZ. After establishing contact on

123.025, they should contact the ground unit for

additional information. All helicopters should

monitor 123.025 at all times.

(a) If the landing zone is not established by

the ground unit when the first helicopter arrives,

then the first helicopter should establish altitude

and orbit location requirements for the other

arriving helicopters. Recommended altitude separation between helicopters is 500 feet (weather and

airspace permitting). Helicopters can orbit on

cardinal headings from the scene coordinates. (See

FIG 10−2−9.)

(b) Upon landing in the LZ, the first

helicopter should update the other helicopters on the

LZ conditions, i.e., space, hazards and terrain.

(c) Before initiating any helicopter movement to leave the LZ, all operators should attempt to

contact other helicopters on 123.025, and state their

position and route of flight intentions for departing

the LZ.

2. Hospital Operations. Because many

hospitals require landing permission and have

established procedures (frequencies to monitor,

primary and secondary routes for approaches and

departures, and orbiting areas if the heliport is

occupied) pilots should always receive a briefing

from the appropriate facility (communication center,

flight following, etc.) before proceeding to the

hospital.

(a) In the event of multiple helicopters

coming into the hospital heliport, the helicopter

nearest to the heliport should contact other inbound

helicopters on 123.025 and establish intentions.

Follow the guidelines established in the LZ

operations.

(b) To facilitate approach times, the pilot−in−

command of the helicopter occupying the hospital

heliport should advise any other operators whether

the patient will be off loaded with the rotor blades

turning or stopped, and the approximate time to do so.

(c) Before making any helicopter movement

to leave the hospital heliport, all operators should

attempt to contact other helicopters on 123.025 and

state their position and route of flight intentions for

departing the heliport.
7/26/12 AIM

Special Operations 10−2−17

FIG 10−2−9

EMS Multiple Helicopter LZ/Heliport Operation

NOTE−

If the LZ/hospital heliport weather conditions or airspace altitude restrictions prohibit the recommended vertical

separation, 1 NM separations should be kept between helicopter orbit areas.

7/26/12 AIM

Bird/Other Wildlife Strike Report Appendix 1−1

Appendix 1. Bird/Other Wildlife Strike Report
AIM 7/26/12

Appendix 1−2 Bird/Other Wildlife Strike Report

FOLD AND TAPE HERE
7/26/12 AIM

Volcanic Activity Reporting Form (VAR) Appendix 2−1

Appendix 2. Volcanic Activity Reporting Form (VAR)

E−mail address: GVN@volcano.si.edu

7/26/12 AIM

Laser Beam Exposure Questionnaire Appendix 3−1

Appendix 3. Laser Beam Exposure Questionnaire

7/26/12 AIM

Abbreviations/Acronyms Appendix 4−1

Appendix 4. Abbreviations/Acronyms

As used in this manual, the following abbreviations/

acronyms have the meanings indicated.

Abbreviation/

Acronym

Meaning

AAWU . . . . . Alaskan Aviation Weather Unit

AAS . . . . . . . Airport Advisory Service

AC . . . . . . . . Advisory Circular

ACAR ..... Aircraft Communications Addressing and

Reporting System

ADCUS .... Advise Customs

ADDS ...... Aviation Digital Data Service

ADF . . . . . . . Automatic Direction Finder

ADIZ ...... Air Defense Identification Zone

ADS−B..... Automatic Dependent

Surveillance−Broadcast

AeroNav .... Aeronautical Navigation Products

AFB . . . . . . . Air Force Base

AFCS ...... Automatic Flight Control System

A/FD ...... Airport/Facility Directory

AFIS ....... Automatic Flight Information Service

AFM . . . . . . . Aircraft Flight Manual

AGL . . . . . . . Above Ground Level

AHRS ...... Attitude Heading Reference System

AIM . . . . . . . Aeronautical Information Manual

AIRMET . . . Airmen’s Meteorological Information

ALD . . . . . . . Available Landing Distance

ALS . . . . . . . Approach Light Systems

AMSL ..... Above Mean Sea Level

ANP . . . . . . . Actual Navigation Performance

AOCC ..... Airline Operations Control Center

AP . . . . . . . . Autopilot System

APV . . . . . . . Approach with Vertical Guidance

AR . . . . . . . . Authorization Required

ARENA .... Areas Noted for Attention

ARFF IC .... Aircraft Rescue and Fire Fighting Incident

Commander

ARINC ..... Aeronautical Radio Incorporated

ARO . . . . . . . Airport Reservations Office

ARSA ...... Airport Radar Service Area

ARSR ...... Air Route Surveillance Radar

ARTCC . . . . . Air Route Traffic Control Center

ARTS . . . . . . Automated Radar Terminal System

ASDE−X ... Airport Surface Detection Equipment −

Model X

ASOS ...... Automated Surface Observing System

ASR . . . . . . . Airport Surveillance Radar

Abbreviation/

Acronym

Meaning

ASRS ...... Aviation Safety Reporting System

ATC . . . . . . . Air Traffic Control

ATCRBS .... Air Traffic Control Radar Beacon System

ATCSCC .... Air Traffic Control System Command

Center

ATCT . . . . . . Airport Traffic Control Tower

ATD . . . . . . . Along−Track Distance

ATIS . . . . . . . Automatic Terminal Information Service

ATT . . . . . . . Attitude Retention System

AWC . . . . . . . Aviation Weather Center

AWOS . . . . . Automated Weather Observing System

AWSS . . . . . . Automated Weather Sensor System

AWTT . . . . . Aviation Weather Technology Transfer

AWW . . . . . . Severe Weather Forecast Alert

BAASS ..... Bigelow Aerospace Advanced Space

Studies

BBS . . . . . . . Bulletin Board System

BC . . . . . . . . Back Course

BECMG .... Becoming group

C/A . . . . . . . . Coarse Acquisition

CARTS . . . . . Common Automated Radar Terminal

System (ARTS) (to include ARTS IIIE and

ARTS IIE)

CAT . . . . . . . Clear Air Turbulence

CD . . . . . . . . Controller Display

CDI . . . . . . . . Course Deviation Indicator

CDR . . . . . . . Coded Departure Route

CERAP ..... Combined Center/RAPCON

CFA . . . . . . . Controlled Firing Area

CFIT ....... Controlled Flight into Terrain

CFR . . . . . . . Code of Federal Regulations

COA . . . . . . . Certificate of Waiver or Authorization

CPDLC ..... Controller Pilot Data Link

Communications

CTAF . . . . . . Common Traffic Advisory Frequency

CVFP ...... Charted Visual Flight Procedure

CVRS ...... Computerized Voice Reservation System

CWA . . . . . . . Center Weather Advisory

CWSU ..... Center Weather Service Unit

DA . . . . . . . . Decision Altitude

DCA . . . . . . . Ronald Reagan Washington National

Airport

DCP . . . . . . . Data Collection Package

DER . . . . . . . Departure End of Runway

DF . . . . . . . . Direction Finder
AIM 7/26/12

Appendix 4−2 Abbreviations/Acronyms

Abbreviation/

Acronym

Meaning

DH . . . . . . . . Decision Height

DME . . . . . . . Distance Measuring Equipment

DME/N ..... Standard DME

DME/P ..... Precision DME

DOD . . . . . . . Department of Defense

DP . . . . . . . . Instrument Departure Procedure

DPU . . . . . . . Data Processor Unit

DRT . . . . . . . Diversion Recovery Tool

DRVSM . . . . Domestic Reduced Vertical Separation

Minimum

DUATS . . . . . Direct User Access Terminal System

DVA . . . . . . . Diverse Vector Area

DVFR ...... Defense Visual Flight Rules

DVRSN .... Diversion

EDCT ...... Expect Departure Clearance Time

EFAS . . . . . . En Route Flight Advisory Service

EFV . . . . . . . Enhanced Flight Visibility

EFVS ...... Enhanced Flight Vision System

ELT . . . . . . . . Emergency Locator Transmitter

EMAS ..... Engineered Materials Arresting System

EPE . . . . . . . Estimate of Position Error

ESV . . . . . . . Expanded Service Volume

ETA . . . . . . . Estimated Time of Arrival

ETD . . . . . . . Estimated Time of Departure

ETE . . . . . . . Estimated Time En Route

EWINS ..... Enhanced Weather Information System

EWR . . . . . . . Newark International Airport

FA . . . . . . . . . Area Forecast

FAA . . . . . . . Federal Aviation Administration

FAF . . . . . . . . Final Approach Fix

FAROS ..... Final Approach Runway Occupancy Signal

FAWP . . . . . . Final Approach Waypoint

FB . . . . . . . . . Fly−by

FCC . . . . . . . Federal Communications Commission

FD . . . . . . . . Flight Director System

FDC . . . . . . . Flight Data Center

FDE . . . . . . . Fault Detection and Exclusion

FIR . . . . . . . . Flight Information Region

FIS . . . . . . . . Flight Information Service

FISDL ..... Flight Information Services Data Link

FLIP ....... Flight Information Publication

FMS . . . . . . . Flight Management System

FMSP ...... Flight Management System Procedure

FO . . . . . . . . Fly−over

FPA . . . . . . . . Flight Path Angle

FPV . . . . . . . Flight Path Vector

FPNM ...... Feet Per Nautical Mile

Abbreviation/

Acronym

Meaning

FSDO ...... Flight Standards District Office

FSS . . . . . . . . Flight Service Station

GBAS ...... Ground Based Augmentation System

GEO . . . . . . . Geostationary Satellite

GLS . . . . . . . GBAS Landing System

GNSS ...... Global Navigation Satellite System

GNSSP ..... Global Navigation Satellite System Panel

GPS . . . . . . . Global Positioning System

GRI . . . . . . . . Group Repetition Interval

GSD . . . . . . . Geographical Situation Display

GUS . . . . . . . Ground Uplink Station

HAT . . . . . . . Height Above Touchdown

HDTA . . . . . . High Density Traffic Airports

HEMS ..... Helicopter Emergency Medical Services

HIRL ...... High Intensity Runway Lights

HIWAS . . . . . Hazardous Inflight Weather Advisory

Service

HRR . . . . . . . Helicopter Rapid Refueling Procedures

HUD . . . . . . . Head−Up Display

Hz . . . . . . . . . Hertz

IAF . . . . . . . . Initial Approach Fix

IAP . . . . . . . . Instrument Approach Procedure

IAS . . . . . . . . Indicated Air Speed

IAWP . . . . . . Initial Approach Waypoint

ICAO ...... International Civil Aviation Organization

IF . . . . . . . . . Intermediate Fix

IFIM ....... International Flight Information Manual

IFR . . . . . . . . Instrument Flight Rules

ILS . . . . . . . . Instrument Landing System

ILS/PRM . . . Instrument Landing System/Precision

Runway Monitor

IM . . . . . . . . . Inner Marker

IMC . . . . . . . Instrument Meteorological Conditions

InFO ....... Information For Operators

INS . . . . . . . . Inertial Navigation System

IOC . . . . . . . . Initial Operational Capability

IR . . . . . . . . . IFR Military Training Route

IRU . . . . . . . . Inertial Reference Unit

ITWS ...... Integrated Terminal Weather System

JFK . . . . . . . . John F. Kennedy International Airport

kHz . . . . . . . . Kilohertz

LAA . . . . . . . Local Airport Advisory

LAAS ...... Local Area Augmentation System

LAHSO .... Land and Hold Short Operations

LAWRS . . . . Limited Aviation Weather Reporting

Station

LDA . . . . . . . Localizer Type Directional Aid
7/26/12 AIM

Abbreviations/Acronyms Appendix 4−3

Abbreviation/

Acronym

Meaning

LDA/PRM . . Localizer Type Directional Aid/Precision

Runway Monitor

LGA . . . . . . . LaGuardia Airport

LIRL ....... Low Intensity Runway Lights

LLWAS . . . . . Low Level Wind Shear Alert System

LLWAS NE . Low Level Wind Shear Alert System

Network Expansion

LLWAS−RS . Low Level Wind Shear Alert System

Relocation/Sustainment

LNAV . . . . . . Lateral Navigation

LOC . . . . . . . Localizer

LOP . . . . . . . Line−of−position

LORAN .... Long Range Navigation System

LP . . . . . . . . . Localizer Performance

LPV . . . . . . . Localizer Performance with Vertical

Guidance

LUAW . . . . . Line Up and Wait

LZ . . . . . . . . . Landing Zone

MAHWP . . . Missed Approach Holding Waypoint

MAP . . . . . . . Missed Approach Point

MAWP . . . . . Missed Approach Waypoint

MDA . . . . . . Minimum Descent Altitude

MEA . . . . . . . Minimum En Route Altitude

MEARTS . . . Micro En Route Automated Radar

Tracking System

METAR . . . . Aviation Routine Weather Report

MHz . . . . . . . Megahertz

MIRL ...... Medium Intensity Runway Lights

MLS . . . . . . . Microwave Landing System

MM . . . . . . . Middle Marker

MOA . . . . . . Military Operations Area

MOCA ..... Minimum Obstruction Clearance Altitude

MRA . . . . . . Minimum Reception Altitude

MRB . . . . . . . Magnetic Reference Bearing

MSA . . . . . . . Minimum Safe Altitude

MSAW . . . . . Minimum Safe Altitude Warning

MSL . . . . . . . Mean Sea Level

MTI . . . . . . . Moving Target Indicator

MTOS . . . . . . Mountain Obscuration

MTR . . . . . . . Military Training Route

MVA . . . . . . . Minimum Vectoring Altitude

MWA . . . . . . Mountain Wave Activity

MWO . . . . . . Meteorological Watch Office

NAS . . . . . . . National Airspace System

NASA ...... National Aeronautics and Space

Administration

NAVAID . . . . Navigational Aid

NAVCEN . . . Coast Guard Navigation Center

Abbreviation/

Acronym

Meaning

NCWF ..... National Convective Weather Forecast

NDB . . . . . . . Nondirectional Radio Beacon

NEXRAD . . . Next Generation Weather Radar

NFDC ...... National Flight Data Center

NGA . . . . . . . National Geospatial−Intelligence Agency

NM . . . . . . . . Nautical Mile

NMAC ..... Near Midair Collision

NOAA ..... National Oceanic and Atmospheric

Administration

NOPAC . . . . North Pacific

NoPT ...... No Procedure Turn Required

NOTAM . . . . Notice to Airmen

NPA . . . . . . . Nonprecision Approach

NRS . . . . . . . Navigation Reference System

NSA . . . . . . . National Security Area

NSW . . . . . . . No Significant Weather

NTAP . . . . . . Notices to Airmen Publication

NTSB ...... National Transportation Safety Board

NTZ . . . . . . . No Transgression Zone

NWS . . . . . . . National Weather Service

OAT . . . . . . . Outside Air Temperature

OBS . . . . . . . Omni−bearing Selector

ODP . . . . . . . Obstacle Departure Procedure

OIS . . . . . . . . Operational Information System

OIS . . . . . . . . Obstacle Identification Surface

OM . . . . . . . . Outer Marker

ORD . . . . . . . Chicago O’Hare International Airport

PA . . . . . . . . . Precision Approach

PAPI . . . . . . . Precision Approach Path Indicator

PAR . . . . . . . Precision Approach Radar

PAR . . . . . . . Preferred Arrival Route

PC . . . . . . . . . Personal Computer

P/CG ....... Pilot/Controller Glossary

PDC . . . . . . . Pre−departure Clearance

PFD . . . . . . . Personal Flotation Device

PinS ....... Point−in−Space

PIREP ...... Pilot Weather Report

POB . . . . . . . Persons on Board

POFZ ...... Precision Obstacle Free Zone

POI . . . . . . . . Principal Operations Inspector

PPS . . . . . . . . Precise Positioning Service

PRM . . . . . . . Precision Runway Monitor

PT . . . . . . . . . Procedure Turn

QICP ...... Qualified Internet Communications

Provider

RA . . . . . . . . Resolution Advisory
AIM 7/26/12

Appendix 4−4 Abbreviations/Acronyms

Abbreviation/

Acronym

Meaning

RAA . . . . . . . Remote Advisory Airport

RAIM ...... Receiver Autonomous Integrity Monitoring

STMP ...... Special Traffic Management Program

SWSL ...... Supplemental Weather Service Locations

RAIS ...... Remote Airport Information Service

RBDT ...... Ribbon Display Terminals

RCAG ..... Remote Center Air/Ground

RCC . . . . . . . Rescue Coordination Center

RCLS ...... Runway Centerline Lighting System

RCO . . . . . . . Remote Communications Outlet

RD . . . . . . . . Rotor Diameter

REIL ....... Runway End Identifier Lights

REL . . . . . . . Runway Entrance Lights

RFM . . . . . . . Rotorcraft Flight Manual

RIL . . . . . . . . Runway Intersection Lights

RLIM ...... Runway Light Intensity Monitor

RMI . . . . . . . Radio Magnetic Indicator

RNAV . . . . . . Area Navigation

RNP . . . . . . . Required Navigation Performance

ROC . . . . . . . Required Obstacle Clearance

RPAT . . . . . . RNP Parallel Approach Runway

Transitions

RVR . . . . . . . Runway Visual Range

RVSM . . . . . . Reduced Vertical Separation Minimum

RWSL . . . . . . Runway Status Light

SAFO ...... Safety Alerts For Operators

SAM . . . . . . . System Area Monitor

SAR . . . . . . . Search and Rescue

SAS . . . . . . . Stability Augmentation System

SBAS ...... Satellite−based Augmentation System

SCAT−1

DGPS ...... Special Category I Differential GPS

SDF . . . . . . . Simplified Directional Facility

SFL . . . . . . . . Sequenced Flashing Lights

SFR . . . . . . . Special Flight Rules

SIAP ....... Standard Instrument Approach Procedure

SID . . . . . . . . Standard Instrument Departure

SIGMET .... Significant Meteorological Information

SM . . . . . . . . Statute Mile

SMGCS .... Surface Movement Guidance Control

System

SNR . . . . . . . Signal−to−noise Ratio

SOIA ...... Simultaneous Offset Instrument

Approaches

SOP . . . . . . . Standard Operating Procedure

SPC . . . . . . . Storm Prediction Center

SPS . . . . . . . . Standard Positioning Service

STAR . . . . . . Standard Terminal Arrival

Abbreviation/

Acronym

Meaning

STARS . . . . . Standard Terminal Automation

Replacement System

TA . . . . . . . . . Traffic Advisory

TAA . . . . . . . Terminal Arrival Area

TAC . . . . . . . Terminal Area Chart

TACAN .... Tactical Air Navigation

TAF . . . . . . . Aerodrome Forecast

TAS . . . . . . . True Air Speed

TCAS ...... Traffic Alert and Collision Avoidance

System

TCH . . . . . . . Threshold Crossing Height

TD . . . . . . . . Time Difference

TDLS ...... Tower Data Link System

TDWR ..... Terminal Doppler Weather Radar

TDZ . . . . . . . Touchdown Zone

TDZE ...... Touchdown Zone Elevation

TDZL ...... Touchdown Zone Lights

TEC . . . . . . . Tower En Route Control

THL . . . . . . . Takeoff Hold Lights

TIBS ....... Telephone Information Briefing Service

TIS . . . . . . . . Traffic Information Service

TIS−B...... Traffic Information Service−Broadcast

TLS . . . . . . . Transponder Landing System

TPP . . . . . . . . Terminal Procedures Publications

TRSA ...... Terminal Radar Service Area

TSO . . . . . . . Technical Standard Order

TWEB ..... Transcribed Weather Broadcast

TWIB ...... Terminal Weather Information for Pilots

System

UA . . . . . . . . Unmanned Aircraft

UAS . . . . . . . Unmanned Aircraft System

UAV . . . . . . . Unmanned Aerial Vehicle

UFO . . . . . . . Unidentified Flying Object

UHF . . . . . . . Ultrahigh Frequency

U.S. ....... United States

USCG ...... United States Coast Guard

UTC . . . . . . . Coordinated Universal Time

UWS . . . . . . . Urgent Weather SIGMET

VAR . . . . . . . Volcanic Activity Reporting

VASI . . . . . . . Visual Approach Slope Indicator

VCOA ..... Visual Climb Over the Airport

VDA . . . . . . . Vertical Descent Angle

VDP . . . . . . . Visual Descent Point

VFR . . . . . . . Visual Flight Rules

VGSI ...... Visual Glide Slope Indicator

VHF . . . . . . . Very High Frequency

VIP . . . . . . . . Video Integrator Processor
7/26/12 AIM

Abbreviations/Acronyms Appendix 4−5

Abbreviation/

Acronym

Meaning

VMC . . . . . . Visual Meteorological Conditions

VMINI ...... Instrument flight minimum speed, utilized

in complying with minimum limit speed

requirements for instrument flight

VNAV . . . . . . Vertical Navigation

VNE ....... Never exceed speed

VNEI ....... Instrument flight never exceed speed,

utilized instead of VNE for compliance with

maximum limit speed requirements for

instrument flight

VOR . . . . . . . Very High Frequency Omni−directional

Range

VORTAC . . . VHF Omni−directional Range/Tactical Air

Navigation

VOT . . . . . . . VOR Test Facility

VR . . . . . . . . VFR Military Training Route

VREF ....... The reference landing approach speed,

usually about 1.3 times Vso plus 50 percent

of the wind gust speed in excess of the

mean wind speed.

VSO ........ The stalling speed or the minimum steady

flight speed in the landing configuration at

maximum weight.

VTF . . . . . . . Vector to Final

VV . . . . . . . . Vertical Visibility

Abbreviation/

Acronym

Meaning

VVI . . . . . . . Vertical Velocity Indicator

VY ........ Speed for best rate of climb

VYI ........ Instrument climb speed, utilized instead of

VY for compliance with the climb

requirements for instrument flight

WA . . . . . . . . AIRMET

WAAS . . . . . Wide Area Augmentation System

WAC . . . . . . . World Aeronautical Chart

WFO . . . . . . . Weather Forecast Office

WGS−84 . . . . World Geodetic System of 1984

WMO . . . . . . World Meteorological Organization

WMS . . Wide−Area Master Station

WMSC ..... Weather Message Switching Center

WMSCR .... Weather Message Switching Center

Replacement

WP . . . . . . . . Waypoint

WRS . . . . . . . Wide−Area Ground Reference Station

WS . . . . . . . . SIGMET

WSO ...... Weather Service Office

WSP . . . . . . . Weather System Processor

WST . . . . . . . Convective Significant Meteorological

Information

WW . . . . . . . Severe Weather Watch Bulletin

7/26/12 Pilot/Controller Glossary

PCG−1

PILOT/CONTROLLER

GLOSSARY

PURPOSE

a. This Glossary was compiled to promote a common understanding of the terms used in the Air Traffic

Control system. It includes those terms which are intended for pilot/controller communications. Those terms

most frequently used in pilot/controller communications are printed in bold italics. The definitions are primarily

defined in an operational sense applicable to both users and operators of the National Airspace System. Use of

the Glossary will preclude any misunderstandings concerning the system’s design, function, and purpose.

b. Because of the international nature of flying, terms used in the Lexicon, published by the International

Civil Aviation Organization (ICAO), are included when they differ from FAA definitions. These terms are

followed by “[ICAO].” For the reader’s convenience, there are also cross references to related terms in other parts

of the Glossary and to other documents, such as the Code of Federal Regulations (CFR) and the Aeronautical

Information Manual (AIM).

c. This Glossary will be revised, as necessary, to maintain a common understanding of the system.

EXPLANATION OF CHANGES

a. Terms Added:

PROTECTED SEGMENT

b. Terms Deleted:

OMEGA

c. Editorial/format changes were made where necessary. Revision bars were not used due to the insignificant

nature of the changes.

Pilot/Controller Glossary 2/9/12

PCG A−1

A

AAI−

(See ARRIVAL AIRCRAFT INTERVAL.)

AAR−

(See AIRPORT ARRIVAL RATE.)

ABBREVIATED IFR FLIGHT PLANS− An

authorization by ATC requiring pilots to submit only

that information needed for the purpose of ATC. It

includes only a small portion of the usual IFR flight

plan information. In certain instances, this may be

only aircraft identification, location, and pilot

request. Other information may be requested if

needed by ATC for separation/control purposes. It is

frequently used by aircraft which are airborne and

desire an instrument approach or by aircraft which are

on the ground and desire a climb to VFR-on-top.

(See VFR-ON-TOP.)

(Refer to AIM.)

ABEAM− An aircraft is “abeam” a fix, point, or

object when that fix, point, or object is approximately

90 degrees to the right or left of the aircraft track.

Abeam indicates a general position rather than a

precise point.

ABORT− To terminate a preplanned aircraft

maneuver; e.g., an aborted takeoff.

ACC [ICAO]−

(See ICAO term AREA CONTROL CENTER.)

ACCELERATE-STOP DISTANCE AVAILABLE−

The runway plus stopway length declared available

and suitable for the acceleration and deceleration of

an airplane aborting a takeoff.

ACCELERATE-STOP DISTANCE AVAILABLE

[ICAO]− The length of the take-off run available plus

the length of the stopway if provided.

ACDO−

(See AIR CARRIER DISTRICT OFFICE.)

ACKNOWLEDGE− Let me know that you have

received and understood this message.

ACL−

(See AIRCRAFT LIST.)

ACLS−

(See AUTOMATIC CARRIER LANDING

SYSTEM.)

ACLT−

(See ACTUAL CALCULATED LANDING TIME.)

ACROBATIC FLIGHT− An intentional maneuver

involving an abrupt change in an aircraft’s attitude, an

abnormal attitude, or abnormal acceleration not

necessary for normal flight.

(See ICAO term ACROBATIC FLIGHT.)

(Refer to 14 CFR Part 91.)

ACROBATIC FLIGHT [ICAO]− Maneuvers intentionally performed by an aircraft involving an abrupt

change in its attitude, an abnormal attitude, or an

abnormal variation in speed.

ACTIVE RUNWAY−

(See RUNWAY IN USE/ACTIVE RUNWAY/DUTY

RUNWAY.)

ACTUAL CALCULATED LANDING TIME−

ACLT is a flight’s frozen calculated landing time. An

actual time determined at freeze calculated landing

time (FCLT) or meter list display interval (MLDI) for

the adapted vertex for each arrival aircraft based upon

runway configuration, airport acceptance rate, airport

arrival delay period, and other metered arrival

aircraft. This time is either the vertex time of arrival

(VTA) of the aircraft or the tentative calculated

landing time (TCLT)/ACLT of the previous aircraft

plus the arrival aircraft interval (AAI), whichever is

later. This time will not be updated in response to the

aircraft’s progress.

ACTUAL NAVIGATION PERFORMANCE

(ANP)−

(See REQUIRED NAVIGATION

PERFORMANCE.)

ADDITIONAL SERVICES− Advisory information

provided by ATC which includes but is not limited to

the following:

a. Traffic advisories.

b. Vectors, when requested by the pilot, to assist

aircraft receiving traffic advisories to avoid observed

traffic.

c. Altitude deviation information of 300 feet or

more from an assigned altitude as observed on a

verified (reading correctly) automatic altitude

readout (Mode C).

d. Advisories that traffic is no longer a factor.
Pilot/Controller Glossary 2/9/12

PCG A−2

e. Weather and chaff information.

f. Weather assistance.

g. Bird activity information.

h. Holding pattern surveillance. Additional services are provided to the extent possible contingent

only upon the controller’s capability to fit them into

the performance of higher priority duties and on the

basis of limitations of the radar, volume of traffic,

frequency congestion, and controller workload. The

controller has complete discretion for determining if

he/she is able to provide or continue to provide a

service in a particular case. The controller’s reason

not to provide or continue to provide a service in a

particular case is not subject to question by the pilot

and need not be made known to him/her.

(See TRAFFIC ADVISORIES.)

(Refer to AIM.)

ADF−

(See AUTOMATIC DIRECTION FINDER.)

ADIZ−

(See AIR DEFENSE IDENTIFICATION ZONE.)

ADLY−

(See ARRIVAL DELAY.)

ADMINISTRATOR− The Federal Aviation Administrator or any person to whom he/she has delegated

his/her authority in the matter concerned.

ADR−

(See AIRPORT DEPARTURE RATE.)

ADS [ICAO]−

(See ICAO term AUTOMATIC DEPENDENT

SURVEILLANCE.)

ADS−B−

(See AUTOMATIC DEPENDENT

SURVEILLANCE−BROADCAST.)

ADS−C−

(See AUTOMATIC DEPENDENT

SURVEILLANCE−CONTRACT.)

ADVISE INTENTIONS− Tell me what you plan to

do.

ADVISORY− Advice and information provided to

assist pilots in the safe conduct of flight and aircraft

movement.

(See ADVISORY SERVICE.)

ADVISORY FREQUENCY− The appropriate frequency to be used for Airport Advisory Service.

(See LOCAL AIRPORT ADVISORY.)

(See UNICOM.)

(Refer to ADVISORY CIRCULAR NO. 90-42.)

(Refer to AIM.)

ADVISORY SERVICE− Advice and information

provided by a facility to assist pilots in the safe

conduct of flight and aircraft movement.

(See ADDITIONAL SERVICES.)

(See EN ROUTE FLIGHT ADVISORY

SERVICE.)

(See LOCAL AIRPORT ADVISORY.)

(See RADAR ADVISORY.)

(See SAFETY ALERT.)

(See TRAFFIC ADVISORIES.)

(Refer to AIM.)

AERIAL REFUELING− A procedure used by the

military to transfer fuel from one aircraft to another

during flight.

(Refer to VFR/IFR Wall Planning Charts.)

AERODROME− A defined area on land or water

(including any buildings, installations and equipment) intended to be used either wholly or in part for

the arrival, departure, and movement of aircraft.

AERODROME BEACON [ICAO]− Aeronautical

beacon used to indicate the location of an aerodrome

from the air.

AERODROME CONTROL SERVICE [ICAO]− Air

traffic control service for aerodrome traffic.

AERODROME CONTROL TOWER [ICAO]− A

unit established to provide air traffic control service

to aerodrome traffic.

AERODROME ELEVATION [ICAO]− The elevation of the highest point of the landing area.

AERODROME TRAFFIC CIRCUIT [ICAO]− The

specified path to be flown by aircraft operating in the

vicinity of an aerodrome.

AERONAUTICAL BEACON− A visual NAVAID

displaying flashes of white and/or colored light to

indicate the location of an airport, a heliport, a

landmark, a certain point of a Federal airway in

mountainous terrain, or an obstruction.

(See AIRPORT ROTATING BEACON.)

(Refer to AIM.)

AERONAUTICAL CHART− A map used in air

navigation containing all or part of the following:
Pilot/Controller Glossary 2/9/12

PCG A−3

topographic features, hazards and obstructions,

navigation aids, navigation routes, designated

airspace, and airports. Commonly used aeronautical

charts are:

a. Sectional Aeronautical Charts (1:500,000)−

Designed for visual navigation of slow or medium

speed aircraft. Topographic information on these

charts features the portrayal of relief and a judicious

selection of visual check points for VFR flight.

Aeronautical information includes visual and radio

aids to navigation, airports, controlled airspace,

restricted areas, obstructions, and related data.

b. VFR Terminal Area Charts (1:250,000)−

Depict Class B airspace which provides for the

control or segregation of all the aircraft within Class

B airspace. The chart depicts topographic information and aeronautical information which includes

visual and radio aids to navigation, airports,

controlled airspace, restricted areas, obstructions,

and related data.

c. World Aeronautical Charts (WAC)

(1:1,000,000)− Provide a standard series of aeronautical charts covering land areas of the world at a size

and scale convenient for navigation by moderate

speed aircraft. Topographic information includes

cities and towns, principal roads, railroads, distinctive landmarks, drainage, and relief. Aeronautical

information includes visual and radio aids to

navigation, airports, airways, restricted areas,

obstructions, and other pertinent data.

d. En Route Low Altitude Charts− Provide

aeronautical information for en route instrument

navigation (IFR) in the low altitude stratum.

Information includes the portrayal of airways, limits

of controlled airspace, position identification and

frequencies of radio aids, selected airports, minimum

en route and minimum obstruction clearance

altitudes, airway distances, reporting points, restricted areas, and related data. Area charts, which are

a part of this series, furnish terminal data at a larger

scale in congested areas.

e. En Route High Altitude Charts− Provide

aeronautical information for en route instrument

navigation (IFR) in the high altitude stratum.

Information includes the portrayal of jet routes,

identification and frequencies of radio aids, selected

airports, distances, time zones, special use airspace,

and related information.

f. Instrument Approach Procedures (IAP) Charts−

Portray the aeronautical data which is required to

execute an instrument approach to an airport. These

charts depict the procedures, including all related

data, and the airport diagram. Each procedure is

designated for use with a specific type of electronic

navigation system including NDB, TACAN, VOR,

ILS/MLS, and RNAV. These charts are identified by

the type of navigational aid(s) which provide final

approach guidance.

g. Instrument Departure Procedure (DP) Charts−

Designed to expedite clearance delivery and to

facilitate transition between takeoff and en route

operations. Each DP is presented as a separate chart

and may serve a single airport or more than one

airport in a given geographical location.

h. Standard Terminal Arrival (STAR) Charts−

Designed to expedite air traffic control arrival

procedures and to facilitate transition between en

route and instrument approach operations. Each

STAR procedure is presented as a separate chart and

may serve a single airport or more than one airport in

a given geographical location.

i. Airport Taxi Charts− Designed to expedite the

efficient and safe flow of ground traffic at an airport.

These charts are identified by the official airport

name; e.g., Ronald Reagan Washington National

Airport.

(See ICAO term AERONAUTICAL CHART.)

AERONAUTICAL CHART [ICAO]− A representation of a portion of the earth, its culture and relief,

specifically designated to meet the requirements of

air navigation.

AERONAUTICAL INFORMATION MANUAL

(AIM)− A primary FAA publication whose purpose

is to instruct airmen about operating in the National

Airspace System of the U.S. It provides basic flight

information, ATC Procedures and general instructional information concerning health, medical facts,

factors affecting flight safety, accident and hazard

reporting, and types of aeronautical charts and their

use.
Pilot/Controller Glossary 2/9/12

PCG A−4

AERONAUTICAL INFORMATION PUBLICATION (AIP) [ICAO]− A publication issued by or with

the authority of a State and containing aeronautical

information of a lasting character essential to air

navigation.

A/FD−

(See AIRPORT/FACILITY DIRECTORY.)

AFFIRMATIVE− Yes.

AFIS−

(See AUTOMATIC FLIGHT INFORMATION

SERVICE − ALASKA FSSs ONLY.)

AFP−

(See AIRSPACE FLOW PROGRAM.)

AIM−

(See AERONAUTICAL INFORMATION

MANUAL.)

AIP [ICAO]−

(See ICAO term AERONAUTICAL

INFORMATION PUBLICATION.)

AIR CARRIER DISTRICT OFFICE− An FAA field

office serving an assigned geographical area, staffed

with Flight Standards personnel serving the aviation

industry and the general public on matters related to

the certification and operation of scheduled air

carriers and other large aircraft operations.

AIR DEFENSE EMERGENCY− A military emergency condition declared by a designated authority.

This condition exists when an attack upon the

continental U.S., Alaska, Canada, or U.S. installations in Greenland by hostile aircraft or missiles is

considered probable, is imminent, or is taking place.

(Refer to AIM.)

AIR DEFENSE IDENTIFICATION ZONE (ADIZ)−

The area of airspace over land or water, extending

upward from the surface, within which the ready

identification, the location, and the control of aircraft

are required in the interest of national security.

a. Domestic Air Defense Identification Zone. An

ADIZ within the United States along an international

boundary of the United States.

b. Coastal Air Defense Identification Zone. An

ADIZ over the coastal waters of the United States.

c. Distant Early Warning Identification Zone

(DEWIZ). An ADIZ over the coastal waters of the

State of Alaska.

d. Land−Based Air Defense Identification Zone.

An ADIZ over U.S. metropolitan areas, which is

activated and deactivated as needed, with dimensions, activation dates and other relevant information

disseminated via NOTAM.

Note: ADIZ locations and operating and flight plan

requirements for civil aircraft operations are specified in 14 CFR Part 99.

(Refer to AIM.)

AIR NAVIGATION FACILITY− Any facility used

in, available for use in, or designed for use in, aid of

air navigation, including landing areas, lights, any

apparatus or equipment for disseminating weather

information, for signaling, for radio-directional

finding, or for radio or other electrical communication, and any other structure or mechanism having a

similar purpose for guiding or controlling flight in the

air or the landing and takeoff of aircraft.

(See NAVIGATIONAL AID.)

AIR ROUTE SURVEILLANCE RADAR− Air route

traffic control center (ARTCC) radar used primarily

to detect and display an aircraft’s position while en

route between terminal areas. The ARSR enables

controllers to provide radar air traffic control service

when aircraft are within the ARSR coverage. In some

instances, ARSR may enable an ARTCC to provide

terminal radar services similar to but usually more

limited than those provided by a radar approach

control.

AIR ROUTE TRAFFIC CONTROL CENTER− A

facility established to provide air traffic control

service to aircraft operating on IFR flight plans

within controlled airspace and principally during the

en route phase of flight. When equipment capabilities

and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft.

(See EN ROUTE AIR TRAFFIC CONTROL

SERVICES.)

(Refer to AIM.)

AIR TAXI− Used to describe a helicopter/VTOL

aircraft movement conducted above the surface but

normally not above 100 feet AGL. The aircraft may

proceed either via hover taxi or flight at speeds more

than 20 knots. The pilot is solely responsible for

selecting a safe airspeed/altitude for the operation

being conducted.

(See HOVER TAXI.)

(Refer to AIM.)
Pilot/Controller Glossary 2/9/12

PCG A−5

AIR TRAFFIC− Aircraft operating in the air or on an

airport surface, exclusive of loading ramps and

parking areas.

(See ICAO term AIR TRAFFIC.)

AIR TRAFFIC [ICAO]− All aircraft in flight or

operating on the maneuvering area of an aerodrome.

AIR TRAFFIC CLEARANCE− An authorization by

air traffic control for the purpose of preventing

collision between known aircraft, for an aircraft to

proceed under specified traffic conditions within

controlled airspace. The pilot-in-command of an

aircraft may not deviate from the provisions of a

visual flight rules (VFR) or instrument flight rules

(IFR) air traffic clearance except in an emergency or

unless an amended clearance has been obtained.

Additionally, the pilot may request a different

clearance from that which has been issued by air

traffic control (ATC) if information available to the

pilot makes another course of action more practicable

or if aircraft equipment limitations or company

procedures forbid compliance with the clearance

issued. Pilots may also request clarification or

amendment, as appropriate, any time a clearance is

not fully understood, or considered unacceptable

because of safety of flight. Controllers should, in

such instances and to the extent of operational

practicality and safety, honor the pilot’s request.

14 CFR Part 91.3(a) states: “The pilot in command

of an aircraft is directly responsible for, and is the

final authority as to, the operation of that aircraft.”

THE PILOT IS RESPONSIBLE TO REQUEST AN

AMENDED CLEARANCE if ATC issues a

clearance that would cause a pilot to deviate from a

rule or regulation, or in the pilot’s opinion, would

place the aircraft in jeopardy.

(See ATC INSTRUCTIONS.)

(See ICAO term AIR TRAFFIC CONTROL

CLEARANCE.)

AIR TRAFFIC CONTROL− A service operated by

appropriate authority to promote the safe, orderly and

expeditious flow of air traffic.

(See ICAO term AIR TRAFFIC CONTROL

SERVICE.)

AIR TRAFFIC CONTROL CLEARANCE [ICAO]−

Authorization for an aircraft to proceed under

conditions specified by an air traffic control unit.

Note 1: For convenience, the term air traffic control

clearance is frequently abbreviated to clearance

when used in appropriate contexts.

Note 2: The abbreviated term clearance may be

prefixed by the words taxi, takeoff, departure, en

route, approach or landing to indicate the particular

portion of flight to which the air traffic control clearance relates.

AIR TRAFFIC CONTROL SERVICE−

(See AIR TRAFFIC CONTROL.)

AIR TRAFFIC CONTROL SERVICE [ICAO]− A

service provided for the purpose of:

a. Preventing collisions:

1. Between aircraft; and

2. On the maneuvering area between aircraft

and obstructions.

b. Expediting and maintaining an orderly flow of

air traffic.

AIR TRAFFIC CONTROL SPECIALIST− A person

authorized to provide air traffic control service.

(See AIR TRAFFIC CONTROL.)

(See FLIGHT SERVICE STATION.)

(See ICAO term CONTROLLER.)

AIR TRAFFIC CONTROL SYSTEM COMMAND

CENTER (ATCSCC) − An Air Traffic Tactical

Operations facility responsible for monitoring and

managing the flow of air traffic throughout the NAS,

producing a safe, orderly, and expeditious flow of

traffic while minimizing delays. The following

functions are located at the ATCSCC:

a. Central Altitude Reservation Function

(CARF). Responsible for coordinating, planning,

and approving special user requirements under the

Altitude Reservation (ALTRV) concept.

(See ALTITUDE RESERVATION.)

b. Airport Reservation Office (ARO).

Responsible for approving IFR flights at designated

high density traffic airports (John F. Kennedy,

LaGuardia, and Ronald Reagan Washington

National) during specified hours.

(Refer to 14 CFR Part 93.)

(Refer to AIRPORT/FACILITY DIRECTORY.)
Pilot/Controller Glossary 2/9/12

PCG A−6

c. U.S. Notice to Airmen (NOTAM) Office.

Responsible for collecting, maintaining, and distributing NOTAMs for the U.S. civilian and military, as

well as international aviation communities.

(See NOTICE TO AIRMEN.)

d. Weather Unit. Monitor all aspects of weather

for the U.S. that might affect aviation including cloud

cover, visibility, winds, precipitation, thunderstorms,

icing, turbulence, and more. Provide forecasts based

on observations and on discussions with meteorologists from various National Weather Service offices,

FAA facilities, airlines, and private weather services.

AIR TRAFFIC SERVICE− A generic term meaning:

a. Flight Information Service.

b. Alerting Service.

c. Air Traffic Advisory Service.

d. Air Traffic Control Service:

1. Area Control Service,

2. Approach Control Service, or

3. Airport Control Service.

AIR TRAFFIC SERVICE (ATS) ROUTES − The

term “ATS Route” is a generic term that includes

“VOR Federal airways,” “colored Federal airways,”

“jet routes,” and “RNAV routes.” The term “ATS

route” does not replace these more familiar route

names, but serves only as an overall title when listing

the types of routes that comprise the United States

route structure.

AIRBORNE− An aircraft is considered airborne

when all parts of the aircraft are off the ground.

AIRBORNE DELAY− Amount of delay to be

encountered in airborne holding.

AIRCRAFT− Device(s) that are used or intended to

be used for flight in the air, and when used in air traffic

control terminology, may include the flight crew.

(See ICAO term AIRCRAFT.)

AIRCRAFT [ICAO]− Any machine that can derive

support in the atmosphere from the reactions of the air

other than the reactions of the air against the earth’s

surface.

AIRCRAFT APPROACH CATEGORY− A

grouping of aircraft based on a speed of 1.3 times the

stall speed in the landing configuration at maximum

gross landing weight. An aircraft must fit in only one

category. If it is necessary to maneuver at speeds in

excess of the upper limit of a speed range for a

category, the minimums for the category for that

speed must be used. For example, an aircraft which

falls in Category A, but is circling to land at a speed

in excess of 91 knots, must use the approach

Category B minimums when circling to land. The

categories are as follows:

a. Category A− Speed less than 91 knots.

b. Category B− Speed 91 knots or more but less

than 121 knots.

c. Category C− Speed 121 knots or more but less

than 141 knots.

d. Category D− Speed 141 knots or more but less

than 166 knots.

e. Category E− Speed 166 knots or more.

(Refer to 14 CFR Part 97.)

AIRCRAFT CLASSES− For the purposes of Wake

Turbulence Separation Minima, ATC classifies

aircraft as Heavy, Large, and Small as follows:

a. Heavy− Aircraft capable of takeoff weights of

300,000 pounds or more whether or not they are

operating at this weight during a particular phase of

flight.

b. Large− Aircraft of more than 41,000 pounds,

maximum certificated takeoff weight, up to but not

including 300,000 pounds.

c. Small− Aircraft of 41,000 pounds or less

maximum certificated takeoff weight.

(Refer to AIM.)

AIRCRAFT CONFLICT− Predicted conflict, within

URET, of two aircraft, or between aircraft and

airspace. A Red alert is used for conflicts when the

predicted minimum separation is 5 nautical miles or

less. A Yellow alert is used when the predicted

minimum separation is between 5 and approximately

12 nautical miles. A Blue alert is used for conflicts

between an aircraft and predefined airspace.

(See USER REQUEST EVALUATION TOOL.)

AIRCRAFT LIST (ACL)− A view available with

URET that lists aircraft currently in or predicted to be

in a particular sector’s airspace. The view contains

textual flight data information in line format and may

be sorted into various orders based on the specific

needs of the sector team.

(See USER REQUEST EVALUATION TOOL.)
Pilot/Controller Glossary 2/9/12

PCG A−7

AIRCRAFT SURGE LAUNCH AND

RECOVERY− Procedures used at USAF bases to

provide increased launch and recovery rates in

instrument flight rules conditions. ASLAR is based

on:

a. Reduced separation between aircraft which is

based on time or distance. Standard arrival separation

applies between participants including multiple

flights until the DRAG point. The DRAG point is a

published location on an ASLAR approach where

aircraft landing second in a formation slows to a

predetermined airspeed. The DRAG point is the

reference point at which MARSA applies as

expanding elements effect separation within a flight

or between subsequent participating flights.

b. ASLAR procedures shall be covered in a Letter

of Agreement between the responsible USAF

military ATC facility and the concerned Federal

Aviation Administration facility. Initial Approach

Fix spacing requirements are normally addressed as

a minimum.

AIRMEN’S METEOROLOGICAL

INFORMATION−

(See AIRMET.)

AIRMET− In-flight weather advisories issued only

to amend the area forecast concerning weather

phenomena which are of operational interest to all

aircraft and potentially hazardous to aircraft having

limited capability because of lack of equipment,

instrumentation, or pilot qualifications. AIRMETs

concern weather of less severity than that covered by

SIGMETs or Convective SIGMETs. AIRMETs

cover moderate icing, moderate turbulence, sustained

winds of 30 knots or more at the surface, widespread

areas of ceilings less than 1,000 feet and/or visibility

less than 3 miles, and extensive mountain

obscurement.

(See AWW.)

(See CONVECTIVE SIGMET.)

(See CWA.)

(See SIGMET.)

(Refer to AIM.)

AIRPORT− An area on land or water that is used or

intended to be used for the landing and takeoff of

aircraft and includes its buildings and facilities, if

any.

AIRPORT ADVISORY AREA− The area within ten

miles of an airport without a control tower or where

the tower is not in operation, and on which a Flight

Service Station is located.

(See LOCAL AIRPORT ADVISORY.)

(Refer to AIM.)

AIRPORT ARRIVAL RATE (AAR)− A dynamic

input parameter specifying the number of arriving

aircraft which an airport or airspace can accept from

the ARTCC per hour. The AAR is used to calculate

the desired interval between successive arrival

aircraft.

AIRPORT DEPARTURE RATE (ADR)− A dynamic

parameter specifying the number of aircraft which

can depart an airport and the airspace can accept per

hour.

AIRPORT ELEVATION− The highest point of an

airport’s usable runways measured in feet from mean

sea level.

(See TOUCHDOWN ZONE ELEVATION.)

(See ICAO term AERODROME ELEVATION.)

AIRPORT/FACILITY DIRECTORY− A publication

designed primarily as a pilot’s operational manual

containing all airports, seaplane bases, and heliports

open to the public including communications data,

navigational facilities, and certain special notices and

procedures. This publication is issued in seven

volumes according to geographical area.

AIRPORT LIGHTING− Various lighting aids that

may be installed on an airport. Types of airport

lighting include:

a. Approach Light System (ALS)− An airport

lighting facility which provides visual guidance to

landing aircraft by radiating light beams in a

directional pattern by which the pilot aligns the

aircraft with the extended centerline of the runway on

his/her final approach for landing. CondenserDischarge Sequential Flashing Lights/Sequenced

Flashing Lights may be installed in conjunction with

the ALS at some airports. Types of Approach Light

Systems are:

1. ALSF-1− Approach Light System with

Sequenced Flashing Lights in ILS Cat-I configuration.

2. ALSF-2− Approach Light System with

Sequenced Flashing Lights in ILS Cat-II configuration. The ALSF-2 may operate as an SSALR when

weather conditions permit.

3. SSALF− Simplified Short Approach Light

System with Sequenced Flashing Lights.
Pilot/Controller Glossary 2/9/12

PCG A−8

4. SSALR− Simplified Short Approach Light

System with Runway Alignment Indicator Lights.

5. MALSF− Medium Intensity Approach Light

System with Sequenced Flashing Lights.

6. MALSR− Medium Intensity Approach Light

System with Runway Alignment Indicator Lights.

7. RLLS− Runway Lead-in Light System

Consists of one or more series of flashing lights

installed at or near ground level that provides positive

visual guidance along an approach path, either

curving or straight, where special problems exist with

hazardous terrain, obstructions, or noise abatement

procedures.

8. RAIL− Runway Alignment Indicator Lights−

Sequenced Flashing Lights which are installed only

in combination with other light systems.

9. ODALS− Omnidirectional Approach Lighting System consists of seven omnidirectional

flashing lights located in the approach area of a

nonprecision runway. Five lights are located on the

runway centerline extended with the first light

located 300 feet from the threshold and extending at

equal intervals up to 1,500 feet from the threshold.

The other two lights are located, one on each side of

the runway threshold, at a lateral distance of 40 feet

from the runway edge, or 75 feet from the runway

edge when installed on a runway equipped with a

VASI.

(Refer to FAAO JO 6850.2, VISUAL GUIDANCE

LIGHTING SYSTEMS.)

b. Runway Lights/Runway Edge Lights− Lights

having a prescribed angle of emission used to define

the lateral limits of a runway. Runway lights are

uniformly spaced at intervals of approximately 200

feet, and the intensity may be controlled or preset.

c. Touchdown Zone Lighting− Two rows of

transverse light bars located symmetrically about the

runway centerline normally at 100 foot intervals. The

basic system extends 3,000 feet along the runway.

d. Runway Centerline Lighting− Flush centerline

lights spaced at 50-foot intervals beginning 75 feet

from the landing threshold and extending to within 75

feet of the opposite end of the runway.

e. Threshold Lights− Fixed green lights arranged

symmetrically left and right of the runway centerline,

identifying the runway threshold.

f. Runway End Identifier Lights (REIL)− Two

synchronized flashing lights, one on each side of the

runway threshold, which provide rapid and positive

identification of the approach end of a particular

runway.

g. Visual Approach Slope Indicator (VASI)− An

airport lighting facility providing vertical visual

approach slope guidance to aircraft during approach

to landing by radiating a directional pattern of high

intensity red and white focused light beams which

indicate to the pilot that he/she is “on path” if he/she

sees red/white, “above path” if white/white, and

“below path” if red/red. Some airports serving large

aircraft have three-bar VASIs which provide two

visual glide paths to the same runway.

h. Precision Approach Path Indicator (PAPI)− An

airport lighting facility, similar to VASI, providing

vertical approach slope guidance to aircraft during

approach to landing. PAPIs consist of a single row of

either two or four lights, normally installed on the left

side of the runway, and have an effective visual range

of about 5 miles during the day and up to 20 miles at

night. PAPIs radiate a directional pattern of high

intensity red and white focused light beams which

indicate that the pilot is “on path” if the pilot sees an

equal number of white lights and red lights, with

white to the left of the red; “above path” if the pilot

sees more white than red lights; and “below path” if

the pilot sees more red than white lights.

i. Boundary Lights− Lights defining the perimeter

of an airport or landing area.

(Refer to AIM.)

AIRPORT MARKING AIDS− Markings used on

runway and taxiway surfaces to identify a specific

runway, a runway threshold, a centerline, a hold line,

etc. A runway should be marked in accordance with

its present usage such as:

a. Visual.

b. Nonprecision instrument.

c. Precision instrument.

(Refer to AIM.)

AIRPORT REFERENCE POINT (ARP)− The

approximate geometric center of all usable runway

surfaces.

AIRPORT RESERVATION OFFICE− Office

responsible for monitoring the operation of slot

controlled airports. It receives and processes requests

for unscheduled operations at slot controlled airports.

AIRPORT ROTATING BEACON− A visual

NAVAID operated at many airports. At civil airports,
Pilot/Controller Glossary 2/9/12

PCG A−9

alternating white and green flashes indicate the

location of the airport. At military airports, the

beacons flash alternately white and green, but are

differentiated from civil beacons by dualpeaked (two

quick) white flashes between the green flashes.

(See INSTRUMENT FLIGHT RULES.)

(See SPECIAL VFR OPERATIONS.)

(See ICAO term AERODROME BEACON.)

(Refer to AIM.)

AIRPORT STREAM FILTER (ASF)− An on/off

filter that allows the conflict notification function to

be inhibited for arrival streams into single or multiple

airports to prevent nuisance alerts.

AIRPORT SURFACE DETECTION EQUIPMENT

(ASDE)− Surveillance equipment specifically designed to detect aircraft, vehicular traffic, and other

objects, on the surface of an airport, and to present the

image on a tower display. Used to augment visual

observation by tower personnel of aircraft and/or

vehicular movements on runways and taxiways.

There are three ASDE systems deployed in the NAS:

a. ASDE−3− a Surface Movement Radar.

b. ASDE−X− a system that uses a X−band Surface

Movement Radar and multilateration. Data from

these two sources are fused and presented on a digital

display.

c. ASDE−3X− an ASDE−X system that uses the

ASDE−3 Surface Movement Radar.

AIRPORT SURVEILLANCE RADAR− Approach

control radar used to detect and display an aircraft’s

position in the terminal area. ASR provides range and

azimuth information but does not provide elevation

data. Coverage of the ASR can extend up to 60 miles.

AIRPORT TAXI CHARTS−

(See AERONAUTICAL CHART.)

AIRPORT TRAFFIC CONTROL SERVICE− A

service provided by a control tower for aircraft

operating on the movement area and in the vicinity of

an airport.

(See MOVEMENT AREA.)

(See TOWER.)

(See ICAO term AERODROME CONTROL

SERVICE.)

AIRPORT TRAFFIC CONTROL TOWER−

(See TOWER.)

AIRSPACE CONFLICT− Predicted conflict of an

aircraft and active Special Activity Airspace (SAA).

AIRSPACE FLOW PROGRAM (AFP)− AFP is a

Traffic Management (TM) process administered by

the Air Traffic Control System Command Center

(ATCSCC) where aircraft are assigned an Expect

Departure Clearance Time (EDCT) in order to

manage capacity and demand for a specific area of the

National Airspace System (NAS). The purpose of the

program is to mitigate the effects of en route

constraints. It is a flexible program and may be

implemented in various forms depending upon the

needs of the air traffic system.

AIRSPACE HIERARCHY− Within the airspace

classes, there is a hierarchy and, in the event of an

overlap of airspace: Class A preempts Class B, Class

B preempts Class C, Class C preempts Class D, Class

D preempts Class E, and Class E preempts Class G.

AIRSPEED− The speed of an aircraft relative to its

surrounding air mass. The unqualified term

“airspeed” means one of the following:

a. Indicated Airspeed− The speed shown on the

aircraft airspeed indicator. This is the speed used in

pilot/controller communications under the general

term “airspeed.”

(Refer to 14 CFR Part 1.)

b. True Airspeed− The airspeed of an aircraft

relative to undisturbed air. Used primarily in flight

planning and en route portion of flight. When used in

pilot/controller communications, it is referred to as

“true airspeed” and not shortened to “airspeed.”

AIRSTART− The starting of an aircraft engine while

the aircraft is airborne, preceded by engine shutdown

during training flights or by actual engine failure.

AIRWAY− A Class E airspace area established in the

form of a corridor, the centerline of which is defined

by radio navigational aids.

(See FEDERAL AIRWAYS.)

(See ICAO term AIRWAY.)

(Refer to 14 CFR Part 71.)

(Refer to AIM.)

AIRWAY [ICAO]− A control area or portion thereof

established in the form of corridor equipped with

radio navigational aids.

AIRWAY BEACON− Used to mark airway segments

in remote mountain areas. The light flashes Morse

Code to identify the beacon site.

(Refer to AIM.)

AIT−

(See AUTOMATED INFORMATION

TRANSFER.)
Pilot/Controller Glossary 2/9/12

PCG A−10

ALERFA (Alert Phase) [ICAO]− A situation wherein

apprehension exists as to the safety of an aircraft and

its occupants.

ALERT− A notification to a position that there

is an aircraft-to-aircraft or aircraft-to-airspace

conflict, as detected by Automated Problem

Detection (APD).

ALERT AREA−

(See SPECIAL USE AIRSPACE.)

ALERT NOTICE− A request originated by a flight

service station (FSS) or an air route traffic control

center (ARTCC) for an extensive communication

search for overdue, unreported, or missing aircraft.

ALERTING SERVICE− A service provided to notify

appropriate organizations regarding aircraft in need

of search and rescue aid and assist such organizations

as required.

ALNOT−

(See ALERT NOTICE.)

ALONG−TRACK DISTANCE (ATD)− The distance

measured from a point-in-space by systems using

area navigation reference capabilities that are not

subject to slant range errors.

ALPHANUMERIC DISPLAY− Letters and numerals used to show identification, altitude, beacon code,

and other information concerning a target on a radar

display.

(See AUTOMATED RADAR TERMINAL

SYSTEMS.)

ALTERNATE AERODROME [ICAO]− An aerodrome to which an aircraft may proceed when it

becomes either impossible or inadvisable to proceed

to or to land at the aerodrome of intended landing.

Note: The aerodrome from which a flight departs

may also be an en-route or a destination alternate

aerodrome for the flight.

ALTERNATE AIRPORT− An airport at which an

aircraft may land if a landing at the intended airport

becomes inadvisable.

(See ICAO term ALTERNATE AERODROME.)

ALTIMETER SETTING− The barometric pressure

reading used to adjust a pressure altimeter for

variations in existing atmospheric pressure or to the

standard altimeter setting (29.92).

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

ALTITUDE− The height of a level, point, or object

measured in feet Above Ground Level (AGL) or from

Mean Sea Level (MSL).

(See FLIGHT LEVEL.)

a. MSL Altitude− Altitude expressed in feet

measured from mean sea level.

b. AGL Altitude− Altitude expressed in feet

measured above ground level.

c. Indicated Altitude− The altitude as shown by an

altimeter. On a pressure or barometric altimeter it is

altitude as shown uncorrected for instrument error

and uncompensated for variation from standard

atmospheric conditions.

(See ICAO term ALTITUDE.)

ALTITUDE [ICAO]− The vertical distance of a level,

a point or an object considered as a point, measured

from mean sea level (MSL).

ALTITUDE READOUT− An aircraft’s altitude,

transmitted via the Mode C transponder feature, that

is visually displayed in 100-foot increments on a

radar scope having readout capability.

(See ALPHANUMERIC DISPLAY.)

(See AUTOMATED RADAR TERMINAL

SYSTEMS.)

(Refer to AIM.)

ALTITUDE RESERVATION− Airspace utilization

under prescribed conditions normally employed for

the mass movement of aircraft or other special user

requirements which cannot otherwise be

accomplished. ALTRVs are approved by the

appropriate FAA facility.

(See AIR TRAFFIC CONTROL SYSTEM

COMMAND CENTER.)

ALTITUDE RESTRICTION− An altitude or altitudes, stated in the order flown, which are to be

maintained until reaching a specific point or time.

Altitude restrictions may be issued by ATC due to

traffic, terrain, or other airspace considerations.

ALTITUDE RESTRICTIONS ARE CANCELED−

Adherence to previously imposed altitude restrictions is no longer required during a climb or descent.

ALTRV−

(See ALTITUDE RESERVATION.)

AMVER−

(See AUTOMATED MUTUAL-ASSISTANCE

VESSEL RESCUE SYSTEM.)

APB−

(See AUTOMATED PROBLEM DETECTION

BOUNDARY.)
Pilot/Controller Glossary 2/9/12

PCG A−11

APD−

(See AUTOMATED PROBLEM DETECTION.)

APDIA−

(See AUTOMATED PROBLEM DETECTION

INHIBITED AREA.)

APPROACH CLEARANCE− Authorization by

ATC for a pilot to conduct an instrument approach.

The type of instrument approach for which a

clearance and other pertinent information is provided

in the approach clearance when required.

(See CLEARED APPROACH.)

(See INSTRUMENT APPROACH

PROCEDURE.)

(Refer to AIM.)

(Refer to 14 CFR Part 91.)

APPROACH CONTROL FACILITY− A terminal

ATC facility that provides approach control service in

a terminal area.

(See APPROACH CONTROL SERVICE.)

(See RADAR APPROACH CONTROL

FACILITY.)

APPROACH CONTROL SERVICE− Air traffic

control service provided by an approach control

facility for arriving and departing VFR/IFR aircraft

and, on occasion, en route aircraft. At some airports

not served by an approach control facility, the

ARTCC provides limited approach control service.

(See ICAO term APPROACH CONTROL

SERVICE.)

(Refer to AIM.)

APPROACH CONTROL SERVICE [ICAO]− Air

traffic control service for arriving or departing

controlled flights.

APPROACH GATE− An imaginary point used

within ATC as a basis for vectoring aircraft to the

final approach course. The gate will be established

along the final approach course 1 mile from the final

approach fix on the side away from the airport and

will be no closer than 5 miles from the landing

threshold.

APPROACH LIGHT SYSTEM−

(See AIRPORT LIGHTING.)

APPROACH SEQUENCE− The order in which

aircraft are positioned while on approach or awaiting

approach clearance.

(See LANDING SEQUENCE.)

(See ICAO term APPROACH SEQUENCE.)

APPROACH SEQUENCE [ICAO]− The order in

which two or more aircraft are cleared to approach to

land at the aerodrome.

APPROACH SPEED− The recommended speed

contained in aircraft manuals used by pilots when

making an approach to landing. This speed will vary

for different segments of an approach as well as for

aircraft weight and configuration.

APPROPRIATE ATS AUTHORITY [ICAO]− The

relevant authority designated by the State responsible

for providing air traffic services in the airspace

concerned. In the United States, the “appropriate ATS

authority” is the Program Director for Air Traffic

Planning and Procedures, ATP-1.

APPROPRIATE AUTHORITY−

a. Regarding flight over the high seas: the relevant

authority is the State of Registry.

b. Regarding flight over other than the high seas:

the relevant authority is the State having sovereignty

over the territory being overflown.

APPROPRIATE OBSTACLE CLEARANCE

MINIMUM ALTITUDE− Any of the following:

(See MINIMUM EN ROUTE IFR ALTITUDE.)

(See MINIMUM IFR ALTITUDE.)

(See MINIMUM OBSTRUCTION CLEARANCE

ALTITUDE.)

(See MINIMUM VECTORING ALTITUDE.)

APPROPRIATE TERRAIN CLEARANCE

MINIMUM ALTITUDE− Any of the following:

(See MINIMUM EN ROUTE IFR ALTITUDE.)

(See MINIMUM IFR ALTITUDE.)

(See MINIMUM OBSTRUCTION CLEARANCE

ALTITUDE.)

(See MINIMUM VECTORING ALTITUDE.)

APRON− A defined area on an airport or heliport

intended to accommodate aircraft for purposes of

loading or unloading passengers or cargo, refueling,

parking, or maintenance. With regard to seaplanes, a

ramp is used for access to the apron from the water.

(See ICAO term APRON.)

APRON [ICAO]− A defined area, on a land

aerodrome, intended to accommodate aircraft for

purposes of loading or unloading passengers, mail or

cargo, refueling, parking or maintenance.

ARC− The track over the ground of an aircraft flying

at a constant distance from a navigational aid by

reference to distance measuring equipment (DME).
Pilot/Controller Glossary 2/9/12

PCG A−12

AREA CONTROL CENTER [ICAO]− An air traffic

control facility primarily responsible for ATC

services being provided IFR aircraft during the en

route phase of flight. The U.S. equivalent facility is

an air route traffic control center (ARTCC).

AREA NAVIGATION (RNAV)− A method of

navigation which permits aircraft operation on any

desired flight path within the coverage of ground− or

space−based navigation aids or within the limits of

the capability of self-contained aids, or a combination

of these.

Note: Area navigation includes performance−

based navigation as well as other operations that

do not meet the definition of performance−based

navigation.

AREA NAVIGATION (RNAV) APPROACH

CONFIGURATION:

a. STANDARD T− An RNAV approach whose

design allows direct flight to any one of three initial

approach fixes (IAF) and eliminates the need for

procedure turns. The standard design is to align the

procedure on the extended centerline with the missed

approach point (MAP) at the runway threshold, the

final approach fix (FAF), and the initial approach/

intermediate fix (IAF/IF). The other two IAFs will be

established perpendicular to the IF.

b. MODIFIED T− An RNAV approach design for

single or multiple runways where terrain or

operational constraints do not allow for the standard

T. The “T” may be modified by increasing or

decreasing the angle from the corner IAF(s) to the IF

or by eliminating one or both corner IAFs.

c. STANDARD I− An RNAV approach design for

a single runway with both corner IAFs eliminated.

Course reversal or radar vectoring may be required at

busy terminals with multiple runways.

d. TERMINAL ARRIVAL AREA (TAA)− The

TAA is controlled airspace established in conjunction

with the Standard or Modified T and I RNAV

approach configurations. In the standard TAA, there

are three areas: straight-in, left base, and right base.

The arc boundaries of the three areas of the TAA are

published portions of the approach and allow aircraft

to transition from the en route structure direct to the

nearest IAF. TAAs will also eliminate or reduce

feeder routes, departure extensions, and procedure

turns or course reversal.

1. STRAIGHT-IN AREA− A 30NM arc

centered on the IF bounded by a straight line

extending through the IF perpendicular to the

intermediate course.

2. LEFT BASE AREA− A 30NM arc centered

on the right corner IAF. The area shares a boundary

with the straight-in area except that it extends out for

30NM from the IAF and is bounded on the other side

by a line extending from the IF through the FAF to the

arc.

3. RIGHT BASE AREA− A 30NM arc centered

on the left corner IAF. The area shares a boundary

with the straight-in area except that it extends out for

30NM from the IAF and is bounded on the other side

by a line extending from the IF through the FAF to the

arc.

ARINC− An acronym for Aeronautical Radio, Inc.,

a corporation largely owned by a group of airlines.

ARINC is licensed by the FCC as an aeronautical

station and contracted by the FAA to provide

communications support for air traffic control and

meteorological services in portions of international

airspace.

ARMY AVIATION FLIGHT INFORMATION

BULLETIN− A bulletin that provides air operation

data covering Army, National Guard, and Army

Reserve aviation activities.

ARO−

(See AIRPORT RESERVATION OFFICE.)

ARRESTING SYSTEM− A safety device consisting

of two major components, namely, engaging or

catching devices and energy absorption devices for

the purpose of arresting both tailhook and/or

nontailhook-equipped aircraft. It is used to prevent

aircraft from overrunning runways when the aircraft

cannot be stopped after landing or during aborted

takeoff. Arresting systems have various names; e.g.,

arresting gear, hook device, wire barrier cable.

(See ABORT.)

(Refer to AIM.)

ARRIVAL AIRCRAFT INTERVAL− An internally

generated program in hundredths of minutes based

upon the AAR. AAI is the desired optimum interval

between successive arrival aircraft over the vertex.

ARRIVAL CENTER− The ARTCC having jurisdiction for the impacted airport.

ARRIVAL DELAY− A parameter which specifies a

period of time in which no aircraft will be metered for

arrival at the specified airport.
Pilot/Controller Glossary 2/9/12

PCG A−13

ARRIVAL SECTOR− An operational control sector

containing one or more meter fixes.

ARRIVAL SECTOR ADVISORY LIST− An

ordered list of data on arrivals displayed at the

PVD/MDM of the sector which controls the meter

fix.

ARRIVAL SEQUENCING PROGRAM− The automated program designed to assist in sequencing

aircraft destined for the same airport.

ARRIVAL TIME− The time an aircraft touches down

on arrival.

ARSR−

(See AIR ROUTE SURVEILLANCE RADAR.)

ARTCC−

(See AIR ROUTE TRAFFIC CONTROL

CENTER.)

ARTS−

(See AUTOMATED RADAR TERMINAL

SYSTEMS.)

ASDA−

(See ACCELERATE-STOP DISTANCE

AVAILABLE.)

ASDA [ICAO]−

(See ICAO Term ACCELERATE-STOP

DISTANCE AVAILABLE.)

ASDE−

(See AIRPORT SURFACE DETECTION

EQUIPMENT.)

ASF−

(See AIRPORT STREAM FILTER.)

ASLAR−

(See AIRCRAFT SURGE LAUNCH AND

RECOVERY.)

ASP−

(See ARRIVAL SEQUENCING PROGRAM.)

ASR−

(See AIRPORT SURVEILLANCE RADAR.)

ASR APPROACH−

(See SURVEILLANCE APPROACH.)

ASSOCIATED− A radar target displaying a data

block with flight identification and altitude

information.

(See UNASSOCIATED.)

ATC−

(See AIR TRAFFIC CONTROL.)

ATC ADVISES− Used to prefix a message of

noncontrol information when it is relayed to an

aircraft by other than an air traffic controller.

(See ADVISORY.)

ATC ASSIGNED AIRSPACE− Airspace of defined

vertical/lateral limits, assigned by ATC, for the

purpose of providing air traffic segregation between

the specified activities being conducted within the

assigned airspace and other IFR air traffic.

(See SPECIAL USE AIRSPACE.)

ATC CLEARANCE−

(See AIR TRAFFIC CLEARANCE.)

ATC CLEARS− Used to prefix an ATC clearance

when it is relayed to an aircraft by other than an air

traffic controller.

ATC INSTRUCTIONS− Directives issued by air

traffic control for the purpose of requiring a pilot to

take specific actions; e.g., “Turn left heading two five

zero,” “Go around,” “Clear the runway.”

(Refer to 14 CFR Part 91.)

ATC PREFERRED ROUTE NOTIFICATION−

URET notification to the appropriate controller of the

need to determine if an ATC preferred route needs to

be applied, based on destination airport.

(See ROUTE ACTION NOTIFICATION.)

(See USER REQUEST EVALUATION TOOL.)

ATC PREFERRED ROUTES− Preferred routes that

are not automatically applied by Host.

ATC REQUESTS− Used to prefix an ATC request

when it is relayed to an aircraft by other than an air

traffic controller.

ATC SECURITY SERVICES − Communications

and security tracking provided by an ATC facility in

support of the DHS, the DOD, or other Federal

security elements in the interest of national security.

Such security services are only applicable within

designated areas. ATC security services do not

include ATC basic radar services or flight following.

ATC SECURITY SERVICES POSITION − The

position responsible for providing ATC security

services as defined. This position does not provide

ATC, IFR separation, or VFR flight following

services, but is responsible for providing security

services in an area comprising airspace assigned to

one or more ATC operating sectors. This position

may be combined with control positions.
Pilot/Controller Glossary 2/9/12

PCG A−14

ATC SECURITY TRACKING − The continuous

tracking of aircraft movement by an ATC facility in

support of the DHS, the DOD, or other security

elements for national security using radar (i.e., radar

tracking) or other means (e.g., manual tracking)

without providing basic radar services (including

traffic advisories) or other ATC services not defined

in this section.

ATCAA−

(See ATC ASSIGNED AIRSPACE.)

ATCRBS−

(See RADAR.)

ATCSCC−

(See AIR TRAFFIC CONTROL SYSTEM

COMMAND CENTER.)

ATCT−

(See TOWER.)

ATD−

(See ALONG−TRACK DISTANCE.)

ATIS−

(See AUTOMATIC TERMINAL INFORMATION

SERVICE.)

ATIS [ICAO]−

(See ICAO Term AUTOMATIC TERMINAL

INFORMATION SERVICE.)

ATS ROUTE [ICAO]− A specified route designed for

channelling the flow of traffic as necessary for the

provision of air traffic services.

Note: The term “ATS Route” is used to mean variously, airway, advisory route, controlled or

uncontrolled route, arrival or departure, etc.

AUTOLAND APPROACH− An autoland approach

is a precision instrument approach to touchdown and,

in some cases, through the landing rollout. An

autoland approach is performed by the aircraft

autopilot which is receiving position information

and/or steering commands from onboard navigation

equipment.

Note: Autoland and coupled approaches are flown

in VFR and IFR. It is common for carriers to require

their crews to fly coupled approaches and autoland

approaches (if certified) when the weather conditions are less than approximately 4,000 RVR.

(See COUPLED APPROACH.)

AUTOMATED INFORMATION TRANSFER− A

precoordinated process, specifically defined in

facility directives, during which a transfer of altitude

control and/or radar identification is accomplished

without verbal coordination between controllers

using information communicated in a full data block.

AUTOMATED MUTUAL-ASSISTANCE VESSEL

RESCUE SYSTEM− A facility which can deliver, in

a matter of minutes, a surface picture (SURPIC) of

vessels in the area of a potential or actual search and

rescue incident, including their predicted positions

and their characteristics.

(See FAAO JO 7110.65, Para 10−6−4, INFLIGHT

CONTINGENCIES.)

AUTOMATED PROBLEM DETECTION (APD)−

An Automation Processing capability that compares

trajectories in order to predict conflicts.

AUTOMATED PROBLEM DETECTION

BOUNDARY (APB)− The adapted distance beyond

a facilities boundary defining the airspace within

which URET performs conflict detection.

(See USER REQUEST EVALUATION TOOL.)

AUTOMATED PROBLEM DETECTION INHIBITED AREA (APDIA)− Airspace surrounding a

terminal area within which APD is inhibited for all

flights within that airspace.

AUTOMATED RADAR TERMINAL SYSTEMS

(ARTS)− A generic term for several tracking systems

included in the Terminal Automation Systems (TAS).

ARTS plus a suffix roman numeral denotes a major

modification to that system.

a. ARTS IIIA. The Radar Tracking and Beacon

Tracking Level (RT&BTL) of the modular,

programmable automated radar terminal system.

ARTS IIIA detects, tracks, and predicts primary as

well as secondary radar-derived aircraft targets. This

more sophisticated computer-driven system upgrades the existing ARTS III system by providing

improved tracking, continuous data recording, and

fail-soft capabilities.

b. Common ARTS. Includes ARTS IIE, ARTS

IIIE; and ARTS IIIE with ACD (see DTAS) which

combines functionalities of the previous ARTS

systems.

c. Programmable Indicator Data Processor

(PIDP). The PIDP is a modification to the

AN/TPX−42 interrogator system currently installed

in fixed RAPCONs. The PIDP detects, tracks, and

predicts secondary radar aircraft targets. These are

displayed by means of computer−generated symbols

and alphanumeric characters depicting flight identifi-
Pilot/Controller Glossary 2/9/12

PCG A−15

cation, aircraft altitude, ground speed, and flight plan

data. Although primary radar targets are not tracked,

they are displayed coincident with the secondary

radar targets as well as with the other symbols and

alphanumerics. The system has the capability of

interfacing with ARTCCs.

AUTOMATED WEATHER SYSTEM− Any of the

automated weather sensor platforms that collect

weather data at airports and disseminate the weather

information via radio and/or landline. The systems

currently consist of the Automated Surface Observing System (ASOS), Automated Weather Sensor

System (AWSS) and Automated Weather Observation System (AWOS).

AUTOMATED UNICOM− Provides completely

automated weather, radio check capability and airport

advisory information on an Automated UNICOM

system. These systems offer a variety of features,

typically selectable by microphone clicks, on the

UNICOM frequency. Availability will be published

in the Airport/Facility Directory and approach charts.

AUTOMATIC ALTITUDE REPORT−

(See ALTITUDE READOUT.)

AUTOMATIC ALTITUDE REPORTING− That

function of a transponder which responds to Mode C

interrogations by transmitting the aircraft’s altitude

in 100-foot increments.

AUTOMATIC CARRIER LANDING SYSTEM−

U.S. Navy final approach equipment consisting of

precision tracking radar coupled to a computer data

link to provide continuous information to the aircraft,

monitoring capability to the pilot, and a backup

approach system.

AUTOMATIC DEPENDENT SURVEILLANCE

(ADS) [ICAO]− A surveillance technique in which

aircraft automatically provide, via a data link, data

derived from on−board navigation and position

fixing systems, including aircraft identification, four

dimensional position and additional data as

appropriate.

AUTOMATIC DEPENDENT SURVEILLANCE−

BROADCAST (ADS-B)− A surveillance system in

which an aircraft or vehicle to be detected is fitted

with cooperative equipment in the form of a data link

transmitter. The aircraft or vehicle periodically

broadcasts its GPS−derived position and other

information such as velocity over the data link, which

is received by a ground−based transmitter/receiver

(transceiver) for processing and display at an air

traffic control facility.

(See GLOBAL POSITIONING SYSTEM.)

(See GROUND−BASED TRANSCEIVER.)

AUTOMATIC DEPENDENT SURVEILLANCE−

CONTRACT (ADS−C)− A data link position

reporting system, controlled by a ground station, that

establishes contracts with an aircraft’s avionics that

occur automatically whenever specific events occur,

or specific time intervals are reached.

AUTOMATIC DIRECTION FINDER− An aircraft

radio navigation system which senses and indicates

the direction to a L/MF nondirectional radio beacon

(NDB) ground transmitter. Direction is indicated to

the pilot as a magnetic bearing or as a relative bearing

to the longitudinal axis of the aircraft depending on

the type of indicator installed in the aircraft. In certain

applications, such as military, ADF operations may

be based on airborne and ground transmitters in the

VHF/UHF frequency spectrum.

(See BEARING.)

(See NONDIRECTIONAL BEACON.)

AUTOMATIC FLIGHT INFORMATION

SERVICE (AFIS) − ALASKA FSSs ONLY− The

continuous broadcast of recorded non−control

information at airports in Alaska where a FSS

provides local airport advisory service. The AFIS

broadcast automates the repetitive transmission of

essential but routine information such as weather,

wind, altimeter, favored runway, breaking action,

airport NOTAMs, and other applicable information.

The information is continuously broadcast over a

discrete VHF radio frequency (usually the ASOS/

AWSS/AWOS frequency.)

AUTOMATIC TERMINAL INFORMATION

SERVICE− The continuous broadcast of recorded

noncontrol information in selected terminal areas. Its

purpose is to improve controller effectiveness and to

relieve frequency congestion by automating the

repetitive transmission of essential but routine

information; e.g., “Los Angeles information Alfa.

One three zero zero Coordinated Universal Time.

Weather, measured ceiling two thousand overcast,

visibility three, haze, smoke, temperature seven one,

dew point five seven, wind two five zero at five,

altimeter two niner niner six. I-L-S Runway Two Five
Pilot/Controller Glossary 2/9/12

PCG A−16

Left approach in use, Runway Two Five Right closed,

advise you have Alfa.”

(See ICAO term AUTOMATIC TERMINAL

INFORMATION SERVICE.)

(Refer to AIM.)

AUTOMATIC TERMINAL INFORMATION

SERVICE [ICAO]− The provision of current, routine

information to arriving and departing aircraft by

means of continuous and repetitive broadcasts

throughout the day or a specified portion of the day.

AUTOROTATION− A rotorcraft flight condition in

which the lifting rotor is driven entirely by action of

the air when the rotorcraft is in motion.

a. Autorotative Landing/Touchdown Autorotation. Used by a pilot to indicate that the landing will

be made without applying power to the rotor.

b. Low Level Autorotation. Commences at an

altitude well below the traffic pattern, usually below

100 feet AGL and is used primarily for tactical

military training.

c. 180 degrees Autorotation. Initiated from a

downwind heading and is commenced well inside the

normal traffic pattern. “Go around” may not be

possible during the latter part of this maneuver.

AVAILABLE LANDING DISTANCE (ALD)− The

portion of a runway available for landing and roll-out

for aircraft cleared for LAHSO. This distance is

measured from the landing threshold to the

hold-short point.

AVIATION WEATHER SERVICE− A service

provided by the National Weather Service (NWS) and

FAA which collects and disseminates pertinent

weather information for pilots, aircraft operators, and

ATC. Available aviation weather reports and

forecasts are displayed at each NWS office and FAA

FSS.

(See EN ROUTE FLIGHT ADVISORY

SERVICE.)

(See TRANSCRIBED WEATHER BROADCAST.)

(See WEATHER ADVISORY.)

(Refer to AIM.)

AWW−

(See SEVERE WEATHER FORECAST

ALERTS.)

AZIMUTH (MLS)− A magnetic bearing extending

from an MLS navigation facility.

Note: Azimuth bearings are described as magnetic

and are referred to as “azimuth” in radio telephone

communications.
Pilot/Controller Glossary 2/9/12

PCG B−1

B

BACK-TAXI− A term used by air traffic controllers

to taxi an aircraft on the runway opposite to the traffic

flow. The aircraft may be instructed to back-taxi to

the beginning of the runway or at some point before

reaching the runway end for the purpose of departure

or to exit the runway.

BASE LEG−

(See TRAFFIC PATTERN.)

BEACON−

(See AERONAUTICAL BEACON.)

(See AIRPORT ROTATING BEACON.)

(See AIRWAY BEACON.)

(See MARKER BEACON.)

(See NONDIRECTIONAL BEACON.)

(See RADAR.)

BEARING− The horizontal direction to or from any

point, usually measured clockwise from true north,

magnetic north, or some other reference point

through 360 degrees.

(See NONDIRECTIONAL BEACON.)

BELOW MINIMUMS− Weather conditions below

the minimums prescribed by regulation for the

particular action involved; e.g., landing minimums,

takeoff minimums.

BLAST FENCE− A barrier that is used to divert or

dissipate jet or propeller blast.

BLAST PAD− A surface adjacent to the ends of a

runway provided to reduce the erosive effect of jet

blast and propeller wash.

BLIND SPEED− The rate of departure or closing of

a target relative to the radar antenna at which

cancellation of the primary radar target by moving

target indicator (MTI) circuits in the radar equipment

causes a reduction or complete loss of signal.

(See ICAO term BLIND VELOCITY.)

BLIND SPOT− An area from which radio

transmissions and/or radar echoes cannot be

received. The term is also used to describe portions

of the airport not visible from the control tower.

BLIND TRANSMISSION−

(See TRANSMITTING IN THE BLIND.)

BLIND VELOCITY [ICAO]− The radial velocity of

a moving target such that the target is not seen on

primary radars fitted with certain forms of fixed echo

suppression.

BLIND ZONE−

(See BLIND SPOT.)

BLOCKED− Phraseology used to indicate that a

radio transmission has been distorted or interrupted

due to multiple simultaneous radio transmissions.

BOUNDARY LIGHTS−

(See AIRPORT LIGHTING.)

BRAKING ACTION (GOOD, FAIR, POOR, OR

NIL)− A report of conditions on the airport

movement area providing a pilot with a degree/

quality of braking that he/she might expect. Braking

action is reported in terms of good, fair, poor, or nil.

(See RUNWAY CONDITION READING.)

BRAKING ACTION ADVISORIES− When tower

controllers have received runway braking action

reports which include the terms “fair,” “poor,” or

“nil,” or whenever weather conditions are conducive

to deteriorating or rapidly changing runway braking

conditions, the tower will include on the ATIS

broadcast the statement, “Braking action advisories

are in effect” on the ATIS broadcast. During the time

braking action advisories are in effect, ATC will issue

the latest braking action report for the runway in use

to each arriving and departing aircraft. Pilots should

be prepared for deteriorating braking conditions and

should request current runway condition information

if not volunteered by controllers. Pilots should also

be prepared to provide a descriptive runway

condition report to controllers after landing.

BREAKOUT− A technique to direct aircraft out of

the approach stream. In the context of close parallel

operations, a breakout is used to direct threatened

aircraft away from a deviating aircraft.

BROADCAST− Transmission of information for

which an acknowledgement is not expected.

(See ICAO term BROADCAST.)

BROADCAST [ICAO]− A transmission of information relating to air navigation that is not addressed to

a specific station or stations.

Pilot/Controller Glossary 2/9/12

PCG C−1

C

CALCULATED LANDING TIME− A term that may

be used in place of tentative or actual calculated

landing time, whichever applies.

CALL FOR RELEASE− Wherein the overlying

ARTCC requires a terminal facility to initiate verbal

coordination to secure ARTCC approval for release

of a departure into the en route environment.

CALL UP− Initial voice contact between a facility

and an aircraft, using the identification of the unit

being called and the unit initiating the call.

(Refer to AIM.)

CANADIAN MINIMUM NAVIGATION PERFORMANCE SPECIFICATION AIRSPACE− That

portion of Canadian domestic airspace within which

MNPS separation may be applied.

CARDINAL ALTITUDES− “Odd” or “Even”

thousand-foot altitudes or flight levels; e.g., 5,000,

6,000, 7,000, FL 250, FL 260, FL 270.

(See ALTITUDE.)

(See FLIGHT LEVEL.)

CARDINAL FLIGHT LEVELS−

(See CARDINAL ALTITUDES.)

CAT−

(See CLEAR-AIR TURBULENCE.)

CATCH POINT− A fix/waypoint that serves as a

transition point from the high altitude waypoint

navigation structure to an arrival procedure (STAR)

or the low altitude ground−based navigation

structure.

CEILING− The heights above the earth’s surface of

the lowest layer of clouds or obscuring phenomena

that is reported as “broken,” “overcast,” or

“obscuration,” and not classified as “thin” or

“partial.”

(See ICAO term CEILING.)

CEILING [ICAO]− The height above the ground or

water of the base of the lowest layer of cloud below

6,000 meters (20,000 feet) covering more than half

the sky.

CENRAP−

(See CENTER RADAR ARTS

PRESENTATION/PROCESSING.)

CENRAP-PLUS−

(See CENTER RADAR ARTS

PRESENTATION/PROCESSING-PLUS.)

CENTER−

(See AIR ROUTE TRAFFIC CONTROL

CENTER.)

CENTER’S AREA− The specified airspace within

which an air route traffic control center (ARTCC)

provides air traffic control and advisory service.

(See AIR ROUTE TRAFFIC CONTROL

CENTER.)

(Refer to AIM.)

CENTER RADAR ARTS PRESENTATION/

PROCESSING− A computer program developed to

provide a back-up system for airport surveillance

radar in the event of a failure or malfunction. The

program uses air route traffic control center radar for

the processing and presentation of data on the ARTS

IIA or IIIA displays.

CENTER RADAR ARTS PRESENTATION/

PROCESSING-PLUS− A computer program

developed to provide a back-up system for airport

surveillance radar in the event of a terminal secondary

radar system failure. The program uses a combination

of Air Route Traffic Control Center Radar and

terminal airport surveillance radar primary targets

displayed simultaneously for the processing and

presentation of data on the ARTS IIA or IIIA

displays.

CENTER TRACON AUTOMATION SYSTEM

(CTAS)− A computerized set of programs designed

to aid Air Route Traffic Control Centers and

TRACONs in the management and control of air

traffic.

CENTER WEATHER ADVISORY− An unscheduled weather advisory issued by Center Weather

Service Unit meteorologists for ATC use to alert

pilots of existing or anticipated adverse weather

conditions within the next 2 hours. A CWA may

modify or redefine a SIGMET.

(See AWW.)

(See AIRMET.)

(See CONVECTIVE SIGMET.)

(See SIGMET.)

(Refer to AIM.)
Pilot/Controller Glossary 2/9/12

PCG C−2

CENTRAL EAST PACIFIC− An organized route

system between the U.S. West Coast and Hawaii.

CEP−

(See CENTRAL EAST PACIFIC.)

CERAP−

(See COMBINED CENTER-RAPCON.)

CERTIFIED TOWER RADAR DISPLAY (CTRD)−

A FAA radar display certified for use in the NAS.

CFR−

(See CALL FOR RELEASE.)

CHAFF− Thin, narrow metallic reflectors of various

lengths and frequency responses, used to reflect radar

energy. These reflectors when dropped from aircraft

and allowed to drift downward result in large targets

on the radar display.

CHARTED VFR FLYWAYS− Charted VFR Flyways are flight paths recommended for use to bypass

areas heavily traversed by large turbine-powered

aircraft. Pilot compliance with recommended

flyways and associated altitudes is strictly voluntary.

VFR Flyway Planning charts are published on the

back of existing VFR Terminal Area charts.

CHARTED VISUAL FLIGHT PROCEDURE

APPROACH− An approach conducted while

operating on an instrument flight rules (IFR) flight

plan which authorizes the pilot of an aircraft to

proceed visually and clear of clouds to the airport via

visual landmarks and other information depicted on

a charted visual flight procedure. This approach must

be authorized and under the control of the appropriate

air traffic control facility. Weather minimums

required are depicted on the chart.

CHASE− An aircraft flown in proximity to another

aircraft normally to observe its performance during

training or testing.

CHASE AIRCRAFT−

(See CHASE.)

CIRCLE-TO-LAND MANEUVER− A maneuver

initiated by the pilot to align the aircraft with a

runway for landing when a straight-in landing from

an instrument approach is not possible or is not

desirable. At tower controlled airports, this maneuver

is made only after ATC authorization has been

obtained and the pilot has established required visual

reference to the airport.

(See CIRCLE TO RUNWAY.)

(See LANDING MINIMUMS.)

(Refer to AIM.)

CIRCLE TO RUNWAY (RUNWAY NUMBER)−

Used by ATC to inform the pilot that he/she must

circle to land because the runway in use is other than

the runway aligned with the instrument approach

procedure. When the direction of the circling

maneuver in relation to the airport/runway is

required, the controller will state the direction (eight

cardinal compass points) and specify a left or right

downwind or base leg as appropriate; e.g., “Cleared

VOR Runway Three Six Approach circle to Runway

Two Two,” or “Circle northwest of the airport for a

right downwind to Runway Two Two.”

(See CIRCLE-TO-LAND MANEUVER.)

(See LANDING MINIMUMS.)

(Refer to AIM.)

CIRCLING APPROACH−

(See CIRCLE-TO-LAND MANEUVER.)

CIRCLING MANEUVER−

(See CIRCLE-TO-LAND MANEUVER.)

CIRCLING MINIMA−

(See LANDING MINIMUMS.)

CLASS A AIRSPACE−

(See CONTROLLED AIRSPACE.)

CLASS B AIRSPACE−

(See CONTROLLED AIRSPACE.)

CLASS C AIRSPACE−

(See CONTROLLED AIRSPACE.)

CLASS D AIRSPACE−

(See CONTROLLED AIRSPACE.)

CLASS E AIRSPACE−

(See CONTROLLED AIRSPACE.)

CLASS G AIRSPACE− That airspace not designated

as Class A, B, C, D or E.

CLEAR AIR TURBULENCE (CAT)− Turbulence

encountered in air where no clouds are present. This

term is commonly applied to high-level turbulence

associated with wind shear. CAT is often encountered

in the vicinity of the jet stream.

(See WIND SHEAR.)

(See JET STREAM.)

CLEAR OF THE RUNWAY−

a. Taxiing aircraft, which is approaching a

runway, is clear of the runway when all parts of the
Pilot/Controller Glossary 2/9/12

PCG C−3

aircraft are held short of the applicable runway

holding position marking.

b. A pilot or controller may consider an aircraft,

which is exiting or crossing a runway, to be clear of

the runway when all parts of the aircraft are beyond

the runway edge and there are no restrictions to its

continued movement beyond the applicable runway

holding position marking.

c. Pilots and controllers shall exercise good

judgement to ensure that adequate separation exists

between all aircraft on runways and taxiways at

airports with inadequate runway edge lines or

holding position markings.

CLEARANCE−

(See AIR TRAFFIC CLEARANCE.)

CLEARANCE LIMIT− The fix, point, or location to

which an aircraft is cleared when issued an air traffic

clearance.

(See ICAO term CLEARANCE LIMIT.)

CLEARANCE LIMIT [ICAO]− The point to which

an aircraft is granted an air traffic control clearance.

CLEARANCE VOID IF NOT OFF BY (TIME)−

Used by ATC to advise an aircraft that the departure

clearance is automatically canceled if takeoff is not

made prior to a specified time. The pilot must obtain

a new clearance or cancel his/her IFR flight plan if not

off by the specified time.

(See ICAO term CLEARANCE VOID TIME.)

CLEARANCE VOID TIME [ICAO]− A time

specified by an air traffic control unit at which a

clearance ceases to be valid unless the aircraft

concerned has already taken action to comply

therewith.

CLEARED APPROACH− ATC authorization for an

aircraft to execute any standard or special instrument

approach procedure for that airport. Normally, an

aircraft will be cleared for a specific instrument

approach procedure.

(See CLEARED (Type of) APPROACH.)

(See INSTRUMENT APPROACH

PROCEDURE.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

CLEARED (Type of) APPROACH− ATC authorization for an aircraft to execute a specific instrument

approach procedure to an airport; e.g., “Cleared ILS

Runway Three Six Approach.”

(See APPROACH CLEARANCE.)

(See INSTRUMENT APPROACH

PROCEDURE.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

CLEARED AS FILED− Means the aircraft is cleared

to proceed in accordance with the route of flight filed

in the flight plan. This clearance does not include the

altitude, DP, or DP Transition.

(See REQUEST FULL ROUTE CLEARANCE.)

(Refer to AIM.)

CLEARED FOR TAKEOFF− ATC authorization

for an aircraft to depart. It is predicated on known

traffic and known physical airport conditions.

CLEARED FOR THE OPTION− ATC authorization for an aircraft to make a touch-and-go, low

approach, missed approach, stop and go, or full stop

landing at the discretion of the pilot. It is normally

used in training so that an instructor can evaluate a

student’s performance under changing situations.

(See OPTION APPROACH.)

(Refer to AIM.)

CLEARED THROUGH− ATC authorization for an

aircraft to make intermediate stops at specified

airports without refiling a flight plan while en route

to the clearance limit.

CLEARED TO LAND− ATC authorization for an

aircraft to land. It is predicated on known traffic and

known physical airport conditions.

CLEARWAY− An area beyond the takeoff runway

under the control of airport authorities within which

terrain or fixed obstacles may not extend above

specified limits. These areas may be required for

certain turbine-powered operations and the size and

upward slope of the clearway will differ depending on

when the aircraft was certificated.

(Refer to 14 CFR Part 1.)

CLIMB TO VFR− ATC authorization for an aircraft

to climb to VFR conditions within Class B, C, D, and

E surface areas when the only weather limitation is

restricted visibility. The aircraft must remain clear of

clouds while climbing to VFR.

(See SPECIAL VFR CONDITIONS.)

(Refer to AIM.)

CLIMBOUT− That portion of flight operation

between takeoff and the initial cruising altitude.
Pilot/Controller Glossary 2/9/12

PCG C−4

CLOSE PARALLEL RUNWAYS− Two parallel

runways whose extended centerlines are separated by

less than 4,300 feet, having a Precision Runway

Monitoring (PRM) system that permits simultaneous

independent ILS approaches.

CLOSED RUNWAY− A runway that is unusable for

aircraft operations. Only the airport management/

military operations office can close a runway.

CLOSED TRAFFIC− Successive operations involving takeoffs and landings or low approaches where

the aircraft does not exit the traffic pattern.

CLOUD− A cloud is a visible accumulation of

minute water droplets and/or ice particles in the

atmosphere above the Earth’s surface. Cloud differs

from ground fog, fog, or ice fog only in that the latter

are, by definition, in contact with the Earth’s surface.

CLT−

(See CALCULATED LANDING TIME.)

CLUTTER− In radar operations, clutter refers to the

reception and visual display of radar returns caused

by precipitation, chaff, terrain, numerous aircraft

targets, or other phenomena. Such returns may limit

or preclude ATC from providing services based on

radar.

(See CHAFF.)

(See GROUND CLUTTER.)

(See PRECIPITATION.)

(See TARGET.)

(See ICAO term RADAR CLUTTER.)

CMNPS−

(See CANADIAN MINIMUM NAVIGATION

PERFORMANCE SPECIFICATION AIRSPACE.)

COASTAL FIX− A navigation aid or intersection

where an aircraft transitions between the domestic

route structure and the oceanic route structure.

CODES− The number assigned to a particular

multiple pulse reply signal transmitted by a

transponder.

(See DISCRETE CODE.)

COMBINED CENTER-RAPCON− An air traffic

facility which combines the functions of an ARTCC

and a radar approach control facility.

(See AIR ROUTE TRAFFIC CONTROL

CENTER.)

(See RADAR APPROACH CONTROL

FACILITY.)

COMMON POINT− A significant point over which

two or more aircraft will report passing or have

reported passing before proceeding on the same or

diverging tracks. To establish/maintain longitudinal

separation, a controller may determine a common

point not originally in the aircraft’s flight plan and

then clear the aircraft to fly over the point.

(See SIGNIFICANT POINT.)

COMMON PORTION−

(See COMMON ROUTE.)

COMMON ROUTE− That segment of a North

American Route between the inland navigation

facility and the coastal fix.

OR

COMMON ROUTE− Typically the portion of a

RNAV STAR between the en route transition end

point and the runway transition start point; however,

the common route may only consist of a single point

that joins the en route and runway transitions.

COMMON TRAFFIC ADVISORY FREQUENCY

(CTAF)− A frequency designed for the purpose of

carrying out airport advisory practices while

operating to or from an airport without an operating

control tower. The CTAF may be a UNICOM,

Multicom, FSS, or tower frequency and is identified

in appropriate aeronautical publications.

(Refer to AC 90-42, Traffic Advisory Practices at

Airports Without Operating Control Towers.)

COMPASS LOCATOR− A low power, low or

medium frequency (L/MF) radio beacon installed at

the site of the outer or middle marker of an instrument

landing system (ILS). It can be used for navigation at

distances of approximately 15 miles or as authorized

in the approach procedure.

a. Outer Compass Locator (LOM)− A compass

locator installed at the site of the outer marker of an

instrument landing system.

(See OUTER MARKER.)

b. Middle Compass Locator (LMM)− A compass

locator installed at the site of the middle marker of an

instrument landing system.

(See MIDDLE MARKER.)

(See ICAO term LOCATOR.)

COMPASS ROSE− A circle, graduated in degrees,

printed on some charts or marked on the ground at an

airport. It is used as a reference to either true or

magnetic direction.

COMPLY WITH RESTRICTIONS− An ATC

instruction that requires an aircraft being vectored
Pilot/Controller Glossary 2/9/12

PCG C−5

back onto an arrival or departure procedure to comply

with all altitude and/or speed restrictions depicted on

the procedure. This term may be used in lieu of

repeating each remaining restriction that appears on

the procedure.

COMPOSITE FLIGHT PLAN− A flight plan which

specifies VFR operation for one portion of flight and

IFR for another portion. It is used primarily in

military operations.

(Refer to AIM.)

COMPOSITE ROUTE SYSTEM− An organized

oceanic route structure, incorporating reduced lateral

spacing between routes, in which composite

separation is authorized.

COMPOSITE SEPARATION− A method of separating aircraft in a composite route system where, by

management of route and altitude assignments, a

combination of half the lateral minimum specified for

the area concerned and half the vertical minimum is

applied.

COMPULSORY REPORTING POINTS− Reporting

points which must be reported to ATC. They are

designated on aeronautical charts by solid triangles or

filed in a flight plan as fixes selected to define direct

routes. These points are geographical locations

which are defined by navigation aids/fixes. Pilots

should discontinue position reporting over compulsory reporting points when informed by ATC that

their aircraft is in “radar contact.”

CONFIDENCE MANEUVER− A confidence maneuver consists of one or more turns, a climb or

descent, or other maneuver to determine if the pilot

in command (PIC) is able to receive and comply with

ATC instructions.

CONFLICT ALERT− A function of certain air traffic

control automated systems designed to alert radar

controllers to existing or pending situations between

tracked targets (known IFR or VFR aircraft) that

require his/her immediate attention/action.

(See MODE C INTRUDER ALERT.)

CONFLICT RESOLUTION− The resolution of

potential conflictions between aircraft that are radar

identified and in communication with ATC by

ensuring that radar targets do not touch. Pertinent

traffic advisories shall be issued when this procedure

is applied.

Note: This procedure shall not be provided utilizing

mosaic radar systems.

CONFORMANCE− The condition established when

an aircraft’s actual position is within the conformance

region constructed around that aircraft at its position,

according to the trajectory associated with the

aircraft’s Current Plan.

CONFORMANCE REGION− A volume, bounded

laterally, vertically, and longitudinally, within which

an aircraft must be at a given time in order to be in

conformance with the Current Plan Trajectory for that

aircraft. At a given time, the conformance region is

determined by the simultaneous application of the

lateral, vertical, and longitudinal conformance

bounds for the aircraft at the position defined by time

and aircraft’s trajectory.

CONSOLAN− A low frequency, long-distance

NAVAID used principally for transoceanic navigations.

CONTACT−

a. Establish communication with (followed by the

name of the facility and, if appropriate, the frequency

to be used).

b. A flight condition wherein the pilot ascertains

the attitude of his/her aircraft and navigates by visual

reference to the surface.

(See CONTACT APPROACH.)

(See RADAR CONTACT.)

CONTACT APPROACH− An approach wherein an

aircraft on an IFR flight plan, having an air traffic

control authorization, operating clear of clouds with

at least 1 mile flight visibility and a reasonable

expectation of continuing to the destination airport in

those conditions, may deviate from the instrument

approach procedure and proceed to the destination

airport by visual reference to the surface. This

approach will only be authorized when requested by

the pilot and the reported ground visibility at the

destination airport is at least 1 statute mile.

(Refer to AIM.)

CONTAMINATED RUNWAY− A runway is

considered contaminated whenever standing water,

ice, snow, slush, frost in any form, heavy rubber, or

other substances are present. A runway is contaminated with respect to rubber deposits or other

friction-degrading substances when the average
Pilot/Controller Glossary 2/9/12

PCG C−6

friction value for any 500-foot segment of the runway

within the ALD fails below the recommended

minimum friction level and the average friction value

in the adjacent 500-foot segments falls below the

maintenance planning friction level.

CONTERMINOUS U.S.− The 48 adjoining States

and the District of Columbia.

CONTINENTAL UNITED STATES− The 49 States

located on the continent of North America and the

District of Columbia.

CONTINUE− When used as a control instruction

should be followed by another word or words

clarifying what is expected of the pilot. Example:

“continue taxi,” “continue descent,” “continue

inbound,” etc.

CONTROL AREA [ICAO]− A controlled airspace

extending upwards from a specified limit above the

earth.

CONTROL SECTOR− An airspace area of defined

horizontal and vertical dimensions for which a

controller or group of controllers has air traffic

control responsibility, normally within an air route

traffic control center or an approach control facility.

Sectors are established based on predominant traffic

flows, altitude strata, and controller workload.

Pilot-communications during operations within a

sector are normally maintained on discrete frequencies assigned to the sector.

(See DISCRETE FREQUENCY.)

CONTROL SLASH− A radar beacon slash representing the actual position of the associated aircraft.

Normally, the control slash is the one closest to the

interrogating radar beacon site. When ARTCC radar

is operating in narrowband (digitized) mode, the

control slash is converted to a target symbol.

CONTROLLED AIRSPACE− An airspace of

defined dimensions within which air traffic control

service is provided to IFR flights and to VFR flights

in accordance with the airspace classification.

a. Controlled airspace is a generic term that covers

Class A, Class B, Class C, Class D, and Class E

airspace.

b. Controlled airspace is also that airspace within

which all aircraft operators are subject to certain pilot

qualifications, operating rules, and equipment

requirements in 14 CFR Part 91 (for specific

operating requirements, please refer to 14 CFR

Part 91). For IFR operations in any class of controlled

airspace, a pilot must file an IFR flight plan and

receive an appropriate ATC clearance. Each Class B,

Class C, and Class D airspace area designated for an

airport contains at least one primary airport around

which the airspace is designated (for specific

designations and descriptions of the airspace classes,

please refer to 14 CFR Part 71).

c. Controlled airspace in the United States is

designated as follows:

1. CLASS A− Generally, that airspace from

18,000 feet MSL up to and including FL 600,

including the airspace overlying the waters within 12

nautical miles of the coast of the 48 contiguous States

and Alaska. Unless otherwise authorized, all persons

must operate their aircraft under IFR.

2. CLASS B− Generally, that airspace from the

surface to 10,000 feet MSL surrounding the nation’s

busiest airports in terms of airport operations or

passenger enplanements. The configuration of each

Class B airspace area is individually tailored and

consists of a surface area and two or more layers

(some Class B airspaces areas resemble upside-down

wedding cakes), and is designed to contain all

published instrument procedures once an aircraft

enters the airspace. An ATC clearance is required for

all aircraft to operate in the area, and all aircraft that

are so cleared receive separation services within the

airspace. The cloud clearance requirement for VFR

operations is “clear of clouds.”

3. CLASS C− Generally, that airspace from the

surface to 4,000 feet above the airport elevation

(charted in MSL) surrounding those airports that

have an operational control tower, are serviced by a

radar approach control, and that have a certain

number of IFR operations or passenger enplanements. Although the configuration of each Class C

area is individually tailored, the airspace usually

consists of a surface area with a 5 nautical mile (NM)

radius, a circle with a 10NM radius that extends no

lower than 1,200 feet up to 4,000 feet above the

airport elevation and an outer area that is not charted.

Each person must establish two-way radio communications with the ATC facility providing air traffic

services prior to entering the airspace and thereafter

maintain those communications while within the

airspace. VFR aircraft are only separated from IFR

aircraft within the airspace.

(See OUTER AREA.)
Pilot/Controller Glossary 2/9/12

PCG C−7

4. CLASS D− Generally, that airspace from the

surface to 2,500 feet above the airport elevation

(charted in MSL) surrounding those airports that

have an operational control tower. The configuration

of each Class D airspace area is individually tailored

and when instrument procedures are published, the

airspace will normally be designed to contain the

procedures. Arrival extensions for instrument

approach procedures may be Class D or Class E

airspace. Unless otherwise authorized, each person

must establish two-way radio communications with

the ATC facility providing air traffic services prior to

entering the airspace and thereafter maintain those

communications while in the airspace. No separation

services are provided to VFR aircraft.

5. CLASS E− Generally, if the airspace is not

Class A, Class B, Class C, or Class D, and it is

controlled airspace, it is Class E airspace. Class E

airspace extends upward from either the surface or a

designated altitude to the overlying or adjacent

controlled airspace. When designated as a surface

area, the airspace will be configured to contain all

instrument procedures. Also in this class are Federal

airways, airspace beginning at either 700 or 1,200

feet AGL used to transition to/from the terminal or en

route environment, en route domestic, and offshore

airspace areas designated below 18,000 feet MSL.

Unless designated at a lower altitude, Class E

airspace begins at 14,500 MSL over the United

States, including that airspace overlying the waters

within 12 nautical miles of the coast of the 48

contiguous States and Alaska, up to, but not

including 18,000 feet MSL, and the airspace above

FL 600.

CONTROLLED AIRSPACE [ICAO]− An airspace

of defined dimensions within which air traffic control

service is provided to IFR flights and to VFR flights

in accordance with the airspace classification.

Note: Controlled airspace is a generic term which

covers ATS airspace Classes A, B, C, D, and E.

CONTROLLED TIME OF ARRIVAL− Arrival time

assigned during a Traffic Management Program. This

time may be modified due to adjustments or user

options.

CONTROLLER−

(See AIR TRAFFIC CONTROL SPECIALIST.)

CONTROLLER [ICAO]− A person authorized to

provide air traffic control services.

CONTROLLER PILOT DATA LINK COMMUNICATIONS (CPDLC)− A two−way digital very

high frequency (VHF) air/ground communications

system that conveys textual air traffic control

messages between controllers and pilots.

CONVECTIVE SIGMET− A weather advisory

concerning convective weather significant to the

safety of all aircraft. Convective SIGMETs are issued

for tornadoes, lines of thunderstorms, embedded

thunderstorms of any intensity level, areas of

thunderstorms greater than or equal to VIP level 4

with an area coverage of 4/10 (40%) or more, and hail

3/4 inch or greater.

(See AIRMET.)

(See AWW.)

(See CWA.)

(See SIGMET.)

(Refer to AIM.)

CONVECTIVE SIGNIFICANT METEOROLOGICAL INFORMATION−

(See CONVECTIVE SIGMET.)

COORDINATES− The intersection of lines of

reference, usually expressed in degrees/minutes/

seconds of latitude and longitude, used to determine

position or location.

COORDINATION FIX− The fix in relation to which

facilities will handoff, transfer control of an aircraft,

or coordinate flight progress data. For terminal

facilities, it may also serve as a clearance for arriving

aircraft.

COPTER−

(See HELICOPTER.)

CORRECTION− An error has been made in the

transmission and the correct version follows.

COUPLED APPROACH− A coupled approach is an

instrument approach performed by the aircraft

autopilot which is receiving position information

and/or steering commands from onboard navigation

equipment. In general, coupled nonprecision approaches must be discontinued and flown manually

at altitudes lower than 50 feet below the minimum

descent altitude, and coupled precision approaches

must be flown manually below 50 feet AGL.

Note: Coupled and autoland approaches are flown

in VFR and IFR. It is common for carriers to require
Pilot/Controller Glossary 2/9/12

PCG C−8

their crews to fly coupled approaches and autoland

approaches (if certified) when the weather

conditions are less than approximately 4,000 RVR.

(See AUTOLAND APPROACH.)

COURSE−

a. The intended direction of flight in the horizontal

plane measured in degrees from north.

b. The ILS localizer signal pattern usually

specified as the front course or the back course.

c. The intended track along a straight, curved, or

segmented MLS path.

(See BEARING.)

(See INSTRUMENT LANDING SYSTEM.)

(See MICROWAVE LANDING SYSTEM.)

(See RADIAL.)

CPDLC−

(See CONTROLLER PILOT DATA LINK

COMMUNICATIONS.)

CPL [ICAO]−

(See ICAO term CURRENT FLIGHT PLAN.)

CRITICAL ENGINE− The engine which, upon

failure, would most adversely affect the performance

or handling qualities of an aircraft.

CROSS (FIX) AT (ALTITUDE)− Used by ATC

when a specific altitude restriction at a specified fix

is required.

CROSS (FIX) AT OR ABOVE (ALTITUDE)− Used

by ATC when an altitude restriction at a specified fix

is required. It does not prohibit the aircraft from

crossing the fix at a higher altitude than specified;

however, the higher altitude may not be one that will

violate a succeeding altitude restriction or altitude

assignment.

(See ALTITUDE RESTRICTION.)

(Refer to AIM.)

CROSS (FIX) AT OR BELOW (ALTITUDE)−

Used by ATC when a maximum crossing altitude at

a specific fix is required. It does not prohibit the

aircraft from crossing the fix at a lower altitude;

however, it must be at or above the minimum IFR

altitude.

(See ALTITUDE RESTRICTION.)

(See MINIMUM IFR ALTITUDES.)

(Refer to 14 CFR Part 91.)

CROSSWIND−

a. When used concerning the traffic pattern, the

word means “crosswind leg.”

(See TRAFFIC PATTERN.)

b. When used concerning wind conditions, the

word means a wind not parallel to the runway or the

path of an aircraft.

(See CROSSWIND COMPONENT.)

CROSSWIND COMPONENT− The wind component measured in knots at 90 degrees to the

longitudinal axis of the runway.

CRUISE− Used in an ATC clearance to authorize a

pilot to conduct flight at any altitude from the

minimum IFR altitude up to and including the

altitude specified in the clearance. The pilot may

level off at any intermediate altitude within this block

of airspace. Climb/descent within the block is to be

made at the discretion of the pilot. However, once the

pilot starts descent and verbally reports leaving an

altitude in the block, he/she may not return to that

altitude without additional ATC clearance. Further, it

is approval for the pilot to proceed to and make an

approach at destination airport and can be used in

conjunction with:

a. An airport clearance limit at locations with a

standard/special instrument approach procedure. The

CFRs require that if an instrument letdown to an

airport is necessary, the pilot shall make the letdown

in accordance with a standard/special instrument

approach procedure for that airport, or

b. An airport clearance limit at locations that are

within/below/outside controlled airspace and without a standard/special instrument approach

procedure. Such a clearance is NOT AUTHORIZATION for the pilot to descend under IFR conditions

below the applicable minimum IFR altitude nor does

it imply that ATC is exercising control over aircraft

in Class G airspace; however, it provides a means for

the aircraft to proceed to destination airport, descend,

and land in accordance with applicable CFRs

governing VFR flight operations. Also, this provides

search and rescue protection until such time as the

IFR flight plan is closed.

(See INSTRUMENT APPROACH

PROCEDURE.)

CRUISE CLIMB− A climb technique employed by

aircraft, usually at a constant power setting, resulting

in an increase of altitude as the aircraft weight

decreases.
Pilot/Controller Glossary 2/9/12

PCG C−9

CRUISING ALTITUDE− An altitude or flight level

maintained during en route level flight. This is a

constant altitude and should not be confused with a

cruise clearance.

(See ALTITUDE.)

(See ICAO term CRUISING LEVEL.)

CRUISING LEVEL−

(See CRUISING ALTITUDE.)

CRUISING LEVEL [ICAO]− A level maintained

during a significant portion of a flight.

CT MESSAGE− An EDCT time generated by the

ATCSCC to regulate traffic at arrival airports.

Normally, a CT message is automatically transferred

from the traffic management system computer to the

NAS en route computer and appears as an EDCT. In

the event of a communication failure between the

traffic management system computer and the NAS,

the CT message can be manually entered by the TMC

at the en route facility.

CTA−

(See CONTROLLED TIME OF ARRIVAL.)

(See ICAO term CONTROL AREA.)

CTAF−

(See COMMON TRAFFIC ADVISORY

FREQUENCY.)

CTAS−

(See CENTER TRACON AUTOMATION

SYSTEM.)

CTRD−

(See CERTIFIED TOWER RADAR DISPLAY.)

CURRENT FLIGHT PLAN [ICAO]− The flight

plan, including changes, if any, brought about by

subsequent clearances.

CURRENT PLAN− The ATC clearance the aircraft

has received and is expected to fly.

CVFP APPROACH−

(See CHARTED VISUAL FLIGHT PROCEDURE

APPROACH.)

CWA−

(See CENTER WEATHER ADVISORY and

WEATHER ADVISORY.)

Pilot/Controller Glossary 2/9/12

PCG D−1

D

D-ATIS−

(See DIGITAL-AUTOMATIC TERMINAL

INFORMATION SERVICE.)

DA [ICAO]−

(See ICAO Term DECISION

ALTITUDE/DECISION HEIGHT.)

DAIR−

(See DIRECT ALTITUDE AND IDENTITY

READOUT.)

DANGER AREA [ICAO]− An airspace of defined

dimensions within which activities dangerous to the

flight of aircraft may exist at specified times.

Note: The term “Danger Area” is not used in

reference to areas within the United States or any

of its possessions or territories.

DAS−

(See DELAY ASSIGNMENT.)

DATA BLOCK−

(See ALPHANUMERIC DISPLAY.)

DEAD RECKONING− Dead reckoning, as applied

to flying, is the navigation of an airplane solely by

means of computations based on airspeed, course,

heading, wind direction, and speed, groundspeed,

and elapsed time.

DECISION ALTITUDE/DECISION HEIGHT

[ICAO]− A specified altitude or height (A/H) in the

precision approach at which a missed approach must

be initiated if the required visual reference to

continue the approach has not been established.

Note 1: Decision altitude [DA] is referenced to

mean sea level [MSL] and decision height [DH] is

referenced to the threshold elevation.

Note 2: The required visual reference means that

section of the visual aids or of the approach area

which should have been in view for sufficient time

for the pilot to have made an assessment of the

aircraft position and rate of change of position, in

relation to the desired flight path.

DECISION HEIGHT− With respect to the operation

of aircraft, means the height at which a decision must

be made during an ILS, MLS, or PAR instrument

approach to either continue the approach or to execute

a missed approach.

(See ICAO term DECISION

ALTITUDE/DECISION HEIGHT.)

DECODER− The device used to decipher signals

received from ATCRBS transponders to effect their

display as select codes.

(See CODES.)

(See RADAR.)

DEFENSE VISUAL FLIGHT RULES− Rules

applicable to flights within an ADIZ conducted under

the visual flight rules in 14 CFR Part 91.

(See AIR DEFENSE IDENTIFICATION ZONE.)

(Refer to 14 CFR Part 91.)

(Refer to 14 CFR Part 99.)

DELAY ASSIGNMENT (DAS)− Delays are distributed to aircraft based on the traffic management

program parameters. The delay assignment is

calculated in 15−minute increments and appears as a

table in Traffic Flow Management System (TFMS).

DELAY INDEFINITE (REASON IF KNOWN)

EXPECT FURTHER CLEARANCE (TIME)− Used

by ATC to inform a pilot when an accurate estimate

of the delay time and the reason for the delay cannot

immediately be determined; e.g., a disabled aircraft

on the runway, terminal or center area saturation,

weather below landing minimums, etc.

(See EXPECT FURTHER CLEARANCE (TIME).)

DELAY TIME− The amount of time that the arrival

must lose to cross the meter fix at the assigned meter

fix time. This is the difference between ACLT and

VTA.

DEPARTURE CENTER− The ARTCC having

jurisdiction for the airspace that generates a flight to

the impacted airport.

DEPARTURE CONTROL− A function of an

approach control facility providing air traffic control

service for departing IFR and, under certain

conditions, VFR aircraft.

(See APPROACH CONTROL FACILITY.)

(Refer to AIM.)

DEPARTURE SEQUENCING PROGRAM− A

program designed to assist in achieving a specified

interval over a common point for departures.
Pilot/Controller Glossary 2/9/12

PCG D−2

DEPARTURE TIME− The time an aircraft becomes

airborne.

DESCENT SPEED ADJUSTMENTS− Speed deceleration calculations made to determine an accurate

VTA. These calculations start at the transition point

and use arrival speed segments to the vertex.

DESIRED COURSE−

a. True− A predetermined desired course direction

to be followed (measured in degrees from true north).

b. Magnetic− A predetermined desired course

direction to be followed (measured in degrees from

local magnetic north).

DESIRED TRACK− The planned or intended track

between two waypoints. It is measured in degrees

from either magnetic or true north. The instantaneous

angle may change from point to point along the great

circle track between waypoints.

DETRESFA (DISTRESS PHASE) [ICAO]− The

code word used to designate an emergency phase

wherein there is reasonable certainty that an aircraft

and its occupants are threatened by grave and

imminent danger or require immediate assistance.

DEVIATIONS−

a. A departure from a current clearance, such as an

off course maneuver to avoid weather or turbulence.

b. Where specifically authorized in the CFRs and

requested by the pilot, ATC may permit pilots to

deviate from certain regulations.

(Refer to AIM.)

DF−

(See DIRECTION FINDER.)

DF APPROACH PROCEDURE− Used under

emergency conditions where another instrument

approach procedure cannot be executed. DF guidance

for an instrument approach is given by ATC facilities

with DF capability.

(See DF GUIDANCE.)

(See DIRECTION FINDER.)

(Refer to AIM.)

DF FIX− The geographical location of an aircraft

obtained by one or more direction finders.

(See DIRECTION FINDER.)

DF GUIDANCE− Headings provided to aircraft by

facilities equipped with direction finding equipment.

These headings, if followed, will lead the aircraft to

a predetermined point such as the DF station or an

airport. DF guidance is given to aircraft in distress or

to other aircraft which request the service. Practice

DF guidance is provided when workload permits.

(See DIRECTION FINDER.)

(See DF FIX.)

(Refer to AIM.)

DF STEER−

(See DF GUIDANCE.)

DH−

(See DECISION HEIGHT.)

DH [ICAO]−

(See ICAO Term DECISION ALTITUDE/

DECISION HEIGHT.)

DIGITAL-AUTOMATIC TERMINAL INFORMATION SERVICE (D-ATIS)− The service provides

text messages to aircraft, airlines, and other users

outside the standard reception range of conventional

ATIS via landline and data link communications to

the cockpit. Also, the service provides a computer−

synthesized voice message that can be transmitted to

all aircraft within range of existing transmitters. The

Terminal Data Link System (TDLS) D-ATIS

application uses weather inputs from local automated

weather sources or manually entered meteorological

data together with preprogrammed menus to provide

standard information to users. Airports with D-ATIS

capability are listed in the Airport/Facility Directory.

DIGITAL TARGET− A computer−generated symbol

representing an aircraft’s position, based on a primary

return or radar beacon reply, shown on a digital

display.

DIGITAL TERMINAL AUTOMATION SYSTEM

(DTAS)− A system where digital radar and beacon

data is presented on digital displays and the

operational program monitors the system performance on a real−time basis.

DIGITIZED TARGET− A computer−generated

indication shown on an analog radar display resulting

from a primary radar return or a radar beacon reply.

DIRECT− Straight line flight between two navigational aids, fixes, points, or any combination thereof.

When used by pilots in describing off-airway routes,

points defining direct route segments become

compulsory reporting points unless the aircraft is

under radar contact.

DIRECT ALTITUDE AND IDENTITY READOUT− The DAIR System is a modification to the
Pilot/Controller Glossary 2/9/12

PCG D−3

AN/TPX-42 Interrogator System. The Navy has two

adaptations of the DAIR System-Carrier Air Traffic

Control Direct Altitude and Identification Readout

System for Aircraft Carriers and Radar Air Traffic

Control Facility Direct Altitude and Identity Readout

System for land-based terminal operations. The

DAIR detects, tracks, and predicts secondary radar

aircraft targets. Targets are displayed by means of

computer-generated symbols and alphanumeric

characters depicting flight identification, altitude,

ground speed, and flight plan data. The DAIR System

is capable of interfacing with ARTCCs.

DIRECTION FINDER− A radio receiver equipped

with a directional sensing antenna used to take

bearings on a radio transmitter. Specialized radio

direction finders are used in aircraft as air navigation

aids. Others are ground-based, primarily to obtain a

“fix” on a pilot requesting orientation assistance or to

locate downed aircraft. A location “fix” is established

by the intersection of two or more bearing lines

plotted on a navigational chart using either two

separately located Direction Finders to obtain a fix on

an aircraft or by a pilot plotting the bearing

indications of his/her DF on two separately located

ground-based transmitters, both of which can be

identified on his/her chart. UDFs receive signals in

the ultra high frequency radio broadcast band; VDFs

in the very high frequency band; and UVDFs in both

bands. ATC provides DF service at those air traffic

control towers and flight service stations listed in the

Airport/Facility Directory and the DOD FLIP IFR En

Route Supplement.

(See DF FIX.)

(See DF GUIDANCE.)

DIRECTLY BEHIND− An aircraft is considered to

be operating directly behind when it is following the

actual flight path of the lead aircraft over the surface

of the earth except when applying wake turbulence

separation criteria.

DISCRETE BEACON CODE−

(See DISCRETE CODE.)

DISCRETE CODE− As used in the Air Traffic

Control Radar Beacon System (ATCRBS), any one

of the 4096 selectable Mode 3/A aircraft transponder

codes except those ending in zero zero; e.g., discrete

codes: 0010, 1201, 2317, 7777; nondiscrete codes:

0100, 1200, 7700. Nondiscrete codes are normally

reserved for radar facilities that are not equipped with

discrete decoding capability and for other purposes

such as emergencies (7700), VFR aircraft (1200), etc.

(See RADAR.)

(Refer to AIM.)

DISCRETE FREQUENCY− A separate radio

frequency for use in direct pilot-controller communications in air traffic control which reduces

frequency congestion by controlling the number of

aircraft operating on a particular frequency at one

time. Discrete frequencies are normally designated

for each control sector in en route/terminal ATC

facilities. Discrete frequencies are listed in the

Airport/Facility Directory and the DOD FLIP IFR En

Route Supplement.

(See CONTROL SECTOR.)

DISPLACED THRESHOLD− A threshold that is

located at a point on the runway other than the

designated beginning of the runway.

(See THRESHOLD.)

(Refer to AIM.)

DISTANCE MEASURING EQUIPMENT− Equipment (airborne and ground) used to measure, in

nautical miles, the slant range distance of an aircraft

from the DME navigational aid.

(See MICROWAVE LANDING SYSTEM.)

(See TACAN.)

(See VORTAC.)

DISTRESS− A condition of being threatened by

serious and/or imminent danger and of requiring

immediate assistance.

DIVE BRAKES−

(See SPEED BRAKES.)

DIVERSE VECTOR AREA− In a radar environment, that area in which a prescribed departure route

is not required as the only suitable route to avoid

obstacles. The area in which random radar vectors

below the MVA/MIA, established in accordance with

the TERPS criteria for diverse departures, obstacles

and terrain avoidance, may be issued to departing

aircraft.

DIVERSION (DVRSN)− Flights that are required to

land at other than their original destination for

reasons beyond the control of the pilot/company, e.g.

periods of significant weather.

DME−

(See DISTANCE MEASURING EQUIPMENT.)
Pilot/Controller Glossary 2/9/12

PCG D−4

DME FIX− A geographical position determined by

reference to a navigational aid which provides

distance and azimuth information. It is defined by a

specific distance in nautical miles and a radial,

azimuth, or course (i.e., localizer) in degrees

magnetic from that aid.

(See DISTANCE MEASURING EQUIPMENT.)

(See FIX.)

(See MICROWAVE LANDING SYSTEM.)

DME SEPARATION− Spacing of aircraft in terms of

distances (nautical miles) determined by reference to

distance measuring equipment (DME).

(See DISTANCE MEASURING EQUIPMENT.)

DOD FLIP− Department of Defense Flight Information Publications used for flight planning, en route,

and terminal operations. FLIP is produced by the

National Geospatial−Intelligence Agency (NGA) for

world-wide use. United States Government Flight

Information Publications (en route charts and

instrument approach procedure charts) are incorporated in DOD FLIP for use in the National Airspace

System (NAS).

DOMESTIC AIRSPACE− Airspace which overlies

the continental land mass of the United States plus

Hawaii and U.S. possessions. Domestic airspace

extends to 12 miles offshore.

DOWNBURST− A strong downdraft which induces

an outburst of damaging winds on or near the ground.

Damaging winds, either straight or curved, are highly

divergent. The sizes of downbursts vary from 1/2

mile or less to more than 10 miles. An intense

downburst often causes widespread damage. Damaging winds, lasting 5 to 30 minutes, could reach speeds

as high as 120 knots.

DOWNWIND LEG−

(See TRAFFIC PATTERN.)

DP−

(See INSTRUMENT DEPARTURE PROCEDURE.)

DRAG CHUTE− A parachute device installed on

certain aircraft which is deployed on landing roll to

assist in deceleration of the aircraft.

DSP−

(See DEPARTURE SEQUENCING PROGRAM.)

DT−

(See DELAY TIME.)

DTAS−

(See DIGITAL TERMINAL AUTOMATION

SYSTEM.)

DUE REGARD− A phase of flight wherein an

aircraft commander of a State-operated aircraft

assumes responsibility to separate his/her aircraft

from all other aircraft.

(See also FAAO JO 7110.65, Para 1−2−1, WORD

MEANINGS.)

DUTY RUNWAY−

(See RUNWAY IN USE/ACTIVE RUNWAY/DUTY

RUNWAY.)

DVA−

(See DIVERSE VECTOR AREA.)

DVFR−

(See DEFENSE VISUAL FLIGHT RULES.)

DVFR FLIGHT PLAN− A flight plan filed for a VFR

aircraft which intends to operate in airspace within

which the ready identification, location, and control

of aircraft are required in the interest of national

security.

DVRSN−

(See DIVERSION.)

DYNAMIC− Continuous review, evaluation, and

change to meet demands.

DYNAMIC RESTRICTIONS− Those restrictions

imposed by the local facility on an “as needed” basis

to manage unpredictable fluctuations in traffic

demands.
Pilot/Controller Glossary 2/9/12

PCG E−1

E

EAS−

(See EN ROUTE AUTOMATION SYSTEM.)

EDCT−

(See EXPECT DEPARTURE CLEARANCE

TIME.)

EFC−

(See EXPECT FURTHER CLEARANCE (TIME).)

ELT−

(See EMERGENCY LOCATOR TRANSMITTER.)

EMERGENCY− A distress or an urgency condition.

EMERGENCY LOCATOR TRANSMITTER− A

radio transmitter attached to the aircraft structure

which operates from its own power source on

121.5 MHz and 243.0 MHz. It aids in locating

downed aircraft by radiating a downward sweeping

audio tone, 2-4 times per second. It is designed to

function without human action after an accident.

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

E-MSAW−

(See EN ROUTE MINIMUM SAFE ALTITUDE

WARNING.)

EN ROUTE AIR TRAFFIC CONTROL SERVICES− Air traffic control service provided aircraft

on IFR flight plans, generally by centers, when these

aircraft are operating between departure and

destination terminal areas. When equipment, capabilities, and controller workload permit, certain

advisory/assistance services may be provided to VFR

aircraft.

(See AIR ROUTE TRAFFIC CONTROL

CENTER.)

(Refer to AIM.)

EN ROUTE AUTOMATION SYSTEM (EAS)− The

complex integrated environment consisting of

situation display systems, surveillance systems and

flight data processing, remote devices, decision

support tools, and the related communications

equipment that form the heart of the automated IFR

air traffic control system. It interfaces with automated

terminal systems and is used in the control of en route

IFR aircraft.

(Refer to AIM.)

EN ROUTE CHARTS−

(See AERONAUTICAL CHART.)

EN ROUTE DESCENT− Descent from the en route

cruising altitude which takes place along the route of

flight.

EN ROUTE FLIGHT ADVISORY SERVICE− A

service specifically designed to provide, upon pilot

request, timely weather information pertinent to

his/her type of flight, intended route of flight, and

altitude. The FSSs providing this service are listed in

the Airport/Facility Directory.

(See FLIGHT WATCH.)

(Refer to AIM.)

EN ROUTE HIGH ALTITUDE CHARTS−

(See AERONAUTICAL CHART.)

EN ROUTE LOW ALTITUDE CHARTS−

(See AERONAUTICAL CHART.)

EN ROUTE MINIMUM SAFE ALTITUDE WARNING− A function of the EAS that aids the controller

by providing an alert when a tracked aircraft is below

or predicted by the computer to go below a

predetermined minimum IFR altitude (MIA).

EN ROUTE SPACING PROGRAM (ESP)− A

program designed to assist the exit sector in

achieving the required in-trail spacing.

EN ROUTE TRANSITION−

a. Conventional STARs/SIDs. The portion of a

SID/STAR that connects to one or more en route

airway/jet route.

b. RNAV STARs/SIDs. The portion of a STAR

preceding the common route or point, or for a SID the

portion following, that is coded for a specific en route

fix, airway or jet route.

ESP−

(See EN ROUTE SPACING PROGRAM.)

ESTABLISHED−To be stable or fixed on a route,

route segment, altitude, heading, etc.

ESTIMATED ELAPSED TIME [ICAO]− The

estimated time required to proceed from one

significant point to another.

(See ICAO Term TOTAL ESTIMATED ELAPSED

TIME.)
Pilot/Controller Glossary 2/9/12

PCG E−2

ESTIMATED OFF-BLOCK TIME [ICAO]− The

estimated time at which the aircraft will commence

movement associated with departure.

ESTIMATED POSITION ERROR (EPE)−

(See Required Navigation Performance)

ESTIMATED TIME OF ARRIVAL− The time the

flight is estimated to arrive at the gate (scheduled

operators) or the actual runway on times for

nonscheduled operators.

ESTIMATED TIME EN ROUTE− The estimated

flying time from departure point to destination

(lift-off to touchdown).

ETA−

(See ESTIMATED TIME OF ARRIVAL.)

ETE−

(See ESTIMATED TIME EN ROUTE.)

EXECUTE MISSED APPROACH− Instructions

issued to a pilot making an instrument approach

which means continue inbound to the missed

approach point and execute the missed approach

procedure as described on the Instrument Approach

Procedure Chart or as previously assigned by ATC.

The pilot may climb immediately to the altitude

specified in the missed approach procedure upon

making a missed approach. No turns should be

initiated prior to reaching the missed approach point.

When conducting an ASR or PAR approach, execute

the assigned missed approach procedure immediately

upon receiving instructions to “execute missed

approach.”

(Refer to AIM.)

EXPECT (ALTITUDE) AT (TIME) or (FIX)− Used

under certain conditions to provide a pilot with an

altitude to be used in the event of two-way

communications failure. It also provides altitude

information to assist the pilot in planning.

(Refer to AIM.)

EXPECT DEPARTURE CLEARANCE TIME

(EDCT)− The runway release time assigned to an

aircraft in a traffic management program and shown

on the flight progress strip as an EDCT.

(See GROUND DELAY PROGRAM.)

EXPECT FURTHER CLEARANCE (TIME)− The

time a pilot can expect to receive clearance beyond a

clearance limit.

EXPECT FURTHER CLEARANCE VIA (AIRWAYS, ROUTES OR FIXES)− Used to inform a

pilot of the routing he/she can expect if any part of the

route beyond a short range clearance limit differs

from that filed.

EXPEDITE− Used by ATC when prompt compliance is required to avoid the development of an

imminent situation. Expedite climb/descent normally indicates to a pilot that the approximate best rate

of climb/descent should be used without requiring an

exceptional change in aircraft handling characteristics.
Pilot/Controller Glossary 2/9/12

PCG F−1

F

FAF−

(See FINAL APPROACH FIX.)

FAST FILE− An FSS system whereby a pilot files a

flight plan via telephone that is recorded and later

transcribed for transmission to the appropriate air

traffic facility. (Alaska only.)

FAWP− Final Approach Waypoint

FCLT−

(See FREEZE CALCULATED LANDING TIME.)

FEATHERED PROPELLER− A propeller whose

blades have been rotated so that the leading and

trailing edges are nearly parallel with the aircraft

flight path to stop or minimize drag and engine

rotation. Normally used to indicate shutdown of a

reciprocating or turboprop engine due to malfunction.

FEDERAL AIRWAYS−

(See LOW ALTITUDE AIRWAY STRUCTURE.)

FEEDER FIX− The fix depicted on Instrument

Approach Procedure Charts which establishes the

starting point of the feeder route.

FEEDER ROUTE− A route depicted on instrument

approach procedure charts to designate routes for

aircraft to proceed from the en route structure to the

initial approach fix (IAF).

(See INSTRUMENT APPROACH

PROCEDURE.)

FERRY FLIGHT− A flight for the purpose of:

a. Returning an aircraft to base.

b. Delivering an aircraft from one location to

another.

c. Moving an aircraft to and from a maintenance

base.− Ferry flights, under certain conditions, may be

conducted under terms of a special flight permit.

FIELD ELEVATION−

(See AIRPORT ELEVATION.)

FILED− Normally used in conjunction with flight

plans, meaning a flight plan has been submitted to

ATC.

FILED EN ROUTE DELAY− Any of the following

preplanned delays at points/areas along the route of

flight which require special flight plan filing and

handling techniques.

a. Terminal Area Delay. A delay within a terminal

area for touch-and-go, low approach, or other

terminal area activity.

b. Special Use Airspace Delay. A delay within a

Military Operations Area, Restricted Area, Warning

Area, or ATC Assigned Airspace.

c. Aerial Refueling Delay. A delay within an

Aerial Refueling Track or Anchor.

FILED FLIGHT PLAN− The flight plan as filed with

an ATS unit by the pilot or his/her designated

representative without any subsequent changes or

clearances.

FINAL−Commonly used to mean that an aircraft is

on the final approach course or is aligned with a

landing area.

(See FINAL APPROACH COURSE.)

(See FINAL APPROACH-IFR.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

FINAL APPROACH [ICAO]− That part of an

instrument approach procedure which commences at

the specified final approach fix or point, or where

such a fix or point is not specified.

a. At the end of the last procedure turn, base turn

or inbound turn of a racetrack procedure, if specified;

or

b. At the point of interception of the last track

specified in the approach procedure; and ends at a

point in the vicinity of an aerodrome from which:

1. A landing can be made; or

2. A missed approach procedure is initiated.

FINAL APPROACH COURSE− A bearing/radial/

track of an instrument approach leading to a runway

or an extended runway centerline all without regard

to distance.

FINAL APPROACH FIX− The fix from which the

final approach (IFR) to an airport is executed and

which identifies the beginning of the final approach

segment. It is designated on Government charts by

the Maltese Cross symbol for nonprecision

approaches and the lightning bolt symbol for

precision approaches; or when ATC directs a
Pilot/Controller Glossary 2/9/12

PCG F−2

lower-than-published glideslope/path intercept altitude, it is the resultant actual point of the

glideslope/path intercept.

(See FINAL APPROACH POINT.)

(See GLIDESLOPE INTERCEPT ALTITUDE.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

FINAL APPROACH-IFR− The flight path of an

aircraft which is inbound to an airport on a final

instrument approach course, beginning at the final

approach fix or point and extending to the airport or

the point where a circle-to-land maneuver or a missed

approach is executed.

(See FINAL APPROACH COURSE.)

(See FINAL APPROACH FIX.)

(See FINAL APPROACH POINT.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

(See ICAO term FINAL APPROACH.)

FINAL APPROACH POINT− The point, applicable

only to a nonprecision approach with no depicted

FAF (such as an on airport VOR), where the aircraft

is established inbound on the final approach course

from the procedure turn and where the final approach

descent may be commenced. The FAP serves as the

FAF and identifies the beginning of the final

approach segment.

(See FINAL APPROACH FIX.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

FINAL APPROACH SEGMENT−

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

FINAL APPROACH SEGMENT [ICAO]− That

segment of an instrument approach procedure in

which alignment and descent for landing are

accomplished.

FINAL CONTROLLER− The controller providing

information and final approach guidance during PAR

and ASR approaches utilizing radar equipment.

(See RADAR APPROACH.)

FINAL GUARD SERVICE− A value added service

provided in conjunction with LAA/RAA only during

periods of significant and fast changing weather

conditions that may affect landing and takeoff

operations.

FINAL MONITOR AID− A high resolution color

display that is equipped with the controller alert

system hardware/software which is used in the

precision runway monitor (PRM) system. The

display includes alert algorithms providing the target

predictors, a color change alert when a target

penetrates or is predicted to penetrate the no

transgression zone (NTZ), a color change alert if the

aircraft transponder becomes inoperative, synthesized voice alerts, digital mapping, and like features

contained in the PRM system.

(See RADAR APPROACH.)

FINAL MONITOR CONTROLLER− Air Traffic

Control Specialist assigned to radar monitor the

flight path of aircraft during simultaneous parallel

and simultaneous close parallel ILS approach

operations. Each runway is assigned a final monitor

controller during simultaneous parallel and simultaneous close parallel ILS approaches. Final monitor

controllers shall utilize the Precision Runway

Monitor (PRM) system during simultaneous close

parallel ILS approaches.

FIR−

(See FLIGHT INFORMATION REGION.)

FIRST TIER CENTER− The ARTCC immediately

adjacent to the impacted center.

FIS−B−

(See FLIGHT INFORMATION

SERVICE−BROADCAST.)

FIX− A geographical position determined by visual

reference to the surface, by reference to one or more

radio NAVAIDs, by celestial plotting, or by another

navigational device.

FIX BALANCING− A process whereby aircraft are

evenly distributed over several available arrival fixes

reducing delays and controller workload.

FLAG− A warning device incorporated in certain

airborne navigation and flight instruments indicating

that:

a. Instruments are inoperative or otherwise not

operating satisfactorily, or

b. Signal strength or quality of the received signal

falls below acceptable values.

FLAG ALARM−

(See FLAG.)

FLAMEOUT− An emergency condition caused by a

loss of engine power.
Pilot/Controller Glossary 2/9/12

PCG F−3

FLAMEOUT PATTERN− An approach normally

conducted by a single-engine military aircraft

experiencing loss or anticipating loss of engine

power or control. The standard overhead approach

starts at a relatively high altitude over a runway

(“high key”) followed by a continuous 180 degree

turn to a high, wide position (“low key”) followed by

a continuous 180 degree turn final. The standard

straight-in pattern starts at a point that results in a

straight-in approach with a high rate of descent to the

runway. Flameout approaches terminate in the type

approach requested by the pilot (normally fullstop).

FLIGHT CHECK− A call-sign prefix used by FAA

aircraft engaged in flight inspection/certification of

navigational aids and flight procedures. The word

“recorded” may be added as a suffix; e.g., “Flight

Check 320 recorded” to indicate that an automated

flight inspection is in progress in terminal areas.

(See FLIGHT INSPECTION.)

(Refer to AIM.)

FLIGHT FOLLOWING−

(See TRAFFIC ADVISORIES.)

FLIGHT INFORMATION REGION− An airspace of

defined dimensions within which Flight Information

Service and Alerting Service are provided.

a. Flight Information Service. A service provided

for the purpose of giving advice and information

useful for the safe and efficient conduct of flights.

b. Alerting Service. A service provided to notify

appropriate organizations regarding aircraft in need

of search and rescue aid and to assist such

organizations as required.

FLIGHT INFORMATION SERVICE− A service

provided for the purpose of giving advice and

information useful for the safe and efficient conduct

of flights.

FLIGHT INFORMATION SERVICE−

BROADCAST (FIS−B)− A ground broadcast service

provided through the ADS−B Broadcast Services

network over the UAT data link that operates on 978

MHz. The FIS−B system provides pilots and flight

crews of properly equipped aircraft with a cockpit

display of certain aviation weather and aeronautical

information.

FLIGHT INSPECTION− Inflight investigation and

evaluation of a navigational aid to determine whether

it meets established tolerances.

(See FLIGHT CHECK.)

(See NAVIGATIONAL AID.)

FLIGHT LEVEL− A level of constant atmospheric

pressure related to a reference datum of 29.92 inches

of mercury. Each is stated in three digits that represent

hundreds of feet. For example, flight level (FL) 250

represents a barometric altimeter indication of

25,000 feet; FL 255, an indication of 25,500 feet.

(See ICAO term FLIGHT LEVEL.)

FLIGHT LEVEL [ICAO]− A surface of constant

atmospheric pressure which is related to a specific

pressure datum, 1013.2 hPa (1013.2 mb), and is

separated from other such surfaces by specific

pressure intervals.

Note 1: A pressure type altimeter calibrated in

accordance with the standard atmosphere:

a. When set to a QNH altimeter setting, will

indicate altitude;

b. When set to a QFE altimeter setting, will

indicate height above the QFE reference datum;

and

c. When set to a pressure of 1013.2 hPa 

(1013.2 mb), may be used to indicate flight levels.

Note 2: The terms ‘height’ and ‘altitude,’ used in

Note 1 above, indicate altimetric rather than

geometric heights and altitudes.

FLIGHT LINE− A term used to describe the precise

movement of a civil photogrammetric aircraft along

a predetermined course(s) at a predetermined altitude

during the actual photographic run.

FLIGHT MANAGEMENT SYSTEMS− A computer system that uses a large data base to allow routes

to be preprogrammed and fed into the system by

means of a data loader. The system is constantly

updated with respect to position accuracy by

reference to conventional navigation aids. The

sophisticated program and its associated data base

ensures that the most appropriate aids are automatically selected during the information update cycle.

FLIGHT MANAGEMENT SYSTEM PROCEDURE− An arrival, departure, or approach procedure

developed for use by aircraft with a slant (/) E or slant

(/) F equipment suffix.
Pilot/Controller Glossary 2/9/12

PCG F−4

FLIGHT PATH− A line, course, or track along which

an aircraft is flying or intended to be flown.

(See COURSE.)

(See TRACK.)

FLIGHT PLAN− Specified information relating to

the intended flight of an aircraft that is filed orally or

in writing with an FSS or an ATC facility.

(See FAST FILE.)

(See FILED.)

(Refer to AIM.)

FLIGHT PLAN AREA (FPA)− The geographical

area assigned to a flight service station (FSS) for the

purpose of establishing primary responsibility for

services that may include search and rescue for VFR

aircraft, issuance of NOTAMs, pilot briefings,

inflight services, broadcast services, emergency

services, flight data processing, international operations, and aviation weather services. Large

consolidated FSS facilities may combine FPAs into

larger areas of responsibility (AOR).

(See FLIGHT SERVICE STATION.)

(See TIE-IN FACILITY.)

FLIGHT RECORDER− A general term applied to

any instrument or device that records information

about the performance of an aircraft in flight or about

conditions encountered in flight. Flight recorders

may make records of airspeed, outside air

temperature, vertical acceleration, engine RPM,

manifold pressure, and other pertinent variables for a

given flight.

(See ICAO term FLIGHT RECORDER.)

FLIGHT RECORDER [ICAO]− Any type of

recorder installed in the aircraft for the purpose of

complementing accident/incident investigation.

Note: See Annex 6 Part I, for specifications relating

to flight recorders.

FLIGHT SERVICE STATION (FSS) − An air traffic

facility which provides pilot briefings, flight plan

processing, en route radio communications, search

and rescue services, and assistance to lost aircraft and

aircraft in emergency situations. FSS also relays ATC

clearances, processes Notices to Airmen, and

broadcasts aviation weather and aeronautical information. In addition, at selected locations, FSS provides

En Route Flight Advisory Service (Flight Watch) and

Airport Advisory Service (AAS) and takes airport

weather observations.

(See FLIGHT PLAN AREA.)

(See TIE-IN FACILITY.)

FLIGHT STANDARDS DISTRICT OFFICE− An

FAA field office serving an assigned geographical

area and staffed with Flight Standards personnel who

serve the aviation industry and the general public on

matters relating to the certification and operation of

air carrier and general aviation aircraft. Activities

include general surveillance of operational safety,

certification of airmen and aircraft, accident

prevention, investigation, enforcement, etc.

FLIGHT TEST− A flight for the purpose of:

a. Investigating the operation/flight characteristics of an aircraft or aircraft component.

b. Evaluating an applicant for a pilot certificate or

rating.

FLIGHT VISIBILITY−

(See VISIBILITY.)

FLIGHT WATCH− A shortened term for use in

air-ground contacts to identify the flight service

station providing En Route Flight Advisory Service;

e.g., “Oakland Flight Watch.”

(See EN ROUTE FLIGHT ADVISORY

SERVICE.)

FLIP−

(See DOD FLIP.)

FLY HEADING (DEGREES)− Informs the pilot of

the heading he/she should fly. The pilot may have to

turn to, or continue on, a specific compass direction

in order to comply with the instructions. The pilot is

expected to turn in the shorter direction to the heading

unless otherwise instructed by ATC.

FLY-BY WAYPOINT− A fly-by waypoint requires

the use of turn anticipation to avoid overshoot of the

next flight segment.

FLY-OVER WAYPOINT− A fly-over waypoint

precludes any turn until the waypoint is overflown

and is followed by an intercept maneuver of the next

flight segment.

FLY VISUAL TO AIRPORT−

(See PUBLISHED INSTRUMENT APPROACH

PROCEDURE VISUAL SEGMENT.)

FMA−

(See FINAL MONITOR AID.)
Pilot/Controller Glossary 2/9/12

PCG F−5

FMS−

(See FLIGHT MANAGEMENT SYSTEM.)

FMSP−

(See FLIGHT MANAGEMENT SYSTEM

PROCEDURE.)

FORMATION FLIGHT− More than one aircraft

which, by prior arrangement between the pilots,

operate as a single aircraft with regard to navigation

and position reporting. Separation between aircraft

within the formation is the responsibility of the flight

leader and the pilots of the other aircraft in the flight.

This includes transition periods when aircraft within

the formation are maneuvering to attain separation

from each other to effect individual control and

during join-up and breakaway.

a. A standard formation is one in which a

proximity of no more than 1 mile laterally or

longitudinally and within 100 feet vertically from the

flight leader is maintained by each wingman.

b. Nonstandard formations are those operating

under any of the following conditions:

1. When the flight leader has requested and ATC

has approved other than standard formation

dimensions.

2. When operating within an authorized altitude

reservation (ALTRV) or under the provisions of a

letter of agreement.

3. When the operations are conducted in

airspace specifically designed for a special activity.

(See ALTITUDE RESERVATION.)

(Refer to 14 CFR Part 91.)

FRC−

(See REQUEST FULL ROUTE CLEARANCE.)

FREEZE/FROZEN− Terms used in referring to

arrivals which have been assigned ACLTs and to the

lists in which they are displayed.

FREEZE CALCULATED LANDING TIME− A

dynamic parameter number of minutes prior to the

meter fix calculated time of arrival for each aircraft

when the TCLT is frozen and becomes an ACLT (i.e.,

the VTA is updated and consequently the TCLT is

modified as appropriate until FCLT minutes prior to

meter fix calculated time of arrival, at which time

updating is suspended and an ACLT and a frozen

meter fix crossing time (MFT) is assigned).

FREEZE HORIZON− The time or point at which an

aircraft’s STA becomes fixed and no longer fluctuates

with each radar update. This setting ensures a

constant time for each aircraft, necessary for the

metering controller to plan his/her delay technique.

This setting can be either in distance from the meter

fix or a prescribed flying time to the meter fix.

FREEZE SPEED PARAMETER− A speed adapted

for each aircraft to determine fast and slow aircraft.

Fast aircraft freeze on parameter FCLT and slow

aircraft freeze on parameter MLDI.

FRICTION MEASUREMENT− A measurement of

the friction characteristics of the runway pavement

surface using continuous self-watering friction

measurement equipment in accordance with the

specifications, procedures and schedules contained

in AC 150/5320−12, Measurement, Construction,

and Maintenance of Skid Resistant Airport Pavement

Surfaces.

FSDO−

(See FLIGHT STANDARDS DISTRICT OFFICE.)

FSPD−

(See FREEZE SPEED PARAMETER.)

FSS−

(See FLIGHT SERVICE STATION.)

FUEL DUMPING− Airborne release of usable fuel.

This does not include the dropping of fuel tanks.

(See JETTISONING OF EXTERNAL STORES.)

FUEL REMAINING− A phrase used by either pilots

or controllers when relating to the fuel remaining on

board until actual fuel exhaustion. When transmitting

such information in response to either a controller

question or pilot initiated cautionary advisory to air

traffic control, pilots will state the APPROXIMATE

NUMBER OF MINUTES the flight can continue

with the fuel remaining. All reserve fuel SHOULD

BE INCLUDED in the time stated, as should an

allowance for established fuel gauge system error.

FUEL SIPHONING− Unintentional release of fuel

caused by overflow, puncture, loose cap, etc.

FUEL VENTING−

(See FUEL SIPHONING.)

Pilot/Controller Glossary 2/9/12

PCG G−1

G

GATE HOLD PROCEDURES− Procedures at

selected airports to hold aircraft at the gate or other

ground location whenever departure delays exceed or

are anticipated to exceed 15 minutes. The sequence

for departure will be maintained in accordance with

initial call-up unless modified by flow control

restrictions. Pilots should monitor the ground

control/clearance delivery frequency for engine

start/taxi advisories or new proposed start/taxi time

if the delay changes.

GBT−

(See GROUND−BASED TRANSCEIVER.)

GCA−

(See GROUND CONTROLLED APPROACH.)

GDP−

(See GROUND DELAY PROGRAM.)

GENERAL AVIATION− That portion of civil

aviation which encompasses all facets of aviation

except air carriers holding a certificate of public

convenience and necessity from the Civil Aeronautics Board and large aircraft commercial operators.

(See ICAO term GENERAL AVIATION.)

GENERAL AVIATION [ICAO]− All civil aviation

operations other than scheduled air services and

nonscheduled air transport operations for remuneration or hire.

GEO MAP− The digitized map markings associated

with the ASR-9 Radar System.

GLIDEPATH−

(See GLIDESLOPE.)

GLIDEPATH [ICAO]− A descent profile determined

for vertical guidance during a final approach.

GLIDEPATH INTERCEPT ALTITUDE−

(See GLIDESLOPE INTERCEPT ALTITUDE.)

GLIDESLOPE− Provides vertical guidance for

aircraft during approach and landing. The glideslope/

glidepath is based on the following:

a. Electronic components emitting signals which

provide vertical guidance by reference to airborne

instruments during instrument approaches such as

ILS/MLS, or

b. Visual ground aids, such as VASI, which

provide vertical guidance for a VFR approach or for

the visual portion of an instrument approach and

landing.

c. PAR. Used by ATC to inform an aircraft making

a PAR approach of its vertical position (elevation)

relative to the descent profile.

(See ICAO term GLIDEPATH.)

GLIDESLOPE INTERCEPT ALTITUDE− The

minimum altitude to intercept the glideslope/path on

a precision approach. The intersection of the

published intercept altitude with the glideslope/path,

designated on Government charts by the lightning

bolt symbol, is the precision FAF; however, when the

approach chart shows an alternative lower glideslope

intercept altitude, and ATC directs a lower altitude,

the resultant lower intercept position is then the FAF.

(See FINAL APPROACH FIX.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

GLOBAL POSITIONING SYSTEM (GPS)− A

space-base radio positioning, navigation, and

time-transfer system. The system provides highly

accurate position and velocity information, and

precise time, on a continuous global basis, to an

unlimited number of properly equipped users. The

system is unaffected by weather, and provides a

worldwide common grid reference system. The GPS

concept is predicated upon accurate and continuous

knowledge of the spatial position of each satellite in

the system with respect to time and distance from a

transmitting satellite to the user. The GPS receiver

automatically selects appropriate signals from the

satellites in view and translates these into threedimensional position, velocity, and time. System

accuracy for civil users is normally 100 meters

horizontally.

GO AHEAD− Proceed with your message. Not to be

used for any other purpose.

GO AROUND− Instructions for a pilot to abandon

his/her approach to landing. Additional instructions

may follow. Unless otherwise advised by ATC, a

VFR aircraft or an aircraft conducting visual

approach should overfly the runway while climbing

to traffic pattern altitude and enter the traffic pattern

via the crosswind leg. A pilot on an IFR flight plan
Pilot/Controller Glossary 2/9/12

PCG G−2

making an instrument approach should execute the

published missed approach procedure or proceed as

instructed by ATC; e.g., “Go around” (additional

instructions if required).

(See LOW APPROACH.)

(See MISSED APPROACH.)

GPD−

(See GRAPHIC PLAN DISPLAY.)

GPS−

(See GLOBAL POSITIONING SYSTEM.)

GRAPHIC PLAN DISPLAY (GPD)− A view

available with URET that provides a graphic display

of aircraft, traffic, and notification of predicted

conflicts. Graphic routes for Current Plans and Trial

Plans are displayed upon controller request.

(See USER REQUEST EVALUATION TOOL.)

GROUND−BASED TRANSCEIVER (GBT)− The

ground−based transmitter/receiver (transceiver) receives automatic dependent surveillance−broadcast

messages, which are forwarded to an air traffic

control facility for processing and display with other

radar targets on the plan position indicator (radar

display).

(See AUTOMATIC DEPENDENT

SURVEILLANCE-BROADCAST.)

GROUND CLUTTER− A pattern produced on the

radar scope by ground returns which may degrade

other radar returns in the affected area. The effect of

ground clutter is minimized by the use of moving

target indicator (MTI) circuits in the radar equipment

resulting in a radar presentation which displays only

targets which are in motion.

(See CLUTTER.)

GROUND COMMUNICATION OUTLET (GCO)−

An unstaffed, remotely controlled, ground/ground

communications facility. Pilots at uncontrolled

airports may contact ATC and FSS via VHF to a

telephone connection to obtain an instrument

clearance or close a VFR or IFR flight plan. They may

also get an updated weather briefing prior to takeoff.

Pilots will use four “key clicks” on the VHF radio to

contact the appropriate ATC facility or six “key

clicks” to contact the FSS. The GCO system is

intended to be used only on the ground.

GROUND CONTROLLED APPROACH− A radar

approach system operated from the ground by air

traffic control personnel transmitting instructions to

the pilot by radio. The approach may be conducted

with surveillance radar (ASR) only or with both

surveillance and precision approach radar (PAR).

Usage of the term “GCA” by pilots is discouraged

except when referring to a GCA facility. Pilots should

specifically request a “PAR” approach when a

precision radar approach is desired or request an

“ASR” or “surveillance” approach when a nonprecision radar approach is desired.

(See RADAR APPROACH.)

GROUND DELAY PROGRAM (GDP)− A traffic

management process administered by the ATCSCC;

when aircraft are held on the ground. The purpose of

the program is to support the TM mission and limit

airborne holding. It is a flexible program and may be

implemented in various forms depending upon the

needs of the AT system. Ground delay programs

provide for equitable assignment of delays to all

system users.

GROUND SPEED− The speed of an aircraft relative

to the surface of the earth.

GROUND STOP (GS)− The GS is a process that

requires aircraft that meet a specific criteria to remain

on the ground. The criteria may be airport specific,

airspace specific, or equipment specific; for example,

all departures to San Francisco, or all departures

entering Yorktown sector, or all Category I and II

aircraft going to Charlotte. GSs normally occur with

little or no warning.

GROUND VISIBILITY−

(See VISIBILITY.)

GS−

(See GROUND STOP.)
Pilot/Controller Glossary 2/9/12

PCG H−1

H

HAA−

(See HEIGHT ABOVE AIRPORT.)

HAL−

(See HEIGHT ABOVE LANDING.)

HANDOFF− An action taken to transfer the radar

identification of an aircraft from one controller to

another if the aircraft will enter the receiving

controller’s airspace and radio communications with

the aircraft will be transferred.

HAR−

(See HIGH ALTITUDE REDESIGN.)

HAT−

(See HEIGHT ABOVE TOUCHDOWN.)

HAVE NUMBERS− Used by pilots to inform ATC

that they have received runway, wind, and altimeter

information only.

HAZARDOUS INFLIGHT WEATHER ADVISORY SERVICE− Continuous recorded hazardous

inflight weather forecasts broadcasted to airborne

pilots over selected VOR outlets defined as an

HIWAS BROADCAST AREA.

HAZARDOUS WEATHER INFORMATION−

Summary of significant meteorological information

(SIGMET/WS), convective significant meteorological information (convective SIGMET/WST), urgent

pilot weather reports (urgent PIREP/UUA), center

weather advisories (CWA), airmen’s meteorological

information (AIRMET/WA) and any other weather

such as isolated thunderstorms that are rapidly

developing and increasing in intensity, or low

ceilings and visibilities that are becoming widespread which is considered significant and are not

included in a current hazardous weather advisory.

HEAVY (AIRCRAFT)−

(See AIRCRAFT CLASSES.)

HEIGHT ABOVE AIRPORT− The height of the

Minimum Descent Altitude above the published

airport elevation. This is published in conjunction

with circling minimums.

(See MINIMUM DESCENT ALTITUDE.)

HEIGHT ABOVE LANDING− The height above a

designated helicopter landing area used for helicopter

instrument approach procedures.

(Refer to 14 CFR Part 97.)

HEIGHT ABOVE TOUCHDOWN− The height of

the Decision Height or Minimum Descent Altitude

above the highest runway elevation in the touchdown

zone (first 3,000 feet of the runway). HAT is

published on instrument approach charts in conjunction with all straight-in minimums.

(See DECISION HEIGHT.)

(See MINIMUM DESCENT ALTITUDE.)

HELICOPTER− A heavier-than-air aircraft supported in flight chiefly by the reactions of the air on

one or more power-driven rotors on substantially

vertical axes.

HELIPAD− A small, designated area, usually with a

prepared surface, on a heliport, airport, landing/takeoff area, apron/ramp, or movement area used for

takeoff, landing, or parking of helicopters.

HELIPORT− An area of land, water, or structure used

or intended to be used for the landing and takeoff of

helicopters and includes its buildings and facilities if

any.

HELIPORT REFERENCE POINT (HRP)− The

geographic center of a heliport.

HERTZ− The standard radio equivalent of frequency

in cycles per second of an electromagnetic wave.

Kilohertz (kHz) is a frequency of one thousand cycles

per second. Megahertz (MHz) is a frequency of one

million cycles per second.

HF−

(See HIGH FREQUENCY.)

HF COMMUNICATIONS−

(See HIGH FREQUENCY COMMUNICATIONS.)

HIGH ALTITUDE REDESIGN (HAR)− A level of

non−restrictive routing (NRR) service for aircraft

that have all waypoints associated with the HAR

program in their flight management systems or

RNAV equipage.

HIGH FREQUENCY− The frequency band between

3 and 30 MHz.

(See HIGH FREQUENCY COMMUNICATIONS.)
Pilot/Controller Glossary 2/9/12

PCG H−2

HIGH FREQUENCY COMMUNICATIONS− High

radio frequencies (HF) between 3 and 30 MHz used

for air-to-ground voice communication in overseas

operations.

HIGH SPEED EXIT−

(See HIGH SPEED TAXIWAY.)

HIGH SPEED TAXIWAY− A long radius taxiway

designed and provided with lighting or marking to

define the path of aircraft, traveling at high speed (up

to 60 knots), from the runway center to a point on the

center of a taxiway. Also referred to as long radius

exit or turn-off taxiway. The high speed taxiway is

designed to expedite aircraft turning off the runway

after landing, thus reducing runway occupancy time.

HIGH SPEED TURNOFF−

(See HIGH SPEED TAXIWAY.)

HIWAS−

(See HAZARDOUS INFLIGHT WEATHER

ADVISORY SERVICE.)

HIWAS AREA−

(See HAZARDOUS INFLIGHT WEATHER

ADVISORY SERVICE.)

HIWAS BROADCAST AREA− A geographical area

of responsibility including one or more HIWAS

outlet areas assigned to a FSS for hazardous weather

advisory broadcasting.

HIWAS OUTLET AREA− An area defined as a 150

NM radius of a HIWAS outlet, expanded as necessary

to provide coverage.

HOLD FOR RELEASE− Used by ATC to delay an

aircraft for traffic management reasons; i.e., weather,

traffic volume, etc. Hold for release instructions

(including departure delay information) are used to

inform a pilot or a controller (either directly or

through an authorized relay) that an IFR departure

clearance is not valid until a release time or additional

instructions have been received.

(See ICAO term HOLDING POINT.)

HOLD IN LIEU OF PROCEDURE TURN− A hold

in lieu of procedure turn shall be established over a

final or intermediate fix when an approach can be

made from a properly aligned holding pattern. The

hold in lieu of procedure turn permits the pilot to

align with the final or intermediate segment of the

approach and/or descend in the holding pattern to an

altitude that will permit a normal descent to the final

approach fix altitude. The hold in lieu of procedure

turn is a required maneuver (the same as a procedure

turn) unless the aircraft is being radar vectored to the

final approach course, when “NoPT” is shown on the

approach chart, or when the pilot requests or the

controller advises the pilot to make a “straight−in”

approach.

HOLD PROCEDURE− A predetermined maneuver

which keeps aircraft within a specified airspace while

awaiting further clearance from air traffic control.

Also used during ground operations to keep aircraft

within a specified area or at a specified point while

awaiting further clearance from air traffic control.

(See HOLDING FIX.)

(Refer to AIM.)

HOLDING FIX− A specified fix identifiable to a

pilot by NAVAIDs or visual reference to the ground

used as a reference point in establishing and

maintaining the position of an aircraft while holding.

(See FIX.)

(See VISUAL HOLDING.)

(Refer to AIM.)

HOLDING POINT [ICAO]− A specified location,

identified by visual or other means, in the vicinity of

which the position of an aircraft in flight is

maintained in accordance with air traffic control

clearances.

HOLDING PROCEDURE−

(See HOLD PROCEDURE.)

HOLD-SHORT POINT− A point on the runway

beyond which a landing aircraft with a LAHSO

clearance is not authorized to proceed. This point

may be located prior to an intersecting runway,

taxiway, predetermined point, or approach/departure

flight path.

HOLD-SHORT POSITION LIGHTS− Flashing

in-pavement white lights located at specified

hold-short points.

HOLD-SHORT POSITION MARKING− The

painted runway marking located at the hold-short

point on all LAHSO runways.

HOLD-SHORT POSITION SIGNS− Red and white

holding position signs located alongside the

hold-short point.
Pilot/Controller Glossary 2/9/12

PCG H−3

HOMING− Flight toward a NAVAID, without

correcting for wind, by adjusting the aircraft heading

to maintain a relative bearing of zero degrees.

(See BEARING.)

(See ICAO term HOMING.)

HOMING [ICAO]− The procedure of using the

direction-finding equipment of one radio station with

the emission of another radio station, where at least

one of the stations is mobile, and whereby the mobile

station proceeds continuously towards the other

station.

HOVER CHECK− Used to describe when a

helicopter/VTOL aircraft requires a stabilized hover

to conduct a performance/power check prior to hover

taxi, air taxi, or takeoff. Altitude of the hover will

vary based on the purpose of the check.

HOVER TAXI− Used to describe a helicopter/VTOL

aircraft movement conducted above the surface and

in ground effect at airspeeds less than approximately

20 knots. The actual height may vary, and some

helicopters may require hover taxi above 25 feet AGL

to reduce ground effect turbulence or provide

clearance for cargo slingloads.

(See AIR TAXI.)

(See HOVER CHECK.)

(Refer to AIM.)

HOW DO YOU HEAR ME?− A question relating to

the quality of the transmission or to determine how

well the transmission is being received.

HZ−

(See HERTZ.)

Pilot/Controller Glossary 2/9/12

PCG I−1

I

I SAY AGAIN− The message will be repeated.

IAF−

(See INITIAL APPROACH FIX.)

IAP−

(See INSTRUMENT APPROACH

PROCEDURE.)

IAWP− Initial Approach Waypoint

ICAO−

(See ICAO Term INTERNATIONAL CIVIL

AVIATION ORGANIZATION.)

ICING− The accumulation of airframe ice.

Types of icing are:

a. Rime Ice− Rough, milky, opaque ice formed by

the instantaneous freezing of small supercooled

water droplets.

b. Clear Ice− A glossy, clear, or translucent ice

formed by the relatively slow freezing or large

supercooled water droplets.

c. Mixed− A mixture of clear ice and rime ice.

Intensity of icing:

a. Trace− Ice becomes perceptible. Rate of

accumulation is slightly greater than the rate of

sublimation. Deicing/anti-icing equipment is not

utilized unless encountered for an extended period of

time (over 1 hour).

b. Light− The rate of accumulation may create a

problem if flight is prolonged in this environment

(over 1 hour). Occasional use of deicing/anti-icing

equipment removes/prevents accumulation. It does

not present a problem if the deicing/anti-icing

equipment is used.

c. Moderate− The rate of accumulation is such that

even short encounters become potentially hazardous

and use of deicing/anti-icing equipment or flight

diversion is necessary.

d. Severe− The rate of accumulation is such that

deicing/anti-icing equipment fails to reduce or

control the hazard. Immediate flight diversion is

necessary.

IDENT− A request for a pilot to activate the aircraft

transponder identification feature. This will help the

controller to confirm an aircraft identity or to identify

an aircraft.

(Refer to AIM.)

IDENT FEATURE− The special feature in the Air

Traffic Control Radar Beacon System (ATCRBS)

equipment. It is used to immediately distinguish one

displayed beacon target from other beacon targets.

(See IDENT.)

IF−

(See INTERMEDIATE FIX.)

IFIM−

(See INTERNATIONAL FLIGHT INFORMATION

MANUAL.)

IF NO TRANSMISSION RECEIVED FOR

(TIME)−Used by ATC in radar approaches to prefix

procedures which should be followed by the pilot in

event of lost communications.

(See LOST COMMUNICATIONS.)

IFR−

(See INSTRUMENT FLIGHT RULES.)

IFR AIRCRAFT− An aircraft conducting flight in

accordance with instrument flight rules.

IFR CONDITIONS− Weather conditions below the

minimum for flight under visual flight rules.

(See INSTRUMENT METEOROLOGICAL

CONDITIONS.)

IFR DEPARTURE PROCEDURE−

(See IFR TAKEOFF MINIMUMS AND

DEPARTURE PROCEDURES.)

(Refer to AIM.)

IFR FLIGHT−

(See IFR AIRCRAFT.)

IFR LANDING MINIMUMS−

(See LANDING MINIMUMS.)

IFR MILITARY TRAINING ROUTES (IR)− Routes

used by the Department of Defense and associated

Reserve and Air Guard units for the purpose of

conducting low-altitude navigation and tactical

training in both IFR and VFR weather conditions

below 10,000 feet MSL at airspeeds in excess of 250

knots IAS.

IFR TAKEOFF MINIMUMS AND DEPARTURE

PROCEDURES− Title 14 Code of Federal
Pilot/Controller Glossary 2/9/12

PCG I−2

Regulations Part 91, prescribes standard takeoff rules

for certain civil users. At some airports, obstructions

or other factors require the establishment of

nonstandard takeoff minimums, departure procedures, or both to assist pilots in avoiding obstacles

during climb to the minimum en route altitude. Those

airports are listed in FAA/DOD Instrument Approach

Procedures (IAPs) Charts under a section entitled

“IFR Takeoff Minimums and Departure Procedures.”

The FAA/DOD IAP chart legend illustrates the

symbol used to alert the pilot to nonstandard takeoff

minimums and departure procedures. When departing IFR from such airports or from any airports where

there are no departure procedures, DPs, or ATC

facilities available, pilots should advise ATC of any

departure limitations. Controllers may query a pilot

to determine acceptable departure directions, turns,

or headings after takeoff. Pilots should be familiar

with the departure procedures and must assure that

their aircraft can meet or exceed any specified climb

gradients.

IF/IAWP− Intermediate Fix/Initial Approach Waypoint. The waypoint where the final approach course

of a T approach meets the crossbar of the T. When

designated (in conjunction with a TAA) this

waypoint will be used as an IAWP when approaching

the airport from certain directions, and as an IFWP

when beginning the approach from another IAWP.

IFWP− Intermediate Fix Waypoint

ILS−

(See INSTRUMENT LANDING SYSTEM.)

ILS CATEGORIES− 1. Category I. An ILS approach

procedure which provides for approach to a height

above touchdown of not less than 200 feet and with

runway visual range of not less than 1,800 feet.−

2. Special Authorization Category I. An ILS

approach procedure which provides for approach to

a height above touchdown of not less than 150 feet

and with runway visual range of not less than 1,400

feet, HUD to DH. 3. Category II. An ILS approach

procedure which provides for approach to a height

above touchdown of not less than 100 feet and with

runway visual range of not less than 1,200 feet (with

autoland or HUD to touchdown and noted on

authorization, RVR 1,000 feet).− 4. Special

Authorization Category II with Reduced Lighting.

An ILS approach procedure which provides for

approach to a height above touchdown of not less

than 100 feet and with runway visual range of not less

than 1,200 feet with autoland or HUD to touchdown

and noted on authorization (no touchdown zone and

centerline lighting are required).− 5. Category III:

a. IIIA.−An ILS approach procedure which

provides for approach without a decision height

minimum and with runway visual range of not less

than 700 feet.

b. IIIB.−An ILS approach procedure which

provides for approach without a decision height

minimum and with runway visual range of not less

than 150 feet.

c. IIIC.−An ILS approach procedure which

provides for approach without a decision height

minimum and without runway visual range

minimum.

ILS PRM APPROACH− An instrument landing

system (ILS) approach conducted to parallel runways

whose extended centerlines are separated by less than

4,300 feet and the parallel runways have a Precision

Runway Monitoring (PRM) system that permits

simultaneous independent ILS approaches.

IM−

(See INNER MARKER.)

IMC−

(See INSTRUMENT METEOROLOGICAL

CONDITIONS.)

IMMEDIATELY−Used by ATC or pilots when such

action compliance is required to avoid an imminent

situation.

INCERFA (Uncertainty Phase) [ICAO]− A situation

wherein uncertainty exists as to the safety of an

aircraft and its occupants.

INCREASE SPEED TO (SPEED)−

(See SPEED ADJUSTMENT.)

INERTIAL NAVIGATION SYSTEM− An RNAV

system which is a form of self-contained navigation.

(See Area Navigation/RNAV.)

INFLIGHT REFUELING−

(See AERIAL REFUELING.)

INFLIGHT WEATHER ADVISORY−

(See WEATHER ADVISORY.)

INFORMATION REQUEST− A request originated

by an FSS for information concerning an overdue

VFR aircraft.
Pilot/Controller Glossary 2/9/12

PCG I−3

INITIAL APPROACH FIX− The fixes depicted on

instrument approach procedure charts that identify

the beginning of the initial approach segment(s).

(See FIX.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

INITIAL APPROACH SEGMENT−

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

INITIAL APPROACH SEGMENT [ICAO]− That

segment of an instrument approach procedure

between the initial approach fix and the intermediate

approach fix or, where applicable, the final approach

fix or point.

INLAND NAVIGATION FACILITY− A navigation

aid on a North American Route at which the common

route and/or the noncommon route begins or ends.

INNER MARKER− A marker beacon used with an

ILS (CAT II) precision approach located between the

middle marker and the end of the ILS runway,

transmitting a radiation pattern keyed at six dots per

second and indicating to the pilot, both aurally and

visually, that he/she is at the designated decision

height (DH), normally 100 feet above the touchdown

zone elevation, on the ILS CAT II approach. It also

marks progress during a CAT III approach.

(See INSTRUMENT LANDING SYSTEM.)

(Refer to AIM.)

INNER MARKER BEACON−

(See INNER MARKER.)

INREQ−

(See INFORMATION REQUEST.)

INS−

(See INERTIAL NAVIGATION SYSTEM.)

INSTRUMENT APPROACH−

(See INSTRUMENT APPROACH

PROCEDURE.)

INSTRUMENT APPROACH PROCEDURE− A

series of predetermined maneuvers for the orderly

transfer of an aircraft under instrument flight

conditions from the beginning of the initial approach

to a landing or to a point from which a landing may

be made visually. It is prescribed and approved for a

specific airport by competent authority.

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

a. U.S. civil standard instrument approach

procedures are approved by the FAA as prescribed

under 14 CFR Part 97 and are available for public

use.

b. U.S. military standard instrument approach

procedures are approved and published by the

Department of Defense.

c. Special instrument approach procedures are

approved by the FAA for individual operators but are

not published in 14 CFR Part 97 for public use.

(See ICAO term INSTRUMENT APPROACH

PROCEDURE.)

INSTRUMENT APPROACH PROCEDURE

[ICAO]− A series of predetermined maneuvers by

reference to flight instruments with specified

protection from obstacles from the initial approach

fix, or where applicable, from the beginning of a

defined arrival route to a point from which a landing

can be completed and thereafter, if a landing is not

completed, to a position at which holding or en route

obstacle clearance criteria apply.

INSTRUMENT APPROACH PROCEDURES

CHARTS−

(See AERONAUTICAL CHART.)

INSTRUMENT DEPARTURE PROCEDURE

(DP)− A preplanned instrument flight rule (IFR)

departure procedure published for pilot use, in

graphic or textual format, that provides obstruction

clearance from the terminal area to the appropriate en

route structure. There are two types of DP, Obstacle

Departure Procedure (ODP), printed either textually

or graphically, and, Standard Instrument Departure

(SID), which is always printed graphically.

(See IFR TAKEOFF MINIMUMS AND

DEPARTURE PROCEDURES.)

(See OBSTACLE DEPARTURE PROCEDURES.)

(See STANDARD INSTRUMENT DEPARTURES.)

(Refer to AIM.)

INSTRUMENT DEPARTURE PROCEDURE (DP)

CHARTS−

(See AERONAUTICAL CHART.)
Pilot/Controller Glossary 2/9/12

PCG I−4

INSTRUMENT FLIGHT RULES− Rules governing

the procedures for conducting instrument flight. Also

a term used by pilots and controllers to indicate type

of flight plan.

(See INSTRUMENT METEOROLOGICAL

CONDITIONS.)

(See VISUAL FLIGHT RULES.)

(See VISUAL METEOROLOGICAL

CONDITIONS.)

(See ICAO term INSTRUMENT FLIGHT

RULES.)

(Refer to AIM.)

INSTRUMENT FLIGHT RULES [ICAO]− A set of

rules governing the conduct of flight under

instrument meteorological conditions.

INSTRUMENT LANDING SYSTEM− A precision

instrument approach system which normally consists

of the following electronic components and visual

aids:

a. Localizer.

(See LOCALIZER.)

b. Glideslope.

(See GLIDESLOPE.)

c. Outer Marker.

(See OUTER MARKER.)

d. Middle Marker.

(See MIDDLE MARKER.)

e. Approach Lights.

(See AIRPORT LIGHTING.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

INSTRUMENT METEOROLOGICAL CONDITIONS− Meteorological conditions expressed in

terms of visibility, distance from cloud, and ceiling

less than the minima specified for visual meteorological conditions.

(See INSTRUMENT FLIGHT RULES.)

(See VISUAL FLIGHT RULES.)

(See VISUAL METEOROLOGICAL

CONDITIONS.)

INSTRUMENT RUNWAY− A runway equipped

with electronic and visual navigation aids for which

a precision or nonprecision approach procedure

having straight-in landing minimums has been

approved.

(See ICAO term INSTRUMENT RUNWAY.)

INSTRUMENT RUNWAY [ICAO]− One of the

following types of runways intended for the

operation of aircraft using instrument approach

procedures:

a. Nonprecision Approach Runway−An instrument runway served by visual aids and a nonvisual

aid providing at least directional guidance adequate

for a straight-in approach.

b. Precision Approach Runway, Category I−An

instrument runway served by ILS and visual aids

intended for operations down to 60 m (200 feet)

decision height and down to an RVR of the order of

800 m.

c. Precision Approach Runway, Category II−An

instrument runway served by ILS and visual aids

intended for operations down to 30 m (100 feet)

decision height and down to an RVR of the order of

400 m.

d. Precision Approach Runway, Category III−An

instrument runway served by ILS to and along the

surface of the runway and:

1. Intended for operations down to an RVR of

the order of 200 m (no decision height being

applicable) using visual aids during the final phase of

landing;

2. Intended for operations down to an RVR of

the order of 50 m (no decision height being

applicable) using visual aids for taxiing;

3. Intended for operations without reliance on

visual reference for landing or taxiing.

Note 1: See Annex 10 Volume I, Part I, Chapter 3,

for related ILS specifications.

Note 2: Visual aids need not necessarily be

matched to the scale of nonvisual aids provided.

The criterion for the selection of visual aids is the

conditions in which operations are intended to be

conducted.

INTEGRITY− The ability of a system to provide

timely warnings to users when the system should not

be used for navigation.

INTERMEDIATE APPROACH SEGMENT−

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

INTERMEDIATE APPROACH SEGMENT

[ICAO]− That segment of an instrument approach

procedure between either the intermediate approach

fix and the final approach fix or point, or between the

end of a reversal, race track or dead reckoning track
Pilot/Controller Glossary 2/9/12

PCG I−5

procedure and the final approach fix or point, as

appropriate.

INTERMEDIATE FIX− The fix that identifies the

beginning of the intermediate approach segment of an

instrument approach procedure. The fix is not

normally identified on the instrument approach chart

as an intermediate fix (IF).

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

INTERMEDIATE LANDING− On the rare occasion

that this option is requested, it should be approved.

The departure center, however, must advise the

ATCSCC so that the appropriate delay is carried over

and assigned at the intermediate airport. An

intermediate landing airport within the arrival center

will not be accepted without coordination with and

the approval of the ATCSCC.

INTERNATIONAL AIRPORT− Relating to international flight, it means:

a. An airport of entry which has been designated

by the Secretary of Treasury or Commissioner of

Customs as an international airport for customs

service.

b. A landing rights airport at which specific

permission to land must be obtained from customs

authorities in advance of contemplated use.

c. Airports designated under the Convention on

International Civil Aviation as an airport for use by

international commercial air transport and/or international general aviation.

(See ICAO term INTERNATIONAL AIRPORT.)

(Refer to AIRPORT/FACILITY DIRECTORY.)

(Refer to IFIM.)

INTERNATIONAL AIRPORT [ICAO]− Any airport

designated by the Contracting State in whose

territory it is situated as an airport of entry and

departure for international air traffic, where the

formalities incident to customs, immigration, public

health, animal and plant quarantine and similar

procedures are carried out.

INTERNATIONAL CIVIL AVIATION ORGANIZATION [ICAO]− A specialized agency of the

United Nations whose objective is to develop the

principles and techniques of international air

navigation and to foster planning and development of

international civil air transport.

a. Regions include:

1. African-Indian Ocean Region

2. Caribbean Region

3. European Region

4. Middle East/Asia Region

5. North American Region

6. North Atlantic Region

7. Pacific Region

8. South American Region

INTERNATIONAL FLIGHT INFORMATION

MANUAL− A publication designed primarily as a

pilot’s preflight planning guide for flights into

foreign airspace and for flights returning to the U.S.

from foreign locations.

INTERROGATOR− The ground-based surveillance

radar beacon transmitter-receiver, which normally

scans in synchronism with a primary radar,

transmitting discrete radio signals which repetitiously request all transponders on the mode being used to

reply. The replies received are mixed with the

primary radar returns and displayed on the same plan

position indicator (radar scope). Also, applied to the

airborne element of the TACAN/DME system.

(See TRANSPONDER.)

(Refer to AIM.)

INTERSECTING RUNWAYS− Two or more

runways which cross or meet within their lengths.

(See INTERSECTION.)

INTERSECTION−

a. A point defined by any combination of courses,

radials, or bearings of two or more navigational aids.

b. Used to describe the point where two runways,

a runway and a taxiway, or two taxiways cross or

meet.

INTERSECTION DEPARTURE− A departure from

any runway intersection except the end of the runway.

(See INTERSECTION.)

INTERSECTION TAKEOFF−

(See INTERSECTION DEPARTURE.)

IR−

(See IFR MILITARY TRAINING ROUTES.)

Pilot/Controller Glossary 2/9/12

PCG J−1

J

JAMMING− Electronic or mechanical interference

which may disrupt the display of aircraft on radar or

the transmission/reception of radio communications/

navigation.

JET BLAST− Jet engine exhaust (thrust stream

turbulence).

(See WAKE TURBULENCE.)

JET ROUTE− A route designed to serve aircraft

operations from 18,000 feet MSL up to and including

flight level 450. The routes are referred to as “J”

routes with numbering to identify the designated

route; e.g., J105.

(See Class A AIRSPACE.)

(Refer to 14 CFR Part 71.)

JET STREAM− A migrating stream of high-speed

winds present at high altitudes.

JETTISONING OF EXTERNAL STORES− Airborne release of external stores; e.g., tiptanks,

ordnance.

(See FUEL DUMPING.)

(Refer to 14 CFR Part 91.)

JOINT USE RESTRICTED AREA−

(See RESTRICTED AREA.)

Pilot/Controller Glossary 2/9/12

PCG K−1

K

KNOWN TRAFFIC− With respect to ATC clearances, means aircraft whose altitude, position, and

intentions are known to ATC.

Pilot/Controller Glossary 2/9/12

PCG L−1

L

LAA−

(See LOCAL AIRPORT ADVISORY.)

LAAS−

(See LOW ALTITUDE ALERT SYSTEM.)

LAHSO− An acronym for “Land and Hold Short

Operation.” These operations include landing and

holding short of an intersecting runway, a taxiway, a

predetermined point, or an approach/departure

flightpath.

LAHSO-DRY− Land and hold short operations on

runways that are dry.

LAHSO-WET− Land and hold short operations on

runways that are wet (but not contaminated).

LAND AND HOLD SHORT OPERATIONS−

Operations which include simultaneous takeoffs and

landings and/or simultaneous landings when a

landing aircraft is able and is instructed by the

controller to hold-short of the intersecting runway/

taxiway or designated hold-short point. Pilots are

expected to promptly inform the controller if the hold

short clearance cannot be accepted.

(See PARALLEL RUNWAYS.)

(Refer to AIM.)

LANDING AREA− Any locality either on land,

water, or structures, including airports/heliports and

intermediate landing fields, which is used, or

intended to be used, for the landing and takeoff of

aircraft whether or not facilities are provided for the

shelter, servicing, or for receiving or discharging

passengers or cargo.

(See ICAO term LANDING AREA.)

LANDING AREA [ICAO]− That part of a movement

area intended for the landing or take-off of aircraft.

LANDING DIRECTION INDICATOR− A device

which visually indicates the direction in which

landings and takeoffs should be made.

(See TETRAHEDRON.)

(Refer to AIM.)

LANDING DISTANCE AVAILABLE (LDA)− The

runway length declared available and suitable for a

landing airplane.

(See ICAO term LANDING DISTANCE

AVAILABLE.)

LANDING DISTANCE AVAILABLE [ICAO]− The

length of runway which is declared available and

suitable for the ground run of an aeroplane landing.

LANDING MINIMUMS− The minimum visibility

prescribed for landing a civil aircraft while using an

instrument approach procedure. The minimum

applies with other limitations set forth in 14 CFR

Part 91 with respect to the Minimum Descent

Altitude (MDA) or Decision Height (DH) prescribed

in the instrument approach procedures as follows:

a. Straight-in landing minimums. A statement of

MDA and visibility, or DH and visibility, required for

a straight-in landing on a specified runway, or

b. Circling minimums. A statement of MDA and

visibility required for the circle-to-land maneuver.

Note: Descent below the established MDA or DH is

not authorized during an approach unless the

aircraft is in a position from which a normal

approach to the runway of intended landing can be

made and adequate visual reference to required

visual cues is maintained.

(See CIRCLE-TO-LAND MANEUVER.)

(See DECISION HEIGHT.)

(See INSTRUMENT APPROACH

PROCEDURE.)

(See MINIMUM DESCENT ALTITUDE.)

(See STRAIGHT-IN LANDING.)

(See VISIBILITY.)

(Refer to 14 CFR Part 91.)

LANDING ROLL− The distance from the point of

touchdown to the point where the aircraft can be

brought to a stop or exit the runway.

LANDING SEQUENCE− The order in which

aircraft are positioned for landing.

(See APPROACH SEQUENCE.)

LAST ASSIGNED ALTITUDE− The last altitude/

flight level assigned by ATC and acknowledged by

the pilot.

(See MAINTAIN.)

(Refer to 14 CFR Part 91.)

LATERAL NAVIGATION (LNAV)– A function of

area navigation (RNAV) equipment which calculates,

displays, and provides lateral guidance to a profile or

path.
Pilot/Controller Glossary 2/9/12

PCG L−2

LATERAL SEPARATION− The lateral spacing of

aircraft at the same altitude by requiring operation on

different routes or in different geographical locations.

(See SEPARATION.)

LDA−

(See LOCALIZER TYPE DIRECTIONAL AID.)

(See LANDING DISTANCE AVAILABLE.)

(See ICAO Term LANDING DISTANCE

AVAILABLE.)

LF−

(See LOW FREQUENCY.)

LIGHTED AIRPORT− An airport where runway and

obstruction lighting is available.

(See AIRPORT LIGHTING.)

(Refer to AIM.)

LIGHT GUN− A handheld directional light signaling

device which emits a brilliant narrow beam of white,

green, or red light as selected by the tower controller.

The color and type of light transmitted can be used to

approve or disapprove anticipated pilot actions where

radio communication is not available. The light gun

is used for controlling traffic operating in the vicinity

of the airport and on the airport movement area.

(Refer to AIM.)

LINE UP AND WAIT (LUAW)− Used by ATC to

inform a pilot to taxi onto the departure runway to line

up and wait. It is not authorization for takeoff. It is

used when takeoff clearance cannot immediately be

issued because of traffic or other reasons.

(See CLEARED FOR TAKEOFF.)

LOCAL AIRPORT ADVISORY (LAA)− A service

provided by facilities, which are located on the

landing airport, have a discrete ground−to−air

communication frequency or the tower frequency

when the tower is closed, automated weather

reporting with voice broadcasting, and a continuous

ASOS/AWSS/AWOS data display, other continuous

direct reading instruments, or manual observations

available to the specialist.

(See AIRPORT ADVISORY AREA.)

LOCAL TRAFFIC− Aircraft operating in the traffic

pattern or within sight of the tower, or aircraft known

to be departing or arriving from flight in local practice

areas, or aircraft executing practice instrument

approaches at the airport.

(See TRAFFIC PATTERN.)

LOCALIZER− The component of an ILS which

provides course guidance to the runway.

(See INSTRUMENT LANDING SYSTEM.)

(See ICAO term LOCALIZER COURSE.)

(Refer to AIM.)

LOCALIZER COURSE [ICAO]− The locus of

points, in any given horizontal plane, at which the

DDM (difference in depth of modulation) is zero.

LOCALIZER OFFSET− An angular offset of the

localizer from the runway extended centerline in a

direction away from the no transgression zone (NTZ)

that increases the normal operating zone (NOZ)

width. An offset requires a 50 foot increase in DH and

is not authorized for CAT II and CAT III approaches.

LOCALIZER TYPE DIRECTIONAL AID− A

NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a

localizer but which is not a part of a complete ILS and

is not aligned with the runway.

(Refer to AIM.)

LOCALIZER USABLE DISTANCE− The maximum distance from the localizer transmitter at a

specified altitude, as verified by flight inspection, at

which reliable course information is continuously

received.

(Refer to AIM.)

LOCATOR [ICAO]− An LM/MF NDB used as an aid

to final approach.

Note: A locator usually has an average radius of

rated coverage of between 18.5 and 46.3 km (10

and 25 NM).

LONG RANGE NAVIGATION−

(See LORAN.)

LONGITUDINAL SEPARATION− The longitudinal spacing of aircraft at the same altitude by a

minimum distance expressed in units of time or

miles.

(See SEPARATION.)

(Refer to AIM.)

LORAN− An electronic navigational system by

which hyperbolic lines of position are determined by

measuring the difference in the time of reception of

synchronized pulse signals from two fixed transmitters. Loran A operates in the 1750-1950 kHz

frequency band. Loran C and D operate in the

100-110 kHz frequency band.

(Refer to AIM.)

LOST COMMUNICATIONS− Loss of the ability to

communicate by radio. Aircraft are sometimes
Pilot/Controller Glossary 2/9/12

PCG L−3

referred to as NORDO (No Radio). Standard pilot

procedures are specified in 14 CFR Part 91. Radar

controllers issue procedures for pilots to follow in the

event of lost communications during a radar approach

when weather reports indicate that an aircraft will

likely encounter IFR weather conditions during the

approach.

(Refer to 14 CFR Part 91.)

(Refer AIM.)

LOW ALTITUDE AIRWAY STRUCTURE− The

network of airways serving aircraft operations up to

but not including 18,000 feet MSL.

(See AIRWAY.)

(Refer to AIM.)

LOW ALTITUDE ALERT, CHECK YOUR ALTITUDE IMMEDIATELY−

(See SAFETY ALERT.)

LOW ALTITUDE ALERT SYSTEM− An automated function of the TPX-42 that alerts the

controller when a Mode C transponder equipped

aircraft on an IFR flight plan is below a

predetermined minimum safe altitude. If requested

by the pilot, Low Altitude Alert System monitoring

is also available to VFR Mode C transponder

equipped aircraft.

LOW APPROACH− An approach over an airport or

runway following an instrument approach or a VFR

approach including the go-around maneuver where

the pilot intentionally does not make contact with the

runway.

(Refer to AIM.)

LOW FREQUENCY− The frequency band between

30 and 300 kHz.

(Refer to AIM.)

LPV− A type of approach with vertical guidance

(APV) based on WAAS, published on RNAV (GPS)

approach charts. This procedure takes advantage of

the precise lateral guidance available from WAAS.

The minima is published as a decision altitude (DA).

LUAW−

(See LINE UP AND WAIT.)

Pilot/Controller Glossary 2/9/12

PCG M−1

M

MAA−

(See MAXIMUM AUTHORIZED ALTITUDE.)

MACH NUMBER− The ratio of true airspeed to the

speed of sound; e.g., MACH .82, MACH 1.6.

(See AIRSPEED.)

MACH TECHNIQUE [ICAO]− Describes a control

technique used by air traffic control whereby turbojet

aircraft operating successively along suitable routes

are cleared to maintain appropriate MACH numbers

for a relevant portion of the en route phase of flight.

The principle objective is to achieve improved

utilization of the airspace and to ensure that

separation between successive aircraft does not

decrease below the established minima.

MAHWP− Missed Approach Holding Waypoint

MAINTAIN−

a. Concerning altitude/flight level, the term

means to remain at the altitude/flight level specified.

The phrase “climb and” or “descend and” normally

precedes “maintain” and the altitude assignment;

e.g., “descend and maintain 5,000.”

b. Concerning other ATC instructions, the term is

used in its literal sense; e.g., maintain VFR.

MAINTENANCE PLANNING FRICTION

LEVEL− The friction level specified in

AC 150/5320-12, Measurement, Construction, and

Maintenance of Skid Resistant Airport Pavement

Surfaces, which represents the friction value below

which the runway pavement surface remains

acceptable for any category or class of aircraft

operations but which is beginning to show signs of

deterioration. This value will vary depending on the

particular friction measurement equipment used.

MAKE SHORT APPROACH− Used by ATC to

inform a pilot to alter his/her traffic pattern so as to

make a short final approach.

(See TRAFFIC PATTERN.)

MAN PORTABLE AIR DEFENSE SYSTEMS

(MANPADS)− MANPADS are lightweight, shoulder−launched, missile systems used to bring down

aircraft and create mass casualties. The potential for

MANPADS use against airborne aircraft is real and

requires familiarity with the subject. Terrorists

choose MANPADS because the weapons are low

cost, highly mobile, require minimal set−up time, and

are easy to use and maintain. Although the weapons

have limited range, and their accuracy is affected by

poor visibility and adverse weather, they can be fired

from anywhere on land or from boats where there is

unrestricted visibility to the target.

MANDATORY ALTITUDE− An altitude depicted

on an instrument Approach Procedure Chart

requiring the aircraft to maintain altitude at the

depicted value.

MANPADS−

(See MAN PORTABLE AIR DEFENSE

SYSTEMS.)

MAP−

(See MISSED APPROACH POINT.)

MARKER BEACON− An electronic navigation

facility transmitting a 75 MHz vertical fan or

boneshaped radiation pattern. Marker beacons are

identified by their modulation frequency and keying

code, and when received by compatible airborne

equipment, indicate to the pilot, both aurally and

visually, that he/she is passing over the facility.

(See INNER MARKER.)

(See MIDDLE MARKER.)

(See OUTER MARKER.)

(Refer to AIM.)

MARSA−

(See MILITARY AUTHORITY ASSUMES

RESPONSIBILITY FOR SEPARATION OF

AIRCRAFT.)

MAWP− Missed Approach Waypoint

MAXIMUM AUTHORIZED ALTITUDE− A published altitude representing the maximum usable

altitude or flight level for an airspace structure or

route segment. It is the highest altitude on a Federal

airway, jet route, area navigation low or high route,

or other direct route for which an MEA is designated

in 14 CFR Part 95 at which adequate reception of

navigation aid signals is assured.

MAYDAY−The international radiotelephony distress

signal. When repeated three times, it indicates
Pilot/Controller Glossary 2/9/12

PCG M−2

imminent and grave danger and that immediate

assistance is requested.

 (See PAN-PAN.)

 (Refer to AIM.)

MCA−

(See MINIMUM CROSSING ALTITUDE.)

MDA−

(See MINIMUM DESCENT ALTITUDE.)

MEA−

(See MINIMUM EN ROUTE IFR ALTITUDE.)

MEARTS−

(See MICRO-EN ROUTE AUTOMATED RADAR

TRACKING SYSTEM.)

METEOROLOGICAL IMPACT STATEMENT−

An unscheduled planning forecast describing

conditions expected to begin within 4 to 12 hours

which may impact the flow of air traffic in a specific

center’s (ARTCC) area.

METER FIX ARC− A semicircle, equidistant from

a meter fix, usually in low altitude relatively close to

the meter fix, used to help CTAS/HOST calculate a

meter time, and determine appropriate sector meter

list assignments for aircraft not on an established

arrival route or assigned a meter fix.

METER FIX TIME/SLOT TIME− A calculated time

to depart the meter fix in order to cross the vertex at

the ACLT. This time reflects descent speed

adjustment and any applicable time that must be

absorbed prior to crossing the meter fix.

METER LIST−

(See ARRIVAL SECTOR ADVISORY LIST.)

METER LIST DISPLAY INTERVAL− A dynamic

parameter which controls the number of minutes

prior to the flight plan calculated time of arrival at the

meter fix for each aircraft, at which time the TCLT is

frozen and becomes an ACLT; i.e., the VTA is

updated and consequently the TCLT modified as

appropriate until frozen at which time updating is

suspended and an ACLT is assigned. When frozen,

the flight entry is inserted into the arrival sector’s

meter list for display on the sector PVD/MDM.

MLDI is used if filed true airspeed is less than or

equal to freeze speed parameters (FSPD).

METERING− A method of time-regulating arrival

traffic flow into a terminal area so as not to exceed a

predetermined terminal acceptance rate.

METERING AIRPORTS− Airports adapted for

metering and for which optimum flight paths are

defined. A maximum of 15 airports may be adapted.

METERING FIX− A fix along an established route

from over which aircraft will be metered prior to

entering terminal airspace. Normally, this fix should

be established at a distance from the airport which

will facilitate a profile descent 10,000 feet above

airport elevation (AAE) or above.

METERING POSITION(S)− Adapted PVDs/

MDMs and associated “D” positions eligible for

display of a metering position list. A maximum of

four PVDs/MDMs may be adapted.

METERING POSITION LIST− An ordered list of

data on arrivals for a selected metering airport

displayed on a metering position PVD/MDM.

MFT−

(See METER FIX TIME/SLOT TIME.)

MHA−

(See MINIMUM HOLDING ALTITUDE.)

MIA−

(See MINIMUM IFR ALTITUDES.)

MICROBURST− A small downburst with outbursts

of damaging winds extending 2.5 miles or less. In

spite of its small horizontal scale, an intense

microburst could induce wind speeds as high as 150

knots

(Refer to AIM.)

MICRO-EN ROUTE AUTOMATED RADAR

TRACKING SYSTEM (MEARTS)− An automated

radar and radar beacon tracking system capable of

employing both short-range (ASR) and long-range

(ARSR) radars. This microcomputer driven system

provides improved tracking, continuous data recording, and use of full digital radar displays.

MICROWAVE LANDING SYSTEM− A precision

instrument approach system operating in the

microwave spectrum which normally consists of the

following components:

a. Azimuth Station.

b. Elevation Station.

c. Precision Distance Measuring Equipment.

(See MLS CATEGORIES.)

MID RVR−

(See VISIBILITY.)

MIDDLE COMPASS LOCATOR−

(See COMPASS LOCATOR.)
Pilot/Controller Glossary 2/9/12

PCG M−3

MIDDLE MARKER− A marker beacon that defines

a point along the glideslope of an ILS normally

located at or near the point of decision height (ILS

Category I). It is keyed to transmit alternate dots and

dashes, with the alternate dots and dashes keyed at the

rate of 95 dot/dash combinations per minute on a

1300 Hz tone, which is received aurally and visually

by compatible airborne equipment.

(See INSTRUMENT LANDING SYSTEM.)

(See MARKER BEACON.)

(Refer to AIM.)

MILES-IN-TRAIL− A specified distance between

aircraft, normally, in the same stratum associated

with the same destination or route of flight.

MILITARY AUTHORITY ASSUMES RESPONSIBILITY FOR SEPARATION OF AIRCRAFT− A

condition whereby the military services involved

assume responsibility for separation between

participating military aircraft in the ATC system. It is

used only for required IFR operations which are

specified in letters of agreement or other appropriate

FAA or military documents.

MILITARY LANDING ZONE− A landing strip used

exclusively by the military for training. A military

landing zone does not carry a runway designation.

MILITARY OPERATIONS AREA−

(See SPECIAL USE AIRSPACE.)

MILITARY TRAINING ROUTES− Airspace of

defined vertical and lateral dimensions established

for the conduct of military flight training at airspeeds

in excess of 250 knots IAS.

(See IFR MILITARY TRAINING ROUTES.)

(See VFR MILITARY TRAINING ROUTES.)

MINIMA−

(See MINIMUMS.)

MINIMUM CROSSING ALTITUDE− The lowest

altitude at certain fixes at which an aircraft must cross

when proceeding in the direction of a higher

minimum en route IFR altitude (MEA).

(See MINIMUM EN ROUTE IFR ALTITUDE.)

MINIMUM DESCENT ALTITUDE− The lowest

altitude, expressed in feet above mean sea level, to

which descent is authorized on final approach or

during circle-to-land maneuvering in execution of a

standard instrument approach procedure where no

electronic glideslope is provided.

(See NONPRECISION APPROACH

PROCEDURE.)

MINIMUM EN ROUTE IFR ALTITUDE (MEA)−

The lowest published altitude between radio fixes

which assures acceptable navigational signal coverage and meets obstacle clearance requirements

between those fixes. The MEA prescribed for a

Federal airway or segment thereof, area navigation

low or high route, or other direct route applies to the

entire width of the airway, segment, or route between

the radio fixes defining the airway, segment, or route.

(Refer to 14 CFR Part 91.)

(Refer to 14 CFR Part 95.)

(Refer to AIM.)

MINIMUM FRICTION LEVEL− The friction level

specified in AC 150/5320-12, Measurement,

Construction, and Maintenance of Skid Resistant

Airport Pavement Surfaces, that represents the

minimum recommended wet pavement surface

friction value for any turbojet aircraft engaged in

LAHSO. This value will vary with the particular

friction measurement equipment used.

MINIMUM FUEL− Indicates that an aircraft’s fuel

supply has reached a state where, upon reaching the

destination, it can accept little or no delay. This is not

an emergency situation but merely indicates an

emergency situation is possible should any undue

delay occur.

(Refer to AIM.)

MINIMUM HOLDING ALTITUDE− The lowest

altitude prescribed for a holding pattern which

assures navigational signal coverage, communications, and meets obstacle clearance requirements.

MINIMUM IFR ALTITUDES (MIA)− Minimum

altitudes for IFR operations as prescribed in 14 CFR

Part 91. These altitudes are published on aeronautical

charts and prescribed in 14 CFR Part 95 for airways

and routes, and in 14 CFR Part 97 for standard

instrument approach procedures. If no applicable

minimum altitude is prescribed in 14 CFR Part 95 or

14 CFR Part 97, the following minimum IFR

altitude applies:

a. In designated mountainous areas, 2,000 feet

above the highest obstacle within a horizontal

distance of 4 nautical miles from the course to be

flown; or
Pilot/Controller Glossary 2/9/12

PCG M−4

b. Other than mountainous areas, 1,000 feet above

the highest obstacle within a horizontal distance of 4

nautical miles from the course to be flown; or

c. As otherwise authorized by the Administrator

or assigned by ATC.

(See MINIMUM CROSSING ALTITUDE.)

(See MINIMUM EN ROUTE IFR ALTITUDE.)

(See MINIMUM OBSTRUCTION CLEARANCE

ALTITUDE.)

(See MINIMUM SAFE ALTITUDE.)

(See MINIMUM VECTORING ALTITUDE.)

(Refer to 14 CFR Part 91.)

MINIMUM NAVIGATION PERFORMANCE

SPECIFICATION− A set of standards which require

aircraft to have a minimum navigation performance

capability in order to operate in MNPS designated

airspace. In addition, aircraft must be certified by

their State of Registry for MNPS operation.

MINIMUM NAVIGATION PERFORMANCE

SPECIFICATION AIRSPACE− Designated airspace

in which MNPS procedures are applied between

MNPS certified and equipped aircraft. Under certain

conditions, non-MNPS aircraft can operate in

MNPSA. However, standard oceanic separation

minima is provided between the non-MNPS aircraft

and other traffic. Currently, the only designated

MNPSA is described as follows:

a. Between FL 285 and FL 420;

b. Between latitudes 27N and the North Pole;

c. In the east, the eastern boundaries of the CTAs

Santa Maria Oceanic, Shanwick Oceanic, and

Reykjavik;

d. In the west, the western boundaries of CTAs

Reykjavik and Gander Oceanic and New York

Oceanic excluding the area west of 60W and south

of 3830’N.

MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)− The lowest published altitude in

effect between radio fixes on VOR airways,

off-airway routes, or route segments which meets

obstacle clearance requirements for the entire route

segment and which assures acceptable navigational

signal coverage only within 25 statute (22 nautical)

miles of a VOR.

(Refer to 14 CFR Part 91.)

(Refer to 14 CFR Part 95.)

MINIMUM RECEPTION ALTITUDE− The lowest

altitude at which an intersection can be determined.

(Refer to 14 CFR Part 95.)

MINIMUM SAFE ALTITUDE−

a. The minimum altitude specified in 14 CFR

Part 91 for various aircraft operations.

b. Altitudes depicted on approach charts which

provide at least 1,000 feet of obstacle clearance for

emergency use within a specified distance from the

navigation facility upon which a procedure is

predicated. These altitudes will be identified as

Minimum Sector Altitudes or Emergency Safe

Altitudes and are established as follows:

1. Minimum Sector Altitudes. Altitudes depicted on approach charts which provide at least

1,000 feet of obstacle clearance within a 25-mile

radius of the navigation facility upon which the

procedure is predicated. Sectors depicted on

approach charts must be at least 90 degrees in scope.

These altitudes are for emergency use only and do not

necessarily assure acceptable navigational signal

coverage.

(See ICAO term Minimum Sector Altitude.)

2. Emergency Safe Altitudes. Altitudes depicted on approach charts which provide at least

1,000 feet of obstacle clearance in nonmountainous

areas and 2,000 feet of obstacle clearance in

designated mountainous areas within a 100-mile

radius of the navigation facility upon which the

procedure is predicated and normally used only in

military procedures. These altitudes are identified on

published procedures as “Emergency Safe Altitudes.”

MINIMUM SAFE ALTITUDE WARNING− A

function of the ARTS III computer that aids the

controller by alerting him/her when a tracked Mode

C equipped aircraft is below or is predicted by the

computer to go below a predetermined minimum safe

altitude.

(Refer to AIM.)

MINIMUM SECTOR ALTITUDE [ICAO]− The

lowest altitude which may be used under emergency

conditions which will provide a minimum clearance

of 300 m (1,000 feet) above all obstacles located in

an area contained within a sector of a circle of 46 km

(25 NM) radius centered on a radio aid to navigation.

MINIMUMS− Weather condition requirements

established for a particular operation or type of
Pilot/Controller Glossary 2/9/12

PCG M−5

operation; e.g., IFR takeoff or landing, alternate

airport for IFR flight plans, VFR flight, etc.

(See IFR CONDITIONS.)

(See IFR TAKEOFF MINIMUMS AND

DEPARTURE PROCEDURES.)

(See LANDING MINIMUMS.)

(See VFR CONDITIONS.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

MINIMUM VECTORING ALTITUDE (MVA)−

The lowest MSL altitude at which an IFR aircraft will

be vectored by a radar controller, except as otherwise

authorized for radar approaches, departures, and

missed approaches. The altitude meets IFR obstacle

clearance criteria. It may be lower than the published

MEA along an airway or J-route segment. It may be

utilized for radar vectoring only upon the controller’s

determination that an adequate radar return is being

received from the aircraft being controlled. Charts

depicting minimum vectoring altitudes are normally

available only to the controllers and not to pilots.

(Refer to AIM.)

MINUTES-IN-TRAIL− A specified interval between aircraft expressed in time. This method would

more likely be utilized regardless of altitude.

MIS−

(See METEOROLOGICAL IMPACT

STATEMENT.)

MISSED APPROACH−

a. A maneuver conducted by a pilot when an

instrument approach cannot be completed to a

landing. The route of flight and altitude are shown on

instrument approach procedure charts. A pilot

executing a missed approach prior to the Missed

Approach Point (MAP) must continue along the final

approach to the MAP.

b. A term used by the pilot to inform ATC that

he/she is executing the missed approach.

c. At locations where ATC radar service is

provided, the pilot should conform to radar vectors

when provided by ATC in lieu of the published

missed approach procedure.

(See MISSED APPROACH POINT.)

(Refer to AIM.)

MISSED APPROACH POINT− A point prescribed

in each instrument approach procedure at which a

missed approach procedure shall be executed if the

required visual reference does not exist.

(See MISSED APPROACH.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

MISSED APPROACH PROCEDURE [ICAO]− The

procedure to be followed if the approach cannot be

continued.

MISSED APPROACH SEGMENT−

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

MLDI−

(See METER LIST DISPLAY INTERVAL.)

MLS−

(See MICROWAVE LANDING SYSTEM.)

MLS CATEGORIES−

a. MLS Category I. An MLS approach procedure

which provides for an approach to a height above

touchdown of not less than 200 feet and a runway

visual range of not less than 1,800 feet.

b. MLS Category II. Undefined until data gathering/analysis completion.

c. MLS Category III. Undefined until data

gathering/analysis completion.

MM−

(See MIDDLE MARKER.)

MNPS−

(See MINIMUM NAVIGATION PERFORMANCE

SPECIFICATION.)

MNPSA−

(See MINIMUM NAVIGATION PERFORMANCE−

SPECIFICATION AIRSPACE.)

MOA−

(See MILITARY OPERATIONS AREA.)

MOCA−

(See MINIMUM OBSTRUCTION CLEARANCE

ALTITUDE.)

MODE− The letter or number assigned to a specific

pulse spacing of radio signals transmitted or received

by ground interrogator or airborne transponder

components of the Air Traffic Control Radar Beacon
Pilot/Controller Glossary 2/9/12

PCG M−6

System (ATCRBS). Mode A (military Mode 3) and

Mode C (altitude reporting) are used in air traffic

control.

(See INTERROGATOR.)

(See RADAR.)

(See TRANSPONDER.)

(See ICAO term MODE.)

(Refer to AIM.)

MODE (SSR MODE) [ICAO]− The letter or number

assigned to a specific pulse spacing of the

interrogation signals transmitted by an interrogator.

There are 4 modes, A, B, C and D specified in Annex

10, corresponding to four different interrogation

pulse spacings.

MODE C INTRUDER ALERT− A function of

certain air traffic control automated systems designed

to alert radar controllers to existing or pending

situations between a tracked target (known IFR or

VFR aircraft) and an untracked target (unknown IFR

or VFR aircraft) that requires immediate attention/

action.

(See CONFLICT ALERT.)

MONITOR− (When used with communication

transfer) listen on a specific frequency and stand by

for instructions. Under normal circumstances do not

establish communications.

MONITOR ALERT (MA)− A function of the TFMS

that provides traffic management personnel with a

tool for predicting potential capacity problems in

individual operational sectors. The MA is an

indication that traffic management personnel need to

analyze a particular sector for actual activity and to

determine the required action(s), if any, needed to

control the demand.

MONITOR ALERT PARAMETER (MAP)− The

number designated for use in monitor alert

processing by the TFMS. The MAP is designated for

each operational sector for increments of 15 minutes.

MOSAIC/MULTI−SENSOR MODE− Accepts positional data from multiple radar or ADS−B sites.

Targets are displayed from a single source within a

radar sort box according to the hierarchy of the

sources assigned.

MOVEMENT AREA− The runways, taxiways, and

other areas of an airport/heliport which are utilized

for taxiing/hover taxiing, air taxiing, takeoff, and

landing of aircraft, exclusive of loading ramps and

parking areas. At those airports/heliports with a

tower, specific approval for entry onto the movement

area must be obtained from ATC.

(See ICAO term MOVEMENT AREA.)

MOVEMENT AREA [ICAO]− That part of an

aerodrome to be used for the takeoff, landing and

taxiing of aircraft, consisting of the maneuvering area

and the apron(s).

MOVING TARGET INDICATOR− An electronic

device which will permit radar scope presentation

only from targets which are in motion. A partial

remedy for ground clutter.

MRA−

(See MINIMUM RECEPTION ALTITUDE.)

MSA−

(See MINIMUM SAFE ALTITUDE.)

MSAW−

(See MINIMUM SAFE ALTITUDE WARNING.)

MTI−

(See MOVING TARGET INDICATOR.)

MTR−

(See MILITARY TRAINING ROUTES.)

MULTICOM− A mobile service not open to public

correspondence used to provide communications

essential to conduct the activities being performed by

or directed from private aircraft.

MULTIPLE RUNWAYS− The utilization of a

dedicated arrival runway(s) for departures and a

dedicated departure runway(s) for arrivals when

feasible to reduce delays and enhance capacity.

MVA−

(See MINIMUM VECTORING ALTITUDE.)
Pilot/Controller Glossary 2/9/12

PCG N−1

N

NAS−

(See NATIONAL AIRSPACE SYSTEM.)

NATIONAL AIRSPACE SYSTEM− The common

network of U.S. airspace; air navigation facilities,

equipment and services, airports or landing areas;

aeronautical charts, information and services; rules,

regulations and procedures, technical information,

and manpower and material. Included are system

components shared jointly with the military.

NATIONAL BEACON CODE ALLOCATION

PLAN AIRSPACE− Airspace over United States

territory located within the North American continent

between Canada and Mexico, including adjacent

territorial waters outward to about boundaries of

oceanic control areas (CTA)/Flight Information

Regions (FIR).

(See FLIGHT INFORMATION REGION.)

NATIONAL FLIGHT DATA CENTER− A facility in

Washington D.C., established by FAA to operate a

central aeronautical information service for the

collection, validation, and dissemination of aeronautical data in support of the activities of government,

industry, and the aviation community. The information is published in the National Flight Data Digest.

(See NATIONAL FLIGHT DATA DIGEST.)

NATIONAL FLIGHT DATA DIGEST− A daily

(except weekends and Federal holidays) publication

of flight information appropriate to aeronautical

charts, aeronautical publications, Notices to Airmen,

or other media serving the purpose of providing

operational flight data essential to safe and efficient

aircraft operations.

NATIONAL SEARCH AND RESCUE PLAN− An

interagency agreement which provides for the

effective utilization of all available facilities in all

types of search and rescue missions.

NAVAID−

(See NAVIGATIONAL AID.)

NAVAID CLASSES− VOR, VORTAC, and TACAN

aids are classed according to their operational use.

The three classes of NAVAIDs are:

a. T− Terminal.

b. L− Low altitude.

c. H− High altitude.

Note: The normal service range for T, L, and H class

aids is found in the AIM. Certain operational

requirements make it necessary to use some of

these aids at greater service ranges than

specified. Extended range is made possible

through flight inspection determinations. Some

aids also have lesser service range due to location,

terrain, frequency protection, etc. Restrictions to

service range are listed in Airport/Facility

Directory.

NAVIGABLE AIRSPACE− Airspace at and above

the minimum flight altitudes prescribed in the CFRs

including airspace needed for safe takeoff and

landing.

(Refer to 14 CFR Part 91.)

NAVIGATION REFERENCE SYSTEM (NRS)−

The NRS is a system of waypoints developed for use

within the United States for flight planning and

navigation without reference to ground based

navigational aids. The NRS waypoints are located in

a grid pattern along defined latitude and longitude

lines. The initial use of the NRS will be in the high

altitude environment in conjunction with the High

Altitude Redesign initiative. The NRS waypoints are

intended for use by aircraft capable of point−to−point

navigation.

NAVIGATION SPECIFICATION [ICAO]− A set of

aircraft and flight crew requirements needed to

support performance−based navigation operations

within a defined airspace. There are two kinds of

navigation specifications:

a. RNP specification. A navigation specification

based on area navigation that includes the

requirement for performance monitoring and alerting, designated by the prefix RNP; e.g., RNP 4, RNP

APCH.

b. RNAV specification. A navigation specification based on area navigation that does not include the

requirement for performance monitoring and alerting, designated by the prefix RNAV; e.g., RNAV 5,

RNAV 1.

Note: The Performance−based Navigation Manual

(Doc 9613), Volume II contains detailed guidance

on navigation specifications.
Pilot/Controller Glossary 2/9/12

PCG N−2

NAVIGATIONAL AID− Any visual or electronic

device airborne or on the surface which provides

point-to-point guidance information or position data

to aircraft in flight.

(See AIR NAVIGATION FACILITY.)

NBCAP AIRSPACE−

(See NATIONAL BEACON CODE ALLOCATION

PLAN AIRSPACE.)

NDB−

(See NONDIRECTIONAL BEACON.)

NEGATIVE− “No,” or “permission not granted,” or

“that is not correct.”

NEGATIVE CONTACT− Used by pilots to inform

ATC that:

a. Previously issued traffic is not in sight. It may

be followed by the pilot’s request for the controller to

provide assistance in avoiding the traffic.

b. They were unable to contact ATC on a

particular frequency.

NFDC−

(See NATIONAL FLIGHT DATA CENTER.)

NFDD−

(See NATIONAL FLIGHT DATA DIGEST.)

NIGHT− The time between the end of evening civil

twilight and the beginning of morning civil twilight,

as published in the American Air Almanac, converted

to local time.

(See ICAO term NIGHT.)

NIGHT [ICAO]− The hours between the end of

evening civil twilight and the beginning of morning

civil twilight or such other period between sunset and

sunrise as may be specified by the appropriate

authority.

Note: Civil twilight ends in the evening when the

center of the sun’s disk is 6 degrees below the

horizon and begins in the morning when the center

of the sun’s disk is 6 degrees below the horizon.

NO GYRO APPROACH− A radar approach/vector

provided in case of a malfunctioning gyro-compass

or directional gyro. Instead of providing the pilot

with headings to be flown, the controller observes the

radar track and issues control instructions “turn

right/left” or “stop turn” as appropriate.

(Refer to AIM.)

NO GYRO VECTOR−

(See NO GYRO APPROACH.)

NO TRANSGRESSION ZONE (NTZ)− The NTZ is

a 2,000 foot wide zone, located equidistant between

parallel runway final approach courses in which

flight is not allowed.

NONAPPROACH CONTROL TOWER− Authorizes aircraft to land or takeoff at the airport controlled

by the tower or to transit the Class D airspace. The

primary function of a nonapproach control tower is

the sequencing of aircraft in the traffic pattern and on

the landing area. Nonapproach control towers also

separate aircraft operating under instrument flight

rules clearances from approach controls and centers.

They provide ground control services to aircraft,

vehicles, personnel, and equipment on the airport

movement area.

NONCOMMON ROUTE/PORTION− That segment

of a North American Route between the inland

navigation facility and a designated North American

terminal.

NONCOMPOSITE SEPARATION− Separation in

accordance with minima other than the composite

separation minimum specified for the area concerned.

NONDIRECTIONAL BEACON− An L/MF or UHF

radio beacon transmitting nondirectional signals

whereby the pilot of an aircraft equipped with

direction finding equipment can determine his/her

bearing to or from the radio beacon and “home” on or

track to or from the station. When the radio beacon is

installed in conjunction with the Instrument Landing

System marker, it is normally called a Compass

Locator.

(See AUTOMATIC DIRECTION FINDER.)

(See COMPASS LOCATOR.)

NONMOVEMENT AREAS− Taxiways and apron

(ramp) areas not under the control of air traffic.

NONPRECISION APPROACH−

(See NONPRECISION APPROACH

PROCEDURE.)

NONPRECISION APPROACH PROCEDURE− A

standard instrument approach procedure in which no

electronic glideslope is provided; e.g., VOR,

TACAN, NDB, LOC, ASR, LDA, or SDF

approaches.

NONRADAR− Precedes other terms and generally

means without the use of radar, such as:

a. Nonradar Approach. Used to describe instrument approaches for which course guidance on final
Pilot/Controller Glossary 2/9/12

PCG N−3

approach is not provided by ground-based precision

or surveillance radar. Radar vectors to the final

approach course may or may not be provided by ATC.

Examples of nonradar approaches are VOR, NDB,

TACAN, and ILS/MLS approaches.

(See FINAL APPROACH COURSE.)

(See FINAL APPROACH-IFR.)

(See INSTRUMENT APPROACH

PROCEDURE.)

(See RADAR APPROACH.)

b. Nonradar Approach Control. An ATC facility

providing approach control service without the use of

radar.

(See APPROACH CONTROL FACILITY.)

(See APPROACH CONTROL SERVICE.)

c. Nonradar Arrival. An aircraft arriving at an

airport without radar service or at an airport served by

a radar facility and radar contact has not been

established or has been terminated due to a lack of

radar service to the airport.

(See RADAR ARRIVAL.)

(See RADAR SERVICE.)

d. Nonradar Route. A flight path or route over

which the pilot is performing his/her own navigation.

The pilot may be receiving radar separation, radar

monitoring, or other ATC services while on a

nonradar route.

(See RADAR ROUTE.)

e. Nonradar Separation. The spacing of aircraft in

accordance with established minima without the use

of radar; e.g., vertical, lateral, or longitudinal

separation.

(See RADAR SEPARATION.)

(See ICAO term NONRADAR SEPARATION.)

NONRADAR SEPARATION [ICAO]− The separation used when aircraft position information is

derived from sources other than radar.

NON−RESTRICTIVE ROUTING (NRR)− Portions

of a proposed route of flight where a user can flight

plan the most advantageous flight path with no

requirement to make reference to ground−based

NAVAIDs.

NOPAC−

(See NORTH PACIFIC.)

NORDO (No Radio)− Aircraft that cannot or do not

communicate by radio when radio communication is

required are referred to as “NORDO.”

(See LOST COMMUNICATIONS.)

NORMAL OPERATING ZONE (NOZ)− The NOZ

is the operating zone within which aircraft flight

remains during normal independent simultaneous

parallel ILS approaches.

NORTH AMERICAN ROUTE− A numerically

coded route preplanned over existing airway and

route systems to and from specific coastal fixes

serving the North Atlantic. North American Routes

consist of the following:

a. Common Route/Portion. That segment of a

North American Route between the inland navigation

facility and the coastal fix.

b. Noncommon Route/Portion. That segment of a

North American Route between the inland navigation

facility and a designated North American terminal.

c. Inland Navigation Facility. A navigation aid on

a North American Route at which the common route

and/or the noncommon route begins or ends.

d. Coastal Fix. A navigation aid or intersection

where an aircraft transitions between the domestic

route structure and the oceanic route structure.

NORTH AMERICAN ROUTE PROGRAM (NRP)−

The NRP is a set of rules and procedures which are

designed to increase the flexibility of user flight

planning within published guidelines.

NORTH MARK− A beacon data block sent by the

host computer to be displayed by the ARTS on a 360

degree bearing at a locally selected radar azimuth and

distance. The North Mark is used to ensure correct

range/azimuth orientation during periods of

CENRAP.

NORTH PACIFIC− An organized route system

between the Alaskan west coast and Japan.

NOTAM−

(See NOTICE TO AIRMEN.)

NOTAM [ICAO]− A notice containing information

concerning the establishment, condition or change in

any aeronautical facility, service, procedure or

hazard, the timely knowledge of which is essential to

personnel concerned with flight operations.

a. I Distribution− Distribution by means of

telecommunication.

b. II Distribution− Distribution by means other

than telecommunications.

NOTICE TO AIRMEN− A notice containing

information (not known sufficiently in advance to

publicize by other means) concerning the
Pilot/Controller Glossary 2/9/12

PCG N−4

establishment, condition, or change in any component (facility, service, or procedure of, or hazard in

the National Airspace System) the timely knowledge

of which is essential to personnel concerned with

flight operations.

a. NOTAM(D)− A NOTAM given (in addition to

local dissemination) distant dissemination beyond

the area of responsibility of the Flight Service

Station. These NOTAMs will be stored and available

until canceled.

b. FDC NOTAM− A NOTAM regulatory in

nature, transmitted by USNOF and given system

wide dissemination.

(See ICAO term NOTAM.)

NOTICES TO AIRMEN PUBLICATION− A

publication issued every 28 days, designed primarily

for the pilot, which contains current NOTAM

information considered essential to the safety of

flight as well as supplemental data to other

aeronautical publications. The contraction NTAP is

used in NOTAM text.

(See NOTICE TO AIRMEN.)

NRR−

(See NON−RESTRICTIVE ROUTING.)

NRS−

(See NAVIGATION REFERENCE SYSTEM.)

NTAP−

(See NOTICES TO AIRMEN PUBLICATION.)

NUMEROUS TARGETS VICINITY (LOCATION)− A traffic advisory issued by ATC to advise

pilots that targets on the radar scope are too numerous

to issue individually.

(See TRAFFIC ADVISORIES.)
Pilot/Controller Glossary 2/9/12

PCG O−1

O

OBSTACLE− An existing object, object of natural

growth, or terrain at a fixed geographical location or

which may be expected at a fixed location within a

prescribed area with reference to which vertical

clearance is or must be provided during flight

operation.

OBSTACLE DEPARTURE PROCEDURE (ODP)−

A preplanned instrument flight rule (IFR) departure

procedure printed for pilot use in textual or graphic

form to provide obstruction clearance via the least

onerous route from the terminal area to the

appropriate en route structure. ODPs are recommended for obstruction clearance and may be flown

without ATC clearance unless an alternate departure

procedure (SID or radar vector) has been specifically

assigned by ATC.

(See IFR TAKEOFF MINIMUMS AND

DEPARTURE PROCEDURES.)

(See STANDARD INSTRUMENT

DEPARTURES.)

(Refer to AIM.)

OBSTACLE FREE ZONE− The OFZ is a three

dimensional volume of airspace which protects for

the transition of aircraft to and from the runway. The

OFZ clearing standard precludes taxiing and parked

airplanes and object penetrations, except for

frangible NAVAID locations that are fixed by

function. Additionally, vehicles, equipment, and

personnel may be authorized by air traffic control to

enter the area using the provisions of FAAO JO

7110.65, Para 3−1−5, VEHICLES/EQUIPMENT/

PERSONNEL ON RUNWAYS. The runway OFZ

and when applicable, the inner-approach OFZ, and

the inner-transitional OFZ, comprise the OFZ.

a. Runway OFZ. The runway OFZ is a defined

volume of airspace centered above the runway. The

runway OFZ is the airspace above a surface whose

elevation at any point is the same as the elevation of

the nearest point on the runway centerline. The

runway OFZ extends 200 feet beyond each end of the

runway. The width is as follows:

1. For runways serving large airplanes, the

greater of:

(a) 400 feet, or

(b) 180 feet, plus the wingspan of the most

demanding airplane, plus 20 feet per 1,000 feet of

airport elevation.

2. For runways serving only small airplanes:

(a) 300 feet for precision instrument runways.

(b) 250 feet for other runways serving small

airplanes with approach speeds of 50 knots, or more.

(c) 120 feet for other runways serving small

airplanes with approach speeds of less than 50 knots.

b. Inner-approach OFZ. The inner-approach OFZ

is a defined volume of airspace centered on the

approach area. The inner-approach OFZ applies only

to runways with an approach lighting system. The

inner-approach OFZ begins 200 feet from the runway

threshold at the same elevation as the runway

threshold and extends 200 feet beyond the last light

unit in the approach lighting system. The width of the

inner-approach OFZ is the same as the runway OFZ

and rises at a slope of 50 (horizontal) to 1 (vertical)

from the beginning.

c. Inner-transitional OFZ. The inner transitional

surface OFZ is a defined volume of airspace along the

sides of the runway and inner-approach OFZ and

applies only to precision instrument runways. The

inner-transitional surface OFZ slopes 3 (horizontal)

to 1 (vertical) out from the edges of the runway OFZ

and inner-approach OFZ to a height of 150 feet above

the established airport elevation.

(Refer to AC 150/5300-13, Chapter 3.)

(Refer to FAAO JO 7110.65, Para 3−1−5,

VEHICLES/EQUIPMENT/PERSONNEL ON

RUNWAYS.)

OBSTRUCTION− Any object/obstacle exceeding

the obstruction standards specified by 14 CFR

Part 77, Subpart C.

OBSTRUCTION LIGHT− A light or one of a group

of lights, usually red or white, frequently mounted on

a surface structure or natural terrain to warn pilots of

the presence of an obstruction.

OCEANIC AIRSPACE− Airspace over the oceans of

the world, considered international airspace, where

oceanic separation and procedures per the International Civil Aviation Organization are applied.

Responsibility for the provisions of air traffic control
Pilot/Controller Glossary 2/9/12

PCG O−2

service in this airspace is delegated to various

countries, based generally upon geographic proximity and the availability of the required resources.

OCEANIC DISPLAY AND PLANNING SYSTEM− An automated digital display system which

provides flight data processing, conflict probe, and

situation display for oceanic air traffic control.

OCEANIC NAVIGATIONAL ERROR REPORT− A

report filed when an aircraft exiting oceanic airspace

has been observed by radar to be off course. ONER

reporting parameters and procedures are contained in

FAAO 7110.82, Monitoring of Navigational Performance In Oceanic Areas.

OCEANIC PUBLISHED ROUTE− A route established in international airspace and charted or

described in flight information publications, such as

Route Charts, DOD Enroute Charts, Chart Supplements, NOTAMs, and Track Messages.

OCEANIC TRANSITION ROUTE− An ATS route

established for the purpose of transitioning aircraft

to/from an organized track system.

ODAPS−

(See OCEANIC DISPLAY AND PLANNING

SYSTEM.)

ODP−

(See OBSTACLE DEPARTURE PROCEDURE.)

OFF COURSE− A term used to describe a situation

where an aircraft has reported a position fix or is

observed on radar at a point not on the ATC-approved

route of flight.

OFF-ROUTE VECTOR− A vector by ATC which

takes an aircraft off a previously assigned route.

Altitudes assigned by ATC during such vectors

provide required obstacle clearance.

OFFSET PARALLEL RUNWAYS− Staggered

runways having centerlines which are parallel.

OFFSHORE/CONTROL AIRSPACE AREA− That

portion of airspace between the U.S. 12 NM limit and

the oceanic CTA/FIR boundary within which air

traffic control is exercised. These areas are

established to provide air traffic control services.

Offshore/Control Airspace Areas may be classified

as either Class A airspace or Class E airspace.

OFT−

(See OUTER FIX TIME.)

OM−

(See OUTER MARKER.)

ON COURSE−

a. Used to indicate that an aircraft is established on

the route centerline.

b. Used by ATC to advise a pilot making a radar

approach that his/her aircraft is lined up on the final

approach course.

(See ON-COURSE INDICATION.)

ON-COURSE INDICATION− An indication on an

instrument, which provides the pilot a visual means

of determining that the aircraft is located on the

centerline of a given navigational track, or an

indication on a radar scope that an aircraft is on a

given track.

ONE-MINUTE WEATHER− The most recent one

minute updated weather broadcast received by a pilot

from an uncontrolled airport ASOS/AWSS/AWOS.

ONER−

(See OCEANIC NAVIGATIONAL ERROR

REPORT.)

OPERATIONAL−

(See DUE REGARD.)

OPERATIONS SPECIFICATIONS [ICAO]− The

authorizations, conditions and limitations associated

with the air operator certificate and subject to the

conditions in the operations manual.

OPPOSITE DIRECTION AIRCRAFT− Aircraft are

operating in opposite directions when:

a. They are following the same track in reciprocal

directions; or

b. Their tracks are parallel and the aircraft are

flying in reciprocal directions; or

c. Their tracks intersect at an angle of more than

135.

OPTION APPROACH− An approach requested and

conducted by a pilot which will result in either a

touch-and-go, missed approach, low approach,

stop-and-go, or full stop landing.

(See CLEARED FOR THE OPTION.)

(Refer to AIM.)

ORGANIZED TRACK SYSTEM− A series of ATS

routes which are fixed and charted; i.e., CEP,

NOPAC, or flexible and described by NOTAM; i.e.,

NAT TRACK MESSAGE.

Pilot/Controller Glossary 7/26/12
Pilot/Controller Glossary 2/9/12

PCG O−3

OROCA− An off-route altitude which provides

obstruction clearance with a 1,000 foot buffer in

nonmountainous terrain areas and a 2,000 foot buffer

in designated mountainous areas within the United

States. This altitude may not provide signal coverage

from ground-based navigational aids, air traffic

control radar, or communications coverage.

OTR−

(See OCEANIC TRANSITION ROUTE.)

OTS−

(See ORGANIZED TRACK SYSTEM.)

OUT−The conversation is ended and no response is

expected.

OUTER AREA (associated with Class C airspace)−

Nonregulatory airspace surrounding designated

Class C airspace airports wherein ATC provides radar

vectoring and sequencing on a full-time basis for all

IFR and participating VFR aircraft. The service

provided in the outer area is called Class C service

which includes: IFR/IFR−standard IFR separation;

IFR/VFR−traffic advisories and conflict resolution;

and VFR/VFR−traffic advisories and, as appropriate,

safety alerts. The normal radius will be 20 nautical

miles with some variations based on site-specific

requirements. The outer area extends outward from

the primary Class C airspace airport and extends from

the lower limits of radar/radio coverage up to the

ceiling of the approach control’s delegated airspace

excluding the Class C charted area and other airspace

as appropriate.

(See CONFLICT RESOLUTION.)

(See CONTROLLED AIRSPACE.)

OUTER COMPASS LOCATOR−

(See COMPASS LOCATOR.)

OUTER FIX− A general term used within ATC to

describe fixes in the terminal area, other than the final

approach fix. Aircraft are normally cleared to these

fixes by an Air Route Traffic Control Center or an

Approach Control Facility. Aircraft are normally

cleared from these fixes to the final approach fix or

final approach course.

OR

OUTER FIX− An adapted fix along the converted

route of flight, prior to the meter fix, for which

crossing times are calculated and displayed in the

metering position list.

OUTER FIX ARC− A semicircle, usually about a

50−70 mile radius from a meter fix, usually in high

altitude, which is used by CTAS/HOST to calculate

outer fix times and determine appropriate sector

meter list assignments for aircraft on an established

arrival route that will traverse the arc.

OUTER FIX TIME− A calculated time to depart the

outer fix in order to cross the vertex at the ACLT. The

time reflects descent speed adjustments and any

applicable delay time that must be absorbed prior to

crossing the meter fix.

OUTER MARKER− A marker beacon at or near the

glideslope intercept altitude of an ILS approach. It is

keyed to transmit two dashes per second on a 400 Hz

tone, which is received aurally and visually by

compatible airborne equipment. The OM is normally

located four to seven miles from the runway threshold

on the extended centerline of the runway.

(See INSTRUMENT LANDING SYSTEM.)

(See MARKER BEACON.)

(Refer to AIM.)

OVER− My transmission is ended; I expect a

response.

OVERHEAD MANEUVER− A series of predetermined maneuvers prescribed for aircraft (often in

formation) for entry into the visual flight rules (VFR)

traffic pattern and to proceed to a landing. An

overhead maneuver is not an instrument flight rules

(IFR) approach procedure. An aircraft executing an

overhead maneuver is considered VFR and the IFR

flight plan is cancelled when the aircraft reaches the

“initial point” on the initial approach portion of the

maneuver. The pattern usually specifies the

following:

a. The radio contact required of the pilot.

b. The speed to be maintained.

c. An initial approach 3 to 5 miles in length.

d. An elliptical pattern consisting of two 180

degree turns.

e. A break point at which the first 180 degree turn

is started.

f. The direction of turns.

g. Altitude (at least 500 feet above the conventional pattern).

h. A “Roll-out” on final approach not less than 1/4

mile from the landing threshold and not less than 300

feet above the ground.

7/26/12 Pilot/Controller Glossary
Pilot/Controller Glossary 2/9/12

PCG O−4

OVERLYING CENTER− The ARTCC facility that

is responsible for arrival/departure operations at a

specific terminal.

Pilot/Controller Glossary 7/26/12
Pilot/Controller Glossary 2/9/12

PCG P−1

P

P TIME−

(See PROPOSED DEPARTURE TIME.)

P-ACP−

(See PREARRANGED COORDINATION

PROCEDURES.)

PAN-PAN− The international radio-telephony urgency signal. When repeated three times, indicates

uncertainty or alert followed by the nature of the

urgency.

(See MAYDAY.)

(Refer to AIM.)

PAR−

(See PRECISION APPROACH RADAR.)

PAR [ICAO]−

(See ICAO Term PRECISION APPROACH

RADAR.)

PARALLEL ILS APPROACHES− Approaches to

parallel runways by IFR aircraft which, when

established inbound toward the airport on the

adjacent final approach courses, are radar-separated

by at least 2 miles.

(See FINAL APPROACH COURSE.)

(See SIMULTANEOUS ILS APPROACHES.)

PARALLEL MLS APPROACHES−

(See PARALLEL ILS APPROACHES.)

PARALLEL OFFSET ROUTE− A parallel track to

the left or right of the designated or established

airway/route. Normally associated with Area Navigation (RNAV) operations.

(See AREA NAVIGATION.)

PARALLEL RUNWAYS− Two or more runways at

the same airport whose centerlines are parallel. In

addition to runway number, parallel runways are

designated as L (left) and R (right) or, if three parallel

runways exist, L (left), C (center), and R (right).

PBCT−

(See PROPOSED BOUNDARY CROSSING

TIME.)

PBN

(See ICAO Term PERFORMANCE−BASED

NAVIGATION.)

PDC−

(See PRE−DEPARTURE CLEARANCE.)

PERFORMANCE−BASED NAVIGATION (PBN)

[ICAO]− Area navigation based on performance

requirements for aircraft operating along an ATS

route, on an instrument approach procedure or in a

designated airspace.

Note: Performance requirements are expressed in

navigation specifications (RNAV specification,

RNP specification) in terms of accuracy, integrity,

continuity, availability, and functionality needed for

the proposed operation in the context of a

particular airspace concept.

PERMANENT ECHO− Radar signals reflected from

fixed objects on the earth’s surface; e.g., buildings,

towers, terrain. Permanent echoes are distinguished

from “ground clutter” by being definable locations

rather than large areas. Under certain conditions they

may be used to check radar alignment.

PHOTO RECONNAISSANCE− Military activity

that requires locating individual photo targets and

navigating to the targets at a preplanned angle and

altitude. The activity normally requires a lateral route

width of 16 NM and altitude range of 1,500 feet to

10,000 feet AGL.

PILOT BRIEFING− A service provided by the FSS

to assist pilots in flight planning. Briefing items may

include weather information, NOTAMS, military

activities, flow control information, and other items

as requested.

(Refer to AIM.)

PILOT IN COMMAND− The pilot responsible for

the operation and safety of an aircraft during flight

time.

(Refer to 14 CFR Part 91.)

PILOT WEATHER REPORT− A report of meteorological phenomena encountered by aircraft in flight.

(Refer to AIM.)

PILOT’S DISCRETION− When used in conjunction with altitude assignments, means that ATC has

offered the pilot the option of starting climb or

descent whenever he/she wishes and conducting the

climb or descent at any rate he/she wishes. He/she

may temporarily level off at any intermediate
Pilot/Controller Glossary 2/9/12

PCG P−2

altitude. However, once he/she has vacated an

altitude, he/she may not return to that altitude.

PIREP−

(See PILOT WEATHER REPORT.)

PITCH POINT− A fix/waypoint that serves as a

transition point from a departure procedure or the low

altitude ground−based navigation structure into the

high altitude waypoint system.

PLANS DISPLAY− A display available in URET

that provides detailed flight plan and predicted

conflict information in textual format for requested

Current Plans and all Trial Plans.

(See USER REQUEST EVALUATION TOOL.)

POFZ−

(See PRECISION OBSTACLE FREE ZONE.)

POINT OUT−

(See RADAR POINT OUT.)

POINT−TO−POINT (PTP)− A level of NRR service

for aircraft that is based on traditional waypoints in

their FMSs or RNAV equipage.

POLAR TRACK STRUCTURE− A system of

organized routes between Iceland and Alaska which

overlie Canadian MNPS Airspace.

POSITION REPORT− A report over a known

location as transmitted by an aircraft to ATC.

(Refer to AIM.)

POSITION SYMBOL− A computer-generated

indication shown on a radar display to indicate the

mode of tracking.

POSITIVE CONTROL− The separation of all air

traffic within designated airspace by air traffic

control.

PRACTICE INSTRUMENT APPROACH− An

instrument approach procedure conducted by a VFR

or an IFR aircraft for the purpose of pilot training or

proficiency demonstrations.

PRE−DEPARTURE CLEARANCE− An application

with the Terminal Data Link System (TDLS) that

provides clearance information to subscribers,

through a service provider, in text to the cockpit or

gate printer.

PREARRANGED COORDINATION− A standardized procedure which permits an air traffic controller

to enter the airspace assigned to another air traffic

controller without verbal coordination. The procedures are defined in a facility directive which ensures

standard separation between aircraft.

PREARRANGED COORDINATION PROCEDURES− A facility’s standardized procedure that

describes the process by which one controller shall

allow an aircraft to penetrate or transit another

controller’s airspace in a manner that assures standard

separation without individual coordination for each

aircraft.

PRECIPITATION− Any or all forms of water

particles (rain, sleet, hail, or snow) that fall from the

atmosphere and reach the surface.

PRECIPITATION RADAR WEATHER DESCRIPTIONS − Existing radar systems cannot detect

turbulence. However, there is a direct correlation

between the degree of turbulence and other weather

features associated with thunderstorms and the

weather radar precipitation intensity. Controllers will

issue (where capable) precipitation intensity as

observed by radar when using weather and radar

processor (WARP) or NAS ground based digital

radars with weather capabilities. When precipitation

intensity information is not available, the intensity

will be described as UNKNOWN. When intensity

levels can be determined, they shall be described as:

a. LIGHT (< 30 dBZ)

b. MODERATE (30 to 40 dBZ)

c. HEAVY (> 40 to 50 dBZ)

d. EXTREME (> 50 dBZ)

(Refer to AC 00−45, Aviation Weather Services.)

PRECISION APPROACH−

(See PRECISION APPROACH PROCEDURE.)

PRECISION APPROACH PROCEDURE− A standard instrument approach procedure in which an

electronic glideslope/glidepath is provided; e.g., ILS,

MLS, and PAR.

(See INSTRUMENT LANDING SYSTEM.)

(See MICROWAVE LANDING SYSTEM.)

(See PRECISION APPROACH RADAR.)
Pilot/Controller Glossary 2/9/12

PCG P−3

PRECISION APPROACH RADAR− Radar equipment in some ATC facilities operated by the FAA

and/or the military services at joint-use civil/military

locations and separate military installations to detect

and display azimuth, elevation, and range of aircraft

on the final approach course to a runway. This

equipment may be used to monitor certain nonradar

approaches, but is primarily used to conduct a

precision instrument approach (PAR) wherein the

controller issues guidance instructions to the pilot

based on the aircraft’s position in relation to the final

approach course (azimuth), the glidepath (elevation),

and the distance (range) from the touchdown point on

the runway as displayed on the radar scope.

Note: The abbreviation “PAR” is also used to

denote preferential arrival routes in ARTCC

computers.

(See GLIDEPATH.)

(See PAR.)

(See PREFERENTIAL ROUTES.)

(See ICAO term PRECISION APPROACH

RADAR.)

(Refer to AIM.)

PRECISION APPROACH RADAR [ICAO]− Primary radar equipment used to determine the position

of an aircraft during final approach, in terms of lateral

and vertical deviations relative to a nominal approach

path, and in range relative to touchdown.

Note: Precision approach radars are designed to

enable pilots of aircraft to be given guidance by

radio communication during the final stages of the

approach to land.

PRECISION OBSTACLE FREE ZONE (POFZ)−

An 800 foot wide by 200 foot long area centered on

the runway centerline adjacent to the threshold

designed to protect aircraft flying precision

approaches from ground vehicles and other aircraft

when ceiling is less than 250 feet or visibility is less

than 3/4 statute mile (or runway visual range below

4,000 feet.)

PRECISION RUNWAY MONITOR (PRM)− Provides air traffic controllers with high precision

secondary surveillance data for aircraft on final

approach to parallel runways that have extended

centerlines separated by less than 4,300 feet. High

resolution color monitoring displays (FMA) are

required to present surveillance track data to

controllers along with detailed maps depicting

approaches and no transgression zone.

PREDICTIVE WIND SHEAR ALERT SYSTEM

(PWS)− A self−contained system used onboard some

aircraft to alert the flight crew to the presence of a

potential wind shear. PWS systems typically monitor

3 miles ahead and 25 degrees left and right of the

aircraft’s heading at or below 1200’ AGL. Departing

flights may receive a wind shear alert after they start

the takeoff roll and may elect to abort the takeoff.

Aircraft on approach receiving an alert may elect to

go around or perform a wind shear escape maneuver.

PREFERENTIAL ROUTES− Preferential routes

(PDRs, PARs, and PDARs) are adapted in ARTCC

computers to accomplish inter/intrafacility controller

coordination and to assure that flight data is posted at

the proper control positions. Locations having a need

for these specific inbound and outbound routes

normally publish such routes in local facility

bulletins, and their use by pilots minimizes flight

plan route amendments. When the workload or traffic

situation permits, controllers normally provide radar

vectors or assign requested routes to minimize

circuitous routing. Preferential routes are usually

confined to one ARTCC’s area and are referred to by

the following names or acronyms:

a. Preferential Departure Route (PDR). A specific

departure route from an airport or terminal area to an

en route point where there is no further need for flow

control. It may be included in an Instrument

Departure Procedure (DP) or a Preferred IFR Route.

b. Preferential Arrival Route (PAR). A specific

arrival route from an appropriate en route point to an

airport or terminal area. It may be included in a

Standard Terminal Arrival (STAR) or a Preferred IFR

Route. The abbreviation “PAR” is used primarily

within the ARTCC and should not be confused with

the abbreviation for Precision Approach Radar.

c. Preferential Departure and Arrival Route

(PDAR). A route between two terminals which are

within or immediately adjacent to one ARTCC’s area.

PDARs are not synonymous with Preferred IFR

Routes but may be listed as such as they do

accomplish essentially the same purpose.

(See PREFERRED IFR ROUTES.)

PREFERRED IFR ROUTES− Routes established

between busier airports to increase system efficiency

and capacity. They normally extend through one or

more ARTCC areas and are designed to achieve

balanced traffic flows among high density terminals.

IFR clearances are issued on the basis of these routes

except when severe weather avoidance procedures or
Pilot/Controller Glossary 2/9/12

PCG P−4

other factors dictate otherwise. Preferred IFR Routes

are listed in the Airport/Facility Directory. If a flight

is planned to or from an area having such routes but

the departure or arrival point is not listed in the

Airport/Facility Directory, pilots may use that part of

a Preferred IFR Route which is appropriate for the

departure or arrival point that is listed. Preferred IFR

Routes are correlated with DPs and STARs and may

be defined by airways, jet routes, direct routes

between NAVAIDs, Waypoints, NAVAID radials/

DME, or any combinations thereof.

(See CENTER’S AREA.)

(See INSTRUMENT DEPARTURE

PROCEDURE.)

(See PREFERENTIAL ROUTES.)

(See STANDARD TERMINAL ARRIVAL.)

(Refer to AIRPORT/FACILITY DIRECTORY.)

(Refer to NOTICES TO AIRMEN PUBLICATION.)

PRE-FLIGHT PILOT BRIEFING−

(See PILOT BRIEFING.)

PREVAILING VISIBILITY−

(See VISIBILITY.)

PRIMARY RADAR TARGET− An analog or digital

target, exclusive of a secondary radar target,

presented on a radar display.

PRM−

(See ILS PRM APPROACH and PRECISION

RUNWAY MONITOR.)

PROCEDURE TURN− The maneuver prescribed

when it is necessary to reverse direction to establish

an aircraft on the intermediate approach segment or

final approach course. The outbound course,

direction of turn, distance within which the turn must

be completed, and minimum altitude are specified in

the procedure. However, unless otherwise restricted,

the point at which the turn may be commenced and

the type and rate of turn are left to the discretion of the

pilot.

(See ICAO term PROCEDURE TURN.)

PROCEDURE TURN [ICAO]− A maneuver in

which a turn is made away from a designated track

followed by a turn in the opposite direction to permit

the aircraft to intercept and proceed along the

reciprocal of the designated track.

Note 1: Procedure turns are designated “left” or

“right” according to the direction of the initial turn.

Note 2: Procedure turns may be designated as

being made either in level flight or while

descending, according to the circumstances of

each individual approach procedure.

PROCEDURE TURN INBOUND− That point of a

procedure turn maneuver where course reversal has

been completed and an aircraft is established inbound

on the intermediate approach segment or final

approach course. A report of “procedure turn

inbound” is normally used by ATC as a position

report for separation purposes.

(See FINAL APPROACH COURSE.)

(See PROCEDURE TURN.)

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

PROFILE DESCENT− An uninterrupted descent

(except where level flight is required for speed

adjustment; e.g., 250 knots at 10,000 feet MSL) from

cruising altitude/level to interception of a glideslope

or to a minimum altitude specified for the initial or

intermediate approach segment of a nonprecision

instrument approach. The profile descent normally

terminates at the approach gate or where the

glideslope or other appropriate minimum altitude is

intercepted.

PROGRESS REPORT−

(See POSITION REPORT.)

PROGRESSIVE TAXI− Precise taxi instructions

given to a pilot unfamiliar with the airport or issued

in stages as the aircraft proceeds along the taxi route.

PROHIBITED AREA−

(See SPECIAL USE AIRSPACE.)

(See ICAO term PROHIBITED AREA.)

PROHIBITED AREA [ICAO]− An airspace of

defined dimensions, above the land areas or territorial

waters of a State, within which the flight of aircraft

is prohibited.

PROMINENT OBSTACLE– An obstacle that meets

one or more of the following conditions:

a. An obstacle which stands out beyond the

adjacent surface of surrounding terrain and immediately projects a noticeable hazard to aircraft in flight.

b. An obstacle, not characterized as low and close

in, whose height is no less than 300 feet above the

departure end of takeoff runway (DER) elevation, is

within 10NM from the DER, and that penetrates that

airport/heliport’s diverse departure obstacle clearance surface (OCS).
Pilot/Controller Glossary 2/9/12

PCG P−5

c. An obstacle beyond 10NM from an airport/heliport that requires an obstacle departure procedure

(ODP) to ensure obstacle avoidance.

(See OBSTACLE.)

(See OBSTRUCTION.)

PROPOSED BOUNDARY CROSSING TIME−

Each center has a PBCT parameter for each internal

airport. Proposed internal flight plans are transmitted

to the adjacent center if the flight time along the

proposed route from the departure airport to the

center boundary is less than or equal to the value of

PBCT or if airport adaptation specifies transmission

regardless of PBCT.

PROPOSED DEPARTURE TIME− The time that the

aircraft expects to become airborne.

PROTECTED AIRSPACE− The airspace on either

side of an oceanic route/track that is equal to one-half

the lateral separation minimum except where

reduction of protected airspace has been authorized.

PROTECTED SEGMENT- The protected segment is

a segment on the amended TFM route that is to be

inhibited from automatic adapted route alteration by

ERAM.

PT−

(See PROCEDURE TURN.)

PTP−

(See POINT−TO−POINT.)

PTS−

(See POLAR TRACK STRUCTURE.)

PUBLISHED INSTRUMENT APPROACH

PROCEDURE VISUAL SEGMENT− A segment on

an IAP chart annotated as “Fly Visual to Airport” or

“Fly Visual.” A dashed arrow will indicate the visual

flight path on the profile and plan view with an

associated note on the approximate heading and

distance. The visual segment should be flown as a

dead reckoning course while maintaining visual

conditions.

PUBLISHED ROUTE− A route for which an IFR

altitude has been established and published; e.g.,

Federal Airways, Jet Routes, Area Navigation

Routes, Specified Direct Routes.

PWS−

(See PREDICTIVE WIND SHEAR ALERT

SYSTEM.)

7/26/12 Pilot/Controller Glossary

Pilot/Controller Glossary 2/9/12

PCG Q−1

Q

Q ROUTE− ‘Q’ is the designator assigned to

published RNAV routes used by the United States.

QNE− The barometric pressure used for the standard

altimeter setting (29.92 inches Hg.).

QNH− The barometric pressure as reported by a

particular station.

QUADRANT− A quarter part of a circle, centered on

a NAVAID, oriented clockwise from magnetic north

as follows: NE quadrant 000-089, SE quadrant

090-179, SW quadrant 180-269, NW quadrant

270-359.

QUEUING−

(See STAGING/QUEUING.)

QUICK LOOK− A feature of the EAS and ARTS

which provides the controller the capability to

display full data blocks of tracked aircraft from other

control positions.

Pilot/Controller Glossary 2/9/12

PCG R−1

R

RAA−

(See REMOTE AIRPORT ADVISORY.)

RADAR− A device which, by measuring the time

interval between transmission and reception of radio

pulses and correlating the angular orientation of the

radiated antenna beam or beams in azimuth and/or

elevation, provides information on range, azimuth,

and/or elevation of objects in the path of the

transmitted pulses.

a. Primary Radar− A radar system in which a

minute portion of a radio pulse transmitted from a site

is reflected by an object and then received back at that

site for processing and display at an air traffic control

facility.

b. Secondary Radar/Radar Beacon (ATCRBS)− A

radar system in which the object to be detected is

fitted with cooperative equipment in the form of a

radio receiver/transmitter (transponder). Radar

pulses transmitted from the searching transmitter/receiver (interrogator) site are received in the

cooperative equipment and used to trigger a

distinctive transmission from the transponder. This

reply transmission, rather than a reflected signal, is

then received back at the transmitter/receiver site for

processing and display at an air traffic control facility.

(See INTERROGATOR.)

(See TRANSPONDER.)

(See ICAO term RADAR.)

(Refer to AIM.)

RADAR [ICAO]− A radio detection device which

provides information on range, azimuth and/or

elevation of objects.

a. Primary Radar− Radar system which uses

reflected radio signals.

b. Secondary Radar− Radar system wherein a

radio signal transmitted from a radar station initiates

the transmission of a radio signal from another

station.

RADAR ADVISORY− The provision of advice and

information based on radar observations.

(See ADVISORY SERVICE.)

RADAR ALTIMETER−

(See RADIO ALTIMETER.)

RADAR APPROACH− An instrument approach

procedure which utilizes Precision Approach Radar

(PAR) or Airport Surveillance Radar (ASR).

(See AIRPORT SURVEILLANCE RADAR.)

(See INSTRUMENT APPROACH

PROCEDURE.)

(See PRECISION APPROACH RADAR.)

(See SURVEILLANCE APPROACH.)

(See ICAO term RADAR APPROACH.)

(Refer to AIM.)

RADAR APPROACH [ICAO]− An approach,

executed by an aircraft, under the direction of a radar

controller.

RADAR APPROACH CONTROL FACILITY− A

terminal ATC facility that uses radar and nonradar

capabilities to provide approach control services to

aircraft arriving, departing, or transiting airspace

controlled by the facility.

(See APPROACH CONTROL SERVICE.)

a. Provides radar ATC services to aircraft

operating in the vicinity of one or more civil and/or

military airports in a terminal area. The facility may

provide services of a ground controlled approach

(GCA); i.e., ASR and PAR approaches. A radar

approach control facility may be operated by FAA,

USAF, US Army, USN, USMC, or jointly by FAA

and a military service. Specific facility nomenclatures are used for administrative purposes only and

are related to the physical location of the facility and

the operating service generally as follows:

1. Army Radar Approach Control (ARAC)

(Army).

2. Radar Air Traffic Control Facility (RATCF)

(Navy/FAA).

3. Radar Approach Control (RAPCON) (Air

Force/FAA).

4. Terminal Radar Approach Control

(TRACON) (FAA).

5. Air Traffic Control Tower (ATCT) (FAA).

(Only those towers delegated approach control

authority.)

RADAR ARRIVAL− An aircraft arriving at an

airport served by a radar facility and in radar contact

with the facility.

(See NONRADAR.)
Pilot/Controller Glossary 2/9/12

PCG R−2

RADAR BEACON−

(See RADAR.)

RADAR CLUTTER [ICAO]− The visual indication

on a radar display of unwanted signals.

RADAR CONTACT−

a. Used by ATC to inform an aircraft that it is

identified on the radar display and radar flight

following will be provided until radar identification

is terminated. Radar service may also be provided

within the limits of necessity and capability. When a

pilot is informed of “radar contact,” he/she

automatically discontinues reporting over compulsory reporting points.

(See RADAR CONTACT LOST.)

(See RADAR FLIGHT FOLLOWING.)

(See RADAR SERVICE.)

(See RADAR SERVICE TERMINATED.)

(Refer to AIM.)

b. The term used to inform the controller that the

aircraft is identified and approval is granted for the

aircraft to enter the receiving controllers airspace.

(See ICAO term RADAR CONTACT.)

RADAR CONTACT [ICAO]− The situation which

exists when the radar blip or radar position symbol of

a particular aircraft is seen and identified on a radar

display.

RADAR CONTACT LOST− Used by ATC to inform

a pilot that radar data used to determine the aircraft’s

position is no longer being received, or is no longer

reliable and radar service is no longer being provided.

The loss may be attributed to several factors

including the aircraft merging with weather or ground

clutter, the aircraft operating below radar line of sight

coverage, the aircraft entering an area of poor radar

return, failure of the aircraft transponder, or failure of

the ground radar equipment.

(See CLUTTER.)

(See RADAR CONTACT.)

RADAR ENVIRONMENT− An area in which radar

service may be provided.

(See ADDITIONAL SERVICES.)

(See RADAR CONTACT.)

(See RADAR SERVICE.)

(See TRAFFIC ADVISORIES.)

RADAR FLIGHT FOLLOWING− The observation

of the progress of radar identified aircraft, whose

primary navigation is being provided by the pilot,

wherein the controller retains and correlates the

aircraft identity with the appropriate target or target

symbol displayed on the radar scope.

(See RADAR CONTACT.)

(See RADAR SERVICE.)

(Refer to AIM.)

RADAR IDENTIFICATION− The process of

ascertaining that an observed radar target is the radar

return from a particular aircraft.

(See RADAR CONTACT.)

(See RADAR SERVICE.)

(See ICAO term RADAR IDENTIFICATION.)

RADAR IDENTIFICATION [ICAO]− The process

of correlating a particular radar blip or radar position

symbol with a specific aircraft.

RADAR IDENTIFIED AIRCRAFT− An aircraft, the

position of which has been correlated with an

observed target or symbol on the radar display.

(See RADAR CONTACT.)

(See RADAR CONTACT LOST.)

RADAR MONITORING−

(See RADAR SERVICE.)

RADAR NAVIGATIONAL GUIDANCE−

(See RADAR SERVICE.)

RADAR POINT OUT− An action taken by a

controller to transfer the radar identification of an

aircraft to another controller if the aircraft will or may

enter the airspace or protected airspace of another

controller and radio communications will not be

transferred.

RADAR REQUIRED− A term displayed on charts

and approach plates and included in FDC NOTAMs

to alert pilots that segments of either an instrument

approach procedure or a route are not navigable

because of either the absence or unusability of a

NAVAID. The pilot can expect to be provided radar

navigational guidance while transiting segments

labeled with this term.

(See RADAR ROUTE.)

(See RADAR SERVICE.)

RADAR ROUTE− A flight path or route over which

an aircraft is vectored. Navigational guidance and

altitude assignments are provided by ATC.

(See FLIGHT PATH.)

(See ROUTE.)

RADAR SEPARATION−

(See RADAR SERVICE.)
Pilot/Controller Glossary 2/9/12

PCG R−3

RADAR SERVICE− A term which encompasses one

or more of the following services based on the use of

radar which can be provided by a controller to a pilot

of a radar identified aircraft.

a. Radar Monitoring− The radar flight-following

of aircraft, whose primary navigation is being

performed by the pilot, to observe and note deviations

from its authorized flight path, airway, or route.

When being applied specifically to radar monitoring

of instrument approaches; i.e., with precision

approach radar (PAR) or radar monitoring of

simultaneous ILS/MLS approaches, it includes

advice and instructions whenever an aircraft nears or

exceeds the prescribed PAR safety limit or

simultaneous ILS/MLS no transgression zone.

(See ADDITIONAL SERVICES.)

(See TRAFFIC ADVISORIES.)

b. Radar Navigational Guidance− Vectoring

aircraft to provide course guidance.

c. Radar Separation− Radar spacing of aircraft in

accordance with established minima.

(See ICAO term RADAR SERVICE.)

RADAR SERVICE [ICAO]− Term used to indicate

a service provided directly by means of radar.

a. Monitoring− The use of radar for the purpose of

providing aircraft with information and advice

relative to significant deviations from nominal flight

path.

b. Separation− The separation used when aircraft

position information is derived from radar sources.

RADAR SERVICE TERMINATED−Used by ATC

to inform a pilot that he/she will no longer be

provided any of the services that could be received

while in radar contact. Radar service is automatically

terminated, and the pilot is not advised in the

following cases:

a. An aircraft cancels its IFR flight plan, except

within Class B airspace, Class C airspace, a TRSA,

or where Basic Radar service is provided.

b. An aircraft conducting an instrument, visual, or

contact approach has landed or has been instructed to

change to advisory frequency.

c. An arriving VFR aircraft, receiving radar

service to a tower-controlled airport within Class B

airspace, Class C airspace, a TRSA, or where

sequencing service is provided, has landed; or to all

other airports, is instructed to change to tower or

advisory frequency.

d. An aircraft completes a radar approach.

RADAR SURVEILLANCE− The radar observation

of a given geographical area for the purpose of

performing some radar function.

RADAR TRAFFIC ADVISORIES− Advisories

issued to alert pilots to known or observed radar

traffic which may affect the intended route of flight

of their aircraft.

(See TRAFFIC ADVISORIES.)

RADAR TRAFFIC INFORMATION SERVICE−

(See TRAFFIC ADVISORIES.)

RADAR VECTORING [ICAO]− Provision of

navigational guidance to aircraft in the form of

specific headings, based on the use of radar.

RADIAL− A magnetic bearing extending from a

VOR/VORTAC/TACAN navigation facility.

RADIO−

a. A device used for communication.

b. Used to refer to a flight service station; e.g.,

“Seattle Radio” is used to call Seattle FSS.

RADIO ALTIMETER− Aircraft equipment which

makes use of the reflection of radio waves from the

ground to determine the height of the aircraft above

the surface.

RADIO BEACON−

(See NONDIRECTIONAL BEACON.)

RADIO DETECTION AND RANGING−

(See RADAR.)

RADIO MAGNETIC INDICATOR− An aircraft

navigational instrument coupled with a gyro compass

or similar compass that indicates the direction of a

selected NAVAID and indicates bearing with respect

to the heading of the aircraft.

RAIS−

(See REMOTE AIRPORT INFORMATION

SERVICE.)

RAMP−

(See APRON.)

RANDOM ALTITUDE− An altitude inappropriate

for direction of flight and/or not in accordance with

FAAO JO 7110.65, Para 4−5−1, VERTICAL

SEPARATION MINIMA.
Pilot/Controller Glossary 2/9/12

PCG R−4

RANDOM ROUTE− Any route not established or

charted/published or not otherwise available to all

users.

RC−

(See ROAD RECONNAISSANCE.)

RCAG−

(See REMOTE COMMUNICATIONS

AIR/GROUND FACILITY.)

RCC−

(See RESCUE COORDINATION CENTER.)

RCO−

(See REMOTE COMMUNICATIONS OUTLET.)

RCR−

(See RUNWAY CONDITION READING.)

READ BACK− Repeat my message back to me.

RECEIVER AUTONOMOUS INTEGRITY MONITORING (RAIM)− A technique whereby a civil

GNSS receiver/processor determines the integrity of

the GNSS navigation signals without reference to

sensors or non-DoD integrity systems other than the

receiver itself. This determination is achieved by a

consistency check among redundant pseudorange

measurements.

RECEIVING CONTROLLER− A controller/facility

receiving control of an aircraft from another

controller/facility.

RECEIVING FACILITY−

(See RECEIVING CONTROLLER.)

RECONFORMANCE− The automated process of

bringing an aircraft’s Current Plan Trajectory into

conformance with its track.

REDUCE SPEED TO (SPEED)−

(See SPEED ADJUSTMENT.)

REIL−

(See RUNWAY END IDENTIFIER LIGHTS.)

RELEASE TIME− A departure time restriction

issued to a pilot by ATC (either directly or through an

authorized relay) when necessary to separate a

departing aircraft from other traffic.

(See ICAO term RELEASE TIME.)

RELEASE TIME [ICAO]− Time prior to which an

aircraft should be given further clearance or prior to

which it should not proceed in case of radio failure.

REMOTE AIRPORT ADVISORY (RAA)− A

remote service which may be provided by facilities,

which are not located on the landing airport, but have

a discrete ground−to−air communication frequency

or tower frequency when the tower is closed,

automated weather reporting with voice available to

the pilot at the landing airport, and a continuous

ASOS/AWSS/AWOS data display, other direct

reading instruments, or manual observation is

available to the FSS specialist.

REMOTE AIRPORT INFORMATION SERVICE

(RAIS)− A temporary service provided by facilities,

which are not located on the landing airport, but have

communication capability and automated weather

reporting available to the pilot at the landing airport.

REMOTE COMMUNICATIONS AIR/GROUND

FACILITY− An unmanned VHF/UHF transmitter/

receiver facility which is used to expand ARTCC

air/ground communications coverage and to facilitate

direct contact between pilots and controllers. RCAG

facilities are sometimes not equipped with emergency frequencies 121.5 MHz and 243.0 MHz.

(Refer to AIM.)

REMOTE COMMUNICATIONS OUTLET− An

unmanned communications facility remotely controlled by air traffic personnel. RCOs serve FSSs.

RTRs serve terminal ATC facilities. An RCO or RTR

may be UHF or VHF and will extend the

communication range of the air traffic facility. There

are several classes of RCOs and RTRs. The class is

determined by the number of transmitters or

receivers. Classes A through G are used primarily for

air/ground purposes. RCO and RTR class O

facilities are nonprotected outlets subject to

undetected and prolonged outages. RCO (O’s) and

RTR (O’s) were established for the express purpose

of providing ground-to-ground communications

between air traffic control specialists and pilots

located at a satellite airport for delivering en route

clearances, issuing departure authorizations, and

acknowledging instrument flight rules cancellations

or departure/landing times. As a secondary function,

they may be used for advisory purposes whenever the

aircraft is below the coverage of the primary

air/ground frequency.

REMOTE TRANSMITTER/RECEIVER−

(See REMOTE COMMUNICATIONS OUTLET.)
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PCG R−5

REPORT− Used to instruct pilots to advise ATC of

specified information; e.g., “Report passing Hamilton VOR.”

REPORTING POINT− A geographical location in

relation to which the position of an aircraft is

reported.

(See COMPULSORY REPORTING POINTS.)

(See ICAO term REPORTING POINT.)

(Refer to AIM.)

REPORTING POINT [ICAO]− A specified geographical location in relation to which the position of

an aircraft can be reported.

REQUEST FULL ROUTE CLEARANCE− Used

by pilots to request that the entire route of flight be

read verbatim in an ATC clearance. Such request

should be made to preclude receiving an ATC

clearance based on the original filed flight plan when

a filed IFR flight plan has been revised by the pilot,

company, or operations prior to departure.

REQUIRED NAVIGATION PERFORMANCE

(RNP)– A statement of the navigational performance

necessary for operation within a defined airspace.

The following terms are commonly associated with

RNP:

a. Required Navigation Performance Level or

Type (RNP-X). A value, in nautical miles (NM), from

the intended horizontal position within which an

aircraft would be at least 95-percent of the total flying

time.

b. Required Navigation Performance (RNP)

Airspace. A generic term designating airspace, route

(s), leg (s), operation (s), or procedure (s) where

minimum required navigational performance (RNP)

have been established.

c. Actual Navigation Performance (ANP). A

measure of the current estimated navigational

performance. Also referred to as Estimated Position

Error (EPE).

d. Estimated Position Error (EPE). A measure of

the current estimated navigational performance. Also

referred to as Actual Navigation Performance (ANP).

e. Lateral Navigation (LNAV). A function of area

navigation (RNAV) equipment which calculates,

displays, and provides lateral guidance to a profile or

path.

f. Vertical Navigation (VNAV). A function of area

navigation (RNAV) equipment which calculates,

displays, and provides vertical guidance to a profile

or path.

RESCUE COORDINATION CENTER− A search

and rescue (SAR) facility equipped and manned to

coordinate and control SAR operations in an area

designated by the SAR plan. The U.S. Coast Guard

and the U.S. Air Force have responsibility for the

operation of RCCs.

(See ICAO term RESCUE CO-ORDINATION

CENTRE.)

RESCUE CO-ORDINATION CENTRE [ICAO]− A

unit responsible for promoting efficient organization

of search and rescue service and for coordinating the

conduct of search and rescue operations within a

search and rescue region.

RESOLUTION ADVISORY−A display indication

given to the pilot by the traffic alert and collision

avoidance systems (TCAS II) recommending a

maneuver to increase vertical separation relative to an

intruding aircraft. Positive, negative, and vertical

speed limit (VSL) advisories constitute the resolution

advisories. A resolution advisory is also classified as

corrective or preventive

RESTRICTED AREA−

(See SPECIAL USE AIRSPACE.)

(See ICAO term RESTRICTED AREA.)

RESTRICTED AREA [ICAO]− An airspace of

defined dimensions, above the land areas or territorial

waters of a State, within which the flight of aircraft

is restricted in accordance with certain specified

conditions.

RESUME NORMAL SPEED− Used by ATC to

advise a pilot that previously issued speed control

restrictions are deleted. An instruction to “resume

normal speed” does not delete speed restrictions that

are applicable to published procedures of upcoming

segments of flight, unless specifically stated by ATC.

This does not relieve the pilot of those speed

restrictions which are applicable to 14 CFR

Section 91.117.

RESUME OWN NAVIGATION− Used by ATC to

advise a pilot to resume his/her own navigational

responsibility. It is issued after completion of a radar
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PCG R−6

vector or when radar contact is lost while the aircraft

is being radar vectored.

(See RADAR CONTACT LOST.)

(See RADAR SERVICE TERMINATED.)

RMI−

(See RADIO MAGNETIC INDICATOR.)

RNAV−

(See AREA NAVIGATION (RNAV).)

RNAV APPROACH− An instrument approach

procedure which relies on aircraft area navigation

equipment for navigational guidance.

(See AREA NAVIGATION (RNAV).)

(See INSTRUMENT APPROACH

PROCEDURE.)

ROAD RECONNAISSANCE− Military activity

requiring navigation along roads, railroads, and

rivers. Reconnaissance route/route segments are

seldom along a straight line and normally require a

lateral route width of 10 NM to 30 NM and an altitude

range of 500 feet to 10,000 feet AGL.

ROGER− I have received all of your last

transmission. It should not be used to answer a

question requiring a yes or a no answer.

(See AFFIRMATIVE.)

(See NEGATIVE.)

ROLLOUT RVR−

(See VISIBILITY.)

ROUTE− A defined path, consisting of one or more

courses in a horizontal plane, which aircraft traverse

over the surface of the earth.

(See AIRWAY.)

(See JET ROUTE.)

(See PUBLISHED ROUTE.)

(See UNPUBLISHED ROUTE.)

ROUTE ACTION NOTIFICATION− URET notification that a PAR/PDR/PDAR has been applied to the

flight plan.

(See ATC PREFERRED ROUTE

NOTIFICATION.)

(See USER REQUEST EVALUATION TOOL.)

ROUTE SEGMENT− As used in Air Traffic Control,

a part of a route that can be defined by two

navigational fixes, two NAVAIDs, or a fix and a

NAVAID.

(See FIX.)

(See ROUTE.)

(See ICAO term ROUTE SEGMENT.)

ROUTE SEGMENT [ICAO]− A portion of a route to

be flown, as defined by two consecutive significant

points specified in a flight plan.

RSA−

(See RUNWAY SAFETY AREA.)

RTR−

(See REMOTE TRANSMITTER/RECEIVER.)

RUNWAY− A defined rectangular area on a land

airport prepared for the landing and takeoff run of

aircraft along its length. Runways are normally

numbered in relation to their magnetic direction

rounded off to the nearest 10 degrees; e.g., Runway

1, Runway 25.

(See PARALLEL RUNWAYS.)

(See ICAO term RUNWAY.)

RUNWAY [ICAO]− A defined rectangular area on a

land aerodrome prepared for the landing and take-off

of aircraft.

RUNWAY CENTERLINE LIGHTING−

(See AIRPORT LIGHTING.)

RUNWAY CONDITION READING− Numerical

decelerometer readings relayed by air traffic

controllers at USAF and certain civil bases for use by

the pilot in determining runway braking action.

These readings are routinely relayed only to USAF

and Air National Guard Aircraft.

(See BRAKING ACTION.)

RUNWAY END IDENTIFIER LIGHTS−

(See AIRPORT LIGHTING.)

RUNWAY GRADIENT− The average slope, measured in percent, between two ends or points on a

runway. Runway gradient is depicted on Government

aerodrome sketches when total runway gradient

exceeds 0.3%.

RUNWAY HEADING− The magnetic direction that

corresponds with the runway centerline extended, not

the painted runway number. When cleared to “fly or

maintain runway heading,” pilots are expected to fly

or maintain the heading that corresponds with the

extended centerline of the departure runway. Drift

correction shall not be applied; e.g., Runway 4, actual

magnetic heading of the runway centerline 044, fly

044.
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RUNWAY IN USE/ACTIVE RUNWAY/DUTY

RUNWAY− Any runway or runways currently being

used for takeoff or landing. When multiple runways

are used, they are all considered active runways. In

the metering sense, a selectable adapted item which

specifies the landing runway configuration or

direction of traffic flow. The adapted optimum flight

plan from each transition fix to the vertex is

determined by the runway configuration for arrival

metering processing purposes.

RUNWAY LIGHTS−

(See AIRPORT LIGHTING.)

RUNWAY MARKINGS−

(See AIRPORT MARKING AIDS.)

RUNWAY OVERRUN− In military aviation exclusively, a stabilized or paved area beyond the end of a

runway, of the same width as the runway plus

shoulders, centered on the extended runway

centerline.

RUNWAY PROFILE DESCENT− An instrument

flight rules (IFR) air traffic control arrival procedure

to a runway published for pilot use in graphic and/or

textual form and may be associated with a STAR.

Runway Profile Descents provide routing and may

depict crossing altitudes, speed restrictions, and

headings to be flown from the en route structure to the

point where the pilot will receive clearance for and

execute an instrument approach procedure. A

Runway Profile Descent may apply to more than one

runway if so stated on the chart.

(Refer to AIM.)

RUNWAY SAFETY AREA− A defined surface

surrounding the runway prepared, or suitable, for

reducing the risk of damage to airplanes in the event

of an undershoot, overshoot, or excursion from the

runway. The dimensions of the RSA vary and can be

determined by using the criteria contained within

AC 150/5300-13, Airport Design, Chapter 3.

Figure 3−1 in AC 150/5300-13 depicts the RSA. The

design standards dictate that the RSA shall be:

a. Cleared, graded, and have no potentially

hazardous ruts, humps, depressions, or other surface

variations;

b. Drained by grading or storm sewers to prevent

water accumulation;

c. Capable, under dry conditions, of supporting

snow removal equipment, aircraft rescue and

firefighting equipment, and the occasional passage of

aircraft without causing structural damage to the

aircraft; and,

d. Free of objects, except for objects that need to

be located in the runway safety area because of their

function. These objects shall be constructed on low

impact resistant supports (frangible mounted structures) to the lowest practical height with the frangible

point no higher than 3 inches above grade.

(Refer to AC 150/5300-13, Airport Design,

Chapter 3.)

RUNWAY TRANSITION−

a. Conventional STARs/SIDs. The portion of a

STAR/SID that serves a particular runway or

runways at an airport.

b. RNAV STARs/SIDs. Defines a path(s) from

the common route to the final point(s) on a STAR. For

a SID, the common route that serves a particular

runway or runways at an airport.

RUNWAY USE PROGRAM− A noise abatement

runway selection plan designed to enhance noise

abatement efforts with regard to airport communities

for arriving and departing aircraft. These plans are

developed into runway use programs and apply to all

turbojet aircraft 12,500 pounds or heavier; turbojet

aircraft less than 12,500 pounds are included only if

the airport proprietor determines that the aircraft

creates a noise problem. Runway use programs are

coordinated with FAA offices, and safety criteria

used in these programs are developed by the Office of

Flight Operations. Runway use programs are

administered by the Air Traffic Service as “Formal”

or “Informal” programs.

a. Formal Runway Use Program− An approved

noise abatement program which is defined and

acknowledged in a Letter of Understanding between

Flight Operations, Air Traffic Service, the airport

proprietor, and the users. Once established, participation in the program is mandatory for aircraft operators

and pilots as provided for in 14 CFR Section 91.129.

b. Informal Runway Use Program− An approved

noise abatement program which does not require a

Letter of Understanding, and participation in the

program is voluntary for aircraft operators/pilots.
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PCG R−8

RUNWAY VISIBILITY VALUE−

(See VISIBILITY.)

RUNWAY VISUAL RANGE−

(See VISIBILITY.)
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PCG S−1

S

SAA−

(See SPECIAL ACTIVITY AIRSPACE.)

SAFETY ALERT− A safety alert issued by ATC to

aircraft under their control if ATC is aware the aircraft

is at an altitude which, in the controller’s judgment,

places the aircraft in unsafe proximity to terrain,

obstructions, or other aircraft. The controller may

discontinue the issuance of further alerts if the pilot

advises he/she is taking action to correct the situation

or has the other aircraft in sight.

a. Terrain/Obstruction Alert− A safety alert issued

by ATC to aircraft under their control if ATC is aware

the aircraft is at an altitude which, in the controller’s

judgment, places the aircraft in unsafe proximity to

terrain/obstructions; e.g., “Low Altitude Alert, check

your altitude immediately.”

b. Aircraft Conflict Alert− A safety alert issued by

ATC to aircraft under their control if ATC is aware of

an aircraft that is not under their control at an altitude

which, in the controller’s judgment, places both

aircraft in unsafe proximity to each other. With the

alert, ATC will offer the pilot an alternate course of

action when feasible; e.g., “Traffic Alert, advise you

turn right heading zero niner zero or climb to eight

thousand immediately.”

Note: The issuance of a safety alert is contingent

upon the capability of the controller to have an

awareness of an unsafe condition. The course of

action provided will be predicated on other traffic

under ATC control. Once the alert is issued, it is

solely the pilot’s prerogative to determine what

course of action, if any, he/she will take.

SAFETY LOGIC SYSTEM− A software enhancement to ASDE−3, ASDE−X, and ASDE−3X, that

predicts the path of aircraft landing and/or departing,

and/or vehicular movements on runways. Visual and

aural alarms are activated when the safety logic

projects a potential collision. The Airport Movement

Area Safety System (AMASS) is a safety logic

system enhancement to the ASDE−3. The Safety

Logic System for ASDE−X and ASDE−3X is an

integral part of the software program.

SAFETY LOGIC SYSTEM ALERTS−

a. ALERT− An actual situation involving two real

safety logic tracks (aircraft/aircraft, aircraft/vehicle,

or aircraft/other tangible object) that safety logic has

predicted will result in an imminent collision, based

upon the current set of Safety Logic parameters.

b. FALSE ALERT−

1. Alerts generated by one or more false

surface−radar targets that the system has interpreted

as real tracks and placed into safety logic.

2. Alerts in which the safety logic software did

not perform correctly, based upon the design

specifications and the current set of Safety Logic

parameters.

3. The alert is generated by surface radar targets

caused by moderate or greater precipitation.

c. NUISANCE ALERT− An alert in which one or

more of the following is true:

1. The alert is generated by a known situation

that is not considered an unsafe operation, such as

LAHSO or other approved operations.

2. The alert is generated by inaccurate secondary radar data received by the Safety Logic System.

3. One or more of the aircraft involved in the

alert is not intending to use a runway (for example,

helicopter, pipeline patrol, non−Mode C overflight,

etc.).

d. VALID NON−ALERT− A situation in which

the safety logic software correctly determines that an

alert is not required, based upon the design

specifications and the current set of Safety Logic

parameters.

e. INVALID NON−ALERT− A situation in which

the safety logic software did not issue an alert when

an alert was required, based upon the design

specifications.

SAIL BACK− A maneuver during high wind

conditions (usually with power off) where float plane

movement is controlled by water rudders/opening

and closing cabin doors.

SAME DIRECTION AIRCRAFT− Aircraft are

operating in the same direction when:

a. They are following the same track in the same

direction; or

b. Their tracks are parallel and the aircraft are

flying in the same direction; or

c. Their tracks intersect at an angle of less than 45

degrees.
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PCG S−2

SAR−

(See SEARCH AND RESCUE.)

SAY AGAIN− Used to request a repeat of the last

transmission. Usually specifies transmission or

portion thereof not understood or received; e.g., “Say

again all after ABRAM VOR.”

SAY ALTITUDE− Used by ATC to ascertain an

aircraft’s specific altitude/flight level. When the

aircraft is climbing or descending, the pilot should

state the indicated altitude rounded to the nearest 100

feet.

SAY HEADING− Used by ATC to request an aircraft

heading. The pilot should state the actual heading of

the aircraft.

SCHEDULED TIME OF ARRIVAL (STA)− A STA

is the desired time that an aircraft should cross a

certain point (landing or metering fix). It takes other

traffic and airspace configuration into account. A

STA time shows the results of the TMA scheduler

that has calculated an arrival time according to

parameters such as optimized spacing, aircraft

performance, and weather.

SDF−

(See SIMPLIFIED DIRECTIONAL FACILITY.)

SEA LANE− A designated portion of water outlined

by visual surface markers for and intended to be used

by aircraft designed to operate on water.

SEARCH AND RESCUE− A service which seeks

missing aircraft and assists those found to be in need

of assistance. It is a cooperative effort using the

facilities and services of available Federal, state and

local agencies. The U.S. Coast Guard is responsible

for coordination of search and rescue for the Maritime

Region, and the U.S. Air Force is responsible for

search and rescue for the Inland Region. Information

pertinent to search and rescue should be passed

through any air traffic facility or be transmitted

directly to the Rescue Coordination Center by

telephone.

(See FLIGHT SERVICE STATION.)

(See RESCUE COORDINATION CENTER.)

(Refer to AIM.)

SEARCH AND RESCUE FACILITY− A facility

responsible for maintaining and operating a search

and rescue (SAR) service to render aid to persons and

property in distress. It is any SAR unit, station, NET,

or other operational activity which can be usefully

employed during an SAR Mission; e.g., a Civil Air

Patrol Wing, or a Coast Guard Station.

(See SEARCH AND RESCUE.)

SECNOT−

(See SECURITY NOTICE.)

SECONDARY RADAR TARGET− A target derived

from a transponder return presented on a radar

display.

SECTIONAL AERONAUTICAL CHARTS−

(See AERONAUTICAL CHART.)

SECTOR LIST DROP INTERVAL− A parameter

number of minutes after the meter fix time when

arrival aircraft will be deleted from the arrival sector

list.

SECURITY NOTICE (SECNOT) − A SECNOT is a

request originated by the Air Traffic Security

Coordinator (ATSC) for an extensive communications search for aircraft involved, or suspected of

being involved, in a security violation.

A SECNOT will include the aircraft identification,

search area, and expiration time. The search area, as

defined by the ATSC, could be a single airport,

multiple airports, a radius of an airport or fix, or a

route of flight. Once the expiration time has been

reached, the SECNOT is considered to be cancelled.

SECURITY SERVICES AIRSPACE − Areas

established through the regulatory process or by

NOTAM, issued by the Administrator under title 14,

CFR, sections 99.7, 91.141, and 91.139, which

specify that ATC security services are required; i.e.,

ADIZ or temporary flight rules areas.

SEE AND AVOID− When weather conditions

permit, pilots operating IFR or VFR are required to

observe and maneuver to avoid other aircraft.

Right-of-way rules are contained in 14 CFR Part 91.

SEGMENTED CIRCLE− A system of visual

indicators designed to provide traffic pattern

information at airports without operating control

towers.

(Refer to AIM.)

SEGMENTS OF AN INSTRUMENT APPROACH

PROCEDURE− An instrument approach procedure

may have as many as four separate segments

depending on how the approach procedure is

structured.

a. Initial Approach− The segment between the

initial approach fix and the intermediate fix or the
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PCG S−3

point where the aircraft is established on the

intermediate course or final approach course.

(See ICAO term INITIAL APPROACH

SEGMENT.)

b. Intermediate Approach− The segment between

the intermediate fix or point and the final approach

fix.

(See ICAO term INTERMEDIATE APPROACH

SEGMENT.)

c. Final Approach− The segment between the final

approach fix or point and the runway, airport, or

missed approach point.

(See ICAO term FINAL APPROACH SEGMENT.)

d. Missed Approach− The segment between the

missed approach point or the point of arrival at

decision height and the missed approach fix at the

prescribed altitude.

(Refer to 14 CFR Part 97.)

(See ICAO term MISSED APPROACH

PROCEDURE.)

SEPARATION− In air traffic control, the spacing of

aircraft to achieve their safe and orderly movement in

flight and while landing and taking off.

(See SEPARATION MINIMA.)

(See ICAO term SEPARATION.)

SEPARATION [ICAO]− Spacing between aircraft,

levels or tracks.

SEPARATION MINIMA− The minimum longitudinal, lateral, or vertical distances by which aircraft are

spaced through the application of air traffic control

procedures.

(See SEPARATION.)

SERVICE− A generic term that designates functions

or assistance available from or rendered by air traffic

control. For example, Class C service would denote

the ATC services provided within a Class C airspace

area.

SEVERE WEATHER AVOIDANCE PLAN− An

approved plan to minimize the affect of severe

weather on traffic flows in impacted terminal and/or

ARTCC areas. SWAP is normally implemented to

provide the least disruption to the ATC system when

flight through portions of airspace is difficult or

impossible due to severe weather.

SEVERE WEATHER FORECAST ALERTS−

Preliminary messages issued in order to alert users

that a Severe Weather Watch Bulletin (WW) is being

issued. These messages define areas of possible

severe thunderstorms or tornado activity. The

messages are unscheduled and issued as required by

the Storm Prediction Center (SPC) at Norman,

Oklahoma.

(See AIRMET.)

(See CONVECTIVE SIGMET.)

(See CWA.)

(See SIGMET.)

SFA−

(See SINGLE FREQUENCY APPROACH.)

SFO−

(See SIMULATED FLAMEOUT.)

SHF−

(See SUPER HIGH FREQUENCY.)

SHORT RANGE CLEARANCE− A clearance

issued to a departing IFR flight which authorizes IFR

flight to a specific fix short of the destination while

air traffic control facilities are coordinating and

obtaining the complete clearance.

SHORT TAKEOFF AND LANDING AIRCRAFT−

An aircraft which, at some weight within its approved

operating weight, is capable of operating from a

runway in compliance with the applicable STOL

characteristics, airworthiness, operations, noise, and

pollution standards.

(See VERTICAL TAKEOFF AND LANDING

AIRCRAFT.)

SIAP−

(See STANDARD INSTRUMENT APPROACH

PROCEDURE.)

SID−

(See STANDARD INSTRUMENT DEPARTURE.)

SIDESTEP MANEUVER− A visual maneuver

accomplished by a pilot at the completion of an

instrument approach to permit a straight-in landing

on a parallel runway not more than 1,200 feet to either

side of the runway to which the instrument approach

was conducted.

(Refer to AIM.)

SIGMET− A weather advisory issued concerning

weather significant to the safety of all aircraft.
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SIGMET advisories cover severe and extreme

turbulence, severe icing, and widespread dust or

sandstorms that reduce visibility to less than 3 miles.

(See AIRMET.)

(See AWW.)

(See CONVECTIVE SIGMET.)

(See CWA.)

(See ICAO term SIGMET INFORMATION.)

(Refer to AIM.)

SIGMET INFORMATION [ICAO]− Information

issued by a meteorological watch office concerning

the occurrence or expected occurrence of specified

en-route weather phenomena which may affect the

safety of aircraft operations.

SIGNIFICANT METEOROLOGICAL INFORMATION−

(See SIGMET.)

SIGNIFICANT POINT− A point, whether a named

intersection, a NAVAID, a fix derived from a

NAVAID(s), or geographical coordinate expressed in

degrees of latitude and longitude, which is

established for the purpose of providing separation,

as a reporting point, or to delineate a route of flight.

SIMPLIFIED DIRECTIONAL FACILITY− A

NAVAID used for nonprecision instrument approaches. The final approach course is similar to that

of an ILS localizer except that the SDF course may be

offset from the runway, generally not more than 3

degrees, and the course may be wider than the

localizer, resulting in a lower degree of accuracy.

(Refer to AIM.)

SIMULATED FLAMEOUT− A practice approach

by a jet aircraft (normally military) at idle thrust to a

runway. The approach may start at a runway (high

key) and may continue on a relatively high and wide

downwind leg with a continuous turn to final. It

terminates in landing or low approach. The purpose

of this approach is to simulate a flameout.

(See FLAMEOUT.)

SIMULTANEOUS ILS APPROACHES− An approach system permitting simultaneous ILS/MLS

approaches to airports having parallel runways

separated by at least 4,300 feet between centerlines.

Integral parts of a total system are ILS/MLS, radar,

communications, ATC procedures, and appropriate

airborne equipment.

(See PARALLEL RUNWAYS.)

(Refer to AIM.)

SIMULTANEOUS MLS APPROACHES−

(See SIMULTANEOUS ILS APPROACHES.)

SINGLE DIRECTION ROUTES− Preferred IFR

Routes which are sometimes depicted on high

altitude en route charts and which are normally flown

in one direction only.

(See PREFERRED IFR ROUTES.)

(Refer to AIRPORT/FACILITY DIRECTORY.)

SINGLE FREQUENCY APPROACH− A service

provided under a letter of agreement to military

single-piloted turbojet aircraft which permits use of

a single UHF frequency during approach for landing.

Pilots will not normally be required to change

frequency from the beginning of the approach to

touchdown except that pilots conducting an en route

descent are required to change frequency when

control is transferred from the air route traffic control

center to the terminal facility. The abbreviation

“SFA” in the DOD FLIP IFR Supplement under

“Communications” indicates this service is available

at an aerodrome.

SINGLE-PILOTED AIRCRAFT− A military turbojet aircraft possessing one set of flight controls,

tandem cockpits, or two sets of flight controls but

operated by one pilot is considered single-piloted by

ATC when determining the appropriate air traffic

service to be applied.

(See SINGLE FREQUENCY APPROACH.)

SKYSPOTTER− A pilot who has received specialized training in observing and reporting inflight

weather phenomena.

SLASH− A radar beacon reply displayed as an

elongated target.

SLDI−

(See SECTOR LIST DROP INTERVAL.)

SLOT TIME−

(See METER FIX TIME/SLOT TIME.)

SLOW TAXI− To taxi a float plane at low power or

low RPM.

SN−

(See SYSTEM STRATEGIC NAVIGATION.)

SPEAK SLOWER− Used in verbal communications

as a request to reduce speech rate.

SPECIAL ACTIVITY AIRSPACE (SAA)− Any

airspace with defined dimensions within the National

Airspace System wherein limitations may be
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imposed upon aircraft operations. This airspace may

be restricted areas, prohibited areas, military

operations areas, air ATC assigned airspace, and any

other designated airspace areas. The dimensions of

this airspace are programmed into URET and can be

designated as either active or inactive by screen entry.

Aircraft trajectories are constantly tested against the

dimensions of active areas and alerts issued to the

applicable sectors when violations are predicted.

(See USER REQUEST EVALUATION TOOL.)

SPECIAL EMERGENCY− A condition of air piracy

or other hostile act by a person(s) aboard an aircraft

which threatens the safety of the aircraft or its

passengers.

SPECIAL INSTRUMENT APPROACH PROCEDURE−

(See INSTRUMENT APPROACH PROCEDURE.)

SPECIAL USE AIRSPACE− Airspace of defined

dimensions identified by an area on the surface of the

earth wherein activities must be confined because of

their nature and/or wherein limitations may be

imposed upon aircraft operations that are not a part of

those activities. Types of special use airspace are:

a. Alert Area− Airspace which may contain a high

volume of pilot training activities or an unusual type

of aerial activity, neither of which is hazardous to

aircraft. Alert Areas are depicted on aeronautical

charts for the information of nonparticipating pilots.

All activities within an Alert Area are conducted in

accordance with Federal Aviation Regulations, and

pilots of participating aircraft as well as pilots

transiting the area are equally responsible for

collision avoidance.

b. Controlled Firing Area− Airspace wherein

activities are conducted under conditions so

controlled as to eliminate hazards to nonparticipating

aircraft and to ensure the safety of persons and

property on the ground.

c. Military Operations Area (MOA)− A MOA is

airspace established outside of Class A airspace area

to separate or segregate certain nonhazardous

military activities from IFR traffic and to identify for

VFR traffic where these activities are conducted.

(Refer to AIM.)

d. Prohibited Area− Airspace designated under

14 CFR Part 73 within which no person may operate

an aircraft without the permission of the using

agency.

(Refer to AIM.)

(Refer to En Route Charts.)

e. Restricted Area− Airspace designated under

14 CFR Part 73, within which the flight of aircraft,

while not wholly prohibited, is subject to restriction.

Most restricted areas are designated joint use and

IFR/VFR operations in the area may be authorized by

the controlling ATC facility when it is not being

utilized by the using agency. Restricted areas are

depicted on en route charts. Where joint use is

authorized, the name of the ATC controlling facility

is also shown.

(Refer to 14 CFR Part 73.)

(Refer to AIM.)

f. Warning Area− A warning area is airspace of

defined dimensions extending from 3 nautical miles

outward from the coast of the United States, that

contains activity that may be hazardous to

nonparticipating aircraft. The purpose of such

warning area is to warn nonparticipating pilots of the

potential danger. A warning area may be located over

domestic or international waters or both.

SPECIAL VFR CONDITIONS− Meteorological

conditions that are less than those required for basic

VFR flight in Class B, C, D, or E surface areas and

in which some aircraft are permitted flight under

visual flight rules.

(See SPECIAL VFR OPERATIONS.)

(Refer to 14 CFR Part 91.)

SPECIAL VFR FLIGHT [ICAO]− A VFR flight

cleared by air traffic control to operate within Class

B, C, D, and E surface areas in metrological

conditions below VMC.

SPECIAL VFR OPERATIONS− Aircraft operating

in accordance with clearances within Class B, C, D,

and E surface areas in weather conditions less than the

basic VFR weather minima. Such operations must be

requested by the pilot and approved by ATC.

(See SPECIAL VFR CONDITIONS.)

(See ICAO term SPECIAL VFR FLIGHT.)

SPEED−

(See AIRSPEED.)

(See GROUND SPEED.)

SPEED ADJUSTMENT− An ATC procedure used to

request pilots to adjust aircraft speed to a specific

value for the purpose of providing desired spacing.
Pilot/Controller Glossary 2/9/12

PCG S−6

Pilots are expected to maintain a speed of plus or

minus 10 knots or 0.02 Mach number of the specified

speed. Examples of speed adjustments are:

a. “Increase/reduce speed to Mach point (number.)”

b. “Increase/reduce speed to (speed in knots)” or

“Increase/reduce speed (number of knots) knots.”

SPEED BRAKES− Moveable aerodynamic devices

on aircraft that reduce airspeed during descent and

landing.

SPEED SEGMENTS− Portions of the arrival route

between the transition point and the vertex along the

optimum flight path for which speeds and altitudes

are specified. There is one set of arrival speed

segments adapted from each transition point to each

vertex. Each set may contain up to six segments.

SQUAWK (Mode, Code, Function)− Activate

specific modes/codes/functions on the aircraft

transponder; e.g., “Squawk three/alpha, two one zero

five, low.”

(See TRANSPONDER.)

STA−

(See SCHEDULED TIME OF ARRIVAL.)

STAGING/QUEUING− The placement, integration,

and segregation of departure aircraft in designated

movement areas of an airport by departure fix, EDCT,

and/or restriction.

STAND BY− Means the controller or pilot must

pause for a few seconds, usually to attend to other

duties of a higher priority. Also means to wait as in

“stand by for clearance.” The caller should

reestablish contact if a delay is lengthy. “Stand by” is

not an approval or denial.

STANDARD INSTRUMENT APPROACH PROCEDURE (SIAP)−

(See INSTRUMENT APPROACH PROCEDURE.)

STANDARD INSTRUMENT DEPARTURE (SID)−

A preplanned instrument flight rule (IFR) air traffic

control (ATC) departure procedure printed for

pilot/controller use in graphic form to provide

obstacle clearance and a transition from the terminal

area to the appropriate en route structure. SIDs are

primarily designed for system enhancement to

expedite traffic flow and to reduce pilot/controller

workload. ATC clearance must always be received

prior to flying a SID.

(See IFR TAKEOFF MINIMUMS AND

DEPARTURE PROCEDURES.)

(See OBSTACLE DEPARTURE PROCEDURE.)

(Refer to AIM.)

STANDARD RATE TURN− A turn of three degrees

per second.

STANDARD TERMINAL ARRIVAL− A preplanned instrument flight rule (IFR) air traffic control

arrival procedure published for pilot use in graphic

and/or textual form. STARs provide transition from

the en route structure to an outer fix or an instrument

approach fix/arrival waypoint in the terminal area.

STANDARD TERMINAL ARRIVAL CHARTS−

(See AERONAUTICAL CHART.)

STANDARD TERMINAL AUTOMATION REPLACEMENT SYSTEM (STARS)−

(See DTAS.)

STAR−

(See STANDARD TERMINAL ARRIVAL.)

STATE AIRCRAFT− Aircraft used in military,

customs and police service, in the exclusive service

of any government, or of any political subdivision,

thereof including the government of any state,

territory, or possession of the United States or the

District of Columbia, but not including any

government-owned aircraft engaged in carrying

persons or property for commercial purposes.

STATIC RESTRICTIONS− Those restrictions that

are usually not subject to change, fixed, in place,

and/or published.

STATIONARY RESERVATIONS− Altitude reservations which encompass activities in a fixed area.

Stationary reservations may include activities, such

as special tests of weapons systems or equipment,

certain U.S. Navy carrier, fleet, and anti-submarine

operations, rocket, missile and drone operations, and

certain aerial refueling or similar operations.

STEP TAXI− To taxi a float plane at full power or

high RPM.

STEP TURN− A maneuver used to put a float plane

in a planing configuration prior to entering an active

sea lane for takeoff. The STEP TURN maneuver

should only be used upon pilot request.

STEPDOWN FIX− A fix permitting additional

descent within a segment of an instrument approach
Pilot/Controller Glossary 2/9/12

PCG S−7

procedure by identifying a point at which a

controlling obstacle has been safely overflown.

STEREO ROUTE− A routinely used route of flight

established by users and ARTCCs identified by a

coded name; e.g., ALPHA 2. These routes minimize

flight plan handling and communications.

STOL AIRCRAFT−

(See SHORT TAKEOFF AND LANDING

AIRCRAFT.)

STOP ALTITUDE SQUAWK− Used by ATC to

inform an aircraft to turn-off the automatic altitude

reporting feature of its transponder. It is issued when

the verbally reported altitude varies 300 feet or more

from the automatic altitude report.

(See ALTITUDE READOUT.)

(See TRANSPONDER.)

STOP AND GO− A procedure wherein an aircraft

will land, make a complete stop on the runway, and

then commence a takeoff from that point.

(See LOW APPROACH.)

(See OPTION APPROACH.)

STOP BURST−

(See STOP STREAM.)

STOP BUZZER−

(See STOP STREAM.)

STOP SQUAWK (Mode or Code)− Used by ATC to

tell the pilot to turn specified functions of the aircraft

transponder off.

(See STOP ALTITUDE SQUAWK.)

(See TRANSPONDER.)

STOP STREAM− Used by ATC to request a pilot to

suspend electronic attack activity.

(See JAMMING.)

STOPOVER FLIGHT PLAN− A flight plan format

which permits in a single submission the filing of a

sequence of flight plans through interim full-stop

destinations to a final destination.

STOPWAY− An area beyond the takeoff runway no

less wide than the runway and centered upon the

extended centerline of the runway, able to support the

airplane during an aborted takeoff, without causing

structural damage to the airplane, and designated by

the airport authorities for use in decelerating the

airplane during an aborted takeoff.

STRAIGHT-IN APPROACH IFR− An instrument

approach wherein final approach is begun without

first having executed a procedure turn, not

necessarily completed with a straight-in landing or

made to straight-in landing minimums.

(See LANDING MINIMUMS.)

(See STRAIGHT-IN APPROACH VFR.)

(See STRAIGHT-IN LANDING.)

STRAIGHT-IN APPROACH VFR− Entry into the

traffic pattern by interception of the extended runway

centerline (final approach course) without executing

any other portion of the traffic pattern.

(See TRAFFIC PATTERN.)

STRAIGHT-IN LANDING− A landing made on a

runway aligned within 30 of the final approach

course following completion of an instrument

approach.

(See STRAIGHT-IN APPROACH IFR.)

STRAIGHT-IN LANDING MINIMUMS−

(See LANDING MINIMUMS.)

STRAIGHT-IN MINIMUMS−

(See STRAIGHT-IN LANDING MINIMUMS.)

STRATEGIC PLANNING− Planning whereby

solutions are sought to resolve potential conflicts.

SUBSTITUTE ROUTE− A route assigned to pilots

when any part of an airway or route is unusable

because of NAVAID status. These routes consist of:

a. Substitute routes which are shown on U.S.

Government charts.

b. Routes defined by ATC as specific NAVAID

radials or courses.

c. Routes defined by ATC as direct to or between

NAVAIDs.

SUNSET AND SUNRISE− The mean solar times of

sunset and sunrise as published in the Nautical

Almanac, converted to local standard time for the

locality concerned. Within Alaska, the end of evening

civil twilight and the beginning of morning civil

twilight, as defined for each locality.

SUPER HIGH FREQUENCY− The frequency band

between 3 and 30 gigahertz (GHz). The elevation and

azimuth stations of the microwave landing system

operate from 5031 MHz to 5091 MHz in this

spectrum.

SUPPLEMENTAL WEATHER SERVICE LOCATION− Airport facilities staffed with contract
Pilot/Controller Glossary 2/9/12

PCG S−8

personnel who take weather observations and

provide current local weather to pilots via telephone

or radio. (All other services are provided by the parent

FSS.)

SUPPS− Refers to ICAO Document 7030 Regional

Supplementary Procedures. SUPPS contain procedures for each ICAO Region which are unique to that

Region and are not covered in the worldwide

provisions identified in the ICAO Air Navigation

Plan. Procedures contained in Chapter 8 are based in

part on those published in SUPPS.

SURFACE AREA− The airspace contained by the

lateral boundary of the Class B, C, D, or E airspace

designated for an airport that begins at the surface and

extends upward.

SURPIC− A description of surface vessels in the area

of a Search and Rescue incident including their

predicted positions and their characteristics.

(Refer to FAAO JO 7110.65, Para 10−6−4,

INFLIGHT CONTINGENCIES.)

SURVEILLANCE APPROACH− An instrument

approach wherein the air traffic controller issues

instructions, for pilot compliance, based on aircraft

position in relation to the final approach course

(azimuth), and the distance (range) from the end of

the runway as displayed on the controller’s radar

scope. The controller will provide recommended

altitudes on final approach if requested by the pilot.

(Refer to AIM.)

SWAP−

(See SEVERE WEATHER AVOIDANCE PLAN.)

SWSL−

(See SUPPLEMENTAL WEATHER SERVICE

LOCATION.)

SYSTEM STRATEGIC NAVIGATION− Military

activity accomplished by navigating along a

preplanned route using internal aircraft systems to

maintain a desired track. This activity normally

requires a lateral route width of 10 NM and altitude

range of 1,000 feet to 6,000 feet AGL with some route

segments that permit terrain following.
Pilot/Controller Glossary 2/9/12

PCG T−1

T

TACAN−

(See TACTICAL AIR NAVIGATION.)

TACAN-ONLY AIRCRAFT− An aircraft, normally

military, possessing TACAN with DME but no VOR

navigational system capability. Clearances must

specify TACAN or VORTAC fixes and approaches.

TACTICAL AIR NAVIGATION− An ultra-high

frequency electronic rho-theta air navigation aid

which provides suitably equipped aircraft a

continuous indication of bearing and distance to the

TACAN station.

(See VORTAC.)

(Refer to AIM.)

TAILWIND− Any wind more than 90 degrees to the

longitudinal axis of the runway. The magnetic

direction of the runway shall be used as the basis for

determining the longitudinal axis.

TAKEOFF AREA−

(See LANDING AREA.)

TAKEOFF DISTANCE AVAILABLE (TODA)– The

takeoff run available plus the length of any remaining

runway or clearway beyond the far end of the takeoff

run available.

(See ICAO term TAKEOFF DISTANCE

AVAILABLE.)

TAKEOFF DISTANCE AVAILABLE [ICAO]− The

length of the takeoff run available plus the length of

the clearway, if provided.

TAKEOFF RUN AVAILABLE (TORA) – The

runway length declared available and suitable for the

ground run of an airplane taking off.

(See ICAO term TAKEOFF RUN AVAILABLE.)

TAKEOFF RUN AVAILABLE [ICAO]− The length

of runway declared available and suitable for the

ground run of an aeroplane take-off.

TARGET− The indication shown on an analog

display resulting from a primary radar return or a

radar beacon reply.

(See ASSOCIATED.)

(See DIGITAL TARGET.)

(See DIGITIZED RADAR TARGET.)

(See PRIMARY RADAR TARGET.)

(See RADAR.)

(See SECONDARY RADAR TARGET.)

(See TARGET SYMBOL.)

(See ICAO term TARGET.)

(See UNASSOCIATED.)

TARGET [ICAO]− In radar:

a. Generally, any discrete object which reflects or

retransmits energy back to the radar equipment.

b. Specifically, an object of radar search or

surveillance.

TARGET RESOLUTION− A process to ensure that

correlated radar targets do not touch. Target

resolution must be applied as follows:

a. Between the edges of two primary targets or the

edges of the ASR-9/11 primary target symbol.

b. Between the end of the beacon control slash and

the edge of a primary target.

c. Between the ends of two beacon control slashes.

Note 1: Mandatory traffic advisories and safety

alerts must be issued when this procedure is used.

Note 2: This procedure must not be used when

utilizing mosaic radar systems or multi−sensor

mode.

TARGET SYMBOL− A computer-generated indication shown on a radar display resulting from a

primary radar return or a radar beacon reply.

TARMAC DELAY− The holding of an aircraft on the

ground either before departure or after landing with

no opportunity for its passengers to deplane.

TARMAC DELAY AIRCRAFT− An aircraft whose

pilot−in−command has requested to taxi to the ramp,

gate, or alternate deplaning area to comply with the

Three−hour Tarmac Rule.

TARMAC DELAY REQUEST− A request by the

pilot−in−command to taxi to the ramp, gate, or

alternate deplaning location to comply with the

Three−hour Tarmac Rule.
Pilot/Controller Glossary 2/9/12

PCG T−2

TAS−

(See TERMINAL AUTOMATION SYSTEMS.)

TAWS−

(See TERRAIN AWARENESS WARNING

SYSTEM.)

TAXI− The movement of an airplane under its own

power on the surface of an airport (14 CFR

Section 135.100 [Note]). Also, it describes the

surface movement of helicopters equipped with

wheels.

(See AIR TAXI.)

(See HOVER TAXI.)

(Refer to 14 CFR Section 135.100.)

(Refer to AIM.)

TAXI PATTERNS− Patterns established to illustrate

the desired flow of ground traffic for the different

runways or airport areas available for use.

TCAS−

(See TRAFFIC ALERT AND COLLISION

AVOIDANCE SYSTEM.)

TCH−

(See THRESHOLD CROSSING HEIGHT.)

TCLT−

(See TENTATIVE CALCULATED LANDING

TIME.)

TDLS−

(See TERMINAL DATA LINK SYSTEM.)

TDZE−

(See TOUCHDOWN ZONE ELEVATION.)

TELEPHONE INFORMATION BRIEFING SERVICE− A continuous telephone recording of

meteorological and/or aeronautical information.

(Refer to AIM.)

TEMPORARY FLIGHT RESTRICTION (TFR) − A

TFR is a regulatory action issued by the FAA via the

U.S. NOTAM System, under the authority of United

States Code, Title 49. TFRs are issued within the

sovereign airspace of the United States and its

territories to restrict certain aircraft from operating

within a defined area on a temporary basis to protect

persons or property in the air or on the ground. While

not all inclusive, TFRs may be issued for disaster or

hazard situations such as: toxic gas leaks or spills,

fumes from flammable agents, aircraft accident/incident sites, aviation or ground resources engaged in

wildlife suppression, or aircraft relief activities

following a disaster. TFRs may also be issued in

support of VIP movements; for reasons of national

security; or when determined necessary for the

management of air traffic in the vicinity of aerial

demonstrations or major sporting events. NAS users

or other interested parties should contact a FSS for

TFR information. Additionally, TFR information can

be found in automated briefings, NOTAM publications, and on the internet at http://www.faa.gov. The

FAA also distributes TFR information to aviation

user groups for further dissemination.

TENTATIVE CALCULATED LANDING TIME− A

projected time calculated for adapted vertex for each

arrival aircraft based upon runway configuration,

airport acceptance rate, airport arrival delay period,

and other metered arrival aircraft. This time is either

the VTA of the aircraft or the TCLT/ACLT of the

previous aircraft plus the AAI, whichever is later.

This time will be updated in response to an aircraft’s

progress and its current relationship to other arrivals.

TERMINAL AREA− A general term used to describe

airspace in which approach control service or airport

traffic control service is provided.

TERMINAL AREA FACILITY− A facility providing air traffic control service for arriving and

departing IFR, VFR, Special VFR, and on occasion

en route aircraft.

(See APPROACH CONTROL FACILITY.)

(See TOWER.)

TERMINAL AUTOMATION SYSTEMS (TAS)−

TAS is used to identify the numerous automated

tracking systems including ARTS IIE, ARTS IIIA,

ARTS IIIE, STARS, and MEARTS.

TERMINAL DATA LINK SYSTEM (TDLS)− A

system that provides Digital Automatic Terminal

Information Service (D−ATIS) both on a specified

radio frequency and also, for subscribers, in a text

message via data link to the cockpit or to a gate

printer. TDLS also provides Pre−departure Clearances (PDC), at selected airports, to subscribers,

through a service provider, in text to the cockpit or to

a gate printer. In addition, TDLS will emulate the

Flight Data Input/Output (FDIO) information within

the control tower.

TERMINAL RADAR SERVICE AREA− Airspace

surrounding designated airports wherein ATC

provides radar vectoring, sequencing, and separation

on a full-time basis for all IFR and participating VFR

aircraft. The AIM contains an explanation of TRSA.
Pilot/Controller Glossary 2/9/12

PCG T−3

TRSAs are depicted on VFR aeronautical charts.

Pilot participation is urged but is not mandatory.

TERMINAL VFR RADAR SERVICE− A national

program instituted to extend the terminal radar

services provided instrument flight rules (IFR)

aircraft to visual flight rules (VFR) aircraft. The

program is divided into four types service referred to

as basic radar service, terminal radar service area

(TRSA) service, Class B service and Class C service.

The type of service provided at a particular location

is contained in the Airport/Facility Directory.

a. Basic Radar Service− These services are

provided for VFR aircraft by all commissioned

terminal radar facilities. Basic radar service includes

safety alerts, traffic advisories, limited radar

vectoring when requested by the pilot, and

sequencing at locations where procedures have been

established for this purpose and/or when covered by

a letter of agreement. The purpose of this service is to

adjust the flow of arriving IFR and VFR aircraft into

the traffic pattern in a safe and orderly manner and to

provide traffic advisories to departing VFR aircraft.

b. TRSA Service− This service provides, in

addition to basic radar service, sequencing of all IFR

and participating VFR aircraft to the primary airport

and separation between all participating VFR

aircraft. The purpose of this service is to provide

separation between all participating VFR aircraft and

all IFR aircraft operating within the area defined as a

TRSA.

c. Class C Service− This service provides, in

addition to basic radar service, approved separation

between IFR and VFR aircraft, and sequencing of

VFR aircraft, and sequencing of VFR arrivals to the

primary airport.

d. Class B Service− This service provides, in

addition to basic radar service, approved separation

of aircraft based on IFR, VFR, and/or weight, and

sequencing of VFR arrivals to the primary airport(s).

(See CONTROLLED AIRSPACE.)

(See TERMINAL RADAR SERVICE AREA.)

(Refer to AIM.)

(Refer to AIRPORT/FACILITY DIRECTORY.)

TERMINAL-VERY HIGH FREQUENCY OMNIDIRECTIONAL RANGE STATION− A very high

frequency terminal omnirange station located on or

near an airport and used as an approach aid.

(See NAVIGATIONAL AID.)

(See VOR.)

TERRAIN AWARENESS WARNING SYSTEM

(TAWS)− An on−board, terrain proximity alerting

system providing the aircrew ‘Low Altitude

warnings’ to allow immediate pilot action.

TERRAIN FOLLOWING− The flight of a military

aircraft maintaining a constant AGL altitude above

the terrain or the highest obstruction. The altitude of

the aircraft will constantly change with the varying

terrain and/or obstruction.

TETRAHEDRON− A device normally located on

uncontrolled airports and used as a landing direction

indicator. The small end of a tetrahedron points in the

direction of landing. At controlled airports, the

tetrahedron, if installed, should be disregarded

because tower instructions supersede the indicator.

(See SEGMENTED CIRCLE.)

(Refer to AIM.)

TF−

(See TERRAIN FOLLOWING.)

THAT IS CORRECT− The understanding you have

is right.

THREE−HOUR TARMAC RULE– Rule that relates

to Department of Transportation (DOT) requirements

placed on airlines when tarmac delays are anticipated

to reach 3 hours.

360 OVERHEAD−

(See OVERHEAD MANEUVER.)

THRESHOLD− The beginning of that portion of the

runway usable for landing.

(See AIRPORT LIGHTING.)

(See DISPLACED THRESHOLD.)

THRESHOLD CROSSING HEIGHT− The theoretical height above the runway threshold at which the

aircraft’s glideslope antenna would be if the aircraft

maintains the trajectory established by the mean ILS

glideslope or MLS glidepath.

(See GLIDESLOPE.)

(See THRESHOLD.)

THRESHOLD LIGHTS−

(See AIRPORT LIGHTING.)

TIBS−

(See TELEPHONE INFORMATION BRIEFING

SERVICE.)

TIE-IN FACILITY– The FSS primarily responsible

for providing FSS services, including telecommunications services for landing facilities or
Pilot/Controller Glossary 2/9/12

PCG T−4

navigational aids located within the boundaries of a

flight plan area (FPA). Three-letter identifiers are

assigned to each FSS/FPA and are annotated as tie-in

facilities in A/FDs, the Alaska Supplement, the

Pacific Supplement, and FAA Order JO 7350.8,

Location Identifiers. Large consolidated FSS

facilities may have many tie-in facilities or FSS

sectors within one facility.

(See FLIGHT PLAN AREA.)

(See FLIGHT SERVICE STATION.)

TIME GROUP− Four digits representing the hour

and minutes from the Coordinated Universal Time

(UTC) clock. FAA uses UTC for all operations. The

term “ZULU” may be used to denote UTC. The word

“local” or the time zone equivalent shall be used to

denote local when local time is given during radio and

telephone communications. When written, a time

zone designator is used to indicate local time; e.g.

“0205M” (Mountain). The local time may be based

on the 24-hour clock system. The day begins at 0000

and ends at 2359.

TIS−B−

(See TRAFFIC INFORMATION

SERVICE−BROADCAST.)

TMA−

(See TRAFFIC MANAGEMENT ADVISOR.)

TMPA−

(See TRAFFIC MANAGEMENT PROGRAM

ALERT.)

TMU−

(See TRAFFIC MANAGEMENT UNIT.)

TODA−

(See TAKEOFF DISTANCE AVAILABLE.)

(See ICAO term TAKEOFF DISTANCE

AVAILABLE.)

TOI−

(See TRACK OF INTEREST.)

TORA−

(See TAKEOFF RUN AVAILABLE.)

(See ICAO term TAKEOFF RUN AVAILABLE.)

TORCHING− The burning of fuel at the end of an

exhaust pipe or stack of a reciprocating aircraft

engine, the result of an excessive richness in the fuel

air mixture.

TOTAL ESTIMATED ELAPSED TIME [ICAO]−

For IFR flights, the estimated time required from

take-off to arrive over that designated point, defined

by reference to navigation aids, from which it is

intended that an instrument approach procedure will

be commenced, or, if no navigation aid is associated

with the destination aerodrome, to arrive over the

destination aerodrome. For VFR flights, the

estimated time required from take-off to arrive over

the destination aerodrome.

(See ICAO term ESTIMATED ELAPSED TIME.)

TOUCH-AND-GO− An operation by an aircraft that

lands and departs on a runway without stopping or

exiting the runway.

TOUCH-AND-GO LANDING−

(See TOUCH-AND-GO.)

TOUCHDOWN−

a. The point at which an aircraft first makes

contact with the landing surface.

b. Concerning a precision radar approach (PAR),

it is the point where the glide path intercepts the

landing surface.

(See ICAO term TOUCHDOWN.)

TOUCHDOWN [ICAO]− The point where the

nominal glide path intercepts the runway.

Note: Touchdown as defined above is only a datum

and is not necessarily the actual point at which the

aircraft will touch the runway.

TOUCHDOWN RVR−

(See VISIBILITY.)

TOUCHDOWN ZONE− The first 3,000 feet of the

runway beginning at the threshold. The area is used

for determination of Touchdown Zone Elevation in

the development of straight-in landing minimums for

instrument approaches.

(See ICAO term TOUCHDOWN ZONE.)

TOUCHDOWN ZONE [ICAO]− The portion of a

runway, beyond the threshold, where it is intended

landing aircraft first contact the runway.

TOUCHDOWN ZONE ELEVATION− The highest

elevation in the first 3,000 feet of the landing surface.

TDZE is indicated on the instrument approach

procedure chart when straight-in landing minimums

are authorized.

(See TOUCHDOWN ZONE.)

TOUCHDOWN ZONE LIGHTING−

(See AIRPORT LIGHTING.)
Pilot/Controller Glossary 2/9/12

PCG T−5

TOWER− A terminal facility that uses air/ground

communications, visual signaling, and other devices

to provide ATC services to aircraft operating in the

vicinity of an airport or on the movement area.

Authorizes aircraft to land or takeoff at the airport

controlled by the tower or to transit the Class D

airspace area regardless of flight plan or weather

conditions (IFR or VFR). A tower may also provide

approach control services (radar or nonradar).

(See AIRPORT TRAFFIC CONTROL SERVICE.)

(See APPROACH CONTROL FACILITY.)

(See APPROACH CONTROL SERVICE.)

(See MOVEMENT AREA.)

(See TOWER EN ROUTE CONTROL

SERVICE.)

(See ICAO term AERODROME CONTROL

TOWER.)

(Refer to AIM.)

TOWER EN ROUTE CONTROL SERVICE− The

control of IFR en route traffic within delegated

airspace between two or more adjacent approach

control facilities. This service is designed to expedite

traffic and reduce control and pilot communication

requirements.

TOWER TO TOWER−

(See TOWER EN ROUTE CONTROL

SERVICE.)

TPX-42− A numeric beacon decoder equipment/

system. It is designed to be added to terminal radar

systems for beacon decoding. It provides rapid target

identification, reinforcement of the primary radar

target, and altitude information from Mode C.

(See AUTOMATED RADAR TERMINAL

SYSTEMS.)

(See TRANSPONDER.)

TRACEABLE PRESSURE STANDARD− The

facility station pressure instrument, with certification/calibration traceable to the National Institute of

Standards and Technology. Traceable pressure

standards may be mercurial barometers, commissioned ASOS/AWSS or dual transducer AWOS, or

portable pressure standards or DASI.

TRACK− The actual flight path of an aircraft over the

surface of the earth.

(See COURSE.)

(See FLIGHT PATH.)

(See ROUTE.)

(See ICAO term TRACK.)

TRACK [ICAO]− The projection on the earth’s

surface of the path of an aircraft, the direction of

which path at any point is usually expressed in

degrees from North (True, Magnetic, or Grid).

TRACK OF INTEREST (TOI)− Displayed data

representing an airborne object that threatens or has

the potential to threaten North America or National

Security. Indicators may include, but are not limited

to: noncompliance with air traffic control instructions

or aviation regulations; extended loss of communications; unusual transmissions or unusual flight

behavior; unauthorized intrusion into controlled

airspace or an ADIZ; noncompliance with issued

flight restrictions/security procedures; or unlawful

interference with airborne flight crews, up to and

including hijack. In certain circumstances, an object

may become a TOI based on specific and credible

intelligence pertaining to that particular aircraft/

object, its passengers, or its cargo.

TRACK OF INTEREST RESOLUTION− A TOI

will normally be considered resolved when: the

aircraft/object is no longer airborne; the aircraft

complies with air traffic control instructions, aviation

regulations, and/or issued flight restrictions/security

procedures; radio contact is re−established and

authorized control of the aircraft is verified; the

aircraft is intercepted and intent is verified to be

nonthreatening/nonhostile; TOI was identified based

on specific and credible intelligence that was later

determined to be invalid or unreliable; or displayed

data is identified and characterized as invalid.

TRAFFIC−

a. A term used by a controller to transfer radar

identification of an aircraft to another controller for

the purpose of coordinating separation action. Traffic

is normally issued:

1. In response to a handoff or point out,

2. In anticipation of a handoff or point out, or

3. In conjunction with a request for control of an

aircraft.

b. A term used by ATC to refer to one or more

aircraft.

TRAFFIC ADVISORIES− Advisories issued to alert

pilots to other known or observed air traffic which

may be in such proximity to the position or intended

route of flight of their aircraft to warrant their

attention. Such advisories may be based on:

a. Visual observation.
Pilot/Controller Glossary 2/9/12

PCG T−6

b. Observation of radar identified and nonidentified aircraft targets on an ATC radar display, or

c. Verbal reports from pilots or other facilities.

Note 1: The word “traffic” followed by additional

information, if known, is used to provide such

advisories; e.g., “Traffic, 2 o’clock, one zero miles,

southbound, eight thousand.”

Note 2: Traffic advisory service will be provided to

the extent possible depending on higher priority

duties of the controller or other limitations; e.g.,

radar limitations, volume of traffic, frequency

congestion, or controller workload. Radar/

nonradar traffic advisories do not relieve the pilot

of his/her responsibility to see and avoid other

aircraft. Pilots are cautioned that there are many

times when the controller is not able to give traffic

advisories concerning all traffic in the aircraft’s

proximity; in other words, when a pilot requests or

is receiving traffic advisories, he/she should not

assume that all traffic will be issued.

(Refer to AIM.)

TRAFFIC ALERT (aircraft call sign), TURN

(left/right) IMMEDIATELY, (climb/descend) AND

MAINTAIN (altitude).

(See SAFETY ALERT.)

TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM− An airborne collision avoidance

system based on radar beacon signals which operates

independent of ground-based equipment. TCAS-I

generates traffic advisories only. TCAS-II generates

traffic advisories, and resolution (collision avoidance) advisories in the vertical plane.

TRAFFIC INFORMATION−

(See TRAFFIC ADVISORIES.)

TRAFFIC INFORMATION SERVICE−

BROADCAST (TIS−B)− The broadcast of ATC

derived traffic information to ADS−B equipped

(1090ES or UAT) aircraft. The source of this traffic

information is derived from ground−based air traffic

surveillance sensors, typically from radar targets.

TIS−B service will be available throughout the NAS

where there are both adequate surveillance coverage

(radar) and adequate broadcast coverage from

ADS−B ground stations. Loss of TIS−B will occur

when an aircraft enters an area not covered by the

GBT network. If this occurs in an area with adequate

surveillance coverage (radar), nearby aircraft that

remain within the adequate broadcast coverage

(ADS−B) area will view the first aircraft. TIS−B may

continue when an aircraft enters an area with

inadequate surveillance coverage (radar); nearby

aircraft that remain within the adequate broadcast

coverage (ADS−B) area will not view the first

aircraft.

TRAFFIC IN SIGHT− Used by pilots to inform a

controller that previously issued traffic is in sight.

(See NEGATIVE CONTACT.)

(See TRAFFIC ADVISORIES.)

TRAFFIC MANAGEMENT ADVISOR (TMA)− A

computerized tool which assists Traffic Management

Coordinators to efficiently schedule arrival traffic to

a metered airport, by calculating meter fix times and

delays then sending that information to the sector

controllers.

TRAFFIC MANAGEMENT PROGRAM ALERT−

A term used in a Notice to Airmen (NOTAM) issued

in conjunction with a special traffic management

program to alert pilots to the existence of the program

and to refer them to either the Notices to Airmen

publication or a special traffic management program

advisory message for program details. The contraction TMPA is used in NOTAM text.

TRAFFIC MANAGEMENT UNIT− The entity in

ARTCCs and designated terminals directly involved

in the active management of facility traffic. Usually

under the direct supervision of an assistant manager

for traffic management.

TRAFFIC NO FACTOR− Indicates that the traffic

described in a previously issued traffic advisory is no

factor.

TRAFFIC NO LONGER OBSERVED− Indicates

that the traffic described in a previously issued traffic

advisory is no longer depicted on radar, but may still

be a factor.

TRAFFIC PATTERN− The traffic flow that is

prescribed for aircraft landing at, taxiing on, or taking

off from an airport. The components of a typical

traffic pattern are upwind leg, crosswind leg,

downwind leg, base leg, and final approach.

a. Upwind Leg− A flight path parallel to the

landing runway in the direction of landing.

b. Crosswind Leg− A flight path at right angles to

the landing runway off its upwind end.

c. Downwind Leg− A flight path parallel to the

landing runway in the direction opposite to landing.

The downwind leg normally extends between the

crosswind leg and the base leg.
Pilot/Controller Glossary 2/9/12

PCG T−7

d. Base Leg− A flight path at right angles to the

landing runway off its approach end. The base leg

normally extends from the downwind leg to the

intersection of the extended runway centerline.

e. Final Approach. A flight path in the direction of

landing along the extended runway centerline. The

final approach normally extends from the base leg to

the runway. An aircraft making a straight-in approach

VFR is also considered to be on final approach.

(See STRAIGHT-IN APPROACH VFR.)

(See TAXI PATTERNS.)

(See ICAO term AERODROME TRAFFIC

CIRCUIT.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

TRAFFIC SITUATION DISPLAY (TSD)− TSD is a

computer system that receives radar track data from

all 20 CONUS ARTCCs, organizes this data into a

mosaic display, and presents it on a computer screen.

The display allows the traffic management coordinator multiple methods of selection and highlighting of

individual aircraft or groups of aircraft. The user has

the option of superimposing these aircraft positions

over any number of background displays. These

background options include ARTCC boundaries, any

stratum of en route sector boundaries, fixes, airways,

military and other special use airspace, airports, and

geopolitical boundaries. By using the TSD, a

coordinator can monitor any number of traffic

situations or the entire systemwide traffic flows.

TRAJECTORY− A URET representation of the path

an aircraft is predicted to fly based upon a Current

Plan or Trial Plan.

(See USER REQUEST EVALUATION TOOL.)

TRAJECTORY MODELING− The automated process of calculating a trajectory.

TRANSCRIBED WEATHER BROADCAST− A

continuous recording of meteorological and aeronautical information that is broadcast on L/MF and VOR

facilities for pilots. (Provided only in Alaska.)

(Refer to AIM.)

TRANSFER OF CONTROL− That action whereby

the responsibility for the separation of an aircraft is

transferred from one controller to another.

(See ICAO term TRANSFER OF CONTROL.)

TRANSFER OF CONTROL [ICAO]− Transfer of

responsibility for providing air traffic control service.

TRANSFERRING CONTROLLER− A controller/

facility transferring control of an aircraft to another

controller/facility.

(See ICAO term TRANSFERRING

UNIT/CONTROLLER.)

TRANSFERRING FACILITY−

(See TRANSFERRING CONTROLLER.)

TRANSFERRING UNIT/CONTROLLER [ICAO]−

Air traffic control unit/air traffic controller in the

process of transferring the responsibility for

providing air traffic control service to an aircraft to

the next air traffic control unit/air traffic controller

along the route of flight.

Note: See definition of accepting unit/controller.

TRANSITION−

a. The general term that describes the change from

one phase of flight or flight condition to another; e.g.,

transition from en route flight to the approach or

transition from instrument flight to visual flight.

b. A published procedure (DP Transition) used to

connect the basic DP to one of several en route

airways/jet routes, or a published procedure (STAR

Transition) used to connect one of several en route

airways/jet routes to the basic STAR.

(Refer to DP/STAR Charts.)

TRANSITION POINT− A point at an adapted

number of miles from the vertex at which an arrival

aircraft would normally commence descent from its

en route altitude. This is the first fix adapted on the

arrival speed segments.

TRANSITION WAYPOINT− The waypoint that

defines the beginning of a runway or en route

transition on an RNAV SID or STAR.

TRANSITIONAL AIRSPACE− That portion of

controlled airspace wherein aircraft change from one

phase of flight or flight condition to another.

TRANSMISSOMETER− An apparatus used to

determine visibility by measuring the transmission of

light through the atmosphere. It is the measurement

source for determining runway visual range (RVR)

and runway visibility value (RVV).

(See VISIBILITY.)

TRANSMITTING IN THE BLIND− A transmission from one station to other stations in

circumstances where two-way communication

cannot be established, but where it is believed that the

called stations may be able to receive the

transmission.
Pilot/Controller Glossary 2/9/12

PCG T−8

TRANSPONDER− The airborne radar beacon

receiver/transmitter portion of the Air Traffic Control

Radar Beacon System (ATCRBS) which automatically receives radio signals from interrogators on the

ground, and selectively replies with a specific reply

pulse or pulse group only to those interrogations

being received on the mode to which it is set to

respond.

(See INTERROGATOR.)

(See ICAO term TRANSPONDER.)

(Refer to AIM.)

TRANSPONDER [ICAO]− A receiver/transmitter

which will generate a reply signal upon proper

interrogation; the interrogation and reply being on

different frequencies.

TRANSPONDER CODES−

(See CODES.)

TRANSPONDER OBSERVED − Phraseology used

to inform a VFR pilot the aircraft’s assigned beacon

code and position have been observed. Specifically,

this term conveys to a VFR pilot the transponder

reply has been observed and its position correlated for

transit through the designated area.

TRIAL PLAN− A proposed amendment which

utilizes automation to analyze and display potential

conflicts along the predicted trajectory of the selected

aircraft.

TRSA−

(See TERMINAL RADAR SERVICE AREA.)

TSD−

(See TRAFFIC SITUATION DISPLAY.)

TURBOJET AIRCRAFT− An aircraft having a jet

engine in which the energy of the jet operates a

turbine which in turn operates the air compressor.

TURBOPROP AIRCRAFT− An aircraft having a jet

engine in which the energy of the jet operates a

turbine which drives the propeller.

TURN ANTICIPATION− (maneuver anticipation).

TVOR−

(See TERMINAL-VERY HIGH FREQUENCY

OMNIDIRECTIONAL RANGE STATION.)

TWEB−

(See TRANSCRIBED WEATHER BROADCAST.)

TWO-WAY RADIO COMMUNICATIONS FAILURE−

(See LOST COMMUNICATIONS.)
Pilot/Controller Glossary 2/9/12

PCG U−1

U

UDF−

(See DIRECTION FINDER.)

UHF−

(See ULTRAHIGH FREQUENCY.)

ULTRAHIGH FREQUENCY− The frequency band

between 300 and 3,000 MHz. The bank of radio

frequencies used for military air/ground voice

communications. In some instances this may go as

low as 225 MHz and still be referred to as UHF.

ULTRALIGHT VEHICLE− An aeronautical vehicle

operated for sport or recreational purposes which

does not require FAA registration, an airworthiness

certificate, nor pilot certification. They are primarily

single occupant vehicles, although some two-place

vehicles are authorized for training purposes.

Operation of an ultralight vehicle in certain airspace

requires authorization from ATC.

(Refer to 14 CFR Part 103.)

UNABLE− Indicates inability to comply with a

specific instruction, request, or clearance.

UNASSOCIATED− A radar target that does not

display a data block with flight identification and

altitude information.

(See ASSOCIATED.)

UNDER THE HOOD− Indicates that the pilot is

using a hood to restrict visibility outside the cockpit

while simulating instrument flight. An appropriately

rated pilot is required in the other control seat while

this operation is being conducted.

(Refer to 14 CFR Part 91.)

UNFROZEN− The Scheduled Time of Arrival (STA)

tags, which are still being rescheduled by traffic

management advisor (TMA) calculations. The

aircraft will remain unfrozen until the time the

corresponding estimated time of arrival (ETA) tag

passes the preset freeze horizon for that aircraft’s

stream class. At this point the automatic rescheduling

will stop, and the STA becomes “frozen.”

UNICOM− A nongovernment communication facility which may provide airport information at certain

airports. Locations and frequencies of UNICOMs are

shown on aeronautical charts and publications.

(See AIRPORT/FACILITY DIRECTORY.)

(Refer to AIM.)

UNPUBLISHED ROUTE− A route for which no

minimum altitude is published or charted for pilot

use. It may include a direct route between NAVAIDs,

a radial, a radar vector, or a final approach course

beyond the segments of an instrument approach

procedure.

(See PUBLISHED ROUTE.)

(See ROUTE.)

UNRELIABLE (GPS/WAAS)− An advisory to

pilots indicating the expected level of service of the

GPS and/or WAAS may not be available. Pilots must

then determine the adequacy of the signal for desired

use.

UPWIND LEG−

(See TRAFFIC PATTERN.)

URET−

(See USER REQUEST EVALUATION TOOL.)

URGENCY− A condition of being concerned about

safety and of requiring timely but not immediate

assistance; a potential distress condition.

(See ICAO term URGENCY.)

URGENCY [ICAO]− A condition concerning the

safety of an aircraft or other vehicle, or of person on

board or in sight, but which does not require

immediate assistance.

USAFIB−

(See ARMY AVIATION FLIGHT INFORMATION

BULLETIN.)

USER REQUEST EVALUATION TOOL (URET)−

User Request Evaluation Tool is an automated tool

provided at each Radar Associate position in selected

En Route facilities. This tool utilizes flight and radar

data to determine present and future trajectories for

all active and proposal aircraft and provides

enhanced, automated flight data management.

UVDF−

(See DIRECTION FINDER.)

Pilot/Controller Glossary 2/9/12

PCG V−1

V

VASI−

(See VISUAL APPROACH SLOPE INDICATOR.)

VCOA−

(See VISUAL CLIMB OVER AIRPORT.)

VDF−

(See DIRECTION FINDER.)

VDP−

(See VISUAL DESCENT POINT.)

VECTOR− A heading issued to an aircraft to provide

navigational guidance by radar.

(See ICAO term RADAR VECTORING.)

VERIFY− Request confirmation of information;

e.g., “verify assigned altitude.”

VERIFY SPECIFIC DIRECTION OF TAKEOFF

(OR TURNS AFTER TAKEOFF)− Used by ATC to

ascertain an aircraft’s direction of takeoff and/or

direction of turn after takeoff. It is normally used for

IFR departures from an airport not having a control

tower. When direct communication with the pilot is

not possible, the request and information may be

relayed through an FSS, dispatcher, or by other

means.

(See IFR TAKEOFF MINIMUMS AND

DEPARTURE PROCEDURES.)

VERTEX− The last fix adapted on the arrival speed

segments. Normally, it will be the outer marker of the

runway in use. However, it may be the actual

threshold or other suitable common point on the

approach path for the particular runway configuration.

VERTEX TIME OF ARRIVAL− A calculated time of

aircraft arrival over the adapted vertex for the runway

configuration in use. The time is calculated via the

optimum flight path using adapted speed segments.

VERTICAL NAVIGATION (VNAV)– A function of

area navigation (RNAV) equipment which calculates,

displays, and provides vertical guidance to a profile

or path.

VERTICAL SEPARATION− Separation between

aircraft expressed in units of vertical distance.

(See SEPARATION.)

VERTICAL TAKEOFF AND LANDING AIRCRAFT− Aircraft capable of vertical climbs and/or

descents and of using very short runways or small

areas for takeoff and landings. These aircraft include,

but are not limited to, helicopters.

(See SHORT TAKEOFF AND LANDING

AIRCRAFT.)

VERY HIGH FREQUENCY− The frequency band

between 30 and 300 MHz. Portions of this band, 108

to 118 MHz, are used for certain NAVAIDs; 118 to

136 MHz are used for civil air/ground voice

communications. Other frequencies in this band are

used for purposes not related to air traffic control.

VERY HIGH FREQUENCY OMNIDIRECTIONAL RANGE STATION−

(See VOR.)

VERY LOW FREQUENCY− The frequency band

between 3 and 30 kHz.

VFR−

(See VISUAL FLIGHT RULES.)

VFR AIRCRAFT− An aircraft conducting flight in

accordance with visual flight rules.

(See VISUAL FLIGHT RULES.)

VFR CONDITIONS− Weather conditions equal to

or better than the minimum for flight under visual

flight rules. The term may be used as an ATC

clearance/instruction only when:

a. An IFR aircraft requests a climb/descent in

VFR conditions.

b. The clearance will result in noise abatement

benefits where part of the IFR departure route does

not conform to an FAA approved noise abatement

route or altitude.

c. A pilot has requested a practice instrument

approach and is not on an IFR flight plan.

Note: All pilots receiving this authorization must

comply with the VFR visibility and distance from

cloud criteria in 14 CFR Part 91. Use of the term

does not relieve controllers of their responsibility to

separate aircraft in Class B and Class C airspace

or TRSAs as required by FAAO JO 7110.65. When

used as an ATC clearance/instruction, the term

may be abbreviated “VFR;” e.g., “MAINTAIN

VFR,” “CLIMB/DESCEND VFR,” etc.
Pilot/Controller Glossary 2/9/12

PCG V−2

VFR FLIGHT−

(See VFR AIRCRAFT.)

VFR MILITARY TRAINING ROUTES− Routes

used by the Department of Defense and associated

Reserve and Air Guard units for the purpose of

conducting low-altitude navigation and tactical

training under VFR below 10,000 feet MSL at

airspeeds in excess of 250 knots IAS.

VFR NOT RECOMMENDED− An advisory

provided by a flight service station to a pilot during

a preflight or inflight weather briefing that flight

under visual flight rules is not recommended. To be

given when the current and/or forecast weather

conditions are at or below VFR minimums. It does

not abrogate the pilot’s authority to make his/her own

decision.

VFR-ON-TOP− ATC authorization for an IFR

aircraft to operate in VFR conditions at any

appropriate VFR altitude (as specified in 14 CFR and

as restricted by ATC). A pilot receiving this

authorization must comply with the VFR visibility,

distance from cloud criteria, and the minimum IFR

altitudes specified in 14 CFR Part 91. The use of this

term does not relieve controllers of their responsibility to separate aircraft in Class B and Class C airspace

or TRSAs as required by FAAO JO 7110.65.

VFR TERMINAL AREA CHARTS−

(See AERONAUTICAL CHART.)

VFR WAYPOINT−

(See WAYPOINT.)

VHF−

(See VERY HIGH FREQUENCY.)

VHF OMNIDIRECTIONAL RANGE/TACTICAL

AIR NAVIGATION−

(See VORTAC.)

VIDEO MAP− An electronically displayed map on

the radar display that may depict data such as airports,

heliports, runway centerline extensions, hospital

emergency landing areas, NAVAIDs and fixes,

reporting points, airway/route centerlines, boundaries, handoff points, special use tracks, obstructions,

prominent geographic features, map alignment

indicators, range accuracy marks, minimum vectoring altitudes.

VISIBILITY− The ability, as determined by

atmospheric conditions and expressed in units of

distance, to see and identify prominent unlighted

objects by day and prominent lighted objects by

night. Visibility is reported as statute miles, hundreds

of feet or meters.

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

a. Flight Visibility− The average forward horizontal distance, from the cockpit of an aircraft in flight,

at which prominent unlighted objects may be seen

and identified by day and prominent lighted objects

may be seen and identified by night.

b. Ground Visibility− Prevailing horizontal visibility near the earth’s surface as reported by the

United States National Weather Service or an

accredited observer.

c. Prevailing Visibility− The greatest horizontal

visibility equaled or exceeded throughout at least half

the horizon circle which need not necessarily be

continuous.

d. Runway Visibility Value (RVV)− The visibility

determined for a particular runway by a transmissometer. A meter provides a continuous indication of

the visibility (reported in miles or fractions of miles)

for the runway. RVV is used in lieu of prevailing

visibility in determining minimums for a particular

runway.

e. Runway Visual Range (RVR)− An instrumentally derived value, based on standard calibrations,

that represents the horizontal distance a pilot will see

down the runway from the approach end. It is based

on the sighting of either high intensity runway lights

or on the visual contrast of other targets whichever

yields the greater visual range. RVR, in contrast to

prevailing or runway visibility, is based on what a

pilot in a moving aircraft should see looking down the

runway. RVR is horizontal visual range, not slant

visual range. It is based on the measurement of a

transmissometer made near the touchdown point of

the instrument runway and is reported in hundreds of

feet. RVR is used in lieu of RVV and/or prevailing

visibility in determining minimums for a particular

runway.

1. Touchdown RVR− The RVR visibility

readout values obtained from RVR equipment

serving the runway touchdown zone.

2. Mid-RVR− The RVR readout values obtained

from RVR equipment located midfield of the runway.
Pilot/Controller Glossary 2/9/12

PCG V−3

3. Rollout RVR− The RVR readout values

obtained from RVR equipment located nearest the

rollout end of the runway.

(See ICAO term FLIGHT VISIBILITY.)

(See ICAO term GROUND VISIBILITY.)

(See ICAO term RUNWAY VISUAL RANGE.)

(See ICAO term VISIBILITY.)

VISIBILITY [ICAO]− The ability, as determined by

atmospheric conditions and expressed in units of

distance, to see and identify prominent unlighted

objects by day and prominent lighted objects by

night.

a. Flight Visibility−The visibility forward from

the cockpit of an aircraft in flight.

b. Ground Visibility−The visibility at an aerodrome as reported by an accredited observer.

c. Runway Visual Range [RVR]−The range over

which the pilot of an aircraft on the centerline of a

runway can see the runway surface markings or the

lights delineating the runway or identifying its

centerline.

VISUAL APPROACH− An approach conducted on

an instrument flight rules (IFR) flight plan which

authorizes the pilot to proceed visually and clear of

clouds to the airport. The pilot must, at all times, have

either the airport or the preceding aircraft in sight.

This approach must be authorized and under the

control of the appropriate air traffic control facility.

Reported weather at the airport must be ceiling at or

above 1,000 feet and visibility of 3 miles or greater.

(See ICAO term VISUAL APPROACH.)

VISUAL APPROACH [ICAO]− An approach by an

IFR flight when either part or all of an instrument

approach procedure is not completed and the

approach is executed in visual reference to terrain.

VISUAL APPROACH SLOPE INDICATOR−

(See AIRPORT LIGHTING.)

VISUAL CLIMB OVER AIRPORT (VCOA)− A

departure option for an IFR aircraft, operating in

visual meteorological conditions equal to or greater

than the specified visibility and ceiling, to visually

conduct climbing turns over the airport to the

published “climb−to” altitude from which to proceed

with the instrument portion of the departure. VCOA

procedures are developed to avoid obstacles greater

than 3 statute miles from the departure end of the

runway as an alternative to complying with climb

gradients greater than 200 feet per nautical mile.

These procedures are published in the ‘Take−Off

Minimums and (Obstacle) Departure Procedures’

section of the Terminal Procedures Publications.

(See AIM.)

VISUAL DESCENT POINT− A defined point on the

final approach course of a nonprecision straight-in

approach procedure from which normal descent from

the MDA to the runway touchdown point may be

commenced, provided the approach threshold of that

runway, or approach lights, or other markings

identifiable with the approach end of that runway are

clearly visible to the pilot.

VISUAL FLIGHT RULES− Rules that govern the

procedures for conducting flight under visual

conditions. The term “VFR” is also used in the

United States to indicate weather conditions that are

equal to or greater than minimum VFR requirements.

In addition, it is used by pilots and controllers to

indicate type of flight plan.

(See INSTRUMENT FLIGHT RULES.)

(See INSTRUMENT METEOROLOGICAL

CONDITIONS.)

(See VISUAL METEOROLOGICAL

CONDITIONS.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

VISUAL HOLDING− The holding of aircraft at

selected, prominent geographical fixes which can be

easily recognized from the air.

(See HOLDING FIX.)

VISUAL METEOROLOGICAL CONDITIONS−

Meteorological conditions expressed in terms of

visibility, distance from cloud, and ceiling equal to or

better than specified minima.

(See INSTRUMENT FLIGHT RULES.)

(See INSTRUMENT METEOROLOGICAL

CONDITIONS.)

(See VISUAL FLIGHT RULES.)

VISUAL SEGMENT−

(See PUBLISHED INSTRUMENT APPROACH

PROCEDURE VISUAL SEGMENT.)
Pilot/Controller Glossary 2/9/12

PCG V−4

VISUAL SEPARATION− A means employed by

ATC to separate aircraft in terminal areas and en route

airspace in the NAS. There are two ways to effect this

separation:

a. The tower controller sees the aircraft involved

and issues instructions, as necessary, to ensure that

the aircraft avoid each other.

b. A pilot sees the other aircraft involved and upon

instructions from the controller provides his/her own

separation by maneuvering his/her aircraft as

necessary to avoid it. This may involve following

another aircraft or keeping it in sight until it is no

longer a factor.

(See SEE AND AVOID.)

(Refer to 14 CFR Part 91.)

VLF−

(See VERY LOW FREQUENCY.)

VMC−

(See VISUAL METEOROLOGICAL

CONDITIONS.)

VOICE SWITCHING AND CONTROL SYSTEM−

The VSCS is a computer controlled switching system

that provides air traffic controllers with all voice

circuits (air to ground and ground to ground)

necessary for air traffic control.

(See VOICE SWITCHING AND CONTROL

SYSTEM.)

(Refer to AIM.)

VOR− A ground-based electronic navigation aid

transmitting very high frequency navigation signals,

360 degrees in azimuth, oriented from magnetic

north. Used as the basis for navigation in the National

Airspace System. The VOR periodically identifies

itself by Morse Code and may have an additional

voice identification feature. Voice features may be

used by ATC or FSS for transmitting instructions/

information to pilots.

(See NAVIGATIONAL AID.)

(Refer to AIM.)

VOR TEST SIGNAL−

(See VOT.)

VORTAC− A navigation aid providing VOR

azimuth, TACAN azimuth, and TACAN distance

measuring equipment (DME) at one site.

(See DISTANCE MEASURING EQUIPMENT.)

(See NAVIGATIONAL AID.)

(See TACAN.)

(See VOR.)

(Refer to AIM.)

VORTICES− Circular patterns of air created by the

movement of an airfoil through the air when

generating lift. As an airfoil moves through the

atmosphere in sustained flight, an area of area of low

pressure is created above it. The air flowing from the

high pressure area to the low pressure area around and

about the tips of the airfoil tends to roll up into two

rapidly rotating vortices, cylindrical in shape. These

vortices are the most predominant parts of aircraft

wake turbulence and their rotational force is

dependent upon the wing loading, gross weight, and

speed of the generating aircraft. The vortices from

medium to heavy aircraft can be of extremely high

velocity and hazardous to smaller aircraft.

(See AIRCRAFT CLASSES.)

(See WAKE TURBULENCE.)

(Refer to AIM.)

VOT− A ground facility which emits a test signal to

check VOR receiver accuracy. Some VOTs are

available to the user while airborne, and others are

limited to ground use only.

(See AIRPORT/FACILITY DIRECTORY.)

(Refer to 14 CFR Part 91.)

(Refer to AIM.)

VR−

(See VFR MILITARY TRAINING ROUTES.)

VSCS−

(See VOICE SWITCHING AND CONTROL

SYSTEM.)

VTA−

(See VERTEX TIME OF ARRIVAL.)

VTOL AIRCRAFT−

(See VERTICAL TAKEOFF AND LANDING

AIRCRAFT.)
Pilot/Controller Glossary 2/9/12

PCG W−1

W

WA−

(See AIRMET.)

(See WEATHER ADVISORY.)

WAAS−

(See WIDE-AREA AUGMENTATION SYSTEM.)

WAKE TURBULENCE− Phenomena resulting from

the passage of an aircraft through the atmosphere.

The term includes vortices, thrust stream turbulence,

jet blast, jet wash, propeller wash, and rotor wash

both on the ground and in the air.

(See AIRCRAFT CLASSES.)

(See JET BLAST.)

(See VORTICES.)

(Refer to AIM.)

WARNING AREA−

(See SPECIAL USE AIRSPACE.)

WAYPOINT− A predetermined geographical position used for route/instrument approach definition,

progress reports, published VFR routes, visual

reporting points or points for transitioning and/or

circumnavigating controlled and/or special use

airspace, that is defined relative to a VORTAC station

or in terms of latitude/longitude coordinates.

WEATHER ADVISORY− In aviation weather

forecast practice, an expression of hazardous weather

conditions not predicted in the area forecast, as they

affect the operation of air traffic and as prepared by

the NWS.

(See AIRMET.)

(See SIGMET.)

WHEN ABLE− When used in conjunction with ATC

instructions, gives the pilot the latitude to delay

compliance until a condition or event has been

reconciled. Unlike “pilot discretion,” when instructions are prefaced “when able,” the pilot is expected

to seek the first opportunity to comply. Once a

maneuver has been initiated, the pilot is expected to

continue until the specifications of the instructions

have been met. “When able,” should not be used

when expeditious compliance is required.

WIDE-AREA AUGMENTATION SYSTEM

(WAAS)− The WAAS is a satellite navigation system

consisting of the equipment and software which

augments the GPS Standard Positioning Service

(SPS). The WAAS provides enhanced integrity,

accuracy, availability, and continuity over and above

GPS SPS. The differential correction function

provides improved accuracy required for precision

approach.

WILCO− I have received your message, understand

it, and will comply with it.

WIND GRID DISPLAY− A display that presents the

latest forecasted wind data overlaid on a map of the

ARTCC area. Wind data is automatically entered and

updated periodically by transmissions from the

National Weather Service. Winds at specific

altitudes, along with temperatures and air pressure

can be viewed.

WIND SHEAR− A change in wind speed and/or wind

direction in a short distance resulting in a tearing or

shearing effect. It can exist in a horizontal or vertical

direction and occasionally in both.

WIND SHEAR ESCAPE– An unplanned abortive

maneuver initiated by the pilot in command (PIC) as

a result of onboard cockpit systems. Wind shear

escapes are characterized by maximum thrust climbs

in the low altitude terminal environment until wind

shear conditions are no longer detected.

WING TIP VORTICES−

(See VORTICES.)

WORDS TWICE−

a. As a request: “Communication is difficult.

Please say every phrase twice.”

b. As information: “Since communications are

difficult, every phrase in this message will be spoken

twice.”

WORLD AERONAUTICAL CHARTS−

(See AERONAUTICAL CHART.)

WS−

(See SIGMET.)

(See WEATHER ADVISORY.)

WST−

(See CONVECTIVE SIGMET.)

(See WEATHER ADVISORY.)

7/26/12 AIM

Index I−1

INDEX

[References are to page numbers]

A

Accident, Aircraft, Reporting, 7−6−1

Accident Cause Factors, 7−5−1

Adherence to Clearance, 4−4−5

ADIZ. See Air Defense Identification Zones

ADS−B. See Automatic Dependent Broadcast Services

ADS−R. See Automatic Dependent

Surveillance−Rebroadcast

Advisories

Braking Action, 4−3−11

Inflight Aviation Weather, 7−1−9

Minimum Fuel, 5−5−6

Runway Friction, 4−3−11

Traffic, 5−5−4

Aerobatic Flight, 8−1−8

Aerodrome Forecast (TAF), 7−1−70, 7−1−71

Aeronautical

Charts, 9−1−1

Publications, 9−1−1

Aeronautical Light Beacons, 2−2−1

AFIS. See Automatic Flight Information Service

AHRS. See Attitude Heading Reference System

Air Ambulance Flights, 4−2−4

Air Defense Identification Zone, Land−Based, 5−6−1

Air Defense Identification Zones, 5−6−1, 5−6−8

Air Route Surveillance Radar, 4−5−7

Air Route Traffic Control Centers, 4−1−1

Air Traffic Control

Aircraft Separation, 4−4−1

Clearances, 4−4−1

Pilot Services, 4−1−1

Air Route Traffic Control Centers, 4−1−1

Airport Reservations, 4−1−21

Approach Control Service, Arriving VFR Aircraft,

4−1−2

Automatic Terminal Information Service, 4−1−7

Communications, Release of IFR Aircraft, Airports

without Operating Control Tower, 4−1−1

Control Towers, 4−1−1

Flight Service Stations, 4−1−1

Ground Vehicle Operations, 4−1−6

Hazardous Area Reporting Service, 4−1−18

IFR Approaches, 4−1−6

Operation Raincheck, 4−1−2

Operation Take−off, 4−1−2

Radar Assistance to VFR Aircraft, 4−1−11

Radar Traffic Information Service, 4−1−8

Recording and Monitoring, 4−1−1

Safety Alert, 4−1−10

Terminal Radar Services for VFR Aircraft, 4−1−12

Tower En Route Control, 4−1−14

Traffic Advisory Practices, Airports Without

Operating Control Towers, 4−1−2

Transponder Operation, 4−1−15

Unicom, Use for ATC Purposes, 4−1−7

Unicom/Multicom, 4−1−6

Air Traffic Control Radar Beacon System, 4−1−15,

4−5−2

Aircraft

Arresting Devices, 2−3−30

Call Signs, 4−2−3

Lights, Use in Airport Operations, 4−3−23

Unmanned, 7−5−2

VFR, Emergency Radar Service, 6−2−1

Aircraft Conflict Alert, 4−1−11

Airport

Aids, Marking, 2−3−1

Holding Position, 2−3−12

Pavement, 2−3−1

Holding Position, 2−3−1

Other, 2−3−1

Runway, 2−3−1

Taxiway, 2−3−1

Airport Advisory/Information Services, 3−5−1

Lighting Aids, 2−1−1

Local Airport Advisory (LAA), 4−1−3

Operations, 4−3−1

Communications, 4−3−16

Exiting the Runway, After Landing, 4−3−21

Flight Check Aircraft, In Terminal Areas, 4−3−24

Flight Inspection, 4−3−24

Gate Holding, Departure Delays, 4−3−17

Intersection Takeoffs, 4−3−12

Low Approach, 4−3−15

Low Level Wind Shear/Microburst Detection

Systems, 4−3−11

Option Approach, 4−3−23

Signals, Hand, 4−3−24

Taxi During Low Visibility, 4−3−20

Traffic Control Light Signals, 4−3−15

Traffic Patterns, 4−3−1, 4−3−2

Use of Aircraft Lights, 4−3−23
AIM 7/26/12

I−2 Index

[References are to page numbers]

Use of Runways, 4−3−6

VFR Flights in Terminal Areas, 4−3−17

VFR Helicopter at Controlled Airports, 4−3−17

With Operating Control Tower, 4−3−1

Without Operating Control Tower, 4−3−5

Remote Airport Advisory (RAA), 3−5−1, 4−1−4

Remote Airport Information Service (RAIS), 3−5−1,

4−1−4

Signs, 2−3−1, 2−3−19

Destination, 2−3−28

Direction, 2−3−25

Information, 2−3−29

Location, 2−3−23

Mandatory Instruction, 2−3−20

Runway Distance Remaining, 2−3−29

Airport Reservations, 4−1−21

Airport Surface Detection Equipment − Model X,

4−5−7

Airport Surveillance Radar, 4−5−7

Airspace, 3−1−1

Basic VFR Weather Minimums, 3−1−1

Class D, 3−2−8

Class E, 3−2−9

Class G, 3−3−1

Controlled, 3−2−1

Advisories, Traffic, 3−2−1

Alerts, Safety, 3−2−1

Class A, 3−2−2

Class B, 3−2−2

Class C, 3−2−4

IFR Requirements, 3−2−1

IFR Separation, 3−2−1

Parachute Jumps, 3−2−2

Ultralight Vehicles, 3−2−2

Unmanned Free Balloons, 3−2−2

VFR Requirements, 3−2−1

Flight Levels, 3−1−2

General Dimensions, Segments, 3−1−1

Military Training Routes, 3−5−1

Other Areas, 3−5−1

Parachute Jumping, 3−5−5

Special Use, 3−4−1

Temporary Flight Restrictions, 3−5−2

Terminal Radar Service Areas, 3−5−9

VFR Cruising Altitudes, 3−1−2

VFR Routes, Published, 3−5−5

Class B Airspace, VFR Transition Routes, 3−5−7

VFR Corridors, 3−5−7

VFR Flyways, 3−5−5

Airway, 5−3−5

Airways, Course Changes, 5−3−7

Alcohol, 8−1−1

Alert, Safety, 4−1−10, 5−5−3

Alert Areas, 3−4−2

Alignment of Elements Approach Slope Indicator,

2−1−5

Alphabet, Phonetic, 4−2−5

ALS. See Approach Light Systems

Altimeter

Density Altitude, 7−5−4

Errors, 7−2−3

Setting, 7−2−1

High Barometric Pressure, 7−2−4

Low Barometric Pressure, 7−2−4

Altitude

Automatic Reporting, 4−1−15

Effects, 8−1−3

Hypoxia, 8−1−3

High Altitude Destinations, 5−1−27

Mandatory, 5−4−6

Maximum, 5−4−6

Minimum, 5−4−6

Ambulance, Air, 4−2−4

Amended Clearances, 4−4−2

Approach

Advance Information, Instrument Approach, 5−4−3

Approach Control, 5−4−2

Clearance, 5−4−25

Contact, 5−4−59, 5−5−2

Direction Finding, Emergency, 6−2−1

Instrument, 5−5−2

Instrument Approach Procedure, Charts, 5−4−4

Instrument Approach Procedures, 5−4−26

Low, 4−3−15

Minimums, 5−4−49

Missed, 5−4−52, 5−5−2

No−Gyro, 5−4−35

Option, 4−3−23

Overhead Approach Maneuver, 5−4−59

Precision, 5−4−34

Surveillance, 5−4−34

Visual, 5−4−57, 5−5−5

Approach Control Service, VFR Arriving Aircraft,

4−1−2

Approach Light Systems, 2−1−1

Approaches

IFR, 4−1−6

Parallel Runways, ILS/MLS, 5−4−36
7/26/12 AIM

Index I−3

[References are to page numbers]

Radar, 5−4−34

Timed, 5−4−31

Area Navigation (RNAV), 1−2−1, 5−1−15, 5−3−6,

5−5−7

Area Navigation (RNAV) Routes, 5−3−6

Area Navigation (RNAV) Standard Terminal Arrival

(STAR), 5−4−1

ARFF (Aircraft Rescue and Fire Fighting) Emergency

Hand Signals, 6−5−1

ARFF (Aircraft Rescue and Fire Fighting) Radio Call

Sign, 6−5−1

Arresting Devices, Aircraft, 2−3−30

ARSR. See Air Route Surveillance Radar

ARTCC. See Air Route Traffic Control Centers

ASDE−X. See Airport Surface Detection

Equipment−Model X

Ash, Volcanic, 7−5−7

ASOS. See Automated Surface Observing System

ASR. See Airport Surveillance Radar; Surveillance

Approach

ATCRBS. See Air Traffic Control Radar Beacon

System

ATCT. See Control Towers

ATIS. See Automatic Terminal Information Service

Attitude Heading Reference System (AHRS), 1−1−19

Authority, Statutory, 1−1−1

Automated Surface Observing System (ASOS), 4−3−28,

7−1−29

Automated Weather Observing System (AWOS),

4−3−28, 7−1−27

Automated Weather Sensor System (AWSS), 4−3−28

Automated Weather Sensor System (AWSS), 7−1−29

Automatic Altitude Reporting, 4−1−15

Automatic Dependent Surveillance−Broadcast Services,

4−5−14

Automatic Dependent Surveillance−Rebroadcast,

4−5−20

Automatic Flight Information Service (AFIS) − Alaska

FSSs Only, 4−1−8

Automatic Terminal Information Service, 4−1−7

AWOS. See Automated Weather Observing System

B

Balloons, Unmanned, 7−5−2

Free, 3−2−2

Beacon

Aeronautical Light, 2−2−1

Code, 2−2−1

Marker, 1−1−10

Nondirectional Radio, 1−1−1

Beacons, Airport/Heliport, 2−1−14

Bird

Bird Strike

Reduction, 7−4−1

Reporting, 7−4−1

Hazards, 7−4−1

Migratory, 7−4−1

Bird/Other Wildlife Strike Reporting, Form. See

Appendix 1

Block Island Reporting Service, 4−1−19

Braking Action Advisories, 4−3−11

Braking Action Reports, 4−3−11

Briefing, Preflight, 7−1−6

C

Call Signs

Aircraft, 4−2−3

Ground Station, 4−2−4

Cape Code Radar Overwater Flight Following, 4−1−19

Carbon Monoxide Poisoning, 8−1−5

CAT. See Clear Air Turbulence

CDR. See Coded Depature Route

Changeover Points, 5−3−8

Charted Visual Flight Procedures, 5−4−58

Charts, Aeronautical, 9−1−1

Class A Airspace, 3−2−2

Definition, 3−2−2

Operating Rules, 3−2−2

Pilot/Equipment Requirements, 3−2−2

Class B Airspace, 3−2−2

ATC Clearances, 3−2−3

Definition, 3−2−2

Flight Procedures, 3−2−3

Mode C Veil, 3−2−3

Operating Rules, 3−2−2
AIM 7/26/12

I−4 Index

[References are to page numbers]

Pilot/Equipment Requirements, VFR Operations,

3−2−2

Proximity Operations, 3−2−4

Separation, 3−2−3

VFR Transition Routes, 3−5−7

Class C Airspace, 3−2−4

Air Traffic Services, 3−2−5

Aircraft Separation, 3−2−5

Definition, 3−2−4

Operating Rules, 3−2−4

Outer Area, 3−2−5

Pilot/Equipment Requirements, 3−2−4

Secondary Airports, 3−2−6

Class D Airspace, 3−2−8

Definition, 3−2−8

Operating Rules, 3−2−8

Pilot/Equipment Requirements, 3−2−8

Separation for VFR Aircraft, 3−2−8

Class E Airspace, 3−2−9

Definition, 3−2−9

Operating Rules, 3−2−9

Pilot/Equipment Requirements, 3−2−9

Separation for VFR Aircraft, 3−2−9

Types, 3−2−9

Vertical Limits, 3−2−9

Class G Airspace, 3−3−1

IFR Requirements, 3−3−1

VFR Requirements, 3−3−1

Clear Air Turbulence, 7−1−49

Clearance

Abbreviated IFR Departure, 5−2−2

Adherence, 4−4−5

Air Traffic, 5−5−1

Air Traffic Control, 4−4−1

Amended, 4−4−2

Approach, 5−4−25

IFR, VFR−on−Top, 4−4−4

IFR Flights, 4−4−5

Issuance, Pilot Responsibility, 4−4−4

Items, 4−4−1

Altitude Data, 4−4−2

Clearance Limit, 4−4−1

Departure Procedure, 4−4−1

Holding Instructions, 4−4−2

Route of Flight, 4−4−1

Pre−Taxi, 5−2−1

Prefix, 4−4−1

Taxi, 5−2−1

VFR Flights, 4−4−5

Void Times, 5−2−4

Clearances, Special VFR Clearances, 4−4−3

Clearing Procedures, Visual, 4−4−10

CNF. See Computer Navigation Fix

Coded Depature Route, 4−4−3

Collision, Avoidance, Judgment, 8−1−8

Communication, Radio

Contact, Reestablishing, 6−4−2

Two−way Failure, 6−4−1

IFR Conditions, 6−4−1

Transponder Usage, 6−4−2

VFR Conditions, 6−4−1

Communications

ARTCC, 5−3−1

Additional Reports, 5−3−4

Position Reporting, 5−3−3

Distress, 6−3−1

Radio, 4−2−1

Phonetic Alphabet, 4−2−5

Release, 4−1−1

Urgency, 6−3−1

Computer Navigation Fix (CNF), 1−1−28

Conflict Alert, Aircraft, 4−1−11

Contact Approach, 5−4−59

Contact Procedures, 4−2−1

Initial Contact, 4−2−1

Control of Lighting Systems, 2−1−11

Control Towers, 4−1−1

Controlled Firing Areas, 3−4−2

Controller, Responsibility, 5−3−8, 5−4−58, 5−5−1

COP. See Changeover Points

CORONA, 7−5−9

Course Lights, 2−2−1

CVFP. See Charted Visual Flight Procedures

D

Decompression Sickness, 8−1−4

Density Altitude, Effects, 7−5−4

Departure, Restrictions, 5−2−4

Departure Control, 5−2−5

Departures, Instrument, 5−5−6

DF. See Direction Finder

Direct User Access Terminal System, 7−1−3
7/26/12 AIM

Index I−5

[References are to page numbers]

Direction Finder, VHF, 1−1−18

Discrete Emergency Frequency, 6−5−1

Distance Measuring Equipment, 1−1−3, 1−1−10,

5−3−12

Distress, 6−3−1

Ditching Procedures, 6−3−3

DME. See Distance Measuring Equipment

Doppler Radar, 1−1−19

DUATS. See Direct User Access System

E

Ear Block, 8−1−4

EFAS. See En Route Flight Advisory Service

EFVS. See Enhanced Flight Vision Systems

ELT. See Emergency Locator Transmitters

Emergency, 6−1−1

Air Piracy, 6−3−6

Airborne Aircraft Inspection, 7−5−8

Aircraft, Overdue, 6−2−5

Body Signals, 6−2−6

Direction Finding Instrument Approach, 6−2−1

Ditching Procedures, 6−3−3

Explosives Detection, FAA K−9 Team Program,

6−2−4

Fuel Dumping, 6−3−7

Inflight Monitoring and Reporting, 6−2−4

Intercept and Escort, 6−2−2

Locator Transmitters, 6−2−2

Obtaining Assistance, 6−3−2

Pilot Authority, 6−1−1

Pilot Responsibility, 6−1−1

Request Assistance Immediately, 6−1−1

Search and Rescue, 6−2−5

Services, 6−2−1

Radar Service for VFR Aircraft in Difficulty,

6−2−1

Survival Equipment, 6−2−6

Transponder Operation, 6−2−1

VFR Search and Rescue Protection, 6−2−6

Emergency Locator Transmitter, 6−2−2

En Route Flight Advisory Service, 7−1−8

Enhanced Flight Vision Systems, 5−4−55

Escort, 6−2−2

Explosives, FAA K−9 Detection Team Program, 6−2−4

F

FAROS. See Final Approach Runway Occupancy

Signal (FAROS)

Final Approach Runway Occupancy Signal (FAROS),

2−1−9

Final Guard, 3−5−1

FIS−B. See Flight Information Service−Broadcast

Fitness, Flight

Alcohol, 8−1−1

Emotion, 8−1−2

Fatigue, 8−1−2

Hypoxia, 8−1−3

Stress, 8−1−2

Flight

Aerobatic, 8−1−8

Fitness, 8−1−1

Illusions, 8−1−5

Over National Forests, 7−4−1

Over National Parks, 7−4−1

Over National Refuges, 7−4−1

Safety, Meteorology, 7−1−1

Vision, 8−1−6

Flight Check Aircraft, 4−3−24

Flight Information Service−Broadcast, 4−5−18

Flight Information Services, 7−1−23

Flight Inspections Aircraft, 4−3−24

Flight Management System, 1−2−3, 5−1−13

Flight Management System Procedures, 5−4−1

Flight Plan

Change, 5−1−29

Proposed Departure Time, 5−1−30

Closing

DVFR, 5−1−30

VFR, 5−1−30

Composite, VFR/IFR, 5−1−11

DVFR Flights, 5−1−10

Explanation of IFR, 5−1−16

Explanation of VFR, 5−1−9

Form 7233−1, 5−1−9, 5−1−17

IFR, Canceling, 5−1−30

IFR Flights, Domestic, 5−1−11

VFR Flights, 5−1−8

Flight Restrictions, Temporary, 3−5−2

Flight Service Stations, 4−1−1

Flights, Outside the United States, 5−1−28

Fly Visual to Airport, 5−4−19
AIM 7/26/12

I−6 Index

[References are to page numbers]

Flying, Mountain, 7−5−3

FMS. See Flight Management System

FMSP. See Flight Management System Procedures

Forms

Bird Strike Incident/Ingestion Report, Appendix 1−1

Volcanic Activity Reporting Form, Appendix 2−1

Frequency, Instrument Landing System, 1−1−11

FSS. See Flight Service Stations

Fuel Dumping, 6−3−7

G

Gate Holding, 4−3−17

GBAS. See Ground Based Augmentation System

Glideslope, Visual Indicators, 2−1−1

Global Navigation Satellite System, 1−1−35, 5−1−13

Global Positioning System, 1−1−19

Database, 1−1−26

Equipment, 1−1−26

GPS Approach Procedures, 1−1−26

GNSS. See Global Navigation Satellite System

GPS. See Global Positioning System

GPS Approach Procedures, 1−1−26

Ground Based Augmentation System (GBAS), 1−1−36

Ground Based Augmentation System (GBAS) Landing

System (GLS), 1−1−35

Ground Station, Call Signs, 4−2−4

Ground Vehicle Operations, 4−1−6

Gulf of Mexico Grid System, 10−1−6

H

Half−Way Signs, 7−5−5

Hand Signals, 4−3−24

Hazard

Antenna Tower, 7−5−1

Bird, 7−4−1

Flight

Obstructions to Flight, 7−5−1

Potential, 7−5−1

VFR in Congested Areas, 7−5−1

Ground Icing Conditions, 7−5−12

Mountain Flying, 7−5−3

Overhead Wires, 7−5−2

Thermal Plumes, 7−5−13

Unmanned Balloons, 7−5−2

Volcanic Ash, 7−5−7

Hazardous Area Reporting Service, 4−1−18

HDTA. See High Density Traffic Airports

Helicopter

IFR Operations, 10−1−1

Landing Area Markings, 2−3−19

VFR Operations at Controlled Airports, 4−3−17

Special Operations, 10−2−1

Wake Turbulence, 7−3−6

High Density Traffic Airports, 4−1−21

Hold, For Release, 5−2−4

Holding, 5−3−8

Holding Position Markings, 2−3−1, 2−3−12

for Instrument Landing Systems, 2−3−12

for Taxiway/Taxiway Intersections, 2−3−12

Holding Position Signs, Surface Painted, 2−3−12

Hypoxia, 8−1−3

I

Icing Terms, 7−1−45

IFR, 4−4−4

Operations, To High Altitude Destinations, 5−1−27

Procedures, Use When Operating VFR, 5−1−2

IFR

Approaches, 4−1−6

Military Training Routes, 3−5−2

Separation Standards, 4−4−7

ILS. See Instrument Landing System

In−Runway Lighting, 2−1−6

Taxiway Centerline Lead−off Lights, 2−1−6

Taxiway Centerline Lead−On Lights, 2−1−6

Touchdown Zone Lighting, 2−1−6

Incident, Aircraft, Reporting, 7−6−1

Inertial Navigation System, 1−1−19

Inertial Reference Unit (IRU), 1−1−19, 5−1−13

Initial Contact, 4−2−1

INS. See Internal Navigation System

Instrument Departure Procedures (DP), 5−2−5

Instrument Landing System, 1−1−8
7/26/12 AIM

Index I−7

[References are to page numbers]

Category, 1−1−11

Compass Locator, 1−1−11

Course, Distortion, 1−1−12

Distance Measuring Equipment, 1−1−10

Frequency, 1−1−11

Glide Path, 1−1−9

Glide Slope, 1−1−9

Critical Area, 1−1−12

Holding Position Markings, 2−3−12

Inoperative Components, 1−1−12

Localizer, 1−1−8

Critical Area, 1−1−12

Locators, Compass, 1−1−8

Marker Beacon, 1−1−10

Minimums, 1−1−11

Instrument Meteorological Conditions (IMC), 5−2−5

Integrated Terminal Weather System, 4−3−11

Intercept, 6−2−2

Interception

Procedures, 5−6−2

Signals, 5−6−6

Interchange Aircraft, 4−2−4

International Flight Plan, IFR, Domestic, International,

5−1−18

International Flight Plan (FAA Form 7233−4)− IFR

Flights (For Domestic or International Flights),

5−1−18

Intersection Takeoffs, 4−3−12

IR. See IFR Military Training Routes

IRU. See Inertial Reference Unit

ITWS. See Integrated Terminal Weather System

K

K−9 Explosives Detection Team, 6−2−4

L

LAHSO. See Land and Hold Short Operations

Land and Hold Short Lights, 2−1−6

Land and Hold Short Operations (LAHSO), 4−3−13

Landing

Minimums, 5−4−49

Priority, 5−4−59

Laser Beam Exposure Questionnaire, Appendix 3−1

Laser Operations, 7−5−10

Law Enforcement Operations

Civil, 5−6−5

Military, 5−6−5

LDA. See Localizer−Type Directional Aid

Leased Aircraft, 4−2−4

Lifeguard, 4−2−4

Light Signals, Traffic Control, 4−3−15

Lighting

Aeronautical Light Beacons, 2−2−1

Aids

Airport, 2−1−1

Approach Light Systems, 2−1−1

Control of Lighting Systems, 2−1−11

In−Runway Lighting, 2−1−6

Pilot Control of Airport Lighting, 2−1−11

Runway End Identifier Lights, 2−1−6

Taxiway Lights, 2−1−15

Airport/Heliport Beacons, 2−1−14

Airport, Radio Control, 4−1−6

Code Beacon, 2−2−1

Course, 2−2−1

Navigation, 2−2−1

Obstruction, 2−2−1

Line Up and Wait , 5−2−1

LLWAS. See Low Level Wind Shear Alert System

Local Airport Advisory (LAA), 3−5−1, 4−1−3

Local Flow Traffic Management Program, 5−4−2

Localizer Performance with Vertical Guidance, 1−1−32

Localizer−Type Directional Aid, 1−1−9

Locator, Compass, 1−1−11

Long Island Sound Reporting Service, 4−1−18

Long Range Navigation, 1−1−18

LORAN. See Long Range Navigation

Low Approach, 4−3−15

Low Level Wind Shear Alert System (LLWAS),

4−3−11, 7−1−53

Low Level Wind Shear/Microburst Detection Systems,

4−3−11

LPV. See Localizer Perfomance with Vertical Guidance

LUAW. See Line Up and Wait

M

MAYDAY, 6−3−1
AIM 7/26/12

I−8 Index

Medical

Carbon Monoxide Poisoning, 8−1−5

Decompression Sickness, 8−1−4

Facts, Pilots, 8−1−1

Flight, Ear Block, 8−1−4

Illness, 8−1−1

Medication, 8−1−1

Sinus Block, 8−1−4

Meteorology, 7−1−1

ATC InFlight Weather Avoidance, 7−1−38

Automated Surface Observing System, 7−1−29

Categorical Outlooks, 7−1−19

Clear Air Turbulence, 7−1−49

Cloud Heights, Reporting, 7−1−42

Direct User Access Terminal System, 7−1−3

Drizzle, Intensity, 7−1−43

En Route Flight Advisory Service, 7−1−8

FAA Weather Services, 7−1−1

ICAO, Weather Formats, 7−1−64

Icing, Airframe, 7−1−44

Inflight Aviation Weather Advisories, 7−1−9

Inflight Weather Broadcasts, 7−1−20

Microbursts, 7−1−49

National Weather Service, Aviation Products, 7−1−1

Pilot Weather Reports, 7−1−43

Precipitation, Intensity, 7−1−42

Preflight Briefing, 7−1−6

Runway Visual Range, 7−1−40

Telephone Information Briefing Service, 7−1−20

Thunderstorms, 7−1−59

Flying, 7−1−60

Transcribed Weather Broadcast, 7−1−20

Turbulence, 7−1−48

Visibility, Reporting, 7−1−42

Weather, Radar Services, 7−1−34

Weather Observing Programs, 7−1−27

Wind Shear, 7−1−49

Microwave Landing System, 1−1−15

Approach Azimuth Guidance, 1−1−15

Data Communications, 1−1−16

Elevation Guidance, 1−1−16

Operational Flexibility, 1−1−17

Range Guidance, 1−1−16

Military NOTAMs, 5−1−4

Military Operations Areas, 3−4−2

Military Training Routes, 3−5−1

IFR, 3−5−2

VFR, 3−5−2

Minimum, Fuel Advisory, 5−5−6

Minimum Safe Altitudes, 5−4−7

Minimum Turning Altitude (MTA), 5−3−8

Minimum Vectoring Altitudes, 5−4−18

Minimums

Approach, 5−4−49

Instrument Landing Systems, 1−1−11

Landing, 5−4−49

Missed Approach, 5−4−52

MLS. See Microwave Landing System

MOA. See Military Operations Areas

Mode C, 4−1−15

Mountain Flying, 7−5−3

Mountain Wave, 7−5−4

Mountainous Areas, 5−6−8

MSA. See Minimum Safe Altitudes

MTA. See Minimum Turning Altitude (MTA)

Multicom, 4−1−6

MVA. See Minimum Vectoring Altitudes

N

National Forests, 7−4−1

National Geospatial−Intelligence Agency (NGA),

5−4−6

National Parks, 7−4−1

National Refuges, 7−4−1

National Security Areas, 3−5−9

National Weather Service, Aviation Products, 7−1−1

NAVAID

Identifier Removal During Maintenance, 1−1−17

Maintenance, 1−1−17

Performance, User Report, 1−1−18

Service Volumes, 1−1−4

with Voice, 1−1−18

Navigation, Aids, 1−1−1

Nondirectional Radio Beacon, 1−1−1

Radio, VHF Omni−directional Range, 1−1−1

Navigation Reference System (NRS), 5−1−16

Navigational

Aids, Radio

Distance Measuring Equipment, 1−1−3

Doppler Radar, 1−1−19

Identifier Removal During Maintenance, 1−1−17

Instrument Landing System, 1−1−8

Localizer−Type Directional Aid, 1−1−9

Long Range Navigation, 1−1−18

Microwave Landing System, 1−1−15

Navaid Service Volumes, 1−1−4
7/26/12 AIM

Index I−9

[References are to page numbers]

NAVAIDs with Voice, 1−1−18

Performance, User Report, 1−1−18

Simplified Directional Facility, 1−1−12

Tactical Air Navigation, 1−1−3

VHF Direction Finder, 1−1−18

VHF Omni−directional Range/Tactical Air

Navigation, 1−1−3

Inertial Navigation System, 1−1−19

NDB. See Nondirectional Radio Beacon

Near Midair Collision, 7−6−2

NGA. See National Geospatial−Intelligence Agency

NMAC. See Near Midair Collision

Nondirectional Radio Beacon, 1−1−1

Nonmovement Area Boundary Markings, 2−3−18

NOTAM. See Notice to Airmen

Notice to Airmen, 5−1−2

FDC NOTAM, 5−1−3

NOTAM Contractions, 5−1−4

NOTAM D, 5−1−3

Notice to Airmen System, 5−1−2

O

Obstacle Departure Procedures, 5−2−5

Obstruction Alert, 4−1−10

Operation Raincheck, 4−1−2

Operation Take−off, 4−1−2

Operational Information System (OIS), 5−1−10

Option Approach, 4−3−23

P

P−static, 7−5−9

PAN−PAN, 6−3−1

PAPI. See Precision Approach Path Indicator

PAR. See Precision Approach; Precision Approach

Radar

Parachute Jumps, 3−2−2, 3−5−5

Phonetic Alphabet, 4−2−5

Pilot

Authority, 6−1−1

Responsibility, 4−1−14, 4−4−1, 4−4−4, 5−4−58,

5−5−1, 6−1−1, 7−3−6

Pilot Control of Airport Lighting, 2−1−11

Pilot Visits to Air Traffic Facilities, 4−1−1

Pilot Weather Reports, 7−1−43

Piracy, Air, Emergency, 6−3−6

PIREPs. See Pilot Weather Reports

Pointer NOTAMs, 5−1−4

Position Reporting, 5−3−3

Pre−departure Clearance Procedures, 5−2−1

Precipitation Static, 7−5−9

Precision Approach, 5−4−34

Precision Approach Path Indicator, 2−1−4

Precision Approach Radar, 4−5−7

Precision Approach Systems, 1−1−36

Preflight, Preparation, 5−1−1

Priority, Landing, 5−4−59

Procedure Turn, 5−4−28

Limitations, 5−4−31

Procedures

Arrival, 5−4−1

En Route, 5−3−1

Instrument Approach, 5−4−26

Interception, 5−6−2

Prohibited Areas, 3−4−1

Publications, Aeronautical, 9−1−1

Published Instrument Approach Procedure Visual

Segment, 5−4−19

Pulsating Visual Approach Slope Indicator, 2−1−5

R

Radar

Air Traffic Control Radar Beacon System, 4−5−2

Airport Route Surveillance Radar, 4−5−7

Airport Surveillance Radar, 4−5−7

Approach Control, 5−4−3

Approaches, 5−4−34

Capabilities, 4−5−1

Doppler, 1−1−19

Limitations, 4−5−1

Monitoring of Instrument Approaches, 5−4−35

Precision Approach, 4−5−7
AIM 7/26/12

I−10 Index

[References are to page numbers]

Precision Approach Radar, 4−5−7

Surveillance, 4−5−7

Vector, 5−5−3

Radar Assistance to VFR Aircraft, 4−1−11

Radar Beacon, Phraseology, 4−1−17

Radar Sequencing and Separation, VFR Aircraft,

TRSA, 4−1−13

Radar Traffic Information Service, 4−1−8

Radio, Communications, 4−2−1

Altitudes, 4−2−6

Contact Procedures, 4−2−1

Directions, 4−2−6

Inoperative Transmitter, 4−2−7

Phonetic Alphabet, 4−2−5

Receiver Inoperative, 4−2−7

Speeds, 4−2−6

Student Pilots, 4−2−4

Technique, 4−2−1

Time, 4−2−6

Transmitter and Receiver Inoperative, 4−2−7

VFR Flights, 4−2−8

RCLS. See Runway Centerline Lighting

Receiver, VOR, Check, 1−1−2

REIL. See Runway End Identifier Lights

REL. See Runway Entrance Lights

Release Time, 5−2−4

Remote Airport Advisory (RAA), 3−5−1, 4−1−4

Remote Airport Information Service (RAIS), 3−5−1,

4−1−4

Required Navigation Performance (RNP), 1−2−1,

5−4−23

Required Navigation Performance (RNP) Operations,

5−1−30, 5−5−7

Rescue Coordination Center

Air Force, 6−2−5

Alaska, 6−2−5

Coast Guard, 6−2−5

Joint Rescue, Hawaii, 6−2−5

Reservations, Airport, 4−1−21

Responsibility

Controller, 5−3−8, 5−4−58, 5−5−1

Pilot, 4−1−14, 4−4−1, 4−4−4, 5−4−58, 5−5−1, 6−1−1,

7−3−6

Restricted Areas, 3−4−1

Restrictions

Departure, 5−2−4

Flight, Temporary, 3−5−2

RIL. See Runway Intersection Lights (RIL)

RNAV. See Area Navigation

RNP. See Required Navigation Performance

Route

Coded Departure Route, 4−4−3

Course Changes, 5−3−7

Route System, 5−3−5

Runway

 Friction Reports, 4−3−11

Aiming Point Markings, 2−3−2

Centerline Markings, 2−3−2

Closed

Lighting, 2−3−18

Marking, 2−3−18

Demarcation Bar, 2−3−4

Designators, 2−3−2

Friction Advisories, 4−3−11

Holding Position Markings, 2−3−12

Markings, 2−3−1

Separation, 4−4−9

Shoulder Markings, 2−3−3

Side Stripe Markings, 2−3−3

Signs, Distance Remaining, 2−3−29

Threshold Bar, 2−3−4

Threshold Markings, 2−3−3

Touchdown Zone Markers, 2−3−2

Runway

 Edge Light Systems, 2−1−6

End Identifier Lights, 2−1−6

Entrance Lights, 2−1−7

Centerline Lighting System, 2−1−6

Status Light (RWSL) System, 2−1−7, 2−1−8

Runway Intersection Lights (RIL), 2−1−9

RWSL System, Runway Status Light (RWSL) System.

See Runway Status Light (RWSL) System

Runway, Visual Range, 7−1−40

Runways, Use, 4−3−6

RVR. See Runway Visual Range

S

Safety

Alert, 5−5−3

Alerts, 3−2−1

Aircraft Conflict, 3−2−1

Mode C Intruder, 3−2−1
7/26/12 AIM

Index I−11

[References are to page numbers]

Terrain/Obstruction, 3−2−1

Aviation, Reporting, 7−6−1

Seaplane, 7−5−6

Safety Alert, 4−1−10

Aircraft Conflict Alert, 4−1−11

Obstruction Alert, 4−1−10

Terrain Alert, 4−1−10

SAR. See Search and Rescue

SCAT−I DGPS. See Special Category I Differential

GPS

Scuba Diving, Decompression Sickness, 8−1−4

SDF. See Simplified Directional Facility

Seaplane, Safety, 7−5−6

Search and Rescue, 6−2−2, 6−2−5

Security, National, 5−6−1

Security Identification Display Area, 2−3−31

See and Avoid, 5−5−4

Separation

IFR, Standards, 4−4−7

Runway, 4−4−9

Visual, 4−4−9, 5−5−5

Wake Turbulence, 7−3−7

Sequenced flashing lights (SFL), 2−1−11

SFL. See Sequenced flashing lights

SIDA. See Security Identifications Display Area

Side−Step Maneuver, 5−4−49

Signs

Airport, 2−3−1

Half−Way, 7−5−5

Simplified Directional Facility, 1−1−12

Sinus Block, 8−1−4

Special Category I Differential GPS (SCAT−I DGPS),

1−1−36

Special Instrument Approach Procedures, 1−1−36,

5−4−28

Special Traffic Management Programs, 4−1−21

Special Use Airspace, 3−4−1

Alert Areas, 3−4−2

Controlled Firing Areas, 3−4−2

Military Operations Areas, 3−4−2

Prohibited Areas, 3−4−1

Restricted Areas, 3−4−1

Warning Areas, 3−4−1

Special Use Airspace (SUA) NOTAMs, 5−1−4

Special VFR Clearances, 4−4−3

Speed, Adjustments, 4−4−7, 5−5−4

Standard Instrument Departures, 5−2−5

Standard Terminal Arrival, 5−4−1

STAR. See Standard Terminal Arrival

Surface Painted Holding Position Signs, 2−3−12

Surveillance Approach, 5−4−34

Surveillance Radar, 4−5−7

Surveillance Systems, 4−5−1

T

TACAN. See Tactical Air Navigation

Tactical Air Navigation, 1−1−3

TAF. See Aerodrome Forecast

Takeoff Hold Lights (THL), 2−1−8

Takeoffs, Intersection, 4−3−12

Taxi

Clearance, 5−2−1

During Low Visibility, 4−3−20

Taxiway

Centerline Markings, 2−3−7

Closed

Lighting, 2−3−18

Marking, 2−3−18

Edge Markings, 2−3−7

Geographic Position Markings, 2−3−10

Holding Position Markings, 2−3−12

Markings, 2−3−1, 2−3−7

Shoulder Markings, 2−3−7

Surface Painted Direction Signs, 2−3−10

Surface Painted Location Signs, 2−3−10

Taxiway Centerline Lead−Off Lights, 2−1−6

Taxiway Lights, 2−1−15

Centerline, 2−1−15

Clearance Bar, 2−1−15

Edge, 2−1−15

Runway Guard, 2−1−15

Stop Bar, 2−1−15

TCAS. See Traffic Alert and Collision Avoidance

System

TDWR. See Terminal Doppler Weather Radar

TDZL. See Touchdown Zone Lights
AIM 7/26/12

I−12 Index

[References are to page numbers]

TEC. See Tower En Route Control

Telephone Information Briefing Service, 7−1−20

Temporary Flight Restrictions, 3−5−2

Terminal Arrival Area (TAA), 5−4−7

Terminal Doppler Weather Radar (TDWR), 4−3−11,

7−1−54

Terminal Radar Service Areas, 3−5−9

Terminal Radar Services for VFR Aircraft, 4−1−12

Terminal Weather Information For Pilots System

(TWIP), 7−1−59

Terrain Alert, 4−1−10

THL. See Takeoff Hold Lights

TIBS. See Telephone Information Briefing Service

Time

Clearance Void, 5−2−4

Release, 5−2−4

TIS. See Traffic Information Service

TIS−B. See Traffic Information Service−Broadcast

TLS. See Transponder Landing System

Touchdown Zone Lights (TDZL), 2−1−6

Tower, Antenna, 7−5−1

Tower En Route Control, 4−1−14

Traffic

Advisories, 5−5−4

Local Flow Traffic Management Program, 5−4−2

Traffic Advisory Practices, Airports Without Operating

Control Towers, 4−1−2

Traffic Alert and Collision Avoidance System, 4−4−10

Traffic Control Light Signals, 4−3−15

Traffic Information Service, 4−5−8

Traffic Information Service (TIS), 4−4−10

Traffic Information Service−Broadcast , 4−5−17

Traffic Patterns, 4−3−2

Transcribed Weather Broadcast, 7−1−20

Transponder Landing System (TLS), 1−1−36

Transponder Operation, 4−1−15

Automatic Altitude Reporting, 4−1−15

Code Changes, 4−1−16

Emergency, 6−2−1

Ident Feature, 4−1−16

Mode C, 4−1−15

Under Visual Flight Rules, 4−1−17

VFR, 4−1−17

Tri−Color Visual Approach Slope Indicator, 2−1−4

TRSA. See Terminal Radar Service Areas

Turbulence, Wake, 7−3−1

Air Traffic Separation, 7−3−7

Helicopters, 7−3−6

Pilot Responsibility, 7−3−6

Vortex Behavior, 7−3−2

Vortex Generation, 7−3−1

Vortex Strength, 7−3−1

TWEB. See Transcribed Weather Broadcast

TWIP. See Terminal Weather Information For Pilots

System

U

Ultralight Vehicles, 3−2−2

Unicom, 4−1−6

Unidentified Flying Object (UFO) Reports, 7−6−3

Unmanned Aircraft, 7−5−2

Urgency, 6−3−1

V

VASI. See Visual Approach Slope Indicator

VCOA. See Visual Climb Over the Airport

VDP. See Visual Descent Points

Vector, Radar, 5−5−3

Vehicle Roadway Markings, 2−3−16

Vertical Navigation, 5−1−13

VFR Corridors, 3−5−7

VFR Flights in Terminal Areas, 4−3−17

VFR Flyways, 3−5−5

VFR Military Training Routes, 3−5−2

VFR Transition Routes, 3−5−7

VFR−on−Top, 5−5−6

VHF, Direction Finder, 1−1−18

VHF Omni−directional Range, 1−1−1

VHF Omni−directional Range/Tactical Air Navigation,

1−1−3

Visual

Approach, 5−4−57, 5−5−5

Clearing Procedures, 4−4−10
7/26/12 AIM

Index I−13

[References are to page numbers]

Glideslope Indicators, 2−1−1

Separation, 4−4−9, 5−5−5

Visual Approach Slope Indicator, 2−1−1

Visual Climb Over the Airport (VCOA), 5−2−8

Visual Descent Points, 5−4−18

Visual Meteorological Conditions (VMC), 5−2−5

Visual Segment, 5−4−19

VNAV. See Vertical Navigation

Void Times, Clearance, 5−2−4

Volcanic, Ash, 7−5−7

Volcanic Activity Reporting, Forms. See Appendix 2

VORSee also VHF Omni−directional Range

Receiver Check, 1−1−2

VOR Receiver Checkpoint Markings, 2−3−16

VORTAC. See VHF Omni−directional Range/Tactical

Air Navigation

VR. See VFR Military Training Routes

W

Waivers, 4−1−23

Wake, Turbulence, 7−3−1

Warning Areas, 3−4−1

Weather

Deviations in Oceanic Controlled Airspace, 7−1−39

ICAO, Weather Formats, 7−1−64

Weather System Processor (WSP), 4−1−23, 4−3−11,

7−1−55

WSP. See Weather System Processor


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