FAA-H-8083-6

Advanced Avionics Handbook

Updated May 2, 2013

Errata as of May 2, 2013

1. In Figure 3-16 on page 3-13, the following errors were discovered and will be corrected 

in the next version of this handbook:

a. The lower right control display indicates a bearing of 087° to COVAR. This should 

be corrected to indicate 079°.

b. The left navigation display indicates a bearing of 051° to COVAR. This should be 

corrected to indicate 079°.

Note: The #2 (blue) bearing pointer on the left navigation display indicating a 

bearing of 079° to COVAR is correct.

c. The upper right control display indicates a bearing of 272° to FOGON. This should 

be corrected to indicate 268° or 269°.

d. The left navigation display indicates a bearing of 270° to FOGON. This should be 

corrected to indicate 268° or 269°since the CDI needle is not exactly centered.

e. On the left navigation display, the #1 (green) CDI bar is set to 268°, but the center 

portion of the bar is not aligned in the center, so the set course is slightly to the right.

Depending on the settings, the bearing to FOGON should be corrected to indicate 

somewhere between 268° and 269°, but not 270°.

f. Both captions stating "FMS" should corrected to "GPS" since right side control 

displays are typical of GPS control units and are much simpler than most FMS units.
1
Advanced Avionics 

Handbook

U.S. Department of Transportation

FEDERAL AVIATION ADMINISTRATION

Flight Standards Service

2009
ii
iii

The Advanced Avionics Handbook is a new publication designed to provide general aviation users with comprehensive 

information on advanced avionics equipment available in technically advanced aircraft. This handbook introduces the pilot 

to flight operations in aircraft with the latest integrated “glass cockpit” advanced avionics systems.

Since the requirements can be updated and the regulations can change, the Federal Aviation Administration (FAA) 

recommends that you contact your local Flight Standards District Office (FSDO), where FAA personnel can assist you 

with questions regarding advanced avionics equipment flight training and/or advanced avionics equipment questions about 

your aircraft.

This publication is available free of charge for download, in PDF format, from the FAA Regulatory Support Division 

(AFS‐600) on the FAA website at www.faa.gov.

The Advanced Avionics Handbook may also be purchased from:

Superintendent of Documents

United States Government Printing Office

Washington, DC 20402-9325

http://bookstore.gpo.gov

This handbook is published by and comments should be sent in email form to:

afs630comments@faa.gov

Preface
iv
v

The FAA wishes to acknowledge the following aviation manufacturers and companies that provided images used in this 

handbook:

Avidyne Corporation

Cirrus Design, Inc.

Garmin Ltd.

Rockwell Collins, Inc.

S-Tec Corporation

The FAA would also like to extend its appreciation to the General Aviation Manufacturers Association (GAMA) for its 

assistance and input in the preparation of this handbook.

Acknowledgments
vi
vii

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

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

Table of Contents .................................................vii

Chapter 1

Introduction to Advanced Avionics...................1-1

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

How To Operate Advanced Avionics Systems..............1-2

Which Advanced Avionics Systems To Use and When 1-2

How Advanced Avionics Systems Affect the Pilot .......1-3

Chapter Summary ..........................................................1-3

Chapter 2

Electronic Flight Instruments.............................2-1

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

Primary Flight Display (PFD)........................................2-2

Primary Flight Instruments.........................................2-2

Cross-Checking the Primary Flight Instruments ....2-2

Common Errors: Altitude Excursions and

Fixation...................................................................2-2

Enhancements to the Primary Flight Instruments...2-3

Primary Flight Instrument Systems............................2-3

Navigation Instruments..............................................2-3

Other Flight Status Information .................................2-4

Making Entries on the PFD........................................2-4

Failures and the Primary Flight Display.....................2-4

Instrument System Failure......................................2-4

PFD Failure.............................................................2-6

Awareness: Using Standby Instruments.................2-6

Essential Skills ...........................................................2-6

Chapter Summary ..........................................................2-6

Chapter 3

Navigation ............................................................3-1

Area Navigation (RNAV) Basics...................................3-2

RNAV Concept ..........................................................3-2

FMS/RNAV Computer ..............................................3-2

FMS/RNAV/Autopilot Interface: Display and

Controls......................................................................3-3

Accessing Information in the FMS.........................3-3

Making Entries in the FMS.....................................3-4

Integrated Avionics Systems ..................................3-4

Learning: Simulators for Learning and Practice.....3-5

Flight Planning...............................................................3-5

Preflight Preparation...................................................3-5

FMS/RNAV Approval For IFR Operations...............3-6

Navigation Database Currency ......................................3-6

Alternative Means of Navigation ...............................3-6

NOTAMs Relevant To GPS.......................................3-6

GPS Signal Availability .............................................3-6

Alternate Airports.......................................................3-7

Aircraft Equipment Suffixes.......................................3-7

Suitability of an RNAV Unit for VFR Flight.............3-7

Programming the Flight Route...................................3-7

The Flight Planning Page ...........................................3-8

En Route Waypoints and Procedural Waypoints....3-8

Entering En Route Waypoints................................3-8

Entering Airways....................................................3-8

Entering Procedures................................................3-9

Risk: Taking Off Without Entering a Flight Plan...3-9

Reviewing the Flight Route ....................................3-9

Catching Errors: Using the FMs Flight Planning 

Function To Cross-Check Calculations......................3-9

Check the Waypoints............................................3-10

Check the Distances..............................................3-10

Check the Desired Tracks.....................................3-11

Check for Route Discontinuities...........................3-11

Maintaining Proficiency: Aeronautical

Knowledge............................................................3-11

Coupling the FMs to the Navigation Indicator(s) ....3-11

Common Error: Displaying the Wrong

Navigation Source ................................................3-12

Awareness: Mode Awareness...............................3-13

Essential Skills .........................................................3-13

En Route Navigation....................................................3-13

Table of Contents
viii

The Active Waypoint ...............................................3-14

Desired Track........................................................3-14

Track.....................................................................3-14

Groundspeed and ETA .........................................3-14

Fuel Used and Time Remaining ...........................3-14

Arriving at the Active Waypoint..............................3-14

Waypoint Alerting ................................................3-15

Turn Anticipation..................................................3-15

Waypoint Sequencing...........................................3-15

Awareness: Making Waypoint Callouts...............3-15

Setting the Course to New Active Waypoint........3-16

En Route Sensitivity.................................................3-16

GPS Signal Status.................................................3-16

Accessing Navigational Information En Route ....3-16

Essential Skills .........................................................3-16

En Route Modifications...............................................3-17

Adding and Deleting Waypoints From the

Programmed Route...................................................3-17

Direct To...................................................................3-17

Risk: What Lies Ahead on a Direct-To Route? ....3-18

Cancel Direct To...................................................3-18

Selecting a Different Instrument Procedure or

Transition .................................................................3-18

Proceeding Directly to the Nearest Airport..............3-18

Essential Skills .........................................................3-18

Descent.........................................................................3-19

Elements of Descent Planning Calculations.............3-19

Manual Descent Calculations...............................3-20

Coordinating Calculations with Aeronautical

Charts....................................................................3-21

Alternate Navigation Planning .............................3-21

Calculating Descents with the FMS .....................3-21

Managing Speed ...................................................3-22

Descent Flying Concepts......................................3-22

Flying the Descent ................................................3-23

Determining Arrival at the Top-of-Descent

Point......................................................................3-23

Early Descents......................................................3-23

Late Descents........................................................3-24

Common Error: Not Considering Winds During 

Descent Planning ..................................................3-25

Essential Skills .........................................................3-25

Intercept And Track Course.........................................3-25

Intercepting and Tracking a Different Course to

the Active Waypoint.................................................3-25

The Nonsequencing Mode........................................3-25

Common Error: Forgetting To Re-Engage

Sequencing Mode After Course Intercept ............3-26

Awareness: Remembering To Make Needed

Mode Changes......................................................3-26

Intercepting and Tracking a Course to a Different 

Waypoint ..................................................................3-26

Common Error: Setting the Wrong Inbound

Course During a Course Intercept ........................3-27

Common Error: Setting the Wrong Active

Waypoint During a Course Intercept....................3-27

Catching Errors: A Helpful Callout Procedure

for Course Intercepts.............................................3-27

Essential Skills .........................................................3-28

Holding ........................................................................3-28

Preprogrammed Holding Patterns.........................3-28

Common Error: Mismanaging the Sequencing/

Nonsequencing Modes During a Hold .................3-30

Essential Skills .........................................................3-30

ARCS...........................................................................3-30

Essential Skills .........................................................3-30

GPS And RNAV (GPS) Approaches...........................3-30

LNAV ..........................................................................3-35

LNAV/VNAV..............................................................3-35

LPV..............................................................................3-35

GPS or RNAV (GPS) Approach Waypoints............3-35

Flying a GPS or RNAV (GPS) Approach................3-35

Terminal Mode .....................................................3-36

Approach Mode ....................................................3-36

Approach Not Active............................................3-36

Vectored Approaches...............................................3-36

Awareness: Briefing the Approach.......................3-37

Common Error: Forgetting To Verify the

Approach Mode ....................................................3-37

Common Error: Using the Wrong Approach 

Minimums.............................................................3-37

Common Error: Forgetting To Reengage

Sequencing Mode Prior to Final Approach

Waypoint...............................................................3-37

Essential Skills .........................................................3-38

Course Reversals..........................................................3-38

Preprogrammed Course Reversals...........................3-38

Common Error: Mismanaging the Sequencing/

Nonsequencing Modes During a Course

Reversal ................................................................3-38

Essential Skills .........................................................3-38

Missed Approaches......................................................3-40

Recognizing the Missed Approach Point.................3-41

Complying With ATC-Issued Missed Approach 

Instructions...............................................................3-41

Setting Up Next Procedure in Hold......................3-41
ix

Common Error: Noncompliance With Initial

Missed Approach Instructions..............................3-42

Essential Skills .........................................................3-42

Ground-based Radio Navigation..................................3-42

Configuring FMs To Receive Ground-Based...........3-42

Radio Navigation Signals.........................................3-42

Tuning and Identifying Radio Navigation

Facilities...................................................................3-42

Displaying Radio Navigation Signals on the

Navigation Indicator.................................................3-42

Awareness: Using All Available Navigation

Resources..................................................................3-42

Flying a Precision Approach Using Ground-based 

Navigation Facilities.................................................3-42

Flying a Nonprecision Approach Using

Ground-Based Navigation Facilities........................3-42

Maintaining Proficiency: Practicing All

Navigation Skills......................................................3-43

Essential Skills .........................................................3-43

Chapter Summary ........................................................3-44

Chapter 4

Automated Flight Control ...................................4-1

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

Autopilot Concepts........................................................4-2

How To Use an Autopilot Function ...........................4-2

Specification of Track and Altitude........................4-2

Engagement of Autopilot Function ........................4-3

Verification of Autopilot Function Engagement ....4-3

How Autopilot Functions Work.................................4-4

Determination of Control Movements Required

To Achieve Goals...................................................4-4

Carrying Out Control Movements..........................4-4

Flight Director................................................................4-4

Flight Director Functions...........................................4-4

Using the Flight Director (FD)...................................4-5

Flight Director Without Autopilot..........................4-5

Flight Director With Autopilot ...............................4-5

Common Error: Blindly Following Flight

Director Cues..........................................................4-5

Common Error: Confusion About Autopilot 

Engagement ............................................................4-5

Follow Route..................................................................4-5

Following a Route Programmed in the FMS .............4-5

GPS Steering (GPSS) Function..................................4-6

Following a VOR Radial............................................4-6

Fly Heading....................................................................4-7

Maintain Altitude ...........................................................4-7

Climbs And Descents.....................................................4-8

Vertical Speed ............................................................4-8

Vertical Speed with Altitude Capture ........................4-8

Catching Errors: Armed Modes Help Prevent 

Forgotten Mode Changes........................................4-8

Common Error: Failure To Arm the Altitude

Mode .....................................................................4-10

Awareness: Altitude Alerting Systems.................4-10

Awareness: Automatic Mode Changes.................4-10

Learning: The Importance of Understanding .......4-10

Power Management..................................................4-11

Essential Skills .........................................................4-11

Course Intercepts .........................................................4-11

Flying an Assigned Heading To Intercept a Course

or VOR Radial..........................................................4-11

Essential Skills .........................................................4-11

Coupled Approaches....................................................4-12

ILS Approaches........................................................4-12

RNAV Approaches With Vertical Guidance ..........4-12

Power Management..................................................4-13

Essential Skills .........................................................4-13

Deciding When To Use The FD/Autopilot..................4-14

Miscellaneous Autopilot Topics..................................4-15

Autopilot Mode Awareness......................................4-15

Positive Exchange of Controls.................................4-15

Preflighting the Autopilot.........................................4-15

Autopilot and Electric Trim System Failures...........4-15

Essential Skills .........................................................4-15

Chapter Summary ........................................................4-16

Chapter 5

Information Systems...........................................5-1

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

Multi-Function Display..................................................5-2

Essential Skills ...........................................................5-2

Moving Maps.................................................................5-2

Using the Moving Map ..............................................5-2

Maintaining the “Big Picture” ................................5-3

Maintaining Awareness of Potential Landing

Sites.........................................................................5-3

Maintaining Awareness on the Airport Surface .....5-3

Identifying Controlled Airspace .............................5-3

Identifying the Missed Approach Point..................5-4

Catching Errors: Using the Moving Map to Detect

Route Programming Errors ........................................5-4

Catching Errors: Using The Moving Map To Detect 

Configuration Errors...................................................5-4

Maintaining Proficiency: Spatial Reasoning Skills....5-5

Failure Indications..................................................5-5

Common Error: Using the Moving Map as a

Primary Navigation Instrument..................................5-5

Awareness: Overreliance On The Moving Map.........5-6
x

Terrain Systems .............................................................5-6

Early Systems.............................................................5-6

Terrain Display...........................................................5-7

Monitoring Surrounding Terrain During

Departure and Arrival.............................................5-7

Evaluating a Direct-To Routing..............................5-8

Terrain Awareness and Warning Systems..................5-8

TAWS A and TAWS B ..........................................5-8

TAWS Alerts..........................................................5-8

Risk: Silencing TAWS Alerts....................................5-8

Risk: Flying in Close Proximity to Terrain................5-9

Cockpit Weather Systems..............................................5-9

Thunderstorms and Precipitation................................5-9

Onboard Weather Radar Systems.............................5-10

Ground Weather Surveillance Radar........................5-10

Limitations of Both Types of Weather Radar

Systems.................................................................5-11

Lightning...............................................................5-12

Clouds...................................................................5-12

Other Weather Products........................................5-12

Using Advanced Weather Data Systems..................5-12

Preflight Overview................................................5-13

Track Progress of Significant Weather En Route .5-13

Investigate Weather Phenomena Reported by

Radio.....................................................................5-13

Broadcast Weather Products Versus Onboard

Weather Sensors ...................................................5-13

Common Error: Skipping the Preflight Weather

Briefing.....................................................................5-14

Traffic Data Systems....................................................5-14

Traffic Data Systems Using Onboard Sensing 

Equipment ................................................................5-14

Traffic Data Systems Receiving Information From 

Ground-based Facilities............................................5-14

Advanced Traffic Data Systems Based On ADS-B .5-15

Using A Traffic Data System ...................................5-15

Setting Sensitivity on a Traffic Data System........5-15

Responding to Traffic Alerts ................................5-15

Error: Overreliance on Traffic Data

System/Failure To Scan........................................5-15

Using a Traffic Data System on the Ground.........5-15

Fuel Management Systems..........................................5-15

Initial Fuel Estimate .................................................5-16

Estimating Amount Of Fuel on Board .....................5-16

Predicting Fuel at a Later Point in the Flight ...........5-16

Determining Endurance............................................5-17

Risk: Stretching Fuel Reserves.................................5-17

Other Cockpit Information System Features ...............5-17

Electronic Checklists................................................5-17

Electronic Charts......................................................5-18

FMS/RNAV Pages on the MFD...............................5-18

Chapter Summary ........................................................5-19

Essential Skills Checklist .................................. E-1

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

Introduction

This handbook is designed as a technical reference for 

pilots who operate aircraft with advanced avionics systems. 

Whether flying a conventional aircraft that features a global 

positioning system (GPS) navigation receiver or a new 

aircraft with the latest integrated “glass cockpit” advanced 

avionics system, you should find this handbook helpful in 

getting started. The arrival of new technology to general 

aviation aircraft has generated noticeable changes in three 

areas: information, automation, and options.

Pilots now have an unprecedented amount of information 

available at their fingertips. Electronic flight instruments use 

innovative techniques to determine aircraft attitude, speed, 

and altitude, presenting a wealth of information in one or 

more integrated presentations. A suite of cockpit information 

systems provides pilots with data about aircraft position, 

planned route, engine health and performance, as well as 

surrounding weather, traffic, and terrain.

Introduction to 

Advanced Avionics

Chapter 1
1-2

Advanced avionics systems can automatically perform many 

tasks that pilots and navigators previously did by hand. For 

example, an area navigation (RNAV) or flight management 

system (FMS) unit accepts a list of points that define a 

flight route, and automatically performs most of the course, 

distance, time, and fuel calculations. Once en route, the FMS 

or RNAV unit can continually track the position of the aircraft 

with respect to the flight route, and display the course, time, 

and distance remaining to each point along the planned route. 

An autopilot is capable of automatically steering the aircraft 

along the route that has been entered in the FMS or RNAV 

system. Advanced avionics perform many functions and 

replace the navigator and pilot in most procedures. However, 

with the possibility of failure in any given system, the pilot 

must be able to perform the necessary functions in the event 

of an equipment failure. Pilot ability to perform in the event of 

equipment failure(s) means remaining current and proficient 

in accomplishing the manual tasks, maintaining control of 

the aircraft manually (referring only to standby or backup 

instrumentation), and adhering to the air traffic control (ATC) 

clearance received or requested. Pilots of modern advanced 

avionics aircraft must learn and practice backup procedures 

to maintain their skills and knowledge. Risk management 

principles require the flight crew to always have a backup 

or alternative plan, and/or escape route. Advanced avionics 

aircraft relieve pilots of much of the minute-to-minute 

tedium of everyday flights, but demand much more initial 

and recurrent training to retain the skills and knowledge 

necessary to respond adequately to failures and emergencies.

The FMS or RNAV unit and autopilot offer the pilot a 

variety of methods of aircraft operation. Pilots can perform 

the navigational tasks themselves and manually control 

the aircraft, or choose to automate both of these tasks and 

assume a managerial role as the systems perform their 

duties. Similarly, information systems now available in the 

cockpit provide many options for obtaining data relevant to 

the flight.

Advanced avionics systems present three important learning 

challenges as you develop proficiency:

1. How to operate advanced avionics systems

2. Which advanced avionics systems to use and when

3. How advanced avionics systems affect the pilot and 

the way the pilot flies

How To Operate Advanced Avionics 

Systems

The first challenge is to acquire the “how-to” knowledge 

needed to operate advanced avionics systems. This handbook 

describes the purpose of each kind of system, overviews the 

basic procedures required to use it, explains some of the 

logic the system uses to perform its function, and discusses 

each system’s general limitations. It is important to note 

that this handbook is not intended as a guide for any one 

manufacturer’s equipment. Rather, the aim is to describe the 

basic principles and concepts that underlie the internal logic 

and processes and the use of each type of advanced avionics 

system. These principles and concepts are illustrated with 

a range of equipment by different manufacturers. It is very 

important that the pilot obtain the manufacturer’s guide for 

each system to be operated, as only those materials contain 

the many details and nuances of those particular systems. 

Many systems allow multiple methods of accomplishing a 

task, such as programming or route selection. A proficient 

pilot tries all methods, and chooses the method that works 

best for that pilot for the specific situation, environment, 

and equipment. Not all aircraft are equipped or connected 

identically for the navigation system installed. In many 

instances, two aircraft with identical navigation units are 

wired differently. Obvious differences include slaved versus 

non-slaved electronic horizontal situation indicators (EHSIs) 

or primary flight display (PFD) units. Optional equipment is 

not always purchased and installed. The pilot should always 

check the equipment list to verify what is actually installed 

in that specific aircraft. It is also essential for pilots using 

this handbook to be familiar with, and apply, the pertinent 

parts of the regulations and the Aeronautical Information 

Manual (AIM).

Advanced avionics equipment, especially navigation 

equipment, is subject to internal and external failure. You 

must always be ready to perform manually the equipment 

functions which are normally accomplished automatically, 

and should always have a backup plan with the skills, 

knowledge, and training to ensure the flight has a safe 

ending.

Which Advanced Avionics Systems To 

Use and When

The second challenge is learning to manage the many 

information and automation resources now available to you 

in the cockpit. Specifically, you must learn how to choose 

which advanced cockpit systems to use, and when. There 

are no definitive rules. In fact, you will learn how different 

features of advanced cockpit avionics systems fall in and 

out of usefulness depending on the situation. Becoming 

proficient with advanced avionics means learning to use the 

right tool for the right job at the right time. In many systems, 

there are multiple methods of accomplishing the same 

function. The competent pilot learns all of these methods and 

chooses the method that works best for the specific situation, 

environment, and equipment. This handbook will help you 

get started in learning this important skill.
1-3

How Advanced Avionics Systems Affect 

the Pilot

The third challenge is learning how advanced avionics 

systems affect the pilot. The additional information provided 

by advanced avionics systems can affect the way you make 

decisions, and the ability to automate pilot tasks can place you 

in the role of system supervisor or manager. These ideas are 

presented throughout the handbook using a series of sidebars 

illustrating some of the issues that arise when pilots work 

with advanced avionics systems. This series is not a complete 

list; rather, its purpose is to convey an attitude and a manner 

of thinking that will help you continue to learn.

The Learning series provides tips that can help expedite 

mastery of advanced avionics. You will learn why taking the 

time to understand how advanced systems work is a better 

learning strategy than simply memorizing the button-pushing 

procedures required to use each system. The importance of 

committing to an ongoing learning process will be explained. 

Because of the limits of human understanding, together with 

the quirks present in computerized electronic systems of 

any kind, you will learn to expect, and be prepared to cope 

with, surprises in advanced systems. Avionics equipment 

frequently receives software and database updates, so you 

must continually learn system functions, capabilities, and 

limitations.

The Awareness series presents examples of how advanced 

avionics systems can enhance pilot awareness of the aircraft 

systems, position, and surroundings. You will also learn 

how (and why) the same systems can sometimes decrease 

awareness. Many studies have demonstrated a natural 

tendency for pilots to sometimes drift out of the loop when 

placed in the passive role of supervising an FMS/RNAV and 

autopilot. You will learn that one way to avoid this pitfall 

is to make smart choices about when to use an automated 

system, and when to assume manual control of the flight; 

how cockpit information systems can be used to keep you in 

touch with the progress of the flight when automated systems 

are used; and how some advanced cockpit systems can be 

set to operate in different modes, with each mode exhibiting 

a different behavior. Keeping track of which modes are 

currently in use and predicting the future behavior of the 

systems is another awareness skill that you must develop to 

operate these aircraft safely.

The Risk series provides insights on how advanced avionics 

systems can help you manage the risk faced in everyday 

flight situations. Information systems offer the immediate 

advantage of providing a more complete picture of any 

situation, allowing you to make better informed decisions 

about potential hazards, such as terrain and weather. Studies 

have shown that these same systems can sometimes have a 

negative effect on pilot risk-taking behavior. You will learn 

about situations in which having more information can 

tempt you to take more risk than you might be willing to 

accept without the information. This series will help you use 

advanced information systems to increase safety, not risk. As 

much as advanced information systems have improved the 

information stream to the cockpit, the inherent limitations of 

the information sources and timeliness are still present; the 

systems are not infallible.

When advanced avionics systems were first introduced, it 

was hoped that those new systems would eliminate pilot 

error. Experience has shown that while advanced avionics 

systems do help reduce many types of errors, they have also 

created new kinds of errors. This handbook takes a practical 

approach to pilot error by providing two kinds of assistance in 

the form of two series: Common Errors and Catching Errors. 

The Common Errors series describes errors commonly made 

by pilots using advanced avionics systems. These errors have 

been identified in research studies in which pilots and flight 

instructors participated. The Catching Errors series illustrates 

how you can use the automation and information resources 

available in the advanced cockpit to catch and correct errors 

when you make them.

The Maintaining Proficiency series focuses on pilot skills that 

are used less often in advanced avionics. It offers reminders 

for getting regular practice with all of the skills you need to 

maintain in your piloting repertoire.

Chapter Summary

This introductory chapter provided a broad perspective into 

the advanced avionics now found in many aircraft. This new 

equipment relieves the pilot of some tedious tasks while 

adding new ones and the requirement for more preflight 

study to learn the advanced capabilities and how to use 

the features. The pilot now has more and sometimes better 

means of fixing position, but has to contend with greater 

data loss when equipment breaks. It is important to maintain 

proficiency with the standby instruments and be proficient 

with the emergency tasks associated with the advanced 

avionics. Since these are electrical devices, the electrical 

generation and backup systems on the aircraft are even more 

important than ever.

Advanced avionics generally incorporate displays allowing 

pictures of the flight route as well as basic flight instrument 

data. While this can be most helpful to you, it can also 

lead you into areas where the pilot has no recourse, if any 

circumstances such as weather or equipment operation 

changes for the worse. You should never fly further into 

marginal conditions with advanced avionics than you would 
1-4

fly with conventional instruments. Advanced avionics do not 

enable an aircraft and pilot to break the laws of physics. 

Advanced avionics were designed to increase safety as well 

as utility of the aircraft. Safety is enhanced by enabling 

better situational awareness. Safety can be increased by 

providing more information for you in an easier to interpret 

presentation.

Safety of flight can be hampered if you are not aware of what 

data the presentation is displaying or confuses that data with 

other information. Safety of flight can be compromised if you 

attempt to use the advanced avionics to substitute for required 

weather or aerodynamic needs. Safety of flight can be negated 

if you attempt to learn the advanced avionics system while 

in flight. You should use advanced avionics to reduce risk. 

Proper use of checklists and systematic training should be 

used to control common error-prone tasks and notice errors 

before they become a threat to safety of flight.
2-1

Introduction

This chapter introduces the electronic flight instrument 

systems available with advanced avionics. You will see how 

electronic flight instrument systems integrate many individual 

instruments into a single presentation called a primary flight 

display (PFD). Since all flight instruments are combined in 

one integrated electronic flight instrument system, a number 

of enhancements to conventional flight instruments are now 

possible. In addition to learning to interpret the primary flight 

and navigation instruments, you must learn to recognize 

failures of the underlying instrument systems based on the 

indications you see in the cockpit. You must also maintain 

proficiency in using the backup/standby instruments that are 

still part of every advanced cockpit. 

Electronic Flight Instruments

Chapter 2
2-2

BRT

DIM

29.92"

5100 FT

Range

View

Aux

GPS2

Bearing

VLOC1

Nav

GPS1

Baro Set

29.92"

VSI Bug

500 FPM

Alt Bug

5020 FT

Hdg Bug

300°

Range View Hdg Sync

OAT

TAS

GS

7°C

157 KTS

140 KTS

SAV

DTK 020°

61.3 NM

00:26:18

VOR

113.10

BRG 323°

5200

5100

4900

50

40

20

00

160

150

140

130

14

4

3

2

20

10

10

20

20

10

10

20

ILS

ILS

20

10

5

0

-20

-10

-5

270°

Tape displays are used to 

depict airspeed and altitude.

An analog gauge is used to 

depict vertical speed.

Bearing

VLOC1

Nav

GPS1

SAV

DTK 020°

61.3 NM

00:26:18

VOR

113.10

BRG 323°

A curvilinear display is

used to show rate of turn.

Range View

Conventional symbology is used to depict

heading and navigational information.

BR

DI 5100 FT

20

A segmented triangle is 

used to show turn coordination.

Figure 2-1. A typical primary flight display (PFD).

Primary Flight Display (PFD)

A PFD presents information about primary flight instruments, 

navigation instruments, and the status of the flight in one 

integrated display. Some systems include powerplant 

information and other systems information in the same 

display. A typical primary flight display is shown in 

Figure 2-1.

Primary Flight Instruments

Flight instrument presentations on a PFD differ from 

conventional instrumentation not only in format, but 

sometimes in location as well. For example, the attitude 

indicator on the PFD in Figure 2-1 is larger than conventional 

round-dial presentations of an artificial horizon. Airspeed and 

altitude indications are presented on vertical tape displays

that appear on the left and right sides of the primary flight 

display. The vertical speed indicator is depicted using 

conventional analog presentation. Turn coordination is 

shown using a segmented triangle near the top of the attitude 

indicator. The rate-of-turn indicator appears as a curved line 

display at the top of the heading/navigation instrument in the 

lower half of the PFD.

Cross-Checking the Primary Flight Instruments

The PFD is not intended to change the fundamental way in 

which you scan your instruments during attitude instrument 

flying. The PFD supports the same familiar control and 

performance, or primary and supporting methods you use 

with conventional flight instruments. For example, when 

using the primary and supporting method to maintain level 

flight, the altimeter is still the primary instrument for pitch, 

while the attitude indicator is a direct indicator and the 

vertical speed indicator provides supporting information. 

However, you need to train your eyes to find and interpret 

these instruments in their new formats and locations.

Common Errors: Altitude Excursions and Fixation

Pilots experienced in the use of conventional flight 

instruments tend to deviate from assigned altitudes during 

their initial experience with the PFD, while they adjust to the 

tape display presentation of altitude information. Another 

common error is the tendency to fixate and correct deviations 

as small as one to two feet at the expense of significant 

deviations on other parameters.
2-3

90

80

70

60

50

40

4

3 6

TAS 64KT

G

Y

X

R

General cruising speed General cruising speed

Best rate of climb speed

Best angle of climb speed Best angle of climb speed

Rotation speed

Flap range

Airborne airspeed Ground airspeed

Figure 2-2. Vertical airspeed (tape type) indicator.

40

30

20

10

40

30

20

10

050 060 070 080 090 100 110 120

1040 B

Figure 2-3. Attitude indicator with symbols to assist in recovery 

from unusual attitude.

Enhancements to the Primary Flight Instruments

Some PFDs offer enhancements to the primary flight 

instruments. Figure 2-2 shows an airspeed indicator that 

displays reference speeds (V-speeds) and operating ranges 

for the aircraft. Operating ranges are depicted using familiar 

color coding on the airspeed indicator. One negative human 

factor concerning this type of presentation should be 

remembered: while most of the displays are intuitive in that 

a high indication (such as climb pitch or vertical speed) is 

corrected by lowering the nose of the aircraft, the situation 

with the usual airspeed vertical tape is the opposite. In most 

current displays, the lower speeds are at the lower side of the 

airspeed indicator, while the upper or higher speeds are in the 

top portion of the airspeed display area. Therefore, if a low 

airspeed is indicated, you must lower the nose of the aircraft 

to increase, which is counterintuitive to the other indications.

Figure 2-3 shows an attitude indicator that presents red 

symbols to assist in recovery from unusual attitudes. The 

symbols on the display recommend a lower pitch attitude. 

Other valuable enhancements include trend indicators, which 

process data to predict and display future performance. For 

example, some systems generate “trend vectors” that predict 

the aircraft’s airspeed, altitude, and bank angle up to several 

seconds into the future.

Primary Flight Instrument Systems

The primary flight instruments that appear on a PFD are driven 

by instrument sensor systems that are more sophisticated than 

conventional instrument systems. The attitude of the aircraft 

may be measured using microelectronic sensors that are more 

sensitive and reliable than traditional gyroscopic instruments. 

These sensors measure pitch, roll, and yaw movements away 

from a known reference attitude. Aircraft heading may be 

determined using a magnetic direction-sensing device such 

as a magnetometer or a magnetic flux valve.

Attitude and heading systems are typically bundled together as 

an attitude heading reference system (AHRS), which contains 

not only the sensors used to measure attitude and heading, 

but also a computer that accepts sensor inputs and performs 

calculations. Some AHRSs must be initialized on the ground 

prior to departure. The initialization procedure allows the 

system to establish a reference attitude used as a benchmark 

for all future attitude changes. As in any navigation system, 

attitude heading reference systems accumulate error over 

time. For this reason, AHRSs continually correct themselves, 

using periods of stable flight to make small corrections to the 

reference attitude. The system’s ability to correct itself can 

be diminished during prolonged periods of turbulence. Some 

AHRSs can be reinitialized in flight, while others cannot. The 

pilot must become familiar with the operating procedures and 

capabilities of a particular system.

Information on altitude and airspeed is provided by sensors 

that measure static and ram air pressure. An air data computer 

(ADC) combines those air pressure and temperature sensors 

with a computer processor that is capable of calculating 

pressure altitude, indicated airspeed, vertical speed, and 

true airspeed. An air data attitude heading reference system 

(ADAHRS) combines all of the systems previously described 

into one integrated unit.

Navigation Instruments

PFDs and multi-function displays (MFDs) typically combine 

several navigation instruments into a single presentation. 

The instrument appearing at the bottom of the PFD in 

Figure 2-1 contains two navigation indicators: a course 

deviation indicator and a bearing pointer. These instruments 

can be displayed in a variety of views, and can be coupled 

to many of the navigation receivers (e.g., instrument landing 

system (ILS), global positioning system (GPS), very high 

frequency (VHF) omnidirectional range (VOR)) available 
2-4

20

10

20

10

10 10

050 060 070 080 090 100 110 120

880 B

Figure 2-4. An attitude indicator with HITS display symbology.

in the aircraft. The pilot must, therefore, be sure to maintain 

an awareness of which navigation receivers are coupled to 

each navigation indicator.

MFDs may provide the same type of display as installed in 

the PFD position, but are usually programmed to display just 

the navigation information with traffic, systems data, radar 

Stormscope®/ Strikefinder®. However, in many systems, the 

MFD can be selected to repeat the information presented 

on the PFD, thereby becoming the standby PFD. The pilot 

should be absolutely certain of and proficient with the standby 

modes of operation.

More sophisticated PFDs present three-dimensional (3D) 

course indications. The primary flight display in Figure 2-4

shows a 3D course indication, called a highway-in-the-sky 

(HITS) display. This display provides both lateral and vertical 

guidance along the planned flight path, while simultaneously 

presenting a 3D picture of the surrounding terrain. Keeping 

the symbolic aircraft within the green boxes on the display 

ensures that the flight remains within the selected GPS 

route and altitude. Consult the AFM and avionics manual 

for required navigational configuration for this function to 

be available.

Other Flight Status Information

An important feature of the PFD is its ability to gather 

information from other aircraft systems and present it to 

the pilot in the integrated display. For example, the PFD in 

Figure 2-5 presents many useful items about the status of the 

flight. The top bar shows the next waypoint in the planned 

flight route, the distance and bearing to the waypoint, and the 

current ground track. The outside air temperature (OAT) is 

shown in the lower left corner of the display. The transponder 

code and status are shown with the current time in the lower 

right corner. This PFD also allows the pilot to tune and 

identify communication and navigation radio frequencies at 

the top of the display.

Making Entries on the PFD

PFDs have evolved and have become more than flight 

displays in many cases. The amount of data available for 

display can overwhelm the pilot with data. Therefore, 

many manufacturers have integrated data control and 

display controls into the display unit itself, usually around 

the perimeter of the unit. These data and display controls 

provide different ways of selecting necessary information, 

such as altimeter settings, radials, and courses. Figure 2-6

illustrates two different kinds of controls for making entries 

on primary flight displays. Some PFDs utilize a single knob 

and button-selectable windows to determine which entry is 

to be made. Other PFDs offer dedicated knobs for making 

entries; quantities are sometimes entered in one location and 

displayed in another. Still other units retain all controls on 

a separate control panel in the console or on the instrument 

panel.

Failures and the Primary Flight Display

Instrument System Failure

The competent pilot is familiar with the behavior of each 

instrument system when failures occur, and is able to 

recognize failure indications when they appear on the primary 

flight display. Manufacturers typically use a bold red “X” 

over, or in place of, the inoperative instruments and provide 

annunciator messages about failed systems. It is the pilot’s 

job to interpret how this information impacts the flight.

The inoperative airspeed, altitude, and vertical speed 

indicators on the PFD in Figure 2-7 indicate the failure of 

the air data computer. As do all electronic flight displays, 

navigation units (area navigation (RNAV)/flight management 

systems (FMS)) and instrumentation sensors rely on steady, 

uninterrupted power sources of 24 VDC or 12 VDC power. 

Any interruptions in the power supplies, such as alternator/

regulator failure, drive belt failure, lightning strikes, wiring 

harness problems, or other electrical failures, can completely 

disrupt the systems, leading to erratic indications or 

completely inoperative units. Especially in standard category 

aircraft not designed or built with the redundancy inherent 

in transport category aircraft, a proficient and prudent pilot 

plans for failures and has alternate plans and procedures 

readily available.
2-5

XPDR 5537 IDNT LCL23:00:34

VOR 1

270°

2

1

1

2

4300

4200

4100

4000

3900

3800

4300

60

20

4000

4000

130

120

110

90

80

70

1

100

9

TAS 100KT

OAT 7°C

ALERTS

NAV1 108.00 113.00 NAV2 108.00 110.60134.000 118.000 COM1

123.800 118.000 COM2

NAV1 108.00 113.00 WPTECA DIS 12.0NM DTK 049° TRK 360°

Next waypoint in the planned route

134.000 118.000 COM1

Current track of aircraft

S

Time

537 IDNT LCL23:00:34

Transponder code

OAT 7°C

Outside air temperature

PT ECA DIS 12.0NM DTK 049° TRK 360° 1

Distance to the active waypoint Cu

Figure 2-5. PFD flight status items.

XPDR 5537 IDNT LCL23:00:34

2

1

1

2

4300

4200

4100

4000

3900

3800

4300

60

20

4000

4000

ALERTS

134.000 118.000 COM1

123.800 118.000 COM2

DTK 049° TRK 360°

BRT

DIM

29.92"

5100 FT

Baro Set

29.92"

VSI Bug

500 FPM

Alt Bug

5020 FT

Hdg Bug

300°

Hdg Sync

5100

5000

4900

50 40

20

00

20

10

10

20

20

10

10

20

ILS

ILS

20

10

5

0

-20

-10

-5

270°

Button selects window.

Hdg Sync

Knob enters value.

Baro

29.9

VSI 

Window displays values. 500

Some primary flight displays use a single 

knob and button selectable windows to 

determine which entry is to be made.

2

1

4300

4200

4100

60

4000

Other primary flight displays offer 

dedicated knobs for making entries.

Figure 2-6. Making entries on a PFD.
2-6

BRT

DIM

29.92"

 0 FT

Range

View

Aux

OFF

Bearing

GPS2

Nav

GPS1

Baro Set

29.92"

VSI Bug

0 FPM

Alt Bug

6500 FT

Hdg Bug

300°

Range View Hdg Sync

OAT

TAS

GS

7°C

- - - KTS

135 KTS

0Q5

BRG 270° 32.8 NM

00:14:34

20

10

10

20

20

10

10

20

270°

Figure 2-7. A PFD indicating a failed air data computer.

BRT

DIM

29.92"

 0 FT

FAST

ERECT

Range View Hdg Sync

TAS

GS

143 KTS

135 KTS

5100

5000

4900

50 40

20

00

160

150

140

130

14

4

3

2

20

10

5

0

-20

-10

-5

M a i n t a i n s t r a i g h t a n d

l e v e l  i g h t , t h e n p r e ss

t h e “ FA S T E R E C T ” b u t t o n .

R E F E R T O B A C K U P G A U G E S

[ A T T I T U D E F A I L ]

Figure 2-8. A PFD indicating a failed AHRS.

The inoperative attitude indicator on the PFD in Figure 2-8

indicates the failure of the AHRS. By understanding which 

flight instruments are supported by which underlying systems 

(e.g., ADC, attitude heading reference system (AHRS)), you 

can quickly understand the source of a failure. It is important 

to be thoroughly familiar with the operation of the systems 

and the abnormal/emergency procedures in the pilot’s 

operating handbook (POH), aircraft flight manual (AFM), 

or avionics guides. 

PFD Failure

The PFD itself can also fail. As a first line of defense, some 

systems offer the reversion capability to display the PFD 

data on the multi-function display (MFD) in the event of a 

PFD failure.

Every aircraft equipped with electronic flight instruments 

must also contain a minimal set of backup/standby 

instruments. Usually conventional “round dial instruments,” 

they typically include an attitude indicator, an airspeed 

indicator, and an altimeter. Pilots with previous experience in 

conventional cockpits must maintain proficiency with these 

instruments; those who have experience only in advanced 

cockpits must be sure to acquire and maintain proficiency 

with conventional instruments.

Awareness: Using Standby Instruments

Because any aircraft system can fail, your regular proficiency 

flying should include practice in using the backup/standby 

instrumentation in your aircraft. The backup/standby 

instrument packages in technically advanced aircraft pro vide 

considerably more information than the “needle, ball, and 

airspeed” indications for partial panel work in aircraft with 

conventional instrumentation. Even so, the loss of primary 

instrumentation creates a distraction that can increase the 

risk of the flight. As in the case of a vacuum failure, the wise 

pilot treats the loss of PFD data as a reason to land as soon 

as practicable.

Essential Skills

1. Correctly interpret flight and navigation instrument 

information displayed on the PFD.

2. Determine what “fail down” modes are installed and 

available. Recognize and compensate appropriately 

for failures of the PFD and supporting instrument 

systems.

3. Accurately determine system options installed and 

actions necessary for functions, data entry and 

retrieval.

4. Know how to select essential presentation modes, 

flight modes, communication and navigation modes, 

and methods mode selection, as well as cancellation.

5. Be able to determine extent of failures and reliable 

information remaining available, to include procedures 

for restoring function(s) or moving displays to the 

MFD or other display.

Chapter Summary

The primary flight instruments can all be displayed 

simultaneously on one reasonably easy-to-read video monitor 

much like the flat panel displays in laptop computers. These 

displays are called primary flight displays (PFDs). You must 

still cross-check around the panel and on the display, but more 
2-7

information is available in a smaller space in easier to read 

colors. These convenient displays receive data from sensors 

such as magnetometers or magnetic flux valves to determine 

heading referenced to magnetic north. The attitude (pitch and 

roll) of the aircraft is sensed by the attitude heading reference 

system (AHRS) and displayed as the attitude gyro would 

be in conventional instrumentation. The altitude, airspeed, 

and outside temperature values are sensed in the air data 

computer (ADC) and presented in the PFD on vertical scales 

or portions of circles.

The multi-function display (MFD) can often display the 

same information as the PFD and can be used as a backup 

PFD. Usually the MFD is used for traffic, route selection, 

and weather and terrain avoidance. However, some PFDs 

also accommodate these same displays, but in a smaller view 

due to the primary flight instrument areas already used in 

the display. You must learn and practice using that specific 

system.

It is important to be very careful in the selection (programming) 

of the various functions and features. In the event of failures, 

which have a large impact on flight safety and situational 

awareness, you must always be ready and able to complete 

the flight safely using only the standby instruments.
2-8
3-1

Introduction

This chapter introduces the topic of navigation in the advanced 

cockpit. You will learn about flight management systems 

(FMS) and area navigation (RNAV) systems, an increasingly 

popular method of navigating that allows pilots to make more 

efficient use of the national airspace system. The increasing 

number of users is attributable to more economical and 

accurate satellite signal receivers and computer chips. RNAV 

systems may use VHF omnidirectional range (VOR); distance 

measuring equipment (DME) (VOR/DME, DME/DME) 

signals; inertial navigation systems (INS); Doppler radar; 

the current version of LOng RAnge Navigation (LORAN), 

LORAN-C (and eLORAN, as it becomes operational); 

and the global positioning system (GPS), to name a few. 

Ground-based LORAN-C is a reliable complement to spacebased GPS systems (United States Department of Defense 

(DOD) GPS, Russian Global Navigation Satellite System 

(GLONASS), and European Galileo in the future).

Navigation

Chapter 3
3-2

Wide area augmentation system (WAAS) of the standard GPS 

furnishes additional error correction information, allowing 

Category I precision approaches (similar to basic instrument 

landing system (ILS) minimums) to units equipped to receive 

and integrate the data. Most general aviation pilots learn 

to work with an FMS unit primarily using GPS signals, 

possibly with WAAS and LORAN-C options. Older RNAV 

units made use of VOR and DME information to compute 

positions within range of the navaids. Newer units contain 

databases that allow route programming with automatic 

sequencing through the selected navigation points. Therefore, 

flight management system (FMS) is the best descriptor of the 

current GPS units integrating VOR (and DME, optionally) 

to allow point-to-point navigation outside established flight 

routes. You will learn to use the FMS data entry controls to 

program a flight route, review the planned route, track and 

make modifications to the planned route while en route, plan 

and execute a descent, and fly an approach procedure that is 

based solely on RNAV signals. You should remember that 

FMS/RNAV units requiring external signals for navigation 

are usually restricted to line-of-sight reception (LORAN-C 

being somewhat of an exception). Therefore, navigation 

information in valleys and canyons that could block satellite 

signals may be severely restricted. Users in those areas 

should pay particular attention to the altitude or elevations 

of the satellites when depending on space-based signals and 

plan flight altitudes to ensure line-of-sight signal reception. 

Review the GPS unit’s documentation sufficiently to 

determine if WAAS is installed and how WAAS corrections 

are indicated.

You will learn how the FMS can automatically perform many 

of the flight planning calculations that were traditionally 

performed by hand, and the importance of keeping flight 

planning skills fresh. You will also discover how the FMS can 

help you detect and correct errors made in the flight planning 

process, how the complexities of the FMS make some new 

kinds of errors possible, and techniques to help avoid them.

Last, you will see how advanced cockpit systems can be used 

to navigate using ground-based navigation facilities such as 

VOR and DME. Maintaining pilot skills using ground-based 

navigation facilities is a simple matter of occasionally using 

them as the primary means of navigation, and as a backup to 

verify position and progress when RNAV is used.

Area Navigation (RNAV) Basics

RNAV Concept

Area Navigation (RNAV) is a navigation technique that 

allows pilots to navigate directly between any two points 

on the globe. Using RNAV, any location on the map can be 

defined in terms of latitude and longitude and characterized 

as a waypoint. Onboard RNAV equipment can determine 

the present position of the aircraft. Using this positional 

information, the equipment can calculate the bearing and 

distance to or from any waypoint and permit navigation 

directly between any two waypoints. In this way, RNAV 

overcomes a fundamental limitation of conventional 

navaid point-to-point navigation techniques, which require 

navigating between electronic navigation transmitters on the 

ground. The following examples illustrate this limitation.

An aircraft equipped with conventional VOR receivers is 

positioned at Point A as shown in the diagram at the top 

of Figure 3-1, and the pilot wishes to navigate directly to 

Point B. Although there appear to be a few VOR stations in 

the vicinity of the aircraft, it is not clear whether reception 

is possible from the aircraft’s present position. If the VOR 

stations are within reception range, the pilot has two choices: 

(1) fly to intercept the closest airway, then track it to the 

intersection; or (2) fly to intercept an extension of the radial 

that defines Point B (assuming reception is possible). Neither 

alternative provides the pilot with a means of flying directly 

to the intersection.

Suppose the same aircraft is positioned at Point A as shown 

at the bottom of Figure 3-1 and the pilot wishes to navigate 

directly to Point C, which is neither a VOR station nor airway 

intersection. This pilot has an even more difficult situation. 

Assuming the VOR stations are within reception range, the 

pilot needs to create two makeshift airways using a navigation 

plotter and chart, fly to intercept one of them, then track 

to Point C (which the pilot has defined as the intersection 

between the two courses). Flying a direct course to Point C 

with any degree of accuracy is not possible. Since RNAV 

systems are not bound by these limitations, the entire airspace 

is available for navigational use. The national airspace system 

can thus accommodate more aircraft. However, when the 

pilot leaves the established airways, he or she also leaves the 

guaranteed obstruction clearances designed into the airway 

system. Always plan flights above the maximum elevation 

figure (MEF) displayed on sectional charts when flying 

off airways, and be aware that manmade obstructions such 

as towers may not be added to charts for some time after 

construction. If flying a new routing, allow for construction, 

which may not be published yet.

FMS/RNAV Computer

RNAV is possible through use of a variety of navigation 

facilities and installed aircraft equipment operated in the 

U.S. National Airspace System. This handbook focuses 

on the more common GPS RNAV, a satellite-based radio 

navigation system available to aircraft equipped with a GPS 

receiver. In addition to its ability to receive signals from 

GPS satellites, a GPS receiver also contains a computer 

processor and a navigation database that includes much of the 
3-3

The pilot must define Point C as the intersection 

between two radials, fly to intercept one of them, 

then track the radial to Point C.

C A

B

A

2. The aircraft can intercept

 the closest airway and 

track it to Point B...

A

1. The aircraft positioned at

 Point A wishes to navigate 

directly to Point B.

3. ...or attempt to intercept 

an extension of the 

 radial that defines

 Point B.

A

1. The aircraft positioned at

 Point A wishes to navigate 

directly to Point C.

Figure 3-1. Limitations of conventional navigation.

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK

TK

. nm

LEG

APT 1 VOR NDB INT USR ACT NAV FPL SET AUX

The display allows you to view information stored in the FMS.

Controls such as buttons and knobs 

allow you to make entries into the FMS.

Figure 3-2. FMS display and controls.

information found on en route and terminal procedure charts. 

The newer, more capable units provide map displays, traffic 

and weather overlays of data, contain VOR/DME/localizer/

glideslope receivers, and can compute fuel usage in addition 

to the navigation route information. For this reason, the more 

descriptive term “FMS” is used in this handbook to refer to 

these GPS receivers.

An FMS allows you to enter a series of waypoints and 

instrument procedures that define a flight route. If these 

waypoints and procedures are included in the navigation 

database, the computer calculates the distances and courses 

between all waypoints in the route. During flight, the FMS 

provides precise guidance between each pair of waypoints 

in the route, along with real-time information about aircraft 

course, groundspeed, distance, estimated time between 

waypoints, fuel consumed, and fuel/flight time remaining 

(when equipped with fuel sensor(s)).

FMS/RNAV/Autopilot Interface: Display and 

Controls

Every avionics device has a display and a collection of 

buttons, keys, and knobs used to operate the unit. The display 

allows the device(s) to present information. The controls 

allow the pilot to enter information and program the avionics 

to accomplish the desired operations or tasks. The display and 

controls for a typical FMS are shown in Figure 3-2.

Accessing Information in the FMS

FMS units contain much more information than they can 

present on the display at any one time. Information pertaining 

to some topics often extends beyond what can be presented on 

a single page. Page groups, or chapters, solve this problem by 

collecting all of the pages pertaining to the same topic. Each 
3-4

A B C D

E F G H

I J K L

M N O P

Q R S T

U V W X

Y Z SPC BKSP

PFD MFD

NAV COM

PFD MENU

FPL PROC

SEL CLR ENT

DFLT MAP

SOFTKEY SELECT

EMERG

PUSH CRSR/PUSH 1-2

FMS/

NAV-COM

PUSH PAN

RANGE

− +

1 2 3

4 5 6

7 8 9

− 0 +

Figure 3-4. An FMS keypad.

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK

TK

. nm

LEG

APT 1 VOR NDB INT USR ACT NAV FPL SET AUX

CRSR

Pages appear on the display and organize 

information by topic. Some topics span 

several pagers to form chapters.

An annunciation is provided to show

the page that is currently displayed.

The first page of the Airport chapter 

is indicated here.

Individual pages are accessed 

by rotating the inner knob.

Some chapters are accessed

by rotating the outer knob.

Some chapters are accessed 

by pressing buttons on the front 

of the computer.

Figure 3-3. Pages and page groups (chapters).

page presents information about a particular topic, and bears 

a page title reflecting its content. For example, the airport 

chapter may be divided into several airport pages, each page 

displaying different information about that airport. One page 

might be navaids. Another page might be the airport taxiway 

diagram. Yet another airport page might indicate available 

services and fixed-base operators. Review the documentation 

for that specific unit and installation to determine what 

information and levels of data are available and require 

updates. Usually, only one page can be displayed at a time. 

The airport page is displayed on the FMS in Figure 3-3.

Figure 3-3 shows how to access pages and chapters on one 

manufacturer’s FMS. Different FMS units have different 

ways of allowing the pilot to switch between chapters and 

pages, and different ways of informing the pilot which chapter 

and page is currently displayed.

Making Entries in the FMS

To enter data, you use the FMS buttons (keyboard or 

individual) and knob controls, or a data source, such as disk 

media or keypad, as shown in Figure 3-4.

FMS units that do not feature keypads typically require the 

pilot to make entries using the same knobs to move among 

chapters and pages. In this case, the knobs have multiple 

purposes and, thus, have different modes of operation. To 

use the knobs for data entry, you must first activate what 

some manufacturers call the “cursor” (or “data entry”) 

mode. Activating the cursor mode allows you to enter data 

by turning the knob. In other units, after activating the data 

entry mode, entries are made by pushing buttons.

Figure 3-5 illustrates the use of cursor mode to enter the 

name of an airport using one FMS. Pressing the inner knob 

engages cursor mode. A flashing cursor appears over one of 

the items on the page, indicating that it is ready for editing. 

Then, the inner knob is used to dial letters and numbers; 

the outer knob is used to move the flashing cursor between 

items on the page.

Integrated Avionics Systems

Some systems integrate FMS/RNAV display and controls 

into existing cockpit displays usually called PFDs and MFDs. 

In this case, there is no separate display to point to and call the 

RNAV display. Figure 3-6 shows a system that uses the PFD 

to provide controls and a display for the FMS. This type of 

system utilizes the same concepts and procedures described 

above to access and enter into the navigation computer.
3-5

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

WPT

114.10

119.000

121.600

APT 5 RING

Flashing cursor Flashing cursor

2 Use the inner knob to dial letters and numbers.

Press the inner knob to engage cursor mode. 

A flashing cursor then appears over one of the 

items on the page, indicating that it is ready 

for editing.

1

3 Use the outer knob to move the flashing 

cursor between items on the page.

Figure 3-5. Making entries using cursor mode.

GPS ENR

274°

2

1

1

2

4300

4200

4100

4000

3900

3800

4300

60

20

4000

4000

130

120

110

90

80

70

1

100

9

TAS 100KT

ALERTS

NAV1 113.90 115.60 NAV2 112.90 112.30122.900 122.800 COM1

118.425 121.600 COM2

WPT KBFK DIS 23.5NM DTK 274° TRK 274°

TRAFFIC

GAG

KAVK

KBFK 274 23.9NM

DTK DIS

PFD pages appear here.

PFD controls

FLIGHT PLAN

KAVK / KBFK

Figure 3-6. An integrated avionics system.

Learning: Simulators for Learning and Practice

Avionics simulators can assist the pilot in developing 

proficiency in the advanced cockpit. Some manufacturers 

offer computer-based simulators that run on a personal 

computer and let the pilot learn how the unit organizes 

and presents information, as well as practice the buttonpushing and knob-twisting procedures needed to access and 

enter data. One very important function that every pilot of 

programmable avionics should learn and remember is how 

to cancel entries and functions. Turbulent flight conditions 

make data entry errors very easy to make. Every pilot should 

know how to revert quickly to the basic aircraft controls and 

functions to effect recovery in times of extreme stress. These 

programs are extremely useful not only for initial learning, 

but also for maintaining proficiency. For more sophisticated 

training, many manufacturers of flight simulators and flight 

training devices are now developing devices with advanced 

cockpit systems. These training platforms allow the pilot to 

work through realistic flying scenarios that teach not only 

the operating procedures required for each system, but also 

how to use the systems most effectively.

Flight Planning

Preflight Preparation

Title 14 of the Code of Federal Regulations (14 CFR) part 91, 

section 91.103 requires you to become familiar with all 

available information before beginning a flight. In addition 

to the required checks of weather, fuel, alternate airports, 

runway lengths, and aircraft performance, there are a number 

of requirements unique to the use of avionics equipment. 

Many of these considerations apply specifically to the use of 

FMS/RNAV under instrument flight rules (IFR). However, 
3-6

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

AMERICAS AERO Database

 Expires 15 FEB 2006

AMERICAS LAND Database 

 Created 06 OCT 2004

Acknowledge?

Check the expiration data for the navigation

database when the RNAV powers up.

Figure 3-7. Checking the navigation database.

a check of these same requirements before operating under 

visual flight rules (VFR) enhances safety and enforces good 

habit patterns, which have been proven to greatly enhance 

aviation safety.

FMS/RNAV Approval for IFR Operations

Only some FMS/RNAV units are approved for IFR navigation, 

and it is important to make this determination before flying 

with any particular unit. Sometimes, this limitation is based 

on the installation (i.e., method of installation, qualifications 

of installer), aircraft approval, availability of approved 

maintenance, and geographic location. No hand-held GPS 

unit is approved for IFR navigation, and many panel-mounted 

units are restricted to VFR use only.

Even when an FMS is approved for IFR, the installation of 

the system in that specific aircraft must also be approved. 

Even if you have an IFR-approved FMS unit, you may not 

use it for IFR navigation unless the installation is approved 

as well. This approval process usually requires a test flight 

to ensure that there are no interfering inputs, signals or 

static emanating from the aircraft in flight. RNAV units that 

do not meet all of these requirements may still be used as 

situation enhancing navigation resources when operating 

under instrument flight rules.

The first place to check when determining IFR certification 

for an FMS is the Pilot’s Operating Handbook (POH) or 

Aircraft Flight Manual (AFM). For every aircraft with an 

IFR approved FMS/RNAV unit, the AFM explicitly states 

that the unit has been approved for IFR navigation and what 

IFR operations are specifically authorized for that installation.

Navigation Database Currency

The navigation database contained in the FMS must be 

current if the system is to be used for IFR navigation and 

approaches. Some units allow en route IFR operations if the 

navigation waypoints are manually verified by the pilot and 

accepted. The effective dates for the navigation database 

are shown on a start-up screen that is displayed as the FMS 

cycles through its startup self-test. Check these dates to ensure 

that the navigation database is current. Figure 3-7 shows the 

start-up screen and effective dates for one popular FMS.

Alternative Means of Navigation

To use some GPS-based RNAV units (those certified under 

Technical Standard Order (TSO) 129) for IFR flight, an 

aircraft must also be equipped with an approved and alternate 

means of IFR navigation (e.g., VOR receiver) appropriate 

to the flight. Ensure that this equipment is onboard and 

operational, and that all required checks have been performed 

(e.g., 30-day VOR check).

The avionics operations manual/handbook should state the 

certification status of the installed system. The supplements 

to the AFM should state the status of the installed equipment, 

including the installed avionics. Most systems require that the 

advanced avionics manuals be on board as a limitation of use.

NOTAMs Relevant to GPS

There are numerous notices to airmen (NOTAMs) that 

apply specifically to users of navigation aids. For example, 

when anomalies are observed in the behavior of the global 

positioning system, or when tests are performed, a GPS 

UNRELIABLE NOTAM is issued. Similarly, published 

instrument procedures that rely on RNAV equipment 

sometimes become “Not Available” when safety concerns 

arise, such as ground-based interference. It is important to 

check all NOTAMs prior to IFR flights and, especially, 

GPS and WAAS NOTAMs before flying. Remember, when 

talking to a flight service station (FSS)/automated flight 

service station (AFSS) briefer, you must specifically request 

GPS/WAAS NOTAMs.

GPS Signal Availability

GPS-based RNAV equipment that uses the DOD GPS relies 

on adequate signal reception throughout the course of a 

flight. Signal reception becomes especially critical during 

instrument approaches when signal reception criteria become 

more stringent. Signal reception is generally predictable, and 

you can request information on likely signal reception for 

the destination airport in the preflight briefing from Flight 

Service. Many GPS RNAV units include a feature called 

receiver autonomous integrity monitoring (RAIM) that 

allows you to view predictions about future signal reception 

at specific locations. WAAS-enabled receivers do not have 

this restriction or limitation due to the error corrections 

available from the WAAS. WAAS is a form of differential 

GPS (DGPS) providing enhanced position accuracy. Each 

Wide Area Reference Station (WRS) provides correction 

data to a Wide Area Master Station (WMS), which computes 

a grid of correction data to be uplinked to a geostationary 

satellite (GEO) from a Ground Earth Station (GES). The 

geostationary satellite transmits the correction data (and 

also navigation data) to the user on the L1 GPS navigation 
3-7

Aircraft Number:

Check Points

(Fixes)

Ident.

Freq. Leg

Fuel Dist. GS

Est.

ETE ETA

Act. ATE ATA

Time Off

Leg

Rem. Rem.

48

060

049

049

084

084

096

352

5000

5000

3000

2000

2000

MDA

720

3000

90

81

120

120

1000

90

90

0.4

21

1.2

1.1

0.7

0.6

0.6

4.5

21.5

18

15

8

55

61

61

57.1

39.1

24.1

16.1

10.6

0

41.9

45.9

44.7

43.6

42.9

42.3

41.3

0.03

016

0.09

0.08

0.05

0.04

0.04

78.6.

Course

Route

Attitude Mag

Crs. DEP

12L3

SJC

1141

ECA

116.0

ECA

116.0

ECA

116.0

ECA

116.0

ECA

116.0

LIN

114.8

Dep:

N1361M KSQL

Dest:

027

Dest:

11/06/06

C – 027

KSQL

TWR 119.0

R – Direct SUNOL, V195 ECA, Direct 027

A – CLB 5000

F – 12L3

T – 0356

Clearance:

Estimated Time En Route = 0.49

SUNCL

TRACY

ECA (IAF)

MOTER

ZOSON (FAF)

RW 10 (MAP)

WRAPS (HOLD)

NAVIGATION LOG

Figure 3-8. A conventional flight plan.

frequency (1575.42 MHz). The user GPS receiver uses the 

downlink WAAS data to correct received navigation data. 

The goal of WAAS is to obtain at least a 7-meter horizontal 

and vertical accuracy.

Local Area Augmentation System (LAAS), when it becomes 

available, is another DGPS mode which is designed to 

provide 1-meter accuracy for precision approaches. It uses 

a local error VHF transmitter near the runway providing a 

direct link from the sensor to the aircraft GPS receiver.

Alternate Airports

It is very important to know what equipment is installed 

in the aircraft. GPS-based FMS/RNAV units certified to 

TSO-C145A or TSO-146A may be used when an alternate 

airport is required in the flight plan for the approaches at the 

destination and alternate airport if the WAAS is operational. 

No other navigation avionics would be required. Units 

certified under TSO-C129 are not authorized for alternate 

approach requirements. The aircraft must have stand-alone 

navigation equipment, such as VOR, and there must be an 

approved instrument approach at the alternate airport based 

on that equipment. (However, once diverted to the alternate 

airport, the pilot could fly a GPS-based approach there, as 

long as there is an operational, ground-based navaid and 

airborne receiver in the aircraft for use as a backup.)

Aircraft Equipment Suffixes

Since air traffic control (ATC) issues clearances based 

on aircraft equipment suffixes, consult the Aeronautical 

Information Manual (AIM) Table 5-1-2, Aircraft Suffixes, 

to ensure that the flight plan includes the correct equipment 

suffix for a particular aircraft. Use the suffix that corresponds 

to the services and/or routing that is needed. For example, if 

the desired route or procedure requires GPS, file the suffix as 

“/G” or “/L,” as appropriate to that aircraft, and operational 

equipment installed. (Remember that minimum equipment list 

(MEL) deferred items can change the status of the aircraft.)

Suitability of an RNAV Unit for VFR Flight

Even when an RNAV receiver is to be used only for 

supplemental (“supplemental” meaning a situation enhancing 

source of navigation information, but not the primary or sole 

source of navigation information) navigation information 

during VFR flight, you should consider these suitability 

factors in the interest of safety. The use of an expired 

navigation database might cause you to stray into airspace 

that was not yet designated at the time the expired navigation 

database was published. Some VFR-only GPS units do not 

alert you when signal reception has faded, which could 

lead to reliance on erroneous position information. Lack of 

attention to the “see and avoid” basic principle of every visual 

meteorological conditions (VMC) flight means too much 

time spent focused inside the cockpit on advanced avionics 

versus staying synchronized with the flight events, possibly 

creating a life-threatening total flight situation.

Programming the Flight Route

The procedures used to program an FMS with your intended 

route of flight are fundamentally the same in all types of 

systems, yet many differences are evident. The primary 

difference between systems lies mainly in the “knob or 

switchology”—the specific design features, operational 

requirements, and layout of the controls and displays used 

to operate the avionics. Be thoroughly familiar with the 

procedures required for each FMS or RNAV unit to be used.

Suppose you have planned a flight from San Carlos Airport 

(KSQL) to Oakdale Airport (O27), as shown in the flight 

plan appearing in Figure 3-8. The planned route proceeds 

directly to SUNOL intersection, then follows V195 until 

reaching ECA, the initial approach fix for the GPS Runway 

10 approach into Oakdale. The distances, bearings, estimated 

times en route, and fuel requirements for the flight have 

all been calculated. The next step is to enter some of these 

details into the FMS.
3-8

NOT FOR USE IN NAVIGATION

TWENTYNINE

PALMS

POMONA RAVON CAJON

REANS

YUCCA 073° 254°

Figure 3-10. Entering waypoints along an airway.

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

FPL

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

VLOC

114.10

116.00

COM

119.000

121.600

FPL

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

VLOC

114.10

116.00

COM

119.000

121.600

W A Y P O I N T I N F O R M A T I O N

TO ACCEPT

PRESS ENT

SW USA

SAN CARLOS

SAN CARLOS CA

KSQL_

W122

FPL

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

VLOC

114.10

116.00

COM

119.000

121.600

KSQL

KSQL

COM ACTIVE FLIGHT PLAN RING W A Y P O I N T I N F O R M A T I O N

Use the inner and outer knobs to enter the name 

of the waypoint, then press the ENT button.

RING COM ACTIVE FLIGHT PLAN

The waypoint now appears in your flight route 

and the FMS is ready to accept more waypoints.

RING

C

COM ACTIVE FLIGHT PLAN

119 000

Engage cursor mode when the flight plan page is selected.

Figure 3-9. Entering en route waypoints in the flight plan.

The Flight Planning Page

Every FMS unit includes a page dedicated to entering a flight 

plan. Typically, entering a flight plan is a simple matter of 

“filling in the blanks”—entering the en route waypoints and 

instrument procedures that make up the planned route.

En Route Waypoints and Procedural Waypoints

Entering a flight route into the FMS unit requires you to 

enter the waypoints that define your route. FMS distinguish 

between two kinds of waypoints: (1) waypoints that are 

published, such as departure, arrival, or approach procedure 

points; and (2) user defined waypoints. The approved system 

software (the internal programming) allows the pilot to 

manually enter airport and en route waypoints. However, 

you are prohibited by the software from entering (or deleting) 

individual waypoints that define a published instrument 

procedure, since misspelling a procedural waypoint name or 

deleting a procedural waypoint (e.g., final approach fix) could 

have disastrous consequences. Any changes to the selected 

database approach procedure will cancel the approach mode. 

Changing to go direct to a waypoint will not, in most units, 

cancel the approach mode (such as receiving radar vectors 

to final and bypassing an intermediate fix).

Entering En Route Waypoints

Looking at the planned route in Figure 3-8, it is apparent 

that San Carlos airport (KSQL), and SUNOL and TRACY 

intersections are not part of any instrument procedure that 

pertains to the planned flight. These waypoints can be entered 

into the unit, as shown in Figure 3-9.

The remaining waypoints in Figure 3-8, starting with the 

initial approach fix at ECA, are part of the Oakdale GPS 

approach procedure. Waypoints that are part of a published 

instrument procedure are entered by a different technique 

that will be introduced later. In some cases, you navigate 

along an airway that contains a string of waypoints, such as 

the one shown in Figure 3-10.

In this case, it is only necessary to enter waypoints along 

the airway that represent course changes. In Figure 3-10,

REANS intersection is a changeover point that joins the 

Pomona 073-degree radial and the Twentynine Palms 

254-degree radial. For this airway segment, you could 

enter POM, REANS, and TNP, keeping in mind that the 

remaining waypoints do not appear in the programmed route.

Entering Airways

More sophisticated FMSs allow you to enter entire airways 

with a single action into the unit. When an airway and 
3-9

BACK EXEC XPND

Modify

Wpt

Arwy

Modified

KSQL 027

KSQL

SUNOL 21.7

027 21.7

No Active Leg

DIST

BRG 060° 21.7

discontinuity

BRG --- ---

FPL

n

m

n

m

GPS ENR

FLAGGED

119.000

121.600

114.10

116.00

1200

A 

C 

T

A 

C 

T

S 

B 

Y

S 

B 

Y

S 

B 

Y

--.- vor

BACK

V195

V301

V334

 SUNOL

 V195 ECA

50nm

ECA

SUNOL

GPS ENR FPL

N

FLAGGED

119.000

121.600

114.10

116.00

1200

A 

C 

T

A 

C 

T

S 

B 

Y

S 

B 

Y

S 

B 

Y

--.- vor

BACK EXEC XPND

Modify Modified

KSQL

SUNOL 21.7

V195 ECA:

TRACY 40.0

SHARR 49.6

ECA 55.0

No Active Leg

DIST

BRG 060° 21.7

BRG 060° 18.3

BRG 060° 9.6

BRG 049° 5.4

FPL

n

m

n

m

n

m

n

m

GPS ENR

FLAGGED

119.000

121.600

114.10

116.00

1200

A 

C 

T

A 

C 

T

S 

B 

Y

S 

B 

Y

S 

B 

Y

--.- vor

This FMS allows you to insert 

an entire airway into your route.

The software performs a 

database search for all of the 

airways, causing all waypoints 

along the airway to be inserted 

into the route.

Modify

Modified

KSQL DIST 119.000 A

C

T

The navigation database looks up

all of the airways that connect to

the previous waypoint in the route.

Figure 3-11. Inserting an airway into a flight route.

endpoint for that airway are selected, all waypoints that 

occur along the airway are automatically inserted into the 

flight plan. Figure 3-11 shows a navigation unit that allows 

airways to be selected.

Entering Procedures

Every IFR-capable FMS offers a menu of published 

instrument procedures, such as departures, arrivals, and 

approaches. When you choose one of these procedures, the 

FMS automatically inserts all waypoints included in that 

procedure into the flight plan. Figure 3-12 illustrates how you 

might choose an approach procedure using one popular FMS.

Risk: Taking Off Without Entering a Flight Plan

The convenience of the FMS, especially the “direct to” 

feature common to all units, creates the temptation to program 

only the first en route waypoint prior to takeoff and then enter 

additional waypoints once airborne. Keep in mind, however, 

that no matter how skilled you become with the avionics, 

programming requires “heads down” time, which reduces 

your ability to scan for traffic, monitor engine instruments, 

etc. A better strategy is to enter all of the flight data before 

you take off.

Reviewing the Flight Route

Once a route has been entered into the FMS, the next step 

is to review the route to ensure it is the desired route. It is 

particularly important to ensure that the programmed route 

agrees with the pilot’s clearance, the en route and terminal 

area charts, and any bearing, distance, time, and fuel 

calculations that have been performed on paper.

Catching Errors: Using the FMS Flight Planning 

Function To Cross-Check Calculations

Using the FMS’s flight planning function to check your 

own flight planning calculations is one example of how 

advanced cockpit systems can decrease the likelihood 

of an error. Alternatively, cross-check the computer’s 

calculations against your own. (Remember the old computer 

programmer’s adage, “Garbage in, garbage out (GIGO).”)

The flight planning page can also be used to review the route 

that you entered into the FMS, as illustrated in Figure 3-13.

Be sure to check at least four things when reviewing your 

route.
3-10

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

PROC

PROCEDURES

VLOC

116.00

114.10

COM

123.850

125.100 Activate Vector-To-Final?

Activate Approach?

Select Approach?

Select Arrival?

Select Departure?

VLOC

116.00

114.10

COM

123.850

125.100

WPT

APR

APT

Load?

Activate?

O27 Public 7

35nm

TRANS

RNAV

10 G 

P

S

VECTORS

VLOC

116.00

114.10

COM

123.850

125.100

WPT

APR

APT

Load?

Activate?

O27 Public

35nm

TRANS

RNAV

10 G 

P

S

VECTORS

APR

RNAV 10

RNAV 28

VOR-A

G

PS

VLOC

116.00

114.10

COM

123.850

125.100

WPT

APR

APT

Load?

Activate?

O27 Public

35nm

TRANS

RNAV

10 G 

P

S

VECTORS

LOADING . . .

TRANS

VECTORS

ECA

MOTER

S

IA

IA

VLOC

116.00

114.10

COM

123.850

125.100

WPT

APR

APT

Load?

Activate?

O27 Public

35nm

TRANS

RNAV

10 G 

P

S

ECA IA

WRAPS

ECA

RW10

ZOSON

MOD

GPS

Press the PROC button and choose the type of procedure you wish to add.

Dial your destination airport and press .

GPS

Choose your approach from the approach menu.

GPS

Choose your transition from the transition menu.

GPS

Press to load the approach into your flight plan.

Figure 3-12. Inserting published instrument procedures into a flight route.

Check the Waypoints

On the flight planning page, compare the sequence of 

waypoints with that prescribed by his or her clearance. Are 

any waypoints missing? Did you mistakenly include any extra 

waypoints in the route? Did you misspell any waypoints? 

Did the computer mistakenly include any extra waypoints 

in the route?

Check the Distances

On the flight planning page, you can see that the computer 

has calculated the distances between the waypoints in the 

route. These distances can be checked against the en route 

charts. A common error is to misspell the name of a waypoint 

and, thus, mistakenly enter a waypoint not appropriate to 

the planned route (e.g., KHEE versus KHEF). Checking the 

waypoint distances for unusual numbers is a good way to 

spot these errors.
3-11

SFO

LGA

Figure 3-14. A great circle route.

ALERTS

FLIGHT PLAN

DTK

KSQL

DIS

TRACY

Approach - RNAV 10

051° 18.0NM

KSQL / O27

SUNOL 060° 1.8NM

FLIGHT PLAN

KSQL / O27

Check the sequence of waypoints.

Check the distances and desired 

tracks between the waypoints.

Engage cursor mode on the flight plan

page. Use the outer knob to scroll

between the waypoints in the route.

Figure 3-13. Reviewing the flight route.

Check the Desired Tracks

On the flight planning page, you can also see the course that 

the computer has calculated between waypoints along the 

route. A desired track between two waypoints represents the 

shortest path between them. The desired track between two 

waypoints may differ from the course seen on the aeronautical 

charts. In fact, there may be a difference of several degrees 

between the desired track and the airway course. Some of 

this difference may be due to the method in which the FMS 

accounts for magnetic variation. Some units use an internal 

database and interpolate, while others compute all values 

from tables.

Unlike the world as printed on paper charts, the earth is round, 

not flat. The shortest distance between two points on the earth 

is not a straight line; it is an arc, as shown in Figure 3-14.

The shortest route between two points on the surface of the 

earth is called a great circle route. To find the great circle 

route that connects two points, imagine a geometric plane 

cutting through the earth that passes through the two points 

and the center of the earth.

On the great circle route from SFO to LGA in 

Figure 3-14, departing SFO, the desired track is a little less 

than 90 degrees. Upon arrival at LGA, it appears to be greater 

than 90 degrees. The desired track heading is constantly 

changing since it is a circle, not a line. If, however, the 

difference exceeds several degrees, you need to investigate 

further to determine the cause.

Check for Route Discontinuities

Some FMS units do not automatically assume that you wish 

to fly between each of the waypoints that have been entered 

into the flight plan. When there is a question about how to 

proceed from one waypoint or instrument procedure to the 

next, some units insert a “discontinuity” in the programmed 

route. A route discontinuity indicates that the FMS needs 

further input from you about how two route segments should 

be connected. A route discontinuity is shown in Figure 3-15.

If you wish to proceed directly from the waypoint that appears 

before the route discontinuity to the waypoint that appears 

after, you can simply delete the discontinuity, as shown in 

Figure 3-15.

If the route discontinuity is left in the flight plan, the unit 

computer will not provide guidance beyond the waypoint 

that occurs before the discontinuity.

Maintaining Proficiency: Aeronautical Knowledge

It is easy to use an FMS without performing your own 

calculations for courses, headings, times, distances, and fuel 

used, but studies have demonstrated that aeronautical skills 

that are not practiced regularly quickly fade, regardless of 

experience level or certificates and ratings held. Abnormal 

and emergency situations (e.g., electrical failure) do occur, 

so it is important to maintain proficiency in at least making 

“rule of thumb” calculations on your own.

Coupling the FMS to the Navigation Indicator(s)

Every advanced avionics cockpit features one or more 

navigation instruments used for course guidance. The 

navigation indicator (e.g., a horizontal situation indicator 

(HSI) or electronic HSI) may include one or more course 

deviation indicators (CDIs), as well as one or more radio 

magnetic indicators (RMIs). When automatic course/ en 

route/ approach tracking is desired, you must couple (or 

connect) the FMS to the autopilot and select “navigation” 

as the source for the autopilot versus “heading” source, for 

example. With VOR navigation, that was sufficient. Now, 

with multiple sources of navigation data available, you must 

also ensure that the proper navigation information source 
3-12

BACK EXEC XPND

Modify

Wpt

Arwy

Library

KSQL

SUNOL 21.7

ECA 55.0

027 21.7

DIST

V195 33.3

BRG 060° 21.7

discontinuity

BRG --- ---

FPL

n

m

n

m

n

m

GPS ENR

FLAGGED

119.000

121.600

114.10

116.00

1200

A 

C 

T

A 

C 

T

S 

B 

Y

S 

B 

Y

S 

B 

Y

--.- vor

BACK EXEC XPND

Active

KSQL 027

KSQL

SUNOL 21.7

ECA 55.0

027 73.3

No Active Leg

DIST ETE

BRG 060° 21.7

V195 33.3

BRG 049° 18.3

FPL

n

m

n

m

n

m

GPS ENR

FLAGGED

119.000

121.600

114.10

116.00

1200

A 

C 

T

A 

C 

T

S 

B 

Y

S 

B 

Y

S 

B 

Y

--.- vor

A route discontinuity appears when the 

FMS cannot proceed from one waypoint 

to the next. A route discontinuity can 

simply be deleted.

S

B

Y

S

B

When a route discontinuity is deleted, Y

the FMS proceeds directly to the next 

waypoint in the programmed route.

Figure 3-15. A route discontinuity and deletion.

was selected in the FMS. Every advanced cockpit offers 

buttons or switches that allow you to choose which navigation 

indications will be shown on which display or instrument.

This situation becomes complicated in aircraft that contain 

dual FMS/RNAV installations and redundant selectable 

displays or instruments. The pilot must learn how to configure 

each navigation instrument to show indications from each 

possible navigation source.

Figure 3-16 shows an example of a primary flight display 

(PFD) navigation indicator that combines a course deviation 

indicator (CDI) and a radio magnetic indicator (RMI), and 

allows the pilot to display indications from one of two FMS 

on either indicator.

Common Error: Displaying the Wrong Navigation 

Source

The annunciations showing which navigation sources are 

displayed on which navigation instruments are often small, so 

there is significant potential for displaying a navigation source 

other than the one you intended to select. The consequences 

of losing track of which navigation signals you are following 

can be significant: you may think you are steering along one 

course when in fact you are steering along a different one. 

Be sure to verify these settings prior to departure, and again 

each time you make changes to any navigation instrument. 

Some installations compound this potential with automatic 

source switching. The most common switching mode is a 

GPS source to be automatically deselected when the VOR 

is set to an ILS localizer frequency and a signal is present. 

Typically, that is not a problem since the pilot intends to 

switch to the ILS anyway. However, the error arises upon 

missed approach, when the pilot selects another frequency 

to follow a VOR missed approach routing. At that point, 

some units revert back to the previous GPS or other RNAV 

routing selected instead of the VOR frequency that the 

pilot just picked. This can result in gross navigation errors 

and loss of obstruction clearances. In some units, this is a 

shop programmable or jumper selected option. Check your 

unit’s features. Always check for correct navigation source 

selection and cross-check against the published procedure. 

Be ready and able to fly and navigate manually.
3-13

Range

View

Aux

OFF

Bearing

GPS2

Nav

GPS1

Range View

TAS

GS

157 KTS

140 KTS

FOGON

BRG 270°

2.8 NM

00:26:18

COVAR

BRG 051°

2.2 NM

0:01:06

160

150

140

130

14

4

3

2

20

10

10

20

20

10

10

20

ILS

ILS

268°

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.30

113.90

COM

122.700

133.000

NAV

GS TRK ETE

DIS DTK BRG

2.8nm m m 

120kt m 1:24

COVAR FOGON FA

1.0 1.0

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.30

113.90

COM

122.700

133.000

NAV

GS TRK ETE

DIS DTK BRG

2.2nm m m 

120kt m 1:06

HAGRO C IA OVAR

1.0 1.0

Indications from this FMS are shown on the horizontal 

situation indicator (green needle).

Indications from this FMS are shown on the bearing 

pointer (blue needle).

Navigation sources can be coupled to navigation indicators using 

the key to the left. Selections are indicated in the boxes to the right.

Figure 3-16. Coupling the FMS to navigation instruments.

Awareness: Mode Awareness

Mode awareness refers to the pilot’s ability to keep track of 

how an advanced avionics cockpit system is configured. As 

shown in Figure 3-16, every advanced avionics system offers 

an annunciation of which mode is currently set—somewhere 

in the cockpit! There is no guarantee that you will notice these 

annunciations in a timely manner. The configuration of these 

systems must remain part of your mode situational awareness 

at all times. One strategy is to include “mode checks” as part 

of your checklist or callout procedures. For example, after 

programming a route into the FMS, verify that the navigation 

indicator shows course guidance from the desired source, and 

that the indication agrees with your estimate of the correct 

direction and distance of flight.

Essential Skills

1. Determine whether the FMS is approved for the 

planned flight operation.

2. Determine if your FMS can be used as a primary 

navigation system for alternate requirements.

3. Understand how entries are made and how the entries 

can be canceled.

4. Understand how that unit(s) is installed, and how it is 

programmed or jumpered for optional functions.

5. Determine which navigation sources are installed and 

functional.

6. Determine the status of the databases.

7. Program the FMS/RNAV with a flight plan, including 

en route waypoints, user waypoints, and published 

instrument procedures.

8. Review the programmed flight route to ensure it is 

free from error.

9. Find the necessary pages for flight information in the 

databases.

10. Determine which sources drive which displays or 

instruments, and where the selection controls are 

located.

11. Determine and understand how to use and program 

optional functions and equipment installed with FMS/

RNAV basic unit.

En Route Navigation

The FMS provides guidance toward each waypoint in the 

programmed flight route, and provides information to help 

you track your progress.
3-14

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK049

TK 049

1.8nm

108 kt

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

Desired track to the active waypoint ed track to the active waypoint

Track of the aircraft over the ground

Distance to the active waypoint

1.8nm

the active waypoint

Groundspeed

Active waypoint Active waypoint

Estimated time of

arrival at the active

waypoint

Figure 3-17. Active waypoint, desired track, track, and ETA at 

active waypoint.

The Active Waypoint

In normal navigation, at any given time, the aircraft is 

progressing to the next waypoint in the programmed flight 

route. This next waypoint is called the active waypoint. FMSs 

typically display the active waypoint on a page dedicated 

to showing flight progress. While “going to” is the normal 

function for navigation, nearly all FMSs have the provision 

to select a point, waypoint, or navaid to navigate “from” that 

point or position. This can be useful for holding, tracking 

NDB bearing, grids, etc., and allows the tracking of a bearing 

with the autopilot engaged and coupled to a navigation 

source. However, if you are doing an ADF approach, the 

primary navigation source must be available to support that 

approach. The page shown in Figure 3-17 indicates that 

TRACY is the active waypoint. The primary flight display 

in Figure 2-5 shows the active waypoint (ECA) at the top 

of the display.

Desired Track

The FMS/PFD/MFD navigation display also shows the 

desired track to the active waypoint. The desired track is 

the intended course for the active leg in the programmed 

flight plan. It is the track that connects the waypoint the 

aircraft just passed to the active waypoint. On the display 

in Figure 3-17, the current desired track is the 049-degree 

course between the SUNOL and TRACY waypoints.

Track

The navigation display shows the aircraft’s track over the 

ground. The track, which is the result of aircraft heading 

and winds, tells you which direction the aircraft is actually 

flying. Winds make it likely that the track and heading will 

be different. You can get a very good sense of what the winds 

are doing by comparing the track and heading of the aircraft. 

If the aircraft is flying a heading of 090 degrees and the track 

is 080 degrees, the winds are coming from the south. Notice 

that having a track indication makes it easy to maintain the 

desired track. To follow the 049-degree desired track to 

TRACY upon leaving SUNOL, simply fly the heading that 

results in a track of 049 degrees. The track display eliminates 

the traditional method of “bracketing” to find a heading that 

lets you fly the desired track.

Groundspeed and ETA

The display in Figure 3-17 also shows groundspeed. Again, 

the navigation display eliminates the need to calculate 

groundspeed using distance and time. Based on groundspeed 

and distance from the active waypoint, the navigation page 

also provides an estimated time of arrival at the active 

waypoint.

Fuel Used and Time Remaining

Many advanced avionics navigation units offer fuel 

calculations and fuel state monitoring. Some units 

automatically load the initial fuel load, while many require the 

pilot to correctly enter the amount of fuel into the unit as the 

beginning fuel on board. Some can have installed transducers 

(sensors) to measure the fuel used, and display fuel used 

and time remaining at the current consumption rate. Some 

lower cost units indicate computed fuel consumption values 

based on fuel burn rates entered by the pilot. This produces 

an estimate of fuel used and fuel remaining. This estimate 

is only as accurate as the values entered by the pilot for fuel 

on board and the consumption rate. Since the pilot is often 

using the AFM chart data, there is potential for interpretation 

error. Then, there is the variation error from the factory charts 

to the specific aircraft being flown. These factors all tend to 

degrade the accuracy of the fuel calculation based solely on 

pilot entered data. Other factors such as a fuel burn that is 

higher than normal, leaks, or other problems are not displayed 

unless the system actually registers and senses fuel tank realtime status. These errors can affect both types of systems. The 

pilot must determine what equipment is installed.

Arriving at the Active Waypoint

As the aircraft reaches the active waypoint, there are four new 

tasks for the pilot: (1) recognizing imminent arrival at the 

active waypoint; (2) leading the turn to avoid overshooting 

the course to the next waypoint; (3) making the next waypoint 

the new active waypoint; and (4) selecting the desired course 

to the new active waypoint.

All FMS/RNAV computers offer a sequencing mode that 

greatly simplifies the performance of the first three of these 

tasks. Sequencing mode provides three services: waypoint 

alerting, turn anticipation, and waypoint sequencing.
3-15

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK060

TK 060

0.3nm

108 kt

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

0.01nm :5.0nm

00:10

WPT

Turn anticipation advises you to begin your turn to 

the desired track to the next waypoint in the flight 

route. Turn anticipation is indicated on this computer 

when the WPT message stops flashing.

0 3 WPT

Waypoint alerting provides a flashing message when

you approach the vicinity of the active waypoint.

Figure 3-18. Waypoint alerting and turn anticipation.

Fly-by

Fly-over

Figure 3-19. Fly-by and fly-over waypoints.

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK051

TK 049

18.2nm

110 kt

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

0.01nm :5.0nm

WPT

18 2

The waypoint sequencing function makes the next

waypoint in the flight plan sequence the new active

waypoint.

Figure 3-20. Waypoint sequencing.

Waypoint Alerting

The first service performed by the sequencing mode 

is waypoint alerting. Just prior to reaching each active 

waypoint, waypoint alerting advises the pilot of imminent 

arrival at the active waypoint. Waypoint alerting is illustrated 

in Figure 3-18.

Turn Anticipation

The second service performed by the sequencing mode is 

turn anticipation. During waypoint alerting and prior to 

reaching the active waypoint, the FMS indicates that it is 

time to begin the turn to fly the desired track to the new 

active waypoint. The timing of turn anticipation is based on 

the aircraft’s observed groundspeed and the angle of the turn 

required to track to the next waypoint. If a standard rate turn 

is begun when the waypoint alerting indication is presented, 

the pilot should roll out on course when the aircraft reaches 

the center of the desired track to the new active waypoint. 

Turn anticipation is also illustrated in Figure 3-18.

When turn anticipation is used, the aircraft does not fly 

directly over the active waypoint. Rather, the computer 

commands a turn that “rounds the corner” to some degree, 

giving priority to having the aircraft roll out on the new 

desired track to the new active waypoint. This function is 

illustrated in the upper illustration in Figure 3-19.

Turn anticipation occurs only when the active waypoint is 

designated as a fly-by waypoint. A fly-by waypoint is one 

for which the computer uses a less stringent standard for 

determining when the aircraft has reached it. By contrast, 

some waypoints are designated as flyover waypoints. The 

FMS will not use turn anticipation for a fly-over waypoint; 

instead, the navigation will lead the aircraft directly over the 

waypoint (hence the name). A missed approach waypoint is a 

typical example of a fly-over waypoint. A fly-over waypoint 

is illustrated in Figure 3-19.

Waypoint Sequencing

The third service performed by sequencing mode is waypoint 

sequencing. Once the aircraft reaches the active waypoint, 

the FMS automatically makes the next waypoint in the flight 

plan sequence the new active waypoint. Waypoint sequencing 

is illustrated in Figure 3-20.

Awareness: Making Waypoint Callouts

To help you stay in touch with the progress of the flight while 

the FMS automatically performs the navigation task, it is 

a good practice to announce your arrival (mentally, single 

pilot; or orally, to the flight crew) at each waypoint in the 

programmed route. For example, when arriving at SUNOL 

intersection, you might announce, “Arriving at SUNOL. 
3-16

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

WPT

114.10

119.000

121.600 ATIS 119.650 

Ground 121.600 

Tower 118.100

Unicom 122.950

APT KLVK Public VK Public Done?

2 Enter the name of the desired airport.

Select the third subpage of the waypoint 

page, which shows radio fequencies for 

any airport in the navigation datebase.

1

Figure 3-21. Accessing communications frequencies in the FMS.

TRACY is next. The course is 051 degrees, and the ETE is 

10 minutes.”

Setting the Course to New Active Waypoint

The last step required when arriving at the active waypoint is 

to set the course to the next waypoint in the planned route. A 

PFD such as the one shown in Figure 3-16 automatically sets 

the new course on the navigation indicator when the RNAV 

computer is engaged in sequencing mode. When an FMS is 

combined with a traditional course deviation indicator, the 

pilot must manually set the new course using the OBS knob, 

unless it is an EHSI, or is slaved. “Slaved” means that there 

is a servo mechanism in the instrument that will respond to 

the navigation unit.

En Route Sensitivity

When operating en route, the FMS maintains a sensitivity 

of 5 nautical miles (NM); that is, a CDI displaying course 

indications from the FMS deflects full-scale when the aircraft 

drifts 5 NM to either side of the desired track to the active 

waypoint. An aircraft is considered to be en route when it is 

more than 30 NM from the origin and destination airports 

programmed into the flight plan. There are and have been 

some units that use different values. Consult your specific 

unit’s documentation.

GPS Signal Status

The FMS/RNAV provides position, track, and groundspeed 

information using signals received from a collection of 

satellites that are in constant orbit around the Earth when 

using the GPS navigation source. Although the GPS is 

highly reliable, satellite reception is sometimes interrupted. 

Consequently, the pilot must ensure at all times that the 

system is operational and that it is receiving adequate GPS 

signals. To simplify this process, all GPS receivers approved 

for IFR navigation have an automated feature that continually 

checks the status of the GPS signals. This function is called 

receiver autonomous integrity monitoring (RAIM). RAIM, 

which requires adequate simultaneous reception of at least 

five GPS satellites for IFR navigation reliability, works 

independently and notifies the pilot when there is a problem 

with GPS signal reception. When reception problems arise, 

the FMS/RNAV provides an alert message that notifies the 

pilot of a GPS reception problem and states that the aircraft 

position information can no longer be considered reliable. 

For this reason, regulations require aircraft that are equipped 

with an RNAV unit using GPS to have an alternate (non-GPS) 

means of IFR navigation on board (e.g., a VOR receiver) 

unless the GPS receiver complies with the requirements of 

WAAS TSO-146B.

For all of the previously mentioned reasons, many 

manufacturers have coupled inertial navigation units with the 

FMS to deliver unequalled reliability in navigation. Many 

more complex FMS units also search or scan for distance 

measuring equipment (DME) signals and VOR signals as 

additional navigational sources to compute a “blended” 

position, which is the best calculation from all of the sources 

and how the FMS is programmed to “consider” the signals 

for accuracy. GPS RNAV units usually use only GPS signal 

sources, but may be able to receive VOR and DME signals 

as well. In the future, many GPS units will probably receive 

eLORAN as well, since it is a long range navigation system 

with greatly improved accuracy as compared to the older 

LORAN-C. One advantage of the LORAN (“e” or “C”) 

system is that it is ground based and can be easily maintained, 

as compared to space-based navigation sources.

Accessing Navigational Information En Route

One of the most useful features of an FMS database is its 

ability to provide quick access to navigational information.

Most units allow the pilot to access information about 

airports, navigation facilities, airway intersections, and other 

kinds of waypoints. Figure 3-21 illustrates how one FMS is 

used to access radio frequencies for an airport.

Essential Skills

1. Select and monitor the en route portion of the 

programmed flight route, determining waypoint 

arrival, approving turn anticipation, and waypoint 

sequencing.

2. Approve or select the correct course automatically 

displayed or manually tuned.

3. Determine if FMS makes fuel calculations and what 

sensors and data entries are required to be made by 

the pilot.

4. Ensure that the track flown is that cleared by air traffic 

control (ATC).
3-17

Adding a Waypoint

Deleting a Waypoint

Adding a Waypoint

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK051

TK

15.8nm

TRACY

LEG

*CRSR* FPL 0 *CRSR*

TRACY

D l ti W i t

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK051

TK

14.7nm

TRACY

LEG

*CRSR* FPL 0 *CRSR*

REIG

Deletin Deleting a Waypoint

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK050 TK

5.2nm

REIGA

LEG

*CRSR* FPL 0 *CRSR*

REIGA

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK050 TK

4.8nm

REIGA

LEG

ENT

*CRSR* FPL 0 *CRSR*

Del REIGA ?

Use cursor mode to select the waypoint you 

want to insert the new waypoint before.

Use the inner and outer knobs to enter the 

new waypoint identifier. Then press to 

confirm your choice.

Use cursor mode to highlight the 

waypoint you want to delete. 

Then press .

Press to confirm your modification.

CLR

ENT

ENT

Figure 3-22. Adding and deleting waypoints.

5. Determine that the display CDI sensitivity is 

satisfactory for the segment being flown.

En Route Modifications

Part of the challenge of using FMS en route is dealing 

with modifications to the planned flight route. This section 

describes five en route modifications.

Adding and Deleting Waypoints From the 

Programmed Route

All FMS/RNAV units allow en route (not published 

departure, arrival or approach) waypoints to be added and 

deleted to the programmed route. These techniques are 

illustrated in Figure 3-22.

ATC may issue instructions to a point defined by a VOR 

radial and DME value. The pilot must know how to enter 

such a waypoint as a user waypoint, name it, and recall it. If 

the unit’s memory is very limited, the pilot should also be 

adept at removing the waypoint.

Direct To

Another simple modification is one that requires the pilot to 

proceed directly to a waypoint. In some cases, the waypoint 

to fly directly toward is one that already appears in the 

programmed flight plan. In this case, the pilot simply selects 

that waypoint in the flight plan and activates the direct-to 

function, as illustrated in Figure 3-23.

The direct-to waypoint now becomes the active waypoint. 

After reaching this waypoint, the system proceeds to the next 

waypoint in the programmed route.

In other cases, you may be asked to fly directly to a waypoint 

that does not already appear in the programmed flight 

route. In this case, one strategy is to add the waypoint to 

the programmed route using the technique illustrated in 

Figure 3-22, and then proceed directly to the waypoint using 

the technique illustrated in Figure 3-23. Another option is 

to use the direct-to function to get the flight started toward 

the assigned waypoint, and then add the new waypoint to the 

appropriate place in the programmed flight plan.
3-18

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

FPL

WAYPOINT DTK DIS

SUNOL 

TRACY

Approach RNAV 10

ACTIVE FLIGHT PLAN

00 KSJC / O27 

M

M 

9.6 

18.3

VLOC

114.10

116.00

COM

125.400

123.850

n

m

n

m

n ECA IA M 15.0 m

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

DRCT

VLOC

114.10

116.00

COM

125.400

123.850

FPL

SELECT WAYPOINT D

NRST

CRS

ECA IA

W121 Activate?

KLVK

049 m

ECA SW USA 

MANTECA

STOCKTON USA

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

FPL

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

00 KSJC / O27 

VLOC

114.10

116.00

COM

125.400

123.850

Approach RNAV 10

ECA IA

MOTER

ZOSONFA

M

M 

M

41.1 

8.0 

5.6 

n

m

n

m

n

m

Press the direct-to button ( ). 

Press twice to confirm your choice.

On the flight plan page, use cursor mode 

to select the waypoint to which you would 

like to proceed direct.

ECA is now the active waypoint. The RNAV has 

built a desired track from the present position 

of the airplane to ECA.

Figure 3-23. Direct-to operation.

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

DRCT

VLOC

114.10

116.00

COM

125.400

123.850

FPL

SELECT WAYPOIN D T

NRST

CRS

ECA IA

W121 Activate?

KLVK

053 m

ECA SW USA 

MANTECA

STOCKTON US PAGE MENU A

Cancel Direct-To NAV?

COM SELECT W D AYPOINT RING

Press , then to access the cancel

direct-to feature.

Figure 3-24. Canceling a direct-to operation.

Risk: What Lies Ahead on a Direct-To Route?

The direct-to function offers a convenient way to shorten your 

time and distance en route if ATC authorizes that track. When 

you perform a direct-to operation, though, remember that the 

system builds a new track from your present position to the 

new waypoint. This track does not necessarily correspond 

to any previously planned airway or route, so it is critical to 

ensure that your new direct route is clear of all significant 

obstructions, terrain, weather, and airspace.

Cancel Direct To

ATC may sometimes cancel a previously issued direct-to 

clearance and ask you to resume the previously cleared 

route. Most FMSs offer a simple way of canceling a direct-to 

operation. Figure 3-24 illustrates the procedure for one FMS.

Selecting a Different Instrument Procedure or 

Transition

ATC will sometimes issue an instrument procedure or 

transition that is different from what you would expect. 

Entering a new procedure or transition is usually a simple 

matter of making new menu choices, as illustrated in 

Figure 3-25. In most units, if you are training or wish to fly 

the approach again, you must learn how to set the selector or 

cursor back to the initial fix, which will restart the approach 

sequence.

Proceeding Directly to the Nearest Airport

One of the most useful features of an FMS is its ability to 

provide you with immediate access to a large navigation 

database. This feature is particularly useful when a suitable 

nearby airport or navigation facility must be located quickly. 

Figure 3-26 shows how to locate and proceed directly to the 

nearest suitable airport using one manufacturer’s system.

Essential Skills

1. Proceed directly to a waypoint in the programmed 

route.
3-19

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK050

TK 050

9.8 nm

ECAi

LEG

ENT

*CRSR* PROC 2 *CRSR*

S e l e c t A p p r o a c h ?

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK050

TK 050

9.7 nm

ECAi ENT

*CRSR* PROC 2 *CRSR*

S e l e c t A p p r A PT

1: KSQL 

2: O27

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK050 TK 050

9.5nm

ECAi

LEG

ENT

*CRSR* APT 8 *CRSR*

RNAV 10

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK050 TK 050

9.3nm

ECAi

LEG

ENT

*CRSR* APT 8 *CRSR*

MOTER

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

DTK050 TK 050

9.1nm

ECAi

LEG

ENT

*CRSR* APT 8 *CRSR*

A D D T O F P L 0 ?

Press and choose Select Approach.

A menu of destination airports appears. Press 

to choose one.

A menu of approaches then appears for the 

airport you selected. Choose one and press .

Finally, a list of transitions appears for the selected

approach. Choose one and press . 

Press to add your 

approach to the flight plan.

PROC

ENT

ENT

ENT

ENT

Figure 3-25. Selecting a different instrument procedure or transition.

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

123.850

125.100

NRST

NEAREST AIRPORT

1Q4 6.7nm VFR

 mul 122.900 rwy 4000ft 

C83 12.1nm GPS 

 uni 123.050 rwy 4500ft

APT BRG DIS APR

KTCY 5.7nm GPS 

 uni 122.800 rwy 4000ft

Use the outer knob to select the nearest page

The first subpage shows the nearest airports.

COM RING NEAREST AIRPORT

APT BRG DIS APR

Highlight any airport in cursor mode and press to

receive guidance directly to that airport.

Figure 3-26. Proceeding directly to the nearest airport.

2. Cancel a programmed or selected waypoint or fix.

3. Select a different instrument procedure or transition.

4. Restart an approach sequence.

5. Immediately find the nearest airport or facility.

6. Edit a flight plan.

7. Enter a user waypoint.

Descent

Making the transition from cruise flight to the beginning 

of an instrument approach procedure sometimes requires 

arriving at a given waypoint at an assigned altitude. When this 

requirement is prescribed by a published arrival procedure or 

issued by ATC, it is called a crossing restriction. Even when 

ATC allows a descent at the pilot’s discretion, you need to 

choose a waypoint and altitude for positioning convenient 
3-20

Wind

Top-of-descent point

Bottom-of-descent point

ECA VOR

Cruising altitude ft 1 1 0 0 0

Assigned altitude ft 3 0 0 0

Cruising speed knot 2 7 0 s To

Descent speed and rate eed and rate

1 8 0 knots @ 1,000 fpm

Figure 3-27. The descent planning task.

to start the approach. In either case, descending from a 

cruising altitude to a given waypoint and altitude requires 

both planning and precise flying.

Elements of Descent Planning Calculations

Figure 3-27 illustrates the basic descent planning task. The 

task begins with an aircraft flying at an assigned cruising 

altitude. The aircraft must descend to an assigned altitude 

and reach that assigned altitude at a designated bottom-ofdescent point. The next step is to choose a descent rate and 

a descent speed. The ultimate goal is to calculate a top-ofdescent point, which is the point at which, if you begin the 

descent and maintain the planned descent rate and airspeed, 

you will reach the assigned altitude at the designated bottomof-descent point.

In a basic aircraft, you must rely on manual calculations to 

perform the descent planning task. In an advanced avionics 

aircraft, there are two descent planning methods available: 

(1) manual calculations, and (2) the vertical navigation 

features of the FMS unit. Skillful pilots use both methods 

and cross-check them against one another in order to reduce 

the possibility of error and help keep the pilot “in the loop.”

Manual Descent Calculations

The simplest technique for calculating the distance required 

to descend uses a descent ratio. The table in Figure 3-28 lists 

a descent ratio for many combinations of planned descent 

speeds and descent rates. Calculating a descent is a simple 

matter of looking up the descent ratio for your target descent 

rate and groundspeed, and multiplying the descent ratio by 

the number of thousands of feet in altitude that you must 

descend. For example, suppose you are asked to descend from 

11,000 feet to meet a crossing restriction at 3,000 feet. Since 

there is a 200-knot speed restriction while approaching the 

destination airport, you choose a descent speed of 190 knots 

and a descent rate of 1,000 feet per minute (fpm). Assuming a 

10-knot headwind component, groundspeed in the descent is 

180 knots. Referring to the table in Figure 3-28, the planned 

descent speed and rate indicate a ratio of 3.0. This means that 

you will need 3 NM for every 1,000 feet of descent. You 

must descend a total of 8,000 feet (11,000 feet – 3,000 feet). 

A total of 24 NM is needed to descend 8,000 feet (3 NM × 

8 = 24 NM), and must, therefore, begin the descent 24 NM 

away from the end-of-descent point.

Another technique for calculating descents is to use the 

formula shown in Figure 3-29. A descent table can be found 

in the front of each set of U.S. Terminal Procedures on 

page D-1. Working through the formula for the ECA VOR 

crossing restriction example, 8 minutes is needed to descend 

8,000 feet at the planned descent rate of 1,000 fpm. At your 

planned descent speed of 180 knots, you will cover 3 NM 

per minute. Thus, in 8 minutes, you will cover 24 NM. Once 

again, you must start the descent 24 NM prior to ECA to meet 

the crossing restriction.

Coordinating Calculations with Aeronautical 

Charts

Regardless of which method is used, it is always a good idea 

to locate the top-of-descent point chosen on the aeronautical 

chart. Figure 3-30 shows a chart that covers the area 

surrounding the ECA VOR. A top-of-descent point 24 NM 

prior to ECA is located 3 NM before PATYY intersection.

Alternate Navigation Planning

Using the aeronautical chart to locate the top-of-descent point 

has a second advantage. Since regulations require you to have 

an alternate means of navigation onboard if the computer 

does not comply with TSO 146B, the aeronautical chart 

allows you to check minimum altitudes for VOR reception 
3-21

90 100 120 140 160 180 200 220 240 260 280 300

1600

1700

1800

1900

1200

1300

1400

1500

700

800

900

1000

1100

600

2000

500

GROUND SPEED (knots)

DESCENT

GRADIENT

RATE

(ft./min)

A descent ratio table is provided for use in planning and executing descent procedures under known or approximate ground speed 

conditions and rates of descent. The ratio expresses the number of nautical miles needed to descend 1,000 ft.

DESCENT RATIO TABLE

3.0

2.5

2.1

1.9

1.7

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.9

0.8

0.8

0.7

3.3

2.8

2.4

2.1

1.9

1.7

1.5

1.4

1.3

1.2

1.1

1.0

1.0

0.9

0.9

0.8

3.7

3.1

2.6

2.3

2.0

1.8

1.7

1.5

1.4

1.3

1.2

1.1

1.1

1.0

1.0

0.9

4.6

3.9

3.3

2.9

2.6

2.3

2.1

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.2

5.3

4.4

3.8

3.3

3.0

2.7

2.4

2.2

2.1

1.9

1.8

1.7

1.6

1.5

1.4

1.3

6.0

5.0

4.3

3.8

3.3

3.0

2.7

2.5

2.3

2.1

2.0

1.9

1.8

1.7

1.6

1.5

6.7

5.6

4.8

4.2

3.7

3.3

3.0

2.8

2.6

2.4

2.2

2.1

2.0

1.9

1.8

1.7

7.3

6.1

5.3

4.6

4.1

3.7

3.3

3.1

2.8

2.6

2.4

2.3

2.2

2.0

1.9

1.8

8.0

6.7

5.7

5.0

4.4

4.0

3.6

3.3

3.1

2.9

2.7

2.5

2.4

2.2

2.1

2.0

8.7

7.2

6.2

5.4

4.8

4.3

3.9

3.6

3.3

3.1

2.9

2.7

2.5

2.4

2.3

2.2

8.7

7.2

6.2

5.4

4.8

4.3

3.9

3.6

3.3

3.1

2.9

2.7

2.5

2.4

2.3

2.2

9.3

7.8

6.7

5.8

5.2

4.7

4.2

3.9

3.6

3.3

3.1

2.9

2.7

2.6

2.5

2.3

10.0

8.3

7.1

6.3

5.6

5.0

4.5

4.2

3.8

3.6

3.3

3.1

2.9

2.8

2.6

2.5

Figure 3-28. Descent ratio table.

11,000 ft – 3,000 ft

1,000 ft/min

180 NM/hr 8,000 ft

1,000 ft/min

X = X 3 NM/min = 3 8 X NM = 24 NM

60 (min/hr)

Descent Rate (ft/min) X

Groundspeed (NM/hr)

60 (min/hr) = NM required

Cruising Altitude (ft) – Descent Altitude (ft)

Figure 3-29. Descent formula.

Figure 3-30. Top-of-descent point on an en route chart.

along the route of flight in case VOR navigation is required 

at any time. The airway that leads to the ECA VOR lists a 

minimum en route altitude (MEA) of 3,000 feet, which is 

the clearance altitude.

Calculating Descents with the FMS

Building a descent with an FMS follows the familiar process 

of entering the basics of the descent into the system, letting 

the system do the math, and then reviewing what the system 

has produced. Most FMS units offer a descent planning or 

vertical navigation (VNAV) page that allows you to enter 

the details of your descent. Figure 3-31 shows the VNAV 

page for one manufacturer’s system. Note that there is an 

entry for each of the descent planning concepts discussed 

above. Computers perform the calculations using the same 

formulas and data.
3-22

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK050

TK 050

12.5nm

ECAi

LEG

*CRSR* ALT 2 *CRSR*

V n v i n 2 : 1 5 

11000 to : 3000

ECA : -00 nm

GS : 180 -1000fpm

12 5nm V n v i n 2 : 1 5

The VNAV function then calculates a top-of-descent 

point and displays the time remaining to reach it. 2

VNAV allows you to enter a descent waypoint and

altitude, descent speed, and descent rate. 1

Figure 3-31. Planning a descent with an advanced avionics unit.

ECA

3 0 0 0 ft

1 0 0 0 0 ft

1 1 0 0 0 ft

Deceleration segment Deceleration segment

The aircraft must slow from 270 knots

to 180 knots to obey speed restrictions.

2 7 0 knots

1 8 0 knots

Figure 3-32. A deceleration segment planned by a more sophisticated FMS.

It is a good idea to cross-check the results of your manual 

descent calculations with the results produced by the 

computer. Many RNAV units do not display a waypoint for 

the planned top-of-descent point. However, there may be an 

“approaching VNAV profile” message that anticipates the 

descent point and cues the pilot to begin descending. Caution 

is advised that some systems calculate the vertical flight 

path dependent on the current airspeed/groundspeed values. 

Lowering the nose and gaining airspeed in the descent may 

confuse you into perceiving a false vertical goal or vertical 

rate, resulting in failure to meet the crossing restriction 

with some systems. Determine if the system recomputes 

the airspeed/groundspeed, or if you must enter the descent 

airspeed during the VNAV programming.

Managing Speed

Up to this point the focus has been on the task of losing 

excess altitude. For example, in the situation shown in 

Figure 3-27, you are faced with the requirement to reduce 

altitude from 11,000 feet to 3,000 feet. Most descent scenarios 

also present the challenge of losing excess speed. In piston 

aircraft of modest performance, losing excess speed seldom 

requires much forethought. Slowing from a cruising speed 

of 120 knots to an approach speed of 100 knots requires little 

planning and can be accomplished quickly at almost any 

point during a descent. Flying higher performance aircraft 

requires a closer look at concepts of excess altitude and 

excess speed. Higher performance piston engines usually 

require descent scheduling to prevent engine shock cooling. 

Either the engines must be cooled gradually before descent, 

or power must be constant and considerable in the descent to 

prevent excessive cooling. In such instances, a much longer 

deceleration and gradual engine cooling must be planned to 

prevent powerplant damage. Additionally, the turbulence 

penetration or VA speeds should be considered with respect 

to weather conditions to avoid high speeds in turbulent 

conditions, which could result in overstressing the airframe. 

Drag devices such as spoilers can be of great advantage for 

such maneuvers. In the scenario in Figure 3-27, a cruising 

speed of 270 knots is inappropriate as the aircraft descends 

below 10,000 feet, and even more so as it enters Class C 

airspace. Therefore, descent planning must include provisions 

for losing excess airspeed to meet these speed restrictions.

Some sophisticated FMSs are able to build in a deceleration 

segment that can allow the aircraft to slow from the cruise 

speed to the desired end-of-descent speed during the descent. 

This type of navigation system allows you to maintain the 

cruise speed up until the top-of-descent point and calculates 

the deceleration simultaneously with the descent. A 

deceleration segment is illustrated in Figure 3-32.

Simple FMS units such as GPS RNAV receivers assume 

that you will slow the aircraft to the planned descent speed 

before reaching the top-of-descent point. ATC timing may 

preclude this plan.
3-23

ECA

3 0 0 0 ft

9 0 0 0 ft

1 1 0 0 0 ft

9 0 0 0

Top-of-descent point

2 4 NM 1 8 NM 1 2 NM 6 NM

0 0 0 ft

7 0 0 0 ft

5 0 0 0 ft

Figure 3-33. Planned descent path as a wire in the sky.

Descent Flying Concepts

Probably the most important descent flying concept to 

understand is that a planned descent is basically a “pathway 

in the sky,” similar to the glideslope associated with an ILS 

procedure. If you start down at the planned top-of-descent 

point, fly a groundspeed of 180 knots, and descend at 1,000 

feet per minute (fpm), you will be flying on a fixed path 

between the top-of-descent point and the bottom-of-descent 

point. If you maintain the 180-knot and 1,000-foot-perminute descent, you will cross a point 18 NM from ECA at 

exactly 9,000 feet, a point 12 NM from ECA at 7,000 feet, 

and a point 6 NM from ECA at exactly 5,000 feet, as shown 

in Figure 3-33.

If you are at a different altitude at any of these points, you 

will not cross ECA at the required 3,000 feet unless corrective 

action is taken. Four things can cause you to drift from a 

planned descent path:

1. Not following the planned descent rate

2. Not following the planned descent speed

3. Unexpected winds

4. Navigation system not recalculating for airspeed 

change of descent

Figure 3-34 shows the effect of each situation on the position 

of the aircraft with respect to the planned descent path.

Flying the Descent

The key to flying a descent is to know your position relative 

to the pathway-in-the-sky at all times. If you drift off the 

path, you need to modify the descent speed and/or descent 

rate in order to rejoin the descent path. Many FMSs do not 

give a direct indication of progress during a descent. You 

must be very familiar with the indirect indications of the 

VNAV descent. In this case, follow the planned descent rate 

and speed as closely as possible and be mindful of altitude 

and position while approaching the crossing restriction fix.

Determining Arrival at the Top-of-Descent Point

All navigation systems provide some type of alert informing 

the pilot of arrival at the planned top of descent point, and that 

it is time to begin the descent at the speed and rate entered 

into the FMS.

If air traffic control is able to accommodate your request, 

the ideal point to begin the descent is at the planned top-ofdescent point. If air traffic control is unable to accommodate 

such a request, one of two scenarios will ensue: an early 

descent or a late descent.

Early Descents

Beginning descent before reaching the planned top-ofdescent point means you must set aside descent planning and 

proceed without the benefit of vertical guidance offered by 

the navigation system. If, during the descent, the navigation 

computer does not display position with respect to the 

planned descent path, you must simply do the best possible 

to arrive at the crossing restriction at the assigned altitude.

If the navigation system does display position with respect 

to the planned descent path, you can usually recapture 

the planned descent path and resume flying with vertical 

guidance from the computer. The basic technique is to 

initiate descent at a reasonable descent rate that is less than 

the planned descent rate. If you follow this initial descent 

rate, you will eventually intercept the planned descent path, 

as shown in Figure 3-35.
3-24

ECA

Flying a greater than planned descent rate 

causes you to descend too quickly and 

end up below the planned descent path.

3 0 0 0 ft

ath.

1 1 0 0 0 ft

180 knots @ fpm 1 0 0 0

180 knots @ fpm 1 5 0 0

ECA

Flying a greater than planned descent speed causes 

you to cover more ground during the descent and 

end up above the planned descent path.

3 0 0 0 ft

1 1 0 0 0 ft

3 0 0 0 ft

1 8 0 knots @ 1,000 fpm

1 1 0 0 0 ft

2 0 0 knots @ 1,000 fpm

ECA

20-knot tailwind

3 0 0 0 ft

20-k

3 0 0 0 ft

1 8 0 knots @ 1,000 fpm

knot tailwind

knots @ 1,000 fpm

An unanticipated tailwind causes you to speed 

up, cover more ground during the descent, 

and drift up above the descent path.

2 0 0

1 1 0 0 0 ft

Figure 3-34. Drifting off the planned descent path.

ECA

Flying a greater than planned descent rate 

causes you to descend too quickly and 

end up below the planned descent path.

3 0 0 0 ft

ath.

1 1 0 0 0 ft

180 knots @ fpm 1 0 0 0

180 knots @ fpm 1 5 0 0

ECA

Flying a greater than planned descent speed causes 

you to cover more ground during the descent and 

end up above the planned descent path.

3 0 0 0 ft

1 1 0 0 0 ft

3 0 0 0 ft

1 8 0 knots @ 1,000 fpm

1 1 0 0 0 ft

2 0 0 knots @ 1,000 fpm

ECA

3 0 0 0 ft

1 1 0 0 0 ft

knots @ 1,000 fpm

An unanticipated headwind 

causes you to slow down 

and cover less ground 

during the descent and end 

up below the descent path.

1 6 0

1 1 0 0 0

1 8 0 knots @ 1,000 fpm

20-knot headwind

Figure 3-35. Early descent scenario.

Late Descents

Beginning the descent beyond the planned top-of-descent 

point means that you will have the same amount of excess 

altitude, but a shorter distance and time to lose it, as shown 

in Figure 3-36.

Since flying beyond the planned top-of-descent point leaves 

less time to lose excess altitude, your goal is to minimize the 

“overrun” distance by slowing the aircraft as soon as a late 

descent scenario is suspected. A lower speed means you will 
3-25

ECA VOR

3 0 0 0 ft

1 1 0 0 0 ft

180 knots @ fp 180 knots @ 1 0 0 0 m

180 knots @ fp 5 0 0 m

Actual descent point Planned top-of-descent point

Figure 3-36. Late descent scenario.

SUNOL 

TRACY

DO NOT USE FOR

NAVIGATION

009°

060°

080°

Figure 3-37. A simple course intercept scenario.

cover less distance in the same amount of time, and thus be 

left with more time to lose altitude.

Common Error: Not Considering Winds During 

Descent Planning

A common error in planning a descent is failing to consider 

winds and their effect on groundspeed. As illustrated in 

Figure 3-34, if you fail to take into account a 20-knot 

tailwind, your groundspeed will be faster than you planned, 

and you will reach the target waypoint before reaching the 

assigned altitude.

Essential Skills

1. Determine the descent airspeed to be used with 

attention to turbulence, aircraft descent profile, and 

powerplant cooling restrictions.

2. Program, observe, and monitor the top of descent, 

descent rate, and level-off altitude.

3. Plan and fly a descent to a crossing restriction.

4. Recognize and correct deviations from a planned 

descent path, and determine which factor changed.

Intercept And Track Course

Intercepting and Tracking a Different Course to 

the Active Waypoint

Figure 3-37 illustrates a common situation. Air traffic control 

instructs you to fly to a waypoint via an inbound course 

different from the desired track calculated by the FMS. In 

the example in Figure 3-37, you are en route to SUNOL 

intersection. The FMS has calculated a desired track of 060 

degrees, but ATC has instructed you to fly a heading of 080 

degrees to intercept a 009-degree course to SUNOL.

The FMS is set to take the aircraft to SUNOL intersection, 

but via an inbound course different from the one ATC has 

cleared you to follow. Therefore, you need to be a means 

of programming the FMS to follow your choice of course 

instead of the desired track that it has identified.

The Nonsequencing Mode

Every IFR-capable FMS/RNAV unit offers an alternative 

mode of operation, the nonsequencing mode, which allows 

you to perform this particular task. Like the OBS knob which 

allows you to select VOR radials, the nonsequencing mode 

allows you to select courses to or from an active waypoint. 

The nonsequencing mode differs from the sequencing mode 

in two important ways:

1. Nonsequencing mode allows you to select a different 

inbound course to the active waypoint. For this reason, 

some manufacturers refer to the nonsequencing mode 

as OBS (hold or suspend) mode, which suggests 

similarity to the OBS knob found on traditional VOR 

indicators. As the OBS knob allows you to select 

inbound VOR radials, the nonsequencing mode allows 

you to select inbound courses to an active waypoint.
3-26

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

114.10

116.00

COM

121.300

135.400

NAV

CRS009 SUNOL DIS DTK BRG

GS TRK ETE

 6.9nm m m 

 85kt m 04:52

5.0 5.0

OBS

0

9

18

27

3

33

24

21

15

12

30

6

TO N

A

V

To switch to the nonsequencing mode, press .

OBS displays above the button to indicate that the

nonsequencing mode is in use.

OB

Once in the nonsequencing mode, 

use the OBS knob 

to dial the inbound 

course of 009°. OBS

Figure 3-38. Setting a different course to the active waypoint.

2. Nonsequencing mode stops the waypoint sequencing 

feature of the FMS/RNAV unit. If engaged in 

nonsequencing mode, the FMS/RNAV program does 

not automatically sequence to the next waypoint in 

the flight plan when the aircraft arrives at the active 

waypoint.

Every FMS/RNAV offers a way to switch to the nonsequencing 

mode. There is typically a button marked OBS (or Hold), and 

an OBS or course selection knob to select an inbound course 

to the active waypoint. Figure 3-38 illustrates the procedure 

for one particular FMS.

Once you switch to nonsequencing mode and select the 

inbound course of 009°, the navigation indicator reflects 

aircraft position with respect to the 009° course. The 

navigation indicator in Figure 3-38 shows that you are 

west of course. The assigned heading of 080° provides an 

acceptable intercept angle. As you fly the 080° heading, the 

needle centers as you reach the 009° course. Once the 009° 

course is reached and the needle has centered, you can turn 

to track the 009° course inbound to SUNOL.

It is important to remember that the nonsequencing 

mode suspends the FMS/RNAV’s waypoint sequencing 

function. If you reach SUNOL and the unit is still set in the 

nonsequencing mode, it will not sequence on to the next 

waypoint. Generally, once established on a direct course to 

waypoint or navaid, switching back to sequencing (releasing 

the Hold or Suspend function) mode allows the FMS/RNAV 

to continue to the programmed point and thence onward 

according to the programmed routing. Setting the computer 

back to the sequencing mode is usually accomplished by 

pressing the OBS (Hold or Suspend) button again.

Common Error: Forgetting To Re-Engage 

Sequencing Mode After Course Intercept

By far the most common error made with the nonsequencing 

mode is forgetting to re-engage the sequencing mode once 

the course has been intercepted. The result is that the FMS 

will not sequence to the next waypoint in the flight route 

upon reaching the active waypoint. The best indicator of this 

event is the “To/From” navigation display showing “From.” 

Normally all FMS fly “To” the waypoint, unless that unit 

does holding patterns. Flying “From” a waypoint can only 

be done in the “OBS”/“Hold”/“Suspend” mode.

Awareness: Remembering To Make Needed Mode 

Changes

The use of the sequencing and nonsequencing modes 

illustrates another aspect of maintaining good mode 

awareness—remembering to make required mode changes 

at future times during the flight. Remembering to do tasks 

planned for the future is a particularly error-prone process 

for human beings. Aviation’s first line of defense against 

such errors is the checklist. Creating your own checklist or 

callout procedures for maneuvers such as course intercepts 

is a good way to minimize this error. For example, a simple 

callout procedure for the course intercept maneuver might 

commence when the aircraft nears the point of interception. 

“Course is alive. Course is captured. Changing back to 

sequencing mode.”

Intercepting and Tracking a Course to a Different 

Waypoint

Figure 3-39 illustrates a slightly more complicated request 

often made by air traffic control. While en route to SUNOL, 

ATC instructs you to fly a heading of 060° to intercept and 

track the 049 course to TRACY. This situation requires two 

separate tasks: changing not only the inbound course, but 

also the active waypoint.

The first step is to change the active waypoint using the 

direct-to function, as illustrated in Figure 3-40. Remember, 

though, that if you use the direct-to function to make TRACY 

the active waypoint, the FMS calculates a desired track that 

takes you from the present position to TRACY intersection.
3-27

SUNOL 

TRACY

DO NOT USE FOR

NAVIGATION

055°

Figure 3-39. A more complicated course intercept scenario.

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

119.000

121.600

NAV

KSQL SUNOL DIS DTK BRG

GS TRK ETE

8.05nm 060 m 060 m 

120kt 060 m 04:00

1. .0

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

119.000

121.600

FPL

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

00 KSQL / KO27 

M

TRACY

KSQL

SUNOL

M 15.0 m 

n 

_ _ _ M m 

n _ _ _

7.6 m 

n 

ECA

M 18.3 m 

n 

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

123.850

125.100

NAV

 TRAC D Y DIS DTK BRG

GS TRK ETE

18.2nm 070 m 070 m 

121kt 060 m 09:06

1. .0

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

125.100

122.800

NAV

 TRACY DIS DTK BRG

GS TRK ETE

21.5nm 049 m 051 m 

120kt 055 m 10:45

6.0 1.0

CRS049

OBS

F

0

9

18

27

3

33

24

21

15

12

30

6

TO N

A

V

C

R

C COM

119 000 1 0

1 SUNOL is the currently the active waypoint, 

which must be changed.

C C COM

119 000

ACTIVE FLIGHT PLAN

00 KSQL / KO27

2 On the flight plan, use the direct-to 

function to proceed directly to TRACY.

C

R

C COM

123 850 1 0

3 The FMS now plans to take you directly to 

TRACY, which is not quite what you want.

6 The course you dialed in becomes the 

new desired track to the active waypoint.

C C COM

125.100 6 0

4 Switch the FMS to the 

nonsequencing mode.

RING

TRACY

1.0

049

5 Dial the inbound course.

Figure 3-40. Intercepting a course to a different waypoint.

The second step, illustrated in Figure 3-40, is to change 

the desired track to TRACY by setting the computer in the 

nonsequencing mode and selecting the inbound course. You 

now continue on the assigned heading until the needle centers, 

then set the FMS back to the sequencing mode, and continue 

inbound on the assigned course to TRACY intersection.

Common Error: Setting the Wrong Inbound Course 

During a Course Intercept

One common error made during course intercepts is to 

select the wrong course to the active waypoint. Some FMSs 

automatically set the course indicator (“slew” the needle) 

to the inbound course. Where this capability does not exist, 

pilots occasionally select the heading that they have been 

assigned to fly to intercept the course instead of the inbound 

course. The outcome of this error is illustrated in Figure 3-41.

Common Error: Setting the Wrong Active Waypoint 

During a Course Intercept

Another common error is failing to realize that ATC has 

instructed you to intercept a course to a different waypoint. 

Figure 3-42 shows the outcome when the pilot neglects to 

set TRACY as the active waypoint in the previous example. 

The FMS offers guidance along the correct course, but to 

the wrong waypoint.

Catching Errors: A Helpful Callout Procedure for 

Course Intercepts

The following is a useful technique for avoiding two errors 

commonly made during course intercept maneuvers. Ask 

yourself the following two questions when working your 

way through any course intercept maneuver:

Question #1: Where am I going?

Point to the active waypoint on the navigation page and make 

sure it shows the waypoint that you wish to fly toward.

Question #2: How am I getting there?

Point out the desired track to the active waypoint on the 

navigation page. If it is not the one you want, engage the 

nonsequencing mode and select the course you want.
3-28

SUNOL 

TRACY

DO NOT USE FOR

NAVIGATION

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

114.10

116.00

COM

121.300

135.400

NAV

 SUNOL DIS DTK BRG

GS TRK ETE

6.9nm 080 m 028 m 

85kt 040 m 04:52

5.0 5.0

CRS080

The assigned heading is mistakenly entered in place

of the course to be intercepted.

The FMS provides guidance along the wrong course.

049°

Figure 3-41. Selecting the wrong course to the active waypoint.

SUNOL 

TRACY

DO NOT USE FOR

NAVIGATION

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

114.10

116.00

COM

121.300

135.400

NAV

 SUNOL DIS DTK BRG

GS TRK ETE

6.9nm 080 m 028 m 

85kt 040 m 04:52

5.0 5.0

CRS049

The course to be intercepted is entered correctly, 

but the waypoint is not.

The FMS provides guidance along the wrong course.

049°

Figure 3-42. Setting the wrong active waypoint.

Essential Skills

1. Program and select a different course to the active 

waypoint.

2. Select the nonsequencing waypoint function (OBS, 

Hold, or Suspend) to select a specified navigation 

point.

3. Reactivate the sequencing function for route 

navigation.

Holding

The FMS/GPS unit’s nonsequencing mode provides an easy 

way to accomplish holding procedures. When instructed to 

hold at a waypoint that appears in the route programmed in 

the FMS/GPS unit, simply engage the nonsequencing mode 

prior to reaching the waypoint. With waypoint sequencing 

suspended, you can determine and fly the appropriate holding 

pattern entry, select the inbound holding course using the 

course selector (OBS in some) knob or buttons, and fly the 

holding pattern while timing the outbound leg. Some FMSs 

can automatically enter the holding pattern, and continue to 

hold if programmed. As the aircraft repeatedly crosses the 

holding waypoint with each turn in the hold, the holding 

waypoint remains the active waypoint. When you are cleared 

out of the holding pattern for the approach or to another 

point, you should select the sequencing mode or cancel the 

suspension before reaching the holding waypoint for the last 

time. When you pass the holding waypoint in sequencing 

mode, the FMS/GPS unit will then sequence to the next 

waypoint in the route. This procedure is demonstrated in 

Figure 3-43.

Preprogrammed Holding Patterns

Some FMS/GPS units insert preprogrammed holding patterns 

into published instrument procedures. The purpose of a 

preprogrammed holding pattern is to relieve you of many of 

the tasks described above for flying a holding pattern.

Figure 3-44 illustrates a preprogrammed holding pattern that 

appears at the end of a missed approach procedure. 

As the FMS/GPS unit shown in Figure 3-44 sequences to 

a preprogrammed holding pattern, the navigation displays a 

message indicating the type of holding entry required based 

on the aircraft’s current track. The system then automatically 

switches to a special nonsequencing mode that not only stops 

waypoint sequencing, but also sets the inbound course to 

the holding waypoint. This special nonsequencing mode 

is different from the nonsequencing mode you engage 

manually. In Figure 3-44, this system uses the term suspend 

mode (SUSP) to signify the nonsequencing mode that is 

automatically engaged during a preprogrammed holding 

procedure. Depending on the type of holding procedure, 

the unit may or may not automatically switch back to the 

sequencing mode after the aircraft crosses the holding fix. 

As always, you must be careful to maintain constant mode 

awareness.
3-29

SANTY

V25 

SANTY

V25 

SANTY

V25 

SANTY

V25 

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.30

114.30

COM

133.000

127.150

NAV

CRS115° SNS DIS DTK BRG

GS TRK ETE

4.79nm 115 m 115 m 

120kt 115 m 02:23

5. .0

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.30

114.30

COM

133.000

127.150

NAV

CRS115° SNS DIS DTK BRG

GS TRK ETE

2.49nm 115 m 071 m 

120kt 295 m 01:18

5.0 5.0

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.30

114.30

COM

133.000

127.150

NAV

CRS115° SNS DIS DTK BRG

GS TRK ETE

2.05nm 115 m 115 m 

120kt 115 m 01:01

5.0 5.0

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.30

114.30

COM

133.000

127.150

NAV

SNS PRB DIS DTK BRG

GS TRK ETE

74.5nm 126 m 126 m 

120kt 126 m 37:15

5.0 5.0

V

OBS

0

9

18

27

3

33

24

21

15 12

30

6

TO N

A

V

9

18 15 12

TO N

A

V

1 1 5

V

OBS

0

9

18

27

3

33

24

21

15 12

30

6

TO N

A

V

9

18 15 2

TO N

A

V

1 1 5

V

OBS

0

9

18

27

3

33

24

21

15 12

30

6

TO N

A

V

9

18 15 2

TO N

A

V

1 1 5

V

OBS

0

9

18

27

3

33

24 21

15 12

30

6

TO N

A

V

9

18 21

15 12

TO N

A

V

1 2 6

SANTY

1 Switch to nonsequencing 

mode prior to reaching SNS.

SANTY

2 Fly the hold. SNS remains the active

waypoint, even after passing it.

SANTY

3 Switch back to sequencing

mode before reaching SNS.

4 PRB becomes the active 

waypoint, and the flight continues.

SNS VOR

SNS VOR

SNS VOR

SNS VOR

PRB VOR

Figure 3-43. Using the nonsequencing mode to fly a hold.
3-30

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

125.100

123.850

NAV

 WRAPS DIS DTK BRG

GS TRK ETE

0.6nm 124 m 130 m 

160kt 304 m 

1. .0

00:05

_ _:_ _ 

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

114.10

116.00

COM

125.400

123.850

00

WAYPOINT DTK DIS

ZOSONFA

RW10 MA

WRAPSMH

hold

ACTIVE FLIGHT PLAN

KSJC / O27

M

_ _ _ _ M _ _n 

m 

_ _ _ _ M _ _n 

m 

_ _ _ _ M _ _n 

m 

_ _:_ _

HOLD PARALLER

A preprogrammed hold is indicated 

by a special waypoint in the flight plan.

The FMS automatically switches to the nonsequencing

mode and sets the inbound course to the hold waypoint.

The FMS displays the appropriate type of hold entry.

C

RING

C COM

125 100 1 0

The FMS automatically starts a timer for the outbound leg.

Figure 3-44. A preprogrammed holding procedure.

Common Error: Mismanaging the Sequencing/

Nonsequencing Modes During a Hold

Mismanagement of the sequencing and nonsequencing 

modes during a holding procedure is another common error. 

Failing to switch the FMS/GPS RNAV to the nonsequencing 

mode prior to reaching the holding waypoint, or prematurely 

switching the unit back to the sequencing mode once 

established in the hold, can prompt the FMS/GPS to sequence 

past the holding waypoint. In this case, you are left without 

guidance along the inbound holding course.

Essential Skills

1. Select a preprogrammed holding pattern, or 

nonsequencing mode.

2. Select and setup a non-preprogrammed holding pattern 

inbound course.

3. Determine the proper sequence of software commands 

for the holding pattern, transition to approach, 

approach, and MAP navigation.

ARCS

FMS and some GPS units simplify the problem of tracking 

arcs, which are curved courses between waypoints. The 

key feature of an arc is that there is no one bearing that 

takes you from one waypoint to the next. Rather, depending 

on its length, an arc requires you to follow a gradually 

changing heading toward the active waypoint. The example 

in Figure 3-45 illustrates how an FMS is used to fly a DME 

arc procedure.

Essential Skills

1. Select an approach procedure with an arc.

2. Select the course, or determine that automatic course 

CDI setting will occur.

GPS and RNAV (GPS) Approaches

An IFR-capable GPS RNAV/FMS with qualified GPS 

receiver(s) can be used as the sole means of navigation 

for several kinds of instrument approach procedures, but 

you need to know which approaches can be used with your 

particular GPS RNAV unit. The following paragraphs review 

the approaches available today.

A GPS overlay approach is illustrated in Figure 3-46. The 

basic benefit of the GPS overlay approach is that it allows 

use of an IFR approved GPS receiver to navigate and fly a 

conventional nonprecision approach. From the previous text, 

you must know how to hold the specific sequences and how 

the unit can be stopped from sequencing through the flight 

plan. Many approaches require holding or a procedure turn 

to orient the aircraft correctly for the approach course. If 

you cannot control the sequencing of the FMS, you will lose 

course guidance upon the turn for outbound holding, as the

FMS/GPS receiver sequences for the course beyond the 

holding fix.

GPS overlay approaches are named for the conventional 

system upon which the approach is based, but include the 

word GPS. The approach in Figure 3-46 is based on an 

existing NDB approach. If the aircraft has an IFR-approved 

FMS/GPS RNAV, you may use that guidance to fly the GPS 

overlay approach. It is not necessary for the aircraft to have 

the conventional navigational equipment on board for that 

approach, but conventional navigational avionics will be 

required for any required alternate, if equipped with a TSO129 GPS receiver. If conventional avionics are installed in 

the aircraft, there is no requirement to use the equipment in 

any way, although monitoring is always a good practice. If 

the installed FMS/GPS receiver is TSO-145A/146A WAAS 

certified, no other navigation equipment is required.

One common pitfall of all advanced avionics approaches is 

the sometimes limited notification of the position along the 

approach path. In many instances, you must read the name 

of the waypoint to confirm where the aircraft is headed. It is 

easy for you to be preoccupied with cross-check and flying 
3-31

JEZJE 

KENIW

DYNER 

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

APR

ARM

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

DTK035° TK 035°

1.3nm

150 kt 0.01nm :1.0nm

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

APR

ARM

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

DTK040° TK 040° 048° To 00:24

1.0nm

150 kt 0.01nm :1.0nm

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU

APR

ARM

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

DTK048° TK 048° 053° To 00:17

0.7nm

150 kt 0.01nm :1.0nm

DO NOT USE FOR

NAVIGATION

OBS

0

9

18

27

3

33

24 21

15

12

30

6

TO N

A

V

0

9

3

12

6

TO N

A

V

0 4 8

If you are using a conventional course 

deviation indicator, you must use the 

OBS knob to adjust the course manually.

The FMS/RNAV automatically adjusts the desired

track as you make your way along the arc.

Figure 3-45. Flying an approach with an arc.

duties to miss a waypoint change and be of the mindset that 

you have one more waypoint to go before descent, or even 

worse, before a missed approach. Two main values always 

to include in the cross-check are:

1. Verification of the waypoint flying “to.”

2. Verification that the distance to the waypoint is 

decreasing. Upon reaching the missed approach point 

(MAP), the system will automatically go to “Suspend,” 

“Hold,” or “OBS” at the MAP, and the distance to go 

will begin counting up or increasing as the distance 

from the MAP behind increases. Acknowledge the 

MAP and the beginning of the MAP segment by an 

action (button, knob, etc.) to allow sequencing to the 

holding point or procedure.

Not all units delay commanding a turn prior to reaching 

the specified turn altitude. You must know the required 

navigation courses and altitudes. The FMS/GPS unit may not 

be 100 percent correct, especially if an ADC is not installed.

Since the FMS/GPS automatically switches to the approach 

sensitivity, you must not attempt to use the “approach” 

mode of the autopilot at that time, unless the autopilot 

documentation specifically directs the use of that mode 

at that time. Using that mode would make the autopilot 

hypersensitive and too responsive to navigation signals.

GPS stand-alone approaches are nonprecision approaches 

based solely on the use of the GPS and an IFR-capable FMS 

with GPS navigation receiver or GPS RNAV. A GPS standalone approach is shown in Figure 3-47.

RNAV (GPS) approaches are designed to accommodate 

aircraft equipped with a wide variety of GPS receivers. An 

RNAV (GPS) approach procedure is shown in Figure 3-48.

A GPS approach typically offers different approach 

minimums (and sometimes different missed approach 

points) depending on the type of GPS receiver, aircraft, and 

installation being used to complete the approach.
3-32

Figure 3-46. A GPS overlay approach.
3-33

Figure 3-47. GPS stand-alone approach.
3-34

Figure 3-48. RNAV (GPS) approach.
3-35

GPS ENR

FLAGGED

119.000

121.600

114.10

116.00

1200

A 

C 

T

A 

C 

T

S 

B 

Y

S 

B 

Y

S 

B 

Y

--.- vor

MSG PROC FPL NAV

GS ETE

DIST BRG

120kt 04:52

9.74 n

m TRK 332° 332°

Lnav/Vnav C345 SUNOL RW34Lm

DTK

346°

119.000 A

C

T 9.74 n

m TRK 332° 332°

This FMS/RNAV provides lateral and vertical 

guidance during an RNAV approach.

Figure 3-49. WAAS data provides lateral and vertical guidance.

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU OBS285

TK 285

0.1nm

QUADSi

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

0.1nm

Initial approach waypoint

RNG

Final approach waypoint

Missed approach waypoint Missed hold waypoint

Figure 3-50. Approach waypoints.

LNAV

LNAV (lateral navigation), like a conventional localizer, 

provides lateral approach course guidance. LNAV minimums 

permit descent to a prescribed minimum descent altitude 

(MDA). The LNAV procedure shown on the chart in 

Figure 3-48 offers an MDA of 1,620 feet.

LNAV/VNAV

LNAV/VNAV (lateral navigation/vertical navigation) 

equipment is similar to ILS in that it provides both lateral 

and vertical approach course guidance. Since precise vertical 

position information is beyond the current capabilities of 

the global positioning system, approaches with LNAV/

VNAV minimums make use of certified barometric VNAV 

(baro-VNAV) systems for vertical guidance and/or the 

wide area augmentation system (WAAS) to improve GPS 

accuracy for this purpose. (Note: WAAS makes use of a 

collection of ground stations that are used to detect and 

correct inaccuracies in the position information derived from 

the global positioning system. Using WAAS, the accuracy 

of vertical position information is increased to within 3 

meters.) To make use of WAAS, however, the aircraft must 

be equipped with an IFR approved GPS receiver with WAAS 

signal reception that integrates WAAS error correction 

signals into its position determining processing. The WAAS 

enabled GPS receiver shown in Figure 3-49 allows the pilot 

to load an RNAV approach and receive guidance along the 

lateral and vertical profile shown on the approach chart in 

Figure 3-48.

It is very important to know what kind of equipment is 

installed in an aircraft, and what it is approved to do. It is 

also important to understand that the VNAV function of 

non-WAAS-capable or non-WAAS-equipped IFR approved 

GPS receivers does not make the aircraft capable of flying 

approaches to LNAV/VNAV minimums.

LPV

LPV can be thought of as “localizer performance with 

vertical guidance.” Procedures with LPV minimums use GPS 

information to generate lateral guidance, and IFR-approved 

GPS/WAAS receivers to generate vertical guidance similar 

to an ILS glideslope. Several manufacturers now offer FMS/

GPS RNAV units capable of flying approaches to LPV 

minimums.

GPS or RNAV (GPS) Approach Waypoints

Figure 3-50 shows a GPS approach loaded into an FMS/GPS 

RNAV. As previously noted, approaches must be selected 

from a specific approach menu in the FMS. The software 

then loads all of the waypoints associated with that procedure 

from the database into the flight route. It is not possible for 

you to enter or delete, separately or individually, waypoints 

associated with the approach procedure.

Once loaded, a GPS or RNAV (GPS) approach is shown in 

the FMS display as a collection of waypoints with a title that 

identifies the approach. Four waypoints in every approach 

procedure have special designations: (1) initial approach 

waypoint; (2) final approach waypoint; (3) missed approach 

waypoint; and (4) missed holding waypoint.

Flying a GPS or RNAV (GPS) Approach

Most FMS require the pilot to choose whether to simply 

load, or load and activate, instrument approach procedures. 

When ATC tells you to expect a certain approach, select 

that approach from the menu and load it into the flight plan. 

Loading an approach adds its component waypoints to the 

end of the flight plan, but does not make them active. Once 

ATC clears you for the approach (or, alternatively, begins 

providing radar vectors to intercept the final approach 

course), you must remember to activate the approach to 

receive course guidance and auto-sequencing. You must be 

careful not to activate the approach until cleared to fly it, 

however, since activating the approach will cause the FMS 

to immediately give course guidance to the initial approach 
3-36

DO NOT USE FOR

NAVIGATION

Range

View

Aux

OFF

Bearing

OFF

Nav

GPS1

Range View

ELTRO

DTK 089°

22.1 NM

00:13:18

160

150

140

130

14

4

3

2

20

10

10

20

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

125.100

122.800

NAV

 ELTRO DIS DTK BRG

GS TRK ETE

22.1nm 089 m 069 m 

99.5kt 067 m 

6.0 1.0

CRS089

13:18 

FA

MOTER

ELTRO

RW 10

ECA VOR

049° Course

ATC gives you a vector to the final approach course. to the final approach

089° Course

ATC gives you a vectort

08

060° Heading

3 Select the approach course on the CDI. 2 Set the FMS to the nonsequencing mode.

C

RING

C COM

125 100 6 0 1 0

1 Set the final approach fix as the active waypoint.

Figure 3-51. A vectored RNAV approach.

fix or closest fix outside the final fix, depending on the unit’s 

programming. In the case of a vectors-to-final approach, 

activating the vector-to-final causes the FMS to draw a course 

line along the final approach course.

Once you have loaded and activated the GPS or RNAV 

(GPS) approach procedure, flying it is similar to flying 

between any other waypoints in a programmed flight route. 

However, you must be prepared for two important changes 

during the approach.

Terminal Mode

The first important change occurs when the aircraft reaches 

a point within 30 NM of the destination airport. At this 

point, regulations require that every GPS-based FMS/

RNAV unit increase its sensitivity and integrity monitoring 

(receiver autonomous integrity monitoring, or RAIM, which 

continuously checks GPS signal reliability and alerts you if 

RAIM requirements are not met). If the system determines 

that RAIM requirements are met, the FMS/GPS RNAV unit 

automatically switches from en route sensitivity to terminal 

sensitivity within 30 NM of the destination airport. Terminal 

mode increases the sensitivity of the course deviation 

indicator (CDI) from 5 NM to 1 NM. The FMS/GPS RNAV 

displays an annunciation to let you know that it has switched 

from en route sensitivity to terminal mode.

Approach Mode

The second important change occurs 2 NM prior to reaching 

the final approach waypoint. At this point, the FMS/GPS 

RNAV unit automatically switches to approach sensitivity. 

At this stage, the FMS/GPS RNAV further increases RAIM 

requirements, and increases the CDI sensitivity from 1 NM 

to 0.3 NM (i.e., a full-scale CDI deflection occurs if you are 

0.3 NM or more from the desired course).

As long as the annunciation for approach mode is displayed, 

you may continue the approach. If, however, the computer 

fails to switch to approach mode, or the approach mode 

annunciation disappears, you must fly the published missed 

approach procedure. You are not authorized to descend 

further or to the MDA. Making changes to the FMS/

GPS RNAV after reaching the 2 NM point could result in 

automatic cancellation of the approach mode.

Approach Not Active

If you arrive at the final approach waypoint and the approach 

mode is not active, you must fly the missed approach 

procedure. There should be no attempt to activate or 

reactivate the approach after reaching the final approach fix 

using any means—simply fly the missed approach procedure.

Vectored Approaches

As in conventional approaches, it is common for air traffic 

control to issue vectors to a GPS or RNAV (GPS) final 

approach course. Flying a vectored GPS or RNAV (GPS) 

approach is a simple matter of using the course intercept 

technique described in the previous section. The technique 

is illustrated again in Figure 3-51.
3-37

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK049

TK 060

9.2nm

ECAi

LEG

Ac t i v t e V e c t o r s ?

E L T R O f D T K 0 8 9 ?

ENT

*CRSR* PROC 1 *CRSR*

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU OBS089

TK 060

21.5nm

ELTROf

OBS

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

RNG 9.2nm ENT

Press and choose this option. PROC

MSG OBS ALT NRST D CLR ENT PULL SCAN

The GPS/RNAV/FMS automatically sets the final 

approach fix as the active waypoint, and automatically 

sets the approach course as the desired track. 

No mode switching by the pilot is necessary.

Figure 3-52. The vectors-to-final feature.

Many FMS/GPS RNAV units offer an automated solution to 

the problem of flying an approach in which the pilot receives 

vectors to the final approach course. Once ATC begins 

providing vectors to intercept the final approach course, you 

should activate the computer’s “vectors-to-final” feature, 

which draws a course line along the final approach course. 

This feature helps you maintain situational awareness while 

being vectored because the assigned heading is clearly seen 

in relation to the final approach course. As already noted, 

you should monitor carefully to ensure that the FMS/GPS 

RNAV unit switches to approach mode within 2 NM of the 

final approach fix (FAF).

Figure 3-51 shows the vectors-to-final feature. The procedure 

required to use the vectors-to-final feature is illustrated in 

Figure 3-52.

When set to use the vectors-to-final feature, many FMS/

GPS RNAV units automatically set the FAF as the active 

waypoint; and set the final approach course as the desired 

track to the active waypoint.

Awareness: Briefing the Approach

As with any instrument approach, you should develop and 

consistently use a briefing technique to ensure that you 

think through all the steps necessary to set up the approach 

correctly. One technique uses the mnemonic ICE-ATM:

I Identify primary navigation frequency

C Course (inbound) set

E Entry (direct, teardrop, parallel)

A Altitudes for transition, initial, final, and missed 

approach segments

T Timing/Distance(s)

M Missed approach procedure

Another briefing technique uses the mnemonic FARS:

F Frequencies set and identified

A Altitudes for transition, initial, final, and missed 

approach segments

R Radial (inbound course) noted and set

S Special notes (including missed approach procedure)

Common Error: Forgetting To Verify the Approach 

Mode

The most common error made during a GPS/RNAV approach 

is to forget to ensure that the approach mode has indeed 

engaged prior to beginning a descent to minimums. Routinely 

checking for the approach indication 2 NM before the final 

approach waypoint not only prevents this type of error, but 

also gives you a minute or so to remedy some situations in 

which the approach mode has not engaged.

Common Error: Using the Wrong Approach 

Minimums

Listing several different approach minimums on a single 

instrument approach chart introduces the possibility of 

another simple type of error: using the wrong approach 

minimums. One way to avoid mix-ups is to verbalize the 

equipment being used and type of procedure being flown, 

and then search for the approach minimums with these details 

in mind. You must be absolutely certain of the certification, 

approval, and installed options of the advanced avionics 

equipment prior to flight planning.

Common Error: Forgetting To Reengage 

Sequencing Mode Prior to Final Approach 

Waypoint

A common mistake made by pilots when they are learning 

to fly vectored approaches without a vectors-to-final feature 

is forgetting to set the FMS/GPS RNAV back to sequencing 

mode once established on the approach course. This error 

prevents the FMS/ GPS RNAV unit from switching to the 

approach mode 2 NM prior to the FAF. If you pass the final 

approach fix and the computer is still in nonsequencing 

mode, the approach mode will be disabled and you must fly 

the missed approach, report the missed approach and request 

another approach.
3-38

DO NOT USE FOR

NAVIGATION

DO NOT USE FOR

NAVIGATION

DO NOT USE FOR

NAVIGATION

1 2 3

292°

131°

CIC

RW26

QUADS 

LODI (1O3)

285°

285°

105°

LIN

056°

171°

191°

236°

CCR

Figure 3-53. Three types of course reversals.

Essential Skills

1. Load and activate a vectored GPS or RNAV (GPS) 

approach.

2. Select a vectored initial approach segment.

3. Determine the correct approach minimums and 

identify all pertinent mode transitions.

4. Determine the published missed approach point 

(MAP), courses, altitudes, and waypoints to fly.

5. Determine how missed approach guidance is selected.

Course Reversals

Figure 3-53 shows three common course reversals: 

(1) 45-degree procedure turn, (2) holding pattern, and 

(3) teardrop procedure.

Course reversals are handled in the same way as holding 

procedures, by using the FMS/GPS’s nonsequencing mode. 

As you arrive at the initial approach waypoint, the unit’s 

nonsequencing mode should be engaged to prevent it from 

immediately sequencing to the next waypoint in the approach. 

After completing the course reversal, be sure to re-engage 

the system’s sequencing mode to continue the approach.

The navigation unit in Figure 3-54 requires that you manually 

switch between the sequencing and nonsequencing modes.

Preprogrammed Course Reversals

Some FMS/GPS units insert preprogrammed course reversals 

into published instrument approach procedures. The purpose 

of a preprogrammed course reversal is to relieve you from 

the mode switching and course selection tasks associated 

with course reversals.

The FMS/GPS unit in Figure 3-55 includes a preprogrammed 

course reversal. This unit automatically sets the outbound 

course for the outbound portion of the course reversal. Once 

the turn inbound has been made, the unit automatically sets 

the inbound course back to the final approach waypoint.

This FMS/GPS unit does not switch between sequencing 

and nonsequencing modes for a 45-degree course reversal 

(although it does for a holding-type course reversal). Whether 

it is done manually, automatically, or not at all, you must be 

sure that the system is engaged in sequencing mode before 

reaching the final approach waypoint after the course reversal 

is completed. The FMS/GPS will switch to the approach 

mode only if the system is engaged in the sequencing mode.

Common Error: Mismanaging the Sequencing/

Nonsequencing Modes During a Course Reversal

Neglecting to switch the FMS/GPS from the nonsequencing 

mode prior to reaching the initial approach waypoint and 

neglecting to switch the system back to the sequencing mode 

prior to passing the final approach waypoint are common 

errors made during course reversals.

Essential Skills

1. Select a type of course reversal procedure.

2. Determine the correct sequence of mode control 

actions to be accomplished by the pilot.
3-39

DO NOT USE FOR

NAVIGATION

DO NOT USE FOR

NAVIGATION

DO NOT USE FOR

NAVIGATION

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK292

TK 292

5.6nm

GIRUCi

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK333

TK 153

1.8nm

108 kt

OBS

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK333

TK 153

3.8nm

108 kt

LEG

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

RNAV 30 KHAF

 5: GIRUCi

 6: WOHLIf

 7: PUXXKOm 6

 8: GIRUCh 12

 GIRUCi

0.1nm :5.0nm

 VNV Off

333° To 01:50

 WOHLIf

0.01nm :1.0nm

 VNV Off

333° To 01:44

RUXKO

WOHLI

*

GIRUC

WOHLI

RUXKO

WOHLI

*

GIRUC

As you approach the initial approach fix in the sequencing mode ...

...switch to the nonsequencing mode prior to reaching the initial

approach fix, twist the inbound course, then fly the procedure

turn. The IAF remains the active waypoint.

When you turn inbound, switch back to sequencing mode. 

When you cross the IAF, the system sequences to the final

approach waypoint.

318°

153°

333°

153°

333°

318°

153°

333°

Figure 3-54. Using the nonsequencing mode to accomplish a course reversal.
3-40

DO NOT USE FOR

NAVIGATION

DO NOT USE FOR

NAVIGATION

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.00

114.80

COM

119.900

119.700

FPL

CC IA

proc. turn

015°m 

011°m 

191°m 

3.1n

m 

8.0n

m 

8.0n CC FA m 

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

00 KSJC / KCCR 

Approach NDB 19R

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.00

114.80

COM

119.900

119.700

NAV

DIS DTK BRG

GS TRK ETE

0.49nm 011 m 181 m 

120kt 001 m 

1. .0

CC IA

00:29 

C

RING

NRST OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.00

114.80

COM

119.700

119.900

NAV

 CCf DIS DTK BRG

GS TRK ETE

2.05nm 191 m 191 m 

120kt 191 m 

1. .0

01:01 

236°

056°

171°

191°

236°

056°

171°

191°

CC

CC

C COM

119

A preprogrammed course reversal.

RING

C COM

119

The unit automatically sets the outbound course.

The unit automatically sets the inbound course after the turn is made.

Figure 3-55. Using the nonsequencing mode to accomplish a course reversal.

CORYN (MAP)

KMRY

SNS VOR (hold fix)

DO NOT USE FOR

NAVIGATION

6,000 feet

1,900 feet

Figure 3-56. A missed approach procedure.

Missed Approaches

The FMS/GPS unit’s nonsequencing mode provides an easy 

way to fly missed approach procedures, such as the one 

illustrated in Figure 3-56.

The missed approach procedure shown in Figure 3-56

requires you to climb to 1,900 feet, turn right and climb to 

6,000 feet, then proceed direct to the SNS VOR.

The FMS/GPS helps you navigate between waypoints, 

which are geographically fixed locations. But where will the 

aircraft reach 1,900 feet on the missed approach procedure at 

Monterey? This depends on what aircraft you are flying and 

the chosen rate of climb. A single-engine airplane might be 

four miles away by the time it reaches 1,900 feet. A small 

jet might reach 1,900 feet by the end of the runway. The 

problem is that, given the way the FMS/GPS system uses 

waypoints, there is no one way to represent the climbs and 

turns required on a missed approach procedure.

To address this issue, all FMS/GPS RNAV units automatically 

suspend waypoint sequencing when you reach the missed 

approach point. The unit waits until you acknowledge the 

passing of the MAP before it continues the sequencing. When 

the aircraft has gained the published altitudes and complied 
3-41

C

RING

CDI OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

110.70

117.30

COM

118.400

133.000

SNS MH

084°m 

CORYNMA 264°m 

RANIE FA

hold 01:00

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

00 KSJC / KMRY

FPL

_ _ _ m _ _._ n

m

_ _._ n

m

APR

C

RING

CDI OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

110.70

117.30

COM

118.400

133.000

SNS MH

084°m 

CORYNMA

RANIE FA

hold 01:00

WAYPOINT DTK DIS

ACTIVE FLIGHT PLAN

00 KSJC / KMRY

FPL

_ _ _ m _ _._ n

m

_ _ _ m _ _._ n

m

_ _ _ m _ _._ n

m TERM

COM ACTIVE FLIGHT PLAN RING

After reaching the missed approach point, the missed

approach point remains the active waypoint, and the

system automatically switches to the nonsequencing

mode (SUSP).

COM ACTIVE FLIGHT PLAN RING

After executing the climbs and turns, you must switch

back to the sequencing mode to proceed to the missed

approach hold waypoint.

When you reach the missed approach hold waypoint,

the system will switch back to the nonsequencing mode

and allow you to fly the hold.

Figure 3-57. Flying a missed approach procedure.

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK285

TK 285

1.4nm

90 kt

APR

ARM

OBS

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

QUADSf MAPYNm

0.01nm :0.3nm

 VNV Off

285° To 00:42

RNG

PULL SCAN

PUSH ON

BRT

PROC CRSR

MSG OBS ALT NRST D CLR ENT

MENU DTK285

TK 285

0.9nm

90 kt

APR

ARM

OBS

APT VOR NDB INT USR ACT NAV 1 FPL SET AUX

QUADSf MAPYNm

0.01nm :0.3nm

 VNV Off

285° To 00:27

RNG 1.4nm QUADSf MAPYNm

The aircraft is 1.4 NM short of the missed approach point.

D CLR ENT PULL SCAN

Arrow pointing TO

RNG PROC CRSR

0.9nm QUADSf MAPYNm

The aircraft is 0.9 NM past the missed approach point.

D CLR ENT PULL SCAN

Arrow pointing FROM

Figure 3-58. Recognizing the missed approach waypoint.

with the initial MAP procedures, you can safely proceed 

to the missed approach holding waypoint, being mindful 

of any altitude requirements. A waypoint for the missed 

approach holding point is included as part of the missed 

approach procedure. In the example above, you can make 

the missed approach holding waypoint the active waypoint, 

and re-engage the sequencing mode upon reaching 6,000 

feet. You now have sequencing mode guidance to the missed 

approach holding waypoint. The procedure for one FMS/GPS 

is illustrated in Figure 3-57.

Since the hold at SNS is part of the published missed 

approach procedure, it can be carried out using the same 

technique used to perform a holding pattern. Some FMS/GPS 

units will automatically switch to the nonsequencing mode 

when you reach the hold fix. Other units may advise you to 

switch manually to the nonsequencing mode.

Recognizing the Missed Approach Point

With any type of navigation equipment, it is important to 

be able to determine when you have reached the missed 

approach point. The missed approach point indications given 

by FMS/GPS units are sometimes subtle. Consider the two 

navigation displays shown in Figure 3-58. The display in the 

top graphic of Figure 3-58 shows the aircraft approaching 

the missed approach point, 1.4 NM away.

Now consider the display in the bottom graphic of 

Figure 3-58. The distance from the missed approach point 

might suggest that the aircraft is now even closer to the 

missed approach point. However, the TO/FROM flag on the 

course deviation indicator shows that the aircraft has in fact 

passed the missed approach point. It is tempting to monitor 

the distance from the missed approach point as it decreases 

to 0.0 NM. The problem is that, depending on how accurately 

the pilot flies, the distance may never reach 0.0 NM. Rather, 

it may simply begin to increase once you have passed abeam 

the missed approach point. It is, thus, important to check not 

only the distance from the missed approach point, but also the 

TO/FROM flag or arrow. In the rush of a missed approach, 

this small clue (arrow direction change) can be difficult to 

read and very easy to misinterpret.

Complying With ATC-Issued Missed Approach 

Instructions

ATC sometimes issues missed approach instructions that 

are different from those published on the approach chart. In 

this case, use the techniques described earlier to insert new 

waypoints into the route, and/or to intercept and track courses 

to those waypoints.

Setting Up Next Procedure in Hold

Once in the missed approach holding pattern, the next task is 

deciding where to go next and programming the new flight 

plan into the FMS/GPS unit. In this high workload situation, 
3-42

it is especially important to be very proficient with the menus, 

functions, and “switchology” of a particular unit. If the 

aircraft is equipped with an autopilot, it is also essential to 

have a thorough understanding of how the autopilot interacts 

and interfaces with the FMS/GPS navigation equipment.

Common Error: Noncompliance With Initial 

Missed Approach Instructions

The immense capability of the FMS/GPS may tempt you 

to follow its directions rather than fly a missed approach 

procedure exactly as published on the instrument approach 

procedure chart. Always fly procedures as published, 

especially with respect to the initial climb and turn 

instructions. GPS as a line-of-sight navigation aid can display 

courses and distances to a ground-based navaid even though 

the navaid is on the other side of a mountain range and itself 

cannot be received, because GPS signals are spaced based.

Essential Skills

1. Acknowledge a missed approach procedure.

2. Set the FMS/GPS for a return to the same approach 

to fly it again.

3. Select a different approach while holding at a missed 

approach holding waypoint.

4. Program an ATC specified hold (user waypoint) point 

for selection after the published MAP/hold procedure.

Ground-Based Radio Navigation

Configuring FMS To Receive Ground-Based

Radio Navigation Signals

Most advanced avionics systems include receivers for 

conventional radio navigation signals from VOR, localizer, 

and glideslope transmitters. To display these signals on the 

navigation display indicator(s), you need two fundamental 

skills.

Tuning and Identifying Radio Navigation Facilities

The first fundamental skill in ground-based radio navigation 

is tuning and identifying a ground-based radio navigation 

facility. Figure 3-59 illustrates how a VOR station can be 

tuned using two different systems.

Some systems automatically attempt to identify ground-based 

radio navigation facilities that are selected by the pilot. Note 

the identifier that appears beside the selected frequency in the 

upper left corner of the PFD in Figure 3-59 (116.00 = ECA).

Displaying Radio Navigation Signals on the 

Navigation Indicator

The second fundamental skill is displaying indications from 

a ground-based radio navigation facility on the navigation 

display indicator in the aircraft. In addition to setting the 

navigation indicator to display indications from different 

navigation sources, you must also know where to look 

to double-check which indications are currently being 

displayed. It is crucial to remain constantly aware of the 

navigation source for each indicator. Many systems use color 

coding to make a visual distinction between different RNAV 

navigation sources (GPS, INS, etc.) and ground-based radio 

navigation sources.

Awareness: Using All Available Navigation 

Resources

Looking at the two systems shown in Figure 3-59, you can 

see that two VOR frequencies appear in the active windows 

at all times, regardless of whether VOR or GPS is being used 

as the primary navigation source. To maximize situational 

awareness and make best use of this resource, it is a good 

practice to keep them tuned to VOR stations along your route 

of flight. If you have two navigation indicators, you can have 

one indicator set to show GPS course indications, with the 

other to show VOR indications. Used in this way, VOR and 

GPS can serve as backups for each another.

Flying a Precision Approach Using Ground-based 

Navigation Facilities

Flying a precision approach requires tuning the required 

frequencies, configuring the navigation indicator to display 

localizer course indications, and flying the approach. For 

aircraft equipped with multiple navigation radios, the 

localizer frequency can go into one receiver, while a second 

navigational facility used as a cross-radial can be set in the 

other receiver. As you come within range of the localizer and 

glideslope, the course deviation and glideslope indicators will 

show position with respect to the localizer and glideslope.

Flying a Nonprecision Approach Using GroundBased Navigation Facilities

Nonprecision approaches such as VOR, localizer, and LDA 

approaches are flown using the same procedures used to 

fly a precision approach. If the aircraft is equipped with an 

autopilot, be sure to develop a thorough understanding of 

how the autopilot works with the FMS. While these systems 

automate some tasks, others (e.g., flying the procedure turn 

course reversal) maybe left to the pilot.
3-43

XPDR 0365 IDNT LCL23:00:34

VOR 1

350° HDG 080° CRS 316°

2

1

1

2

4200

4100

4000

3900

3800

3700

3600

60

20

3900

5000

130

120

110

90

80

70

1

100

9

TAS 100KT

OAT15°C

ALERTS

NAV1 114.10 116.00ECA

NAV2 113.90 114.80

123.850 125.100 COM1

125.900 121.600 COM2

WPT ECA DIS 12.0NM DTK 049° TRK 090°

C

RING

CDI OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

116.00

114.10

COM

125.100

123.850

NAV

 ECA DIS DTK BRG

GS TRK ETE

12.0nm 049 m 049 m 

124kt 350 m 

1.0 1.0

TRACY

05:48 

OBS

0

18

9

27

3

33

24

21

15 12

30

6

TO N

A

V

C

V

VOL/ ID

PUSH

2 Identify the VOR.

COM RING

1 Dial the VOR frequency using the knobs to the left.

4 Dial the VOR radial. l the VOR radial.

3 Press to show indications from the VOR receiver on the navigation indicator. CDI

NAV1 114.10 116.00ECA WPT ECA DIS

3

1 Dial the VOR frequency.

9° TRK 090° 123.850 125.100 CO

O g

3 Dial the desired radial.

2 Set the CDI to reflect indications from the VOR receiver.

Figure 3-59. Tuning navigation radio frequencies.

Maintaining Proficiency: Practicing All Navigation 

Skills

Advanced avionics systems offer you several ways to 

navigate. Numerous studies have demonstrated the potential 

for deterioration of navigational skills that are not regularly 

practiced. It is important to get regular practice using groundbased navigation facilities as well as RNAV sources. One way 

to maintain proficiency is to consistently use ground-based 

navigational facilities as a backup to RNAV systems.

Essential Skills

1. Select any type of ground-based radio navigation 

approach.

2. Correctly tune and set up the conventional navigation 

receiver for that procedure.

3. Correctly monitor the navaid for properly identification 

and validity.

4. Correctly select and be able to use the desired 

navigation source for the autopilot.
3-44

Chapter Summary

Navigation has been freed from the constraints of channeling 

all flight traffic along one path. The area navigation 

capabilities found in advanced avionics receiving signals 

from other than conventional line-of-sight ground-based 

aviation navaids and the compact size and reliability of 

microchips now allow efficient, accurate air travel. Integrated 

databases facilitated by large reliable memory modules 

help you to select routes, approaches, and avoid special use 

airspace.

With this freedom of movement, you must expend more 

time learning the system and how to do the preflight entries 

or programming. In addition to current charts, you must now 

verify the currency of the advanced avionics databases. The 

aircraft owner must also allocate the funding to maintain the 

currency of the databases.

You now have access to a tremendous amount of data. The 

methods of data selection and display must be learned and 

then decisions made about which display formats to use at 

which times. VOR/DMEs are simple receivers to tune and 

use. To use current flight management systems and area 

navigation units, you may need to study books that are 

larger than the actual units themselves. You must know the 

quality of maintenance for advanced avionics units and the 

qualifications of the systems to determine appropriate uses 

of the equipment.

Since advanced avionics have different displays, navigation 

sources, functions, and features, the pilot must always be 

aware of the mode selected, the data source(s), and the 

function selected. Pilot lack of attention to navigation can 

have dire consequences, including notification of the next 

of kin.
4-1

Introduction

This chapter introduces automated flight control in the 

advanced avionics cockpit. You will learn to use an autopilot 

system that can significantly reduce workload during critical 

phases of flight. The two-axis autopilot system installed in 

most general aviation aircraft controls the pitch and roll of the 

aircraft. The autopilot can operate independently, controlling 

heading and altitude, or it can be coupled to a navigation 

system and fly a programmed course or an approach with 

glideslope. In addition to learning how to use the autopilot, 

you must also learn when to use it and when not to use it.

Automated Flight Control

Chapter 4
4-2

You will learn how the autopilot and the flight management 

system (FMS)/area navigation (RNAV) unit combine to 

create a fairly automated form of flight that places you in 

a managerial role. While the autopilot relieves you from 

manually manipulating the flight controls, you must maintain 

vigilance over the system to ensure that it performs the 

intended functions and the aircraft remains within acceptable 

parameters of altitudes, airspeeds, and airspace limits.

Autopilot Concepts

An autopilot can be capable of many very time intensive 

tasks, helping the pilot focus on the overall status of the 

aircraft and flight. Good use of an autopilot helps automate 

the process of guiding and controlling the aircraft. Autopilots 

can automate tasks, such as maintaining an altitude, 

climbing or descending to an assigned altitude, turning to 

and maintaining an assigned heading, intercepting a course, 

guiding the aircraft between waypoints that make up a 

route programmed into an FMS, and flying a precision or 

nonprecision approach. You must accurately determine the 

installed options, type of installation, and basic and optional 

functions available in your specific aircraft.

Many advanced avionics installations really include two 

different, but integrated, systems. One is the autopilot 

system, which is the set of servo actuators that actually do 

the control movement and the control circuits to make the 

servo actuators move the correct amount for the selected 

task. The second is the flight director (FD) component. The 

FD is the brain of the autopilot system. Most autopilots can 

fly straight and level. When there are additional tasks of 

finding a selected course (intercepting), changing altitudes, 

and tracking navigation sources with cross winds, higher 

level calculations are required. 

The FD is designed with the computational power to 

accomplish these tasks and usually displays the indications to 

the pilot for guidance as well. Most flight directors accept data 

input from the air data computer (ADC), Attitude Heading 

Reference System (AHRS), navigation sources, the pilot’s 

control panel, and the autopilot servo feedback, to name 

some examples. The downside is that you must program the 

FD to display what you are to do. If you do not preprogram 

the FD in time, or correctly, FD guidance may be inaccurate.

The programming of the FD increases the workload for the 

pilot. If that increased workload is offset by allowing the 

autopilot to control the aircraft, then the overall workload 

is decreased. However, if you elect to use the FD display, 

but manually fly the aircraft, then your workload is greatly 

increased.

In every instance, you must be absolutely sure what modes the 

FD/autopilot is in and include that indicator or annunciator 

in the crosscheck. You must know what that particular 

mode in that specific FD/autopilot system is programmed to 

accomplish, and what actions will cancel those modes. Due to 

numerous available options, two otherwise identical aircraft 

can have very different avionics and autopilot functional 

capabilities.

How To Use an Autopilot Function

The following steps are required to use an autopilot function:

1. Specify desired track as defined by heading, course, 

series of waypoints, altitude, airspeed, and/or vertical 

speed.

2. Engage the desired autopilot function(s) and verify 

that, in fact, the selected modes are engaged by 

monitoring the annunciator panel.

3. Verify that desired track is being followed by the 

aircraft.

4. Verify that the correct navigation source is selected 

to guide the autopilot’s track.

5. Be ready to fly the aircraft manually to ensure proper 

course/clearance tracking in case of autopilot failure 

or misprogramming.

6. Allow the FD/autopilot to accomplish the modes 

selected and programmed without interference, or 

disengage the unit. Do not attempt to “help” the 

autopilot perform a task. In some instances this has 

caused the autopilot to falsely sense adverse conditions 

and trim to the limit to accomplish its tasking. In more 

than a few events, this has resulted in a total loss of 

control and a crash.

Specification of Track and Altitude

A track is a specific goal, such as a heading or course. A 

goal can also be a level altitude, a selected airspeed, or a 

selected vertical speed to be achieved with the power at 

some setting. Every autopilot uses knobs, buttons, dials, 

or other controls that allow the pilot to specify goals. 

Figure 4-1 shows an autopilot combined with conventional 

navigation instruments. Most autopilots have indicators for 

the amount of servo travel or trim being used. These can be 

early indicators of adverse conditions, such as icing or power 

loss. Rarely will a trim indicator ever indicate full travel in 

normal operation. Consistently full or nearly full travel of 

the trim servos may be a sign of a trim servo failure, a shift 

in weight resulting in a balance problem, or airfoil problems 

such as icing or inadvertent control activation.
4-3

YD ARM BARO

AP FD HDG NAV APR REV ALT

ALT SEL

DN

UP

FT

OBS

0

9

18

27

3

33

24

21

15

12

30

6

TO N

A

V

SET

Knobs on the autopilot control panel can be used 

to enter assigned altitudes and vertical speeds.

ARM BARO

The OBS knob on the 

CDI is used to specify

 target courses.

YD

Th

CD

 ta

A heading knob on the

direction indicator is used

to specify target headings.

Figure 4-1. A simple autopilot.

BRT

DIM

29.92"

5000 FT

Range

View

Aux

OFF

Bearing

GPS2

Nav

GPS1

Baro Set

29.92"

VSI Bug

0 FPM

Alt Bug

5000 FT

Hdg Bug

270°

Range View Hdg Sync

OAT

TAS

GS

7°C

143 KTS

135 KTS

BDL

BRG 264°

32.8 NM

00:14:34

KHPN

BRG 234°

96.4nm

00:42:50

5200

5100

4900

50

40

20

00

160

150

140

130

14

4

3

2

20

10

10

20

20

10

10

20

20

10

5

0

-20

-10

-5

268° 332° / 12

Vertical speed

selection

Altimeter setting

Vertical speed

Altitude Altitude

Heading

Vertical speed

indicator

This primary flight display offers separate windows used to input course, heading, altitude, and vertical speed targets.

Figure 4-2. Entering goals on a primary flight display.

Primary flight displays (PFDs) often integrate all controls 

that allow modes to be entered for the autopilot. The PFD 

shown in Figure 4-2 offers knobs that allow you to enter 

modes without turning attention away from the primary flight 

instruments. Modes entered using the controls on a PFD are 

transferred to the autopilot.

Engagement of Autopilot Function

Every autopilot offers a collection of buttons that allow you 

to choose and engage autopilot modes and functions. Buttons 

used to engage autopilot modes appear along the bottom 

of the autopilot shown in Figure 4-1. The system shown 

in Figure 4-3 does not use a separate device for autopilot 

controls; it integrates the autopilot function buttons into 

another cockpit display.

Verification of Autopilot Function Engagement

It is very important to verify that an autopilot mode has 

engaged, and the aircraft is tracking the intended flight 
4-4

230

23

AP YD

FD HDG

NAV APR

ALT MENU

VS NOSE UP

FLC NOSE DOWN

NAV1 10

NAV2 10

Figure 4-3. An integrated avionics system with an autopilot.

0

0

WPT KGNB DIS 53.5NM DTK 274° TRK 360°

GPS AP YD ALT

KGNB

GPS

IS

AP

D

A

5N

D 

53.

YD

DTK 2

LT

M

AL

Figure 4-4. Engaged autopilot modes shown at the top of a PFD.

profile. Every autopilot displays which autopilot modes are 

currently engaged, and most indicate an armed mode that 

activates when certain parameters are met, such as localizer 

interception. The autopilot shown in Figure 4-1 displays the 

active modes on the front of the unit, just above the controls. 

The integrated autopilot shown in Figure 4-4 displays the 

currently engaged autopilot mode along the top of the PFD.

How Autopilot Functions Work

Once an autopilot mode has been engaged, the autopilot:

1. Determines which control movements are required to 

follow the flight profile entered by the pilot, and 

2. Moves the controls to affect tracking of the flight 

profile.

Determination of Control Movements Required To 

Achieve Goals

Suppose you wish to use the autopilot/FD to turn to an 

assigned heading of 270°. The heading knob is used to 

select the new heading. Before any control movements are 

made, the autopilot/FD must first determine which control 

movements are necessary (e.g., left or right turn). To do so, 

the FD/autopilot must first determine the aircraft’s current 

heading and bank angle, determine amount and direction 

of the turn, and then choose an appropriate bank angle, 

usually up to 30° or less. To make these determinations, the 

FD gathers and processes information from the aircraft’s 

ADC (airspeed and altitude), magnetic heading reference 

instrument, and navigation systems.

Carrying Out Control Movements

Once the FD/autopilot has determined which control 

movements are necessary to achieve the flight change, 

the autopilot has the task of carrying out those control 

movements. Every autopilot system features a collection of 

electromechanical devices, called servos, that actuate the 

aircraft control surfaces. These servos translate electrical 

commands into motion, the “muscle” that actually moves 

the control surfaces.

Flight Director

Flight Director Functions

An FD is an extremely useful aid that displays cues to guide 

pilot or autopilot control inputs along a selected and computed 

flightpath. [Figure 4-5] The flight director usually receives 

input from an ADC and a flight data computer. The ADC 

supplies altitude, airspeed and temperature data, heading 

data from magnetic sources such as flux valves, heading 

selected on the HSI (or PFD/multi-function display (MFD)/

electronic horizontal situation indicator (EHSI)), navigation 

data from FMS, very high frequency omnidirectional range 

(VOR)/distance measuring equipment (DME), and RNAV 

sources. The flight data computer integrates all of the data 

such as speed, position, closure, drift, track, desired course, 

and altitude into a command signal. 

The command signal is displayed on the attitude indicator 

in the form of command bars, which show the pitch and roll 
4-5

20

10

20

10

10 10

880 B

050 060 070 080090100110 120

Heading

20

10

Degrees of attitude

Horizon

Figure 4-5. A flight director.

inputs necessary to achieve the selected targets. To use the 

flight director command bars, which are usually shaped as 

inverted chevrons, or V-shaped symbols, the pilot simply flies 

to the bars. Some older models use crossed bars, leading the 

pilot to the selected point. In both types, you simply keep 

the aircraft symbol on the attitude indicator aligned with the 

command bars, or allow the autopilot to make the actual 

control movements to fly the selected track and altitude.

Using the Flight Director (FD)

Flight Director Without Autopilot

The FD and autopilot systems are designed to work together, 

but it is possible to use the flight director without engaging 

the autopilot, or the autopilot without the FD, depending 

on the installation. Without autopilot engagement, the FD 

presents all processed information to the pilot in the form of 

command bar cues, but you must manually fly the airplane 

to follow these cues to fly the selected flightpath. In effect, 

you “tell” the FD what needs to happen and the FD command 

bars “tell” you what to do. This adds to your workload, since 

you must program the FD for each procedure or maneuver to 

be accomplished, while actually flying the aircraft. In many 

cases, you will have a decreased workload if you simply 

disable the FD and fly using only the flight instruments.

Flight Director With Autopilot

When the aircraft includes both a flight director and an 

autopilot, you may elect to use flight director cues without 

engaging the autopilot. It may or may not be possible to use 

the autopilot without also engaging the flight director. You 

need to be familiar with the system installed. When you 

engage the autopilot, it simply follows the cues generated by 

the flight director to control the airplane along the selected 

lateral and vertical paths.

Common Error: Blindly Following Flight Director 

Cues

The convenience of flight director cues can invite fixation or 

overreliance on the part of the pilot. As with all automated 

systems, you must remain aware of the overall situation. 

Never assume that flight director cues are following a route 

or course that is free from error. Rather, be sure to include 

navigation instruments and sources in your scan. Remember, 

the equipment will usually perform exactly as programmed. 

Always compare the displays to ensure that all indications 

agree. If in doubt, fly the aircraft to remain on cleared track 

and altitude, and reduce automation to as minimal as possible 

during the problem processing period. The first priority for 

a pilot always is to fly the aircraft.

Common Error: Confusion About Autopilot 

Engagement

Pilots sometimes become confused about whether or not 

flight director cues are being automatically carried out by 

the autopilot, or left to be followed manually by the pilot. 

Verification of the autopilot mode and engagement status 

of the autopilot is a necessary technique for maintaining 

awareness of who is flying the aircraft.

Follow Route

The FD/autopilot’s navigation function can be used to guide 

the aircraft along the course selected on the navigation 

indicator. Since the navigation display in most advanced 

avionics cockpits can present indications from a variety of 

navigation systems, you can use the autopilot’s navigation 

function to follow a route programmed into the FMS using 

VOR, global positioning system (GPS), inertial navigation 

system (INS), or other navigation data sources.

Following a Route Programmed in the FMS

Figure 4-6 demonstrates how to use the navigation function to 

follow a route programmed into the FMS. With the navigation 

function engaged, the FD/auto-pilot steers the aircraft along 

the desired course to the active waypoint. Deviations from 

the desired course to the new active waypoint are displayed 

on the navigation indicator. When the aircraft reaches the 

active waypoint, the FMS computer automatically sequences 

to the next waypoint in the route, unless waypoint sequencing 

is suspended.

It is important to note that the normal navigation function 

provides only lateral guidance. It does not attempt to control 

the vertical path of the aircraft at any time. You must always 

ensure the correct altitude or vertical speed is maintained.
4-6

Range

View

Aux

OFF

Bearing

OFF

Nav

GPS1

Baro Set

29.92"

VSI Bug

0 FPM

Alt Bug

5000 FT

Hdg Bug

270°

Range View Hdg Sync

SUNOL

BRG 060°

6.8 NM

00:04:15

-20

-10

270°

C

RING

CDI OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

114.00

116.00

COM

119.000

120.600

NAV

 SUNOL DIS DTK BRG

GS TRK ETE

6.80nm 059 m 060 m 

96kt 060 m 

1.0 1.0

KSQL

04:15 

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV

COM RING

The CDI is coupled to the area navigation computer, so the autopilot streets the aircraft

along the desired track to the active waypoint showing on the navigation computer.

COM

V

VOL/

ID

PUSH

11

11

GPS

N Hd B SUNOL

-20

VS

The autopilot NAV function steers the aircraft to keep the CDI needle centered.

Figure 4-6. Using the navigation function to follow the programmed flight route.

When combined, use of the FMS and the FD/autopilot’s 

navigation function result in an automated form of flight that 

was formerly limited to very complex and expensive aircraft. 

This same level of avionics can now be found in single-engine 

training airplanes. While it is easy to be complacent and let 

down your guard, you must continuously monitor and stay 

aware of automated systems status and function and the 

track of the aircraft in relation to the flight plan and air traffic 

control (ATC) clearance.

GPS Steering (GPSS) Function

Many autopilots offer a global positioning system steering 

(GPSS) function. GPSS does all of the same actions as 

the navigation function, but achieves a higher degree of 

precision by accepting inputs directly from the GPS receiver. 

Consequently, the GPSS function follows the desired track to 

the active waypoint more aggressively, permitting only small 

excursions from the desired course. On some installations, 

pressing the autopilot NAV button twice engages the GPSS 

function.

Following a VOR Radial

The FD/autopilot’s navigation function can also be used to 

directly track VOR radials. The navigation display must be 

configured to show indications from one of the aircraft’s VOR 

receivers. Once you have tuned and identified a VOR station 

and selected the desired radial, you can select the navigation 

mode to track the selected radial. Figure 4-7 demonstrates 

how to use the navigation mode to follow a VOR radial.

When the navigation mode is used to follow a route defined 

by VOR radials, you must still tune and identify each new 

VOR facility manually and select the appropriate radials 

along the way. The autopilot’s navigation function cannot 

automatically manipulate the VOR receiver. However, some 

highly automated FMS units tune and identify VORs along a 

defined route, such as Victor or Jet routes. You should check 

the FMS documentation and installed options.
4-7

Range

View

Aux

OFF

Bearing

OFF

Nav

VLOC1

Baro Set

29.92"

VSI Bug

0 FPM

Alt Bug

5000 FT

Hdg Bug

270°

Range View Hdg Sync

ECA BRG 058°

38.8 NM

00:24:15

15

24

33

6 3

N

30

W 21

S

12

E

-20

-10

060°

C

RING

CDI OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

114.00

116.00

COM

119.000

120.600

NAV

 SUNOL DIS DTK BRG

GS TRK ETE

6.80nm 059 m 060 m 

96kt 060 m 

1.0 1.0

KSQL

04:15 

-20

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV

CO

The CDI is coupled to the VOR receiver, so the NAV function 

steers the aircraft along the desired track to the selected radial.

Figure 4-7. Using the navigation mode to follow a VOR radial.

Depending on the FMS, the highly automated flight that 

results when the navigation mode is used to follow a 

published route from the database uses a different skill set 

from using the navigation mode to track discreetly tuned VOR 

radials. Learning how to select preprogrammed routes from 

the database of airways can be challenging. Programming 

or tuning discreet VORs en route in turbulent conditions 

presents different challenges. Either skill set can result in a 

greater sharing of duties between pilot and technology and 

an increase in safety.

Fly Heading

The heading mode is used to steer the aircraft automatically 

along a pilot selected heading. Using the FD/autopilot to fly 

a heading is a simple matter of selecting the assigned heading 

and then engaging the heading function or, more commonly, 

accomplished by first engaging the heading mode and gently 

turning the heading selection knob to the new heading. Gently 

turning the knob with the mode already engaged allows you 

to make a smooth change from level to turning flight. Many 

autopilots make an abrupt bank if engaged when there is a big 

change to be made in heading or track. The heading function 

is illustrated in Figure 4-8.

You should note that, when using the heading mode, the FD/

autopilot ignores the pilot-programmed route in the FMS or 

any VOR radials you set. When in heading mode, the FD/

autopilot will fly the selected heading until fuel starvation.

Maintain Altitude

The autopilot’s altitude mode maintains an assigned 

barometric altitude. When the altitude mode is engaged, the 

autopilot seeks to maintain the same barometric pressure 

(altitude) that the aircraft was flying at the time that the 

altitude mode was engaged. Figure 4-9 shows how to engage 

the altitude mode for one manufacturer’s autopilot.

In addition to determining and carrying out the pitch 

commands necessary to maintain the flight’s assigned 

altitude, most autopilots are also able to trim the aircraft. 
4-8

5 5 0 0 ft

YD ARM BARO

AP FD HDG NAV APR REV ALT

ALT SEL

DN

UP

FT

Press the altitude button when 

aircraft reaches the desired altitude.

YD ARM BARO

LT S

The autopilot maintains the altitude until fuel starvation.

ALT

Figure 4-9. Maintaining an altitude using the altitude hold mode.

060° Heading

YD ARM BARO

AP FD HDG NAV APR REV ALT

ALT SEL

DN

UP

FT

Press to engage the heading function.

60° Heading

The autopilot maintains the heading until fuel starvation.

HDG

06

SET

YD ARM

Set the heading bug to the desired heading.

Figure 4-8. Flying an assigned heading using the heading mode.

An autotrim system is capable of automatically making any 

needed adjustments to the pitch trim to maintain the aircraft 

at the desired altitude and in a properly trimmed condition. 

Pitch control pressure applied with the altitude hold mode 

engaged will cause the autopilot to trim against you.

Climbs and Descents

Vertical Speed

The autopilot’s vertical speed mode allows you to perform 

constant-rate climbs and descents. Figure 4-10 illustrates 

the use of the vertical speed mode for one autopilot that is 

integrated with a PFD.

When you engage the vertical speed mode, the FD/autopilot 

will attempt to maintain the specified vertical speed until you 

choose a different setting in autopilot, the aircraft reaches an 

assigned altitude set into the assigned altitude selector/alerter, 

or the autopilot is disconnected. If an altitude selector is not 

installed or functioning, the pilot has the task of leveling off 

at the assigned altitude, which requires monitoring progress 

and manually engaging the autopilot’s altitude hold function 

once the aircraft reaches the desired altitude. You must be 

very careful to specify an appropriate vertical speed, as the 

aircraft will fly itself into a stall if you command the autopilot 

to climb at a rate greater than the aircraft’s powerplant(s) is/

are capable of supporting. You also need to monitor descent 

airspeeds diligently to ensure compliance with VNE/VMO and 

VA or turbulence penetration speeds if there is doubt about 

smooth air conditions. As discussed in the previous chapter, 

you should be cognizant of the powerplant temperatures 

reciprocating powered aircraft and bleed air requirements 

for turbine-powered aircraft.

Vertical Speed With Altitude Capture

Some FD/autopilots have an altitude select/capture feature. 

The altitude select/capture feature is illustrated in Figure 4-11.

The altitude select/capture feature combines use of the 

activated vertical speed mode and an armed altitude hold 

mode. To use this feature, the vertical speed function is 

initially engaged. The altitude hold mode usually arms 

automatically when a different altitude is selected for capture 

and vertical speed is activated. With an altitude select/capture 

option or feature, the altitude hold mode disengages the 

vertical speed mode upon capture of the selected altitude once 

the vertical speed function completes the necessary climb or 

descent. Once the aircraft reaches the assigned altitude, the 

vertical speed function automatically disengages, and the 

altitude mode changes from armed to engaged. The change 

from vertical speed mode to altitude hold mode is the capture 

mode, or transition mode. Any changes made by the pilot 

during this short phase usually result in a cancellation of the 

capture action, allowing the aircraft to continue the climb or 

descent past the selected altitude. Again, be familiar with the 

aircraft’s equipment. Let the system complete programmed 

tasks, and understand what it will do if interrupted.

Many FD/autopilot altitude selectors include an altitude alert 

feature, an auditory alert that sounds or chimes as the aircraft 

approaches or departs the selected altitude.

Catching Errors: Armed Modes Help Prevent 

Forgotten Mode Changes

You have already seen how remembering to make a needed 

mode change in the future can be an error-prone process. Not 

canceling the armed function allows the altitude select mode 

to relieve the pilot from needing to remember to engage the 

function manually once the aircraft has reached the selected 

altitude. Do not interrupt the altitude armed or capture mode, 

unless prepared to manually control the process.
4-9

5 0 0 fpm

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV VS

Baro Set

29.92"

VSI Bug

500 FPM

5000 FT

Hdg Sync

1 Enter the desired vertical speed.

AP

VS

2 Press the vertical speed button 

3 The autopilot attempts to maintain the dialed vertical speed.

VS

Figure 4-10. Performing a constant-rate climb or descent using the vertical speed function.

5 0 0 fpm

7 0 0 0 ft

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV ALT VS

BRT

DIM

29.92"

7000 FT

Baro Set

29.92"

VSI Bug

500 FPM

Alt Bug

7000 FT

Hdg Bug

270°

Hdg Sync

5200

5100

4900

50 40

20

00

20

10

5

0

-20

-10

-5

2 Simultaneously press to engage the vertical speed

function and to arm the altitude function.

1 Enter the target altitude and desired vertical speed.

3 The autopilot attempts to maintain the target vertical

speed until reaching and capturing the target altitude.

VS

ALT

Figure 4-11. Climbs and descents to capture using the altitude select/capture feature.
4-10

0

0

WPT KGNB DIS 53.5NM DTK 274° TRK 274°

GPS AP YD VS 800 FPM ALT

Armed functions are shown in white.

WPT KGNB DIS 53 5NM DTK 274°

Engaged functions are shown in green.

AP = autopilot engaged

YD = yaw dampener

VS = vertical speed engaged

Figure 4-12. A mode annunciator showing armed and engaged 

autopilot modes.

The indications on the autopilot in Figure 4-11 do not 

distinguish between functions that are armed or engaged.

The more sophisticated annunciator shown in Figure 4-12 uses 

color coding to distinguish between armed and engaged 

autopilot functions.

Common Error: Failure To Arm the Altitude Mode

The most common error made by pilots during climbs and 

descents is failure to arm the altitude mode to capture the 

assigned altitude. In many instances, this happens when the 

crew does not correctly adjust the altitude selector or alerter. 

Sometimes, this malfunction occurs when the altitude is 

adjusted at the same time the system is attempting to go 

into the capture mode. This situation typically results in the 

aircraft climbing or descending beyond the assigned altitude, 

which may result in an altitude deviation. Altitude deviations 

are among the most common mishaps reported by pilots to 

NASA’s Aviation Safety and Reporting System (ASRS). In 

any event, always monitor the actions of the FD/autopilot 

system and be prepared to fly the aircraft manually.

Awareness: Altitude Alerting Systems

Altitude alerting systems were mandated for commercial 

jet transports in the early 1970s in response to a growing 

number of altitude deviations in airline operations. Although 

they helped reduce the total number of altitude deviations, 

altitude alerting systems also made possible a new kind of 

error. Altitude deviation reports submitted to the Aviation 

Safety and Reporting System (ASRS) indicate that pilots 

sometimes rely too much on the altitude alerting system, 

using it as a substitute for maintaining altitude awareness. 

Instead of monitoring altitude, pilots sometimes simply listen 

for the alert. This phenomenon is one instance of what human 

factors experts call primary-secondary task inversion—when 

an alert or alarm designed as a secondary backup becomes 

the primary source of information. In the case of the altitude 

alerting system, when the alerting system is missed, or you 

are distracted, nothing is left to prevent an altitude deviation. 

You must remember that the altitude alerting system is 

designed as a backup, and be careful not to let the alerting 

system become the primary means of monitoring altitude. 

Most airline operators have a standard operating procedure 

that requires pilots to call out approaching target altitudes 

before the altitude alerting system gives the alert. Common 

errors occur when setting 10,000 feet versus 11,000 feet. 

Too many ones and zeros can confuse a fatigued, busy pilot, 

resulting in setting an incorrect altitude.

Awareness: Automatic Mode Changes

Distinguishing between “armed” and “engaged” adds 

complexity to the process of maintaining mode awareness. 

In addition to autopilot functions that are engaged by the 

pilot, some autopilot functions engage and disengage 

automatically. Automatic mode changes add to the challenge 

of keeping track of which autopilot functions are currently 

engaged and which functions are set to become engaged. 

You can minimize confusion by always verifying the status 

annunciations on the FMs, PFD/MFD, and the autopilot 

mode annunciator after any change of heading, altitude, 

or vertical speed. The verification process forces you to 

carefully consider the configuration of the FMS and FD/

autopilot. Determine if engaging the autopilot cancels certain 

FD modes. Some units interact, and when the autopilot is 

engaged, some FD modes are automatically canceled, notably 

altitude hold or selection.

Learning: The Importance of Understanding

One way to learn the steps required to use an autopilot is 

simply to memorize them. This approach focuses solely on 

the button and control manipulations required to perform each 

procedure. Although this approach to learning may appear 

to be the quickest, studies have shown that pilots who take 

the time to develop a deeper understanding of how a system 

works give themselves three important advantages. These 

pilots are better able to:

1. Work through situations that differ from the ones they 

learned and practiced during training,

2. Transition from one manufacturer’s system to another, 

and

3. Recall procedures after not having practiced them for 

some time.

Investing time to understand FD/autopilot functions pays off. 

For example, in many systems, once the aircraft reaches the 

selected altitude and levels off as indicated by the altitude 

mode annunciator, the pilot can select the next altitude in 

the window. Then, upon receiving the clearance to climb 
4-11

or descend, the pilot must select only the vertical mode. In 

many systems, the vertical speed mode is indicated and the 

altitude mode is indicated as “armed” and ready to capture 

the selected altitude. Only the power requires pilot manual 

control.

Power Management

Unless the aircraft has an autothrottle system, you must adjust 

the power to an appropriate setting when performing any 

climb, descent, or level-off. You cannot allow the aircraft 

to exceed any applicable speed limitations during a descent. 

During a climb at a vertical speed that the aircraft cannot 

sustain, the FD/autopilot may command a pitch that results 

in a stall.

Essential Skills

1. Use the FD/autopilot to climb or descend to and 

automatically capture an assigned altitude.

2. Determine the indications of the armed or capture 

mode, and what pilot actions will cancel those modes.

3. Determine if the system allows resetting of the armed 

or capture mode, or if manual control is the only option 

after cancellation of these modes.

4. Determine the available methods of activating the 

altitude armed or capture mode.

5. Determine the average power necessary for normal 

climbs and descents. Practice changing the power to 

these settings in coordination with making the FD/

autopilot mode changes.

6. Determine and record maximum climb vertical speeds 

and power settings for temperatures and altitudes. 

Ensure the values are in agreement with values in 

AFM/POH for conditions. Make note of highest 

practical pitch attitude values, conditions, and loading. 

Remember powerplant factors (e.g., minimum 

powerplant temperature, bleed air requirements) and 

airframe limitations (e.g., VA in setting power).

Course Intercepts

Flying an Assigned Heading To Intercept a 

Course or VOR Radial

You can use the navigation mode in combination with the 

heading function to fly an assigned heading to intercept 

a course. The procedure illustrated in Figure 4-13 takes 

advantage of the ability to arm the navigation mode while 

the heading mode is engaged.

Figure 4-13 illustrates selecting the assigned heading, setting 

up your FD/FMS autopilot for the assigned course, engaging 

the heading mode, and arming the navigation function. Once 

the aircraft reaches the course, the autopilot automatically 

disengages the heading function and engages the navigation 

mode. 

On most FD/autopilots, courses can be intercepted by first 

using the heading “bug” to select an intercept course and then 

engaging the heading function. Alternatively, engaging the 

navigation function in some units causes the FD/autopilot 

to select an intercept heading, engage the heading function, 

and arm the navigation function. This can be a cause for 

conflict if ATC assigns an intercept heading, but the FD is 

programmed to use one angle. In those instances, you need 

to set the heading into the FD/autopilot, fly, and control 

the intercept until the aircraft is close enough to complete 

the intercept and capture without deviating from the ATC 

instructions. At that point you can select and arm the 

navigation mode, which completes the intercept and begins 

tracking the selected course.

Essential Skills

1. Use the FD/autopilot to fly an assigned heading to 

capture and track a VOR and/or RNAV course.

2. Determine if the FD/autopilot uses preprogrammed 

intercepts or set headings for navigation course 

interceptions.

3. Determine the indications of navigation mode armed 

conditions.

4. Determine parameters of preprogrammed intercept 

modes, if applicable.

5. Determine minimum and maximum intercept angle 

limitations, if any.
4-12

Range

View

Aux

OFF

Bearing

OFF

Nav

GPS1

Baro Set

29.92"

VSI Bug

0 FPM

Alt Bug

5000 FT

Hdg Bug

270°

Range View Hdg Sync

SAC

DTK 240°

19.1 NM

00:07:22

-20

-10

270°

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

HDG NAV

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV

HDG NAV

1 Enter the desired heading and engage the heading function.

3 As the autopilot captures the course, the heading function automatically 

disengages, and the navigation function switches from armed to engaged.

2 Arm the navigation function.

Figure 4-13. Flying an assigned heading to intercept a course.

Coupled Approaches

The approach function is similar to the navigation mode, but 

flies the selected course with the higher degree of precision 

necessary for instrument approaches and allows glideslope 

tracking in the vertical dimension. Most autopilots feature 

a separate button that allows you to engage the approach 

function, as shown in Figure 4-14. (NOTE: Usually, this 

mode is not used with most GPS receivers. The GPS approach 

RNP (required navigation performance) of 0.3 induces the 

necessary flight tracking precision. This mode is used only 

if specifically stated as a command in the avionics handbook 

for that equipment in that aircraft).

Like the navigation function, the approach mode can be used 

to execute precision and nonprecision approaches that rely 

on types of ground-based navigation facilities (e.g., VOR, 

VOR/DME, and localizer approaches).

ILS Approaches

Coupled ILS approaches make use of the autopilot’s 

glideslope function. Figure 4-15 shows the procedure for 

one type of autopilot.

Note that you cannot directly arm or engage the glideslope 

function. The autopilot must usually be engaged first in 

the approach and altitude modes. When the FD/autopilot 

begins to sense the glideslope, the glideslope function will 

automatically arm. When the aircraft intercepts the glideslope, 

the glideslope function engages automatically, and uses the 

aircraft’s pitch control to remain on the glideslope. It is 

important to note that, generally, the glideslope function 

can capture the glideslope only from below or on glideslope.

RNAV Approaches With Vertical Guidance 

Coupled RNAV approaches with vertical guidance work in 

the same way as coupled ILS approaches. Lateral and vertical 

guidance commands are generated by the FMS/NAV and 

sent to the FD/autopilot. The same approach and glideslope 
4-13

YD ARM BARO

AP FD HDG NAV APR REV ALT

ALT SEL

DN

UP

Press to engage the approach function. APR

The autopilot should maintain a greater 

accuracy of track in the approach mode.

NAV

APR

Figure 4-14. Flying a coupled nonprecision approach.

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV APR ALT

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV APR ALT GS

DECR INCR

HDG NAV APR REV ALT VS

VS

AP

VS x 100

NAV APR GS

AP

NAV APR GS

When the glideslope has been captured, the autopilot

automatically disengages the altitude function and 

engages the glideslope function. The pilot must 

adjust power and drag (flaps and landing gear) to 

control airspeed.

AP

NAV APR ALT GS

When the aircraft comes within reception range of the

glideslope, the autopilot automatically arms the 

glideslope function.

AP

NAV APR ALT

Use the approach and altitude functions to establish

the aircraft on the localizer.

X

X

X

Figure 4-15. Flying a coupled precision approach.

functions of the autopilot are used in the same way to carry 

out the lateral and vertical guidance and control of the aircraft. 

This process is transparent to the pilot. Most “VNAV” 

functions do not qualify as approach vertical functions and 

many FMS/GPS units inhibit that function during approaches.

Power Management

Since most autopilots are not capable of manipulating power 

settings, you must manage the throttle to control airspeed 

throughout all phases of the approach. The power changes 

needed during altitude changes must supply the necessary 

thrust to overcome the drag. The pilot must coordinate the 

powerplant settings with the commands given to the FD/

autopilot. Remember, the FD/autopilot can control the 

aircraft’s pitch attitude only for altitude or airspeed, but not 

both. The FD/autopilot attempts to perform as programmed 

by you, the pilot. If the climbing vertical speed selection 

is too great, the aircraft increases the pitch attitude until it 

achieves that vertical speed, or the wing stalls. Selection of 

an airspeed or descent rate that is too great for the power 

selected can result in speeds beyond the airframe limitations. 

Leveling off from a descent, without restoring a cruise power 

setting results in a stall as the FD/autopilot attempts to hold 

the altitude selected.

Essential Skills

1. Use the FD/autopilot to couple to a precision approach.

2. Use the FD/autopilot to couple to a nonprecision 

approach.

3. Use the FD/autopilot to couple to an RNAV approach.

4. Determine the power setting required to fly the 

approaches.

5. Determine the power settings necessary for leveloff 

during nonprecision approaches and go-around 

power settings for both precision and nonprecision 

approaches.
4-14

6. Determine the speeds available for the minimum 

recommended powerplant settings. It is useful to 

determine if an ATC clearance can be accepted for 

climbs, altitudes, and descents.

Deciding When To Use the FD/Autopilot

In addition to learning how to use the FD/autopilot, you must 

also learn when to use it. Since there are no definitive rules 

about when an FD/autopilot should or should not be used, 

you must learn to consider the benefits and disadvantages of 

using the FD/autopilot in any given situation.

One of the most valuable benefits of using the FD/autopilot 

is delegating the constant task of manipulating the aircraft’s 

controls to the equipment, which do nothing other than 

comply with the pilot’s programming. This allows you 

more time to manage and observe the entire flight situation. 

Managing the flight versus actually moving the controls 

allows more time for:

1. Programming. Especially when flying under IFR, 

changes to a route are inevitable. Even when the 

pilot is proficient in using FMS/RNAV, this task 

requires focusing some attention on the programming 

task. The FD/autopilot keeps the aircraft on the 

programmed heading or course and altitude while the 

pilot makes the necessary changes to the flight plan. 

If programmed correctly, the aircraft maintains the 

correct track and altitude.

2. Distracting tasks/workload. Similarly, the FD/

autopilot is used to control basic aircraft movement 

while the pilot focuses attention on tasks such as 

reviewing charts, briefing and configuring for an 

instrument approach, updating weather information, 

etc. The FD/autopilot can also be a great help in 

other high workload situations, such as flying in a 

busy terminal area or executing a missed approach in 

adverse weather conditions.

3. Maintaining autopilot skills. The FD/autopilot’s ability 

to help manage pilot workload depends heavily on the 

pilot’s proficiency in using it. Regular practice with the 

various autopilot functions (especially the approach 

functions) is essential to develop and maintain the 

knowledge and skills necessary to maximize its 

utilization.

4. Emergencies. The FD/autopilot can be extremely 

useful during an emergency. It can reduce pilot 

workload and facilitate efforts to troubleshoot the 

emergency.

Disadvantages of using the FD/autopilot include the 

following:

1. Forgetting to maintain manual flying skills. It is 

important to practice flying without the FD/autopilot 

often enough to maintain proficiency in basic flying 

skills and the instrument cross-check and scan. One 

common pitfall of advanced avionics is the pilot’s 

tendency to forget to maintain hard-earned skills for 

instrument flight. All equipment will fail at some time. 

The competent pilot is ready and prepared to make a 

transition to aircraft piloting at any time.

2. Turbulence. The pilot’s operating handbook (POH) 

and FD/autopilot flight manual supplements for many 

aircraft discourage or prohibit use of the autopilot’s 

altitude hold function during moderate or severe 

turbulence. Some FD/autopilot systems may default 

or disengage if certain trim or control limits are 

encountered during turbulent conditions. You should 

consult the flight manual to ensure the aircraft is 

not operated outside specified limits. The aircraft’s 

flightpath and mode indications should always be 

monitored to ensure what modes are active.

3. Minimum altitude. Autopilots are certified for use 

above a specified minimum altitude above ground 

level (AGL). Some higher performance and higher 

service ceiling aircraft require autopilot control above 

certain airspeeds and altitudes. The flight manual 

and operations manual (if any) should be consulted 

to ensure that the pilot does not operate the aircraft 

outside specified limits. For higher safety standards, 

commercial operators must observe restrictions in 

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

sections 121.579, 125.328, and 135.93, according to 

their regulatory classification. Adoption of these limits 

by private operators would add a safety margin to 

flights conducted under 14 CFR part 91 regulations 

in many cases.

4. Possible malfunction. If at any time the pilot observes 

unexpected or uncommanded behavior from the 

autopilot, he or she should disengage the autopilot 

until determination of the cause and its resolution. 

Most autopilot systems have multiple methods of 

disengagement; you should be immediately aware of 

all of them. Also be aware of the methods to cancel 

the FD display to avoid confusing information.
4-15

Miscellaneous Autopilot Topics

Autopilot Mode Awareness

In addition to performing the basic aircraft control and 

navigation function described previously, some autopilots 

are capable of automatically switching from one function 

to another. These automatic mode changes can complicate 

the task of maintaining mode awareness, but every autopilot 

has some form of flight mode annunciator that shows which 

autopilot functions are currently engaged. The autopilot 

shown in Figure 4-4 displays the name of any autopilot 

mode that is currently engaged just above the button used to 

engage the function. It is important to develop two habits:

1. Checking the flight mode annunciator after entering a 

command to ensure that the selected function is indeed 

armed or engaged, as appropriate.

2. Including the flight mode annunciator in the scan to 

maintain continuous awareness of what mode is active 

and what is armed to activate next.

Positive Exchange of Controls

When control of the aircraft is transferred between two pilots, 

it is important to acknowledge this exchange verbally. The 

pilot relinquishing control of the aircraft should state, “You 

have the flight controls.” The pilot assuming control of the 

aircraft should state, “I have the flight controls,” and then 

the pilot relinquishing control should restate, “You have 

the flight controls.” Following these procedures reduces the 

possibility of confusion about who is flying the aircraft at 

any given time.

Using an FD/autopilot system can present an opportunity for 

confusion. When engaging the autopilot, it is a good idea to 

announce that the autopilot is being engaged, what autopilot 

mode is being used, and then to confirm the settings using 

the flight mode annunciator. It has been general practice 

for many years in many aircraft to first engage the FD to 

determine what instructions it was going to transmit to the 

autopilot. This is determined by reading the FD’s command 

bars. If the commands shown agree with your perception of 

the control motions to be made, then engage the autopilot 

to fly the entered course and vertical mode. A caution at 

this point: some FDs cancel the altitude hold mode when 

the autopilot is engaged. Always ensure that, after autopilot 

engagement, the desired modes are still active.

Preflighting the Autopilot

The POH or aircraft flight manual (AFM) supplement 

for each FD/autopilot system contains a preflight check 

procedure that must be performed before departure. As 

with other preflight inspection items, this check allows you 

to ensure that the autopilot is operating correctly, before 

depending on it in the air.

Autopilot and Electric Trim System Failures

It is vital that you become immediately familiar with the 

procedures required to disconnect or disable the electric trim 

and autopilot systems. Electric trim and autopilot failures can 

occur in the form of failure indications; unusual, unexpected, 

or missing actions; or, in the extreme case, a runaway servo 

actuator in the autopilot or trim system.

The first and closest method of disconnecting a malfunctioning 

autopilot is the autopilot disconnect switch, typically mounted 

on the control yoke. This switch is usually a red button, often 

mistaken by new pilots for the radio transmit button. You 

need to know which buttons activate which functions.

Most systems may be disconnected by the mode buttons on 

the autopilot control panel. However, there are some failures 

(shorted relays, wires, etc.) that remove control of the servo 

actuator from the control unit itself. In those rare instances, 

the pilot must find and pull the circuit breakers that interrupt 

power to both the trim and autopilot systems. Some trim 

systems have separate circuit breakers for trim motors that 

operate different control surfaces (roll, pitch, yaw). Many 

pilots have installed small plastic collars on the autopilot 

to facilitate finding and pulling the correct autopilot circuit 

breaker to kill the power to that circuit. Ensure that you 

understand all functions and equipment are lost if those (and 

in fact, any circuit breaker) are disabled. In too many cases, a 

circuit breaker installed in an aircraft supplies power to more 

functions than the label implies. To be absolutely sure, check 

the wiring diagrams, and do not pull circuit breakers unless 

the POH/AFM directs that specific action.

Another method of maintaining flight control when faced 

with a failed trim or autopilot system is the control yoke. Most 

autopilot and trim systems use a simple clutch mechanism 

that allows you to overpower the system by forcing the 

control yoke in the desired direction. This is usually checked 

during the afterstart/pretakeoff/ runup check.

Essential Skills

1. Demonstrate the proper preflight and ground check of 

the FD/autopilot system.

2. Demonstrate all methods used to disengage and 

disconnect an autopilot.

3. Demonstrate how to select the different modes and 

explain what each mode is designed to do and when 

it will become active.

4. Explain the flight director (FD) indications and 

autopilot annunciators, and how the dimming function 

is controlled.
4-16

Chapter Summary

Automated flight control can make a long flight easy for 

you by relieving you of the tedious second-by-second 

manipulation and control of the aircraft. Overdependence 

on automated flight controls can cost you hard-earned 

aircraft handling skills, and allow you to lose the situational 

awareness important to safe flight. You must practice your 

skills and cross-check.

Automated flight controls require you to study and learn the 

system’s programming and mode selection actions. You must 

also learn what actions disconnect the autopilot, whether 

commanded or not. In preflight planning you must determine 

the limitations on the autopilot and what the installation in 

that aircraft permits.

It is important for you to be aware of what functions are 

automated and what activates those functions, and the 

actions or conditions that cancel or inhibit those functions. 

Remember that, in most aircraft, you must set the power 

and manage the powerplant(s). Even in very expensive 

aircraft equipped with autothrottle, you must monitor the 

powerplant(s) and be ready to intervene to ensure operation 

within safe parameters.
5-1

Introduction

This chapter introduces information systems available in 

the advanced avionics cockpit. These systems support you 

in following flight progress, and in avoiding terrain, traffic, 

and weather hazards en route. A moving map continuously 

displays the aircraft’s position relative to the intended route 

of flight, and helps you maintain the “big picture” (situational 

awareness) as your flight progresses. A Terrain Awareness 

and Warning System (TAWS) color codes surrounding 

terrain to make it easily apparent when terrain poses a 

threat. Weather systems provide in-flight access to many of 

the same weather products available on the ground. A fuel 

management system makes predictions about fuel remaining 

at each waypoint along the route, and helps monitor actual 

fuel use as your flight progresses.

Information Systems

Chapter 5
5-2

OAT 7°C

TOPO TERRAIN STRMSCP NEXRAD XM LTNG BACK

MAP WPT AUX NRST

Pages are selected using these knobs.

You can overlay information provided by different cockpit information systems 

on a single page using the keys that appear along the bottom of the display.

Some MFD pages have subpages. This page annunciator shows

that the first subpage of the MAP page is currently selected.

Figure 5-1. Selecting pages on an MFD.

Since the volume of information now available in the cockpit 

cannot be presented on a single display, or would clutter 

a single display to the point of unintelligibility, you must 

decide what information is needed at any given point in your 

flight. You will learn how information systems can be used to 

enhance situational awareness and increase the safety margin. 

It is important to avoid the pitfalls of using enhanced weather, 

traffic, and terrain information to fly closer to hazardous 

situations. This negates any safety advantage created by 

advanced avionics. Advanced avionics aircraft crash due to 

the same causes as aircraft with traditional instrumentation.

Multi-Function Display

A multi-function display (MFD) presents information 

drawn from a variety of aircraft information systems. 

Many installations allow overlay or inclusion of systems 

indications in the primary flight display (PFD), in addition to 

the primary flight instrument indications. By allowing you to 

view information provided by any one or combination of the 

installed systems, the MFD prevents the need for a separate 

display for each system. As does the flight management 

system (FMS)/area navigation (RNAV) unit, the MFD allows 

you to select different pages from different chapters that 

display information provided by various aircraft systems. 

Other controls allow you to combine information from 

multiple systems on one page. In many installations, the MFD 

serves as the backup or faildown display for the PFD. You 

should have a working knowledge of the faildown selection 

procedures and how to select the necessary data displays for 

the current flight phase. The controls provided by one MFD 

are shown in Figure 5-1.

Invest the time required to become a skilled user of the 

MFD. Familiarity with the capabilities of the MFD not only 

increases the information available, but also allows quick 

access to that information for safe flight decision-making.

Essential Skills

1. Program the multi-function display to show data 

provided by any aircraft system.

2. Determine how many data displays can be combined 

in one display.

3. Know how to select the PFD displays on the MFD, if 

available.

4. Determine which data displays can be overlaid onto 

the PFD as well as the MFD.

Moving Maps

The moving map function uses the MFD to provide a 

pictorial view of the present position of the aircraft, the 

route programmed into the FMS, the surrounding airspace, 

and geographical features. Moving maps offer a number 

of options that allow you to specify what information is 

presented on the MFD and how it is displayed. Moving maps 

typically offer several different map orientations (e.g., north 

up, track up), a range control that allows you to “zoom” in 

and out to see different volumes of airspace, and a means to 

adjust the amount of detail shown on the display (declutter). 

The moving map display does not replace looking outside the 

aircraft to avoid other aircraft and obstructions.

Using the Moving Map

A moving map display has a variety of uses that can aid your 

awareness of position and surroundings during almost any 

phase of flight. Verification of the displayed data with a chart 

accomplishes three functions:

1. Provides you practice for retention of your map 

reading skills.

2. Contributes to your readiness for continued safe 

navigation to a destination in the event of equipment 

problems.

3. Ensures that you maintain situational awareness.
5-3

ECA

WAGER

5

338

1

1652

200

46

13.7

2300

23.0

NAV1 116.00 114.00 NAV2 113.90 114.80125.900 121.600 COM1

123.850 119.000 COM2

GS 156kts DIS 38.2NM ETE 00:15 ETA 04:10

ENGINE MAP DCLTR

MAP WPT AUX NRST

MAP - NAVIGATION MAP

TRACK UP

30NM

Figure 5-2. A moving map provides the “big picture.”

HDG UP

1NM 16

13

MAP WPT AUX NRST

31

Figure 5-3. Using the moving map on the airport surface.

Maintaining the “Big Picture”

Moving map displays can help you verify a basic understanding 

of the planned route and aircraft position with respect to the 

route, nearby terrain, and upcoming waypoints. For example, 

the moving map display in Figure 5-2 shows the aircraft 

slightly to the left of the programmed flight route, presumably 

heading in the correct direction, and operating to the west 

of rising terrain.

Maintaining Awareness of Potential Landing Sites

The moving map in Figure 5-2 makes several nearby 

alternative airports visually apparent. A classic technique 

used by pilots to maintain awareness is to periodically ask 

the question, “Where would I go if I lost engine power?” The 

moving map can be used in this way to maintain preparedness 

for an emergency, if you are aware of the map scale and 

aircraft capabilities.

Maintaining Awareness on the Airport Surface

On most units, you can change the range on the moving map 

to see a more detailed picture of the airport surface while 

operating on the ground. This feature is especially useful 

when the arrangement of runways and taxiways is complex. 

The moving map in Figure 5-3 shows the aircraft prepared 

to taxi onto one of two possible runways.

Identifying Controlled Airspace

Most moving map displays can portray surrounding airspace 

as well as the vertical limits of each airspace segment. This 

feature is particularly useful during visual flight rules (VFR) 

flights, but can also serve to remind you of speed restrictions 

that apply to airspace transitions during instrument flight 

rules (IFR) flight.
5-4

C

RING

CDI OBS MSG FPL PROC

COM GPS

C

V

PWR

VOL/ SQ

PUSH

VOL/ ID

PUSH

VLOC

117.30

113.90

COM

120.900

125.675

NAV

 CEBCA DIS DTK BRG

GS TRK ETE

0.2 3 nm 08 m 308 m 

120kt 308 m 

0.3 0.3

BOCRA

00:24 APR

MA

Figure 5-4. The missed approach point shown on two different 

displays.

ECA

WAGER

5

338

1

1652

200

46

13.7

2300

23.0

NAV1 116.00 114.00 NAV2 113.90 114.80 125.900 121.600 COM1

123.850 119.000 COM2

GS 156kts DIS 53.2NM ETE 00:21

ENGINE MAP DCLTR

MAP WPT AUX NRST

MAP - NAVIGATION MAP

TRACK UP

30NM

Figure 5-5. Moving maps help make route programming errors 

evident.

Range

242

Map TAWS Trip Nrst Chkist Setup Engine

NEXTSUNOL

8.0nm 4m04s 45 Gal Rg

+ ABV 11nm

/ STRK

24

w

30

33

N

S

E

21

15

12

3

6

037

030

000

Gal Rg

SUNOL

DESTKOAK

TO BRG

GS

UTC

8.0nm 4m04s 45

26.9nm 13m13s43

Gal Rg

119

22:59:26

Kt

SUNOL

ALTAM

KLVK

C83

Emerg.

Checklist

Clear

Strikes

Lightning

Strike

Trac

Above

Declutter

Base Map

Base

View

Center

Figure 5-6. A reminder that the FMS/RNAV is set in the 

nonsequencing mode.

Identifying the Missed Approach Point

The moving map display is an especially useful aid for 

recognizing arrival at various points, including the missed 

approach point during an instrument approach. The moving 

map display complements the distance readout on the PFD/

MFD/FMS. Figure 5-4 shows two indications of an aircraft 

arriving at a missed approach point. The position of the 

aircraft on the moving map is very clear, and the range setting 

has been used to provide a more detailed view of the missed 

approach waypoint.

CAUTION: Some units can be set to change ranges 

automatically. In some instances, this can lead to a loss of 

situational awareness as you forget or miss a scale change. 

This can lead to sudden pilot realization at some point that 

the aircraft is too high, too far, or moving too fast. Manual 

switching (pilot selection) of the range display ensures that 

you are constantly aware of the distances and closure rates 

to points.

Catching Errors: Using the Moving Map to Detect 

Route Programming Errors

Moving maps are particularly useful for catching errors 

made while entering modifications to the programmed 

route during flight. Misspelled waypoints are often difficult 

to detect among a list of waypoints. The moving map in 

Figure 5-5 shows a route containing a misspelled waypoint. 

It is easy to detect the mistake when the information is shown 

pictorially. For this reason, a display such as a moving map is 

sometimes referred to as an error-evident display. The PFD 

selected track indicates incorrect settings. Always be ready 

and able to fly the aircraft according to any air traffic control 

(ATC) clearance or instructions. Disengaging all automation 

and then reestablishing heading, track, and altitude control is 

the pilot’s first priority at all times. Then, when the aircraft 

is on an assigned track at a safe altitude, pilot time can be 

expended to reprogram as necessary.

Catching Errors: Using The Moving Map To 

Detect Configuration Errors

Moving maps can help you discover errors made in 

programming the FMS/RNAV and PFD. The moving map 

display shown in Figure 5-6 removes the depiction of the leg 

to the active waypoint when the FMS/RNAV is engaged in 

the nonsequencing mode. This feature provides an easy way 

to detect the common error of forgetting to set the computer 

back to the sequencing mode.
5-5

10NM

MAP WPT AUX NRST

FAFIX

IAFIX

VOR 1

348° The pilot turns to intercept

the course shown on the

mis-set course deviation

indicator.

The moving map suggests 

that something is wrong

with the indications shown

on the course deviation

indicator: the aircraft is 

about to depart the RNAV 

approach course. 

Figure 5-7. Discovering an incorrect navigation source selection 

using the moving map.

OBS

0

9

18

27

3

33

24 21

15

12

30

6

TO N

A

V

Figure 5-8. Can you determine your position from a simple CDI?

Range

KGDM

KGRE

KEEN

KAFW

SB3 C44

43M

OB5

3B0

1B6

BB5

5B6

70

40

100

SFC 

70

30

70

30

DEST

TO

TIME

- - -

22:59:26

- - -

- - - - - - UTC 22:59:26

KORH

KMHT

KOWD

KBED

KPVD

KBOS

Nav Source

Not Communicating

A

C

K

PWR RPM

FUEL

REM

OIL

LEAN

OAT

GPH

Gal

F

C

USED

h m

PSI

I

N

H

G

Map TAWS Trip Nrst Chkist Setup Engine

+ ABV 11nm

/ STRK

037

030

000

Emerg.

Checklist

Clear

Strikes

Lightning

Strike

Trac

Above

Declutter

Base Map

Base

View

Center

Figure 5-9. An MFD indicating a loss of position information.

The moving map shown in Figure 5-7 allows you to discover 

a more serious programming error quickly. In this situation, 

the pilot is attempting an RNAV approach. However, the 

course deviation indicator (CDI) has erroneously been set 

to display very high frequency (VHF) omnidirectional range 

(VOR) course indications. The CDI suggests that the aircraft 

is well to the west of course. The moving map display shows 

the true situation—the aircraft is on the RNAV approach 

course, but is about to depart it.

Maintaining Proficiency: Spatial Reasoning Skills

Consider the CDI shown in Figure 5-8. What is the position 

of the aircraft with respect to the VOR station? Interpreting 

this type of display requires more effort than interpreting the 

moving map, which automatically displays the solution to 

the position-finding problem. Pilots should expend the effort 

to practice this skill set. Those who learn to navigate using 

ground-based radio navigation aids are forced to develop 

spatial reasoning and visualization skills, but a Federal 

Aviation Administration (FAA) study showed that this type 

of skill tends to fade quickly when not used. Be sure to keep 

your spatial reasoning and visualization skills sharp.

Failure Indications

Failure indications on the moving map can be quite subtle. 

The MFD in Figure 5-9 reflects a loss of position information, 

indicated by the removal of the aircraft symbol, compass 

labels, and other subtle differences. Be familiar with the 

failure indications specific to your equipment.

Common Error: Using the Moving Map as a 

Primary Navigation Instrument

The rich detail offered by the moving map display invites 

you to use the display as a primary navigation instrument, but 

you need to resist this temptation. The moving map display 

is designed to provide supplemental navigation information, 
5-6

but is not approved as a substitute for primary navigation 

instruments. The moving map is not required to meet any 

certification standards for accuracy or information as are 

the primary navigation CDI and related system components. 

Bear in mind that the apparent accuracy of the moving map 

display can be affected by factors as simple as the range 

setting of the display. An aircraft 10 miles off course can 

appear to be centered on an airway when the range is set to 

cover great distances.

Awareness: Overreliance on the Moving Map

With the position of the aircraft conveniently displayed at 

all times on a color screen in front of you, it is easy to let 

the computers do the work of monitoring flight progress. 

Numerous studies have demonstrated that pilots have a 

tendency to monitor and process navigational information 

from conventional sources (e.g., outside reference or 

conventional navigation instruments) much less actively 

when a moving map display is available. In a National 

Aeronautics and Space Administration (NASA) study, two 

groups of pilots were asked to navigate along a circuit of 

checkpoints during a VFR cross-country flight. One group 

navigated using a sectional chart and pilotage. The other 

group had the same sectional chart plus an RNAV computer 

and a moving map. After completing the circuit, both groups 

were asked to navigate the circuit again, this time with no 

navigational resources. Pilots who had navigated with only 

the sectional chart performed well, finding the checkpoints 

again with reasonable accuracy. The performance was less 

favorable by pilots who had the FMS/RNAV and moving map 

available. While half of these pilots found the checkpoints 

with reasonable accuracy, one-fourth of the pilots made larger 

errors in identifying the checkpoints. The remaining pilots 

were wholly unable to find their way back to the airport of 

origin. This study makes two important points:

1. The existence of information about aircraft position 

and geographical surroundings in an FMS/RNAV 

and moving map display does not mean that the pilot 

maintains true situational awareness or involvement 

with the operation of the flight to a degree needed for 

a safe outcome.

2. The key to the successful use of a moving map display 

is to use the display as a supplement—not a substitute—

for active involvement in the navigational process.

What does it take to use a moving map and remain “in the 

loop,” or situationally aware? In a second NASA study, 

pilots who used an FMS/RNAV and moving map display 

were asked to act as “tour guides,” pointing out geographical 

features to a passenger while navigating the same set of crosscountry checkpoints. When confronted with a surprise request 

to navigate around the circuit again with the FMS/RNAV and 

map turned off, these pilots performed as well as anyone else. 

The simple task of pointing out geographical features was 

enough to avoid the out-of-the-loop phenomenon.

A moving map provides a wealth of information about your 

route of flight and gives you the opportunity to consider many 

similar questions along the way. Where would you land if you 

lost engine power? Which alternate airport would you use if 

weather at your destination deteriorated below minimums? 

Which nearby VOR stations could be used (and should be 

tuned as the flight progresses) in the event that the global 

positioning system (GPS) signal or other RNAV navigation 

data source is lost? Is a more direct routing possible? Diligent 

pilots continually ask questions like these.

Terrain Systems

Terrain systems provide information about significant 

terrain along your route of flight. Terrain systems were 

designed to help reduce controlled flight into terrain (CFIT) 

accidents. Remember, however, that use of these terrain 

proximity information systems for primary terrain avoidance 

is prohibited. The terrain proximity map is intended only 

to enhance situational awareness; it remains the pilot’s 

responsibility to ensure terrain avoidance at all times. 

Safe flight practices include pilot knowledgeability of the 

maximum elevation figures (MEF), published in blue for each 

grid square on sectional charts, and planning flight altitudes 

above those elevations. Despite all efforts by the charting 

agency to be current, there will always be obstructions 

in place before the documentation arrives for charting. 

Therefore, the competent pilot always allows for sufficient 

clearance for unknown towers and buildings. Experienced 

pilots have learned that many aircraft cannot outclimb certain 

mountainous slopes. You should always fly down (descend) 

into a valley or canyon, rather than attempting to fly up the 

valley and become trapped in a box canyon too narrow for a 

turn and too steep to climb over. One regularly overlooked 

factor is the loss of power generally associated with the higher 

elevations at which canyons and steep slopes are often found.

Early Systems

Various terrain avoidance systems have been certificated 

and used in the past. One early system was termed Ground 

Proximity Warning System (GPWS, often pronounced 

“GipWhiz”). One major shortcoming of the system was a lack 

of predictive terrain warnings. Most early systems simply 

used a radar altimeter as the sensor. The radar altimeter 

simply indicated the altitude of the aircraft above the ground 

immediately below the airframe. The subsequently developed 

enhanced GPWS (EGPWS or eGPWS) used GPS location 

data combined with a worldwide terrain database to predict 

that a canyon wall was just ahead and a climb should be 
5-7

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NAV1 117.95 115.40 NAV2 108.00 117.95123.750 119.925 COM1

135.975 120.050 COM2

GS 123kts DIS 53.2NM ETE 25:58 ESA 16800

ENGINE MAP DCLTR

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MAP - NAVIGATION MAP

NORTH UP

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NAV1 117.95 115.40 GS 123kts DIS 53.2NM ETE 25:58 ESA 16800 123.750 119.925 COM1

Color coding is used to depict the height of surrounding terrain relative to the current altitude of the aircraft. 

At its present altitude, this aircraft will not clear the terrain on its way to KRIL.

Figure 5-10. Terrain depicted on an MFD.

started. The older GPWS had no indication of a very close 

hazard. However, the system did prevent numerous gear-up 

landings and offered warnings when terrain presented a slope 

to much higher terrain.

Terrain Display

The most basic type (not necessarily certified) of terrain 

system is the terrain display. A terrain display uses the 

MFD to plot the position of the aircraft against a pictorial 

presentation of surrounding terrain. A terrain display usually 

relies on a GPS location signal to compare the position and 

altitude of the aircraft against the terrain found in an internal 

topographical database. Figure 5-10 shows the position of 

the aircraft and surrounding terrain displayed on an MFD.

Terrain displays use a simple color-coding convention to 

portray the difference between the present altitude of the 

aircraft and the height of the surrounding terrain. Terrain 

more than 1,000 feet below the aircraft is coded black. Terrain 

less than 1,000 feet but more than 100 feet below the aircraft 

is coded yellow. Terrain less than 100 feet below the aircraft 

is coded red. Man-made obstacles (e.g., radio towers, power 

lines, buildings) generally do not appear in a topographical 

database.

Monitoring Surrounding Terrain During Departure 

and Arrival

Terrain displays are especially useful during departure and 

arrival phases of flight. For example, the aircraft shown 

in Figure 5-10 has departed Denver and is heading for a 

waypoint situated in high terrain in the Rocky Mountains. 

A pilot with good situational awareness has many concerns 

during the departure. For instance, is climb performance 

meeting expectations? The terrain display reduces the need 

for you to perform mental calculations by verifying that 

the depiction of the terrain that lies ahead of the aircraft is 

steadily changing from red to yellow to black. If the terrain 

depiction remains red as the aircraft approaches, you know 

there is a problem. Similarly, if the aircraft has been assigned 

a heading and altitude vector by air traffic control, the terrain 

display provides a simple way of monitoring the safety of 

these directives. If the equipment is not certified as meeting 

TAWS requirements (see Title 14 of the Code of Federal 

Regulations (14 CFR) part 91, section 91.223), the accuracy 

can be in doubt.
5-8

Evaluating a Direct-To Routing

One of the risks involved in proceeding directly to a waypoint 

is that you may be yet unaware of any significant terrain 

between the present position and the waypoint. A terrain 

display offers a convenient way of seeing clearly what lies 

between here and there as reported and documented in the 

database. Always consult the MEF values along the path of 

flight to ensure terrain and obstruction clearance.

Terrain Awareness and Warning Systems

A terrain awareness and warning system (TAWS) offers 

you all of the features of a terrain display along with a 

sophisticated warning system that alerts you to potential 

threats posed by surrounding terrain. A terrain awareness 

and warning system uses the aircraft’s GPS navigation signal 

and altimetry systems to compare the position and trajectory 

of the aircraft against a more detailed terrain and obstacle 

database. This database attempts to detail every obstruction 

that could pose a threat to an aircraft in flight.

TAWS A and TAWS B

There are presently two classes of certified terrain awareness 

and warning systems that differ in the capabilities they 

provide to the pilot: TAWS A and TAWS B.

A TAWS A system provides indications for the following 

potentially hazardous situations:

1. Excessive rate of descent

2. Excessive closure rate to terrain

3. Altitude loss after takeoff

4. Negative climb rate

5. Flight into terrain when not in landing configuration

6. Excessive downward deviation from glideslope

7. Premature descent

8. Terrain along future portions of the intended flight 

route

A TAWS B system provides indications of imminent contact 

with the ground in three potentially hazardous situations:

1. Excessive rate of descent

2. Excessive closure rate to terrain (per Advisory Circular 

(AC) 23-18, to 500 feet above terrain)

3. Negative climb rate or altitude loss after takeoff

TAWS Alerts

Aural alerts issued by a terrain awareness and warning system 

warn you about specific situations that present a terrain 

collision hazard. Using a predictive “look ahead” function 

based on the aircraft’s ground speed, the terrain system alerts 

you to upcoming terrain. At a closure time of approximately 

1 minute, a “Caution! Terrain!” alert is issued. This alert 

changes to the more serious “Terrain! Terrain!” alert when the 

closure time reaches 30 seconds. In some areas of the world, 

this terrain warning may very well be too late, depending on 

the performance of the aircraft. You need to determine the 

equipment’s criteria and note if the unit makes allowances for 

lower power output of the powerplant(s) at higher elevations, 

resulting in lower climb rates than may be programmed into 

the unit for that aircraft.

A second type of aural alert warns about excessive descent 

rates sensed by the system (“Sink Rate!”) or inadvertent loss 

of altitude after takeoff (“Don’t Sink!”). 

The introduction of terrain awareness and warning systems 

has sharply reduced the number of CFIT accidents. Despite 

this significant leap forward in safety, incidents and accidents 

involving terrain still happen. In the modern TAWS-equipped 

cockpit, some of these incidents have been related to pilot 

reaction to TAWS alerts. TAWS sometimes gives nuisance 

alerts that desensitize the pilot to TAWS alerts, which can 

result in the pilot’s decision to ignore a valid alert deemed 

unnecessary by the pilot. Most TAWS systems contain 

software logic that attempts to recognize and remain silent in 

situations in which proximity to terrain is normal. This logic 

is partly based on the aircraft’s distance from the runway 

of intended landing. For example, flying at an altitude of 

200 feet AGL when 3,500 feet away from the runway is 

reasonable, but flying at an altitude of 200 feet AGL when 

5 miles from the runway is not reasonable. TAWS’ logic 

attempts to silence itself in normal situations, and to sound 

in abnormal situations.

Risk: Silencing TAWS Alerts

Despite efforts to minimize nuisance alerts, they still occur 

occassionally. For this reason, most TAWS systems offer a 

terrain inhibit switch that allows you to silence TAWS alerts. 

There have been cases in which pilots have used the inhibit 

switch or ignored TAWS alerts, thinking they were nuisance 

alerts, when in fact the alerts were valid indications of a 

dangerous situation. For this reason, you should train yourself 

to respond to TAWS alerts just as you would to any other sort 

of emergency. Always, if in any doubt, set “Full Power and 

Climb” at VX or VY, depending on the equipment manual 

and AFM/POH. The practice of simply ignoring or disabling 

TAWS alerts based on pilot intuition has not proved to be a 

safe one. Your manufacturer’s reference manual and aircraft 

flight manual supplement will prescribe specific procedures 

for responding to TAWS alerts.

The only current, fully certified systems, known as TAWS, 

are certified under Technical Standards Order (TSO)-C151. 
5-9

TAWS equipment is required for turbine-powered airplanes 

having six or more passenger seats and manufactured after 

certain dates (see 14 CFR part 91, section 91.223). TAWS is 

now an affordable option in many advanced avionics due to 

decreased cost and increased capabilities of computer circuits 

and components. All aircraft would be safer with TAWS and 

crews trained to use the technology.

Risk: Flying in Close Proximity to Terrain

A display that plainly shows your position with respect to 

surrounding terrain is sometimes cited as the most reassuring 

system available in the advanced avionics cockpit. The 

same display can also invite the unwary pilot to attempt 

risky maneuvers. Suppose that, on a VFR flight to an airport 

located in hilly terrain, you encounter a layer of fog at 

1,100 feet. In an aircraft with no terrain system, you would 

not consider proceeding to the airport because you have a 

personal minimum of 1,500 feet. With a ceiling of less than 

1,500 feet, you deem the situation simply too risky. With the 

surrounding terrain neatly displayed in front of you, however, 

you may feel more confident and be tempted to give it a try. 

However, a wise pilot remembers that, unless the equipment 

is TAWS certified, accuracy is suspect. Even with TAWS 

certification, the information presented is no better than 

the database accuracy. Consult the equipment handbook or 

manual to determine the accuracy of the database in that area.

CFIT accidents are still occurring despite the advent of 

advanced avionics. What has happened here? Psychologist 

Gerald J. S. Wilde coined the phrase risk homeostasis to refer 

to a tendency for humans to seek target levels of risk. Our 

hill-flying scenario illustrates the concept. After pondering 

the perceived risks, you decide that having the terrain display 

gives you the same level of perceived risk with a 1,000-foot 

ceiling as you felt you had at 1,500 feet without the terrain 

display. You see no need to “give away” this new margin 

of perceived safety. Rather, you decide to use it to your 

advantage. Equipped with the terrain display, your new 

minimum ceiling becomes 1,000 feet, and you continue on 

your way to the airport.

Wilde does not support the idea of using technology to seek 

target levels of risk. Rather, he argues that safety measures 

such as seat belt laws and anti-lock brakes have not resulted 

in drastic reductions in highway fatalities in part because, 

in response to the added sense of safety provided by these 

measures, drivers have emboldened their driving behavior 

to maintain existing levels of risk.

Another issue is the lack of training in the new equipment 

and its uses. The functions of TAWS and basically how 

it works have been previously described, yet there is no 

training program outside the military that teaches anyone to 

fly based on the TAWS display. It requires much precision 

flight training to learn the timing and skills to fly from a 

display depicting a myriad of data and converting that data 

into close and low terrain flight directions. All advanced 

avionics are designed to help the pilot avoid a hazard, not 

enable the pilot to get closer to it. TAWS is not a terrain 

flight following system.

Cockpit Weather Systems

Advanced avionics cockpit weather systems provide many 

of the same weather products available on the ground and 

have a variety of uses that can enhance awareness of weather 

that may be encountered during almost any phase of flight. 

Radar images, satellite weather pictures, Aviation Routine 

Weather Reports (METARs), terminal weather forecasts 

(TAFs), significant meteorological information (SIGMETs), 

Airmen’s Meteorological Information (AIRMETs), and other 

products are now readily accessible at any time during flight. 

Weather products provided by cockpit weather systems are 

typically presented on an MFD. Some installations allow 

the overlay of this data in the PFD. You must learn the 

procedures required to show each kind of weather product 

on the MFD and/or PFD, and how to interpret each type 

of weather product. Know the limitations of each type of 

product, and the ways in which cockpit weather systems can 

be used to gather information and remain clear of weather 

hazards throughout the flight.

Thunderstorms and Precipitation

Thunderstorms and general areas of precipitation are 

detected through the use of radar. In the advanced avionics 

cockpit, radar data can come from one of two sources: 

an onboard weather radar system or a ground weather 

surveillance radar system, such as the Next Generation 

Radar (NEXRAD) system. Ground weather surveillance 

system data is transmitted to the cockpit via a broadcast (or 

datalink) weather service. Onboard weather radar and ground 

weather surveillance radar systems each offer advantages and 

disadvantages to the pilot. Some aircraft use a combination 

of both systems.

While onboard radar is real time, many downloaded radar 

images and other reports are delayed for some time period 

for various reasons. Given the nature of thunderstorms and 

other weather hazards, this delay could prove hazardous. You 

must know the true quality and age of the data.

Most MFDs are capable of presenting radar data together 

with aircraft position and the programmed route, as shown 

in Figure 5-11.
5-10

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GS 123kts DIS 53.2NM ETE 25:58 ESA 16800

ENGINE NEXRAD ECHO TOP CLD TOP LTNG CELL MOV SIG / AIR METAR LEGEND MORE WX

MAP WPT AUX NRST

MAP - NAVIGATION MAP

NORTH UP

30NM

Figure 5-11. Radar data shown on an MFD.

0

Figure 5-12. A radar beam allows you to see some weather cells, 

but not others.

Onboard Weather Radar Systems

Onboard weather radar uses an adjustable aircraft mounted 

radar antenna to detect, in real time, weather phenomena near 

the aircraft. The coverage of an onboard weather radar system 

is similar to a flashlight beam, as illustrated in Figure 5-12.

You should always remember that the radar displays only 

areas of water or moisture (rain, sleet, snow, and hail). Radar 

does not display turbulence or lightning.

Although the tilt of the radar antenna can be adjusted upward 

and downward, the weather phenomena that the weather 

radar can detect are limited in both direction and range. The 

radar system in Figure 5-12 fails to detect the two cells that 

lie below and beyond the radar beam.

As illustrated in Figure 5-12, you must be careful not to 

assume that the only cells in the area are the ones shown on 

the radar display. The two additional cells in Figure 5-12 are 

present, but not detected by the onboard weather radar 

system.

When a cell is detected by an onboard weather radar system, 

that cell often absorbs or reflects all of the radio signals sent 

out by the radar system. This phenomenon, called attenuation, 

prevents the radar from detecting any additional cells that 

might lie behind the first cell. Figure 5-13 illustrates radar 

attenuation, in which one cell “shadows” another cell.

A simple color-coding scheme, as shown in Figure 5-14, is 

used to represent the intensity of radar echoes detected by 

an onboard weather radar system.

Ground Weather Surveillance Radar

Ground weather surveillance integrates weather information 

from many ground radar stations. The weather information 

collected from many sources is then used to create a 

composite picture that covers large volumes of airspace. 

These composite radar images can then be transmitted to 

aircraft equipped with weather data receivers.
5-11

10

20

30

40

Cells detected by onboard radar Actual situation

Figure 5-13. Radar attenuation.

10

20

30

40

Onboard weather radial symbology

Level 4 (Magenta) Intense to Extreme

Level 3 (Red) Strong to Very Strong

Level 2 (Yellow) Moderate

Level 1 (Green) Weak

Level 0 (Black) Background

Figure 5-14. Color coding of intensity on an onboard weather 

radar system.

NEXRAD

AGE: 5min

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Ground weather surveillance radar symbology

Figure 5-15. Color coding of intensity on a NEXRAD display.

Except in those areas for which no ground radar coverage 

is available, the range of ground weather surveillance 

radar systems is essentially unlimited. Ground radars have 

the luxury of large antennas; big, heavy power supplies; 

and powerful transmitters—without the constraints of 

aerodynamic drag, power, weight, and equipment volume 

restrictions and concerns.

Unlike onboard weather radar systems, weather data received 

from a ground weather surveillance radar system is not realtime information. The process of collecting, composing, 

transmitting, and receiving weather information naturally 

takes time. Therefore, the radar data reflect recent rather than 

current weather conditions.

The color-coding scheme used by one ground weather 

surveillance radar system (NEXRAD) is shown in 

Figure 5-15. Note that this color-coding scheme is slightly 

more sophisticated than that for the onboard system in 

Figure 5-13. It is capable of distinguishing rain, snow, and 

mixtures of the two.

Limitations of Both Types of Weather Radar 

Systems

Weather radar does not detect most other kinds of hazardous 

weather such as fog, icing, and turbulence. The absence of 

radar return on a radar display does not in any way mean 
5-12

LIGHTNING MODE

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Figure 5-16. Lightning strikes shown on an MFD.

CLD TOP

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NAV1 116.00 114.80 NAV2 113.90 114.60 123.850 125.100 COM1

118.600 120.600 COM2

GS 123kts DIS 53.2NM ETE 25:58 ESA 16800

ENGINE NEXRAD ECHO TOP CLD TOP LTNG CELL MOV SIG / AIR METAR LEGEND MORE WX

MAP WPT AUX NRST

MAP - NAVIGATION MAP

NORTH UP

30NM

Figure 5-17. Cloud cover and cloud tops shown on an MFD.

“clear skies.” Skillful users of weather radar are able to 

recover clues of other weather phenomena, such as hail and 

turbulence, from radar data.

A second limitation of weather radar is that the earliest 

(cumulus) stage of a thunderstorm is usually free of 

precipitation and may not be detected by radar. Convective 

wind shear, severe turbulence, and icing are characteristic 

of thunderstorms during the cumulus stage.

The pilot must beware of areas that offer no radar coverage. 

In many cases, these areas appear blank on a weather display. 

The absence of weather hazards as shown on a screen does 

not imply the actual absence of weather hazards.

Lightning

Most MFDs are also capable of depicting electrical activity 

that is indicative of lightning. Like radar data, lightning data 

can come from two sources: onboard and broadcast weather 

systems. Both systems have strengths and limitations and 

work together to present a more complete weather picture. 

Lightning data is an excellent complement to radar data for 

detecting the presence of thunderstorms.

An onboard lightning detection system consists of a 

simple antenna and processing unit that senses electrical 

discharges in the atmosphere and attempts to determine 

which electromagnetic signals have the “signature” of 

lightning strikes. Lightning detectors or spherics receivers, 

such as Stormscope® and Strikefinder ®, have been known 

to indicate areas of static consistent with turbulence even 

where there was no rain associated with the turbulence. The 

MFD in Figure 5-16 depicts lightning strikes detected by 

a lightning detection system. Onboard lightning detection 

systems provide real-time information about electrical 

discharges. Estimates of the direction (or azimuth) of 

electrical discharges provided by an onboard lightning system 

are usually quite accurate. Estimates of the range (or distance) 

of electrical discharges tend to be less accurate.

Broadcast (or data link) weather services are also capable of 

transmitting lightning data to the cockpit. The symbology 

used to present lightning data derived from these sources is 

similar to that used by onboard lightning detection systems. 

The lightning data provided by ground weather surveillance 

systems is also a delayed weather product. Since the lightning 

data provided by a broadcast service is derived from multiple 

sensors, estimates of the range of electrical discharges are 

more accurate than those provided by onboard systems.

Clouds

Weather products that describe cloud coverage are generally 

available only from broadcast weather services. One popular 

broadcast weather service offers graphical displays of visible 

cloud cover along with the cloud top altitude as determined 

from satellite imagery. Figure 5-17 shows an MFD that 

depicts cloud cover and cloud tops.

Other Weather Products

Broadcast weather services offer many of the other weather 

products that can be obtained during a pre-flight briefing 

on the ground. Broadcast weather services can also provide 

graphical wind data, SIGMETs and AIRMETs, freezing 

levels, temporary flight restrictions, surface analyses, and 

hurricane tracks. The MFD in Figure 5-18 shows METAR 

and TAF data.

Using Advanced Weather Data Systems

The increased availability of weather information is changing 

the way pilots think about weather briefing and the weather 

decision-making process. You are no longer limited to 

obtaining weather forecast products prior to a flight, only 

to discover different actual flight conditions in the air. Now 
5-13

MAP WPT AUX NRST

AIRPORT

METAR

TAF

HAYWARD EXECUTIVE

HAYWARD CA

KHWD PUBLIC

WIND DIR: 300

WIND SPD: 6KT

VISIBILITY: 10SM 

CLOUDS: 

 9000FT FEW 

TEMPERATURE: 11 C

DEW POINT: 1 C

ALTIMETER: 30.11 IN

ORIGINAL METAR TEXT: 

SA KHWD 162154Z

NONE

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ENGINE MAP INFO DP STAR APR WX

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WPT - WEATHER INFORMATION

NORTH UP

METAR window

TAF window

Figure 5-18. METAR and TAF data shown on an MFD.

more than ever, weather briefing is an activity that begins 

prior to departure and continues until the flight is completed.

Preflight Overview

A broadcast weather service allows you to see these products 

in the cockpit. Most systems offer a movable cursor that 

allows scrolling through the display to center on any location 

along the route. This capability, combined with the MFD’s 

range control, allows you to look for significant weather 

anywhere along the planned route of flight prior to departure.

Track Progress of Significant Weather En Route

The same scroll and range control features allow you to look 

ahead and check for weather conditions along upcoming 

portions of the flight route. Weather forecasts, such as TAFs, 

SIGMETs, and AIRMETs, issued after departure can be 

easily checked en route.

Investigate Weather Phenomena Reported by Radio

You can use cockpit weather systems to further investigate 

advisories received from HIWAS and other radio broadcasts. 

Another practical use is to check the METAR for a destination 

airport before flying in range of the airport’s ATIS broadcast. 

When you suspect that changing weather conditions have 

made continuation to the destination airport inadvisable, the 

radar and satellite features can be used to search for alternate 

airports. Since not all weather products can be viewed at once, 

a key pilot skill is the ability to determine which weather 

products to display at what times.

Broadcast Weather Products Versus Onboard 

Weather Sensors

Onboard weather sensor systems and broadcast weather 

services contribute to the weather decision-making process 

in slightly different ways. Broadcast weather services provide 

delayed information over a wider coverage area. Broadcast 

weather services are useful for making strategic decisions 

about which areas to fly into and which areas to avoid. Using 

a broadcast weather product to attempt to find a hole in a line 

of thunderstorms is inappropriate, since you cannot know if 

the current location of the thunderstorm cells is the same as 

when the broadcast weather product was generated. Onboard 

weather sensor systems provide real-time information about 

weather phenomena in the immediate proximity of the 

aircraft. Onboard weather sensor systems are useful when 

making immediate, close-range decisions about flying in 

the vicinity of potentially hazardous weather phenomena. 

You must keep in mind the limitations of onboard weather 

systems.
5-14

Traffic Display Symbology

+03

Non-Threat Traffic

Outside of protected distance and altitude range.

Proximity Intruder Traffic

Within protected distance and altitude range, but 

still not considered a threat.

Traffic Advisory (TA)

Within protected range and considered a threat. 

TCAS will issue an aural warning (e.g., Traffic! 

Traffic!).

Resolution Advisory (RA)

Within protected range and considered an immediate 

threat. TCAS will issue a vertical avoidance 

command (e.g., Climb! Climb! Climb!). 

Figure 5-19. Traffic display symbology.

Common Error: Skipping the Preflight Weather 

Briefing

The easy availability of weather information in the cockpit 

can lure you to skip the preflight weather briefing. Time 

pressure adds further incentive to simply jump in and go. 

Keep in mind that flight services stations (FSS)/automated 

flight service stations (AFSS) offer many advantages over 

an advanced weather data system, so do not use advanced 

avionics weather data systems as a substitute for a pre-flight 

weather briefing. As a simple example, when talking to an 

FSS/AFSS weather briefer, it is possible to get a better overall 

picture of the weather system and pilot reports not yet entered 

into the system. The FSS/AFSS briefer can also supply more 

Notice to Airmen (NOTAM) and other detailed information 

for your particular route of flight; without such briefing, the 

pilot might expend many precious moments searching for 

a critical bit of information, instead of managing the flight. 

Often, it is much easier to get a thorough briefing on the 

ground than attempting to read small reports on a bouncing 

MFD in a small airplane in turbulent conditions.

Traffic Data Systems

A traffic data system is designed to help you visually acquire 

and remain aware of nearby aircraft that pose potential 

collision threats. All traffic data systems provide aural alerts 

when the aircraft comes within a certain distance of any other 

detected aircraft. Traffic data systems coupled with MFDs can 

provide visual representations of surrounding traffic. Most 

traffic data systems allow you to set the sensitivity of the 

system and display only traffic that exists within a specific 

distance from the aircraft.

There are two basic types of traffic data systems available 

today: one using onboard sensors to detect nearby aircraft, the 

other relying on traffic information transmitted from ground 

facilities to the cockpit.

Traffic Data Systems Using Onboard Sensing 

Equipment

Traffic collision avoidance systems (TCAS) and traffic 

advisory (TA) systems use onboard sensing equipment to 

locate nearby aircraft and provide alerts and advisories. Both 

TCAS and TA systems work by querying the transponders of 

nearby aircraft to determine their distance, bearing, altitude, 

and movement relative to your aircraft. In addition, TCAS 

and TA systems use Mode C information from transponders 

to determine altitude and vertical movement of surrounding 

aircraft. Using these capabilities, TCAS and TA systems 

provide traffic alerts and advisories.

TCAS I and TA systems can issue a TA whenever another 

active transponder-equipped aircraft comes within an 

approximately 40-second range of the aircraft. Traffic 

advisories take the form of an aural alert: “Traffic! Traffic!”

Advanced TCAS systems (TCAS II) can also issue a 

resolution advisory (RA) when another active transponderequipped aircraft comes within an approximately 25-second 

range of the aircraft. RAs take the form of an avoidance 

command that instructs you how to fly the aircraft in order 

to avoid the threat. An aural alert is issued that instructs the 

pilot to perform a vertical avoidance maneuver. Example 

aural alerts are: “Climb! Climb!” and “Descend! Descend!”

TCAS and traffic advisory systems use similar symbology to 

present traffic information. Figure 5-19 shows four common 

traffic symbols used on traffic displays. The resolution 

advisory symbols appear only when an advanced TCAS II 

system is used. The colors used to display traffic symbols 

vary with the capabilities of the display.

Despite their many advantages, TCAS and traffic advisory 

systems have several important limitations. For example, 

TCAS and traffic advisory systems cannot detect aircraft that 

do not have active transponders. Another limitation of TCAS 

and traffic advisory systems is that they give unwanted alerts 

when the pilot is purposefully operating in the vicinity of 

other aircraft. For example, two aircraft making approaches 

to parallel runways will probably receive traffic alerts. These 

alerts can be distracting.

Traffic Data Systems Receiving Information From 

Ground-based Facilities

The traffic information service (TIS) is a second type of 

traffic data system. Unlike TCAS, the TIS system does not 

require each aircraft to have an onboard sensor that locates 

nearby aircraft. However, each aircraft must have operational 
5-15

and active transponders to be indicated on the ATC system. 

Rather, TIS captures traffic information that appears on radar 

scopes at nearby air traffic control facilities and broadcasts 

that information to appropriately equipped aircraft. In order 

to use TIS, aircraft must be equipped with a transponder 

capable of receiving TIS broadcasts. When TIS is operational, 

TIS-capable aircraft can observe traffic information in the 

cockpit and receive traffic advisories for proximate aircraft.

There is an important limitation of TIS. TIS data is only 

transmitted from approach radar facilities. No information 

is broadcast from en route (air route traffic control center 

(ARTCC)) facilities, so the effective coverage of TIS is 

limited to larger metropolitan areas. Some approach radar 

facilities are not equipped to send TIS information. Note that 

the aircraft must be within range (approximately 50 NM) and 

within line of site of the TIS station to receive broadcasts.

Advanced Traffic Data Systems Based on ADS-B

Future traffic avoidance systems will probably be able to 

determine position and digitally exchange information with 

airborne and ground-based facilities. Using the automatic 

dependent surveillance—broadcast (ADS-B) system, 

participating aircraft will continuously broadcast their own 

position, altitude, airspeed, trajectory, and identification to 

air traffic control facilities. ADS-B aircraft continuously 

receive the same information from like equipped aircraft 

in the area (line of sight), which allows onboard displays 

for surrounding traffic. ADS-B has been used with much 

success in Alaskan trials and requires less infrastructure to 

be usable. ADS-B equipment is demonstrating promise for 

better traffic separation on transoceanic routes well out of 

range of land-based systems. ADS-B signals are transmitted 

on the 978 MHz channel. The information gathered from all 

participating aircraft can then be transmitted back to each TIS 

aircraft to provide a detailed picture of the traffic situation, 

even if those aircraft do not have ADS-B onboard.

Using a Traffic Data System

Setting Sensitivity on a Traffic Data System

Most traffic data systems allow you to adjust sensitivity and 

configure the system to track targets occurring only within a 

specified distance and altitude. More sophisticated traffic data 

systems automatically adjust sensitivity throughout different 

phases of flight. It is important to become familiar with the 

use of these controls and features.

Responding to Traffic Alerts

You must develop skill in the task of visually acquiring 

aircraft identified by an advanced avionics traffic data system. 

This task requires you to use angles and distances displayed 

on a traffic display to help guide your visual search out the 

window. Since both the directions and altitudes of intruding 

aircraft provided to the aircraft’s traffic data receiver are 

subject to error, you must widen your scan to all areas around 

the location presented on the traffic display.

When responding to air traffic control requests to acquire and 

maintain visual separation from nearby targets, be careful not 

to acknowledge contact with targets that have been observed 

only on a traffic display. Do not report having the traffic “in 

sight” before visual acquisition of a target.

Error: Overreliance on Traffic Data System/Failure 

To Scan

Keep in mind that a traffic data system is designed to enhance 

“see and avoid” capabilities. You must avoid any tendency 

to rely too much on traffic data systems, or to use traffic data 

systems as a substitute for visual scanning and acquisition of 

surrounding traffic. Because of the limitations of advanced 

traffic data systems, think of them as supplemental to your 

traffic awareness while you continue to assume primary 

responsibility to see and avoid other aircraft. Remember, 

too, that systems can and do fail. Traffic data systems are 

quite complex and any failure from the other aircraft’s 

transponder/GPS/encoder to your receiver/decoder/GPS/ 

traffic computer and display encoder will reduce data on 

your display. Power spikes, weather (lightning), and other 

onboard aircraft disturbances are all unknown and changing. 

As experience is gained with the system, better designs will 

eliminate problems yet to be discovered.

Using a Traffic Data System on the Ground

Most traffic data systems automatically switch to a standby 

mode when the aircraft is on the ground or operating below 

a minimum speed. The same systems typically allow you to 

override this feature and manually activate the traffic data 

system at any time. There are a number of ways to exploit 

this capability. When departing from an uncontrolled airport, 

the traffic data system can help you learn of other traffic in 

the vicinity of the airport. When operating in low-visibility 

conditions, the same feature can help inform of other 

aircraft operating on the airport surface. One potential future 

application of ADS-B is allowing controllers and pilots to 

monitor aircraft better on taxiways and runways. You must 

check equipment documentation to determine when the 

transponder actually transmits, where the selection controls 

are located, and how to use those controls.

Fuel Management Systems

A fuel management system can help you make the fuel 

calculations needed for in-flight decisions about potential 

routing, fuel stops, and diversions. A fuel management 

system offers the advantage of precise fuel calculations 

based on time, distance, winds, and fuel flow measured by 
5-16

INTIAL USABLE FUEL Adjust level with right knob

Fuel Added = 30 Gallons

- 81 Gal (Full)

- 60 Gal

- 40 Gal

- 20 Gal

FUEL ADDED

BRT

DIM

Fuel Units

U.S. Gallons

Fuel 

Full

Fuel to

Tabs

Fuel 

Done

You can dial any initial fuel quantity or choose one of 

two preselected quantities (Tabs or Full).

Figure 5-20. Making an initial fuel estimate.

PWR 242

24

21 w

SUNOL

DESTWRAPS

TO BRG

UTC

1 m27s Gal.RMNG

22:59:26

RPM

FUEL

REM

OIL

L EAN

OAT

GPH

Gal

F

C

USED

h m

PSI

% IH

NG

3.5 52 N

M

75.9 0h32m 44 Gal.RMNG N

M

TIME22:59:26

Estimated fuel remaining at destination g

Actual fuel remaining

Figure 5-21. Fuel remaining and endurance shown on an MFD.

other aircraft systems. When a route has been programmed 

into the FMS, the fuel management function is capable of 

displaying currently available fuel and aircraft endurance and 

providing an estimate of fuel remaining as the aircraft crosses 

each waypoint in the programmed route. A fuel management 

function is useful not only for making primary fuel 

calculations, but also for backing up calculations performed 

by the pilot. If there are leaks, plumbing malfunctions, or 

inadequate leaning, the fuel display can be deceptive. You 

must always land at the earliest gauge indication of low 

fuel in the tanks, time of normal landing, or any sign of fuel 

value disagreement with the flight planning. Errors can be 

determined when the aircraft is safely on the ground.

Initial Fuel Estimate

Many fuel management functions lack a fuel quantity 

sensor. Without access to this raw data of fuel quantity, fuel 

management functions perform calculations using an initial 

fuel estimate that was provided by the pilot prior to departure. 

Figure 5-20 illustrates how an initial fuel estimate is given 

for one manufacturer’s fuel management unit.

It is important to make accurate estimates of initial fuel 

because the fuel management function uses this estimate in 

making predictions about fuel levels at future times during 

the flight. For example, if you overestimate the initial fuel by 

eight gallons and plan to land with seven gallons of reserve 

fuel, you could observe normal fuel indications from the fuel 

management system, yet experience fuel exhaustion before 

the end of the flight. The accuracy of the fuel calculations 

made by the fuel management function is only as good as 

the accuracy of the initial fuel estimate.

You must know the capacity of the aircraft fuel tanks and 

amount of fuel required to fill the tanks to any measured 

intermediate capacity (e.g., “tabs”). When full fuel capacity 

is entered into the fuel management system, the tanks must 

be filled to the filler caps. For some aircraft, even a fraction 

of an inch of space between the filler cap and the fuel can 

mean that the tanks have been filled only to several gallons 

under maximum capacity. Objects can plug lines, preventing 

the fuel from flowing to the pickup point. Some aircraft have 

bladders and dividers in the fuel system. A bladder can move 

within the tank area and not actually hold the quantity of fuel 

specified. Always check to ensure that the fuel servicing 

total matches the quantity needed to fill the tank(s) to the 

specified level.

Estimating Amount of Fuel on Board

Since the fuel management function’s predictions are often 

based on the initial quantity entered, it is important to 

monitor the fuel gauges to ensure agreement with the fuel 

management function of the FMS as the flight progresses. 

It is always prudent to use the most conservative of these 

measures when estimating fuel on board.

Predicting Fuel at a Later Point in the Flight

A primary function of the fuel management function or 

system is to allow you to predict fuel remaining at a future 

time in the flight. The fuel management system uses a 

combination of the currently available fuel and the current 

rate of fuel consumption to arrive at the measures. Some 

units require the current or estimated fuel burn rate to be 

entered. Some units have optional sensors for fuel flow and/

or quantity. Be absolutely sure of what equipment is installed 

in your specific aircraft and how to use it. Since the rate of 

fuel consumption instantly changes when power or mixture 

is adjusted, (usually with altitude) the fuel management 

function or system should continually update its predictions. 

It is common for the fuel management system to calculate 

fuel remaining at the arrival of the active waypoint, and the 

last waypoint in the route programmed into the FMS/RNAV. 

These measures are shown on the MFD in Figure 5-21.
5-17

KCMI

KTIP

K96

2KO

C16

KDEC

DEC

30NM

MAP WPT AUX NRST

5

338

1

1652

200

46

13.7

2300

23.0

NAV1 116.00 115.40ECA

NAV2 113.90 117.95

123.850 125.100 COM1

118.600 120.600 COM2

GS 123kts DIS 53.2NM ETE 25:58 ESA 16800

ENGINE MAP OCLTR

MAP WPT AUX NRST

MAP - NAVIGATION MAP

NORTH UP

The inner fuel ring indicates when the fuel will reach pilot-specified fuel reserve minimums.

123.850 125.100 COM1

118 600 120 600

ETE 25:58 ESA 16800

The outer fuel ring indicates when fuel will be exhausted.

Figure 5-22. A fuel range ring.

When no route is programmed into the FMS/RNAV, the 

fuel management function may not display information due 

to lack of data.

Determining Endurance

Most fuel management function or systems display the 

amount of fuel remaining, as well as the endurance of the 

aircraft given the current fuel flow. Most systems display 

the aircraft endurance in hours and minutes, as shown in 

Figure 5-21.

Some units show a fuel range ring on the MFD that indicates 

the distance the aircraft can fly given current fuel and fuel 

flow. This feature, illustrated in Figure 5-22, is useful for 

making fuel stop or alternate airport planning decisions. It 

may or may not include allowances for winds. Many units 

allow you to specify personal minimum fuel reserves. In 

this case, the fuel range ring indicates the point at which the 

aircraft will reach reserve fuel minimums.

Risk: Stretching Fuel Reserves

The availability of predictive information about fuel burn and 

fuel availability introduces the possibility of flying closer and 

closer to fuel minimums or stretching fuel holdings farther 

than would be appropriate with “back of the envelope” 

calculations in a traditional aircraft. You must be aware of this 

tendency and discipline yourself to using fuel management 

systems to increase safety rather than stretch the limits. 

Refueling the aircraft offers a good opportunity to compare 

the amount of fuel burned with that predicted by the fuel 

management system and your own calculations. It is always 

a good exercise to determine why the fuel management 

function or system’s numbers differ from what is actually 

pumped into the tank(s). Was it improper leaning? More/

less winds? Are the EGT/CHT gauges indicating properly?

Other Cockpit Information System 

Features

Electronic Checklists

Some systems are capable of presenting checklists that appear 

in the aircraft operating manual on the MFD. The MFD in 

Figure 5-23 depicts a pretaxi checklist while the aircraft is 

parked on the ramp.

In some cases, checklists presented on an MFD are approved 

for use as primary aircraft checklists. It is important to note 
5-18

PREFLIGHT

1. Cabin

h. Fuel Selector

i. Flaps

j. Oil Annunciator 

k. Lights 

l. Bat 1 and 2 Master Switches

m. Alternate Static Source

n. Fire Extinguisher

o. Emergency Egress Hammer 

p. CAPS Handle

2. Left Fuselage

a. Com 1 Antenna (top)

b. Wing/fuselage Fairing 

c. Com 2 Antenna (underside)

d. Baggage Door

e. Static Button 

f. Parachute Cover

3. Empennage

a. Tiedown 

b. Horizontal and Vertical Stabilizers 

c. Elevator and Tab

a. Required Documents 

b. Avionics Power Switch

c. Bat 2 Master Switch

d. Voltmeter 

e. Flap Position Light

f. Bat 1 Master Switch

g. Fuel Quantity

Select Fullest Tank

100%, Check Light ON

On

Check Operation 

OFF 

NORMAL

Charged and Available 

Available 

Pin Removed

Condition and Attachment

Check 

Condition and Attachment

Closed and Secure

Clear

Sealed and Secure

Remove 

Condition

Condition and Movement

On Board 

OFF 

ON 

23-25 Volts 

OUT 

ON 

Check

.......................................................

............................................................

................................................................ ..................................................................... ................................................................

................................................................ ......................................................................

..................................................... ...........................................................

......................................................................... ................................................................. .................................................... .................................................... ........................................... ............................................. ............................................................

..........................................................................

........................................................................

...................................................

..................................

...........................................................

.................................................

..........................

........................................ ........................................

Map Trip Nrst Chkist Setup

BRT

DIM

Before

Take-o

InFlight

Landing

Shut down

Perf.

Data

Emerg.

Checklist

Done

Back

Figure 5-23. A pretakeoff checklist shown on an MFD.

off On

MAP WX TRFC TERR AUX

RNG

RNG

ONLY

DIS: 22.3 NM

WOHLI

(FAF)

GIRUC (IAF)

(7.1)

5000

2026

949

(MAP)

RUXKO

289

TRK: 342° GS: 120kt POS: 1.2W°ABC

RNG: 160 NM

2417

2360

WOODSIDE

OSI

2572

1960

Figure 5-24. An instrument approach procedure shown on an MFD.

that electronic checklists are only available when the aircraft’s 

electrical system is powered up. In almost all instances, the 

aircraft must have emergency checklists in paper (or plastic) 

form in the event of power or electrical failure. You should 

be well versed in the use and contents of the checklists and 

be able to find them in times of stress. Some climates dictate 

minimum battery use until the engine is started. For those 

circumstances, it is important to be competent in the use of 

paper checklists for normal procedures until the electronic 

checklist in the MFD becomes available.

Electronic Charts

Some systems are capable of presenting terminal and 

approach procedure charts on the MFD. Figure 5-24 shows 

an instrument procedure presented on an MFD.

Note that the position of the aircraft is superimposed on the 

instrument approach chart. Electronic charts are also useful 

when taxiing, as they can help improve navigation on the 

airport surface and reduce runway and taxiway incursions.

FMS/RNAV Pages on the MFD

Some advanced avionics systems are able to draw information 

from the FMS/RNAV and present it on the MFD, in a larger 

format. The MFD in Figure 5-25 lists nearest airports and 

allows you to select any airport to see information about 

that airport.
5-19

ID BRG NM Freq. Name

Nearest Airport s

KSCK

L53 

O20 

1Q4 

KTCY

1O3 

KMOD

O27 

C83 

F72 

KCPU

O88 

E27 

KLVK

O70 

O15

236

314

308

184

205

332

129

098

241

318

044

289

330

230

017

119

2.2

12.2 

13.7 

14.5 

17.5 

18.2 

20.2 

20.7 

21.1 

26.5 

29.6 

29.7 

29.9 

32.4 

34.0 

34.4

120.30

122.90

122.80

122.90

122.80

122.90

125.30

122.80

123.05

122.90

122.80

122.80

122.90

118.10

122.80

122.80

STOCKTON METRO

LODI AIRPARK 

KINGDON 

NEW JERUSALEM 

TRACY MUN 

LODI

MODESTO CITY-CO-SHAM

OAKDALE 

BYRON 

FRANKLIN

CALAVERAS CO-RASMUSSEN 

RIO VISTA MUN 

ELK GROVE 

LIVERMORE MUN 

WESTOVER-AMADOR CO

TURLOCK MUN

Map Trip Nrst Chkist Setup

BRT

DIM

Emerg.

Checklist

Airport

Info

Type

AIRPORT

Filter

ON

Figure 5-25. A nearest airport page shown on an MFD.

Some advanced avionics systems can integrate information 

from several systems in a single display. The display in 

Figure 5-26 presents the route programmed into the FMS, 

together with fuel predictions for each waypoint made by the 

fuel management function.

Chapter Summary

In addition to primary flight instruments, advanced avionics 

(utilizing microchips) can also display landmarks, weather 

in real time or near real time, traffic, terrain, systems status 

(including fuel state) and endurance in, with, or next to the 

selected navigation route. None of these functions allows 

you to disregard the requirement “to see and avoid” traffic, 

obstructions, or hazardous weather. These options are 

designed to enhance safety—not to extend the limits of 

operations.

In all cases, you must accurately determine what equipment 

is installed and authorized. You must know the limitations 

of the data presented and all of the details of the displays, 

especially refresh rates and delays from data acquisition to 

presentation. The onboard data is never an adequate substitute 

for a timely and thorough preflight briefing.
5-20

MaMapp Trip Trip Nrst NrstChkist Chklst SetuSet up p

Time

UTC

GS

TRK

kt s

5nm

11:29:00

18:29:00

200

305

WPT BRG DTK NM ETE ETA

SUNOL

TRACY 

OXJEF 

OXJEF 

IPDEW 

RW29R 

ORANG 

ORANG

060

051 

065 

-----

293 

293 

327 

-----

17.3

35.6

55.0

65.0

70.0

75.0

81.1

91.1

0:07

0:15

0:23

0:27

0:29

0:31

0:34

0:38

17:55

18:03

18:11

18:15

18:17

18:19

18:22

18:26

065

Fuel(Gal.)

To:

Dest :

52.5

50.4 

48.2 

47.1 

46.5 

46.0 

45.3 

44.1

BRT

DIM

Emerg.

Checklist

Figure 5-26. A trip page summarizes your route and predicted fuel consumption.
E-1

Chapter 2: Electronic Flight Instruments

Primary Flight Display

1. Correctly interpret flight and navigation instrument 

information displayed on the PFD.

2. Determine what “fail down” modes are installed and 

available. Recognize and compensate appropriately 

for failures of the PFD and supporting instrument 

systems.

3. Accurately determine system options installed and 

actions necessary for functions, data entry and 

retrieval.

4. Know how to select essential presentation modes, 

flight modes, communication and navigation modes, 

and methods of mode selection and cancellation.

5. Be able to determine extent of failures and reliable 

information remaining available, including procedures 

for restoring function(s) or moving displays to the 

MFD or other display.

Chapter 3: Navigation

Flight Planning

1. Determine if the FMS is approved for the planned 

flight operation.

2. Determine if your FMS can be used as a primary 

navigation system for alternate requirements.

3. Understand how entries are made and canceled.

4. Understand how each unit is installed, and how it is 

programmed or jumpered for optional functions.

5. Determine which navigation sources are installed and 

functional.

6. Determine the status of the databases.

7. Program the FMS/RNAV with a flight plan, including 

en route waypoints, user waypoints, and published 

instrument procedures.

8. Review the programmed flight route to ensure it is 

free from error.

9. Find the necessary pages for flight information in the 

databases.

Essential Skills Checklist

10. Determine which sources drive which displays or 

instruments, and where the selection controls are 

located.

11. Determine and understand how to use and program 

optional functions and equipment installed with FMS/

RNAV basic unit.

En Route

1. Select and monitor the en route portion of the 

programmed flight route, determining waypoint 

arrival, approving turn anticipation, and waypoint 

sequencing.

2. Approve or select the correct course automatically 

displayed or manually tuned.

3. Determine if the FMS makes fuel calculations and 

what sensors and data entries are required to be made 

by the pilot.

4. Ensure that the track flown is that cleared by air traffic 

control (ATC).

5. Determine that the display CDI sensitivity is 

satisfactory for the segment being flown.

En Route Modifications

1. Proceed directly to a waypoint in the programmed 

route.

2. Cancel a programmed or selected waypoint or fix.

3. Select a different instrument procedure or transition.

4. Restart an approach sequence.

5. Immediately find the nearest airport or facility.

6. Edit a flight plan.

7. Enter a user waypoint.
E-2

Descent

1. Determine the descent airspeed to be used with 

concern to turbulence, aircraft descent profile, and 

powerplant cooling restrictions.

2. Program, observe, and monitor the top of descent, 

descent rate, and level-off altitude.

3. Plan and fly a descent to a crossing restriction.

4. Recognize and correct deviations from a planned 

descent path, and determine which factor changed.

Intercept and Track Course

1. Program and select a different course to the active 

waypoint.

2. Select the nonsequencing waypoint function (OBS, 

Hold, or Suspend) to select a specified navigation 

point.

3. Reactivate the sequencing function for route 

navigation.

Holds

1. Select a preprogrammed holding pattern, or 

nonsequencing mode.

2. Select and set up a non-preprogrammed holding 

pattern inbound course.

3. Determine the proper sequence of software commands 

for the holding pattern, transition to approach, 

approach, and MAP navigation.

Arcs

1. Select an approach procedure with an arc.

2. Select the course, or determine that automatic course 

CDI setting will occur.

GPS and RNAV (GPS) Approaches

1. Load and activate a vectored GPS or RNAV (GPS) 

approach.

2. Select a vectored initial approach segment.

3. Determine the correct approach minimums and 

identify all pertinent mode transitions.

4. Determine the published missed approach point 

(MAP), courses, altitudes, and waypoints to fly.

5. Determine how missed approach guidance is 

selected.

Course Reversals

1. Select a type of course reversal procedure.

2. Determine the correct sequence of mode control 

actions to be accomplished by the pilot.

Missed Approaches

1. Acknowledge a missed approach procedure.

2. Set the FMS/GPS for a return to the same approach 

to fly it again.

3. Select a different approach while holding at a missed 

approach holding waypoint.

4. Program an ATC specified hold point (user waypoint) 

for selection after the published MAP/hold procedure.

Ground-Based Radio Navigation

1. Select any type of ground-based radio navigation 

approach.

2. Correctly tune and set up the conventional navigation 

receiver for the procedure in number 1.

3. Correctly monitor the navaid for proper identification 

and validity.

4. Correctly select and be able to use the desired 

navigation source for the autopilot.

Chapter 4: Automated Flight Control

Climbs and Descents

1. Use the FD/autopilot to climb or descend to and 

automatically capture an assigned altitude.

2. Determine the indications of the ARM or capture 

modes, and what pilot actions will cancel those 

modes.

3. Determine if the system allows resetting of the armed 

or capture modes or if manual control is the only 

option after cancellation of these modes.

4. Determine the available methods of activating the 

altitude armed or capture mode(s).

5. Determine the average power necessary for normal 

climbs and descents. Practice changing the power to 

these settings in coordination with making the FD/

autopilot mode changes.
E-3

6. Determine and record maximum climb vertical speeds 

and power settings for temperatures and altitudes. 

Ensure the values are in agreement with values in 

the AFM/POH for the conditions present. Make 

note of the highest practical pitch attitude values, 

conditions, and loading. Remember powerplant 

factors (e.g., minimum powerplant temperature, bleed 

air requirements) and airframe limitations (e.g., VA in 

setting power).

Course Intercepts

1. Use the FD/autopilot to fly an assigned heading to 

capture and track a VOR and/or RNAV course.

2. Determine if the FD/autopilot uses preprogrammed 

intercepts or set headings for navigation course 

interceptions.

3. Determine the indications of navigation mode armed 

conditions.

4. Determine parameters of preprogrammed intercept 

modes, if applicable.

5. Determine minimum and maximum intercept angle 

limitations, if any.

Coupled Approaches

1. Use the FD/autopilot to couple to a precision 

approach.

2. Use the FD/autopilot to couple to a nonprecision 

approach.

3. Use the FD/autopilot to couple to an RNAV 

approach.

4. Determine the power setting required to fly the 

approaches.

5. Determine the power settings necessary for leveloff during nonprecision approaches and go-around 

power settings for both precision and nonprecision 

approaches.

6. Determine the speeds available for the minimum 

recommended powerplant settings (useful for 

determining if an ATC clearance can be accepted for 

climbs, altitudes, and descents).

Miscellaneous Autopilot Topics

1. Demonstrate the proper preflight and ground check of 

the FD/autopilot system.

2. Demonstrate all methods used to disengage and 

disconnect an autopilot.

3. Demonstrate how to select the different modes and 

explain what each mode is designed to do and when 

it will become active.

4. Explain the flight director (FD) indications and 

autopilot annunciators, and how the dimming function 

is controlled.

Chapter 5: Cockpit Information Systems

Multi-Function Display

1. Program the multi-function display to show data

provided by any aircraft system.

2. Determine how many data displays can be 

combined in one display.

3. Know how to select the PFD displays on the MFD, 

if available.

4. Determine which data displays can be overlaid onto

the PFD and the MFD.
E-4
G-1

Active waypoint. The waypoint being used by the 

FMS/RNAV as the reference navigation point for course 

guidance.

ADAHRS. See air data attitude and heading reference 

system.

ADC. See air data computer.

ADS-B. See automatic dependent surveillance—broadcast.

Advanced avionics information system. Any cockpit 

electronic (avionics) system designed to provide information 

or data to the pilot about aircraft status or position, planned 

routing, surrounding terrain, traffic, weather, fuel, etc. 

Advanced avionics systems are generally evidenced by visual 

displays of integrated information in lieu of mechanical or 

stand alone instruments for one or two data sets each.

AHRS. See Attitude Heading Reference System.

Air Data Attitude and Heading Reference System 

(ADAHRS). An integrated flight instrument system that 

combines the functions of an air data computer (the “AD” 

short for ADC) and an Attitude Heading Reference System 

(AHRS) into one unit. 

Air Data Computer (ADC). The system that receives ram 

air, static air, and temperature information from sensors, and 

provides information such as altitude, indicated airspeed, 

vertical speed, and wind direction and velocity to other 

cockpit systems.

Altitude alerting system. The system that allows the pilot 

to receive a visual and/or auditory alert when the airplane 

approaches or deviates from a preselected altitude.

Altitude capture. An autopilot function that enables 

the autopilot to level the airplane at a selected altitude 

automatically.

Altitude function. An autopilot function that maintains the 

present altitude of the airplane.

Glossary

Annunciator panel. Grouping of annunciator lights that is 

usually accompanied with a test switch, which when pressed 

illuminates all the lights to confirm they are in working order.

Approach mode/function. An autopilot function or mode 

that allows the pilot to capture and track any VOR radial or 

localizer with a higher degree of accuracy.

Area navigation (RNAV). A method of navigation that 

permits operations along any desired flightpath within the 

area of coverage of station-referenced navigation aids (e.g., 

GPS, VOR/DME, DME/DME, eLORAN), or within the 

limits of a self-contained navigation system (INS, doppler 

radar), or any combination.

Armed. A system mode or function that is set to become 

actively engaged at a later time, when certain conditions 

are met.

Attenuation. See radar attenuation.

Attitude Heading Reference System (AHRS). An 

integrated flight instrument system that provides attitude, 

heading, rate of turn, and slip/skid information.

Automatic dependent surveillance—broadcast (ADS-B).

A surveillance system in which an aircraft or vehicle to be 

detected is fitted with cooperative equipment in the form of 

a data link transmitter. The aircraft or vehicle periodically 

broadcasts its GPS-derived position and other information 

(e.g., velocity) over the data link, which is received by 

a ground-based transmitter/ receiver (transceiver) for 

processing and display at an air traffic control facility.

Automatic mode change. Any change in mode or system 

status initiated by the system, rather than by a deliberate 

mode change action taken by the pilot.
G-2

Autopilot. An aircraft flight control system that automatically 

manipulates the roll, pitch, and, in some cases, the yaw 

control surfaces of the airplane to capture and track the route 

programmed into the FMS/RNAV, or altitudes, vertical 

speeds, headings, and courses selected by the pilot.

Autopilot flight mode annunciator. A display that presents 

the names of autopilot functions that are either armed or 

engaged. It is the only reliable source of information about 

what autopilot functions are in use.

Autothrottle system. A system that automatically 

manipulates the thrust setting of the airplane to help follow 

the vertical trajectory portion or selected airspeed of the 

planned flight route.

Autotrim system. The system that automatically adjusts 

the pitch trim of the airplane in response to trim commands 

generated by the autopilot.

Bottom-of-descent point. The end point of the descent, as 

calculated by the FMS/RNAV.

Broadcast weather service. A weather service that prepares 

weather products and transmits them to participating aircraft, 

also known as a data link weather service.

Chapter. Associated group of electronic “pages” of 

information from databases found in FMS and GPS RNAV 

units similar in contents, such as airports, VORs, software/

unit settings, and feature selections.

Command bars. A flight director display that presents roll 

and pitch instructions (generally, V-shaped visual cues) 

to help the pilot maintain the flightpath/flight track to the 

selected point. The pilot keeps the airplane symbol aligned 

with the command bars on the flight director, or centered on 

the FD crossbars (e.g., older Cessna units).

Crossing restriction. A directive issued or published by 

air traffic control that instructs the pilot to cross a given 

waypoint at a specified altitude, and sometimes at a specified 

airspeed.

Cursor mode. The function offered by the FMS/RNAV 

that allows data entry into an avionics unit such as the FMS 

and RNAV.

Data link weather service. See broadcast weather service.

Deceleration segment. A planned portion of a descent 

designed to permit the aircraft to slow to meet a terminal 

area speed restriction, crossing restriction, or other speed 

restriction.

Desired track. The great circle course computed by the 

FMS/RNAV, it goes from the past waypoint to the next 

(active) waypoint.

Distance measuring equipment (DME). Line-of-sight 

limited airborne equipment (transceiver) using paired pulse 

replies from ground-based transponder to determine slant 

range distance by time between airborne transmission of 

pulses and return of pulses from the ground transponder.

DME. See distance measuring equipment.

EHSI. See electronic horizontal situation indicator.

Electronic flight instruments. Flight instruments that use 

electronic devices to prepare and/or present information such 

as airspeed, attitude, altitude, and position.

Electronic horizontal situation indicator (EHSI).

Electronically generated HSI display, either CRT or LCD 

type, indicating all standard HSI functions on a video screen 

instead of using mechanical components.

eLORAN. See long range navigation.

Engaged. A system mode or function that is actively 

performing its function.

Error-evident display. Any display that presents information 

in a way that makes errors more obvious and detectable.

FD. See flight director.

Faildown. The substitute display or backup instrument 

mode available if the primary component fails. In some 

systems, for example, the MFD can substitute for the PFD 

if the PFD fails. The PFD information “fails down” to the 

MFD. In other systems, the substitute for the PFD might be 

the conventional standby instruments and the standby or 

secondary navigation CDI.

Flight director. Electronic flight calculator that analyzes 

the navigation selections, signals, and aircraft parameters. 

It presents steering instructions on the flight display as 

command bars or crossbars for the pilot to position the nose 

of the aircraft over or follow.

Flight management system (FMS). A computer system 

containing a database to allow programming of routes, 

approaches, and departures that can supply navigation data 

to the flight director/autopilot from various sources, and 

can calculate flight data such as fuel consumption, time 

remaining, possible range, and other values.
G-3

Fly-by waypoint. A waypoint designed to permit early turns, 

thus allowing the aircraft to roll out onto the center of the 

desired track to the next waypoint.

Fly-over waypoint. A waypoint that precludes any turn 

until the waypoint is overflown, and is followed by either 

an intercept maneuver of the next flight segment or direct 

flight to the next waypoint.

FMS. See flight management system.

Fuel management system or function. An advanced 

avionics system that assists the pilot in managing fuel by 

considering fuel flow, airspeed, and winds to help predict 

fuel remaining at each waypoint along the programmed route, 

total endurance, and the viability of alternative routings or 

diversions. Stand-alone systems may integrate the output data 

into the FMS/RNAV or provide a discreet display, while the 

fuel management function is an integral portion of the FMS/

RNAV system. In either instance, the fuel data management 

goals are similar.

Fuel range ring. A graphical depiction of the point at which 

an aircraft is predicted to exhaust its fuel reserves or reach a 

point at which only reserve fuel remains.

Glideslope (GS) function. The autopilot function that 

manipulates the pitch of the aircraft to track a glideslope 

signal or APV guidance during a precision approach.

Global Positioning System (GPS). A Global Navigation 

Satellite System (GNSS) navigation system that can 

determine position and track the movement of an aircraft. A 

global positioning system (GPS) receiver must be installed 

on board the aircraft to receive and interpret signals from the 

satellite-based system.

Global Positioning System Steering (GPSS). The autopilot 

function that receives signals directly from the GPS/FMS/

RNAV to steer the aircraft along the desired track to the 

active waypoint set in the GPS receiver.

GPS. See Global Positioning System.

GPS overlay approach. A conventional nonprecision 

approach procedure that can be flown using RNAV 

equipment.

GPS stand-alone approach. A nonprecision approach 

procedure based solely on the use of the global positioning 

system and an IFR-certified FMS/RNAV unit using GPS 

signals.

GPSS. See Global Positioning System Steering.

Great circle route. The shortest distance between two 

points when traveling on the surface of the earth; defined 

by a geometric plane that passes through the two points and 

the center of the earth.

Ground weather surveillance radar system. Any groundbased facility equipped to gather information about significant 

weather across a wide area.

Heading function. The flight director/autopilot function that 

steers the aircraft along a specified magnetic heading.

Highway in the sky (HITS). A type of electronic flight 

instrument that superimposes a 3-dimensional portrayal 

of a planned lateral and vertical aircraft trajectory onto an 

artificial horizon display.

HITS. See highway in the sky.

ILS. See instrument landing system.

Inertial navigation system (INS). Self-contained internal 

navigation system using sensors to measure changes in 

motion of aircraft, acceleration and deceleration, airspeed, 

altitude, and heading to maintain current position of aircraft. 

Also called “position keeping” because an interruption of the 

system requires the pilot to initialize or enter the beginning 

point of aircraft position reference.

INS. See inertial navigation system.

Instrument landing system. A ground-based precision 

instrument approach system usually consisting of a localizer, 

glideslope, outer marker, middle marker, and approach 

lights.

LNAV. Lateral (azimuth) navigation guidance. A type of 

navigation associated with nonprecision approach procedures 

or en route navigation.

LNAV/VNAV. Lateral navigation/vertical navigation 

minimums provided for RNAV systems that include both 

lateral and vertical navigation (e.g., WAAS avionics 

approved for LNAV/VNAV, certified barometric VNAV 

with IFR approach certified GPS). Procedure minimums 

altitude is published as DA (decision altitude).
G-4

Localizer Performance with Vertical Guidance (LPV). 

Provides lateral containment areas comparable to an ILS 

localizer and decision heights between those of LNAV/

VNAV approaches and Category I ILS approaches. Approach 

procedure minimums that use WAAS to provide Localizer 

Performance with Vertical guidance (LPV). WAAS avionics 

equipment is required to fly to LPV minimums, which are 

published as DA (decision altitude).

Long range navigation (LORAN). LOng RAnge Navigation 

ground-based electronic navigation system using hyperbolic 

lines of position determined by measuring the difference in 

the time of reception of synchronized pulse signals from 

fixed transmitters. LORAN-C and eLORAN operate in the 

100–110 kHz frequency band. Enhanced LORAN (eLORAN) 

is planned to operate using more stable timing signals and 

stations from other chains for greater accuracy than the 

current LORAN-C system.

LPV. See localizer performance with vertical guidance.

LORAN-C. See long range navigation.

Magnetic flux valve. A type of magnetometer using coils of 

wire as the transmitting portion of a synchronous repeating 

system, conventionally used to stabilize and correct a slaved 

gyroscopic heading (azimuth) indicator by sensing changes 

in the earth’s magnetic field.

Magnetometer. The device that measures the strength of 

the earth’s magnetic field to determine aircraft heading, and 

similar to the flux valve in function.

MFD. See multi-function display.

Mode awareness. The pilot’s ability to monitor how system 

settings are configured throughout the flight.

Moving map. A graphical depiction of aircraft position, route 

programmed into the FMS/RNAV, surrounding geographical 

features, and any other information about the immediate 

flight environment such as traffic and weather that may be 

available from other avionics systems.

Multi-function display (MFD). A cockpit display capable of 

presenting information received from a variety of advanced 

avionics systems.

Navigation database. The information stored in the FMS/

RNAV; contains most of the time-sensitive navigational 

information found on en route and procedural charts.

Navigation function. An autopilot function that allows 

you to track the route programmed in the FMS/RNAV or 

navigation receiver, such as a VOR radial.

Next Generation Radar System. A network of radar 

stations operated by the National Weather Service used to 

detect precipitation and wind. These data are used to prepare 

weather radar products that can be supplied to the cockpit 

via a broadcast weather service.

NEXRAD. See Next Generation Radar System.

Nonsequencing mode. The FMS/RNAV navigation mode 

that does not automatically sequence between waypoints in 

the programmed route. The nonsequencing mode maintains 

the current active waypoint indefinitely, and allows the pilot 

to specify desired track to or from that waypoint.

No-further-input prediction. A technique to help pilots 

maintain awareness of how advanced avionics systems are 

configured, and of the likely future behavior of the aircraft. 

No-further-input predictions are made by considering what 

the aircraft will do if the pilot makes no further entries or 

commands.

Nuisance alert. A term used to describe a “false alarm” 

provided by an avionics system designed to detect surrounding 

hazards such as proximate traffic and terrain.

OBS mode. The name for the nonsequencing mode on some 

FMS/RNAV units. See nonsequencing mode.

Onboard lightning detection systems. An onboard weather 

detection system that senses electrical discharges that suggest 

the presence of thunderstorm cells.

Onboard weather radar. An onboard system capable of 

detecting significant masses of precipitation. The primary use 

of weather radar is to aid the pilot in avoiding thunderstorms 

and their associated hazards.

Page. Any one of a collection of information displays that 

can appear on the FMS/RNAV unit. Every page has a title 

and presents information related to a particular navigation 

topic (e.g., airport elevation, runways, communication 

frequencies). Pages are usually in divisions called “chapters,” 

which group pages of similar information by topic 

(e.g., airports, approaches, VORs).

PFD. See primary flight display.
G-5

Preprogrammed holding pattern (preprogrammed hold).

A hold that is published as a part of an instrument procedure 

(e.g., approach, missed approach) and has been loaded into 

the FMS/RNAV. Some FMS/RNAV units automatically 

enter and fly the holding procedure when it is encountered. 

Others must be flown around the depicted holding pattern, 

usually by changing the heading (bug). Some units require 

switching to the nonsequencing or OBS mode so the active 

waypoint remains set to the designated holding fix.

Preprogrammed course reversal. A course reversal 

(commonly called a “procedure turn”) that appears as part 

of an instrument approach procedure that has been loaded 

into the FMS/RNAV. Many FMS/RNAV units automatically 

attempt to perform the course reversal procedure when it is 

encountered. Others require the pilot to navigate the depicted 

procedural track manually or by using the heading mode to 

fly the depicted track.

Primary flight display (PFD). An electronic flight display 

that presents the primary flight instruments, navigation 

instruments, and other information about the status of the 

flight in one integrated presentation. Primary-secondary task 

inversion. Situation in which the pilot ceases to monitor the 

situation directly and simply listens for system alerts.

RA. See resolution advisory.

Radar attenuation. The absorption or reflection of radar 

signals by a weather cell, preventing that radar from detecting 

any additional cells that might lie behind the first cell.

RAIM. See receiver autonomous integrity monitoring. 

Receiver autonomous integrity monitoring. The selfmonitoring function performed by a TSO-129 certified GPS 

receivers to ensure that adequate GPS signals are being 

received at all times. The GPS will alert the pilot whenever 

the integrity monitoring determines that the GPS signals do 

not meet the criteria for safe navigation use.

Receiver autonomous integrity monitoring. The selfmonitoring function performed by a TSO-129 certified 

GPS receiver to ensure that adequate GPS signals are being 

received at all times. The GPS alerts the pilot whenever the 

integrity monitoring determines that the GPS signals do not 

meet the criteria for safe navigation use.

Resolution advisory (RA). A warning issued by the Traffic 

Collision Avoidance System (TCAS) indicating an immediate 

threat of collision with another aircraft. This warning takes 

the form of a command to perform a vertical avoidance 

maneuver (e.g., “Climb! Climb!”) These commands are 

products of TCAS II equipment. These commands take 

precedence over ATC instructions, but must be reported to 

ATC immediately upon receipt and execution.

Risk homeostasis. A term coined by psychologist Gerald J. 

S. Wilde, a tendency for humans to seek target levels of risk.

RNAV. See Area Navigation.

RNAV (GPS) approach. An approach procedure based on 

GPS signals for guidance.

Route discontinuity. A point of uncertainty in a route that 

has been programmed into an FMS/RNAV. Most systems 

display this message when there is no routing to connect the 

last waypoint to the next point, or there is a missing next 

point. FMS/RNAV units will not plan to go direct unless 

certain programming parameters are met.

Sequencing mode. The FMS/RNAV mode that automatically 

sequences along the waypoints in the programmed route. The 

sequencing mode alerts the pilot to upcoming waypoints, and 

offers guidance to each successive waypoint in the route.

Stand-alone approach. An instrument approach that relies 

solely on the use of RNAV equipment. If flown with GPS/

WAAS enabled certified equipment in accordance with 

TSO-C145A or TSO-146A installed in accordance with 

the provisions of AC 20-130A or 138A, no conventional 

navigation equipment alternate approach (VOR/ILS) 

requirements are necessary, as when flying with TSO-C129 

certified equipment.

Subpage. An additional page of information about a 

particular topic that can be displayed on an FMS/RNAV. 

Many pages require the use of several subpages to show all 

information pertaining to any one topic.

SUSP. See suspend mode.
G-6

Suspend mode. For some FMS/RNAV units, the name 

used to describe the nonsequencing mode when it has been 

automatically set by the computer, or pilot.

TA. See traffic advisory.

Tape display. A vertical display format used to portray, 

for example, airspeed and altitude on many primary flight 

displays. Also used for vertical speeds and many other value 

displays such as power settings and powerplant speeds.

TAWS. See terrain awareness and warning system.

TCAS. See Traffic Alert and Collision Avoidance System.

Terminal Arrival Area. The published or assigned track 

by which aircraft are transitioned from the en route structure 

to the terminal area. A terminal arrival area consists of a 

designated volume of airspace designed to allow aircraft 

to enter a protected area with obstacle clearance and signal 

reception guaranteed where the initial approach course is 

intercepted.

Terminal mode. One name used for the FMS/RNAV 

sensitivity mode in which the aircraft is operating within 30 

NM of an airport. In terminal mode, the required navigation 

performance sensitivity of the course deviation indicator 

becomes 1 NM. Also called approach arm mode.

Terrain and obstacle database. An electronic database 

storing details of the significant terrain features and obstacles 

that could potentially pose a threat to aircraft flight. Some 

obstructions, especially manmade, may not be in the database, 

even if it is current. Do not plan a flight based on dependence 

on the database to keep the aircraft clear of obstacles and 

obstructions to navigation.

Terrain Awareness and Warning System (TAWS).

An onboard system that can alert the pilot to a number of 

potential hazards presented by proximate terrain such as 

excessive rate of descent, excessive closure rate to terrain, 

and altitude loss after takeoff.

Terrain display. A pictorial display that shows surrounding 

terrain and obstacles that present a potential threat to 

your aircraft, given your present altitude. Draws terrain 

information from a terrain and obstacle database.

Terrain inhibit switch. A switch that allows the pilot to 

suppress all visual and auditory warnings given by a terrain 

system. Often used to silence nuisance alerts when in 

deliberate operation in the vicinity of terrain.

Terrain system. Any cockpit system that provides the pilot 

with a pictorial view of surrounding terrain, and in some 

cases, visual and/or auditory alerts when the aircraft is 

operating in close proximity to terrain.

TIS. See traffic information service.

Top-of-descent point. The point that the RNAV computer

calculates to be the ideal location at which to begin a descent 

to the planned crossing restriction, given the descent speed 

and rate that has been entered by the pilot.

Topographical database. A volume of information stored 

in an advanced cockpit system that details the topographical 

features of the earth’s surface. Used by several systems 

to assess aircraft position and altitude with respect to 

surrounding terrain.

Traffic Advisory (TA). A warning issued by a traffic system 

that alerts the pilot to other aircraft that have moved within a 

prescribed “safety zone” that surrounds the aircraft.

Traffic Alert and Collision Avoidance System. An onboard 

system that detects the presence of some aircraft operating 

in the vicinity of the airplane by querying the transponders 

of nearby aircraft and presenting their locations and relative 

altitudes on a display. Alerts and warnings are issued when 

nearby aircraft are deemed to be a threat to safety. Traffic 

advisory systems such as ADS-B are an offshoot of newer 

technologies, but do not yet offer the reliability or accuracy 

of proven, certified TCAS units.

Traffic data system. An advanced avionics system designed 

to aid the pilot in visually acquiring and maintaining 

awareness of nearby aircraft that pose potential collision 

threats.

Traffic display. A pictorial display showing any aircraft 

operating in the vicinity that have been detected by a traffic 

data system.

Traffic Information Service (TIS). A groundbased 

advanced avionics traffic display system which receives 

transmissions on locations of nearby aircraft from radarequipped air traffic control facilities and provides alerts and 

warnings to the pilot.

Turn anticipation. The function performed by FMS/

RNAV units to advise the pilot when to begin a turn to 

the next waypoint in the programmed flight route to avoid 

overshooting the programmed track.
G-7

Vectors to final. A function of FMS/RNAV units allowing 

the pilot to perform a vectored approach procedure without 

being required to switch to the nonsequencing mode manually 

and set the active waypoint and course.

Vertical speed mode. An FD/autopilot mode that allows 

constant-rate climbs and descents by selecting a vertical 

speed on the flight director or autopilot control panel.

Very high frequency omnidirectional range (VOR). 

Ground-based electronic navaid transmitting 360° azimuth 

signals on assigned frequencies ranging from 108.0 to 117.9 

mHz to serve as the basis for the National Airspace System 

(NAS). The signals are identified by discreet Morse code 

identifiers and may have voice capabilities for ATC and FSS/

AFSS communications.

VOR. See very high frequency omnidirectional range.

WAAS. See Wide Area Augmentation System.

Waypoint. A named geographical location used to define 

routes and terminal area procedures. Modern advanced 

navigation avionics such as FMS/RNAV units are able to 

locate and follow courses to and from waypoints that occur 

anywhere in the airspace.

Waypoint alerting. The function performed by the FMS/

RNAV to alert the pilot at some time or distance prior to, or 

when reaching, the active waypoint.

Waypoint sequencing. The action performed by the FMS/

RNAV when the aircraft effectively has reached the active 

waypoint, and then automatically switches to the next 

waypoint in the programmed route. (See turn anticipation.)

Wide Area Augmentation System (WAAS). A ground and 

satellite integrated navigational error correction system that 

provides accuracy enhancements to signals received from 

the Global Positioning System. WAAS provides extremely 

accurate lateral and vertical navigation signals to aircraft 

equipped with GPS/WAAS-enabled certified equipment 

in accordance with TSO-C145A or TSO-146A installed in 

accordance with the provisions of Advisory Circular (AC) 

20-130A or AC 20‐138A.
G-8