Instrument Flying Handbook (FAA-H-8083-15B) Note

An errata sheet indicating the content and grammatical errors discovered in this handbook

since its publication can be found at http://www.faa.gov/regulations_policies/

handbooks_manuals/aviation/  These errors will be corrected in the next version of the

handbook.
Instrument

Flying Handbook

U.S. Department

of Transportation

FEDERAL AVIATION 

ADMINISTRATION

FAA-H-8083-15B

Instrument Flying Handbook

U.S. Department of Transportation

FEDERAL AVIATION ADMINISTRATION

Flight Standards Service

2012
ii
iii

This Instrument Flying Handbook is designed for use by instrument flight instructors and pilots preparing for instrument 

rating tests. Instructors may find this handbook a valuable training aid as it includes basic reference material for knowledge 

testing and instrument flight training. Other Federal Aviation Administration (FAA) publications should be consulted for 

more detailed information on related topics.

This handbook conforms to pilot training and certification concepts established by the FAA. There are different ways of 

teaching, as well as performing, flight procedures and maneuvers and many variations in the explanations of aerodynamic 

theories and principles. This handbook adopts selected methods and concepts for instrument flying. The discussion and 

explanations reflect the most commonly used practices and principles. Occasionally the word “must” or similar language 

is used where the desired action is deemed critical. The use of such language is not intended to add to, interpret, or relieve 

a duty imposed by Title 14 of the Code of Federal Regulations (14 CFR).

All of the aeronautical knowledge and skills required to operate in instrument meteorological conditions (IMC) are detailed. 

Chapters are dedicated to human and aerodynamic factors affecting instrument flight, the flight instruments, attitude instrument 

flying for airplanes, basic flight maneuvers used in IMC, attitude instrument flying for helicopters, navigation systems, the 

National Airspace System (NAS), the air traffic control (ATC) system, instrument flight rules (IFR) flight procedures, and 

IFR emergencies. Clearance shorthand and an integrated instrument lesson guide are also included.

This handbook supersedes FAA-H-8081-15A, Instrument Flying Handbook, dated 2007.

This handbook may be purchased from the Superintendent of Documents, United States Government Printing Office (GPO), 

Washington, DC 20402-9325, or from GPO's website.

http://bookstore.gpo.gov

This handbook is also available for download, in PDF format, from the Regulatory Support Division’s (AFS-600) website.

http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs600

This handbook is published by the United States Department of Transportation, Federal Aviation Administration, Airman 

Testing Standards Branch, AFS-630, P.O. Box 25082, Oklahoma City, OK 73125.

Comments regarding this publication should be sent, in email form, to the following address.

AFS630comments@faa.gov

Preface
iv
v

This handbook was produced as a combined Federal Aviation Administration (FAA) and industry effort. The FAA wishes 

to acknowledge the following contributors:

The laboratory of Dale Purves, M.D. and Mr. Al Seckel in providing imagery (found in Chapter 3) for visual illusions 

from the book, The Great Book of Optical Illusions, Firefly Books, 2004 

Sikorsky Aircraft Corporation and Robinson Helicopter Company for imagery provided in Chapter 2

Garmin Ltd. for providing flight system information and multiple display systems to include integrated flight, GPS and 

communication systems; information and hardware used with WAAS, LAAS; and information concerning encountering 

emergencies with high-technology systems

Universal Avionics System Corporation for providing background information of the Flight Management System and 

an overview on Vision–1 and Traffic Alert and Collision Avoidance systems (TCAS)

Meggitt/S-Tec for providing detailed autopilot information regarding installation and use

Cessna Aircraft Company in providing instrument panel layout support and information on the use of onboard systems

Kearfott Guidance and Navigation Corporation in providing background information on the Ring-LASAR gyroscope 

and its history

Honeywell International Inc., for Terrain Awareness Systems (TAWS) and various communication and radio systems 

sold under the Bendix-King name

Chelton Flight Systems and Century Flight Systems, Inc., for providing autopilot information relating to Highway in 

the Sky (Chelton) and HSI displays (Century)

Avidyne Corporation for providing displays with alert systems developed and sold by Ryan International, 

L3 Communications, and Tectronics 

Additional appreciation is extended to the Aircraft Owners and Pilots Association (AOPA), the AOPA Air Safety

Institute, and the National Business Aviation Association (NBAA) for their technical support and input.

Acknowledgments
vi
vii

Is an Instrument Rating Necessary?

The answer to this question depends entirely upon individual 

needs. Pilots may not need an instrument rating if they fly in 

familiar uncongested areas, stay continually alert to weather 

developments, and accept an alternative to their original plan. 

However, some cross-country destinations may take a pilot 

to unfamiliar airports and/or through high activity areas in 

marginal visual or instrument meteorological conditions 

(IMC). Under these conditions, an instrument rating may 

be an alternative to rerouting, rescheduling, or canceling 

a flight. Many accidents are the result of pilots who lack 

the necessary skills or equipment to fly in marginal visual 

meteorological conditions (VMC) or IMC and attempt flight 

without outside references.

Pilots originally flew aircraft strictly by sight, sound, and 

feel while comparing the aircraft’s attitude to the natural 

horizon. As aircraft performance increased, pilots required 

more inflight information to enhance the safe operation of 

their aircraft. This information has ranged from a string tied 

to a wing strut, to development of sophisticated electronic 

flight information systems (EFIS) and flight management 

systems (FMS). Interpretation of the instruments and aircraft 

control have advanced from the “one, two, three” or “needle, 

ball, and airspeed” system to the use of “attitude instrument 

flying” techniques.

Navigation began by using ground references with dead 

reckoning and has led to the development of electronic 

navigation systems. These include the automatic direction 

finder (ADF), very-high frequency omnidirectional range 

(VOR), distance measuring equipment (DME), tactical air 

navigation (TACAN), long range navigation (LORAN), 

global positioning system (GPS), instrument landing system 

(ILS), microwave landing system (MLS), and inertial 

navigation system (INS).

Perhaps you want an instrument rating for the same basic 

reason you learned to fly in the first place—because you like 

flying. Maintaining and extending your proficiency, once you 

have the rating, means less reliance on chance and more on 

skill and knowledge. Earn the rating—not because you might 

Introduction

need it sometime, but because it represents achievement and 

provides training you will use continually and build upon 

as long as you fly. But most importantly it means greater 

safety in flying.

Instrument Rating Requirements

A private or commercial pilot must have an instrument 

rating and meet the appropriate currency requirements if 

that pilot operates an aircraft using an instrument flight 

rules (IFR) flight plan in conditions less than the minimums 

prescribed for visual flight rules (VFR), or in any flight in 

Class A airspace. 

You will need to carefully review the aeronautical knowledge 

and experience requirements for the instrument rating as 

outlined in Title 14 of the Code of Federal Regulations 

(14 CFR) part 61. After completing the Federal Aviation 

Administration (FAA) Knowledge Test issued for the 

instrument rating, and all the experience requirements have 

been satisfied, you are eligible to take the practical test. The 

regulations specify minimum total and pilot-in-command 

time requirements. This minimum applies to all applicants 

regardless of ability or previous aviation experience.

Training for the Instrument Rating

A person who wishes to add the instrument rating to his or 

her pilot certificate must first make commitments of time, 

money, and quality of training. There are many combinations 

of training methods available. Independent studies may be 

adequate preparation to pass the required FAA Knowledge 

Test for the instrument rating. Occasional periods of ground 

and flight instruction may provide the skills necessary to 

pass the required test. Or, individuals may choose a training 

facility that provides comprehensive aviation education and 

the training necessary to ensure the pilot will pass all the 

required tests and operate safely in the National Airspace 

System (NAS). The aeronautical knowledge may be 

administered by educational institutions, aviation-oriented 

schools, correspondence courses, and appropriately rated 

instructors. Each person must decide for themselves which 

training program best meets his or her needs and at the same 

time maintain a high quality of training. Interested persons 
viii

should make inquiries regarding the available training at 

nearby airports, training facilities, in aviation publications, 

and through the FAA Flight Standards District Office 

(FSDO).

Although the regulations specify minimum requirements, 

the amount of instructional time needed is determined not 

by the regulation, but by the individual’s ability to achieve 

a satisfactory level of proficiency. A professional pilot with 

diversified flying experience may easily attain a satisfactory 

level of proficiency in the minimum time required by 

regulation. Your own time requirements will depend upon a 

variety of factors, including previous flying experience, rate 

of learning, basic ability, frequency of flight training, type of 

aircraft flown, quality of ground school training, and quality 

of flight instruction, to name a few. The total instructional 

time you will need, the scheduling of such time, is up to the 

individual most qualified to judge your proficiency—the 

instructor who supervises your progress and endorses your 

record of flight training.

You can accelerate and enrich much of your training by 

informal study. An increasing number of visual aids and 

programmed instrument courses is available. The best course 

is one that includes a well-integrated flight and ground school 

curriculum. The sequential nature of the learning process 

requires that each element of knowledge and skill be learned 

and applied in the right manner at the right time.

Part of your instrument training may utilize a flight simulator, 

flight training device, basic aviation training device (BATD), 

or an advanced aviation training device (AATD). This 

ground-based flight training equipment is a valuable tool 

for developing your instrument cross-check and learning 

procedures, such as intercepting and tracking, holding 

patterns, and instrument approaches. Once these concepts are 

fully understood, you can then continue with inflight training 

and refine these techniques for full transference of your new 

knowledge and skills.

Holding the instrument rating does not necessarily make you a 

competent all-weather pilot. The rating certifies only that you 

have complied with the minimum experience requirements, 

that you can plan and execute a flight under IFR, that you 

can execute basic instrument maneuvers, and that you have 

shown acceptable skill and judgment in performing these 

activities. Your instrument rating permits you to fly into 

instrument weather conditions with no previous instrument 

weather experience. Your instrument rating is issued on 

the assumption that you have the good judgment to avoid 

situations beyond your capabilities. The instrument training 

program you undertake should help you to develop not only 

essential flying skills but also the judgment necessary to use 

the skills within your own limits.

Regardless of the method of training selected, the curriculum 

in Appendix B, Instrument Training Lesson Guide, provides 

guidance as to the minimum training required for the addition 

of an instrument rating to a private or commercial pilot 

certificate.

Maintaining the Instrument Rating

Once you hold the instrument rating, you may not act as pilotin-command under IFR or in weather conditions less than the 

minimums prescribed for VFR, unless you meet the recent 

flight experience requirements outlined in 14 CFR part 61. 

These procedures must be accomplished within the preceding 

6 months and include six instrument approaches, holding 

procedures, and intercepting and tracking courses through the 

use of navigation systems. If you do not meet the experience 

requirements during these 6 months, you have another 6 

months to meet these minimums. If the requirements are 

still not met, you must pass an instrument proficiency check, 

which is an inflight evaluation by a qualified instrument 

flight instructor using tasks outlined in the instrument rating 

practical test standards (PTS).

The instrument currency requirements must be accomplished 

under actual or simulated instrument conditions. You may log 

instrument flight time during the time for which you control 

the aircraft solely by reference to the instruments. This can 

be accomplished by wearing a view-limiting device, such as 

a hood, flying an approved flight-training device, or flying 

in actual IMC.

It takes only one harrowing experience to clarify the 

distinction between minimum practical knowledge and a 

thorough understanding of how to apply the procedures and 

techniques used in instrument flight. Your instrument training 

is never complete; it is adequate when you have absorbed 

every foreseeable detail of knowledge and skill to ensure a 

solution will be available if and when you need it.
ix

Preface....................................................................iii

Acknowledgments..................................................v

Introduction...........................................................vii

Is an Instrument Rating Necessary? ............................vii

Instrument Rating Requirements.................................vii

Training for the Instrument Rating..............................vii

Maintaining the Instrument Rating.............................viii

Table of Contents ..................................................ix

Chapter 1

The National Airspace System...........................1-1

Introduction....................................................................1-1

Airspace Classification...............................................1-2

Special Use Airspace..................................................1-2

Federal Airways .........................................................1-4

Other Routing.............................................................1-5

IFR En Route Charts......................................................1-6

Airport Information ....................................................1-6

Charted IFR Altitudes ................................................1-6

Navigation Features....................................................1-7

Types of NAVAIDs................................................1-7

Identifying Intersections.........................................1-7

Other Route Information.......................................1-10

Weather Information and Communication

Features.................................................................1-10

New Technologies .......................................................1-10

Terminal Procedures Publications ...............................1-12

Departure Procedures...............................................1-12

Standard Terminal Arrival Routes ...........................1-12

Instrument Approach Procedure Charts ......................1-12

Margin Identification................................................1-12

The Pilot Briefing .....................................................1-16

The Plan View..........................................................1-16

Terminal Arrival Area (TAA)......................................1-18

Course Reversal Elements in Plan View and

Profile View..............................................................1-20

Procedure Turns....................................................1-20

Holding in Lieu of Procedure Turn ......................1-20

Teardrop Procedure ..............................................1-21

The Profile View...................................................1-21

Landing Minimums..................................................1-23

Airport Sketch /Airport Diagram .............................1-27

Inoperative Components...........................................1-27

RNAV Instrument Approach Charts........................1-30

Chapter 2

The Air Traffic Control System...........................2-1

Introduction....................................................................2-1

Communication Equipment ...........................................2-2

Navigation/Communication Equipment.....................2-2

Radar and Transponders.............................................2-3

Mode C (Altitude Reporting)..................................2-3

Communication Procedures...........................................2-4

Communication Facilities..............................................2-4

Flight Service Stations (FSS).....................................2-4

ATC Towers...............................................................2-5

Terminal Radar Approach Control (TRACON).........2-6

Tower En Route Control (TEC).................................2-7

Air Route Traffic Control Center (ARTCC) ..............2-7

Center Approach/Departure Control ..........................2-7

ATC Inflight Weather Avoidance Assistance..............2-11

ATC Radar Weather Displays..................................2-11

Weather Avoidance Assistance................................2-11

Approach Control Facility ...........................................2-12

Approach Control Advances........................................2-12

Precision Runway Monitor (PRM) ..........................2-12

PRM Radar ...........................................................2-12

PRM Benefits........................................................2-13

Control Sequence .........................................................2-13

Letters of Agreement (LOA)....................................2-14

Chapter 3

Human Factors ....................................................3-1

Introduction....................................................................3-1

Sensory Systems for Orientation ...................................3-2

Eyes............................................................................3-2

Vision Under Dim and Bright Illumination............3-3

Table of Contents
x

Ears.............................................................................3-4

Nerves.........................................................................3-5

Illusions Leading to Spatial Disorientation....................3-5

Vestibular Illusions ....................................................3-5

The Leans................................................................3-5

Coriolis Illusion ......................................................3-6

Graveyard Spiral.....................................................3-6

Somatogravic Illusion.............................................3-6

Inversion Illusion....................................................3-6

Elevator Illusion......................................................3-6

Visual Illusions...........................................................3-7

False Horizon..........................................................3-7

Autokinesis.............................................................3-7

Postural Considerations .................................................3-7

Demonstration of Spatial Disorientation .......................3-7

Climbing While Accelerating.....................................3-8

Climbing While Turning ............................................3-8

Diving While Turning ................................................3-8

Tilting to Right or Left...............................................3-8

Reversal of Motion.....................................................3-8

Diving or Rolling Beyond the Vertical Plane ............3-8

Coping with Spatial Disorientation................................3-8

Optical Illusions.............................................................3-9

Runway Width Illusion ..............................................3-9

Runway and Terrain Slopes Illusion ..........................3-9

Featureless Terrain Illusion........................................3-9

Water Refraction ........................................................3-9

Haze............................................................................3-9

Fog..............................................................................3-9

Ground Lighting Illusions..........................................3-9

How To Prevent Landing Errors Due to

Optical Illusions.............................................................3-9

Chapter 4

Aerodynamic Factors..........................................4-1

Introduction....................................................................4-1

The Wing....................................................................4-2

Review of Basic Aerodynamics.....................................4-2

The Four Forces..........................................................4-2

Lift ..........................................................................4-2

Weight.....................................................................4-3

Thrust......................................................................4-3

Drag ........................................................................4-3

Newton’s First Law, the Law of Inertia .....................4-4

Newton’s Second Law, the Law of Momentum.........4-4

Newton’s Third Law, the Law of Reaction................4-4

Atmosphere ....................................................................4-4

Layers of the Atmosphere ..........................................4-5

International Standard Atmosphere (ISA)..................4-5

Pressure Altitude.....................................................4-5

Density Altitude......................................................4-6

Lift..................................................................................4-6

Pitch/Power Relationship ...........................................4-6

Drag Curves...................................................................4-6

Regions of Command.................................................4-7

Control Characteristics ...........................................4-7

Speed Stability............................................................4-8

Normal Command ..................................................4-8

Reversed Command................................................4-8

Trim................................................................................4-8

Slow-Speed Flight..........................................................4-8

Small Airplanes..........................................................4-9

Large Airplanes........................................................4-10

Climbs..........................................................................4-10

Acceleration in Cruise Flight ...................................4-10

Turns............................................................................4-10

Rate of Turn..............................................................4-11

Radius of Turn..........................................................4-11

Coordination of Rudder and Aileron Controls.........4-11

Load Factor..................................................................4-12

Icing .............................................................................4-13

Types of Icing ..............................................................4-13

Structural Icing.........................................................4-13

Induction Icing .........................................................4-13

Clear Ice ...................................................................4-13

Rime Ice ...................................................................4-14

Mixed Ice..................................................................4-14

General Effects of Icing on Airfoils.........................4-14

Piper PA-34-200T (Des Moines, Iowa)................4-16

Tailplane Stall Symptoms ........................................4-16

Propeller Icing ..........................................................4-16

Effects of Icing on Critical Aircraft Systems...........4-16

Flight Instruments.................................................4-16

Stall Warning Systems..........................................4-17

Windshields ..........................................................4-17

Antenna Icing ...........................................................4-17

Summary ..................................................................4-17

Chapter 5

Flight Instruments ...............................................5-1

Introduction....................................................................5-1

Pitot/Static Systems .......................................................5-2

Static Pressure ............................................................5-2

Blockage of the Pitot-Static System...........................5-2

Blocked Pitot System..............................................5-2

Blocked Static System............................................5-3

Effects of Flight Conditions....................................5-3

Pitot/Static Instruments..................................................5-3

Sensitive Altimeter.....................................................5-3

Principle of Operation.............................................5-3

Altimeter Errors......................................................5-4

Cold Weather Altimeter Errors...............................5-5
xi

ICAO Cold Temperature Error Table ........................5-5

Nonstandard Pressure on an Altimeter ...................5-6

Altimeter Enhancements (Encoding) .....................5-7

Reduced Vertical Separation Minimum (RVSM) ..5-7

Vertical Speed Indicator (VSI)...................................5-8

Dynamic Pressure Type Instruments.............................5-8

Airspeed Indicator (ASI)............................................5-8

Types of Airspeed...................................................5-9

Airspeed Color Codes...........................................5-10

Magnetism....................................................................5-10

The Basic Aviation Magnetic Compass ..................5-10

Magnetic Compass Overview...............................5-10

Magnetic Compass Errors.....................................5-12

The Vertical Card Magnetic Compass.....................5-15

The Flux Gate Compass System ..............................5-15

Remote Indicating Compass.....................................5-15

Gyroscopic Systems.....................................................5-16

Power Sources .........................................................5-17

Pneumatic Systems ..............................................5-17

Vacuum Pump Systems........................................5-17

Electrical Systems.................................................5-17

Gyroscopic Instruments...............................................5-19

Attitude Indicators....................................................5-19

Heading Indicators ...................................................5-19

Turn Indicators.........................................................5-20

Turn-and-Slip Indicator ........................................5-20

Turn Coordinator ..................................................5-21

Flight Support Systems................................................5-22

Attitude and Heading Reference System (AHRS)...5-22

Air Data Computer (ADC).......................................5-22

Analog Pictorial Displays............................................5-23

Horizontal Situation Indicator (HSI) .......................5-23

Attitude Direction Indicator (ADI) ..........................5-23

Flight Director System (FDS) ..................................5-23

Integrated Flight Control System ............................5-25

Autopilot Systems.................................................5-25

Flight Management Systems (FMS)............................5-26

Electronic Flight Instrument Systems......................5-27

Primary Flight Display (PFD)......................................5-27

Synthetic Vision .......................................................5-28

Multi-Function Display (MFD)................................5-28

Advanced Technology Systems...................................5-28

Automatic Dependent Surveillance—Broadcast 

(ADS-B) ...................................................................5-28

Safety Systems.............................................................5-29

Radio Altimeters.......................................................5-29

Traffic Advisory Systems ........................................5-29

Traffic Information System ..................................5-29

Traffic Alert Systems ...........................................5-30

Traffic Avoidance Systems...................................5-30

Terrain Alerting Systems .....................................5-34

Required Navigation Instrument System Inspection ...5-36

Systems Preflight Procedures...................................5-36

Before Engine Start ..................................................5-36

After Engine Start.....................................................5-37

Taxiing and Takeoff.................................................5-37

Engine Shut Down ...................................................5-38

Chapter 6, Section I

Airplane Attitude Instrument Flying Using

Analog Instrumentation ......................................6-1

Introduction....................................................................6-1

Learning Methods..........................................................6-2

Attitude Instrument Flying Using the Control and 

Performance Method .................................................6-2

Control Instruments ...............................................6-2

Performance Instruments .......................................6-2

Navigation Instruments ..........................................6-2

Procedural Steps in Using Control

and Performance .....................................................6-2

Aircraft Control During Instrument Flight .............6-3

Attitude Instrument Flying Using the Primary and 

Supporting Method.....................................................6-4

Pitch Control...........................................................6-4

Bank Control...........................................................6-7

Power Control.........................................................6-8

Trim Control ...........................................................6-8

Airplane Trim .........................................................6-8

Helicopter Trim ....................................................6-10

Example of Primary and Support Instruments.........6-10

Fundamental Skills.......................................................6-10

Instrument Cross-Check...........................................6-10

Common Cross-Check Errors...............................6-11

Instrument Interpretation..........................................6-13

Chapter 6, Section II

Airplane Attitude Instrument Flying Using an 

Electronic Flight Display...................................6-15

Introduction..................................................................6-15

Learning Methods........................................................6-16

Control and Performance Method ............................6-18

Control Instruments..............................................6-18

Performance Instruments......................................6-19

Navigation Instruments.........................................6-19

The Four-Step Process Used to Change Attitude.....6-19

Establish................................................................6-19

Trim ......................................................................6-20

Cross-Check..........................................................6-20

Adjust....................................................................6-20
xii

Applying the Four-Step Process...............................6-20

Pitch Control.........................................................6-20

Bank Control.........................................................6-20

Power Control.......................................................6-21

Attitude Instrument Flying—Primary and

Supporting Method...................................................6-21

Pitch Control.........................................................6-22

Straight-and-Level Flight......................................6-22

Primary Pitch ........................................................6-22

Primary Bank........................................................6-23

Primary Yaw.........................................................6-23

Primary Power ......................................................6-24

Fundamental Skills of Attitude Instrument Flying ......6-24

Instrument Cross-Check...........................................6-24

Scanning Techniques...................................................6-24

Selected Radial Cross-Check ...................................6-24

Starting the Scan...................................................6-24

Trend Indicators....................................................6-26

Common Errors............................................................6-27

Fixation.....................................................................6-27

Omission...................................................................6-28

Emphasis ..................................................................6-28

Chapter 7, Section I

Airplane Basic Flight Maneuvers Using

Analog Instrumentation ......................................7-1

Introduction....................................................................7-1

Straight-and-Level Flight...............................................7-2

Pitch Control ..............................................................7-2

Attitude Indicator....................................................7-2

Altimeter.................................................................7-3

Vertical Speed Indicator (VSI)...............................7-4

Airspeed Indicator (ASI) ........................................7-6

Bank Control ..............................................................7-6

Attitude Indicator....................................................7-6

Heading Indicator ...................................................7-7

Turn Coordinator ....................................................7-7

Turn-and-Slip Indicator (Needle and Ball).............7-8

Power Control ............................................................7-8

Power Settings........................................................7-9

Airspeed Changes in Straight-and-Level Flight ...7-11

Trim Technique ........................................................7-12

Common Errors in Straight-and-Level Flight .........7-12

Pitch ......................................................................7-12

Heading.................................................................7-13

Power....................................................................7-13

Trim ......................................................................7-13

Straight Climbs and Descents......................................7-14

Climbs ......................................................................7-14

Entry .....................................................................7-14

Leveling Off..........................................................7-16

Descents....................................................................7-16

Entry .....................................................................7-17

Leveling Off..........................................................7-17

Common Errors in Straight Climbs and Descents....7-17

Turns............................................................................7-19

Standard Rate Turns.................................................7-19

Turns to Predetermined Headings............................7-20

Timed Turns.............................................................7-21

Compass Turns.........................................................7-21

Steep Turns...............................................................7-22

Climbing and Descending Turns..............................7-24

Change of Airspeed During Turns...........................7-24

Common Errors in Turns..........................................7-25

Pitch ......................................................................7-25

Bank......................................................................7-25

Power....................................................................7-26

Trim ......................................................................7-26

Errors During Compass Turns..............................7-26

Approach to Stall .........................................................7-26

Unusual Attitudes and Recoveries...............................7-26

Recognizing Unusual Attitudes................................7-27

Recovery from Unusual Attitudes............................7-27

Nose-High Attitudes.................................................7-27

Nose-Low Attitudes .................................................7-28

Common Errors in Unusual Attitudes......................7-28

Instrument Takeoff.......................................................7-29

Common Errors in Instrument Takeoffs ..................7-29

Basic Instrument Flight Patterns..................................7-30

Racetrack Pattern......................................................7-30

Procedure Turn.........................................................7-30

Standard 45° Procedure Turn ...................................7-30

80/260 Procedure Turn.............................................7-31

Teardrop Patterns .....................................................7-31

Circling Approach Patterns......................................7-32

Pattern I.................................................................7-32

Pattern II ...............................................................7-32

Chapter 7, Section II

Airplane Basic Flight Maneuvers Using an 

Electronic Flight Display...................................7-33

Introduction..................................................................7-33

Straight-and-Level Flight.............................................7-34

Pitch Control ............................................................7-34

Attitude Indicator..................................................7-34

Altimeter...............................................................7-36

Partial Panel Flight ...............................................7-36

VSI Tape...............................................................7-36
xiii

Airspeed Indicator (ASI) ......................................7-37

Bank Control ............................................................7-37

Attitude Indicator..................................................7-37

Horizontal Situation Indicator (HSI) ....................7-38

Heading Indicator .................................................7-38

Turn Rate Indicator...............................................7-38

Slip/Skid Indicator................................................7-39

Power Control ..........................................................7-39

Power Settings......................................................7-39

Airspeed Changes in Straight-and-Level Flight ...7-40

Trim Technique ........................................................7-43

Common Errors in Straight-and-Level Flight ..........7-43

Pitch ......................................................................7-43

Heading.................................................................7-44

Power....................................................................7-45

Trim ......................................................................7-45

Straight Climbs and Descents......................................7-46

Entry .........................................................................7-46

Constant Airspeed Climb From

Cruise Airspeed ....................................................7-46

Constant Airspeed Climb from

Established Airspeed ............................................7-47

Constant Rate Climbs...........................................7-47

Leveling Off..........................................................7-48

Descents....................................................................7-49

Entry .........................................................................7-49

Leveling Off..........................................................7-50

Common Errors in Straight Climbs and Descents....7-50

Turns............................................................................7-51

Standard Rate Turns.................................................7-51

Establishing A Standard Rate Turn ......................7-51

Common Errors ....................................................7-51

Turns to Predetermined Headings............................7-52

Timed Turns.............................................................7-53

Compass Turns.........................................................7-53

Steep Turns...............................................................7-53

Unusual Attitude Recovery Protection .................7-55

Common Errors Leading to Unusual Attitudes....7-58

Instrument Takeoff.......................................................7-60

Common Errors in Instrument Takeoffs ..................7-61

Basic Instrument Flight Patterns..................................7-61

Chapter 8

Helicopter Attitude Instrument Flying ...............8-1

Introduction....................................................................8-1

Flight Instruments..........................................................8-2

Instrument Flight............................................................8-2

Instrument Cross-Check.............................................8-2

Instrument Interpretation............................................8-3

Aircraft Control..........................................................8-3

Straight-and-Level Flight...............................................8-3

Pitch Control ..............................................................8-3

Attitude Indicator....................................................8-3

Altimeter.................................................................8-4

Vertical Speed Indicator (VSI)...............................8-5

Airspeed Indicator ..................................................8-5

Bank Control ..............................................................8-5

Attitude Indicator....................................................8-5

Heading Indicator ...................................................8-6

Turn Indicator.........................................................8-7

Common Errors During Straight-and-Level Flight....8-7

Power Control During Straight-and-Level Flight ......8-7

Common Errors During Airspeed Changes..............8-10

Straight Climbs (Constant Airspeed an

Constant Rate)..............................................................8-10

Entry .........................................................................8-10

Level Off ..................................................................8-12

Straight Descents (Constant Airspeed and

Constant Rate)..............................................................8-12

Entry .........................................................................8-12

Level Off ..................................................................8-13

Common Errors During Straight Climbs

and Descents.............................................................8-13

Turns............................................................................8-13

Turn to a Predetermined Heading ............................8-13

Timed Turns.............................................................8-13

Change of Airspeed in Turns....................................8-14

Compass Turns.........................................................8-15

30° Bank Turn.......................................................8-15

Climbing and Descending Turns..............................8-15

Common Errors During Turns .................................8-15

Unusual Attitudes.........................................................8-16

Common Errors During Unusual

Attitude Recoveries..................................................8-16

Emergencies.................................................................8-16

Autorotations............................................................8-17

Common Errors During Autorotations.................8-17

Servo Failure ............................................................8-17

Instrument Takeoff.......................................................8-17

Common Errors During Instrument Takeoffs..........8-18

Changing Technology..................................................8-18

Chapter 9

Navigation Systems ............................................9-1

Introduction....................................................................9-1

Basic Radio Principles...................................................9-2

How Radio Waves Propagate.....................................9-2

Ground Wave..........................................................9-2

Sky Wave................................................................9-2

Space Wave ............................................................9-2
xiv

Disturbances to Radio Wave Reception.....................9-3

Traditional Navigation Systems.....................................9-3

Nondirectional Radio Beacon (NDB) ........................9-3

NDB Components...................................................9-3

ADF Components...................................................9-3

Function of ADF.....................................................9-4

Operational Errors of ADF .....................................9-8

Very High Frequency Omnidirectional

Range (VOR)..............................................................9-8

VOR Components.................................................9-10

Function of VOR ..................................................9-11

VOR Operational Errors.......................................9-14

VOR Accuracy......................................................9-16

VOR Receiver Accuracy Check ...........................9-16

VOR Test Facility (VOT).....................................9-16

Certified Checkpoints ...........................................9-16

Distance Measuring Equipment (DME)...................9-17

DME Components................................................9-17

Function of DME..................................................9-17

DME Arc ..............................................................9-17

Intercepting Lead Radials.....................................9-18

DME Errors ..........................................................9-19

Area Navigation (RNAV) ........................................9-19

VOR/DME RNAV................................................9-22

VOR/DME RNAV Components ..........................9-23

Function of VOR/DME RNAV............................9-23

VOR/DME RNAV Errors.....................................9-24

Advanced Technologies...............................................9-24

Global Navigation Satellite System (GNSS)............9-24

Global Positioning System (GPS)............................9-25

GPS Components..................................................9-25

Function of GPS ...................................................9-26

GPS Substitution...................................................9-27

GPS Substitution for ADF or DME......................9-27

To Determine Aircraft Position Over a

DME Fix ...............................................................9-27

To Fly a DME Arc................................................9-27

To Navigate TO or FROM an NDB/Compass

Locator..................................................................9-28

To Determine Aircraft Position Over an NDB/

Compass Locator ..................................................9-28

To Determine Aircraft Position Over a Fix 

Made up of an NDB/Compass Locator Bearing 

Crossing a VOR/LOC Course ..............................9-28

To Hold Over an NDB/Compass Locator: ...........9-28

IFR Flight Using GPS...........................................9-28

GPS Instrument Approaches.................................9-29

Departures and Instrument Departure

Procedures (DPs) ..................................................9-31

GPS Errors............................................................9-31

System Status........................................................9-31

GPS Familiarization..............................................9-31

Differential Global Positioning Systems (DGPS)....9-32

Wide Area Augmentation System (WAAS) ............9-32

General Requirements ..........................................9-32

Instrument Approach Capabilities........................9-32

Local Area Augmentation System (LAAS) .............9-33

Inertial Navigation System (INS).............................9-34

INS Components...................................................9-34

INS Errors.............................................................9-34

Instrument Approach Systems.....................................9-35

Instrument Landing Systems (ILS) ..........................9-35

ILS Components...................................................9-35

Approach Lighting Systems (ALS)..........................9-38

ILS Airborne Components....................................9-38

ILS Function.............................................................9-40

ILS Errors.................................................................9-40

Marker Beacons....................................................9-40

Operational Errors ................................................9-42

Simplified Directional Facility (SDF)......................9-42

Localizer Type Directional Aid (LDA)....................9-43

Microwave Landing System (MLS).........................9-43

Approach Azimuth Guidance ...............................9-43

Required Navigation Performance...............................9-44

Flight Management Systems (FMS)............................9-44

Function of FMS ......................................................9-46

Head-Up Display (HUD).............................................9-46

Radar Navigation (Ground-Based) ..............................9-46

Functions of Radar Navigation.................................9-47

Airport Surface Detection Equipment ..................9-48

Radar Limitations.....................................................9-48

Chapter 10

IFR Flight............................................................10-1

Introduction..................................................................10-1

Sources of Flight Planning Information.......................10-2

Aeronautical Information Manual (AIM).................10-2

Airport/Facility Directory (A/FD)............................10-2

Notices to Airmen Publication (NTAP)...................10-2

POH/AFM ................................................................10-2

IFR Flight Plan.............................................................10-2

Filing in Flight..........................................................10-2

Cancelling IFR Flight Plans.....................................10-3

Clearances....................................................................10-3

Examples..................................................................10-4

Clearance Separations..............................................10-4

Departure Procedures (DPs) ........................................10-5

Obstacle Departure Procedures (ODP).....................10-5

Standard Instrument Departures...............................10-5
xv

Radar-Controlled Departures ...................................10-5

Departures From Airports Without an Operating

Control Tower ..........................................................10-7

En Route Procedures....................................................10-7

ATC Reports ............................................................10-7

Position Reports .......................................................10-7

Additional Reports ...................................................10-7

Planning the Descent and Approach ........................10-8

Standard Terminal Arrival Routes (STARs)............10-9

Substitutes for Inoperative or Unusable

Components............................................................10-10

Holding Procedures....................................................10-10

Standard Holding Pattern (No Wind).....................10-10

Standard Holding Pattern (With Wind)..................10-10

Holding Instructions...............................................10-10

Standard Entry Procedures.....................................10-11

Time Factors...........................................................10-12

DME Holding.........................................................10-13

Approaches ................................................................10-13

Compliance With Published Standard Instrument 

Approach Procedures .............................................10-13

Instrument Approaches to Civil Airports...............10-13

Approach to Airport Without an Operating

Control Tower.....................................................10-13

Approach to Airport With an Operating

Tower, With No Approach Control....................10-15

Approach to an Airport With an Operating

Tower, With an Approach Control .....................10-15

Radar Approaches..................................................10-15

Radar Monitoring of Instrument Approaches ........10-18

Timed Approaches From a Holding Fix.................10-18

Approaches to Parallel Runways............................10-20

Side-Step Maneuver...............................................10-20

Circling Approaches...............................................10-20

IAP Minimums.......................................................10-21

Missed Approaches................................................10-21

Landing...................................................................10-22

Instrument Weather Flying ........................................10-22

Flying Experience...................................................10-22

Recency of Experience .......................................10-22

Airborne Equipment and Ground Facilities........10-22

Weather Conditions................................................10-22

Turbulence ..........................................................10-22

Structural Icing ...................................................10-23

Fog ......................................................................10-24

Volcanic Ash ......................................................10-24

Thunderstorms....................................................10-24

Wind Shear .........................................................10-25

VFR-On-Top ..........................................................10-26

VFR Over-The-Top................................................10-26

Conducting an IFR Flight ..........................................10-26

Preflight ..................................................................10-26

Departure................................................................10-31

En Route.................................................................10-32

Arrival ....................................................................10-33

Chapter 11

Emergency Operations .....................................11-1

Introduction..................................................................11-1

Unforecast Adverse Weather.......................................11-2

Inadvertent Thunderstorm Encounter.......................11-2

Inadvertent Icing Encounter.....................................11-2

Precipitation Static ...................................................11-3

Aircraft System Malfunctions......................................11-3

Electronic Flight Display Malfunction.....................11-4

Alternator/Generator Failure ....................................11-4

Techniques for Electrical Usage...............................11-5

Master Battery Switch ..........................................11-5

Operating on the Main Battery .............................11-5

Loss of Alternator/Generator for Electronic Flight 

Instrumentation.........................................................11-5

Techniques for Electrical Usage...............................11-6

Standby Battery ....................................................11-6

Operating on the Main Battery .............................11-6

Analog Instrument Failure ...........................................11-7

Pneumatic System Failure............................................11-7

Pitot/Static System Failure...........................................11-8

Communication/Navigation System Malfunction .......11-8

GPS Nearest Airport Function.....................................11-9

Nearest Airports Using the PFD...............................11-9

Additional Information for a Specific Airport....11-10

Nearest Airports Using the MFD ...........................11-10

Navigating the MFD Page Groups .....................11-10

Nearest Airport Page Group ...............................11-10

Nearest Airports Page Soft Keys........................11-10

Situational Awareness................................................11-11

Traffic Avoidance...................................................11-12

Appendix A..........................................................A-1

Clearance Shorthand

Appendix B..........................................................B-1

Instrument Training Lesson Guide

Glossary ..............................................................G-1

Index ......................................................................I-1
xvi
1-1

Introduction

The National Airspace System (NAS) is the network of 

United States airspace: air navigation facilities, equipment, 

services, airports or landing areas, aeronautical charts, 

information/services, rules, regulations, procedures, technical 

information, manpower, and material. Included are system 

components shared jointly with the military. The system’s 

present configuration is a reflection of the technological 

advances concerning the speed and altitude capability of jet 

aircraft, as well as the complexity of microchip and satellitebased navigation equipment. To conform to international 

aviation standards, the United States adopted the primary 

elements of the classification system developed by the 

International Civil Aviation Organization (ICAO).

This chapter is a general discussion of airspace classification; 

en route, terminal, and approach procedures; and operations 

within the NAS. Detailed information on the classification 

of airspace, operating procedures, and restrictions is found 

in the Aeronautical Information Manual (AIM).

The National 

Airspace System

Chapter 1
1-2

Airspace Classification

Airspace in the United States [Figure 1-1] is designated 

as follows: 

1. Class A. Generally, airspace from 18,000 feet mean 

sea level (MSL) up to and including flight level (FL) 

600, including the airspace overlying the waters 

within 12 nautical miles (NM) of the coast of the 

48 contiguous states and Alaska. Unless otherwise 

authorized, all pilots must operate their aircraft under 

instrument flight rules (IFR).

2. Class B. Generally, 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, 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 air traffic control 

(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.

3. Class C. Generally, 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 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 NM radius, an outer circle with a 10 NM radius 

that extends from 1,200 feet to 4,000 feet above the 

airport elevation and an outer area. Each aircraft 

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.

4. Class D. Generally, 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 

normally designed to contain the procedures. Arrival 

extensions for instrument approach procedures (IAPs) 

may be Class D or Class E airspace. Unless otherwise 

authorized, each aircraft 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.

5. Class E. Generally, if the airspace is not Class A, B, 

C, or D, and is controlled airspace, then 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 is configured to contain all 

instrument procedures. Also in this class are federal 

airways, airspace beginning at either 700 or 1,200 feet 

above ground level (AGL) used to transition to and 

from the terminal or en route environment, and 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 NM 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.

6. Class G. Airspace not designated as Class A, B, C, 

D, or E. Class G airspace is essentially uncontrolled 

by ATC except when associated with a temporary 

control tower.

Special Use Airspace

Special use airspace is the designation for airspace in which 

certain activities must be confined or where limitations may 

be imposed on aircraft operations that are not part of those 

activities. Certain special use airspace areas can create 

limitations on the mixed use of airspace. The special use 

airspace depicted on instrument charts includes the area name 

or number, effective altitude, time and weather conditions 

of operation, the controlling agency, and the chart panel 

location. On National Aeronautical Navigation Products 

(AeroNav Products) en route charts, this information is 

available on one of the end panels.

Prohibited areas contain airspace of defined dimensions 

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. The area is 

charted as a “P” followed by a number (e.g., “P-123”).

Restricted areas are areas where operations are hazardous to 

nonparticipating aircraft and contain airspace 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 may be 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 (e.g., artillery firing, aerial 

gunnery, or guided missiles). IFR flights may be authorized 

to transit the airspace and are routed accordingly. Penetration 
1-3

14,500' MSL

Nontowered

airport with 

no instrument 

approach

Nontowered

airport with 

instrument 

approach

700'

AGL 700'

AGL

18,000' MSL 

FL 600 

1,200'

AGL

700'

AGL

1,200'

AGL 1,200'

AGL

(Not to scale)

Class A 

Class B 

Class C 

Class D 

Class E 

Class G

Class G Class G Class G 

*Exception: temporary tower or control tower present

**True only below 10,000 feet

 True only during day at or below 1,200 feet AGL (see 14 CFR part 91) 

Class A Class B Class C Class D Class E Class G 

ATC clearance 

Instrument 

Rating 

Yes 

No 

N/A 

N/A 

N/A 

Yes 

N/A 

ATC clearance

Private or Student

certification—

local restrictions

apply.

Yes

Yes

3 statute miles

Clear of clouds

All

Yes

 Radar

 Instrument

 approaches

 Weather

 Control tower

 High density

Prior two-way 

communications 

Student 

certificate 

Yes 

Yes 

3 statute miles 

500' below, 

1,000' above, 

2,000' horizontal 

IFR aircraft 

Yes 

Radar 

 Instrument 

 approaches 

 Weather 

 Control tower 

Prior two-way 

communications 

Student 

certificate 

Yes 

Yes 

3 statute miles 

500' below, 

1,000' above, 

2,000' horizontal 

Runway 

operations 

Workload 

permitting 

Instrument 

 approaches 

 Weather 

 Control tower 

Prior two-way 

communications* 

Student 

certificate 

Yes, under IFR 

flight plan* 

Yes 

3 statute miles** 

500' below,** 

1,000' above, 

2,000' horizontal 

None 

Workload 

permitting 

Instrument 

 approaches 

 Weather 

None

Student

certificate

None

N/A

1 statute mile†

Clear of clouds†

None

Workload

permitting

Control tower

AGL—above ground level 

FL—flight level 

MSL—mean sea level 

Figure 1-1. Airspace classifications.
1-4

of restricted areas without authorization from the using 

or controlling agency may be extremely hazardous to the 

aircraft and its occupants. ATC facilities apply the following 

procedures when aircraft are operating on an IFR clearance 

(including those cleared by ATC to maintain visual flight 

rules (VFR)-On-Top) via a route that lies within joint-use 

restricted airspace:

1. If the restricted area is not active and has been released 

to the Federal Aviation Administration (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 FAA, the ATC facility will issue a 

clearance that will ensure the aircraft avoids the 

restricted airspace.

Restricted areas are charted with an “R” followed by a 

number (e.g., “R-5701”) and are depicted on the en route 

chart appropriate for use at the altitude or FL being flown.

Warning areas are similar in nature to restricted areas; 

however, the U.S. Government does not have sole jurisdiction 

over the airspace. A warning area is airspace of defined 

dimensions, extending from 12 NM outward from the coast of 

the United States, containing activity that may be hazardous 

to nonparticipating aircraft. The purpose of such areas is 

to warn nonparticipating pilots of the potential danger. A 

warning area may be located over domestic or international 

waters or both. The airspace is designated with a “W” 

followed by a number (e.g., “W-123”).

Military operations areas (MOAs) consist of airspace with 

defined vertical and lateral limits established for the purpose 

of separating certain military training activities from IFR 

traffic. Whenever an MOA is being used, nonparticipating 

IFR traffic may be cleared through an MOA if IFR separation 

can be provided by ATC. Otherwise, ATC will reroute or 

restrict nonparticipating IFR traffic. MOAs are depicted on 

sectional, VFR terminal area, and en route low altitude charts 

and are not numbered (e.g., “Boardman MOA”).

Alert areas are depicted on aeronautical charts with an 

“A” followed by a number (e.g., “A-123”) to inform 

nonparticipating pilots of areas that may contain a high 

volume of pilot training or an unusual type of aerial activity. 

Pilots should exercise caution in alert areas. All activity 

within an alert area shall be conducted in accordance with 

regulations, without waiver, and pilots of participating 

aircraft, as well as pilots transiting the area, shall be equally 

responsible for collision avoidance.

Military Training Routes (MTRs) are routes used by military 

aircraft to maintain proficiency in tactical flying. These routes 

are usually established below 10,000 feet MSL for operations 

at speeds in excess of 250 knots. Some route segments may 

be defined at higher altitudes for purposes of route continuity. 

Routes are identified as IFR (IR) and VFR (VR) followed by 

a number. MTRs with no segment above 1,500 feet AGL are 

identified by four number characters (e.g., IR1206, VR1207). 

MTRs that include one or more segments above 1,500 feet 

AGL are identified by three number characters (e.g., IR206, 

VR207). IFR low altitude en route charts depict all IR routes 

and all VR routes that accommodate operations above 1,500 

feet AGL. IR routes are conducted in accordance with IFR 

regardless of weather conditions.

Temporary flight restrictions (TFRs) are put into effect 

when traffic in the airspace would endanger or hamper air 

or ground activities in the designated area. For example, a 

forest fire, chemical accident, flood, or disaster-relief effort 

could warrant a TFR, which would be issued as a Notice to 

Airmen (NOTAM).

National Security Areas (NSAs) consist of airspace with 

defined vertical and lateral dimensions established at 

locations where there is a requirement for increased security 

and safety of ground facilities. Flight in NSAs may be 

temporarily prohibited by regulation under the provisions of 

Title 14 of the Code of Federal Regulations (14 CFR) part 99 

and prohibitions will be disseminated via NOTAM.

Federal Airways

The primary means for routing aircraft operating under 

IFR is the Federal Airways System. Each Federal airway is 

based on a centerline that extends from one navigational aid 

(NAVAID)/waypoint/fix/intersection to another NAVAID/

waypoint/fix/intersection specified for that airway. A Federal 

airway includes the airspace within parallel boundary lines 

4 NM to each side of the centerline. As in all instrument 

flight, courses are magnetic, and distances are in NM. The 

airspace of a Federal airway has a floor of 1,200 feet AGL, 

unless otherwise specified. A Federal airway does not include 

the airspace of a prohibited area.

Victor airways include the airspace extending from 1,200 

feet AGL up to, but not including 18,000 feet MSL. The 

airways are designated on sectional and IFR low altitude en 

route charts with the letter “V” followed by a number (e.g., 

“V23”). Typically, Victor airways are given odd numbers 

when oriented north/south and even numbers when oriented 

east/west. If more than one airway coincides on a route 

segment, the numbers are listed serially (e.g., “V287-495-

500”). [Figure 1-2]
1-5

Figure 8-2. Victor airways, and charted IFR altitudes. 

Altitude change 

V287-495-500

confluence of airways

V520 (even)

oriented east/west

Victor Airway V23

V595 MRA 9300

No altitude change

V287 MOCA *3400

V165 (odd)

oriented north/south

Altitude change 

Figure 1-2. Victor airways and charted IFR altitudes.

Jet routes exist only in Class A airspace, from 18,000 feet MSL 

to FL 450, and are depicted on high-altitude en route charts. 

The letter “J” precedes a number to label the airway (e.g., J12).

Area navigation (RNAV) routes have been established in 

both the low-altitude and the high-altitude structures in recent 

years and are depicted on the en route low and high chart 

series. High altitude RNAV routes are identified with a “Q” 

prefix (except the Q-routes in the Gulf of Mexico) and low 

altitude RNAV routes are identified with a “T” prefix. RNAV 

routes and data are depicted in aeronautical blue. 

In addition to the published routes, a random RNAV route 

may be flown under IFR if it is approved by ATC. Random 

RNAV routes are direct routes, based on RNAV 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 random 

RNAV routes. These routes can only be approved in a 

radar environment. Factors that are 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.

Other Routing

Preferred IFR routes have been established between 

major terminals to guide pilots in planning their routes of 

flight, minimizing route changes, and aiding in the orderly 

management of air traffic on Federal airways. Low and high 

altitude preferred routes are listed in the Airport/Facility 

Directory (A/FD). To use a preferred route, reference the 

departure and arrival airports; if a routing exists for your 

flight, then airway instructions are listed.
1-6

Tower En Route Control (TEC) is an ATC program that 

uses overlapping approach control radar services to provide 

IFR clearances. By using TEC, a pilot is routed by airport 

control towers. Some advantages include abbreviated filing 

procedures and reduced traffic separation requirements. TEC 

is dependent upon the ATC’s workload, and the procedure 

varies among locales.

The latest version of Advisory Circular (AC) 90-91, North 

American Route Program (NRP), provides guidance to users 

of the NAS for participation in the NRP. All flights operating 

at or above FL 290 within the conterminous United States 

and Canada are eligible to participate in the NRP, the primary 

purpose of which is to allow operators to plan minimum time/

cost routes that may be off the prescribed route structure. NRP 

aircraft are not subject to route-limiting restrictions (e.g., 

published preferred IFR routes) beyond a 200 NM radius of 

their point of departure or destination.

IFR En Route Charts

The objective of IFR en route flight is to navigate within the 

lateral limits of a designated airway at an altitude consistent 

with the ATC clearance. Your ability to fly instruments 

safely and competently in the system is greatly enhanced by 

understanding the vast array of data available to the pilot on 

instrument charts. AeroNav Products maintains and produces 

the charts for the U.S. Government.

En route high-altitude charts provide aeronautical information 

for en route instrument navigation at or above 18,000 feet 

MSL. Information includes the portrayal of Jet and RNAV 

routes, identification and frequencies of radio aids, selected 

airports, distances, time zones, special use airspace, and 

related information. Established jet routes from 18,000 feet 

MSL to FL 450 use NAVAIDs not more than 260 NM apart. 

The charts are revised every 56 days.

To effectively depart from one airport and navigate en route 

under instrument conditions, a pilot needs the appropriate 

IFR en route low-altitude chart(s). The IFR low altitude en 

route chart is the instrument equivalent of the sectional chart. 

When folded, the cover of the AeroNav Products en route 

chart displays an index map of the United States showing the 

coverage areas. Cities near congested airspace are shown in 

black type and their associated area chart is listed in the box 

in the lower left-hand corner of the map coverage box. Also 

noted is an explanation of the off-route obstruction clearance 

altitude (OROCA). The effective date of the chart is printed 

on the other side of the folded chart. Information concerning 

MTRs is also included on the chart cover. The en route charts 

are revised every 56 days.

When the AeroNav Products en route chart is unfolded, the 

legend is displayed and provides information concerning 

airports, NAVAIDs, communications, air traffic services, 

and airspace.

Airport Information

Airport information is provided in the legend, and the 

symbols used for the airport name, elevation, and runway 

length are similar to the sectional chart presentation. 

Associated city names are shown for public airports only. 

FAA identifiers are shown for all airports. ICAO identifiers 

are also shown for airports outside of the contiguous United 

States. Instrument approaches can be found at airports with 

blue or green symbols, while the brown airport symbol 

denotes airports that do not have instrument approaches. 

Stars are used to indicate the part-time nature of tower 

operations, Automatic Terminal Information Service (ATIS) 

frequencies, part-time or on request lighting facilities, and 

part-time airspace classifications. A box after an airport name 

with a “C” or “D” inside (e.g., ) indicates Class C and D 

airspace, respectively, per Figure 1-3. 

Charted IFR Altitudes

The minimum en route altitude (MEA) ensures a navigation 

signal strong enough for adequate reception by the aircraft 

navigation (NAV) receiver and obstacle clearance along the 

airway. Communication is not necessarily guaranteed with 

MEA compliance. The obstacle clearance, within the limits of 

the airway, is typically 1,000 feet in non-mountainous areas 

and 2,000 feet in designated mountainous areas. MEAs can 

be authorized with breaks in the signal coverage; if this is 

the case, the AeroNav Products en route chart notes “MEA 

GAP” parallel to the affected airway. MEAs are usually 

bidirectional; however, they can be single-directional. Arrows 

are used to indicate the direction to which the MEA applies.

The minimum obstruction clearance altitude (MOCA), as the 

name suggests, provides the same obstruction clearance as 

an MEA; however, the NAV signal reception is ensured only 

within 22 NM of the closest NAVAID defining the route. The 

MOCA is listed below the MEA and indicated on AeroNav 

Products charts by a leading asterisk (e.g., “*3400”—see 

Figure 1-2, V287 at bottom left).

The minimum reception altitude (MRA) identifies the lowest 

altitude at which an intersection can be determined from 

an off-course NAVAID. If the reception is line-of-sight 

based, signal coverage only extends to the MRA or above. 

However, if the aircraft is equipped with distance measuring 

equipment (DME) and the chart indicates the intersection can 

be identified with such equipment, the pilot could define the 
1-7

Figure 1-3. En route airport legend. Figure 8-3. En route airport legend. 

fix without attaining the MRA. On AeroNav Products charts, 

the MRA is indicated by the symbol and the altitude 

preceded by “MRA” (e.g., “MRA 9300”). [Figure 1-2]

The minimum crossing altitude (MCA) is charted when 

a higher MEA route segment is approached. The MCA is 

usually indicated when a pilot is approaching steeply rising 

terrain and obstacle clearance and/or signal reception is 

compromised. In this case, the pilot is required to initiate a 

climb so the MCA is reached by the time the intersection is 

crossed. On AeroNav Products charts, the MCA is indicated 

by the symbol , and the Victor airway number, altitude, 

and the direction to which it applies (e.g. “V24 8000 SE”).

The maximum authorized altitude (MAA) is the highest 

altitude at which the airway can be flown with assurance 

of receiving adequate navigation signals. Chart depictions 

appear as “MAA-15000.”

When an MEA, MOCA, and/or MAA change on a segment 

other than at a NAVAID, a sideways “T” ( ) is depicted 

on the chart. If there is an airway break without the symbol, 

one can assume the altitudes have not changed (see the upper 

left area of Figure 1-2). When a change of MEA to a higher 

MEA is required, the climb may commence at the break, 

ensuring obstacle clearance. [Figure 1-4]

Navigation Features

Types of NAVAIDs

Very high frequency omnidirectional ranges (VORs) are the 

principal NAVAIDs that support the Victor and Jet airways. 

Many other navigation tools are also available to the pilot. 

For example, nondirectional beacons (NDBs) can broadcast 

signals accurate enough to provide stand-alone approaches, 

and DME allows the pilot to pinpoint a reporting point on the 

airway. Though primarily navigation tools, these NAVAIDs 

can also transmit voice broadcasts.

Tactical air navigation (TACAN) channels are represented 

as the two- or three-digit numbers following the three-letter 

identifier in the NAVAID boxes. The AeroNav Products 

terminal procedures provide a frequency-pairing table for 

the TACAN-only sites. On AeroNav Products charts, veryhigh frequencies and ultra-high frequencies (VHF/UHF) 

NAVAIDs (e.g., VORs) are depicted in black, while low 

frequencies and medium frequencies (LF/MF) are depicted 

as brown. [Figure 1-5]

Identifying Intersections

Intersections along the airway route are established by a variety 

of NAVAIDs. An open triangle indicates the location of an 

ATC reporting point at an intersection. If the triangle is solid 

, a report is compulsory. [Figure 1-4] NDBs, localizers, 
1-8

Figure 8-4b. Legend from en route low altitude chart. 

Figure 1-4. Legend from en route low attitude chart, air traffic services and airspace information section.
1-9

Figure 8-4a. Legend from en route low altitude chart. Figure 1-5. Legend from en route low attitude chart. 
1-10

the controller may provide the holding direction and the 

statement “as published.” [Figure 1-4]

Boundaries separating the jurisdiction of Air Route Traffic 

Control Centers (ARTCC) are depicted on charts with blue 

serrations . The name of the controlling 

facility is printed on the corresponding side 

of the division line. ARTCC remote sites are 

depicted as blue serrated boxes and contain 

the center name, sector name, and the sector frequency. 

[Figure 1-4]

Weather Information and Communication Features

En route NAVAIDs also provide weather information and 

serve communication functions. When a NAVAID is shown 

as a shadowed box, an automated 

flight service station (AFSS) of the 

same name is directly associated with 

the facility. If an AFSS is located 

without an associated NAVAID, the 

shadowed box is smaller and contains only the name and 

identifier. The AFSS frequencies are provided above the 

box. (Frequencies 122.2 and 255.4, 

and emergency frequencies 121.5 and 

243.0 are not listed.)

A Remote Communications Outlet (RCO) associated with 

a NAVAID is designated by a thin-lined box with the 

controlling AFSS frequency above 

the box and the name under the box. 

Without an associated facility, the 

thin-lined RCO box contains the 

AFSS name and remote frequency.

Automated Surface Observing 

Station (ASOS), Automated Weather Observing Station 

(AWOS), Hazardous Inflight Weather Advisory Service 

(HIWAS), and Transcribed Weather Broadcast (TWEB) 

are continuously transmitted over 

selected NAVAIDs and depicted 

in the NAVAID box. ASOS/

AWOS are depicted by a white 

“A”, HIWAS by a “H” and TWEB broadcasts by a “T” in a 

solid black circle in the upper right or left corner.

New Technologies

Technological advances have made multifunction displays 

and moving maps more common in newer aircraft. Even older 

aircraft are being retrofitted to include “glass” in the flight 

deck. [Figure 1-6] Moving maps improve pilot situational 

awareness (SA) by providing a picture of aircraft location 

in relation to NAVAIDS, waypoints, airspace, terrain, and 

and off-route VORs are used to establish intersections. NDBs 

are sometimes collocated with intersections, in which case 

passage of the NDB would mark the intersection. A bearing to 

an off-route NDB also can provide intersection identification. 

A localizer course used to identify an intersection is depicted 

by a feathered arrowhead symbol on the en route chart 

( ). If feathered markings appear on 

the left-hand side of the arrowhead ( ), 

a back course (BC) signal is transmitted. On AeroNav Products 

en route charts, the localizer symbol is only depicted to identify 

an intersection.

Off-route VORs remain the most common means of 

identifying intersections when traveling on an airway. Arrows 

depicted next to the intersection indicate the NAVAID 

to be used for identification. Another means of identifying an 

intersection is with the use of DME. A hollow arrowhead 

indicates DME is authorized for intersection identification. If 

the DME mileage at the intersection is a cumulative distance 

of route segments, the mileage is totaled and indicated by 

a D-shaped symbol with a mileage number inside . 

[Figure 1-4] Approved IFR global positioning system (GPS) 

units can also be used to report intersections.

Other Route Information

DME and GPS provide valuable route information concerning 

such factors as mileage, position, and ground speed. Even 

without this equipment, information is provided on the charts 

for making the necessary calculations using time and distance. 

The en route chart depicts point-to-point distances on the 

airway system. Distances from VOR to VOR are charted with 

a number inside of a box . To differentiate distances when 

two airways coincide, the word “TO” with the three-letter VOR 

identifier appear to the left of the distance boxes .

VOR changeover points (COPs) are depicted on the charts by 

this symbol . The numbers indicate the distance at which 

to change the VOR frequency. The frequency change might 

be required due to signal reception or conflicting frequencies. 

If a COP does not appear on an airway, the frequency should 

be changed midway between the facilities. A COP at an 

intersection may indicate a course change.

Occasionally an “x” appears at a separated segment of an 

airway that is not an intersection. The “x” is a mileage 

breakdown or computer navigation fix and may indicate a 

course change.

Today’s computerized system of ATC has greatly reduced 

the need for holding en route. However, published holding 

patterns are still found on charts at junctures 

where ATC has deemed it necessary to enable 

traffic flow. When a holding pattern is charted, Holding Pattern

NAME

Name

000.0 000.0
1-11

XPDR 5537 IDNT LCL23:00:34

VOR 1 

270°

2

1

1

2

3300

3200

3100

4000

2900

2800

2300

3600

3500

3400

3300

3200

3100

60

20

3000

3000

130

120

110

90

80

70

1

100

9

TAS 100KT

OAT 7°C

5

338 

1

1652 

200 

46 

13.7 

2300 

23.0 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

MAP - NAVIGATION MAP

MFD provide navigation information - moving map 

MAP DCLTR

Figure 1-6. Moving map display.

Figure 1-7. Example of an electronic flight bag.

hazardous weather. GPS systems can be certified for terminal 

area and en route use as well as approach guidance. 

Additional breakthroughs in display technology are the 

new electronic chart systems or electronic flight bags that 

facilitate the use of electronic documents in the general 

aviation flight deck. [Figure 1-7] An electronic chart or 

flight bag is a self-powered electronic library that stores and 

displays en route charts and other essential documents on a 

screen. These electronic devices can store the digitized United 

States terminal procedures, en route charts, the complete 

A/FD, in addition to 14 CFR and the AIM. Full touch-screen 

based computers allow pilots to view airport approach and 

area charts electronically while flying. With FAA approval, 

an operator may replace paper charts as well as other paper 

materials including minimum equipment lists (MELs), 

standard operating procedures (SOPs), standard instrument 

departures (SIDs), standard terminal arrival routes (STARs), 

checklists, and flight deck manuals. As with paper flight 

publications, the electronic database needs to be current 

to provide accurate information regarding NAVAIDS, 

waypoints, and terminal procedures. Databases are updated 

every 28 days and are available from various commercial 

vendors. Pilots should be familiar with equipment operation, 

capabilities, and limitations prior to use.
1-12

Terminal Procedures Publications

While the en route charts provide the information necessary 

to safely transit broad regions of airspace, the United States 

Terminal Procedures Publication (TPP) enables pilots to 

guide their aircraft in the airport area. Whether departing or 

arriving, these procedures exist to make the controllers’ and 

pilots’ jobs safer and more efficient. Available in booklets by 

region (published by AeroNav Products), the TPP includes 

approach procedures, STARs, Departure Procedures (DPs), 

and airport diagrams.

Departure Procedures

There are two types of DPs: Obstacle Departure Procedures 

(ODP) and SIDs. [Figure 1-8] Both types of DPs provide 

obstacle clearance protection to aircraft in instrument 

meteorological conditions (IMC), while reducing 

communications and departure delays. DPs are published in 

text and/or charted graphic form. Regardless of the format, all 

DPs provide a way to depart the airport and transition to the 

en route structure safely. When possible, pilots are strongly 

encouraged to file and fly a DP at night, during marginal 

visual meteorological conditions (VMC) and IMC.

All DPs provide obstacle clearance provided the aircraft 

crosses the end of the runway at least 35 feet AGL; climbs 

to 400 feet above airport elevation before turning; and climbs 

at least 200 feet per nautical mile (FPNM), unless a higher 

climb gradient is specified to the assigned altitude. ATC may 

vector an aircraft off a previously assigned DP; however, 

the 200 FPNM or the FPNM specified in the DP is required.

Textual ODPs are listed by city and airport in the IFR TakeOff Minimums and DPs section of the TPP. SIDs are depicted 

in the TPP following the approach procedures for the airport. 

Standard Terminal Arrival Routes

STARs depict prescribed routes to transition the instrument 

pilot from the en route structure to a fix in the terminal area 

from which an instrument approach can be conducted. If a 

pilot does not have the appropriate STAR, write “No STAR” 

in the flight plan. However, if the controller is busy, the pilot 

might be cleared along the same route and, if necessary, the 

controller has the pilot copy the entire text of the procedure.

STARs are listed alphabetically at the beginning of the 

AeroNav Products booklet. Figure 1-9 shows an example 

of a STAR, and the legend for STARs and DPs printed in 

AeroNav Products booklets.

Instrument Approach Procedure Charts 

The instrument approach procedure (IAP) chart provides 

the method to descend and land safely in low visibility 

conditions. The FAA establishes an IAP after thorough 

analyses of obstructions, terrain features, and navigational 

facilities. Maneuvers, including altitude changes, course 

corrections, and other limitations, are prescribed in the IAP. 

The approach charts reflect the criteria associated with the 

United States Standard for Terminal Instrument Approach 

Procedures (TERPs), which prescribes standardized methods 

for use in designing instrument flight procedures.

In addition to the AeroNav Products, other governmental 

and corporate entities produce approach procedures. The 

U.S. Military IAPs are established and published by the 

Department of Defense and are available to the public 

upon request. Special IAPs are approved by the FAA for 

individual operators and are not available to the general 

public. Foreign country standard IAPs are established and 

published according to the individual country’s publication 

procedures. The information presented in the following 

sections highlight features of the United States TPP.

The instrument approach chart is divided into six main 

sections, which include the margin identification, pilot 

briefing (and notes), plan view, profile view, landing 

minimums, and airport diagram. [Figure 1-10] An 

examination of each section follows.

Margin Identification

The margin identification, at the top and bottom of the chart, 

depicts the airport location and procedure identification. 

The civil approach plates are organized by city, then airport 

name and state. For example, Orlando Executive in Orlando, 

Florida, is alphabetically listed under “O” for Orlando. 

Military approaches are organized by airport name first.

The chart’s amendment status appears below the city 

and state in the bottom margin. The amendment number 

is followed by the five-digit julian-date of the last chart 

change.“05300” is read, “the 300th day of 2005.” At the 

center of the top margin is the FAA chart reference number 

and the approving authority. At the bottom center, the 

airport’s latitude and longitude coordinates are provided. If 

a chart is original, the date of issuance can be used instead 

of the julian-date.

The procedure chart title (top and bottom margin area of 

Figure 1-10) is derived from the type of navigational facility 

providing final approach course guidance. A runway number 

is listed when the approach course is aligned within 30o 

of the runway centerline. This type of approach allows a 

straight-in landing under the right conditions. The type of 

approach followed by a letter identifies approaches that do 

not have straight-in landing minimums. Examples include 

procedure titles at the same airport, which have only 

circling minimums. The first approach of this type created 
1-13

L1

L1

TAKE-OFF MINIMUMS AND (OBSTACLE) DEPARTURE PROCEDURES

TAKE-OFF MINIMUMS AND (OBSTACLE) DEPARTURE PROCEDURES

10322

10322

SC-1

INSTRUMENT APPROACH PROCEDURE CHARTS

IFR TAKE-OFF MINIMUMS AND (OBSTACLE) DEPARTURE PROCEDURES

NAME TAKE-OFF MINIMUMS NAME TAKE-OFF MINIMUMS

ADA, OK

ADA MUNI (ADH)AMDT 3 09127 (FAA)

TAKE-OFF MINIMUMS:Rwy 13, 300-11⁄4 or std. w/

min. climb of 307' per NM to 1300. Rwy 17, 300-11⁄4 or

std. w/ min. climb of 326' per NM to 1300.

DEPARTURE PROCEDURE:Rwy 17, climb heading

174° to 1600 before proceeding on course.

NOTE: Rwy 13, bush 316' from DER, 43' right of

centerline, 9' AGL/988' MSL. Tower 5477' from DER,

872' left of centerline, 120' AGL/1117' MSL. Post 123'

from DER, 73' right of centerline, 3' AGL/982' MSL.

Tower 1.08 NM from DER, 9' left of centerline, 160'

AGL/1160' MSL. Rwy 17, tower 1.02 NM from DER,

1411' right of centerline, 165' AGL/1165' MSL. Pole

1017' from DER, 449' left of centerline, 90' AGL/1053'

MSL. Trees beginning 83' from DER, 272' left ofcenterline, up to 82' AGL/1041' MSL. Trees beginning

32' from DER, 100' right of centerline, up to 58' AGL/

1037' MSL.Rwy 31, trees beginning 2179' from DER,988' right of centerline, up to 64' AGL/1083' MSL.

Obstruction light on amom 703' from DER, 548' right

of centerline, 6' AGL/1042' MSL. Rwy 35, treesbeginning 75' from DER, 72' left of centerline, up to 56'

AGL/1065' MSL. Trees beginning 132' from DER, 261'

right of centerline, up to 51' AGL/1050' MSL.

ALTUS, OK

ALTUS/QUARTZ MOUNTAIN RGNL (AXS)

ORIG 09267 (FAA)

NOTE: Rwy 35, terrain 51' from DER, 410' right of

centerline, 1435' MSL. Trees beginning 1215' from DER,765' left of centerline, up to 40' AGL/1470' MSL.

ALTUS AFB (KLTS)

ALTUS, OK . . . . . . . . . . . . . . . . . .09295

TAKE-OFF OBSTACLES: 174° Assault Strip, Aircraft

taxiing 87' from DER, 360' left of centerline, 65' AGL/

1425' MSL, aircraft taxiing between 1038' and 2525' from

DER, 717' left of centerline, 65' AGL/1425' MSL.

ALVA, OK

ALVA RGNL

DEPARTURE PROCEDURE: Rwys 8, 35, climb on

runway heading to 2000 before turning.

Civil Airports and Selected Military Airports

ALL USERS: Airports that have Departure Procedures (DPs) designed specifically to assist pilots in

avoiding obstacles during the climb to the minimum enroute altitude , and/or airports that have civil

IFR take-off minimums other than standard, are listed below. Take-off Minimums and Departure

Procedures apply to all runways unless otherwise specified. Altitudes, unless otherwise indicated, are

minimum altitudes in MSL.

DPs specifically designed for obstacle avoidance are referred to as Obstacle Departure Procedures(ODPs) and are described below in text, or published separately as a graphic procedure. If the

(Obstacle) DP is published as a graphic procedure, its name will be listed below, and it can be found in

either this volume (civil), or a separate Departure Procedure volume (military), as appropriate. Users

will recognize graphic obstacle DPs by the term "(OBSTACLE)" included in the procedure title; e.g.,

TETON TWO (OBSTACLE). If not assigned a SID or radar vector by ATC, an ODP may be flown

without ATC clearance to ensure obstacle clearance.Graphic DPs designed by ATC to standardize traffic flows, ensure aircraft separation and enhance

capacity are referred to as "Standard Instrument Departures (SIDs)". SIDs also provide obstacle

clearance and are published under the appropriate airport section. ATC clearance must be receivedprior to flying a SID.CIVIL USERS NOTE: Title 14 Code of Federal Regulations Part 91 prescribes standard take-off rules

and establishes take-off minimums for certain operators as follows: (1) Aircraft having two engines orless - one statute mile. (2) Aircraft having more than two engines - one-half statute mile. These

standard minima apply in the absence of any different minima listed below.

MILITARY USERS NOTE: Civil (nonstandard) take-off minima are published below. For military takeoff minima, refer to appropriate service directives.

16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61

SE-3, 16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61, 3- ES

Figure 1-8. Obstacle departure procedures (ODP) and standard instrument departures (SID).
1-14

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Figure 1-9. DP chart legend and STAR.

S

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Issuing authority

Procedure ID

Coverage

area/

effective

date

Amendment #

City/airport

Latitude/longitude coordinates

PILOT BRIEFING

AND 

PROCEDURE NOTES

AIRPORT

DIAGRAM

PLAN VIEW PROFILE MINIMUMS SE-3, 16 DEC 2010 to 13 JAN 2011

SE-3, 16 DEC 2010 ot 13 JAN 2011

Figure 1-10. Instrument approach chart.
1-16

at the airport is labeled with the letter A, and the lettering 

continues in alphabetical order (e.g., “VOR-A or “LDA-B”). 

The letter designation signifies the expectation is for the 

procedure to culminate in a circling approach to land. As a 

general rule, circling-only approaches are designed for one 

of the two following reasons:

• The final approach course alignment with the runway 

centerline exceeds 30o.

• The descent gradient is greater than 400 FPNM from 

the final approach fix (FAF) to the threshold crossing 

height (TCH). When this maximum gradient is 

exceeded, the circling-only approach procedure may 

be designed to meet the gradient criteria limits. 

Further information on this topic can be found in the 

Instrument Procedures Handbook, Chapter 4, under 

Approach Naming Chart Conventions.

To distinguish between the left, right, and center runways, 

an “L,” “R,” or “C” follows the runway number (e.g., “ILS 

RWY 16R”). In some cases, an airport might have more than 

one circling approach, shown as VOR-A, VOR/DME-B, etc. 

More than one navigational system separated by a slash 

indicates more than one type of equipment is required to 

execute the final approach (e.g., VOR/DME RWY 31). 

More than one navigational system separated by “or” 

indicates either type of equipment may be used to execute 

the final approach (e.g., VOR or GPS RWY 15). Multiple 

approaches of the same type, to the same runway and using 

the same guidance, have an additional letter from the end of 

the alphabet, number, or term in the title (e.g., ILS Z RWY 

28, SILVER ILS RWY 28, or ILS 2 RWY 28). VOR/DME 

RNAV approaches are identified as VOR/DME RNAV 

RWY (runway number). Helicopters have special IAPs 

designated with COPTER in the procedure identification 

(e.g., COPTER LOC/DME 25L). Other types of navigation 

systems may be required to execute other portions of the 

approach prior to intercepting the final approach segment 

or during the missed approach.

The Pilot Briefing

The pilot briefing is located at the top of the chart and 

provides the pilot with information required to complete 

the published approach procedure. Included in the pilot 

briefing are the NAVAID providing approach guidance, 

its frequency, the final approach course, and runway 

information. A notes section contains additional procedural 

information. For example, a procedural note might indicate 

restrictions for circling maneuvers. Some other notes might 

concern a local altimeter setting and the resulting change 

in the minimums. The use of RADAR may also be noted in 

this section. Additional notes may be found in the plan view.

When a triangle containing a “T” ( ) appears in the notes 

section, it signifies the airport has nonstandard IFR takeoff 

minimums. Pilots should refer to the DPs section of the TPP 

to determine takeoff minimums.

When a triangle containing an “A” ( ) appears in the notes 

section, it signifies the airport has nonstandard IFR alternate 

minimums. Civil pilots should refer to the Alternate Minimums 

Section of the TPP to determine alternate minimums. Military 

pilots should refer to appropriate regulations.

When a triangle containing an “A” NA ( ) appears in 

the notes area, it signifies that Alternate Minimums are Not 

Authorized due to unmonitored facility or the absence of 

weather reporting service.

Communication frequencies are listed in the order in which 

they would be used during the approach. Frequencies for 

weather and related facilities are included, where applicable, 

such as ATIS, ASOS, AWOS, and AFSSs.

The Plan View

The plan view provides a graphical overhead view of the 

procedure and depicts the routes that guide the pilot from 

the en route segments to the initial approach fix (IAF). 

[Figure 1-10] During the initial approach, the aircraft has 

departed the en route phase of flight and is maneuvering to enter 

an intermediate or final segment of the instrument approach. 

An initial approach can be made along prescribed routes within 

the terminal area, which may be along an arc, radial, course, 

heading, radar vector, or a combination thereof. Procedure turns 

and high-altitude teardrop penetrations are initial approach 

segments. Features of the plan view, including the procedure 

turn, obstacle elevation, minimum safe altitude (MSA), and 

procedure track are depicted in Figure 1-11. Terrain is depicted 

in the plan view portion of all IAPs if the terrain within the 

plan view exceeds 4,000 feet above the airport elevation, or if 

within a 6 NM radius of the airport reference point the terrain 

rises at least 2,000 feet above the airport elevation.

Some AeroNav Products charts contain a reference or 

distance circle with a specified radius (10 NM is most 

common). Normally, approach features within the plan 

view are shown to scale; however, only the data within the 

reference circle is always drawn to scale. 

Concentric dashed circles, or concentric rings around the 

distance circle, are used when the information necessary to 

the procedure will not fit to scale within the limits of the plan 

view area. They serve as a means to systematically arrange 

this information in its relative position outside and beyond 

the reference circle. These concentric rings are labeled en 

route facilities and feeder facilities. 
1-17

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,2-ES

PILOT BRIEFING

AND 

PROCEDURE NOTES

AIRPORT

DIAGRAM PLAN VIEW

PROFILE MINIMUMS

Additional 

equipment

requirement

Nonprecision FAF

Main procedure

Highest obstacle

IAF

NAVAID ID

Obstacle

Main procedure

No procedure turn

Holding pattern

Figure 1-11. IAP plan view and symbol legends.

INSTRUMENT APPROACH PROCEDURES (CHARTS) 

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1-18

The primary airport depicted in the plan view is drawn 

with enough detail to show the runway orientation and final 

approach course alignment. Airports other than the primary 

approach airport are not normally depicted in the AeroNav 

Products plan view. 

Known spot elevations are indicated on the plan view with a 

dot in MSL altitude. The largest dot and number combination 

indicates the highest elevation. An inverted “V” with a dot in 

the center depicts an obstacle ( ). The highest obstacle is 

indicated with a bolder, larger version of the same symbol. 

[Figure 1-11]

The MSA circle appears in the plan view, except in approaches 

for which the Terminal Arrival Area (TAA) format is used or 

appropriate NAVAIDs (e.g., VOR or NDB) are unavailable. 

The MSA is provided for emergency purposes only and 

guarantees 1,000 feet obstruction clearance in the sector 

indicated with reference to the bearings in the circle. For 

conventional navigation systems, the MSA is normally based 

on the primary omnidirectional facility (NAVAID) 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 for 

straight-in approaches or the airport waypoint 

for circling approaches. For GPS approaches, the MSA center 

header is the missed approach waypoint. The MSL altitudes 

appear in boxes within the circle, which is typically a 25 NM 

radius unless otherwise indicated. The MSA circle header 

refers to the letter identifier of the NAVAID or waypoint that 

describes the center of the circle. 

NAVAIDs necessary for the completion of the instrument 

procedure include the facility name, letter identifier, and 

Morse code sequence. They may also furnish the frequency, 

Morse code, and channel. A heavy-lined NAVAID box 

depicts the primary NAVAID used for the approach. An 

“I” in front of the NAVAID identifier (in Figure 1-11, 

“I-AVL”) listed in the NAVAID box indicates a localizer. 

The requirement for an ADF, DME, or RADAR in the 

approach is noted in the plan view.

Intersections, fixes, radials, and course lines describe route 

and approach sequencing information. The main procedure 

or final approach course is a thick, solid line ( ). 

A DME arc, which is part of the main procedure course, 

is also represented as a thick, solid line ( ). A 

feeder route is depicted with a medium line ( ) and 

provides heading, altitude, and distance information. (All 

three components must be designated on the chart to provide 

a navigable course.) Radials, such as lead radials, are shown 

by thin lines ( ). The missed approach track is drawn 

using a thin, hash marked line with a directional arrow 

( ). A visual flightpath segment 

appears as a thick dashed line with a directional arrow 

(Visual Flightpath ). IAFs are charted IAF when associated 

with a NAVAID or when freestanding.

The missed approach holding pattern track is represented with 

a thin, dashed line. When collocated, the missed approach 

holding pattern and procedure turn holding pattern are 

indicated as a solid, black line. Arrival holding patterns are 

depicted as thin, solid lines.

Terminal Arrival Area (TAA)

The design objective of the TAA procedure is to provide 

a transition method for arriving aircraft with GPS/RNAV 

equipment. TAAs also eliminate or reduce the need for 

feeder routes, departure extensions, and procedure turns or 

course reversal. The TAA is controlled airspace established 

in conjunction with the standard or modified RNAV 

approach configurations.

The standard TAA has 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. When crossing the boundary of each of these areas or 

when released by ATC within the area, the pilot is expected 

to proceed direct to the appropriate waypoint IAF for the 

approach area being flown. A pilot has the option in all areas 

of proceeding directly to the holding pattern.

The TAA has a “T” structure that normally provides a No 

Procedure Turn (NoPT) for aircraft using the approach. 

[Figure 1-12] The TAA provides the pilot and air traffic 

controller with an efficient method for routing traffic from 

the en route to the terminal structure. The basic “T” contained 

in the TAA normally aligns the procedure on runway 

centerline with the missed approach point (MAP) located 

at the threshold, the FAF 5 NM from the threshold, and the 

intermediate fix (IF) 5 NM from the FAF.

In order to accommodate descent from a high en route altitude 

to the initial segment altitude, a hold in lieu of a procedure 

turn provides the aircraft with an extended distance for the 

necessary descent gradient. The holding pattern constructed for 

this purpose is always established on the center IAF waypoint. 

Other modifications may be required for parallel runways or 

special operational requirements. When published, the RNAV 

chart depicts the TAA through the use of icons representing 

each TAA associated with the RNAV procedure. These 

icons are depicted in the plan view of the approach, generally 

arranged on the chart in accordance with their position relative 

to the aircraft’s arrival from the en route structure.
1-19

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Missed approach text

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PILOT BRIEFING

AND 

PROCEDURE NOTES

AIRPORT PLAN VIEW DIAGRAM

PROFILE MINIMUMS

Figure 1-12. Basic “T” design of terminal arrival area (TAA) and legend.

INSTRUMENT APPROACH PROCEDURES (CHARTS) 

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Procedure Turns Figure 1-13. 45° procedure turn.

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Holding in Lieu of Procedure Turn Figure 1-14. Holding in lieu of procedure turn.

Course Reversal Elements in Plan View and 

Profile View

Course reversals included in an IAP are depicted in one of 

three different ways: a 45°/180° procedure turn, a holding 

pattern in lieu of procedure turn, or a teardrop procedure. 

The maneuvers are required when it is necessary to reverse 

direction to establish the aircraft inbound on an intermediate 

or final approach course. Components of the required 

procedure are depicted in the plan view and the profile view. 

The maneuver must be completed within the distance and 

at the minimum altitude specified in the profile view. Pilots 

should coordinate with the appropriate ATC facility relating 

to course reversal during the IAP.

Procedure Turns

A procedure turn barbed arrow indicates 

the direction or side of the outbound course on which 

the procedure turn is made. [Figure 1-13] Headings are 

provided for course reversal using the 45° 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. Some of the options are the 45° procedure turn, the 

racetrack pattern, the teardrop procedure turn, or the 80°/260° 

course reversal. The absence of the procedure turn barbed 

arrow in the plan view indicates that a procedure turn is 

not authorized for that procedure. A maximum procedure 

turn speed of not greater than 200 knots indicated airspeed 

(KIAS) should be observed when turning outbound over the 

IAF and throughout the procedure turn maneuver to ensure 

staying within the obstruction clearance area. The normal 

procedure turn distance is 10 NM. This may be reduced to 

a minimum of 5 NM where only Category A or helicopter 

aircraft are operated, or increased to as much as 15 NM to 

accommodate high performance aircraft. Descent below the 

procedure turn altitude begins after the aircraft is established 

on the inbound course.

The procedure turn is not required when the symbol “NoPT” 

appears, when radar vectoring to the final approach is 

provided, when conducting a timed approach, or when the 

procedure turn is not authorized. Pilots should contact the 

appropriate ATC facility when in doubt if a procedure turn 

is required.

Holding in Lieu of Procedure Turn

A holding pattern in lieu of a procedure turn may be specified 

for course reversal in some procedures. [Figure 1-14] In such 

cases, the holding pattern is established over an intermediate 

fix (IF) or a FAF. The holding pattern distance or time 

specified in the profile view must be observed. 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 neither 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 advise ATC upon receipt of their approach clearance. 

When holding in lieu of a procedure turn, the holding pattern 

must be followed, except when RADAR VECTORING to 

the final approach course is provided or when NoPT is shown 

on the approach course.
1-21

Figure 1-15. Teardrop procedure. Dothan Teardrop 

Teardrop Procedure

When a teardrop procedure turn is depicted and a course 

reversal is required, unless otherwise authorized by ATC, 

this type of procedure must be executed. [Figure 1-15] The 

teardrop procedure consists of departure from an IAF on the 

published 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 shall be assumed 

to commence at a point 10 NM prior to the FAF. 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 NM from the facility.

The Profile View

The profile view is a depiction of the procedure from the side 

and illustrates the vertical approach path altitudes, headings, 

distances, and fixes. [Figures 1-10, 1-11, and 1-12] The 

view includes the minimum altitude and the maximum 

distance for the procedure turn, altitudes over prescribed 

fixes, distances between fixes, and the missed approach 

procedure. The profile view aids in the pilot’s interpretation 

of the IAP. The profile view is not drawn to scale. 

[Figures 1-10, 1-11, 1-12, and 1-16]

The precision approach glideslope (GS) intercept altitude 

is a minimum altitude for GS interception after completion 

of the procedure turn, illustrated by an altitude number and 

“zigzag” line. It applies to precision approaches, and except 

where otherwise prescribed, also applies as a minimum 

altitude for crossing the FAF when the GS is inoperative 

or not used. Precision approach profiles also depict the GS 

angle of descent, threshold crossing height (TCH), and GS 

altitude at the outer marker (OM).

For nonprecision approaches, a final descent is initiated and 

the final segment begins at either the FAF or the final approach 

point (FAP). The FAF is identified by use of the Maltese cross 

symbol in the profile view ( ). [Figure 1-11] When no FAF 

is depicted, the final approach point is the point at which the 

aircraft is established inbound on the final approach course. 

[Figure 1-16] 

Stepdown fixes in nonprecision procedures are provided 

between the FAF and the airport for authorizing a lower 

minimum descent altitude (MDA) after passing an 

obstruction. Stepdown fixes can be identified by NAVAID, 

NAVAID fix, waypoint, or radar and are depicted by a hash 

marked line ( ). Normally, there is only one stepdown fix 

between the FAF and the MAP, but there can be several. 

If the stepdown fix cannot be identified for any reason, the 

minimum altitude at the stepdown fix becomes the MDA for 

the approach. However, circling minimums apply if they are 

higher than the stepdown fix minimum altitude, and a circling 

approach is required.

The visual descent point (VDP) is a defined point on the 

final approach course of a nonprecision straight-in approach 

procedure. A normal descent from the MDA to the runway 

touchdown point may be commenced, provided visual 

reference is established. The VDP is identified on the profile 

view of the approach chart by the symbol “V.” [Figure 1-12]

The MAP varies depending upon the approach flown. For 

the ILS, the MAP is at the decision altitude/decision height 

(DA/DH). For nonprecision procedures, the pilot determines 

the MAP by timing from FAF when the approach aid is away 

from the airport, by a fix or NAVAID when the navigation 

facility is located on the field, or by waypoints as defined 

by GPS or VOR/DME RNAV. The pilot may execute the 

MAP early, but pilots should, unless otherwise cleared by 

ATC, fly the IAP as specified on the approach plate to the 

MAP at or above the MDA or DA/DH before executing a 

turning maneuver.

A complete description of the MAP appears in the pilot 

briefing section. [Figure 1-16] Icons indicating what is to 

be accomplished at the MAP are located in the profile view. 

When initiating a missed approach, the pilot is directed to 

climb straight ahead (e.g., “Climb to 2,000”) or commence 

a turning climb to a specified altitude (e.g., “Climbing right 

turn to 2,000.”). In some cases, the procedure directs the pilot 

to climb straight ahead to an initial altitude, then turn or enter 
1-22

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PILOT BRIEFING

AND 

PROCEDURE NOTES

AIRPORT

DIAGRAM

PLAN VIEW PROFILE MINIMUMS

Figure 1-16. More IAP profile view features.

FAF Maltese cross 

Glideslope intercept for full ILS

MAP 0.4 NM from runway for obstacle clearance 

Stepdown fix—cannot descend from 5,300' until 4 DME from LMT is identified. 

Glideslope outer marker altitude

Glideslope descent angle

speed
1-23

Figure 1-17. Final Approach Angle for Vertical Path Computers Vertical descent angle (VDA).

a climbing turn to the holding altitude (e.g., “Climb to 900, 

then climbing right turn to 2,500 direct ABC VOR and hold.”)

When the MAP specifies holding at a facility or fix, the pilot 

proceeds according to the missed approach track and pattern 

depicted on the plan view. An alternate MAP may also be 

issued by ATC. The textual description also specifies the 

NAVAID(s) or radials that identify the holding fix.

The profile view also depicts minimum, maximum, 

recommended, and mandatory block altitudes used in 

approaches. The minimum altitude is depicted with the 

altitude underscored ( ). On final approach, aircraft are 

required to maintain an altitude at or above the depicted 

altitude until reaching the subsequent fix. The maximum 

altitude is depicted with the altitude overscored ( ), 

and aircraft must remain at or below the depicted altitude. 

Mandatory altitudes are depicted with the altitude both 

underscored and overscored ( ), and altitude is to be 

maintained at the depicted value. Recommended altitudes 

are advisory altitudes and are neither over- nor underscored. 

When an over- or underscore spans two numbers, a 

mandatory block altitude is indicated, and aircraft are 

required to maintain altitude within the range of the two 

numbers. [Figures 1-11 and 1-12]

The Vertical Descent Angle (VDA) found on nonprecision 

approach charts provides the pilot with information required 

to establish a stabilized approach descent from the FAF or 

stepdown fix to the TCH. [Figure 1-17] Pilots can use the 

published angle and estimated or actual groundspeed to find 

a target rate of descent using the rate of descent table in the 

back of the TPP.

Landing Minimums

The minimums section sets forth the lowest altitude and 

visibility requirements for the approach, whether precision 

or nonprecision, straight-in or circling, or radar vectored. 

When a fix is incorporated in a nonprecision final segment, 

two sets of minimums may be published depending upon 

how the fix can be identified. Two sets of minimums may 

also be published when a second altimeter source is used 

in the procedure. The minimums ensure that final approach 

obstacle clearance is provided from the start of the final 

segment to the runway or MAP, whichever occurs last. The 

same minimums apply to both day and night operations unless 

different minimums are specified in the notes section of the 

pilot briefing. Published circling minimums provide obstacle 

clearance when pilots remain within the appropriate area of 

protection. [Figure 1-18]

Minimums are specified for various aircraft approach 

categories based upon a value 1.3 times the stalling speed 

of the aircraft in the landing configuration at maximum 

certified gross landing weight. 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 next higher category should 

be used. For example, an aircraft that falls into category 

A, but is circling to land at a speed in excess of 91 knots, 

should use approach category B minimums when circling 

to land. [Figure 1-19]

The minimums for straight-in and circling appear directly 

under each aircraft category. [Figure 1-19] When there is 

no solid division line between minimums for each category 

on the rows for straight-in or circling, the minimums apply 

to the two or more categories.

The terms used to describe the minimum approach altitudes 

differ between precision and nonprecision approaches. 

Precision approaches use DH, which is referenced to the 

height above threshold elevation (HAT). Nonprecision 

approaches use MDA, referenced to “feet MSL.” The MDA 

is also referenced to HAT for straight-in approaches, or 

height above airport (HAA) for circling approaches. On 

AeroNav Products charts, the figures listed parenthetically 

are for military operations and are not used in civil aviation.

Visibility figures are provided in statute miles or runway 

visual range (RVR), which is reported in hundreds of feet. 

RVR is measured by a transmissometer, which represents the 

horizontal distance measured at points along the runway. 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 is horizontal visual range, not 

slant visual range, and is used in lieu of prevailing visibility 

in determining minimums for a particular runway. It is 

illustrated in hundreds of feet if less than a mile (i.e., “24” 

is an RVR of 2,400 feet). [Figures 1-19 and 1-20]

Visibility figures are depicted after the DA/DH or MDA in the 

minimums section. If visibility in statute miles is indicated, 
1-24 INSTRUMENT APPROACH PROCEDURES (CHARTS) 

Vertical descent angle

16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61

Figure 1-18. IAP profile legend.

SE-2, 16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61, 2- ES

PILOT BRIEFING

AND 

PROCEDURE NOTES

AIRPORT

DIAGRAM PLAN VIEW

PROFILE MINIMUMS
1-25

16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61

Figure 1-19. Descent rate table.

SE-3, 16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61, 3- ES

PILOT BRIEFING

AND 

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AIRPORT

DIAGRAM

PLAN VIEW PROFILE MINIMUMS

RVR
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Figure 1-20. Terms/landing minima data.

All minima step in parentheses not applicable to Civil Pilots. Military Pilots refer to appropriate regulations. 

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1-27

an altitude number, hyphen, and a whole or fractional 

number appear; for example, 530-1, which indicates “530 

feet MSL” and 1 statute mile visibility. This is the descent 

minimum for the approach. The RVR value is separated 

from the minimum altitude with a slash, such as “1065/24,” 

which indicates 1,065 feet MSL and an RVR of 2,400 feet. 

If RVR is prescribed for the procedure, but not available, a 

conversion table is used to provide the equivalent visibility 

in this case, of 1⁄2 statute mile visibility. [Figure 1-20] The 

conversion table is also available in the TPP.

When an alternate airport is required, standard IFR alternate 

minimums apply. For aircraft other than helicopters, precision 

approach procedures require a 600-feet ceiling and 2 statute 

miles visibility; nonprecision approaches require an 800-feet 

ceiling and 2 statute miles visibility. Helicopter alternate 

minimums are a ceiling that is 200 feet above the minimum 

for the approach to be flown and visibility of at least 1 

statute mile, but not less than the minimum visibility for the 

approach to be flown. When a black triangle with a white “A” 

appears in the notes section of the pilot briefing, it indicates 

non-standard IFR alternate minimums exist for the airport. 

If an “NA” appears after the “A” ( ), then alternate 

minimums are not authorized. This information is found in 

the beginning of the TPP.

In addition to the COPTER approaches, instrumentequipped helicopters may fly standard approach procedures. 

The required visibility minimum may be reduced to one-half 

the published visibility minimum for category A aircraft, 

but in no case may it be reduced to less than 1⁄4 mile or 

1,200 feet RVR.

Two terms are specific to helicopters. Height above landing 

(HAL) means height above a designated helicopter landing 

area used for helicopter IAPs. “Point in space approach” 

refers to a helicopter IAP to a MAP more than 2,600 feet 

from an associated helicopter landing area.

Airport Sketch /Airport Diagram

Prior to all flights, pilots should take the time and study the 

airport layout for all of the airports that they intend to land, 

including those that may be used as an alternate. During 

the flight planning phase, study the taxi procedures for the 

departure airport and landing procedures for the arrival 

airport. The expected taxi route should be checked against 

the airport diagram or taxi chart, and special attention should 

be given to the unique or complex intersections along the taxi 

route. Pilots should identify critical times and locations on the 

taxi route (e.g., transitioning through complex intersections, 

crossing intervening runways, entering and lining up on the 

runway for takeoff, and approaching and lining up on the 

runway for landing).

By knowing the layout of the airport and their particular 

procedures, pilots are able to anticipate, understand, and 

safely execute all ATC directives and procedures. A major 

contributor to runway incursions is pilots not knowing 

the airport layout and procedures. This lack of situational 

awareness causes unnecessary accidents that can be avoided 

by proper flight planning. The FAA believes that following 

the aircraft’s progress on the airport diagram to be sure that 

the instructions received from ATC are being followed is 

one of the key procedures in reducing runway incursions. To 

do this, pilots must take the time prior to the flight to study 

all procedures so that they are not trying to learn about the 

airport while they are receiving ATC instructions.

The airport sketch, located on the bottom of the chart, includes 

many helpful features. IAPs for some of the larger airports 

devote an entire page to an airport diagram. Airport sketch 

information concerning runway orientation, lighting, final 

approach bearings, airport beacon, and obstacles all serve to 

guide the pilot in the final phases of flight. See Figure 1-21 for 

a legend of airport diagram/airport sketch features (see also 

Figure 1-10 for an example of an airport diagram).

The airport elevation is indicated in a separate box at the 

top left of the airport sketch. The touchdown zone elevation 

(TDZE), which is the highest elevation within the first 3,000 

feet of the runway, is designated at the approach end of the 

procedure’s runway.

Beneath the airport sketch is a time and speed table when 

applicable. The table provides the distance and the amount 

of time required to transit the distance from the FAF to the 

MAP for selected groundspeeds.

The approach lighting systems and the visual approach lights 

are depicted on the airport sketch. White on black symbols 

( ) are used for identifying pilot-controlled lighting (PCL). 

Runway lighting aids are also noted (e.g., REIL, HIRL), as is 

the runway centerline lighting (RCL). [Figure 1-22]

The airport diagram shows the paved runway configuration 

in solid black, while the taxiways and aprons are shaded 

gray. Other runway environment features are shown, such 

as the runway identification, dimensions, magnetic heading, 

displaced threshold, arresting gear, usable length, and slope.

Inoperative Components

Certain procedures can be flown with inoperative components. 

According to the Inoperative Components Table, for 

example, an instrument landing system (ILS) approach 

with a malfunctioning Medium Intensity Approach Lighting 

System with Runway Alignment Indicator Lights (MALSR = 

MALS with RAIL) can be flown if the minimum visibility is 
1-28

INSTRUMENT APPROACH PROCEDURES (CHARTS) 

16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61

Figure 1-21. Airport legend and diagram.

SE-4, 16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61, 4- ES

PILOT BRIEFING

AND 

PROCEDURE NOTES

AIRPORT

DIAGRAM

PLAN VIEW PROFILE MINIMUMS
1-29

INSTRUMENT APPROACH PROCEDURES (CHARTS) 

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Figure 1-22. Approach lighting legend.

INSTRUMENT APPROACH PROCEDURES (CHARTS) 

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increased by 1⁄4 mile. [Figure 1-23] A note in this section 

might read, “Inoperative Table does not apply to ALS or 

HIRL Runway 13L.”

RNAV Instrument Approach Charts

To avoid unnecessary duplication and proliferation of 

approach charts, approach minimums for unaugmented 

GPS, Wide Area Augmentation System (WAAS), Local 

Area Augmentation System (LAAS) are published on 

the same approach chart as lateral navigation/vertical 

navigation (LNAV/VNAV). Other types of equipment 

may be authorized to conduct the approach based on the 

minima notes in the front of the TPP approach chart books. 

Approach charts titled “RNAV RWY XX” may be used 

by aircraft with navigation systems that meet the required 

navigational performance (RNP) values for each segment 

of the approach. [Figure 1-24]

The chart may contain as many as four lines of approach 

minimums: global landing system (GLS), WAAS and LAAS, 

LNAV/VNAV, LNAV, and circling. LNAV/VNAV is an 

instrument approach with lateral and vertical guidance with 

integrity limits similar to barometric vertical navigation 

(BARO VNAV).

RNAV procedures that incorporate a final approach stepdown 

fix may be published without vertical navigation on a separate 

chart also titled RNAV. During a transition period when GPS 

procedures are undergoing revision to a new title, both RNAV 

and GPS approach charts and formats are published. ATC 

clearance for the RNAV procedure authorizes a properly 

certificated pilot to utilize any landing minimums for which 

the aircraft is certified.

Chart terminology changes slightly to support the new 

procedure types:

1. DA replaces the term 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 IAPs 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 is 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 approach 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.

2. MDA continues to be used only for the LNAV and 

circling procedures.

3. TCH has been traditionally used in precision 

approaches as the height of the GS 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 that may be 

using the IAP, the typical TCH is 30 to 50 feet.

The minima format changes slightly:

1. Each line of minima on the RNAV IAP is titled to 

reflect the RNAV system applicable (e.g., LPV, LNAV/

VNAV, and LNAV). Circling minima is also provided.

2. The minima title box also indicates the nature of the 

minimum altitude for the IAP. For example: DA is 

published next to the minima line title for minimums 

supporting vertical guidance, and MDA is published 

where the minima line supports only lateral guidance. 

During an approach where an MDA is used, descent 

below MDA is not authorized.

3. Where two or more systems share the same minima, 

each line of minima is displayed separately.

For more information concerning government charts, the 

AeroNav Products can be contacted by telephone or via their 

internet address at:

National Aeronautical Navigation Products (AeroNav Products)

Telephone 800-626-3677

www.aeronav.faa.gov
1-31

Figure 1-23. IAP inoperative components table.
1-32

SW-1, 16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61, 1- WS

PILOT BRIEFING

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PROCEDURE NOTES

AIRPORT

DIAGRAM

PLAN VIEW PROFILE MINIMUMS Field elevation PAPI Approach lights Touchdown zone elevation

Figure 1-24. RNAV instrument approach charts.

SE-4, 16 DEC 2010 to 13 JAN 2011

1102 NAJ 31 ot 0102 CED61, 4- ES

PILOT BRIEFING

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PROCEDURE NOTES

AIRPORT

DIAGRAM

PLAN VIEW PROFILE MINIMUMS Runway lights

pilot controlled

VASI

Alternate minimumsnot authorized
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The Air Traffic 

Control System

Chapter 2

Introduction

This chapter covers the communication equipment, 

communication procedures, and air traffic control (ATC) 

facilities and services available for a flight under instrument 

flight rules (IFR) in the National Airspace System (NAS).
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Figure 2-2. Audio panel.

Figure 2-1. Typical navigation/communication installation.

Communication Equipment

Navigation/Communication Equipment

Civilian pilots communicate with ATC on frequencies in 

the very high frequency (VHF) range between 118.000 and 

136.975 MHz. To derive full benefit from the ATC system, 

radios capable of 25 kHz spacing are required (e.g., 134.500, 

134.575, 134.600). If ATC assigns a frequency that cannot 

be selected, ask for an alternative frequency.

Figure 2-1 illustrates a typical radio panel installation 

consisting of a communications transceiver on the left and 

a navigational receiver on the right. Many radios allow the 

pilot to have one or more frequencies stored in memory and 

one frequency active for transmitting and receiving (called 

simplex operation). It is possible to communicate with some 

flight service stations (FSS) by transmitting on 122.1 MHz 

(selected on the communication radio) and receiving on a 

VHF omnidirectional range (VOR) frequency (selected on 

the navigation radio). This is called duplex operation.

An audio panel allows a pilot to adjust the volume of the 

selected receiver(s) and to select the desired transmitter. 

[Figure 2-2] The audio panel has two positions for receiver 

selection, cabin speaker, and headphone (some units might 

have a center “OFF” position). Use of a hand-held microphone 

and the cabin speaker introduces the distraction of reaching 

for and hanging up the microphone. A headset with a boom 

microphone is recommended for clear communications. The 

microphone should be positioned close to the lips to reduce 
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Figure 2-3. Boom microphone, headset, and push-to-talk switch.

Figure 2-4. Combination GPS-com unit.

Headset

Push-to-talk switch

Boom microphone

the possibility of ambient flight deck noise interfering with 

transmissions to the controller. Headphones deliver the 

received signal directly to the ears; therefore, ambient noise 

does not interfere with the pilot’s ability to understand the 

transmission. [Figure 2-3]

Switching the transmitter selector between COM1 and 

COM2 changes both transmitter and receiver frequencies. 

It is necessary only when a pilot wants to monitor one 

frequency while transmitting on another. One example is 

listening to Automatic Terminal Information Service (ATIS) 

on one receiver while communicating with ATC on the 

other. Monitoring a navigation receiver to check for proper 

identification is another reason to use the switch panel.

Most audio switch panels also include a marker beacon 

receiver. All marker beacons transmit on 75 MHz, so there 

is no frequency selector.

Figure 2-4 illustrates an increasingly popular form of 

navigation/communication radio; it contains a global 

positioning system (GPS) receiver and a communications 

transceiver. Using its navigational capability, this unit can 

determine when a flight crosses an airspace boundary or fix 

and can automatically select the appropriate communications 

frequency for that location in the communications radio.

Radar and Transponders

ATC radars have a limited ability to display primary returns, 

which is energy reflected from an aircraft’s metallic structure. 

Their ability to display secondary returns (transponder replies 

to ground interrogation signals) makes possible the many 

advantages of automation.

A transponder is a radar beacon transmitter/receiver installed 

in the instrument panel. ATC beacon transmitters send out 

interrogation signals continuously as the radar antenna 

rotates. When an interrogation is received by a transponder, a 

coded reply is sent to the ground station where it is displayed 

on the controller’s scope. A reply light on the transponder 

panel flickers every time it receives and replies to a radar 

interrogation. Transponder codes are assigned by ATC.

When a controller asks a pilot to “ident” and the ident button 

is pushed, the return on the controller’s scope is intensified for 

precise identification of a flight. When requested, briefly push 

the ident button to activate this feature. It is good practice 

for pilots to verbally confirm that they have changed codes 

or pushed the ident button.

Mode C (Altitude Reporting)

Primary radar returns indicate only range and bearing from 

the radar antenna to the target; secondary radar returns can 

display altitude, Mode C, on the control scope if the aircraft 

is equipped with an encoding altimeter or blind encoder. In 

either case, when the transponder’s function switch is in the 

ALT position, the aircraft’s pressure altitude is sent to the 

controller. Adjusting the altimeter’s Kollsman window has 

no effect on the altitude read by the controller.

Transponders, when installed, must be ON at all times when 

operating in controlled airspace; altitude reporting is required 

by regulation in Class B and Class C airspace and inside a 

30-mile circle surrounding the primary airport in Class B 

airspace. Altitude reporting should also be ON at all times.
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r 

R 0 

q Q 9 

p P 8 

o 

O 7 

n N 6 

5 5 5 

4 4 4 

3 3 3 

2 2 2 

1 1 1 

z 

Z Z 

y Y Y 

x X X 

W W w 

v V V 

u 

U U 

t T T 

s S S 

r 

R R 

q Q Q 

p P P 

o 

O O 

n N N 

m M M 

L L L 

k K K 

j J J 

i I I 

h h H 

G G g 

f F F 

e 

E E 

d D D 

c 

C C 

b B B 

a A A 

a A 

b A Character Phonic 

(Pronunciation) Morse Code Telephony 

Figure 2-5. Figure 9-5. Phonetic pronunciation guide. Phonetic Pronunciation Guide. 

Communication Procedures

Clarity in communication is essential for a safe instrument 

flight. This requires pilots and controllers to use terms that 

are understood by both—the Pilot/Controller Glossary in the 

Aeronautical Information Manual (AIM) is the best source of 

terms and definitions. The AIM is revised twice a year and 

new definitions are added, so the glossary should be reviewed 

frequently. Because clearances and instructions are comprised 

largely of letters and numbers, a phonetic pronunciation guide 

has been developed for both. [Figure 2-5]

ATC must follow the guidance of the Air Traffic Control 

Manual when communicating with pilots. The manual 

presents the controller with different situations and prescribes 

precise terminology that must be used. This is advantageous 

for pilots because once they have recognized a pattern or 

format, they can expect future controller transmissions 

to follow that format. Controllers are faced with a wide 

variety of communication styles based on pilot experience, 

proficiency, and professionalism.

Pilots should study the examples in the AIM, listen to 

other pilots communicate, and apply the lessons learned 

to their own communications with ATC. Pilots should ask 

for clarification of a clearance or instruction. If necessary, 

use plain English to ensure understanding, and expect the 

controller to reply in the same way. A safe instrument flight 

is the result of cooperation between controller and pilot.

Communication Facilities

The controller’s primary responsibility is separation of 

aircraft operating under IFR. This is accomplished with ATC 

facilities, to include the FSS, airport traffic control tower 

(ATCT), terminal radar approach control (TRACON), and 

air route traffic control center (ARTCC).

Flight Service Stations (FSS)

A pilot’s first contact with ATC is usually through FSS, 

either by radio or telephone. FSSs provide pilot briefings, 

receive and process flight plans, relay ATC clearances, 

originate Notices to Airmen (NOTAMs), and broadcast 

aviation weather. Some facilities provide En Route Flight 

Advisory Service (EFAS), take weather observations, 

and advise United States Customs and Immigration of 

international flights.

Telephone contact with Flight Service can be obtained 

by dialing 1-800-WX-BRIEF. This number can be used 

anywhere in the United States and connects to the nearest 

FSS based on the area code from which the call originates. 

There are a variety of methods of making radio contact: 

direct transmission, remote communication outlets (RCOs), 

ground communication outlets (GCOs), and by using duplex 

transmissions through navigational aids (NAVAIDs). The 

best source of information on frequency usage is the Airport/

Facility Directory (A/FD) and the legend panel on sectional 

charts also contains contact information.
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Altitude—37,000 feet Destination—Minneapolis 

Call sign—Northwest 196 Departure point—San Diego

Figure 9-6. Flight Strip. Figure 2-6. Flight strip.

The briefer sends a flight plan to the host computer at the 

ARTCC (Center). After processing the flight plan, the 

computer sends flight strips to the tower, to the radar facility 

that handles the departure route, and to the Center controller 

whose sector the flight first enters. Figure 2-6 shows a typical 

strip. These strips are delivered approximately 30 minutes 

prior to the proposed departure time. Strips are delivered to 

en route facilities 30 minutes before the flight is expected to 

enter their airspace. If a flight plan is not opened, it will “time 

out” 2 hours after the proposed departure time.

When departing an airport in Class G airspace, a pilot receives 

an IFR clearance from the FSS by radio or telephone. It 

contains either a clearance void time, in which case an aircraft 

must be airborne prior to that time, or a release time. Pilots 

should not take off prior to the release time. Pilots can help 

the controller by stating how soon they expect to be airborne. 

If the void time is, for example, 10 minutes past the hour and 

an aircraft is airborne at exactly 10 minutes past the hour, 

the clearance is void—a pilot must take off prior to the void 

time. A specific void time may be requested when filing a 

flight plan.

ATC Towers

Several controllers in the tower cab are involved in handling 

an instrument flight. Where there is a dedicated clearance 

delivery position, that frequency is found in the A/FD and 

on the instrument approach chart for the departure airport. 

Where there is no clearance delivery position, the ground 

controller performs this function. At the busiest airports, pretaxi clearance is required; the frequency for pre-taxi clearance 

can be found in the A/FD. Taxi clearance should be requested 

not more than 10 minutes before proposed taxi time.

It is recommended that pilots read their IFR clearance back to 

the clearance delivery controller. Instrument clearances can 

be overwhelming when attempting to copy them verbatim, 

but they follow a format that allows a pilot to be prepared 

when responding “Ready to copy.” The format is: clearance 

limit (usually the destination airport); route, including any 

departure procedure; initial altitude; frequency (for departure 

control); and transponder code. With the exception of the 

transponder code, a pilot knows most of these items before 

engine start. One technique for clearance copying is writing 

C-R-A-F-T.

Assume an IFR flight plan has been filed from Seattle, 

Washington to Sacramento, California via V-23 at 7,000 

feet. Traffic is taking off to the north from Seattle-Tacoma 

(Sea-Tac) airport and, by monitoring the clearance delivery 

frequency, a pilot can determine the departure procedure 

being assigned to southbound flights. The clearance limit 

is the destination airport, so write “SAC” after the letter C. 

Write “SEATTLE TWO – V23” after R for Route because 

departure control issued this departure to other flights. Write 

“70” after the A, the departure control frequency printed on 

the approach charts for Sea-Tac after F, and leave the space 

after the letter T blank—the transponder code is generated by 

computer and can seldom be determined in advance. Then, 

call clearance delivery and report “Ready to copy.”

As the controller reads the clearance, check it against what 

is already written down; if there is a change, draw a line 

through that item and write in the changed item. Chances 

are the changes are minimal, and most of the clearance is 

copied before keying the microphone. Still, it is worthwhile 

to develop clearance shorthand to decrease the verbiage that 

must be copied (see Appendix 1).

Pilots are required to have either the text of a departure 

procedure (DP) or a graphic representation (if one is 

available), and should review it before accepting a clearance. 

This is another reason to find out ahead of time which DP is 

in use. If the DP includes an altitude or a departure control 

frequency, those items are not included in the clearance.

The last clearance received supersedes all previous clearances. 

For example, if the DP says “Climb and maintain 2,000 feet, 

expect higher in 6 miles,” but upon contacting the departure 

controller a new clearance is received: “Climb and maintain 

8,000 feet,” the 2,000 feet restriction has been canceled. This 

rule applies in both terminal and Center airspace.
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Figure 2-7. Figure 9-7. Combined radar and beacon antenna. Combined Radar and Beacon Antenna. 

160 

102 

057 

013 

348 

289 

277 

250 

Figure 9-8. Minimum Vectoring Altitude Chart. 

Figure 2-8. Minimum vectoring altitude (MVA) chart.

When reporting “ready to copy” an IFR clearance before 

the strip has been received from the Center computer, pilots 

are advised “clearance on request.” The controller initiates 

contact when it has been received. This time can be used for 

taxi and pre-takeoff checks.

The local controller is responsible for operations in the Class 

D airspace and on the active runways. At some towers, 

designated as IFR towers, the local controller has vectoring 

authority. At visual flight rules (VFR) towers, the local 

controller accepts inbound IFR flights from the terminal radar 

facility and cannot provide vectors. The local controller also 

coordinates flights in the local area with radar controllers. 

Although Class D airspace normally extends 2,500 feet above 

field elevation, towers frequently release the top 500 feet to 

the radar controllers to facilitate overflights. Accordingly, 

when a flight is vectored over an airport at an altitude that 

appears to enter the tower controller’s airspace, there is no 

need to contact the tower controller—all coordination is 

handled by ATC.

The departure radar controller may be in the same building 

as the control tower, but it is more likely that the departure 

radar position is remotely located. The tower controller will 

not issue a takeoff clearance until the departure controller 

issues a release.

Terminal Radar Approach Control (TRACON)

TRACONs are considered terminal facilities because they 

provide the link between the departure airport and the en route 

structure of the NAS. Terminal airspace normally extends 30 

nautical miles (NM) from the facility with a vertical extent of 

10,000 feet; however, dimensions vary widely. Class B and 

Class C airspace dimensions are provided on aeronautical 

charts. At terminal radar facilities, the airspace is divided 

into sectors, each with one or more controllers, and each 

sector is assigned a discrete radio frequency. All terminal 

facilities are approach controls and should be addressed 

as “Approach” except when directed to do otherwise (e.g., 

“Contact departure on 120.4.”).

Terminal radar antennas are located on or adjacent to the 

airport. Figure 2-7 shows a typical configuration. Terminal 

controllers can assign altitudes lower than published 

procedural altitudes called minimum vectoring altitudes 

(MVAs). These altitudes are not published or accessible 

to pilots, but are displayed at the controller’s position. 

[Figure 2-8] However, when pilots are assigned an altitude 

that seems to be too low, they should query the controller 

before descending.

When a pilot accepts a clearance and reports ready for takeoff, 

a controller in the tower contacts the TRACON for a release. 

An aircraft is not cleared for takeoff until the departure 

controller can fit the flight into the departure flow. A pilot may 

have to hold for release. When takeoff clearance is received, 

the departure controller is aware of the flight and is waiting 

for a call. All of the information the controller needs is on 

the departure strip or the computer screen; there is no need to 

repeat any portion of the clearance to that controller. Simply 

establish contact with the facility when instructed to do so 

by the tower controller. The terminal facility computer picks 
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up the transponder and initiates tracking as soon as it detects 

the assigned code. For this reason, the transponder should 

remain on standby until takeoff clearance has been received.

The aircraft appears on the controller’s radar display as a 

target with an associated data block that moves as the aircraft 

moves through the airspace. The data block includes aircraft 

identification, aircraft type, altitude, and airspeed.

A TRACON controller uses Airport Surveillance Radar 

(ASR) to detect primary targets and Automated Radar 

Terminal Systems (ARTS) to receive transponder signals; 

the two are combined on the controller’s scope. [Figure 2-9]

At facilities with ASR-3 equipment, radar returns from 

precipitation are not displayed as varying levels of intensity, 

and controllers must rely on pilot reports and experience 

to provide weather avoidance information. With ASR-9 

equipment, the controller can select up to six levels of 

intensity. Light precipitation does not require avoidance 

tactics but precipitation levels of moderate, heavy, or 

extreme should cause pilots to plan accordingly. Along 

with precipitation, the pilot must additionally consider the 

temperature, which if between –20° and +5 °C causes icing 

even during light precipitation. The returns from higher levels 

of intensity may obscure aircraft data blocks, and controllers 

may select the higher levels only on pilot request. When 

uncertainty exists about the weather ahead, ask the controller 

if the facility can display intensity levels—pilots of small 

aircraft should avoid intensity levels 3 or higher.

Tower En Route Control (TEC)

At many locations, instrument flights can be conducted 

entirely in terminal airspace. These tower en route control 

(TEC) routes are generally for aircraft operating below 

10,000 feet, and they can be found in the A/FD. Pilots desiring 

to use TEC should include that designation in the remarks 

section of the flight plan.

Pilots are not limited to the major airports at the city pairs 

listed in the A/FD. For example, a tower en route flight from 

an airport in New York (NYC) airspace could terminate 

at any airport within approximately 30 miles of Bradley 

International (BDL) airspace, such as Hartford (HFD). 

[Figure 2-10]

A valuable service provided by the automated radar 

equipment at terminal radar facilities is the Minimum Safe 

Altitude Warnings (MSAW). This equipment predicts an 

aircraft’s position in 2 minutes based on present path of 

flight—the controller issues a safety alert if the projected 

path encounters terrain or an obstruction. An unusually 

rapid descent rate on a nonprecision approach can trigger 

such an alert.

Air Route Traffic Control Center (ARTCC)

ARTCC facilities are responsible for maintaining separation 

between IFR flights in the en route structure. Center radars 

(Air Route Surveillance Radar (ARSR)) acquire and track 

transponder returns using the same basic technology as 

terminal radars. [Figure 2-11]

Earlier Center radars display weather as an area of slashes 

(light precipitation) and Hs (moderate rainfall), as illustrated 

in Figure 2-12. Because the controller cannot detect higher 

levels of precipitation, pilots should be wary of areas 

showing moderate rainfall. Newer radar displays show 

weather as three levels of blue. Controllers can select the 

level of weather to be displayed. Weather displays of higher 

levels of intensity can make it difficult for controllers to 

see aircraft data blocks, so pilots should not expect ATC 

to keep weather displayed continuously.

Center airspace is divided into sectors in the same manner 

as terminal airspace; additionally, most Center airspace is 

divided by altitudes into high and low sectors. Each sector 

has a dedicated team of controllers and a selection of radio 

frequencies because each Center has a network of remote 

transmitter/receiver sites. All Center frequencies can be found 

in the back of the A/FD in the format shown in Figure 2-13;

they are also found on en route charts.

Each ARTCC’s area of responsibility covers several states; 

when flying from the vicinity of one remote communication 

site toward another, expect to hear the same controller on 

different frequencies.

Center Approach/Departure Control

The majority of airports with instrument approaches do not 

lie within terminal radar airspace and, when operating to or 

from these airports, pilots communicate directly with the 

Center controller. Departing from a tower-controlled airport, 

the tower controller provides instructions for contacting the 

appropriate Center controller. When departing an airport 

without an operating control tower, the clearance includes 

instructions such as “Upon entering controlled airspace, 

contact Houston Center on 126.5.” Pilots are responsible 

for terrain clearance until reaching the controller’s MVA. 

Simply hearing “Radar contact” does not relieve a pilot of 

this responsibility.

If obstacles in the departure path require a steeperthan-standard climb gradient (200 feet per nautical mile 

(FPNM)), then the controller advises the pilot. However, 

it is the pilot’s responsibility to check the departure airport 

listing in the A/FD to determine if there are trees or wires 

in the departure path. When in doubt, ask the controller for 

the required climb gradient.
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Academy Planned View Display 

° 

° 

° ° ° ° 

0013 31 29 89 A 

ILS 28R OP 

LVL LO 03 04 

12 49 

EM 

2AAL12 

7AAL13 

3DAL191 

5NWA194 

4N1212T 

CD 

SD050 

CN 

SD 

SN 

ILLEGAL ENTRY 

MHD 

B AAL629 1104 A 

D DAL629 1102 M 

C N41463 1124 B 

F N44125 RDR 

A UAL246 1103 C 

N 

085 

AAL728 

030 20 

N 

7N 

5N 4N 

UAL132 

040 22 

N 

N 

C 

040 

N44125 

RDR 15 S 

055 

ARTS III. 

System data area

Untracked target

Nonselect code with mode C 

Trackball position symbol

(inhibited when not in use)

Targets in suspend status

Coast/suspend tabular list

Readout area

Preview area

Arrival/departure tabular list

Tracked target center

Controlled partial data block

Partial data as seen by S

if worked by N

Tracked primary target

Untracked target select

code with mode C

Figure 2-9. The top image is a display as seen by controllers in an air traffic facility. It is an ARTS III (Automated Radar Terminal 

System). The display shown provides an explanation of the symbols in the graphic. The lower figure is an example of the Digital Bright 

Radar Indicator Tower Equipment (DBRITE) screen as seen by tower personnel. It provides tower controllers with a visual display 

of the airport surveillance radar, beacon signals, and data received from ARTS III. The display shown provides an explanation of the 

symbols in the graphic.

Outer marker 

Radar 

Indicates downwind alignment 

guide for 100L and 28R 

Delta 4210 

Aircraft number: N1388V

Type aircraft: Cessna 421

Alt: 4,000’ Descending, 180 knots

Obstacles 

VOR location 

Airport center 

Runway 16 

Indicates downwind alignment 

guide for 100R and 28L 

Various controls for the tower operator to select 

Runway’s 100R

Runway’s 100L

Scale: one line = 1 mile 

BRITE Scope screen 
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Figure 2-10. A portion of the New York area tower en route list (from the A/FD). Figure 9-10. A portion of the New York area Tower En Route List. 
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Figure 2-11. Center radar displays.

Figure 2-12. A center controller’s scope.

Figure 2-13. A/FD center frequencies listing.

A common clearance in these situations is “When able, 

proceed direct to the Astoria VOR...” The words “when able” 

mean to proceed to the waypoint, intersection, or NAVAID 

when the pilot is able to navigate directly to that point using 

onboard available systems providing proper guidance, usable 

signal, etc. If provided such guidance while flying VFR, the 

pilot remains responsible for terrain and obstacle clearance. 

Using the standard climb gradient, an aircraft is 2 miles 

from the departure end of the runway before it is safe to 

turn (400 feet above ground level (AGL)). When a Center 

controller issues a heading, a direct route, or says “direct 

when able,” the controller becomes responsible for terrain 

and obstruction clearance.

Another common Center clearance is “Leaving (altitude) 

fly (heading) or proceed direct when able.” This keeps the 

terrain/obstruction clearance responsibility in the flight deck 

until above the minimum IFR altitude. A controller cannot 

issue an IFR clearance until an aircraft is above the minimum 

IFR altitude unless it is able to climb in VFR conditions.

On a Center controller’s scope, 1 NM is about 1

⁄28 of an inch. 

When a Center controller is providing Approach/Departure 

control services at an airport many miles from the radar 

antenna, estimating headings and distances is very difficult. 

Controllers providing vectors to final must set the range on 

their scopes to not more than 125 NM to provide the greatest 

possible accuracy for intercept headings. Accordingly, at 

locations more distant from a Center radar antenna, pilots 

should expect a minimum of vectoring.
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ATC radar systems cannot 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 is normally 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 implies 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.

Weather Avoidance Assistance

ATC’s first duty priority is to separate aircraft and issue 

safety alerts. ATC provides additional services to the extent 

possible, contingent upon higher priority duties and other 

factors including limitations of radar, volume of traffic, 

frequency congestion, and workload. Subject to the above 

factors/limitations, controllers issue pertinent information 

on weather or chaff areas; and if requested, assist pilots, to 

the extent possible, in avoiding areas of precipitation. Pilots 

should respond to a weather advisory by acknowledging the 

advisory and, if desired, requesting an alternate course of 

action, such as:

1. Request to deviate off course by stating the direction 

and number of degrees or miles needed to deviate from 

the original course;

2. Request a change of altitude; or

3. Request routing assistance to avoid the affected 

area. Because ATC radar systems cannot detect the 

presence or absence of clouds and turbulence, such 

assistance conveys no guarantee that the pilot will not 

encounter hazards associated with convective activity. 

Pilots wishing to circumnavigate precipitation areas 

by a specific distance should make their desires 

clearly known to ATC at the time of the request for 

services. Pilots must advise ATC when they can 

resume normal navigation.

IFR pilots shall not deviate from their assigned course or 

altitude without an ATC clearance. Plan ahead for possible 

course deviations because hazardous convective conditions 

can develop quite rapidly. This is important to consider 

because the precipitation data displayed on ARTCC radar 

scopes can be up to 6 minutes old, and thunderstorms can 

develop at rates exceeding 6,000 feet per minute (fpm). When 

encountering weather conditions that threaten the safety of 

the aircraft, the pilot may exercise emergency authority as 

ATC Inflight Weather Avoidance 

Assistance

ATC Radar Weather Displays

ATC radar systems 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, or the denser its reflective surface, the stronger 

the return. Radar weather processors indicate the intensity 

of reflective returns in terms of decibels with respect to the 

radar reflectively factor (dBZ). 

ATC systems cannot detect the presence or absence of 

clouds. ATC radar 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.”

All ATC facilities using radar weather processors with the 

ability to determine precipitation intensity describes the 

intensity to pilots as:

1. “LIGHT” (< 30 dBZ)

2. “MODERATE” (30 to 40 dBZ)

3. “HEAVY” (>40 to 50 dBZ)

4. “EXTREME” (>50 dBZ)

ARTCC controllers do not use the term “LIGHT” because 

their systems do not display “LIGHT” precipitation 

intensities. ATC facilities that, due to equipment limitations, 

cannot display the intensity levels of precipitation, 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 states, “INTENSITY UNKNOWN.”

ARTCC facilities normally use a Weather and Radar 

Processor (WARP) to display a mosaic of data obtained from 

multiple NEXRAD sites. The WARP processor is only used 

in ARTCC facilities. 

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 secondary 

system, the narrowband ARSR is utilized. The ARSR system 

can display two distinct levels of precipitation intensity that 

is described to pilots as “MODERATE” (30 to 40 dBZ) and 

“HEAVY to EXTREME” (>40 dBZ). 
2-12

Figure 2-14. High-resolution ATC displays used in PRM.

stated in 14 CFR part 91, section 91.3 should an immediate 

deviation from the assigned clearance be necessary and time 

does not permit approval by ATC.

Generally, when weather disrupts the flow of air traffic, 

greater workload demands are placed on the controller. 

Requests for deviations from course and other services 

should be made as far in advance as possible to better 

assure the controller’s ability to approve these requests 

promptly. When requesting approval to detour around 

weather activity, include the following information to 

facilitate the request:

1. The proposed point where detour commences; 

2. The proposed route and extent of detour (direction 

and distance);

3. The point where original route will be resumed;

4. Flight conditions (instrument meteorological 

conditions (IMC) or visual meteorological conditions 

(VMC);

5. Whether the aircraft is equipped with functioning 

airborne radar; and

6. Any further deviation that may become necessary.

To a large degree, the assistance that might be rendered 

by ATC depends upon the weather information available 

to controllers. Due to the extremely transitory nature of 

hazardous weather, the controller’s displayed precipitation 

information may be of limited value.

Obtaining IFR clearance or approval to circumnavigate 

hazardous weather can often be accommodated more readily 

in the en route areas away from terminals because there 

is usually less congestion and, therefore, greater freedom 

of action. In terminal areas, the problem is more acute 

because of traffic density, ATC coordination requirements, 

complex departure and arrival routes, and adjacent airports. 

As a consequence, controllers are less likely to be able to 

accommodate all requests for weather detours in a terminal 

area. Nevertheless, pilots should not hesitate to advise 

controllers of any observed hazardous weather and should 

specifically advise controllers if they desire circumnavigation 

of observed weather.

Pilot reports (PIREPs) of flight conditions help define the 

nature and extent of weather conditions in a particular area. 

These reports are disseminated by radio and electronic means 

to other pilots. Provide PIREP information to ATC regarding 

pertinent flight conditions, such as:

1. Turbulence;

2. Visibility;

3. Cloud tops and bases; and

4. The presence of hazards such as ice, hail, and lightning.

Approach Control Facility

An approach control facility is a terminal ATC facility 

that provides approach control service in the terminal area. 

Services are provided for arriving and departing VFR and 

IFR aircraft and, on occasion, en route aircraft. In addition, 

for airports with parallel runways with ILS or LDA 

approaches, the approach control facility provides monitoring 

of the approaches. 

Approach Control Advances

Precision Runway Monitor (PRM)

Over the past few years, a new technology has been installed 

at airports that permits a decreased separation distance 

between parallel runways. The system is called a Precision 

Runway Monitor (PRM) and is comprised of high-update 

radar, high-resolution ATC displays, and PRM-certified 

controllers. [Figure 2-14]

PRM Radar

The PRM uses a Monopulse Secondary Surveillance Radar 

(MSSR) that employs electronically-scanned antennas. 

Because the PRM has no scan rate restrictions, it is capable 

of providing a faster update rate (up to 1.0 second) over 

conventional systems, thereby providing better target 

presentation in terms of accuracy, resolution, and track 

prediction. The system is designed to search, track, process, 

and display SSR-equipped aircraft within airspace of over 

30 miles in range and over 15,000 feet in elevation. Visual 

and audible alerts are generated to warn controllers to take 

corrective actions. 
2-13

26L

8R 

Intersection Alpha 

NO TRANSGRESSION ZONE (NTZ) NO TRANSGRESSION ZONE (NTZ)

26R

8L 

Figure 9-XX. ATC displays used in PRM. 

Intersection Beta 

Figure 2-15. Aircraft management using PRM. (Note the no transgression zone (NTZ) and how the aircraft are separated.)

PRM Benefits

Typically, PRM is used with dual approaches with 

centerlines separated less than 4,300 feet but not less 

than 3,000 feet (under most conditions). [Figure 2-15]

Separating the two final approach courses is a No 

Transgression Zone (NTZ) with surveillance of that zone 

provided by two controllers, one for each active approach. 

The system tracking software provides PRM monitor 

controllers with aircraft identification, position, speed, 

projected position, as well as visual and aural alerts. 

Control Sequence

The IFR system is flexible and accommodating if pilots 

do their homework, have as many frequencies as possible 

written down before they are needed, and have an alternate 

in mind if the flight cannot be completed as planned. 

Pilots should familiarize themselves with all the facilities 

and services available along the planned route of flight. 

[Figure 2-16] Always know where the nearest VFR 

conditions can be found, and be prepared to head in that 

direction if the situation deteriorates.

A typical IFR flight, with departure and arrival at airports with 

control towers, would use the ATC facilities and services in 

the following sequence:

1. FSS: Obtain a weather briefing for a departure, 

destination and alternate airports, and en route 

conditions, and then file a flight plan by calling 

1-800-WX-BRIEF.

2. ATIS: Preflight complete, listen for present conditions 

and the approach in use.

3. Clearance Delivery: Prior to taxiing, obtain a 

departure clearance.
2-14

Figure 2-16. ATC facilities, services, and radio call signs.
2-15

4. Ground Control: Noting that the flight is IFR, receive 

taxi instructions.

5. Tower: Pre-takeoff checks complete, receive clearance 

to takeoff.

6. Departure Control: Once the transponder “tags up” 

with the ARTS, the tower controller instructs the pilot 

to contact Departure to establish radar contact.

7. ARTCC: After departing the departure controller’s 

airspace, aircraft is handed off to Center, who 

coordinates the flight while en route. Pilots may 

be in contact with multiple ARTCC facilities; they 

coordinate the hand-offs.

8. EFAS/ Hazardous Inflight Weather Advisory Service 

(HIWAS): Coordinate with ATC before leaving their 

frequency to obtain inflight weather information.

9. ATIS: Coordinate with ATC before leaving their 

frequency to obtain ATIS information.

10. Approach Control: Center hands off to approach 

control where pilots receive additional information 

and clearances.

11. Tower: Once cleared for the approach, pilots are 

instructed to contact tower control; the flight plan is 

canceled by the tower controller upon landing.

A typical IFR flight, with departure and arrival at airports 

without operating control towers, would use the ATC 

facilities and services in the following sequence:

1. FSS: Obtain a weather briefing for departure, 

destination, and alternate airports, and en route 

conditions, and then file a flight plan by calling 

1-800-WX-BRIEF. Provide the latitude/longitude 

description for small airports to ensure that Center is 

able to locate departure and arrival locations.

2. FSS or UNICOM: ATC clearances can be filed and 

received on the UNICOM frequency if the licensee 

has made arrangements with the controlling ARTCC; 

otherwise, file with FSS via telephone. Be sure all 

preflight preparations are complete before filing. The 

clearance includes a clearance void time. Pilots must 

be airborne prior to the void time.

3. ARTCC: After takeoff, establish contact with Center. 

During the flight, pilots may be in contact with multiple 

ARTCC facilities; ATC coordinates the hand-offs.

4. EFAS/HIWAS: Coordinate with ATC before leaving 

their frequency to obtain inflight weather information.

5. Approach Control: Center hands off to approach 

control where pilots receive additional information 

and clearances. If a landing under VMC is possible, 

pilots may cancel their IFR clearance before landing.

Letters of Agreement (LOA)

The ATC system is indeed a system and very little happens by 

chance. As a flight progresses, controllers in adjoining sectors 

or adjoining Centers coordinate its handling by telephone 

or by computer. Where there is a boundary between the 

airspace controlled by different facilities, the location and 

altitude for hand-off is determined by Letters of Agreement 

(LOA) negotiated between the two facility managers. This 

information is not available to pilots in any Federal Aviation 

Administration (FAA) publication. For this reason, it is good 

practice to note on the en route chart the points at which 

hand-offs occur. Each time a flight is handed off to a different 

facility, the controller knows the altitude and location—this 

was part of the hand-off procedure.
2-16
3-1

Introduction

Human factors is a broad field that examines the interaction 

between people, machines, and the environment for the 

purpose of improving performance and reducing errors. As 

aircraft became more reliable and less prone to mechanical 

failure, the percentage of accidents related to human factors 

increased. Some aspect of human factors now accounts for 

over 80 percent of all accidents. Pilots, who have a good 

understanding of human factors, are better equipped to plan 

and execute a safe and uneventful flight.

Flying in instrument meteorological conditions (IMC) can 

result in sensations that are misleading to the body’s sensory 

system. A safe pilot needs to understand these sensations and 

effectively counteract them. Instrument flying requires a pilot 

to make decisions using all available resources.

The elements of human factors covered in this chapter include 

sensory systems used for orientation and illusions in flight. 

For more information about physiological and psychological 

factors, medical factors, aeronautical decision-making 

(ADM), and crew resource management (CRM), refer to the 

Pilot’s Handbook of Aeronautical Knowledge.

Human 

Factors

Chapter 3
3-2

Figure 3-1. Rubik’s cube graphic depicting the visual processing of information.

Sensory Systems for Orientation

Orientation is the awareness of the position of the aircraft 

and of oneself in relation to a specific reference point. 

Disorientation is the lack of orientation, and spatial 

disorientation specifically refers to the lack of orientation 

with regard to position in space and to other objects.

Orientation is maintained through the body’s sensory organs 

in three areas: visual, vestibular, and postural. The eyes 

maintain visual orientation. The motion sensing system in 

the inner ear maintains vestibular orientation. The nerves in 

the skin, joints, and muscles of the body maintain postural 

orientation. When healthy human beings are in their natural 

environment, these three systems work well. When the 

human body is subjected to the forces of flight, these senses 

can provide misleading information. It is this misleading 

information that causes pilots to become disoriented.

Eyes

Of all the senses, vision is most important in providing 

information to maintain safe flight. Even though the human 

eye is optimized for day vision, it is also capable of vision 

in very low light environments. During the day, the eye uses 

receptors called cones, while at night, vision is facilitated 

by the use of rods. Both of 

these provide a level of vision 

optimized for the lighting 

conditions that they were 

intended. That is, cones are 

ineffective at night and rods 

are ineffective during the day.

Rods, which contain rhodopsin 

(called visual purple), are 

especially sensitive to light 

and increased light washes out 

the rhodopsin compromising 

the night vision. Hence, when 

strong light is momentarily 

introduced at night, vision 

may be totally ineffective as 

the rods take time to become 

effective again in darkness. 

Smoking, alcohol, oxygen 

deprivation, and age affect 

vision, especially at night. It 

should be noted that at night, 

oxygen deprivation, such 

as one caused from a climb 

to a high altitude, causes a 

significant reduction in vision. 

A return back to the lower 

altitude does not restore a pilot’s vision in the same transitory 

period used at the climb altitude. 

The eye also has two blind spots. The day blind spot is the 

location on the light sensitive retina where the optic nerve 

fiber bundle (which carries messages from the eye to the 

brain) passes through. This location has no light receptors, 

and a message cannot be created there to be sent to the brain. 

The night blind spot is due to a concentration of cones in an 

area surrounding the fovea on the retina. Because there are 

no rods in this area, direct vision on an object at night will 

disappear. As a result, off-center viewing and scanning at 

night is best for both obstacle avoidance and to maximize 

situational awareness (SA). (See the Pilot’s Handbook of 

Aeronautical Knowledge and the Aeronautical Information 

Manual (AIM) for detailed reading.)

The brain also processes visual information based upon color, 

relationship of colors, and vision from objects around us. 

Figure 3-1 demonstrates the visual processing of information. 

The brain assigns color based on many items, to include an 

object’s surroundings. In the figure below, the orange square 

on the shaded side of the cube is actually the same color 

as the brown square in the center of the cube’s top face. 
3-3

Figure 3-2. Shepard’s tables illustrating problems with perception as both tables are the same length.

Isolating the orange square from surrounding influences 

will reveal that it is actually brown. The application to a real 

environment is evident when processing visual information 

that is influenced by surroundings. The ability to pick out an 

airport in varied terrain or another aircraft in a light haze are 

examples of problems with interpretation that make vigilance 

all the more necessary.

Figure 3-2 illustrates problems with perception. Both tables 

are the same lengths. Objects are easily misinterpreted in 

size to include both length and width. Being accustomed to 

a 75-foot-wide runway on flat terrain is most likely going to 

influence a pilot’s perception of a wider runway on uneven 

terrain simply because of the inherent processing experience.

Vision Under Dim and Bright Illumination

Under conditions of dim illumination, aeronautical charts and 

aircraft instruments can become unreadable unless adequate 

flight deck lighting is available. In darkness, vision becomes 

more sensitive to light. This process is 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 flight deck lighting.

Red light distorts colors (filters the red spectrum), especially 

on aeronautical charts, and makes it very difficult for the 

eyes to focus on objects inside the aircraft. Pilots should 

use it only where optimum outside night vision capability is 

necessary. White flight deck lighting (dim lighting) should 

be available when needed for map and instrument reading, 

especially under IMC conditions.

Since any degree of dark adaptation is lost within a few 

seconds of viewing a bright light, pilots should close one eye 

when using a light to preserve some degree of night vision. 

During night flights in the vicinity of lightning, flight deck 

lights should be turned up to help prevent loss of night vision 

due to the bright flashes. Dark adaptation is also impaired by 

exposure to cabin pressure altitudes above 5,000 feet, carbon 

monoxide inhaled through smoking, deficiency of Vitamin 

A in the diet, and prolonged exposure to bright sunlight.

During flight in visual meteorological conditions (VMC), 

the eyes are the major orientation source and usually 

provide accurate and reliable information. Visual cues 

usually prevail over false sensations from other sensory 

systems. When these visual cues are taken away, as they 

are in IMC, false sensations can cause the pilot to quickly 

become disoriented.

An effective way to counter these false sensations is to 

recognize the problem, disregard the false sensations, rely 

on the flight instruments, and use the eyes to determine the 

aircraft attitude. The pilot must have an understanding of 

the problem and the skill to control the aircraft using only 

instrument indications.
3-4

YAW 

ROLL 

YAW 

PITCH 

PITCH 

ROLL 

Eardrum 

Eustachian tube

Bone 

Ear canal

Bone

Ear canal

Eardrum

Eustachian tube

The semicircular tubes are 

arranged at approximately 

right angles to each other, in 

the roll, pitch, and yaw axes. 

Figure 3-4. Angular acceleration and the semicircular tubes.

Saccule 

Semicircular canals

Utricle 

Cochlea 

Tubular ducts

containing endolymph

Ampullae 

Semicircular canals

Endolymph fluid

Cupola 

Filaments of hair cells

Hair cells

Vestibular nerve

Ampulla of a

semicircular

canal

Cupola 

Sensory hairs

Otolith organ

Vestibular nerve

The motion sensing system is 

located in each inner ear in the 

approximate position shown. 

Figure 3-3. Inner ear orientation.

Ears

The inner ear has two major parts concerned with orientation: 

the semicircular canals and the otolith organs. [Figure 3-3] The 

semicircular canals detect angular acceleration of the body, 

while the otolith organs detect linear acceleration and gravity. 

The semicircular canals consist of three tubes at approximate 

right angles to each other, each located on one of three axes: 

pitch, roll, or yaw as illustrated in Figure 3-4. Each canal is 

filled with a fluid called endolymph fluid. In the center of 

the canal is the cupola, a gelatinous structure that rests upon 

sensory hairs located at the end of the vestibular nerves. It 

is the movement of these hairs within the fluid that causes 

sensations of motion.

Because of the friction between the fluid and the canal, it 

may take about 15–20 seconds for the fluid in the ear canal 

to reach the same speed as the canal’s motion.

To illustrate what happens during a turn, visualize the 

aircraft in straight-and-level flight. With no acceleration of 

the aircraft, the hair cells are upright, and the body senses 

that no turn has occurred. Therefore, the position of the hair 

cells and the actual sensation correspond.

Placing the aircraft into a turn puts the semicircular canal and 

its fluid into motion, with the fluid within the semicircular 

canal lagging behind the accelerated canal walls. [Figure 3-5]

This lag creates a relative movement of the fluid within the 

canal. The canal wall and the cupula move in the opposite 

direction from the motion of the fluid.

The brain interprets the movement of the hairs to be a turn in 

the same direction as the canal wall. The body correctly senses 

that a turn is being made. If the turn continues at a constant 

rate for several seconds or longer, the motion of the fluid in 
3-5

Normal 

Accelerating 

Head tilted back 

Figure 3-6. Linear acceleration.

Endolymph 

Tube 

Cupola 

No turning 

No sensation. 

Start of turn 

Sensation of turning 

as moving fluid deflects 

hairs. 

Constant rate turn 

No sensation after fluid 

accelerates to same 

speed as tube wall. 

Turn stopped 

Sensation of turning in 

opposite direction as moving 

fluid deflects hairs in opposite 

direction. 

Figure 3-5. Angular acceleration.

the canals catches up with the canal walls. The hairs are no 

longer bent, and the brain receives the false impression that 

turning has stopped. Thus, the position of the hair cells and 

the resulting sensation during a prolonged, constant turn in 

either direction results in the false sensation of no turn.

When the aircraft returns to straight-and-level flight, the fluid 

in the canal moves briefly in the opposite direction. This sends 

a signal to the brain that is falsely interpreted as movement 

in the opposite direction. In an attempt to correct the falsely 

perceived turn, the pilot may reenter the turn placing the 

aircraft in an out-of-control situation.

The otolith organs detect linear acceleration and gravity in a 

similar way. Instead of being filled with a fluid, a gelatinous 

membrane containing chalk-like crystals covers the sensory 

hairs. When the pilot tilts his or her head, the weight of these 

crystals causes this membrane to shift due to gravity, and 

the sensory hairs detect this shift. The brain orients this new 

position to what it perceives as vertical. Acceleration and 

deceleration also cause the membrane to shift in a similar 

manner. Forward acceleration gives the illusion of the head 

tilting backward. [Figure 3-6] As a result, during takeoff and 

while accelerating, the pilot may sense a steeper than normal 

climb resulting in a tendency to nose-down.

Nerves

Nerves in the body’s skin, muscles, and joints constantly 

send signals to the brain, which signals the body’s relation to 

gravity. These signals tell the pilot his or her current position. 

Acceleration is felt as the pilot is pushed back into the seat. 

Forces, created in turns, can lead to false sensations of the 

true direction of gravity and may give the pilot a false sense 

of which way is up. 

Uncoordinated turns, especially climbing turns, can cause 

misleading signals to be sent to the brain. Skids and slips 

give the sensation of banking or tilting. Turbulence can create 

motions that confuse the brain as well. Pilots need to be aware 

that fatigue or illness can exacerbate these sensations and 

ultimately lead to subtle incapacitation.

Illusions Leading to Spatial 

Disorientation

The sensory system responsible for most of the illusions 

leading to spatial disorientation is the vestibular system. 

Visual illusions can also cause spatial disorientation.

Vestibular Illusions

The Leans

A condition called “the leans” can result when a banked 

attitude, to the left for example, may be entered too slowly 

to set in motion the fluid in the “roll” semicircular tubes. 

[Figure 3-5] An abrupt correction of this attitude sets the 

fluid in motion, creating the illusion of a banked attitude to 

the right. The disoriented pilot may make the error of rolling 

the aircraft into the original left banked attitude, or if level 

flight is maintained, feel compelled to lean in the perceived 

vertical plane until this illusion subsides. 
3-6

Graveyard spiral 

Graveyard spin Correct path

Figure 3-7. Graveyard spiral.

Coriolis Illusion

The coriolis illusion occurs when a pilot has been in a turn 

long enough for the fluid in the ear canal to move at the same 

speed as the canal. A movement of the head in a different 

plane, such as looking at something in a different part of the 

flight deck, may set the fluid moving and create the illusion 

of turning or accelerating on an entirely different axis. 

This action causes the pilot to think the aircraft is doing a 

maneuver that it is not. The disoriented pilot may maneuver 

the aircraft into a dangerous attitude in an attempt to correct 

the aircraft’s perceived attitude.

For this reason, it is important that pilots develop an 

instrument cross-check or scan that involves minimal 

head movement. Take care when retrieving charts and 

other objects in the flight deck—if something is dropped, 

retrieve it with minimal head movement and be alert for 

the coriolis illusion.

Graveyard Spiral

As in other illusions, a pilot in a prolonged coordinated, 

constant-rate turn, will have the illusion of not turning. During 

the recovery to level flight, the pilot experiences the sensation 

of turning in the opposite direction. The disoriented pilot may 

return the aircraft to its original turn. Because an aircraft tends 

to lose altitude in turns unless the pilot compensates for the 

loss in lift, the pilot may notice a loss of altitude. The absence 

of any sensation of turning creates the illusion of being in a 

level descent. The pilot may pull back on the controls in an 

attempt to climb or stop the descent. This action tightens the 

spiral and increases the loss of altitude; hence, this illusion is 

referred to as a graveyard spiral. [Figure 3-7] At some point, 

this could lead to a loss of control by the pilot.

Somatogravic Illusion

A rapid acceleration, such as experienced during takeoff, 

stimulates the otolith organs in the same way as tilting the 

head backwards. This action creates the somatogravic illusion 

of being in a nose-up attitude, especially in situations without 

good visual references. The disoriented pilot may push the 

aircraft into a nose-low or dive attitude. A rapid deceleration 

by quick reduction of the throttle(s) can have the opposite 

effect with the disoriented pilot pulling the aircraft into a 

nose-up or stall attitude.

Inversion Illusion

An abrupt change from climb to straight-and-level flight can 

stimulate the otolith organs enough to create the illusion of 

tumbling backwards or inversion illusion. The disoriented 

pilot may push the aircraft abruptly into a nose-low attitude, 

possibly intensifying this illusion.

Elevator Illusion

An abrupt upward vertical acceleration, as can occur in 

an updraft, can stimulate the otolith organs to create the 

illusion of being in a climb. This is called elevator illusion. 

The disoriented pilot may push the aircraft into a nose-low 
3-7

Skid, slip, and uncoordinated turns feel alike. 

Pilots feel they are being forced sideways in their seat.

Level Coordinated turn Pull out 

Level skid Forward slip Uncoordinated turn 

Figure 3-8. Sensations from centrifugal force.

attitude. An abrupt downward vertical acceleration, usually 

in a downdraft, has the opposite effect with the disoriented 

pilot pulling the aircraft into a nose-up attitude.

Visual Illusions

Visual illusions are especially hazardous because pilots rely 

on their eyes for correct information. Two illusions that lead 

to spatial disorientation, false horizon and autokinesis, are 

concerned with only the visual system. 

False Horizon

A sloping cloud formation, an obscured horizon, an aurora 

borealis, a dark scene spread with ground lights and stars, 

and certain geometric patterns of ground lights can provide 

inaccurate visual information, or false horizon, for aligning 

the aircraft correctly with the actual horizon. The disoriented 

pilot may place the aircraft in a dangerous attitude. 

Autokinesis

In the dark, a stationary light will appear to move about when 

stared at for many seconds. The disoriented pilot could lose 

control of the aircraft in attempting to align it with the false 

movements of this light called autokinesis.

Postural Considerations

The postural system sends signals from the skin, joints, and 

muscles to the brain that are interpreted in relation to the 

Earth’s gravitational pull. These signals determine posture. 

Inputs from each movement update the body’s position to 

the brain on a constant basis. “Seat of the pants” flying is 

largely dependent upon these signals. Used in conjunction 

with visual and vestibular clues, these sensations can be 

fairly reliable. However, because of the forces acting upon 

the body in certain flight situations, many false sensations 

can occur due to acceleration forces overpowering gravity. 

[Figure 3-8] These situations include uncoordinated turns, 

climbing turns, and turbulence.

Demonstration of Spatial Disorientation

There are a number of controlled aircraft maneuvers a pilot 

can perform to experiment with spatial disorientation. While 

each maneuver normally creates a specific illusion, any false 

sensation is an effective demonstration of disorientation. Thus, 

even if there is no sensation during any of these maneuvers, 

the absence of sensation is still an effective demonstration 

in that it shows the inability to detect bank or roll. There are 

several objectives in demonstrating these various maneuvers.

1. They teach pilots to understand the susceptibility of 

the human system to spatial disorientation.

2. They demonstrate that judgments of aircraft attitude 

based on bodily sensations are frequently false.

3. They help lessen the occurrence and degree of 

disorientation through a better understanding of the 

relationship between aircraft motion, head movements, 

and resulting disorientation.

4. They help instill a greater confidence in relying on 

flight instruments for assessing true aircraft attitude.
3-8

A pilot should not attempt any of these maneuvers at 

low altitudes or in the absence of an instructor pilot or an 

appropriate safety pilot.

Climbing While Accelerating

With the pilot’s eyes closed, the instructor pilot maintains 

approach airspeed in a straight-and-level attitude for several 

seconds, and then accelerates while maintaining straightand-level attitude. The usual illusion during this maneuver, 

without visual references, is that the aircraft is climbing.

Climbing While Turning

With the pilot’s eyes still closed and the aircraft in a straightand-level attitude, the instructor pilot now executes, with a 

relatively slow entry, a well-coordinated turn of about 1.5 

positive G (approximately 50° bank) for 90°. While in the 

turn, without outside visual references and under the effect of 

the slight positive G, the usual illusion produced is that of a 

climb. Upon sensing the climb, the pilot should immediately 

open the eyes and see that a slowly established, coordinated 

turn produces the same feeling as a climb.

Diving While Turning

Repeating the previous procedure, with the exception that 

the pilot’s eyes should be kept closed until recovery from 

the turn is approximately one-half completed can create this 

sensation. With the eyes closed, the usual illusion is that the 

aircraft is diving.

Tilting to Right or Left

While in a straight-and-level attitude, with the pilot’s eyes 

closed, the instructor pilot executes a moderate or slight 

skid to the left with wings level. This creates the illusion of 

the body being tilted to the right. The same illusion can be 

sensed with a skid to the right with wings level, except the 

body feels it is being tilted to the left.

Reversal of Motion

This illusion can be demonstrated in any of the three planes of 

motion. While straight and level, with the pilot’s eyes closed, 

the instructor pilot smoothly and positively rolls the aircraft 

to approximately a 45° bank attitude. This creates the illusion 

of a strong sense of rotation in the opposite direction. After 

this illusion is noted, the pilot should open his or her eyes 

and observe that the aircraft is in a banked attitude. 

Diving or Rolling Beyond the Vertical Plane

This maneuver may produce extreme disorientation. While 

in straight-and-level flight, the pilot should sit normally, 

either with eyes closed or gaze lowered to the floor. The 

instructor pilot starts a positive, coordinated roll toward a 

30° or 40° angle of bank. As this is in progress, the pilot 

tilts his or her head forward, looks to the right or left, then 

immediately returns his or her head to an upright position. 

The instructor pilot should time the maneuver so the roll is 

stopped as the pilot returns his or her head upright. An intense 

disorientation is usually produced by this maneuver, and the 

pilot experiences the sensation of falling downward into the 

direction of the roll.

In the descriptions of these maneuvers, the instructor pilot is 

doing the flying, but having the pilot do the flying can also 

be a very effective demonstration. The pilot should close his 

or her eyes and tilt their head to one side. The instructor pilot 

tells the pilot what control inputs to perform. The pilot then 

attempts to establish the correct attitude or control input with 

eyes closed and head tilted. While it is clear the pilot has no 

idea of the actual attitude, he or she will react to what the 

senses are saying. After a short time, the pilot will become 

disoriented, and the instructor pilot then tells the pilot to 

look up and recover. The benefit of this exercise is the pilot 

experiences the disorientation while flying the aircraft.

Coping with Spatial Disorientation

To prevent illusions and their potentially disastrous 

consequences, pilots can:

1. Understand the causes of these illusions and remain 

constantly alert for them. Take the opportunity to 

understand and then experience spatial disorientation 

illusions in a device, such as a Barany chair, a 

Vertigon, or a Virtual Reality Spatial Disorientation 

Demonstrator.

2. Always obtain and understand preflight weather 

briefings.

3. Before flying in marginal visibility (less than 3 miles) 

or where a visible horizon is not evident such as flight 

over open water during the night, obtain training and 

maintain proficiency in airplane control by reference 

to instruments. 

4. Do not continue flight into adverse weather conditions 

or into dusk or darkness unless proficient in the use of 

flight instruments. If intending to fly at night, maintain 

night-flight currency and proficiency. Include crosscountry and local operations at various airfields.

5. Ensure that when outside visual references are used, 

they are reliable, fixed points on the Earth’s surface.

6. Avoid sudden head movement, particularly during 

takeoffs, turns, and approaches to landing.

7. Be physically tuned for flight into reduced visibility. 

Ensure proper rest, adequate diet, and, if flying at 

night, allow for night adaptation. Remember that 

illness, medication, alcohol, fatigue, sleep loss, and 
3-9

Water Refraction

Rain on the windscreen can create an illusion of being at a 

higher altitude due to the horizon appearing lower than it is. 

This can result in the pilot flying a lower approach.

Haze

Atmospheric haze can create an illusion of being at a greater 

distance and height from the runway. As a result, the pilot 

has a tendency to be low on the approach. Conversely, 

extremely clear air (clear bright conditions of a high attitude 

airport) can give the pilot the illusion of being closer than 

he or she actually is, resulting in a high approach that may 

cause an overshoot or go around. The diffusion of light due 

to water particles on the windshield can adversely affect 

depth perception. The lights and terrain features normally 

used to gauge height during landing become less effective 

for the pilot.

Fog

Flying into fog can create an illusion of pitching up. Pilots 

who do not recognize this illusion often steepen the approach 

quite abruptly.

Ground Lighting Illusions

Lights along a straight path, such as a road or 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 

often fly a higher approach.

How To Prevent Landing Errors Due to 

Optical Illusions

To prevent these illusions and their potentially hazardous 

consequences, pilots can:

1. Anticipate the possibility of visual illusions during 

approaches to unfamiliar airports, particularly at night 

or in adverse weather conditions. Consult airport 

diagrams and the Airport/Facility Directory (A/FD) 

for information on runway slope, terrain, and lighting.

2. Make frequent reference to the altimeter, especially 

during all approaches, day and night.

3. If possible, conduct aerial visual inspection of 

unfamiliar airports before landing.

4. Use Visual Approach Slope Indicator (VASI) or 

Precision Approach Path Indicator (PAPI) systems 

for a visual reference or an electronic glideslope, 

whenever they are available.

mild hypoxia are likely to increase susceptibility to 

spatial disorientation.

8. Most importantly, become proficient in the use of 

flight instruments and rely upon them. Trust the 

instruments and disregard your sensory perceptions.

The sensations that lead to illusions during instrument 

flight conditions are normal perceptions experienced by 

pilots. These undesirable sensations cannot be completely 

prevented, but through training and awareness, pilots can 

ignore or suppress them by developing absolute reliance 

on the flight instruments. As pilots gain proficiency in 

instrument flying, they become less susceptible to these 

illusions and their effects.

Optical Illusions

Of the senses, vision is the most important for safe 

flight. However, various terrain features and atmospheric 

conditions can create optical illusions. These illusions 

are primarily associated with landing. Since pilots 

must transition from reliance on instruments to visual 

cues outside the flight deck for landing at the end of an 

instrument approach, it is imperative they be aware of the 

potential problems associated with these illusions and take 

appropriate corrective action. The major illusions leading 

to landing errors are described below.

Runway Width Illusion

A narrower-than-usual runway can create an illusion the 

aircraft is at a higher altitude than it actually is, especially 

when runway length-to-width relationships are comparable. 

[Figure 3-9A] 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-than-usual 

runway can have the opposite effect with the risk of leveling 

out high and landing hard or overshooting the runway.

Runway and Terrain Slopes Illusion

An upsloping runway, upsloping terrain, or both can create 

an illusion the aircraft is at a higher altitude than it actually 

is. [Figure 3-9B] The pilot who does not recognize this 

illusion will fly a lower approach. Downsloping runways and 

downsloping approach terrain can have the opposite effect.

Featureless Terrain Illusion

An absence of surrounding ground features, as in an 

overwater approach, over darkened areas, or terrain made 

featureless by snow, can create an illusion the aircraft is at 

a higher altitude than it actually is. This illusion, sometimes 

referred to as the “black hole approach,” causes pilots to fly 

a lower approach than is desired.
3-10

25

25

Normal Approach 

Normal Approach 

25 25

25 Normal Approach 

25 Normal Approach 

Downsloping runway Upsloping runway 

Downsloping runway Upsloping runway 

Narrower runway Wider runway 

Narrower runway Wider runway

Normal approach 

Approach due to illusion 

Figure 3-9A

Runway width illusion

• A narrower-than-usual runway can 

 created an illusion that the aircraft 

 is higher than it actually is, leading 

 to a lower approach.

• A wider-than-usual runway can 

 create an illusion that the aircraft is 

 lower than it actually is, leading to 

 a higher approach.

Figure 3-9B

Runway slope illusion

• A downsloping runway can create 

 the illusion that the aircraft is lower 

 than it actually is, leading to a 

 higher approach.

• An upsloping runway can create 

 the illusion that the aircraft is higher 

 than it actually is, leading to a lower 

 approach.

Figure 3-9. Runway width and slope illusions.

5. Utilize the visual descent point (VDP) found on many 

nonprecision instrument approach procedure charts.

6. Recognize that the chances of being involved in an 

approach accident increase when some emergency or 

other activity distracts from usual procedures.

7. Maintain optimum proficiency in landing procedures.
4-1

Introduction

Several factors affect aircraft performance including the 

atmosphere, aerodynamics, and aircraft icing. Pilots need an 

understanding of these factors for a sound basis for prediction 

of aircraft response to control inputs, especially with regard 

to instrument approaches, while holding, and when operating 

at reduced airspeed in instrument meteorological conditions 

(IMC). Although these factors are important to the pilot flying 

visual flight rules (VFR), they must be even more thoroughly 

understood by the pilot operating under instrument flight 

rules (IFR). Instrument pilots rely strictly on instrument 

indications to precisely control the aircraft; therefore, they 

must have a solid understanding of basic aerodynamic 

principles in order to make accurate judgments regarding 

aircraft control inputs. 

Aerodynamic 

Factors

Chapter 4
4-2

Leading edge

Mean camber line

Mean chord line Lower camber

Upper camber

Trailing edge

Figure 4-1. The airfoil.

Relative wind

Chord line

V 

L 

D 

R 

C/4 

C 

MC/4

Figure 4-2. Angle of attack and relative wind.

The Wing

To understand aerodynamic forces, a pilot needs to 

understand basic terminology associated with airfoils. 

Figure 4-1 illustrates a typical airfoil. 

The chord line is the straight line intersecting the leading 

and trailing edges of the airfoil, and the term chord refers 

to the chord line longitudinal length (length as viewed from 

the side).

The mean camber is a line located halfway between the 

upper and lower surfaces. Viewing the wing edgewise, the 

mean camber connects with the chord line at each end. The 

mean camber is important because it assists in determining 

aerodynamic qualities of an airfoil. The measurement of 

the maximum camber; inclusive of both the displacement 

of the mean camber line and its linear measurement from 

the end of the chord line, provide properties useful in 

evaluating airfoils. 

Review of Basic Aerodynamics

The instrument pilot must understand the relationship 

and differences between several factors that affect the 

performance of an aircraft in flight. Also, it is crucial to 

understand how the aircraft reacts to various control and 

power changes, because the environment in which instrument 

pilots fly has inherent hazards not found in visual flying. The 

basis for this understanding is found in the four forces acting 

on an aircraft and Newton’s Three Laws of Motion.

Relative Wind is the direction of the airflow with respect to 

an airfoil. 

Angle of Attack (AOA) is the acute angle measured between 

the relative wind, or flightpath and the chord of the airfoil. 

[Figure 4-2]

Flightpath is the course or track along which the aircraft is 

flying or is intended to be flown. 

The Four Forces

The four basic forces [Figure 4-3] acting upon an aircraft in 

flight are lift, weight, thrust, and drag.

Lift

Lift is a component of the total aerodynamic force on an 

airfoil and acts perpendicular to the relative wind. Relative 

wind is the direction of the airflow with respect to an airfoil. 

This force acts straight up from the average (called mean) 

center of pressure (CP), which is called the center of lift. It 

should be noted that it is a point along the chord line of an 

airfoil through which all aerodynamic forces are considered 

to act. The magnitude of lift varies proportionately with 

speed, air density, shape and size of the airfoil, and AOA. 

During straight-and-level flight, lift and weight are equal.
4-3

Roll 

Pitch 

Yaw 

x 

z y 

Left

aileron

Right aileron

Rudder 

Vertical

stabilizer

Horizontal

stabilizer

Elevator 

Wing 

Lift Weight

Drag

Thrust

Figure 4-3. The four forces and three axes of rotation.

Weight

Weight is the force exerted by an aircraft from the pull of 

gravity. It acts on an aircraft through its center of gravity (CG) 

and is straight down. This should not be confused with the 

center of lift, which can be significantly different from the 

CG. As an aircraft is descending, weight is greater than lift.

Thrust

Thrust is the forward force produced by the powerplant/

propeller or rotor. It opposes or overcomes the force of drag. 

As a general rule, it acts parallel to the longitudinal axis.

Drag

Drag is the net aerodynamic force parallel to the relative 

wind and is generally a sum of two components: induced 

drag and parasite drag.

Induced Drag

Induced drag is caused from the creation of lift and increases 

with AOA. Therefore, if the wing is not producing lift, induced 

drag is zero. Conversely, induced drag decreases with airspeed. 

Parasite Drag

Parasite drag is all drag not caused from the production of 

lift. Parasite drag is created by displacement of air by the 

aircraft, turbulence generated by the airfoil, and the hindrance 

of airflow as it passes over the surface of the aircraft or 

components. All of these forces create drag not from the 

production of lift but the movement of an object through an 

air mass. Parasite drag increases with speed and includes skin 

friction drag, interference drag, and form drag.

• Skin Friction Drag

Covering the entire “wetted” surface of the aircraft is a thin 

layer of air called a boundary layer. The air molecules on the 

surface have zero velocity in relation to the surface; however, 

the layer just above moves over the stagnant molecules 

below because it is pulled along by a third layer close to 

the free stream of air. The velocities of the layers increase 

as the distance from the surface increases until free stream 

velocity is reached, but all are affected by the free stream. 

The distance (total) between the skin surface and where free 

stream velocity is reached is called the boundary layer. At 

subsonic levels the cumulative layers are about the thickness 

of a playing card, yet their motion sliding over one another 

creates a drag force. This force retards motion due to the 

viscosity of the air and is called skin friction drag. Because 

skin friction drag is related to a large surface area its affect 

on smaller aircraft is small versus large transport aircraft 

where skin friction drag may be considerable.

• Interference Drag

Interference drag is generated by the collision of airstreams 

creating eddy currents, turbulence, or restrictions to smooth 

flow. For instance, the airflow around a fuselage and around 

the wing meet at some point, usually near the wing’s root. 

These airflows interfere with each other causing a greater drag 

than the individual values. This is often the case when external 

items are placed on an aircraft. That is, the drag of each item 

individually, added to that of the aircraft, are less than that 

of the two items when allowed to interfere with one another.
4-4

Outside

force

Net

forces

Path 

Apply down

elevator

Path 

Net forces

Figure 4-4. Newton’s First Law of Motion: the Law of Inertia.

Time 

300 hp 2,000 lb

150 hp 2,000 lb

= Acceleration Force 

Mass 

Figure 4-5. Newton’s Second Law of Motion: the Law of Momentum.

• Form Drag

Form drag is the drag created because of the shape of a 

component or the aircraft. If one were to place a circular 

disk in an air stream, the pressure on both the top and bottom 

would be equal. However, the airflow starts to break down 

as the air flows around the back of the disk. This creates 

turbulence and hence a lower pressure results. Because the 

total pressure is affected by this reduced pressure, it creates 

a drag. Newer aircraft are generally made with consideration 

to this by fairing parts along the fuselage (teardrop) so that 

turbulence and form drag is reduced.

Total lift must overcome the total weight of the aircraft, which 

is comprised of the actual weight and the tail-down force used 

to control the aircraft’s pitch attitude. Thrust must overcome 

total drag in order to provide forward speed with which to 

produce lift. Understanding how the aircraft’s relationship 

between these elements and the environment provide proper 

interpretation of the aircraft’s instruments.

Newton’s First Law, the Law of Inertia

Newton’s First Law of Motion is the Law of Inertia. It states 

that a body at rest will remain at rest, and a body in motion 

will remain in motion, at the same speed and in the same 

direction until affected by an outside force. The force with 

which a body offers resistance to change is called the force of 

inertia. Two outside forces are always present on an aircraft 

in flight: gravity and drag. The pilot uses pitch and thrust 

controls to counter or change these forces to maintain the 

desired flightpath. If a pilot reduces power while in straightand-level flight, the aircraft will slow due to drag. However, 

as the aircraft slows there is a reduction of lift, which causes 

the aircraft to begin a descent due to gravity. [Figure 4-4]

Newton’s Second Law, the Law of Momentum

Newton’s Second Law of Motion is the Law of Momentum, 

which states that a body will accelerate in the same direction 

as the force acting upon that body, and the acceleration 

will be directly proportional to the net force and inversely 

proportional to the mass of the body. Acceleration refers 

either to an increase or decrease in velocity, although 

deceleration is commonly used to indicate a decrease. This 

law governs the aircraft’s ability to change flightpath and 

speed, which are controlled by attitude (both pitch and bank) 

and thrust inputs. Speeding up, slowing down, entering 

climbs or descents, and turning are examples of accelerations 

that the pilot controls in everyday flight. [Figure 4-5]

Newton’s Third Law, the Law of Reaction

Newton’s Third Law of Motion is the Law of Reaction, 

which states that for every action there is an equal and 

opposite reaction. As shown in Figure 4-6, the action of 

the jet engine’s thrust or the pull of the propeller lead to the 

reaction of the aircraft’s forward motion. This law is also 

responsible for a portion of the lift that is produced by a wing, 

from the downward deflection of the airflow around it. This 

downward force of the relative wind results in an equal but 

opposite (upward) lifting force created by the airflow over 

the wing. [Figure 4-6]

Atmosphere

The atmosphere is the envelope of air which surrounds the 

Earth. A given volume of dry air contains about 78 percent 

nitrogen, 21 percent oxygen, and about 1 percent other gases 

such as argon, carbon dioxide, and others to a lesser degree. 
4-5

Reaction Action 

Action 

Reaction 

Figure 4-6. Newton’s Third Law of Motion: the Law of Reaction.

Although seemingly light, air does have weight and a one 

square inch column of the atmosphere at sea level weighs 

approximately 14.7 pounds. About one-half of the air by 

weight is within the first 18,000 feet. The remainder of the 

air is spread over a vertical distance in excess of 1,000 miles. 

Air density is a result of the relationship between temperature 

and pressure. Air density is inversely related to temperature 

and directly related to pressure. For a constant pressure to be 

maintained as temperature increases, density must decrease, 

and vice versa. For a constant temperature to be maintained 

as pressure increases, density must increase, and vice versa. 

These relationships provide a basis for understanding 

instrument indications and aircraft performance.

Layers of the Atmosphere

There are several layers to the atmosphere with the 

troposphere being closest to the Earth’s surface extending to 

about 60,000 feet at the equator. Following is the stratosphere, 

mesosphere, ionosphere, thermosphere, and finally the 

exosphere. The tropopause is the thin layer between the 

troposphere and the stratosphere. It varies in both thickness 

and altitude but is generally defined where the standard 

lapse (generally accepted at 2 °C per 1,000 feet) decreases 

significantly (usually down to 1 °C or less).

International Standard Atmosphere (ISA)

The International Civil Aviation Organization (ICAO) 

established the ICAO Standard Atmosphere as a way 

of creating an international standard for reference and 

performance computations. Instrument indications and 

aircraft performance specifications are derived using this 

standard as a reference. Because the standard atmosphere is 

a derived set of conditions that rarely exist in reality, pilots 

need to understand how deviations from the standard affect 

both instrument indications and aircraft performance.

In the standard atmosphere, sea level pressure is 29.92 inches 

of mercury ("Hg) and the temperature is 15 °C (59 °F). The 

standard lapse rate for pressure is approximately a 1 "Hg 

decrease per 1,000 feet increase in altitude. The standard 

lapse rate for temperature is a 2 °C (3.6 °F) decrease per 

1,000 feet increase, up to the top of the stratosphere. Since 

all aircraft performance is compared and evaluated in 

the environment of the standard atmosphere, all aircraft 

performance instrumentation is calibrated for the standard 

atmosphere. Because the actual operating conditions rarely, 

if ever, fit the standard atmosphere, certain corrections must 

apply to the instrumentation and aircraft performance. For 

instance, at 10,000 ISA predicts that the air pressure should be 

19.92 "Hg (29.92 "Hg – 10 "Hg = 19.92 "Hg) and the outside 

temperature at –5 °C (15 °C – 20 °C). If the temperature 

or the pressure is different than the International Standard 

Atmosphere (ISA) prediction an adjustment must be made to 

performance predictions and various instrument indications. 

Pressure Altitude

Pressure altitude is the height above the standard datum 

plane (SDP). The aircraft altimeter is essentially a sensitive 

barometer calibrated to indicate altitude in the standard 

atmosphere. If the altimeter is set for 29.92 "Hg SDP, the 

altitude indicated is the pressure altitude-the altitude in the 

standard atmosphere corresponding to the sensed pressure.

The SDP is a theoretical level where the pressure of the 

atmosphere is 29.92 "Hg and the weight of air is 14.7 psi. 

As atmospheric pressure changes, the SDP may be below, 

at, or above sea level. Pressure altitude is important as a 

basis for determining aircraft performance, as well as for 

assigning flight levels to aircraft operating at or above 18,000 

feet. The pressure altitude can be determined by either of 

two methods: (1) by setting the barometric scale of the 

altimeter to 29.92 "Hg and reading the indicated altitude, or 

(2) by applying a correction factor to the indicated altitude 

according to the reported altimeter setting.

Density Altitude

Density altitude is pressure altitude corrected for nonstandard 

temperature. As the density of the air increases (lower 

density altitude), aircraft performance increases. Conversely, 

as air density decreases (higher density altitude), aircraft 

performance decreases. A decrease in air density means a 

high density altitude; an increase in air density means a lower 

density altitude. Density altitude is used in calculating aircraft 

performance. Under standard atmospheric conditions, air at 

each level in the atmosphere has a specific density; under 

standard conditions, pressure altitude and density altitude 

identify the same level. Density altitude, then, is the vertical 

distance above sea level in the standard atmosphere at which 

a given density is to be found. It can be computed using 
4-6

1.8 

1.6 

1.4 

1.2 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

0 2 4 6 8 10 12 14 16 18 20 22 24 

CL-MAX 

2 11 20 

Angle of Attack (degrees)

Lift Coefficient - CL 

Stall 

1.5 

Figure 4-8. Relationship of lift to AOA.

Altitude and Temperature Effects

TO FIND the effect of altitude temperature

CONNECT the temperature and airport altitude by straight line

READ the increase in take-off distance and the decrease in rate of 

climb from standard sea level values here 

120

110

100

90

80

70

60

50

40

30

20

10

0

−10

−20

−30

−40

18

14

12

10

8

6

4

2

0

−2

Airport pressure altitude—Thousand of feet

(read your altmeter set to 29.92 "Hg)

90

280 80

200

140

100

60

40

20

0

70

60

40

20

0

Percent decrease

in rate of climb

Add this percent to your

normal take off distance

Figure 4-7. Koch chart sample.

a Koch Chart or a flight computer with a density altitude 

function. [Figure 4-7]

If a chart is not available, the density altitude can be estimated 

by adding 120 feet for every degree Celsius above the ISA. For 

example, at 3,000 feet PA, the ISA prediction is 9 °C (15 °C – 

[lapse rate of 2 °C per 1,000 feet x 3 = 6 °C]). However, if the 

actual temperature is 20 °C (11 °C more than that predicted 

by ISA) then the difference of 11 °C is multiplied by 120 feet 

equaling 1,320. Adding this figure to the original 3,000 feet 

provides a density altitude of 4,320 feet (3,000 feet + 1,320 feet).

Lift

Lift always acts in a direction perpendicular to the relative 

wind and to the lateral axis of the aircraft. The fact that lift is 

referenced to the wing, not to the Earth’s surface, is the source 

of many errors in learning flight control. Lift is not always 

“up.” Its direction relative to the Earth’s surface changes as 

the pilot maneuvers the aircraft.

The magnitude of the force of lift is directly proportional to 

the density of the air, the area of the wings, and the airspeed. 

It also depends upon the type of wing and the AOA. Lift 

increases with an increase in AOA up to the stalling angle, 

at which point it decreases with any further increase in AOA. 

In conventional aircraft, lift is therefore controlled by varying 

the AOA and speed.

Pitch/Power Relationship

An examination of Figure 4-8 illustrates the relationship 

between pitch and power while controlling flightpath and 

airspeed. In order to maintain a constant lift, as airspeed is 

reduced, pitch must be increased. The pilot controls pitch 

through the elevators, which control the AOA. When back 

pressure is applied on the elevator control, the tail lowers 

and the nose rises, thus increasing the wing’s AOA and lift. 

Under most conditions the elevator is placing downward 

pressure on the tail. This pressure requires energy that is 

taken from aircraft performance (speed). Therefore, when 

the CG is closer to the aft portion of the aircraft the elevator 

downward forces are less. This results in less energy used for 

downward forces, in turn resulting in more energy applied 

to aircraft performance.

Thrust is controlled by using the throttle to establish or 

maintain desired airspeeds. The most precise method 

of controlling flightpath is to use pitch control while 

simultaneously using power (thrust) to control airspeed. In 

order to maintain a constant lift, a change in pitch requires a 

change in power, and vice versa.

If the pilot wants the aircraft to accelerate while maintaining 

altitude, thrust must be increased to overcome drag. As 

the aircraft speeds up, lift is increased. To prevent gaining 

altitude, the pitch angle must be lowered to reduce the AOA 

and maintain altitude. To decelerate while maintaining 

altitude, thrust must be decreased to less than the value of 

drag. As the aircraft slows down, lift is reduced. To prevent 

losing altitude, the pitch angle must be increased in order to 

increase the AOA and maintain altitude.

Drag Curves

When induced drag and parasite drag are plotted on a graph, 

the total drag on the aircraft appears in the form of a “drag 

curve.” Graph A of Figure 4-9 shows a curve based on thrust 

versus drag, which is primarily used for jet aircraft. Graph B 
4-7

Jet Aircraft 

Airspeed 

Thrust Required 

4,000 

3,000 

2,000 

1,000 

0 

0 100 200 300 400 500 

Induced drag

Parasite

drag Total drag

Minimum

drag or

L/DMAX

Propeller-Driven Aircraft 

Airspeed 

0 100 200 300 400 500 

27 

25 

23 

18 

0 

Power Required Inches Hg 

A B 

Parasite

power

required

Total power

required

Minimum

power

required

L/DMAX 

Induced drag

Region of

reversed

command

Region of

normal

command

Airspeed 

Power Required 

1 2 

Figure 4-9. Thrust and power required curves.

Figure 4-10. Regions of command.

of Figure 4-9 is based on power versus drag, and it is used 

for propeller-driven aircraft. This chapter focuses on power 

versus drag charts for propeller-driven aircraft.

Understanding the drag curve can provide valuable insight 

into the various performance parameters and limitations of 

the aircraft. Because power must equal drag to maintain a 

steady airspeed, the curve can be either a drag curve or a 

power required curve. The power required curve represents 

the amount of power needed to overcome drag in order to 

maintain a steady speed in level flight.

The propellers used on most reciprocating engines achieve 

peak propeller efficiencies in the range of 80 to 88 percent. 

As airspeed increases, the propeller efficiency increases until 

it reaches its maximum. Any airspeed above this maximum 

point causes a reduction in propeller efficiency. An engine 

that produces 160 horsepower will have only about 80 

percent of that power converted into available horsepower, 

approximately 128 horsepower. The remainder is lost energy. 

This is the reason the thrust and power available curves 

change with speed.

Regions of Command

The drag curve also illustrates the two regions of command: 

the region of normal command, and the region of reversed 

command. The term “region of command” refers to the 

relationship between speed and the power required to 

maintain or change that speed. “Command” refers to the input 

the pilot must give in terms of power or thrust to maintain a 

new speed once reached.

The “region of normal command” occurs where power must 

be added to increase speed. This region exists at speeds higher 

than the minimum drag point primarily as a result of parasite 

drag. The “region of reversed command” occurs where 

additional power is needed to maintain a slower airspeed. This 

region exists at speeds slower than the minimum drag point

(L/DMAX on the thrust required curve, Figure 4-9) and is 

primarily due to induced drag. Figure 4-10 shows how one 

power setting can yield two speeds, points 1 and 2. This is 

because at point 1 there is high induced drag and low parasite 

drag, while at point 2 there is high parasite drag and low 

induced drag.

Control Characteristics

Most flying is conducted in the region of normal command: 

for example, cruise, climb, and maneuvers. The region of 

reversed command may be encountered in the slow-speed 

phases of flight during takeoff and landing; however, for 

most general aviation aircraft, this region is very small and 

is below normal approach speeds.

Flight in the region of normal command is characterized 

by a relatively strong tendency of the aircraft to maintain 

the trim speed. Flight in the region of reversed command is 
4-8

Region of

normal

command

Region of

reversed

command

Power

deficit

Excess

power

Airspeed 

Little or no excess

power or power deficit

Power Required 

Excess

power

B C 

A 

Power

deficit

Figure 4-11. Region of speed stability.

characterized by a relatively weak tendency of the aircraft to 

maintain the trim speed. In fact, it is likely the aircraft exhibits 

no inherent tendency to maintain the trim speed in this area. 

For this reason, the pilot must give particular attention to 

precise control of airspeed when operating in the slow-speed 

phases of the region of reversed command.

Operation in the region of reversed command does not imply 

that great control difficulty and dangerous conditions exist. 

However, it does amplify errors of basic flying technique—

making proper flying technique and precise control of the 

aircraft very important.

Speed Stability

Normal Command

The characteristics of flight in the region of normal command 

are illustrated at point A on the curve in Figure 4-11. If 

the aircraft is established in steady, level flight at point A, 

lift is equal to weight, and the power available is set equal 

to the power required. If the airspeed is increased with no 

changes to the power setting, a power deficiency exists. 

The aircraft has a natural tendency to return to the initial 

speed to balance power and drag. If the airspeed is reduced 

with no changes to the power setting, an excess of power 

exists. The aircraft has a natural tendency to speed up to 

regain the balance between power and drag. Keeping the 

aircraft in proper trim enhances this natural tendency. The 

static longitudinal stability of the aircraft tends to return the 

aircraft to the original trimmed condition.

An aircraft flying in steady, level flight at point C is in 

equilibrium. [Figure 4-11] If the speed were increased 

or decreased slightly, the aircraft would tend to remain at 

that speed. This is because the curve is relatively flat and 

a slight change in speed does not produce any significant 

excess or deficiency in power. It has the characteristic of 

neutral stability (i.e., the aircraft’s tendency is to remain at 

the new speed).

Reversed Command

The characteristics of flight in the region of reversed command 

are illustrated at point B on the curve in Figure 4-10. If the 

aircraft is established in steady, level flight at point B, lift is 

equal to weight, and the power available is set equal to the 

power required. When the airspeed is increased greater than 

point B, an excess of power exists. This causes the aircraft 

to accelerate to an even higher speed. When the aircraft is 

slowed to some airspeed lower than point B, a deficiency 

of power exists. The natural tendency of the aircraft is to 

continue to slow to an even lower airspeed.

This tendency toward instability happens because the 

variation of excess power to either side of point B magnifies 

the original change in speed. Although the static longitudinal 

stability of the aircraft tries to maintain the original trimmed 

condition, this instability is more of an influence because of 

the increased induced drag due to the higher AOA in slowspeed flight.

Trim

The term trim refers to employing adjustable aerodynamic 

devices on the aircraft to adjust forces so the pilot does not 

have to manually hold pressure on the controls. One means is 

to employ trim tabs. A trim tab is a small, adjustable hinged 

surface, located on the trailing edge of the elevator, aileron, 

or rudder control surfaces. (Some aircraft use adjustable 

stabilizers instead of trim tabs for pitch trim.) Trimming is 

accomplished by deflecting the tab in the direction opposite 

to that in which the primary control surface must be held. 

The force of the airflow striking the tab causes the main 

control surface to be deflected to a position that corrects the 

unbalanced condition of the aircraft.

Because the trim tabs use airflow to function, trim is a function 

of speed. Any change in speed results in the need to re-trim the 

aircraft. An aircraft properly trimmed in pitch seeks to return 

to the original speed before the change. It is very important 

for instrument pilots to keep the aircraft in constant trim. This 

reduces the pilot’s workload significantly, allowing attention 

to other duties without compromising aircraft control.

Slow-Speed Flight

Anytime an aircraft is flying near the stalling speed or the 

region of reversed command, such as in final approach for a 

normal landing, the initial part of a go around, or maneuvering 

in slow flight, it is operating in what is called slow-speed flight. 

If the aircraft weighs 4,000 pounds, the lift produced by the 

aircraft must be 4,000 pounds. When lift is less than 4,000 

pounds, the aircraft is no longer able to sustain level flight, and 

consequently descends. During intentional descents, this is an 

important factor and is used in the total control of the aircraft. 
4-9

Uncontrolled Turbulence 

Controlled Vortices 

Figure 4-13. Vortex generators.

Plain 

Split 

Fowler 

Slotted 

Figure 4-12. Plain and split flaps.

accept minor speed changes knowing that when the pitch is 

returned to the initial setting, the speed returns to the original 

setting. This reduces the pilot’s workload.

Aircraft are usually slowed to a normal landing speed when 

on the final approach just prior to landing. When slowed to 

65 knots, (1.3 VSO), the airplane will be close to point C. 

[Figure 4-14] At this point, precise control of the pitch and 

power becomes more crucial for maintaining the correct speed. 

Pitch and power coordination is necessary because the speed 

stability is relatively neutral since the speed tends to remain 

at the new value and not return to the original setting. In 

addition to the need for more precise airspeed control, the pilot 

normally changes the aircraft’s configuration by extending 

landing flaps. This configuration change means the pilot must 

be alert to unwanted pitch changes at a low altitude.

However, because lift is required during low speed flight 

and is characterized by high AOA, flaps or other high lift 

devices are needed to either change the camber of the airfoil, 

or delay the boundary level separation. Plain and split flaps 

[Figure 4-12] are most commonly used to change the camber 

of an airfoil. It should be noted that with the application of 

flaps, the aircraft will stall at a lower AOA. For example, 

if the basic wing stalls at 18° without flaps, then with the 

addition of flaps to the CL-MAX position, the new AOA that 

the wing will stall is 15°. However, the value of lift (flaps 

extended to the CL-MAX position) produces more lift than lift 

at 18° on the basic wing.

Delaying the boundary layer separation is another way to 

increase CL-Max. Several methods are employed (such as 

suction and use of a blowing boundary layer control), but the 

most common device used on general aviation light aircraft 

is the vortex generator. Small strips of metal placed along 

the wing (usually in front of the control surfaces) create 

turbulence. The turbulence in turn mixes high energy air from 

outside the boundary layer with boundary layer air. The effect 

is similar to other boundary layer devices. [Figure 4-13]

Small Airplanes

Most small airplanes maintain a speed well in excess of 1.3 

times VSO on an instrument approach. An airplane with a 

stall speed of 50 knots (VSO) has a normal approach speed 

of 65 knots. However, this same airplane may maintain 90 

knots (1.8 VSO) while on the final segment of an instrument 

approach. The landing gear will most likely be extended at 

the beginning of the descent to the minimum descent altitude, 

or upon intercepting the glideslope of the instrument landing 

system. The pilot may also select an intermediate flap setting 

for this phase of the approach. The airplane at this speed has 

good positive speed stability, as represented by point A on 

Figure 4-11. Flying in this regime permits the pilot to make 

slight pitch changes without changing power settings, and 
4-10

Horizontal

component of lift

Resultant lift

Vertical

component of lift

Weight 

L 

L 

L 

W 

Figure 4-14. Forces in a turn.

Excess power is the available power over and above that 

required to maintain horizontal flight at a given speed. 

Although the terms power and thrust are sometimes 

used interchangeably (erroneously implying they are 

synonymous), distinguishing between the two is important 

when considering climb performance. Work is the product of 

a force moving through a distance and is usually independent 

of time. Power implies work rate or units of work per unit 

of time, and as such is a function of the speed at which the 

force is developed. Thrust, also a function of work, means 

the force which imparts a change in the velocity of a mass.

During takeoff, the aircraft does not stall even though it 

may be in a climb near the stall speed. The reason is that 

excess power (used to produce thrust) is used during this 

flight regime. Therefore, it is important if an engine fails 

after takeoff, to compensate the loss of thrust with pitch 

and airspeed.

For a given weight of the aircraft, the angle of climb depends 

on the difference between thrust and drag, or the excess 

thrust. When the excess thrust is zero, the inclination of the 

flightpath is zero, and the aircraft is in steady, level flight. 

When thrust is greater than drag, the excess thrust allows a 

climb angle depending on the amount of excess thrust. When 

thrust is less than drag, the deficiency of thrust induces an 

angle of descent.

Acceleration in Cruise Flight

Aircraft accelerate in level flight because of an excess of 

power over what is required to maintain a steady speed. This 

is the same excess power used to climb. Upon reaching the 

desired altitude with pitch being lowered to maintain that 

altitude, the excess power now accelerates the aircraft to its 

cruise speed. However, reducing power too soon after level 

off results in a longer period of time to accelerate.

Turns

Like any moving object, an aircraft requires a sideward force 

to make it turn. In a normal turn, this force is supplied by 

banking the aircraft in order to exert lift inward, as well as 

upward. The force of lift is separated into two components 

at right angles to each other. [Figure 4-14] The upward 

acting lift together with the opposing weight becomes the 

vertical lift component. The horizontally acting lift and its 

opposing centrifugal force are the horizontal lift component, 

or centripetal force. This horizontal lift component is the 

sideward force that causes an aircraft to turn. The equal and 

opposite reaction to this sideward force is centrifugal force, 

which is merely an apparent force as a result of inertia.

If allowed to slow several knots, the airplane could enter 

the region of reversed command. At this point, the airplane 

could develop an unsafe sink rate and continue to lose speed 

unless the pilot takes a prompt corrective action. Proper pitch 

and power coordination is critical in this region due to speed 

instability and the tendency of increased divergence from 

the desired speed.

Large Airplanes

Pilots of larger airplanes with higher stall speeds may find the 

speed they maintain on the instrument approach is near 1.3 

VSO, putting them near point C [Figure 4-11] the entire time 

the airplane is on the final approach segment. In this case, 

precise speed control is necessary throughout the approach. It 

may be necessary to temporarily select excessive, or deficient 

thrust in relation to the target thrust setting in order to quickly 

correct for airspeed deviations.

For example, a pilot is on an instrument approach at 1.3 

VSO, a speed near L/DMAX, and knows that a certain power 

setting maintains that speed. The airplane slows several knots 

below the desired speed because of a slight reduction in the 

power setting. The pilot increases the power slightly, and the 

airplane begins to accelerate, but at a slow rate. Because the 

airplane is still in the “flat part” of the drag curve, this slight 

increase in power will not cause a rapid return to the desired 

speed. The pilot may need to increase the power higher 

than normally needed to maintain the new speed, allow the 

airplane to accelerate, then reduce the power to the setting 

that maintains the desired speed.

Climbs

The ability for an aircraft to climb depends upon an excess 

power or thrust over what it takes to maintain equilibrium. 
4-11

Radius≈1,500 Radius≈3,500 Radius≈6,500 Radius≈8,000 Radius≈3,500 Radius≈2,000 

Figure 4-15. Turns.

The relationship between the aircraft’s speed and bank angle 

to the rate and radius of turns is important for instrument 

pilots to understand. The pilot can use this knowledge to 

properly estimate bank angles needed for certain rates of turn, 

or to determine how much to lead when intercepting a course.

Rate of Turn

The rate of turn, normally measured in degrees per second, 

is based upon a set bank angle at a set speed. If either one 

of these elements changes, the rate of turn changes. If the 

aircraft increases its speed without changing the bank angle, 

the rate of turn decreases. Likewise, if the speed decreases 

without changing the bank angle, the rate of turn increases.

Changing the bank angle without changing speed also causes 

the rate of turn to change. Increasing the bank angle without 

changing speed increases the rate of turn, while decreasing 

the bank angle reduces the rate of turn.

The standard rate of turn, 3° per second, is used as the main 

reference for bank angle. Therefore, the pilot must understand 

how the angle of bank varies with speed changes, such 

as slowing down for holding or an instrument approach. 

Figure 4-15 shows the turn relationship with reference to a 

constant bank angle or a constant airspeed, and the effects on 

rate of turn and radius of turn. A rule of thumb for determining 

the standard rate turn is to divide the airspeed by ten and 

add 7. An aircraft with an airspeed of 90 knots takes a bank 

angle of 16° to maintain a standard rate turn (90 divided by 

10 plus 7 equals 16°).

Radius of Turn

The radius of turn varies with changes in either speed or 

bank. If the speed is increased without changing the bank 

angle, the radius of turn increases, and vice versa. If the speed 

is constant, increasing the bank angle reduces the radius of 

turn, while decreasing the bank angle increases the radius of 

turn. This means that intercepting a course at a higher speed 

requires more distance, and therefore, requires a longer lead. 

If the speed is slowed considerably in preparation for holding 

or an approach, a shorter lead is needed than that required for 

cruise flight.

Coordination of Rudder and Aileron Controls

Any time ailerons are used, adverse yaw is produced. Adverse 

yaw is caused when the ailerons are deflected as a roll motion 

(as in turn) is initiated. In a right turn, the right aileron is 

deflected upward while the left is deflected downward. Lift is 

increased on the left side and reduced on the right, resulting 

in a bank to the right. However, as a result of producing lift 

on the left, induced drag is also increased on the left side. 

The drag causes the left wing to slow down, in turn causing 

the nose of the aircraft to initially move (left) in the direction 

opposite of the turn. Correcting for this yaw with rudder, when 

entering and exiting turns, is necessary for precise control of 

the airplane when flying on instruments. The pilot can tell if 

the turn is coordinated by checking the ball in the turn-andslip indicator or the turn coordinator. [Figure 4-16]

As the aircraft banks to enter a turn, a portion of the wing’s 

vertical lift becomes the horizontal component; therefore, 

without an increase in back pressure, the aircraft loses altitude 

during the turn. The loss of vertical lift can be offset by 

increasing the pitch in one-half bar width increments. Trim 

may be used to relieve the control pressures; however, if used, 

it has to be removed once the turn is complete.

In a slipping turn, the aircraft is not turning at the rate 

appropriate to the bank being used, and the aircraft falls to 

the inside of the turn. The aircraft is banked too much for the 

rate of turn, so the horizontal lift component is greater than 

the centrifugal force. A skidding turn results from excess of 
4-12

2 MIN TURN DC ELEC

L R

TURN COORDINATOR

2 MIN.

D.C.

ELEC.

L R

NO PITCH

INFORMATION

2 MIN TURN DC ELEC

L R

TURN COORDINATOR

2 MIN.

D.C.

ELEC.

L R

NO PITCH

INFORMATION

2 MIN TURN DC ELEC

L R

TURN COORDINATOR

2 MIN.

D.C.

ELEC.

L R

NO PITCH

INFORMATION

Skidding Turn

Skidding Turn

Slipping Turn

Slipping Turn

Coordinated Turn

rudder into turn

Coordinated Turn

Note the slight differences in rudder placement.

Figure 4-16. Adverse yaw.

centrifugal force over the horizontal lift component, pulling 

the aircraft toward the outside of the turn. The rate of turn 

is too great for the angle of bank, so the horizontal lift 

component is less than the centrifugal force.

An inclinometer, located in the turn coordinator, or turn and 

bank indicator indicates the quality of the turn, and should 

be centered when the wings are banked. If the ball is off of 

center on the side toward the turn, the aircraft is slipping and 

rudder pressure should be added on that side to increase the 

rate of turn or the bank angle should be reduced. If the ball 

is off of center on the side away from the turn, the aircraft 

is skidding and rudder pressure toward the turn should be 

relaxed or the bank angle should be increased. If the aircraft 

is properly rigged, the ball should be in the center when the 

wings are level; use rudder and/or aileron trim if available.

The increase in induced drag (caused by the increase in 

AOA necessary to maintain altitude) results in a minor loss 

of airspeed if the power setting is not changed.

Load Factor

Any force applied to an aircraft to deflect its flight from a 

straight line produces a stress on its structure; the amount of 

this force is termed load factor. A load factor is the ratio of 

the aerodynamic force on the aircraft to the gross weight of 

the aircraft (e.g., lift/weight). For example, a load factor of 3 

means the total load on an aircraft’s structure is three times 

its gross weight. When designing an aircraft, it is necessary 

to determine the highest load factors that can be expected in 

normal operation under various operational situations. These 

“highest” load factors are called “limit load factors.”

Aircraft are placed in various categories (i.e., normal, utility, 

and acrobatic) depending upon the load factors they are 

designed to take. For reasons of safety, the aircraft must be 

designed to withstand certain maximum load factors without 

any structural damage.
4-13

Figure 4-17. Clear ice. Clear Ice 

The specified load may be expected in terms of aerodynamic 

forces, as in turns. In level flight in undisturbed air, the 

wings are supporting not only the weight of the aircraft, but 

centrifugal force as well. As the bank steepens, the horizontal 

lift component increases, centrifugal force increases, and the 

load factor increases. If the load factor becomes so great that 

an increase in AOA cannot provide enough lift to support 

the load, the wing stalls. Since the stalling speed increases 

directly with the square root of the load factor, the pilot 

should be aware of the flight conditions during which the 

load factor can become critical. Steep turns at slow airspeed, 

structural ice accumulation, and vertical gusts in turbulent 

air can increase the load factor to a critical level.

Icing

One of the greatest hazards to flight is aircraft icing. The 

instrument pilot must be aware of the conditions conducive to 

aircraft icing. These conditions include the types of icing, the 

effects of icing on aircraft control and performance, effects 

of icing on aircraft systems, and the use and limitations of 

aircraft deice and anti-ice equipment. Coping with the hazards 

of icing begins with preflight planning to determine where 

icing may occur during a flight and ensuring the aircraft is 

free of ice and frost prior to takeoff. This attention to detail 

extends to managing deice and anti-ice systems properly 

during the flight, because weather conditions may change 

rapidly, and the pilot must be able to recognize when a change 

of flight plan is required.

Types of Icing

Structural Icing

Structural icing refers to the accumulation of ice on the 

exterior of the aircraft. Ice forms on aircraft structures and 

surfaces when super-cooled droplets impinge on them and 

freeze. Small and/or narrow objects are the best collectors 

of droplets and ice up most rapidly. This is why a small 

protuberance within sight of the pilot can be used as an “ice 

evidence probe.” It is generally one of the first parts of the 

airplane on which an appreciable amount of ice forms. An 

aircraft’s tailplane is a better collector than its wings, because 

the tailplane presents a thinner surface to the airstream.

Induction Icing

Ice in the induction system can reduce the amount of air 

available for combustion. The most common example of 

reciprocating engine induction icing is carburetor ice. Most 

pilots are familiar with this phenomenon, which occurs when 

moist air passes through a carburetor venturi and is cooled. As 

a result of this process, ice may form on the venturi walls and 

throttle plate, restricting airflow to the engine. This may occur 

at temperatures between 20 °F (–7 °C) and 70 °F (21 °C). 

The problem is remedied by applying carburetor heat, which 

uses the engine’s own exhaust as a heat source to melt the 

ice or prevent its formation. On the other hand, fuel-injected 

aircraft engines usually are less vulnerable to icing but still 

can be affected if the engine’s air source becomes blocked 

with ice. Manufacturers provide an alternate air source that 

may be selected in case the normal system malfunctions.

In turbojet aircraft, air that is drawn into the engines creates 

an area of reduced pressure at the inlet, which lowers the 

temperature below that of the surrounding air. In marginal 

icing conditions (i.e., conditions where icing is possible), 

this reduction in temperature may be sufficient to cause ice 

to form on the engine inlet, disrupting the airflow into the 

engine. Another hazard occurs when ice breaks off and is 

ingested into a running engine, which can cause damage to 

fan blades, engine compressor stall, or combustor flameout. 

When anti-icing systems are used, runback water also can 

refreeze on unprotected surfaces of the inlet and, if excessive, 

reduce airflow into the engine or distort the airflow pattern in 

such a manner as to cause compressor or fan blades to vibrate, 

possibly damaging the engine. Another problem in turbine 

engines is the icing of engine probes used to set power levels 

(for example, engine inlet temperature or engine pressure ratio 

(EPR) probes), which can lead to erroneous readings of engine 

instrumentation operational difficulties or total power loss.

The type of ice that forms can be classified as clear, rime, or 

mixed, based on the structure and appearance of the ice. The 

type of ice that forms varies depending on the atmospheric 

and flight conditions in which it forms. Significant structural 

icing on an aircraft can cause serious aircraft control and 

performance problems.

Clear Ice

A glossy, transparent ice formed by the relatively slow 

freezing of super cooled water is referred to as clear ice. 

[Figure 4-17] The terms “clear” and “glaze” have been used 
4-14

Rime Ice 

CL (coefficient of lift) 

Angle of Attack 

Clean

airfoil

Airfoil

with ice

CD (coefficient of drag) 

Angle of Attack 

Clean

airfoil

Airfoil

with ice

Figure 4-20. Aerodynamic effects of icing.

Figure 4-19. Rime ice.

Figure 4-18. Clear Ice Buildup with Horns Clear ice buildup with horns.

for essentially the same type of ice accretion. This type of 

ice is denser, harder, and sometimes more transparent than 

rime ice. With larger accretions, clear ice may form “horns.” 

[Figure 4-18] Temperatures close to the freezing point, large 

amounts of liquid water, high aircraft velocities, and large 

droplets are conducive to the formation of clear ice.

Rime Ice

A rough, milky, opaque ice formed by the instantaneous or 

very rapid freezing of super cooled droplets as they strike 

the aircraft is known as rime ice. [Figure 4-19] The rapid 

freezing results in the formation of air pockets in the ice, 

giving it an opaque appearance and making it porous and 

brittle. For larger accretions, rime ice may form a streamlined 

extension of the wing. Low temperatures, lesser amounts of 

liquid water, low velocities, and small droplets are conducive 

to the formation of rime ice.

Mixed Ice

Mixed ice is a combination of clear and rime ice formed on 

the same surface. It is the shape and roughness of the ice 

that is most important from an aerodynamic point of view.

General Effects of Icing on Airfoils

The most hazardous aspect of structural icing is its aerodynamic 

effects. [Figure 4-20] Ice alters the shape of an airfoil, reducing 

the maximum coefficient of lift and AOA at which the aircraft 

stalls. Note that at very low AOAs, there may be little or no 

effect of the ice on the coefficient of lift. Therefore, when 

cruising at a low AOA, ice on the wing may have little effect 

on the lift. However, note that the ice significantly reduces 

the CL-max, and the AOA at which it occurs (the stall angle) 

is much lower. Thus, when slowing down and increasing the 

AOA for approach, the pilot may find that ice on the wing, 

which had little effect on lift in cruise now, causes stall to 
4-15

Angle of Attack 

Upper Surface Frost Leading Edge Ice Formations 

CL-MAX 

w

f

i

Figure 4-21. Effect of ice and frost on lift.

C of L 

CG 

Weight 

Tail download

Figure 4-22. Downward force on the tailplane.

occur at a lower AOA and higher speed. Even a thin layer of 

ice at the leading edge of a wing, especially if it is rough, can 

have a significant effect in increasing stall speed. For large 

ice shapes, especially those with horns, the lift may also be 

reduced at a lower AOA. The accumulation of ice affects the 

coefficient of drag of the airfoil. [Figure 4-20] Note that the 

effect is significant even at very small AOAs.

A significant reduction in CL-max and a reduction in the 

AOA where stall occurs can result from a relatively small 

ice accretion. A reduction of CL-max by 30 percent is not 

unusual, and a large horn ice accretion can result in reductions 

of 40 percent to 50 percent. Drag tends to increase steadily 

as ice accretes. An airfoil drag increase of 100 percent is not 

unusual, and for large horn ice accretions, the increase can 

be 200 percent or even higher.

Ice on an airfoil can have other effects not depicted in these 

curves. Even before airfoil stall, there can be changes in the 

pressure over the airfoil that may affect a control surface at 

the trailing edge. Furthermore, on takeoff, approach, and 

landing, the wings of many aircraft are multi-element airfoils 

with three or more elements. Ice may affect the different 

elements in different ways. Ice may also affect the way in 

which the air streams interact over the elements.

Ice can partially block or limit control surfaces, which 

limits or makes control movements ineffective. Also, if the 

extra weight caused by ice accumulation is too great, the 

aircraft may not be able to become airborne and, if in flight, 

the aircraft may not be able to maintain altitude. Therefore 

any accumulation of ice or frost should be removed before 

attempting flight.

Another hazard of structural icing is the possible uncommanded 

and uncontrolled roll phenomenon, referred to as roll upset, 

associated with severe inflight icing. Pilots flying aircraft 

certificated for flight in known icing conditions should be 

aware that severe icing is a condition outside of the aircraft’s 

certification icing envelope. Roll upset may be caused by 

airflow separation (aerodynamic stall), which induces selfdeflection of the ailerons and loss of or degraded roll handling 

characteristics [Figure 4-21]. These phenomena can result 

from severe icing conditions without the usual symptoms of 

ice accumulation or a perceived aerodynamic stall.

Most aircraft have a nose-down pitching moment from the 

wings because the CG is ahead of the CP. It is the role of the 

tailplane to counteract this moment by providing a downward 

force. [Figure 4-22] The result of this configuration is that 

actions which move the wing away from stall, such as 

deployment of flaps or increasing speed, may increase the 

negative AOA of the tail. With ice on the tailplane, it may 

stall after full or partial deployment of flaps. [Figure 4-23]

Since the tailplane is ordinarily thinner than the wing, it is a 

more efficient collector of ice. On most aircraft the tailplane 

is not visible to the pilot, who therefore cannot observe how 

well it has been cleared of ice by any deicing system. Thus, it 

is important that the pilot be alert to the possibility of tailplane 

stall, particularly on approach and landing.
4-16

Weight 

Icing 

CG 

Aircraft nose

pitches down

Figure 4-23. Ice on the tailplane.

Piper PA-34-200T (Des Moines, Iowa)

The pilot of this flight, which took place on January 9, 

1996, said that upon crossing the runway threshold and 

lowering the flaps 25°, “the airplane pitched down.” The 

pilot “immediately released the flaps and added power, but 

the airplane was basically uncontrollable at this point.” The 

pilot reduced power and lowered the flaps before striking 

the runway on its centerline and sliding 1,000 feet before 

coming to a stop. The accident resulted in serious injury to 

the pilot, the sole occupant.

Examination of the wreckage revealed heavy impact 

damage to the airplane’s forward fuselage, engines, and 

wings. Approximately one-half inch of rime ice was 

observed adhering to the leading edges of the left and right 

horizontal stabilizers and along the leading edge of the 

vertical stabilizer.

The National Transportation Safety Board (NTSB) 

determined the probable cause of the accident was the pilot’s 

failure to use the airplane’s deicing system, which resulted 

in an accumulation of empennage ice and a tailplane stall. 

Factors relating to this accident were the icing conditions 

and the pilot’s intentional flight into those known conditions.

Tailplane Stall Symptoms

Any of the following symptoms, occurring singly or in 

combination, may be a warning of tailplane icing:

• Elevator control pulsing, oscillations, or vibrations;

• Abnormal nose-down trim change;

• Any other unusual or abnormal pitch anomalies 

(possibly resulting in pilot induced oscillations);

• Reduction or loss of elevator effectiveness;

• Sudden change in elevator force (control would move 

nose-down if unrestrained); and

• Sudden uncommanded nose-down pitch.

If any of the above symptoms occur, the pilot should:

• Immediately retract the flaps to the previous setting 

and apply appropriate nose-up elevator pressure;

• Increase airspeed appropriately for the reduced flap 

extension setting;

• Apply sufficient power for aircraft configuration 

and conditions. (High engine power settings may 

adversely impact response to tailplane stall conditions 

at high airspeed in some aircraft designs. Observe the 

manufacturer’s recommendations regarding power 

settings.);

• Make nose-down pitch changes slowly, even in 

gusting conditions, if circumstances allow; and

• If a pneumatic deicing system is used, operate the 

system several times in an attempt to clear the tailplane 

of ice. 

Once a tailplane stall is encountered, the stall condition 

tends to worsen with increased airspeed and possibly may 

worsen with increased power settings at the same flap 

setting. Airspeed, at any flap setting, in excess of the airplane 

manufacturer’s recommendations, accompanied by uncleared 

ice contaminating the tailplane, may result in a tailplane stall 

and uncommanded pitch down from which recovery may not 

be possible. A tailplane stall may occur at speeds less than 

the maximum flap extended speed (VFE).

Propeller Icing

Ice buildup on propeller blades reduces thrust for the same 

aerodynamic reasons that wings tend to lose lift and increase 

drag when ice accumulates on them. The greatest quantity 

of ice normally collects on the spinner and inner radius of 

the propeller. Propeller areas on which ice may accumulate 

and be ingested into the engine normally are anti-iced rather 

than deiced to reduce the probability of ice being shed into 

the engine.

Effects of Icing on Critical Aircraft Systems

In addition to the hazards of structural and induction icing, 

the pilot must be aware of other aircraft systems susceptible 

to icing. The effects of icing do not produce the performance 

loss of structural icing or the power loss of induction icing 

but can present serious problems to the instrument pilot. 

Examples of such systems are flight instruments, stall 

warning systems, and windshields.

Flight Instruments

Various aircraft instruments including the airspeed indicator, 

altimeter, and rate-of-climb indicator utilize pressures 

sensed by pitot tubes and static ports for normal operation. 
4-17

When covered by ice these instruments display incorrect 

information thereby presenting serious hazard to instrument 

flight. Detailed information on the operation of these 

instruments and the specific effects of icing is presented in 

Chapter 5, Flight Instruments.

Stall Warning Systems

Stall warning systems provide essential information to pilots. 

These systems range from a sophisticated stall warning vane 

to a simple stall warning switch. Icing affects these systems 

in several ways resulting in possible loss of stall warning to 

the pilot. The loss of these systems can exacerbate an already 

hazardous situation. Even when an aircraft’s stall warning 

system remains operational during icing conditions, it may 

be ineffective because the wing stalls at a lower AOA due 

to ice on the airfoil.

Windshields

Accumulation of ice on flight deck windows can severely 

restrict the pilot’s visibility outside of the aircraft. Aircraft 

equipped for flight into known icing conditions typically have 

some form of windshield anti-icing to enable the pilot to see 

outside the aircraft in case icing is encountered in flight. One 

system consists of an electrically heated plate installed onto 

the airplane’s windshield to give the pilot a narrow band of 

clear visibility. Another system uses a bar at the lower end 

of the windshield to spray deicing fluid onto it and prevent 

ice from forming. On high performance aircraft that require 

complex windshields to protect against bird strikes and 

withstand pressurization loads, the heating element often is 

a layer of conductive film or thin wire strands through which 

electric current is run to heat the windshield and prevent ice 

from forming.

Antenna Icing

Because of their small size and shape, antennas that do not lay 

flush with the aircraft’s skin tend to accumulate ice rapidly. 

Furthermore, they often are devoid of internal anti-icing 

or deicing capability for protection. During flight in icing 

conditions, ice accumulations on an antenna may cause it to 

begin to vibrate or cause radio signals to become distorted 

and it may cause damage to the antenna. If a frozen antenna 

breaks off, it can damage other areas of the aircraft in addition 

to causing a communication or navigation system failure.

Summary

Ice-contaminated aircraft have been involved in many 

accidents. Takeoff accidents have usually been due to failure 

to deice or anti-ice critical surfaces properly on the ground. 

Proper deicing and anti-icing procedures are addressed in 

two other pilot guides, Advisory Circular (AC) 120-58, Pilot 

Guide: Large Aircraft Ground Deicing and AC 135-17, Pilot 

Guide: Small Aircraft Ground Deicing.

The pilot of an aircraft, which is not certificated or equipped 

for flight in icing conditions, should avoid all icing conditions. 

The aforementioned guides provide direction on how to do 

this, and on how to exit icing conditions promptly and safely 

should they be inadvertently encountered.

The pilot of an aircraft, which is certificated for flight in 

icing conditions can safely operate in the conditions for 

which the aircraft was evaluated during the certification 

process but should never become complacent about icing. 

Even short encounters with small amounts of rough icing 

can be very hazardous. The pilot should be familiar with all 

information in the Aircraft Flight Manual (AFM) or Pilot’s 

Operating Handbook (POH) concerning flight in icing 

conditions and follow it carefully. Of particular importance 

are proper operation of ice protection systems and any 

airspeed minimums to be observed during or after flight 

in icing conditions. There are some icing conditions for 

which no aircraft is evaluated in the certification process, 

such as super-cooled large drops (SLD). These subfreezing 

water droplets, with diameters greater than 50 microns, 

occur within or below clouds and sustained flight in these 

conditions can be very hazardous. The pilot should be familiar 

with any information in the AFM or POH relating to these 

conditions, including aircraft-specific cues for recognizing 

these hazardous conditions within clouds.

The information in this chapter is an overview of the hazards 

of aircraft icing. For more detailed information refer to 

AC 91-74, Pilot Guide: Flight in Icing Conditions, AC 91-

51, Effect of Icing on Aircraft Control and Airplane Deice 

and Anti-Ice Systems, AC 20-73, Aircraft Ice Protection 

and AC 23.143-1, Ice Contaminated Tailplane Stall (ICTS).
4-18
5-1

Flight Instruments

Chapter 5

Introduction

Aircraft became a practical means of transportation when 

accurate flight instruments freed the pilot from the necessity 

of maintaining visual contact with the ground. Flight 

instruments are crucial to conducting safe flight operations 

and it is important that the pilot have a basic understanding 

of their operation. The basic flight instruments required 

for operation under visual flight rules (VFR) are airspeed 

indicator (ASI), altimeter, and magnetic direction indicator. 

In addition to these, operation under instrument flight rules 

(IFR) requires a gyroscopic rate-of-turn indicator, slip-skid 

indicator, sensitive altimeter adjustable for barometric 

pressure, clock displaying hours, minutes, and seconds with 

a sweep-second pointer or digital presentation, gyroscopic 

pitch-and-bank indicator (artificial horizon), and gyroscopic 

direction indicator (directional gyro or equivalent).
5-2

30.0

29.9

29.8

Ram air Pitot tube

Static port

Baffle plate

Drain hole

Heater (100 watts)

Static hole

Static hole

Static chamber

Heater (35 watts)

Pitot pressure chamber

Pitot heater switch

Alternate static source

Drain hole

Figure 3-1. A typical electrically heated poitot-static head. 

Figure 5-1. A typical electrically heated pitot-static head.

Aircraft that are flown in instrument meteorological 

conditions (IMC) are equipped with instruments that provide 

attitude and direction reference, as well as navigation 

instruments that allow precision flight from takeoff to landing 

with limited or no outside visual reference.

The instruments discussed in this chapter are those required 

by Title 14 of the Code of Federal Regulations (14 CFR) 

part 91, and are organized into three groups: pitot-static 

instruments, compass systems, and gyroscopic instruments. 

The chapter concludes with a discussion of how to preflight 

these systems for IFR flight. This chapter addresses additional 

avionics systems such as Electronic Flight Information 

Systems (EFIS), Ground Proximity Warning System 

(GPWS), Terrain Awareness and Warning System (TAWS), 

Traffic Alert and Collision Avoidance System (TCAS), 

Head Up Display (HUD), etc., that are increasingly being 

incorporated into general aviation aircraft.

Pitot/Static Systems

Pitot pressure, or impact air pressure, is sensed through an 

open-end tube pointed directly into the relative wind flowing 

around the aircraft. The pitot tube connects to the ASI or an 

air data computer depending on your aircraft's configuration. 

Static Pressure

Static pressure is also used by the ASI as well as the other 

pitot static instruments for determining altitude and vertical 

speed. Static pressure may be sensed at one or more locations 

on an aircraft. Some may be flush mounted on the fuselage or 

integrated into the electrically heated pitot tube. [Figure 5-1]

These ports are in locations proven by flight tests to be in 

undisturbed air, and they may be paired, one on either side of 

the aircraft. This dual location prevents lateral movement of 

the aircraft from giving erroneous static pressure indications. 

The areas around the static ports may be heated with electric 

heater elements to prevent ice forming over the port and 

blocking the entry of the static air.

Three basic pressure-operated instruments are found in 

aircraft instrument panels flown under IFR. These are the 

ASI, sensitive altimeter, and vertical speed indicator (VSI). 

All three instruments receive static air pressure for operation 

with only the ASI receiving both pitot and static pressure. 

[Figure 5-2]

Blockage of the Pitot-Static System

Errors in the ASI and VSI almost always indicate a blockage 

of the pitot tube, the static port(s), or both. Moisture 

(including ice), dirt, or even insects can cause a blockage in 

both systems. During preflight, it is very important to make 

sure the pitot tube cover is removed and that static port 

openings are checked for blockage and damage.

Blocked Pitot System

If the pitot tube drain hole becomes obstructed, the pitot 

system can become partially or completely blocked. When 

dynamic pressure cannot enter the pitot tube opening, the ASI 

no longer operates. If the drain hole is open, static pressure 

equalizes on both sides of the diaphram in the ASI and the 
5-3

30.0 

29.9 

29.8 

Figure 3-2. A typical pitot-static system. Figure 5-2. A typical pitot-static system.

indicated airspeed slowly drops to zero. If the pitot tube ram 

pressure hole and drain hole become obstructed, the ASI 

operates like an altimeter as the aircraft climbs and descends. 

Refer to the Pilot’s Handbook of Aeronautical Knowledge 

(FAA-H-8083-25A) for more in depth information on 

blocked pitot systems along with different scenarios and 

how they effect the ASI.

Blocked Static System

When a static system becomes blocked but the pitot tube 

remains clear the ASI continues to operate but is inaccurate. 

When the aircraft is operated above the altitude where the 

static ports became blocked the airspeed indicates lower 

than the actual airspeed because the trapped static pressure 

is higher than normal for that altitude. The opposite holds 

true for operations at lower altitudes; a faster than actual 

airspeed is displayed due to the relatively low static pressure 

trapped in the system. 

A blockage of the static system can also affect the altimeter 

and VSI. Trapped static pressure causes the altimeter to 

freeze at the altitude where the blockage occurred. In the case 

of the VSI, a blocked static system produces a continuous 

zero indication.

An alternate static source is provided in some aircraft to 

provide static pressure should the primary static source 

become blocked. The alternate static source is normally found 

inside of the flight deck. Due to the venturi effect of the air 

flowing around the fuselage, the air pressure inside the flight 

deck is lower than the exterior pressure.

When the alternate static source pressure is used, the 

following instrument indications are observed:

1. The altimeter indicates a slightly higher altitude than 

actual.

2. The ASI indicates an airspeed greater than the actual 

airspeed.

3. The VSI shows a momentary climb and then stabilizes 

if the altitude is held constant.

For more information on static system blockages and how to 

best react to such situations, refer to the Pilot’s Handbook of 

Aeronautical Knowledge (FAA-H-8083-25A). 

Effects of Flight Conditions

The static ports are located in a position where the air at 

their surface is as undisturbed as possible. But under some 

flight conditions, particularly at a high angle of attack with 

the landing gear and flaps down, the air around the static 

port may be disturbed to the extent that it can cause an error 

in the indication of the altimeter and ASI. Because of the 

importance of accuracy in these instruments, part of the 

certification tests for an aircraft is a check of position error 

in the static system.

The Pilot’s Operating Handbook (POH)/Aircraft Flight 

Manual (AFM) contains any corrections that must be applied 

to the airspeed for the various configurations of flaps and 

landing gear.

Pitot/Static Instruments

Sensitive Altimeter

A sensitive altimeter is an aneroid barometer that measures 

the absolute pressure of the ambient air and displays it in 

terms of feet or meters above a selected pressure level.

Principle of Operation

The sensitive element in a sensitive altimeter is a stack of 

evacuated, corrugated bronze aneroid capsules. [Figure 5-3]

The air pressure acting on these aneroids tries to compress 

them against their natural springiness, which tries to expand 

them. The result is that their thickness changes as the air 

pressure changes. Stacking several aneroids increases the 

dimension change as the pressure varies over the usable 

range of the instrument.

Below 10,000 feet, a striped segment is visible. Above this 

altitude, a mask begins to cover it, and above 15,000 feet, 

all of the stripes are covered. [Figure 5-4]

Another configuration of the altimeter is the drum-type. 

[Figure 5-5] These instruments have only one pointer that 
5-4

A crosshatched area appears on some 

altimeters when displaying an altitude 

below 10,000 feet MSL.

10,000 ft. pointer 

Altimeter setting window 

Static port 

Barometric scale adjustment knob 

Aneroid 

Crosshatch flag 

Altitude indication scale 

100 ft. pointer 

1,000 ft. pointer 

Figure 3-3. Sensitive altimeter componements.

Figure 5-3. Sensitive altimeter components.

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

Figure 3-4. Three-pointer altimeter. Figure 5-4. Three-pointer altimeter.

I 

4 

5 

6 

7 

9 

2 

0 

8 

3 

0 6, 5 0 0 

ALT 

M B 

2 9 9 2 

I N H G 

Figure 3-5. Drum-type altimeter. Figure 5-5. Drum-type altimeter.

makes one revolution for every 1,000 feet. Each number 

represents 100 feet and each mark represents 20 feet. A drum, 

marked in thousands of feet, is geared to the mechanism that 

drives the pointer. To read this type of altimeter, first look at 

the drum to get the thousands of feet, and then at the pointer 

to get the feet and hundreds of feet.

A sensitive altimeter is one with an adjustable barometric scale 

allowing the pilot to set the reference pressure from which the 

altitude is measured. This scale is visible in a small window 

called the Kollsman window. A knob on the instrument adjusts 

the scale. The range of the scale is from 28.00 to 31.00 inches 

of mercury ("Hg), or 948 to 1,050 millibars.

Rotating the knob changes both the barometric scale and the 

altimeter pointers in such a way that a change in the barometric 

scale of 1 "Hg changes the pointer indication by 1,000 feet. 

This is the standard pressure lapse rate below 5,000 feet. 

When the barometric scale is adjusted to 29.92 "Hg or 1,013.2 

millibars, the pointers indicate the pressure altitude. The pilot 

displays indicate altitude by adjusting the barometric scale 

to the local altimeter setting. The altimeter then indicates the 

height above the existing sea level pressure.

Altimeter Errors

A sensitive altimeter is designed to indicate standard changes 

from standard conditions, but most flying involves errors 

caused by nonstandard conditions and the pilot must be able 

to modify the indications to correct for these errors. There 

are two types of errors: mechanical and inherent.

Mechanical Altimeter Errors

A preflight check to determine the condition of an altimeter 

consists of setting the barometric scale to the local altimeter 
5-5

5,000 foot pressure level 

4,000 foot pressure level 

3,000 foot pressure level 

2,000 foot pressure level 

1,000 foot pressure level 

Sea level 

30°C 15°C 0°C 

Figure 5-6. Figure 3-6. Effects of nonstandard temperature on an altimeter. The loss of altitude experienced when flying into an area where the air is colder (more dense) than standard.

setting. The altimeter should indicate the surveyed elevation 

of the airport. If the indication is off by more than 75 feet from 

the surveyed elevation, the instrument should be referred 

to a certificated instrument repair station for recalibration. 

Differences between ambient temperature and/or pressure 

causes an erroneous indication on the altimeter.

Inherent Altimeter Error

 When the aircraft is flying in air that is warmer than standard, 

the air is less dense and the pressure levels are farther apart. 

When the aircraft is flying at an indicated altitude of 5,000 

feet, the pressure level for that altitude is higher than it would 

be in air at standard temperature, and the aircraft is higher 

than it would be if the air were cooler. If the air is colder 

than standard, it is denser and the pressure levels are closer 

together. When the aircraft is flying at an indicated altitude 

of 5,000 feet, its true altitude is lower than it would be if the 

air were warmer. [Figure 5-6]

Cold Weather Altimeter Errors

A correctly calibrated pressure altimeter indicates true 

altitude above mean sea level (MSL) when operating within 

the International Standard Atmosphere (ISA) parameters of 

pressure and temperature. Nonstandard pressure conditions are 

corrected by applying the correct local area altimeter setting. 

Temperature errors from ISA result in true altitude being 

higher than indicated altitude whenever the temperature is 

warmer than ISA and true altitude being lower than indicated 

altitude whenever the temperature is colder than ISA. 

True altitude variance under conditions of colder than ISA 

temperatures poses the risk of inadequate obstacle clearance. 

Under extremely cold conditions, pilots may need to add an 

appropriate temperature correction determined from the chart 

in Figure 5-7 to charted IFR altitudes to ensure terrain and 

obstacle clearance with the following restrictions:

• Altitudes specifically assigned by Air Traffic Control 

(ATC), such as “maintain 5,000 feet” shall not be 

corrected. Assigned altitudes may be rejected if the 

pilot decides that low temperatures pose a risk of 

inadequate terrain or obstacle clearance.

• If temperature corrections are applied to charted 

IFR altitudes (such as procedure turn altitudes, final 

approach fix crossing altitudes, etc.), the pilot must 

advise ATC of the applied correction.

ICAO Cold Temperature Error Table

The cold temperature induced altimeter error may be 

significant when considering obstacle clearances when 

temperatures are well below standard. Pilots may wish to 

increase their minimum terrain clearance altitudes with a 

corresponding increase in ceiling from the normal minimum 

when flying in extreme cold temperature conditions. Higher 

altitudes may need to be selected when flying at low terrain 

clearances. Most flight management systems (FMS) with 

air data computers implement a capability to compensate 

for cold temperature errors. Pilots flying with these systems 

should ensure they are aware of the conditions under which 

the system automatically compensates. If compensation is 

applied by the FMS or manually, ATC must be informed 

that the aircraft is not flying the assigned altitude. Otherwise, 

vertical separation from other aircraft may be reduced creating 

a potentially hazardous situation. The table in Figure 5-7, 

derived from International Civil Aviation Organization 
5-6

Reported 

Temp ° C

Height Above Airport in Feet

+10

0

-10

-20

-30

-40

-50

200 300 400 500 600 700 800 900 1,000 1,500 2,000 3,000 4,000 5,000

10 10 10 10 20 20 20 20 20 30 40 60 80 90

20 20 30 30 40 40 50 50 60 90 120 170 230 280

20 30 40 50 60 70 80 90 100 150 200 290 390 490

30 50 60 70 90 100 120 130 140 210 280 420 570 710

40 60 80 100 120 130 150 170 190 280 380 570 760 950

50 80 100 120 150 170 190 220 240 360 480 720 970 1,210

60 90 120 150 180 210 240 270 300 450 590 890 1,190 1,500

Figure 3-7. ICAO Cold Temperature Error.

Figure 5-7. International Civil Aviation Organization (ICAO) cold temperature error table.

(ICAO) standard formulas, shows how much error can exist 

when the temperature is extremely cold. To use the table, find 

the reported temperature in the left column, and then read 

across the top row to the height above the airport/reporting 

station. Subtract the airport elevation from the altitude of the 

final approach fix (FAF). The intersection of the column and 

row is the amount of possible error.

Example: The reported temperature is –10 degrees Celsius 

(°C) and the FAF is 500 feet above the airport elevation. The 

reported current altimeter setting may place the aircraft as 

much as 50 feet below the altitude indicated by the altimeter.

When using the cold temperature error table, the altitude 

error is proportional to both the height above the reporting 

station elevation and the temperature at the reporting 

station. For IFR approach procedures, the reporting station 

elevation is assumed to be airport elevation. It is important 

to understand that corrections are based upon the temperature 

at the reporting station, not the temperature observed at the 

aircraft’s current altitude and height above the reporting 

station and not the charted IFR altitude.

To see how corrections are applied, note the following example:

Airport Elevation 496 feet

Airport Temperature –50 °C

A charted IFR approach to the airport provides the following 

data:

Minimum Procedure Turn Altitude 1,800 feet

Minimum FAF Crossing Altitude 1,200 feet

Straight-in Minimum Descent Altitude 800 feet

Circling Minimum Descent Altitude (MDA) 1,000 feet

The Minimum Procedure Turn Altitude of 1,800 feet is used 

as an example to demonstrate determination of the appropriate 

temperature correction. Typically, altitude values are rounded 

up to the nearest 100-foot level. The charted procedure turn 

altitude of 1,800 feet minus the airport elevation of 500 feet 

equals 1,300 feet. The altitude difference of 1,300 feet falls 

between the correction chart elevations of 1,000 feet and 1,500 

feet. At the station temperature of –50 °C, the correction falls 

between 300 feet and 450 feet. Dividing the difference in 

compensation values by the difference in altitude above the 

airport gives the error value per foot. 

In this case, 150 feet divided by 500 feet = 0.33 feet for each 

additional foot of altitude above 1,000 feet. This provides a 

correction of 300 feet for the first 1,000 feet and an additional 

value of 0.33 times 300 feet, or 99 feet, which is rounded to 

100 feet. 300 feet + 100 feet = total temperature correction 

of 400 feet. For the given conditions, correcting the charted 

value of 1,800 feet above MSL (equal to a height above the 

reporting station of 1,300 feet) requires the addition of 400 

feet. Thus, when flying at an indicated altitude of 2,200 feet, 

the aircraft is actually flying a true altitude of 1,800 feet.

Minimum Procedure Turn Altitude 

1,800 feet charted = 2,200 feet corrected

Minimum FAF Crossing Altitude

1,200 feet charted = 1,500 feet corrected

Straight-in MDA

800 feet charted = 900 feet corrected

Circling MDA

1,000 feet charted = 1,200 feet corrected

Nonstandard Pressure on an Altimeter

Maintaining a current altimeter setting is critical because the 

atmosphere pressure is not constant. That is, in one location 

the pressure might be higher than the pressure just a short 

distance away. Take an aircraft whose altimeter setting is set 

to 29.92" of local pressure. As the aircraft moves to an area 

of lower pressure (Point A to B in Figure 5-8) and the pilot 

fails to readjust the altimeter setting (essentially calibrating 

it to local pressure), then as the pressure decreases, the true 

altitude is lower. Adjusting the altimeter settings compensates 

for this. When the altimeter shows an indicated altitude of 

5,000 feet, the true altitude at Point A (the height above 
5-7

28.86 "Hg 1,000 feet

27.82 "Hg 2,000 feet

26.82 "Hg 3,000 feet

25.84 "Hg 4,000 feet

24.90 "Hg 5,000 feet

28.4 

28.5 

28.3 

28.2 

30.0 

29.9 

29.8 

Figure 3-9. Effects of nonstandard pressure on an altimeter.

29.92 "Hg

Figure 5-8. Effects of nonstandard pressure on an altimeter of an 

aircraft flown into air of lower than standard pressure (air is less 

dense).

mean sea level) is only 3,500 feet at Point B. The fact that 

the altitude indication is not always true lends itself to the 

memory aid, “When flying from hot to cold or from a high 

to a low, look out below.” [Figure 5-8]

Altimeter Enhancements (Encoding) 

It is not sufficient in the airspace system for only the pilot 

to have an indication of the aircraft’s altitude; the air traffic 

controller on the ground must also know the altitude of the 

aircraft. To provide this information, the aircraft is typically 

equipped with an encoding altimeter.

When the ATC transponder is set to Mode C, the encoding 

altimeter supplies the transponder with a series of pulses 

identifying the flight level (in increments of 100 feet) at 

which the aircraft is flying. This series of pulses is transmitted 

to the ground radar where they appear on the controller’s 

scope as an alphanumeric display around the return for the 

aircraft. The transponder allows the ground controller to 

identify the aircraft and determine the pressure altitude at 

which it is flying.

A computer inside the encoding altimeter measures the 

pressure referenced from 29.92 "Hg and delivers this data to 

the transponder. When the pilot adjusts the barometric scale 

to the local altimeter setting, the data sent to the transponder 

is not affected. This is to ensure that all Mode C aircraft are 

transmitting data referenced to a common pressure level. ATC 

equipment adjusts the displayed altitudes to compensate for 

local pressure differences allowing display of targets at correct 

altitudes. 14 CFR part 91 requires the altitude transmitted by 

the transponder to be within 125 feet of the altitude indicated 

on the instrument used to maintain flight altitude.

Reduced Vertical Separation Minimum (RVSM)

Below 31,000 feet, a 1,000 foot separation is the minimum 

required between usable flight levels. Flight levels (FLs) 

generally start at 18,000 feet where the local pressure is 

29.92 "Hg or greater. All aircraft 18,000 feet and above use 

a standard altimeter setting of 29.92 "Hg, and the altitudes 

are in reference to a standard hence termed FL. Between FL 

180 and FL 290, the minimum altitude separation is 1,000 

feet between aircraft. However, for flight above FL 290 

(primarily due to aircraft equipage and reporting capability; 

potential error) ATC applied the requirement of 2,000 feet of 

separation. FL 290, an altitude appropriate for an eastbound 

aircraft, would be followed by FL 310 for a westbound 

aircraft, and so on to FL 410, or seven FLs available for flight. 

With 1,000-foot separation, or a reduction of the vertical 

separation between FL 290 and FL 410, an additional six 

FLs become available. This results in normal flight level and 

direction management being maintained from FL 180 through 

FL 410. Hence the name is Reduced Vertical Separation 

Minimum (RVSM). Because it is applied domestically, it is 

called United States Domestic Reduced Vertical Separation 

Minimum (DRVSM).

However, there is a cost to participate in the DRVSM program 

which relates to both aircraft equipage and pilot training. For 

example, altimetry error must be reduced significantly and 

operators using RVSM must receive authorization from the 

appropriate civil aviation authority. RVSM aircraft must meet 

required altitude-keeping performance standards. Additionally, 

operators must operate in accordance with RVSM policies/

procedures applicable to the airspace where they are flying.

The aircraft must be equipped with at least one automatic 

altitude control—

• Within a tolerance band of ±65 feet about an acquired 

altitude when the aircraft is operated in straight-andlevel flight.

• Within a tolerance band of ±130 feet under no 

turbulent, conditions for aircraft for which application 

for type certification occurred on or before April 9, 

1997 that are equipped with an automatic altitude 

control system with flight management/performance 

system inputs.

That aircraft must be equipped with an altitude alert system 

that signals an alert when the altitude displayed to the flight 

crew deviates from the selected altitude by more than (in most 

cases) 200 feet. For each condition in the full RVSM flight 
5-8

FL Without RVSM With RVSM

7 Usable Flight Levels 13 Usable Flight Levels

410

400

390

380

370

360

350

340

330

320

310

300

290

Figure 3-9. Increase aircraft permitted between FL180 to FL410. Figure 5-9. Increase in aircraft permitted between FL 180 and FL 410.

Figure 5-10. Rate of climb or descent in thousands of feet per minute.

envelope, the largest combined absolute value for residual 

static source error plus the avionics error may not exceed 200 

feet. Aircraft with TCAS must have compatibility with RVSM 

Operations. Figure 5-9 illustrates the increase in aircraft 

permitted between FL 180 and FL 410. Most noteworthy, 

however, is the economization that aircraft can take advantage 

of by the higher FLs being available to more aircraft. 

Vertical Speed Indicator (VSI)

The VSI in Figure 5-10 is also called a vertical velocity 

indicator (VVI), and was formerly known as a rate-of-climb 

indicator. It is a rate-of-pressure change instrument that gives 

an indication of any deviation from a constant pressure level.

Inside the instrument case is an aneroid very much like the one 

in an ASI. Both the inside of this aneroid and the inside of the 

instrument case are vented to the static system, but the case 

is vented through a calibrated orifice that causes the pressure 

inside the case to change more slowly than the pressure inside 

the aneroid. As the aircraft ascends, the static pressure becomes 

lower. The pressure inside the case compresses the aneroid, 

moving the pointer upward, showing a climb and indicating 

the rate of ascent in number of feet per minute (fpm).

When the aircraft levels off, the pressure no longer changes. 

The pressure inside the case becomes equal to that inside 

the aneroid, and the pointer returns to its horizontal, or 

zero, position. When the aircraft descends, the static 

pressure increases. The aneroid expands, moving the pointer 

downward, indicating a descent. 

The pointer indication in a VSI lags a few seconds behind the 

actual change in pressure. However, it is more sensitive than 

an altimeter and is useful in alerting the pilot of an upward or 

downward trend, thereby helping maintain a constant altitude. 

Some of the more complex VSIs, called instantaneous vertical 

speed indicators (IVSI), have two accelerometer-actuated air 

pumps that sense an upward or downward pitch of the aircraft 

and instantaneously create a pressure differential. By the time 

the pressure caused by the pitch acceleration dissipates, the 

altitude pressure change is effective. 

Dynamic Pressure Type Instruments

Airspeed Indicator (ASI)

An ASI is a differential pressure gauge that measures the 

dynamic pressure of the air through which the aircraft is 

flying. Dynamic pressure is the difference in the ambient 

static air pressure and the total, or ram, pressure caused by 

the motion of the aircraft through the air. These two pressures 

are taken from the pitot-static system.

The mechanism of the ASI in Figure 5-11 consists of a thin, 

corrugated phosphor bronze aneroid, or diaphragm, that 

receives its pressure from the pitot tube. The instrument 

case is sealed and connected to the static ports. As the 

pitot pressure increases or the static pressure decreases, the 

diaphragm expands. This dimensional change is measured by 

a rocking shaft and a set of gears that drives a pointer across 

the instrument dial. Most ASIs are calibrated in knots, or 

nautical miles per hour; some instruments show statute miles 

per hour, and some instruments show both.
5-9

100

200

50

150

Ram air

Static air line

Pitot tube

Long lever

Sector

Handstaff pinion

Diaphragm

Pitot connection

Figure 3-11. Mechanism of an airspeed indicator. Figure 5-11. Mechanism of an ASI.

Figure 5-12. A true ASI allows the pilot to correct IAS for 

nonstandard temperature and pressure.

120 

130 

140 

150 

2 4 6 

MPH 

TEMP 

30 30 + 0 - 

AIRSPEED 

TRUE SPEED 

KNOTS 

I80 40 

60 

I60 

80 

I00 I20 

I40 

40 

I40 

I20 

60 

80 

100 

Figure 3-12. A true airspeed indicator allows the pilot to

correct indicated airspeed for nonstandard temperature and

pressure.

Some aircraft are equipped with true ASIs that have a 

temperature-compensated aneroid bellows inside the 

instrument case. This bellows modifies the movement of 

the rocking shaft inside the instrument case so the pointer 

shows the actual TAS. 

The TAS indicator provides both true and IAS. These 

instruments have the conventional airspeed mechanism, 

with an added subdial visible through cutouts in the regular 

dial. A knob on the instrument allows the pilot to rotate the 

subdial and align an indication of the outside air temperature 

with the pressure altitude being flown. This alignment causes 

the instrument pointer to indicate the TAS on the subdial. 

[Figure 5-12]

Types of Airspeed

Just as there are several types of altitude, there are multiple 

types of airspeed: indicated airspeed (IAS), calibrated 

airspeed (CAS), equivalent airspeed (EAS), and true airspeed 

(TAS).

Indicated Airspeed (IAS)

IAS is shown on the dial of the instrument, uncorrected for 

instrument or system errors.

Calibrated Airspeed (CAS) 

CAS is the speed at which the aircraft is moving through 

the air, which is found by correcting IAS for instrument 

and position errors. The POH/AFM has a chart or graph to 

correct IAS for these errors and provide the correct CAS for 

the various flap and landing gear configurations.

Equivalent Airspeed (EAS) 

EAS is CAS corrected for compression of the air inside the 

pitot tube. EAS is the same as CAS in standard atmosphere 

at sea level. As the airspeed and pressure altitude increase, 

the CAS becomes higher than it should be, and a correction 

for compression must be subtracted from the CAS.

True Airspeed (TAS) 

TAS is CAS corrected for nonstandard pressure and 

temperature. TAS and CAS are the same in standard 

atmosphere at sea level. Under nonstandard conditions, TAS 

is found by applying a correction for pressure altitude and 

temperature to the CAS. 
5-10

Figure 3-13. A Machmeter shows the ratio of the speed of

sound to the true airspeed the aircraft is flying.

Figure 5-13. A Machmeter shows the ratio of the speed of sound to 

the TAS the aircraft is flying.

240

220 

200 

I80 

I60 I40 I20 

I00 

80 

60 

40 

KNOTS 

Figure 3-14. A maximum allowable airspeed indicator has a

movable pointer that indicates the never-exceed speed, which

changes with altitude to avoid the onset of transonic shock waves.

Figure 5-14. A maximum allowable ASI has a movable pointer that 

indicates the never-exceed speed, which changes with altitude to 

avoid the onset of transonic shock waves.

or striped. The maximum airspeed pointer is actuated by an 

aneroid, or altimeter mechanism, that moves it to a lower 

value as air density decreases. By keeping the airspeed pointer 

at a lower value than the maximum pointer, the pilot avoids 

the onset of transonic shock waves.

Airspeed Color Codes

The dial of an ASI is color coded to alert the pilot, at a 

glance, of the significance of the speed at which the aircraft 

is flying. These colors and their associated airspeeds are 

shown in Figure 5-15.

Magnetism

The Earth is a huge magnet, spinning in space, surrounded 

by a magnetic field made up of invisible lines of flux. These 

lines leave the surface at the magnetic North Pole and reenter 

at the magnetic South Pole.

Lines of magnetic flux have two important characteristics: 

any magnet that is free to rotate aligns with them, and an 

electrical current is induced into any conductor that cuts 

across them. Most direction indicators installed in aircraft 

make use of one of these two characteristics.

The Basic Aviation Magnetic Compass 

One of the oldest and simplest instruments for indicating 

direction is the magnetic compass. It is also one of the basic 

instruments required by 14 CFR part 91 for both VFR and 

IFR flight.

Magnetic Compass Overview

A magnet is a piece of material, usually a metal containing 

iron, which attracts and holds lines of magnetic flux. 

Regardless of size, every magnet has two poles: a north 

pole and a south pole. When one magnet is placed in the 

Mach Number 

As an aircraft approaches the speed of sound, the air flowing 

over certain areas of its surface speeds up until it reaches 

the speed of sound, and shock waves form. The IAS at 

which these conditions occur changes with temperature. 

Therefore, in this case, airspeed is not entirely adequate to 

warn the pilot of the impending problems. Mach number 

is more useful. Mach number is the ratio of the TAS of 

the aircraft to the speed of sound in the same atmospheric 

conditions. An aircraft flying at the speed of sound is flying 

at Mach 1.0. Some older mechanical Machmeters not driven 

from an air data computer use an altitude aneroid inside 

the instrument that converts pitot-static pressure into Mach 

number. These systems assume that the temperature at any 

altitude is standard; therefore, the indicated Mach number is 

inaccurate whenever the temperature deviates from standard. 

These systems are called indicated Machmeters. Modern 

electronic Machmeters use information from an air data 

computer system to correct for temperature errors. These 

systems display true Mach number.

Most high-speed aircraft are limited to a maximum Mach 

number at which they can fly. This is shown on a Machmeter 

as a decimal fraction. [Figure 5-13] For example, if the 

Machmeter indicates .83 and the aircraft is flying at 30,000 

feet where the speed of sound under standard conditions is 

589.5 knots, the airspeed is 489.3 knots. The speed of sound 

varies with the air temperature. If the aircraft were flying at 

Mach .83 at 10,000 feet where the air is much warmer, its 

airspeed would be 530 knots.

Maximum Allowable Airspeed 

Some aircraft that fly at high subsonic speeds are equipped 

with maximum allowable ASIs like the one in Figure 5-14. 

This instrument looks much like a standard ASI, calibrated 

in knots, but has an additional pointer colored red, checkered, 
5-11

Airspeed for best single-engine rate-of-climb 

at gross weight and Sea Level 

80 

60 

I20 

I00 

I60 

I40 I20 

I00 

200 

I80 

Figure 3-15. Color codes for an airspeed indicator. 

240

220 

200 

I80 

I60 I40 I20 

I00 

80 

60 

40 

KNOTS 

Blue radial line 

Green arc 

White arc 

Yellow arc 

Red radial line 

Figure 5-15. Color codes for an ASI.

Figure 5-16. A magnetic compass. The vertical line is called the 

lubber line.

N-S E-W 

Figure 3-16. A Magnetic compass.

field of another, the unlike poles attract each other and like 

poles repel.

An aircraft magnetic compass, such as the one in Figure 5-16, 

has two small magnets attached to a metal float sealed inside a 

bowl of clear compass fluid similar to kerosene. A graduated 

scale, called a card, is wrapped around the float and viewed 

through a glass window with a lubber line across it. The card 

is marked with letters representing the cardinal directions, 

north, east, south, and west, and a number for each 30° 

between these letters. The final “0” is omitted from these 

directions; for example, 3 = 30°, 6 = 60°, and 33 = 330°. 

There are long and short graduation marks between the letters 

and numbers, with each long mark representing 10° and each 

short mark representing 5°.

Magnetic Compass Construction

The float and card assembly has a hardened steel pivot in its 

center that rides inside a special, spring-loaded, hard-glass 

jewel cup. The buoyancy of the float takes most of the weight 

off the pivot, and the fluid damps the oscillation of the float 

and card. This jewel-and-pivot type mounting allows the float 

freedom to rotate and tilt up to approximately 18° angle of 

bank. At steeper bank angles, the compass indications are 

erratic and unpredictable.

The compass housing is entirely full of compass fluid. To 

prevent damage or leakage when the fluid expands and 

contracts with temperature changes, the rear of the compass 

case is sealed with a flexible diaphragm, or with a metal 

bellows in some compasses.

Magnetic Compass Theory of Operations

The magnets align with the Earth’s magnetic field and the 

pilot reads the direction on the scale opposite the lubber line. 

Note that in Figure 5-16, the pilot sees the compass card from 

its backside. When the pilot is flying north as the compass 

shows, east is to the pilot’s right, but on the card “33”, which 

represents 330° (west of north), is to the right of north. The 

reason for this apparent backward graduation is that the card 

remains stationary, and the compass housing and the pilot 

turn around it, always viewing the card from its backside.

Magnetic fields caused by aircraft electronics and wiring 

can effect the accuracy of the magnetic compass. This 

induced error is called compass deviation. Compensator 

assemblies mounted on the compass allow aviation 
5-12

0Ň

15ŇN

30ŇN

45ŇN

60ŇN

70 ̊N 70 ̊N

70 ̊N 70 ̊N

15ŇS

30ŇS

45ŇS

60ŇN

0Ň

15ŇN

30ŇN

45ŇN

60ŇN

60ŇN

15ŇS

30ŇS

45ŇS

180 ̊W 165ŇW 150ŇW 135ŇW 120ŇW 105ŇW 90ŇW 75ŇW 60ŇW 45ŇW 30ŇW 15ŇW 0Ň 180 ̊W

180 ̊W 180 ̊W

15ŇE 30ŇE 45ŇE 60ŇE 75ŇE 90ŇE 105ŇE 120ŇE 135ŇE 150ŇE 165ŇE

165ŇW 150ŇW 135ŇW 120ŇW 105ŇW 90ŇW 75ŇW 60ŇW 45ŇW 30ŇW 15ŇW 0Ň 15ŇE 30ŇE 45ŇE 60ŇE 75ŇE 90ŇE 105ŇE 120ŇE 135ŇE 150ŇE 165ŇE

60

50

40

30

20

10

10

20

0

0

10

0

20

10

0

0

20

10

130

110 100 90

80 70

60 50

40

30

80

70

20

10

-40

-90

-100

-110

-120

-130

-50

-40

-30

-20

-10

-30

-20

-10

-20

-30

-10

-10

-80

-70

-60

-20

-10

-10

Main field declination (D)

Contour interval: 2 degrees

 red contours positive (east)

 blue negative (west)

 pink (agonic) zero line.

Mercator Projection.

 Position of dip poles

Figure 5-17. Isogonic lines are lines of equal variation.

maintenance technicians (AMTs) to calibrate the compass 

by creating magnetic fields inside of the compass housing. 

The compensator assembly has two shafts whose ends have 

screwdriver slots accessible from the front of the compass. 

Each shaft rotates one or two small compensating magnets. 

The end of one shaft is marked E-W, and its magnets affect 

the compass when the aircraft is pointed east or west. The 

other shaft is marked N-S and its magnets affect the compass 

when the aircraft is pointed north or south.

Magnetic Compass Errors

The magnetic compass is the simplest instrument in the panel, 

but it is subject to a number of errors that must be considered.

Variation 

The Earth rotates about its geographic axis; maps and charts 

are drawn using meridians of longitude that pass through the 

geographic poles. Directions measured from the geographic 

poles are called true directions. The north magnetic pole to 

which the magnetic compass points is not collocated with 

the geographic north pole, but is some 1,300 miles away; 

directions measured from the magnetic poles are called 

magnetic directions. In aerial navigation, the difference 

between true and magnetic directions is called variation. This 

same angular difference in surveying and land navigation is 

called declination.

Figure 5-17 shows the isogonic lines that identify the number 

of degrees of variation in their area. The line that passes near 

Chicago is called the agonic line. Anywhere along this line 

the two poles are aligned, and there is no variation. East of 

this line, the magnetic pole is to the west of the geographic 

pole and a correction must be applied to a compass indication 

to get a true direction.

Flying in the Washington, D.C. area, for example, the 

variation is 10° west. If the pilot wants to fly a true course of 

south (180°), the variation must be added to this resulting in 

a magnetic course to fly of 190°. Flying in the Los Angeles, 

CA area, the variation is 14° east. To fly a true course of 180° 

there, the pilot would have to subtract the variation and fly a 

magnetic course of 166°. The variation error does not change 

with the heading of the aircraft; it is the same anywhere along 

the isogonic line.

Deviation 

The magnets in a compass align with any magnetic field. 

Local magnetic fields in an aircraft caused by electrical 

current flowing in the structure, in nearby wiring or any 

magnetized part of the structure, conflict with the Earth’s 

magnetic field and cause a compass error called deviation.

Deviation, unlike variation, is different on each heading, but 

it is not affected by the geographic location. Variation error 

cannot be reduced or changed, but deviation error can be 

minimized when a pilot or AMT performs the maintenance 

task known as “swinging the compass.”

Some airports have a compass rose, which is a series of lines 

marked out on a taxiway or ramp at some location where there 
5-13

030 

060 

E 

120 

S 

150 

210 

240 

W 

300 

330 

N 

Figure 3-18. A Compass rose upon which deviation error is compensated for. 

True north

Figure 5-18. Utilization of a compass rose aids compensation for 

deviation errors.

Figure 3-19. A compass correction card shows the deviation

correction for any heading.

Figure 5-19. A compass correction card shows the deviation 

correction for any heading.

is no magnetic interference. Lines, oriented to magnetic north, 

are painted every 30°, as shown in Figure 5-18.

The pilot or AMT aligns the aircraft on each magnetic 

heading and adjusts the compensating magnets to minimize 

the difference between the compass indication and the actual 

magnetic heading of the aircraft. Any error that cannot be 

removed is recorded on a compass correction card, like the 

one in Figure 5-19, and placed in a cardholder near the 

compass. If the pilot wants to fly a magnetic heading of 

120° and the aircraft is operating with the radios on, the pilot 

should fly a compass heading of 123°.

The corrections for variation and deviation must be applied 

in the correct sequence as shown below starting from the 

true course desired.

Step 1: Determine the Magnetic Course

True Course (180°) ± Variation (+10°) = Magnetic Course (190°)

The Magnetic Course (190°) is steered if there is no deviation 

error to be applied. The compass card must now be considered 

for the compass course of 190°. 

Step 2: Determine the Compass Course

Magnetic Course (190°, from step 1) ± Deviation (–2°, from 

correction card) = Compass Course (188°)

NOTE: Intermediate magnetic courses between those listed 

on the compass card need to be interpreted. Therefore, to 

steer a true course of 180°, the pilot would follow a compass 

course of 188°. 

To find true course when the compass course is known, remove 

the variation and deviation corrections previously applied:

Compass Course ± Deviation = Magnetic Course ± Variation 

= True Course

Northerly Turning Errors

The center of gravity of the float assembly is located lower 

than the pivotal point. As the airplane turns, the force that 

results from the magnetic dip causes the float assembly to 

swing in the same direction that the float turns. The result 

is a false northerly turn indication. Because of this lead of 

the compass card, or float assembly, a northerly turn should 

be stopped prior to arrival at the desired heading. This 

compass error is amplified with the proximity to either pole. 

One rule of thumb to correct for this leading error is to stop 

the turn 15° plus half of the latitude (i.e., if the airplane is 

being operated in a position around the 40° of latitude, the 

turn should be stopped 15° + 20° = 35° prior to the desired 

heading). [Figure 5-20A]

Southerly Turning Errors

When turning in a southerly direction, the forces are such that 

the compass float assembly lags rather than leads. The result 

is a false southerly turn indication. The compass card, or float 

assembly, should be allowed to pass the desired heading prior 

to stopping the turn. As with the northerly error, this error is 

amplified with the proximity to either pole. To correct this 

lagging error, the aircraft should be allowed to pass the desired 

heading prior to stopping the turn. The same rule of 15° plus 

half of the latitude applies here (i.e., if the airplane is being 

operated in a position around the 30° of latitude, the turn 

should be stopped 15° + 15° + 30° after passing the desired 

heading). [Figure 5-20B]

Acceleration Error

The magnetic dip and the forces of inertia cause magnetic 

compass errors when accelerating and decelerating on Easterly 

and westerly headings. Because of the pendulous-type 

mounting, the aft end of the compass card is tilted upward 

when accelerating, and downward when decelerating during 
5-14

NORTH

South

Figure 3-21. The effects of acceleration error.

OBS 

N 

E 

S 

W 

3 

33 

24 21 

15 12 

30

6

NAV

GS 

View is from the pilot’s

perspective, and the 

movable card is reset 

after each turn

Figure 5-21. The effects of acceleration error.

21 S 15 12 21 S 15 12 21 S 15 12

Dip effect

CARD

CARD

Left turn No error Right turn

Dip effect

DIP DIP DIP

B

3 N 33 30

3 N 33 30

3

N 33 30

CARD

Dip effect

CARD

Dip effect

Left turn No error Right turn A

DIP DIP

DIP

Figure 5-20. Northerly turning error.

changes of airspeed. When accelerating on either an easterly 

or westerly heading , the error appears as a turn indication 

toward north. When decelerating on either of these headings, 

the compass indicates a turn toward south. The word "ANDS" 

(Acceleration-North/Deceleration-South) may help you to 

remember the acceleration error. [Figure 5-21]

Oscillation Error 

Oscillation is a combination of all of the other errors, and it 

results in the compass card swinging back and forth around 

the heading being flown. When setting the gyroscopic 

heading indicator to agree with the magnetic compass, use 

the average indication between the swings.
5-15

N 

W 

S 

E 

33 

30 

24 

21 

15 

12 

6 

3 

Figure 3-22. A vertical card magnetic compass. Figure 5-22. Vertical card magnetic compass.

Figure 3-23. The soft iron frame of the flux valve accepts the

flux from the Earth’s magnetic field each time the current in the 

center coil reverse. This flux causes current to flow in the three 

picked coils.

Figure 5-23. The soft iron frame of the flux valve accepts the flux from 

the Earth’s magnetic field each time the current in the center coil 

reverses. This flux causes current to flow in the three pickup coils.

Figure 3-24. The current in each of the three pickup coils

changes with the heading of the aircraft.

Figure 5-24. The current in each of the three pickup coils changes 

with the heading of the aircraft.

The Vertical Card Magnetic Compass

The floating magnet type of compass not only has all the 

errors just described, but also lends itself to confused reading. 

It is easy to begin a turn in the wrong direction because its card 

appears backward. East is on what the pilot would expect to be 

the west side. The vertical card magnetic compass eliminates 

some of the errors and confusion. The dial of this compass 

is graduated with letters representing the cardinal directions, 

numbers every 30°, and marks every 5°. The dial is rotated by 

a set of gears from the shaft-mounted magnet, and the nose 

of the symbolic airplane on the instrument glass represents 

the lubber line for reading the heading of the aircraft from 

the dial. Eddy currents induced into an aluminum-damping 

cup damp oscillation of the magnet. [Figure 5-22]

The Flux Gate Compass System

As mentioned earlier, the lines of flux in the Earth’s magnetic 

field have two basic characteristics: a magnet aligns with 

these lines, and an electrical current is induced, or generated, 

in any wire crossed by them.

The flux gate compass that drives slaved gyros uses the 

characteristic of current induction. The flux valve is a small, 

segmented ring, like the one in Figure 5-23, made of soft iron 

that readily accepts lines of magnetic flux. An electrical coil 

is wound around each of the three legs to accept the current 

induced in this ring by the Earth’s magnetic field. A coil 

wound around the iron spacer in the center of the frame has 

400-Hz alternating current (A.C.) flowing through it. During 

the times when this current reaches its peak, twice during each 

cycle, there is so much magnetism produced by this coil that 

the frame cannot accept the lines of flux from the Earth’s field.

But as the current reverses between the peaks, it demagnetizes 

the frame so it can accept the flux from the Earth’s field. As 

this flux cuts across the windings in the three coils, it causes 

current to flow in them. These three coils are connected in 

such a way that the current flowing in them changes as the 

heading of the aircraft changes. [Figure 5-24]

The three coils are connected to three similar but smaller coils 

in a synchro inside the instrument case. The synchro rotates 

the dial of a radio magnetic indicator (RMI) or a horizontal 

situation indicator (HSI).

Remote Indicating Compass

Remote indicating compasses were developed to compensate 

for the errors and limitations of the older type of heading 

indicators. The two panel-mounted components of a typical 
5-16

33

30

24

2I

I5

I2

6

3

N

S

E

W

Figure 5-26. Driven by signals from a flux valve, the compass card 

in this RMI indicates the heading of the aircraft opposite the upper 

center index mark. The green pointer is driven by the ADF. The 

yellow pointer is driven by the VOR receiver.

33

30

24

2I

I5

I2

6

3

Slaving control compensator unit Slaving meter 

Pictorial navigation indicator (HSI) 

Figure 5-25. The pictorial navigation indicator is commonly 

referred to as an HSI.

system are the pictorial navigation indicator and the slaving 

control and compensator unit. [Figure 5-25] The pictorial 

navigation indicator is commonly referred to as an HSI.

The slaving control and compensator unit has a pushbutton 

that provides a means of selecting either the “slaved gyro” 

or “free gyro” mode. This unit also has a slaving meter 

and two manual heading-drive buttons. The slaving meter 

indicates the difference between the displayed heading 

and the magnetic heading. A right deflection indicates a 

clockwise error of the compass card; a left deflection indicates 

a counterclockwise error. Whenever the aircraft is in a turn 

and the card rotates, the slaving meter shows a full deflection 

to one side or the other. When the system is in “free gyro” 

mode, the compass card may be adjusted by depressing the 

appropriate heading-drive button.

A separate unit, the magnetic slaving transmitter is mounted 

remotely; usually in a wingtip to eliminate the possibility of 

magnetic interference. It contains the flux valve, which is 

the direction-sensing device of the system. A concentration 

of lines of magnetic force, after being amplified, becomes 

a signal relayed to the heading indicator unit, which is also 

remotely mounted. This signal operates a torque motor in 

the heading indicator unit that processes the gyro unit until 

it is aligned with the transmitter signal. The magnetic slaving 

transmitter is connected electrically to the HSI.

There are a number of designs of the remote indicating 

compass; therefore, only the basic features of the system are 

covered here. Instrument pilots must become familiar with 

the characteristics of the equipment in their aircraft.

As instrument panels become more crowded and the pilot’s 

available scan time is reduced by a heavier flight deck 

workload, instrument manufacturers have worked toward 

combining instruments. One good example of this is the 

RMI in Figure 5-26. The compass card is driven by signals 

from the flux valve, and the two pointers are driven by an 

automatic direction finder (ADF) and a very high frequency 

omnidirectional range (VOR).

Gyroscopic Systems

Flight without reference to a visible horizon can be safely 

accomplished by the use of gyroscopic instrument systems 

and the two characteristics of gyroscopes, which are rigidity 

and precession. These systems include attitude, heading, 

and rate instruments, along with their power sources. These 

instruments include a gyroscope (or gyro) that is a small wheel 

with its weight concentrated around its periphery. When this 

wheel is spun at high speed, it becomes rigid and resists tilting 

or turning in any direction other than around its spin axis.

Attitude and heading instruments operate on the principle 

of rigidity. For these instruments, the gyro remains rigid 

in its case and the aircraft rotates about it. Rate indicators, 

such as turn indicators and turn coordinators, operate on the 

principle of precession. In this case, the gyro precesses (or 

rolls over) proportionate to the rate the aircraft rotates about 

one or more of its axes.
5-17

2 MIN TURN DC ELEC 

L R 

Figure 3-27. A venturi tube provides the low pressure inside the 

instrument case to drive the gyros. 

- - 

Figure 5-27. A venturi tube system that provides necessary vacuum 

to operate key instruments.

Vacuum Pump Systems

Wet-Type Vacuum Pump

Steel-vane air pumps have been used for many years to 

evacuate the instrument cases. The vanes in these pumps 

are lubricated by a small amount of engine oil metered into 

the pump and discharged with the air. In some aircraft the 

discharge air is used to inflate rubber deicer boots on the 

wing and empennage leading edges. To keep the oil from 

deteriorating the rubber boots, it must be removed with an 

oil separator like the one in Figure 5-28.

The vacuum pump moves a greater volume of air than is 

needed to supply the instruments with the suction needed, 

so a suction-relief valve is installed in the inlet side of the 

pump. This spring-loaded valve draws in just enough air to 

maintain the required low pressure inside the instruments, 

as is shown on the suction gauge in the instrument panel. 

Filtered air enters the instrument cases from a central air 

filter. As long as aircraft fly at relatively low altitudes, enough 

air is drawn into the instrument cases to spin the gyros at a 

sufficiently high speed.

Dry Air Vacuum Pump

As flight altitudes increase, the air is less dense and more air 

must be forced through the instruments. Air pumps that do not 

mix oil with the discharge air are used in high flying aircraft.

Steel vanes sliding in a steel housing need to be lubricated, 

but vanes made of a special formulation of carbon sliding 

inside carbon housing provide their own lubrication in a 

microscopic amount as they wear.

Pressure Indicating Systems

Figure 5-29 is a diagram of the instrument pneumatic system 

of a twin-engine general aviation airplane. Two dry air 

pumps are used with filters in their inlets to filter out any 

contaminants that could damage the fragile carbon vanes in 

the pump. The discharge air from the pump flows through 

a regulator, where excess air is bled off to maintain the 

pressure in the system at the desired level. The regulated air 

then flows through inline filters to remove any contamination 

that could have been picked up from the pump, and from 

there into a manifold check valve. If either engine should 

become inoperative or either pump should fail, the check 

valve isolates the inoperative system and the instruments are 

driven by air from the operating system. After the air passes 

through the instruments and drives the gyros, it is exhausted 

from the case. The gyro pressure gauge measures the pressure 

drop across the instruments.

Electrical Systems

Many general aviation aircraft that use pneumatic attitude 

indicators use electric rate indicators and/or the reverse. Some 

Power Sources 

Aircraft and instrument manufacturers have designed 

redundancy in the flight instruments so that any single failure 

does not deprive the pilot of the ability to safely conclude 

the flight. Gyroscopic instruments are crucial for instrument 

flight; therefore, they are powered by separate electrical or 

pneumatic sources.

Pneumatic Systems 

Pneumatic gyros are driven by a jet of air impinging on 

buckets cut into the periphery of the wheel. On many aircraft 

this stream of air is obtained by evacuating the instrument 

case with a vacuum source and allowing filtered air to flow 

into the case through a nozzle to spin the wheel.

Venturi Tube Systems 

Aircraft that do not have a pneumatic pump to evacuate the 

instrument case can use venturi tubes mounted on the outside 

of the aircraft, similar to the system shown in Figure 5-27. Air 

flowing through the venturi tube speeds up in the narrowest 

part and, according to Bernoulli’s principle, the pressure 

drops. This location is connected to the instrument case by 

a piece of tubing. The two attitude instruments operate on 

approximately 4 "Hg of suction; the turn-and-slip indicator 

needs only 2 "Hg, so a pressure-reducing needle valve is 

used to decrease the suction. Air flows into the instruments 

through filters built into the instrument cases. In this system, 

ice can clog the venturi tube and stop the instruments when 

they are most needed. 
5-18

Figure 3-29. Twin-engine instrument pressure system using a carbon-vane dry-type air pump.

Figure 5-29. Twin-engine instrument pressure system using a carbon-vane, dry-type air pump.

Figure 3-28. Single-engine instrument vacuum system using a steel-vane wet-type vacuum pump.

Figure 5-28. Single-engine instrument vacuum system using a steel-vane, wet-type vacuum pump.
5-19

20 20 

I0 I0

2 0 

I 0 

Figure 3-30. The dial of this attitude indicator has reference

lines to show pitch and roll.

10° 

20° 

30° 

45° 

60° 

Figure 5-30. The dial of this attitude indicator has reference lines 

to show pitch and roll.

instruments identify their power source on their dial, but it 

is extremely important that pilots consult the POH/AFM to 

determine the power source of all instruments to know what 

action to take in the event of an instrument failure. Direct 

current (D.C.) electrical instruments are available in 14- or 

28-volt models, depending upon the electrical system in 

the aircraft. A.C. is used to operate some attitude gyros and 

autopilots. Aircraft with only D.C. electrical systems can use 

A.C. instruments via installation of a solid-state D.C. to A.C. 

inverter, which changes 14 or 28 volts D.C. into three-phase 

115-volt, 400-Hz A.C.

Gyroscopic Instruments

Attitude Indicators

The first attitude instrument (AI) was originally referred to as 

an artificial horizon, later as a gyro horizon; now it is more 

properly called an attitude indicator. Its operating mechanism 

is a small brass wheel with a vertical spin axis, spun at a high 

speed by either a stream of air impinging on buckets cut into 

its periphery, or by an electric motor. The gyro is mounted in 

a double gimbal, which allows the aircraft to pitch and roll 

about the gyro as it remains fixed in space.

A horizon disk is attached to the gimbals so it remains in 

the same plane as the gyro, and the aircraft pitches and 

rolls about it. On early instruments, this was just a bar that 

represented the horizon, but now it is a disc with a line 

representing the horizon and both pitch marks and bank-angle 

lines. The top half of the instrument dial and horizon disc 

is blue, representing the sky; and the bottom half is brown, 

representing the ground. A bank index at the top of the 

instrument shows the angle of bank marked on the banking 

scale with lines that represent 10°, 20°, 30°, 45°, and 60°. 

[Figure 5-30]

A small symbolic aircraft is mounted in the instrument case 

so it appears to be flying relative to the horizon. A knob at the 

bottom center of the instrument case raises or lowers the aircraft 

to compensate for pitch trim changes as the airspeed changes. 

The width of the wings of the symbolic aircraft and the dot in the 

center of the wings represent a pitch change of approximately 2°.

For an AI to function properly, the gyro must remain 

vertically upright while the aircraft rolls and pitches around 

it. The bearings in these instruments have a minimum of 

friction; however, even this small amount places a restraint 

on the gyro producing precession and causing the gyro to tilt. 

To minimize this tilting, an erection mechanism inside the 

instrument case applies a force any time the gyro tilts from 

its vertical position. This force acts in such a way to return 

the spinning wheel to its upright position.

The older artificial horizons were limited in the amount of 

pitch or roll they could tolerate, normally about 60° in pitch 

and 100° in roll. After either of these limits was exceeded, 

the gyro housing contacted the gimbals, applying such a 

precessing force that the gyro tumbled. Because of this 

limitation, these instruments had a caging mechanism that 

locked the gyro in its vertical position during any maneuvers 

that exceeded the instrument limits. Newer instruments do 

not have these restrictive tumble limits; therefore, they do 

not have a caging mechanism.

When an aircraft engine is first started and pneumatic or electric 

power is supplied to the instruments, the gyro is not erect. A 

self-erecting mechanism inside the instrument actuated by the 

force of gravity applies a precessing force, causing the gyro to 

rise to its vertical position. This erection can take as long as 5 

minutes, but is normally done within 2 to 3 minutes.

Attitude indicators are free from most errors, but depending 

upon the speed with which the erection system functions, 

there may be a slight nose-up indication during a rapid 

acceleration and a nose-down indication during a rapid 

deceleration. There is also a possibility of a small bank angle 

and pitch error after a 180° turn. These inherent errors are 

small and correct themselves within a minute or so after 

returning to straight-and-level flight.

Heading Indicators

A magnetic compass is a dependable instrument used as a 

backup instrument. Although very reliable, it has so many 

inherent errors that it has been supplemented with gyroscopic 

heading indicators.

The gyro in a heading indicator is mounted in a double gimbal, 

as in an attitude indicator, but its spin axis is horizontal 

permitting sensing of rotation about the vertical axis of the 
5-20

30 33 

24 2I 

I5 I2 

6 3 

Figure 3-31. The heading indicator is not north-seeking, but

must be set to agree with the magnetic compass.

Figure 5-31. The heading indicator is not north seeking, but must 

be set periodically (about every 15 minutes) to agree with the 

magnetic compass.

Plane of Precession 

Plane of Force 

Plane of Rotation 

FORCE 

Figure 3-32. Precession causes a force applied to a spinning

wheel to be felt 90 degree from the point of application in the 

direction of rotation.

Figure 5-32. Precession causes a force applied to a spinning 

wheel to be felt 90° from the point of application in the direction 

of rotation.

aircraft. Gyro heading indicators, with the exception of slaved 

gyro indicators, are not north seeking, therefore they must 

be manually set to the appropriate heading by referring to 

a magnetic compass. Rigidity causes them to maintain this 

heading indication, without the oscillation and other errors 

inherent in a magnetic compass.

Older directional gyros use a drum-like card marked in the 

same way as the magnetic compass card. The gyro and the 

card remain rigid inside the case with the pilot viewing the 

card from the back. This creates the possibility the pilot might 

start a turn in the wrong direction similar to using a magnetic 

compass. A knob on the front of the instrument, below the 

dial, can be pushed in to engage the gimbals. This locks the 

gimbals allowing the pilot to rotate the gyro and card until 

the number opposite the lubber line agrees with the magnetic 

compass. When the knob is pulled out, the gyro remains rigid 

and the aircraft is free to turn around the card.

Directional gyros are almost all air-driven by evacuating the 

case and allowing filtered air to flow into the case and out 

through a nozzle, blowing against buckets cut in the periphery 

of the wheel. The Earth constantly rotates at 15° per hour 

while the gyro is maintaining a position relative to space, thus 

causing an apparent drift in the displayed heading of 15° per 

hour. When using these instruments, it is standard practice to 

compare the heading indicated on the directional gyro with 

the magnetic compass at least every 15 minutes and to reset 

the heading as necessary to agree with the magnetic compass. 

Heading indicators like the one in Figure 5-31 work on the 

same principle as the older horizontal card indicators, except 

that the gyro drives a vertical dial that looks much like the 

dial of a vertical card magnetic compass. The heading of the 

aircraft is shown against the nose of the symbolic aircraft on 

the instrument glass, which serves as the lubber line. A knob 

in the front of the instrument may be pushed in and turned 

to rotate the gyro and dial. The knob is spring loaded so it 

disengages from the gimbals as soon as it is released. This 

instrument should be checked about every 15 minutes to see 

if it agrees with the magnetic compass.

Turn Indicators

Attitude and heading indicators function on the principle 

of rigidity, but rate instruments such as the turn-andslip indicator operate on precession. Precession is the 

characteristic of a gyroscope that causes an applied force to 

produce a movement, not at the point of application, but at 

a point 90° from the point of application in the direction of 

rotation. [Figure 5-32]

Turn-and-Slip Indicator

The first gyroscopic aircraft instrument was the turn indicator 

in the needle and ball, or turn-and-bank indicator, which 

has more recently been called a turn-and-slip indicator. 

[Figure 5-33]

The inclinometer in the instrument is a black glass ball sealed 

inside a curved glass tube that is partially filled with a liquid 

for damping. This ball measures the relative strength of the 

force of gravity and the force of inertia caused by a turn. 

When the aircraft is flying straight-and-level, there is no 

inertia acting on the ball, and it remains in the center of the 

tube between two wires. In a turn made with a bank angle 

that is too steep, the force of gravity is greater than the inertia 

and the ball rolls down to the inside of the turn. If the turn is 
5-21

2 MIN TURN DC ELEC 

L R 

Figure 3-33 Turn-and slip indicator. Figure 5-33. Turn-and-slip indicator.

Gyro rotation

Inclinometer

Gimbal rotation

Standard rate

turn index

Horizontal gyro

Gyro rotation

Gimbal

Standard rate

turn index

Canted gyro

Gimbal rotation

Figure 3-34. The rate gyro in a turn-and-slip indicator and turn coordinator.

Figure 5-34. The rate gyro in both turn-and-slip indicator and turn 

coordinator.

made with too shallow a bank angle, the inertia is greater than 

gravity and the ball rolls upward to the outside of the turn.

The inclinometer does not indicate the amount of bank, nor 

does it indicate slip; it only indicates the relationship between 

the angle of bank and the rate of yaw.

The turn indicator is a small gyro spun either by air or by an 

electric motor. The gyro is mounted in a single gimbal with its 

spin axis parallel to the lateral axis of the aircraft and the axis 

of the gimbal parallel with the longitudinal axis. [Figure 5-34]

When the aircraft yaws, or rotates about its vertical axis, it 

produces a force in the horizontal plane that, due to precession, 

causes the gyro and its gimbal to rotate about the gimbal’s 

axis. It is restrained in this rotation plane by a calibration 

spring; it rolls over just enough to cause the pointer to deflect 

until it aligns with one of the doghouse-shaped marks on the 

dial, when the aircraft is making a standard rate turn.

The dial of these instruments is marked “2 MIN TURN.” 

Some turn-and-slip indicators used in faster aircraft are 

marked “4 MIN TURN.” In either instrument, a standard 

rate turn is being made whenever the needle aligns with a 

doghouse. A standard rate turn is 3° per second. In a 2 minute 

instrument, if the needle is one needle width either side of 

the center alignment mark, the turn is 3° per second and the 

turn takes 2 minutes to execute a 360° turn. In a 4 minute 

instrument, the same turn takes two widths deflection of the 

needle to achieve 3° per second.

Turn Coordinator

The major limitation of the older turn-and-slip indicator is that 

it senses rotation only about the vertical axis of the aircraft. 

It tells nothing of the rotation around the longitudinal axis, 

which in normal flight occurs before the aircraft begins to turn.

A turn coordinator operates on precession, the same as the 

turn indicator, but its gimbals frame is angled upward about 

30° from the longitudinal axis of the aircraft. [Figure 5-34]

This allows it to sense both roll and yaw. Therefore during 

a turn, the indicator first shows the rate of banking and once 

stabilized, the turn rate. Some turn coordinator gyros are 

dual-powered and can be driven by either air or electricity.

Rather than using a needle as an indicator, the gimbal moves 

a dial that is the rear view of a symbolic aircraft. The bezel 

of the instrument is marked to show wings-level flight and 

bank angles for a standard rate turn. [Figure 5-35]

The inclinometer, similar to the one in a turn-and-slip 

indicator, is called a coordination ball, which shows the 

relationship between the bank angle and the rate of yaw. The 

turn is coordinated when the ball is in the center, between the 

marks. The aircraft is skidding when the ball rolls toward the 

outside of the turn and is slipping when it moves toward the 
5-22

Figure 5-36. The Kearfott Attitude Heading Reference System (AHRS) on the left incorporates a Monolithic Ring Laser Gyro (MRLG) 

(center), which is housed in an Inertial Sensor Assembly (ISA) on the right.

TURN COORDINATOR 

2 MIN. 

D.C. 

ELEC. 

L R 

NO PITCH 

INFORMATION 

Figure 3-35. A turn coordinator senses rotation about 

both the roll and yaw axes.

Figure 5-35. A turn coordinator senses rotation about both roll 

and yaw axes.

inside of the turn. A turn coordinator does not sense pitch. 

This is indicated on some instruments by placing the words 

“NO PITCH INFORMATION” on the dial.

Flight Support Systems

Attitude and Heading Reference System (AHRS)

As aircraft displays have transitioned to new technology, 

the sensors that feed them have also undergone significant 

change. Traditional gyroscopic flight instruments have 

been replaced by Attitude and Heading Reference Systems 

(AHRS) improving reliability and thereby reducing cost and 

maintenance. 

The function of an AHRS is the same as gyroscopic systems; 

that is, to determine which way is level and which way is 

north. By knowing the initial heading the AHRS can determine 

both the attitude and magnetic heading of the aircraft. 

The genesis of this system was initiated by the development 

of the ring-LASAR gyroscope developed by Kearfott located 

in Little Falls, New Jersey. [Figure 5-36] Their development 

of the Ring-LASAR gyroscope in the 1960s/1970s was 

in support of Department of Defense (DOD) programs to 

include cruise missile technology. With the precision of 

these gyroscopes, it became readily apparent that they could 

be leveraged for multiple tasks and functions. Gyroscopic 

miniaturization has become so common that solid-state 

gyroscopes are found in products from robotics to toys.

Because the AHRS system replaces separate gyroscopes, 

such as those associated with an attitude indicator, magnetic 

heading indicator and turn indicator these individual systems 

are no longer needed. As with many systems today, AHRS 

itself had matured with time. Early AHRS systems used 

expensive inertial sensors and flux valves. However, today the 

AHRS for aviation and general aviation in particular are small 

solid-state systems integrating a variety of technology such 

as low cost inertial sensors, rate gyros, and magnetometers, 

and have capability for satellite signal reception.

Air Data Computer (ADC)

An Air Data Computer (ADC) [Figure 5-37] is an aircraft 

computer that receives and processes pitot pressure, static 
5-23

G 

S 

HDG 

NAV

33 

30 

24 

2I 

I5 

I2 

6 3 

Heading select bug 

Compass warning flag 

Heading select knob 

NAV warning flag 

Lubber line 

Course select knob 

Course deviation bar (CDI) 

Course deviation scale 

Course select pointer 

Compass card 

Symbolic aircraft 

Glideslope

deviation scale

Dual glideslope

pointers

TO/FROM indicator 

Figure 5-38. Horizontal situation indicator (HSI). Figure 3-37. HSI 

Figure 5-37. Air data computer (Collins). 

pressure, and temperature to calculate very precise altitude, 

IAS, TAS, and air temperature. The ADC outputs this 

information in a digital format that can be used by a variety 

of aircraft systems including an EFIS. Modern ADCs are 

small solid-state units. Increasingly, aircraft systems such as 

autopilots, pressurization, and FMS utilize ADC information 

for normal operations. 

NOTE: In most modern general aviation systems, both the 

AHRS and ADC are integrated within the electronic displays 

themselves thereby reducing the number of units, reducing 

weight, and providing simplification for installation resulting 

in reduced costs.

Analog Pictorial Displays

Horizontal Situation Indicator (HSI) 

The HSI is a direction indicator that uses the output from 

a flux valve to drive the dial, which acts as the compass 

card. This instrument, shown in Figure 5-38, combines the 

magnetic compass with navigation signals and a glideslope. 

This gives the pilot an indication of the location of the aircraft 

with relationship to the chosen course.

In Figure 5-38, the aircraft heading displayed on the rotating 

azimuth card under the upper lubber line is North or 360°. 

The course-indicating arrowhead shown is set to 020; the 

tail indicates the reciprocal, 200°. The course deviation bar 

operates with a VOR/Localizer (VOR/LOC) navigation 

receiver to indicate left or right deviations from the course 

selected with the course-indicating arrow, operating in the 

same manner that the angular movement of a conventional 

VOR/LOC needle indicates deviation from course.

The desired course is selected by rotating the course-indicating 

arrow in relation to the azimuth card by means of the course 

select knob. This gives the pilot a pictorial presentation: the 

fixed aircraft symbol and course deviation bar display the 

aircraft relative to the selected course, as though the pilot were 

above the aircraft looking down. The TO/FROM indicator is 

a triangular pointer. When the indicator points to the head of 

the course arrow, it shows that the course selected, if properly 

intercepted and flown, takes the aircraft to the selected facility. 

When the indicator points to the tail of the course arrow, it 

shows that the course selected, if properly intercepted and 

flown, takes the aircraft directly away from the selected facility.

The glideslope deviation pointer indicates the relation of 

the aircraft to the glideslope. When the pointer is below the 

center position, the aircraft is above the glideslope, and an 

increased rate of descent is required. In most installations, 

the azimuth card is a remote indicating compass driven by 

a fluxgate; however, in few installations where a fluxgate is 

not installed, or in emergency operation, the heading must 

be checked against the magnetic compass occasionally and 

reset with the course select knob.

Attitude Direction Indicator (ADI) 

Advances in attitude instrumentation combine the gyro 

horizon with other instruments such as the HSI, thereby 

reducing the number of separate instruments to which the 

pilot must devote attention. The attitude direction indicator 

(ADI) is an example of such technological advancement. 

A flight director incorporates the ADI within its system, 

which is further explained below (Flight Director System). 

However, an ADI need not have command cues; however, 

it is normally equipped with this feature.

Flight Director System (FDS)

A Flight Director System (FDS) combines many instruments 

into one display that provides an easily interpreted 

understanding of the aircraft’s flightpath. The computed 

solution furnishes the steering commands necessary to obtain 

and hold a desired path. 
5-24

XPDR 5537 IDNT LCL23:00:34

VOR 1

270°

2

1

1

2

4300

4200

4100

3900

3900

3800

4300

3600

3500

3400

3300

3200

3100

20

80

4000

4000 130

120

110

90

80

70

1 1009

TAS 100KT

OAT 7°C

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NMDTK _ _ _°T TRK 360°T

Figure 3-39. A typical cue that the pilot would follow

TRAFFIC 

TRAFFIC 

Figure 5-39. A typical cue that a pilot would follow.

G 

S 

HDG 

NAV

33

30

24

2I

I5

I2

6 3

Figure 3-40 Integrated flight system. 

Figure 5-40. Components of a typical FDS.

Major components of an FDS include an ADI, also called 

a Flight Director Indicator (FDI), an HSI, a mode selector, 

and a flight director computer. It should be noted that a flight 

director in use does not infer the aircraft is being manipulated 

by the autopilot (coupled), but is providing steering 

commands that the pilot (or the autopilot, if coupled) follows. 

Typical flight directors use one of two display systems for 

steerage. The first is a set of command bars, one horizontal 

and one vertical. The command bars in this configuration 

are maintained in a centered position (much like a centered 

glideslope). The second uses a miniature aircraft aligned to 

a command cue. 

A flight director displays steerage commands to the pilot on 

the ADI. As previously mentioned, the flight director receives 

its signals from one of various sources and provides that to the 

ADI for steerage commands. The mode controller provides 

signals through the ADI to drive the steering bars, e.g., the 

pilot flies the aircraft to place the delta symbol in the V of the 

steering bars. “Command” indicators tell the pilot in which 

direction and how much to change aircraft attitude to achieve 

the desired result. 

The computed command indications relieve the pilot of 

many of the mental calculations required for instrument 

flight. The yellow cue in the ADI [Figure 5-39] provides all 

steering commands to the pilot. It is driven by a computer that 

receives information from the navigation systems, the ADC, 

AHRS, and other sources of data. The computer processes this 

information, providing the pilot with a single cue to follow. 

Following the cue provides the pilot with the necessary threedimensional flight trajectory to maintain the desired path. 

One of the first widely used flight directors was developed 

by Sperry and was called the Sperry Three Axis Attitude 

Reference System (STARS). Developed in the 1960s, it was 

commonly found on both commercial and business aircraft 

alike. STARS (with a modification) and successive flight 

directors were integrated with the autopilots and aircraft 

providing a fully integrated flight system. 

The flight director/autopilot system described below is 

typical of installations in many general aviation aircraft. 

The components of a typical flight director include the mode 

controller, ADI, HSI, and annunciator panel. These units are 

illustrated in Figure 5-40.

The pilot may choose from among many modes including 

the HDG (heading) mode, the VOR/LOC (localizer tracking) 

mode, or the AUTO Approach (APP) or G/S (automatic 

capture and tracking of instrument landing system (ILS) 

localizers and glidepath) mode. The auto mode has a fully 

automatic pitch selection computer that takes into account 

aircraft performance and wind conditions, and operates once 

the pilot has reached the ILS glideslope. More sophisticated 

systems allow more flight director modes. 
5-25

Figure 5-41. The S-TEC/Meggit Corporation Integrated Autopilot installed in the Cirrus.

Figure 5-42. An Autopilot by Century.

Integrated Flight Control System 

The integrated flight control system integrates and merges 

various systems into a system operated and controlled by one 

principal component. Figure 5-41 illustrates key components 

of the flight control system that was developed from the 

onset as a fully integrated system comprised of the airframe, 

autopilot, and FDS. This trend of complete integration, once 

seen only in large commercial aircraft, is now becoming 

common in general aviation.

Autopilot Systems

An autopilot is a mechanical means to control an aircraft 

using electrical, hydraulic, or digital systems. Autopilots can 

control three axes of the aircraft: roll, pitch, and yaw. Most 

autopilots in general aviation control roll and pitch. 

Autopilots also function using different methods. The first 

is position based. That is, the attitude gyro senses the degree 

of difference from a position such as wings level, a change 

in pitch, or a heading change.

Determining whether a design is position based and/or rate 

based lies primarily within the type of sensors used. In order 

for an autopilot to possess the capability of controlling an 

aircraft’s attitude (i.e., roll and pitch), that system must be 

provided with constant information on the actual attitude 

of that aircraft. This is accomplished by the use of several 

different types of gyroscopic sensors. Some sensors are 

designed to indicate the aircraft’s attitude in the form of 

position in relation to the horizon, while others indicate rate 

(position change over time). 

Rate-based systems use the turn-and-bank sensor for the 

autopilot system. The autopilot uses rate information on 

two of the aircraft’s three axes: movement about the vertical 

axis (heading change or yaw) and about the longitudinal 

axis (roll). This combined information from a single sensor 

is made possible by the 30° offset in the gyro’s axis to the 

longitudinal axis. 

Other systems use a combination of both position and ratebased information to benefit from the attributes of both systems 

while newer autopilots are digital. Figure 5-42 illustrates an 

autopilot by Century.

Figure 5-43 is a diagram layout of a rate-based autopilot by 

S-Tec, which permits the purchaser to add modular capability 

form basic wing leveling to increased capability. 
5-26

Figure 3-43. S-Tec auto pilot 

NO PITCH INFORMATION

L R 

TURN COORDINATOR 

2 MIN. 

PWR 

ST HD TRK 

LO HI 

RDY 

ALT TRIM 

UP 

DN 

20 20 

I0 I0

2 0 

I 0 

Figure 5-43. A diagram layout of an autopilot by S-Tec.

Flight Management Systems (FMS)

In the mid-1970s, visionaries in the avionics industry such 

as Hubert Naimer of Universal, and followed by others such 

as Ed King, Jr., were looking to advance the technology of 

aircraft navigation. As early as 1976, Naimer had a vision 

of a “Master Navigation System” that would accept inputs 

from a variety of different types of sensors on an aircraft 

and automatically provide guidance throughout all phases 

of flight.

At that time aircraft navigated over relatively short distances 

with radio systems, principally VOR or ADF. For long-range 

flight inertial navigation systems (INS), Omega, Doppler, 

and Loran were in common use. Short-range radio systems 

usually did not provide area navigation (RNAV) capability. 

Long-range systems were only capable of en route pointto-point navigation between manually entered waypoints 

described as longitude and latitude coordinates, with typical 

systems containing a limited number of waypoints. 

The laborious process of manually entering cryptic latitude 

and longitude data for each flight waypoint created high 

crew workloads and frequently resulted in incorrect data 

entry. The requirement of a separate control panel for each 

long-range system consumed precious flight deck space and 

increased the complexity of interfacing the systems with 

display instruments, flight directors, and autopilots. 

The concept employed a master computer interfaced with all 

of the navigation sensors on the aircraft. A common control 

display unit (CDU) interfaced with the master computer 

would provide the pilot with a single control point for all 

navigation systems, thereby reducing the number of required 

flight deck panels. Management of the various individual 

sensors would be transferred from the pilot to the new 

computer.

Since navigation sensors rarely agree exactly about position, 

Naimer believed that blending all available sensor position 

data through a highly sophisticated, mathematical filtering 

system would produce a more accurate aircraft position. He 

called the process output the “Best Computed Position.” 

By using all available sensors to keep track of position, the 

system could readily provide area navigation capability. 

The master computer, not the individual sensors, would 

be integrated into the airplane, greatly reducing wiring 

complexity. 

To solve the problems of manual waypoint entry, a preloaded database of global navigation information would 

be readily accessible by the pilot through the CDU. Using 

such a system a pilot could quickly and accurately construct 

a flight plan consisting of dozens of waypoints, avoiding 

the tedious typing of data and the error potential of latitude/

longitude coordinates. Rather than simply navigating point-
5-27

Figure 5-44. A Control Display Unit (CDU) used to control the 

flight management system (FMS).

to-point, the master system would be able to maneuver the 

aircraft, permitting use of the system for terminal procedures 

including departures, arrivals, and approaches. The system 

would be able to automate any aspect of manual pilot 

navigation of the aircraft. When the first system, called the 

UNS-1, was released by Universal in 1982, it was called a 

flight management system (FMS). [Figure 5-44]

An FMS uses an electronic database of worldwide 

navigational data including navigation aids, airways and 

intersections, Standard Instrument Departures (SIDs), 

STARs, and Instrument Approach Procedures (IAPs) together 

with pilot input through a CDU to create a flight plan. The 

FMS provides outputs to several aircraft systems including 

desired track, bearing and distance to the active waypoint, 

lateral course deviation and related data to the flight guidance 

system for the HSI displays, and roll steering command for 

the autopilot/flight director system. This allows outputs from 

the FMS to command the airplane where to go and when and 

how to turn. To support adaptation to numerous aircraft types, 

an FMS is usually capable of receiving and outputting both 

analog and digital data and discrete information. Currently, 

electronic navigation databases are updated every 28 days.

The introduction of the Global Positioning System (GPS) has 

provided extremely precise position at low cost, making GPS 

the dominant FMS navigation sensor today. Currently, typical 

FMS installations require that air data and heading information 

be available electronically from the aircraft. This limits FMS 

usage in smaller aircraft, but emerging technologies allow 

this data from increasingly smaller and less costly systems.

Some systems interface with a dedicated Distance Measuring 

Equipment (DME) receiver channel under the control of the 

FMS to provide an additional sensor. In these systems, the 

FMS determines which DME sites should be interrogated 

for distance information using aircraft position and the 

navigation database to locate appropriate DME sites. The 

FMS then compensates aircraft altitude and station altitude 

with the aid of the database to determine the precise distance 

to the station. With the distances from a number of sites the 

FMS can compute a position nearly as accurately as GPS.

Aimer visualized three-dimensional aircraft control with an 

FMS. Modern systems provide Vertical Navigation (VNAV) as 

well as Lateral Navigation (LNAV) allowing the pilot to create 

a vertical flight profile synchronous with the lateral flight plan. 

Unlike early systems, such as Inertial Reference Systems (IRS) 

that were only suitable for en route navigation, the modern 

FMS can guide an aircraft during instrument approaches.

Today, an FMS provides not only real-time navigation 

capability but typically interfaces with other aircraft systems 

providing fuel management, control of cabin briefing and 

display systems, display of uplinked text and graphic weather 

data and air/ground data link communications.

Electronic Flight Instrument Systems

Modern technology has introduced into aviation a new 

method of displaying flight instruments, such as electronic 

flight instrument systems, integrated flight deck displays, and 

others. For the purpose of the practical test standards, any 

flight instrument display that utilizes LCD or picture tube like 

displays is referred to as “electronic flight instrument display” 

and/or a glass flight deck. In general aviation there is typically 

a primary flight display (PFD) and a multi-function display 

(MFD). Although both displays are in many cases identical, 

the PFD provides the pilot instrumentation necessary for 

flight to include altitude, airspeed, vertical velocity, attitude, 

heading and trim and trend information. 

Glass flight decks (a term coined to describe electronic flight 

instrument systems) are becoming more widespread as cost 

falls and dependability continually increases. These systems 

provide many advantages such as being lighter, more reliable, 

no moving parts to wear out, consuming less power, and 

replacing numerous mechanical indicators with a single glass 

display. Because the versatility offered by glass displays is 

much greater than that offered by analog displays, the use of 

such systems only increases with time until analog systems 

are eclipsed. 

Primary Flight Display (PFD)

PFDs provide increased situational awareness (SA) to the 

pilot by replacing the traditional six instruments used for 

instrument flight with an easy-to-scan display that provides 

the horizon, airspeed, altitude, vertical speed, trend, trim, 
5-28

Figure 5-46. The benefits of realistic visualization imagery, as 

illustrated by Synthetic Vision manufactured by Chelton Flight 

Systems. The system provides the pilot a realistic, real-time, threedimensional depiction of the aircraft and its relation to terrain 

around it.

XPDR 5537 IDNT LCL10:12:34

INSET PFD CDI XPDR IDENT TMR/REF NRST ALERTS

VOR 1 

270°

2

1

1

2

4300

4200

4100

3900

3900

3800

4300

3600

3500

3400

3300

3200

3100

20

80

4000

4000

130

120

110

90

80

70

1 1009

TAS 106KT

OAT 6°C

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

OAT 6°C

Figure 5-45. Two primary flight displays (Avidyne on the left and Garmin on the right).

rate of turn among other key relevant indications. Examples 

of PFDs are illustrated in Figure 5-45.

Synthetic Vision

Synthetic vision provides a realistic depiction of the aircraft 

in relation to terrain and flightpath. Systems such as those 

produced by Chelton Flight Systems, Universal Flight 

Systems, and others provide for depictions of terrain and 

course. Figure 5-46 is an example of the Chelton Flight 

System providing both 5-dimensional situational awareness 

and a synthetic highway in the sky, representing the desired 

flightpath. Synthetic vision is used as a PFD, but provides 

guidance in a more normal, outside reference format.

Multi-Function Display (MFD)

In addition to a PFD directly in front of the pilot, an MFD 

that provides the display of information in addition to primary 

flight information is used within the flight deck. [Figure 5-47]

Information such as a moving map, approach charts, Terrain 

Awareness Warning System, and weather depiction can all 

be illustrated on the MFD. For additional redundancy both 

the PFD and MFD can display all critical information that 

the other normally presents thereby providing redundancy 

(using a reversionary mode) not normally found in general 

aviation flight decks. 

Advanced Technology Systems

Automatic Dependent Surveillance—Broadcast 

(ADS-B)

Although standards for Automatic Dependent Surveillance 

(Broadcast) (ADS-B) are still under continuing development, 

the concept is simple: aircraft broadcast a message on 

a regular basis, which includes their position (such as 

latitude, longitude and altitude), velocity, and possibly 

other information. Other aircraft or systems can receive this 

information for use in a wide variety of applications. The 

key to ADS-B is GPS, which provides three-dimensional 

position of the aircraft.

As an simplified example, consider air-traffic radar. The radar 

measures the range and bearing of an aircraft. The bearing is 

measured by the position of the rotating radar antenna when it 

receives a reply to its interrogation from the aircraft, and the 

range by the time it takes for the radar to receive the reply. 

An ADS-B based system, on the other hand, would listen 

for position reports broadcast by the aircraft. [Figure 5-48]

These position reports are based on satellite navigation 

systems. These transmissions include the transmitting 

aircraft’s position, which the receiving aircraft processes into 
5-29

Figure 5-47. Example of a multi-function display (MFD).

usable pilot information. The accuracy of the system is now 

determined by the accuracy of the navigation system, not 

measurement errors. Furthermore the accuracy is unaffected 

by the range to the aircraft as in the case of radar. With radar, 

detecting aircraft speed changes require tracking the data and 

changes can only be detected over a period of several position 

updates. With ADS-B, speed changes are broadcast almost 

instantaneously and received by properly equipped aircraft. 

Additionally, other information can be obtained by properly 

equipped aircraft to include notices to airmen (NOTAM), 

weather, etc. [Figures 5-49 and 5-50] At the present time, 

ADS-B is predominantly available along the east coast of 

the United States where it is matured.

Safety Systems

Radio Altimeters

A radio altimeter, commonly referred to as a radar altimeter, 

is a system used for accurately measuring and displaying the 

height above the terrain directly beneath the aircraft. It sends 

a signal to the ground and processes the timed information. 

Its primary application is to provide accurate absolute altitude 

information to the pilot during approach and landing. In 

advanced aircraft today, the radar altimeter also provides its 

information to other onboard systems such as the autopilot 

and flight directors while they are in the glideslope capture 

mode below 200-300 feet above ground level (AGL).

A typical system consists of a receiver-transmitter (RT) 

unit, antenna(s) for receiving and transmitting the signal, 

and an indicator. [Figure 5-51] Category II and III precision 

approach procedures require the use of a radar altimeter and 

specify the exact minimum height above the terrain as a 

decision height (DH) or radio altitude (RA).

Traffic Advisory Systems 

Traffic Information System 

The Traffic Information Service (TIS) is a ground-based 

service providing information to the flight deck via data 

link using the S-mode transponder and altitude encoder. TIS 

improves the safety and efficiency of “see and avoid” flight 

through an automatic display that informs the pilot of nearby 

traffic. The display can show location, direction, altitude 

and the climb/descent trend of other transponder-equipped 

aircraft. TIS provides estimated position, altitude, altitude 
5-30

Figure 5-48. Aircraft equipped with Automatic Dependent Surveillance—Broadcast (ADS-B) continuously broadcast their identification, 

altitude, direction, and vertical trend. The transmitted signal carries significant information for other aircraft and ground stations alike. 

Other ADS-equipped aircraft receive this information and process it in a variety of ways. It is possible that in a saturated environment 

(assuming all aircraft are ADS equipped), the systems can project tracks for their respective aircraft and retransmit to other aircraft 

their projected tracks, thereby enhancing collision avoidance. At one time, there was an Automatic Dependent Surveillance—Addressed 

(ADS-A) and that is explained in the Pilot’s Handbook of Aeronautical Knowledge.

trend, and ground track information for up to several aircraft 

simultaneously within about 7 NM horizontally, 3,500 feet 

above and 3,500 feet below the aircraft. [Figure 5-52] This 

data can be displayed on a variety of MFDs. [Figure 5-53]

Figure 5-54 displays the pictorial concept of the traffic 

information system. Noteworthy is the requirement to have 

Mode S and that the ground air traffic station processes the 

Mode S signal.

Traffic Alert Systems 

Traffic alert systems receive transponder information from 

nearby aircraft to help determine their relative position to the 

equipped aircraft. They provide three-dimensional location 

of other aircraft [Figures 5-55, 5-56, and 5-57] and are cost 

effective alternatives to TCAS equipage for smaller aircraft. 

Traffic Avoidance Systems

Traffic Alert and Collision Avoidance System (TCAS) 

The TCAS is an airborne system developed by the FAA that 

operates independently from the ground-based ATC system. 

TCAS was designed to increase flight deck awareness of 

proximate aircraft and to serve as a “last line of defense” for 

the prevention of mid-air collisions. 

There are two levels of TCAS systems. TCAS I was developed 

to accommodate the general aviation (GA) community and 

the regional airlines. This system issues traffic advisories 

(TAs) to assist pilots in visual acquisition of intruder aircraft. 

TCAS I provides approximate bearing and relative altitude 

of aircraft with a selectable range. It provides the pilot with 

TA alerting him or her to potentially conflicting traffic. The 

pilot then visually acquires the traffic and takes appropriate 

action for collision avoidance. 
5-31

Figure 5-49. An aircraft equipped with ADS will receive identification, altitude in hundreds of feet (above or below using + or–), direction 

of the traffic, and aircraft descent or climb using an up or down arrow. The yellow target is an illustration of how a non-ADS equipped 

aircraft would appear on an ADS-equipped aircraft’s display.

Figure 5-50. An aircraft equipped with ADS has the ability to upload and display weather.

140 

A 

D 

S 

T 

I 

S 

GS 250 4.0NM 

UPS350 LRG 

GS 240 

120° /15 

SDF 

42 NM 

11:10 

VEC 1.0 MIN

-27 ALT +27

+10 

FDX514 

+12 

-08

ABX123

UPS350 

+09 

Suveillance ADS. 

+05 

-09 

UPS189 E

12 15

S

Aircraft direction

Aircraft identification

Altitude in relation 

to your aircraft

Aircraft is descending

270 

IN Out Pan WX Data Link 

Service: 

Available 

Zoom: 

20nm 

10.0 

24

30

Weather ADS-B. 
5-32

MODE 

MAP WPT AUX NRST

VOLTS 28.1 

SATZ AMPS 0 

 RUDDER TRIM 

L R 

ELECTRICAL 

5

476 

1

1497 

212 

61.9 

10.0 

2420 

27.4 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 3-51. Aircrafts MFD when using TIS. 

ALERTS 

MAP - TRAFFIC MAP

TRAFFIC MODE

OPERATE

FLAPS

ELEV

TRIM

UP

DN TA OFF SCALE

HDG UP 

12NM

6NM

++05 05 

-03 

Figure 5-53. Multi-function display (MFD).

Receiver-transmitter (RT)

Radar altimeter indicator

Figure 5-51. Components of a radar altimeter.

3,500' 3,500' 

7 NM

Figure 5-52. Coverage provided by a traffic information system.
5-33

OFF 

ALT GND ON TST 

SBY 

FLT ID 

CRSR FLT ID BRT 

IDT 

VFR 

KT 73 TSD XPDR 

Mode S Transponder 

Mode S Sensor 

Data link control display unit 

Figure 3-52. Traffic information system concept. Figure 5-54. Concept of the traffic information system.

Figure 3-51A. Theory of a typical alert system. Figure 5-55. Theory of a typical alert system.

Figure 5-56. A Skywatch System. Figure 3-51C. TAS600 

SEL 

MENU 

VIEW BRT RNG DATA 

NORM 2700 ft

1013mb 

20 nm

+02 

0.0 

-05 
5-34

Figure 5-57. Alert System by Avidyne (Ryan).

Figure 3-52. TCAS II 

1 RNG 5 

.5 

0 

1 

.5 4 

2 

6 

4 

2 

-05 12 

03 

Figure 5-58. An example of a resolution advisory being provided 

to the pilot. In this case, the pilot is requested to climb, with 1,750 

feet being the appropriate rate of ascent to avoid traffic conflict. 

This visual indication plus the audio warning provide the pilot with 

excellent traffic awareness that augments see-and-avoid practices.

TCAS II is a more sophisticated system which provides the 

same information of TCAS I. It also analyzes the projected 

flightpath of approaching aircraft and issues resolution 

advisories to the pilot to resolve potential mid-air collisions. 

Additionally, if communicating with another TCAS II 

equipped aircraft, the two systems coordinate the resolution 

alerts provided to their respective flight crews. [Figure 5-58]

Terrain Alerting Systems 

Ground Proximity Warning System (GPWS)

An early application of technology to reduce controlled 

flight into terrain (CFIT) was the GPWS. In airline use 

since the early 1970s, GPWS uses the radio altimeter, speed, 

and barometric altitude to determine the aircraft’s position 

relative to the ground. The system uses this information in 

determining aircraft clearance above the Earth and provides 

limited predictability about aircraft position relative to rising 

terrain. It does this based upon algorithms within the system 

and developed by the manufacturer for different airplanes or 

helicopters. However, in mountainous areas the system is 

unable to provide predictive information due to the unusual 

slope encountered. 

This inability to provide predictive information was evidenced 

in 1999 when a DH-7 crashed in South America. The crew 

had a GPWS onboard, but the sudden rise of the terrain 

rendered it ineffective; the crew continued unintentionally 

into a mountain with steep terrain. Another incident involved 

Secretary of Commerce Brown who, along with all on board, 

was lost when the crew flew over rapidly rising terrain where 

the GPWS capability is offset by terrain gradient. However, 

the GPWS is tied into and considers landing gear status, flap 

position, and ILS glideslope deviation to detect unsafe aircraft 

operation with respect to terrain, excessive descent rate, 

excessive closure rate to terrain, unsafe terrain clearance while 

not in a landing configuration, excessive deviation below an 

ILS glideslope. It also provides advisory callouts.

Generally, the GPWS is tied into the hot bus bar of the electrical 

system to prevent inadvertent switch off. This was demonstrated 

in an accident involving a large four-engine turboprop airplane. 

While on final for landing with the landing gear inadvertently 

up, the crew failed to heed the GPWS warning as the aircraft 

crossed a large berm close to the threshold. In fact, the crew 

attempted without success to shut the system down and attributed 

the signal to a malfunction. Only after the mishap did the crew 

realize the importance of the GPWS warning.

Terrain Awareness and Warning System (TAWS)

A TAWS uses GPS positioning and a database of terrain and 

obstructions to provide true predictability of the upcoming 

terrain and obstacles. The warnings it provides pilots are 

both aural and visual, instructing the pilot to take specific 

action. Because TAWS relies on GPS and a database of 

terrain/obstacle information, predictability is based upon 

aircraft location and projected location. The system is time 

based and therefore compensates for the performance of the 

aircraft and its speed. [Figure 5-59] 

Head-Up Display (HUD)

The HUD is a display system that provides a projection of 

navigation and air data (airspeed in relation to approach 

reference speed, altitude, left/right and up/down glideslope) 

on a transparent screen between the pilot and the windshield. 

The concept of a HUD is to diminish the shift between 

looking at the instrument panel and outside. Virtually any 
5-35

Figure 5-59. A six-frame sequence illustrating the manner in which TAWS operates. A TAWS installation is aircraft specific and provides 

warnings and cautions based upon time to potential impact with terrain rather than distance. The TAWS is illustrated in an upper left 

window while aircrew view is provided out of the windscreen. illustrates the aircraft in relation to the outside terrain while and 

 illustrate the manner in which the TAWS system displays the terrain. is providing a caution of terrain to be traversed, while 

provides an illustration of a warning with an aural and textural advisory (red) to pull up. also illustrates a pilot taking appropriate 

action (climb in this case) while illustrates that a hazard is no longer a factor.
5-36

Figure 5-60. A head-up display (HUD).

7 7 

5 5 

5 5 

10 10 

24 25 26 W 

100 

90 

80 

70 

60 

50 

 63 

2 

CRS 

360 

HDG 

360 

VOR2 

- - . - NM 

GSPD 

59 KTS 

VOR1 

6 

- - - 

TRACK 

00500 

29.89 IN 

KDVT 25L 

ON RWY 36L 

2000 

1000 

1480

60

4 

3 

2 

1 

1 

2 

3 

4 

Figure 3-54. A Head Up Display on a Gulfstream. 

information desired can be displayed on the HUD if it is 

available in the aircraft’s flight computer. The display for 

the HUD can be projected on a separate panel near the 

windscreen or as shown in Figure 5-60 on an eye piece. Other 

information may be displayed, including a runway target in 

relation to the nose of the aircraft, which allows the pilot to 

see the information necessary to make the approach while 

also being able to see out the windshield.

Required Navigation Instrument System 

Inspection

Systems Preflight Procedures

Inspecting the instrument system requires a relatively small 

part of the total time required for preflight activities, but its 

importance cannot be overemphasized. Before any flight 

involving aircraft control by instrument reference, the pilot 

should check all instruments and their sources of power for 

proper operation. 

NOTE: The following procedures are appropriate for 

conventional aircraft instrument systems. Aircraft equipped 

with electronic instrument systems utilize different 

procedures.

Before Engine Start

1. Walk-around inspection: Check the condition of all 

antennas and check the pitot tube for the presence 

of any obstructions and remove the cover. Check 

the static ports to be sure they are free from dirt 

and obstructions, and ensure there is nothing on the 

structure near the ports that would disturb the air 

flowing over them.

2. Aircraft records: Confirm that the altimeter and static 

system have been checked and found within approved 

limits within the past 24 calendar months. Check the 

replacement date for the emergency locator transmitter 

(ELT) batteries noted in the maintenance record, and 

be sure they have been replaced within this time 

interval.

3. Preflight paperwork: Check the Airport/Facility 

Directory (A/FD) and all NOTAMs for the condition 

and frequencies of all the navigation aid (NAVAIDs) 

that are used on the flight. Handbooks, en route charts, 

approach charts, computer and flight log should be 

appropriate for the departure, en route, destination, 

and alternate airports.

4. Radio equipment: Switches OFF.

5. Suction gauge: Proper markings as applicable if 

electronic flight instrumentation is installed.

6. ASI: Proper reading, as applicable. If electronic 

flight instrumentation is installed, check emergency 

instrument.
5-37

7. Attitude indicator: Uncaged, if applicable. If electronic 

flight instrumentation is installed, check emergency 

system to include its battery as appropriate.

8. Altimeter: Set the current altimeter setting and ensure 

that the pointers indicate the elevation of the airport.

9. VSI: Zero indication, as applicable (if electronic flight 

instrumentation is installed).

10. Heading indicator: Uncaged, if applicable.

11. Turn coordinator: If applicable, miniature aircraft 

level, ball approximately centered (level terrain). 

12. Magnetic compass: Full of fluid and the correction 

card is in place and current.

13. Clock: Set to the correct time and running.

14. Engine instruments: Proper markings and readings, 

as applicable if electronic flight instrumentation is 

installed.

15. Deicing and anti-icing equipment: Check availability 

and fluid quantity.

16. Alternate static-source valve: Be sure it can be opened 

if needed, and that it is fully closed.

17. Pitot tube heater: Check by watching the ammeter 

when it is turned on, or by using the method specified 

in the POH/AFM.

After Engine Start

1. When the master switch is turned on, listen to the 

gyros as they spin up. Any hesitation or unusual noises 

should be investigated before flight.

2. Suction gauge or electrical indicators: Check the 

source of power for the gyro instruments. The suction 

developed should be appropriate for the instruments 

in that particular aircraft. If the gyros are electrically 

driven, check the generators and inverters for proper 

operation.

3. Magnetic compass: Check the card for freedom of 

movement and confirm the bowl is full of fluid. 

Determine compass accuracy by comparing the 

indicated heading against a known heading (runway 

heading) while the airplane is stopped or taxiing 

straight. Remote indicating compasses should also be 

checked against known headings. Note the compass 

card correction for the takeoff runway heading.

4. Heading indicator: Allow 5 minutes after starting 

engines for the gyro to spin up. Before taxiing, or 

while taxiing straight, set the heading indicator to 

correspond with the magnetic compass heading. A 

slaved gyrocompass should be checked for slaving 

action and its indications compared with those of the 

magnetic compass. If an electronic flight instrument 

system is installed, consult the flight manual for proper 

procedures.

5. Attitude indicator: Allow the same time as noted 

above for gyros to spin up. If the horizon bar erects 

to the horizontal position and remains at the correct 

position for the attitude of the airplane, or if it begins 

to vibrate after this attitude is reached and then slowly 

stops vibrating altogether, the instrument is operating 

properly. If an electronic flight instrument system 

is installed, consult the flight manual for proper 

procedures.

6. Altimeter: With the altimeter set to the current reported 

altimeter setting, note any variation between the 

known field elevation and the altimeter indication. If 

the indication is not within 75 feet of field elevation, 

the accuracy of the altimeter is questionable and 

the problem should be referred to a repair station 

for evaluation and possible correction. Because the 

elevation of the ramp or hangar area might differ 

significantly from field elevation, recheck when in 

the run-up area if the error exceeds 75 feet. When 

no altimeter setting is available, set the altimeter 

to the published field elevation during the preflight 

instrument check.

7. VSI: The instrument should read zero. If it does not, 

tap the panel gently. If an electronic flight instrument 

system is installed, consult the flight manual for proper 

procedures.

8. Engine instruments: Check for proper readings. 

9. Radio equipment: Check for proper operation and set 

as desired.

10. Deicing and anti-icing equipment: Check operation.

Taxiing and Takeoff

Ensuring the functionality of the turn coordinator, heading 

indicator, magnetic compass, and attitude indicator prior 

to taxiing and takeoff is essential to flight safety. Runway 

incursion is an incident at an airport that adversely affects 

runway safety and pilots must mitigate this risk by ensuring 

that all of the directional flight instruments are checked 

properly before taxiing or taking off so that the position 

of the aircraft in relation to the runway and other traffic is 

always known. 

1. Turn coordinator: During taxi turns, check the 

miniature aircraft for proper turn indications. The ball 

or slip/skid should move freely. The ball or slip/skid 

indicator should move opposite to the direction of 

turns. The turn instrument should indicate the direction 

of the turn. While taxiing straight, the miniature 

aircraft (as appropriate) should be level.
5-38

2. Heading indicator: Before takeoff, recheck the heading 

indicator. If the magnetic compass and deviation card 

are accurate, the heading indicator should show the 

known taxiway or runway direction when the airplane 

is aligned with them (within 5°).

3. Attitude indicator: If the horizon bar fails to remain 

in the horizontal position during straight taxiing, or 

tips in excess of 5° during taxi turns, the instrument is 

unreliable. Adjust the miniature aircraft with reference 

to the horizon bar for the particular airplane while on 

the ground. For some tricycle-gear airplanes, a slightly 

nose-low attitude on the ground gives a level flight 

attitude at normal cruising speed.

Engine Shut Down

When shutting down the engine, note any abnormal 

instrument indications.
6-1

Introduction

Attitude instrument flying is defined as the control of an 

aircraft’s spatial position by using instruments rather than 

outside visual references. Today’s aircraft come equipped 

with analog and/or digital instruments. Analog instrument 

systems are mechanical and operate with numbers 

representing directly measurable quantities, such as a watch 

with a sweep second hand. In contrast, digital instrument 

systems are electronic and operate with numbers expressed 

in digits. Although more manufacturers are providing aircraft 

with digital instrumentation, analog instruments remain more 

prevalent. This section acquaints the pilot with the use of 

analog flight instruments.

Airplane Attitude 

Instrument Flying

Chapter 6, Section I

Using Analog Instrumentation
6-2

30 W 24 

Turning

Figure 6-1. Control instruments.

Any flight, regardless of the aircraft used or route flown, 

consists of basic maneuvers. In visual flight, aircraft attitude 

is controlled by using certain reference points on the 

aircraft with relation to the natural horizon. In instrument 

flight, the aircraft attitude is controlled by reference to 

the flight instruments. Proper interpretation of the flight 

instruments provides essentially the same information that 

outside references do in visual flight. Once the role of each 

instrument in establishing and maintaining a desired aircraft 

attitude is learned, a pilot is better equipped to control the 

aircraft in emergency situations involving failure of one or 

more key instruments. 

Learning Methods

The two basic methods used for learning attitude instrument 

flying are “control and performance” and “primary and 

supporting.” Both methods utilize the same instruments and 

responses for attitude control. They differ in their reliance on 

the attitude indicator and interpretation of other instruments. 

Attitude Instrument Flying Using the Control and 

Performance Method 

Aircraft performance is achieved by controlling the aircraft 

attitude and power. Aircraft attitude is the relationship 

of both the aircraft’s pitch and roll axes in relation to the 

Earth’s horizon. An aircraft is flown in instrument flight by 

controlling the attitude and power, as necessary, to produce 

both controlled and stabilized flight without reference to a 

visible horizon. This overall process is known as the control 

and performance method of attitude instrument flying. 

Starting with basic instrument maneuvers, this process can 

be applied through the use of control, performance, and 

navigation instruments resulting in a smooth flight from 

takeoff to landing. 

Control Instruments 

The control instruments display immediate attitude and power 

indications and are calibrated to permit those respective 

adjustments in precise increments. In this discussion, the 

term “power” is used in place of the more technically correct 

term “thrust or drag relationship.” Control is determined 

by reference to the attitude and power indicators. Power 

indicators vary with aircraft and may include manifold 

pressure, tachometers, fuel flow, etc. [Figure 6-1]

Performance Instruments 

The performance instruments indicate the aircraft’s actual 

performance. Performance is determined by reference to 

the altimeter, airspeed, or vertical speed indicator (VSI). 

[Figure 6-2]

Navigation Instruments 

The navigation instruments indicate the position of the aircraft 

in relation to a selected navigation facility or fix. This group 

of instruments includes various types of course indicators, 

range indicators, glideslope indicators, and bearing pointers. 

[Figure 6-3] Newer aircraft with more technologically 

advanced instrumentation provide blended information, 

giving the pilot more accurate positional information.

Procedural Steps in Using Control and 

Performance

1. Establish an attitude and power setting on the 

control instruments that results in the desired 

performance. Known or computed attitude changes 

and approximated power settings helps to reduce the 

pilot’s workload.

2. Trim (fine tune the control forces) until control 

pressures are neutralized. Trimming for hands-off 

flight is essential for smooth, precise aircraft control. 
6-3

30 W 24

Figure 6-2. Performance instruments.

Figure 6-3. Navigation instruments.

It allows a pilot to attend to other flight deck duties 

with minimum deviation from the desired attitude. 

3. Cross-check the performance instruments to determine 

if the established attitude or power setting is providing 

the desired performance. The cross-check involves 

both seeing and interpreting. If a deviation is noted, 

determine the magnitude and direction of adjustment 

required to achieve the desired performance.

4. Adjust the attitude and/or power setting on the control 

instruments as necessary.

Aircraft Control During Instrument Flight

Attitude Control

Proper control of aircraft attitude is the result of proper use 

of the attitude indicator, knowledge of when to change the 
6-4

Figure 6-4. Pitch instruments.

30 W 24

attitude, and then smoothly changing the attitude a precise 

amount. The attitude reference provides an immediate, direct, 

and corresponding indication of any change in aircraft pitch 

or bank attitude. 

Pitch Control

Changing the “pitch attitude” of the miniature aircraft or 

fuselage dot by precise amounts in relation to the horizon 

makes pitch changes. These changes are measured in degrees, 

or fractions thereof, or bar widths depending upon the type of 

attitude reference. The amount of deviation from the desired 

performance determines the magnitude of the correction. 

Bank Control

Bank changes are made by changing the “bank attitude” 

or bank pointers by precise amounts in relation to the bank 

scale. The bank scale is normally graduated at 0°, 10°, 20°, 

30°, 60°, and 90° and is located at the top or bottom of the 

attitude reference. Bank angle use normally approximates 

the degrees to turn, not to exceed 30°. 

Power Control

Proper power control results from the ability to smoothly 

establish or maintain desired airspeeds in coordination 

with attitude changes. Power changes are made by throttle 

adjustments and reference to the power indicators. Power 

indicators are not affected by such factors as turbulence, 

improper trim, or inadvertent control pressures. Therefore, 

in most aircraft little attention is required to ensure the power 

setting remains constant.

Experience in an aircraft teaches a pilot approximately how 

far to move the throttle to change the power a given amount. 

Power changes are made primarily by throttle movement, 

followed by an indicator cross-check to establish a more 

precise setting. The key is to avoid fixating on the indicators 

while setting the power. Knowledge of approximate power 

settings for various flight configurations helps the pilot avoid 

overcontrolling power. 

Attitude Instrument Flying Using the Primary and 

Supporting Method

Another basic method for teaching attitude instrument flying 

classifies the instruments as they relate to control function, 

as well as aircraft performance. All maneuvers involve some 

degree of motion about the lateral (pitch), longitudinal (bank/

roll), and vertical (yaw) axes. Attitude control is stressed in 

this handbook in terms of pitch control, bank control, power 

control, and trim control. Instruments are grouped as they 

relate to control function and aircraft performance as pitch 

control, bank control, power control, and trim.

Pitch Control

Pitch control is controlling the rotation of the aircraft 

about the lateral axis by movement of the elevators. 

After interpreting the pitch attitude from the proper flight 

instruments, exert control pressures to effect the desired pitch 

attitude with reference to the horizon. These instruments 

include the attitude indicator, altimeter, VSI, and airspeed 

indicator. [Figure 6-4] The attitude indicator displays a 

direct indication of the aircraft’s pitch attitude while the other 

pitch attitude control instruments indirectly indicate the pitch 

attitude of the aircraft.

Attitude Indicator

The pitch attitude control of an aircraft controls the angular 

relationship between the longitudinal axis of the aircraft and 

the actual horizon. The attitude indicator gives a direct and 

immediate indication of the pitch attitude of the aircraft. The 

aircraft controls are used to position the miniature aircraft 

in relation to the horizon bar or horizon line for any pitch 

attitude required. [Figure 6-5]
6-5

Figure 6-5. Attitude indicator.

30.0 

29.9 

29.8 

Figure 6-6. Pitch correction using the attitude indicator.

30.0 

29.9 

29.8 

Figure 6-7. Pitch correction using the altimeter.

Altimeter

If the aircraft is maintaining level flight, the altimeter 

needles maintain a constant indication of altitude. If the 

altimeter indicates a loss of altitude, the pitch attitude must 

be adjusted upward to stop the descent. If the altimeter 

indicates a gain in altitude, the pitch attitude must be 

adjusted downward to stop the climb. [Figure 6-7] The 

altimeter can also indicate the pitch attitude in a climb 

or descent by how rapidly the needles move. A minor 

adjustment in pitch attitude may be made to control the rate 

at which altitude is gained or lost. Pitch attitude is used only 

to correct small altitude changes caused by external forces, 

such as turbulence or up and down drafts.

Vertical Speed Indicator (VSI)

In flight at a constant altitude, the VSI (sometimes referred 

to as vertical velocity indicator or rate-of-climb indicator) 

remains at zero. If the needle moves above zero, the pitch 

attitude must be adjusted downward to stop the climb and 

return to level flight. Prompt adjustments to the changes in 

the indications of the VSI can prevent any significant change 

in altitude. [Figure 6-8] Turbulent air causes the needle to 

fluctuate near zero. In such conditions, the average of the 

The miniature aircraft should be placed in the proper position 

in relation to the horizon bar or horizon line before takeoff. 

The aircraft operator’s manual explains this position. As soon 

as practicable in level flight and at desired cruise airspeed, 

the miniature aircraft should be moved to a position that 

aligns its wings in front of the horizon bar or horizon line. 

This adjustment can be made any time varying loads or other 

conditions indicate a need. Otherwise, the position of the 

miniature aircraft should not be changed for flight at other than 

cruise speed. This is to make sure that the attitude indicator 

displays a true picture of pitch attitude in all maneuvers.

When using the attitude indicator in applying pitch attitude 

corrections, control pressure should be extremely light. 

Movement of the horizon bar above or below the miniature 

aircraft of the attitude indicator in an airplane should not 

exceed one-half the bar width. [Figure 6-6] If further change 

is required, an additional correction of not more than one-half 

horizon bar wide normally counteracts any deviation from 

normal flight.
6-6

Figure 6-8. Vertical speed indicator.

Figure 6-9. Pitch attitude has lowered.

fluctuations should be considered as the correct reading. 

Reference to the altimeter helps in turbulent air because it is 

not as sensitive as the VSI. 

Vertical speed is represented in feet per minute (fpm). 

[Figure 6-8] The face of the instrument is graduated with 

numbers such as 1, 2, 3, etc. These represent thousands of feet 

up or down in a minute. For instance, if the pointer is aligned 

with .5 (1⁄2 of a thousand or 500 fpm), the aircraft climbs 500 

feet in one minute. The instrument is divided into two regions: 

one for climbing (up) and one for descending (down).

During turbulence, it is not uncommon to see large 

fluctuations on the VSI. It is important to remember that small 

corrections should be employed to avoid further exacerbating 

a potentially divergent situation.

Overcorrecting causes the aircraft to overshoot the desired 

altitude; however, corrections should not be so small that 

the return to altitude is unnecessarily prolonged. As a guide, 

the pitch attitude should produce a rate of change on the VSI 

about twice the size of the altitude deviation. For example, 

if the aircraft is 100 feet off the desired altitude, a 200 fpm 

rate of correction would be used.

During climbs or descents, the VSI is used to change the altitude 

at a desired rate. Pitch attitude and power adjustments are made 

to maintain the desired rate of climb or descent on the VSI.

When pressure is applied to the controls and the VSI shows 

an excess of 200 fpm from that desired, overcontrolling is 

indicated. For example, if attempting to regain lost altitude at 

the rate of 500 fpm, a reading of more than 700 fpm would 

indicate overcontrolling. Initial movement of the needle 

indicates the trend of vertical movement. The time for the VSI 

to reach its maximum point of deflection after a correction is 

called lag. The lag is proportional to speed and magnitude of 

pitch change. In an airplane, overcontrolling may be reduced 

by relaxing pressure on the controls, allowing the pitch attitude 

to neutralize. In some helicopters with servo-assisted controls, 

no control pressures are apparent. In this case, overcontrolling 

can be reduced by reference to the attitude indicator.

Some aircraft are equipped with an instantaneous vertical 

speed indicator (IVSI). The letters “IVSI” appear on the face 

of the indicator. This instrument assists in interpretation by 

instantaneously indicating the rate of climb or descent at a 

given moment with little or no lag as displayed in a VSI. 

Occasionally, the VSI is slightly out of calibration and 

indicates a gradual climb or descent when the aircraft is 

in level flight. If readjustments cannot be accomplished, 

the error in the indicator should be considered when the 

instrument is used for pitch control. For example, an 

improperly set VSI may indicate a descent of 100 fpm when 

the aircraft is in level flight. Any deviation from this reading 

would indicate a change in pitch attitude.

Airspeed Indicator

The airspeed indicator gives an indirect reading of the 

pitch attitude. With a constant power setting and a constant 

altitude, the aircraft is in level flight and airspeed remains 

constant. If the airspeed increases, the pitch attitude has 

lowered and should be raised. [Figure 6-9] If the airspeed 

decreases, the pitch attitude has moved higher and should 

be lowered. [Figure 6-10] A rapid change in airspeed 

indicates a large change in pitch; a slow change in airspeed 

indicates a small change in pitch. Although the airspeed 

indicator is used as a pitch instrument, it may be used in 

level flight for power control. Changes in pitch are reflected 

immediately by a change in airspeed. There is very little 

lag in the airspeed indicator.
6-7

Figure 6-10. Pitch attitude has moved higher.

Figure 6-11. Bank instruments.

30 W 24

Pitch Attitude Instrument Cross-Check

The altimeter is an important instrument for indicating pitch 

attitude in level flight except when used in conditions of 

exceptionally strong vertical currents, such as thunderstorms. 

With proper power settings, any of the pitch attitude 

instruments can be used to hold reasonably level flight 

attitude. However, only the altimeter gives the exact altitude 

information. Regardless of which pitch attitude control 

instrument indicates a need for a pitch attitude adjustment, 

the attitude indicator, if available, should be used to make 

the adjustment. Common errors in pitch attitude control are:

• Overcontrolling;

• Improperly using power; and

• Failing to adequately cross-check the pitch attitude 

instruments and take corrective action when pitch 

attitude change is needed.

Bank Control

Bank control is controlling the angle made by the wing and 

the horizon. After interpreting the bank attitude from the 

appropriate instruments, exert the necessary pressures to 

move the ailerons and roll the aircraft about the longitudinal 

axis. As illustrated in Figure 6-11, these instruments include:

• Attitude indicator

• Heading indicator

• Magnetic compass

• Turn coordinator/turn-and-slip indicator

Attitude Indicator

As previously discussed, the attitude indicator is the only 

instrument that portrays both instantly and directly the actual 

flight attitude and is the basic attitude reference.

Heading Indicator

The heading indicator supplies the pertinent bank and heading 

information and is considered a primary instrument for bank.

Magnetic Compass

The magnetic compass provides heading information and is 

considered a bank instrument when used with the heading 

indicator. Care should be exercised when using the magnetic 

compass as it is affected by acceleration, deceleration in 

flight caused by turbulence, climbing, descending, power 

changes, and airspeed adjustments. Additionally, the 

magnetic compass indication will lead and lag in its reading 

depending upon the direction of turn. As a result, acceptance 

of its indication should be considered with other instruments 

that indicate turn information. These include the already 

mentioned attitude and heading indicators, as well as the 

turn-and-slip indicator and turn coordinator. 
6-8

DC ELEC 

L R 

Figure 6-12. Turn coordinator and turn-and-slip indicator.

Figure 6-13. An increase in power—increasing airspeed accordingly in level flight.

Turn Coordinator/Turn-and-Slip Indicator

Both of these instruments provide turn information. 

[Figure 6-12] The turn coordinator provides both bank rate 

and then turn rate once stabilized. The turn-and-slip indicator 

provides only turn rate.

Power Control

A power change to adjust airspeed may cause movement 

around some or all of the aircraft axes. The amount and 

direction of movement depends on how much or how rapidly 

the power is changed, whether single-engine or multiengine 

airplane or helicopter. The effect on pitch attitude and 

airspeed caused by power changes during level flight is 

illustrated in Figures 6-13 and 6-14. During or immediately 

after adjusting the power control(s), the power instruments 

should be cross-checked to see if the power adjustment is 

as desired. Whether or not the need for a power adjustment 

is indicated by another instrument(s), adjustment is made 

by cross-checking the power instruments. Aircraft are 

powered by a variety of powerplants, each powerplant 

having certain instruments that indicate the amount of power 

being applied to operate the aircraft. During instrument 

flight, these instruments must be used to make the required 

power adjustments. 

As illustrated in Figure 6-15, power indicator instruments 

include:

• Airspeed indicator

• Engine instruments

Airspeed Indicator

The airspeed indicator provides an indication of power 

best observed initially in level flight where the aircraft is in 

balance and trim. If in level flight the airspeed is increasing, 

it can generally be assumed that the power has increased, 

necessitating the need to adjust power or re-trim the aircraft.

Engine Instruments

Engine instruments, such as the manifold pressure (MP) 

indicator, provide an indication of aircraft performance for a 

given setting under stable conditions. If the power conditions 

are changed, as reflected in the respective engine instrument 

readings, there is an affect upon the aircraft performance, 

either an increase or decrease of airspeed. When the propeller 

rotational speed (revolutions per minute (RPM) as viewed 

on a tachometer) is increased or decreased on fixed-pitch 

propellers, the performance of the aircraft reflects a gain or 

loss of airspeed as well. 

Trim Control

Proper trim technique is essential for smooth and accurate 

instrument flying and utilizes instrumentation illustrated in 

Figure 6-16. The aircraft should be properly trimmed while 

executing a maneuver. The degree of flying skill, which 

ultimately develops, depends largely upon how well the 

aviator learns to keep the aircraft trimmed.

Airplane Trim

An airplane is correctly trimmed when it is maintaining a 

desired attitude with all control pressures neutralized. By 

relieving all control pressures, it is much easier to maintain the 
6-9

Figure 6-14. Pitch control and power adjustment required to bring aircraft to level flight.

Figure 6-15. Power instruments.

Figure 6-16. Trim instruments.

30 W 24 

30 W 24 
6-10

• Heading Indicator—supplies the most pertinent bank 

or heading information and is primary for bank. 

 • Airspeed Indicator—supplies the most pertinent 

information concerning performance in level flight 

in terms of power output and is primary for power. 

Although the attitude indicator is the basic attitude reference, 

the concept of primary and supporting instruments does not 

devalue any particular flight instrument, when available, in 

establishing and maintaining pitch-and-bank attitudes. It is the 

only instrument that instantly and directly portrays the actual 

flight attitude. It should always be used, when available, in 

establishing and maintaining pitch-and-bank attitudes. The 

specific use of primary and supporting instruments during 

basic instrument maneuvers is presented in more detail in 

Chapter 7, Airplane Basic Flight Maneuvers. 

Fundamental Skills

During attitude instrument training, two fundamental flight 

skills must be developed. They are instrument cross-check 

and instrument interpretation, both resulting in positive 

aircraft control. Although these skills are learned separately 

and in deliberate sequence, a measure of proficiency in 

precision flying is the ability to integrate these skills into 

unified, smooth, positive control responses to maintain any 

prescribed flightpath.

Instrument Cross-Check

The first fundamental skill is cross-checking (also called 

“scanning” or “instrument coverage”). Cross-checking is the 

continuous and logical observation of instruments for attitude 

and performance information. In attitude instrument flying, 

the pilot maintains an attitude by reference to instruments, 

producing the desired result in performance. Observing and 

interpreting two or more instruments to determine attitude and 

performance of an aircraft is called cross-checking. Although 

no specific method of cross-checking is recommended, those 

instruments that give the best information for controlling the 

aircraft in any given maneuver should be used. The important 

instruments are the ones that give the most pertinent 

information for any particular phase of the maneuver. These 

are usually the instruments that should be held at a constant 

indication. The remaining instruments should help maintain 

the important instruments at the desired indications, which 

is also true in using the emergency panel.

Cross-checking is mandatory in instrument flying. In 

visual flight, a level attitude can be maintained by outside 

references. However, even then the altimeter must be checked 

to determine if altitude is being maintained. Due to human 

error, instrument error, and airplane performance differences 

in various atmospheric and loading conditions, it is impossible 

to establish an attitude and have performance remain constant 

aircraft at a certain attitude. This allows more time to devote 

to the navigation instruments and additional flight deck duties. 

An aircraft is placed in trim by:

• Applying control pressure(s) to establish a desired 

attitude. Then, the trim is adjusted so that the aircraft 

maintains that attitude when flight controls are 

released. The aircraft is trimmed for coordinated flight 

by centering the ball of the turn-and-slip indicator. 

• Moving the rudder trim in the direction where the 

ball is displaced from center. Aileron trim may then 

be adjusted to maintain a wings-level attitude. 

• Using balanced power or thrust when possible to aid 

in maintaining coordinated flight. Changes in attitude, 

power, or configuration may require trim adjustments. 

Use of trim alone to establish a change in aircraft 

attitude usually results in erratic aircraft control. 

Smooth and precise attitude changes are best attained 

by a combination of control pressures and subsequent 

trim adjustments. The trim controls are aids to smooth 

aircraft control.

Helicopter Trim

A helicopter is placed in trim by continually cross-checking 

the instruments and performing the following: 

• Using the cyclic-centering button. If the helicopter is 

so equipped, this relieves all possible cyclic pressures. 

• Using the pedal adjustment to center the ball of the 

turn indicator. Pedal trim is required during all power 

changes and is used to relieve all control pressures 

held after a desired attitude has been attained. 

An improperly trimmed helicopter requires constant control 

pressures, produces tension, distracts attention from crosschecking, and contributes to abrupt and erratic attitude 

control. The pressures felt on the controls should be only 

those applied while controlling the helicopter. 

Adjust the pitch attitude, as airspeed changes, to maintain 

desired attitude for the maneuver being executed. The bank 

must be adjusted to maintain a desired rate of turn, and the 

pedals must be used to maintain coordinated flight. Trim must 

be adjusted as control pressures indicate a change is needed.

Example of Primary and Support Instruments

Straight-and-level flight at a constant airspeed means that an 

exact altitude is to be maintained with zero bank (constant 

heading). The primary pitch, bank, and power instruments 

used to maintain this flight condition are: 

• Altimeter—supplies the most pertinent altitude 

information and is primary for pitch. 
6-11

Figure 6-17. Radial cross-check.

for a long period of time. These variables make it necessary 

for the pilot to constantly check the instruments and make 

appropriate changes in airplane attitude using cross-checking 

of instruments. Examples of cross-checking are explained in 

the following paragraphs. 

Selected Radial Cross-Check

When the selected radial cross-check is used, a pilot spends 

80 to 90 percent of flight time looking at the attitude indicator, 

taking only quick glances at the other flight instruments (for 

this discussion, the five instruments surrounding the attitude 

indicator are called the flight instruments). With this method, 

the pilot’s eyes never travel directly between the flight 

instruments but move by way of the attitude indicator. The 

maneuver being performed determines which instruments to 

look at in the pattern. [Figure 6-17]

Inverted-V Cross-Check

In the inverted-V cross-check, the pilot scans from the 

attitude indicator down to the turn coordinator, up to the 

attitude indicator, down to the VSI, and back up to the attitude 

indicator. [Figure 6-18]

Rectangular Cross-Check

In the rectangular cross-check, the pilot scans across 

the top three instruments (airspeed indicator, attitude 

indicator, and altimeter), and then drops down to scan 

the bottom three instruments (VSI, heading indicator, and 

turn instrument). This scan follows a rectangular path 

(clockwise or counterclockwise rotation is a personal 

choice). [Figure 6-19]

This cross-checking method gives equal weight to the 

information from each instrument, regardless of its 

importance to the maneuver being performed. However, this 

method lengthens the time it takes to return to an instrument 

critical to the successful completion of the maneuver. 

Common Cross-Check Errors

A beginner might cross-check rapidly, looking at the 

instruments without knowing exactly what to look for. With 

increasing experience in basic instrument maneuvers and 

familiarity with the instrument indications associated with 

them, a pilot learns what to look for, when to look for it, 

and what response to make. As proficiency increases, a pilot 

cross-checks primarily from habit, suiting scanning rate and 

sequence to the demands of the flight situation. Failure to 

maintain basic instrument proficiency through practice can 

result in many of the following common scanning errors, 

both during training and at any subsequent time.

Fixation, or staring at a single instrument, usually occurs for 

a reason, but has poor results. For example, a pilot may stare 
6-12

Figure 6-18. Inverted-V cross-check.

Figure 6-19. Rectangular cross-check.
6-13

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0 

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Figure 6-20. Power and attitude equal performance.

at the altimeter reading 200 feet below the assigned altitude, 

and wonder how the needle got there. While fixated on the 

instrument, increasing tension may be unconsciously exerted 

on the controls, which leads to an unnoticed heading change 

that leads to more errors. Another common fixation is likely 

when initiating an attitude change. For example, a shallow 

bank is established for a 90° turn and, instead of maintaining 

a cross-check of other pertinent instruments, the pilot stares at 

the heading indicator throughout the turn. Since the aircraft is 

turning, there is no need to recheck the heading indicator for 

approximately 25 seconds after turn entry. The problem here 

may not be entirely due to cross-check error. It may be related 

to difficulties with instrument interpretation. Uncertainty 

about reading the heading indicator (interpretation) or 

uncertainty because of inconsistency in rolling out of turns 

(control) may cause the fixation. 

Omission of an instrument from a cross-check is another 

likely fault. It may be caused by failure to anticipate 

significant instrument indications following attitude 

changes. For example, in a roll-out from a 180° steep turn, 

straight-and-level flight is established with reference only 

to the attitude indicator, and the pilot neglects to check the 

heading indicator for constant heading information. Because 

of precession error, the attitude indicator temporarily shows 

a slight error, correctable by quick reference to the other 

flight instruments.

Emphasis on a single instrument, instead of on the combination 

of instruments necessary for attitude information, is an 

understandable fault during the initial stages of training. It 

is a natural tendency to rely on the instrument that is most 

readily understood, even when it provides erroneous or 

inadequate information. Reliance on a single instrument is 

poor technique. For example, a pilot can maintain reasonably 

close altitude control with the attitude indicator, but cannot 

hold altitude with precision without including the altimeter 

in the cross-check. 

Instrument Interpretation

The second fundamental skill, instrument interpretation, 

requires more thorough study and analysis. It begins by 

understanding each instrument’s construction and operating 

principles. Then, this knowledge must be applied to the 

performance of the aircraft being flown, the particular 

maneuvers to be executed, the cross-check and control 

techniques applicable to that aircraft, and the flight conditions.

For example, a pilot uses full power in a small airplane for a 

5-minute climb from near sea level, and the attitude indicator 

shows the miniature aircraft two bar widths (twice the 

thickness of the miniature aircraft wings) above the artificial 

horizon. [Figure 6-20] The airplane is climbing at 500 fpm 

as shown on the VSI, and at airspeed of 90 knots, as shown 

on the airspeed indicator. With the power available in this 

particular airplane and the attitude selected by the pilot, the 

performance is shown on the instruments. Now, set up the 

identical picture on the attitude indicator in a jet airplane. 

With the same airplane attitude as shown in the first example, 

the VSI in the jet reads 2,000 fpm and the airspeed indicator 

reads 250 knots. 
6-14

As the performance capabilities of the aircraft are learned, 

a pilot interprets the instrument indications appropriately 

in terms of the attitude of the aircraft. If the pitch attitude 

is to be determined, the airspeed indicator, altimeter, VSI, 

and attitude indicator provide the necessary information. If 

the bank attitude is to be determined, the heading indicator, 

turn coordinator, and attitude indicator must be interpreted. 

For each maneuver, learn what performance to expect and 

the combination of instruments to be interpreted in order 

to control aircraft attitude during the maneuver. It is the 

two fundamental flight skills, instrument cross-check and 

instrument interpretation, that provide the smooth and 

seamless control necessary for basic instrument flight as 

discussed at the beginning of the chapter.
6-15

Introduction

Attitude instrument flying is defined as the control of an 

aircraft’s spatial position by using instruments rather than 

outside visual references. As noted in Section I, today’s 

aircraft come equipped with analog and/or digital instruments. 

Section II acquaints the pilot with the use of digital instruments 

known as an electronic flight display (EFD).

The improvements in avionics coupled with the introduction 

of EFDs to general aviation aircraft offer today’s pilot an 

unprecedented array of accurate instrumentation to use in 

the support of instrument flying. 

Airplane Attitude 

Instrument Flying

Chapter 6, Section II

Using an Electronic Flight Display
6-16

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Fig 4-17 primary flight display (PFD) 

DC ELEC 

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Figure 6-21. Primary flight display (PFD) and analog counterparts.

Until recently, most general aviation aircraft were equipped 

with individual instruments utilized collectively to safely 

maneuver the aircraft by instrument reference alone. With 

the release of the EFD system, the conventional instruments 

have been replaced by multiple liquid crystal display (LCD) 

screens. The first screen is installed in front of the left seat 

pilot position and is referred to as the primary flight display 

(PFD). [Figure 6-21] The second screen is positioned in 

approximately the center of the instrument panel and is 

referred to as the multifunction display (MFD). [Figure 6-22]

The pilot can use the MFD to display navigation information 

(moving maps), aircraft systems information (engine 

monitoring), or should the need arise, a PFD. [Figure 6-23]

With just these two screens, aircraft designers have been able 

to declutter instrument panels while increasing safety. This 

has been accomplished through the utilization of solid-state 

instruments that have a failure rate far lower than those of 

conventional analog instrumentation.

However, in the event of electrical failure, the pilot still 

has emergency instruments as a backup. These instruments 

either do not require electrical power, or as in the case 

of many attitude indicators, they are battery equipped. 

[Figure 6-24]

Pilots flying under visual flight rules (VFR) maneuver their 

aircraft by reference to the natural horizon, utilizing specific 

reference points on the aircraft. In order to operate the aircraft 

in other than VFR weather, with no visual reference to the 

natural horizon, pilots need to develop additional skills. 

These skills come from the ability to maneuver the aircraft by 

reference to flight instruments alone. These flight instruments 

replicate all the same key elements that a VFR pilot utilizes 

during a normal flight. The natural horizon is replicated on 

the attitude indicator by the artificial horizon.

Understanding how each flight instrument operates and 

what role it plays in controlling the attitude of the aircraft 

is fundamental in learning attitude instrument flying. When 

the pilot understands how all the instruments are used in 

establishing and maintaining a desired aircraft attitude, the 

pilot is better prepared to control the aircraft should one 

or more key instruments fail or if the pilot should enter 

instrument flight conditions.

Learning Methods

There are two basic methods utilized for learning attitude 

instrument flying. They are “control and performance” and 

“primary and supporting.” These methods rely on the same 

flight instruments and require the pilot to make the same 

adjustments to the flight and power controls to control aircraft 

attitude. The main difference between the two methods is the 

importance that is placed on the attitude indicator and the 

interpretation of the other flight instruments.
6-17

Figure 6-22. Multifunction display (MFD).

Figure 6-23. Reversionary displays.

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ALERTS 

BACKUP PATH - AHRS using backup 

data path. 

TRAFFIC FAIL - Traffic device 

has failed. 

XPDR1 CONFIG - XPDR1 config 

error. config service req’d. 

TRAFFIC 

Fig 4-19 reversionary mode (failed PFD) 
6-18

Figure 6-24. Emergency back-up of the airspeed indicator, attitude indicator, and altitude indicator.

XPDR 5537 IDNT LCL23:00:34 

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Figure 6-25. Control instruments.

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Figure 4-21. Control Instruments. 

Control and Performance Method

Aircraft performance is accomplished by controlling the 

aircraft attitude and power output. Aircraft attitude is the 

relationship of its longitudinal and lateral axes to the Earth’s 

horizon. When flying in instrument flight conditions, the 

pilot controls the attitude of the aircraft by referencing the 

flight instruments and manipulating the power output of the 

engine to achieve the performance desired. This method can 

be used to achieve a specific performance level enabling a 

pilot to perform any basic instrument maneuver.

The instrumentation can be broken up into three different 

categories: control, performance, and navigation.

Control Instruments

The control instruments depict immediate attitude and power 

changes. The instrument for attitude display is the attitude 

indicator. Power changes are directly reflected on the manifold 

pressure gauge and the tachometer. [Figure 6-25] All three 

of these instruments can reflect small adjustments, allowing 

for precise control of aircraft attitude.
6-19

Figure 6-26. Performance instruments.

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Airspeed indicator

Vertical speed indicator

Heading indicator

Slip/skid indicator

Pitch indicator

In addition, the configuration of the power indicators installed 

in each aircraft may vary to include the following types of 

power indicators: tachometers, manifold pressure indicator, 

engine pressure ratio indicator, fuel flow gauges, etc. 

The control instruments do not indicate how fast the aircraft 

is flying or at what altitude it is flying. In order to determine 

these variables and others, a pilot needs to refer to the 

performance instruments.

Performance Instruments

The performance instruments directly reflect the performance 

the aircraft is achieving. The speed of the aircraft can be 

referenced on the airspeed indicator. The altitude can be 

referenced on the altimeter. The aircraft’s climb performance 

can be determined by referencing the vertical speed indicator 

(VSI). [Figure 6-26] Other performance instruments 

available are the heading indicator, pitch attitude indicator, 

and the slip/skid indicator.

The performance instruments most directly reflect a change 

in acceleration, which is defined as change in velocity 

or direction. Therefore, these instruments indicate if the 

aircraft is changing airspeed, altitude, or heading, which are 

horizontal, vertical, or lateral vectors.

Navigation Instruments

The navigation instruments are comprised of global 

positioning system (GPS) displays and indicators, very high 

frequency omnidirectional range/nondirectional radio beacon 

(VOR/NDB) indicators, moving map displays, localizer, and 

glideslope (GS) indicators. [Figure 6-27] The instruments 

indicate the position of the aircraft relative to a selected 

navigation facility or fix. Navigation instruments allow 

the pilot to maneuver the aircraft along a predetermined 

path of ground-based or spaced-based navigation signals 

without reference to any external visual cues. The navigation 

instruments can support both lateral and visual inputs.

The Four-Step Process Used to Change Attitude

In order to change the attitude of the aircraft, the pilot must 

make the proper changes to the pitch, bank, or power settings 

of the aircraft. Four steps (establish, trim, cross-check, and 

adjust) have been developed in order to aid in the process. 

Establish

Any time the attitude of the aircraft requires changing, the 

pilot must adjust the pitch and/or bank in conjunction with 

power to establish the desired performance. The changes 

in pitch and bank require the pilot to reference the attitude 

indicator in order to make precise changes. Power changes 

should be verified on the tachometer, manifold pressure 

gauge, etc. To ease the workload, the pilot should become 
6-20

Figure 6-27. Navigation instruments.

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MAP - NAVIGATION MAP 

VOR 1 

DME TUNING DME MODE NAV1 

Course deviation indicator

NAV controls

COM frequency window

NAV frequency window COM controls

Com section

audio panel

NAV section

audio panel

DME tuning window

Glideslope/vertical guidance indicator

Moving map

VOR GPS/NDB

familiar with the approximate pitch and power changes 

necessary to establish a specified attitude.

Trim

Another important step in attitude instrument flying is 

trimming the aircraft. Trim is utilized to eliminate the need 

to apply force to the control yoke in order to maintain the 

desired attitude. When the aircraft is trimmed appropriately, 

the pilot is able to relax pressure on the control yoke and 

momentarily divert attention to another task at hand without 

deviating from the desired attitude. Trimming the aircraft is 

very important, and poor trim is one of the most common 

errors instructors note in instrument students. 

Cross-Check

Once the initial attitude changes have been made, the pilot 

should verify the performance of the aircraft. Cross-checking 

the control and performance instruments requires the pilot 

to visually scan the instruments, as well as interpret the 

indications. All the instruments must be utilized collectively 

in order to develop a full understanding of the aircraft attitude. 

During the cross-check, the pilot needs to determine the 

magnitude of any deviations and determine how much of a 

change is required. All changes are then made based on the 

control instrument indications.

Adjust

The final step in the process is adjusting for any deviations 

that have been noted during the cross-check. Adjustments 

should be made in small increments. The attitude indicator 

and the power instruments are graduated in small increments 

to allow for precise changes to be made. The pitch should be 

made in reference to bar widths on the miniature airplane. 

The bank angle can be changed in reference to the roll scale 

and the power can be adjusted in reference to the tachometer, 

manifold pressure gauge, etc.

By utilizing these four steps, pilots can better manage the 

attitude of their aircraft. One common error associated with 

this process is making a larger than necessary change when 

a deviation is noted. Pilots need to become familiar with the 

aircraft and learn how great a change in attitude is needed to 

produce the desired performance.

Applying the Four-Step Process

In attitude instrument flight, the four-step process is used to 

control pitch attitude, bank attitude, and power application of 

the aircraft. The EFD displays indications precisely enough 

that a pilot can apply control more accurately. 

Pitch Control

The pitch control is indicated on the attitude indicator,which 

spans the full width of the PFD. Due to the increased size 

of the display, minute changes in pitch can be made and 

corrected. The pitch scale on the attitude indicator is graduated 

in 5-degree increments that allow the pilot to make corrections 

with precision to approximately 1⁄2 degree. The miniature 

airplane utilized to represent the aircraft in conventional 

attitude indicators is replaced in glass panel displays by a 

yellow chevron. [Figure 6-28] Representing the nose of the 

aircraft, the point of the chevron affords the pilot a much 

more precise indication of the degree of pitch and allows 

the pilot to make small, precise changes should the desired 

aircraft performance change. When the desired performance 

is not being achieved, precise pitch changes should be made 

by referencing the point of the yellow chevron.

Bank Control

Precise bank control can be developed utilizing the roll 

pointer in conjunction with the roll index displayed on the 

attitude indicator. The roll index is sectioned by hash marks at 

0°, 10°, 20°, 30°, 45°, 60° and the horizon line, which depicts 

90° of bank. [Figure 6-29] The addition of the 45° hash mark 

is an improvement over conventional attitude indicators. 
6-21

Figure 6-28. The chevron’s relationship to the horizon line indicates

the pitch of the aircraft.

VOR 1 

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Figure 4-24. Pitch Control 

Figure 6-29. Bank indicator index lines.

XPDR 5537 IDNT LCL23:00:34 

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OAT 7°C 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _°T TRK 360°T

 0° 

10° 

20° 

30° 

45° 

60° 

Figure 4-25. Bank Control 

In addition to the roll index, the instrument pilot utilizes 

the turn rate indicator to maintain the aircraft in a standard 

rate turn (3° per second). Most instrument maneuvers can 

be done comfortably, safely, and efficiently by utilizing a 

standard rate turn. 

Power Control

The power instruments indicate how much power is being 

generated by the engine. They are not affected by turbulence, 

improper trim, or control pressures. All changes in power 

should be made with reference to power instruments and 

cross-checked on performance instruments.

Power control needs to be learned from the beginning of 

flight training. Attitude instrument flying demands increased 

precision when it comes to power control. As experience 

increases, pilots begin to know approximately how much 

change in throttle position is required to produce the desired 

change in airspeed. Different aircraft demand differing 

amounts of throttle change to produce specific performance. 

It is imperative that the pilot make the specific changes on the 

power instruments and allow the performance to stabilize. 

Avoid the tendency to overcontrol. 

One common error encountered with glass panel displays 

is associated with the precision of the digital readouts. 

This precision causes pilots to focus too much attention on 

establishing the exact power setting. 

Control and power instruments are the foundation for precise 

attitude instrument flying. The keys to attitude instrument 

flying are establishing the desired aircraft attitude on the 

attitude indicator and selecting the desired engine output on 

the power instruments. Cross-checking is the vital ingredient 

in maintaining precise attitude instrument flight.

Attitude Instrument Flying—Primary and 

Supporting Method

The second method for performing attitude instrument 

flight is a direct extension of the control/power method. 

By utilizing the primary and supporting flight instruments 

in conjunction with the control and power instruments, the 

pilot can precisely maintain aircraft attitude. This method 

utilizes the same instruments as the control/power method; 

however, it focuses more on the instruments that depict the 

most accurate indication for the aspect of the aircraft attitude 

being controlled. The four key elements (pitch, bank, roll, 

and trim) are discussed in detail.

Similar to the control/power method, all changes to aircraft 

attitude need to be made using the attitude indicator and the 

power instruments (tachometer, manifold pressure gauge, 

etc.). The following explains how each component of the 

aircraft attitude is monitored for performance.
6-22

Figure 6-30. Pitch of the aircraft.

XPDR 5537 IDNT LCL23:00:34

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ALERTS

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

N-S E-W

5

338

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1652

200

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13.7

2300

23.0 Artificial horizon

Slip/skid indicator

Pitch attitude of aircraft

Pitch Control

The pitch of the aircraft refers to the angle between the 

longitudinal axis of the aircraft and the natural horizon. When 

flying in instrument meteorological conditions (IMC), the 

natural horizon is unavailable for reference and an artificial 

horizon is utilized in its place. [Figure 6-30] The only 

instrument capable of depicting the aircraft attitude is the 

attitude indicator displayed on the PFD. The attitude and 

heading reference system (AHRS) is the engine that drives 

the attitude display. The AHRS unit is capable of precisely 

tracking minute changes in the pitch, bank, and yaw axes, 

thereby making the PFD very accurate and reliable. The 

AHRS unit determines the angle between the aircraft’s 

longitudinal axis and the horizon line on initialization. There 

is no need or means for the pilot to adjust the position of the 

yellow chevron, which represents the nose of the aircraft. 

Straight-and-Level Flight

In straight-and-level flight, the pilot maintains a constant 

altitude, airspeed and, for the most part, heading for extended 

periods of time. To achieve this, the three primary instruments 

that need to be referenced in order to maintain these three 

variables are the altitude, airspeed, and heading indicators. 

Primary Pitch

When the pilot is maintaining a constant altitude, the primary 

instrument for pitch is the altimeter. As long as the aircraft 

maintains a constant airspeed and pitch attitude, the altitude 

should remain constant. 

Two factors that cause the altitude to deviate are turbulence 

and momentary distractions. When a deviation occurs, a 

change in the pitch needs to be made on the attitude indicator. 

Small deviations require small corrections, while large 

deviations require larger corrections. Pilots should avoid 

making large corrections that result in rapid attitude changes, 

for this may lead to spatial disorientation. Smooth, timely 

corrections should be made to bring the aircraft back to the 

desired attitude.

Pay close attention to indications on the PFD. An increase 

in pitch of 2.5° produces a climb rate of 450 feet per minute 

(fpm). Small deviations do not require large attitude changes. 

A rule of thumb for correcting altitude deviations is to 

establish a change rate of twice the altitude deviation, not to 

exceed 500 fpm. For example, if the aircraft is off altitude 

by 40 feet, 2 × 40 = 80 feet, so a descent of approximately 

100 fpm allows the aircraft to return to the desired altitude 

in a controlled, timely fashion.

In addition to the primary instrument, there are also 

supporting instruments that assist the pilot in cross-checking 

the pitch attitude. The supporting instruments indicate trend, 

but they do not indicate precise attitude indications. Three 

instruments (vertical speed, airspeed, and altitude trend 

tape) indicate when the pitch attitude has changed and that 

the altitude is changing. [Figure 6-31] When the altitude is 

constant, the VSI and altitude trend tape are not shown on 

the PFD. When these two trend indicators are displayed, the 
6-23

Figure 6-31. Supporting instruments.

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Figure 4-27. Supporting Instruments 

270° 

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Altitude trend vector

Turn rate trend vector

Airspeed trend (increasing)

Figure 6-32. Primary bank.

XPDR 5537 IDNT LCL23:00:34 

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ALERTS 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Roll scale zero

Slip/skid indicator

Skidding turn 

270° 

Roll pointer

Standard rate

Heading

1/2 standard rate

Turn rate trend vector

regarding the direction and rate of altitude deviations. The 

pilot is thus able to make corrections to the pitch attitude 

before a large deviation in altitude occurs. The airspeed 

indicator depicts an increase if the pitch attitude is lowered. 

Conversely, when the pitch attitude increases, the pilot should 

note a decrease in the airspeed.

Primary Bank

When flying in IMC, pilots maintain preplanned or assigned 

headings. With this in mind, the primary instrument for bank 

angle is the heading indicator. Heading changes are displayed 

instantaneously. The heading indicator is the only instrument 

that displays the current magnetic heading, provided that 

it is matched to the magnetic compass with all deviation 

adjustments accounted for. [Figure 6-32]

There are supporting instruments associated with bank as 

well. The turn rate trend indicator shows the pilot when the 

aircraft is changing heading. The magnetic compass is also 

useful for maintaining a heading; however, it is influenced 

by several errors in various phases of flight.

Primary Yaw

The slip/skid indicator is the primary instrument for yaw. 

It is the only instrument that can indicate if the aircraft is 

pilot is made aware that the pitch attitude of the aircraft has 

changed and may need adjustment. Notice in Figure 6-31

that the aircraft is descending at a rate of 500 fpm. 

The instrument cross-check necessitates utilizing these 

supporting instruments to better manage altitude control. 

The VSI and trend tape provide the pilot with information 
6-24

to include the stand-by flight instruments as well as the 

engine indications in the scan. Due to the size of the 

attitude instrument display, scanning techniques have been 

simplified because the attitude indicator is never out of 

peripheral view.

Selected Radial Cross-Check

The radial scan is designed so that your eyes remain on the 

attitude indicator 80–90 percent of the time. The remainder 

of the time is spent transitioning from the attitude indicator 

to the various other flight instruments. [Figure 6-33]

The radial scan pattern works well for scanning the PFD. The 

close proximity of the instrument tape displays necessitates 

very little eye movement in order to focus in on the desired 

instrument. While the eyes move in any direction, the 

extended artificial horizon line allows the pilot to keep the 

pitch attitude in his or her peripheral vision. This extended 

horizon line greatly reduces the tendency to fixate on one 

instrument and completely ignore all others. Because of 

the size of the attitude display, some portion of the attitude 

indicator is always visible while viewing another instrument 

display on the PFD.

Starting the Scan

Start the scan in the center of the PFD on the yellow chevron. 

Note the pitch attitude and then transition the eyes upward to 

the slip/skid indicator. Ensure that the aircraft is coordinated 

by aligning the split triangle symbol. The top of the split 

triangle is referred to as the roll pointer. The lower portion of 

the split triangle is the slip/skid indicator. If the lower portion 

of the triangle is off to one side, step on the rudder pedal on 

the same side to offset it. [Figure 6-34 NOTE: The aircraft 

is not changing heading. There is no trend vector on the turn 

rate indicator.]

While scanning that region, check the roll pointer and assure 

that the desired degree of roll is being indicated on the bank 

scale. The roll index and the bank scale remain stationary at 

the top of the attitude indicator. The index is marked with 

angles of 10°, 20°, 30°, 45°, and 60° in both directions. If 

the desired bank angle is not indicated, make the appropriate 

aileron corrections. Verify the bank angle is correct and 

continue scanning back to the yellow chevron. 

Scan left to the airspeed tape and verify that the airspeed is 

as desired, then return back to the center of the display. Scan 

right to the altimeter tape. Verify that the desired altitude 

is being maintained. If it is not, make the appropriate pitch 

change and verify the result. Once the desired altitude has been 

verified, return to the center of the display. Transition down to 

the heading indicator to verify the desired heading. When the 

heading has been confirmed, scan to the center of the display.

moving through the air with the longitudinal axis of the 

aircraft aligned with the relative wind. 

Primary Power

The primary power instrument for straight-and-level flight is 

the airspeed indicator. The main focus of power is to maintain 

a desired airspeed during level flight. No other instrument 

delivers instantaneous indication.

Learning the primary and supporting instruments for 

each variable is the key to successfully mastering attitude 

instrument flying. At no point does the primary and supporting 

method devalue the importance of the attitude indicator or the 

power instruments. All instruments (control, performance, 

primary, and supporting) must be utilized collectively. 

Fundamental Skills of Attitude Instrument 

Flying

When first learning attitude instrument flying, it is very 

important that two major skills be mastered. Instrument crosscheck and instrument interpretation comprise the foundation 

for safely maneuvering the aircraft by reference to instruments 

alone. Without mastering both skills, the pilot is not able to 

maintain precise control of aircraft attitude. 

Instrument Cross-Check

The first fundamental skill is cross-checking (also call 

“scanning”). Cross-checking is the continuous observation of 

the indications on the control and performance instruments. 

It is imperative that the new instrument pilot learn to 

observe and interpret the various indications in order to 

control the attitude and performance of the aircraft. Due to 

the configuration of some glass panel displays, such as the 

Garmin G1000, one or more of the performance instruments 

may be located on an MFD installed to the right of the pilot’s 

direct forward line of sight. 

How a pilot gathers the necessary information to control 

the aircraft varies by individual pilot. No specific method of 

cross-checking (scanning) is recommended; the pilot must 

learn to determine which instruments give the most pertinent 

information for any particular phase of a maneuver. With 

practice, the pilot is able to observe the primary instruments 

quickly and cross-check with the supporting instruments 

in order to maintain the desired attitude. At no time during 

instrument flying should the pilot stop cross-checking 

the instrumentation.

Scanning Techniques

Since most of the primary and supporting aircraft attitude 

information is displayed on the PFD, standard scanning 

techniques can be utilized. It is important to remember 
6-25

Figure 6-33. Selected radial cross-check.

XPDR 5537 IDNT LCL23:00:34

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ALERTS

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 4-30. Selected Radial Cross-Check

Slip/skid indicator

Heading

Airspeed indicator

Altitude indicator

Vertical speed indicator

Artificial horizon

Pitch Attitude

Slip/skid indicator

Airspeed indicator

Altitude indicator/VSI

Heading indicator

SCAN PATTERN

Scan pattern should start with 

left (airspeed indicator), then 

right (altitude indicator/VSI), 

then up (slip/skid indicator), 

then down (heading indicator). 

The pilot should return attention 

back to the center (pitch 

attitude) before proceeding to 

the next direction. For example: 

left, center, right, center, up, 

center, down, center. 

XPDR 5537 IDNT LCL23:00:34 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 4-31. Starting the Scan 

Roll pointer

Slip/skid indicator

Rudder

Figure 6-34. Roll pointer and slip/skid indicator.
6-26

150 

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TAS 120KT 

Figure 4-32. Airspeed Trend Indicators 

150 

140 

130 

110 

100 

90 

1 

120 

9 

 120KT 

Airspeed trend indicator 

shows airspeed will be 

approximately 126 kts in 

6 seconds.

Figure 6-35. Airspeed trend indicators.

Figure 6-36. Airspeed indicators with no trend present.

150 

140 

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90 

1 

120 

9 

TAS 120KT 

Figure 4-33. Airspeed Indicators No trend present 

Airspeed indicator

showing stabilized 

airspeed (no trend 

indicator present).

Figure 6-37. Altimeter trend indicators.

Figure 4-34. Altimeter Trend Indicators 

Trend indicator shows

altitude will be approximately 1,780 ft in 6 

seconds. 

VSI arrow has moved up 

to indicate a 1,500 fpm 

Note

rate of climb. 

1,500 fpm ÷ 60 sec = 25 ft 

25 ft per sec x 6 sec = 150 ft 

150 ft + 1,630 ft = 1,780 ft 

2 

1 

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It is also important to include the engine indications in the 

scan. Individualized scan methods may require adjustment 

if engine indications are presented on a separate MFD. A 

modified radial scan can be performed to incorporate these 

instruments into the scan pattern. Another critical component 

to include in the scan is the moving map display located on 

the MFD. To aid in situational awareness and facilitate a 

more centralized scan, a smaller inset map can be displayed 

in the lower left corner of the PFD screen.

Trend Indicators

One improvement the glass panel displays brought to the 

general aviation industry is the trend vector. Trend vectors 

are colored lines that appear on the airspeed and altitude 

tapes, as well as on the turn rate indicator. The color of 

the line may vary depending on the airplane manufacturer. 

For example, on a Cirrus SR-20, the trend vector lines are 

magenta and on the B-737 they are green. These colored lines 

indicate what the associated airspeed, altitude, or heading 

will be in 6 seconds for the Cirrus SR-20 and 10 seconds 

for the B-737 if the current rate is maintained. The example 

shown in Figure 6-35 uses the color and data that represents 

the trend vector for a Cirrus SR-20. The trend vector is not 

displayed if there is no change to the associated tape and the 

value remains constant [Figure 6-36] or if there is a failure 

in some portion of the system that would preclude the vector 

from being determined.

Trend vectors are a very good source of information for the 

new instrument rated pilot(s). Pilots who utilize good scanning 

techniques can pick up subtle deviations from desired 

parameters and make small correction to the desired attitude. 

As soon as a trend is indicated on the PFD, a conscientious 

pilot can adjust to regain the desired attitude. [Figure 6-37]

Another advancement in attitude instrument flying is the 

turn rate trend indicator. As in the cases of airspeed, altitude, 

and vertical speed trend indicators, the turn rate trend 

indicator depicts what the aircraft’s heading will be in 6 

seconds. While examining the top of the heading indicator, 

notice two white lines on the exterior of the compass rose. 

[Figure 6-38] These two tick marks located on both sides 

of the top of the heading indicator show half-standard rate 

turns as well as standard rate turns. 

In Figure 6-39, when the aircraft begins its turn to the left, 

the magenta trend indicator elongates proportionally with the 

rate of turn. To initiate a half-standard rate turn, position the 
6-27

XPDR 5537 IDNT LCL23:00:34 

GPS TERM 

197° 

HDG 357° CRS 152°

2 

1 

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OAT 7°C 

ALERTS 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

TRAFFIC 

Figure 4-35. HSI Trend Indicator elongates proportionate to the rate of turn. 

Heading

1/2 standard rate

Standard rate

Turn rate trend vector

Figure 6-38. Horizontal situation indicator (HSI) trend indicator elongates proportionally with the rate of turn.

VOR1 

197° 

HDG 357° CRS 152°

Figure 4-36. HSI Trend Indicator elongates proportionate to the 

rate of turn (enlarge). 

Heading

1/2 standard rate

Standard rate

Turn rate trend vector

Figure 6-39. HSI indicator (enlargement).

indicator on the first tick mark. A standard rate turn would 

be indicated by the trend indicator extending to the second 

tick mark. A turn rate in excess of standard rate would be 

indicated by the trend indicator extending past the second tick 

mark. This trend indicator shows what the aircraft’s heading 

will be in 6 seconds, but is limited to indicate no more than 

24° in front of the aircraft or 4° per second. When the aircraft 

exceeds a turning rate of 25° in 6 seconds, the trend indicator 

has an arrowhead attached to it.

Trend indicators are very useful when leveling off at a specific 

altitude, when rolling out on a heading, or when stabilizing 

airspeed. One method of determining when to start to level 

off from a climb or descent is to start leveling at 10 percent 

of the vertical speed rate prior to the desired altitude.

As the aircraft approaches the desired altitude, adjust the 

pitch attitude to keep the trend indicator aligned with the 

target altitude. As the target approaches, the trend indicator 

gradually shrinks until altitude stabilizes. Trend indicators 

should be used as a supplement, not as a primary means of 

determining pitch change. 

Common Errors

Fixation

Fixation, or staring at one instrument, is a common error 

observed in pilots first learning to utilize trend indicators. 

The pilot may initially fixate on the trend indicator and make 

adjustments with reference to that alone. Trend indicators are 

not the only tools to aid the pilot in maintaining the desired 
6-28

power or attitude; they should be used in conjunction with the 

primary and supporting instruments in order to better manage 

the flight. With the introduction of airspeed tapes, the pilot 

can monitor airspeed to within one knot. Fixation can lead 

to attempting to keep the airspeed to an unnecessarily tight 

tolerance. There is no need to hold airspeed to within one 

knot; the Instrument Rating Practical Test Standards (PTS) 

allows greater latitude.

Omission

Another common error associated with attitude instrument 

flying is omission of an instrument from the cross-check. Due 

to the high reliability of the PFD and associated components, 

pilots tend to omit the stand-by instruments as well as the 

magnetic compass from their scans. An additional reason 

for the omission is the position of the stand-by instruments. 

Pilots should continue to monitor the stand-by instruments 

in order to detect failures within those systems. One of the 

most commonly omitted instruments from the scan is the 

slip/skid indicator.

Emphasis

In initial training, placing emphasis on a single instrument 

is very common and can become a habit if not corrected. 

When the importance of a single instrument is elevated above 

another, the pilot begins to rely solely on that instrument 

for guidance. When rolling out of a 180° turn, the attitude 

indicator, heading indicator, slip/skid indicator, and altimeter 

need to be referenced. If a pilot omits the slip/skid indicator, 

coordination is sacrificed.
7-1

Introduction

Instrument flying techniques differ according to aircraft 

type, class, performance capability, and instrumentation. 

Therefore, the procedures and techniques that follow need 

to be modified to suit individual aircraft. Recommended 

procedures, performance data, operating limitations, and 

flight characteristics of a particular aircraft are available in the 

Pilot’s Operating Handbook/Airplane Flight Manual (POH/

AFM) for study before practicing the flight maneuvers. 

The flight maneuvers discussed in Chapter 7-I assume the 

use of a single-engine, propeller-driven small airplane with 

retractable gear and flaps and a panel with instruments 

representative of those discussed earlier in Chapter 5, Flight 

Instruments. With the exception of the instrument takeoff, all 

of the maneuvers can be performed on “partial panel,” with 

the attitude gyro and heading indicator covered or inoperative. 

Airplane Basic 

Flight Maneuvers

Chapter 7, Section I

Using Analog Instrumentation
7-2

30.0 

29.9 

29.8 

Figure 5-2. Pitch attitude and airspeed in level fiight, fast cruise speed. 

Figure 7-2. Pitch attitude and airspeed in level flight, fast 

cruise speed.

30.0 

29.9 

29.8 

Figure 5-1. Pitch attitude and airspeed in level fiight, slow cruise speed. 

Figure 7-1. Pitch attitude and airspeed in level flight, slow 

cruise speed.

30.0 

29.9 

29.8 

Figure 5-3. Pitch attitude and airspeed in level fiight, normal cruise speed. 

Figure 7-3. Pitch attitude and airspeed in level flight, normal 

cruise speed.

Straight-and-Level Flight

Pitch Control

The pitch attitude of an airplane is the angle between the 

longitudinal axis of the airplane and the actual horizon. In 

level flight, the pitch attitude varies with airspeed and load. 

For training purposes, the latter factor can normally be 

disregarded in small airplanes. At a constant airspeed, there is 

only one specific pitch attitude for level flight. At slow cruise 

speeds, the level flight attitude is nose high with indications 

as in Figure 7-1; at fast cruise speeds, the level-flight attitude 

is nose low. [Figure 7-2] Figure 7-3 shows the indications 

for the attitude at normal cruise speeds. The instruments used 

to determine the pitch attitude of the aircraft are the attitude 

indicator, the altimeter, the vertical speed indicator (VSI), 

and the airspeed indicator (ASI).

Attitude Indicator

The attitude indicator gives the direct indication of pitch 

attitude. The desired pitch attitude is gained by using the 

elevator control to raise or lower the miniature aircraft in 

relation to the horizon bar. This corresponds to the way pitch 

attitude is adjusted in visual flight by raising or lowering 

the nose of the airplane in relation to the natural horizon. 

However, unless the airspeed is constant, and until the 

level flight attitude for that airspeed has been identified and 

established, there is no way to know whether level flight as 
7-3

Figure 7-4. Pitch correction for level flight, one-half bar width.

Figure 7-5. Pitch correction for level flight, one bar width.

Figure 7-6. Pitch correction for level flight, one-and-one-half 

bar width.

Figure 5-4. Pitch correction for level flight, half-bar width 

Figure 5-5. Pitch correction for level flight, two-bar width 

Figure 5-6. Pitch correction for level flight, three-bar width 

indicated on the attitude indicator is resulting in level flight 

as shown on the altimeter, VSI, and ASI. If the miniature 

aircraft of the attitude indicator is properly adjusted on the 

ground before takeoff, it shows approximately level flight at 

normal cruise speed when the pilot completes the level off 

from a climb. If further adjustment of the miniature aircraft 

is necessary, the other pitch instruments must be used to 

maintain level flight while the adjustment is made. 

To practice pitch control for level flight using only the 

attitude indicator, use the following exercise. Restrict the 

displacement of the horizon bar to a one-half bar width, a 

bar width up or down, then a one-and-one-half bar width. 

One-half, one, and one-and-one-half bar width nose-high 

attitudes are shown in Figures 7-4, 7-5, and 7-6. 

An instructor pilot can demonstrate these normal pitch 

corrections and compare the indications on the attitude 

indicator with the airplane’s position to the natural horizon. 

Pitch attitude changes for corrections to level flight by 

reference to instruments are much smaller than those 

commonly used for visual flight. With the airplane correctly 

trimmed for level flight, the elevator displacement and the 

control pressures necessary to effect these standard pitch 

changes are usually very slight. The following are a few 

helpful hints to help determine how much elevator control 

pressure is required. 

First, a tight grip on the controls makes it difficult to feel 

control pressure changes. Relaxing and learning to control 

the aircraft usually takes considerable conscious effort during 

the early stages of instrument training. 

Second, make smooth and small pitch changes with positive 

pressure. With practice, a pilot can make these small pitch 

corrections up or down, “freezing” (holding constant) the 

one-half, full, and one-and-one-half bar widths on the 

attitude indicator. 

Third, with the airplane properly trimmed for level flight, 

momentarily release all pressure on the elevator control 

when becoming aware of tenseness. This is a reminder that 

the airplane is stable; except under turbulent conditions, it 

maintains level flight if left alone. Even when no control 

change is called for, it is difficult to resist the impulse to 

move the controls. This may be one of the most difficult 

initial training problems in instrument flight. 

Altimeter

At constant power, any deviation from level flight (except 

in turbulent air) is the result of a pitch change. Therefore, 

the altimeter gives an indirect indication of the pitch attitude 

in level flight, assuming constant power. Since the altitude 
7-4

Figure 7-7. Using the altimeter for pitch interpretation, a high 

altitude means a nose-high pitch attitude.

Figure 7-8. Pitch correction following altitude increase—lower 

nose to correct altitude error.

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Figure 5-7. Using the altimeter for pitch interpretation, a high altitude means a 

 nose-high pitch attitude. 

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29.9 

29.8 

Figure 5-8. Pitch correction following altitude increase-lower nose to correct 

 attitude error. 

should remain constant when the airplane is in level flight, 

any deviation from the desired altitude signals the need for a 

pitch change. If the aircraft is gaining altitude, the nose must 

be lowered. [Figures 7-7 and 7-8]

The rate of movement of the altimeter needle is as important 

as its direction of movement in maintaining level flight 

without the use of the attitude indicator. An excessive pitch 

deviation from level flight results in a relatively rapid change 

of altitude; a slight pitch deviation causes a slow change. 

Thus, if the altimeter needle moves rapidly clockwise, assume 

a considerable nose-high deviation from level flight attitude. 

Conversely, if the needle moves slowly counterclockwise to 

indicate a slightly nose-low attitude, assume that the pitch 

correction necessary to regain the desired altitude is small. 

As the altimeter is added to the attitude indicator in a crosscheck, a pilot learns to recognize the rate of movement of 

the altimeter needle for a given pitch change as shown on 

the attitude indicator. 

To practice precision control of pitch in an airplane without 

an attitude indicator, make small pitch changes by visual 

reference to the natural horizon and note the rate of movement 

of the altimeter. Note what amount of pitch change gives 

the slowest steady rate of change on the altimeter. Then 

practice small pitch corrections by accurately interpreting 

and controlling the rate of needle movement. 

An instructor pilot can demonstrate an excessive nose-down 

deviation (indicated by rapid movement of the altimeter 

needle) and then, as an example, show the result of improper 

corrective technique. The normal impulse is to make a 

large pitch correction in a hurry, but this inevitably leads 

to overcontrolling. The needle slows down, then reverses 

direction, and finally indicates an excessive nose-high 

deviation. The result is tension on the controls, erratic control 

response, and increasingly extreme control movements. The 

correct technique, which is slower and smoother, returns the 

airplane to the desired attitude more quickly, with positive 

control and no confusion. 

When a pitch error is detected, corrective action should be 

taken promptly, but with light control pressures and two 

distinct changes of attitude: (1) a change of attitude to stop 

the needle movement and (2) a change of attitude to return 

to the desired altitude. 

When the altimeter indicates an altitude deviation, apply 

just enough elevator pressure to decrease the rate of needle 

movement. If it slows down abruptly, ease off some of the 

pressure until the needle continues to move, but ease off 

slowly. Slow needle movement means the airplane attitude 

is close to level flight. Add slightly more corrective pressure 

to stop the direction of needle movement. At this point, level 

flight is achieved; a reversal of needle movement means 

the aircraft has passed through it. Relax control pressures 

carefully, continuing to cross-check since changing airspeed 

causes changes in the effectiveness of a given control 

pressure. Next, adjust the pitch attitude with elevator pressure 

for the rate of change of altimeter needle movement that is 

correlated with normal pitch corrections and return to the 

desired altitude. 

As a rule of thumb, for errors of less than 100 feet, use a half 

bar width correction. [Figures 7-9 and 7-10] For errors in 

excess of 100 feet, use an initial full bar width correction. 

[Figures 7-11 and 7-12] Practice predetermined altitude 

changes using the altimeter alone, then in combination with 

the attitude indicator. 

Vertical Speed Indicator (VSI)

The VSI, like the altimeter, gives an indirect indication of 

pitch attitude and is both a trend and a rate instrument. As 

a trend instrument, it shows immediately the initial vertical 

movement of the airplane, which disregarding turbulence 

can be considered a reflection of pitch change. To maintain 

level flight, use the VSI in conjunction with the altimeter and 

attitude indicator. Note any positive or negative trend of the 

needle from zero and apply a very light corrective elevator 
7-5

Figure 7-9. Altitude error, less than 100 feet.

Figure 7-10. Pitch correction, less than 100 feet—one-half bar low 

to correct altitude error.

Figure 7-11. Altitude error, greater than 100 feet.

Figure 7-12. Pitch correction, greater than 100 feet—one bar 

correction initially.

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29.8 

Figure 5-9. Altitude error, less than 100 feet. 

30.0 

29.9 

29.8 

Figure 5-10. Pitch correction, less than 100 feet- 1/2 bar low to correct altitude error. 

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29.9 

29.8 

Figure 5-11. Altitude error, greater than 100 feet. 

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29.9 

29.8 

Figure 5-12. Pitch correction, freater than 100 feet-1 bar correction initially. 

pressure. As the needle returns to zero, relax the corrective 

pressure. If control pressures have been smooth and light, the 

needle reacts immediately and slowly, and the altimeter shows 

little or no change of altitude. As a rate instrument, the VSI 

requires consideration of lag characteristics. 

Lag refers to the delay involved before the needle attains a 

stable indication following a pitch change. Lag is directly 

proportional to the speed and magnitude of a pitch change. 

If a slow, smooth pitch change is initiated, the needle moves 

with minimum lag to a point of deflection corresponding 

to the extent of the pitch change, and then stabilizes as the 

aerodynamic forces are balanced in the climb or descent. 

A large and abrupt pitch change produces erratic needle 

movement, a reverse indication, and introduces greater time 

delay (lag) before the needle stabilizes. Pilots are cautioned 

not to chase the needle when flight through turbulent 

conditions produces erratic needle movements. The apparent 

lag in airspeed indications with pitch changes varies greatly 

among different airplanes and is due to the time required for 

the airplane to accelerate or decelerate when the pitch attitude 

is changed. There is no appreciable lag due to the construction 

or operation of the instrument. Small pitch changes, smoothly 

executed, result in an immediate change of airspeed.

When using the VSI as a rate instrument and combining it 

with the altimeter and attitude indicator to maintain level 

flight, a pilot should know that the amount the altimeter 

needle moves from the desired altitude governs the rate that 

should be used to return to that altitude. A rule of thumb is to 

make an attitude change that results in a vertical-speed rate 

approximately double the error in altitude. For example, if 

altitude is off by 100 feet, the rate of return to the desired 

altitude should be approximately 200 feet per minute (fpm). 

If it is off by more than 100 feet, the correction should 

be correspondingly greater, but should never exceed the 

optimum rate of climb or descent for the airplane at a given 

airspeed and configuration. 

A deviation of more than 200 fpm from the desired rate 

of return is considered overcontrolling. For example, if 

attempting to change altitude by 200 feet, a rate in excess of 

400 fpm indicates overcontrolling. 

When returning to an altitude, the VSI is the primary pitch 

instrument. Occasionally, the VSI is slightly out of calibration 

and may indicate a climb or descent when the airplane is in 

level flight. If the instrument cannot be adjusted, take the 

error into consideration when using it for pitch control. For 
7-6

Figure 7-13. Constant power plus constant pitch equals constant 

speed.

Figure 7-14. Constant power plus decreased pitch equals increased 

airspeed.

Figure 7-15. Constant power plus increased pitch equals decreased 

airspeed.

Constant Airspeed Constant Pitch

Increased Airspeed Decreased Pitch

Decreased Airspeed Increased Pitch

Figure 5-13. Constant power plus constant pitch equals constant airspeed. 

Figure 5-14. Constant power plus decreased pitch equals increased airspeed.. 

Figure 5-15. Constant power plus increased pitch equals decreased airspeed. 

example, if the needle indicates a descent of 200 fpm while 

in level flight, use this indication as the zero position. 

Airspeed Indicator (ASI)

The ASI presents an indirect indication of the pitch attitude. 

In non-turbulent conditions with a constant power setting and 

pitch attitude, airspeed remains constant. [Figure 7-13] As the 

pitch attitude lowers, airspeed increases, and the nose should 

be raised. [Figure 7-14] As the pitch attitude rises, airspeed 

decreases, and the nose should be lowered. [Figure 7-15] A 

rapid change in airspeed indicates a large pitch change, and 

a slow change of airspeed indicates a small pitch change. 

Pitch control in level flight is a question of cross-check and 

interpretation of the instrument panel for the instrument 

information that enables a pilot to visualize and control 

pitch attitude. Regardless of individual differences in 

cross-check technique, all pilots should use the instruments 

that give the best information for controlling the airplane 

in any given maneuver. Pilots should also check the other 

instruments to aid in maintaining the primary instruments 

at the desired indication. 

As noted previously, the primary instrument is the one 

that gives the most pertinent information for a particular 

maneuver. It is usually the one that should be held at a 

constant indication. Which instrument is primary for pitch 

control in level flight, for example? This question should 

be considered in the context of specific airplane, weather 

conditions, pilot experience, operational conditions, and 

other factors. Attitude changes must be detected and 

interpreted instantly for immediate control action in highperformance airplanes. On the other hand, a reasonably 

proficient instrument pilot in a slower airplane may rely 

more on the altimeter for primary pitch information, 

especially if it is determined that too much reliance on the 

attitude indicator fails to provide the necessary precise 

attitude information. Whether the pilot decides to regard 

the altimeter or the attitude indicator as primary depends 

on which approach will best help control the attitude. In 

this handbook, the altimeter is normally considered as the 

primary pitch instrument during level flight. 

Bank Control

The bank attitude of an airplane is the angle between the 

airplane’s wings and the natural horizon. To maintain a 

straight-and-level flightpath, the wings of the airplane are 

kept level with the horizon (assuming the airplane is in 

coordinated flight). The instruments used for bank control 

are the attitude indicator, the heading indicator, and the 

turn coordinator. Figure 7-16 illustrates coordinated flight. 

The aircraft is banked left with the attitude indicator and 

turn coordinator indicating the bank. The heading indicator 

indicates a left turn by apparent clockwise rotation of the 

compass card behind the airplane silhouette. 

Attitude Indicator

The attitude indicator shows any change in bank attitude 

directly and instantly and is, therefore, a direct indicator. On 

the standard attitude indicator, the angle of bank is shown 

pictorially by the relationship of the miniature aircraft to the 

artificial horizon bar and by the alignment of the pointer with 

the banking scale at the top of the instrument. On the face of 

the standard three-inch instrument, small angles of bank can 

be difficult to detect by reference to the miniature aircraft, 

especially if leaning to one side or changing a seating position 
7-7

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29.9 

29.8 

Bank control 

Figure 5-16. Instruments used for bank control. 

Figure 7-16. Instruments used for bank control.

Figure 7-17. Bank interpretation with the attitude indicator.

0° 

30° 

45° 

60° 

90° 

slightly. The position of the scale pointer is a good check 

against the apparent miniature aircraft position. Disregarding 

precession error, small deviations from straight coordinated 

flight can be readily detected on the scale pointer. The 

banking index may be graduated as shown in Figure 7-17, 

or it may be graduated in 30° increments.

The instrument depicted in Figure 7-17 has a scale pointer 

that moves in the same direction of bank shown by the 

miniature aircraft. In this case, the aircraft is in a left 15° 

bank. Precession errors in this instrument are common 

and predictable, but the obvious advantage of the attitude 

indicator is an immediate indication of both pitch attitude 

and bank attitude in a single glance. Even with the precession 

errors associated with many attitude indicators, the quick 

attitude presentation requires less visual effort and time for 

positive control than other flight instruments. 

Heading Indicator

The bank attitude of an aircraft in coordinated flight is shown 

indirectly on the heading indicator, since banking results in 

a turn and change in heading. Assuming the same airspeed 

in both instances, a rapid movement of the heading indicator 

(azimuth card in a directional gyro) indicates a large angle 

of bank, whereas slow movement reflects a small angle of 

bank. Note the rate of movement of the heading indicator 

and compare it to the attitude indicator’s degrees of bank. 

The attitude indicator’s precession error makes a precise 

check of heading information necessary in order to maintain 

straight flight. 

When deviations from straight flight are noted on the heading 

indicator, correct to the desired heading using a bank angle no 

greater than the number of degrees to be turned. In any case, 

limit bank corrections to a bank angle no greater than that 

required for a standard rate turn. Use of larger bank angles 

requires a very high level of proficiency, and normally results 

in overcontrolling and erratic bank control. 

Turn Coordinator

The miniature aircraft of the turn coordinator gives an 

indirect indication of the bank attitude of the airplane. 

When the miniature aircraft is level, the airplane is in 

straight flight. When the miniature airplane is aligned with 

one of the alignment marks and the aircraft is rolling to the 

left or right the indication represents the roll rate, with the 

alignment marks indicating a roll of 3 degrees per second 

in the direction of the miniature aircraft. This can be seen 

in level flight when a bank is introduced either to the left 

or the right. The turn coordinator’s indicator will indicate 

the rolling motion although there is no turn being made. 

Conversely, a pedal input to the right or left causes the aircraft 

to turn momentarily about its vertical axis (with no rolling 

motion) with an indication of turn on the turn coordinator. 

After the turn becomes stabilized and the aircraft is no 

longer rolling, the turn coordinator displays the rate of turn 

with the alignment marks equaling a turn of 3 degrees per 

second. The turn coordinator is able to display both roll and 

turn parameters because its electrically-powered gyroscope 

is canted at an angle. As a result, the turn-and-slip indicator 

provides both roll and turn indications. Autopilots in general 

aviation today use this instrument in determining both roll 

and turn information. After the completion of a turn, return 

to straight flight is accomplished by coordinated aileron and 
7-8

Figure 7-18. Skid indication.

Figure 7-19. Slip indication.

OFF 

2 MIN TURN DC ELEC 

L R 

Figure 5-18. Slip indication. 

OFF 

2 MIN TURN DC ELEC 

L R 

Figure 5-19. Skid indication. 

rudder pressure to level the miniature aircraft. Include the 

miniature aircraft in the cross-check and correct for even 

the smallest deviations from the desired position. When 

this instrument is used to maintain straight flight, control 

pressures must be applied very lightly and smoothly.

The ball of the turn coordinator is actually a separate 

instrument, conveniently located under the miniature 

aircraft because the two instruments are used together. 

The ball instrument indicates the quality of the turn. If the 

ball is off-center, the airplane is slipping or skidding. That 

is, if the coordinator’s miniature airplane is tilted left and 

the ball is displaced to the right, the aircraft is in a skid. 

[Figure 7-18] If however, the miniature airplane is tilted to 

the right with the ball off-center to the right, the aircraft is in 

a slip. [Figure 7-19] If the wings are level and the airplane 

is properly trimmed, the ball remains in the center, and the 

airplane is in straight flight. If the ball is not centered, the 

airplane is improperly trimmed.

To maintain straight-and-level flight with proper trim, note 

the direction of ball displacement. If the ball is to the left of 

center and the left wing is low, apply left rudder pressure 

to center the ball and correct the slip. At the same time, 

apply right aileron pressure as necessary to level the wings, 

cross-checking the heading indicator and attitude indicator 

while centering the ball. If the wings are level and the ball is 

displaced from the center, the airplane is skidding. Note the 

direction of ball displacement and use the same corrective 

technique as for an indicated slip. Center the ball (left ball/

left rudder, right ball/right rudder), use aileron as necessary 

for bank control and retrim. 

To trim the airplane using only the turn coordinator, use 

aileron pressure to level the miniature aircraft and rudder 

pressure to center the ball. Hold these indications with control 

pressures, gradually releasing them while applying rudder 

trim sufficient to relieve all rudder pressure. Apply aileron 

trim, if available, to relieve aileron pressure. With a full 

instrument panel, maintain a wings-level attitude by reference 

to all available instruments while trimming the airplane. 

Turn-and-Slip Indicator (Needle and Ball)

Unlike the turn coordinator that provides three indications 

(roll, turn, and trim), the turn-and-slip indicator provides 

two: turn-rate and trim. Although the turn-and-slip indicator 

needle provides an indication of turn only, it provides an 

indirect indication of aircraft attitude when used with roll 

indicators, such as a heading indicator or magnetic compass. 

As with the turn coordinator (after stabilizing from a roll), 

when the turn-and-slip indicator’s needle is aligned with the 

alignment marks, the aircraft is in a standard turn of 3 degrees 

per second or 360° in 2 minutes.

The ball of the turn-and-bank indicator provides important 

trim in the same manner that the ball in the turn coordinator 

does. Figures 7-18 and 7-19 provide a comparison of the 

two instruments.

Power Control

Power produces thrust which, with the appropriate angle of 

attack of the wing, overcomes the forces of gravity, drag, 

and inertia to determine airplane performance. 

Power control must be related to its effect on altitude and 

airspeed, since any change in power setting results in a change 

in the airspeed or the altitude of the airplane. At any given 

airspeed, the power setting determines whether the airplane 

is in level flight, in a climb, or in a descent. If the power is 

increased in straight-and-level flight and the airspeed held 

constant, the airplane climbs. If power is decreased while 

the airspeed is held constant, the airplane descends. On the 

other hand, if altitude is held constant, the power applied 

determines the airspeed. 

The relationship between altitude and airspeed determines the 

need for a change in pitch or power. If the airspeed is not the 

desired value, always check the altimeter before deciding that 

a power change is necessary. Think of altitude and airspeed 

as interchangeable; altitude can be traded for airspeed by 

lowering the nose or convert airspeed to altitude by raising 

the nose. If altitude is higher than desired and airspeed is 
7-9

Figure 7-20. Airspeed low and altitude high—lower pitch.

Figure 7-21. Airspeed and altitude high—lower pitch and reduce power.

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INCHES MERCURY ABSOLUTE

MANIFOLD 

PRESSURE 

35

10 50

15

25

40

30

20

45

35

10 50

15

25

40

30

20

45

Figure 5-20. Airspeed low and altitude high corrected with slighly lowered pitch. 

INCHES MERCURY

ABSOLUTE

MANIFOLD 

PRESSURE 

35

10 50

15

25

40

30

20

45

35

10 50

15

25

40

30

20

45

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Figure 5-21. Airspeed and altitude high (lower pitch and reduce power). 

low, or vice versa, a change in pitch alone may return the 

airplane to the desired altitude and airspeed. [Figure 7-20] If 

both airspeed and altitude are high or if both are low, then a 

change in both pitch and power is necessary in order to return 

to the desired airspeed and altitude. [Figure 7-21] 

For changes in airspeed in straight-and-level flight, pitch, 

bank, and power must be coordinated in order to maintain 

constant altitude and heading. When power is changed to 

vary airspeed in straight-and-level flight, a single-engine, 

propeller-driven airplane tends to change attitude around all 

axes of movement. Therefore, to maintain constant altitude 

and heading, apply various control pressures in proportion 

to the change in power. When power is added to increase 

airspeed, the pitch instruments indicate a climb unless 

forward elevator control pressure is applied as the airspeed 

changes. With an increase in power, the airplane tends to 

yaw and roll to the left unless counteracting aileron and 

rudder pressures are applied. Keeping ahead of these changes 

requires increasing cross-check speed, which varies with the 

type of airplane and its torque characteristics, the extent of 

power, and speed change involved. 

Power Settings

Power control and airspeed changes are much easier when 

approximate power settings necessary to maintain various 

airspeeds in straight-and-level flight are known in advance. 

However, to change airspeed by any appreciable amount, the 

common procedure is to underpower or overpower on initial 

power changes to accelerate the rate of airspeed change. 

(For small speed changes, or in airplanes that decelerate 

or accelerate rapidly, overpowering or underpowering is 

not necessary.)

Consider the example of an airplane that requires 23 inches 

of mercury ("Hg) of manifold pressure to maintain a normal 

cruising airspeed of 120 knots, and 18 "Hg of manifold 

pressure to maintain an airspeed of 100 knots. The reduction 

in airspeed from 120 knots to 100 knots while maintaining 

straight-and-level flight is discussed below and illustrated in 

Figures 7-22, 7-23, and 7-24. 

Instrument indications, prior to the power reduction, are 

shown in Figure 7-22. The basic attitude is established and 

maintained on the attitude indicator. The specific pitch, 

bank, and power control requirements are detected on these 

primary instruments: 

Altimeter—Primary Pitch 

Heading Indicator—Primary Bank 

Airspeed Indicator—Primary Power 

Supporting pitch-and-bank instruments are shown in 

Figure 7-23. Note that the supporting power instrument is 

the manifold pressure gauge (or tachometer if the propeller 

is fixed pitch). However, when a smooth power reduction to 

approximately 15 "Hg (underpower) is made, the manifold 

pressure gauge becomes the primary power instrument. 

[Figure 7-23] With practice, power setting can be changed 

with only a brief glance at the power instrument, by sensing 
7-10

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Figure 5-22. Straight-and-level flight (normal cruising speed). 

Primary pitch

Supporting pitch and bank

Primary power

Supporting bank

Primary bank

Supporting pitch

Supporting power

Figure 7-22. Straight-and-level flight (normal cruising speed).

30.0 

29.9 

29.8 

Figure 5-23. Straight-and-level flight (airspeed decreasing). 

Primary pitch

Supporting pitch and bank

Supporting bank

Primary bank

Supporting pitch

Primary power as

airspeed approaches

desired value

Primary power

as throttle is set

Figure 7-23. Straight-and-level flight (airspeed decreasing).
7-11

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29.8 

Figure 5-24. Straight-and-level flight (reduced airspeed stabilized). 

Supporting power

Primary pitch

Supporting pitch and bank

Supporting bank

Primary bank

Supporting pitch

Primary power

Figure 7-24. Straight-and-level flight (reduced airspeed stabilized).

the movement of the throttle, the change in sound, and the 

changes in the feel of control pressures. 

As thrust decreases, increase the speed of the cross-check 

and be ready to apply left rudder, back-elevator, and aileron 

control pressure the instant the pitch-and-bank instruments 

show a deviation from altitude and heading. As proficiency 

is obtained, a pilot learns to cross-check, interpret, and 

control the changes with no deviation of heading and 

altitude. Assuming smooth air and ideal control technique 

as airspeed decreases, a proportionate increase in airplane 

pitch attitude is required to maintain altitude. Similarly, 

effective torque control means counteracting yaw with 

rudder pressure. 

As the power is reduced, the altimeter is primary for 

pitch, the heading indicator is primary for bank, and the 

manifold pressure gauge is momentarily primary for power 

(at 15 "Hg in this example). Control pressures should be 

trimmed off as the airplane decelerates. As the airspeed 

approaches the desired airspeed of 100 knots, the manifold 

pressure is adjusted to approximately 18 "Hg and becomes 

the supporting power instrument. The ASI again becomes 

primary for power. [Figure 7-24]

Airspeed Changes in Straight-and-Level Flight

Practice of airspeed changes in straight-and-level flight provides 

an excellent means of developing increased proficiency in all 

three basic instrument skills and brings out some common 

errors to be expected during training in straight-and-level flight. 

Having learned to control the airplane in a clean configuration 

(minimum drag conditions), increase proficiency in crosscheck and control by practicing speed changes while extending 

or retracting the flaps and landing gear. While practicing, be 

sure to comply with the airspeed limitations specified in the 

POH/AFM for gear and flap operation. 

Sudden and exaggerated attitude changes may be necessary 

in order to maintain straight-and-level flight as the landing 

gear is extended and the flaps are lowered in some airplanes. 

The nose tends to pitch down with gear extension, and when 

flaps are lowered, lift increases momentarily (at partial flap 

settings) followed by a marked increase in drag as the flaps 

near maximum extension. 

Control technique varies according to the lift and drag 

characteristics of each airplane. Accordingly, knowledge of 

the power settings and trim changes associated with different 

combinations of airspeed, gear, and flap configurations 

reduces instrument cross-check and interpretation problems. 

For example, assume that in straight-and-level flight 

instruments indicate 120 knots with power at 23 "Hg/2,300 

revolutions per minute (rpm), gear and flaps up. After 

reduction in airspeed, with gear and flaps fully extended, 

straight-and-level flight at the same altitude requires 25 "Hg 

manifold pressure/2,500 rpm. Maximum gear extension 

speed is 115 knots; maximum flap extension speed is 105 
7-12

knots. Airspeed reduction to 95 knots, gear and flaps down, 

can be made in the following manner:

1. Maintain rpm at 2,500, since a high power setting is 

used in full drag configuration.

2. Reduce manifold pressure to 10 "Hg. As the airspeed 

decreases, increase cross-check speed.

3. Make trim adjustments for an increased angle of attack 

and decrease in torque.

4. Lower the gear at 115 knots. The nose may tend to 

pitch down and the rate of deceleration increases. 

Increase pitch attitude to maintain constant altitude, 

and trim off some of the back-elevator pressures. 

If full flaps are lowered at 105 knots, cross-check, 

interpretation, and control must be very rapid. A 

simpler technique is to stabilize attitude with gear 

down before lowering the flaps. 

5. Since 18 "Hg manifold pressure will hold level 

flight at 100 knots with the gear down, increase 

power smoothly to that setting until the ASI shows 

approximately 105 knots. The attitude indicator now 

shows approximately two-and-a-half bar width nosehigh in straight-and-level flight.

6. Actuate the flap control and simultaneously increase 

power to the predetermined setting (25 "Hg) for the 

desired airspeed, and trim off the pressures necessary 

to hold constant altitude and heading. The attitude 

indicator now shows a bar width nose-low in straightand-level flight at 95 knots. 

Proficiency in straight-and-level flight is attained when a 

pilot can consistently maintain constant altitude and heading 

with smooth pitch, bank, power, and trim control during the 

pronounced changes in aircraft attitude. 

Trim Technique

Proper trim technique is essential for smooth and precise 

aircraft control during all phases of flight. By relieving all 

control pressures, it is much easier to hold a given attitude 

constant and devote more attention to other flight deck duties. 

An aircraft is trimmed by applying control pressures to 

establish a desired attitude, then adjusting the trim so the 

aircraft maintains that attitude when the flight controls are 

released. Trim the aircraft for coordinated flight by centering 

the ball of the turn-and-slip indicator, by using rudder trim in 

the direction the ball is displaced from the center. Differential 

power control on multiengine aircraft is an additional factor 

affecting coordinated flight. Use balanced power or thrust, 

when possible, to aid in maintaining coordinated flight. 

Changes in attitude, power, or configuration requires a trim 

adjustment in most cases. Using trim alone to establish a 

change in aircraft attitude invariably leads to erratic aircraft 

control. Smooth and precise attitude changes are best attained 

by a combination of control pressures and trim adjustments. 

Therefore, when used correctly, trim adjustment is an aid to 

smooth aircraft control.

Common Errors in Straight-and-Level Flight 

Pitch

Pitch errors usually result from the following faults: 

1. Improper adjustment of the attitude indicator’s 

miniature aircraft to the wings-level attitude. 

Following the initial level off from a climb, check the 

attitude indicator and make any necessary adjustment 

in the miniature aircraft for level flight indication at 

normal cruise airspeed. 

2. Insufficient cross-check and interpretation of pitch 

instruments. For example, the airspeed indication is 

low. The pilot, believing a nose-high attitude exists, 

applies forward pressure without noting that a low 

power setting is the cause of the airspeed discrepancy. 

Increase cross-check speed to include all relevant 

instrument indications before making a control input. 

3. Uncaging the attitude indicator (if caging feature is 

present) when the airplane is not in level flight. The 

altimeter and heading indicator must be stabilized with 

airspeed indication at normal cruise before pulling 

out the caging knob to obtain correct indications in 

straight-and-level flight at normal cruise airspeed. 

4. Failure to interpret the attitude indicator in terms of 

the existing airspeed. 

5. Late pitch corrections. Pilots commonly like to leave 

well enough alone. When the altimeter indicates a 20 

foot error, there is a reluctance to correct it, perhaps 

because of fear of overcontrolling. If overcontrolling 

is the anticipated error, practice small corrections and 

find the cause of overcontrolling. If any deviation is 

tolerated, errors increase.

6. Chasing the vertical speed indications. This tendency 

can be corrected by proper cross-check of other 

pitch instruments, as well as by increasing overall 

understanding of instrument characteristics. 

7. Using excessive pitch corrections for the altimeter 

evaluation. Rushing a pitch correction by making a 

large pitch change usually aggravates the existing 

error, saving neither time nor effort. 
7-13

8. Failure to maintain established pitch corrections, 

a common error associated with cross-check and 

trim errors. For example, having established a 

pitch change to correct an altitude error, there is a 

tendency to slow down the cross-check, waiting for 

the airplane to stabilize in the new pitch attitude. To 

maintain the attitude, continue to cross-check and 

trim off the pressures. 

9. Fixations during cross-check. After initiating a 

heading correction, for example, there is a tendency 

to become preoccupied with bank control and miss 

errors in pitch attitude. Likewise, during an airspeed 

change, unnecessary gazing at the power instrument 

is common. A small error in power setting is of less 

consequence than large altitude and heading errors. 

The airplane will not decelerate any faster by staring 

at the manifold pressure gauge. 

Heading

Heading errors usually result from the following faults: 

1. Failure to cross-check the heading indicator, especially 

during changes in power or pitch attitude. 

2. Misinterpretation of changes in heading, with resulting 

corrections in the wrong direction. 

3. Failure to note and remember a preselected heading. 

4. Failure to observe the rate of heading change and its 

relation to bank attitude. 

5. Overcontrolling in response to heading changes, 

especially during changes in power settings. 

6. Anticipating heading changes with premature 

application of rudder control. 

7. Failure to correct small heading deviations. Unless 

zero error in heading is the goal, a pilot will tolerate 

larger and larger deviations. Correction of a 1 degree 

error takes a lot less time and concentration than 

correction of a 20° error. 

8. Correcting with improper bank attitude. If correcting a 

10° heading error with 20° of bank, the airplane rolls 

past the desired heading before the bank is established, 

requiring another correction in the opposite direction. 

Do not multiply existing errors with errors in 

corrective technique. 

9. Failure to note the cause of a previous heading error 

and thus repeating the same error. For example, the 

airplane is out of trim, with a left wing low tendency. 

Repeated corrections for a slight left turn are made, 

yet trim is ignored.

10. Failure to set the heading indicator properly or failure 

to uncage it.

Power

Power errors usually result from the following faults: 

1. Failure to know the power settings and pitch attitudes 

appropriate to various airspeeds and airplane 

configurations. 

2. Abrupt use of throttle.

3. Failure to lead the airspeed when making power 

changes. For example, during airspeed reduction in 

level flight, especially with gear and flaps extended, 

adjust the throttle to maintain the slower speed 

before the airspeed actually reaches the desired 

speed. Otherwise, the airplane decelerates to a speed 

lower than that desired, resulting in additional power 

adjustments. The amount of lead depends upon how 

fast the airplane responds to power changes. 

4. Fixation on airspeed or manifold pressure instruments 

during airspeed changes, resulting in erratic control 

of both airspeed and power. 

Trim

Trim errors usually result from the following faults: 

1. Improper adjustment of seat or rudder pedals for 

comfortable position of legs and feet. Tension in the 

ankles makes it difficult to relax rudder pressures. 

2. Confusion about the operation of trim devices that 

differ among various airplane types. Some trim wheels 

are aligned appropriately with the airplane’s axes; 

others are not. Some rotate in a direction contrary to 

what is expected. 

3. Faulty sequence in trim technique. Trim should be 

used not as a substitute for control with the wheel 

(stick) and rudders, but to relieve pressures already 

held to stabilize attitude. As proficiency is gained, little 

conscious effort is required to trim off the pressures 

as they occur. 

4. Excessive trim control. This induces control pressures 

that must be held until the airplane is trimmed 

properly. Use trim frequently and in small amounts. 

5. Failure to understand the cause of trim changes. Lack 

of understanding the basic aerodynamics related to 

basic instrument skills causes a pilot to continually 

lag behind the airplane.
7-14

30.0 

29.9 

29.8 

Figure 5-25. Climb entry for constant-airspeed climb. 

Supporting pitch and bank

Supporting bank

Primary bank

Supporting pitch

Primary power

Figure 7-25. Climb entry for constant airspeed climb.

Straight Climbs and Descents

Climbs

For a given power setting and load condition, there is only 

one attitude that gives the most efficient rate of climb. The 

airspeed and climb power setting that determines this climb 

attitude are given in the performance data found in the POH/

AFM. Details of the technique for entering a climb vary 

according to airspeed on entry and the type of climb (constant 

airspeed or constant rate) desired. (Heading and trim control 

are maintained as discussed in straight-and-level flight.) 

Entry

To enter a constant-airspeed climb from cruising airspeed, 

raise the miniature aircraft to the approximate nose-high 

indication for the predetermined climb speed. The attitude 

varies according to the type of airplane. Apply light backelevator pressure to initiate and maintain the climb attitude. 

The pressures vary as the airplane decelerates. Power may 

be advanced to the climb power setting simultaneously with 

the pitch change or after the pitch change is established and 

the airspeed approaches climb speed. If the transition from 

level flight to climb is smooth, the VSI shows an immediate 

trend upward, continues to move slowly, and then stops at 

a rate appropriate to the stabilized airspeed and attitude. 

(Primary and supporting instruments for the climb entry are 

shown in Figure 7-25.) 

Once the airplane stabilizes at a constant airspeed and attitude, 

the ASI is primary for pitch and the heading indicator remains 

primary for bank. [Figure 7-26] Monitor the tachometer or 

manifold pressure gauge as the primary power instrument to 

ensure the proper climb power setting is being maintained. 

If the climb attitude is correct for the power setting selected, 

the airspeed will stabilize at the desired speed. If the airspeed 

is low or high, make an appropriately small pitch correction. 

To enter a constant airspeed climb, first complete the airspeed 

reduction from cruise airspeed to climb speed in straightand-level flight. The climb entry is then identical to entry 

from cruising airspeed, except that power must be increased 

simultaneously to the climb setting as the pitch attitude is 

increased. Climb entries on partial panel are more easily 

and accurately controlled if entering the maneuver from 

climbing speed. 

The technique for entering a constant-rate climb is very 

similar to that used for entry to a constant-airspeed climb 

from climb airspeed. As the power is increased to the 

approximate setting for the desired rate, simultaneously 

raise the miniature aircraft to the climbing attitude for the 

desired airspeed and rate of climb. As the power is increased, 

the ASI is primary for pitch control until the vertical speed 

approaches the desired value. As the vertical speed needle 

stabilizes, it becomes primary for pitch control and the ASI 

becomes primary for power control. [Figure 7-27] 
7-15

30.0 

29.9 

29.8 

Figure 5-26. Stabilized climb at constant airspeed. 

Supporting pitch and bank

Primary pitch

Supporting bank

Primary bank

Supporting pitch

Figure 7-26. Stabilized climb at constant airspeed.

30.0 

29.9 

29.8 

Figure 5-27. Stabilized climb at constant rate. 

Supporting pitch and bank

Primary power

Supporting bank

Primary bank

Primary pitch

Figure 7-27. Stabilized climb at constant rate.
7-16

30.0 

29.9 

29.8 

Figure 5-28. Airspeed low and vertical speed high-reduce pitch. 

Supporting pitch and bank

Primary power

Supporting bank

Primary bank

Primary pitch

Figure 7-28. Airspeed low and vertical speed high—reduce pitch.

Pitch and power corrections must be promptly and closely 

coordinated. For example, if the vertical speed is correct, but 

the airspeed is low, add power. As the power is increased, 

the miniature aircraft must be lowered slightly to maintain 

constant vertical speed. If the vertical speed is high and the 

airspeed is low, lower the miniature aircraft slightly and note 

the increase in airspeed to determine whether or not a power 

change is also necessary. [Figure 7-28] Familiarity with the 

approximate power settings helps to keep pitch and power 

corrections at a minimum. 

Leveling Off

To level off from a climb and maintain an altitude, it is 

necessary to start the level off before reaching the desired 

altitude. The amount of lead varies with rate of climb and 

pilot technique. If the airplane is climbing at 1,000 fpm, it 

continues to climb at a decreasing rate throughout the transition 

to level flight. An effective practice is to lead the altitude by 

10 percent of the vertical speed shown (500 fpm/ 50-foot lead, 

1,000 fpm/100-foot lead). 

To level off at cruising airspeed, apply smooth, steady 

forward-elevator pressure toward level flight attitude for 

the speed desired. As the attitude indicator shows the pitch 

change, the vertical speed needle moves slowly toward zero, 

the altimeter needle moves more slowly, and the airspeed 

shows acceleration. [Figure 7-29] When the altimeter, attitude 

indicator, and VSI show level flight, constant changes in pitch 

and torque control have to be made as the airspeed increases. 

As the airspeed approaches cruising speed, reduce power to 

the cruise setting. The amount of lead depends upon the rate 

of acceleration of the airplane. 

To level off at climbing airspeed, lower the nose to the 

pitch attitude appropriate to that airspeed in level flight. 

Power is simultaneously reduced to the setting for that 

airspeed as the pitch attitude is lowered. If power reduction 

is at a rate proportionate to the pitch change, airspeed will 

remain constant. 

Descents

A descent can be made at a variety of airspeeds and attitudes 

by reducing power, adding drag, and lowering the nose to 

a predetermined attitude. The airspeed eventually stabilizes 

at a constant value. Meanwhile, the only flight instrument 

providing a positive attitude reference is the attitude indicator. 

Without the attitude indicator (such as during a partial panel 

descent), the ASI, altimeter, and VSI show varying rates of 

change until the airplane decelerates to a constant airspeed at 

a constant attitude. During the transition, changes in control 

pressure and trim, as well as cross-check and interpretation, 

must be accurate to maintain positive control. 
7-17

30.0 

29.9 

29.8 

Figure 5-29. Level-off at cruising speed. 

Primary pitch

Supporting pitch and bank

Supporting bank

Primary bank

Supporting pitch

Primary power as

airspeed approaches

desired value

Figure 7-29. Level off at cruising speed.

Entry

The following method for entering descents is effective 

with or without an attitude indicator. First, reduce airspeed 

to a selected descent airspeed while maintaining straightand-level flight, then make a further reduction in power 

(to a predetermined setting). As the power is adjusted, 

simultaneously lower the nose to maintain constant airspeed, 

and trim off control pressures. 

During a constant airspeed descent, any deviation from the 

desired airspeed calls for a pitch adjustment. For a constant 

rate descent, the entry is the same, but the VSI is primary for 

pitch control (after it stabilizes near the desired rate), and the 

ASI is primary for power control. Pitch and power must be 

closely coordinated when corrections are made, as they are 

in climbs. [Figure 7-30] 

Leveling Off

The level off from a descent must be started before reaching 

the desired altitude. The amount of lead depends upon the 

rate of descent and control technique. With too little lead, 

the airplane tends to overshoot the selected altitude unless 

technique is rapid. Assuming a 500 fpm rate of descent, lead 

the altitude by 100–150 feet for a level off at an airspeed 

higher than descending speed. At the lead point, add power to 

the appropriate level flight cruise setting. [Figure 7-31] Since 

the nose tends to rise as the airspeed increases, hold 

forward elevator pressure to maintain the vertical speed at 

the descending rate until approximately 50 feet above the 

altitude, and then smoothly adjust the pitch attitude to the 

level flight attitude for the airspeed selected. 

To level off from a descent at descent airspeed, lead the 

desired altitude by approximately 50 feet, simultaneously 

adjusting the pitch attitude to level flight and adding power to 

a setting that holds the airspeed constant. [Figure 7-32] Trim 

off the control pressures and continue with the normal 

straight-and-level flight cross-check. 

Common Errors in Straight Climbs and Descents

Common errors result from the following faults:

1. Overcontrolling pitch on climb entry. Until the pitch 

attitudes related to specific power settings used in 

climbs and descents are known, larger than necessary 

pitch adjustments are made. One of the most difficult 

habits to acquire during instrument training is to 

restrain the impulse to disturb a flight attitude until 

the result is known. Overcome the inclination to 

make a large control movement for a pitch change, 

and learn to apply small control pressures smoothly, 

cross-checking rapidly for the results of the change, 

and continuing with the pressures as instruments show 

the desired results. Small pitch changes can be easily 

controlled, stopped, and corrected; large changes are 

more difficult to control. 
7-18

30.0 

29.9 

29.8 

Figure 5-31. Level-off airspeed higher than descent airspeed. 

Supporting pitch and bank

Supporting bank

Primary bank

Primary pitch

Add power at

100'-150' lead

Figure 7-31. Level off airspeed higher than descent airspeed.

30.0 

29.9 

29.8 

Figure 5-30. Constant airspeed descent, airspeed high-reduce power.. 

Supporting pitch and bank

Supporting bank

Primary bank

Primary pitch

Primary power

Figure 7-30. Constant airspeed descent, airspeed high—reduce power.
7-19

30.0 

29.9 

29.8 

Figure 5-32. Level-off at descent airspeed. 

Supporting pitch and bank

Supporting bank

Primary bank

Supporting pitch

Primary power

at 50' lead

Primary power

Figure 7-32. Level off at descent airspeed.

2. Failure to vary the rate of cross-check during 

speed, power, or attitude changes or climb or 

descent entries. 

3. Failure to maintain a new pitch attitude. For example, 

raising the nose to the correct climb attitude, and as 

the airspeed decreases, either overcontrol and further 

increase the pitch attitude or allow the nose to lower. 

As control pressures change with airspeed changes, 

cross-check must be increased and pressures readjusted. 

4. Failure to trim off pressures. Unless the airplane is 

trimmed, there is difficulty in determining whether 

control pressure changes are induced by aerodynamic 

changes or by the pilot’s own movements. 

5. Failure to learn and use proper power settings. 

6. Failure to cross-check both airspeed and vertical speed 

before making pitch or power adjustments. 

7. Improper pitch and power coordination on slow-speed 

level offs due to slow cross-check of airspeed and 

altimeter indications. 

8. Failure to cross-check the VSI against the other 

pitch control instruments, resulting in chasing the 

vertical speed. 

9. Failure to note the rate of climb or descent to determine 

the lead for level offs, resulting in overshooting or 

undershooting the desired altitude. 

10. Ballooning (allowing the nose to pitch up) on level 

offs from descents, resulting from failure to maintain 

descending attitude with forward-elevator pressure as 

power is increased to the level flight cruise setting. 

11. Failure to recognize the approaching straight-and-level 

flight indications as level off is completed. Maintain 

an accelerated cross-check until positively established 

in straight-and-level flight. 

Turns

Standard Rate Turns

A standard rate turn is one in which the pilot will do a 

complete 360° circle in 2 minutes or 3 degrees per second. 

A standard rate turn, although always 3 degrees per second, 

requires higher angles of bank as airspeed increases. To 

enter a standard rate level turn, apply coordinated aileron 

and rudder pressures in the desired direction of turn. Pilots 

commonly roll into turns at a much too rapid rate. During 

initial training in turns, base control pressures on the rate of 

cross-check and interpretation. Maneuvering an airplane faster 

than the capability to keep up with the changes in instrument 

indications only creates the need to make corrections. 

A rule of thumb to determine the approximate angle of bank 

required for a standard rate turn is to use 15 percent of the 

true airspeed. A simple way to determine this amount is to 
7-20

30.0 

29.9 

29.8 

Figure 5-33. Standard-rate turn, constant airspeed. 

Primary bank initially supporting pitch

Primary bank

Supporting pitch

Primary bank

as turn is

established

Primary power

Primary pitch

Figure 7-33. Standard rate turn, constant airspeed.

divide the airspeed by 10 and add one-half the result. For 

example, at 100 knots, approximately 15° of bank is required 

(100 ÷ 10 = 10 + 5 = 15); at 120 knots, approximately 18° 

of bank is needed for a standard rate turn.

On the roll-in, use the attitude indicator to establish 

the approximate angle of bank, and then check the turn 

coordinator’s miniature aircraft for a standard rate turn 

indication or the aircraft’s turn-and-bank indicator. Maintain 

the bank for this rate of turn, using the turn coordinator’s 

miniature aircraft as the primary bank reference and the 

attitude indicator as the supporting bank instrument. 

[Figure 7-33] Note the exact angle of bank shown on 

the banking scale of the attitude indicator when the turn 

coordinator indicates a standard rate turn. 

During the roll-in, check the altimeter, VSI, and attitude 

indicator for the necessary pitch adjustments as the vertical 

lift component decreases with an increase in bank. If constant 

airspeed is to be maintained, the ASI becomes primary for 

power, and the throttle must be adjusted as drag increases. As 

the bank is established, trim off the pressures applied during 

pitch and power changes. 

To recover to straight-and-level flight, apply coordinated 

aileron and rudder pressures opposite to the direction of 

the turn. Strive for the same rate of roll-out used to roll into 

the turn; fewer problems are encountered in estimating the 

lead necessary for roll-out on exact headings, especially on 

partial panel maneuvers. Upon initiation of the turn recovery, 

the attitude indicator becomes the primary bank instrument. 

When the airplane is approximately level, the heading 

indicator is the primary bank instrument as in straight-andlevel flight. Pitch, power, and trim adjustments are made as 

changes in vertical lift component and airspeed occur. The 

ball should be checked throughout the turn, especially if 

control pressures are held rather than trimmed off. 

Some airplanes are very stable during turns, requiring only 

slight trim adjustments that permit hands-off flight while 

the airplane remains in the established attitude. Other 

airplanes require constant, rapid cross-check and control 

during turns to correct overbanking tendencies. Due to the 

interrelationship of pitch, bank, and airspeed deviations 

during turns, cross-check must be fast in order to prevent 

an accumulation of errors. 

Turns to Predetermined Headings

As long as an airplane is in a coordinated bank, it continues 

to turn. Thus, the roll-out to a desired heading must be started 

before the heading is reached. The amount of lead varies with 

the relationship between the rate of turn, angle of bank, and 

rate of recovery. For small heading changes, use a bank angle 

that does not exceed the number of degrees to be turned. Lead 

the desired heading by one-half the number of degrees of 

bank used. For example, if a 10° bank is used during a change 

in heading, start the roll-out 5 degrees before reaching the 

desired heading. For larger changes in heading, the amount 
7-21

30.0 

29.9 

29.8 

Figure 5-34. Turn coordinator calibration. 

Supporting pitch and bank

Supporting pitch

Primary power

Primary pitch

Primary bank

Figure 7-34. Turn coordinator calibration.

of lead varies since the angle of bank for a standard rate turn 

varies with the true airspeed.

Practice with a lead of one-half the angle of bank until 

the precise lead a given technique requires is determined. 

If rates of roll-in and roll-out are consistent, the precise 

amount of lead suitable to a particular roll-out technique 

can be determined. 

Timed Turns

A timed turn is a turn in which the clock and the turn 

coordinator are used to change heading by a specific number 

of degrees in a given time. For example, in a standard rate turn 

(3 degrees per second), an airplane turns 45° in 15 seconds; in 

a half standard rate turn, the airplane turns 45° in 30 seconds. 

Prior to performing timed turns, the turn coordinator should 

be calibrated to determine the accuracy of its indications. 

[Figure 7-34] Establish a standard rate turn as indicated by 

the turn coordinator, and as the sweep-second hand of the 

clock passes a cardinal point (12, 3, 6, 9), check the heading 

on the heading indicator. While holding the indicated rate 

of turn constant, note the indicated heading changes at 10 

second intervals. If the airplane turns more than or less than 

30° in that interval, a respectively larger or smaller deflection 

of the miniature aircraft of the turn coordinator is necessary 

to produce a standard rate turn. After calibrating the turn 

coordinator during turns in each direction, note the corrected 

deflections, if any, and apply them during all timed turns. 

The same cross-check and control technique is used in making 

a timed turn that is used to execute turns to predetermined 

headings, except the clock is substituted for the heading 

indicator. The miniature aircraft of the turn coordinator is 

primary for bank control, the altimeter is primary for pitch 

control, and the ASI is primary for power control. Start the 

roll-in when the clock’s second hand passes a cardinal point, 

hold the turn at the calibrated standard rate indication (or 

half-standard rate for small heading changes), and begin the 

roll-out when the computed number of seconds has elapsed. 

If the rates of roll-in and roll-out are the same, the time taken 

during entry and recovery does not need to be considered in 

the time computation. 

Practice timed turns with a full instrument panel and check 

the heading indicator for the accuracy of turns. If the turns are 

executed without the gyro heading indicator, use the magnetic 

compass at the completion of the turn to check turn accuracy, 

taking compass deviation errors into consideration. 

Compass Turns

In most small airplanes, the magnetic compass is the only 

direction-indicating instrument independent of other airplane 

instruments and power sources. Because of its operating 

characteristics, called compass errors, pilots are prone to 

use it only as a reference for setting the heading indicator, 

but knowledge of magnetic compass characteristics permits 

full use of the instrument to turn the airplane to correct and 

maintain headings.
7-22

W 24 21 

Figure 5-35 

210 

Figure 7-35. North and south turn error.

Remember the following points when making turns to 

magnetic compass headings or when using the magnetic 

compass as a reference for setting the heading indicator: 

1. If on a north heading and a turn is started to the east or 

west, the compass indication lags or indicates a turn 

in the opposite direction. 

2. If on a south heading and a turn is started toward 

the east or west, the compass indication precedes 

the turn, indicating a greater amount of turn than is 

actually occurring. 

3. When on an east or west heading, the compass indicates 

correctly when starting a turn in either direction. 

4. If on an east or west heading, acceleration results in 

a north turn indication; deceleration results in a south 

turn indication. 

5. When maintaining a north or south heading, no error 

results from diving, climbing, or changing airspeed. 

With an angle of bank between 15° and 18°, the amount of 

lead or lag to be used when turning to northerly or southerly 

headings varies with, and is approximately equal to, the 

latitude of the locality over which the turn is being made. 

When turning to a heading of north, the lead for roll-out must 

include the number of degrees of change of latitude, plus the 

lead normally used in recovery from turns. During a turn to 

a south heading, maintain the turn until the compass passes 

south the number of degrees of latitude, minus normal rollout lead. [Figure 7-35]

For example, when turning from an easterly direction to 

north, where the latitude is 30°, start the roll-out when the 

compass reads 37° (30° plus one-half the 15° angle of bank, 

or whatever amount is appropriate for the rate of roll-out). 

When turning from an easterly direction to south, start the 

roll-out when the magnetic compass reads 203° (180° plus 

30° minus one-half the angle of bank). When making similar 

turns from a westerly direction, the appropriate points at 

which to begin the roll-out would be 323° for a turn to north 

and 157° for a turn to south. 

When turning to a heading of east or west from a northerly 

direction, start the roll-out approximately 10° to 12° before 

the east or west indication is reached. When turning to an east 

or west heading from a southerly direction, start the rollout 

approximately 5 degrees before the east or west indication 

is reached. When turning to other headings, the lead or lag 

must be interpolated. 

Abrupt changes in attitude or airspeed and the resulting erratic 

movements of the compass card make accurate interpretations 

of the instrument very difficult. Proficiency in compass turns 

depends on knowledge of compass characteristics, smooth 

control technique, and accurate bank-and-pitch control. 

Steep Turns

For purposes of instrument flight training in conventional 

airplanes, any turn greater than a standard rate is considered 

steep. [Figure 7-36] The exact angle of bank at which a 

normal turn becomes steep is unimportant. What is important 

is learning to control the airplane with bank attitudes in 

excess of those normally used on instruments. Practicing 

steep turns will not only increase proficiency in the basic 

instrument flying skills, but also enable smooth, quick, and 

confident reactions to unexpected abnormal flight attitudes 

under instrument flight conditions. 

Pronounced changes occur in the effects of aerodynamic 

forces on aircraft control at progressively greater bank 

attitudes. Skill in cross-check, interpretation, and control is 

increasingly necessary in proportion to the amount of these 

changes, though the techniques for entering, maintaining, and 

recovering from the turn are the same in principle for steep 

turns as for shallower turns. 

Enter a steep turn in the same way as a shallower turn, 

but prepare to cross-check rapidly as the turn steepens. 

Because of the greatly reduced vertical lift component, pitch 

control is usually the most difficult aspect of this maneuver. 

Unless immediately noted and corrected with a pitch 
7-23

30.0 

29.9 

29.8 

Figure 5-36. Steep left turn. 

Figure 7-36. Steep left turn.

30.0 

29.9 

29.8 

Figure 7-37. Diving spiral.

elevator pressure will maintain constant altitude. However, 

overbanking to excessively steep angles without adjusting 

pitch as the bank changes occur requires increasingly 

stronger elevator pressure. The loss of vertical lift and 

increase in wing loading finally reach a point at which 

further application of back-elevator pressure tightens the 

turn without raising the nose. 

How does a pilot recognize overbanking and low pitch 

attitude? What should a pilot do to correct them? If a rapid 

downward movement of the altimeter needle or vertical speed 

needle, together with an increase in airspeed, is observed 

despite application of back elevator pressure, the airplane is in 

a diving spiral. [Figure 7-37] Immediately shallow the bank 

with smooth and coordinated aileron and rudder pressures, 

hold or slightly relax elevator pressure, and increase the crosscheck of the attitude indicator, altimeter, and VSI. Reduce 

power if the airspeed increase is rapid. When the vertical 

speed trends upward, the altimeter needle moves slower as 

the vertical lift increases. When the elevator is effective in 

raising the nose, hold the bank attitude shown on the attitude 

indicator and adjust elevator control pressures smoothly for 

the nose-high attitude appropriate to the bank maintained. 

If pitch control is consistently late on entries to steep turns, 

rollout immediately to straight-and-level flight and analyze 

possible errors. Practice shallower turns initially and learn the 

attitude changes and control responses required, then increase 

the banks as a quicker and more accurate cross-check and 

control techniques are developed.

The power necessary to maintain constant airspeed increases 

as the bank and drag increase. With practice, the power 

increase, the loss of vertical lift results in rapid movement 

of the altimeter, vertical speed, and airspeed needles. The 

faster the rate of bank change, the more suddenly the lift 

changes occur. If a cross-check is fast enough to note the 

immediate need for pitch changes, smooth, steady back-
7-24

30.0 

29.9 

29.8 

Figure 5-38. Change of airspeed in turn. 

Supporting pitch and bank

Supporting pitch

Primary pitch

Primary bank

Primary power as

airspeed approaches

desired value

Primary power

as throttle is set

Figure 7-38. Change of airspeed during turn.

settings appropriate to specific bank attitudes are learned, and 

adjustments can be made without undue attention to airspeed 

and power instruments. During training in steep turns, as in 

any other maneuver, attend to the most important tasks first. 

Keep the pitch attitude relatively constant, and more time 

can be devoted to cross-check and instrument interpretation. 

During recovery from steep turns to straight-and-level 

flight, elevator and power control must be coordinated with 

bank control in proportion to the changes in aerodynamic 

forces. Back elevator pressures must be released and power 

decreased. The common errors associated with steep turns are 

the same as those discussed later in this section. Remember, 

errors are more exaggerated, more difficult to correct, and 

more difficult to analyze unless rates of entry and recovery 

are consistent with the level of proficiency in the three basic 

instrument flying skills. 

Climbing and Descending Turns

To execute climbing and descending turns, combine the 

technique used in straight climbs and descents with the various 

turn techniques. The aerodynamic factors affecting lift and 

power control must be considered in determining power 

settings, and the rate of cross-check and interpretation must be 

increased to enable control of bank as well as pitch changes. 

Change of Airspeed During Turns

Changing airspeed during turns is an effective maneuver for 

increasing proficiency in all three basic instrument skills. 

Since the maneuver involves simultaneous changes in all 

components of control, proper execution requires rapid 

cross-check and interpretation as well as smooth control. 

Proficiency in the maneuver also contributes to confidence in 

the instruments during attitude and power changes involved 

in more complex maneuvers. Pitch and power control 

techniques are the same as those used during changes in 

airspeed in straight-and-level flight. 

The angle of bank necessary for a given rate of turn is 

proportional to the true airspeed. Since the turns are executed 

at a standard rate, the angle of bank must be varied in direct 

proportion to the airspeed change in order to maintain a 

constant rate of turn. During a reduction of airspeed, decrease 

the angle of bank and increase the pitch attitude to maintain 

altitude and a standard rate turn. 

The altimeter and turn coordinator indications should remain 

constant throughout the turn. The altimeter is primary for 

pitch control and the miniature aircraft of the turn coordinator 

is primary for bank control. The manifold pressure gauge (or 

tachometer) is primary for power control while the airspeed 

is changing. As the airspeed approaches the new indication, 

the ASI becomes primary for power control. 

Two methods of changing airspeed in turns may be used. In the 

first method, airspeed is changed after the turn is established. 

[Figure 7-38] In the second method, the airspeed change is 

initiated simultaneously with the turn entry. The first method 

is easier, but regardless of the method used, the rate of crosscheck must be increased as power is reduced. As the airplane 

decelerates, check the altimeter and VSI for necessary pitch 

changes and the bank instruments for required bank changes. 
7-25

If the miniature aircraft of the turn coordinator indicates a 

deviation from the desired deflection, adjust the bank. Adjust 

pitch attitude to maintain altitude. When approaching the 

desired airspeed, pitch attitude becomes primary for power 

control and the manifold pressure gauge (or tachometer) is 

adjusted to maintain the desired airspeed. Trim is important 

throughout the maneuver to relieve control pressures. 

Until control technique is very smooth, frequent cross-check 

of the attitude indicator is essential to prevent overcontrolling 

and to provide approximate bank angles appropriate to the 

changing airspeeds. 

Common Errors in Turns

Pitch

Pitch errors result from the following faults:

1. Preoccupation with bank control during turn entry 

and recovery. If 5 seconds are required to roll into a 

turn, check the pitch instruments as bank pressures 

are initiated. If bank control pressure and rate of bank 

change are consistent, a sense of the time required 

for an attitude change is developed. During the 

interval, check pitch, power, and trim—as well as 

bank—controlling the total attitude instead of one 

factor at a time. 

2. Failure to understand or remember the need for 

changing the pitch attitude as the vertical lift 

component changes, resulting in consistent loss of 

altitude during entries. 

3. Changing the pitch attitude before it is necessary. This 

fault is very likely if a cross-check is slow and rate 

of entry too rapid. The error occurs during the turn 

entry due to a mechanical and premature application 

of back-elevator control pressure. 

4. Overcontrolling the pitch changes. This fault 

commonly occurs with the previous error. 

5. Failure to properly adjust the pitch attitude as the 

vertical lift component increases during the roll-out, 

resulting in consistent gain in altitude on recovery 

to headings. 

6. Failure to trim during turn entry and following turn 

recovery (if turn is prolonged). 

7. Failure to maintain straight-and-level cross-check 

after roll-out. This error commonly follows a perfectly 

executed turn. 

8. Erratic rates of bank change on entry and recovery, 

resulting from failure to cross-check the pitch 

instruments with a consistent technique appropriate 

to the changes in lift. 

Bank

Bank and heading errors result from the following faults:

1. Overcontrolling, resulting in overbanking upon turn 

entry, overshooting and undershooting headings, as 

well as aggravated pitch, airspeed, and trim errors. 

2. Fixation on a single bank instrument. On a 90° change 

of heading, for example, leave the heading indicator 

out of the cross-check for approximately 20 seconds 

after establishing a standard rate turn, since at 3° 

per second the turn will not approach the lead point 

until that time has elapsed. Make the cross-check 

selective, checking only what needs to be checked at 

the appropriate time. 

3. Failure to check for precession of the horizon bar 

following recovery from a turn. If the heading indicator 

shows a change in heading when the attitude indicator 

shows level flight, the airplane is turning. If the ball 

is centered, the attitude gyro has precessed; if the ball 

is not centered, the airplane may be in a slipping or 

skidding turn. Center the ball with rudder pressure, 

check the attitude indicator and heading indicator, stop 

the heading change if it continues, and retrim. 

4. Failure to use the proper degree of bank for the amount 

of heading change desired. Rolling into a 20° bank 

for a heading change of 10° will normally overshoot 

the heading. Use the bank attitude appropriate to the 

amount of heading change desired. 

5. Failure to remember the heading to which the aircraft 

is being turned. This fault is likely when rushing 

the maneuver. 

6. Turning in the wrong direction, due to misreading or 

misinterpreting the heading indicator, or to confusion 

regarding the location of points on the compass. Turn 

in the shortest direction to reach a given heading, 

unless there is a specific reason to turn the long way 

around. Study the compass rose and visualize at least 

the positions of the eight major points around the 

azimuth. A number of methods can be used to make 

quick computations for heading changes. For example, 

to turn from a heading of 305° to a heading of 110°, 

would a pilot turn right or left for the shortest way 

around? Subtracting 200 from 305 and adding 20, 

gives 125° as the reciprocal of 305°; therefore, execute 

the turn to the right. Likewise, to figure the reciprocal 

of a heading less than 180°, add 200 and subtract 20. 

Computations are done more quickly using multiples 

of 100s and 10s than by adding or subtracting 180° 

from the actual heading; therefore, the method 

suggested above may save time and confusion. 
7-26

7. Failure to check the ball of the turn coordinator when 

interpreting the instrument for bank information. If the 

roll rate is reduced to zero, the miniature aircraft of 

the turn coordinator indicates only direction and rate 

of turn. Unless the ball is centered, do not assume the 

turn is resulting from a banked attitude. 

Power

Power and airspeed errors result from the following faults:

1. Failure to cross-check the ASI as pitch changes 

are made. 

2. Erratic use of power control. This may be due to 

improper throttle friction control, inaccurate throttle 

settings, chasing the airspeed readings, abrupt or 

overcontrolled pitch-and-bank changes, or failure 

to recheck the airspeed to note the effect of a 

power adjustment. 

3. Poor coordination of throttle control with pitch-andbank changes associated with slow cross-check or 

failure to understand the aerodynamic factors related 

to turns.

Trim

Trim errors result from the following faults:

1. Failure to recognize the need for a trim change due 

to slow cross-check and interpretation. For example, 

a turn entry at a rate too rapid for a cross-check leads 

to confusion in cross-check and interpretation with 

resulting tension on the controls. 

2. Failure to understand the relationship between trim 

and attitude/power changes. 

3. Chasing the vertical speed needle. Overcontrolling 

leads to tension and prevents sensing the pressures to 

be trimmed off. 

4. Failure to trim following power changes. 

Errors During Compass Turns

In addition to the faults discussed above, the following errors 

connected with compass turns should be noted: 

1. Faulty understanding or computation of lead and lag. 

2. Fixation on the compass during the roll-out. Until 

the airplane is in straight-and-level unaccelerated 

flight, it is unnecessary to read the indicated heading. 

Accordingly, after the roll-out, cross-check for 

straight-and-level flight before checking the accuracy 

of the turn.

Approach to Stall

Practicing approach to stall recoveries in various airplane 

configurations should build confidence in a pilot’s ability to 

control the airplane in unexpected situations. Approach to 

stall should be practiced from straight flight and from shallow 

banks. The objective is to practice recognition and recovery 

from the approach to a stall. 

Prior to stall recovery practice, select a safe altitude above 

the terrain, an area free of conflicting air traffic, appropriate 

weather, and the availability of radar traffic advisory service. 

Approaches to stalls are accomplished in the following 

configurations: 

1. Takeoff configuration—should begin from level flight 

near liftoff speed. Power should be applied while 

simultaneously increasing the angle of attack to induce 

an indication of a stall. 

2. Clean configuration—should begin from a reduced 

airspeed, such as pattern airspeed, in level flight. 

Power should be applied while simultaneously 

increasing the angle of attack to induce an indication 

of a stall. 

3. Approach or landing configuration—should be 

initiated at the appropriate approach or landing 

airspeed. The angle of attack should be smoothly 

increased to induce an indication of a stall. 

Recoveries should be prompt in response to a stall warning 

device or an aerodynamic indication by smoothly reducing 

the angle of attack and applying maximum power or as 

recommended by the POH/AFM. The recovery should be 

completed without an excessive loss of altitude and on a 

predetermined heading, altitude, and airspeed. 

Unusual Attitudes and Recoveries

An unusual attitude is an airplane attitude not normally 

required for instrument flight. Unusual attitudes may 

result from a number of conditions, such as turbulence, 

disorientation, instrument failure, confusion, preoccupation 

with flight deck duties, carelessness in cross-checking, 

errors in instrument interpretation, or lack of proficiency in 

aircraft control. Since unusual attitudes are not intentional 

maneuvers during instrument flight, except in training, they 

are often unexpected, and the reaction of an inexperienced 

or inadequately trained pilot to an unexpected abnormal 

flight attitude is usually instinctive rather than intelligent 

and deliberate. This individual reacts with abrupt muscular 
7-27

30.0 

29.9 

29.8 

Figure 5-39. Unusual attitude-nose high. 

Gaining altitude

Climbing right turn

Airspeed decreasing

Figure 7-39. Unusual attitude—nose-high.

effort, which is purposeless and even hazardous in turbulent 

conditions, at excessive speeds, or at low altitudes. However, 

with practice, the techniques for rapid and safe recovery from 

unusual attitudes can be mastered. 

When an unusual attitude is noted during the cross-check, 

the immediate problem is not how the airplane got there, but 

what it is doing and how to get it back to straight-and-level 

flight as quickly as possible. 

Recognizing Unusual Attitudes

As a general rule, any time an instrument rate of movement 

or indication other than those associated with the basic 

instrument flight maneuvers is noted, assume an unusual 

attitude and increase the speed of cross-check to confirm the 

attitude, instrument error, or instrument malfunction. 

Nose-high attitudes are shown by the rate and direction of 

movement of the altimeter needle, vertical speed needle, and 

airspeed needle, as well as the immediately recognizable 

indication of the attitude indicator (except in extreme 

attitudes). [Figure 7-39] Nose-low attitudes are shown 

by the same instruments, but in the opposite direction. 

[Figure 7-40]

Recovery from Unusual Attitudes

In moderate unusual attitudes, the pilot can normally 

reorient by establishing a level flight indication on the 

attitude indicator. However, the pilot should not depend on 

this instrument if the attitude indicator is the spillable type, 

because its upset limits may have been exceeded or it may 

have become inoperative due to mechanical malfunction. 

If it is the nonspillable-type instrument and is operating 

properly, errors up to 5 degrees of pitch-and-bank may result 

and its indications are very difficult to interpret in extreme 

attitudes. As soon as the unusual attitude is detected, the 

recommended recovery procedures stated in the POH/AFM 

should be initiated. If there are no recommended procedures 

stated in the POH/AFM, the recovery should be initiated by 

reference to the ASI, altimeter, VSI, and turn coordinator. 

Nose-High Attitudes

If the airspeed is decreasing, or below the desired airspeed, 

increase power (as necessary in proportion to the observed 

deceleration), apply forward elevator pressure to lower the 

nose and prevent a stall, and correct the bank by applying 

coordinated aileron and rudder pressure to level the 

miniature aircraft and center the ball of the turn coordinator. 

The corrective control applications are made almost 

simultaneously, but in the sequence given above. A level 

pitch attitude is indicated by the reversal and stabilization 
7-28

30.0 

29.9 

29.8 

Figure 5-40. Unusual attitude-nose low. 

Losing altitude

Diving left turn

Airspeed increasing

Figure 7-40. Unusual attitude—nose-low.

of the ASI and altimeter needles. Straight coordinated flight 

is indicated by the level miniature aircraft and centered ball 

of the turn coordinator. 

Nose-Low Attitudes

If the airspeed is increasing, or is above the desired airspeed, 

reduce power to prevent excessive airspeed and loss of 

altitude. Correct the bank attitude with coordinated aileron 

and rudder pressure to straight flight by referring to the turn 

coordinator. Raise the nose to level flight attitude by applying 

smooth back elevator pressure. All components of control 

should be changed simultaneously for a smooth, proficient 

recovery. However, during initial training a positive, 

confident recovery should be made by the numbers, in the 

sequence given above. A very important point to remember 

is that the instinctive reaction to a nose-down attitude is to 

pull back on the elevator control. 

After initial control has been applied, continue with a 

fast cross-check for possible overcontrolling, since the 

necessary initial control pressures may be large. As the rate 

of movement of altimeter and ASI needles decreases, the 

attitude is approaching level flight. When the needles stop 

and reverse direction, the aircraft is passing through level 

flight. As the indications of the ASI, altimeter, and turn 

coordinator stabilize, incorporate the attitude indicator into 

the cross-check. 

The attitude indicator and turn coordinator should be checked 

to determine bank attitude and then corrective aileron 

and rudder pressures should be applied. The ball should 

be centered. If it is not, skidding and slipping sensations 

can easily aggravate disorientation and retard recovery. If 

entering the unusual attitude from an assigned altitude (either 

by an instructor or by air traffic control (ATC) if operating 

under instrument flight rules (IFR)), return to the original 

altitude after stabilizing in straight-and-level flight. 

Common Errors in Unusual Attitudes

Common errors associated with unusual attitudes include 

the following faults: 

1. Failure to keep the airplane properly trimmed. A flight 

deck interruption when holding pressures can easily 

lead to inadvertent entry into unusual attitudes. 

2 Disorganized flight deck. Hunting for charts, logs, 

computers, etc., can seriously distract attention from 

the instruments. 

3. Slow cross-check and fixations. The impulse is to 

stop and stare when noting an instrument discrepancy 

unless a pilot has trained enough to develop the skill 

required for immediate recognition. 
7-29

4. Attempting to recover by sensory sensations other than 

sight. The discussion of disorientation in Chapter 3, 

Human Factors, indicates the importance of trusting 

the instruments. 

5. Failure to practice basic instrument skills. All of the 

errors noted in connection with basic instrument skills 

are aggravated during unusual attitude recoveries until 

the elementary skills have been mastered. 

Instrument Takeoff

Competency in instrument takeoffs will provide the 

proficiency and confidence necessary for use of flight 

instruments during departures under conditions of low 

visibility, rain, low ceilings, or disorientation at night. A 

sudden rapid transition from “visual” to “instrument” flight 

can result in serious disorientation and control problems. 

Instrument takeoff techniques vary with different types of 

airplanes, but the method described below is applicable 

whether the airplane is single- or multiengine; tricycle gear 

or conventional gear. 

Align the airplane with the centerline of the runway with 

the nosewheel or tailwheel straight. Lock the tailwheel, if 

so equipped, and hold the brakes firmly to avoid creeping 

while preparing for takeoff. Set the heading indicator with 

the nose index on the 5 degree mark nearest the published 

runway heading to allow instant detection of slight changes in 

heading during the takeoff. Make certain that the instrument 

is uncaged (if it has a caging feature) by rotating the knob 

after uncaging and checking for constant heading indication. 

If using an electric heading indicator with a rotatable needle, 

rotate the needle so that it points to the nose position, under 

the top index. Advance the throttle to an rpm that will provide 

partial rudder control. Release the brakes, advancing the 

power smoothly to takeoff setting. 

During the takeoff roll, hold the heading constant on the 

heading indicator by using the rudder. In multiengine, 

propeller-driven airplanes, also use differential throttle to 

maintain direction. The use of brakes should be avoided, 

except as a last resort, as it usually results in overcontrolling 

and extending the takeoff roll. Once the brakes are released, 

any deviation in heading must be corrected instantly. 

As the airplane accelerates, cross-check both heading 

indicator and ASI rapidly. The attitude indicator may precess 

to a slight nose-up attitude. As flying speed is approached 

(approximately 15–25 knots below takeoff speed), smoothly 

apply elevator control for the desired takeoff attitude on the 

attitude indicator. This is approximately a two bar width 

climb indication for most small airplanes. 

Continue with a rapid cross-check of heading indicator and 

attitude indicator as the airplane leaves the ground. Do not 

pull it off; let it fly off while holding the selected attitude 

constant. Maintain pitch-and-bank control by referencing 

the attitude indicator, and make coordinated corrections in 

heading when indicated on the heading indicator. Crosscheck the altimeter and VSI for a positive rate of climb 

(steady clockwise rotation of the altimeter needle, and the VSI 

showing a stable rate of climb appropriate to the airplane). 

When the altimeter shows a safe altitude (approximately 100 

feet), raise the landing gear and flaps, maintaining attitude by 

referencing the attitude indicator. Because of control pressure 

changes during gear and flap operation, overcontrolling is 

likely unless the pilot notes pitch indications accurately and 

quickly. Trim off control pressures necessary to hold the 

stable climb attitude. Check the altimeter, VSI, and airspeed 

for a smooth acceleration to the predetermined climb speed 

(altimeter and airspeed increasing, vertical speed stable). At 

climb speed, reduce power to climb setting (unless full power 

is recommended for climb by the POH/AFM and trim). 

Throughout the instrument takeoff, cross-check and 

interpretation must be rapid and control positive and smooth. 

During liftoff, gear and flap retraction, power reduction, and 

the changing control reactions demand rapid cross-check, 

adjustment of control pressures, and accurate trim changes. 

Common Errors in Instrument Takeoffs

Common errors during the instrument takeoff include 

the following: 

1. Failure to perform an adequate flight deck check 

before the takeoff. Pilots have attempted instrument 

takeoffs with inoperative airspeed indicators (pitot 

tube obstructed), gyros caged, controls locked, and 

numerous other oversights due to haste or carelessness. 

2. Improper alignment on the runway. This may result 

from improper brake application, allowing the 

airplane to creep after alignment or from alignment 

with the nosewheel or tailwheel cocked. In any case, 

the result is a built-in directional control problem as 

the takeoff starts. 

3. Improper application of power. Abrupt application 

of power complicates directional control. Add power 

with a smooth, uninterrupted motion. 

4. Improper use of brakes. Incorrect seat or rudder pedal 

adjustment, with feet in an uncomfortable position, 

frequently cause inadvertent application of brakes and 

excessive heading changes. 
7-30

E 

C 

D 

B 

Figure 5-41 

Start 

End 

Figure 7-41. Racetrack pattern (entire pattern in level flight).

5. Overcontrolling rudder pedals. This fault may be 

caused by late recognition of heading changes, tension 

on the controls, misinterpretation of the heading 

indicator (and correcting in the wrong direction), 

failure to appreciate changing effectiveness of rudder 

control as the aircraft accelerates, and other factors. If 

heading changes are observed and corrected instantly 

with small movement of the rudder pedals, swerving 

tendencies can be reduced. 

6. Failure to maintain attitude after becoming airborne. 

If the pilot reacts to seat-of-the-pants sensations when 

the airplane lifts off, pitch control is guesswork. 

The pilot may either allow excessive pitch or apply 

excessive forward elevator pressure, depending on the 

reaction to trim changes. 

7. Inadequate cross-check. Fixations are likely during trim 

changes, attitude changes, gear and flap retractions, 

and power changes. Once an instrument or a control 

input is applied, continue the cross-check and note the 

effect during the next cross-check sequence. 

8. Inadequate interpretation of instruments. Failure to 

understand instrument indications immediately indicates 

that further study of the maneuver is necessary. 

Basic Instrument Flight Patterns

Flight patterns are basic maneuvers, flown by sole reference 

to the instruments rather than outside visual clues, for the 

purpose of practicing basic attitude flying. The patterns 

simulate maneuvers encountered on instrument flights, 

such as holding patterns, procedure turns, and approaches.

After attaining a reasonable degree of proficiency in basic 

maneuvers, apply these skills to the various combinations of 

individual maneuvers. The following practice flight patterns 

are directly applicable to operational instrument flying. 

Racetrack Pattern

1. Time 3 minutes straight-and-level flight from A to B. 

[Figure 7-41] During this interval, reduce airspeed to 

the holding speed appropriate for the aircraft. 

2. Start a 180° standard rate turn to the right at B. Rollout at C on the reciprocal of the heading originally 

used at A. 

3. Time a 1 minute straight-and-level flight from C to D. 

4. Start a 180° standard rate turn to the right at D, rollingout on the original heading. 

5. Fly 1 minute on the original heading, adjusting the 

outbound leg so that the inbound segment is 1 minute.

NOTE: This pattern is an exercise combining use of the clock 

with basic maneuvers.

Procedure Turn

A procedure turn is a maneuver that facilitates:

• A reversal in flight direction.

• A descent from an initial approach fix or assigned 

altitude to a permissible altitude (usually the procedure 

turn altitude).

• An interception of the inbound course at a sufficient 

distance allowing the aircraft to become aligned with 

the final approach.

Procedure turn types include the 45° turn, the 80/260 turn, and 

the teardrop turn. All of these turns are normally conducted no 

more than 10 nautical miles (NM) from the primary airport. 

The procedure turn altitude generally provides a minimum 

of 1,000' obstacle clearance in the procedure turn area (not 

necessarily within the 10 NM arc around the primary airport). 

Turns may have to be increased or decreased but should not 

exceed 30° of a bank angle.

Standard 45° Procedure Turn

1. Start timing at point A (usually identified on approach 

procedures by a fix). For example, fly outbound on a 

heading of 360° for a given time (2 minutes, in this 

example). [Figure 7-42]

2. After flying outbound for 2 minutes (point B), turn left 

45° to a heading of 315° using a standard rate turn. 

After roll-out and stabilizing, fly this new heading 

of 315° for 40 seconds and the aircraft will be at the 

approximate position of C. 
7-31

B 

C 

D 

Start 

End 

Figure 5-42 

Figure 7-42. Standard procedure turn (entire pattern in level flight).

Start 

B 

C 

End 

Figure 5-43 

D 

Figure 7-43. 80/260 procedure turn (entire pattern in level flight).

Figure 5-44 

C 

C 

C 

D 

D 

D 

B 

30° of heading 

20° of heading 

10° of heading 

Turning point. 

10° 20° 

30° 

Figure 7-44. Teardrop pattern (entire pattern in level flight).

3. At point C, turn 225° right (using a standard rate turn) 

which will provide a heading of 180°. The timing is 

such that in a no wind environment, the pilot will be 

aligned with the final approach course of 180° at D. 

Wind conditions, however must be considered during 

the execution of the procedure turn. Compensating 

for wind may result in changes to outbound time, 

procedure turn heading and/or time and minor changes 

in the inbound turn.

80/260 Procedure Turn

1. Start timing at point A (usually identified on approach 

procedures by a fix). For example, fly outbound on a 

heading of 360° for 2 minutes. [Figure 7-43]

2. At B, enter a left standard rate turn of 80° to a heading 

of 280°. 

3. At the completion of the 80° turn to 280° (Point C), 

immediately turn right 260°, rolling-out on a heading 

of 180° (Point D) and also the reciprocal of the 

entry heading. 

Teardrop Patterns

There are three typical teardrop procedure turns. A 30°, 20°, 

and a 10° teardrop pattern. The below steps indicate actions 

for all three starting on a heading of 360°. [Figure 7-44]

1. At point B (after stabilizing on the outbound course) 

turn left:

• 30° to a heading of 330° and time for 1 minute

• 20° to a heading of 340° and time for 2 minutes

• 10° to a heading of 350° and time for 3 minutes

2. After the appropriate time above (Point C), make a 

standard rate turn to the right for:

• 30° teardrop—210° to the final course heading 

of 180° (Point D)

• 20° teardrop—200° to the final course heading 

of 180° (Point D)

• 10° teardrop—190° to the final course heading 

of 180° (Point D)
7-32

C 

B 

D 

Figure 5-45 I 

E 

Figure 7-45. Circling approach pattern I (imaginary runway).

B 

D 

E 

C 

Figure 5-45 II 

Figure 7-46. Circling approach pattern II (imaginary runway).

By using the different teardrop patterns, a pilot is afforded the 

ability to manage time more efficiently. For instance, a 10° 

pattern for 3 minutes provides about three times the distance 

(and time) than a 30° pattern. Pattern selection should be 

based upon an individual assessment of the procedure turn 

requirements to include wind, complexity, the individual 

preparedness, etc. 

Circling Approach Patterns

Pattern I

1. At A, start timing for 2 minutes from A to B; reduce 

airspeed to approach speed. [Figure 7-45]

2. At B, make a standard rate turn to the left for 45°. 

3. At the completion of the turn, time for 45 seconds 

to C. 

4. At C, turn to the original heading; fly 1 minute to D, 

lowering the landing gear and flaps. 

5. At D, turn right 180°, rolling-out at E on the reciprocal 

of the entry heading. 

6. At E, enter a 500 fpm rate descent. At the end of a 500 

foot descent, enter a straight constant-airspeed climb, 

retracting gear and flaps.

Pattern II

Steps:

1. At A, start timing for 2 minutes from A to B; reduce 

airspeed to approach speed. [Figure 7-46]

2. At B, make a standard rate turn to the left for 45°. 

3. At the completion of the turn, time for 1 minute to C. 

4. At C, turn right for 180° to D; fly for 1-1/2 minutes 

to E, lowering the landing gear and flaps. 

5. At E, turn right for 180°, rolling-out at F. 

6. At F, enter a 500 fpm rate descent. At the end of a 500 

foot descent, enter a straight constant-airspeed climb, 

retracting gear and flaps. 
7-33

Introduction

The previous chapters have laid the foundation for instrument 

flying. The pilot’s ability to use and interpret the information 

displayed and apply corrective action is required to maneuver 

the aircraft and maintain safe flight. A pilot must recognize 

that each aircraft make and model flown may require a 

different technique. Aircraft weight, speed, and configuration 

changes require the pilot to vary his or her technique in order 

to perform successful attitude instrument flying. A pilot must 

become familiar with all sections of the Pilot’s Operating 

Handbook/Airplane Flight Manual (POH/AFM) prior to 

performing any flight maneuver.

Chapter 7, Section II describes basic attitude instrument 

flight maneuvers and explains how to perform each one 

by interpreting the indications presented on the electronic 

flight display (EFD). In addition to normal flight maneuvers, 

“partial panel” flight is addressed. With the exception of the 

instrument takeoff, all flight maneuvers can be performed on 

“partial panel” with the Attitude Heading Reference System 

(AHRS) unit simulated or rendered inoperative.

Airplane Basic 

Flight Maneuvers

Chapter 7, Section II

Using an Electronic Flight Display
7-34

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

270° 

2 

1 

1 

2 

4300 

4200 

4100 

3900 

3900 

3800 

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1 

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TAS 106KT 

OAT 7°C 

5

338 

1

1652 

200 

46 

13.7 

1800 

18.0 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

ALERTS 

Figure 5-47. Pitch Attitude and Airspeed in Level Flight, Slow Cruise Speed. 

Attitude indicator

Vertical speed indicator

Airspeed indicator

Airspeed trend vector

Altimeter indicator

Altitude trend vector

Figure 7-47. Pitch attitude and airspeed in level flight, slow 

cruise speed.

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

270° 

2 

1 

1 

2 

4100 

4000 

3900 

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6 

135 

4 

TAS 135KT 

OAT 7°C 

ALERTS 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

ENGINE MAP DCLTR 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

MAP - NAVIGATION MAP

Figure 5-48. Pitch Attitude and Airspeed in Level Flight, Fast Cruise Speed. Figure 7-48. Pitch attitude decreasing and airspeed increasing—indicates need to increase pitch.

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

270°

2 

1 

1 

2 

4300 

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1 

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9 

TAS 120KT 

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Figure 5-49. Pitch Attitude and Airspeed in Level Flight, Normal Cruise Speed. 

5° 

4° 

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1° 

Figure 7-49. Various pitch attitudes (right), aircraft shown in 

level flight.

Straight-and-Level Flight

Pitch Control

The pitch attitude of an airplane is the angle between the 

longitudinal axis of the airplane and the actual horizon. 

In level flight, the pitch attitude varies with airspeed and 

load. For training purposes, the latter factor can normally 

be disregarded in small airplanes. At a constant airspeed, 

there is only one specific pitch attitude for level flight. At 

slow cruise speeds, the level flight attitude is nose-high with 

indications as in Figure 7-47; at fast cruise speeds, the level 

flight attitude is nose-low. [Figure 7-48] Figure 7-49 shows 

the indications for the attitude at normal cruise speeds.

The instruments that directly or indirectly indicate pitch on 

the primary flight display (PFD) are the attitude indicator, 

altimeter, vertical speed indicator (VSI), airspeed indicator 

(ASI), and both airspeed and altitude trend indicators.

Attitude Indicator

The attitude indicator gives the pilot a direct indication of 

the pitch attitude. The increased size of the attitude display 

on the EFD system greatly increases situational awareness 

for the pilot. Most attitude indicators span the entire width 

of the PFD screen. 
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Figure 7-51. Figure 5-51. Pitch Correction for Level Flight, three-bar width. Pitch illustrated at 10°.

The aircraft pitch attitude is controlled by changing the 

deflection of the elevator. As the pilot pulls back on the 

control yoke causing the elevator to rise, the yellow chevron 

begins to show a displacement up from the artificial horizon 

line. This is caused by the AHRS unit sensing the changing 

angle between the longitudinal plane of the earth and the 

longitudinal axis of the aircraft. 

The attitude indicator displayed on the PFD screen is a 

representation of outside visual cues. Rather than rely on the 

natural horizon visible during visual flight rules (VFR) flight, 

the pilot must rely on the artificial horizon of the PFD screen.

During normal cruise airspeed, the point of the yellow 

chevron (aircraft symbol) is positioned on the artificial 

horizon. Unlike conventional attitude indicators, the EFD 

attitude indicator does not allow for manipulating the position 

of the chevron in relationship to the artificial horizon. The 

position is fixed and therefore always display the pitch angle 

as calculated by the AHRS unit.

The attitude indicator only shows pitch attitude and does 

not indicate altitude. A pilot should not attempt to maintain 

level flight using the attitude indicator alone. It is important 

for the pilot to understand how small displacements both up 

and down can affect the altitude of the aircraft. To achieve 

this, the pilot should practice increasing the pitch attitude 

incrementally to become familiar with how each degree of 

pitch changes the altitude. [Figures 7-50 and 7-51] In both 

cases, the aircraft will slow and gain altitude.

The full height of the chevron is approximately 5 degrees 

and provides an accurate reference for pitch adjustment. It is 

imperative that the pilot make the desired changes to pitch by 

referencing the attitude indicator and then trimming off any 

excess control pressures. Relieving these pressures allow for 

a more stabilized flight and reduces pilot work load. Once the 

aircraft is trimmed for level flight, the pilot must smoothly 

and precisely manipulate the elevator control forces in order 

to change the pitch attitude. 

To master the ability to smoothly control the elevator, a pilot 

must develop a very light touch on the control yoke. The 

thumb and two fingers are normally sufficient to move the 

control yoke. The pilot should avoid griping the yoke with 

a full fist. When a pilot grips the yoke with a full fist, there 

is a tendency to apply excess pressures, thus changing the 

aircraft attitude.

Practice making smooth, small pitch changes both up and 

down until precise corrections can be made. With practice, 

a pilot is able to make pitch changes in 1 degree increments, 

smoothly controlling the attitude of the aircraft. 

The last step in mastering elevator control is trim. Trimming 

the aircraft to relieve any control pressures is essential 

for smooth attitude instrument flight. To accomplish this, 

momentarily release the control yoke. Note which way the 

aircraft pitch attitude wants to move. Grasp the control yoke 

again and then reapply the pressure to return the attitude to the 

previous position. Apply trim in the direction of the control 

pressure. Small applications of trim make large changes in 

the pitch attitude. Be patient and make multiple changes to 

trim, if necessary.

Once the aircraft is in trim, relax on the control yoke as 

much as practicable. When pressure is held on the yoke, 

unconscious pressures are applied to the elevator and ailerons, 

which displaces the aircraft from its desired flightpath. If the 

aircraft is in trim, in calm, non-turbulent air, a pilot should be 

able to release the control yoke and maintain level flight for 

extended periods of time. This is one of the hardest skills to 

learn prior to successfully flying in instrument meteorological 

conditions (IMC). 
7-36

Altimeter

At constant power, any deviation from level flight (except 

in turbulent air) must be the result of a pitch change. If the 

power is constant, the altimeter gives an indirect indication 

of the pitch attitude in level flight. Since the altitude should 

remain constant when the airplane is in level flight, any 

deviation from the desired altitude signals the need for a 

pitch change. For example, if the aircraft is gaining altitude, 

the nose must be lowered.

In the PFD, as the pitch starts to change, the altitude trend 

indicator on the altitude tape begins to show a change in 

the direction of displacement. The rate at which the trend 

indicator grows and the altimeter numbers change aids the 

pilot in determining how much of a pitch change is necessary 

to stop the trend. 

As a pilot becomes familiar with a specific aircraft’s 

instruments, he or she learns to correlate pitch changes, 

altimeter tapes, and altitude trend indicators. By adding the 

altitude tape display and the altitude trend indicator into the 

scan along with the attitude indicator, a pilot starts to develop 

the instrument cross-check.

Partial Panel Flight

One important skill to practice is partial panel flight by 

referencing the altimeter as the primary pitch indicator. 

Practice controlling the pitch by referencing the altitude 

tape and trend indicator alone without the use of the attitude 

indicator. Pilots need to learn to make corrections to altitude 

deviations by referencing the rate of change of the altitude 

tape and trend indicator. When operating in IMC and in a 

partial panel configuration, the pilot should avoid abrupt 

changes to the control yoke. Reacting abruptly to altitude 

changes can lead to large pitch changes and thus a larger 

divergence from the initial altitude. 

When a pilot is controlling pitch by the altitude tape and 

altitude trend indicators alone, it is possible to overcontrol 

the aircraft by making a larger than necessary pitch 

correction. Overcontrolling causes the pilot to move from 

a nose-high attitude to a nose-low attitude and vice versa. 

Small changes to pitch are required to insure prompt 

corrective actions are taken to return the aircraft to its 

original altitude with less confusion.

When an altitude deviation occurs, two actions need to be 

accomplished. First, make a smooth control input to stop 

the needle movement. Once the altitude tape has stopped 

moving, make a change to the pitch attitude to start back to 

the entry altitude.

During instrument flight with limited instrumentation, it is 

imperative that only small and precise control inputs are 

made. Once a needle movement is indicated denoting a 

deviation in altitude, the pilot needs to make small control 

inputs to stop the deviation. Rapid control movements only 

compound the deviation by causing an oscillation effect. 

This type of oscillation can quickly cause the pilot to become 

disoriented and begin to fixate on the altitude. Fixation on 

the altimeter can lead to a loss of directional control as well 

as airspeed control.

As a general rule of thumb, for altitude deviations less than 

100 feet, utilize a pitch change of 1 degree, which equates to 

1

⁄5 of the thickness of the chevron. Small incremental pitch 

changes allow the performance to be evaluated and eliminate 

overcontrolling of the aircraft.

Instrumentation needs to be utilized collectively, but failures 

will occur that leave the pilot with only limited instrumentation. 

That is why partial panel flying training is important. If the 

pilot understands how to utilize each instrument independently, 

no significant change is encountered in carrying out the flight 

when other instruments fail.

VSI Tape

The VSI tape provides for an indirect indication of pitch 

attitude and gives the pilot a more immediate indication of a 

pending altitude deviation. In addition to trend information, 

the vertical speed also gives a rate indication. By using the 

VSI tape in conjunction with the altitude trend tape, a pilot has 

a better understanding of how much of a correction needs to 

be made. With practice, the pilot will learn the performance 

of a particular aircraft and know how much pitch change 

is required in order to correct for a specific rate indication.

Unlike older analog VSIs, new glass panel displays have 

instantaneous VSIs. Older units had a lag designed into the 

system that was utilized to indicate rate information. The 

new glass panel displays utilize a digital air data computer 

that does not indicate a lag. Altitude changes are shown 

immediately and can be corrected for quickly.

The VSI tape should be used to assist in determining what 

pitch changes are necessary to return to the desired altitude. 

A good rule of thumb is to use a vertical speed rate of change 

that is double the altitude deviation. However, at no time 

should the rate of change be more than the optimum rate of 

climb or descent for the specific aircraft being flown. For 

example, if the altitude is off by 200 feet from the desired 

altitude, then a 400 feet per minute (fpm) rate of change 

would be sufficient to get the aircraft back to the original 
7-37

altitude. If the altitude has changed by 700 feet, then doubling 

that would necessitate a 1,400 fpm change. Most aircraft 

are not capable of that, so restrict changes to no more than 

optimum climb and descent. An optimum rate of change 

would vary between 500 and 1,000 fpm.

One error the instrument pilot encounters is overcontrolling. 

Overcontrolling occurs when a deviation of more than 200 

fpm is indicated over the optimum rate of change. For 

example, an altitude deviation of 200 feet is indicated on 

the altimeter, a vertical speed rate of 400 feet should be 

indicated on the gauge. If the vertical speed rate showed 

600 fpm (200 more than optimum), the pilot would be 

overcontrolling the aircraft. 

When returning to altitude, the primary pitch instrument 

is the VSI tape. If any deviation from the desired vertical 

speed is indicated, make the appropriate pitch change using 

the attitude indicator.

As the aircraft approaches the target altitude, the vertical speed 

rate can be slowed in order to capture the altitude in a more 

stabilized fashion. Normally within 10 percent of the rate of 

climb or descent from the target altitude, begin to slow the 

vertical speed rate in order to level off at the target altitude. 

This allows the pilot to level at the desired altitude without 

rapid control inputs or experiencing discomfort due to G-load.

Airspeed Indicator (ASI)

The ASI presents an indirect indication of the pitch attitude. 

At a constant power setting and pitch attitude, airspeed 

remains constant. As the pitch attitude lowers, airspeed 

increases, and the nose should be raised. 

As the pitch attitude is increased, the nose of the aircraft 

raises, which results in an increase in the angle of attack as 

well as an increase in induced drag. The increased drag begins 

to slow the momentum of the aircraft, which is indicated on 

the ASI. The airspeed trend indicator shows a trend as to 

where the airspeed will be in 6 seconds. Conversely, if the 

nose of the aircraft should begin to fall, the angle of attack, 

as well as induced drag, decreases.

There is a lag associated with the ASI when using it as a pitch 

instrument. It is not a lag associated with the construction 

of the ASI, but a lag associated with momentum change. 

Depending on the rate of momentum change, the ASI may not 

indicate a pitch change in a timely fashion. If the ASI is being 

used as the sole reference for pitch change, it may not allow 

for a prompt correction. However, if smooth pitch changes 

are executed, modern glass panel displays are capable of 

indicating 1 knot changes in airspeed and also capable of 

projecting airspeed trends.

When flying by reference to flight instruments alone, it 

is imperative that all of the flight instruments be crosschecked for pitch control. By cross-checking all pitch related 

instruments, the pilot can better visualize the aircraft attitude 

at all times.

As previously stated, the primary instrument for pitch is the 

instrument that gives the pilot the most pertinent information 

for a specific parameter. When in level flight and maintaining 

a constant altitude, what instrument shows a direct indication 

of altitude? The only instrument that is capable of showing 

altitude is the altimeter. The other instruments are supporting 

instruments that are capable of showing a trend away from 

altitude, but do not directly indicate an altitude.

The supporting instruments forewarn of an impending 

altitude deviation. With an efficient cross-check, a proficient 

pilot is better able to maintain altitude.

Bank Control

This discussion assumes the aircraft is being flown in 

coordinated flight, which means the longitudinal axis of the 

aircraft is aligned with the relative wind. On the PFD, the 

attitude indicator shows if the wings are level. The turn rate 

indicator, slip/skid indicator, and the heading indicator also 

indicate whether or not the aircraft is maintaining a straight 

(zero bank) flightpath.

Attitude Indicator

The attitude indicator is the only instrument on the PFD that 

has the capability of displaying the precise bank angle of the 

aircraft. This is made possible by the display of the roll scale 

depicted as part of the attitude indicator.

Figure 7-52 identifies the components that make up the 

attitude indicator display. Note that the top of the display is 

blue, representing sky, the bottom is brown, depicting dirt, 

and the white line separating them is the horizon. The lines 

parallel to the horizon line are the pitch scale, which is marked 

in 5 degree increments and labeled every 10 degrees. The 

pitch scale always remains parallel to the horizon.

The curved line in the blue area is the roll scale. The triangle 

on the top of the scale is the zero index. The hash marks on 

the scale represent the degree of bank. [Figure 7-53] The 

roll scale always remains in the same position relative to 

the horizon line. 
7-38

0° 

30° 

45° 

60° 

90° 

Figure 5-52. Bank Interpretation with the Attitude Incicator. 

Figure 7-53. Attitude indicator showing a 15° left bank.

VOR 1 

270° 270° 

Figure 5-54. Slip/Skid & Turn Rate Indication.

Slip/Skid indicator

Turn rate indicator

Turn rate trend vector

Figure 7-54. Slip/skid and turn rate indicator.

Figure 5-53. Attitude Indicator. 

Roll pointer

Roll scale

Slip/Skid indicator

Roll scale zero

Pitch scale

Aircraft symbol

Horizon line

Figure 7-52. Attitude indicator.

The roll pointer indicates the direction and degree of bank. 

[Figure 7-53] The roll pointer is aligned with the aircraft 

symbol. The roll pointer indicates the angle of the lateral axis 

of the aircraft compared to the natural horizon. The slip/skid 

indicator will show if the longitudinal axis of the aircraft is 

aligned with the relative wind, which is coordinated flight. 

With the roll index and the slip/skid indicator aligned, any 

deflection, either right or left of the roll index causes the 

aircraft to turn in that direction. With the small graduations 

on the roll scale, it is easy to determine the bank angle within 

approximately 1 degree. In coordinated flight, if the roll 

index is aligned with the roll pointer, the aircraft is achieving 

straight flight. 

An advantage of EFDs is the elimination of the precession 

error. Precession error in analog gauges is caused by forces 

being applied to a spinning gyro. With the new solid state 

instruments, precession error has been eliminated.

Since the attitude indicator is capable of showing precise 

pitch and bank angles, the only time that the attitude indicator 

is a primary instrument is when attempting to fly at a specific 

bank angle or pitch angle. Other times, the attitude instrument 

can be thought of as a control instrument. 

Horizontal Situation Indicator (HSI)

The horizontal situation indicator (HSI) is a rotating 360° 

compass card that indicates magnetic heading. The HSI is the 

only instrument that is capable of showing exact headings. The 

magnetic compass can be used as a backup instrument in case 

of an HSI failure; however, due to erratic, unstable movements, 

it is more likely to be used a supporting instrument. 

In order for the pilot to achieve the desired rate of change, 

it is important for him or her to understand the relationship 

between the rate at which the HSI changes heading displays 

and the amount of bank angle required to meet that rate of 

change. A very small rate of heading change means the bank 

angle is small, and it takes more time to deviate from the 

desired straight flightpath. A larger rate of heading change 

means a greater bank angle happens at a faster rate.

Heading Indicator

The heading indicator is the large black box with a white 

number that indicates the magnetic heading of the aircraft. 

[Figure 7-54] The aircraft heading is displayed to the nearest 

degree. When this number begins to change, the pilot should 

be aware that straight flight is no longer being achieved.

Turn Rate Indicator

The turn rate indicator gives an indirect indication of bank. 

It is a magenta trend indicator capable of displaying halfstandard as well as standard rate turns to both the left and 
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Figure 7-55. An aircraft decreasing in airspeed while gaining 

altitude. In this case, the pilot has decreased pitch.

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Figure 7-56. Figure shows both an increase in speed and altitude 

where pitch adjustment alone is insufficient. In this situation, a 

reduction of power is also necessary.

right. [Figure 7-54] The turn indicator is capable of indicating 

turns up to 4 degrees per second by extending the magenta 

line outward from the standard rate mark. If the rate of turn 

has exceeded 4 degrees per second, the magenta line can 

not precisely indicate where the heading will be in the next 

6 seconds; the magenta line freezes and an arrowhead will 

be displayed. This alerts the pilot to the fact that the normal 

range of operation has been exceeded. 

Slip/Skid Indicator

The slip/skid indicator is the small portion of the lower 

segmented triangle displayed on the attitude indicator. This 

instrument depicts whether the aircraft’s longitudinal axis is 

aligned with the relative wind. [Figure 7-54]

The pilot must always remember to cross-check the roll index 

to the roll pointer when attempting to maintain straight flight. 

Any time the heading remains constant and the roll pointer and 

the roll index are not aligned, the aircraft is in uncoordinated 

flight. To make a correction, the pilot should apply rudder 

pressure to bring the aircraft back to coordinated flight.

Power Control

Power produces thrust which, with the appropriate angle of 

attack of the wing, overcomes the forces of gravity, drag, 

and inertia to determine airplane performance.

Power control must be related to its effect on altitude and 

airspeed, since any change in power setting results in a change 

in the airspeed or the altitude of the airplane. At any given 

airspeed, the power setting determines whether the airplane 

is in level flight, in a climb, or in a descent. If the power is 

increased in straight-and-level flight and the airspeed held 

constant, the airplane climbs; if power is decreased while 

the airspeed is held constant, the airplane descends. On the 

other hand, if altitude is held constant, the power applied 

determines the airspeed. 

The relationship between altitude and airspeed determines the 

need for a change in pitch or power. If the airspeed is off the 

desired value, always check the altimeter before deciding that 

a power change is necessary. Think of altitude and airspeed 

as interchangeable; altitude can be traded for airspeed by 

lowering the nose, or convert airspeed to altitude by raising 

the nose. If altitude is higher than desired and airspeed is 

low, or vice versa, a change in pitch alone may return the 

airplane to the desired altitude and airspeed. [Figure 7-55] If 

both airspeed and altitude are high or if both are low, then a 

change in both pitch and power is necessary in order to return 

to the desired airspeed and altitude. [Figure 7-56] 

For changes in airspeed in straight-and-level flight, pitch, bank, 

and power must be coordinated in order to maintain constant 

altitude and heading. When power is changed to vary airspeed 

in straight-and-level flight, a single-engine, propeller-driven 

airplane tends to change attitude around all axes of movement. 

Therefore, to maintain constant altitude and heading, apply 

various control pressures in proportion to the change in power. 

When power is added to increase airspeed, the pitch instruments 

indicate a climb unless forward-elevator control pressure is 

applied as the airspeed changes. With an increase in power, the 

airplane tends to yaw and roll to the left unless counteracting 

aileron and rudder pressures are applied. Keeping ahead of 

these changes requires increasing cross-check speed, which 

varies with the type of airplane and its torque characteristics, 

the extent of power and speed change involved. 

Power Settings

Power control and airspeed changes are much easier when 

approximate power settings necessary to maintain various 

airspeeds in straight-and-level flight are known in advance. 

However, to change airspeed by any appreciable amount, the 

common procedure is to underpower or overpower on initial 
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Figure 5-13. Straight-and-level flight (normal cruising speed).

Supporting bank

Figure 7-57. Straight-and-level flight (normal cruising speed).

power changes to accelerate the rate of airspeed change. (For 

small speed changes, or in airplanes that decelerate or accelerate 

rapidly, overpowering or underpowering is not necessary.) 

Consider the example of an airplane that requires 23 inches 

of mercury ("Hg) to maintain a normal cruising airspeed of 

120 knots, and 18 "Hg to maintain an airspeed of 100 knots. 

The reduction in airspeed from 120 knots to 100 knots while 

maintaining straight-and-level flight is discussed below and 

illustrated in Figures 7-57, 7-58, and 7-59. 

Instrument indications, prior to the power reduction, are 

shown in Figure 7-57. The basic attitude is established and 

maintained on the attitude indicator. The specific pitch, 

bank, and power control requirements are detected on these 

primary instruments: 

Altimeter—Primary Pitch 

Heading Indicator—Primary Bank 

Airspeed Indicator—Primary Power 

Supporting pitch and bank instruments are shown in 

Figure 7-57. Note that the supporting power instrument is 

the manifold pressure gauge (or tachometer if the propeller 

is fixed pitch). However, when a smooth power reduction to 

approximately 15 "Hg (underpower) is made, the manifold 

pressure gauge becomes the primary power instrument. 

[Figure 7-58] With practice, power setting can be changed 

with only a brief glance at the power instrument, by sensing 

the movement of the throttle, the change in sound, and the 

changes in the feel of control pressures. 

As the thrust decreases, increase the speed of the cross-check 

and be ready to apply left rudder, back-elevator, and aileron 

control pressure the instant the pitch and bank instruments 

show a deviation from altitude and heading. As proficiency 

is obtained, a pilot will learn to cross-check, interpret, and 

control the changes with no deviation of heading and altitude. 

Assuming smooth air and ideal control technique, as airspeed 

decreases, a proportionate increase in airplane pitch attitude 

is required to maintain altitude. Similarly, effective torque 

control means counteracting yaw with rudder pressure. 

As the power is reduced, the altimeter is primary for 

pitch, the heading indicator is primary for bank, and the 

manifold pressure gauge is momentarily primary for power 

(at 15 "Hg in Figure 7-58). Control pressures should be 

trimmed off as the airplane decelerates. As the airspeed 

approaches the desired airspeed of 100 knots, the manifold 

pressure is adjusted to approximately 18 "Hg and becomes 

the supporting power instrument. The ASI again becomes 

primary for power. [Figure 7-59]

Airspeed Changes in Straight-and-Level Flight

Practice of airspeed changes in straight-and-level flight 

provides an excellent means of developing increased 

proficiency in all three basic instrument skills and brings 

out some common errors to be expected during training 

in straight-and-level flight. Having learned to control the 

airplane in a clean configuration (minimum drag conditions), 

increase proficiency in cross-check and control by practicing 

speed changes while extending or retracting the flaps and 

landing gear. While practicing, be sure to comply with the 
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OAT 7°C 

ALERTS 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 5-58. Power Control - Straight and level flight (airspeed decreasing). 

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Primary 

power 

as throttle 

is set

Primary bank

Primary pitch

Primary power as 

A/S approaches

desired value

Figure 7-58. Straight-and-level flight (airspeed decreasing).

XPDR 5537 IDNT LCL23:00:34 

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Supporting 

power

Primary bank

Primary pitch Primary power

Figure 5-59. Power Control - Straight and level flight (reduced airspeed stabilized). 

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Figure 7-59. Straight-and-level flight (reduced airspeed stabilized).
7-42

XPDR 5537 IDNT LCL23:00:34 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

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WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 5-60. Cross-check supporting instruments. 

ALERTS

Figure 7-60. Cross-check supporting instruments.

1. Maintain rpm at 2,500, since a high power setting is 

used in full drag configuration.

2. Reduce manifold pressure to 10 "Hg. As the airspeed 

decreases, increase cross-check speed.

3. Make trim adjustments for an increased angle of attack 

and decrease in torque.

4. Lower the gear at 115 knots. The nose may tend to 

pitch down and the rate of deceleration increases. 

Increase pitch attitude to maintain constant altitude 

and trim off some of the back-elevator pressures. 

If full flaps are lowered at 105 knots, cross-check, 

interpretation, and control must be very rapid. A 

simpler technique is to stabilize attitude with gear 

down before lowering the flaps. 

5. Since 18 "Hg manifold pressure holds level flight at 

100 knots with the gear down, increase power smoothly 

to that setting as the ASI shows approximately 105 

knots, and retrim. The attitude indicator now shows 

approximately two-and-a-half bar width nose-high in 

straight-and-level flight.

6. Actuate the flap control and simultaneously increase 

power to the predetermined setting (25 "Hg) for the 

desired airspeed, and trim off the pressures necessary 

to hold constant altitude and heading. The attitude 

indicator now shows a bar width nose-low in straightand-level flight at 95 knots. 

airspeed limitations specified in the POH/AFM for gear and 

flap operation.

Sudden and exaggerated attitude changes may be necessary 

in order to maintain straight-and-level flight as the landing 

gear is extended and the flaps are lowered in some airplanes. 

The nose tends to pitch down with gear extension, and when 

flaps are lowered, lift increases momentarily (at partial flap 

settings) followed by a marked increase in drag as the flaps 

near maximum extension. 

Control technique varies according to the lift and drag 

characteristics of each airplane. Accordingly, knowledge of 

the power settings and trim changes associated with different 

combinations of airspeed, gear, and flap configurations 

reduces instrument cross-check and interpretation problems. 

[Figure 7-60]

For example, assume that in straight-and-level flight 

instruments indicate 120 knots with power at 23 "Hg 

manifold pressure/2,300 revolutions per minute (rpm), gear 

and flaps up. After reduction in airspeed, with gear and flaps 

fully extended, straight-and-level flight at the same altitude 

requires 25 "Hg manifold pressure/2,500 rpm. Maximum 

gear extension speed is 115 knots; maximum flap extension 

speed is 105 knots. Airspeed reduction to 95 knots, gear and 

flaps down, can be made in the following manner:
7-43

XPDR 5537 IDNT LCL23:00:34 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 5-61. Insufficient cross-check

ALERTS 

270° 

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Figure 7-61. Insufficient cross-check. The problem is power and not nose-high. In this case, the pilot decreased pitch inappropriately.

Trim Technique

Trim control is one of the most important flight habits to 

cultivate. Trimming refers to relieving any control pressures 

that need to be applied by the pilot to the control surfaces to 

maintain a desired flight attitude. The desired result is for the 

pilot to be able to take his or her hands off the control surfaces 

and have the aircraft remain in the current attitude. Once the 

aircraft is trimmed for hands-off flight, the pilot is able to 

devote more time to monitoring the flight instruments and 

other aircraft systems.

In order to trim the aircraft, apply pressure to the control surface 

that needs trimming and roll the trim wheel in the direction 

pressure is being held. Relax the pressure that is being applied to 

the control surface and monitor the primary instrument for that 

attitude. If the desired performance is achieved, fly hands off. If 

additional trimming is required, redo the trimming steps.

An aircraft is trimmed for a specific airspeed, not pitch attitude 

or altitude. Any time an aircraft changes airspeed, there is 

a need to re-trim. For example, an aircraft is flying at 100 

knots straight-and-level. An increase of 50 rpm causes the 

airspeed to increase. As the airspeed increases, additional lift 

is generated and the aircraft climbs. Once the additional thrust 

has stabilized at some higher altitude, the airspeed will again 

stabilize at 100 knots. 

This demonstrates how trim is associated with airspeed and 

not altitude. If the initial altitude is to be maintained, forward 

pressure would need to be applied to the control wheel while 

the trim wheel needs to be rolled forward to eliminate any 

control pressures. Rolling forward on the trim wheel is equal 

to increasing for a trimmed airspeed. Any time the airspeed 

is changed, re-trimming is required. Trimming can be 

accomplished during any transitional period; however, prior 

to final trimming, the airspeed must be held constant. If the 

airspeed is allowed to change, the trim is not adjusted properly 

and the altitude varies until the airspeed for which the aircraft 

is trimmed is achieved.

Common Errors in Straight-and-Level Flight

Pitch

Pitch errors usually result from the following errors:

1. Improper adjustment of the yellow chevron (aircraft 

symbol) on the attitude indicator. 

Corrective Action: Once the aircraft has leveled off and 

the airspeed has stabilized, make small corrections to 

the pitch attitude to achieve the desired performance. 

Cross-check the supporting instruments for validation.

2. Insufficient cross-check and interpretation of pitch 

instruments. [Figure 7-61]
7-44

Example: The airspeed indication is low. The pilot, 

believing a nose-high pitch attitude exists, applies 

forward pressure without noting that a low power setting 

is the cause of the airspeed discrepancy. 

Corrective Action: Increase the rate of cross-check of all 

the supporting flight instruments. Airspeed and altitude 

should be stabilized before making a control input.

3. Acceptance of deviations.

Example: A pilot has an altitude range of ±100 feet 

according to the practical test standards for straight-and 

level-flight. When the pilot notices that the altitude has 

deviated by 60 feet, no correction is made because the 

altitude is holding steady and is within the standards.

Corrective Action: The pilot should cross-check the 

instruments and, when a deviation is noted, prompt 

corrective actions should be taken in order to bring the 

aircraft back to the desired altitude. Deviations from 

altitude should be expected but not accepted. 

4. Overcontrolling—excessive pitch changes.

Example: A pilot notices a deviation in altitude. In an 

attempt to quickly return to altitude, the pilot makes a 

large pitch change. The large pitch change destabilizes 

the attitude and compounds the error.

Corrective Action: Small, smooth corrections 

should be made in order to recover to the desired 

altitude (0.5° to 2° depending on the severity of the 

deviation). Instrument flying is comprised of small 

corrections to maintain the aircraft attitude. When 

flying in IMC, a pilot should avoid making large 

attitude changes in order to avoid loss of aircraft 

control and spatial disorientation.

5. Failure to maintain pitch corrections.

Pitch changes need to be made promptly and held 

for validation. Many times pilots make corrections 

and allow the pitch attitude to change due to not 

trimming the aircraft. It is imperative that any time a 

pitch change is made; the trim is readjusted in order 

to eliminate any control pressures that are being held. 

A rapid cross-check aids in avoiding any deviations 

from the desired pitch attitude.

Example: A pilot notices a deviation in altitude. A 

change in the pitch attitude is accomplished but no 

adjustment to the trim is made. Distractions cause 

the pilot to slow the cross-check and an inadvertent 

reduction in the pressure to the control column 

commences. The pitch attitude then changes, thus 

complicating recovery to the desired altitude.

Corrective Action: The pilot should initiate a pitch 

change and then immediately trim the aircraft to 

relieve any control pressures. A rapid cross-check 

should be established in order to validate the desired 

performance is being achieved.

6. Fixation during cross-check.

Devoting an unequal amount of time to one instrument 

either for interpretation or assigning too much 

importance to an instrument. Equal amounts of time 

should be spent during the cross-check to avoid an 

unnoticed deviation in one of the aircraft attitudes.

Example: A pilot makes a correction to the pitch 

attitude and then devotes all of the attention to the 

altimeter to determine if the pitch correction is valid. 

During this time, no attention is paid to the heading 

indicator, which shows a turn to the left. [Figure 7-62]

Corrective Action: The pilot should monitor all 

instrumentation during the cross-check. Do not fixate 

on one instrument waiting for validation. Continue to 

scan all instruments to avoid allowing the aircraft to 

begin a deviation in another attitude.

Heading

Heading errors usually result from but are not limited to the 

following errors:

1. Failure to cross-check the heading indicator, especially 

during changes in power or pitch attitude.

2. Misinterpretation of changes in heading, with resulting 

corrections in the wrong direction.

3. Failure to note and remember a preselected heading.

4. Failure to observe the rate of heading change and its 

relation to bank attitude.

5. Overcontrolling in response to heading changes, 

especially during changes in power settings.

6. Anticipating heading changes with premature 

application of rudder pressure.

7. Failure to correct small heading deviations. Unless 

zero error in heading is the goal, a pilot will tolerate 

larger and larger deviations. Correction of a 1 degree 

error takes far less time and concentration than 

correction of a 20° error.

8. Correcting with improper bank attitude. If correcting 

a 10° heading error with a 20° bank correction, the 

aircraft will roll past the desired heading before the 

bank is established, requiring another correction in 

the opposite direction. Do not multiply existing errors 

with errors in corrective technique.
7-45

XPDR 5537 IDNT LCL23:00:34 

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ALERTS 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 7-62. The pilot has fixated on pitch and altitude, leaving bank indications unattended. Note the trend line to the left. Figure 5-62. Fixation during cross-check 

9. Failure to note the cause of a previous heading error 

and thus repeating the same error. For example, the 

airplane is out of trim with a left wing low tendency. 

Repeated corrections for a slight left turn are made, 

yet trim is ignored.

Power

Power errors usually result from but are not limited to the 

following errors:

1. Failure to become familiar with the aircraft’s specific 

power settings and pitch attitudes.

2. Abrupt use of throttle. 

3. Failure to lead the airspeed when making power 

changes, climbs, or descents.

Example: When leveling off from a descent, increase 

the power in order to avoid the airspeed from bleeding 

off due to the decrease in momentum of the aircraft. 

If the pilot waits to bring in the power until after the 

aircraft is established in the level pitch attitude, the 

aircraft will have already decreased below the speed 

desired, which will require additional adjustment in 

the power setting. 

4. Fixation on airspeed tape or manifold pressure 

indications during airspeed changes, resulting in 

erratic control of airspeed, power, as well as pitch and 

bank attitudes.

Trim

Trim errors usually result from the following faults:

1. Improper adjustment of seat or rudder pedals for 

comfortable position of legs and feet. Tension in the 

ankles makes it difficult to relax rudder pressures.

2. Confusion about the operation of trim devices, which 

differ among various airplane types. Some trim 

wheels are aligned appropriately with the airplane’s 

axes; others are not. Some rotate in a direction 

contrary to expectations.

3. Failure to understand the principles of trim and 

that the aircraft is being trimmed for airspeed, not a 

pitch attitude.

4. Faulty sequence in trim techniques. Trim should be 

utilized to relieve control pressures, not to change 

pitch attitudes. The proper trim technique has the pilot 

holding the control wheel first and then trimming to 

relieve any control pressures. Continuous trim changes 

are required as the power setting is changed. Utilize 

the trim continuously, but in small amounts.
7-46

XPDR 5537 IDNT LCL10:12:34 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Current procedure 

Before procedure 

2300 

23.0 

Primary

power

Primary bank

Primary pitch

Figure 5-19. Constant airspeed climb from cruise airspeed

 500 

Figure 7-63. Constant airspeed climb from cruise airspeed.

Straight Climbs and Descents

Each aircraft has a specific pitch attitude and airspeed that 

corresponds to the most efficient climb rate for a specified 

weight. The POH/AFM contains the speeds that produce the 

desired climb. These numbers are based on maximum gross 

weight. Pilots must be familiar with how the speeds vary with 

weight so they can compensate during flight. 

Entry

Constant Airspeed Climb From Cruise Airspeed

To enter a constant airspeed climb from cruise airspeed, 

slowly and smoothly apply aft elevator pressure in order 

to raise the yellow chevron (aircraft symbol) until the tip 

points to the desired degree of pitch. [Figure 7-63] Hold 

the aft control pressure and smoothly increase the power 

to the climb power setting. This increase in power may be 

initiated either prior to initiating the pitch change or after 

having established the desired pitch setting. Consult the POH/

AFM for specific climb power settings if anything other than 

a full power climb is desired. Pitch attitudes vary depending 

on the type of aircraft being flown. As airspeed decreases, 

control forces need to be increased in order to compensate 

for the additional elevator deflection required to maintain 

attitude. Utilize trim to eliminate any control pressures. By 

effectively using trim, the pilot is better able to maintain the 

desired pitch without constant attention. The pilot is thus 

able to devote more time to maintaining an effective scan of 

all instrumentation.

The VSI should be utilized to monitor the performance of the 

aircraft. With a smooth pitch transition, the VSI tape should 

begin to show an immediate trend upward and stabilize on a 
7-47

XPDR 5537 IDNT LCL10:12:34 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Current procedure 

Before procedure 2300 

23.0 

Supporting pitch and bank

Supporting 

power

Primary bank

Primary pitch

Primary power

Figure 7-64. Constant airspeed climb from established airspeed.

rate of climb equivalent to the pitch and power setting being 

utilized. Depending on current weight and atmospheric 

conditions, this rate will be different. This requires the pilot to 

be knowledgeable of how weight and atmospheric conditions 

affect aircraft performance.

Once the aircraft is stabilized at a constant airspeed and pitch 

attitude, the primary flight instrument for pitch will be the ASI 

and the primary bank instrument will be the heading indicator. 

The primary power instrument will be the tachometer or the 

manifold pressure gauge depending on the aircraft type. If the 

pitch attitude is correct, the airspeed should slowly decrease to 

the desired speed. If there is any variation in airspeed, make 

small pitch changes until the aircraft is stabilized at the desired 

speed. Any change in airspeed requires a trim adjustment.

Constant Airspeed Climb from Established Airspeed

In order to enter a constant airspeed climb, first complete the 

airspeed reduction from cruise airspeed to climb airspeed. 

Maintain straight-and-level flight as the airspeed is reduced. 

The entry to the climb is similar to the entry from cruise 

airspeed with the exception that the power must be increased 

when the pitch attitude is raised. [Figure 7-64] Power added 

after the pitch change shows a decrease in airspeed due to 

the increased drag encountered. Power added prior to a pitch 

change causes the airspeed to increase due to the excess thrust. 

Constant Rate Climbs

Constant rate climbs are very similar to the constant airspeed 

climbs in the way the entry is made. As power is added, 

smoothly apply elevator pressure to raise the yellow chevron 
7-48

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WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360° Supporting pitch and bank Supporting pitch until 

desired vertical speed

is achieved, then it

becomes the primary

instrument for pitch. 

Primary bank

Primary for pitch until 

desired vertical speed 

is achieved. Then

airspeed becomes 

primary for power.

Figure 7-65. Constant rate climbs.

to the desired pitch attitude that equates to the desired vertical 

speed rate. The primary instrument for pitch during the initial 

portion of the maneuver is the ASI until the vertical speed 

rate stabilizes and then the VSI tape becomes primary. The 

ASI then becomes the primary instrument for power. If any 

deviation from the desired vertical speed is noted, small 

pitch changes will be required in order to achieve the desired 

vertical speed. [Figure 7-65]

When making changes to compensate for deviations in 

performance, pitch, and power, pilot inputs need to be 

coordinated to maintain a stable flight attitude. For instance, 

if the vertical speed is lower than desired but the airspeed 

is correct, an increase in pitch momentarily increases the 

vertical speed. However, the increased drag quickly starts 

to degrade the airspeed if no increase in power is made. A 

change to any one variable mandates a coordinated change 

in the other.

Conversely, if the airspeed is low and the pitch is high, a 

reduction in the pitch attitude alone may solve the problem. 

Lower the nose of the aircraft very slightly to see if a power 

reduction is necessary. Being familiar with the pitch and 

power settings for the aircraft aids in achieving precise 

attitude instrument flying.

Leveling Off

Leveling off from a climb requires a reduction in the pitch 

prior to reaching the desired altitude. If no change in pitch 

is made until reaching the desired altitude, the momentum 

of the aircraft causes the aircraft to continue past the desired 

altitude throughout the transition to a level pitch attitude. The 

amount of lead to be applied depends on the vertical speed 

rate. A higher vertical speed requires a larger lead for level 

off. A good rule of thumb to utilize is to lead the level off 

by 10 percent of the vertical speed rate (1,000 fpm ÷ 10 = 

100 feet lead). 

To level off at the desired altitude, refer to the attitude display 

and apply smooth forward elevator pressure toward the desired 

level pitch attitude while monitoring the VSI and altimeter 

tapes. The rates should start to slow and airspeed should 

begin to increase. Maintain the climb power setting until the 

airspeed approaches the desired cruise airspeed. Continue to 

monitor the altimeter to maintain the desired altitude as the 

airspeed increases. Prior to reaching the cruise airspeed, the 

power must be reduced to avoid overshooting the desired 

speed. The amount of lead time that is required depends on 

the speed at which the aircraft accelerates. Utilization of the 

airspeed trend indicator can assist by showing how quickly 

the aircraft will arrive at the desired speed.
7-49

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WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Current procedure 

Before procedure 

1800 

18.0 

Figure 7-66. The top image illustrates a reduction of power and descending at 500 fpm to an altitude of 5,000 feet. The bottom image Figure 5-22. Level-off airspeed higher than descent airspeed. 

illustrates an increase in power and the initiation of leveling off.

To level off at climbing airspeed, lower the nose to the 

appropriate pitch attitude for level flight with a simultaneous 

reduction in power to a setting that maintains the desired 

speed. With a coordinated reduction in pitch and power, there 

should be no change in the airspeed.

Descents

Descending flight can be accomplished at various airspeeds 

and pitch attitudes by reducing power, lowering the nose 

to a pitch attitude lower than the level flight attitude, or 

adding drag. Once any of these changes have been made, the 

airspeed eventually stabilizes During this transitional phase, 

the only instrument that displays an accurate indication of 

pitch is the attitude indicator. Without the use of the attitude 

indicator (such as in partial panel flight), the ASI tape, the 

VSI tape, and the altimeter tape shows changing values until 

the aircraft stabilizes at a constant airspeed and constant rate 

of descent. The altimeter tape continues to show a descent. 

Hold pitch constant and allow the aircraft to stabilize. During 

any change in attitude or airspeed, continuous application of 

trim is required to eliminate any control pressures that need 

to be applied to the control yoke. An increase in the scan rate 

during the transition is important since changes are being 

made to the aircraft flightpath and speed. [Figure 7-66]

Entry

Descents can be accomplished with a constant rate, constant 

airspeed, or a combination. The following method can 

accomplish any of these with or without an attitude indicator. 

Reduce the power to allow the aircraft to decelerate to the 

desired airspeed while maintaining straight-and-level flight. 

As the aircraft approaches the desired airspeed, reduce the 
7-50

power to a predetermined value. The airspeed continues to 

decrease below the desired airspeed unless a simultaneous 

reduction in pitch is performed. The primary instrument 

for pitch is the ASI tape. If any deviation from the desired 

speed is noted, make small pitch corrections by referencing 

the attitude indicator and validate the changes made with the 

airspeed tape. Utilize the airspeed trend indicator to judge 

if the airspeed is increasing and at what rate. Remember to 

trim off any control pressures.

The entry procedure for a constant rate descent is the same 

except the primary instrument for pitch is the VSI tape. The 

primary instrument for power is the ASI. When performing 

a constant rate descent while maintaining a specific airspeed, 

coordinated use of pitch and power is required. Any change 

in pitch directly affects the airspeed. Conversely, any change 

in airspeed has a direct impact on vertical speed as long as 

the pitch is being held constant. 

Leveling Off

When leveling off from a descent with the intention of 

returning to cruise airspeed, first start by increasing the 

power to cruise prior to increasing the pitch back toward 

the level flight attitude. A technique used to determine 

how soon to start the level off is to lead the level off by an 

altitude corresponding to 10 percent of the rate of descent. 

For example, if the aircraft is descending at 1,000 fpm, start 

the level off 100 feet above the level off altitude. If the pitch 

attitude change is started late, there is a tendency to overshoot 

the desired altitude unless the pitch change is made with 

a rapid movement. Avoid making any rapid changes that 

could lead to control issues or spatial disorientation. Once 

in level pitch attitude, allow the aircraft to accelerate to the 

desired speed. Monitor the performance on the airspeed and 

altitude tapes. Make adjustments to the power in order to 

correct any deviations in the airspeed. Verify that the aircraft 

is maintaining level flight by cross-checking the altimeter 

tape. If deviations are noticed, make an appropriate smooth 

pitch change in order to arrive back at desired altitude. Any 

change in pitch requires a smooth coordinated change to the 

power setting. Monitor the airspeed in order to maintain the 

desired cruise airspeed.

To level off at a constant airspeed, the pilot must again 

determine when to start to increase the pitch attitude toward 

the level attitude. If pitch is the only item that is changing, 

airspeed varies due to the increase in drag as the aircraft’s 

pitch increases. A smooth coordinated increase in power 

needs to be made to a predetermined value in order to 

maintain speed. Trim the aircraft to relieve any control 

pressure that may have to be applied.

Common Errors in Straight Climbs and Descents

Climbing and descending errors usually result from but are 

not limited to the following errors:

1. Overcontrolling pitch on beginning the climb. Aircraft 

familiarization is the key to achieving precise attitude 

instrument flying. Until the pilot becomes familiar with 

the pitch attitudes associated with specific airspeeds, 

the pilot must make corrections to the initial pitch 

settings. Changes do not produce instantaneous and 

stabilized results; patience must be maintained while 

the new speeds and vertical speed rates stabilize. Avoid 

the temptations to make a change and then rush into 

making another change until the first one is validated. 

Small changes produce more expeditious results and 

allow for a more stabilized flightpath. Large changes 

to pitch and power are more difficult to control and can 

further complicate the recovery process.

2. Failure to increase the rate of instrument cross-check. 

Any time a pitch or power change is made, an increase 

in the rate a pilot cross-checks the instrument is 

required. A slow cross-check can lead to deviations 

in other flight attitudes.

3. Failure to maintain new pitch attitudes. Once a 

pitch change is made to correct for a deviation, that 

pitch attitude must be maintained until the change 

is validated. Utilize trim to assist in maintaining the 

new pitch attitude. If the pitch is allowed to change, 

it is impossible to validate whether the initial pitch 

change was sufficient to correct the deviation. The 

continuous changing of the pitch attitude delays the 

recovery process.

4. Failure to utilize effective trim techniques. If control 

pressures have to be held by the pilot, validation of the 

initial correction is impossible if the pitch is allowed to 

vary. Pilots have the tendency to either apply or relax 

additional control pressures when manually holding 

pitch attitudes. Trim allows the pilot to fly without 

holding pressure on the control yoke.

5. Failure to learn and utilize proper power settings. 

Any time a pilot is not familiar with an aircraft’s 

specific pitch and power settings, or does not 

utilize them, a change in flightpaths takes longer. 

Learn pitch and power settings in order to expedite 

changing the flightpath.

6. Failure to cross-check both airspeed and vertical speed 

prior to making adjustments to pitch and or power. It is 

possible that a change in one may correct a deviation 

in the other. 
7-51

7. Uncoordinated use of pitch and power during level 

offs. During level offs, both pitch and power settings 

need to be made in unison in order to achieve the 

desired results. If pitch is increased before adding 

power, additional drag is generated thereby reducing 

airspeed below the desired value.

8. Failure to utilize supporting pitch instruments leads to 

chasing the VSI. Always utilize the attitude indicator 

as the control instrument on which to change the pitch.

9. Failure to determine a proper lead time for level off 

from a climb or descent. Waiting too long can lead to 

overshooting the altitude.

10. Ballooning—Failure to maintain forward control 

pressure during level off as power is increased. 

Additional lift is generated causing the nose of the 

aircraft to pitch up.

Turns

Standard Rate Turns

The previous sections have addressed flying straight-andlevel as well as climbs and descents. However, attitude 

instrument flying is not accomplished solely by flying 

in a straight line. At some point, the aircraft needs to be 

turned to maneuver along victor airways, global positioning 

system (GPS) courses, and instrument approaches. The 

key to instrument flying is smooth, controlled changes to 

pitch and bank. Instrument flying should be a slow but 

deliberate process that takes the pilot from departure airport 

to destination airport without any radical flight maneuvers.

A turn to specific heading should be made at standard rate. 

Standard rate is defined as a turning rate of 3 degrees per 

second, which yields a complete 360° turn in 2 minutes. 

A turning rate of 3 degrees per second allows for a timely 

heading change, as well as allowing the pilot sufficient time to 

cross-check the flight instruments and avoid drastic changes 

to the aerodynamic forces being exerted on the aircraft. At no 

time should the aircraft be maneuvered faster than the pilot 

is comfortable cross-checking the flight instruments. Most 

autopilots are programmed to turn at standard rate. 

Establishing A Standard Rate Turn

In order to initiate a standard rate turn, approximate the 

bank angle and then establish that bank angle on the attitude 

indicator. A rule of thumb to determine the approximate angle 

of bank is to use 15 percent of the true airspeed. A simple 

way to determine this amount is to divide the airspeed by 

10 and add one-half the result. For example, at 100 knots, 

approximately 15° of bank is required (100/10 = 10 + 5 = 

15); at 120 knots, approximately 18° of bank is needed for a 

standard-rate turn. Cross-check the turn rate indicator, located 

on the HSI, to determine if that bank angle is sufficient to 

deliver a standard rate turn. Slight modifications may need 

to be made to the bank angle in order to achieve the desired 

performance. The primary bank instrument in this case is the 

turn rate indicator since the goal is to achieve a standard rate 

turn. The turn rate indicator is the only instrument that can 

specifically indicate a standard rate turn. The attitude indicator 

is used only to establish a bank angle (control instrument) but 

can be utilized as a supporting instrument by cross-checking 

the bank angle to determine if the bank is greater or less than 

what was calculated.

As the aircraft rolls into the bank, the vertical component 

of lift begins to decrease. [Figure 7-67] As this happens, 

additional lift must be generated to maintain level flight. 

Apply aft control pressure on the yoke sufficient to stop any 

altitude loss trend. With the increase in lift that needs to be 

generated, additional induced drag is also generated. This 

additional drag causes the aircraft to start to decelerate. To 

counteract this, apply additional thrust by adding power to the 

power lever. Once altitude and airspeed is being maintained, 

utilize the trim wheel to eliminate any control forces that need 

to be held on the control column. 

When rolling out from a standard rate turn, the pilot needs 

to utilize coordinated aileron and rudder and roll-out to a 

wings level attitude utilizing smooth control inputs. The 

roll-out rate should be the same as the roll-in rate in order to 

estimate the lead necessary to arrive at the desired heading 

without over- or undershooting. 

During the transition from the turn back to straight flight, the 

attitude indicator becomes the primary instrument for bank. 

Once the wings are level, the heading indicator becomes 

the primary instrument for bank. As bank decreases, the 

vertical component increases if the pitch attitude is not 

decreased sufficiently to maintain level flight. An aggressive 

cross-check keeps the altimeter stationary if forward control 

pressure is applied to the control column. As the bank angle is 

decreased, the pitch attitude should be decreased accordingly 

in order to arrive at the level pitch attitude when the aircraft 

reaches zero bank. Remember to utilize the trim wheel to 

eliminate any excess control forces that would otherwise 

need to be held. 

Common Errors

1. One common error associated with standard rate turns 

is due to pilot inability to hold the appropriate bank 

angle that equates to a standard rate. The primary bank 

instrument during the turn is the turn rate indicator; 

however, the bank angle varies slightly. With an 
7-52

XPDR 5537 IDNT LCL10:12:34 

INSET PFD CDI XPDR IDENT TMR/REF NRST ALERTS 

VOR 1 

305° 

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TAS 126KT 

OAT 6°C 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

Primary bank initially WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

supporting pitch

Supporting pitch

Primary bank

Primary pitch

Primary bank as turn is established

Primary power

Figure 5-23. Standard rate turn constant airspeed. Figure 7-67. Standard rate turn—constant airspeed.

aggressive cross-check, a pilot should be able to 

minimize errors arising from over- or underbanking.

2. Another error normally encountered during standard 

rate turns is inefficient or lack of adequate crosschecking. Pilots need to establish an aggressive 

cross-check in order to detect and eliminate all 

deviations from altitude, airspeed, and bank angle 

during a maneuver.

3. Fixation is a major error associated with attitude 

instrument flying in general. Pilots training for their 

instrument rating tend to focus on what they perceive 

to be the most important task at hand and abandon 

their cross-check by applying all of their attention to 

the turn rate indicator. A modified radial scan works 

well to provide the pilot with adequate scanning of all 

instrumentation during the maneuver.

Turns to Predetermined Headings

Turning the aircraft is one of the most basic maneuvers that a 

pilot learns during initial flight training. Learning to control 

the aircraft, maintaining coordination, and smoothly rolling 

out on a desired heading are all keys to proficient attitude 

instrument flying.

EFDs allow the pilot to better utilize all instrumentation during 

all phases of attitude instrument flying by consolidating all 

traditional instrumentation onto the PFD. The increased size 

of the attitude indicator, which stretches the entire width of 

the PFD, allows the pilot to maintain better pitch control 

while the introduction of the turn rate indicator positioned 

directly on the compass rose aids the pilot in determining 

when to begin a roll-out for the desired heading. 

When determining what bank angle to utilize when making a 

heading change, a general rule states that for a small heading 

change, do not use a bank angle that is greater than the total 

number of degrees of change needed. For instance, if a 

heading change of 20° is needed, a bank angle of not more 

than 20° is required. Another rule of thumb that better defines 

the bank angle is half the total number of degrees of heading 

change required, but never greater than standard rate. The 

exact bank angle that equates to a standard rate turn varies 

due to true airspeed.

With this in mind and the angle of bank calculated, the next step 

is determining when to start the roll-out process. For example:
7-53

An aircraft begins a turn from a heading of 030° to a heading 

of 120°. With the given airspeed, a standard rate turn has 

yielded a 15° bank. The pilot wants to begin a smooth 

coordinated roll-out to the desired heading when the heading 

indicator displays approximately 112°. The necessary 

calculations are:

15° bank (standard rate) ÷ 2 = 7.5°

120° – 7.5° = 112.5°

By utilizing this technique, the pilot is better able to judge 

if any modifications need to be made to the amount of lead 

once the amount of over- or undershooting is established.

Timed Turns

Timed turns to headings are performed in the same fashion 

with an EFD as with an analog equipped aircraft. The 

instrumentation used to perform this maneuver is the turn rate 

indicator as well as the clock. The purpose of this maneuver 

is to allow the pilot to gain proficiency in scanning as well 

as to further develop the pilot’s ability to control the aircraft 

without standard instrumentation.

Timed turns become essential when controlling the aircraft 

with a loss of the heading indicator. This may become 

necessary due to a loss of the AHRS unit or the magnetometer. 

In any case, the magnetic compass is still available for 

navigation. The reason for timed turns instead of magnetic 

compass turns is the simplicity of the maneuver. Magnetic 

compass turns require the pilot to take into account various 

errors associated with the compass; timed turns do not.

Prior to initiating a turn, determine if the standard rate indication 

on the turn rate indicator actually delivers a 3 degrees per 

second turn. To accomplish this, a calibration must be made. 

Establish a turn in either direction at the indicated standard 

rate. Start the digital timer as the compass rolls past a cardinal 

heading. Stop the timer once the compass card rolls through 

another cardinal heading. Roll wings level and compute the 

rate of turn. If the turn rate indicator is calibrated and indicating 

correctly, 90° of heading change should take 30 seconds. If 

the time taken to change heading by 90° is more or less than 

30 seconds, then a deflection above or below the standard rate 

line needs to be made to compensate for the difference. Once 

the calibration has been completed in one direction, proceed 

to the opposite direction. When both directions have been 

calibrated, apply the calibrated calculations to all timed turns.

In order to accomplish a timed turn, the amount of heading 

change needs to be established. For a change in heading from 

120° to a heading of 360°, the pilot calculates the difference 

and divides that number by 3. In this case, 120° divided by 

3° per second equals 40 seconds. This means that it would 

take 40 seconds for an aircraft to change heading 120° if that 

aircraft were held in a perfect standard rate turn. Timing for 

the maneuver should start as the aircraft begins rolling into 

the standard rate turn. Monitor all flight instruments during 

this maneuver. The primary pitch instrument is the altimeter. 

The primary power instrument is the ASI and the primary 

bank instrument is the turn rate indicator.

Once the calculated time expires, start a smooth coordinated 

roll-out. As long as the pilot utilizes the same rate of roll-in as 

roll-out, the time it takes for both will not need to be included 

in the calculations. With practice, the pilot should level the 

wings on the desired heading. If any deviation has occurred, 

make small corrections to establish the correct heading.

Compass Turns

The magnetic compass is the only instrument that requires 

no other source of power for operation. In the event of an 

AHRS or magnetometer failure, the magnetic compass is 

the instrument the pilot uses to determine aircraft heading. 

For a more detailed explanation on the use of the magnetic 

compass, see page 7-21.

Steep Turns

For the purpose of instrument flight training, a steep turn is 

defined as any turn in excess of standard rate. A standard 

rate turn is defined as 3 degrees per second. The bank angle 

that equates to a turn rate of 3 degrees per second varies 

according to airspeed. As airspeed increases, the bank angle 

must be increased. The exact bank angle that equates to a 

standard rate turn is unimportant. Normal standard rate turn 

bank angles range from 10° to 20°. The goal of training in 

steep turn maneuvers is pilot proficiency in controlling the 

aircraft with excessive bank angles. 

Training in excessive bank angles challenges the pilot in 

honing cross-checking skills and improves altitude control 

throughout a wider range of flight attitudes. Although the 

current instrument flight check practical test standards (PTS) 

do not call for a demonstration of steep turns on the certification 

check flight, this does not eliminate the need for the instrument 

pilot-in-training to demonstrate proficiency to an instructor. 

Training in steep turns teaches the pilot to recognize and to 

adapt to rapidly changing aerodynamic forces that necessitate 

an increase in the rate of cross-checking all flight instruments. 

The procedures for entering, maintaining, and exiting a 

steep turn are the same as for shallower turns. Proficiency in 

instrument cross-check and interpretation is increased due to 

the higher aerodynamic forces and increased speed at which 

the forces are changing.
7-54

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

270° 

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TAS 126KT 

OAT 7°C 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

ALERTS 

Figure 7-68. Steep left turn.

Performing the Maneuver

To enter a steep turn to the left, roll into a coordinated 45° 

bank turn to the left. An advantage that glass panel displays 

have over analog instrumentation is a 45° bank indication on 

the roll scale. This additional index on the roll scale allows 

the pilot to precisely roll into the desired bank angle instead 

of having to approximate it as is necessary with analog 

instrumentation. [Figure 7-68]

As soon as the bank angle increases from level flight, the 

vertical component of lift begins to decrease. If the vertical 

component of lift is allowed to continue to decrease, a 

pronounced loss of altitude is indicated on the altimeter 

along with the VSI tape, as well as the altitude trend 

indicator. Additionally, the airspeed begins to increase due 

to the lowered pitch attitude. It is very important to have 

a comprehensive scan developed prior to training in steep 

turns. Utilization of all of the trend indicators, as well the 

VSI, altimeter, and ASI, is essential in learning to fly steep 

turns by reference to instruments alone.

In order to avoid a loss of altitude, the pilot begins to slowly 

increase back pressure on the control yoke in order to increase 

the pitch attitude. The pitch change required is usually no 

more than 3 degrees to 5 degrees, depending on the type of 

aircraft. As the pilot increases back pressure, the angle of 

attack increases, thus increasing the vertical component of 

lift. When a deviation in altitude is indicated, proper control 

force corrections need to be made. During initial training of 

steep turns, pilots have a tendency to overbank. Over banking 

is when the bank angle exceeds 50°. As the outboard wing 

begins to travel faster through the air, it begins to generate a 

greater and greater differential in lift compared to the inboard 

wing. As the bank angle continues to progress more and 

more steeply past 45°, the two components of lift (vertical 

and horizontal) become inversely proportionate. 

Once the angle has exceeded 45°, the horizontal component 

of lift is now the greater force. If altitude should continue to 

decrease and the pilot only applies back yoke pressure, the 

aircraft’s turn radius begins to tighten due to the increased 

horizontal force. If aft control pressure continues to increase, 

there comes a point where the loss of the vertical component 

of lift and aerodynamic wing loading prohibits the nose of 

the aircraft from being raised. Any increase in pitch only 

tightens the turning radius. 

The key to successfully performing a steep turn by reference 

to instruments alone is the thorough understanding of the 

aerodynamics involved, as well as a quick and reliable crosscheck. The pilot should utilize the trim to avoid holding 

control forces for any period of time. With time and practice, 

a flight instructor can demonstrate how to successfully fly 

steep turns with and without the use of trim. Once the aircraft 

is trimmed for the maneuver, accomplishing the maneuver is 

virtually a hands-off effort. This allows additional time for 

cross-checking and interpreting the instruments.

It is imperative when correcting for a deviation in altitude, 

that the pilot modify the bank angle ±5° in order to vary the 

vertical component of lift, not just adjust back pressure. These 

two actions should be accomplished simultaneously.

During the recovery from steep turns to straight-and-level 

flight, aft control forces must be varied with the power control 

to arrive back at entry altitude, heading and airspeed.

Steps:

1. Perform clearing turns.

2. Roll left into a 45° bank turn and immediately begin to 

increase the pitch attitude by approximately 3° to 5°.

3. As the bank rolls past 30°, increase power to maintain 

the entry airspeed.

4. Apply trim to eliminate any aft control wheel forces.

5. Begin rolling out of the steep turn approximately 20° 

prior to the desired heading.

6. Apply forward control pressure and place the pitch 

attitude in the level cruise pitch attitude.

7. Reduce power to the entry power setting to maintain 

the desired airspeed.

8. Re-trim the aircraft as soon as practical or continue 

into a right hand steep turn and continue from step 3.
7-55

GPS ENR 

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ALERTS 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 7-69. Unusual attitude recovery protection. Note the brown horizon line is visible at the bottom.

9. Once the maneuver is complete, establish cruise flight 

and accomplish all appropriate checklist items.

Unusual Attitude Recovery Protection

Unusual attitudes are some of the most hazardous situations 

for a pilot to be in. Without proper recovery training 

on instrument interpretation and aircraft control, a pilot 

can quickly aggravate an abnormal flight attitude into a 

potentially fatal accident.

Analog gauges require the pilot to scan between instruments 

to deduce the aircraft attitude. Individually, these gauges lack 

the necessary information needed for a successful recovery.

EFDs have additional features to aid in recognition and 

recovery from unusual flight attitudes. The PFD displays 

all the flight instruments on one screen. Each instrument is 

superimposed over a full-screen representation of the attitude 

indicator. With this configuration, the pilot no longer needs 

to transition from one instrument to another.

The new unusual attitude recovery protection allows the 

pilot to be able to quickly determine the aircraft’s attitude 

and make a safe, proper, and prompt recovery. Situational 

awareness is increased by the introduction of the large 

full-width artificial horizon depicted on the PFD. This now 

allows for the attitude indicator to be in view during all 

portions of the scan.

One problem with analog gauges is that the attitude indicator 

displays a complete blue or brown segment when the pitch 

attitude is increased toward 90° nose-up or nose-down. 

With the EFDs, the attitude indicator is designed to retain 

a portion of both sky and land representation at all times. 

This improvement allows the pilot to always know the 

quickest way to return to the horizon. Situational awareness 

is greatly increased.

NOTE: The horizon line starts moving downward at 

approximately 47° pitch up. From this point on, the brown 

segment remains visible to show the pilot the quickest way 

to return to the level pitch attitude. [Figure 7-69] 

NOTE: The horizon line starts moving upward at 

approximately 27° pitch down. From this point on, the blue 

segment remains visible to show the pilot the quickest way 

to return to the level pitch attitude. [Figure 7-70]

It is imperative to understand that the white line on the 

attitude indicator is the horizon line. The break between the 

blue and brown symbols is only a reference and should not 

be thought of as the artificial horizon.

Another important advancement is the development of the 

unusual attitude recovery protection that is built into the PFD 

software and made capable by the AHRS. In the case of a nosehigh unusual attitude, the unusual attitude recovery protection 

displays red chevrons that point back to the horizon line. These 
7-56

GPS ENR 

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20 20 

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40 40 

20 20 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

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WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

ALERTS 

Figure 5-27. Horizon line starts moving upward at approximately 27 deg pitch down. Figure 7-70. Horizon line starts moving upward at 27°. Note that the blue sky remains visible at 17° nose-down.

chevrons are positioned at 50° up on the attitude indicator. 

The chevrons appear when the aircraft approaches a nose-high 

attitude of 30°. The software automatically declutters the PFD 

leaving only airspeed, heading, attitude, altimeter, VSI tape, 

and the trend vectors. The decluttered information reappears 

when the pitch attitude falls below 25°.

For nose-low unusual attitudes, the chevrons are displayed 

when the pitch exceeds 15° nose-down. If the pitch continues 

to decrease, the unusual attitude recovery protection declutters the screen at 20° nose-down. The decluttered 

information reappears when the pitch increases above 15°.

Additionally, there are bank limits that trigger the unusual 

attitude protection. If the aircraft’s bank increases beyond 

60°, a continuation of the roll index occurs to indicate the 

shortest direction to roll the wings back to level. At 65°, the 

PFD de-clutters. All information reappears when the bank 

decreases below 60°.

In Figure 7-71, the aircraft has rolled past 60°. Observe the 

white line that continues from the end of the bank index. 

This line appears to indicate the shortest distance back to 

wings level. 

When experiencing a failure of the AHRS unit, all unusual 

attitude protection is lost. The failure of the AHRS results 

in the loss of all heading and attitude indications on the PFD. 

In addition, all modes of the autopilot, except for roll and 

altitude hold, are lost.

The following picture series represents how important this 

technology is in increasing situational awareness, and how 

critical it is in improving safety.

Figure 7-72 shows the unusual attitude protection with valid 

AHRS and air data computer (ADC) inputs. The bright red 

chevrons pointing down to the horizon indicate a nose-high 

unusual attitude that can be easily recognized and corrected.

NOTE: The red chevrons point back to the level pitch attitude. 

The trend indicators show where the airspeed and altitude will 

be in 6 seconds. The trend indicator on the heading indicator 

shows which direction the aircraft is turning. The slip/skid 

indicator clearly shows if the aircraft is coordinated. This 

information helps the pilot determine which type of unusual 

attitude the aircraft has taken. 

Now look at Figure 7-73. The display shows the same 

airspeed as the picture above; however, the AHRS unit has 

failed. The altimeter and the VSI tape are the only clear 

indications that the aircraft is in a nose-high attitude. The 

one key instrument that is no longer present is the slip/skid 

indicator. There is not a standby turn coordinator installed 

in the aircraft for the pilot to reference.

 

The magnetic compass indicates a heading is being 

maintained; however, it is not as useful as a turn coordinator 

or slip/skid indicator.
7-57

GPS ENR 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

ALERTS 

Figure 5-28. Aircraft rolled past 60 degrees. Figure 7-71. Aircraft rolled past 60°.

GPS ENR 

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NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 5-29. Unusual attitude protection with valid AHRS and ADC inputs. Figure 7-72. Unusual attitude protection with valid AHRS.
7-58

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

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TAS 134KT 

OAT 7°C 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

HDG

ATTITUDE FAIL 

HDG 273° CRS 071° 

TRAFFIC

Figure 5-30. AHRS unit failed. Figure 7-73. AHRS unit failed.

Figure 7-74 depicts an AHRS and ADC failure. In this failure 

scenario, there are no indications of the aircraft’s attitude. The 

manufacturer recommends turning on the autopilot, which is 

simply a wing leveler. 

With a failure of the primary instrumentation on the PFD, the 

only references available are the standby instruments. The 

standby instrumentation consists of an analog ASI, attitude 

indicator, altimeter, and magnetic compass. There is no 

standby turn coordinator installed.

In extreme nose-high or nose-low pitch attitudes, as well 

as high bank angles, the analog attitude indicator has the 

potential to tumble, rendering it unusable.

Autopilot Usage

The autopilot is equipped with inputs from a turn coordinator 

installed behind the MFD screen. This turn coordinator is 

installed solely for the use of the autopilot to facilitate the 

roll mode, which is simply a wing leveler. This protection 

is always available, barring a failure of the turn coordinator 

(to aid the pilot if the aircraft attains an unusual attitude).

NOTE: The pilot is not able to gain access to the turn 

coordinator. This instrument is installed behind the MFD 

panel. [Figure 7-75] 

Most EFD equipped aircraft are coming from the factory with 

autopilots installed. However, the purchaser of the aircraft 

can specify if an autopilot is to be installed. Extreme caution 

should be utilized when flying an EFD equipped aircraft 

without an autopilot in IMC with an AHRS and ADC failure.

The autopilot should be utilized to reduce workload, which 

affords the pilot more time to monitor the flight. Utilization 

of the autopilot also decreases the chances of entry into an 

unusual attitude.

Flying an EFD-equipped aircraft without the use of an autopilot 

has been shown to increase workload and decrease situational 

awareness for pilots first learning to flying the new system.

Common Errors Leading to Unusual Attitudes

The following errors have the potential to disrupt a pilot’s 

situational awareness and lead to unusual attitudes.

1. Improper trimming techniques. A failure to keep the 

aircraft trimmed for level flight at all times can turn 

a momentary distraction into an emergency situation 

if the pilot stops cross-checking.

2. Poor crew resource management (CRM) skills. Failure 

to perform all single-pilot resource management 

duties efficiently. A major cause of CRM-related 

accidents comes from the failure of the pilot to 

maintain an organized flight deck. Items that are 

being utilized for the flight portion should be neatly 

arranged for easy access. A disorganized flight deck 

can lead to a distraction that causes the pilot to cease 

cross-checking the instruments long enough to enter 

an unusual attitude.
7-59

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

4100 

OAT 7°C 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

HDG

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TRAFFIC

Figure 5-31. AHRS and ADC failure. Figure 7-74. AHRS ADC failure.

Figure 7-75. This autopilot requires roll information from a turn coordinator.
7-60

3. Fixation is displayed when a pilot focuses far too 

much attention on one instrument because he or 

she perceives something is wrong or a deviation is 

occurring. It is important for the instrument pilot to 

remember that a cross-check of several instruments 

for corroboration is more valuable than checking a 

single instrument.

4. Attempting to recover by sensory sensations other 

than sight. Recovery by instinct almost always leads 

to erroneous corrections due to the illusions that are 

prevalent during instrument flight.

5. Failure to practice basic attitude instrument flying. 

When a pilot does not fly instrument approach 

procedures or even basic attitude instrument flying 

maneuvers for long periods of time, skill levels 

diminish. Pilots should avoid flying in IMC if they are 

not proficient. They should seek a qualified instructor to 

receive additional instruction prior to entry into IMC.

Instrument Takeoff

The reason for learning to fly by reference to instruments 

alone is to expand a pilot’s abilities to operate an aircraft 

in visibility less than VFR. Another valuable maneuver 

to learn is the instrument takeoff. This maneuver requires 

the pilot to maneuver the aircraft during the takeoff roll by 

reference to flight instruments alone with no outside visual 

reference. With practice, this maneuver becomes as routine 

as a standard rate turn. 

The reason behind practicing instrument takeoffs is to reduce 

the disorientation that can occur during the transitional phase 

of quickly moving the eyes from the outside references inside 

to the flight instruments.

One EFD system currently offers what is trademarked as 

synthetic vision. Synthetic vision is a three-dimensional 

computer-generated representation of the terrain that lies 

ahead of the aircraft. The display shows runways as well 

as a depiction of the terrain features based on a GPS terrain 

database. Similar to a video game, the display generates a 

runway the pilot can maneuver down in order to maintain 

directional control. As long as the pilot tracks down the 

computer-generated runway, the aircraft remains aligned 

with the actual runway.

Not all EFD systems have such an advanced visioning system. 

With all other systems, the pilot needs to revert to the standard 

procedures for instrument takeoffs. Each aircraft may require 

a modification to the maneuver; therefore, always obtain 

training on any new equipment to be used.

In order to accomplish an instrument takeoff, the aircraft 

needs to be maneuvered on the centerline of the runway 

facing the direction of departure with the nose or tail wheel 

straight. Assistance from the instructor may be necessary 

if the pilot has been taxiing while wearing a view limiting 

device. Lock the tail wheel, if so equipped, and hold the 

brakes firmly to prevent the aircraft from creeping. Crosscheck the heading indicator on the PFD with the magnetic 

compass and adjust for any deviations noted on the compass 

card. Set the heading to the nearest 5 degree mark closest 

to the runway heading. This allows the pilot to quickly 

detect any deviations from the desired heading and allows 

prompt corrective actions during the takeoff roll. Using the 

omnibearing select (OBS) mode on the GPS, rotate the OBS 

selector until the needle points to the runway heading. This 

adds additional situational awareness during the takeoff roll. 

Smoothly apply power to generate sufficient rudder authority 

for directional control. Release the brakes and continue to 

advance the power to the takeoff setting.

As soon as the brakes are released, any deviation in heading 

needs to be corrected immediately. Avoid using brakes to 

control direction as this increases the takeoff roll, as well as 

provides the potential of overcontrolling the aircraft. 

Continuously cross-check the ASI and the heading indicator 

as the aircraft accelerates. As the aircraft approaches 15-25 

knots below the rotation speed, smoothly apply aft elevator 

pressure to increase the pitch attitude to the desired takeoff 

attitude (approximately 7° for most small airplanes). With 

the pitch attitude held constant, continue to cross-check the 

flight instruments and allow the aircraft to fly off of the 

runway. Do not pull the aircraft off of the runway. Pulling 

the aircraft off of the runway imposes left turning tendencies 

due to P-Factor, which will yaw the aircraft to the left and 

destabilize the takeoff.

Maintain the desired pitch and bank attitudes by referencing 

the attitude indicator and cross-check the VSI tape for an 

indication of a positive rate of climb. Take note of the magenta 

6-second altimeter trend indicator. The trend should show 

positive. Barring turbulence, all trend indications should 

be stabilized. The airspeed trend indicator should not be 

visible at this point if the airspeed is being held constant. An 

activation of the airspeed trend indicator shows that the pitch 

attitude is not being held at the desired value and, therefore, 

the airspeed is changing. The desired performance is to be 

climbing at a constant airspeed and vertical speed rate. Use 

the ASI as the primary instrument for the pitch indication.
7-61

Once the aircraft has reached a safe altitude (approximately 

100 feet for insufficient runway available for landing should 

an engine failure occur) retract the landing gear and flaps while 

referencing the ASI and attitude indicator to maintain the 

desired pitch. As the configuration is changed, an increase in 

aft control pressure is needed in order to maintain the desired 

pitch attitude. Smoothly increase the aft control pressure to 

compensate for the change in configuration. Anticipate the 

changes and increase the rate of cross-check. The airspeed tape 

and altitude tape increases while the VSI tape is held constant. 

Allow the aircraft to accelerate to the desired climb speed. 

Once the desired climb speed is reached, reduce the power to 

the climb power setting as printed in the POH/AFM. Trim the 

aircraft to eliminate any control pressures. 

Common Errors in Instrument Takeoffs

Common errors associated with the instrument takeoff 

include, but are not limited to, the following:

1. Failure to perform an adequate flight deck check 

before the takeoff. Pilots have attempted instrument 

takeoff with inoperative airspeed indicators (pitot 

tube obstructed), controls locked, and numerous 

other oversights due to haste or carelessness. It is 

imperative to cross-check the ASI as soon as possible. 

No airspeed is indicated until 20 knots of true airspeed 

is generated in some systems.

2. Improper alignment on the runway. This may result 

from improper brake applications, allowing the 

airplane to creep after alignment, or from alignment 

with the nosewheel or tailwheel cocked. In any case, 

the result is a built-in directional control problem as 

the takeoff starts.

3. Improper application of power. Abrupt applications 

of power complicate directional control. Power 

should be applied in a smooth and continuous 

manner to arrive at the takeoff power setting within 

approximately 3 seconds.

4. Improper use of brakes. Incorrect seat or rudder pedal 

adjustment, with feet in an uncomfortable position, 

frequently causes inadvertent application of brakes 

and excessive heading changes.

5. Overcontrolling rudder pedals. This fault may be 

caused by late recognition of heading changes, tension 

on the controls, misinterpretation of the heading 

indicator (and correcting in the wrong direction), 

failure to appreciate changing effectiveness of rudder 

control as the aircraft accelerates, and other factors. If 

heading changes are observed and corrected instantly 

with small movement of the rudder pedals, swerving 

tendencies can be reduced.

6. Failure to maintain attitude after becoming airborne. 

If the pilot reacts to seat-of-the-pants sensations when 

the airplane lifts off, pitch control is guesswork. 

The pilot may either allow excessive pitch or apply 

excessive forward-elevator pressure, depending on 

the reaction to trim changes. 

7. Inadequate cross-check. Fixations are likely during the 

trim changes, attitude changes, gear and flap retractions, 

and power changes. Once an instrument or a control 

input is applied, continue the cross-check and note the 

effect control during the next cross-check sequence.

8. Inadequate interpretation of instruments. Failure 

to understand instrument indications immediately 

indicates that further study of the maneuver is necessary.

Basic Instrument Flight Patterns

After attaining a reasonable degree of proficiency in basic 

maneuvers, apply these skills to the various combinations 

of individual maneuvers. The practice flight patterns, 

beginning on page 7-30, are directly applicable to operational 

instrument flying. 
7-62
8-1

Introduction

Attitude instrument flying in helicopters is essentially visual 

flying with the flight instruments substituted for the various 

reference points on the helicopter and the natural horizon. 

Control changes, required to produce a given attitude by 

reference to instruments, are identical to those used in 

helicopter visual flight rules (VFR) flight, and pilot thought 

processes are the same. Basic instrument training is intended to 

be a building block toward attaining an instrument rating. 

Helicopter Attitude 

Instrument Flying

Chapter 8
8-2

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Start radial scan pattern

Figure 8-1. A radial scan pattern of the flight instruments enables the helicopter pilot to fully comprehend the condition and direction 

of the helicopter.

Flight Instruments

When flying a helicopter with reference to the flight 

instruments, proper instrument interpretation is the basis 

for aircraft control. Skill, in part, depends on understanding 

how a particular instrument or system functions, including 

its indications and limitations (see Chapter 5, Flight 

Instruments). With this knowledge, a pilot can quickly 

interpret an instrument indication and translate that 

information into a control response. 

Instrument Flight

To achieve smooth, positive control of the helicopter during 

instrument flight, three fundamental skills must be developed. 

They are instrument cross-check, instrument interpretation, 

and aircraft control. 

Instrument Cross-Check

Cross-checking, sometimes referred to as scanning, is the 

continuous and logical observation of instruments for attitude 

and performance information. In attitude instrument flying, 

an attitude is maintained by reference to the instruments, 

which produces the desired result in performance. Due to 

human error, instrument error, and helicopter performance 

differences in various atmospheric and loading conditions, 

it is difficult to establish an attitude and have performance 

remain constant for a long period of time. These variables 

make it necessary to constantly check the instruments and 

make appropriate changes in the helicopter’s attitude. The 

actual technique may vary depending on what instruments 

are installed and where they are installed, as well as 

pilot experience and proficiency level. This discussion 

concentrates on the six basic flight instruments. [Figure 8-1] 

At first, there may be a tendency to cross-check rapidly, 

looking directly at the instruments without knowing exactly 

what information is needed. However, with familiarity and 

practice, the instrument cross-check reveals definite trends 

during specific flight conditions. These trends help a pilot 

control the helicopter as it makes a transition from one flight 

condition to another. 

When full concentration is applied to a single instrument, a 

problem called fixation is encountered. This results from a 

natural human inclination to observe a specific instrument 

carefully and accurately, often to the exclusion of other 

instruments. Fixation on a single instrument usually results 

in poor control. For example, while performing a turn, there 

is a tendency to watch only the turn-and-slip indicator instead 

of including other instruments in the cross-check. This 

fixation on the turn-and-slip indicator often leads to a loss of 

altitude through poor pitch-and-bank control. Look at each 
8-3

instrument only long enough to understand the information 

it presents, and then proceed to the next one. Similarly, too 

much emphasis can be placed on a single instrument, instead 

of relying on a combination of instruments necessary for 

helicopter performance information. This differs from fixation 

in that other instruments are included in a cross-check, but too 

much attention is placed on one particular instrument. 

During performance of a maneuver, there is sometimes 

a failure to anticipate significant instrument indications 

following attitude changes. For example, during level off 

from a climb or descent, a pilot may concentrate on pitch 

control, while forgetting about heading or roll information. 

This error, called omission, results in erratic control of 

heading and bank. 

In spite of these common errors, most pilots can adapt well to 

flight by instrument reference after instruction and practice. 

Many find that they can control the helicopter more easily 

and precisely by instruments. 

Instrument Interpretation

The flight instruments together give a picture of what is 

happening. No one instrument is more important than the 

next; however, during certain maneuvers or conditions, 

those instruments that provide the most pertinent and useful 

information are termed primary instruments. Those which 

back up and supplement the primary instruments are termed 

supporting instruments. For example, since the attitude 

indicator is the only instrument that provides instant and 

direct aircraft attitude information, it should be considered 

primary during any change in pitch or bank attitude. After 

the new attitude is established, other instruments become 

primary, and the attitude indicator usually becomes the 

supporting instrument. 

Aircraft Control

Controlling a helicopter is the result of accurately interpreting 

the flight instruments and translating these readings 

into correct control responses. Aircraft control involves 

adjustment to pitch, bank, power, and trim in order to achieve 

a desired flight path. 

Pitch attitude control is controlling the movement of 

the helicopter about its lateral axis. After interpreting 

the helicopter’s pitch attitude by reference to the pitch 

instruments (attitude indicator, altimeter, airspeed 

indicator, and vertical speed indicator (VSI)), cyclic control 

adjustments are made to affect the desired pitch attitude. In 

this chapter, the pitch attitudes depicted are approximate 

and vary with different helicopters. 

Bank attitude control is controlling the angle made by the 

lateral tilt of the rotor and the natural horizon or the movement 

of the helicopter about its longitudinal axis. After interpreting 

the helicopter’s bank instruments (attitude indicator, heading 

indicator, and turn indicator), cyclic control adjustments are 

made to attain the desired bank attitude. 

Power control is the application of collective pitch with 

corresponding throttle control, where applicable. In straightand-level flight, changes of collective pitch are made to 

correct for altitude deviation if the error is more than 100 

feet or the airspeed is off by more than 10 knots. If the error 

is less than that amount, a pilot should use a slight cyclic 

climb or descent. 

In order to fly a helicopter by reference to the instruments, it 

is important to know the approximate power settings required 

for a particular helicopter in various load configurations and 

flight conditions. 

Trim, in helicopters, refers to the use of the cyclic centering 

button, if the helicopter is so equipped, to relieve all 

possible cyclic pressures. Trim also refers to the use of pedal 

adjustment to center the ball of the turn indicator. Pedal trim 

is required during all power changes. 

The proper adjustment of collective pitch and cyclic friction 

helps a pilot relax during instrument flight. Friction should 

be adjusted to minimize overcontrolling and to prevent 

creeping, but not applied to such a degree that control 

movement is limited. In addition, many helicopters equipped 

for instrument flight contain stability augmentation systems 

or an autopilot to help relieve pilot workload. 

Straight-and-Level Flight

Straight-and-level unaccelerated flight consists of maintaining 

the desired altitude, heading, airspeed, and pedal trim. 

Pitch Control

The pitch attitude of a helicopter is the angular relation of 

its longitudinal axis to the natural horizon. If available, the 

attitude indicator is used to establish the desired pitch attitude. 

In level flight, pitch attitude varies with airspeed and center of 

gravity (CG). At a constant altitude and a stabilized airspeed, 

the pitch attitude is approximately level. [Figure 8-2] 

Attitude Indicator

The attitude indicator gives a direct indication of the pitch 

attitude of the helicopter. In visual flight, attain the desired 

pitch attitude by using the cyclic to raise and lower the nose 
8-4

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Figure 6-3. The initial pitch correction at normal 

cruise is one bar width. Figure 8-3. The initial pitch correction at normal cruise is one bar 

width or less.

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Figure 8-2. The flight instruments for pitch control are the airspeed indicator, attitude indicator, altimeter, and vertical speed indicator.

of the helicopter in relation to the natural horizon. During 

instrument flight, follow exactly the same procedure in 

raising or lowering the miniature aircraft in relation to the 

horizon bar. 

There is some delay between control application and resultant 

instrument change. This is the normal control lag in the 

helicopter and should not be confused with instrument lag. 

The attitude indicator may show small misrepresentations 

of pitch attitude during maneuvers involving acceleration, 

deceleration, or turns. This precession error can be detected 

quickly by cross-checking the other pitch instruments. 

If the miniature aircraft is properly adjusted on the ground, it 

may not require readjustment in flight. If the miniature aircraft 

is not on the horizon bar after level off at normal cruising 

airspeed, adjust it as necessary while maintaining level flight 

with the other pitch instruments. Once the miniature aircraft 

has been adjusted in level flight at normal cruising airspeed, 

leave it unchanged so it gives an accurate picture of pitch 

attitude at all times. 

When making initial pitch attitude corrections to maintain 

altitude, the changes of attitude should be small and smoothly 

applied. The initial movement of the horizon bar should not 

exceed one bar width high or low. [Figure 8-3] If a further 

adjustment is required, an additional correction of onehalf bar normally corrects any deviation from the desired 

altitude. This one-and-one-half bar correction is normally the 

maximum pitch attitude correction from level flight attitude. 

After making the correction, cross-check the other pitch 

instruments to determine whether the pitch attitude change 

is sufficient. If additional correction is needed to return to 

altitude, or if the airspeed varies more than 10 knots from 

that desired, adjust the power. 

Altimeter

The altimeter gives an indirect indication of the pitch 

attitude of the helicopter in straight-and-level flight. Since 

the altitude should remain constant in level flight, deviation 

from the desired altitude indicates a need for a change in 

pitch attitude and power as necessary. When losing altitude, 

raise the pitch attitude and adjust power as necessary. When 

gaining altitude, lower the pitch attitude and adjust power 

as necessary. Indications for power changes are explained 

in the next paragraph.

The rate at which the altimeter moves helps to determine pitch 

attitude. A very slow movement of the altimeter indicates 
8-5

a small deviation from the desired pitch attitude, while a 

fast movement of the altimeter indicates a large deviation 

from the desired pitch attitude. Make any corrective action 

promptly with small control changes. Also, remember that 

movement of the altimeter should always be corrected by 

two distinct changes. The first is a change of attitude to stop 

the altimeter movement; the second is a change of attitude to 

return smoothly to the desired altitude. If altitude and airspeed 

are more than 100 feet and 10 knots low, respectively, apply 

power in addition to an increase of pitch attitude. If the 

altitude and airspeed are high by more than 100 feet and 10 

knots, reduce power and lower the pitch attitude. 

There is a small lag in the movement of the altimeter; 

however, for all practical purposes, consider that the altimeter 

gives an immediate indication of a change or a need for 

change in pitch attitude. Since the altimeter provides the 

most pertinent information regarding pitch in level flight, it 

is considered primary for pitch. 

Vertical Speed Indicator (VSI)

The VSI gives an indirect indication of the pitch attitude of 

the helicopter and should be used in conjunction with the 

other pitch instruments to attain a high degree of accuracy 

and precision. The instrument indicates zero when in level 

flight. Any movement of the needle from the zero position 

shows a need for an immediate change in pitch attitude to 

return it to zero. Always use the VSI in conjunction with 

the altimeter in level flight. If a movement of the VSI is 

detected, immediately use the proper corrective measures 

to return it to zero. If the correction is made promptly, there 

is usually little or no change in altitude. If the needle of the 

VSI does not indicate zero, the altimeter indicates a gain or 

loss of altitude. 

The initial movement of the vertical speed needle is 

instantaneous and indicates the trend of the vertical movement 

of the helicopter. A period of time is necessary for the VSI to 

reach its maximum point of deflection after a correction has 

been made. This time element is commonly referred to as 

instrument lag. The lag is directly proportional to the speed 

and magnitude of the pitch change. When employing smooth 

control techniques and small adjustments in pitch attitude are 

made, lag is minimized, and the VSI is easy to interpret. 

Overcontrolling can be minimized by first neutralizing the 

controls and allowing the pitch attitude to stabilize, then 

readjusting the pitch attitude by noting the indications of the 

other pitch instruments. 

Occasionally, the VSI may be slightly out of calibration. 

This could result in the instrument indicating a slight climb 

or descent even when the helicopter is in level flight. If the 

instrument cannot be calibrated properly, this error must be 

taken into consideration when using the VSI for pitch control. 

For example, if a descent of 100 feet per minute (fpm) is the 

vertical speed indication when the helicopter is in level flight, 

use that indication as level flight. Any deviation from that 

reading would indicate a change in attitude. 

Airspeed Indicator

The airspeed indicator gives an indirect indication of 

helicopter pitch attitude. With a given power setting and 

pitch attitude, the airspeed remains constant. If the airspeed 

increases, the nose is too low and should be raised. If 

the airspeed decreases, the nose is too high and should 

be lowered. A rapid change in airspeed indicates a large 

change in pitch attitude, and a slow change in airspeed 

indicates a small change in pitch attitude. There is very little 

lag in the indications of the airspeed indicator. If, while 

making attitude changes, there is some lag between control 

application and change of airspeed, it is most likely due to 

cyclic control lag. Generally, a departure from the desired 

airspeed, due to an inadvertent pitch attitude change, also 

results in a change in altitude. For example, an increase in 

airspeed due to a low pitch attitude results in a decrease 

in altitude. A correction in the pitch attitude regains both 

airspeed and altitude. 

Bank Control

The bank attitude of a helicopter is the angular relation of 

its lateral axis to the natural horizon. To maintain a straight 

course in visual flight, keep the lateral axis of the helicopter 

level with the natural horizon. Assuming the helicopter is in 

coordinated flight, any deviation from a laterally level attitude 

produces a turn. [Figure 8-4]

Attitude Indicator

The attitude indicator gives a direct indication of the bank 

attitude of the helicopter. For instrument flight, the miniature 

aircraft and the horizon bar of the attitude indicator are 

substituted for the actual helicopter and the natural horizon. 

Any change in bank attitude of the helicopter is indicated 

instantly by the miniature aircraft. For proper interpretation 

of this instrument, imagine being in the miniature aircraft. If 

the helicopter is properly trimmed and the rotor tilts, a turn 

begins. The turn can be stopped by leveling the miniature 

aircraft with the horizon bar. The ball in the turn-and-slip 

indicator should always be kept centered through proper 

pedal trim.

The angle of bank is indicated by the pointer on the banking 

scale at the top of the instrument. Small bank angles, which 

may not be seen by observing the miniature aircraft, can 

easily be determined by referring to the banking scale pointer. 
8-6

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0° bank

30° bank

45° bank

60° bank

90° bank

Banking scale pointer

Banking pointer

Horizon

Miniature aircraft

Figure 8-5. The banking scale at the top of the attitude indicator indicates varying degrees of bank. In this example, the helicopter is 

banked approximately 15° to the right.

Figure 8-4. The flight instruments used for bank control are the attitude, heading, and turn indicators.

A O M 

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Figure 6-4. The Bank Instruments. 

Pitch-and-bank attitudes can be determined simultaneously 

on the attitude indicator. Even though the miniature aircraft 

is not level with the horizon bar, pitch attitude can be 

established by observing the relative position of the miniature 

aircraft and the horizon bar. [Figure 8-5]

The attitude indicator may show small misrepresentations 

of bank attitude during maneuvers that involve turns. This 

precession error can be detected immediately by closely 

cross-checking the other bank instruments during these 

maneuvers. Precession is normally noticed when rolling 

out of a turn. If, upon completion of a turn, the miniature 

aircraft is level and the helicopter is still turning, make a 

small change of bank attitude to center the turn needle and 

stop the movement of the heading indicator. 

Heading Indicator

In coordinated flight, the heading indicator gives an indirect 

indication of a helicopter’s bank attitude. When a helicopter is 

banked, it turns. When the lateral axis of a helicopter is level, 

it flies straight. Therefore, in coordinated flight when the 

heading indicator shows a constant heading, the helicopter is 

level laterally. A deviation from the desired heading indicates 

a bank in the direction the helicopter is turning. A small angle 

of bank is indicated by a slow change of heading; a large angle 

of bank is indicated by a rapid change of heading. If a turn 

is noticed, apply opposite cyclic until the heading indicator 
8-7

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Figure 8-6. Coordinated flight is indicated by centering of the ball. Turn Indicator A - Power is added to increase airspeed, nose up and yaws to the right. 

indicates the desired heading, simultaneously ensuring the 

ball is centered. When making the correction to the desired 

heading, do not use a bank angle greater than that required 

to achieve a standard rate turn. In addition, if the number 

of degrees of change is small, limit the bank angle to the 

number of degrees to be turned. Bank angles greater than 

these require more skill and precision in attaining the desired 

results. During straight-and-level flight, the heading indicator 

is the primary reference for bank control. 

Turn Indicator

During coordinated flight, the needle of the turn-and-slip 

indicator gives an indirect indication of the bank attitude 

of the helicopter. When the needle is displaced from the 

vertical position, the helicopter is turning in the direction of 

the displacement. Thus, if the needle is displaced to the left, 

the helicopter is turning left. Bringing the needle back to 

the vertical position with the cyclic produces straight flight. 

A close observation of the needle is necessary to accurately 

interpret small deviations from the desired position. 

Cross-check the ball of the turn-and-slip indicator to 

determine if the helicopter is in coordinated flight. 

[Figure 8-6] If the rotor is laterally level and pedal pressure 

properly compensates for torque, the ball remains in the 

center. To center the ball, level the helicopter laterally by 

reference to the other bank instruments, then center the ball 

with pedal trim. Torque correction pressures vary as power 

changes are made. Always check the ball after such changes. 

Common Errors During Straight-and-Level Flight

1. Failure to maintain altitude 

2. Failure to maintain heading 

3. Overcontrolling pitch and bank during corrections 

4. Failure to maintain proper pedal trim 

5. Failure to cross-check all available instruments 

Power Control During Straight-and-Level Flight

Establishing specific power settings is accomplished through 

collective pitch adjustments and throttle control, where 

necessary. For reciprocating-powered helicopters, power 

indication is observed on the manifold pressure gauge. 

For turbine-powered helicopters, power is observed on the 

torque gauge. (Although most instrument flight rules (IFR)-

certified helicopters are turbine powered, depictions within 

this chapter use a reciprocating-powered helicopter as this 

is where training is most likely conducted.) 

At any given airspeed, a specific power setting determines 

whether the helicopter is in level flight, in a climb, or in a 

descent. For example, cruising airspeed maintained with 

cruising power results in level flight. If a pilot increases the 

power setting and holds the airspeed constant, the helicopter 

climbs. Conversely, if the pilot decreases power and holds 

the airspeed constant, the helicopter descends. 
8-8

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20

I0 I0

I0 I0

20 20

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

 6-7a Flight instrument indications in straight-and-level flight with power increasing. Figure 8-7. Flight instrument indications in straight-and-level flight with power increasing.

If the altitude is held constant, power determines the airspeed. 

For example, at a constant altitude, cruising power results 

in cruising airspeed. Any deviation from the cruising power 

setting results in a change of airspeed. When power is added 

to increase airspeed, the nose of the helicopter pitches up and 

yaws to the right in a helicopter with a counterclockwise main 

rotor blade rotation. [Figure 8-7] When power is reduced 

to decrease airspeed, the nose pitches down and yaws to the 

left. [Figure 8-8] The yawing effect is most pronounced 

in single-rotor helicopters and is absent in helicopters with 

counter-rotating rotors. To counteract the yawing tendency 

of the helicopter, apply pedal trim during power changes. 

To maintain a constant altitude and airspeed in level flight, 

coordinate pitch attitude and power control. The relationship 

between altitude and airspeed determines the need for a 

change in power and/or pitch attitude. If the altitude is 

constant and the airspeed is high or low, change the power to 

obtain the desired airspeed. During the change in power, make 

an accurate interpretation of the altimeter, then counteract 

any deviation from the desired altitude by an appropriate 

change of pitch attitude. If the altitude is low and the airspeed 

is high, or vice versa, a change in pitch attitude alone may 

return the helicopter to the proper altitude and airspeed. If 

both airspeed and altitude are low, or if both are high, changes 

in both power and pitch attitude are necessary.

To make power control easy when changing airspeed, it is 

necessary to know the approximate power settings for the 

various airspeeds at which the helicopter is flown. When the 

airspeed is to be changed by any appreciable amount, adjust 

the power so that it is over or under that setting necessary 

to maintain the new airspeed. As the power approaches the 

desired setting, include the manifold pressure in the crosscheck to determine when the proper adjustment has been 

accomplished. As the airspeed is changing, adjust the pitch 

attitude to maintain a constant altitude. A constant heading 

should be maintained throughout the change. As the desired 

airspeed is approached, adjust power to the new cruising 

power setting and further adjust pitch attitude to maintain 

altitude. The instrument indications for straight-and-level 

flight at normal cruise and during the transition from normal 

cruise to slow cruise are illustrated in Figures 8-9 and 8-10. 

After the airspeed stabilizes at slow cruise, the attitude 

indicator shows an approximate level pitch attitude. 

The altimeter is the primary pitch instrument during level 

flight, whether flying at a constant airspeed or during a 

change in airspeed. Altitude should not change during 

airspeed transitions, and the heading indicator remains the 

primary bank instrument. Whenever the airspeed is changed 

by an appreciable amount, the manifold pressure gauge is 

momentarily the primary instrument for power control. 

When the airspeed approaches the desired reading, the 

airspeed indicator again becomes the primary instrument 

for power control. 
8-9

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20

I0 I0

I0 I0

20 20

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

 6-7b Flight instrument indications in straight-and-level flight with power decreasing. Figure 8-8. Flight instrument indications in straight-and-level flight with power decreasing.

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20 

I0 I0

I0 I0

20 20 

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

Supporting pitch and bank Primary pitch

Primary power Supporting bank Primary bank Supporting pitch

Remains constant

Figure 6-6. Flight instrument indications in straight-and level flight at normal cruise speed. Figure 8-9. Flight instrument indications in straight-and-level flight at normal cruise speed.
8-10

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20

I0 I0

I0 I0

20 20

STBY PWR TEST 

Supporting pitch and bank Primary pitch

Supporting bank Primary bank Supporting pitch

Primary power as airspeed

approaches desired value

Remains constant

Figure 6-7. Flight instrument indications in straight-and level flight with airspeed decreasing. Figure 8-10. Flight instrument indications in straight-and-level flight with airspeed decreasing.

increase power to the climb power setting and adjust pitch 

attitude to the approximate climb attitude. A helicopter may 

or may not have an exact “climb attitude.” To slow down 

to climb (versus cruise) airspeed, the nose must be raised. 

Depending on power and horizontal stabilizer configuration 

and effectiveness, the nose may be level during an established 

climb or slightly nose high. Many helicopters are very capable 

of climbing and never raising the nose. A short deceleration 

period may be necessary to slow to a more efficient climb 

airspeed, but the attitude indicator is often level after 

the climb is stabilized. The increase in power causes the 

helicopter to start climbing and only very slight back cyclic 

pressure is needed to complete the change from level to climb 

attitude. The attitude indicator should be used to accomplish 

the pitch change. If the transition from level flight to a climb 

is smooth, the VSI shows an immediate upward trend and 

then stops at a rate appropriate to the stabilized airspeed and 

attitude. Primary and supporting instruments for climb entry 

are illustrated in Figure 8-11. 

When the helicopter stabilizes at a constant airspeed and 

attitude, the airspeed indicator becomes primary for pitch. 

The manifold pressure continues to be primary for power and 

should be monitored closely to determine if the proper climb 

power setting is being maintained. Primary and supporting 

instruments for a stabilized constant airspeed climb are shown 

in Figure 8-12. 

To produce straight-and-level flight, the cross-check of the 

pitch-and-bank instruments should be combined with the 

power control instruments. With a constant power setting, a 

normal cross-check should be satisfactory. When changing 

power, the speed of the cross-check must be increased to 

cover the pitch and bank instruments adequately. This is 

necessary to counteract any deviations immediately. 

Common Errors During Airspeed Changes

1. Improper use of power 

2. Overcontrolling pitch attitude 

3. Failure to maintain heading 

4. Failure to maintain altitude 

5. Improper pedal trim 

Straight Climbs (Constant Airspeed and 

Constant Rate)

For any power setting and load condition, there is only 

one airspeed that gives the most efficient rate of climb. 

To determine this, consult the climb data for the type of 

helicopter being flown. The technique varies according to 

the airspeed on entry and whether a constant airspeed or 

constant rate climb is made. 

Entry

To enter a constant airspeed climb from cruise airspeed when 

the climb speed is lower than cruise speed, simultaneously 
8-11

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20

I0 I0

I0 I0

20 20

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

Primary pitch

Supporting pitch and bank

Supporting bank Primary bank Supporting pitch

Remains constant

Primary power

Primary pitch

Figure 6-9. Flight instrument indications in a stabilized, constant-airspeed climb. 

Figure 8-11. Flight instrument indications during climb entry for a constant-airspeed climb.

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20

I0 I0

I0 I0

20 20

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

Primary pitch

Supporting pitch and bank

Supporting bank Primary bank Supporting pitch

Remains constant

Primary power

Primary pitch

Figure 6-9. Flight instrument indications in a stabilized, constant-airspeed climb. Figure 8-12. Flight instrument indications in a stabilized constant-airspeed climb.
8-12

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20 

I0 I0

I0 I0

20 20 

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

Primary power

Supporting direct pitch and bank

Supporting bank Primary bank Primary pitch

Remains constant

Figure 6-10. Flight instrument indications in a stabilized, constant-rate climb. Figure 8-13. Flight instrument indications in a stabilized constant-rate climb.

The technique and procedures for entering a constant rate climb 

are very similar to those previously described for a constant 

airspeed climb. For training purposes, a constant rate climb is 

entered from climb airspeed. Use the rate appropriate for the 

particular helicopter being flown. Normally, in helicopters with 

low climb rates, 500 fpm is appropriate. In helicopters capable 

of high climb rates, use a rate of 1,000 fpm. 

To enter a constant rate climb, increase power to the 

approximate setting for the desired rate. As power is applied, 

the airspeed indicator is primary for pitch until the vertical 

speed approaches the desired rate. At this time, the VSI 

becomes primary for pitch. Change pitch attitude by reference 

to the attitude indicator to maintain the desired vertical speed. 

When the VSI becomes primary for pitch, the airspeed 

indicator becomes primary for power. [Figure 8-13] Adjust 

power to maintain desired airspeed. Pitch attitude and power 

corrections should be closely coordinated. To illustrate this, 

if the vertical speed is correct but the airspeed is low, add 

power. As power is increased, it may be necessary to lower 

the pitch attitude slightly to avoid increasing the vertical rate. 

Adjust the pitch attitude smoothly to avoid overcontrolling. 

Small power corrections are usually sufficient to bring the 

airspeed back to the desired indication. 

Level Off

The level off from a constant airspeed climb must be started 

before reaching the desired altitude. Although the amount 

of lead varies with the type of helicopter being flown and 

pilot technique, the most important factor is vertical speed. 

As a rule of thumb, use 10 percent of the vertical velocity 

as the lead point. For example, if the rate of climb is 500 

fpm, initiate the level off approximately 50 feet before the 

desired altitude. When the proper lead altitude is reached, the 

altimeter becomes primary for pitch. Adjust the pitch attitude 

to the level flight attitude for that airspeed. Cross-check the 

altimeter and VSI to determine when level flight has been 

attained at the desired altitude. If cruise airspeed is higher 

than climb airspeed, leave the power at the climb power 

setting until the airspeed approaches cruise airspeed, and 

then reduce it to the cruise power setting. The level off from 

a constant rate climb is accomplished in the same manner as 

the level off from a constant airspeed climb. 

Straight Descents (Constant Airspeed 

and Constant Rate)

A descent may be performed at any normal airspeed the 

helicopter can attain, but the airspeed must be determined 

prior to entry. The technique is determined by the type of 

descent, a constant airspeed, or a constant rate. 

Entry

If airspeed is higher than descending airspeed, and a constant 

airspeed descent is desired, reduce power to a descent 

power setting and maintain a constant altitude using cyclic 

pitch control. This slows the helicopter. As the helicopter 
8-13

approaches the descending airspeed, the airspeed indicator 

becomes primary for pitch and the manifold pressure is 

primary for power. Holding the airspeed constant causes the 

helicopter to descend. For a constant rate descent, reduce the 

power to the approximate setting for the desired rate. If the 

descent is started at the descending airspeed, the airspeed 

indicator is primary for pitch until the VSI approaches the 

desired rate. At this time, the VSI becomes primary for 

pitch, and the airspeed indicator becomes primary for power. 

Coordinate power and pitch attitude control as previously 

described on page 8-10 for constant rate climbs. 

Level Off

The level off from a constant airspeed descent may be 

made at descending airspeed or at cruise airspeed, if this is 

higher than descending airspeed. As in a climb level off, the 

amount of lead depends on the rate of descent and control 

technique. For a level off at descending airspeed, the lead 

should be approximately 10 percent of the vertical speed. At 

the lead altitude, simultaneously increase power to the setting 

necessary to maintain descending airspeed in level flight. At 

this point, the altimeter becomes primary for pitch, and the 

airspeed indicator becomes primary for power. 

To level off at an airspeed higher than descending airspeed, 

increase the power approximately 100 to 150 feet prior to 

reaching the desired altitude. The power setting should be that 

which is necessary to maintain the desired airspeed in level 

flight. Hold the vertical speed constant until approximately 

50 feet above the desired altitude. At this point, the altimeter 

becomes primary for pitch and the airspeed indicator becomes 

primary for power. The level off from a constant rate descent 

should be accomplished in the same manner as the level off 

from a constant airspeed descent. 

Common Errors During Straight Climbs and 

Descents

1. Failure to maintain heading 

2. Improper use of power 

3. Poor control of pitch attitude 

4. Failure to maintain proper pedal trim 

5. Failure to level off on desired altitude 

Turns

Turns made by reference to the flight instruments should 

be made at a precise rate. Turns described in this chapter 

are those not exceeding a standard rate of 3° per second 

as indicated on the turn-and-slip indicator. True airspeed 

determines the angle of bank necessary to maintain a standard 

rate turn. A rule of thumb to determine the approximate angle 

of bank required for a standard rate turn is to use 15 percent 

of the airspeed. A simple way to determine this amount is 

to divide the airspeed by 10 and add one-half the result. For 

example, at 60 knots approximately 9° of bank is required 

(60 ÷ 10 = 6, 6 + 3 = 9); at 80 knots approximately 12° of 

bank is needed for a standard rate turn. 

To enter a turn, apply lateral cyclic in the direction of the 

desired turn. The entry should be accomplished smoothly, 

using the attitude indicator to establish the approximate bank 

angle. When the turn indicator indicates a standard rate turn, 

it becomes primary for bank. The attitude indicator now 

becomes a supporting instrument. During level turns, the 

altimeter is primary for pitch, and the airspeed indicator is 

primary for power. Primary and supporting instruments for a 

stabilized standard rate turn are illustrated in Figure 8-14. If 

an increase in power is required to maintain airspeed, slight 

forward cyclic pressure may be required since the helicopter 

tends to pitch up as collective pitch is increased. Apply pedal 

trim, as required, to keep the ball centered. 

To recover to straight-and-level flight, apply cyclic in the 

direction opposite the turn. The rate of roll-out should be the 

same as the rate used when rolling into the turn. As the turn 

recovery is initiated, the attitude indicator becomes primary 

for bank. When the helicopter is approximately level, the 

heading indicator becomes primary for bank as in straightand-level flight. Cross-check the airspeed indicator and ball 

closely to maintain the desired airspeed and pedal trim. 

Turn to a Predetermined Heading

A helicopter turns as long as its lateral axis is tilted; 

therefore, the recovery must start before the desired heading 

is reached. The amount of lead varies with the rate of turn 

and piloting technique. 

As a guide, when making a 3° per second rate of turn, use a 

lead of one-half the bank angle. For example, if using a 12° 

bank angle, use half of that, or 6°, as the lead point prior to the 

desired heading. Use this lead until the exact amount required 

by a particular technique can be determined. The bank angle 

should never exceed the number of degrees to be turned. 

As in any standard rate turn, the rate of recovery should be 

the same as the rate of entry. During turns to predetermined 

headings, cross-check the primary and supporting pitch, bank, 

and power instruments closely. 

Timed Turns

A timed turn is a turn in which the clock and turn-and-slip 

indicator are used to change heading a definite number of 

degrees in a given time. For example, using a standard rate 

turn, a helicopter turns 45° in 15 seconds. Using a half-standard 

rate turn, the helicopter turns 45° in 30 seconds. Timed turns 

can be used if the heading indicator becomes inoperative. 
8-14

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 30 

24 

2I 

I5 I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20 

I0 I0

I0 I0

20 20 

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

Primary bank initially

Supporting pitch

Primary bank as

turn is established

Supporting pitch

Primary pitch

Remains constant

Figure 6-11. Flight instrument indications in a stabilized turn to the left. 

Primary power

Figure 8-14. Flight instrument indications in a standard-rate turn to the left.

Prior to performing timed turns, the turn coordinator should 

be calibrated to determine the accuracy of its indications. 

To do this, establish a standard rate turn by referring to the 

turn-and-slip indicator. Then, as the sweep second hand of 

the clock passes a cardinal point (12, 3, 6, or 9), check the 

heading on the heading indicator. While holding the indicated 

rate of turn constant, note the heading changes at 10-second 

intervals. If the helicopter turns more or less than 30° in 

that interval, a smaller or larger deflection of the needle is 

necessary to produce a standard rate turn. After the turnand-slip indicator has been calibrated during turns in each 

direction, note the corrected deflections, if any, and apply 

them during all timed turns. 

Use the same cross-check and control technique in making 

timed turns that is used to make turns to a predetermined 

heading, but substitute the clock for the heading indicator. 

The needle of the turn-and-slip indicator is primary for 

bank control, the altimeter is primary for pitch control, and 

the airspeed indicator is primary for power control. Begin 

the roll-in when the clock’s second hand passes a cardinal 

point; hold the turn at the calibrated standard rate indication 

or half-standard rate for small changes in heading; then 

begin the roll-out when the computed number of seconds 

has elapsed. If the roll-in and roll-out rates are the same, the 

time taken during entry and recovery need not be considered 

in the time computation. 

If practicing timed turns with a full instrument panel, 

check the heading indicator for the accuracy of the turns. 

If executing turns without the heading indicator, use the 

magnetic compass at the completion of the turn to check turn 

accuracy, taking compass deviation errors into consideration. 

Change of Airspeed in Turns

Changing airspeed in turns is an effective maneuver for 

increasing proficiency in all three basic instrument skills. 

Since the maneuver involves simultaneous changes in all 

components of control, proper execution requires a rapid 

cross-check and interpretation, as well as smooth control. 

Proficiency in the maneuver also contributes to confidence in 

the instruments during attitude and power changes involved 

in more complex maneuvers. 

Pitch and power control techniques are the same as those 

used during airspeed changes in straight-and-level flight. 

As discussed previously, the angle of bank necessary for a 

given rate of turn is proportional to the true airspeed. Since 

the turns are executed at standard rate, the angle of bank 

must be varied in direct proportion to the airspeed change in 

order to maintain a constant rate of turn. During a reduction 

of airspeed, decrease the angle of bank and increase the pitch 

attitude to maintain altitude and a standard rate turn. 
8-15

Altimeter and turn indicator readings should remain constant 

throughout the turn. The altimeter is primary for pitch control, 

and the turn needle is primary for bank control. Manifold 

pressure is primary for power control while the airspeed is 

changing. As the airspeed approaches the new indication, the 

airspeed indicator becomes primary for power control. 

Two methods of changing airspeed in turns may be used. 

In the first method, airspeed is changed after the turn is 

established. In the second method, the airspeed change 

is initiated simultaneously with the turn entry. The first 

method is easier, but regardless of the method used, the rate 

of cross-check must be increased as power is reduced. As 

the helicopter decelerates, check the altimeter and VSI for 

needed pitch changes and the bank instruments for needed 

bank changes. If the needle of the turn-and-slip indicator 

shows a deviation from the desired deflection, change the 

bank. Adjust pitch attitude to maintain altitude. When the 

airspeed approaches that desired, the airspeed indicator 

becomes primary for power control. Adjust the power to 

maintain the desired airspeed. Use pedal trim to ensure the 

maneuver is coordinated. 

Until control technique is very smooth, frequently crosscheck the attitude indicator to keep from overcontrolling 

and to provide approximate bank angles appropriate for the 

changing airspeeds. 

Compass Turns

The use of gyroscopic heading indicators makes heading 

control very easy. However, if the heading indicator fails 

or the helicopter is not equipped with one, use the magnetic 

compass for heading reference. When making compass-only 

turns, a pilot needs to adjust for the lead or lag created by 

acceleration and deceleration errors so that the helicopter rolls 

out on the desired heading. When turning to a heading of north, 

the lead for the roll-out must include the number of degrees 

of latitude plus the lead normally used in recovery from turns. 

During a turn to a south heading, maintain the turn until the 

compass passes south the number of degrees of latitude, minus 

the normal roll-out lead. For example, when turning from an 

easterly direction to north, where the latitude is 30°, start the 

roll-out when the compass reads 37° (30° plus one-half the 

15° angle of bank or whatever amount is appropriate for the 

rate of roll-out). When turning from an easterly direction to 

south, start the roll-out when the magnetic compass reads 

203° (180° plus 30° minus one-half the angle of bank). When 

making similar turns from a westerly direction, the appropriate 

points at which to begin the roll-out would be 323° for a turn 

to north and 157° for a turn to south. 

30° Bank Turn

A turn using 30° of bank is seldom necessary or advisable 

in instrument meteorological conditions (IMC) and is 

considered an unusual attitude in a helicopter. However, it 

is an excellent maneuver to practice to increase the ability to 

react quickly and smoothly to rapid changes of attitude. Even 

though the entry and recovery techniques are the same as for 

any other turn, it is more difficult to control pitch because 

of the decrease in vertical lift as the bank increases. Also, 

because of the decrease in vertical lift, there is a tendency 

to lose altitude and/or airspeed. Therefore, to maintain a 

constant altitude and airspeed, additional power is required. 

Do not initiate a correction, however, until the instruments 

indicate the need for one. During the maneuver, note the 

need for a correction on the altimeter and VSI, check the 

attitude indicator, and then make the necessary adjustments. 

After making a change, check the altimeter and VSI again 

to determine whether or not the correction was adequate. 

Climbing and Descending Turns

For climbing and descending turns, the techniques described 

previously for straight climbs, descents, and standard rate 

turns are combined. For practice, simultaneously turn and 

start the climb or descent. The primary and supporting 

instruments for a stabilized constant airspeed left climbing 

turn are illustrated in Figure 8-15. The level off from a 

climbing or descending turn is the same as the level off from 

a straight climb or descent. To return to straight-and-level 

flight, stop the turn and then level off, or level off and then 

stop the turn, or simultaneously level off and stop the turn. 

During climbing and descending turns, keep the ball of the 

turn indicator centered with pedal trim. 

Common Errors During Turns

1. Failure to maintain desired turn rate 

2. Failure to maintain altitude in level turns 

3. Failure to maintain desired airspeed 

4. Variation in the rate of entry and recovery 

5. Failure to use proper lead in turns to a heading 

6. Failure to properly compute time during timed turns 

7. Failure to use proper leads and lags during the 

compass turns 

8. Improper use of power 

9. Failure to use proper pedal trim 
8-16

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 30 

24 

2I 

I5 I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20

I0 I0

I0 I0

20 20

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

Primary pitch Supporting pitch and bank

Primary bank Supporting pitch

Remains constant

Figure 6-12. Flight instrument indications for a stabilized left climbing turn at a constant airspeed. 

Primary power

Figure 8-15. Flight instrument indications for a stabilized left climbing turn at a constant airspeed.

Unusual Attitudes

Any maneuver not required for normal helicopter instrument 

flight is an unusual attitude and may be caused by any one 

or combination of factors, such as turbulence, disorientation, 

instrument failure, confusion, preoccupation with flight deck 

duties, carelessness in cross-checking, errors in instrument 

interpretation, or lack of proficiency in aircraft control. Due 

to the instability characteristics of the helicopter, unusual 

attitudes can be extremely critical. As soon as an unusual 

attitude is detected, make a recovery to straight-and-level 

flight as soon as possible with a minimum loss of altitude. 

To recover from an unusual attitude, a pilot should correct 

bank-and-pitch attitude and adjust power as necessary. All 

components are changed almost simultaneously, with little 

lead of one over the other. A pilot must be able to perform 

this task with and without the attitude indicator. If the 

helicopter is in a climbing or descending turn, adjust bank, 

pitch, and power. The bank attitude should be corrected 

by referring to the turn-and-slip indicator and attitude 

indicator. Pitch attitude should be corrected by reference to 

the altimeter, airspeed indicator, VSI, and attitude indicator. 

Adjust power by referring to the airspeed indicator and 

manifold pressure. 

Since the displacement of the controls used in recovery from 

unusual attitudes may be greater than those used for normal 

flight, make careful adjustments as straight-and-level flight 

is approached. Cross-check the other instruments closely to 

avoid overcontrolling. 

Common Errors During Unusual Attitude 

Recoveries

1. Failure to make proper pitch correction 

2. Failure to make proper bank correction 

3. Failure to make proper power correction 

4. Overcontrolling pitch and/or bank attitude 

5. Overcontrolling power 

6. Excessive loss of altitude 

Emergencies

Emergencies during instrument flight are handled similarly 

to those occurring during VFR flight. A thorough knowledge 

of the helicopter and its systems, as well as good aeronautical 

knowledge and judgment, is the best preparation for 

emergency situations. Safe operations begin with preflight 

planning and a thorough preflight inspection. Plan a route 

of flight to include adequate landing sites in the event of an 

emergency landing. Make sure all resources, such as maps, 

publications, flashlights, and fire extinguishers, are readily 

available for use in an emergency. 

During any emergency, first fly the aircraft. This means 

ensure the helicopter is under control, and determine 
8-17

emergency landing sites. Then perform the emergency 

checklist memory items, followed by items written in the 

rotorcraft flight manual (RFM). When all these items are 

under control, notify air traffic control (ATC). Declare any 

emergency on the last assigned ATC frequency. If one was 

not issued, transmit on the emergency frequency 121.5. Set 

the transponder to the emergency squawk code 7700. This 

code triggers an alarm or special indicator in radar facilities. 

When experiencing most in-flight emergencies, such as low 

fuel or complete electrical failure, land as soon as possible. 

In the event of an electrical fire, turn off all nonessential 

equipment and land immediately. Some essential electrical 

instruments, such as the attitude indicator, may be required 

for a safe landing. A navigation radio failure may not require 

an immediate landing if the flight can continue safely. In 

this case, land as soon as practical. ATC may be able to 

provide vectors to a safe landing area. For specific details 

on what to do during an emergency, refer to the RFM for 

the helicopter. 

Autorotations

Both straight-ahead and turning autorotations should be 

practiced by reference to instruments. This training ensures 

prompt corrective action to maintain positive aircraft control 

in the event of an engine failure. 

To enter autorotation, reduce collective pitch smoothly to 

maintain a safe rotor RPM and apply pedal trim to keep the 

ball of the turn-and-slip indicator centered. The pitch attitude 

of the helicopter should be approximately level as shown by 

the attitude indicator. The airspeed indicator is the primary 

pitch instrument and should be adjusted to the recommended 

autorotation speed. The heading indicator is primary for bank 

in a straight-ahead autorotation. In a turning autorotation, a 

standard rate turn should be maintained by reference to the 

needle of the turn-and-slip indicator. 

Common Errors During Autorotations

1. Uncoordinated entry due to improper pedal trim 

2. Poor airspeed control due to improper pitch attitude 

3. Poor heading control in straight-ahead autorotations 

4. Failure to maintain proper rotor RPM 

5. Failure to maintain a standard rate turn during turning 

autorotations 

Servo Failure

Most helicopters certified for single-pilot IFR flight are required 

to have autopilots, which greatly reduces pilot workload. If an 

autopilot servo fails, however, resume manual control of the 

helicopter. The amount of workload increase depends on which 

servo fails. If a cyclic servo fails, a pilot may want to land 

immediately because the workload increases tremendously. If 

an antitorque or collective servo fails, continuing to the next 

suitable landing site might be possible. 

Instrument Takeoff

The procedures and techniques described here should be 

modified as necessary to conform to those set forth in the 

operating instructions for the particular helicopter being 

flown. During training, instrument takeoffs should not 

be attempted except when receiving instruction from an 

appropriately certificated, proficient flight instructor pilot. 

Adjust the miniature aircraft in the attitude indicator, as 

appropriate, for the aircraft being flown. After the helicopter 

is aligned with the runway or takeoff pad, to prevent forward 

movement of a helicopter equipped with a wheel-type landing 

gear, set the parking brakes or apply the toe brakes. If the 

parking brake is used, it must be unlocked after the takeoff 

has been completed. Apply sufficient friction to the collective 

pitch control to minimize overcontrolling and to prevent 

creeping. Excessive friction should be avoided since it limits 

collective pitch movement. 

After checking all instruments for proper indications, start 

the takeoff by applying collective pitch and a predetermined 

power setting. Add power smoothly and steadily to gain 

airspeed and altitude simultaneously and to prevent settling to 

the ground. As power is applied and the helicopter becomes 

airborne, use the antitorque pedals initially to maintain the 

desired heading. At the same time, apply forward cyclic to 

begin accelerating to climbing airspeed. During the initial 

acceleration, the pitch attitude of the helicopter, as read on the 

attitude indicator, should be one- to two-bar widths low. The 

primary and supporting instruments after becoming airborne 

are illustrated in Figure 8-16. As the airspeed increases to the 

appropriate climb airspeed, adjust pitch gradually to climb 

attitude. As climb airspeed is reached, reduce power to the 

climb power setting and transition to a fully coordinated 

straight climb. 

During the initial climb out, minor heading corrections 

should be made with pedals only until sufficient airspeed is 

attained to transition to fully coordinated flight. Throughout 

the instrument takeoff, instrument cross-check and 

interpretations must be rapid and accurate and aircraft control 

positive and smooth. 
8-18

A O M 

N 3 

33 

3 

4 

I 

0 

2 

2 I 

3 

VERTICAL SPEED 

THOUSAND FT PER MIN 

UP 

DOWN 

.5 

.5 

33 

30 

24 

2I 

I5 

I2 

6 

3 

2 MIN TURN DC ELEC 

L R 

30.0 

29.9 

29.8 

I00 FEET 

I 

4 5 6 

7 

9 

2 

0 

8 

3 

CALIBRATED 

TO 

20,000 FEET 

ALT 

20 20

I0 I0

I0 I0

20 20

STBY PWR TEST 

IN Hg

ALg.

MANIFOLD 

PRESS 

25

5

15

30

20

10

35

25

5

15

30

20

10

35

110 

100 

90 

80 

70 

60 

50 

110 

100 

90 

80 

70 

60 

50 

E R 

%RPM 

Supporting pitch

Primary pitch and supporting bank

Supporting bank Supporting pitch

Supporting pitch

Primary bank

Remains constant

Figure 6-13. Flight instrument indications during an instrument takeoff. Figure 8-16. Flight instrument indications during an instrument takeoff.

Common Errors During Instrument Takeoffs

1. Failure to maintain heading 

2. Overcontrolling pedals 

3. Failure to use required power 

4. Failure to adjust pitch attitude as climbing airspeed 

is reached 

Changing Technology

Advances in technology have brought about changes in 

the instrumentation found in all types of aircraft, including 

helicopters. Electronic displays commonly referred to as 

“glass cockpits” are becoming more common. Primary flight 

displays (PFDs) and multi-function displays (MFDs) are 

changing not only what information is available to a pilot 

but also how that information is displayed.

Illustrations of technological advancements in instrumentation 

are described as follows. In Figure 8-17, a typical PFD 

depicts an aircraft flying straight-and-level at 3,000 feet and 

100 knots. Figure 8-18 illustrates a nose-low pitch attitude in 

a right turn. MFDs can be configured to provide navigation 

information, such as the moving map in Figure 8-19 or 

information pertaining to aircraft systems as in Figure 8-20.
8-19

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

270° 

2 

1 

1 

2 

3300 

3200 

3100 

4000 

2900 

2800 

2300 

3600 

3500 

3400 

3300 

3200 

3100 

60 

20 

3000 

3000 

130 

120 

110 

90 

80 

70 

1 

100 

9 

TAS 100KT 

OAT 7°C 

NAV1 108.00 113.00

NAV2 108.00 110.60

134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

PFD depicts flying straight and level 

Figure 8-17. PFD indications during straight-and-level flight.

XPDR 5537 IDNT LCL23:00:34 

VOR 1 

270° 

2 

1 

1 

2 

-500 

3200 

3100 

3000 

4000 

2800 

2700 

2600 

3600 

3500 

3400 

3300 

3200 

3100 

20 

80 

2900 

3000 

130 

120 

110 

100 

90 

80 

6 

105 

4 

TAS 107KT 

OAT 7°C 

NAV1 108.00 113.00

NAV2 108.00 110.60

134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

3100 

3000 

2900 

20 

80 

3000 

3100 

3000 

2900 

80 

70 

2975 -125 

3100 

3000 

2900 

70 

30 

2950 -250 

3000 

3000 

2900 

45 

05 

2925 -375 

 Pitch attitude nose-low right turn 

Figure 8-18. PFD indications during a nose-low pitch attitude in a right turn.
8-20

XPDR 5537 IDNT LCL23:00:34

VOR 1 

270°

2

1

1

2

3300

3200

3100

4000

2900

2800

2300

3600

3500

3400

3300

3200

3100

60

20

3000

3000

130

120

110

90

80

70

1

100

9

TAS 100KT

OAT 7°C

5

338 

1

1652 

200 

46 

13.7 

2300 

23.0 

NAV1 108.00 113.00

NAV2 108.00 110.60

134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NMDTK _ _ _°T TRK 360°T

MFD provide navigation information - moving map 

Figure 8-19. MFD display of a moving map.

Figure 8-20. MFD display of aircraft systems.
9-1

Introduction

This chapter provides the basic radio principles applicable to 

navigation equipment, as well as an operational knowledge 

of how to use these systems in instrument flight. This 

information provides the framework for all instrument 

procedures, including standard instrument departure 

procedures (SIDS), departure procedures (DPs), holding 

patterns, and approaches, because each of these maneuvers 

consists mainly of accurate attitude instrument flying and 

accurate tracking using navigation systems.

Navigation 

Systems

Chapter 9
9-2

Not refracted 

Ionosphere 

Figure 7-1. Ground, space, and sky wave propagation. 

Ground wave 

Space wave 

Sky wave 

Figure 9-1. Ground, space, and sky wave propogation.

Basic Radio Principles

A radio wave is an electromagnetic (EM) wave with 

frequency characteristics that make it useful. The wave 

travels long distances through space (in or out of the 

atmosphere) without losing too much strength. An antenna 

is used to convert electric current into a radio wave so it can 

travel through space to the receiving antenna, which converts 

it back into an electric current for use by a receiver.

How Radio Waves Propagate

All matter has a varying degree of conductivity or resistance 

to radio waves. The Earth itself acts as the greatest resistor 

to radio waves. Radiated energy that travels near the ground 

induces a voltage in the ground that subtracts energy from the 

wave, decreasing the strength of the wave as the distance from 

the antenna becomes greater. Trees, buildings, and mineral 

deposits affect the strength to varying degrees. Radiated 

energy in the upper atmosphere is likewise affected as the 

energy of radiation is absorbed by molecules of air, water, 

and dust. The characteristics of radio wave propagation vary 

according to the signal frequency and the design, use, and 

limitations of the equipment.

Ground Wave

A ground wave travels across the surface of the Earth. You 

can best imagine a ground wave’s path as being in a tunnel 

or alley bounded by the surface of the Earth and by the 

ionosphere, which keeps the ground wave from going out 

into space. Generally, the lower the frequency, the farther 

the signal travels.

Ground waves are usable for navigation purposes because 

they travel reliably and predictably along the same route 

day after day and are not influenced by too many outside 

factors. The ground wave frequency range is generally from 

the lowest frequencies in the radio range (perhaps as low as 

100 Hz) up to approximately 1,000 kHz (1 MHz). Although 

there is a ground wave component to frequencies above this, 

up to 30 MHz, the ground wave at these higher frequencies 

loses strength over very short distances.

Sky Wave

The sky wave, at frequencies of 1 to 30 MHz, is good for 

long distances because these frequencies are refracted or 

“bent” by the ionosphere, causing the signal to be sent back 

to Earth from high in the sky and received great distances 

away. [Figure 9-1] Used by high frequency (HF) radios in 

aircraft, messages can be sent across oceans using only 50 

to 100 watts of power. Frequencies that produce a sky wave 

are not used for navigation because the pathway of the signal 

from transmitter to receiver is highly variable. The wave is 

“bounced” off of the ionosphere, which is always changing 

due to the varying amount of the sun’s radiation reaching it 

(night/day and seasonal variations, sunspot activity, etc.). The 

sky wave is, therefore, unreliable for navigation purposes.

For aeronautical communication purposes, the sky wave 

(HF) is about 80 to 90 percent reliable. HF is being gradually 

replaced by more reliable satellite communication.

Space Wave

When able to pass through the ionosphere, radio waves 

of 15 MHz and above (all the way up to many GHz), are 

considered space waves. Most navigation systems operate 

with signals propagating as space waves. Frequencies above 

100 MHz have nearly no ground or sky wave components. 

They are space waves, but (except for global positioning 

system (GPS)) the navigation signal is used before it reaches 

the ionosphere so the effect of the ionosphere, which can 

cause some propagation errors, is minimal. GPS errors 

caused by passage through the ionosphere are significant 

and are corrected for by the GPS receiver system.

Space waves have another characteristic of concern to users. 

Space waves reflect off hard objects and may be blocked if 

the object is between the transmitter and the receiver. Site 

and terrain error, as well as propeller/rotor modulation error 

in very high omnidirectional range (VOR) systems, is caused 

by this bounce. Instrument landing system (ILS) course 

distortion is also the result of this phenomenon, which led 

to the need for establishment of ILS critical areas.
9-3

33 

30 

24 

21 

15 

12 

6 

3 

W 

S 

E 

N 

HDG

Figure 7-2. ADF indicator instrument and receiver. 

OFF 

VOL 

RST SET ET FRQ FLT ADF BFO 

A D F 

F R Q 

ADF KR 87 TSD 

Figure 9-2. ADF indicator instrument and receiver.

Generally, space waves are “line of sight” receivable, but 

those of lower frequencies “bend” somewhat over the 

horizon. The VOR signal at 108 to 118 MHz is a lower 

frequency than distance measuring equipment (DME) at 962 

to 1213 MHz. Therefore, when an aircraft is flown “over the 

horizon” from a VOR/DME station, the DME is normally 

the first to stop functioning.

Disturbances to Radio Wave Reception

Static distorts the radio wave and interferes with normal 

reception of communications and navigation signals. Lowfrequency airborne equipment, such as automatic direction 

finder (ADF) and LORAN (LOng RAnge Navigation) 

,are particularly subject to static disturbance. Using very 

high frequency (VHF) and ultra-high frequency (UHF) 

frequencies avoids many of the discharge noise effects. 

Static noise heard on navigation or communication radio 

frequencies may be a warning of interference with navigation 

instrument displays. Some of the problems caused by 

precipitation static (P-static) are:

• Complete loss of VHF communications.

• Erroneous magnetic compass readings.

• Aircraft flying with one wing low while using 

the autopilot.

• High-pitched squeal on audio.

• Motorboat sound on audio.

• Loss of all avionics.

• Inoperative very-low frequency (VLF) navigation 

system.

• Erratic instrument readouts.

• Weak transmissions and poor radio reception.

• St. Elmo’s Fire.

Traditional Navigation Systems

Nondirectional Radio Beacon (NDB)

The nondirectional radio beacon (NDB) is a ground-based 

radio transmitter that transmits radio energy in all directions. 

The ADF, when used with an NDB, determines the bearing 

from the aircraft to the transmitting station. The indicator 

may be mounted in a separate instrument in the aircraft 

panel. [Figure 9-2] The ADF needle points to the NDB 

ground station to determine the relative bearing (RB) to the 

transmitting station. It is the number of degrees measured 

clockwise between the aircraft’s heading and the direction 

from which the bearing is taken. The aircraft’s magnetic 

heading (MH) is the direction the aircraft is pointed with 

respect to magnetic north. The magnetic bearing (MB) is the 

direction to or from a radio transmitting station measured 

relative to magnetic north. 

NDB Components

The ground equipment, the NDB, transmits in the frequency 

range of 190 to 535 kHz. Most ADFs also tune the AM 

broadcast band frequencies above the NDB band (550 to 

1650 kHz). However, these frequencies are not approved 

for navigation because stations do not continuously identify 

themselves, and they are much more susceptible to sky wave 

propagation especially from dusk to dawn. NDB stations 

are capable of voice transmission and are often used for 

transmitting the Automated Weather Observing System 

(AWOS). The aircraft must be in operational range of the 

NDB. Coverage depends on the strength of the transmitting 

station. Before relying on ADF indications, identify the 

station by listening to the Morse code identifier. NDB stations 

are usually two letters or an alpha-numeric combination.

ADF Components

The airborne equipment includes two antennas: a receiver 

and the indicator instrument. The “sense” antenna (nondirectional) receives signals with nearly equal efficiency 

from all directions. The “loop” antenna receives signals 

better from two directions (bidirectional). When the loop 

and sense antenna inputs are processed together in the ADF 

radio, the result is the ability to receive a radio signal well in 

all directions but one, thus resolving all directional ambiguity.

The indicator instrument can be one of four kinds: fixedcard ADF, rotatable compass-card ADF, or radio magnetic 
9-4

33 

30 

24 

21 

15 

12 

6 

3 

S 

W 

E 

N 

Figure 9-3. Figure 7-3. Relative bearing (RB) on a fixed-card indicator. Note Relative bearing (RB) on a fixed-card indicator. 

that the card always indicates 360° or north. In this case, the RB 

to the station is 135° to the right. If the aircraft were on a magnetic 

heading of 360°, then the magnetic bearing (MB) would also be 135°. 

33 

30 

24 

21 

15 

12 

3 6 

W S 

E 

N 

HDG

Figure 7-4. Relative bearing (RB) on a movable-card indicator. Figure 9-4. Relative bearing (RB) on a movable-card indicator. By 

placing the aircraft’s magnetic heading (MH) of 045° under the 

top index, the RB of 135° to the right is also the magnetic bearing 

(no wind conditions), which takes you to the transmitting station. 

33 

30 

24 

21 

15 

12 

6 

3 

S 

W 

E 

N ADF needle 

VOR needle 

Figure 7-5. Radio magnetic indicator (RMI). Figure 9-5. Radio magnetic indicator (RMI). Because the aircraft’s 

magnetic heading (MH) is automatically changed, the relative 

bearing (RB), in this case 095°, indicates the magnetic bearing 

(095°) to the station (no wind conditions) and the MH that takes 

you there.

indicator (RMI) with either one needle or dual needle. Fixedcard ADF (also known as the relative bearing indicator (RBI)) 

always indicates zero at the top of the instrument, with the 

needle indicating the RB to the station. Figure 9-3 indicates 

an RB of 135°; if the MH is 045°, the MB to the station is 

180°. (MH + RB = MB to the station.) 

The movable-card ADF allows the pilot to rotate the aircraft’s 

present heading to the top of the instrument so that the head 

of the needle indicates MB to the station and the tail indicates 

MB from the station. Figure 9-4 indicates a heading of 045°, 

MB to the station of 180°, and MB from the station of 360°.

The RMI differs from the movable-card ADF in that it 

automatically rotates the azimuth card (remotely controlled 

by a gyrocompass) to represent aircraft heading. The RMI 

has two needles, which can be used to indicate navigation 

information from either the ADF or the VOR receiver. When 

a needle is being driven by the ADF, the head of the needle 

indicates the MB TO the station tuned on the ADF receiver. 

The tail of the needle is the bearing FROM the station. When 

a needle of the RMI is driven by a VOR receiver, the needle 

indicates where the aircraft is radially with respect to the 

VOR station. The needle points the bearing TO the station 

as read on the azimuth card. The tail of the needle points to 

the radial of the VOR the aircraft is currently on or crossing. 

Figure 9-5 indicates a heading of 360°, the MB to the station 

is 005°, and the MB from the station is 185°.

Function of ADF

The ADF can be used to plot your position, track inbound 

and outbound, and intercept a bearing. These procedures 
9-5

are used to execute holding patterns and nonprecision 

instrument approaches.

Orientation

The ADF needle points TO the station, regardless of aircraft 

heading or position. The RB indicated is thus the angular 

relationship between the aircraft heading and the station, 

measured clockwise from the nose of the aircraft. Think of 

the nose/tail and left/right needle indications, visualizing the 

ADF dial in terms of the longitudinal axis of the aircraft. 

When the needle points to 0°, the nose of the aircraft points 

directly to the station; with the pointer on 210°, the station 

is 30° to the left of the tail; with the pointer on 090°, the 

station is off the right wingtip. The RB alone does not indicate 

aircraft position. The RB must be related to aircraft heading 

in order to determine direction to or from the station.

Station Passage

When you are near the station, slight deviations from 

the desired track result in large deflections of the needle. 

Therefore, it is important to establish the correct drift 

correction angle as soon as possible. Make small heading 

corrections (not over 5°) as soon as the needle shows a 

deviation from course, until it begins to rotate steadily toward 

a wingtip position or shows erratic left/right oscillations. You 

are abeam a station when the needle points 90° off your track. 

Hold your last corrected heading constant and time station 

passage when the needle shows either wingtip position or 

settles at or near the 180° position. The time interval from 

the first indications of station proximity to positive station 

passage varies with altitude—a few seconds at low levels to 

3 minutes at high altitude.

Homing

The ADF may be used to “home” in on a station. Homing 

is flying the aircraft on any heading required to keep the 

needle pointing directly to the 0° RB position. To home in 

on a station, tune the station, identify the Morse code signal, 

and then turn the aircraft to bring the ADF azimuth needle to 

the 0° RB position. Turns should be made using the heading 

indicator. When the turn is complete, check the ADF needle 

and make small corrections as necessary.

Figure 9-6 illustrates homing starting from an initial MH of 

050° and an RB of 310°, indicating a 50° left turn is needed 

to produce an RB of zero. Turn left, rolling out at 50° minus 

50° equals 360°. Small heading corrections are then made 

to zero the ADF needle.

If there is no wind, the aircraft homes to the station on a direct 

track over the ground. With a crosswind, the aircraft follows 

a circuitous path to the station on the downwind side of the 

direct track to the station.

Tracking

Tracking uses a heading that maintains the desired track 

to or from the station regardless of crosswind conditions. 

Interpretation of the heading indicator and needle is done to 

maintain a constant MB to or from the station. 

To track inbound, turn to the heading that produces a zero 

RB. Maintain this heading until off-course drift is indicated 

by displacement of the needle, which occurs if there is a 

crosswind (needle moving left = wind from the left; needle 

moving right = wind from the right). A rapid rate of bearing 

change with a constant heading indicates either a strong 

crosswind or close proximity to the station or both. When 

there is a definite (2° to 5°) change in needle reading, turn in 

the direction of needle deflection to intercept the initial MB. 

The angle of interception must be greater than the number 

of degrees of drift, otherwise the aircraft slowly drifts due to 

the wind pushing the aircraft. If repeated often enough, the 

track to the station appears circular and the distance greatly 

increased as compared to a straight track. The intercept angle 

depends on the rate of drift, the aircraft speed, and station 

proximity. Initially, it is standard to double the RB when 

turning toward your course.

For example, if your heading equals your course and the 

needle points 10° left, turn 20° left, twice the initial RB. 

[Figure 9-7] This is your intercept angle to capture the 

RB. Hold this heading until the needle is deflected 20° in 

the opposite direction. That is, the deflection of the needle 

equals the interception angle (in this case 20°). The track has 

been intercepted, and the aircraft remains on track as long 

as the RB remains the same number of degrees as the wind 

correction angle (WCA), the angle between the desired track 

and the heading of the aircraft necessary to keep the aircraft 

tracking over the desired track. Lead the interception to avoid 

overshooting the track. Turn 10° toward the inbound course. 

You are now inbound with a 10° left correction angle. 

NOTE: In Figure 9-7, for the aircraft closest to the station, 

the WCA is 10° left and the RB is 10° right. If those values 

do not change, the aircraft tracks directly to the station. If you 

observe off-course deflection in the original direction, turn 

again to the original interception heading. When the desired 

course has been re-intercepted, turn 5° toward the inbound 

course, proceeding inbound with a 15° drift correction. If the 

initial 10° drift correction is excessive, as shown by needle 

deflection away from the wind, turn to parallel the desired 

course and let the wind drift you back on course. When the 

needle is again zeroed, turn into the wind with a reduced 

drift correction angle.
9-6

WIND

ADF

HDG 050° 050°

33

30

24

21

15

12

6 3

W

S

E

N

33

30

24 2I

I5 I2

6 3

ADF

HDG 360° 360°

33

30

24

21

15 12

6 3

W

S

E

N

33

30

24 2I

I5 I2

6 3

ADF

HDG 330° 330°

33

30

24

21

15 12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

ADF

HDG 320° 320°

33

30

24

21

15 12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

ADF

HDG 310° 310°

30 33

24

21

15

12

6 3

W

S

E

N

30 33

24 2I

I5 I2

6 3

Station

OBS

N

E

S

W

3

33

24 21

15 12

30

6

NAV

GS

Instrument view is from 

the pilot’s perspective, 

and the movable card is 

reset after each turn

Figure 9-6. ADF homing with a crosswind.
9-7

Figure 9-7. ADF tracking inbound.

OBS

N

E

S

W

3

33

24 21

15 12

30

6

NAV

GS

Instrument view is from 

the pilot’s perspective, 

and the movable card is 

reset after each turn

ADF

HDG 005° 005°

ADF

HDG 360° 360°

ADF

HDG 340° 340°

ADF

HDG 340° 340°

ADF

HDG 350° 350°

005°

33

30

24

21

15 12

6 3

W

S

E

N 33

30

24 2I

I5 I2

6 3

33

30

24

21

15 12

6 3

W

S

E

N

33

30

24 2I

I5 I2

6 3

33

30

24

21

15 12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

33

30

24

21

15 12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

33

30

24

21

15 12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

WCA = 10° LEFT

RB = 10° RIGHT

Station

WIND
9-8

Operational Errors of ADF

Some of the common pilot-induced errors associated with 

ADF navigation are listed below to help you avoid making 

the same mistakes. The errors are:

1. Failure to keep the heading indicator set so that it 

agrees with the corrected magnetic compass reading. 

Initiating an ADF approach without verifying that the 

heading indicator agrees with the corrected compass 

indicator reading may cause the pilot to believe that 

he is on course but still impact the terrain (CFIT).

2. Improper tuning and station identification. Many pilots 

have made the mistake of homing or tracking to the 

wrong station.

3. Positively identifying any malfunctions of the RMI 

slaving system or ignoring the warning flag.

4. Dependence on homing rather than proper tracking. 

This commonly results from sole reliance on the 

ADF indications rather than correlating them with 

heading indications.

5. Poor orientation due to failure to follow proper steps 

in orientation and tracking.

6. Careless interception angles, very likely to happen if 

you rush the initial orientation procedure.

7. Overshooting and undershooting predetermined 

MBs, often due to forgetting the course interception 

angles used.

8. Failure to maintain selected headings. Any heading 

change is accompanied by an ADF needle change. 

The instruments must be read in combination before 

any interpretation is made.

9. Failure to understand the limitations of the ADF and 

the factors that affect its use.

10. Overcontrolling track corrections close to the station 

(chasing the ADF needle) due to failure to understand 

or recognize station approach. 

Very High Frequency Omnidirectional Range 

(VOR)

VOR is the primary navigational aid (NAVAID) used by civil 

aviation in the National Airspace System (NAS). The VOR 

ground station is oriented to magnetic north and transmits 

azimuth information to the aircraft, providing 360 courses 

TO or FROM the VOR station. When DME is installed with 

the VOR, it is referred to as a VOR/DME and provides both 

azimuth and distance information. When military tactical air 

navigation (TACAN) equipment is installed with the VOR, 

it is known as a VORTAC and provides both azimuth and 

distance information.

To track outbound, the same principles apply: needle moving 

left = wind from the left, needle moving right = wind from the 

right. Wind correction is made toward the needle deflection. 

The only exception is while the turn to establish the WCA is 

being made, the direction of the azimuth needle deflections is 

reversed. When tracking inbound, needle deflection decreases 

while turning to establish the WCA, and needle deflection 

increases when tracking outbound. Note the example of 

course interception and outbound tracking in Figure 9-8.

Intercepting Bearings

ADF orientation and tracking procedures may be applied to 

intercept a specified inbound or outbound MB. To intercept 

an inbound bearing of 355°, the following steps may be used. 

[Figure 9-9]

1. Determine your position in relation to the station by 

paralleling the desired inbound bearing. In this case, 

turn to a heading of 355°. Note that the station is to 

the right front of the aircraft.

2. Determine the number of degrees of needle deflection 

from the nose of the aircraft. In this case, the needle’s 

RB from the aircraft’s nose is 40° to the right. A rule 

of thumb for interception is to double this RB amount 

as an interception angle (80°). 

3. Turn the aircraft toward the desired MB the number of 

degrees determined for the interception angle, which 

as indicated (in two above) is twice the initial RB (40°) 

or, in this case, 80°. Therefore, the right turn is 80° 

from the initial MB of 355° or a turn to 075° magnetic 

(355° + 80° + 075°).

4. Maintain this interception heading of 075° until the 

needle is deflected the same number of degrees “left” 

from the zero position as the angle of interception 080° 

(minus any lead appropriate for the rate at which the 

bearing is changing).

5. Turn left 80° and the RB (in a no wind condition and 

with proper compensation for the rate of the ADF 

needle movement) should be 0° or directly off the 

nose. Additionally, the MB should be 355° indicating 

proper interception of the desired course.

NOTE: The rate of an ADF needle movement, or any bearing 

pointer for that matter, is faster as aircraft position becomes 

closer to the station or waypoint (WP). 

Interception of an outbound MB can be accomplished by the 

same procedures as for the inbound intercept, except that 

it is necessary to substitute the 180° position for the zero 

position on the needle.
9-9

WIND

330°

ADF

HDG 015° 015°

33

30

24

21

15

12

6 3

W

S

E

N

33

30

24 2I

I5 I2

6 3

ADF

HDG 015° 015°

33

30

24

21

15

12

6 3

W

S

E

N

33

30

24 2I

I5 I2

6 3

ADF

HDG 350° 350°

33

30

24

21

15

12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

ADF

HDG 340° 340°

33

30

24

21

15

12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

ADF

HDG 330° 330°

33 30

24

21

15 12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

ADF

HDG 330° 330°

33

30

24

21

15 12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

015°

Station

OBS

N

E

S

W

3

33

24 21

15 12

30

6

NAV

GS

Instrument view is from 

the pilot’s perspective, 

and the movable card is 

reset after each turn

Figure 9-8. ADF interception and tracking outbound.
9-10

225° 

180° 360° 

A 

B 

A-1 

Figure 7-10. VOR radials. 

Magnetic North 

Magnetic South 

Figure 9-10. VOR radials.

355°

75°

ADF

HDG 075° 075°

ADF

HDG 355° 355°

0 10 20 30 40 50 60 70 80

INBOUND

INTERCEPTION

355°

355°

33

30

24

21

15

12

6 3

W

S

E

N

33 30

24 2I

I5

6

I2

3

33

30

24

21

15

12

6 3

W

S

E

N

33 30

24 2I

I5 I2

6 3

Station

OBS

N

E

S

W

3

33

24 21

15 12

30

6

NAV

GS

Instrument view is from 

the pilot’s perspective, 

and the movable card is 

reset after each turn

Figure 9-9. Interception of bearing.

well as voice transmissions for communication and relay of 

weather and other information.

VORs are classified according to their operational uses. The 

standard VOR facility has a power output of approximately 

200 watts, with a maximum usable range depending upon 

the aircraft altitude, class of facility, location of the facility, 

terrain conditions within the usable area of the facility, and 

other factors. Above and beyond certain altitude and distance 

limits, signal interference from other VOR facilities and a 

weak signal make it unreliable. Coverage is typically at least 

40 miles at normal minimum instrument flight rules (IFR) 

altitudes. VORs with accuracy problems in parts of their 

service volume are listed in Notices to Airmen (NOTAMs) 

and in the Airport/Facility Directory (A/FD) under the name 

of the NAVAID.

VOR Components

The ground equipment consists of a VOR ground station, 

which is a small, low building topped with a flat white disc, 

upon which are located the VOR antennas and a fiberglass 

cone-shaped tower. [Figure 9-11] The station includes an 

automatic monitoring system. The monitor automatically 

turns off defective equipment and turns on the standby 

transmitter. Generally, the accuracy of the signal from the 

ground station is within 1°.

The courses oriented FROM the station are called radials. The 

VOR information received by an aircraft is not influenced 

by aircraft attitude or heading. [Figure 9-10] Radials can 

be envisioned to be like the spokes of a wheel on which the 

aircraft is on one specific radial at any time. For example, 

aircraft A (heading 180°) is inbound on the 360° radial; after 

crossing the station, the aircraft is outbound on the 180° 

radial at A1. Aircraft B is shown crossing the 225° radial. 

Similarly, at any point around the station, an aircraft can be 

located somewhere on a specific VOR radial. Additionally, 

a VOR needle on an RMI always points to the course that 

takes you to the VOR station where conversely the ADF 

needle points to the station as a RB from the aircraft. In 

the example above, the ADF needle at position A would be 

pointed straight ahead, at A1 to the aircraft’s 180° position 

(tail) and at B to the aircraft’s right. 

The VOR receiver measures and presents information to 

indicate bearing TO or FROM the station. In addition to the 

navigation signals transmitted by the VOR, a Morse code 

signal is transmitted concurrently to identify the facility, as 
9-11

OBS

N

E

S

W

3

33

24

21

15

12

30

6

FR

TO N

A

V

OBS knob

CDI needle

Course index

Unreliable signal flag

FROM indicator

Approximately 2 degrees

in the VOR mode

TO indicator

Figure 9-12. The VOR indicator instrument.

Figure 9-11.Figure 7-11. VOR transmitter (ground station). VOR transmitter ground station. 

VOR facilities are aurally identified by Morse code, or 

voice, or both. The VOR can be used for ground-to-air 

communication without interference with the navigation 

signal. VOR facilities operate within the 108.0 to 117.95 MHz 

frequency band and assignment between 108.0 and 112.0 

MHz is in even-tenth increments to preclude any conflict 

with ILS localizer frequency assignment, which uses the 

odd tenths in this range.

The airborne equipment includes an antenna, a receiver, and 

the indicator instrument. The receiver has a frequency knob to 

select any of the frequencies between 108.0 to 117.95 MHz. 

The ON/OFF/volume control turns on the navigation receiver 

and controls the audio volume. The volume has no effect on 

the operation of the receiver. You should listen to the station 

identifier before relying on the instrument for navigation.

VOR indicator instruments have at least the essential 

components shown in the instrument illustrated in Figure 9-12.

Omnibearing Selector (OBS)

The desired course is selected by turning the omnibearing 

selector (OBS) knob until the course is aligned with the 

course index mark or displayed in the course window.

Course Deviation Indicator (CDI)

The course deviation indicator (CDI) is composed of an 

instrument face and a needle hinged to move laterally across 

the instrument face. The needle centers when the aircraft is 

on the selected radial or its reciprocal. Full needle deflection 

from the center position to either side of the dial indicates the 

aircraft is 12° or more off course, assuming normal needle 

sensitivity. The outer edge of the center circle is 2° off course; 

with each dot representing an additional 2°.

TO/FROM Indicator

The TO/FROM indicator shows whether the selected course, 

if intercepted and flown, takes the aircraft TO or FROM the 

station. It does not indicate whether the aircraft is heading 

to or from the station.

Flags or Other Signal Strength Indicators

The device that indicates a usable or an unreliable signal may 

be an “OFF” flag. It retracts from view when signal strength 

is sufficient for reliable instrument indications. Alternately, 

insufficient signal strength may be indicated by a blank or 

OFF in the TO/FROM window.

The indicator instrument may also be a horizontal situation 

indicator (HSI), which combines the heading indicator 

and CDI. [Figure 9-13] The combination of navigation 

information from VOR/Localizer (LOC) with aircraft heading 

information provides a visual picture of the aircraft’s location 

and direction. This decreases pilot workload especially 

with tasks such as course intercepts, flying a back-course 

approach, or holding pattern entry. (See Chapter 5, Flight 

Instruments, for operational characteristics.) [Figure 9-14]

Function of VOR

Orientation

The VOR does not account for the aircraft heading. It only 

relays the aircraft direction from the station and has the same 

indications regardless of which way the nose is pointing. Tune 

the VOR receiver to the appropriate frequency of the selected 

VOR ground station, turn up the audio volume, and identify 

the station’s signal audibly. Then, rotate the OBS to center 

the CDI needle and read the course under or over the index.

In Figure 9-12, 360° TO is the course indicated, while in 

Figure 9-15, 180° TO is the course. The latter indicates that 

the aircraft (which may be heading in any direction) is, at 

this moment, located at any point on the 360° radial (line 

from the station) except directly over the station or very 
9-12

XPDR 5537 IDNT LCL10:12:34 

INSET PFD CDI XPDR IDENT TMR/REF NRST ALERTS 

VOR 1 

270° 

HDG 270° CRS 270° 

2 

1 

1 

2 

 500 

5300 

5200 

5100 

5000 

4900 

4800 

4300 

3600 

3500 

3400 

3300 

3200 

3100 

20 

80 

5040 

5000 

130 

120 

110 

90 

80 

70 

1 

100 

9 

TAS 106KT 

OAT 6°C 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 270°

Heading

Lubber line Heading select bug

Course select pointer

Course deviation scale

Course deviation indicator (CDI)

Compass card

Selected heading box

Figure 9-14. An HSI display as seen on the pilot’s primary flight display (PFD) on an electronic flight instrument. Note that only attributes 

related to the HSI are labeled.

G

S

HDG

NAV

33

30

24

2I

I5

I2

6

3

Heading select bug

Compass warning flag

Heading select knob

NAV warning flag

Lubber line

Course deviation bar (CDI)

Course deviation scale

Course select pointer

Compass card

Symbolic aircraft

Glideslope pointer

Course select knob

Figure 9-13. A typical horizontal situation indicator (HSI).
9-13

HDG 215° CRS 180° 

VOR 

215° 

HDG 330° CRS 180° 

VOR 

330° 

VOR 

VOR 

270° 90° 360° 180° 

260°

250°

240°

230°

220°

210°

200°

190°

340°

330°

320

3

°

10°

300°

290°

280°

80°

70°

60°

50°

40

3

°

0°

20°

160°

170°

150°

140°

130°

120°

110°

100°

ELECTRONIC FLIGHT 

INSTRUMENTS ANALOG SYSTEMS 

OBS N E 

S 

W 

3 

33 

24 

21 

15 

12 

30 

6 

FR

OBS N E 

S 

W 

3 

33 

24 

21 

15 

12 

30 

6 

TO 

TO 

FROM 

Figure 9-15. CDI interpretation. The CDI as typically found on analog systems (right) and as found on electronic flight instruments (left).
9-14

close to it, as in Figure 9-15. The CDI deviates from side 

to side as the aircraft passes over or nearly over the station 

because of the volume of space above the station where the 

zone of confusion exists. This zone of confusion is caused 

by lack of adequate signal directly above the station due to 

the radiation pattern of the station’s antenna, and because 

the resultant of the opposing reference and variable signals 

is small and constantly changing.

The CDI in Figure 9-15 indicates 180°, meaning that the 

aircraft is on the 180° or the 360° radial of the station. The TO/

FROM indicator resolves the ambiguity. If the TO indicator is 

showing, then it is 180° TO the station. The FROM indication 

indicates the radial of the station the aircraft is presently on. 

Movement of the CDI from center, if it occurs at a relatively 

constant rate, indicates the aircraft is moving or drifting off 

the 180°/360° line. If the movement is rapid or fluctuating, 

this is an indication of impending station passage (the aircraft 

is near the station). To determine the aircraft’s position 

relative to the station, rotate the OBS until FROM appears 

in the window, and then center the CDI needle. The index 

indicates the VOR radial where the aircraft is located. The 

inbound (to the station) course is the reciprocal of the radial.

If the VOR is set to the reciprocal of the intended course, the 

CDI reflects reverse sensing. To correct for needle deflection, 

turn away from the needle. To avoid this reverse sensing 

situation, set the VOR to agree with the intended course.

A single NAVAID allows a pilot to determine the aircraft’s 

position relative to a radial. Indications from a second 

NAVAID are needed in order to narrow the aircraft’s position 

down to an exact location on this radial.

Tracking TO and FROM the Station

To track to the station, rotate the OBS until TO appears, 

then center the CDI. Fly the course indicated by the index. 

If the CDI moves off center to the left, follow the needle by 

correcting course to the left, beginning with a 20° correction.

When flying the course indicated on the index, a left deflection 

of the needle indicates a crosswind component from the left. 

If the amount of correction brings the needle back to center, 

decrease the left course correction by half. If the CDI moves 

left or right now, it should do so much more slowly, and smaller 

heading corrections can be made for the next iteration.

Keeping the CDI centered takes the aircraft to the station. 

To track to the station, the OBS value at the index is not 

changed. To home to the station, the CDI needle is periodically 

centered, and the new course under the index is used for the 

aircraft heading. Homing follows a circuitous route to the 

station, just as with ADF homing.

To track FROM the station on a VOR radial, you should 

first orient the aircraft’s location with respect to the station 

and the desired outbound track by centering the CDI needle 

with a FROM indication. The track is intercepted by either 

flying over the station or establishing an intercept heading. 

The magnetic course of the desired radial is entered under the 

index using the OBS and the intercept heading held until the 

CDI centers. Then the procedure for tracking to the station 

is used to fly outbound on the specified radial.

Course Interception

If the desired course is not the one being flown, first orient 

the aircraft’s position with respect to the VOR station and the 

course to be flown, and then establish an intercept heading. 

The following steps may be used to intercept a predetermined 

course, either inbound or outbound. Steps 1–3 may be omitted 

when turning directly to intercept the course without initially 

turning to parallel the desired course.

1. Determine the difference between the radial to be 

intercepted and the radial on which the aircraft is 

located (205° – 160° = 045°).

2. Double the difference to determine the interception 

angle, which will not be less than 20° nor greater 

than 90° (45° × 2 = 090°). 205° + 090° = 295° for 

the intercept). 

3. Rotate the OBS to the desired radial or inbound course.

4. Turn to the interception heading.

5. Hold this heading constant until the CDI center, which 

indicates the aircraft is on course. (With practice in 

judging the varying rates of closure with the course 

centerline, pilots learn to lead the turn to prevent 

overshooting the course.)

6. Turn to the MH corresponding to the selected course, 

and follow tracking procedures inbound or outbound.

Course interception is illustrated in Figure 9-16.

VOR Operational Errors

Typical pilot-induced errors include:

1. Careless tuning and identification of station.

2. Failure to check receiver for accuracy/sensitivity.

3. Turning in the wrong direction during an orientation. 

This error is common until visualizing position rather 

than heading.

4. Failure to check the ambiguity (TO/FROM) indicator, 

particularly during course reversals, resulting in reverse 

sensing and corrections in the wrong direction.
9-15

HDG 295° CRS 025°

VOR 1

295°

HDG 340° CRS 340°

VOR 1

340°

After needle centers 

track inbound on

205° radial.

Maintain heading of

295° 

Present position, 

inboundon 160° 

radial.

0 10 20 30 40 50 60 70 80

OBS

N

E

S

W

3

33

24 21

15

30

12

6

TO 33

30

24 2I

I5 I2

6 3

33 30

24 2I

I5 I2

6 3

OBS

N

E

S

W

3

33

24 21

15

30

12

6

TO

33 30

24 2I

I5 I2

6 3

OBS

N

E

S

W

3

33

24 21

15 12

30

6

TO

205° 025° 

160° 

295° 

A 

3

2

1 

1

2

3

OBS

N

E

S

W

3

33

24 21

15 12

30

6

NAV

GS

Instrument view is from 

the pilot’s perspective, 

and the movable card is 

reset after each turn

As VOR needle 

centers, lead the turn 

to track inbound.

NOTES

HDG 025° CRS 025°

VOR1

025°

Figure 9-16. Course interception (VOR).
9-16

5. Failure to parallel the desired radial on a track 

interception problem. Without this step, orientation 

to the desired radial can be confusing. Since pilots 

think in terms of left and right of course, aligning the 

aircraft position to the radial/course is essential.

6. Overshooting and undershooting radials on 

interception problems.

7. Overcontrolling corrections during tracking, especially 

close to the station.

8. Misinterpretation of station passage. On VOR 

receivers not equipped with an ON/OFF flag, a 

voice transmission on the combined communication 

and navigation radio (NAV/COM) in use for VOR 

may cause the same TO/FROM fluctuations on the 

ambiguity meter as shown during station passage. 

Read the whole receiver—TO/FROM, CDI, and 

OBS—before you make a decision. Do not utilize a 

VOR reading observed while transmitting.

9. Chasing the CDI, resulting in homing instead of 

tracking. Careless heading control and failure to 

bracket wind corrections make this error common.

VOR Accuracy

The effectiveness of the VOR depends upon proper use and 

adjustment of both ground and airborne equipment.

The accuracy of course alignment of the VOR is generally 

plus or minus 1°. On some VORs, minor course roughness 

may be observed, evidenced by course needle or brief flag 

alarm. 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.

Certain propeller revolutions per minute (rpm) settings or 

helicopter rotor speeds can cause the VOR CDI to fluctuate 

as much as plus or minus 6°. Slight changes to the RPM 

setting normally smooths out this roughness. Pilots are urged 

to check for this modulation phenomenon prior to reporting 

a VOR station or aircraft equipment for unsatisfactory 

operation.

VOR Receiver Accuracy Check

VOR system course sensitivity may be checked by noting 

the number of degrees of change as the OBS is rotated to 

move the CDI from center to the last dot on either side. The 

course selected should not exceed 10° or 12° either side. In 

addition, Title 14 of the Code of Federal Regulations (14 

CFR) part 91 provides for certain VOR equipment accuracy 

checks, and an appropriate endorsement, within 30 days prior 

to flight under IFR. To comply with this requirement and to 

ensure satisfactory operation of the airborne system, use the 

following means for checking VOR receiver accuracy:

1. VOR test facility (VOT) or a radiated test signal from 

an appropriately rated radio repair station.

2. Certified checkpoints on the airport surface.

3. Certified airborne checkpoints.

VOR Test Facility (VOT)

The Federal Aviation Administration (FAA) VOT transmits 

a test signal that 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. 

Locations of VOTs are published in the A/FD. 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 

flight service station (FSS.) 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.

To use the VOT service, tune in the VOT frequency 108.0 

MHz on the VOR receiver. With the CDI centered, the 

OBS should read 0° with the TO/FROM indication showing 

FROM or the OBS should read 180° with the TO/FROM 

indication showing TO. Should the VOR receiver operate an 

RMI, it would indicate 180° on any OBS setting.

A radiated VOT from an appropriately rated radio repair 

station serves the same purpose as an FAA VOT signal, and 

the check is made in much the same manner as a VOT with 

some differences.

The frequency normally approved by the Federal 

Communications Commission (FCC) is 108.0 MHz; 

however, repair stations are not permitted to radiate the 

VOR test signal continuously. The owner or operator of the 

aircraft must make arrangements with the repair station to 

have the test signal transmitted. 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.

Certified Checkpoints

Airborne and ground checkpoints 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. Locations of these checkpoints are 

published in the A/FD.
9-17

Should an error in excess of ±4° be indicated through use of 

a ground check, or ±6° using the airborne check, IFR flight 

shall not be attempted without first correcting the source of 

the error. No correction other than the correction card figures 

supplied by the manufacturer should be applied in making 

these VOR receiver checks.

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 variation between the two 

indicated bearings is 4°.

Distance Measuring Equipment (DME)

When used in conjunction with the VOR system, DME makes 

it possible for pilots to determine an accurate geographic 

position of the aircraft, including the bearing and distance TO 

or FROM the station. The aircraft DME transmits interrogating 

radio frequency (RF) pulses, which are received by the DME 

antenna at the ground facility. The signal triggers ground 

receiver equipment to respond to the interrogating aircraft. The 

airborne DME equipment measures the elapsed time between 

the interrogation signal sent by the aircraft and reception of the 

reply pulses from the ground station. This time measurement is 

converted into distance in nautical miles (NM) from the station.

Some DME receivers provide a groundspeed in knots by 

monitoring the rate of change of the aircraft’s position relative 

to the ground station. Groundspeed values are accurate only 

when tracking directly to or from the station.

DME Components

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

navigation facilities established by the FAA provide course 

and distance information from collocated components under 

a frequency pairing plan. DME operates on frequencies 

in the UHF spectrum between 962 MHz and 1213 MHz. 

Aircraft receiving equipment that 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. 

Some aircraft have separate VOR and DME receivers, each 

of which must be tuned to the appropriate navigation facility. 

The airborne equipment includes an antenna and a receiver.

The pilot-controllable features of the DME receiver include:

Channel (Frequency) Selector

Many DMEs are channeled by an associated VHF radio, or 

there may be a selector switch so a pilot can select which 

VHF radio is channeling the DME. For a DME with its own 

frequency selector, use the frequency of the associated VOR/

DME or VORTAC station.

ON/OFF/Volume Switch

The DME identifier is heard as a Morse code identifier with 

a tone somewhat higher than that of the associated VOR or 

LOC. It is heard once for every three or four times the VOR 

or LOC identifier is heard. If only one identifier is heard about 

every 30 seconds, the DME is functional, but the associated 

VOR or LOC is not.

Mode Switch

The mode switch selects between distance (DIST) or distance 

in NMs, groundspeed, and time to station. There may also be 

one or more HOLD functions that permit the DME to stay 

channeled to the station that was selected before the switch 

was placed in the hold position. This is useful when you make 

an ILS approach at a facility that has no collocated DME, 

but there is a VOR/DME nearby.

Altitude

Some DMEs correct for slant-range error.

Function of DME

A DME is used for determining the distance from a ground 

DME transmitter. Compared to other VHF/UHF NAVAIDs, 

a DME is very accurate. The distance information can be 

used to determine the aircraft position or flying a track that 

is a constant distance from the station. This is referred to as 

a DME arc.

DME Arc

There are many instrument approach procedures (IAPs) that 

incorporate DME arcs. The procedures and techniques given 

here for intercepting and maintaining such arcs are applicable 

to any facility that provides DME information. Such a facility 

may or may not be collocated with the facility that provides 

final approach guidance.

As an example of flying a DME arc, refer to Figure 9-17 and 

follow these steps:

1. Track inbound on the OKT 325° radial, frequently 

checking the DME mileage readout.

2. A 0.5 NM lead is satisfactory for groundspeeds of 

150 knots or less; start the turn to the arc at 10.5 

miles. At higher groundspeeds, use a proportionately 

greater lead.

3. Continue the turn for approximately 90°. The roll-out 

heading is 055° in a no wind condition.

4. During the last part of the intercepting turn, monitor 

the DME closely. If the arc is being overshot (more 

than 1.0 NM), continue through the originally planned 

roll-out heading. If the arc is being undershot, roll-out 

of the turn early.
9-18

055° 

OKT VORTAC 

325° 

325° 

10 DME arc 

Figure 7-16. DME arc interception. 

Lead points 10.5 NM 

Lead points 9.5 NM 

Figure 9-17. DME arc interception.

The procedure for intercepting the 10 DME when outbound 

is basically the same, the lead point being 10 NM minus 0.5 

NM or 9.5 NM.

When flying a DME arc with wind, it is important to keep a 

continuous mental picture of the aircraft’s position relative to 

the facility. Since the wind-drift correction angle is constantly 

changing throughout the arc, wind orientation is important. 

In some cases, wind can be used in returning to the desired 

track. High airspeeds require more pilot attention because of 

the higher rate of deviation and correction.

Maintaining the arc is simplified by keeping slightly inside 

the curve; thus, the arc is turning toward the aircraft and 

interception may be accomplished by holding a straight 

course. When outside the curve, the arc is “turning away” 

and a greater correction is required.

To fly the arc using the VOR CDI, center the CDI needle upon 

completion of the 90° turn to intercept the arc. The aircraft’s 

heading is found very near the left or right side (270° or 90° 

reference points) of the instrument. The readings at that side 

location on the instrument give primary heading information 

while on the arc. Adjust the aircraft heading to compensate 

for wind and to correct for distance to maintain the correct 

arc distance. Recenter the CDI and note the new primary 

heading indicated whenever the CDI gets 2°– 4° from center.

With an RMI, in a no wind condition, pilots should 

theoretically be able to fly an exact circle around the facility 

by maintaining an RB of 90° or 270°. In actual practice, 

a series of short legs are flown. To maintain the arc in 

Figure 9-18, proceed as follows:

1. With the RMI bearing pointer on the wingtip reference 

(90° or 270° position) and the aircraft at the desired 

DME range, maintain a constant heading and allow the 

bearing pointer to move 5°– 10° behind the wingtip. 

This causes the range to increase slightly.

2. Turn toward the facility to place the bearing pointer 

5°– 10° ahead of the wingtip reference, and then 

maintain heading until the bearing pointer is again 

behind the wingtip. Continue this procedure to 

maintain the approximate arc.

3. If a crosswind causes the aircraft to drift away from 

the facility, turn the aircraft until the bearing pointer is 

ahead of the wingtip reference. If a crosswind causes 

the aircraft to drift toward the facility, turn until the 

bearing is behind the wingtip.

4. As a guide in making range corrections, change the 

RB 10°– 20° for each half-mile deviation from the 

desired arc. For example, in no-wind conditions, if the 

aircraft is 1⁄2 to 1 mile outside the arc and the bearing 

pointer is on the wingtip reference, turn the aircraft 

20° toward the facility to return to the arc.

Without an RMI, orientation is more difficult since there is 

no direct azimuth reference. However, the procedure can be 

flown using the OBS and CDI for azimuth information and 

the DME for arc distance.

Intercepting Lead Radials

A lead radial is the radial at which the turn from the arc to the 

inbound course is started. When intercepting a radial from a 

DME arc, the lead varies with arc radius and groundspeed. 

For the average general aviation aircraft, flying arcs such 

as those depicted on most approach charts at speeds of 150 

knots or less, the lead is under 5°. There is no difference 

between intercepting a radial from an arc and intercepting it 

from a straight course.

With an RMI, the rate of bearing movement should be 

monitored closely while flying the arc. Set the course of the 

radial to be intercepted as soon as possible and determine 

the approximate lead. Upon reaching this point, start the 

intercepting turn. Without an RMI, the technique for radial 

interception is the same except for azimuth information, 

which is available only from the OBS and CDI.
9-19

005° Radial 

10° 

10° 

20° 

20° 

11 DME arc 

9 DME arc 

Desired arc 10 DME 

OBS

N

E

S

W

3

33

24 21

15

12

30

6

NAV

GS

33 

30 

24 

21 

15 

12 

6 3 

S 

W 

E 

N HDG

33 

30 

24 

21 

15 

12 

6 3 

S 

W 

E 

N 

HDG

33 

30 

24 

21 

15 

12 

6 3 

W 

S 

E 

N 

HDG

Figure 7-17. Using DME and RMI to maintain arc. 

Instrument view is from 

the pilot’s perspective, 

and the movable card is 

reset after each turn

Figure 9-18. Using DME and RMI to maintain an arc.

The technique for intercepting a localizer from a DME arc 

is similar to intercepting a radial. At the depicted lead radial 

(LR 223 or LR 212 in Figures 9-19, 9-20, and 9-21), a 

pilot having a single VOR/LOC receiver should set it to the 

localizer frequency. If the pilot has dual VOR/LOC receivers, 

one unit may be used to provide azimuth information and the 

other set to the localizer frequency. Since these lead radials 

provide 7° of lead, a half-standard rate turn should be used 

until the LOC needle starts to move toward center.

DME Errors

A DME/DME fix (a location based on two DME lines of 

position from two DME stations) provides a more accurate 

aircraft location than using a VOR and a DME fix.

DME signals are line-of-sight; the mileage readout is the 

straight line distance from the aircraft to the DME ground 

facility and is commonly referred to as slant range distance. 

Slant range refers to the distance from the aircraft’s antenna 

to the ground station (A line at an angle to the ground 

transmitter. GPS systems provide distance as the horizontal 

measurement from the WP to the aircraft. Therefore, at 3,000 

feet and 0.5 miles the DME (slant range) would read 0.6 NM 

while the GPS distance would show the actual horizontal 

distance of .5 DME. This error is smallest at low altitudes and/

or at long ranges. It is greatest when the aircraft is closer to 

the facility, at which time the DME receiver displays altitude 

(in NM) above the facility. Slant range error is negligible if 

the aircraft is one mile or more from the ground facility for 

each 1,000 feet of altitude above the elevation of the facility.
9-20

INSET MAP DCLTR 

NAV1 108.00 113.00

NAV2 108.00 110.60

134.000 118.000 COM1

123.800 118.000 COM2

GS 120KT XTK 8.15NM ETE 08:28 ESA 3100FT

MAP - NAVIGATION MAP

B 

S E - 3 , 3 1 A U G 2 0 0 6 t o 2 8 S E P 2 0 0 6 

IAP 

Figure 7-18a. Localizer interception from DME arc. Figure 9-19. An aircraft is displayed heading southwest to intercept the localizer approach, using the 16 NM DME arc off of ORM.
9-21

INSET PFD CDI DCLTR 

NAV1 108.00 113.00

NAV2 108.00 110.60

134.000 118.000 COM1

123.800 118.000 COM2

GS 120KT XTK 8.15NM ETE 08:28 ESA 3100FT

MAP - NAVIGATION MAP

B 

Figure 7-18b. Localizer interception from DME arc. 

Figure 9-20. The same aircraft illustrated in Figure 9-19 shown on the ORM radial near TIGAE intersection turning inbound for the 

localizer. 
9-22

ENGINE MAP DCLTR 

NAV1 108.00 113.00

NAV2 108.00 110.60

134.000 118.000 COM1

123.800 118.000 COM2

GS 120KT XTK 8.15NM ETE 08:28 ESA 3100FT

MAP - NAVIGATION MAP

B 

Figure 7-18c. Localizer interception from DME arc. 

Figure 9-21. Aircraft is illustrated inbound on the localizer course.

Area Navigation (RNAV)

Area navigation (RNAV) equipment includes VOR/DME, 

LORAN, GPS, and inertial navigation systems (INS). RNAV 

equipment is capable of computing the aircraft position, 

actual track, groundspeed, and then presenting meaningful 

information to the pilot. This information may be in the form 

of distance, cross-track error, and time estimates relative to 

the selected track or WP. In addition, the RNAV equipment 

installations must be approved for use under IFR. The Pilot’s 

Operating Handbook/Airplane Flight Manual (POH/AFM) 

should always be consulted to determine what equipment is 

installed, the operations that are approved, and the details of 

equipment use. Some aircraft may have equipment that allows 

input from more than one RNAV source, thereby providing 

a very accurate and reliable navigation source.

VOR/DME RNAV

VOR RNAV is based on information generated by the present 

VORTAC or VOR/DME system to create a WP using an 

airborne computer. As shown in Figure 9-22, the value of 

side A is the measured DME distance to the VOR/DME. Side 

B, the distance from the VOR/DME to the WP, and angle 1 

(VOR radial or the bearing from the VORTAC to the WP) 

are values set in the flight deck control. The bearing from 

the VOR/DME to the aircraft, angle 2, is measured by the 

VOR receiver. The airborne computer continuously compares 
9-23

248° 

308° 

0 10 20 30 40 50 60 70

ANGLE 3

ANGLE 1

ANGLE 2

VOR/DME 

C 

A 

B 

Figure 7-19. RNAV computation. 

Waypoint 

Figure 9-22. RNAV computation.

Figure 9-23. Onboard RNAV receivers have changed significantly. 

Originally, RNAV receivers typically computed combined data 

from VOR, VORTAC, and/or DME. That is generally not the case 

now. Today, GPS such as the GNC 300 and the Bendix King KLS 

88 LORAN receivers compute waypoints based upon embedded 

databases and aircraft positional information.

angles 1 and 2 and determines angle 3 and side C, which is 

the distance in NMs and magnetic course from the aircraft 

to the WP. This is presented as guidance information on the 

flight deck display.

VOR/DME RNAV Components

Although RNAV flight deck instrument displays vary among 

manufacturers, most are connected to the aircraft CDI with a 

switch or knob to select VOR or RNAV guidance. There is 

usually a light or indicator to inform the pilot whether VOR 

or RNAV is selected. [Figure 9-23] The display includes the 

WP, frequency, mode in use, WP radial and distance, DME 

distance, groundspeed, and time to station.

Most VOR/DME RNAV systems have the following 

airborne controls:

1. OFF/ON/Volume control to select the frequency of the 

VOR/DME station to be used.

2. MODE select switch used to select VOR/DME 

mode, with:

a. Angular course width deviation (standard VOR 

operation); or

b. Linear cross-track deviation as standard (±5 NM 

full scale CDI).

3. RNAV mode, with direct to WP with linear cross-track 

deviation of ±5 NM.

4. RNAV/APPR (approach mode) with linear deviation 

of ±1.25 NM as full scale CDI deflection.

5. WP select control. Some units allow the storage of more 

than one WP; this control allows selection of any WP 

in storage.

6. Data input controls. These controls allow user input 

of WP number or ident, VOR or LOC frequency, WP 

radial and distance.

While DME groundspeed readout is accurate only when 

tracking directly to or from the station in VOR/DME mode, 

in RNAV mode the DME groundspeed readout is accurate 

on any track.

Function of VOR/DME RNAV

The advantages of the VOR/DME RNAV system stem from 

the ability of the airborne computer to locate a WP wherever it 

is convenient, as long as the aircraft is within reception range 

of both nearby VOR and DME facilities. A series of these 

WPs make up an RNAV route. In addition to the published 

routes, a random RNAV route may be flown under IFR if 

it is approved by air traffic control (ATC). RNAV DPs and 

standard terminal arrival routes (STARs) are contained in 

the DP and STAR booklets.

VOR/DME RNAV approach procedure charts are also 

available. Note in the VOR/DME RNAV chart excerpt shown 

in Figure 9-24 that the WP identification boxes contain the 

following information: WP name, coordinates, frequency, 

identifier, radial distance (facility to WP), and reference facility 

elevation. The initial approach fix (IAF), final approach fix 

(FAF), and missed approach point (MAP) are labeled.

To fly a route or to execute an approach under IFR, the RNAV 

equipment installed in the aircraft must be approved for the 

appropriate IFR operations.

In vertical navigation (VNAV) mode, vertical guidance is 

provided, as well as horizontal guidance in some installations. 

A WP is selected at a point where the descent begins, 

and another WP is selected where the descent ends. The 
9-24

OBS 

E 

N 

S 

W 

3 

33 

21 24 

15 12 

30 

6 

TO 

Waypoint 

135° 

225° 

OBS 

N 

E 

S 

W 

3 

33 

24 21 

12 15 

30 

6 

TO 

33 30 

24 2I 

I5 I2 

6 3 

12 NM

OBS

N

E

S

W

3

33

24 21

15 12

30

6

NAV

GS

Instrument view is 

from the pilot’s 

perspective, and 

the movable card is 

reset after each turn

Figure 9-25. Aircraft/DME/waypoint relationship.

E C - 1 , 

E C - 1 , 

Figure 7-21. VOR/DME RNAV Rwy 25 approach (excerpt). 

16 DEC 2010 to 13 JAN 2011

16 DEC 2010 to 13 JAN 2011

Figure 9-24. VOR/DME RNAV RWY 25 approach (excerpt).

RNAV equipment computes the rate of descent relative to 

the groundspeed; on some installations, it displays vertical 

guidance information on the GS indicator. When using this 

type of equipment during an instrument approach, the pilot 

must keep in mind that the vertical guidance information 

provided is not part of the nonprecision approach. Published 

nonprecision approach altitudes must be observed and 

complied with, unless otherwise directed by ATC.

To fly to a WP using RNAV, observe the following procedure 

[Figure 9-25]:

1. Select the VOR/DME frequency.

2. Select the RNAV mode.

3. Select the radial of the VOR that passes through the 

WP (225°).

4. Select the distance from the DME to the WP (12 NM).

5. Check and confirm all inputs, and center the CDI needle 

with the TO indicator showing.

6. Maneuver the aircraft to fly the indicated heading plus or 

minus wind correction to keep the CDI needle centered.

7. The CDI needle indicates distance off course of 1 NM 

per dot; the DME readout indicates distance in NM 

from the WP; the groundspeed reads closing speed 

(knots) to the WP; and the time to station (TTS) reads 

time to the WP.

VOR/DME RNAV Errors

The limitation of this system is the reception volume. 

Published approaches have been tested to ensure this is not 

a problem. Descents/approaches to airports distant from the 

VOR/DME facility may not be possible because, during 

the approach, the aircraft may descend below the reception 

altitude of the facility at that distance.

Advanced Technologies

Global Navigation Satellite System (GNSS)

The Global Navigation Satellite System (GNSS) is a 

constellation of satellites providing a high-frequency signal 

that contains time and distance that is picked up by a receiver 
9-25

Figure 9-26. A typical example (GNS 480) of a stand-alone GPS 

receiver and display.

Figure 9-27. Typical GPS satellite array.

thereby. [Figure 9-26] The receiver that picks up multiple 

signals from different satellites is able to triangulate its 

position from these satellites. 

Three GNSSs exist today: the GPS, a United States system; the 

Russian GNSS (GLONASS); and Galileo, a European system.

1. GLONASS is a network of 24 satellites that can be 

picked up by any GLONASS receiver, allowing the 

user to pinpoint their position. 

2. Galileo planned to be a network of 30 satellites that 

continuously transmit high-frequency radio signals 

containing time and distance data that can be picked 

up by a Galileo receiver with operational expectancy 

by 2013.

3. The GPS came on line in 1992 with 24 satellites and 

today utilizes 30 satellites.

Global Positioning System (GPS)

The GPS is a satellite-based radio navigation system that 

broadcasts a signal that is used by receivers to determine 

precise position anywhere in the world. The receiver tracks 

multiple satellites and determines a measurement that is then 

used to determine the user location. [Figure 9-27]

The Department of Defense (DOD) developed and deployed 

GPS as a space-based positioning, velocity, and time system. 

The DOD is responsible for operation of the GPS satellite 

constellation, and constantly monitors the satellites to ensure 

proper operation. The GPS system permits Earth-centered 

coordinates to be determined and provides aircraft position 

referenced to the DOD World Geodetic System of 1984 

(WGS-84). Satellite navigation systems are unaffected 

by weather and provide global navigation coverage that 

fully meets the civil requirements for use as the 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 IAPs. Navigational values, 

such as distance and bearing to a WP and groundspeed, are 

computed from the aircraft’s current position (latitude and 

longitude) and the location of the next WP. Course guidance 

is provided as a linear deviation from the desired track of a 

Great Circle route between defined WPs. 

GPS may not be approved for IFR use in other countries. 

Prior to its use, pilots should ensure that GPS is authorized 

by the appropriate countries.

GPS Components

GPS consists of three distinct functional elements: space, 

control, and user.

The space element consists of over 30 Navstar satellites. This 

group of satellites is called a constellation. The space element 

consists of 24 Navigation System using Timing and Ranging 

(NAVSTAR) satellites in 6 orbital planes. The satellites in 

each plane are spaced 60° apart for complete coverage and 

are located (nominally) at about 11,000 miles above the 

Earth. The planes are arranged so that there are always five 

satellites in view at any time on the Earth. Presently, there are 

at least 31 Block II/IIA/IIR and IIR-M satellites in orbit with 

the additional satellites representing replacement satellites 

(upgraded systems) and spares. Recently, the Air Force 

received funding for procurement of 31 Block IIF satellites. 

The GPS constellation broadcasts a pseudo-random code 

timing signal and data message that the aircraft equipment 

processes to obtain satellite position and status data. By 

knowing the precise location of each satellite and precisely 

matching timing with the atomic clocks on the satellites, the 
9-26

aircraft receiver/processor can accurately measure the time 

each signal takes to arrive at the receiver and, therefore, 

determine aircraft position.

The control element consists of a network of ground-based 

GPS monitoring and control stations that ensure the accuracy 

of satellite positions and their clocks. In its present form, it 

has five monitoring stations, three ground antennas, and a 

master control station.

The user element consists of antennas and receiver/processors 

on board the aircraft that provide positioning, velocity, 

and precise timing to the user. GPS equipment used while 

operating under IFR must meet the standards set forth in 

Technical Standard Order (TSO) C-129 (or equivalent); meet 

the airworthiness installation requirements; be “approved” for 

that type of IFR operation; and be operated in accordance with 

the applicable POH/AFM or flight manual supplement.

An updatable GPS database that supports the appropriate 

operations (e.g., en route, terminal, and instrument 

approaches) is required when operating under IFR. The 

aircraft GPS navigation database contains WPs from the 

geographic areas where GPS navigation has been approved 

for IFR operations. The pilot selects the desired WPs from 

the database and may add user-defined WPs for the flight.

Equipment approved in accordance with TSO C-115a, visual 

flight rules (VFR), and hand-held GPS systems do not meet 

the requirements of TSO C-129 and are not authorized for 

IFR navigation, instrument approaches, or as a principal 

instrument flight reference. During IFR operations, these 

units (TSO C-115a) may be considered only an aid to 

situational awareness.

Prior to GPS/WAAS IFR operation, the pilot must review 

appropriate NOTAMs and aeronautical information. This 

information is available on request from an flight service 

station (FSS). The FAA does provide NOTAMs to advise 

pilots of the status of the WAAS and level of service 

available. 

Function of GPS

GPS operation is based on the concept of ranging and 

triangulation from a group of satellites in space that act 

as precise reference points. 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).

The aircraft GPS receiver measures distance from a satellite 

using the travel time of a radio signal. Each satellite transmits 

a specific code, called a course/acquisition (CA) code, which 

contains information about satellite position, the GPS system 

time, and the health and accuracy of the transmitted data. 

Knowing the speed at which the signal traveled (approximately 

186,000 miles per second) and the exact broadcast time, 

the distance traveled by the signal can be computed from 

the arrival time. The distance derived from this method of 

computing distance is called a pseudo-range because it is not 

a direct measurement of distance, but a measurement based 

on time. In addition to knowing the distance to a satellite, a 

receiver needs to know the satellite’s exact position in space, 

its ephemeris. Each satellite transmits information about its 

exact orbital location. The GPS receiver uses this information 

to establish the precise position of the satellite.

Using the calculated pseudo-range and position information 

supplied by the satellite, the GPS receiver/processor 

mathematically determines its position by triangulation 

from several satellites. The GPS receiver needs at least four 

satellites to yield a three-dimensional position (latitude, 

longitude, and altitude) and time solution. The GPS receiver 

computes navigational values (distance and bearing to 

a WP, groundspeed, etc.) by using the aircraft’s known 

latitude/longitude and referencing these to a database built 

into the receiver.

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. RAIM needs 

a minimum of five satellites in view or four satellites and 

a barometric altimeter baro-aiding to detect an integrity 

anomaly. For receivers capable of doing so, RAIM needs 

six satellites in view (or five satellites with baro-aiding) 

to isolate a corrupt satellite signal and remove it from the 

navigation solution.

Generally, there are two types of RAIM messages. One 

type indicates that there are not enough satellites available 

to provide RAIM and another type indicates that the RAIM 

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.

Aircraft using GPS navigation equipment under IFR for 

domestic en route, terminal operations, and certain IAPs, 

must be equipped with an approved and operational alternate 

means of navigation appropriate to the flight. 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. Active monitoring of alternative navigation 

equipment is not required if the GPS receiver uses RAIM for 

integrity monitoring. Active monitoring of an alternate means 
9-27

of navigation is required when the RAIM capability of the 

GPS equipment is lost. In situations where the loss of RAIM 

capability is predicted to occur, the flight must rely on other 

approved equipment, delay departure, or cancel the flight.

GPS Substitution

IFR En Route and Terminal Operations

GPS systems, certified for IFR en route and terminal 

operations, may be used as a substitute for ADF and DME 

receivers when conducting the following operations within 

the United States NAS.

1. Determining the aircraft position over a DME fix. 

This includes en route operations at and above 24,000 

feet mean sea level (MSL) (FL 240) when using GPS 

for navigation.

2. Flying a DME arc.

3. Navigating TO/FROM an NDB/compass locator.

4. Determining the aircraft position over an NDB/

compass locator.

5. Determining the aircraft position over a fix defined 

by an NDB/compass locator bearing crossing a VOR/

LOC course.

6. Holding over an NDB/compass locator.

GPS Substitution for ADF or DME 

Using GPS as a substitute for ADF or DME is subject to the 

following restrictions:

1. This equipment must be installed in accordance with 

appropriate airworthiness installation requirements and 

operated within the provisions of the applicable POH/

AFM or supplement.

2. The required integrity for these operations must be 

provided by at least en route RAIM or equivalent.

3. WPs, fixes, intersections, and facility locations to be 

used for these operations must be retrieved from the 

GPS airborne database. The database must be current. 

If the required positions cannot be retrieved from the 

airborne database, the substitution of GPS for ADF and/

or DME is not authorized

4. Procedures must be established for use when RAIM 

outages are predicted or occur. This may require the 

flight to rely on other approved equipment or require 

the aircraft to be equipped with operational NDB and/or 

DME receivers. Otherwise, the flight must be rerouted, 

delayed, canceled, or conducted under VFR.

5. The CDI must be set to terminal sensitivity (1 

NM) when tracking GPS course guidance in the 

terminal area.

6. A non-GPS approach procedure must exist at the 

alternate airport when one is required. If the non-GPS 

approaches on which the pilot must rely require DME 

or ADF, the aircraft must be equipped with DME or 

ADF avionics as appropriate.

7. Charted requirements for ADF and/or DME can be met 

using the GPS system, except for use as the principal 

instrument approach navigation source.

NOTE: The following provides guidance that is not specific 

to any particular aircraft GPS system. For specific system 

guidance, refer to the POH/AFM, or supplement, or contact 

the system manufacturer.

To Determine Aircraft Position Over a DME Fix:

1. Verify aircraft GPS system integrity monitoring is 

functioning properly and indicates satisfactory integrity.

2. If the fix is identified by a five-letter name that is 

contained in the GPS airborne database, select either 

the named fix as the active GPS WP or the facility 

establishing the DME fix as the active GPS WP. When 

using a facility as the active WP, the only acceptable 

facility is the DME facility that is charted as the one 

used to establish the DME fix. If this facility is not in 

the airborne database, it is not authorized for use.

3. If the fix is identified by a five-letter name that is not 

contained in the GPS airborne database, or if the fix 

is not named, select the facility establishing the DME 

fix or another named DME fix as the active GPS WP.

4. When selecting the named fix as the active GPS WP, 

a pilot is over the fix when the GPS system indicates 

the active WP.

5. If selecting the DME providing facility as the active 

GPS WP, a pilot is over the fix when the GPS distance 

from the active WP equals the charted DME value, and 

the aircraft is established on the appropriate bearing 

or course.

To Fly a DME Arc:

1. Verify aircraft GPS system integrity monitoring is 

functioning properly and indicates satisfactory integrity.

2. Select from the airborne database the facility providing 

the DME arc as the active GPS WP. The only 

acceptable facility is the DME facility on which the arc 

is based. If this facility is not in your airborne database, 

you are not authorized to perform this operation.

3. Maintain position on the arc by reference to the GPS 

distance instead of a DME readout.
9-28

To Navigate TO or FROM an NDB/Compass 

Locator:

1. Verify aircraft GPS system integrity monitoring is 

functioning properly and indicates satisfactory integrity.

2. Select the NDB/compass locator facility from the 

airborne database as the active WP. If the chart depicts 

the compass locator collocated with a fix of the same 

name, use of that fix as the active WP in place of the 

compass locator facility is authorized.

3. Select and navigate on the appropriate course to or 

from the active WP.

To Determine Aircraft Position Over an NDB/

Compass Locator:

1. Verify aircraft GPS system integrity monitoring is 

functioning properly and indicates satisfactory integrity.

2. Select the NDB/compass locator facility from the 

airborne database. When using an NDB/compass 

locator, the facility must be charted and be in the 

airborne database. If the facility is not in the airborne 

database, pilots are not authorized to use a facility WP 

for this operation.

3. A pilot is over the NDB/compass locator when the 

GPS system indicates arrival at the active WP.

To Determine Aircraft Position Over a Fix Made up 

of an NDB/Compass Locator Bearing Crossing a 

VOR/LOC Course:

1. Verify aircraft GPS system integrity monitoring is 

functioning properly and indicates satisfactory integrity.

2. A fix made up by a crossing NDB/compass locator 

bearing is identified by a five-letter fix name. Pilots 

may select either the named fix or the NDB/compass 

locator facility providing the crossing bearing to 

establish the fix as the active GPS WP. When using 

an NDB/compass locator, that facility must be charted 

and be in the airborne database. If the facility is not 

in the airborne database, pilots are not authorized to 

use a facility WP for this operation.

3. When selecting the named fix as the active GPS WP, 

pilot is over the fix when the GPS system indicates 

the pilot is at the WP.

4. When selecting the NDB/compass locator facility 

as the active GPS WP, pilots are over the fix when 

the GPS bearing to the active WP is the same as 

the charted NDB/compass locator bearing for the 

fix flying the prescribed track from the non-GPS 

navigation source.

To Hold Over an NDB/Compass Locator:

1. Verify aircraft GPS system integrity monitoring is 

functioning properly and indicates satisfactory integrity.

2. Select the NDB/compass locator facility from the 

airborne database as the active WP. When using a 

facility as the active WP, the only acceptable facility 

is the NDB/compass locator facility which is charted. 

If this facility is not in the airborne database, its use 

is not authorized.

3. Select nonsequencing (e.g., “HOLD” or “OBS”) mode 

and the appropriate course in accordance with the 

POH/AFM or supplement.

4. Hold using the GPS system in accordance with the 

POH/AFM or supplement.

IFR Flight Using GPS

Preflight preparations should ensure that the GPS is properly 

installed and certified with a current database for the type 

of operation. The GPS operation must be conducted in 

accordance with the FAA-approved POH/AFM or flight 

manual supplement. Flightcrew members must be thoroughly 

familiar with the particular GPS equipment installed in the 

aircraft, the receiver operation manual, and the POH/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. Using the equipment in 

flight under VFR conditions prior to attempting IFR operation 

allows for further familiarization.

Required preflight preparations should include checking 

NOTAMs relating to the IFR flight when using GPS as a 

supplemental method of navigation. GPS satellite outages 

are issued as GPS NOTAMs both domestically and 

internationally. Pilots may obtain GPS RAIM availability 

information for an airport by specifically requesting GPS 

aeronautical information from an FSS during preflight 

briefings. GPS RAIM aeronautical information can be 

obtained for a 3-hour period: the estimated time of arrival 

(ETA), and 1 hour before to 1 hour after the ETA hour, or 

a 24-hour time frame for a specific airport. FAA briefers 

provide RAIM information for a period of 1 hour before to 1 

hour after the ETA, unless a specific timeframe is requested 

by the pilot. If flying a published GPS departure, the pilot 

should also request a RAIM prediction for the departure 

airport. Some GPS receivers have the capability to predict 

RAIM availability. The pilot should also ensure that the 
9-29

Figure 7-26. GPS approach. 

16 DEC 2010 ot 13 JAN 2011

- 

SE-3, 16 DEC 2010 to 13 JAN 2011

Figure 9-28. A GPS stand-alone approach.

required underlying ground-based navigation facilities and 

related aircraft equipment appropriate to the route of flight, 

terminal operations, instrument approaches for the destination, 

and alternate airports/heliports are operational for the ETA. 

If the required ground-based facilities and equipment are 

not available, the flight should be rerouted, rescheduled, 

canceled, or conducted under VFR.

Except for programming and retrieving information from 

the GPS receiver, planning the flight is accomplished in a 

similar manner to conventional NAVAIDs. Departure WP, 

DP, route, STAR, desired approach, IAF, and destination 

airport are entered into the GPS receiver according to the 

manufacturer’s instructions. During preflight, additional 

information may be entered for functions such as ETA, fuel 

planning, winds aloft, etc.

When the GPS receiver is turned on, it begins an internal 

process of test and initialization. When the receiver is 

initialized, the user develops the route by selecting a WP 

or series of WPs, verifies the data, and selects the active 

flight plan. This procedure varies widely among receivers 

made by different manufacturers. GPS is a complex system, 

offering little standardization between receiver models. It is 

the pilot’s responsibility to be familiar with the operation of 

the equipment in the aircraft.

The GPS receiver provides navigational values such as track, 

bearing, groundspeed, and distance. These are computed from 

the aircraft’s present latitude and longitude to the location of 

the next WP. Course guidance is provided between WPs. The 

pilot has the advantage of knowing the aircraft’s actual track 

over the ground. As long as track and bearing to the WP are 

matched up (by selecting the correct aircraft heading), the 

aircraft is going directly to the WP.

GPS Instrument Approaches

There is a mixture of GPS overlay approaches (approaches 

with “or GPS” in the title) and GPS stand-alone approaches 

in the United States.

NOTE: GPS instrument approach operations outside the United 

States must be authorized by the appropriate country authority.

While conducting these IAPs, ground-based NAVAIDs are 

not required to be operational and associated aircraft avionics 

need not be installed, operational, turned on, or monitored; 

however, monitoring backup navigation systems is always 

recommended when available.

Pilots should have a basic understanding of GPS approach 

procedures and practice GPS IAPs under visual meteorological 

conditions (VMC) until thoroughly proficient with all 

aspects of their equipment (receiver and installation) prior 

to attempting flight in instrument meteorological conditions 

(IMC). [Figure 9-28]
9-30

All IAPs must be retrievable from the current GPS database 

supplied by the manufacturer or other FAA-approved 

source. Flying point to point on the approach does not 

assure compliance with the published approach procedure. 

The proper RAIM sensitivity is not available and the CDI 

sensitivity does 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 are not available as overlays.

GPS approaches are requested and approved by ATC using 

the GPS title, such as “GPS RWY 24” or “RNAV RWY 35.” 

Using the manufacturer’s recommended procedures, the 

desired approach and the appropriate IAF are selected from 

the GPS receiver database. 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 ensure terrain clearance.

When an approach has been loaded in the flight plan, GPS 

receivers give an “arm” annunciation 30 NM straight 

line distance from the airport/heliport reference point. 

The approach mode should be “armed” when within 30 

NM distance so the receiver changes from en route CDI 

(±5 NM) and RAIM (±2 NM) sensitivity to ±1 NM terminal 

sensitivity. Where the IAWP is within 30 NM, a CDI 

sensitivity change occurs once the approach mode is armed 

and the aircraft is within 30 NM. Where the IAWP is beyond 

the 30 NM point, CDI sensitivity does not change until the 

aircraft is within 30 NM even if the approach is armed earlier. 

Feeder route obstacle clearance is predicated on the receiver 

CDI and RAIM being in terminal CDI sensitivity within 30 NM 

of the airport/heliport reference point; therefore, the receiver 

should always be armed no later than the 30 NM annunciation.

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 WPs by the receiver and to resume 

automatic GPS navigation sequencing once the maneuver 

is complete. The same WP may appear in the route of flight 

more than once and consecutively (e.g., IAWP, final approach 

waypoint (FAWP), missed approach waypoint (MAWP) on a 

procedure turn). Care must be exercised to ensure the receiver 

is sequenced to the appropriate WP for the segment of the 

procedure being flown, especially if one or more fly-over WPs 

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

turn is not flown). The pilot may need to sequence past one or 

more fly-overs of the same WP in order to start GPS automatic 

sequencing at the proper place in the sequence of WPs.

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 that is aligned with the runway. 

Assigned altitudes must be maintained until established on a 

published segment of the approach. Required altitudes at WPs 

outside the FAWP or step-down fixes must be considered. 

Calculating the distance to the FAWP may be required in 

order to descend at the proper location.

When within 2 NM of the FAWP with the approach mode 

armed, the approach mode switches to active, which results 

in RAIM and CDI sensitivity changing to the approach 

mode. Beginning 2 NM prior to the FAWP, the full scale 

CDI sensitivity changes smoothly from ±1 NM to ±0.3 NM 

at the FAWP. As sensitivity changes from ±1 NM to ±0.3 

NM approaching the FAWP, and the CDI not centered, 

the corresponding increase in CDI displacement may give 

the impression the aircraft is moving further away from 

the intended course even though it is on an acceptable 

intercept heading. If digital track displacement information 

(cross-track error) is available in the approach mode, it 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 helps prevent 

problems in interpreting the CDI display during ramp-down. 

Requesting or accepting vectors, which causes the aircraft 

to intercept the final approach course within 2 NM of the 

FAWP, is not recommended.

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. Overriding an 

automatically selected sensitivity during an approach cancels 

the approach mode annunciation. If the approach mode is 

not armed by 2 NM prior to the FAWP, the approach mode 

does not become active at 2 NM prior to the FAWP and 

the equipment will flag. In these conditions, the RAIM and 

CDI sensitivity do not ramp down, and the pilot should not 

descend to minimum descent altitude (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.

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 
9-31

causes CDI sensitivity to change immediately to terminal 

(±1 NM) sensitivity, and the receiver continues to navigate 

to the MAWP. The receiver does not sequence past the 

MAWP. Turns should not begin prior to the MAWP. If the 

missed approach is not activated, the GPS receiver displays 

an extension of the inbound final approach course and the 

along track distance (ATD) increases from the MAWP until 

it is manually sequenced after crossing the MAWP.

Missed approach routings in which the first track is via a course 

rather than direct to the next WP require additional action 

by the pilot to set the course. Being familiar with all of the 

required inputs is especially critical during this phase of flight.

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 provided automatically by the 

receiver. (Terminal RAIM for departure may not be available 

unless the WPs 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 WP. 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. Turning areas are based 

on this speed also. Missed approach routings in which the 

first track is via a course rather than direct to the next WP 

require additional action by the pilot to set the course. Being 

familiar with all of the required inputs is especially critical 

during this phase of flight.

GPS Errors

Normally, with 30 satellites in operation, the GPS 

constellation is expected to be available continuously 

worldwide. Whenever there are fewer than 24 operational 

satellites, GPS navigational capability may not be available 

at certain geographic locations. Loss of signals may also 

occur in valleys surrounded by high terrain, and any time 

the aircraft’s GPS antenna is “shadowed” by the aircraft’s 

structure (e.g., when the aircraft is banked).

Certain receivers, transceivers, mobile radios, and portable 

receivers can cause signal interference. Some VHF 

transmissions may cause “harmonic interference.” Pilots 

can isolate the interference by relocating nearby portable 

receivers, changing frequencies, or turning off suspected 

causes of the interference while monitoring the receiver’s 

signal quality data page.

GPS position data can be affected by equipment characteristics 

and various geometric factors, which typically cause errors 

of less than 100 feet. Satellite atomic clock inaccuracies, 

receiver/processors, signals reflected from hard objects 

(multi-path), ionospheric and tropospheric delays, and 

satellite data transmission errors may cause small position 

errors or momentary loss of the GPS signal.

System Status

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 United States 

Coast Guard navigation information service: (703) 313-5907 

or on the internet at www.navcen.uscg.gov. Additionally, 

satellite status is available through the NOTAM system. 

The GPS receiver verifies the integrity (usability) of the 

signals received from the GPS constellation through 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 five 

satellites in view or four satellites and a barometric altimeter 

(baro-aiding) to detect an integrity anomaly. For receivers 

capable of doing so, RAIM needs six satellites in view (or 

five satellites with baro-aiding) to isolate the corrupt satellite 

signal and remove it from the navigation solution. 

RAIM messages vary somewhat between receivers; however, 

there are two most commonly used 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. 

Selective Availability. Selective availability 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. Selective availability was discontinued on 

May 1, 2000, but many GPS receivers are designed to assume 

that selective availability is still active. New receivers may 

take advantage of the discontinuance of selective availability 

based on the performance values in ICAO Annex 10 and do 

not need to be designed to operate outside of that performance. 

GPS Familiarization

Pilots should practice GPS approaches under VMC until 

thoroughly proficient with all aspects of their equipment 
9-32

(receiver and installation) prior to attempting flight by IFR in 

IMC. Some of the tasks which the pilot should practice are: 

1. Utilizing the 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 WP 

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). 

Differential Global Positioning Systems (DGPS)

Differential global positioning systems (DGPS) are designed 

to improve the accuracy of GNSS by measuring changes in 

variables to provide satellite positioning corrections.

Because multiple receivers receiving the same set of satellites 

produce similar errors, a reference receiver placed at a known 

location can compute its theoretical position accurately and 

can compare that value to the measurements provided by the 

navigation satellite signals. The difference in measurement 

between the two signals is an error that can be corrected by 

providing a reference signal correction. 

As a result of this differential input accuracy of the 

satellite system can be increased to meters. The Wide 

Area Augmentation System (WAAS) and Local Area 

Augmentation System (LAAS) are examples of differential 

global positioning systems.

Wide Area Augmentation System (WAAS)

The WAAS is designed to improve the accuracy, integrity, 

and availability of GPS signals. WAAS allows GPS to be 

used as the aviation navigation system from takeoff through 

Category I precision approaches. ICAO has defined Standards 

for satellite-based augmentation systems (SBAS), and 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 Japanese Multifunctional Transport Satellite (MTSAT) 

Satellite-based Augmentation System. The result will be a 

worldwide seamless navigation capability similar to GPS but 

with greater accuracy, availability, and integrity. 

Unlike traditional ground-based navigation aids, WAAS 

will cover a more extensive service area in which surveyed 

wide-area ground reference stations are linked to the WAAS 

network. Signals from the GPS satellites are monitored by 

these stations to determine satellite clock and ephemeris 

corrections. Each station in the network relays the data to a 

wide-area master station where the correction information is 

computed. A correction message is prepared and uplinked to 

a geostationary satellite (GEO) via a ground uplink and then 

broadcast on the same frequency as GPS to WAAS receivers 

within the broadcast coverage area. [Figure 9-29]

In addition to providing the correction signal, WAAS 

provides an additional 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. [Figure 9-30] As a result, performance improvement 

is sufficient to enable approach procedures with GPS/WAAS 

glidepaths. At this time the FAA has completed installation of 

25 wide area ground reference systems, two master stations, 

and four ground uplink stations. 

General Requirements

WAAS avionics must be certified in accordance with 

TSO-C145A, Airborne Navigation Sensors Using the GPS 

Augmented by the WAAS; or TSO-146A for stand-alone 

systems. GPS/WAAS operation must be conducted in 

accordance with the FAA-approved aircraft flight manual 

(AFM) and flight manual supplements. Flight manual 

supplements must state the level of approach procedure that 

the receiver supports. 

Instrument Approach Capabilities

WAAS receivers support all basic GPS approach functions 

and provide additional capabilities with the key benefit to 

generate an electronic glidepath, independent of ground 

equipment or barometric aiding. This eliminates several 

problems, such as cold temperature effects, incorrect 

altimeter setting, or lack of a local altimeter source, and 

allows approach procedures to be built without the cost 
9-33

Wide Area Reference Station 

receives GPS signal 

GPS 

Satellites 

1 

 Wide Area Reference Station 

 Wide Area Reference Station 

 data is sent to a Wide Area 

 Master Station for correction 

GPS 2 Satellites 

 Wide Area Reference Station 

 Wide Area Master station uplinks corrected 

 signal to GEO Synchronous Satellites 

 GUS 

GEO Synchronous 3 Satellites 

 Wide Area Reference Station 

 Wide Area Master station 

 GUS 

 GEO Synchronous Satellites sends updated 

 WAAS signal to aircraft equipped with WAAS 

 receivers 

GEO Synchronous 

Satellites 

4 

Figure 7-27a. LAAS representation. 

Wide Area Augmentation System (WAAS) 

Figure 9-29. WAAS satellite representation.

of installing ground stations at each airport. A new class 

of approach procedures, which provide vertical guidance 

requirements for precision approaches, has been developed 

to support satellite navigation use for aviation applications. 

These new procedures called Approach with Vertical 

Guidance (APV) include approaches such as the LNAV/

VNAV procedures presently being flown with barometric 

vertical navigation. 

Local Area Augmentation System (LAAS)

LAAS is a ground-based augmentation system that uses a 

GPS-reference facility located on or in the vicinity of the 

airport being serviced. This facility has a reference receiver 

that measures GPS satellite pseudo-range and timing and 

retransmits the signal. Aircraft landing at LAAS-equipped 

airports are able to conduct approaches to Category I level and 

above for properly equipped aircraft. [Figures 9-31 and 9-32]
9-34

The local area augmentation system (LAAS) ground facility 

receives the data from the GPS ground reference receivers. 

GPS reference receivers, which are serving the local area 

(such as an airport) receive the GPS signal from the GPS 

constellation (one or more satellites). 

The corrected signal is then sent and transmitted as a VHF 

signal, called a VHF data broadcast. 

The broadcast signal is received by appropriately equipped 

aircraft which provide the pilot with highly refined GPS 

guidance. 

GPS 

Reference 

Receiver 

GPS 

Reference 

Receiver 

LAAS 

Ground 

Facility 

VHF Data 

Broadcast 

LAAS 

Ground 

Facility 

VHF Data 

Broadcast 

Figure 7-28a. LAAS representation. 

4 

3 

2 

1 

GPS 

Reference 

Receiver 

Figure 9-31. LAAS representation.

50 ft. 

10 ft. 

Figure 7-27b. WAAS satellite representation 

You are here 

GPS Accuracy WAAS Accuracy 

Figure 9-30. WAAS provides performance enhancement for GPS 

approach procedures through real-time monitoring. 

Inertial Navigation System (INS)

Inertial Navigation System (INS) is a system that navigates 

precisely without any input from outside of the aircraft. It is 

fully self-contained. The INS is initialized by the pilot, who 

enters into the system the exact location of the aircraft on the 

ground before the flight. The INS is also programmed with 

WPs along the desired route of flight.

INS Components

INS is considered a stand-alone navigation system, especially 

when more than one independent unit is onboard. The 

airborne equipment consists of an accelerometer to measure 

acceleration—which, when integrated with time, gives 

velocity—and gyros to measure direction.

Later versions of the INS, called inertial reference systems 

(IRS), utilize laser gyros and more powerful computers; 

therefore, the accelerometer mountings no longer need to 

be kept level and aligned with true north. The computer 

system can handle the added workload of dealing with the 

computations necessary to correct for gravitational and 

directional errors. Consequently, these newer systems are 

sometimes called strap down systems, as the accelerometers 

and gyros are strapped down to the airframe rather than being 

mounted on a structure that stays fixed with respect to the 

horizon and true north.

INS Errors

The principal error associated with INS is degradation of 

position with time. INS computes position by starting with 

accurate position input which is changed continuously as 

accelerometers and gyros provide speed and direction inputs. 

Both accelerometers and gyros are subject to very small 

errors; as time passes, those errors probably accumulate.
9-35

Figure 7-28. LAAS representation. 

Reference Receiver 

GPS Satellites 

LAAS Facility 

VHF Transmitter 

Figure 9-32. The LAAS system working with GPS satellites, 

reference receivers and radio transmitters which are located on 

or in the vicinity of the airport. 

While the best INS/IRS display errors of 0.1 to 0.4 NM after 

flights across the North Atlantic of 4 to 6 hours, smaller and 

less expensive systems are being built that show errors of 1 

to 2 NM per hour. This accuracy is more than sufficient for 

a navigation system that can be combined with and updated 

by GPS. The synergy of a navigation system consisting of an 

INS/IRS unit in combination with a GPS resolves the errors 

and weaknesses of both systems. GPS is accurate all the time 

it is working but may be subject to short and periodic outages. 

INS is made more accurate because it is continually updated 

and continues to function with good accuracy if the GPS has 

moments of lost signal.

Instrument Approach Systems

Most navigation systems approved for en route and terminal 

operations under IFR, such as VOR, NDB, and GPS, may also 

be approved to conduct IAPs. The most common systems in 

use in the United States are the ILS, simplified directional 

facility (SDF), localizer-type directional aid (LDA), and 

microwave landing system (MLS). These systems operate 

independently of other navigation systems. There are new 

systems being developed, such as WAAS and LAAS. Other 

systems have been developed for special use.

Instrument Landing Systems (ILS)

The ILS system provides both course and altitude guidance 

to a specific runway. The ILS system is used to execute a 

precision instrument approach procedure or precision approach. 

[Figure 9-33] The system consists of the following components:

1. A localizer providing horizontal (left/right) guidance 

along the extended centerline of the runway.

2. A glideslope (GS) providing vertical (up/down) 

guidance toward the runway touchdown point, usually 

at a 3° slope.

3. Marker beacons providing range information along 

the approach path.

4. Approach lights assisting in the transition from 

instrument to visual flight.

The following supplementary elements, though not specific 

components of the system, may be incorporated to increase 

safety and utility:

1. Compass locators providing transition from en route 

NAVAIDs to the ILS system and assisting in holding 

procedures, tracking the localizer course, identifying 

the marker beacon sites, and providing a FAF for 

ADF approaches.

2. DME collocated with the GS transmitter providing 

positive distance-to-touchdown information or DME 

associated with another nearby facility (VOR or standalone), if specified in the approach procedure.

ILS approaches are categorized into three different types of 

approaches based on the equipment at the airport and the 

experience level of the pilot. Category I approaches provide 

for approach height above touchdown of not less than 200 feet. 

Category II approaches provide for approach to a height above 

touchdown of not less than 100 feet. Category III approaches 

provide lower minimums for approaches without a decision 

height minimum. While pilots need only be instrument rated 

and the aircraft be equipped with the appropriate airborne 

equipment to execute Category I approaches, Category II 

and III approaches require special certification for the pilots, 

ground equipment, and airborne equipment.

ILS Components

Ground Components

The ILS uses a number of different ground facilities. These 

facilities may be used as a part of the ILS system, as well as 

part of another approach. For example, the compass locator 

may be used with NDB approaches.

Localizer

The localizer (LOC) ground antenna array is located on the 

extended centerline of the instrument runway of an airport, 

located at the departure end of the runway to prevent it from 

being a collision hazard. This unit radiates a field pattern, 

which develops a course down the centerline of the runway 

toward the middle markers (MMs) and outer markers 

(OMs) and a similar course along the runway centerline in 

the opposite direction. These are called the front and back 
9-36

OBS 

N 

E 

S 

W 

3 

33 

24 21 

15 12 

30 

6 

GS 

NAV 

OBS 

N 

E 

S 

W 

3 

33 

24 21 

15 12 

30 

6 

GS 

NAV 

OBS 

N 

E 

S 

W 

3 

33 

24 21 

15 12 

30 

6 

GS 

NAV 

I20 

I00 

90 

40 

KNOTS 

I40 I20 

II0 

80 

60 

40 

KNOTS 

240

I30 

I00 

80 

60 

40 

KNOTS 

240

220 

200 

I80 

I50 I20 

I00 

80 

60 

40 

KNOTS 

240

220 

200 

I60 

I60 I40 I20 

I00 

80 

60 

40 

KNOTS 

–

–

OBS 

N 

E 

S 

W 

3 

33 

24 21 

15 12 

30 

6 

GS 

NAV 

90Hz 150Hz 

OBS 

N 

E 

S 

W 

3 

33 

24 21 

15 12 

30 

6 

GS 

NAV 

Figure 7-29. Instrument landing systems. 

Point of intersection

runway and glideslope

extended.

Figure 9-33. Instrument landing systems.

courses, respectively. The localizer provides course guidance, 

transmitted at 108.1 to 111.95 MHz (odd tenths only), 

throughout the descent path to the runway threshold from a 

distance of 18 NM from the antenna to an altitude of 4,500 

feet above the elevation of the antenna site. [Figure 9-34]

The localizer course width is defined as the angular 

displacement at any point along the course between a full 

“fly-left” (CDI needle fully deflected to the left) and a full 

“fly-right” indication (CDI needle fully deflected to the right). 

Each localizer facility is audibly identified by a three-letter 

designator transmitted at frequent regular intervals. The ILS 

identification is preceded by the letter “I” (two dots). For 

example, the ILS localizer at Springfield, Missouri, transmits 

the identifier ISGF. The localizer includes a voice feature on 
9-37

35° 

10° 

10° 

10 NM 

35° 

18 NM 

Figure 9-34. Localizer coverage limits. Figure 7-30. Localizer coverage limits. 

2.5° 

2.5° 

Outer Marker Beacons 

Middle Marker Beacons 

Figure 7-31. Localizer receiver indications and aircraft 

displacement. 

 ́  ́ 

Figure 9-35. Localizer receiver indications and aircraft displacement.

its frequency for use by the associated ATC facility in issuing 

approach and landing instructions.

The localizer course is very narrow, normally 5°. This 

results in high needle sensitivity. With this course width, 

a full-scale deflection shows when the aircraft is 2.5° to 

either side of the centerline. This sensitivity permits accurate 

orientation to the landing runway. With no more than onequarter scale deflection maintained, the aircraft will be 

aligned with the runway.

Glideslope (GS)

GS describes the systems that generate, receive, and indicate 

the ground facility radiation pattern. The glidepath is the 

straight, sloped line the aircraft should fly in its descent from 

where the GS intersects the altitude used for approaching the 

FAF to the runway touchdown zone. The GS equipment is 

housed in a building approximately 750 to 1,250 feet down 

the runway from the approach end of the runway and between 

400 and 600 feet to one side of the centerline.

The course projected by the GS equipment is essentially the 

same as would be generated by a localizer operating on its 

side. The GS projection angle is normally adjusted to 2.5° 

to 3.5° above horizontal, so it intersects the MM at about 

200 feet and the OM at about 1,400 feet above the runway 

elevation. At locations where standard minimum obstruction 

clearance cannot be obtained with the normal maximum GS 

angle, the GS equipment is displaced farther from the approach 

end of the runway if the length of the runway permits; or the GS 

angle may be increased up to 4°.

Unlike the localizer, the GS transmitter radiates signals only 

in the direction of the final approach on the front course. The 

system provides no vertical guidance for approaches on the back 

course. The glidepath is normally 1.4° thick. At 10 NM from 

the point of touchdown, this represents a vertical distance of 

approximately 1,500 feet, narrowing to a few feet at touchdown.

Marker Beacons

Two VHF marker beacons, outer and middle, are normally 

used in the ILS system. [Figure 9-35] A third beacon, the 

inner, is used where Category II operations are certified. A 

marker beacon may also be installed to indicate the FAF on 

the ILS back course.

The OM is located on the localizer front course 4–7 miles 

from the airport to indicate a position at which an aircraft, at 

the appropriate altitude on the localizer course, will intercept 

the glidepath. The MM is located approximately 3,500 feet 
9-38

from the landing threshold on the centerline of the localizer 

front course at a position where the GS centerline is about 200 

feet above the touchdown zone elevation. The inner marker 

(IM), where installed, is located on the front course between 

the MM and the landing threshold. It indicates the point at 

which an aircraft is at the decision height on the glidepath 

during a Category II ILS approach. The back-course marker, 

where installed, indicates the back-course FAF.

Compass Locator

Compass locators are low-powered NDBs and are received 

and indicated by the ADF receiver. When used in conjunction 

with an ILS front course, the compass locator facilities are 

collocated with the outer and/or MM facilities. The coding 

identification of the outer locator consists of the first two 

letters of the three-letter identifier of the associated LOC. 

For example, the outer locator at Dallas/Love Field (DAL) is 

identified as “DA.” The middle locator at DAL is identified 

by the last two letters “AL.”

Approach Lighting Systems (ALS)

Normal approach and letdown on the ILS is divided into two 

distinct stages: the instrument approach stage using only radio 

guidance, and the visual stage, when visual contact with the 

ground runway environment is necessary for accuracy and 

safety. The most critical period of an instrument approach, 

particularly during low ceiling/visibility conditions, is the 

point at which the pilot must decide whether to land or 

execute a missed approach. As the runway threshold is 

approached, the visual glidepath separates into individual 

lights. At this point, the approach should be continued by 

reference to the runway touchdown zone markers. The 

approach lighting system (ALS) provides lights that will 

penetrate the atmosphere far enough from touchdown to 

give directional, distance, and glidepath information for safe 

visual transition.

Visual identification of the ALS by the pilot must be 

instantaneous, so it is important to know the type of ALS 

before the approach is started. Check the instrument approach 

chart and the A/FD for the particular type of lighting facilities 

at the destination airport before any instrument flight. With 

reduced visibility, rapid orientation to a strange runway can 

be difficult, especially during a circling approach to an airport 

with minimum lighting facilities or to a large terminal airport 

located in the midst of distracting city and ground facility 

lights. Some of the most common ALS systems are shown 

in Figure 9-36.

A high-intensity flasher system, often referred to as “the 

rabbit,” is installed at many large airports. The flashers consist 

of a series of brilliant blue-white bursts of light flashing in 

sequence along the approach lights, giving the effect of a ball 

of light traveling towards the runway. Typically, “the rabbit” 

makes two trips toward the runway per second.

Runway end identifier lights (REIL) are installed for rapid and 

positive identification of the approach end of an instrument 

runway. The system consists of a pair of synchronized 

flashing lights placed laterally on each side of the runway 

threshold facing the approach area.

The visual approach slope indicator (VASI) gives visual 

descent guidance information during the approach to a 

runway. The standard VASI consists of light bars that 

project a visual glidepath, which provides safe obstruction 

clearance within the approach zone. The normal GS angle 

is 3°; however, the angle may be as high as 4.5° for proper 

obstacle clearance. On runways served by ILS, the VASI 

angle normally coincides with the electronic GS angle. 

Visual left/right course guidance is obtained by alignment 

with the runway lights. The standard VASI installation 

consists of either 2-, 3-, 4-, 6-, 12-, or 16-light units arranged 

in downwind and upwind light bars. Some airports serving 

long-bodied aircraft have three-bar VASIs that provide two 

visual glidepaths to the same runway. The first glidepath 

encountered is the same as provided by the standard VASI. 

The second glidepath is about 25 percent higher than the first 

and is designed for the use of pilots of long-bodied aircraft.

The basic principle of VASI is that of color differentiation 

between red and white. Each light projects a beam having 

a white segment in the upper part and a red segment in the 

lower part of the beam. From a position above the glidepath 

the pilot sees both bars as white. Lowering the aircraft with 

respect to the glidepath, the color of the upwind bars changes 

from white to pink to red. When on the proper glidepath, 

the landing aircraft will overshoot the downwind bars and 

undershoot the upwind bars. Thus the downwind (closer) 

bars are seen as white and the upwind bars as red. From 

a position below the glidepath, both light bars are seen as 

red. Moving up to the glidepath, the color of the downwind 

bars changes from red to pink to white. When below the 

glidepath, as indicated by a distinct all-red signal, a safe 

obstruction clearance might not exist. A standard two-bar 

VASI is illustrated in Figure 9-37.

ILS Airborne Components

Airborne equipment for the ILS system includes receivers 

for the localizer, GS, marker beacons, ADF, DME, and the 

respective indicator instruments.

The typical VOR receiver is also a localizer receiver with 

common tuning and indicating equipment. Some receivers 

have separate function selector switches, but most switch 

between VOR and LOC automatically by sensing if odd 
9-39

ALSF-2 ALSF-1 SSALR/MALSR MALSF 

ODALS 

REIL 

THRESHOLD 

Figure 9-36. Precision and nonprecision ALS configuration.

Below glidepath On glidepath Above glidepath 

Far Bar 

Near Bar 

Far Bar 

Near Bar 

Far Bar 

Near Bar 

Figure 9-37. Standard two-bar VASI. Figure 7-33. Standard 2-bar VASI. 

tenths between 108 and 111.95 MHz have been selected. 

Otherwise, tuning of VOR and localizer frequencies is 

accomplished with the same knobs and switches, and the CDI 

indicates “on course” as it does on a VOR radial.

Though some GS receivers are tuned separately, in a typical 

installation the GS is tuned automatically to the proper 

frequency when the localizer is tuned. Each of the 40 localizer 

channels in the 108.10 to 111.95 MHz band is paired with a 

corresponding GS frequency.

When the localizer indicator also includes a GS needle, the 

instrument is often called a cross-pointer indicator. The 

crossed horizontal (GS) and vertical (localizer) needles are 
9-40

free to move through standard five-dot deflections to indicate 

position on the localizer course and glidepath.

When the aircraft is on the glidepath, the needle is horizontal, 

overlying the reference dots. Since the glidepath is much 

narrower than the localizer course (approximately 1.4° from 

full up to full down deflection), the needle is very sensitive 

to displacement of the aircraft from on-path alignment. With 

the proper rate of descent established upon GS interception, 

very small corrections keep the aircraft aligned.

The localizer and GS warning flags disappear from view on 

the indicator when sufficient voltage is received to actuate the 

needles. The flags show when an unstable signal or receiver 

malfunction occurs.

The OM is identified by a low-pitched tone, continuous dashes 

at the rate of two per second, and a purple/blue marker beacon 

light. The MM is identified by an intermediate tone, alternate 

dots and dashes at the rate of 95 dot/dash combinations per 

minute, and an amber marker beacon light. The IM, where 

installed, is identified by a high-pitched tone, continuous dots 

at the rate of six per second, and a white marker beacon light. 

The back-course marker (BCM), where installed, is identified 

by a high-pitched tone with two dots at a rate of 72 to 75 twodot combinations per minute and a white marker beacon light. 

Marker beacon receiver sensitivity is selectable as high or low 

on many units. The low-sensitivity position gives the sharpest 

indication of position and should be used during an approach. 

The high-sensitivity position provides an earlier warning that 

the aircraft is approaching the marker beacon site.

ILS Function

The localizer needle indicates, by deflection, whether the 

aircraft is right or left of the localizer centerline, regardless of 

the position or heading of the aircraft. Rotating the OBS has 

no effect on the operation of the localizer needle, although 

it is useful to rotate the OBS to put the LOC inbound course 

under the course index. When inbound on the front course, or 

outbound on the back course, the course indication remains 

directional. (See Figure 9-38, aircraft C, D, and E.)

Unless the aircraft has reverse sensing capability and it is in 

use, when flying inbound on the back course or outbound on 

the front course, heading corrections to on-course are made 

opposite the needle deflection. This is commonly described 

as “flying away from the needle.” (See Figure 9-38, aircraft A 

and B.) Back course signals should not be used for an approach 

unless a back course approach procedure is published for that 

particular runway and the approach is authorized by ATC.

Once you have reached the localizer centerline, maintain 

the inbound heading until the CDI moves off center. Drift 

corrections should be small and reduced proportionately as 

the course narrows. By the time you reach the OM, your drift 

correction should be established accurately enough on a wellexecuted approach to permit completion of the approach, 

with heading corrections no greater than 2°.

The heaviest demand on pilot technique occurs during 

descent from the OM to the MM, when you maintain 

the localizer course, adjust pitch attitude to maintain the 

proper rate of descent, and adjust power to maintain proper 

airspeed. Simultaneously, the altimeter must be checked 

and preparation made for visual transition to land or for a 

missed approach. You can appreciate the need for accurate 

instrument interpretation and aircraft control within the ILS 

as a whole, when you notice the relationship between CDI 

and glidepath needle indications and aircraft displacement 

from the localizer and glidepath centerlines.

Deflection of the GS needle indicates the position of the 

aircraft with respect to the glidepath. When the aircraft is 

above the glidepath, the needle is deflected downward. When 

the aircraft is below the glidepath, the needle is deflected 

upward. [Figure 9-39]

ILS Errors

The ILS and its components are subject to certain errors, 

which are listed below. Localizer and GS signals are subject to 

the same type of bounce from hard objects as space waves.

1. Reflection. Surface vehicles and even other aircraft 

flying below 5,000 feet above ground level (AGL) 

may disturb the signal for aircraft on the approach.

2. False courses. In addition to the desired course, GS 

facilities inherently produce additional courses at 

higher vertical angles. The angle of the lowest of 

these false courses occurs at approximately 9°– 12°. 

An aircraft flying the LOC/GS course at a constant 

altitude would observe gyrations of both the GS needle 

and GS warning flag as the aircraft passed through the 

various false courses. Getting established on one of 

these false courses results in either confusion (reversed 

GS needle indications) or in the need for a very high 

descent rate. However, if the approach is conducted 

at the altitudes specified on the appropriate approach 

chart, these false courses are not encountered.

Marker Beacons

The very low power and directional antenna of the marker 

beacon transmitter ensures that the signal is not received 

any distance from the transmitter site. Problems with signal 

reception are usually caused by the airborne receiver not 

being turned on or by incorrect receiver sensitivity.
9-41

36

18

OBS N

E

S

W

3

33

24 21

15 12

30

6

33 30

24 2I

I5 I2

6 3

HDG 330° CRS 180°

LOC1

330°

As you begin procedure turn, 

course needle shows 

divergence from course 

centerline increasing.

B

C

While on the procedure turn 

inbound the course needle 

becomes directional. Start

the turn to final approach 

course when the needle 

comes alive (needle moves 

away from side) and is 

moving toward center.

OBS N

E

S

W

3

33

24 21

15 12

30

6

33 30

24 2I

I2 I5

6 3

HDG 135° CRS 180°

LOC1

135°

OBS

N

E

S

W

3

33

24 21

15 12

30

6

NAV

GS

Instrument view is from 

the pilot’s perspective, 

and the movable card is 

reset after each turn

OBS N

E

S

W

3

33

24 21

15 12

30

33

6

30

24 2I

I5 I2

6 3

Maintain course with the 

needle centered.

HDG 180° CRS 180°

LOC1

180° D

HDG 350° CRS 180°

LOC1

350°

OBS N

E

S

W

3

33

24 21

15 12

30

6

33 30

24 2I

I5 I2

6 3

As you fly northbound of the 

instrument runway (in this case 

Localizer 18), with the radio 

tuned to the Localizer 

frequency (and identified), the 

course needle is not directional. 

Correct left to center the course 

needle.

A

E

A

D

B

C

FAF

Localizer inbound 

course is 180°

As you fly a missed approach 

along the back course, the 

needle, indicating “fly left” is 

directional. 

In this case fly left to get on 

course.

OBS N

E

S

W

3

33

24 21

15 12

30

33

6

30

24 2I

I5 I2

6 3 HDG 180° CRS 180°

LOC1

180°

E

Figure 9-38. Localizer course indications. To follow indications displayed in the aircraft, start from A and proceed through E.
9-42

OBS 

FR

TO 

N 

E 

S 

W 

3 

33 

24 21 

12 15 

30 

6 

NAV 1 

Figure 7-35. Glide-slope receiver indications and aircraft displacement. 

Outer Marker Beacons 

Middle Marker Beacons 

OBS 

FR

TO 

N 

E 

S 

W 

3 

33 

24 21 

12 15 

30 

6 

NAV 1 

4300 

4200 

4100 

4000 

3900 

3800 

3600 

3500 

3400 

3300 

3200 

3100 

20 

80 

4000 

4400 

4300 

4200 

4100 

4000 

3900 

3800 

3600 

3500 

3400 

3300 

3200 

3100 

20 

80 

4000 

4000 

 

 

Figure 9-39. A GS receiver indication and aircraft displacement. An analog system is on the left and the same indication on the Garmin 

PFD on the right.

Some marker beacon receivers, to decrease weight and cost, 

are designed without their own power supply. These units 

utilize a power source from another radio in the avionics 

stack, often the ADF. In some aircraft, this requires the ADF 

to be turned on in order for the marker beacon receiver to 

function, yet no warning placard is required. Another source 

of trouble may be the “HIGH/LOW/OFF” three-position 

switch, which both activates the receiver and selects receiver 

sensitivity. Usually, the “test” feature only tests to see if 

the light bulbs in the marker beacon lights are working. 

Therefore, in some installations, there is no functional way 

for the pilot to ascertain the marker beacon receiver is actually 

on except to fly over a marker beacon transmitter and see if 

a signal is received and indicated (e.g., audibly, and visually 

via marker beacon lights).

Operational Errors

1. Failure to understand the fundamentals of ILS ground 

equipment, particularly the differences in course 

dimensions. Since the VOR receiver is used on the 

localizer course, the assumption is sometimes made 

that interception and tracking techniques are identical 

when tracking localizer courses and VOR radials. 

Remember that the CDI sensing is sharper and faster 

on the localizer course.

2. Disorientation during transition to the ILS due to poor 

planning and reliance on one receiver instead of on all 

available airborne equipment. Use all the assistance 

available; a single receiver may fail.

3. Disorientation on the localizer course, due to the first 

error noted above.

4. Incorrect localizer interception angles. A large 

interception angle usually results in overshooting 

and possible disorientation. When intercepting, 

if possible, turn to the localizer course heading 

immediately upon the first indication of needle 

movement. An ADF receiver is an excellent aid to 

orient you during an ILS approach if there is a locator 

or NDB on the inbound course.

5. Chasing the CDI and glidepath needles, especially 

when you have not sufficiently studied the approach 

before the flight.

Simplified Directional Facility (SDF)

The simplified directional facility (SDF) provides a final 

approach course similar to the ILS localizer. The SDF course 

may or may not be aligned with the runway and the course 

may be wider than a standard ILS localizer, resulting in less 
9-43

Figure 7-36. MLS coverage volumes, 3-D representation 

40°L 

40°R 

20,000’ 

Figure 9-40. MLS coverage volumes, 3-D representation.

precision. Usable off-course indications are limited to 35° 

either side of the course centerline. Instrument indications 

in the area between 35° and 90° from the course centerline 

are not controlled and should be disregarded.

The SDF must provide signals sufficient to allow satisfactory 

operation of a typical aircraft installation within a sector 

which extends from the center of the SDF antenna system 

to distances of 18 NM covering a sector 10° either side of 

centerline up to an angle 7° above the horizontal. The angle 

of convergence of the final approach course and the extended 

runway centerline must not exceed 30°. Pilots should note 

this angle since the approach course originates at the antenna 

site, and an approach continued beyond the runway threshold 

would lead the aircraft to the SDF offset position rather than 

along the runway centerline.

The course width of the SDF signal emitted from the 

transmitter is fixed at either 6° or 12°, as necessary, to provide 

maximum flyability and optimum approach course quality. 

A three-letter identifier is transmitted in code on the SDF 

frequency; there is no letter “I” (two dots) transmitted before 

the station identifier, as there is with the LOC. For example, 

the identifier for Lebanon, Missouri, SDF is LBO.

Localizer Type Directional Aid (LDA)

The localizer type directional aid (LDA) is of comparable 

utility and accuracy to a localizer but is not part of a 

complete ILS. The LDA course width is between 3° and 6° 

and thus provides a more precise approach course than an 

SDF installation. Some LDAs are equipped with a GS. The 

LDA course is not aligned with the runway, but straight-in 

minimums may be published where the angle between the 

runway centerline and the LDA course does not exceed 30°. If 

this angle exceeds 30°, only circling minimums are published. 

The identifier is three letters preceded by “I” transmitted in 

code on the LDA frequency. For example, the identifier for 

Van Nuys, California, LDA is I-BUR.

Microwave Landing System (MLS)

The microwave landing system (MLS) provides precision 

navigation guidance for exact alignment and descent of aircraft 

on approach to a runway. It provides azimuth, elevation, and 

distance. Both lateral and vertical guidance may be displayed 

on conventional course deviation indicators or incorporated 

into multipurpose flight deck displays. Range information 

can be displayed by conventional DME indicators and also 

incorporated into multipurpose displays. [Figure 9-40]

The system may be divided into five functions, which are 

approach azimuth, back azimuth, approach elevation, range; 

and data communications. The standard configuration of 

MLS ground equipment includes an azimuth station to 

perform functions as indicated 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. 

Approach Azimuth Guidance

The azimuth station transmits MLS angle and data on one 

of 200 channels within the frequency range of 5031 to 5091 

MHz. 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. The azimuth coverage extends 

laterally at least 40° on either side of the runway centerline 

in a standard configuration, in elevation up to an angle of 15° 

and to at least 20,000 feet, and in range to at least 20 NM. 

MLS requires separate airborne equipment to receive and 

process the signals from what is normally installed in general 

aviation aircraft today. It has data communications capability, 

and can provide audible information about the condition 

of the transmitting system and other pertinent data such as 

weather, runway status, etc. The MLS transmits an audible 

identifier consisting of four letters beginning with the letter 

M, in Morse code at a rate of at least six per minute. The 

MLS system monitors itself and transmits ground-to-air data 

messages about the system’s operational condition. During 

periods of routine or emergency maintenance, the coded 

identification is missing from the transmissions. At this time 

there are only a few systems installed. 
9-44

Required Navigation Performance

RNP is a navigation system that provides a specified level 

of accuracy defined by a lateral area of confined airspace in 

which an RNP-certified aircraft operates. The continuing 

growth of aviation places increasing demands on airspace 

capacity and emphasizes the need for the best use of the 

available airspace. These factors, along with the accuracy of 

modern aviation navigation systems and the requirement for 

increased operational efficiency in terms of direct routings 

and track-keeping accuracy, have resulted in the concept 

of required navigation performance—a statement of the 

navigation performance accuracy necessary for operation 

within a defined airspace. RNP can include both performance 

and functional requirements and is indicated by the RNP type. 

These standards are intended for designers, manufacturers, 

and installers of avionics equipment, as well as service 

providers and users of these systems for global operations. 

The minimum aviation system performance specification 

(MASPS) provides guidance for the development of airspace 

and operational procedures needed to obtain the benefits of 

improved navigation capability. [Figure 9-41]

The RNP type defines the total system error (TSE) that 

is allowed in lateral and longitudinal dimensions within 

a particular airspace. The TSE, which takes account of 

navigation system errors (NSE), computation errors, display 

errors and flight technical errors (FTE), must not exceed the 

specified RNP value for 95 percent of the flight time on any 

part of any single flight. RNP combines the accuracy standards 

laid out in the ICAO Manual (Doc 9613) with specific accuracy 

requirements, as well as functional and performance standards, 

for the RNAV system to realize a system that can meet future 

air traffic management requirements. The functional criteria 

for RNP address the need for the flightpaths of participating 

aircraft to be both predictable and repeatable to the declared 

levels of accuracy. More information on RNP is contained in 

subsequent chapters.

The term RNP is also applied as a descriptor for airspace, 

routes, and procedures (including departures, arrivals, 

and IAPs). The descriptor can apply to a unique approach 

procedure or to a large region of airspace. RNP applies to 

navigation performance within a designated airspace and 

includes the capability of both the available infrastructure 

(navigation aids) and the aircraft.

RNP type is used to specify navigation requirements for the 

airspace. The following are ICAO RNP Types: RNP-1.0, 

RNP-4.0, RNP-5.0, and RNP-10.0. The required performance 

is obtained through a combination of aircraft capability and 

the level of service provided by the corresponding navigation 

infrastructure. From a broad perspective:

Aircraft Capability + Level of Service = Access

In this context, aircraft capability refers to the airworthiness 

certification and operational approval elements (including 

avionics, maintenance, database, human factors, pilot 

procedures, training, and other issues). The level of service 

element refers to the NAS infrastructure, including published 

routes, signal-in-space performance and availability, and air 

traffic management. When considered collectively, these 

elements result in providing access. Access provides the 

desired benefit (airspace, procedures, routes of flight, etc.).

RNP levels are actual distances from the centerline of the 

flightpath, which must be maintained for aircraft and obstacle 

separation. Although additional FAA-recognized RNP 

levels may be used for specific operations, the United States 

currently supports three standard RNP levels:

• RNP 0.3 – Approach

• RNP 1.0 – Departure, Terminal

• RNP 2.0 – En route

RNP 0.3 represents a distance of 0.3 NM either side of a 

specified flightpath centerline. The specific performance that 

is required on the final approach segment of an instrument 

approach is an example of this RNP level. At the present 

time, a 0.3 RNP level is the lowest level used in normal 

RNAV operations. Specific airlines, using special procedures, 

are approved to use RNP levels lower than RNP 0.3, but 

those levels are used only in accordance with their approved 

operations specifications (OpsSpecs). For aircraft equipment to 

qualify for a specific RNP type, it must maintain navigational 

accuracy at least 95 percent of the total flight time.

Flight Management Systems (FMS)

A flight management system (FMS) is not a navigation 

system in itself. Rather, it is a system that automates the 

tasks of managing the onboard navigation systems. FMS may 

perform other onboard management tasks, but this discussion 

is limited to its navigation function.

FMS is an interface between flight crews and flightdeck 

systems. FMS can be thought of as a computer with a large 

database of airport and NAVAID locations and associated 

data, aircraft performance data, airways, intersections, 

DPs, and STARs. FMS also has the ability to accept and 

store numerous user-defined WPs, flight routes consisting 

of departures, WPs, arrivals, approaches, alternates, etc. 

FMS can quickly define a desired route from the aircraft’s 

current position to any point in the world, perform flight 

plan computations, and display the total picture of the flight 

route to the crew.
9-45

36 

EN ROUTE 

TERMINAL 

FINAL APPROACH 

2.0 NM

2.0 NM

1.0 NM

1.0 NM

0.3 NM

0.3 NM

36 

18 

APPROACH TERMINAL ENROUTE DEPARTURE 

RNP 0.3 RNP 1.0 RNP 2.0 RNP 1.0

Figure 9-41. Required navigation performance.

FMS also has the capability of controlling (selecting) VOR, 

DME, and LOC NAVAIDs, and then receiving navigational 

data from them. INS, LORAN, and GPS navigational data 

may also be accepted by the FMS computer. The FMS may 

act as the input/output device for the onboard navigation 

systems, so that it becomes the “go-between” for the crew 

and the navigation systems.
9-46

The Universal UNS-1 The Avidyne The Garmin system

Figure 9-42. Typical display and control unit(s) in general aviation. The Universal UNS-1 (left) controls and integrates all other systems. The 

Avidyne (center) and Garmin systems (right) illustrate and are typical of completely integrated systems. Although the Universal CDU is not 

typically found on smaller general aviation aircraft, the difference in capabilities of the CDUs and stand-alone sytems is diminishing each year.

Function of FMS

At startup, the crew programs the aircraft location, departure 

runway, DP (if applicable), WPs defining the route, approach 

procedure, approach to be used, and routing to alternate. This 

may be entered manually, be in the form of a stored flight 

plan, or be a flight plan developed in another computer and 

transferred by disk or electronically to the FMS computer. 

The crew enters this basic information in the control/display 

unit (CDU). [Figure 9-42]

Once airborne, the FMS computer channels the appropriate 

NAVAIDs and takes radial/distance information or 

channels two NAVAIDs, taking the more accurate distance 

information. FMS then indicates position, track, desired 

heading, groundspeed, and position relative to desired track. 

Position information from the FMS updates the INS. In more 

sophisticated aircraft, the FMS provides inputs to the HSI, 

RMI, glass flight deck navigation displays, head-up display 

(HUD), autopilot, and autothrottle systems.

Head-Up Display (HUD)

The HUD is a display system that provides a projection of 

navigation and air data (airspeed in relation to approach 

reference speed, altitude, left/right and up/down GS) on a 

transparent screen between the pilot and the windshield. 

Other information may be displayed, including a runway 

target in relation to the nose of the aircraft. This allows the 

pilot to see the information necessary to make the approach 

while also being able to see out the windshield, which 

diminishes the need to shift between looking at the panel to 

looking outside. Virtually any information desired can be 

displayed on the HUD if it is available in the aircraft’s flight 

computer and if the display is user definable. [Figure 9-43]

Radar Navigation (Ground-Based)

Radar works by transmitting a pulse of RF energy in a specific 

direction. The return of the echo or bounce of that pulse from 

a target is precisely timed. From this, the distance traveled 

by the pulse and its echo is determined and displayed on a 

radar screen in such a manner that the distance and bearing to 

this target can be instantly determined. The radar transmitter 

must be capable of delivering extremely high power levels 

toward the airspace under surveillance, and the associated 

radar receiver must be able to detect extremely small signal 

levels of the returning echoes.

The radar display system provides the controller with a maplike presentation upon which appear all the radar echoes 

of aircraft within detection range of the radar facility. By 

means of electronically-generated range marks and azimuthindicating devices, the controller can locate each radar target 

with respect to the radar facility, or can locate one radar target 

with respect to another.

Another device, a video-mapping unit, generates an actual 

airway or airport map and presents it on the radar display 

equipment. Using the video-mapping feature, the air traffic 

controller not only can view the aircraft targets, but can see 

these targets in relation to runways, navigation aids, and 

hazardous ground obstructions in the area. Therefore, radar 

becomes a NAVAID, as well as the most significant means 

of traffic separation.

In a display presenting perhaps a dozen or more targets, 

a primary surveillance radar system cannot identify one 

specific radar target, and it may have difficulty “seeing” a 

small target at considerable distance—especially if there is 

a rain shower or thunderstorm between the radar site and 

the aircraft. This problem is solved with the Air Traffic 

Control Radar Beacon System (ATCRBS), sometimes 

called secondary surveillance radar (SSR), which utilizes 

a transponder in the aircraft. The ground equipment is an 

interrogating unit, in which the beacon antenna is mounted 

so it rotates with the surveillance antenna. The interrogating 
9-47

Figure 9-43. Example of a head-up display (top) and a head-down 

display (bottom). The head-up display presents information in front of 

the pilot along his/her normal field of view while a head-down display 

may present information beyond the normal head-up field of view.

unit transmits a coded pulse sequence that actuates the aircraft 

transponder. The transponder answers the coded sequence 

by transmitting a preselected coded sequence back to the 

ground equipment, providing a strong return signal and 

positive aircraft identification, as well as other special data 

such as aircraft altitude.

Functions of Radar Navigation

The radar systems used by ATC are air route surveillance 

radar (ARSR), airport surveillance radar (ASR), and 

precision approach radar (PAR) and airport surface detection 

equipment (ASDE). Surveillance radars scan through 360° 

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.

ARSR is a long-range radar system designed primarily to 

cover large areas and provide a display of aircraft while en 

route between terminal areas. The ARSR enables air route 

traffic control center (ARTCC) controllers to provide radar 

service when the aircraft are within the ARSR coverage. 

In some instances, ARSR may enable ARTCC to provide 

terminal radar services similar to but usually more limited 

than those provided by a radar approach control.

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. 

Nonprecision instrument approaches are available at airports 

that have an approved surveillance radar approach procedure. 

ASR provides radar vectors to the final approach course and 

then azimuth information to the pilot during the approach. 

In addition to range (distance) from the runway, the pilot 

is advised of MDA, when to begin descent, and when the 

aircraft is at the MDA. If requested, recommended altitudes 

are furnished each mile while on final.

PAR is designed to be used as a landing aid displaying range, 

azimuth, and elevation information rather than as an aid for 

sequencing and spacing aircraft. PAR equipment may be 

used as a primary landing aid, or it may be used to monitor 

other types of approaches. 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°, and elevation to 7°, only the final approach area is 

covered. The controller’s scope is divided into two parts. The 

upper half presents altitude and distance information, and the 

lower half presents azimuth and distance.

PAR is a system 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 10–30 seconds before it occurs 

and when to start descent. The published decision height (DH) 

is 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 
9-48

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 to the pilot 

until the aircraft reaches the published decision altitude (DA)/

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.

Airport Surface Detection Equipment

Radar equipment is specifically designed to detect all 

principal features on the surface of an airport, including 

aircraft and vehicular traffic, and to present the entire image 

on a radar indicator console in the control tower. It is used 

to augment visual observation by tower personnel of aircraft 

and/or vehicular movements on runways and taxiways.

Radar Limitations

1. It is very important for the aviation community to 

recognize the fact that there are limitations to radar 

service and that ATC may not always be able to issue 

traffic advisories concerning aircraft which are not 

under ATC control and cannot be seen on radar.

2. The characteristics of radio waves are such that they 

normally travel in a continuous straight line unless 

they are “bent” by abnormal atmospheric phenomena 

such as temperature inversions; reflected or attenuated 

by dense objects such as heavy clouds, precipitation, 

ground obstacles, mountains, etc.; or screened by high 

terrain features.

3. Primary radar energy that strikes dense objects is 

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.

4. Relatively low altitude aircraft are not seen if they are 

screened by mountains or are below the radar beam 

due to curvature of the Earth.

5. The amount of reflective surface of an aircraft 

determines the size of the radar return. Therefore, 

a small light airplane or a sleek jet fighter is more 

difficult to see on primary radar than a large 

commercial jet or military bomber.

6. All ARTCC radar in the conterminous United States 

and many ASR have the capability to interrogate Mode 

C and display altitude information to the controller 

from appropriately-equipped aircraft. However, 

a number of ASR do not have Mode C display 

capability; therefore, altitude information must be 

obtained from the pilot.
10-1

Introduction

This chapter is a discussion of conducting a flight under 

instrument flight rules (IFR). It also explains the sources for 

flight planning, the conditions associated with instrument 

flight, and the procedures used for each phase of IFR flight: 

departure, en route, and approach. The chapter concludes 

with an example of an IFR flight that applies many of the 

procedures discussed in the chapter.

IFR Flight

Chapter 10
10-2

Sources of Flight Planning Information

The following resources are available for a pilot planning a 

flight conducted under IFR.

National Aeronautical Navigation Products (AeroNav 

Products) Group publications:

• IFR en route charts

• Area charts 

• United States Terminal Procedures Publications (TPP) 

The Federal Aviation Administration (FAA) publications:

• Aeronautical Information Manual (AIM)

• Airport/Facility Directory (A/FD)

• Notices to Airmen Publication (NTAP) for flight 

planning in the National Airspace System (NAS)

Pilots should also consult the Pilot’s Operating Handbook/

Airplane Flight Manual (POH/AFM) for flight planning 

information pertinent to the aircraft to be flown.

A review of the contents of all the listed publications helps 

determine which material should be referenced for each flight. 

As a pilot becomes more familiar with these publications, the 

flight planning process becomes quicker and easier.

Aeronautical Information Manual (AIM)

The AIM provides the aviation community with basic 

flight information and air traffic control (ATC) procedures 

used in the United States NAS. An international version 

called the Aeronautical Information Publication contains 

parallel information, as well as specific information on the 

international airports used by the international community.

Airport/Facility Directory (A/FD)

The A/FD contains information on airports, communications, 

and navigation aids (NAVAIDs) pertinent to IFR flight. It 

also includes very-high frequency omnidirectional range 

(VOR) receiver checkpoints, flight service station (FSS), 

weather service telephone numbers, and air route traffic 

control center (ARTCC) frequencies. Various special 

notices essential to flight are also included, such as landand-hold-short operations (LAHSO) data, the civil use of 

military fields, continuous power facilities, and special 

flight procedures.

In the major terminal and en route environments, preferred 

routes have been established to guide pilots in planning their 

routes of flight, to minimize route changes, and to aid in the 

orderly management of air traffic using the Federal airways. 

The A/FD lists both high and low altitude preferred routes.

Notices to Airmen Publication (NTAP)

The NTAP is a publication containing current Notices to 

Airmen (NOTAMs) that are essential to the safety of flight, 

as well as supplemental data affecting the other operational 

publications listed. It also includes current Flight Data Center 

(FDC) NOTAMs, which are regulatory in nature, issued to 

establish restrictions to flight or to amend charts or published 

instrument approach procedures (IAPs).

POH/AFM

The POH/AFM contain operating limitations, performance, 

normal and emergency procedures, and a variety of other 

operational information for the respective aircraft. Aircraft 

manufacturers have done considerable testing to gather and 

substantiate the information in the aircraft manual. Pilots should 

refer to it for information relevant to a proposed flight.

IFR Flight Plan

As specified in Title 14 of the Code of Federal Regulations 

(14 CFR) part 91, no person may operate an aircraft in 

controlled airspace under IFR unless that person has filed 

an IFR flight plan. Flight plans may be submitted to the 

nearest FSS or air traffic control tower (ATCT) either in 

person, by telephone (1-800-WX-BRIEF), by computer 

(using the direct user access terminal system (DUATS)), 

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. The AIM provides guidance 

for completing and filing FAA Form 7233-1, Flight Plan. 

These forms are available at flight service stations (FSSs) 

and are generally found in flight planning rooms at airport 

terminal buildings. [Figure 10-1]

Filing in Flight

IFR flight plans may be filed from the air under various 

conditions, including:

1. A flight outside controlled airspace before proceeding 

into IFR conditions in controlled airspace.

2. A visual flight rules (VFR) flight expecting IFR 

weather conditions en route in controlled airspace.

In either of these situations, the flight plan may be filed with 

the nearest FSS or directly with the ARTCC. A pilot who 

files with the FSS submits the information normally entered 

during preflight filing, except for “point of departure,” 

together with present position and altitude. FSS then relays 

this information to the ARTCC. The ARTCC then clears the 

pilot from present position or from a specified navigation fix.
10-3

Figure 10-1. Flight plan from. Figure 10-1. Flight plan form.

A pilot who files directly with the ARTCC reports present 

position and altitude, and submits only the flight plan 

information normally relayed from the FSS to the ARTCC. 

Be aware that traffic saturation frequently prevents ARTCC 

personnel from accepting flight plans by radio. In such 

cases, a pilot is advised to contact the nearest FSS to file 

the flight plan.

Cancelling IFR Flight Plans

An IFR flight plan may be cancelled any time a pilot is 

operating in VFR conditions outside Class A airspace by 

stating “cancel my IFR flight plan” to the controller or air-toground station. After cancelling an IFR flight plan, the pilot 

should change to the appropriate air-to-ground frequency, 

transponder code as directed, and VFR altitude/flight level.

ATC separation and information services (including radar 

services, where applicable) are discontinued when an IFR 

flight plan is cancelled. If VFR radar advisory service is 

desired, a pilot must specifically request it. Be aware that 

other procedures may apply when cancelling an IFR flight 

plan within areas such as Class C or Class B airspace.

When operating on an IFR flight plan to an airport with 

an operating control tower, a flight plan is cancelled 

automatically upon landing. If operating on an IFR flight 

plan to an airport without an operating control tower, the 

pilot is responsible for cancelling the flight plan. This can 

be done by telephone after landing if there is no operating 

FSS or other means of direct communications with ATC. 

When there is no FSS or air-to-ground communications are 

not possible below a certain altitude, a pilot may cancel an 

IFR flight plan while still airborne and able to communicate 

with ATC by radio. If using this procedure, be certain the 

remainder of the flight can be conducted under VFR. It is 

essential that IFR flight plans be cancelled expeditiously. This 

allows other IFR traffic to utilize the airspace.

Clearances

An ATC clearance allows an aircraft to proceed under 

specified traffic conditions within controlled airspace 

for the purpose of providing separation between known 

aircraft. A major contributor to runway incursions is lack 

of communication with ATC and not understanding the 

instructions that they give. The primary way the pilot and 

ATC communicate is by voice. The safety and efficiency 

of taxi operations at airports with operating control towers 

depend on this communication loop. ATC uses standard 

phraseology and require readbacks and other responses from 

the pilot in order to verify that clearances and instructions 

are understood. In order to complete the communication 
10-4

loop, the controllers must also clearly understand the pilot’s 

readback and other responses. Pilots can help enhance the 

controller’s understanding by responding appropriately and 

using standard phraseology. Regulatory requirements, the 

AIM, approved flight training programs, and operational 

manuals provide information for pilots on standard ATC 

phraseology and communications requirements.

Examples

A flight filed for a short distance at a relatively low altitude 

in an area of low traffic density might receive a clearance 

as follows:

“Cessna 1230 Alpha, cleared to Doeville airport direct, 

cruise 5,000.”

The term “cruise” in this clearance means a pilot is authorized 

to fly at any altitude from the minimum IFR altitude up to 

and including 5,000 feet and may level off at any altitude 

within this block of airspace. A climb or descent within the 

block may be made at the pilot’s discretion. However, once 

a pilot reports leaving an altitude within the block, the pilot 

may not return to that altitude without further ATC clearance.

When ATC issues a cruise clearance in conjunction with 

an unpublished route, an appropriate crossing altitude is 

specified to ensure terrain clearance until the aircraft reaches a 

fix, point, or route where the altitude information is available. 

The crossing altitude ensures IFR obstruction clearance to 

the point at which the aircraft enters a segment of a published 

route or IAP.

Once a flight plan is filed, ATC issues the clearance with 

appropriate instructions, such as the following:

“Cessna 1230 Alpha is cleared to Skyline airport via 

the Crossville 055 radial, Victor 18, maintain 5,000. 

Clearance void if not off by 1330.”

Or a more complex clearance, such as:

“Cessna 1230 Alpha is cleared to Wichita Midcontinent airport via Victor 77, left turn after takeoff, 

proceed direct to the Oklahoma City VORTAC. 

Hold west on the Oklahoma City 277 radial, climb to 

5,000 in holding pattern before proceeding on course. 

Maintain 5,000 to CASHION intersection. Climb to 

and maintain 7,000. Departure control frequency will 

be 121.05, Squawk 0412.”

Clearance delivery may issue the following “abbreviated 

clearance” which includes a departure procedure (DP):

“Cessna 1230 Alpha, cleared to La Guardia as filed, 

RINGOES 8 departure Phillipsburg transition, 

maintain 8,000. Departure control frequency will be 

120.4, Squawk 0700.”

This clearance may be readily copied in shorthand as follows:

“CAF RNGO8 PSB M80 DPC 120.4 SQ 0700.”

The information contained in this DP clearance is abbreviated 

using clearance shorthand (see appendix 1). The pilot should 

know the locations of the specified navigation facilities, 

together with the route and point-to-point time, before 

accepting the clearance.

The DP enables a pilot to study and understand the details 

of a departure before filing an IFR flight plan. It provides 

the information necessary to set up communication and 

navigation equipment and be ready for departure before 

requesting an IFR clearance.

Once the clearance is accepted, a pilot is required to comply 

with ATC instructions. A clearance different from that issued 

may be requested if the pilot considers another course of 

action more practicable or if aircraft equipment limitations 

or other considerations make acceptance of the clearance 

inadvisable.

A pilot should also request clarification or amendment, as 

appropriate, any time a clearance is not fully understood 

or considered unacceptable for safety of flight. The pilot 

is responsible for requesting an amended clearance if ATC 

issues a clearance that would cause a pilot to deviate from 

a rule or regulation or would place the aircraft in jeopardy.

Clearance Separations

ATC provides the pilot on an IFR clearance with separation 

from other IFR traffic. This separation is provided:

1. Vertically—by assignment of different altitudes.

2. Longitudinally—by controlling time separation 

between aircraft on the same course.

3. Laterally—by assignment of different flightpaths.

4. By radar—including all of the above.

ATC does not provide separation for an aircraft operating:

1. Outside controlled airspace.

2. On an IFR clearance:

a) With “VFR-On-Top” authorized instead of a 

specific assigned altitude.

b) Specifying climb or descent in “VFR conditions.”

c) At any time in VFR conditions, since uncontrolled 

VFR flights may be operating in the same 

airspace.
10-5

In addition to heading and altitude assignments, ATC 

occasionally issues speed adjustments to maintain the 

required separations. For example:

“Cessna 30 Alpha, slow to 100 knots.”

A pilot who receives speed adjustments is expected to 

maintain that speed plus or minus 10 knots. If for any reason 

the pilot is not able to accept a speed restriction, the pilot 

should advise ATC.

At times, ATC may also employ visual separation techniques 

to keep aircraft safely separated. A pilot who obtains visual 

contact with another aircraft may be asked to maintain visual 

separation or to follow the aircraft. For example:

“Cessna 30 Alpha, maintain visual separation with 

that traffic, climb and maintain 7,000.”

The pilot’s acceptance of instructions to maintain visual 

separation or to follow another aircraft is an acknowledgment 

that the aircraft is maneuvered as necessary to maintain safe 

separation. It is also an acknowledgment that the pilot accepts 

the responsibility for wake turbulence avoidance.

In the absence of radar contact, ATC relies on position reports 

to assist in maintaining proper separation. Using the data 

transmitted by the pilot, the controller follows the progress of 

each flight. ATC must correlate the pilots’ reports to provide 

separation; therefore, the accuracy of each pilot’s report can 

affect the progress and safety of every other aircraft operating 

in the area on an IFR flight plan.

Departure Procedures (DPs)

Instrument departure procedures are preplanned IFR 

procedures that provide obstruction clearance from the 

terminal area to the appropriate en route structure and 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 when one is 

available. [Figure 10-2]

There are two types of DPs: Obstacle Departure Procedures 

(ODP), printed either textually or graphically, and Standard 

Instrument Departures (SID), always printed graphically. All 

DPs, either textual or graphic, may be designed using either 

conventional or area navigation (RNAV) criteria. RNAV 

procedures have RNAV printed in the title (e.g., SHEAD 

TWO DEPARTURE (RNAV)). 

Obstacle Departure Procedures (ODP)

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 have 

(OBSTACLE) printed in the procedure title (e.g., GEYSR 

THREE DEPARTURE (OBSTACLE), CROWN ONE 

DEPARTURE (RNAV)(OBSTACLE)). 

Standard Instrument Departures

SIDs are 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. 

ODPs are found in section C of each booklet published 

regionally by the AeroNav Products, TPP, along with “IFR 

Take-off Minimums” while SIDs are collocated with the 

approach procedures for the applicable airport. Additional 

information on the development of DPs can be found in 

paragraph 5-2-7 of the AIM. However, the following points 

are important to remember.

1. The pilot of IFR aircraft operating from locations 

where DP procedures are effective may expect an ATC 

clearance containing a DP. The use of a DP requires 

pilot possession of at least the textual description of 

the approved DP.

2. If a pilot does not possess a preprinted DP or for 

any other reason does not wish to use a DP, he or 

she is expected to advise ATC. Notification may 

be accomplished by filing “NO DP” in the remarks 

section of the filed flight plan or by advising ATC.

3. If a DP is accepted in a clearance, a pilot must comply 

with it.

Radar-Controlled Departures

On IFR departures from airports in congested areas, a pilot 

normally receives navigational guidance from departure 

control by radar vector. When a departure is to be vectored 

immediately following takeoff, the pilot is advised before 

takeoff of the initial heading to be flown. This information is 

vital in the event of a loss of two-way radio communications 

during departure.

The radar departure is normally simple. Following takeoff, 

contact departure control on the assigned frequency when 

advised to do so by the control tower. At this time, departure 

control verifies radar contact and gives headings, altitude, and 

climb instructions to move an aircraft quickly and safely out 

of the terminal area. A pilot is expected to fly the assigned 

headings and altitudes until informed by the controller of 

the aircraft’s position with respect to the route given in 
10-6

SE-4, 16 DEC 2010 ot 13 JAN 2011

SE-4, 16 DEC 2010 to 13 JAN 2011

Figure 10-2 Figure 10-2. Departure procedure (DP). . Departure procedure (DP).

the clearance, whom to contact next, and to “resume own 

navigation.”

Departure control provides vectors to either a navigation 

facility, or an en route position appropriate to the departure 

clearance, or transfer to another controller with further radar 

surveillance capabilities. [Figure 10-2]

A radar controlled departure does not relieve the pilot of 

responsibilities as pilot-in-command. Be prepared before 

takeoff to conduct navigation according to the ATC clearance 

with navigation receivers checked and properly tuned. While 

under radar control, monitor instruments to ensure continuous 

orientation to the route specified in the clearance and record 

the time over designated checkpoints.
10-7

Position Reports

Position reports are required over each compulsory reporting 

point (shown on the chart as a solid triangle) along the route 

being flown regardless of altitude, including those with 

a VFR-on-top clearance. Along direct routes, reports are 

required of all IFR flights over each point used to define 

the route of flight. Reports at reporting points (shown as an 

open triangle) are made only when requested by ATC. A 

pilot should discontinue position reporting over designated 

reporting points when informed by ATC that the aircraft 

is in “RADAR CONTACT.” Position reporting should be 

resumed when ATC advises “RADAR CONTACT LOST” 

or “RADAR SERVICE TERMINATED.”

Position reports should include the following items:

1. Identification

2. Position

3. Time

4. Altitude or flight level (include actual altitude or flight 

level when operating on a clearance specifying VFRon-top)

5. Type of flight plan (not required in IFR position reports 

made directly to ARTCCs or approach control)

6. Estimated time of arrival (ETA) and name of next 

reporting point

7. The name only of the next succeeding reporting point 

along the route of flight

8. Pertinent remarks

En route position reports are submitted normally to 

the ARTCC controllers via direct controller-to-pilot 

communications channels using the appropriate ARTCC 

frequencies listed on the en route chart.

Whenever an initial contact with a controller is to be followed 

by a position report, the name of the reporting point should 

be included in the call-up. This alerts the controller that such 

information is forthcoming. For example:

“Atlanta Center, Cessna 1230 Alpha at JAILS 

intersection.”

“Cessna 1230 Alpha Atlanta Center.”

“Atlanta Center, Cessna 1230 Alpha at JAILS 

intersection, 5,000, estimating Monroeville at 1730.”

Additional Reports

In addition to required position reports, the following reports 

should be made to ATC without a specific request.

1. At all times:

Departures From Airports Without an Operating 

Control Tower

When departing from airports that have neither an operating 

tower nor an FSS, a pilot should telephone the flight plan 

to the nearest ATC facility at least 30 minutes before the 

estimated departure time. If weather conditions permit, depart 

VFR and request IFR clearance as soon as radio contact is 

established with ATC. 

If weather conditions make it undesirable to fly VFR, 

telephone clearance request. In this case, the controller would 

probably issue a short-range clearance pending establishment 

of radio contact and might restrict the departure time to a 

certain period. For example:

“Clearance void if not off by 0900.”

This would authorize departure within the allotted period and 

permit a pilot to proceed in accordance with the clearance. In 

the absence of any specific departure instructions, a pilot would 

be expected to proceed on course via the most direct route.

En Route Procedures

Procedures en route vary according to the proposed route, 

the traffic environment, and the ATC facilities controlling 

the flight. Some IFR flights are under radar surveillance and 

controlled from departure to arrival and others rely entirely 

on pilot navigation.

Where ATC has no jurisdiction, it does not issue an IFR 

clearance. It has no control over the flight, nor does the pilot 

have any assurance of separation from other traffic.

ATC Reports

All pilots are required to report unforecast weather conditions 

or other information related to safety of flight to ATC. The 

pilot-in-command of each aircraft operated in controlled 

airspace under IFR shall report as soon as practical to 

ATC any malfunctions of navigational, approach, or 

communication equipment occurring in flight:

1. Loss of VOR, tactical air navigation (TACAN) or 

automatic direction finder (ADF) receiver capability.

2. Complete or partial loss of instrument landing system 

(ILS) receiver capability.

3. Impairment of air-to-ground communications 

capability.

The pilot-in-command shall include within the report 

(1) aircraft identification, (2) equipment affected, (3) degree 

to which the pilot to operate under IFR within the ATC 

system is impaired, and (4) nature and extent of assistance 

desired from ATC.
10-8

Planning the Descent and Approach

ATC arrival procedures and flight deck workload are affected 

by weather conditions, traffic density, aircraft equipment, 

and radar availability.

When landing at an airport with approach control services and 

where two or more IAPs are published, information on the 

type of approach to expect is provided in advance of arrival 

or vectors are provided to a visual approach. This information 

is broadcast either on automated terminal information 

service (ATIS) or by a controller. It is not furnished when 

the visibility is 3 miles or more and the ceiling is at or above 

the highest initial approach altitude established for any low 

altitude IAP for the airport.

The purpose of this information is to help the pilot plan arrival 

actions; however, it is not an ATC clearance or commitment 

and is subject to change. Fluctuating weather, shifting 

winds, blocked runway, etc., are conditions that may result 

in changes to the approach information previously received. 

It is important for a pilot to advise ATC immediately if he 

or she is unable to execute the approach or prefers another 

type of approach.

If the destination is an airport without an operating control 

tower and has automated weather data with broadcast 

capability, the pilot should monitor the automated surface 

observing system/automated weather observing system 

(ASOS/AWOS) frequency to ascertain the current weather for 

the airport. ATC should be advised that weather information 

has been received and what the pilot’s intentions are.

When the approach to be executed has been determined, the 

pilot should plan for and request a descent to the appropriate 

altitude prior to the initial approach fix (IAF) or transition 

route depicted on the IAP. When flying the transition route, 

a pilot should maintain the last assigned altitude until ATC 

gives the instructions “cleared for the approach.” Lower 

altitudes can be requested to bring the transition route 

altitude closer to the required altitude at the initial approach 

fix. When ATC uses the phrase “at pilot’s discretion” in the 

altitude information of a clearance, the pilot has the option 

to start a descent at any rate and may level off temporarily 

at any intermediate altitude. However, once an altitude has 

been vacated, return to that altitude is not authorized without 

a clearance. When ATC has not used the term “at pilot’s 

discretion” nor imposed any descent restrictions, initiate 

descent promptly upon acknowledgment of the clearance.

Descend at an optimum rate (consistent with the operating 

characteristics of the aircraft) to 1,000 feet above the assigned 

altitude. Then attempt to descend at a rate of between 500 and 

1,500 fpm until the assigned altitude is reached. If at anytime 

a) When vacating any previously assigned altitude 

or flight level for a newly assigned altitude or 

flight level

b) When an altitude change is made if operating on 

a clearance specifying VFR-on-top

c) When unable to climb/descend at a rate of at least 

500 feet per minute (fpm)

d) When an approach has been missed (Request 

clearance for specific action (to alternative 

airport, another approach, etc.))

e) Change in 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 upon reaching a holding fix 

or point to which cleared

g) When leaving any assigned holding fix or point

NOTE: The reports in (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, global positioning system 

(GPS) anomalies while using installed IFRcertified GPS/Global Navigation Satellite 

Systems (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.

i) Any information relating to the safety of flight.

2. When not in radar contact:

a) When leaving the 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 any time it becomes 

apparent that an estimate as previously submitted 

is in error in excess of 3 minutes.

Any pilot who encounters weather conditions that have not 

been forecast, or hazardous conditions which have been 

forecast, is expected to forward a report of such weather to 

ATC.
10-9

Figure 10-3. Standard terminal arrival route (STAR). 

SC-4, 16 DEC 2010 ot 13 JAN 2011

SC-4, 16 DEC 2010 to 13 JAN 2011

Figure 10-3. Standard terminal arrival route (STAR).

a pilot is unable to maintain a descent rate of at least 500 fpm, 

advise ATC. Also advise ATC if it is necessary to level off 

at an intermediate altitude during descent. An exception to 

this is when leveling off at 10,000 feet mean sea level (MSL) 

on descent or 2,500 feet above airport elevation (prior to 

entering a Class B, Class C, or Class D surface area) when 

required for speed reduction.

Standard Terminal Arrival Routes (STARs)

Standard Terminal Arrival Routes (STARs) (as described 

in Chapter 1) have been established to simplify clearance 

delivery procedures for arriving aircraft at certain areas 

having high density traffic. A STAR serves a purpose 

parallel to that of a DP for departing traffic. [Figure 10-3]
10-10

Abeam 

Figure 10-4. Standard holding pattern - no winid. Figure 10-4. Standard holding pattern—no wind.

The following points regarding STARs are important to 

remember:

1. All STARs are contained in the Terminal Procedures 

Publication (TPP), along with the IAP charts for the 

destination airport. The AIM also describes STAR 

procedures.

2. If the destination is a location for which STARs 

have been published, a pilot may be issued a 

clearance containing a STAR whenever ATC deems 

it appropriate. To accept the clearance, a pilot must 

possess at least the approved textual description.

3. It is the pilot’s responsibility to either accept or refuse 

an issued STAR. If a STAR will not or cannot be used, 

advise ATC by placing “NO STAR” in the remarks 

section of the filed flight plan or by advising ATC.

4. If a STAR is accepted in a clearance, compliance is 

mandatory.

Substitutes for Inoperative or Unusable 

Components

The basic ground components of an ILS are the localizer, 

glideslope, outer marker, middle marker, and inner marker 

(when installed). A compass locator or precision radar may 

be substituted for the outer or middle marker. Distance 

measuring equipment (DME), VOR, or nondirectional 

beacon (NDB) fixes authorized in the standard IAP or 

surveillance radar may be substituted for the outer marker.

Additionally, IFR-certified GPS equipment, operated in 

accordance with Advisory Circular (AC) 90-94, Guidelines 

for Using Global Positioning System Equipment for IFR 

En Route and Terminal Operations and for Nonprecision 

Instrument Approaches in the United States National 

Airspace System, may be substituted for ADF and DME 

equipment, except when flying NDB IAP. Specifically, GPS 

can be substituted for ADF and DME equipment when:

1. Flying a DME arc;

2. Navigating TO/FROM an NDB;

3. Determining the aircraft position over an NDB;

4. Determining the aircraft position over a fix made up 

of a crossing NDB bearing;

5. Holding over an NDB;

6. Determining aircraft position over a DME fix.

Holding Procedures

Depending upon traffic and weather conditions, holding may 

be required. Holding is a predetermined maneuver that keeps 

aircraft within a specified airspace while awaiting further 

clearance from ATC. A standard holding pattern uses right 

turns, and a nonstandard holding pattern uses left turns. The 

ATC clearance always specifies left turns when a nonstandard 

pattern is to be flown. 

Standard Holding Pattern (No Wind)

In a standard holding pattern with no winds [Figure 10-4], the 

aircraft follows the specified course inbound to the holding 

fix, turns 180° to the right, flies a parallel straight course 

outbound for 1 minute, turns 180° to the right, and flies the 

inbound course to the fix.

Standard Holding Pattern (With Wind)

A standard symmetrical holding pattern cannot be flown 

when winds exist. In those situations, the pilot is expected to:

1. Compensate for the effect of a known wind except 

when turning.

2. Adjust outbound timing to achieve a 1-minute (11

⁄2

minutes above 14,000 feet) inbound leg.

Figure 10-5 illustrates the holding track followed with a left 

crosswind. The effect of wind is counteracted by applying 

drift corrections to the inbound and outbound legs and by 

applying time allowances to the outbound leg.

Holding Instructions

If an aircraft arrives at a clearance limit before receiving 

clearance beyond the fix, ATC expects the pilot to maintain 

the last assigned altitude and begin holding in accordance 

with the charted holding pattern. If no holding pattern is 

charted and holding instructions have not been issued, enter 

a standard holding pattern on the course on which the aircraft 

approached the fix and request further clearance as soon as 

possible. Normally, when no delay is anticipated, ATC issues 

holding instructions at least 5 minutes before the estimated 

arrival at the fix. Where a holding pattern is not charted, the 

ATC clearance specifies the following:

1. Direction of holding from the fix in terms of the eight 

cardinal compass points (N, NE, E, SE, etc.)
10-11

Figure 10-5. Drift correction in holding pattern.

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 is specified in minutes on pilot request or 

if the controller considers it necessary).

5. Direction of turn, if left turns are to be made, because 

the pilot requests or the controller considers it 

necessary.

6. Time to expect-further-clearance (EFC) and any 

pertinent additional delay information.

ATC instructions are also issued whenever:

1. It is determined that a delay will exceed 1 hour.

2. A revised EFC is necessary.

3. In a terminal area having a number of NAVAIDs 

and approach procedures, a clearance limit may not 

indicate clearly which approach procedures will 

be used. On initial contact, or as soon as possible 

thereafter, approach control advises the pilot of the 

type of approach to expect.

4. Ceiling and/or visibility is reported as being at or 

below the highest “circling minimums” established 

for the airport concerned. ATC transmits a report of 

current weather conditions and subsequent changes, 

as necessary.

5. An aircraft is holding while awaiting approach 

clearance, and the pilot advises ATC that reported 

weather conditions are below minimums applicable 

to the operation. In this event, ATC issues suitable 

instructions to aircraft desiring either to continue 

holding while awaiting weather improvement or 

proceed to another airport.

Standard Entry Procedures

The entry procedures given in the AIM evolved from 

extensive experimentation under a wide range of operational 

conditions. The standardized procedures should be followed 

to ensure that an aircraft remains within the boundaries of 

the prescribed holding airspace.

When a speed reduction is required, start the reduction when 

3 minutes or less from the holding fix. Cross the holding fix 

initially at or below the maximum holding airspeed (MHA). 

The purpose of the speed reduction is to prevent overshooting 

the holding airspace limits, especially at locations where 

adjacent holding patterns are close together.

All aircraft may hold at the following altitudes and maximum 

holding airspeeds:

Altitude Mean Sea Level (MSL) Airspeed (KIAS)

Up to 6,000 feet 200

6,001 – 14,000 feet 230

14,001 feet and above 265

The following are exceptions to the maximum holding 

airspeeds:

1. Holding patterns from 6,001 to 14,000 feet may 

be restricted to a maximum airspeed of 210 knots 

indicated airspeed (KIAS). This nonstandard pattern 

is depicted by an icon.

2. Holding patterns may be restricted to a maximum 

airspeed of 175 KIAS. This nonstandard pattern is 

depicted by an icon. Holding patterns restricted to 

175 KIAS are generally found on IAPs applicable to 

category A and B aircraft only.

3. Holding patterns at Air Force airfields only—310 

KIAS maximum, unless otherwise depicted.

4. Holding patterns at Navy airfields only—230 KIAS 

maximum, unless otherwise depicted.

5. The pilot of an aircraft unable to comply with 

maximum airspeed restrictions should notify ATC.
10-12

a

c

b

Figure 10-6. Holding pattern entry procedures. 

Figure 10-6. Holding pattern entry procedures. 240° 

330° 

240° 

330° 

045° 

315° 

0° 

Figure 10-7Figure 10-7. . Holding—outbound timing. Holding -outbound timing 

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. Additionally, paragraph 5-3-7 in the AIM should be 

reviewed. [Figure 10-6]

1. Parallel Procedure. When approaching the holding fix 

from anywhere in sector (a), fly to the fix. Afterwards, 

turn to a heading to parallel the holding course 

outbound. Fly outbound for 1 minute, turn in the 

direction of the holding pattern through more than 

180°, and return to the holding fix or intercept the 

holding course inbound. 

2. 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° teardrop entry within the pattern 

(on the holding side) for a period of 1 minute, then 

turn in the direction of the holding pattern to intercept 

the inbound holding course. 

3. 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. 

A pilot should make all turns during entry and while holding at:

1. 3° per second, or

2. 30° bank angle, or

3. A bank angle provided by a flight director system.

Time Factors

The holding pattern entry time reported to ATC is the initial 

time of arrival over the fix. Upon entering a holding pattern, the 

initial outbound leg is flown for 1 minute at or below 14,000 

feet MSL, and for 11

⁄2 minutes above 14,000 feet MSL. Timing 

for subsequent outbound legs should be adjusted as necessary 

to achieve proper inbound leg time. The pilot should begin 

outbound timing over or abeam the fix, whichever occurs later. 

If the abeam position cannot be determined, start timing when 

the turn to outbound is completed. [Figure 10-7]
10-13

Time leaving the holding fix must be known to ATC before 

succeeding aircraft can be cleared to the vacated airspace. 

Leave the holding fix:

1. When ATC issues either further clearance en route or 

approach clearance;

2. As prescribed in 14 CFR part 91 (for IFR operations; 

two-way radio communications failure, and 

responsibility and authority of the pilot-in-command); 

or

3. After the IFR flight plan has been cancelled, if the 

aircraft is holding in VFR conditions.

DME Holding

The same entry and holding procedures apply to DME 

holding, but distances (nautical miles) are used instead of 

time values. The length of the outbound leg is specified by 

the controller, and the end of this leg is determined by the 

DME readout.

Approaches

Compliance With Published Standard Instrument 

Approach Procedures

Compliance with the approach procedures shown on the 

approach charts provides necessary navigation guidance 

information for alignment with the final approach courses, 

as well as obstruction clearance. Under certain conditions, 

a course reversal maneuver or procedure turn may be 

necessary. However, this procedure is not authorized when:

1. The symbol “NoPT” appears on the approach course 

on the plan view of the approach chart.

2. Radar vectoring is provided to the final approach 

course.

3. A holding pattern is published in lieu of a procedure 

turn.

4. Executing a timed approach from a holding fix.

5. Otherwise directed by ATC.

Instrument Approaches to Civil Airports

Unless otherwise authorized, when an instrument letdown to 

an airport is necessary, the pilot should use a standard IAP 

prescribed for that airport. IAPs are depicted on IAP charts 

and are found in the TPP.

ATC approach procedures depend upon the facilities available 

at the terminal area, the type of instrument approach executed, 

and the existing weather conditions. The ATC facilities, 

NAVAIDs, and associated frequencies appropriate to each 

standard instrument approach are given on the approach 

chart. Individual charts are published for standard approach 

procedures associated with the following types of facilities:

1. Nondirectional beacon (NDB)

2. Very-high frequency omnirange (VOR)

3. Very-high frequency omnirange with distance 

measuring equipment (VORTAC or VOR/DME)

4. Localizer (LOC)

5. Instrument landing system (ILS)

6. Localizer-type directional aid (LDA)

7. Simplified directional facility (SDF)

8. Area navigation (RNAV)

9. Global positioning system (GPS)

An IAP can be flown in one of two ways: as a full approach 

or with the assistance of radar vectors. When the IAP is flown 

as a full approach, pilots conduct their own navigation using 

the routes and altitudes depicted on the instrument approach 

chart. A full approach allows the pilot to transition from 

the en route phase, to the instrument approach, and then to 

a landing with minimal assistance from ATC. This type of 

procedure may be requested by the pilot but is most often 

used in areas without radar coverage. A full approach also 

provides the pilot with a means of completing an instrument 

approach in the event of a communications failure.

When an approach is flown with the assistance of radar 

vectors, ATC provides guidance in the form of headings and 

altitudes, which position the aircraft to intercept the final 

approach. From this point, the pilot resumes navigation, 

intercepts the final approach course, and completes the 

approach using the IAP chart. This is often a more expedient 

method of flying the approach, as opposed to the full 

approach, and allows ATC to sequence arriving traffic. A 

pilot operating in radar contact can generally expect the 

assistance of radar vectors to the final approach course.

Approach to Airport Without an Operating Control 

Tower

Figure 10-8 shows an approach procedure at an airport 

without an operating control tower. When approaching 

such a facility, the pilot should monitor the AWOS/ASOS 

if available for the latest weather conditions. When direct 

communication between the pilot and controller is no 

longer required, the ARTCC or approach controller issues a 

clearance for an instrument approach and advises “change to 

advisory frequency approved.” When the aircraft arrives on 

a “cruise” clearance, ATC does not issue further clearance 

for approach and landing.

If an approach clearance is required, ATC authorizes the pilots 

to execute his or her choice of standard instrument approach 

(if more than one is published for the airport) with the 
10-14

Figure 10-8. Approach: an approach procedure at an airport without an operating control tower. 

SE-4, 16 DEC 2010 to 13 JAN 2011

SE-4, 16 DEC 2010 to 13 JAN 2011

Figure 10-8. Monroeville, Alabama (MVC) VOR or GPS Rwy 3 Approach: An approach procedure at an airport without an operating 

control tower.
10-15

phrase “Cleared for the approach” and the communications 

frequency change required, if any. From this point on, there 

is no contact with ATC. The pilot is responsible for closing 

the IFR flight plan before landing, if in VFR conditions, or 

by telephone after landing.

Unless otherwise authorized by ATC, a pilot is expected to 

execute the complete IAP shown on the chart.

Approach to Airport With an Operating Tower, 

With No Approach Control

When an aircraft approaches an airport with an operating 

control tower, but no approach control, ATC issues a 

clearance to an approach/outer fix with the appropriate 

information and instructions as follows:

1. Name of the fix

2. Altitude to be maintained

3. Holding information and expected approach clearance 

time, if appropriate 

4. Instructions regarding further communications, 

including:

a) facility to be contacted

b) time and place of contact

c) frequency/ies to be used

If ATIS is available, a pilot should monitor that frequency 

for information such as ceiling, visibility, wind direction and 

velocity, altimeter setting, instrument approach, and runways 

in use prior to initial radio contact with the tower. If ATIS is 

not available, ATC provides weather information from the 

nearest reporting station.

Approach to an Airport With an Operating Tower, 

With an Approach Control

Where radar is approved for approach control service, it is 

used to provide vectors in conjunction with published IAPs. 

Radar vectors can provide course guidance and expedite 

traffic to the final approach course of any established IAP.

Figure 10-9 shows an IAP chart with maximum ATC 

facilities available.

Approach control facilities that provide this radar service 

operate in the following manner:

1. 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,

2. When radar hand-offs are effected between ARTCC 

and approach control, or between two approach 

control facilities, aircraft are cleared to the airport or 

to a fix so located that the hand-off is completed prior 

to the time the aircraft reaches the fix.

a) When the radar hand-offs are utilized, successive 

arriving flights may be handed off to approach 

control with radar separation in lieu of vertical 

separation.

b) After hand-off to approach control, an aircraft 

is vectored to the appropriate final approach 

course.

3. Radar vectors and altitude/flight levels are issued 

as required for spacing and separating aircraft; do 

not deviate from the headings issued by approach 

control.

4. Aircraft are normally informed when it becomes 

necessary to be vectored 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. The pilot is not expected to turn inbound on 

the final approach course unless an approach clearance 

has been issued. This clearance is normally issued with 

the final vector for interception of the final approach 

course, and the vector enables the pilot to establish the 

aircraft on the final approach course prior to reaching 

the final approach fix.

5. Once the aircraft is established inbound on the final 

approach course, radar separation is maintained with 

other aircraft, and the pilot is expected to complete 

the approach using the NAVAID designated in the 

clearance (ILS, VOR, NDB, GPS, etc.) as the primary 

means of navigation.

6. After passing the final approach fix inbound, the 

pilot is expected to proceed direct to the airport and 

complete the approach or to execute the published 

missed approach procedure.

7. Radar service is automatically terminated when the 

landing is completed or when the pilot is instructed to 

change to advisory frequency at uncontrolled airports, 

whichever occurs first.

Radar Approaches

With a radar approach, the pilot receives course and altitude 

guidance from a controller who monitors the progress of the 

flight with radar. This is an option should the pilot experience 

an emergency or distress situation.

The only airborne radio equipment required for radar 

approaches is a functioning radio transmitter and receiver. 
10-16

Figure 10-9. Approach: an instrument procedure chart with maximum ATC facilities available. 

SC-4, 16 DEC 2010 to 13 JAN 2011

SC-4, 16 DEC 2010 to 13 JAN 2011

Figure 10-9. Gulfport, Mississippi (GPT) ILS or LOC Rwy 14 Approach: An instrument procedure chart with maximum ATC facilities 

available.
10-17

N6 

06271 

RADAR MINS 

TROY, AL Amdt. 7, DEC 22, 2005 (FAA) ELEV 397 

TROY MUNI 

RADAR1 - 121.1 319.25 

DA/ HAT/ DA/ HAT/ 

RWY GS/TCH/RPI CAT MDA-VIS HAA CEIL-VIS CAT MDA-VIS HAA CEIL-VIS 

PAR 7 2.9/51/ ABCD 642 -1 250 (300-1) 

ASR 7 AB 920 -1 528 (600-1) C 920 -11⁄2 528 (600-11⁄2) 

D 920 -13⁄4 528 (600-13⁄4) 

CIRCLING AB 940 -1 543 (600-1) C 960 -11⁄2 563 (600-11⁄2) 

D 980 -2 583 (600-2) 

When control tower closed, procedure not authorized. 

1Opr by US Army 1430-2230Z++ Mon-Fri exc hol. 

WRIGHT AAF (LHW), (FORT STEWART) GA (30 NOV 00 USA) ELEV 48 

RADAR 1 - (U) 118.775 267.15 

DH/ HAT/ 

RWY GS/TCH/RPI CAT MDA-VIS HAA CEIL-VIS 

ASR 33R ABCD 380-3⁄4 338 (400-3⁄4) 

6L AB 620-1 573 (600-1) 

6 

Figure 10-10. Radar instrument approach minimums for Troy, Alabama.

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). 

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. 

PAR and ASR minimums are published on separate pages 

in the FAA TPP. Figure 10-10.

PAR is one in which a controller provides highly accurate 

navigational guidance in azimuth and elevation to a pilot. 

The controller gives the pilot headings to fly that direct the 

aircraft to, and keep the aircraft aligned with, the extended 

centerline of the landing runway. The pilot is told to anticipate 

glidepath interception approximately 10 to 30 seconds before 

it occurs and when to start descent. The published decision 

height (DH) is 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 

is 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 to the pilot until the aircraft 

reaches the published DH. Advisory course and glidepath 

information is furnished by the controller until the aircraft 

passes over the landing threshold. At this point, the pilot is 

advised of any deviation from the runway centerline. Radar 

service is automatically terminated upon completion of the 

approach. 

ASR is one in which a controller provides navigational 

guidance in azimuth only. 

The controller furnishes the pilot with 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 is not as 

great and higher minimums apply. Guidance in elevation 

is not possible, but the pilot is advised when to commence 
10-18

descent to the Minimum Descent Altitude (MDA) or, if 

appropriate, to an intermediate step-down fix Minimum 

Crossing Altitude (MCA) and subsequently to the prescribed 

MDA. In addition, the pilot is 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, heliport, or MAP, as appropriate. 

If requested by the pilot, recommended altitudes are 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 is provided until the 

aircraft reaches the MAP. 

Radar service is automatically terminated at the completion 

of a radar approach. 

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 nogyro vector or approach. The pilot of an aircraft not equipped 

with a directional gyro or other stabilized compass who 

desires 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 is advised after the aircraft has been turned onto final 

approach to make turns at half standard rate. 

Radar Monitoring of Instrument Approaches

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 NAVAID as the primary aid for the approach. 

Prior to starting final approach, the pilot is advised of the 

frequency on which the advisories are transmitted. If, for 

any reason, radar advisories cannot be furnished, the pilot 

is so advised. 

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). 

2. Trend advisories with respect to elevation and/or 

azimuth radar position and movement are provided. 

3. If, after repeated advisories, the aircraft proceeds 

outside the PAR safety limit or if a radical deviation 

is observed, the pilot is advised to execute a missed 

approach unless the prescribed visual reference with 

the surface is established. 

Radar service is automatically terminated upon completion 

of the approach. [Figure 10-11]

Timed Approaches From a Holding Fix

Timed approaches from a holding fix are conducted when 

many aircraft are waiting for an approach clearance. Although 

the controller does not specifically state “timed approaches 

are in progress,” the assigning of a time to depart the FAF 

inbound (nonprecision approach), or the outer marker or fix 

used in lieu of the outer marker inbound (precision approach), 

indicates that timed approach procedures are being utilized.

In lieu of holding, the controller may use radar vectors to the 

final approach course to establish a distance between aircraft 

that ensures the appropriate time sequence between the FAF 

and outer marker or fix used in lieu of the outer marker and 

the airport. Each pilot in the approach sequence is given 

advance notice of the time they should leave the holding point 

on approach to the airport. When a time to leave the holding 

point is received, the pilot should adjust the flightpath in order 

to leave the fix as closely as possible to the designated time.

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 MAP is available, none require a 

course reversal.

4. If only one MAP 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 should not 

execute a procedure turn.
10-19

SE-4, 16 DEC 2010 to 13 JAN 2011

SE-4, 16 DEC 2010 to 13 JAN 2011

Figure 10-11. ILS RWY 7 Troy, Alabama.
10-20

A 

B 

C 

D 

E 

Defining size of areas, radii (r) vary 

with the approach category 

Figure 10-12. Circling approach area radii.

Approaches to Parallel Runways

Procedures permit ILS instrument approach operations to dual 

or triple parallel runway configurations. A parallel approach 

is an ATC procedure that permits parallel ILS approach to 

airports with parallel runways separated by at least 2,500 

feet between centerlines. Wherever parallel approaches 

are in progress, pilots are informed that approaches to both 

runways are in use.

Simultaneous approaches are permitted to runways:

1. With centerlines separated by 4,300 to 9,000 feet;

2. Equipped with final monitor controllers;

3. Requiring radar monitoring to ensure separation 

between aircraft on the adjacent parallel approach 

course.

The approach procedure chart includes the note “simultaneous 

approaches authorized RWYS 14L and 14R,” identifying 

the appropriate runways. When advised that simultaneous 

parallel approaches are in progress, pilots must advise 

approach control immediately of malfunctioning or 

inoperative components.

Parallel approach operations demand heightened pilot 

situational awareness. The close proximity of adjacent 

aircraft conducting simultaneous parallel approaches 

mandates strict compliance with all ATC clearances and 

approach procedures. Pilots should pay particular attention 

to the following approach chart information: name and 

number of the approach, localizer frequency, inbound course, 

glideslope intercept altitude, DA/DH, missed approach 

instructions, special notes/procedures, and the assigned 

runway location and proximity to adjacent runways. Pilots 

also need to exercise strict radio discipline, which includes 

continuous monitoring of communications and the avoidance 

of lengthy, unnecessary radio transmissions.

Side-Step Maneuver

ATC may authorize a side-step maneuver to either one of 

two parallel runways that are separated by 1,200 feet or less, 

followed by a straight-in landing on the adjacent runway. 

Aircraft executing a side-step maneuver are cleared for a 

specified nonprecision approach and landing on the adjacent 

parallel runway. For example, “Cleared ILS runway 7 left 

approach, side-step to runway 7 right.” The pilot is expected 

to commence the side-step maneuver as soon as possible 

after the runway or runway environment is in sight. Landing 

minimums to the adjacent runway are based on nonprecision 

criteria and therefore higher than the precision minimums 

to the primary runway, but are normally lower than the 

published circling minimums.

Circling Approaches

Landing minimums listed on the approach chart under 

“CIRCLING” apply when it is necessary to circle the airport, 

maneuver for landing, or when no straight-in minimums are 

specified on the approach chart. [Figure 10-11]

The circling minimums published on the instrument approach 

chart provide a minimum of 300 feet of obstacle clearance in 

the circling area. [Figure 10-12] During a circling approach, 

the pilot should maintain visual contact with the runway of 

intended landing and fly no lower than the circling minimums 

until positioned to make a final descent for a landing. It is 

important to remember that circling minimums are only 

minimums. If the ceiling allows it, fly at an altitude that more 

nearly approximates VFR traffic pattern altitude. This makes 

any maneuvering safer and brings the view of the landing 

runway into a more normal perspective.

Figure 10-13 shows patterns that can be used for circling 

approaches. Pattern A can be flown when the final approach 

course intersects the runway centerline at less than a 90° 

angle, and the runway is in sight early enough to establish a 

base leg. If the runway becomes visible too late to fly pattern 

A, circle as shown in B. Fly pattern C if it is desirable to land 

opposite the direction of the final approach, and the runway 

is sighted in time for a turn to downwind leg. If the runway 

is sighted too late for a turn to downwind, fly pattern “D.” 

Regardless of the pattern flown, the pilot must maneuver the 

aircraft to remain within the designated circling area. Refer to 

section A (“Terms and Landing Minima Data”) in the front 

of each TPP for a description of circling approach categories.

The criteria for determining the pattern to be flown are 

based on personal flying capabilities and knowledge of the 
10-21

A

Pattern A can be flown when the 

final approach course 

intersects the runway 

centerline at less than 

a 90° angle, and the 

runway is in sight early 

enough to establish a 

base leg. 

Circle runway if the runway 

becomes visible too late to fly 

pattern A.

If it is desirable 

to land opposite 

the direction of 

the final approach, and the 

runway is sighted 

in time for a turn 

to downwind leg,

fly pattern C. 

If the runway is 

sighted too late 

for a turn to 

downwind, 

fly pattern D.

B C D

Figure 10-13. Circling approaches.

performance characteristics of the aircraft. In each instance, 

the pilot must consider all factors: airport design, ceiling and 

visibility, wind direction and velocity, final approach course 

alignment, distance from the final approach fix to the runway, 

and ATC instructions.

IAP Minimums

Pilots may not operate an aircraft at any airport below 

the authorized MDA or continue an approach below the 

authorized DA/DH unless:

1. The aircraft is continuously in a position from which 

a descent to a landing on the intended runway can be 

made at a normal descent rate using normal maneuvers;

2. The flight visibility is not less than that prescribed for 

the approach procedure being used; and

3. At least one of the following visual references for the 

intended runway is visible and identifiable to the pilot:

a) Approach light system

b) Threshold

c) Threshold markings

d) Threshold lights

e) Runway end identifier lights (REIL)

f) Visual approach slope indicator (VASI)

g) Touchdown zone or touchdown zone markings

h) Touchdown zone lights

i) Runway or runway markings

j) Runway lights

Missed Approaches

A MAP is formulated for each published instrument approach 

and allows the pilot to return to the airway structure while 

remaining clear of obstacles. The procedure is shown on the 

approach chart in text and graphic form. Since the execution 

of a missed approach occurs when the flight deck workload is 

at a maximum, the procedure should be studied and mastered 

before beginning the approach.

When a MAP is initiated, a climb pitch attitude should be 

established while setting climb power. Configure the aircraft 

for climb, turn to the appropriate heading, advise ATC that 

a missed approach is being executed, and request further 

clearances.

If the missed approach is initiated prior to reaching the MAP, 

unless otherwise cleared by ATC, continue to fly the IAP as 

specified on the approach chart. Fly to the MAP at or above 

the MDA or DA/DH before beginning a turn.

If visual reference is lost while circling-to-land from an 

instrument approach, execute the appropriate MAP. Make 

the initial climbing turn toward the landing runway and then 

maneuver to intercept and fly the missed approach course.

Pilots should immediately execute the MAP:

1. Whenever the requirements for operating below DA/

DH or MDA are not met when the aircraft is below 

MDA, or upon arrival at the MAP and at any time 

after that until touchdown;

2. Whenever an identifiable part of the airport is not 

visible to the pilot during a circling maneuver at or 

above MDA; or 

3. When so directed by ATC.
10-22

Landing

According to 14 CFR part 91, no pilot may land when the 

flight visibility is less than the visibility prescribed in the 

standard IAP being used. ATC provides the pilot with the 

current visibility reports appropriate to the runway in use. 

This may be in the form of prevailing visibility, runway visual 

value (RVV), or runway visual range (RVR). However, only 

the pilot can determine if the flight visibility meets the landing 

requirements indicated on the approach chart. If the flight 

visibility meets the minimum prescribed for the approach, 

then the approach may be continued to a landing. If the flight 

visibility is less than that prescribed for the approach, then 

the pilot must execute a missed approach regardless of the 

reported visibility.

The landing minimums published on IAP charts are based on 

full operation of all components and visual aids associated 

with the instrument approach chart being used. Higher 

minimums are required with inoperative components or 

visual aids. For example, if the ALSF-1 approach lighting 

system were inoperative, the visibility minimums for an ILS 

would need to be increased by one-quarter mile. If more 

than one component is inoperative, each minimum is raised 

to the highest minimum required by any single component 

that is inoperative. ILS glideslope inoperative minimums 

are published on instrument approach charts as localizer 

minimums. Consult the “Inoperative Components or Visual 

Aids Table” (printed on the inside front cover of each 

TPP) for a complete description of the effect of inoperative 

components on approach minimums.

Instrument Weather Flying

Flying Experience

The more experience a pilot has in VFR and IFR flight, 

the more proficient a pilot becomes. VFR experience can 

be gained by flying in terminal areas with high traffic 

activity. This type of flying forces the pilot to polish the 

skill of dividing his or her attention between aircraft control, 

navigation, communications, and other flight deck duties. 

IFR experience can be gained through night flying which 

also promotes both instrument proficiency and confidence. 

The progression from flying at night under clear, moonlit 

conditions to flying at night without moonlight, natural 

horizon, or familiar landmarks teaches a pilot to trust the 

aircraft instruments with minimal dependence upon what 

can be seen outside the aircraft. It is a pilot’s decision to 

proceed with an IFR flight or to wait for more acceptable 

weather conditions.

Recency of Experience

Currency as an instrument pilot is an equally important 

consideration. No person may act as pilot in command of an 

aircraft under IFR or in weather conditions less than VFR 

minimums unless he or she has met the requirements of Part 

91. Remember, these are minimum requirements.

Airborne Equipment and Ground Facilities

Regulations specify minimum equipment for filing an IFR 

flight plan. It is the pilot’s responsibility to determine the 

adequacy of the aircraft and navigation/communication 

(NAV/COM) equipment for the proposed IFR flight. 

Performance limitations, accessories, and general condition 

of the equipment are directly related to the weather, route, 

altitude, and ground facilities pertinent to the flight, as well 

as to the flight deck workload.

Weather Conditions

In addition to the weather conditions that might affect a 

VFR flight, an IFR pilot must consider the effects of other 

weather phenomena (e.g., thunderstorms, turbulence, icing, 

and visibility).

Turbulence

Inflight turbulence can range from occasional light bumps to 

extreme airspeed and altitude variations that make aircraft 

control difficult. To reduce the risk factors associated with 

turbulence, pilots must learn methods of avoidance, as well as 

piloting techniques for dealing with an inadvertent encounter.

Turbulence avoidance begins with a thorough preflight 

weather briefing. Many reports and forecasts are available to 

assist the pilot in determining areas of potential turbulence. 

These include the Severe Weather Warning (WW), SIGMET 

(WS), Convective SIGMET (WST), AIRMET (WA), Severe 

Weather Outlook (AC), Center Weather Advisory (CWA), 

Area Forecast (FA), and Pilot Reports (UA or PIREPs). Since 

thunderstorms are always indicative of turbulence, areas 

of known and forecast thunderstorm activity is always of 

interest to the pilot. In addition, clear air turbulence (CAT) 

associated with jet streams, strong winds over rough terrain, 

and fast moving cold fronts are good indicators of turbulence.

Pilots should be alert while in flight for the signposts of 

turbulence. For example, clouds with vertical development 

such as cumulus, towering cumulus, and cumulonimbus are 

indicators of atmospheric instability and possible turbulence. 

Standing lenticular clouds lack vertical development but 

indicate strong mountain wave turbulence. While en route, 

pilots can monitor hazardous inflight weather advisory 

service (HIWAS) broadcast for updated weather advisories, 

or contact the nearest FSS or En Route Flight Advisory 

Service (EFAS) for the latest turbulence-related PIREPs.
10-23

Figure 10-14. Maintaining an instrument scan in severe turbulence can be difficult.

To avoid turbulence associated with strong thunderstorms, 

circumnavigate cells by at least 20 miles. Turbulence may 

also be present in the clear air above a thunderstorm. To 

avoid this, fly at least 1,000 feet above the top for every 10 

knots of wind at that level, or fly around the storm. Finally, 

do not underestimate the turbulence beneath a thunderstorm. 

Never attempt to fly under a thunderstorm. The possible 

results of turbulence and wind shear under the storm could 

be disastrous.

When moderate to severe turbulence is encountered, aircraft 

control is difficult, and a great deal of concentration is 

required to maintain an instrument scan. [Figure 10-14]

Pilots should immediately reduce power and slow the 

aircraft to the recommended turbulence penetration speed 

as described in the POH/AFM. To minimize the load factor 

imposed on the aircraft, the wings should be kept level and the 

aircraft’s pitch attitude should be held constant. The aircraft 

is allowed to fluctuate up and down because maneuvering 

to maintain a constant altitude only increases the stress on 

the aircraft. If necessary, the pilot should advise ATC of 

the fluctuations and request a block altitude clearance. In 

addition, the power should remain constant at a setting that 

maintains the recommended turbulence penetration airspeed.

The best source of information on the location and intensity 

of turbulence are PIREPs. Therefore, pilots are encouraged to 

familiarize themselves with the turbulence reporting criteria 

found in the AIM, which also describes the procedure for 

volunteering PIREPs relating to turbulence.

Structural Icing

The very nature of flight in instrument meteorological 

conditions (IMC) means operating in visible moisture such 

as clouds. At the right temperatures, this moisture can 

freeze on the aircraft, causing increased weight, degraded 

performance, and unpredictable aerodynamic characteristics. 

Understanding avoidance and early recognition followed 

by prompt action are the keys to avoiding this potentially 

hazardous situation.

Structural icing refers to the accumulation of ice on the 

exterior of the aircraft and is broken down into three 

classifications: rime ice, clear ice, and mixed ice. For ice 

to form, there must be moisture present in the air, and the 

air must be cooled to a temperature of 0 °C (32 °F) or less. 

Aerodynamic cooling can lower the surface temperature of 

an airfoil and cause ice to form on the airframe even though 

the ambient temperature is slightly above freezing.

Rime ice forms if the droplets are small and freeze 

immediately when contacting the aircraft surface. This type 

of ice usually forms on areas such as the leading edges of 

wings or struts. It has a somewhat rough-looking appearance 

and a milky-white color.
10-24

Figure 10-14. Temperature ranges for ice formation. 

0 °C to –10 °C

–10 °C to –15 °C

–15 °C to –20°C

Clear 

Mixed clear and rime 

Rime 

Figure 10-15. Temperature ranges for ice formation.

Clear ice is usually formed from larger water droplets or 

freezing rain that can spread over a surface. This is the most 

dangerous type of ice since it is clear, hard to see, and can 

change the shape of the airfoil.

Mixed ice is a mixture of clear ice and rime ice. It has the 

bad characteristics of both types and can form rapidly. Ice 

particles become embedded in clear ice, building a very 

rough accumulation. The table in Figure 10-15 lists the 

temperatures at which the various types of ice form.

Structural icing is a condition that can only get worse. 

Therefore, during an inadvertent icing encounter, it is 

important the pilot act to prevent additional ice accumulation. 

Regardless of the level of anti-ice or deice protection offered 

by the aircraft, the first course of action should be to leave 

the area of visible moisture. This might mean descending 

to an altitude below the cloud bases, climbing to an altitude 

that is above the cloud tops, or turning to a different course. 

If this is not possible, then the pilot must move to an altitude 

where the temperature is above freezing. Pilots should report 

icing conditions to ATC and request new routing or altitude 

if icing will be a hazard. Refer to the AIM for information 

on reporting icing intensities.

Fog

Instrument pilots must learn to anticipate conditions leading 

to the formation of fog and take appropriate action early in 

the progress of the flight. Before a flight, close examination 

of current and forecast weather should alert the pilot to the 

possibility of fog formation. When fog is a consideration, 

pilots should plan adequate fuel reserves and alternate landing 

sites. En route, the pilot must stay alert for fog formation 

through weather updates from EFAS, ATIS, and ASOS/

AWOS sites.

Two conditions lead to the formation of fog. Either the air 

is cooled to saturation, or sufficient moisture is added to the 

air until saturation occurs. In either case, fog can form when 

the temperature/dewpoint spread is 5° or less. Pilots planning 

to arrive at their destination near dusk with decreasing 

temperatures should be particularly concerned about the 

possibility of fog formation.

Volcanic Ash

Volcanic eruptions create volcanic ash clouds containing 

an abrasive dust that poses a serious safety threat to flight 

operations. Adding to the danger is the fact that these ash 

clouds are not easily discernible from ordinary clouds when 

encountered at some distance from the volcanic eruption.

When an aircraft enters a volcanic ash cloud, dust particles 

and smoke may become evident in the cabin, often along with 

the odor of an electrical fire. Inside the volcanic ash cloud, 

the aircraft may also experience lightning and St. Elmo’s fire 

on the windscreen. The abrasive nature of the volcanic ash 

can pit the windscreens, thus reducing or eliminating forward 

visibility. The pitot-static system may become clogged, 

causing instrument failure. Severe engine damage is probable 

in both piston and jet-powered aircraft.

Every effort must be made to avoid volcanic ash. Since 

volcanic ash clouds are carried by the wind, pilots should plan 

their flights to remain upwind of the ash-producing volcano. 

Visual detection and airborne radar are not considered 

a reliable means of avoiding volcanic ash clouds. Pilots 

witnessing volcanic eruptions or encountering volcanic ash 

should immediately pass this information along in the form of 

a pilot report. The National Weather Service (NWS) monitors 

volcanic eruptions and estimates ash trajectories. This 

information is passed along to pilots in the form of SIGMETs.

As for many other hazards to flight, the best source of 

volcanic information comes from PIREPs. Pilots who 

witness a volcanic eruption or encounter volcanic ash in flight 

should immediately inform the nearest agency. Volcanic 

Ash Forecast Transport and Dispersion (VAFTAD) charts 

are also available; these depict volcanic ash cloud locations 

in the atmosphere following an eruption and also forecast 

dispersion of the ash concentrations over 6- and 12-hour 

time intervals. See AC 00-45, Aviation Weather Services.

Thunderstorms

A thunderstorm packs just about every weather hazard known 

to aviation into one vicious bundle. Turbulence, hail, rain, 

snow, lightning, sustained updrafts and downdrafts, and 

icing conditions are all present in thunderstorms. Do not 

take off in the face of an approaching thunderstorm or fly an 

aircraft that is not equipped with thunderstorm detection in 

clouds or at night in areas of suspected thunderstorm activity. 

[Figure 10-16]

There is no useful correlation between the external visual 

appearance of thunderstorms and the severity or amount of 

turbulence or hail within them. All thunderstorms should be 

considered hazardous, and thunderstorms with tops above 

35,000 feet should be considered extremely hazardous.
10-25

Figure 10-16. A thunderstorm packs just about every weather hazard 

known to aviation into one vicious bundle.

25 25 

Tailwind Shearing to Headwind or Calm Headwind Shearing to Tailwind or Calm

Front Front 

OM(outer marker) OM(outer marker)

Figure 10-17. Glideslope deviations due to wind shear encounter.

Weather radar, airborne or ground based, normally reflects 

the areas of moderate to heavy precipitation (radar does not 

detect turbulence). The frequency and severity of turbulence 

generally increases with the radar reflectivity closely 

associated with the areas of highest liquid water content of 

the storm. A flightpath through an area of strong or very 

strong radar echoes separated by 20 to 30 miles or less may 

not be considered free of severe turbulence.

The probability of lightning strikes occurring to aircraft is 

greatest when operating at altitudes where temperatures are 

between –5 ° C and +5 ° C. In addition, an aircraft flying in the 

clear air near a thunderstorm is also susceptible to lightning 

strikes. Thunderstorm avoidance is always the best policy.

Wind Shear

Wind shear can be defined as a change in wind speed and/or 

wind direction in a short distance. It can exist in a horizontal 

or vertical direction and occasionally in both. Wind shear can 

occur at all levels of the atmosphere but is of greatest concern 

during takeoffs and landings. It is typically associated 

with thunderstorms and low-level temperature inversions; 

however, the jet stream and weather fronts are also sources 

of wind shear.

As Figure 10-17 illustrates, while an aircraft is on an 

instrument approach, a shear from a tailwind to a headwind 

causes the airspeed to increase and the nose to pitch up with 

a corresponding balloon above the glidepath. A shear from 

a headwind to a tailwind has the opposite effect, and the 

aircraft will sink below the glidepath.

A headwind shear followed by a tailwind/downdraft shear is 

particularly dangerous because the pilot has reduced power 

and lowered the nose in response to the headwind shear. This 

leaves the aircraft in a nose-low, power-low configuration 

when the tailwind shear occurs, which makes recovery more 

difficult, particularly near the ground. This type of wind 

shear scenario is likely while making an approach in the 

face of an oncoming thunderstorm. Pilots should be alert for 

indications of wind shear early in the approach phase and be 

ready to initiate a missed approach at the first indication. It 

may be impossible to recover from a wind shear encounter 

at low altitude.

To inform pilots of hazardous wind shear activity, some 

airports have installed a Low-Level Wind Shear Alert 

System (LLWAS) consisting of a centerfield wind indicator 

and several surrounding boundary-wind indicators. With 
10-26

this system, controllers are alerted of wind discrepancies 

(an indicator of wind shear possibility) and provide this 

information to pilots. A typical wind shear alert issued to a 

pilot would be:

“Runway 27 arrival, wind shear alert, 20 knot loss 3 

mile final, threshold wind 200 at 15”

In plain language, the controller is advising aircraft arriving 

on runway 27 that at about 3 miles out they can expect 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° at 15 knots.

Pilots encountering wind shear are encouraged to pass along 

pilot reports. Refer to AIM for additional information on 

wind shear PIREPs.

VFR-On-Top

Pilots on IFR flight plans operating in VFR weather 

conditions may request VFR-on-top in lieu of an assigned 

altitude. This permits them to select an altitude or flight level 

of their choice (subject to any ATC restrictions).

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 contains a top report 

(or a statement that no top report is available) and a request 

to report upon reaching VFR-on-top. Additionally, the ATC 

authorization may contain a clearance limit, routing, and 

an alternative clearance if VFR-on-top is not reached by a 

specified altitude.

A pilot on an IFR flight plan, operating in VFR conditions, 

may request to climb/descend in VFR conditions. 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 part 91.

2. Comply with the VFR visibility and distance-fromcloud criteria in 14 CFR part 91.

3. Comply with IFR applicable to this flight (minimum IFR 

altitudes, position reporting, radio communications, 

course to be flown, adherence to ATC clearance, etc.).

Pilots operating on a VFR-on-top clearance should advise 

ATC before any altitude change to ensure the exchange of 

accurate traffic information.

ATC authorization to “maintain VFR-on-top” is not intended 

to restrict pilots to operating only above an obscuring 

meteorological formation (layer). Rather, it permits operation 

above, below, between layers, or in areas where there is no 

meteorological obstruction. It is imperative pilots understand, 

however, that clearance to operate “VFR-on-top/VFR 

conditions” does not imply cancellation of the IFR flight plan.

Pilots operating VFR-on-top/VFR conditions may receive 

traffic information from ATC on other pertinent IFR or 

VFR aircraft. However, when operating in VFR weather 

conditions, it is the pilot’s responsibility to be vigilant to see 

and avoid other aircraft.

This clearance must be requested by the pilot on an IFR flight 

plan. VFR-on-top is not permitted in certain areas, such as 

Class A airspace. Consequently, IFR flights operating VFRon-top must avoid such airspace.

VFR Over-The-Top

VFR over-the-top must not be confused with VFR-ontop. VFR-on-top is an IFR clearance that allows the pilot 

to fly VFR altitudes. VFR over-the-top is strictly a VFR 

operation in which the pilot maintains VFR cloud clearance 

requirements while operating on top of an undercast layer. 

This situation might occur when the departure airport and the 

destination airport are reporting clear conditions, but a low 

overcast layer is present in between. The pilot could conduct 

a VFR departure, fly over the top of the undercast in VFR 

conditions, then complete a VFR descent and landing at the 

destination. VFR cloud clearance requirements would be 

maintained at all times, and an IFR clearance would not be 

required for any part of the flight.

Conducting an IFR Flight

To illustrate some of the concepts introduced in this chapter, 

follow along on a typical IFR flight from the Birmingham 

International Airport (BHM), Birmingham, Alabama to 

Gulfport-Biloxi International Airport (GPT), Gulfport, 

Mississippi. [Figure 10-18] For this trip, a Cessna 182 with 

a call sign of N1230A is flown. The aircraft is equipped with 

dual navigation and communication radios, a transponder, 

and a GPS system approved for IFR en route, terminal, and 

approach operations.

Preflight

The success of the flight depends largely upon the 

thoroughness of the preflight planning. The evening before 

the flight, pay close attention to the weather forecast and 

begin planning the flight.
10-27

Figure 10-17. Route Planning. 

GREENWOOD 

122.1R 

KEWANEE 

113.8 EWA 8 5 

N 32 ° 2 2 . 01' W 8 8 ° 2 7 . 5 0' 

Figure 10-18. Route planning.

Figure 10-17. Route planning, Gulfport-Biloxi. 

S

C

-

4

,

16

DE

C

20

1

0

t

o13

J

A

N

201

1

1

102

NA

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02

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61

,

4-CS
10-28

The Weather Channel indicates a large, low-pressure system 

has settled in over the Midwest, pulling moisture up from 

the Gulf of Mexico and causing low ceilings and visibility 

with little chance for improvement over the next couple of 

days. To begin planning, gather all the necessary charts and 

materials, and verify everything is current. This includes en 

route charts, approach charts, DPs, STAR charts, the GPS 

database, as well as an A/FD, some navigation logs, and the 

aircraft’s POH/AFM. The charts cover both the departure 

and arrival airports and any contingency airports that will 

be needed if the flight cannot be completed as planned. This 

is also a good time for the pilot to consider recent flight 

experience, pilot proficiency, fitness, and personal weather 

minimums to fly this particular flight.

Check the A/FD to become familiar with the departure and 

arrival airport, and check for any preferred routing between 

BHM and GPT. Next, review the approach charts and any 

DP or STAR that pertains to the flight. Finally, review the 

en route charts for potential routing, paying close attention 

to the minimum en route and obstacle clearance altitudes.

After this review, select the best option. For this flight, the 

Birmingham Three Departure [Figure 10-2] to Brookwood 

VORTAC, V 209 to Kewanee VORTAC, direct to Gulfport 

using GPS would be a logical route. An altitude of 4,000 feet 

meets all the regulatory requirements and falls well within 

the performance capabilities of the aircraft.

Next, call 1-800-WX-BRIEF to obtain an outlook-type 

weather briefing for the proposed flight. This provides 

forecast conditions for departure and arrival airports, as well 

as the en route portion of the flight including forecast winds 

aloft. This also is a good opportunity to check the available 

NOTAMs.

The weather briefer confirms the predictions of the Weather 

Channel giving forecast conditions that are at or near 

minimum landing minimums at both BHM and GPT for 

the proposed departure time. The briefer provides NOTAM 

information for GPT indicating that the localizer to runway 

32 is scheduled to be out of service and that runway 18/36 is 

closed until further notice. Also check for temporary flight 

restrictions (TFRs) along the proposed route. 

After receiving a weather briefing, continue flight planning 

and begin to transfer some preliminary information onto 

the navigation log, listing each fix along the route and the 

distances, frequencies, and altitudes. Consolidating this 

information onto an organized navigation log keeps the 

workload to a minimum during the flight.

Next, obtain a standard weather briefing online for the 

proposed route. A check of current conditions indicates 

low IFR conditions at both the departure airport and the 

destination, with visibility of one-quarter mile:

SURFACE WEATHER OBSERVATIONS

METAR KBHM 111155Z VRB04KT 1⁄4 SM FG –RA VV004 

06/05 A2994 RMK A02 SLP140

METAR KGPT 111156Z 24003KT 1⁄4 SM FG OVC001 08/07 

A2962 RMK A02 SLP033

The small temperature/dewpoint spread is causing the low 

visibility and ceilings. Conditions should improve later in 

the day as temperatures increase. A check of the terminal 

forecast confirms this theory:

TERMINAL FORECASTS

TAF KBHM 111156Z 111212 VRB04KT 1⁄4 SM FG VV004 

TEMPO1316 3⁄4 SM OVC004 

FM1600 VRB05KT 2SM BR OVC007 TEMPO 1720 3SM 

DZ BKN009

FM2000 22008KT 3SM –RA OVC015 TEMP 2205 3SM 

–RA OVC025 FM0500 23013KT P6SM OVC025 

FM0800 23013KT P6SM BKN030 PROB40 1012 2SM BR 

OVC030

TAF KGPT 111153Z 111212 24004KT 1⁄4 SM FG OVC001 

BECMG 1317 3SM BR 0VC004 

FM1700 24010KT 4SM –RA OVC006 FM0400 24010 5SM 

SCT080 TEMPO 0612 P6SM SKC

In addition to the terminal forecast, the area forecast also 

indicates gradual improvement along the route. Since the 

terminal forecast only provides information for a 5-mile 

radius around a terminal area, checking the area forecast 

provides a better understanding of the overall weather picture 

along the route, as well as potential hazards:

SYNOPSIS AND VFR CLOUDS/WEATHER FORECASTS 

SYNOPSIS... AREA OF LOW PRESSURE CNTD OV AL 

RMNG GENLY STNRY BRNGNG MSTR AND WD SPRD 

IFR TO E TN. ALF...LOW PRES TROF ACRS CNTR PTN 

OF THE DFW FA WILL GDLY MOV EWD DURG PD.

NRN LA, AR, NRN MS

SWLY WND THRUT THE PD. 16Z CIG OVC006. SCT 

–SHRA. OTLK... IFR SRN 1⁄2 ... CIG SCT – BKN015 

TOPS TO FL250 SWLY WND THRUT THE PD. 17Z AGL 

BKN040. OTLK...MVFR CIG VIS.
10-29

LA MS CSTL WTRS

CIG OVC001 – OVC006. TOPS TO FL240. VIS 1⁄4 – 3⁄4 SM 

FG. SWLY WND. 16Z CIG OVC010 VIS 2 SM BR. OCNL 

VIS 3-5SM –RN BR OVC009. OTLK...MVFR CIG VIS.

FL

CIG BKN020 TOPS TO FL180. VIS 1–3 SM BR. SWLY 

WND. 18Z BRK030. OTLK...MVFR CIG.

At this time, there are no SIGMETs or PIREPs reported. 

However, there are several AIRMETs, one for IFR 

conditions, one for turbulence that covers the entire route, 

and another for icing conditions that covers an area just north 

of the route:

WAUS44 KKCI 111150

DFWS WA 0111150

AIRMET SIERRA FOR IFR VALID UNTIL 111800

AIRMET IFR...OK TX LA AR MS AL FL

TS IMPLY SEV OR GTR TURB SEV ICE LLWS AND 

IFR CONDS.

NON MSL HGHTS DENOTED BY AGL OR CIG.

A recheck of NOTAMs for Gulfport confirms that the 

localizer to runway 32 is out of service until further notice 

and runway 18/36 is closed. If runway 6 is planned for the 

departure, confirm that the climb restriction for the departure 

can be met.

GPT 12/006 GPT LOC OS UFN

GPT 12/008 GPT MIRL RWY 18/36 OS UFN

Since the weather is substantially better to the east, Pensacola 

Regional Airport is a good alternate with current conditions 

and a forecast of marginal VFR.

METAR KPNS 111150Z 21010Z 3SM BKN014 OVC025 

09/03 A2973 

TAF KPNS 111152Z 111212 22010KT 3 SM BR OVC020 

BECMG 1317 4 SM BR OVC025 

FM1700 23010KT 4SM –RA OVC030 

FM 0400 25014KT 5SM OVC050 TEMPO1612 P6SM 

OVC080

If weather minimums are below a pilot’s personal minimums, 

a delay in departure to wait for improved conditions is 

a good decision. This time can be used to complete the 

navigation log, which is the next step in planning an IFR 

flight. [Figure 10-19] 

Use the POH/AFM to compute a true airspeed, cruise power 

setting, and fuel burn based on the forecast temperatures 

aloft and cruising pressure altitude. Also, compute weightand-balance information and determine takeoff and landing 

distances. There will be a crosswind if weather conditions 

require a straight-in landing on runway 14 at GPT. Therefore, 

compute the landing distance assuming a 10-knot crosswind 

and determine if the runway length is adequate to allow 

landing. Determine the estimated flight time and fuel burn 

using the winds aloft forecast and considering Pensacola 

Regional Airport as an alternate airport. With full tanks, the 

flight can be made nonstop with adequate fuel for flight to 

the destination, alternate, and the reserve requirement.

Next, check the surface analysis chart, which shows where 

the pressure systems are found. The weather depiction chart 

shows areas of IFR conditions and can be used to find areas 

of improving conditions. These charts provide information a 

pilot needs should a diversion to VFR conditions be required. 

For this flight, the radar depicts precipitation along the route, 

and the latest satellite photo confirms what the weather 

depiction chart showed.

When the navigation log is finished, complete the flight plan 

in preparation for filing with flight service. [Figure 10-20]

Call an FSS for an updated weather briefing. Birmingham 

INTL airport is now reporting 700 overcast with 3 miles 

visibility, and Gulfport-Biloxi is now 400 overcast with 2 

miles visibility. The alternate, Pensacola Regional Airport, 

continues to report adequate weather conditions with 2,000 

overcast and 3 miles visibility in light rain.

Several pilot reports have been submitted for light icing 

conditions; however, all the reports are north of the route 

of flight and correspond to the AIRMET that was issued 

earlier. No pilot reports have included cloud tops, but the 

area forecast predicted cloud tops to flight level 240. Since 

the weather conditions appear to be improving, a flight plan 

can be filed using the completed form.

Analyze the latest weather minimums to determine if they 

exceed personal minimums. With the absence of icing 

reported along the route and steadily rising temperatures, 
10-30

FLIGHT LOG 

ATIS 

TIME DISTANCE FUEL 

TAKE OFF LANDING TOTAL REQUIRED AVAILABLE 

ROUTE 

(Check Point) REMARKS MAG 

CRSE 

IDENT 

FREQ 

ALTITUDE 

GND SPD 

ETE 

ATE 

ETE 

ATE 

LEG 

REMAINING 

DEPERTURE ARRIVAL 

INFORMATION 

CEILING 

VISIBILITY 

ALTIMETER 

WINDS 

TEMP / DEWPOINT 

REMARKS 

RWY IN USE 

INFORMATION 

CEILING 

VISIBILITY 

ALTIMETER 

WINDS 

TEMP / DEWPOINT 

REMARKS 

RWY IN USE 

1600 E 228 51 Gal 87 Gal 

Brookwood OKW 

111.0 

31 

197 230 +16 16:16 4000 120 3 Gal 

Kewanee EWA 

113.8 

80 

117 

225 +40 16:56 4000 

120 8 Gal 

Rascagoula 

Regional 

PNS 91 

0 

085 +35 3000 

158 18 Gal 

Appr 17 

0 

+08 17:58 2 Gal 

Mindo 110 

17 

195 +54 17:50 4000 

125 12 Gal 

118 

1+58 

Figure 10-18. Flight plan from. Figure 10-19. Navigation log.

structural icing should not be a problem. Make a note to do an 

operational check of the pitot heat during preflight and to take 

evasive action immediately should even light icing conditions 

be encountered in flight. This may require returning to BHM 

or landing at an intermediate spot before reaching GPT. The 

go/no-go decision is constantly reevaluated during the flight. 

Once at the airport, conduct a thorough preflight inspection. 

A quick check of the logbooks indicates all airworthiness 

requirements have been met to conduct this IFR flight 

including an altimeter, static, and transponder test within 

the preceding 24 calendar months. In addition, a log on 

the clipboard indicates the VOR system has been checked 
10-31

Figure 10-19. Flight plan form. 

OKW V 209 EWA MINDO 

Gulfport, 

Biloxi 1 58 

04 20 PNS 

blue/white 

James Jones, 841 Oak St. Gardendail, Al. 205-555-6028 

2 

X N/230A C182/G 140 BHM 1600 4000 

Figure 10-20. Flight plan form. 

within the preceding 30 days. Turn on the master switch and 

pitot heat, and quickly check the heating element before it 

becomes too hot. Then, complete the rest of the walk-around 

procedure. Since this is a flight in actual IFR conditions, place 

special emphasis on IFR equipment during the walk-around, 

including the alternator belt and antennas. After completing 

the preflight, organize charts, pencils, paper, and navigation 

log in the flight deck for quick, easy access. This is also the 

time to enter the planned flight into the GPS.

Departure

After starting the engine, tune in ATIS and copy the 

information to the navigation log. The conditions remain the 

same as the updated weather briefing with the ceiling at 700 

overcast and visibility at 3 miles. Call clearance delivery to 

receive a clearance:

“Clearance Delivery, Cessna 1230A IFR to Gulfport 

Biloxi with information Kilo, ready to copy.”

“Cessna 1230A is cleared to Gulfport-Biloxi via the 

Birmingham Three Departure, Brookwood, Victor 

209 Kewanee then direct Mindo, Gulfport. Climb and 

maintain 4,000. Squawk 0321.”

Read back the clearance and review the DP. Although a 

departure frequency was not given in the clearance, note that 

on the DP, the departure control frequency is listed as 123.8 

for the southern sector. Since a departure from runway 24 

is anticipated, note the instruction to climb to 2,100 prior 

to turning. After tuning in the appropriate frequencies and 

setting up navigation equipment for the departure routing, 

contact ground control (noting that this is IFR) and receive 

the following clearance:

“Cessna 1230A taxi to runway 24 via taxiway Mike.”

Read back the clearance and aircraft call sign. After a review 

of the taxi instructions on the airport diagram, begin to taxi 

and check the flight instruments for proper indications.

Hold short of runway 24 and complete the before takeoff 

checklist and engine run-up. Advise the tower when ready 

for takeoff. The tower gives the following clearance:

“Cessna 30A cleared for takeoff runway 24. 

Caution wake turbulence from 737 departing to the 

northwest.”
10-32

Taxi into position. Note the time off on the navigation log, 

verify that the heading indicator and magnetic compass are 

in agreement, the transponder is in the ALT position, all the 

necessary lights, equipment, and pitot heat are on. Start the 

takeoff roll. To avoid the 737’s wake turbulence, make note 

of its lift off point and take off prior to that point.

En Route

After departure, climb straight ahead to 2,100 feet as directed 

by the Birmingham Three Departure. While continuing a 

climb to the assigned altitude of 4,000 feet, the following 

instructions are received from the tower:

“Cessna 30A contact Departure.”

Acknowledge the clearance and contact departure on the 

frequency designated by the DP. State the present altitude 

so the departure controller can check the encoded altitude 

against indicated altitude:

“Birmingham Departure Cessna 1230A climbing 

through 2,700 heading 240.”

Departure replies:

“Cessna 30A proceed direct to Brookwood and resume 

own navigation. Contact Atlanta Center on 134.05.”

Acknowledge the clearance, contact Atlanta Center and 

proceed direct to Brookwood VORTAC, using the IFRapproved GPS equipment. En route to Kewanee, VORTAC 

Atlanta Center issues the following instructions:

“Cessna 1230A contact Memphis Center on 

125.975.”

Acknowledge the instructions and contact Memphis Center 

with aircraft ID and present altitude. Memphis Center 

acknowledges contact:

“Cessna 1230A, Meridian altimeter is 29.87. Traffic 

at your 2 o’clock and 6 miles is a King Air at 5,000 

climbing to 12,000.”

Even when on an IFR flight plan, pilots are still responsible 

for seeing and avoiding other aircraft. Acknowledge the call 

from Memphis Center and inform them of negative contact 

with traffic due to IMC.

“Roger, altimeter setting 29.87. Cessna 1230A is in 

IMC negative contact with traffic.”

Continue the flight, and at each fix note the arrival time on 

the navigation log to monitor progress. 

To get an update of the weather at the destination and issue 

a pilot report, contact the FSS servicing the area. To find the 

nearest FSS, locate a nearby VOR and check above the VOR 

information box for a frequency. In this case, the nearest VOR 

is Kewanee VORTAC which lists a receive-only frequency 

of 122.1 for Greenwood FSS. Request a frequency change 

from Memphis and then attempt to contact Greenwood on 

122.1 while listening over the Kewanee VORTAC frequency 

of 113.8:

“Greenwood Radio Cessna 1230A receiving on 

frequency 113.8, over.”

“Cessna 30A, this is Greenwood, go ahead.”

“Greenwood Radio, Cessna 30A is currently 30 miles 

south of the Kewanee VORTAC at 4,000 feet en 

route to Gulfport. Requesting an update of en route 

conditions and current weather at GPT, as well as 

PNS.”

“Cessna 30A, Greenwood Radio, current weather at 

Gulfport is 400 overcast with 3 miles visibility in light 

rain. The winds are from 140 at 7 and the altimeter 

is 29.86. Weather across your route is generally IFR 

in light rain with ceilings ranging from 300 to 1,000 

overcast with visibilities between 1 and 3 miles. 

Pensacola weather is much better with ceilings now 

at 2,500 and visibility 6 miles. Checking current 

NOTAMs at GPT shows the localizer out of service 

and runway 18/36 closed.”

“Roger, Cessna 30A copies the weather. I have a 

PIREP when you are ready to copy.”

“Cessna 30A go ahead with your PIREP.”

“Cessna 30A is a Cessna 182 located on the Kewanee 

195° radial at 30 miles level at 4,000 feet. I am 

currently in IMC conditions with a smooth ride. 

Outside air temperature is plus 1° Celsius. Negative 

icing.”

“Cessna 30A thank you for the PIREP.”

With the weather check and PIREP complete, return to 

Memphis Center:

“Memphis Center, Cessna 1230A is back on your 

frequency.”

“Cessna 1230A, Memphis Center, roger, contact 

Houston Center now on frequency 126.8.”
10-33

“Roger, contact Houston Center frequency 126.8, 

Cessna 1230A.”

“Houston Center, Cessna 1230A level at 4,000 

feet.”

“Cessna 30A, Houston Center area altimeter 29.88.”

Arrival

40 miles north of Gulfport, tune in ATIS on number two 

communication radio. The report reveals there has been no 

change in the weather and ATIS is advertising ILS runway 

14 as the active approach.

Houston Center completes a hand off to Gulfport approach 

control with instructions to contact approach:

“Gulfport Approach, Cessna 1230A level 4,000 feet 

with information TANGO. Request GPS Runway 14 

approach.”

“Cessna 30A, Gulfport Approach, descend and 

maintain 3,000 feet.”

“Descend to 3,000, Cessna 30A.”

Begin a descent to 3,000 and configure your navigation radios 

for the approach. The GPS automatically changes from the 

en route mode to the terminal mode. This change affects the 

sensitivity of the CDI. Tune in the VORTAC frequency of 

109.0 on the number one navigation radio and set in the final 

approach course of 133° on the OBS. This setup helps with 

situational awareness should the GPS lose signal.

“Cessna 30A your position is 7 miles from MINDO, 

maintain 3,000 feet until MINDO, cleared for the GPS 

runway 14 approach.”

Read back the clearance and concentrate on flying the aircraft. 

At MINDO descend to 2,000 as depicted on the approach 

chart. At BROWA turn to the final approach course of 

133°. Just outside the Final Approach Way Point (FAWP) 

AVYUM, the GPS changes to the approach mode and the 

CDI becomes even more sensitive. Gulfport approach control 

issues instructions to contact Gulfport tower:

“Cessna 30A contact Tower on 123.7.”

“123.7, Cessna 30A.”

“Tower, Cessna 1230A outside AVYUM on the GPS 

runway 14.”

“Cessna 30A Gulfport Tower, the ceiling is now 600 

overcast and the visibility is 4 miles.”

“Cleared to land runway 14, Cessna 30A.”

Continue the approach, complete the appropriate checklists, 

cross AVYUM, and begin the final descent. At 700 feet MSL 

visual contact with the airport is possible. Slow the aircraft 

and configure it to allow a normal descent to landing. As 

touch down is completed, Gulfport Tower gives further 

instructions:

“Cessna 30A turn left at taxiway Bravo and contact 

ground on 120.4.”

“Roger, Cessna 30A.”

Taxi clear of the runway and complete the appropriate 

checklists. The tower automatically cancels the IFR flight 

plan.
10-34
11-1

Introduction

Changing weather conditions, air traffic control (ATC), the 

aircraft, and the pilot are all variables that make instrument 

flying an unpredictable and challenging operation. The safety 

of the flight depends upon the pilot’s ability to manage these 

variables while maintaining positive aircraft control and 

adequate situational awareness. This chapter discusses the 

recognition and suggested remedies for such abnormal and 

emergency events related to unforecasted, adverse weather; 

aircraft system malfunctions; communication/navigation 

system malfunctions; and loss of situational awareness.

Emergency 

Operations

Chapter 11
11-2

Unforecast Adverse Weather

Inadvertent Thunderstorm Encounter

A pilot should avoid flying through a thunderstorm of any 

intensity. However, certain conditions may be present 

that could lead to an inadvertent thunderstorm encounter. 

For example, flying in areas where thunderstorms are 

embedded in large cloud masses may make thunderstorm 

avoidance difficult, even when the aircraft is equipped 

with thunderstorm detection equipment. Therefore, pilots 

must be prepared to deal with an inadvertent thunderstorm 

penetration. At the very least, a thunderstorm encounter 

subjects the aircraft to turbulence that could be severe. The 

pilot and passengers should tighten seat belts and shoulder 

harnesses, and secure any loose items in the cabin.

As with any emergency, the first order of business during 

an inadvertent thunderstorm encounter must be to fly the 

aircraft. The pilot workload is heavy; therefore, increased 

concentration is necessary to maintain an instrument scan. 

If a pilot inadvertently enters a thunderstorm, it is better to 

maintain a course straight through the thunderstorm rather 

than turning around. A straight course minimizes the amount 

of time in the thunderstorm, and turning maneuvers only 

increase structural stress on the aircraft.

Reduce power to a setting that maintains a speed at the 

recommended turbulence penetration speed as described in the 

Pilot’s Operating Handbook/Airplane Flight Manual (POH/

AFM), and try to minimize additional power adjustments. 

Concentrate on maintaining a level attitude while allowing 

airspeed and altitude to fluctuate. Similarly, if using the 

autopilot, disengage the altitude hold and speed hold modes, 

as they only increase the aircraft’s maneuvering—thereby 

increasing structural stress.

During a thunderstorm encounter, the potential for icing 

also exists. As soon as possible, turn on anti-icing/deicing 

equipment and carburetor heat, if equipped. Icing can be 

rapid at any altitude and may lead to power failure and/or 

loss of airspeed indication.

Lightning is also present in a thunderstorm and can 

temporarily blind a pilot. To reduce this risk, turn up flight 

deck lights to the highest intensity, concentrate on the flight 

instruments, and resist the urge to look outside.

Inadvertent Icing Encounter

Because icing is unpredictable in nature, pilots may find 

themselves in icing conditions even though they have done 

everything practicable to avoid it. In order to stay alert to this 

possibility while operating in visible moisture, pilots should 

monitor the outside air temperature (OAT).

The effects of ice on aircraft are cumulative—thrust 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, two to three inches 

of ice can form on the leading edge of the airfoil in less than 5 

minutes. It takes only 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.

A pilot can expect icing when flying in visible precipitation, 

such as rain or cloud droplets, and the temperature is 

between +02 and –10° Celsius. When icing is detected, a 

pilot should do one of two things, particularly if the aircraft 

is not equipped with deicing equipment: leave 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.

If neither option is available, consider an immediate landing 

at the nearest suitable airport. Even if the aircraft is equipped 

with anti-icing/deicing equipment, it is not designed to allow 

aircraft to operate indefinitely in icing conditions. Antiicing/deicing equipment gives a pilot more time to get out of 

the icing conditions. Report icing to ATC and request new 

routing or altitude. Be sure to report the type of aircraft, and 

use the following terms when reporting icing to ATC: 

1. Trace. Ice becomes perceptible. Rate of accumulation 

is slightly greater than sublimation. Anti-icing/deicing 

equipment is not utilized unless encountered for an 

extended period of time (over 1 hour).

2. Light. The rate of accumulation may create a problem 

if flight is prolonged in this environment (over 1 

hour). Occasional use of anti-icing/deicing equipment 

removes/prevents accumulation. It does not present a 

problem if anti-icing/deicing equipment is used.

3. Moderate. The rate of accumulation is such that even 

short encounters become potentially hazardous and 

use of anti-icing/deicing equipment or flight diversion 

is necessary.

4. Severe. The rate of accumulation is such that antiicing/deicing equipment fails to reduce or control the 

hazard. Immediate flight diversion is necessary.

Early ice detection is critical and is particularly difficult during 

night flight. Use a flashlight to check for ice accumulation on 

the wings. At the first indication of ice accumulation, take 

action to get out of the icing conditions. Refer to the POH/

AFM for the proper use of anti-icing/deicing equipment. 
11-3

Figure 11-2. One example of a static wick installed on aircraft 

control surface to bleed off static charges built up during flight. 

Figure 11-2. One example of a static wick installed on aircraft 

control surface to bleed off static charges built up during flight. 

This prevents static buildup and St. Elmo’s fire by allowing the 

static electricity to dissipate harmlessly.

Figure 11-1. St. Elmo’s Fire is harmless but may affect both communication and navigation radios, especially the lower frequencies 

such as those used on the automatic direction finding (ADF).

Precipitation Static

Precipitation static, often referred to as P-static, occurs 

when accumulated static electricity is discharged from the 

extremities of the aircraft. This discharge has the potential 

to create problems for the instrument pilot. These problems 

range from the serious, such as erroneous magnetic compass 

readings and the complete loss of very high frequency (VHF) 

communications to the annoyance of high-pitched audio 

squealing and St. Elmo’s fire. [Figure 11-1]

Precipitation static is caused when an aircraft encounters 

airborne particles during flight (e.g., rain or snow) and 

develops a negative charge. It can also result from 

atmospheric electric fields in thunderstorm clouds. When 

a significant negative voltage level is reached, the aircraft 

discharges it, which can create electrical disturbances. This 

electrical discharge builds with time as the aircraft flies in 

precipitation. It is usually encountered in rain, but snow can 

cause the same effect. As the static buildup increases, the 

effectiveness of both communication and navigation systems 

decreases to the point of potential unusability. 

To reduce the problems associated with P-static, the pilot 

should ensure the aircraft’s static wicks are properly maintained 

and accounted for. Broken or missing static wicks should be 

replaced before an instrument flight. [Figure 11-2]

Aircraft System Malfunctions

Preventing aircraft system malfunctions that might lead 

to an inflight emergency begins with a thorough preflight 
11-4

ALERTS

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

MAP 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

GS 120KT XTK 0.07NM ETE 24:24 ESA 2800FT

ALERTS

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 11-3. Illustrates the system (in this case the G1000) when the PFD display fails and it the reversionary mode is used. 

DCLTR 

Normal Mode 

Display Failure / Reversionary Mode 

MAP - NAVIGATION MAP

Figure 11-3. G1000 PFD display in normal mode and in the reversionary mode activated upon system failure.

inspection. In addition to those items normally checked 

prior to a visual flight rules (VFR) flight, pilots intending to 

fly under instrument flight rules (IFR) should pay particular 

attention to the alternator belt, antennas, static wicks, antiicing/deicing equipment, pitot tube, and static ports.

During taxi, verify the operation and accuracy of all flight 

instruments. In addition, during the run-up, verify that the 

operation of the pneumatic system(s) is within acceptable 

parameters. It is critical that all systems are determined to be 

operational before departing into IFR conditions.

Electronic Flight Display Malfunction

When a pilot becomes familiar and comfortable with the 

new electronic displays, he or she also tends to become more 

reliant on the system. The system then becomes a primary 

source of navigation and data acquisition instead of the 

supplementary source of data as initially intended. 

Complete reliance on the moving map for navigation becomes 

a problem during a failure of one, more, or all of the flight 

display screens. Under these conditions, the systems revert to 

a composite mode (called reversionary), which eliminates the 

moving map display and combines the primary flight display 

(PFD) with the engine indicating system. [Figure 11-3] If a 

pilot has relied on the display for navigation information and 

situational awareness, he or she lacks any concept of critical 

data such as the aircraft’s position, the nearest airport, or 

proximity to other aircraft.

The electronic flight display (EFD) is a supplementary source 

of navigation data and does not replace en route charts. 

To maintain situational awareness, a pilot must follow the 

flight on the en route chart while monitoring the PFD. It is 

important for the pilot to know the location of the closest 

airport as well as surrounding traffic relative to the location 

of his or her aircraft. This information becomes critical 

should the EFD fail. 

For the pilot who utilizes the electronic database as a 

substitute for the Airport/Facilities Directory (A/FD), screen 

failure or loss of electrical power can mean the pilot is no 

longer able to access airport information. Once the pilot 

loses the ability to call up airport information, aeronautical 

decision-making (ADM) is compromised. 
11-5

Figure 11-4. Ammeter (left) and loadmeter (right).

Figure 11-5. The double rocker switch. 

Figure 11-5. Double rocker switch seen on many aircraft.

6

7

5

4

3

IN.

Hg.

+ 60

- 60

30

30

0

A

M

P

V

A

C ALT AMPS 

0 30 60 

Figure 11-4. Ammeter & Loadmeter. 

Ammeter 

Loadmeter 

Alternator/Generator Failure

Depending upon the aircraft being flown, an alternator failure 

is indicated in different ways. Some aircraft use an ammeter 

that indicates the state of charge or discharge of the battery. 

[Figure 11-4] A positive indication on the ammeter indicates 

a charge condition; a negative indication reveals a discharge 

condition. Other aircraft use a loadmeter to indicate the load 

being carried by the alternator. [Figure 11-4] 

Sometimes an indicator light is also installed in the aircraft to 

alert the pilot to an alternator failure. On some aircraft, such 

as the Cessna 172, the light is located on the lower left side 

making it difficult to see its illumination if charts are open. 

Ensure that these safety indicators are visible during flight. 

When a loss of the electrical charging system is experienced, 

the pilot has approximately 40 minutes of battery life 

remaining before the system fails entirely. The time 

mentioned is an approximation and should not be relied upon 

as specific to all aircraft. In addition, the battery charge that 

exists in a battery may not be full, altering the time available 

before electrical exhaustion occurs. At no time should a pilot 

consider continuing a flight once the electrical charging 

system has failed. Land at the nearest suitable airport.

Techniques for Electrical Usage

Master Battery Switch

One technique for conserving the main battery charge is 

to fly the aircraft to the airport of intended landing while 

operating with minimal power. If a two-position battery 

master/alternator rocker switch is installed, it can be utilized 

to isolate the main battery from the electrical system and 

conserve power. [Figure 11-5]

Operating on the Main Battery

While en route to the airport of intended landing, reduce the 

electrical load as much as practical. Turn off all unnecessary 

electrical items, such as duplicate radios, non-essential 

lighting, etc. If unable to turn off radios, lights, etc., manually, 

consider pulling circuit breakers to isolate those pieces of 

equipment from the electrical system. Maximum time of 

useful voltage may be between 30 and 40 minutes and is 

influenced by many factors, that degrade the useful time. 

Loss of Alternator/Generator for Electronic Flight 

Instrumentation

With the increase in electrical components being installed 

in modern technically advanced aircraft, the power supply 

and the charging system need increased attention and 
11-6

Figure 11-6. The standby battery must be armed to work 

correctly and arming should be done prior to departure. 

Double rocker switch 

Figure 11-6. Note the double rocker switch and the standby battery 

switch in this aircraft. The standby battery must be armed to work 

correctly; arming should be done prior to departure.

understanding. Traditional round dial aircraft do not rely 

as heavily on electrical power for the primary six-pack 

instrumentation. Modern EFDs utilize the electrical system 

to power the Attitude Heading Reference System (AHRS), 

air data computer (ADC), engine indicating system (EIS), 

etc. A loss of an alternator or generator was considered an 

abnormality in traditionally-equipped aircraft; however, 

a failure of this magnitude is considered an emergency in 

technically advanced aircraft. 

Due to the increased demand for electrical power, it is 

necessary for manufacturers to install a standby battery in 

conjunction with the primary battery. The standby battery is 

held in reserve and kept charged in case of a failure of the 

charging system and a subsequent exhaustion of the main 

battery. The standby battery is brought online when the main 

battery voltage is depleted to a specific value, approximately 

19 volts. Generally, the standby battery switch must be in 

the ARM position for this to occur but pilots should refer to 

the aircraft flight manual (AFM) for specifics on an aircraft’s 

electrical system. The standby battery powers the essential 

bus and allows the PFD to be utilized. 

The essential bus usually powers the following components:

1. AHRS (Attitude and Heading Reference System)

2. ADC (Air Data Computer)

3. PFD (Primary Flight Display)

4. Navigation Radio #1

5. Communication Radio #1

6. Standby Indicator Light

Techniques for Electrical Usage

Standby Battery

One technique for conserving the main battery charge is to 

fly the aircraft to the airport of intended landing while using 

the standby battery. A two-position battery master/ alternator 

rocker switch is installed on most aircraft with EFDs, which 

can be utilized to isolate the main battery from the electrical 

system. By switching the MASTER side off, the battery is 

taken offline and the standby battery comes online to power the 

essential bus. However, the standby battery switch must be in 

the ARM position for this to occur. [Figure 11-6] Utilization 

of the standby battery first reserves the main battery for use 

when approaching to land. With this technique, electrical 

power may be available for the use of flaps, gear, lights, etc. Do 

not rely on any power to be available after the standby battery 

has exhausted itself. Once the charging system has failed, 

flight with a powered electrical system is not guaranteed.

Operating on the Main Battery

While en route to the airport of intended landing, reduce the 

electrical load as much as practical. Turn off all unnecessary 

electrical items, such as duplicate radios, non-essential 

lighting, etc. If unable to turn off radios, lights, etc., manually, 

consider pulling circuit breakers to isolate those pieces of 

equipment from the electrical system. Keep in mind that 

once the standby battery has exhausted its charge, the flight 

deck may become very dark depending on what time of 

day the failure occurs. The priority during this emergency 

situation is landing the aircraft as soon as possible without 

jeopardizing safety. 

A standby attitude indicator, altimeter, airspeed indicator (ASI) 

and magnetic compass are installed in each aircraft for use 

when the PFD instrumentation is unavailable. [Figure 11-7]

These would be the only instruments left available to the pilot. 

Navigation would be limited to pilotage and dead reckoning 

unless a hand-held transceiver with a global positioning 

system (GPS)/navigation function is onboard.

Once an alternator failure has been detected, the pilot must 

reduce the electrical load on the battery and land as soon as 

practical. Depending upon the electrical load and condition 

of the battery, there may be sufficient power available for 

45 minutes of flight—or for only a matter of minutes. Pilots 

should also know which systems on the aircraft are electric and 
11-7

ALERTS

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

N-S E-W 

Figure 11-7. Emergency instrumentation available to the pilot on electronic flight instrumented aircraft. Figure 11-7. The stand-by instrumentation available to the pilot on Electronic Flight Instrumented Aircraft. 

those that continue to operate without electrical power. Pilots 

can attempt to troubleshoot alternator failure by following the 

established alternator failure procedure published in the POH/

AFM. If the alternator cannot be reset, advise ATC of the 

situation and inform them of the impending electrical failure.

Analog Instrument Failure

A warning indicator, or an inconsistency between indications 

on the attitude indicator and the supporting performance 

instruments, usually identifies system or instrument failure. 

Aircraft control must be maintained while identifying the 

failed component(s). Expedite the cross-check and include 

all flight instruments. The problem may be individual 

instrument failure or a system failure affecting multiple 

instruments.

One method of identification involves an immediate 

comparison of the attitude indicator with the rate-of-turn 

indicator and vertical speed indicator (VSI). Along with 

providing pitch-and-bank information, this technique 

compares the static system with the suction or pressure system 

and the electrical system. Identify the failed component(s) 

and use the remaining functional instruments to maintain 

aircraft control.

Attempt to restore the inoperative component(s) by checking 

the appropriate power source, changing to a backup or 

alternate system, and resetting the instrument if possible. 

Covering the failed instrument(s) may enhance a pilot’s 

ability to maintain aircraft control and navigate the aircraft. 

Usually, the next step is to advise ATC of the problem and, 

if necessary, declare an emergency before the situation 

deteriorates beyond the pilot’s ability to recover.

Pneumatic System Failure

One possible cause of instrument failure is a loss of the 

suction or pressure source. This pressure or suction is 

supplied by a vacuum pump mechanically driven off the 

engine. Occasionally these pumps fail, leaving the pilot with 

inoperative attitude and heading indicators. 

Figure 11-8 illustrates inoperative vacuum driven attitude 

and heading indicators that can fail progressively. As the 

gyroscopes slow down, they may wander, which, if connected 

to the autopilot and/or flight director, can cause incorrect 

movement or erroneous indications. In Figure 11-8, the 

aircraft is actually level and at 2,000 feet mean sea level 

(MSL). It is not in a turn to the left which the pilot may 

misinterpret if he or she fails to see the off or failed flags. 

If that occurs, the pilot may transform a normally benign 

situation into a hazardous situation. Again, good decisionmaking by the pilot only occurs after a careful analysis of 

systems.

Many small aircraft are not equipped with a warning system 

for vacuum failure; therefore, the pilot should monitor the 
11-8

O 

F 

F 

30.0 

29.9 

29.8 

Figure 11-8. Vacuum failure. Figure 11-8. Vacuum failure - inoperative attitude and heading indicators. 

system’s vacuum/pressure gauge. This can be a hazardous 

situation with the potential to lead the unsuspecting pilot into 

a dangerous unusual attitude that would require a partial panel 

recovery. It is important that pilots practice instrument flight 

without reference to the attitude and heading indicators in 

preparation for such a failure.

Pitot/Static System Failure

A pitot or static system failure can also cause erratic and 

unreliable instrument indications. When a static system 

problem occurs, it affects the ASI, altimeter, and the VSI. 

In most aircraft, provisions have been made for the pilot to 

select an alternate static source. Check the POH/AFM for 

the location and operation of the alternate static source. In 

the absence of an alternate static source, in an unpressurized 

aircraft, the pilot could break the glass on the VSI. The VSI 

is not required for instrument flight, and breaking the glass 

provides the altimeter and the ASI a source of static pressure. 

This procedure could cause additional instrument errors.

Communication/Navigation System 

Malfunction

Avionics equipment has become very reliable, and the 

likelihood of a complete communications failure is remote. 

However, each IFR flight should be planned and executed in 

anticipation of a two-way radio failure. At any given point 

during a flight, the pilot must know exactly what route to fly, 

what altitude to fly, and when to continue beyond a clearance 

limit. Title 14 of the Code of Federal Regulations (14 CFR) 

part 91 describes the procedures to be followed in case of a 

two-way radio communications failure. If operating in VFR 

conditions at the time of the failure, the pilot should continue 

the flight under VFR and land as soon as practicable. If the 

failure occurs in IFR conditions, or if VFR conditions cannot 

be maintained, the pilot must continue the flight:

1. Along 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.

The pilot should maintain 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, part 

91 for IFR operations); or

3. The altitude or flight level ATC has advised may be 

expected in a further clearance. 

In addition to route and altitude, the pilot must also plan the 

progress of the flight to leave the clearance limit.
11-9

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 11-9. The default soft key Menu that is displayed on the 

PFD contains a “NRST” (Nearest Airport) soft key. By pressing this 

soft key, a text box is opened which will display the nearest 25 

airports. 

ALERTS 

TMR/REF NRST ALERTS 

5NM MAP WPT 1200 GND R LCL 16 

Figure 11-9. The default soft key menu that is displayed on the PFD contains a “NRST” (Nearest Airport) soft key. Pressing this soft 

key opens a text box that displays the nearest 25 airports. 

GPS Nearest Airport Function

Procedures for accessing the nearest airport information vary 

by the type of display installed in an aircraft. Pilots can obtain 

information relative to the nearest airport by using the PFD, 

multi-function display (MFD), or the nearest function on the 

GPS receiver. The following examples are based on a popular 

system. Pilots should become familiar with the operational 

characteristics of the equipment to be used.

Nearest Airports Using the PFD

With the advancements in electronic databases, diverting to 

alternate airports has become easier. Simply by pressing a soft 

key on the PFD, pilots can access information for up to 25 of 

the nearest airports that meet the criteria set in the systems 

configuration page. [Figure 11-9] Pilots are able to specify 

what airports are acceptable for their aircraft requirements 

based on landing surface and length of runway.

When the text box opens, the flashing cursor is located over 

the nearest airport that meets the criteria set in the auxiliary 

setup page as shown in Figure 11-10. Scrolling through the 

25 airports is accomplished by turning the outer FMS knob, 

which is located on the lower right corner of the display 

screen. Turning the FMS knob clockwise moves the blinking 

cursor to the next closest airport. By continuing to turn the 

knob, the pilot is able to scroll through all 25 nearest airports. 

Each airport box contains the information illustrated in 

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 expectfurther-clearance time if one has been received. If an 

expect-further-clearance time has not been received, 

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.

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. 

If no expect-further-clearance time has been received, 

leave the clearance limit upon arrival over it, 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. [Figure 11-8]

While following these procedures, set the transponder to 

code 7600, and use all means possible to reestablish two-way 

radio communication with ATC. This includes monitoring 

navigational aids (NAVAIDs), attempting radio contact with 

other aircraft, and attempting contact with a nearby flight 

service station (FSS).
11-10

Figure 11-11. Information on the Nearest Airport Page. 

Airport identifier 

Best approach available 

Airport symbol 

Distance to the airport 

from present position 

Longest runway available 

Communication frequency and type 

Figure 11-11. Information shown on the nearest airport page.

Figure 11-12. Additional Information for Specific Airport. 

Airport identifier 

Airport symbol 

Closest city 

Name of the airport 

Type of airport 

Field elevation 

Geographic region 

Fuel available 

Lat/long coordinates

Figure 11-12. Information shown on the additional information 

page that will aid the pilot in making a more informed decision 

about which airport to choose when diverting.

ALERTS 

Figure 11-10. KGNV would be flashing 

Flashing 

Figure 11-10. An enlargement of the box shown in the lower right 

of Figure 11-9. Note that KGNV would be flashing.

Nearest Airports Using the MFD

A second way to determine the nearest airport is by 

referencing the NRST Page Group located on the MFD. This 

method provides additional information to the pilot; however, 

it may require additional steps to view. [Figure 11-13]

Navigating the MFD Page Groups

Most display systems are designed for ease of navigation 

through the different screens on the MFD. Notice the 

various page groups in the lower right corner of the MFD 

screen. Navigation through these four page groups is 

accomplished by turning the outer FMS knob clockwise. 

[Figure 11-14]

Within each page group are specific pages that provide 

additional information pertaining to that specific group. Once 

the desired page group and page is selected, the MFD remains 

in that configuration until the page is changed or the CLR 

button is depressed for more than 2 seconds. Holding the CLR 

button returns the display to the default moving map page.

Nearest Airport Page Group

The nearest airport page contains specific areas of interest 

for the airport selected. [Figure 11-15] The pilot is furnished 

information regarding runways, frequencies, and types of 

approaches available. 

Nearest Airports Page Soft Keys

Figure 11-16 illustrates four specific soft keys that allow 

the pilot to access independent windows of the airport page. 

Selection of each of these windows can also be accomplished 

by utilizing the MENU hard key. 

Figure 11-11, which the pilot can utilize to determine which 

airport best suits their individual needs.

Additional Information for a Specific Airport

In addition to the information that is presented on the first 

screen, the pilot can view additional information as shown in 

Figure 11-12 by highlighting the airport identifier and then 

pressing the enter key.

From this menu or the previous default nearest airport screen, 

the pilot is able to activate the Direct-To function, which 

provides a direct GPS course to the airport. In addition, 

the pilot can auto-tune communication frequencies by 

highlighting the appropriate frequency and then pressing 

the enter key. The frequency is placed in the stand-by box 

of either COM1 or COM2, whichever frequency has the 

cyan box around it.
11-11

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 11-13. Nearest Airports Using the MFD. 

MAP DCLTR ALERTS 

MAP - NAVIGATION MAP

Figure 11-13. The MFD is another means of viewing the nearest airports.

DCLTR ALERTS 

Figure 11-14. Navigating The MFD Page Groups. Figure 11-14. Page groups. As the FMS outer knob is rotated, the 

current page group is indicated by highlighting the specific group 

indicator. Notice that the MAP page group is highlighted.

The soft keys and functions are as follows: Scroll through 

each section with the cursor, then press enter to accept the 

selection.

1. APT. Allows the user access to scroll through the 

25 nearest airports. The white arrow indicates which 

airport is selected. The INFORMATION window 

is slaved to the white arrow. The INFORMATION 

window decodes the airport identifier. Scroll through 

the 25 airports by turning the outer FMS knob.

2. RNWY. Moves the cursor into the Runways section 

and allows the user to scroll through the available 

runways at a specific airport that is selected in 

conjunction with the APT soft key. A green arrow 

indicates additional runways to view.

3. FREQ. Moves the cursor into the Frequencies section 

and allows the pilot to highlight and auto-tune the 

frequency into the selected standby box.

4. APR. Moves the cursor into the Approach section and 

allows the pilot to review approaches and load them 

into the flight plan. When the APR soft key is selected, 

an additional soft key appears. The LD APR (Load 

Approach) soft key must be pressed once the desired 

instrument approach procedure has been highlighted. 

Once the soft key is pressed, the screen changes to the 

PROC Page Group. From this page, the pilot is able to 

choose the desired approach, the transition, and choose 

the option to activate the approach or just load it into 

the flight plan.

Situational Awareness

Situational awareness is not simply a mental picture of 

aircraft location; rather, it is an overall assessment of each 

element of the environment and how it affects a flight. On 

one end of the situational awareness spectrum is a pilot who 
11-12

RNWY 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 11-15. Nearest Airport Page Group. 

MAP APT FREQ APR ALERTS 

NRST - NEAREST AIRPORTS

Figure 11-15. The page group of nearest airports has been selected.

is knowledgeable of every aspect of the flight; consequently, 

this pilot’s decision-making is proactive. With good 

situational awareness, this pilot is able to make decisions 

well ahead of time and evaluate several different options. 

On the other end of the situational awareness spectrum is a 

pilot who is missing important pieces of the puzzle: “I knew 

exactly where I was when I ran out of fuel.” Consequently, 

this pilot’s decision-making is reactive. With poor situational 

awareness, a pilot lacks a vision of future events and is forced 

to make decisions quickly, often with limited options.

During a typical IFR flight, a pilot operates at varying levels 

of situational awareness. For example, a pilot may be cruising 

to his or her destination with a high level of situational 

awareness when ATC issues an unexpected standard terminal 

arrival route (STAR). Since the pilot was not expecting the 

STAR and is not familiar with it, situational awareness is 

lowered. However, after becoming familiar with the STAR 

and resuming normal navigation, the pilot returns to a higher 

level of situational awareness.

Factors that reduce situational awareness include: distractions, 

unusual or unexpected events, complacency, high workload, 

unfamiliar situations, and inoperative equipment. In some 

situations, a loss of situational awareness may be beyond a 

pilot’s control. For example, a pneumatic system failure and 

associated loss of the attitude and heading indicators could 

cause a pilot to find his or her aircraft in an unusual attitude. 

In this situation, established procedures must be used to 

regain situational awareness.

Pilots should be alert to a loss of situational awareness 

anytime they are in a reactive mindset. To regain situational 

awareness, reassess the situation and seek additional 

information from other sources, such as the navigation 

instruments or ATC.

Traffic Avoidance

EFDs have the capability of displaying transponder-equipped 

aircraft on the MFD, as well as the inset map on the PFD. 

However, due to the limitations of the systems, not all traffic 

is displayed. Some traffic information service (TIS) units 

display only eight intruding targets within the service volume. 

The normal service volume has altitude limitations of 3,500 

feet below the aircraft to 3,500 feet above the aircraft. The 

lateral limitation is 7 NM. [Figure 11-17] Pilots unfamiliar 

with the limitations of the system may rely on the aural 

warnings to alert them to approaching traffic. 

In addition to an outside visual scan of traffic, a pilot should 

incorporate any traffic information electronically displayed, 

such as TIS. This innovation in traffic alerting reinforces and 

adds synergy to the ability to see and avoid. However, it is 

an aid and not a replacement for the responsibilities of the 
11-13

RNWY 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

MAP APT FREQ APR ALERTS 

NRST - NEAREST AIRPORTS

APT RNWY 

APT RNWY FREQ APR 

The white arrow 

indicates which 

airport is selected. 

A 

A Airport Runway Frequency Approach B C D 

Figure 11-16. The four soft keys at the bottom of the MFD are airport (A), runway (B), frequency (C), and approach (D).

RNWY 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NMDTK _ _ _°T TRK 360°T

MAP APT FREQ APR ALERTS 

NRST - NEAREST AIRPORTS

APT RNWY FREQ

Green arrow indicates 

additional runways to view. 

Figure 11-16b. RNWY – Moves the cursor into the Runways area 

and allows the user access to scroll through the available runways 

at a specific airport that is selected in conjunction with the APT 

soft key. 

B 

RNWY 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

MAP APT FREQ APR ALERTS 

RNWY FREQ APR 

Figure 11-16c. FREQ – Moves the cursor into the Frequencies 

section and allows the pilot to highlight and auto-tune the 

frequency into the selected stand-by box. 

Standby box

C NRST - NEAREST AIRPORTS

RNWY 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

MAP APT FREQ APR ALERTS 

NRST - NEAREST AIRPORTS

RNWY

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NMDTK _ _ _°T TRK 360°T

M BUS E

39.3 VOLTS 0.0

M BATT E

0.0 AMPS 0.0

ELECTRICAL 

5

476 

1

1497 

212 

61.9 

10.0 

1960 

27.4 

NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1

123.800 118.000 COM2

GS 0KT XTK 0.00NM ETE 02:58 ESA 2600FT

WPT - APPROACH LOADING

NORTH UP 

FREQ APR 

5NM 1 

2 

3 

From this page, the pilot is able to choose the desired 

approach, transition, and choose the option to activate 

the approach or just load it into the flight plan.

D 
11-14

Figure 11-17. The area surrounding the aircraft for coverage 

using TIS . 3,500' 3,500' 

7 NMI 

Figure 11-17. The area surrounding the aircraft for coverage 

using TIS.

MODE 

MAP WPT AUX NRST

VOLTS 28.1 

SATZ AMPS 0 

 RUDDER TRIM 

L R 

ELECTRICAL 

5

476 

1

1497 

212 

61.9 

10.0 

2420 

27.4 

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

WPT _ _ _ _ _ _ DIS _ _ ._ NM DTK _ _ _° TRK 360°

Figure 11-18. Aircrafts MFD when using TIS. 

ALERTS 

MAP - TRAFFIC MAP

TRAFFIC MODE

OPERATE

FLAPS

ELEV

TRIM

UP

DN TA OFF SCALE

HDG UP 

12NM

6NM

++05 05 

-03 

Figure 11-18. A typical display on aircraft MFD when using TIS. 

pilot. Systems such as TIS provide a visual representation 

of nearby traffic and displays a symbol on the moving map 

display with relative information about altitude, vertical 

trends, and direction of flight. [Figure 11-18]

It is important to remember that most systems display only a 

specific maximum number of targets allowed. Therefore, it 

does not mean that the targets displayed are the only aircraft 

in the vicinity. The system displays only the closest aircraft. 

In addition, the system does not display aircraft that are not 

equipped with transponders. The display may not show any 

aircraft; however, a Piper Cub with no transponder could be 

flying in the area. TIS coverage can be sporadic and is not 

available in some areas of the United States. Traffic advisory 

software is to be utilized only for increased situational 

awareness and not the sole means of traffic avoidance. There is 

no substitute for a good visual scan of the surrounding sky.
A-1

The following shorthand system is recommended by the 

Federal Aviation Administration (FAA). Applicants for the 

instrument rating may use any shorthand system, in any 

language, which ensures accurate compliance with air traffic 

control (ATC) instructions. No shorthand system is required 

by regulation and no knowledge of shorthand is required for 

the FAA Knowledge Test; however, because of the vital need 

for reliable communication between the pilot and controller, 

clearance information should be unmistakably clear.

The following symbols and contractions represent words 

and phrases frequently used in clearances. Most are used 

regularly by ATC personnel. By practicing this shorthand, 

omitting the parenthetical words, you will be able to copy 

long clearances as fast as they are read.

Example: CAF RH RV V18 40 SQ 0700 DPC 120.4

Cleared as filed, maintain runway heading for radar vector 

to Victor 18, climb to 4,000, squawk 0700, departure control 

frequency is 120.4.

Words and Phrases Shorthand

Above..........................................................................ABV

Above (Altitude, Hundreds of Feet) ............................... 70

Adjust speed to 250 knots......................................... 250 K

Advise .........................................................................ADZ

After (Passing) ..................................................................<

Airway (Designation)................................................... V26

Airport.............................................................................. A

Alternate Instructions...................................................... ( )

Altitude 6,000–17,000 .............................................60-170

And...................................................................................&

Approach........................................................................AP

Approach Control........................................................ APC

Area Navigation.......................................................RNAV

Arriving..............................................................................

At..................................................................................... @

At or Above....................................................................

At or Below....................................................................

(ATC) Advises...............................................................CA

(ATC) Clears or Cleared.................................................. C

(ATC) Requests .............................................................CR

Appendix A

Back Course ...................................................................BC

Bearing...........................................................................BR

Before (Reaching, Passing)...............................................>

Below..........................................................................BLO

Below (Altitude, Hundreds of Feet)................................ 70

Center.......................................................................... CTR

Clearance Void if Not Off By (Time).............................v<

Cleared as Filed........................................................... CAF

Cleared to Airport ............................................................ A

Cleared to Climb/Descend at Pilot’s Discretion ............PD

Cleared to Cross............................................................... X

Cleared to Depart From the Fix ....................................... D

Cleared to the Fix..............................................................F

Cleared to Hold and Instructions Issued .......................... H

Cleared to Land.................................................................L

Cleared to the Outer Marker ............................................ O

Climb to (Altitude, Hundreds of Feet)........................... 70

Contact Approach ..........................................................CT

Contact (Denver) Approach Control............................(den

Contact (Denver) Center............................................(DEN

Course ..........................................................................CRS

Cross ................................................................................ X

Cruise .............................................................................

Delay Indefinite............................................................ DLI

Depart (Direction, if Specified)................................ T ( )

Departure Control ....................................................... DPC

Descend To (Altitude, Hundreds of Feet)...................... 70

Direct..............................................................................DR

Direction (Bound)

Eastbound ...................................................................EB

Westbound.................................................................WB

Northbound.................................................................NB

Southbound................................................................. SB

Inbound........................................................................IB

Outbound....................................................................OB

DME Fix (Mile)............................................................

Each................................................................................EA

Enter Control Area.......................................................

Estimated Time of Arrival .......................................... ETA

Expect ............................................................................EX

Expect-Further-Clearance ............................................EFC

Clearance Shorthand
A-2

Fan Marker.................................................................... FM

Final ..................................................................................F

Final Approach...............................................................FA

Flight Level.................................................................... FL

Flight Planned Route....................................................FPR

For Further Clearance ..................................................FFC

For Further Headings...................................................FFH

From.............................................................................. FM

Ground ....................................................................... GND

GPS Approach .............................................................GPS

Heading...................................................................... HDG

Hold (Direction).......................................................... H-W

Holding Pattern ............................................................

ILS Approach................................................................ILS

Increase Speed 30 Knots...........................................+30 K

Initial Approach .................................................................I

Instrument Departure Procedure ....................................DP

Intersection.................................................................... XN

Join or Intercept Airway/Jet Route/Track or Course ........

Left Turn After Takeoff...................................................

Locator Outer Marker ................................................ LOM

Magnetic ..........................................................................M

Maintain ........................................................................

Maintain VFR Conditions On Top ............................. VFR

Middle Compass Locator.............................................. ML

Middle Marker .............................................................MM

Missed Approach ..........................................................MA

Nondirectional Beacon Approach...............................NDB

Out of (Leave) Control Area........................................

Outer Marker.................................................................OM

Over (Station)..............................................................OKC

On Course ......................................................................OC

Precision Approach Radar .......................................... PAR

Procedure Turn............................................................... PT

Radar Vector..................................................................RV

Radial (080° Radial) .................................................. 080R

Reduce Speed 20 Knots.............................................-20 K

Remain This Frequency ...............................................RTF

Remain Well to Left Side .............................................. LS

Remain Well to Right Side ............................................ RS

Report Crossing .............................................................RX

Report Departing............................................................RD

Report Leaving...............................................................RL

Report on Course .....................................................R-CRS

Report Over....................................................................RO

Report Passing ............................................................... RP

Report Reaching.............................................................RR

Report Starting Procedure Turn.................................RSPT

Reverse Course ..............................................................RC

Right Turn After Takeoff.................................................

Runway Heading............................................................RH

Runway (Number) .....................................................RY18

Squawk...........................................................................SQ

Standby .....................................................................STBY

Straight-in Approach........................................................SI

Surveillance Radar Approach ..................................... ASR

Takeoff (Direction)...................................................T N

Tower................................................................................Z

Turn Left ........................................................................ TL

Turn Right......................................................................TR

Until .................................................................................../

Until Advised (By)........................................................ UA

Until Further Advised ................................................. UFA

VFR Conditions On Top..............................................OTP

Via................................................................................VIA

Victor (Airway Number).............................................. V14

Visual Approach ........................................................... VA

VOR..............................................................................

VOR Approach ..............................................................VR

VORTAC......................................................................

While in Control Area..................................................
B-1

Introduction

Flight instructors may use this guide in the development of 

lesson plans. The lessons are arranged in a logical learning 

sequence and use the building-block technique. Each lesson 

includes ground training appropriate to the flight portion of 

the lesson. It is vitally important that the flight instructor brief 

the student on the objective of the lesson and how it will be 

accomplished. Debriefing the student’s performance is also 

necessary to motivate further progress. To ensure steady 

progress, student pilots should master the objective of each 

lesson before advancing to the next lesson. Lessons should 

be arranged to take advantage of each student’s knowledge 

and skills.

Flight instructors must monitor progress closely during 

training to guide student pilots in how to properly divide 

their attention. The importance of this division of attention 

or “cross-check” cannot be overemphasized. Cross-check and 

proper instrument interpretation are essential components 

of “attitude instrument flying” that enables student pilots to 

accurately visualize the aircraft’s attitude at all times.

When possible, each lesson should incorporate radio 

communications, basic navigation, and emergency procedures 

so the student pilot is exposed to the entire IFR experience 

with each flight. Cross-reference the Instrument Training 

Lesson Guide with this handbook and the Instrument 

Practical Test Standards for a comprehensive instrument 

rating training program.

Lesson 1—Ground and flight evaluation 

of student’s knowledge and performance

Aircraft systems

Aircraft performance

Preflight planning

Use of checklists

Basic flight maneuvers

Radio communications procedures

Navigation systems

Appendix B

Instrument Training Lesson Guide

Lesson 2—Preflight preparation and 

flight by reference to instruments

Ground Training

Instrument system preflight procedures

Attitude instrument flying

Fundamental instrument skills

Instrument cross-check techniques

Flight Training

Aircraft and instrument preflight inspection

Use of checklists

Fundamental instrument skills

Basic flight maneuvers

Instrument approach (demonstrated)

Postflight procedures

Lesson 3—Flight instruments and human 

factors

Ground Training

Human factors

Flight instruments and systems

Aircraft systems

Navigation instruments and systems

Flight Training

Aircraft and instrument preflight inspection

Radio communications

Checklist procedures

Attitude instrument flying

Fundamental instrument skills

Basic flight maneuvers

Spatial disorientation demonstration

Navigation systems

Postflight procedures

Lesson 4—Attitude instrument flying

Ground Training

Human factors

Flight instruments and systems
B-2

Aircraft systems

Navigation instruments and systems

Attitude instrument flying

Fundamental instrument skills

Basic flight maneuvers

Flight Training

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Attitude instrument flying

Fundamental instrument skills

Basic flight maneuvers

Spatial disorientation

Navigation

Postflight procedures

Lesson 5—Aerodynamic factors and 

basic flight maneuvers

Ground Training

Basic aerodynamic factors

Basic instrument flight patterns

Emergency procedures

Flight Training

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Basic instrument flight patterns

Emergency procedures

Navigation

Postflight procedures

Lesson 6—Partial panel operations

Ground Training

ATC system

Flight instruments

Partial panel operations

Flight Training

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Basic instrument flight patterns

Emergency procedures

Partial panel practice

Navigation

Postflight procedures

Lesson 7—Recovery from unusual 

attitudes

Ground Training

Attitude instrument flying

ATC system

NAS overview

Flight Training

Preflight

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Instrument takeoff

Navigation

Partial panel practice

Recovery from unusual attitudes

Postflight procedures

Lesson 8—Navigation systems

Ground Training

ATC clearances

Departure procedures

IFR en route charts

Flight Training

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Intercepting and tracking

Holding

Postflight procedures

Lesson 9—Review and practice

Ground Training

Aerodynamic factors

Flight instruments and systems

Attitude instrument flying

Navigation systems

NAS

ATC

Emergency procedures

Flight Training

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Review and practice as determined by the flight instructor
B-3

Instrument takeoff

Radio communications

Navigation systems

Emergency procedures

Postflight procedures

Lessons 10 through 19—Orientation, 

intercepting, tracking, and holding using 

each navigation system installed in the 

aircraft

Ground Training

Preflight planning

Navigation systems

NAS

ATC

Emergencies

Flight Training

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Departure procedures

En route navigation

Terminal operations

Partial panel operation

Instrument approach

Missed approach

Approach to a landing

Postflight procedures

Lessons 20 and 21—Cross-country 

flights

Ground Training

Preflight planning

Aircraft performance

Navigation systems

NAS

ATC

Emergencies

Flight Training

Emergency procedures

Partial panel operation

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Departure procedures

En route navigation

Terminal operations

Instrument approach

Missed approach

Approach to a landing

Postflight procedures

Lessons 22 and 23—Review and practice

Ground Training

Human factors

Aerodynamic factors

Flight instruments and systems

Attitude instrument flying

Basic flight maneuvers

Navigation systems

NAS

ATC

Emergency operations

Flight Training

Aircraft and instrument preflight inspection

Checklist procedures

Radio communications

Review and practice as determined by the flight instructor

Instrument takeoff

Partial panel operations

Unusual attitude recoveries

Radio communications

Navigation systems

Emergency procedures

Postflight procedures

Lessons 24 and subsequent—Practical 

test preparation

Ground Training

Title 14 of the Code of Federal Regulations (14 CFR) parts

61, 71, 91, 95, and 97

Instrument Flying Handbook

Practical test standards

Administrative requirements

Equipment requirements

Applicant’s requirements

Flight Training

Review and practice until the student can consistently 

perform all required tasks in accordance with the appropriate 

practical test standards.

NOTE: It is the recommending instructor’s responsibility to 

ensure that the applicant meets 14 CFR part 61 requirements 

and is prepared for the practical test, including: training, 

knowledge, experience, and the appropriate instructor 

endorsements.
B-4
G-1

Absolute accuracy. The ability to determine present position 

in space independently, and is most often used by pilots.

Absolute altitude. The actual distance between an aircraft 

and the terrain over which it is flying.

Absolute pressure. Pressure measured from the reference 

of zero pressure, or a vacuum.

A.C. Alternating current.

Acceleration error. A magnetic compass error apparent when 

the aircraft accelerates while flying on an easterly or westerly 

heading, causing the compass card to rotate toward North.

Accelerometer. A part of an inertial navigation system 

(INS) that accurately measures the force of acceleration in 

one direction.

ADF. See automatic direction finder.

ADI. See attitude director indicator.

ADM. See aeronautical decision-making.

ADS–B. See automatic dependent surveillance–broadcast.

Adverse yaw. A flight condition at the beginning of a turn in 

which the nose of the aircraft starts to move in the direction 

opposite the direction the turn is being made, caused by the 

induced drag produced by the downward-deflected aileron 

holding back the wing as it begins to rise.

Aeronautical decision-making (ADM). A systematic 

approach to the mental process used by pilots to consistently 

determine the best course of action in response to a given 

set of circumstances.

A/FD. See Airport/Facility Directory.

Glossary

Agonic line. An irregular imaginary line across the surface of 

the Earth along which the magnetic and geographic poles are in 

alignment, and along which there is no magnetic variation.

Aircraft approach category. A performance grouping of 

aircraft based on a speed of 1.3 times the stall speed in the 

landing configuration at maximum gross landing weight.

Air data computer (ADC). An aircraft computer that 

receives and processes pitot pressure, static pressure, and 

temperature to calculate very precise altitude, indicated 

airspeed, true airspeed, and air temperature.

AIRMET. Inflight weather advisory issued as an amendment 

to the area forecast, concerning weather phenomena of 

operational interest to all aircraft and that is potentially 

hazardous to aircraft with limited capability due to lack of 

equipment, instrumentation, or pilot qualifications.

Airport diagram. The section of an instrument approach 

procedure chart that shows a detailed diagram of the 

airport. This diagram includes surface features and airport 

configuration information.

Airport/Facility Directory (A/FD). An FAA publication 

containing information on all airports, communications, 

and NAVAIDs.

Airport surface detection equipment (ASDE). Radar 

equipment specifically designed to detect all principal 

features and traffic on the surface of an airport, presenting the 

entire image on the control tower console; used to augment 

visual observation by tower personnel of aircraft and/or 

vehicular movements on runways and taxiways.

Airport surveillance radar (ASR). Approach control 

radar used to detect and display an aircraft’s position in the 

terminal area.
G-2

Airport surveillance radar approach. An instrument 

approach in which ATC issues instructions for pilot 

compliance based on aircraft position in relation to the final 

approach course and the distance from the end of the runway 

as displayed on the controller’s radar scope.

Air route surveillance radar (ARSR). Air route traffic 

control center (ARTCC) radar used primarily to detect 

and display an aircraft’s position while en route between 

terminal areas.

Air route traffic control center (ARTCC). Provides ATC 

service to aircraft operating on IFR flight plans within 

controlled airspace and principally during the en route phase 

of flight.

Airspeed indicator. A differential pressure gauge that 

measures the dynamic pressure of the air through which the 

aircraft is flying. Displays the craft’s airspeed, typically in 

knots, to the pilot.

Air traffic control radar beacon system (ATCRBS). 

Sometimes called secondary surveillance radar (SSR), which 

utilizes a transponder in the aircraft. The ground equipment is 

an interrogating unit, in which the beacon antenna is mounted 

so it rotates with the surveillance antenna. The interrogating 

unit transmits a coded pulse sequence that actuates the aircraft 

transponder. The transponder answers the coded sequence by 

transmitting a preselected coded sequence back to the ground 

equipment, providing a strong return signal and positive 

aircraft identification, as well as other special data.

Airway. An airway is based on a centerline that extends from 

one navigation aid or intersection to another navigation aid 

(or through several navigation aids or intersections); used 

to establish a known route for en route procedures between 

terminal areas.

Alert area. An area in which there is a high volume of pilot 

training or an unusual type of aeronautical activity.

Almanac data. Information the global positioning system 

(GPS) receiver can obtain from one satellite which describes 

the approximate orbital positioning of all satellites in the 

constellation. This information is necessary for the GPS 

receiver to know what satellites to look for in the sky at a 

given time.

ALS. See approach lighting system.

Alternate airport. An airport designated in an IFR flight 

plan, providing a suitable destination if a landing at the 

intended airport becomes inadvisable. 

Alternate static source valve. A valve in the instrument static 

air system that supplies reference air pressure to the altimeter, 

airspeed indicator, and vertical speed indicator if the normal 

static pickup should become clogged or iced over. 

Altimeter setting. Station pressure (the barometric pressure 

at the location the reading is taken) which has been corrected 

for the height of the station above sea level.

AME. See aviation medical examiner.

Amendment status. The circulation date and revision 

number of an instrument approach procedure, printed above 

the procedure identification.

Ammeter. An instrument installed in series with an electrical 

load used to measure the amount of current flowing through 

the load.

Aneroid. The sensitive component in an altimeter or 

barometer that measures the absolute pressure of the air. 

It is a sealed, flat capsule made of thin disks of corrugated 

metal soldered together and evacuated by pumping all of 

the air out of it.

Aneroid barometer. An instrument that measures the 

absolute pressure of the atmosphere by balancing the weight 

of the air above it against the spring action of the aneroid.

Angle of attack. The acute angle formed between the 

chord line of an airfoil and the direction of the air striking 

the airfoil.

Anti-ice. Preventing the accumulation of ice on an aircraft 

structure via a system designed for that purpose.

Approach lighting system (ALS). Provides lights that will 

penetrate the atmosphere far enough from touchdown to give 

directional, distance, and glide path information for safe 

transition from instrument to visual flight.

Area chart. Part of the low-altitude en route chart series, 

this chart furnishes terminal data at a larger scale for 

congested areas.

Area navigation (RNAV). Allows a pilot to fly a selected 

course to a predetermined point without the need to overfly 

ground-based navigation facilities, by using waypoints.

ARSR. See air route surveillance radar.

ARTCC. See air route traffic control center.
G-3

ASDE. See airport surface detection equipment.

ASOS. See automated surface observing station.

ASR. See airport surveillance radar.

ATC. Air Traffic Control.

ATCRBS. See air traffic control radar beacon system.

ATIS. See automatic terminal information service. 

Atmospheric propagation delay. A bending of the 

electromagnetic (EM) wave from the satellite that creates 

an error in the GPS system.

Attitude and heading reference systems (AHRS). System 

composed of three-axis sensors that provide heading, attitude, 

and yaw information for aircraft. AHRS are designed to 

replace traditional mechanical gyroscopic flight instruments 

and provide superior reliability and accuracy.

Attitude director indicator (ADI). An aircraft attitude 

indicator that incorporates flight command bars to provide 

pitch and roll commands.

Attitude indicator. The foundation for all instrument flight, 

this instrument reflects the airplane’s attitude in relation to 

the horizon.

Attitude instrument flying. Controlling the aircraft by 

reference to the instruments rather than by outside visual 

cues.

Autokinesis. Nighttime visual illusion that a stationary light 

is moving, which becomes apparent after several seconds of 

staring at the light.

Automated Weather Observing System (AWOS). 

Automated weather reporting system consisting of various 

sensors, a processor, a computer-generated voice subsystem, 

and a transmitter to broadcast weather data.

Automated Surface Observing Station (ASOS). Weather 

reporting system which provides surface observations every 

minute via digitized voice broadcasts and printed reports.

Automatic dependent surveillance–broadcast (ADS-B). A 

device used in aircraft that repeatedly broadcasts a message 

that includes position (such as latitude, longitude, and 

altitude), velocity, and possibly other information. 

Automatic direction finder (ADF). Electronic navigation 

equipment that operates in the low- and medium-frequency 

bands. Used in conjunction with the ground-based 

nondirectional beacon (NDB), the instrument displays the 

number of degrees clockwise from the nose of the aircraft 

to the station being received. 

Automatic terminal information service (ATIS). The 

continuous broadcast of recorded non-control information in 

selected terminal areas. Its purpose is to improve controller 

effectiveness and relieve frequency congestion by automating 

repetitive transmission of essential but routine information.

Aviation medical examiner (AME). A physician with 

training in aviation medicine designated by the Civil 

Aerospace Medical Institute (CAMI).

AWOS. See automated weather observing system.

Azimuth card. A card that may be set, gyroscopically 

controlled, or driven by a remote compass.

Back course (BC). The reciprocal of the localizer course 

for an ILS. When flying a back-course approach, an aircraft 

approaches the instrument runway from the end at which the 

localizer antennas are installed.

Baro-aiding. A method of augmenting the GPS integrity 

solution by using a non-satellite input source. To ensure that 

baro-aiding is available, the current altimeter setting must 

be entered as described in the operating manual.

Barometric scale. A scale on the dial of an altimeter to which 

the pilot sets the barometric pressure level from which the 

altitude shown by the pointers is measured.

BC. See back course.

Block altitude. A block of altitudes assigned by ATC to 

allow altitude deviations; for example, “Maintain block 

altitude 9 to 11 thousand.”

Cage. The black markings on the ball instrument indicating 

its neutral position.

Calibrated. The instrument indication compared with a 

standard value to determine the accuracy of the instrument.

Calibrated orifice. A hole of specific diameter used to delay 

the pressure change in the case of a vertical speed indicator.
G-4

Calibrated airspeed. The speed at which the aircraft 

is moving through the air, found by correcting IAS for 

instrument and position errors.

CAS. Calibrated airspeed.

CDI. Course deviation indicator.

Changeover point (COP). A point along the route or 

airway segment between two adjacent navigation facilities 

or waypoints where changeover in navigation guidance 

should occur.

Circling approach. A maneuver initiated by the pilot to 

align the aircraft with a runway for landing when a straightin landing from an instrument approach is not possible or is 

not desirable.

Class A airspace. Airspace from 18,000 feet MSL up to and 

including FL 600, including the airspace overlying the waters 

within 12 NM of the coast of the 48 contiguous states and 

Alaska; and designated international airspace beyond 12 NM 

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.

Class B airspace. Airspace from the surface to 10,000 feet 

MSL surrounding the nation’s busiest airports in terms of 

IFR operations or passenger numbers. The configuration of 

each Class B airspace is individually tailored and consists 

of a surface area and two or more layers, and is designed to 

contain all published instrument procedures once an aircraft 

enters the airspace. For all aircraft, an ATC clearance is 

required to operate in the area, and aircraft so cleared receive 

separation services within the airspace.

Class C airspace. Airspace from the surface to 4,000 feet 

above the airport elevation (charted in MSL) surrounding 

those airports having an operational control tower, serviced 

by radar approach control, and having a certain number of IFR 

operations or passenger numbers. 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 from 

1,200 feet to 4,000 feet above the airport elevation.

Class D airspace. 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 is normally designed to contain the procedures.

Class E airspace. Airspace that is not Class A, Class B, Class 

C, or Class D, and is controlled airspace.

Class G airspace. Airspace that is uncontrolled, except 

when associated with a temporary control tower, and has 

not been designated as Class A, Class B, Class C, Class D, 

or Class E airspace.

Clean configuration. A configuration in which all flight 

control surfaces have been placed to create minimum drag. 

In most aircraft this means flaps and gear retracted.

Clearance. ATC permission for an aircraft to proceed under 

specified traffic conditions within controlled airspace, for the 

purpose of providing separation between known aircraft.

Clearance delivery. Control tower position responsible for 

transmitting departure clearances to IFR flights.

Clearance limit. The fix, point, or location to which an 

aircraft is cleared when issued an air traffic clearance.

Clearance on request. An IFR clearance not yet received 

after filing a flight plan.

Clearance void time. Used by ATC, the time at which the 

departure clearance is automatically canceled if takeoff has 

not been made. The pilot must obtain a new clearance or 

cancel the IFR flight plan if not off by the specified time.

Clear ice. Glossy, clear, or translucent ice formed by the 

relatively slow freezing of large, supercooled water droplets.

Compass course. A true course corrected for variation and 

deviation errors.

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 ILS.

Compass rose. A small circle graduated in 360° increments, 

printed on navigational charts to show the amount of 

compass variation at different locations, or on instruments 

to indicate direction.

Computer navigation fix. A point used to define a 

navigation track for an airborne computer system such as 

GPS or FMS.

Concentric rings. Dashed-line circles depicted in the plan 

view of IAP charts, outside of the reference circle, that show 

en route and feeder facilities.
G-5

Cone of confusion. A cone-shaped volume of airspace 

directly above a VOR station where no signal is received, 

causing the CDI to fluctuate.

Control and performance. A method of attitude instrument 

flying in which one instrument is used for making attitude 

changes, and the other instruments are used to monitor the 

progress of the change.

Control display unit. A display interfaced with the master 

computer, providing the pilot with a single control point 

for all navigations systems, thereby reducing the number of 

required flight deck panels.

Controlled airspace. An airspace of defined dimensions 

within which ATC service is provided to IFR and VFR flights 

in accordance with the airspace classification. It includes 

Class A, Class B, Class C, Class D, and Class E airspace.

Control pressures. The amount of physical exertion on the 

control column necessary to achieve the desired attitude.

Convective weather. Unstable, rising air found in 

cumiliform clouds.

Convective SIGMET. Weather advisory concerning 

convective weather significant to the safety of all aircraft, 

including thunderstorms, hail, and tornadoes.

Coordinated flight. Flight with a minimum disturbance of 

the forces maintaining equilibrium, established via effective 

control use.

COP. See changeover point.

Coriolis illusion. The illusion of rotation or movement in an 

entirely different axis, caused by an abrupt head movement, 

while in a prolonged constant rate turn that has ceased 

stimulating the brain’s motion sensing system.

Crew resource management (CRM). The effective 

use of all available resources—human, hardware, and 

information.

Critical areas. Areas where disturbances to the ILS localizer 

and glide slope courses may occur when surface vehicles or 

aircraft operate near the localizer or glide slope antennas.

CRM. See crew resource management.

Cross-check. The first fundamental skill of instrument flight, 

also known as “scan,” the continuous and logical observation 

of instruments for attitude and performance information.

Cruise clearance. An ATC clearance issued to allow a 

pilot to conduct flight at any altitude from the minimum 

IFR altitude up to and including the altitude specified in the 

clearance. Also authorizes a pilot to proceed to and make an 

approach at the destination airport.

Current induction. An electrical current being induced into, 

or generated in, any conductor that is crossed by lines of flux 

from any magnet.

DA. See decision altitude.

D.C. Direct current.

Dark adaptation. Physical and chemical adjustments of the 

eye that make vision possible in relative darkness.

Deceleration error. A magnetic compass error that occurs 

when the aircraft decelerates while flying on an easterly 

or westerly heading, causing the compass card to rotate 

toward South.

Decision altitude (DA). A specified altitude in the precision 

approach, charted in feet MSL, at which a missed approach 

must be initiated if the required visual reference to continue 

the approach has not been established.

Decision height (DH). A specified altitude in the precision 

approach, charted in height above threshold elevation, 

at which a decision must be made either to continue the 

approach or to execute a missed approach.

Deice. The act of removing ice accumulation from an 

aircraft structure.

Density altitude. Pressure altitude corrected for nonstandard 

temperature. Density altitude is used in computing the 

performance of an aircraft and its engines.

Departure procedure (DP). Preplanned IFR ATC departure, 

published for pilot use, in textual and graphic format.

Deviation. A magnetic compass error caused by local 

magnetic fields within the aircraft. Deviation error is different 

on each heading.

DGPS. Differential global positioning system.

DH. See decision height.
G-6

Differential Global Positioning System (DGPS). A system 

that improves the accuracy of Global Navigation Satellite 

Systems (GNSS) by measuring changes in variables to 

provide satellite positioning corrections.

Direct indication. The true and instantaneous reflection of 

aircraft pitch-and-bank attitude by the miniature aircraft, 

relative to the horizon bar of the attitude indicator.

Direct User Access Terminal System (DUATS). A system 

that provides current FAA weather and flight plan filing 

services to certified civil pilots, via personal computer, 

modem, or telephone access to the system. Pilots can request 

specific types of weather briefings and other pertinent data 

for planned flights.

Distance circle. See reference circle.

Distance measuring equipment (DME). A pulse-type 

electronic navigation system that shows the pilot, by an 

instrument-panel indication, the number of nautical miles 

between the aircraft and a ground station or waypoint.

DME. See distance measuring equipment.

DME arc. A flight track that is a constant distance from the 

station or waypoint.

DOD. Department of Defense.

Doghouse. A turn-and-slip indicator dial mark in the shape 

of a doghouse.

Domestic Reduced Vertical Separation Minimum 

(DRVSM). Additional flight levels between FL 290 and FL 

410 to provide operational, traffic, and airspace efficiency.

Double gimbal. A type of mount used for the gyro in an 

attitude instrument. The axes of the two gimbals are at right 

angles to the spin axis of the gyro, allowing free motion in 

two planes around the gyro.

DP. See departure procedure.

Drag. The net aerodynamic force parallel to the relative 

wind, usually the sum of two components: induced drag 

and parasite drag.

Drag curve. The curve created when plotting induced drag 

and parasite drag.

DUATS. See direct user access terminal system.

Duplex. Transmitting on one frequency and receiving on a 

separate frequency.

Eddy currents. Current induced in a metal cup or disc when 

it is crossed by lines of flux from a moving magnet.

EFAS. See En Route Flight Advisory Service.

EFC. See expect-further-clearance.

Electronic flight display (EFD). For the purpose of 

standardization, any flight instrument display that uses 

LCD or other image-producing system (Cathode Ray Tube 

[CRT], etc.)

Elevator illusion. The sensation of being in a climb or 

descent, caused by the kind of abrupt vertical accelerations 

that result from up- or downdrafts.

Emergency. A distress or urgent condition.

Emphasis error. The result of giving too much attention 

to a particular instrument during the cross-check, instead of 

relying on a combination of instruments necessary for attitude 

and performance information.

EM wave. Electromagnetic wave.

Encoding altimeter. A special type of pressure altimeter 

used to send a signal to the air traffic controller on the ground, 

showing the pressure altitude the aircraft is flying.

En route facilities ring. Depicted in the plan view of IAP 

charts, a circle which designates NAVAIDs, fixes, and 

intersections that are part of the en route low altitude airway 

structure.

En Route Flight Advisory Service (EFAS). An en route 

weather-only AFSS service.

En route high-altitude charts. Aeronautical charts for en 

route instrument navigation at or above 18,000 feet MSL.

En route low-altitude charts. Aeronautical charts for en 

route IFR navigation below 18,000 feet MSL.

Equivalent airspeed. Airspeed equivalent to CAS in 

standard atmosphere at sea level. As the airspeed and pressure 

altitude increase, the CAS becomes higher than it should be, 

and a correction for compression must be subtracted from 

the CAS.
G-7

Expect-further-clearance (EFC). The time a pilot can 

expect to receive clearance beyond a clearance limit.

FAA. Federal Aviation Administration.

FAF. See final approach fix.

False horizon. Inaccurate visual information for aligning the 

aircraft, caused by various natural and geometric formations 

that disorient the pilot from the actual horizon.

Federal airways. Class E airspace areas that extend upward 

from 1,200 feet to, but not including, 18,000 feet MSL, unless 

otherwise specified.

Feeder facilities. Used by ATC to direct aircraft to 

intervening fixes between the en route structure and the 

initial approach fix.

Final approach. Part of an instrument approach 

procedure in which alignment and descent for landing are 

accomplished. 

Final approach fix (FAF). The fix from which the IFR 

final approach to an airport is executed, and which identifies 

the beginning of the final approach segment. An FAF is 

designated on government charts by a Maltese cross symbol 

for nonprecision approaches, and a lightning bolt symbol for 

precision approaches.

Fixating. Staring at a single instrument, thereby interrupting 

the cross-check process.

FL. See flight level.

Flight configurations. Adjusting the aircraft control surfaces 

(including flaps and landing gear) in a manner that will 

achieve a specified attitude.

Flight director indicator (FDI). One of the major components 

of a flight director system, it provides steering commands that 

the pilot (or the autopilot, if coupled) follows.

Flight level (FL). A measure of altitude (in hundreds of feet) 

used by aircraft flying above 18,000 feet with the altimeter 

set at 29.92" Hg.

Flight management system (FMS). Provides pilot and crew 

with highly accurate and automatic long-range navigation 

capability, blending available inputs from long- and shortrange sensors.

Flightpath. The line, course, or track along which an aircraft 

is flying or is intended to be flown.

Flight patterns. Basic maneuvers, flown by reference to the 

instruments rather than outside visual cues, for the purpose 

of practicing basic attitude flying. The patterns simulate 

maneuvers encountered on instrument flights such as holding 

patterns, procedure turns, and approaches.

Flight strips. Paper strips containing instrument flight 

information, used by ATC when processing flight plans.

FMS. See flight management system.

Form drag. The drag created because of the shape of a 

component or the aircraft.

Fundamental skills. Pilot skills of instrument cross-check, 

instrument interpretation, and aircraft control.

Glideslope (GS). Part of the ILS that projects a radio beam 

upward at an angle of approximately 3° from the approach 

end of an instrument runway. The glideslope provides 

vertical guidance to aircraft on the final approach course for 

the aircraft to follow when making an ILS approach along 

the localizer path.

Glideslope intercept altitude. The minimum altitude of an 

intermediate approach segment prescribed for a precision 

approach that ensures obstacle clearance.

Global landing system (GLS). An instrument approach with 

lateral and vertical guidance with integrity limits (similar to 

barometric vertical navigation (BRO VNAV).

Global navigation satellite systems (GNSS). Satellite 

navigation systems that provide autonomous geo-spatial 

positioning with global coverage. It allows small electronic 

receivers to determine their location (longitude, latitude, and 

altitude) to within a few meters using time signals transmitted 

along a line of sight by radio from satellites. 

GNSS. See global navigation satellite systems.

Global positioning system (GPS). Navigation system 

that uses satellite rather than ground-based transmitters for 

location information.
G-8

Goniometer. As used in radio frequency (RF) antenna 

systems, a direction-sensing device consisting of two fixed 

loops of wire oriented 90° from each other, which separately 

sense received signal strength and send those signals to two 

rotors (also oriented 90°) in the sealed direction-indicating 

instrument. The rotors are attached to the direction-indicating 

needle of the instrument and rotated by a small motor until 

minimum magnetic field is sensed near the rotors.

GPS. See global positioning system.

GPS Approach Overlay Program. An authorization for 

pilots to use GPS avionics under IFR for flying designated 

existing nonprecision instrument approach procedures, with 

the exception of LOC, LDA, and SDF procedures.

Graveyard spiral. The illusion of the cessation of a turn 

while still in a prolonged, coordinated, constant rate turn, 

which can lead a disoriented pilot to a loss of control of the 

aircraft.

Great circle route. The shortest distance across the surface 

of a sphere (the Earth) between two points on the surface.

Ground proximity warning system (GPWS). A system 

designed to determine an aircraft’s clearance above the Earth 

and provides limited predictability about aircraft position 

relative to rising terrain.

Groundspeed. Speed over the ground, either closing speed to 

the station or waypoint, or speed over the ground in whatever 

direction the aircraft is going at the moment, depending upon 

the navigation system used.

GS. See glide slope.

GWPS. See ground proximity warning system.

HAA. See height above airport.

HAL. See height above landing.

HAT. See height above touchdown elevation.

Hazardous attitudes. Five aeronautical decision-making 

attitudes that may contribute to poor pilot judgment: 

antiauthority, impulsivity, invulnerability, machismo, and 

resignation.

Hazardous Inflight Weather Advisory Service (HIWAS). 

Service providing recorded weather forecasts broadcast to 

airborne pilots over selected VORs.

Head-up display (HUD). A special type of flight viewing 

screen that allows the pilot to watch the flight instruments 

and other data while looking through the windshield of the 

aircraft for other traffic, the approach lights, or the runway.

Height above airport (HAA). The height of the MDA above 

the published airport elevation.

Height above landing (HAL). The height above a designated 

helicopter landing area used for helicopter instrument 

approach procedures.

Height above touchdown elevation (HAT). The DA/DH or 

MDA above the highest runway elevation in the touchdown 

zone (first 3,000 feet of the runway).

HF. High frequency.

Hg. Abbreviation for mercury, from the Latin 

hydrargyrum.

HIWAS. See Hazardous Inflight Weather Advisory 

Service.

Holding. A predetermined maneuver that keeps aircraft 

within a specified airspace while awaiting further clearance 

from ATC.

Holding pattern. A racetrack pattern, involving two turns 

and two legs, used to keep an aircraft within a prescribed 

airspace with respect to a geographic fix. A standard pattern 

uses right turns; nonstandard patterns use left turns.

Homing. Flying the aircraft on any heading required to keep 

the needle pointing to the 0° relative bearing position.

Horizontal situation indicator (HSI). A flight navigation 

instrument that combines the heading indicator with a CDI, 

in order to provide the pilot with better situational awareness 

of location with respect to the courseline.

HSI. See horizontal situation indicator.

HUD. See head-up display.

Human factors. A multidisciplinary field encompassing the 

behavioral and social sciences, engineering, and physiology, 

to consider the variables that influence individual and 

crew performance for the purpose of optimizing human 

performance and reducing errors.
G-9

Hypoxia. A state of oxygen deficiency in the body sufficient 

to impair functions of the brain and other organs.

IAF. See initial approach fix.

IAP. See instrument approach procedures.

IAS. See indicated airspeed.

ICAO. See International Civil Aviation Organization.

Ident. Air Traffic Control request for a pilot to push 

the button on the transponder to identify return on the 

controller’s scope.

IFR. See instrument flight rules.

ILS. See instrument landing system.

ILS categories. Categories of instrument approach 

procedures allowed at airports equipped with the following 

types of instrument landing systems:

ILS Category I: 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.

ILS Category II: 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.

ILS Category IIIA: Provides for approach without 

a decision height minimum and with runway visual 

range of not less than 700 feet.

ILS Category IIIB: Provides for approach without 

a decision height minimum and with runway visual 

range of not less than 150 feet.

ILS Category IIIC: Provides for approach without a 

decision height minimum and without runway visual 

range minimum.

IMC. See instrument meteorological conditions.

Indicated airspeed (IAS). Shown on the dial of the 

instrument airspeed indicator on an aircraft. Directly related 

to calibrated airspeed (CAS), IAS includes instrument errors 

and position error.

Indirect indication. A reflection of aircraft pitch-and-bank 

attitude by the instruments other than the attitude indicator.

Induced drag. Drag caused by the same factors that produce 

lift; its amount varies inversely with airspeed. As airspeed 

decreases, the angle of attack must increase, in turn increasing 

induced drag.

Induction icing. A type of ice in the induction system that 

reduces the amount of air available for combustion. The most 

commonly found induction icing is carburetor icing.

Inertial navigation system (INS). A computer-based 

navigation system that tracks the movement of an aircraft 

via signals produced by onboard accelerometers. The initial 

location of the aircraft is entered into the computer, and all 

subsequent movement of the aircraft is sensed and used to 

keep the position updated. An INS does not require any inputs 

from outside signals.

Initial approach fix (IAF). The fix depicted on IAP charts 

where the instrument approach procedure (IAP) begins unless 

otherwise authorized by ATC.

Inoperative components. Higher minimums are prescribed 

when the specified visual aids are not functioning; this 

information is listed in the Inoperative Components Table found 

in the United States Terminal Procedures Publications.

INS. See inertial navigation system.

Instantaneous vertical speed indicator (IVSI). Assists in 

interpretation by instantaneously indicating the rate of climb 

or descent at a given moment with little or no lag as displayed 

in a vertical speed indicator (VSI).

Instrument approach procedures (IAP). A series of 

predetermined maneuvers for the orderly transfer of an 

aircraft under IFR from the beginning of the initial approach 

to a landing or to a point from which a landing may be 

made visually.

Instrument flight rules (IFR). Rules and regulations 

established by the Federal Aviation Administration to govern 

flight under conditions in which flight by outside visual 

reference is not safe. IFR flight depends upon flying by 

reference to instruments in the flight deck, and navigation is 

accomplished by reference to electronic signals.

Instrument landing system (ILS). An electronic system 

that provides both horizontal and vertical guidance to a 

specific runway, used to execute a precision instrument 

approach procedure.

Instrument meteorological conditions (IMC).

Meteorological conditions expressed in terms of visibility, 

distance from clouds, and ceiling less than the minimums 

specified for visual meteorological conditions, requiring 

operations to be conducted under IFR.
G-10

Instrument takeoff. Using the instruments rather than 

outside visual cues to maintain runway heading and execute 

a safe takeoff.

Interference drag. Drag generated by the collision of 

airstreams creating eddy currents, turbulence, or restrictions 

to smooth flow.

International Civil Aviation Organization (ICAO). The 

United Nations agency for developing the principles and 

techniques of international air navigation, and fostering planning 

and development of international civil air transport.

International standard atmosphere (IAS). A model of 

standard variation of pressure and temperature. 

Inversion illusion. The feeling that the aircraft is tumbling 

backwards, caused by an abrupt change from climb to straightand-level flight while in situations lacking visual reference.

Inverter. A solid-state electronic device that converts D.C. 

into A.C. current of the proper voltage and frequency to 

operate A.C. gyro instruments.

Isogonic lines. Lines drawn across aeronautical charts to 

connect points having the same magnetic variation.

IVSI. See instantaneous vertical speed indicator.

Jet route. A route designated to serve flight operations from 

18,000 feet MSL up to and including FL 450.

Jet stream. A high-velocity narrow stream of winds, usually 

found near the upper limit of the troposphere, which flows 

generally from west to east.

KIAS. Knots indicated airspeed.

Kollsman window. A barometric scale window of a 

sensitive altimeter used to adjust the altitude for the 

altimeter setting.

LAAS. See local area augmentation system.

Lag. The delay that occurs before an instrument needle attains 

a stable indication.

Land as soon as possible. ATC instruction to pilot. Land 

without delay at the nearest suitable area, such as an open 

field, at which a safe approach and landing is assured.

Land as soon as practical. ATC instruction to pilot. The 

landing site and duration of flight are at the discretion of the 

pilot. Extended flight beyond the nearest approved landing 

area is not recommended.

Land immediately. ATC instruction to pilot. The urgency 

of the landing is paramount. The primary consideration is 

to ensure the survival of the occupants. Landing in trees, 

water, or other unsafe areas should be considered only as 

a last resort.

LDA. See localizer-type directional aid.

Lead radial. The radial at which the turn from the DME arc 

to the inbound course is started.

Leans, the. A physical sensation caused by an abrupt 

correction of a banked attitude entered too slowly to 

stimulate the motion sensing system in the inner ear. The 

abrupt correction can create the illusion of banking in the 

opposite direction.

Lift. A component of the total aerodynamic force on an airfoil 

and acts perpendicular to the relative wind.

Lines of flux. Invisible lines of magnetic force passing 

between the poles of a magnet.

L/MF. See low or medium frequency.

LMM. See locator middle marker.

Load factor. The ratio of a specified load to the total weight 

of the aircraft. The specified load is expressed in terms of 

any of the following: aerodynamic forces, inertial forces, or 

ground or water reactions.

Loadmeter. A type of ammeter installed between the generator 

output and the main bus in an aircraft electrical system.

LOC. See localizer.

Local area augmentation system (LAAS). A differential 

global positioning system (DGPS) that improves the accuracy 

of the system by determining position error from the GPS 

satellites, then transmitting the error, or corrective factors, 

to the airborne GPS receiver.
G-11

Localizer (LOC). The portion of an ILS that gives left/right 

guidance information down the centerline of the instrument 

runway for final approach.

Localizer-type directional aid (LDA). 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. Some 

LDAs are equipped with a glide slope.

Locator middle marker (LMM). Nondirectional radio 

beacon (NDB) compass locator, collocated with a middle 

marker (MM).

Locator outer marker (LOM). NDB compass locator, 

collocated with an outer marker (OM).

LOM. See locator outer marker.

Long range navigation (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 to 1950 kHz 

frequency band. LORAN C and D operate in the 100 to 110 

kHz frequency band.

LORAN. See long range navigation.

Low or medium frequency. A frequency range between 

190–535 kHz with the medium frequency above 300 

kHz. Generally associated with nondirectional beacons 

transmitting a continuous carrier with either a 400 or 1,020 

Hz modulation.

Lubber line. The reference line used in a magnetic compass 

or heading indicator.

MAA. See maximum authorized altitude.

Mach number. The ratio of the true airspeed of the aircraft 

to the speed of sound in the same atmospheric conditions, 

named in honor of Ernst Mach, late 19th century physicist. 

Mach meter. The instrument that displays the ratio of the 

speed of sound to the true airspeed an aircraft is flying.

Magnetic bearing (MB). The direction to or from a radio 

transmitting station measured relative to magnetic north.

Magnetic heading (MH). The direction an aircraft is pointed 

with respect to magnetic north.

Mandatory altitude. An altitude depicted on an instrument 

approach chart with the altitude value both underscored and 

overscored. Aircraft are required to maintain altitude at the 

depicted value.

Mandatory block altitude. An altitude depicted on an 

instrument approach chart with two underscored and 

overscored altitude values between which aircraft are 

required to maintain altitude.

MAP. See missed approach point.

Margin identification. The top and bottom areas on an 

instrument approach chart that depict information about 

the procedure, including airport location and procedure 

identification.

Marker beacon. A low-powered transmitter that directs its 

signal upward in a small, fan-shaped pattern. Used along the 

flight path when approaching an airport for landing, marker 

beacons indicate both aurally and visually when the aircraft 

is directly over the facility.

Maximum altitude. An altitude depicted on an instrument 

approach chart with overscored altitude value at which or 

below aircraft are required to maintain altitude.

Maximum authorized altitude (MAA). A published altitude 

representing the maximum usable altitude or flight level for 

an airspace structure or route segment.

MB. See magnetic bearing.

MCA. See minimum crossing altitude.

MDA. See minimum descent altitude.

MEA. See minimum en route altitude.

Mean sea level. The average height of the surface of the 

sea at a particular location for all stages of the tide over a 

19-year period. 

MFD. See multi-function display.

MH. See magnetic heading.

MHz. Megahertz.
G-12

Microwave landing system (MLS). A precision instrument 

approach system operating in the microwave spectrum which 

normally consists of an azimuth station, elevation station, 

and precision distance measuring equipment.

Mileage breakdown. A fix indicating a course change 

that appears on the chart as an “x” at a break between two 

segments of a federal airway.

Military operations area (MOA). Airspace established for 

the purpose of separating certain military training activities 

from IFR traffic.

Military training route (MTR). Airspace of defined vertical 

and lateral dimensions established for the conduct of military 

training at airspeeds in excess of 250 knots indicated airspeed 

(KIAS).

Minimum altitude. An altitude depicted on an instrument 

approach chart with the altitude value underscored. Aircraft are 

required to maintain altitude at or above the depicted value.

Minimum crossing altitude (MCA). The lowest allowed 

altitude at certain fixes an aircraft must cross when proceeding 

in the direction of a higher minimum en route altitude 

(MEA).

Minimum descent altitude (MDA). The lowest altitude (in 

feet MSL) to which descent is authorized on final approach, 

or during circle-to-land maneuvering in execution of a 

nonprecision approach.

Minimum en route altitude (MEA). The lowest published 

altitude between radio fixes that ensures acceptable 

navigational signal coverage and meets obstacle clearance 

requirements between those fixes.

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 ensures acceptable navigational signal coverage 

only within 25 statute (22 nautical) miles of a VOR.

Minimum reception altitude (MRA). The lowest altitude 

at which an airway intersection can be determined.

Minimum safe altitude (MSA). The minimum altitude 

depicted on approach charts which provides at least 1,000 feet 

of obstacle clearance for emergency use within a specified 

distance from the listed navigation facility.

Minimum vectoring altitude (MVA). An IFR altitude lower 

than the minimum en route altitude (MEA) that provides 

terrain and obstacle clearance.

Minimums section. The area on an IAP chart that displays the 

lowest altitude and visibility requirements for the approach.

Missed approach. A maneuver conducted by a pilot when an 

instrument approach cannot be completed to a landing.

Missed approach point (MAP). A point prescribed in each 

instrument approach at which a missed approach procedure 

shall be executed if the required visual reference has not 

been established.

Mixed ice. A mixture of clear ice and rime ice.

MLS. See microwave landing system.

MM. Middle marker.

MOA. See military operations area.

MOCA. See minimum obstruction clearance altitude.

Mode C. Altitude reporting transponder mode.

MRA. See minimum reception altitude.

MSA. See minimum safe altitude.

MSL. See mean sea level.

MTR. See military training route.

Multi-function display (MFD). Small screen (CRT or LCD) 

in an aircraft that can be used to display information to the 

pilot in numerous configurable ways. Often an MFD will be 

used in concert with a Primary Flight Display.

MVA. See minimum vectoring altitude.

NACG. See National Aeronautical Charting Group.

NAS. See National Airspace System.

National Airspace System (NAS). The common network of 

United States 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.
G-13

National Aeronautical Charting Group (NACG). A 

Federal agency operating under the FAA, responsible for 

publishing charts such as the terminal procedures and en 

route charts.

National Route Program (NRP). A set of rules and 

procedures designed to increase the flexibility of user flight 

planning within published guidelines.

National Security Area (NSA). Areas consisting 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. Regulatory prohibitions are 

disseminated via NOTAMs.

National Transportation Safety Board (NTSB). A United 

States Government independent organization responsible for 

investigations of accidents involving aviation, highways, 

waterways, pipelines, and railroads in the United States. 

NTSB is charged by congress to investigate every civil 

aviation accident in the United States.

NAVAID. Naviagtional aid.

NAV/COM. Navigation and communication radio.

NDB. See nondirectional radio beacon.

NM. Nautical mile.

NOAA. National Oceanic and Atmospheric Administration.

No-gyro approach. A radar approach that may be used 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.

Nondirectional radio beacon (NDB). A ground-based radio 

transmitter that transmits radio energy in all directions.

Nonprecision approach. A standard instrument approach 

procedure in which only horizontal guidance is provided.

No procedure turn (NoPT). Term used with the appropriate 

course and altitude to denote that the procedure turn is not 

required.

NoPT. See no procedure turn.

Notice to Airmen (NOTAM). A notice filed with an aviation 

authority to alert aircraft pilots of any hazards en route or at 

a specific location. The authority in turn provides means of 

disseminating relevant NOTAMs to pilots.

NRP. See National Route Program.

NSA. See National Security Area.

NTSB. See National Transportation Safety Board.

NWS. National Weather Service.

Obstacle departure procedures (ODP). Obstacle clearance 

protection provided to aircraft in instrument meteorological 

conditions (IMC).

ODP. See obstacle departure procedures. 

OM. Outer marker.

Omission error. The failure to anticipate significant 

instrument indications following attitude changes; for 

example, concentrating on pitch control while forgetting 

about heading or roll information, resulting in erratic control 

of heading and bank.

Optical illusion. A misleading visual image. For the 

purpose of this handbook, the term refers to the brain’s 

misinterpretation of features on the ground associated 

with landing, which causes a pilot to misread the spatial 

relationships between the aircraft and the runway.

Orientation. Awareness of the position of the aircraft and 

of oneself in relation to a specific reference point.

Otolith organ. An inner ear organ that detects linear 

acceleration and gravity orientation.

Outer marker. A marker beacon at or near the glide slope 

intercept altitude of an ILS approach. It is normally located 

four to seven miles from the runway threshold on the 

extended centerline of the runway.

Overcontrolling. Using more movement in the control 

column than is necessary to achieve the desired pitch-and 

bank condition.

Overpower. To use more power than required for the purpose 

of achieving a faster rate of airspeed change.
G-14

P-static. See precipitation static.

PAPI. See precision approach path indicator.

PAR. See precision approach radar.

Parasite drag. Drag caused by the friction of air moving 

over the aircraft structure; its amount varies directly with 

the airspeed.

PFD. See primary flight display.

PIC. See pilot-in-command.

Pilot-in-command (PIC). The pilot responsible for the 

operation and safety of an aircraft.

Pilot report (PIREP). Report of meteorological phenomena 

encountered by aircraft.

Pilot’s Operating Handbook/Airplane Flight Manual 

(POH/AFM). FAA-approved documents published by the 

airframe manufacturer that list the operating conditions for 

a particular model of aircraft.

PIREP. See pilot report.

Pitot pressure. Ram air pressure used to measure airspeed.

Pitot-static head. A combination pickup used to sample pitot 

pressure and static air pressure.

Plan view. The overhead view of an approach procedure on 

an instrument approach chart. The plan view depicts the routes 

that guide the pilot from the en route segments to the IAF.

POH/AFM. See Pilot’s Operating Handbook/Airplane 

Flight Manual.

Point-in-space approach. A type of helicopter instrument 

approach procedure to a missed approach point more than 

2,600 feet from an associated helicopter landing area.

Position error. Error in the indication of the altimeter, ASI, 

and VSI caused by the air at the static system entrance not 

being absolutely still.

Position report. A report over a known location as 

transmitted by an aircraft to ATC.

Precession. The characteristic of a gyroscope that causes an 

applied force to be felt, not at the point of application, but 

90° from that point in the direction of rotation.

Precipitation static (P-static). A form of radio interference 

caused by rain, snow, or dust particles hitting the antenna and 

inducing a small radio-frequency voltage into it.

Precision approach. A standard instrument approach 

procedure in which both vertical and horizontal guidance 

is provided.

Precision approach path indicator (PAPI). A system of 

lights similar to the VASI, but consisting of one row of lights 

in two- or four-light systems. A pilot on the correct glide slope 

will see two white lights and two red lights. See VASI.

Precision approach radar (PAR). A type of radar used 

at an airport to guide an aircraft through the final stages of 

landing, providing horizontal and vertical guidance. The 

radar operator directs the pilot to change heading or adjust 

the descent rate to keep the aircraft on a path that allows it 

to touch down at the correct spot on the runway.

Precision runway monitor (PRM). System allows 

simultaneous, independent Instrument Flight Rules (IFR) 

approaches at airports with closely spaced parallel runways.

Preferred IFR routes. Routes established in the major 

terminal and en route environments to increase system 

efficiency and capacity. IFR clearances are issued based on 

these routes, listed in the A/FD except when severe weather 

avoidance procedures or other factors dictate otherwise.

Pressure altitude. Altitude above the standard 29.92" Hg 

plane.

Prevailing visibility. The greatest horizontal visibility 

equaled or exceeded throughout at least half the horizon 

circle (which is not necessarily continuous).

Primary and supporting. A method of attitude instrument 

flying using the instrument that provides the most direct 

indication of attitude and performance.

Primary flight display (PFD). A display that provides 

increased situational awareness to the pilot by replacing the 

traditional six instruments used for instrument flight with 

an easy-to-scan display that provides the horizon, airspeed, 

altitude, vertical speed, trend, trim, rate of turn among other 

key relevant indications.

PRM. See precision runway monitor.

Procedure turn. A maneuver prescribed when it is necessary 

to reverse direction to establish an aircraft on the intermediate 

approach segment or final approach course.
G-15

Profile view. Side view of an IAP chart illustrating the vertical 

approach path altitudes, headings, distances, and fixes.

Prohibited area. Designated airspace within which flight of 

aircraft is prohibited.

Propeller/rotor modulation error. Certain propeller RPM 

settings or helicopter rotor speeds can cause the VOR course 

deviation indicator (CDI) to fluctuate as much as ±6°. Slight 

changes to the RPM setting will normally smooth out this 

roughness.

Rabbit, the. High-intensity flasher system installed at many 

large airports. The flashers consist of a series of brilliant 

blue-white bursts of light flashing in sequence along the 

approach lights, giving the effect of a ball of light traveling 

towards the runway.

Radar. Radio Detection And Ranging.

Radar approach. The controller provides vectors while 

monitoring the progress of the flight with radar, guiding 

the pilot through the descent to the airport/heliport or to a 

specific runway.

Radials. The courses oriented from a station.

Radio or radar altimeter. An electronic altimeter that 

determines the height of an aircraft above the terrain by 

measuring the time needed for a pulse of radio-frequency 

energy to travel from the aircraft to the ground and return.

Radio frequency (RF). A term that refers to alternating 

current (AC) having characteristics such that, if the current is 

input to antenna, an electromagnetic (EM) field is generated 

suitable for wireless broadcasting and/or communications.

Radio magnetic indicator (RMI). An electronic navigation 

instrument that combines a magnetic compass card with two 

bearing pointers (typically). Generally, one pointer is for the 

ADF while the other is for an RNAV or VOR navigation 

system. The pointers are typically different colors and of 

different widths for ease of identification. Sometimes a 

function switch is provided to allow the #2 pointer to be 

slaved to either a VOR or RNAV system. The card of the 

RMI acts as a gyro-stabilized magnetic compass (usually 

corrected for north via a flux valve) and shows the magnetic 

heading the aircraft is flying.

Radio wave. An electromagnetic wave (EM wave) with 

frequency characteristics useful for radio transmission.

RAIM. See receiver autonomous integrity monitoring.

Random RNAV routes. 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.

Ranging signals. Transmitted from the GPS satellite, these 

allow the aircraft’s receiver to determine range (distance) 

from each satellite.

RB. See relative bearing.

RBI. See relative bearing indicator.

RCO. See remote communications outlet.

Receiver autonomous integrity monitoring (RAIM).

A system used to verify the usability of the received GPS 

signals and warns the pilot of any malfunction in the 

navigation system. This system is required for IFR-certified 

GPS units. 

Recommended altitude. An altitude depicted on an 

instrument approach chart with the altitude value neither 

underscored nor overscored. The depicted value is an 

advisory value.

Receiver-transmitter (RT). A system that permits selection 

of a unique channel or frequency whereupon a signal (typically 

communication) can be transmitted and received.

Reduced vertical separation minimum (RVSM). Reduces 

the vertical separation between flight level (FL) 290–410 

from 2,000 feet to 1,000 feet and makes six additional FLs 

available for operation. Also see DRVSM.

Reference circle (also, distance circle). The circle depicted 

in the plan view of an IAP chart that typically has a 10 NM 

radius, within which chart the elements are drawn to scale.

Regions of command. The “regions of normal and reversed 

command” refers to the relationship between speed and the 

power required to maintain or change that speed in flight.

REIL. See runway end identifier lights.

Relative bearing (RB). The angular difference between the 

aircraft heading and the direction to the station, measured 

clockwise from the nose of the aircraft.

Relative bearing indicator (RBI). Also known as the fixedcard ADF, zero is always indicated at the top of the instrument 

and the needle indicates the relative bearing to the station.
G-16

Relative wind. Direction of the airflow produced by an object 

moving through the air. The relative wind for an airplane in 

flight flows in a direction parallel with and opposite to the 

direction of flight; therefore, the actual flight path of the 

airplane determines the direction of the relative wind.

Remote communications outlet (RCO). An unmanned 

communications facility that is remotely controlled by air 

traffic personnel.

Required navigation performance (RNP). A specified level 

of accuracy defined by a lateral area of confined airspace in 

which an RNP-certified aircraft operates.

Restricted area. Airspace designated under 14 CFR part 

73 within which the flight of aircraft, while not wholly 

prohibited, is subject to restriction.

Reverse sensing. The VOR needle appearing to indicate the 

reverse of normal operation.

RF. Radio frequency.

Rhodopsin. The photosensitive pigments that initiate the 

visual response in the rods of the eye.

Rigidity. The characteristic of a gyroscope that prevents its 

axis of rotation tilting as the Earth rotates.

Rime ice. Rough, milky, opaque ice formed by the 

instantaneous freezing of small supercooled water droplets.

Risk. The future impact of a hazard that is not eliminated 

or controlled.

RMI. See radio magnetic indicator.

RNAV. See area navigation.

RNP. See required navigation performance.

Runway end identifier lights (REIL). A pair of synchronized 

flashing lights, located laterally on each side of the runway 

threshold, providing rapid and positive identification of the 

approach end of a runway.

Runway visibility value (RVV). The visibility determined 

for a particular runway by a transmissometer.

Runway visual range (RVR). The instrumentally derived 

horizontal distance a pilot should be able to see down the 

runway from the approach end, based on either the sighting 

of high-intensity runway lights, or the visual contrast of 

other objects.

RVR. See runway visual range.

RVV. See runway visibility value.

St. Elmo’s Fire. A corona discharge which lights up the aircraft 

surface areas where maximum static discharge occurs.

Satellite ephemeris data. Data broadcast by the GPS 

satellite containing very accurate orbital data for that 

satellite, atmospheric propagation data, and satellite clock 

error data.

Scan. The first fundamental skill of instrument flight, also 

known as “cross-check;” the continuous and logical observation 

of instruments for attitude and performance information.

SDF. See simplified directional facility.

Selective availability. A satellite technology permitting the 

Department of Defense (DOD) to create, in the interest of 

national security, a significant clock and ephemeris error in 

the satellites, resulting in a navigation error.

Semicircular canal. An inner ear organ that detects angular 

acceleration of the body.

Sensitive altimeter. A form of multipointer pneumatic 

altimeter with an adjustable barometric scale that allows the 

reference pressure to be set to any desired level.

SIDS. See standard instrument departure procedures.

SIGMET. The acronym for Significant Meteorological 

information. A weather advisory issued concerning weather 

significant to the safety of all aircraft.

Signal-to-noise ratio. An indication of signal strength 

received compared to background noise, which is a measure 

of how adequate the received signal is.
G-17

Simplex. Transmission and reception on the same 

frequency.

Simplified directional facility (SDF). A NAVAID used 

for nonprecision instrument approaches. The final approach 

course is similar to that of an ILS localizer; however, the 

SDF course may be offset from the runway, generally not 

more than 3°, and the course may be wider than the localizer, 

resulting in a lower degree of accuracy.

Single-pilot resource management (SRM). The ability for 

crew or pilot to manage all resources effectively to ensure 

the outcome of the flight is successful.

Situational awareness. Pilot knowledge of where the 

aircraft is in regard to location, air traffic control, weather, 

regulations, aircraft status, and other factors that may affect 

flight.

Skidding turn. An uncoordinated turn in which the rate of 

turn is too great for the angle of bank, pulling the aircraft to 

the outside of the turn.

Skin friction drag. Drag generated between air molecules 

and the solid surface of the aircraft.

Slant range. The horizontal distance from the aircraft antenna 

to the ground station, due to line-of-sight transmission of the 

DME signal.

Slaved compass. A system whereby the heading gyro is 

“slaved to,” or continuously corrected to bring its direction 

readings into agreement with a remotely located magnetic 

direction sensing device (usually this is a flux valve or flux 

gate compass).

Slipping turn. An uncoordinated turn in which the aircraft 

is banked too much for the rate of turn, so the horizontal lift 

component is greater than the centrifugal force, pulling the 

aircraft toward the inside of the turn.

Small airplane. An airplane of 12,500 pounds or less 

maximum certificated takeoff weight.

Somatogravic illusion. The misperception of being 

in a nose-up or nose-down attitude, caused by a rapid 

acceleration or deceleration while in flight situations that 

lack visual reference.

Spatial disorientation. The state of confusion due to 

misleading information being sent to the brain from various 

sensory organs, resulting in a lack of awareness of the aircraft 

position in relation to a specific reference point.

Special use airspace. Airspace in which flight activities are 

subject to restrictions that can create limitations on the mixed 

use of airspace. Consists of prohibited, restricted, warning, 

military operations, and alert areas.

SRM. See single-pilot resource management.

SSR. See secondary surveillance radar.

SSV. See standard service volume.

Standard holding pattern. A holding pattern in which all 

turns are made to the right.

Standard instrument departure procedures (SIDS). 

Published procedures to expedite clearance delivery and to 

facilitate transition between takeoff and en route operations.

Standard rate turn. A turn in which an aircraft changes its 

direction at a rate of 3° per second. The turn indicators are 

typically 2 minute or 4 minute instruments. In a 2 minute 

instrument, if the needle is one needle width either side of 

the center alignment mark, the turn is 3° per second and the 

turn takes 2 minutes to execute a 360° turn. In a 4 minute 

instrument, the same turn takes two widths deflection of the 

needle to achieve 3° per second. The 4 minute turn instrument 

is usually found on high performance aircraft.

Standard service volume (SSV). Defines the limits of the 

volume of airspace which the VOR serves.

Standard terminal arrival route (STAR). A preplanned 

IFR ATC arrival procedure published for pilot use in graphic 

and/or textual form.

STAR. See standard terminal arrival route.

Static longitudinal stability. The aerodynamic pitching 

moments required to return the aircraft to the equilibrium 

angle of attack.

Static pressure. Pressure of air that is still, or not moving, 

measured perpendicular to the surface of the aircraft.

Steep turns. In instrument flight, any turn greater than standard 

rate; in visual flight, anything greater than a 45° bank.

Stepdown fix. The point after which additional descent is 

permitted within a segment of an IAP.

Strapdown system. An INS in which the accelerometers 

and gyros are permanently “strapped down” or aligned with 

the three axes of the aircraft.
G-18

Stress. The body’s response to demands placed upon it.

Structural icing. The accumulation of ice on the exterior 

of the aircraft.

Suction relief valve. A relief valve in an instrument vacuum 

system required to maintain the correct low pressure inside 

the instrument case for the proper operation of the gyros.

Synchro. A device used to transmit indications of angular 

movement or position from one location to another.

Synthetic vision. A realistic display depiction of the aircraft 

in relation to terrain and flight path.

TAA. See terminal arrival area.

TACAN. See tactical air navigation.

Tactical air navigation (TACAN). An electronic navigation 

system used by military aircraft, providing both distance and 

direction information.

TAWS. See terrain awareness and warning system.

TCAS. See traffic alert collision avoidance system. 

TCH. See threshold crossing height.

TDZE. See touchdown zone elevation.

TEC. See Tower En Route Control.

Technique. The manner in which procedures are executed.

Temporary flight restriction (TFR). Restriction to flight 

imposed in order to:

1. Protect persons and property in the air or on the 

surface from an existing or imminent flight associated 

hazard;

2. Provide a safe environment for the operation of 

disaster relief aircraft;

3. Prevent an unsafe congestion of sightseeing aircraft 

above an incident;

4. Protect the President, Vice President, or other public 

figures; and,

5. Provide a safe environment for space agency 

operations.

Pilots are expected to check appropriate NOTAMs during 

flight planning when conducting flight in an area where a 

temporary flight restriction is in effect.

Tension. Maintaining an excessively strong grip on the control 

column, usually resulting in an overcontrolled situation.

Terminal Instrument Approach Procedure (TERP). 

Prescribes standardized methods for use in designing 

instrument flight procedures.

Terminal arrival area (TAA). A procedure to provide a 

new transition method for arriving aircraft equipped with 

FMS and/or GPS navigational equipment. The TAA contains 

a “T” structure that normally provides a NoPT for aircraft 

using the approach.

TERP. See terminal instrument approach procedure. 

Terrain Awareness and Warning System (TAWS). A 

timed-based system that provides information concerning 

potential hazards with fixed objects by using GPS positioning 

and a database of terrain and obstructions to provide true 

predictability of the upcoming terrain and obstacles.

TFR. See temporary flight restriction.

Threshold crossing height (TCH). The theoretical height 

above the runway threshold at which the aircraft’s glide 

slope antenna would be if the aircraft maintains the trajectory 

established by the mean ILS glide slope or MLS glide path.

Thrust (aerodynamic force). The forward aerodynamic 

force produced by a propeller, fan, or turbojet engine as it 

forces a mass of air to the rear, behind the aircraft.

Time and speed table. A table depicted on an instrument 

approach procedure chart that identifies the distance from the 

FAF to the MAP, and provides the time required to transit 

that distance based on various groundspeeds.

Timed turn. A turn in which the clock and the turn 

coordinator are used to change heading a definite number of 

degrees in a given time.

TIS. See traffic information service.

Title 14 of the Code of Federal Regulations (14 CFR).

The federal aviation regulations governing the operation of 

aircraft, airways, and airmen.

Touchdown zone elevation (TDZE). 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.
G-19

Tower En Route Control (TEC). The control of IFR en route 

traffic within delegated airspace between two or more adjacent 

approach control facilities, designed to expedite traffic and 

reduce control and pilot communication requirements.

TPP. See United States Terminal Procedures Publication.

Tracking. Flying a heading that will maintain the desired track 

to or from the station regardless of crosswind conditions.

Traffic Alert Collision Avoidance System (TCAS). 

An airborne system developed by the FAA that operates 

independently from the ground-based Air Traffic Control 

system. Designed to increase flight deck awareness of 

proximate aircraft and to serve as a “last line of defense” for 

the prevention of mid-air collisions.

Traffic information service (TIS). A ground-based service 

providing information to the flight deck via data link using 

the S-mode transponder and altitude encoder to improve the 

safety and efficiency of “see and avoid” flight through an 

automatic display that informs the pilot of nearby traffic.

Transcribed Weather Broadcast (TWEB). Meteorological 

and aeronautical data recorded on tapes and broadcast over 

selected NAVAIDs. Generally, the broadcast contains routeoriented data with specially prepared NWS forecasts, inflight 

advisories, and winds aloft. It also includes selected current 

information such as weather reports (METAR/SPECI), 

NOTAMs, and special notices.

Transponder. The airborne portion of the ATC radar 

beacon system.

Transponder code. One of 4,096 four-digit discrete codes 

ATC assigns to distinguish between aircraft.

Trend. Immediate indication of the direction of aircraft 

movement, as shown on instruments.

Trim. Adjusting the aerodynamic forces on the control 

surfaces so that the aircraft maintains the set attitude without 

any control input.

TWEB. See Transcribed Weather Broadcast.

True airspeed. Actual airspeed, determined by applying a 

correction for pressure altitude and temperature to the CAS.

UHF. See ultra-high frequency.

Ultra-high frequency (UHF). The range of electromagnetic 

frequencies between 962 MHz and 1213 MHz.

Uncaging. Unlocking the gimbals of a gyroscopic instrument, 

making it susceptible to damage by abrupt flight maneuvers 

or rough handling.

Underpower. Using less power than required for the purpose 

of achieving a faster rate of airspeed change.

United States Terminal Procedures Publication (TPP).

Booklets published in regional format by the NACO that 

include DPs, STARs, IAPs, and other information pertinent 

to IFR flight.

Unusual attitude. An unintentional, unanticipated, or 

extreme aircraft attitude.

User-defined waypoints. Waypoint location and other data 

which may be input by the user, this is the only GPS database 

information that may be altered (edited) by the user.

Variation. Compass error caused by the difference in 

the physical locations of the magnetic north pole and the 

geographic north pole.

VASI. See visual approach slope indicator.

VDP. See visual descent point.

Vectoring. Navigational guidance by assigning headings.

Venturi tube. A specially shaped tube attached to the outside 

of an aircraft to produce suction to allow proper operation 

of gyro instruments.

Vertical speed indicator (VSI). A rate-of-pressure change 

instrument that gives an indication of any deviation from a 

constant pressure level.

Very-high frequency (VHF). A band of radio frequencies 

falling between 30 and 300 MHz.

Very-high frequency omnidirectional range (VOR).

Electronic navigation equipment in which the flight deck 

instrument identifies the radial or line from the VOR station, 

measured in degrees clockwise from magnetic north, along 

which the aircraft is located.

Vestibule. The central cavity of the bony labyrinth of the ear, 

or the parts of the membranous labyrinth that it contains.

VFR. See visual flight rules.

VFR-on-top. ATC authorization for an IFR aircraft to operate 

in VFR conditions at any appropriate VFR altitude.
G-20

VFR over-the-top. A VFR operation in which an aircraft 

operates in VFR conditions on top of an undercast.

Victor airways. Airways based on a centerline that extends 

from one VOR or VORTAC navigation aid or intersection, 

to another navigation aid (or through several navigation aids 

or intersections); used to establish a known route for en route 

procedures between terminal areas.

Visual approach slope indicator (VASI). A visual aid of 

lights arranged to provide descent guidance information 

during the approach to the runway. A pilot on the correct 

glide slope will see red lights over white lights.

Visual descent point (VDP). 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 

runway environment is clearly visible to the pilot.

Visual flight rules (VFR). Flight rules adopted by the 

FAA governing aircraft flight using visual references. VFR 

operations specify the amount of ceiling and the visibility the 

pilot must have in order to operate according to these rules. 

When the weather conditions are such that the pilot can not 

operate according to VFR, he or she must use instrument 

flight rules (IFR).

Visual meteorological conditions (VMC). Meteorological 

conditions expressed in terms of visibility, distance from 

cloud, and ceiling meeting or exceeding the minimums 

specified for VFR.

VMC. See visual meteorological conditions.

VOR. See very-high frequency omnidirectional range.

VORTAC. 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.

VOR test facility (VOT). A ground facility which emits a 

test signal to check VOR receiver accuracy. Some VOTs are 

available to the user while airborne, while others are limited 

to ground use only.

VOT. See VOR test facility.

VSI. See vertical speed indicator.

WAAS. See wide area augmentation system.

Warning area. An area containing hazards to any aircraft 

not participating in the activities being conducted in the 

area. Warning areas may contain intensive military training, 

gunnery exercises, or special weapons testing.

Waypoint. A designated geographical location used for route 

definition or progress-reporting purposes and is defined in 

terms of latitude/longitude coordinates.

WCA. See wind correction angle.

Weather and radar processor (WARP). A device that 

provides real-time, accurate, predictive and strategic weather 

information presented in an integrated manner in the National 

Airspace System (NAS).

Weight. The force exerted by an aircraft from the pull of 

gravity.

Wide area augmentation system (WAAS). A differential 

global positioning system (DGPS) that improves the accuracy 

of the system by determining position error from the GPS 

satellites, then transmitting the error, or corrective factors, 

to the airborne GPS receiver.

Wind correction angle (WCA). The angle between the 

desired track and the heading of the aircraft necessary to 

keep the aircraft tracking over the desired track.

Wind shear. A change in wind speed and/or wind direction 

in a short distance.

Work. A measurement of force used to produce movement.

Zone of confusion. Volume of space above the station where 

a lack of adequate navigation signal directly above the VOR 

station causes the needle to deviate.
I-1

A

acceleration error .........................................................5-13

acceleration in cruise flight ..........................................4-10

adf components...........................................................9-3

advanced technologies.................................................9-24

advanced technology systems......................................5-28

aerodynamic factors............................................... 4-1, 5-1

aerodynamics .................................................................4-2

aeronautical information manual (aim).............. 1-1, 10-2

aircraft control................................................................8-3

during instrument flight..............................................6-3

aircraft system malfunctions........................................11-3

air data computer (adc) .............................................5-22

airplane trim...................................................................6-8

airport/facility directory (a/fd) ..................................10-2

airport sketch/airport diagram......................................1-27

air route traffic control center (artcc) .......................2-7

airspace classification.....................................................1-2

Class A .......................................................................1-2

Class C........................................................................1-2

Class D .......................................................................1-2

Class E........................................................................1-2

Class G .......................................................................1-2

airspeed ..........................................................................5-9

indicated airspeed (ias).............................................5-9

calibrated airspeed (cas) ..........................................5-9

equivalent airspeed (eas)..........................................5-9

mach number............................................................5-10

true airspeed (tas)....................................................5-9

airspeed changes

common errors..........................................................8-10

in straight-and-level flight .............................. 7-11, 7-40

airspeed color codes.....................................................5-10

airspeed indicator (ASI).5-8, 6-6, 6-8, 6-10, 7-6, 7-37, 8-5

air traffic control (atc).................................................2-1

alternator/generator failure...........................................11-5

altimeter ...............................................6-10, 7-3, 7-36, 8-4

enhancements (encoding)...........................................5-7

analog instrument failure .............................................11-7

analog pictorial displays ..............................................5-23

angle of attack................................................................4-2

applying the four-step process.....................................6-20

approach azimuth guidance..........................................9-43

approach control advances...........................................2-12

precision runway monitor (prm).............................2-12

prm benefits............................................................2-13

prm radar ................................................................2-12

approach control facility ..............................................2-12

approaches..................................................................10-13

lighting systems (als).............................................9-38

to airport with an operating tower..........................10-15

to airport without an operating control 

tower.......................................................................10-13

to parallel runways.................................................10-20

to stall .......................................................................7-26

area navigation (rnav)..............................................9-22

atc inflight weather avoidance assistance .................2-11

atc radar weather displays.........................................2-11

atc reports .................................................................10-7

atc towers....................................................................2-5

atmosphere .....................................................................4-4

layers of the atmosphere.............................................4-5

attitude and heading reference system (ahrs)...........5-22

attitude control ...............................................................6-3

attitude direction indicator (adi) ................................5-23

attitude indicator .. 5-19, 6-4, 7-2, 7-6, 7-34, 7-37, 8-3, 8-5

attitude instrument flying

fundamental skills.....................................................6-24

primary and supporting method ...............................6-21

using the control and performance method ................6-2

using the primary and supporting method..................6-4

automated flight service stations (afss).......................2-4

automatic dependent surveillance—broadcast

(ads-b).......................................................................5-28

autopilot systems..........................................................5-25

usage.........................................................................7-58

autorotations.................................................................8-17

common errors..........................................................8-17

aviation magnetic compass..........................................5-10

Index
I-2

B

bank..............................................................................7-25

bank control .......................... 6-4, 6-7, 6-20, 7-6, 7-37, 8-5

blockage of the pitot-static system.................................5-2

pitot system ................................................................5-2

static system ...............................................................5-3

C

cancelling ifr flight plans...........................................10-3

center approach/departure control..................................2-7

certified checkpoints ....................................................9-16

change of airspeed

during turns ..............................................................7-24

in turns......................................................................8-14

circling approaches ....................................................10-20

patterns.....................................................................7-32

clearances.....................................................................10-3

separations................................................................10-4

climbing and descending turns........................... 7-24, 8-15

climbing while accelerating ...........................................3-8

climbing while turning...................................................3-8

climbs................................................................. 4-10, 7-14

common cross-check errors .........................................6-11

communication equipment.............................................2-2

communication facilities................................................2-4

communication/navigation system malfunction ..........11-8

communication procedures............................................2-4

compass locator............................................................9-38

compass turns............................................ 7-21, 7-53, 8-15

compliance with published standard instrument

approach procedures ..................................................10-13

conducting an ifr flight ............................................10-26

constant airspeed climb

from cruise airspeed .................................................7-46

from established airspeed .........................................7-47

constant rate climbs......................................................7-47

control and performance method .................................6-18

control instruments............................................... 6-2, 6-18

control sequence...........................................................2-13

coping with spatial disorientation ..................................3-8

course deviation indicator (cdi) .................................9-11

course interception.......................................................9-14

course reversal elements in plan view and profile 

view..............................................................................1-20

procedure turns.........................................................1-20

holding in lieu of procedure turn..............................1-20

teardrop procedure....................................................1-21

D

density altitude ...............................................................4-5

departure procedures (dps)................................ 1-12, 10-5

departures and instrument departure 

procedures (dps)..........................................................9-31

departures from airports without an operating control 

tower ............................................................................10-7

descents.............................................................. 7-16, 7-49

differential global positioning systems (dgps) ..........9-32

distance measuring equipment (dme) ........................9-17

arc .............................................................................9-17

components .............................................................9-17

function.....................................................................9-17

holding....................................................................10-13

disturbances to radio wave reception.............................9-3

diving or rolling beyond the vertical plane ....................3-8

diving while turning.......................................................3-8

drag ................................................................................4-3

induced drag ...............................................................4-3

parasite drag ...............................................................4-3

skin friction drag ........................................................4-3

interference drag.........................................................4-3

form drag ....................................................................4-4

drag curves.....................................................................4-6

dry air vacuum pump ...................................................5-17

dynamic pressure type instruments................................5-8

E

ears.................................................................................3-4

electrical systems.........................................................5-17

electronic flight display malfunction ...........................11-4

electronic flight instrument systems.............................5-27

emergencies..................................................................8-16

engine instruments.........................................................6-8

en route procedures......................................................10-7

errors during compass turns.........................................7-26

establishing a standard rate turn...................................7-51

eyes ................................................................................3-2

F

federal airways...............................................................1-4

filing in flight................................................................10-2

flags or other signal strength indicators.......................9-11

flight director system (fds).........................................5-23

flight instruments ................................................. 4-16, 8-2

flight management systems (fms) ........... 5-26, 5-27, 9-44

function.....................................................................9-46

flight services station (FFS) ...........................................2-4

flightpath ........................................................................4-2

flight support systems ..................................................5-22

flux gate compass system.............................................5-15

four forces......................................................................4-2

drag.............................................................................4-3

lift ....................................................................... 4-2, 4-6
I-3

thrust...........................................................................4-3

weight.........................................................................4-3

function of adf.............................................................9-4

G

glideslope (gs) ............................................................9-37

global navigation satellite system (gnss) ..................9-24

global positioning system (gps) ....................... 5-27, 9-25

components...............................................................9-25

errors.........................................................................9-31

function.....................................................................9-26

instrument approaches..............................................9-29

nearest airport function.............................................11-9

substitution ...............................................................9-27

substitution for adf or dme ..................................9-27

ground proximity warning system (gpws) ................5-34

ground wave...................................................................9-2

gyroscopic instruments ................................................5-19

gyroscopic systems ......................................................5-16

H

heading.........................................................................7-44

heading indicator................. 5-19, 6-7, 6-10, 7-7, 7-38, 8-6

head-up display (hud)...................................... 5-34, 9-46

height above landing (hal)........................................1-27

helicopter trim..............................................................6-10

holding instructions....................................................10-10

holding procedures.....................................................10-10

homing ...........................................................................9-5

horizontal situation indicator (hsi) ................... 5-23, 7-38

how radio waves propagate............................................9-2

how to prevent landing errors due to optical illusions...3-9

I

iap minimums...........................................................10-21

icao cold temperature error table ................................5-5

icing..............................................................................4-13

antenna icing.............................................................4-17

clear ice.....................................................................4-13

effects of icing on critical aircraft systems...............4-16

general effects of icing on airfoils............................4-14

induction icing..........................................................4-13

mixed ice ..................................................................4-14

propeller icing...........................................................4-16

rime ice.....................................................................4-14

structural icing.............................................. 4-13, 10-23

ifr en route charts.........................................................1-6

airport information .....................................................1-6

charted ifr altitudes ..................................................1-6

navigation features .....................................................1-7

ifr flight plan..............................................................10-2

ifr flight using gps....................................................9-28

illusions leading to spatial disorientation.......................3-5

inadvertent icing encounter..........................................11-2

inadvertent thunderstorm encounter ............................11-2

inertial navigation system (ins)..................................9-34

ins components.......................................................9-34

ins errors.................................................................9-34

inoperative components...............................................1-27

instrument approach capabilities..................................9-32

instrument approaches to civil airports......................10-13

instrument approach procedure charts.........................1-12

margin identification.................................................1-12

pilot briefing .............................................................1-16

plan view ..................................................................1-16

instrument approach procedure (iap)..........................1-12

approach systems......................................................9-35

cross-check .............................................. 6-10, 6-24, 8-2

instrument flight.............................................................8-2

instrument flight patterns................................... 7-30, 7-61

instrument flying common errors.................................6-27

emphasis...................................................................6-28

fixation......................................................................6-27

omission ...................................................................6-28

instrument interpretation...................................... 6-13, 8-3

instrument landing systems (ils)................................9-35

airborne components................................................9-38

components...............................................................9-35

errors.........................................................................9-40

function.....................................................................9-40

instrument takeoff..................................... 7-29, 7-60, 8-17

common errors....................................... 7-29, 7-61, 8-18

instrument weather flying ..........................................10-22

integrated flight control system....................................5-25

intercepting bearings......................................................9-8

intercepting lead radials...............................................9-18

International Civil Aviation Organization (icao)........1-1

international standard atmosphere (isa) .......................4-5

intersections ...................................................................1-7

inverted-V cross-check ................................................6-11

L

landing........................................................................10-22

landing minimums .......................................................1-23

large airplanes..............................................................4-10

law of inertia, the ...........................................................4-4

law of momentum, the ...................................................4-4

law of reaction, the.........................................................4-4

learning methods.................................................. 6-2, 6-16

letters of agreement (loa)..........................................2-15
I-4

leveling off......................................................... 7-16, 7-17

load factor ....................................................................4-12

local area augmentation system (laas).....................9-33

localizer........................................................................9-35

localizer type directional aid (lda)............................9-43

loss of alternator/generator for electronic flight 

instrumentation ............................................................11-5

M

magnetic compass................................................ 5-10, 6-7

acceleration error......................................................5-13

construction ..............................................................5-11

deviation ...................................................................5-12

induced errors...........................................................5-11

northerly turning errors ............................................5-13

oscillation error.........................................................5-14

southerly turning errors............................................5-13

theory of operations..................................................5-11

variation....................................................................5-12

magnetism....................................................................5-10

marker beacons .................................................. 9-37, 9-40

master battery switch ...................................................11-5

maximum allowable airspeed ......................................5-10

microwave landing system (mls)...............................9-43

missed approaches .....................................................10-21

multi-function display (mfd)......................................5-28

N

National Aeronautical Navigation Services 

(aeronav services) .................................................10-2

National Airspace System (nas)..................................1-1

navaids ...........................................................................1-7

navigating the mfd page groups...............................11-10

nearest airport page group ......................................11-10

nearest airports page soft keys................................11-10

nearest airports using the mfd ..............................11-10

nearest airports using the pfd..................................11-9

navigation/communication equipment...........................2-2

navigation instruments......................................... 6-2, 6-19

ndb components...........................................................9-3

nerves.............................................................................3-5

Newton’s First Law........................................................4-4

Newton’s Second Law...................................................4-4

Newton’s Third Law......................................................4-4

nondirectional radio beacon (ndb)...............................9-3

nonprecision approaches..............................................1-23

nose-high attitudes.......................................................7-27

nose-low attitudes ........................................................7-28

Notices to Airmen Publication (ntap).......................10-2

O

obstacle departure procedures (odp)................ 1-12, 10-5

omnibearing selector (obs) ........................................9-11

operating on the main battery ............................ 11-5, 11-6

operational errors of adf..............................................9-8

optical illusions..............................................................3-9

featureless terrain illusion ..........................................3-9

fog................................................................... 3-9, 10-24

ground lighting illusions.............................................3-9

haze.............................................................................3-9

runway width illusion.................................................3-9

runway and terrain slopes illusion..............................3-9

water refraction...........................................................3-9

other routing...................................................................1-5

P

partial panel flight ........................................................7-36

performance instruments...................................... 6-2, 6-19

pitch.................................................................... 7-25, 7-43

pitch attitude instrument cross-check.............................6-7

pitch control ........................ 6-4, 6-20, 6-22, 7-2, 7-34, 8-3

pitch/power relationship.................................................4-6

pitot/static instruments...................................................5-3

pitot/static system failure .............................................11-8

pitot/static systems.........................................................5-2

planning the descent and approach ..............................10-8

pneumatic system failure .............................................11-7

pneumatic systems.......................................................5-17

poh/afm....................................................................10-2

point in space approach................................................1-27

position reports.............................................................10-7

postural considerations...................................................3-7

power.................................................................. 7-26, 7-45

control....................................... 6-4, 6-8, 6-21, 7-8, 7-39

control during straight-and-level flight.......................8-7

settings.............................................................. 7-9, 7-39

sources......................................................................5-17

precipitation static........................................................11-3

precision approaches....................................................1-23

preferred ifr..................................................................1-5

pressure altitude .............................................................4-5

pressure indicating systems..........................................5-17

primary bank ................................................................6-23

primary flight display (pfd)........................................5-27

primary pitch................................................................6-22

primary power..............................................................6-24

primary yaw .................................................................6-23

procedural steps in using control and performance .......6-2

procedure turn ..............................................................7-30
I-5

R

racetrack pattern...........................................................7-30

radar ...............................................................................2-3

radar and transponders...................................................2-3

Mode C (altitude reporting)........................................2-3

radar approaches ........................................................10-15

radar-controlled departures..........................................10-5

radar limitations...........................................................9-48

radar monitoring of instrument approaches...............10-18

radar navigation (ground-based)..................................9-46

radio altimeters.............................................................5-29

radio principles...............................................................9-2

recognizing unusual attitudes.......................................7-27

recovery from unusual attitudes...................................7-27

rectangular cross-check................................................6-11

reduced vertical separation minimum (rvsm).............5-7

regions of command.......................................................4-7

control characteristics.................................................4-7

relative wind...................................................................4-2

remote indicating compass...........................................5-15

required navigation instrument system inspection.......5-36

required navigation performance .................................9-44

reversal of motion ..........................................................3-8

rnav instrument approach charts..............................1-30

route information .........................................................1-10

S

safety systems ..............................................................5-29

scanning techniques.....................................................6-24

selected radial cross-check................................. 6-11, 6-24

sensitive altimeter ..........................................................5-3

altimeter errors ...........................................................5-4

cold weather altimeter errors......................................5-5

inherent altimeter error...............................................5-5

principle of operation .................................................5-3

sensory systems for orientation......................................3-2

servo failure .................................................................8-17

side-step maneuver.....................................................10-20

simplified directional facility (sdf)............................9-42

situational awareness .................................................11-11

sky wave.........................................................................9-2

slip/skid indicator.........................................................7-39

slow-speed flight............................................................4-8

small airplanes ...............................................................4-9

sources of flight planning information.........................10-2

space wave .....................................................................9-2

spatial disorientation ....................................... 3-2, 3-5, 3-7

special use airspace ........................................................1-2

speed stability.................................................................4-8

normal command........................................................4-8

reversed command......................................................4-8

stall warning systems...................................................4-17

standard 45° procedure turn.........................................7-30

standard entry procedures..........................................10-11

standard holding pattern (no wind)............................10-10

standard holding pattern (with wind).........................10-10

standard instrument departures....................................10-5

standard rate turns.............................................. 7-19, 7-51

standard terminal arrival routes (stars) ......... 1-12, 10-9

standby battery.............................................................11-6

static pressure.................................................................5-2

station passage ...............................................................9-5

steep turns .......................................................... 7-22, 7-53

straight-and-level flight........................6-22, 7-2, 7-34, 8-3

common errors......................................... 7-12, 7-43, 8-7

straight climbs and descents............................... 7-14, 7-46

common errors....................................... 7-17, 7-50, 8-13

straight climbs (constant airspeed and constant rate) ..8-10

straight descents (constant airspeed and 

constant rate) ..............................................................8-12

substitutes for inoperative or unusable components..10-10

synthetic vision ............................................................5-28

systems preflight procedures........................................5-36

T

tailplane stall symptoms...............................................4-16

teardrop patterns...........................................................7-31

techniques for electrical usage ........................... 11-5, 11-6

temporary flight restrictions (tfrs)..............................1-4

terminal arrival area (taa) .........................................1-18

terminal procedures publications.................................1-12

departure procedures................................................1-12

marginal identification..............................................1-12

standard terminal arrival routes................................1-12

terminal radar approach control (tracon).................2-6

terrain alerting systems................................................5-34

terrain awareness and warning system (taws)..........5-34

the four-step process used to change attitude ..............6-19

adjust ........................................................................6-20

cross-check ...............................................................6-20

establish....................................................................6-19

trim ...........................................................................6-20

tilting to right or left.......................................................3-8

timed approaches from a holding fix .........................10-18

timed turns ................................................ 7-21, 7-53, 8-13

time factors.................................................................10-12

tower en route control (tec)................................. 1-6, 2-7

tracking ..........................................................................9-5

tracking to and from the station ...................................9-14

traditional navigation systems........................................9-3

traffic advisory systems................................................5-29

traffic alert and collision avoidance system (tcas)...5-30
I-6

traffic alert systems......................................................5-30

traffic avoidance.........................................................11-12

traffic avoidance systems.............................................5-30

traffic information system............................................5-29

transponders...................................................................2-3

trim.....................................................4-8, 6-20, 7-26, 7-45

control.........................................................................6-8

technique ........................................................ 7-12, 7-43

turn-and-slip indicator.......................................... 5-20, 7-8

turn coordinator.................................................... 5-21, 7-7

turn coordinator/turn-and-slip indicator.........................6-8

turn indicator........................................................ 5-20, 8-7

turn rate indicator.........................................................7-38

turns..................................................4-10, 7-19, 7-51, 8-13

common errors................................................ 7-25, 8-15

coordination of rudder and aileron controls.............4-11

radius of turn ............................................................4-11

rate of turn ................................................................4-11

turns to predetermined headings............... 7-20, 7-52, 8-13

U

unforecast adverse weather..........................................11-2

unusual attitude recovery protection............................7-55

unusual attitudes...........................................................8-16

unusual attitudes and recoveries ..................................7-26

common errors.......................................... 7-28, 7-58, 8-16

V

vacuum pump systems.................................................5-17

venturi tube systems.....................................................5-17

vertical card magnetic compass...................................5-15

vertical descent angle (vda).......................................1-23

vertical speed indicator (vsi)..................5-8, 6-5, 7-4, 8-5

very high frequency omnidirectional range (vor).......9-8

function.....................................................................9-11

operational errors......................................................9-14

receiver accuracy check............................................9-16

test facility (vot)....................................................9-16

vestibular illusions.........................................................3-5

coriolis illusion...........................................................3-6

elevator illusion ..........................................................3-6

graveyard spiral..........................................................3-6

inversion illusion ........................................................3-6

leans, the.....................................................................3-5

somatogravic illusion .................................................3-6

vfr-on-top................................................................10-26

vfr over-the-top.......................................................10-26

visibility figures ...........................................................1-23

vision under dim and bright illumination.......................3-3

visual illusions ...............................................................3-7

false horizon ...............................................................3-7

autokinesis..................................................................3-7

vor accuracy..............................................................9-16

vor components.........................................................9-10

vor/dme rnav.......................................................9-22

components...............................................................9-23

function.....................................................................9-23

errors.........................................................................9-24

vsi tape .......................................................................7-36

W

weather avoidance assistance.......................................2-11

weather conditions.....................................................10-22

thunderstorms.........................................................10-24

turbulence ...............................................................10-22

volcanic ash ............................................................10-24

wind shear...............................................................10-25

weather information and communication features.......1-10

wet-type vacuum pump................................................5-17

wide area augmentation system (waas)....................9-32

wind shear..................................................................10-25

windshields ..................................................................4-17

wing................................................................................4-2