Instrument Flying Handbook
InstrumentFlying Handbook
U.S. Department
of Transportation
FEDERAL AVIATION
ADMINISTRATION
FAA-H-8083-15A
Instrument Flying
Handbook
U.S. Department of Transportation
FEDERAL AVIATION ADMINISTRATION
Flight Standards Service
2007
ii
iii
This Instrument Flying Handbook is designed for use by instrument fl ight instructors and pilots preparing for instrument
rating tests. Instructors may fi nd this handbook a valuable training aid as it includes basic reference material for knowledge
testing and instrument fl ight training. Other Federal Aviation Administration (FAA) publications should be consulted for
more detailed information on related topics.
This handbook conforms to pilot training and certifi cation concepts established by the FAA. There are different ways of
teaching, as well as performing, fl ight procedures and maneuvers and many variations in the explanations of aerodynamic
theories and principles. This handbook adopts selected methods and concepts for instrument fl ying. The discussion and
explanations refl ect the most commonly used practices and principles. Occasionally the word “must” or similar language
is used where the desired action is deemed critical. The use of such language is not intended to add to, interpret, or relieve
a duty imposed by Title 14 of the Code of Federal Regulations (14 CFR).
All of the aeronautical knowledge and skills required to operate in instrument meteorological conditions (IMC) are detailed.
Chapters are dedicated to human and aerodynamic factors affecting instrument fl ight, the fl ight instruments, attitude instrument
fl ying for airplanes, basic fl ight maneuvers used in IMC, attitude instrument fl ying for helicopters, navigation systems, the
National Airspace System (NAS), the air traffi c control (ATC) system, instrument fl ight rules (IFR) fl ight procedures, and
IFR emergencies. Clearance shorthand and an integrated instrument lesson guide are also included.
This handbook supersedes FAA-H-8081-15, Instrument Flying Handbook, dated 2001.
This handbook may be purchased from the Superintendent of Documents, United States Government Printing Offi ce (GPO),
Washington, DC 20402-9325, or from GPO's web site.
http://bookstore.gpo.gov
This handbook is also available for download, in PDF format, from the Regulatory Support Division's (AFS-600) web
site.
http://www.faa.gov/about/offi ce_org/headquarters_offi ces/avs/offi ces/afs/afs600
This handbook is published by the United States Department of Transportation, Federal Aviation Administration, Airman
Testing Standards Branch, AFS-630, P.O. Box 25082, Oklahoma City, OK 73125.
Comments regarding this publication should be sent, in email form, to the following address.
AFS630comments@faa.gov
Preface
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This handbook was produced as a combined Federal Aviation Administration (FAA) and industry effort. The FAA wishes
to acknowledge the following contributors:
The laboratory of Dale Purves, M.D. and Mr. Al Seckel in providing imagery (found in Chapter 1) for visual illusions
from the book, The Great Book of Optical Illusions, Firefl y Books, 2004
Sikorsky Aircraft Corporation and Robinson Helicopter Company for imagery provided in Chapter 9
Garmin Ltd. for providing fl ight system information and multiple display systems to include integrated fl ight, GPS and
communication systems; information and hardware used with WAAS, LAAS; and information concerning encountering
emergencies with high-technology systems
Universal Avionics System Corporation for providing background information of the Flight Management System and
an overview on Vision–1 and Traffi c Alert and Collision Avoidance systems (TCAS)
Meggitt/S-Tec for providing detailed autopilot information regarding installation and use
Cessna Aircraft Company in providing instrument panel layout support and information on the use of onboard systems
Kearfott Guidance and Navigation Corporation in providing background information on the Ring-LASAR gyroscope
and its history
Honeywell International Inc., for Terrain Awareness Systems (TAWS) and various communication and radio systems
sold under the Bendix-King name
Chelton Flight Systems and Century Flight Systems, Inc., for providing autopilot information relating to Highway in
the Sky (Chelton) and HSI displays (Century)
Avidyne Corporation for providing displays with alert systems developed and sold by Ryan International, L3
Communications, and Tectronics.
Additional appreciation is extended to the Aircraft Owners and Pilots Association (AOPA), the AOPA Air Safety Foundation,
and the National Business Aviation Association (NBAA) for their technical support and input.
Acknowledgements
vi
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Is an Instrument Rating Necessary?
The answer to this question depends entirely upon individual
needs. Pilots may not need an instrument rating if they fl y in
familiar uncongested areas, stay continually alert to weather
developments, and accept an alternative to their original plan.
However, some cross-country destinations may take a pilot
to unfamiliar airports and/or through high activity areas in
marginal visual or instrument meteorological conditions
(IMC). Under these conditions, an instrument rating may
be an alternative to rerouting, rescheduling, or canceling
a fl ight. Many accidents are the result of pilots who lack
the necessary skills or equipment to fl y in marginal visual
meteorological conditions (VMC) or IMC and attempt fl ight
without outside references.
Pilots originally fl ew aircraft strictly by sight, sound, and
feel while comparing the aircraft’s attitude to the natural
horizon. As aircraft performance increased, pilots required
more infl ight information to enhance the safe operation of
their aircraft. This information has ranged from a string tied
to a wing strut, to development of sophisticated electronic
fl ight information systems (EFIS) and fl ight management
systems (FMS). Interpretation of the instruments and aircraft
control have advanced from the “one, two, three” or “needle,
ball, and airspeed” system to the use of “attitude instrument
fl ying” techniques.
Navigation began by using ground references with dead
reckoning and has led to the development of electronic
navigation systems. These include the automatic direction
fi nder (ADF), very-high frequency omnidirectional range
(VOR), distance measuring equipment (DME), tactical air
navigation (TACAN), long range navigation (LORAN),
global positioning system (GPS), instrument landing system
(ILS), microwave landing system (MLS), and inertial
navigation system (INS).
Perhaps you want an instrument rating for the same basic
reason you learned to fl y in the fi rst place—because you like
fl ying. Maintaining and extending your profi ciency, once you
have the rating, means less reliance on chance and more on
skill and knowledge. Earn the rating—not because you might
Introduction
need it sometime, but because it represents achievement and
provides training you will use continually and build upon
as long as you fl y. But most importantly it means greater
safety in fl ying.
Instrument Rating Requirements
A private or commercial pilot must have an instrument
rating and meet the appropriate currency requirements if
that pilot operates an aircraft using an instrument fl ight
rules (IFR) fl ight plan in conditions less than the minimums
prescribed for visual fl ight rules (VFR), or in any fl ight in
Class A airspace.
You will need to carefully review the aeronautical knowledge
and experience requirements for the instrument rating as
outlined in Title 14 of the Code of Federal Regulations
(14 CFR) part 61. After completing the Federal Aviation
Administration (FAA) Knowledge Test issued for the
instrument rating, and all the experience requirements have
been satisfi ed, you are eligible to take the practical test. The
regulations specify minimum total and pilot-in-command
time requirements. This minimum applies to all applicants
regardless of ability or previous aviation experience.
Training for the Instrument Rating
A person who wishes to add the instrument rating to his or
her pilot certifi cate must fi rst make commitments of time,
money, and quality of training. There are many combinations
of training methods available. Independent studies may be
adequate preparation to pass the required FAA Knowledge
Test for the instrument rating. Occasional periods of ground
and fl ight instruction may provide the skills necessary to
pass the required test. Or, individuals may choose a training
facility that provides comprehensive aviation education and
the training necessary to ensure the pilot will pass all the
required tests and operate safely in the National Airspace
System (NAS). The aeronautical knowledge may be
administered by educational institutions, aviation-oriented
schools, correspondence courses, and appropriately rated
instructors. Each person must decide for themselves which
training program best meets his or her needs and at the same
time maintain a high quality of training. Interested persons
viii
should make inquiries regarding the available training at
nearby airports, training facilities, in aviation publications,
and through the FAA Flight Standards District Office
(FSDO).
Although the regulations specify minimum requirements,
the amount of instructional time needed is determined not
by the regulation, but by the individual’s ability to achieve
a satisfactory level of profi ciency. A professional pilot with
diversifi ed fl ying experience may easily attain a satisfactory
level of proficiency in the minimum time required by
regulation. Your own time requirements will depend upon a
variety of factors, including previous fl ying experience, rate
of learning, basic ability, frequency of fl ight training, type of
aircraft fl own, quality of ground school training, and quality
of fl ight instruction, to name a few. The total instructional
time you will need, the scheduling of such time, is up to the
individual most qualifi ed to judge your profi ciency—the
instructor who supervises your progress and endorses your
record of fl ight training.
You can accelerate and enrich much of your training by
informal study. An increasing number of visual aids and
programmed instrument courses is available. The best course
is one that includes a well-integrated fl ight and ground school
curriculum. The sequential nature of the learning process
requires that each element of knowledge and skill be learned
and applied in the right manner at the right time.
Part of your instrument training may utilize a fl ight simulator,
fl ight training device, or a personal computer-based aviation
training device (PCATD). This ground-based fl ight training
equipment is a valuable tool for developing your instrument
cross-check and learning procedures, such as intercepting and
tracking, holding patterns, and instrument approaches. Once
these concepts are fully understood, you can then continue
with infl ight training and refi ne these techniques for full
transference of your new knowledge and skills.
Holding the instrument rating does not necessarily make you a
competent all-weather pilot. The rating certifi es only that you
have complied with the minimum experience requirements,
that you can plan and execute a fl ight under IFR, that you
can execute basic instrument maneuvers, and that you have
shown acceptable skill and judgment in performing these
activities. Your instrument rating permits you to fl y into
instrument weather conditions with no previous instrument
weather experience. Your instrument rating is issued on
the assumption that you have the good judgment to avoid
situations beyond your capabilities. The instrument training
program you undertake should help you to develop not only
essential fl ying skills but also the judgment necessary to use
the skills within your own limits.
Regardless of the method of training selected, the curriculum
in Appendix B, Instrument Training Lesson Guide, provides
guidance as to the minimum training required for the addition
of an instrument rating to a private or commercial pilot
certifi cate.
Maintaining the Instrument Rating
Once you hold the instrument rating, you may not act as pilotin-
command under IFR or in weather conditions less than the
minimums prescribed for VFR, unless you meet the recent
fl ight experience requirements outlined in 14 CFR part 61.
These procedures must be accomplished within the preceding
6 months and include six instrument approaches, holding
procedures, and intercepting and tracking courses through the
use of navigation systems. If you do not meet the experience
requirements during these 6 months, you have another 6
months to meet these minimums. If the requirements are
still not met, you must pass an instrument profi ciency check,
which is an infl ight evaluation by a qualifi ed instrument
fl ight instructor using tasks outlined in the instrument rating
practical test standards (PTS).
The instrument currency requirements must be accomplished
under actual or simulated instrument conditions. You may log
instrument fl ight time during the time for which you control
the aircraft solely by reference to the instruments. This can
be accomplished by wearing a view-limiting device, such as
a hood, fl ying an approved fl ight-training device, or fl ying
in actual IMC.
It takes only one harrowing experience to clarify the
distinction between minimum practical knowledge and a
thorough understanding of how to apply the procedures and
techniques used in instrument fl ight. Your instrument training
is never complete; it is adequate when you have absorbed
every foreseeable detail of knowledge and skill to ensure a
solution will be available if and when you need it. ix
Preface ...................................................................iii
Acknowledgements ................................................v
Introduction ...........................................................vii
Is an Instrument Rating Necessary? ............................ vii
Instrument Rating Requirements ................................. vii
Training for the Instrument Rating .............................. vii
Maintaining the Instrument Rating ............................viii
Table of Contents ..................................................ix
Chapter 1
Human Factors ....................................................1-1
Introduction ....................................................................1-1
Sensory Systems for Orientation ...................................1-2
Eyes ............................................................................1-2
Vision Under Dim and Bright Illumination ............1-3
Ears .............................................................................1-4
Nerves .........................................................................1-5
Illusions Leading to Spatial Disorientation ....................1-5
Vestibular Illusions ....................................................1-5
The Leans ................................................................1-5
Coriolis Illusion ......................................................1-6
Graveyard Spiral .....................................................1-6
Somatogravic Illusion .............................................1-6
Inversion Illusion ....................................................1-6
Elevator Illusion ......................................................1-6
Visual Illusions ...........................................................1-7
False Horizon ..........................................................1-7
Autokinesis .............................................................1-7
Postural Considerations .................................................1-7
Demonstration of Spatial Disorientation .......................1-7
Climbing While Accelerating .....................................1-8
Climbing While Turning ............................................1-8
Diving While Turning ................................................1-8
Tilting to Right or Left ...............................................1-8
Reversal of Motion .....................................................1-8
Diving or Rolling Beyond the Vertical Plane ............1-8
Coping with Spatial Disorientation ................................1-8
Optical Illusions .............................................................1-9
Runway Width Illusion ..............................................1-9
Runway and Terrain Slopes Illusion ..........................1-9
Featureless Terrain Illusion ........................................1-9
Water Refraction ........................................................1-9
Haze ............................................................................1-9
Fog ..............................................................................1-9
Ground Lighting Illusions ..........................................1-9
How To Prevent Landing Errors Due To Optical
Illusions ..........................................................................1-9
Physiological and Psychological Factors .....................1-11
Stress ........................................................................1-11
Medical Factors ............................................................1-12
Alcohol .....................................................................1-12
Fatigue ......................................................................1-12
Acute Fatigue ........................................................1-12
Chronic Fatigue ....................................................1-13
IMSAFE Checklist ...................................................1-13
Hazard Identifi cation ....................................................1-13
Situation 1 ................................................................1-13
Situation 2 ................................................................1-13
Risk Analysis ............................................................1-13
Crew Resource Management (CRM) and Single-Pilot
Resource Management (SRM) .....................................1-14
Situational Awareness ..................................................1-14
Flight Deck Resource Management .............................1-14
Human Resources .....................................................1-14
Equipment ................................................................1-14
Information Workload ..............................................1-14
Task Management ........................................................1-15
Aeronautical Decision-Making (ADM) .......................1-15
The Decision-Making Process .................................1-16
Defi ning the Problem ...............................................1-16
Choosing a Course of Action ...................................1-16
Implementing the Decision and Evaluating
the Outcome .............................................................1-16
Improper Decision-Making Outcomes ....................1-16
Models for Practicing ADM ........................................1-17
Perceive, Process, Perform .......................................1-17
The DECIDE Model .................................................1-17
Hazardous Attitudes and Antidotes .............................1-18
Table of Contents
x
Chapter 2
Aerodynamic Factors ..........................................2-1
Introduction ....................................................................2-1
The Wing ....................................................................2-2
Review of Basic Aerodynamics .....................................2-2
The Four Forces .........................................................2-2
Lift ..........................................................................2-2
Weight .....................................................................2-3
Thrust ......................................................................2-3
Drag ........................................................................2-3
Newton’s First Law, the Law of Inertia .....................2-4
Newton’s Second Law, the Law of Momentum ........2-4
Newton’s Third Law, the Law of Reaction ................2-4
Atmosphere ....................................................................2-4
Layers of the Atmosphere ..........................................2-5
International Standard Atmosphere (ISA) ..................2-5
Pressure Altitude .....................................................2-5
Density Altitude ......................................................2-5
Lift ..................................................................................2-6
Pitch/Power Relationship ...........................................2-6
Drag Curves ...................................................................2-6
Regions of Command .................................................2-7
Control Characteristics ...........................................2-7
Speed Stability ............................................................2-7
Normal Command ..................................................2-7
Reversed Command ................................................2-8
Trim ................................................................................2-8
Slow-Speed Flight ..........................................................2-8
Small Airplanes ..........................................................2-9
Large Airplanes ..........................................................2-9
Climbs ..........................................................................2-10
Acceleration in Cruise Flight ...................................2-10
Turns ............................................................................2-10
Rate of Turn .............................................................2-10
Radius of Turn ..........................................................2-11
Coordination of Rudder and Aileron Controls .........2-11
Load Factor ..................................................................2-11
Icing .............................................................................2-12
Types of Icing ..............................................................2-13
Structural Icing .........................................................2-13
Induction Icing .........................................................2-13
Clear Ice ...................................................................2-13
Rime Ice ...................................................................2-13
Mixed Ice ..................................................................2-14
General Effects of Icing on Airfoils .........................2-14
Piper PA-34-200T (Des Moines, Iowa) ................2-15
Tailplane Stall Symptoms ........................................2-16
Propeller Icing ..........................................................2-16
Effects of Icing on Critical Aircraft Systems ...........2-16
Flight Instruments .................................................2-16
Stall Warning Systems ..........................................2-16
Windshields ..........................................................2-16
Antenna Icing ...........................................................2-17
Summary ......................................................................2-17
Chapter 3
Flight Instruments ...............................................3-1
Introduction ....................................................................3-1
Pitot/Static Systems .......................................................3-2
Static Pressure ............................................................3-2
Blockage Considerations ............................................3-2
Indications of Pitot Tube Blockage ........................3-3
Indications from Static Port Blockage ....................3-3
Effects of Flight Conditions ....................................3-3
Pitot/Static Instruments ..................................................3-3
Sensitive Altimeter .....................................................3-3
Principle of Operation .............................................3-3
Altimeter Errors ......................................................3-4
Cold Weather Altimeter Errors ...............................3-5
ICAO Cold Temperature Error Table ........................3-5
Nonstandard Pressure on an Altimeter ...................3-6
Altimeter Enhancements (Encoding) .....................3-7
Reduced Vertical Separation Minimum (RVSM) ..3-7
Vertical Speed Indicator (VSI) ...................................3-8
Dynamic Pressure Type Instruments .............................3-8
Airspeed Indicator (ASI) ............................................3-8
Types of Airspeed ...................................................3-9
Airspeed Color Codes ...........................................3-10
Magnetism ....................................................................3-10
The Basic Aviation Magnetic Compass ..................3-11
Magnetic Compass Overview ...............................3-11
Magnetic Compass Induced Errors .......................3-12
The Vertical Card Magnetic Compass .....................3-14
The Flux Gate Compass System ..............................3-14
Remote Indicating Compass .....................................3-15
Gyroscopic Systems .....................................................3-16
Power Sources .........................................................3-16
Pneumatic Systems ..............................................3-16
Vacuum Pump Systems ........................................3-17
Electrical Systems .................................................3-18
Gyroscopic Instruments ...............................................3-18
Attitude Indicators ....................................................3-18
Heading Indicators ...................................................3-19
Turn Indicators .........................................................3-20
Turn-and-Slip Indicator ........................................3-20
Turn Coordinator ..................................................3-21
Flight Support Systems ................................................3-22
Attitude and Heading Reference System (AHRS) ...3-22
Air Data Computer (ADC) .......................................3-22
Analog Pictorial Displays ............................................3-22
Horizontal Situation Indicator (HSI) .......................3-22
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Attitude Direction Indicator (ADI) .........................3-23
Flight Director System (FDS) ..................................3-23
Integrated Flight Control System ............................3-24
Autopilot Systems .................................................3-24
Flight Management Systems (FMS) ............................3-25
Electronic Flight Instrument Systems ......................3-27
Primary Flight Display (PFD) ......................................3-27
Synthetic Vision .......................................................3-27
Multi-Function Display (MFD) ................................3-28
Advanced Technology Systems ...................................3-28
Automatic Dependent Surveillance—
Broadcast (ADS-B) ..................................................3-28
Safety Systems .............................................................3-30
Radio Altimeters ......................................................3-30
Traffi c Advisory Systems ........................................3-31
Traffi c Information System ..................................3-31
Traffi c Alert Systems ...........................................3-31
Traffi c Avoidance Systems ...................................3-31
Terrain Alerting Systems .....................................3-34
Required Navigation Instrument System Inspection ...3-34
Systems Prefl ight Procedures ...................................3-34
Before Engine Start ..................................................3-36
After Engine Start .....................................................3-37
Taxiing and Takeoff .................................................3-37
Engine Shut Down ...................................................3-37
Chapter 4, Section I
Airplane Attitude Instrument Flying
Using Analog Instrumentation ...........................4-1
Introduction ....................................................................4-1
Learning Methods ..........................................................4-2
Attitude Instrument Flying Using the Control and
Performance Method .................................................4-2
Control Instruments ...............................................4-2
Performance Instruments .......................................4-2
Navigation Instruments ..........................................4-2
Procedural Steps in Using Control and
Performance ............................................................4-2
Aircraft Control During Instrument Flight .............4-3
Attitude Instrument Flying Using the Primary and
Supporting Method .....................................................4-4
Pitch Control ...........................................................4-4
Bank Control ...........................................................4-7
Power Control .........................................................4-8
Trim Control ...........................................................4-8
Airplane Trim .........................................................4-8
Helicopter Trim ....................................................4-10
Example of Primary and Support Instruments .........4-10
Fundamental Skills.......................................................4-10
Instrument Cross-Check ...........................................4-10
Common Cross-Check Errors ...............................4-11
Instrument Interpretation ..........................................4-13
Chapter 4, Section II
Airplane Attitude Instrument Flying
Using an Electronic Flight Display ..................4-15
Introduction ..................................................................4-15
Learning Methods ........................................................4-16
Control and Performance Method ............................4-18
Control Instruments ..............................................4-18
Performance Instruments ......................................4-19
Navigation Instruments .........................................4-19
The Four-Step Process Used to Change Attitude .....4-20
Establish ................................................................4-20
Trim ......................................................................4-20
Cross-Check ..........................................................4-20
Adjust ....................................................................4-20
Applying the Four-Step Process ...............................4-20
Pitch Control .........................................................4-20
Bank Control .........................................................4-20
Power Control .......................................................4-21
Attitude Instrument Flying—Primary and
Supporting Method ...................................................4-21
Pitch Control .........................................................4-21
Straight-and-Level Flight ......................................4-22
Primary Pitch ........................................................4-22
Primary Bank ........................................................4-23
Primary Yaw .........................................................4-23
Primary Power ......................................................4-23
Fundamental Skills of Attitude Instrument Flying ......4-23
Instrument Cross-Check ...........................................4-24
Scanning Techniques ...................................................4-24
Selected Radial Cross-Check ...................................4-24
Starting the Scan ...................................................4-24
Trend Indicators ....................................................4-26
Common Errors ............................................................4-28
Fixation .....................................................................4-28
Omission ...................................................................4-28
Emphasis ..................................................................4-28
Chapter 5, Section I
Airplane Basic Flight Maneuvers
Using Analog Instrumentation ...........................5-1
Introduction ....................................................................5-1
Straight-and-Level Flight ...............................................5-2
Pitch Control ..............................................................5-2
Attitude Indicator ....................................................5-2
Altimeter .................................................................5-3
Vertical Speed Indicator (VSI) ...............................5-4
xii
Airspeed Indicator (ASI) ........................................5-6
Bank Control ..............................................................5-6
Attitude Indicator ....................................................5-6
Heading Indicator ...................................................5-7
Turn Coordinator ....................................................5-7
Turn-and-Slip Indicator (Needle and Ball) .............5-8
Power Control ............................................................5-8
Power Settings ........................................................5-9
Airspeed Changes in Straight-and-Level Flight ...5-11
Trim Technique ........................................................5-12
Common Errors in Straight-and-Level Flight .........5-12
Pitch ......................................................................5-12
Heading .................................................................5-13
Power ....................................................................5-13
Trim ......................................................................5-13
Straight Climbs and Descents ......................................5-14
Climbs ......................................................................5-14
Entry .....................................................................5-14
Leveling Off ..........................................................5-16
Descents ...................................................................5-16
Entry .....................................................................5-17
Leveling Off ..........................................................5-17
Common Errors in Straight Climbs and Descents ...5-17
Turns ............................................................................5-19
Standard Rate Turns .................................................5-19
Turns to Predetermined Headings ............................5-20
Timed Turns .............................................................5-21
Compass Turns .........................................................5-21
Steep Turns ...............................................................5-22
Climbing and Descending Turns ..............................5-24
Change of Airspeed During Turns ...........................5-24
Common Errors in Turns ..........................................5-25
Pitch ......................................................................5-25
Bank ......................................................................5-25
Power ....................................................................5-26
Trim ......................................................................5-26
Errors During Compass Turns ..............................5-26
Approach to Stall .........................................................5-26
Unusual Attitudes and Recoveries ...............................5-26
Recognizing Unusual Attitudes ................................5-27
Recovery from Unusual Attitudes ............................5-27
Nose-High Attitudes .................................................5-27
Nose-Low Attitudes .................................................5-28
Common Errors in Unusual Attitudes ......................5-28
Instrument Takeoff .......................................................5-29
Common Errors in Instrument Takeoffs ..................5-29
Basic Instrument Flight Patterns ..................................5-30
Racetrack Pattern ......................................................5-30
Procedure Turn .........................................................5-30
Standard 45° Procedure Turn ...................................5-30
80/260 Procedure Turn .............................................5-31
Teardrop Patterns .....................................................5-31
Circling Approach Patterns ......................................5-32
Pattern I .................................................................5-32
Pattern II ...............................................................5-32
Chapter 5, Section II
Airplane Basic Flight Maneuvers
Using an Electronic Flight Display ..................5-33
Introduction ..................................................................5-33
Straight-and-Level Flight .............................................5-34
Pitch Control ............................................................5-34
Attitude Indicator ..................................................5-34
Altimeter ...............................................................5-36
Partial Panel Flight ...............................................5-36
VSI Tape ...............................................................5-36
Airspeed Indicator (ASI) ......................................5-37
Bank Control ............................................................5-37
Attitude Indicator ..................................................5-37
Horizontal Situation Indicator (HSI) ....................5-38
Heading Indicator .................................................5-38
Turn Rate Indicator ...............................................5-38
Slip/Skid Indicator ................................................5-39
Power Control ..........................................................5-39
Power Settings ......................................................5-39
Airspeed Changes in Straight-and-Level Flight ...5-40
Trim Technique ........................................................5-43
Common Errors in Straight-and-Level Flight ..........5-43
Pitch ......................................................................5-43
Heading .................................................................5-44
Power ....................................................................5-45
Trim ......................................................................5-45
Straight Climbs and Descents ......................................5-46
Entry .........................................................................5-46
Constant Airspeed Climb From Cruise
Airspeed ................................................................5-46
Constant Airspeed Climb from Established
Airspeed ................................................................5-47
Constant Rate Climbs ...........................................5-47
Leveling Off ..........................................................5-48
Descents ...................................................................5-49
Entry .........................................................................5-49
Leveling Off ..........................................................5-50
Common Errors in Straight Climbs and Descents ...5-50
Turns ............................................................................5-51
Standard Rate Turns .................................................5-51
Establishing A Standard Rate Turn ......................5-51
Common Errors ....................................................5-51
Turns to Predetermined Headings ............................5-52
xiii
Timed Turns .............................................................5-53
Compass Turns .........................................................5-53
Steep Turns ...............................................................5-53
Unusual Attitude Recovery Protection .................5-55
Common Errors Leading to Unusual Attitudes ....5-58
Instrument Takeoff .......................................................5-60
Common Errors in Instrument Takeoffs ..................5-61
Basic Instrument Flight Patterns ..................................5-61
Chapter 6
Helicopter Attitude Instrument Flying ...............6-1
Introduction ....................................................................6-1
Flight Instruments ..........................................................6-2
Instrument Flight ............................................................6-2
Instrument Cross-Check .............................................6-2
Instrument Interpretation ............................................6-3
Aircraft Control ..........................................................6-3
Straight-and-Level Flight ...............................................6-3
Pitch Control ..............................................................6-3
Attitude Indicator ....................................................6-3
Altimeter .................................................................6-4
Vertical Speed Indicator (VSI) ...............................6-5
Airspeed Indicator ..................................................6-5
Bank Control ..............................................................6-5
Attitude Indicator ....................................................6-5
Heading Indicator ...................................................6-6
Turn Indicator .........................................................6-7
Common Errors During Straight-and-Level Flight ....6-7
Power Control During Straight-and-Level Flight ......6-7
Common Errors During Airspeed Changes .............6-10
Straight Climbs (Constant Airspeed and
Constant Rate) ..............................................................6-10
Entry .........................................................................6-10
Level Off ..................................................................6-12
Straight Descents (Constant Airspeed and
Constant Rate) ..............................................................6-12
Entry .........................................................................6-12
Level Off ..................................................................6-13
Common Errors During Straight Climbs and
Descents ...................................................................6-13
Turns ............................................................................6-13
Turn to a Predetermined Heading ............................6-13
Timed Turns .............................................................6-13
Change of Airspeed in Turns ...................................6-14
Compass Turns .........................................................6-15
30° Bank Turn ......................................................6-15
Climbing and Descending Turns ..............................6-15
Common Errors During Turns .................................6-15
Unusual Attitudes .........................................................6-16
Common Errors During Unusual Attitude
Recoveries ................................................................6-16
Emergencies .................................................................6-16
Autorotations ............................................................6-17
Common Errors During Autorotations .................6-17
Servo Failure ............................................................6-17
Instrument Takeoff .......................................................6-17
Common Errors During Instrument Takeoffs ..........6-18
Changing Technology ..................................................6-18
Chapter 7
Navigation Systems ............................................7-1
Introduction ....................................................................7-1
Basic Radio Principles ...................................................7-2
How Radio Waves Propagate .....................................7-2
Ground Wave ..........................................................7-2
Sky Wave ................................................................7-2
Space Wave ............................................................7-2
Disturbances to Radio Wave Reception .....................7-3
Traditional Navigation Systems .....................................7-3
Nondirectional Radio Beacon (NDB) ........................7-3
NDB Components ...................................................7-3
ADF Components ...................................................7-3
Function of ADF .....................................................7-4
Operational Errors of ADF .....................................7-8
Very High Frequency Omnidirectional
Range (VOR) ..............................................................7-8
VOR Components .................................................7-10
Function of VOR ..................................................7-12
VOR Operational Errors .......................................7-14
VOR Accuracy ......................................................7-16
VOR Receiver Accuracy Check ...........................7-16
VOR Test Facility (VOT) .....................................7-16
Certifi ed Checkpoints ...........................................7-16
Distance Measuring Equipment (DME) ...................7-16
DME Components ................................................7-17
Function of DME ..................................................7-17
DME Arc ..............................................................7-17
Intercepting Lead Radials .....................................7-19
DME Errors ..........................................................7-19
Area Navigation (RNAV) ........................................7-19
VOR/DME RNAV ................................................7-23
VOR/DME RNAV Components ..........................7-23
Function of VOR/DME RNAV ............................7-23
VOR/DME RNAV Errors .....................................7-24
Long Range Navigation (LORAN) ..........................7-24
LORAN Components ...........................................7-25
Function of LORAN .............................................7-26
LORAN Errors ......................................................7-26
Advanced Technologies ...............................................7-26
Global Navigation Satellite System (GNSS) ...........7-26
xiv
Global Positioning System (GPS) ............................7-27
GPS Components ..................................................7-27
Function of GPS ...................................................7-28
GPS Substitution ...................................................7-28
GPS Substitution for ADF or DME .....................7-29
To Determine Aircraft Position Over a DME
Fix: ........................................................................7-29
To Fly a DME Arc: ...............................................7-29
To Navigate TO or FROM an NDB/Compass
Locator: .................................................................7-29
To Determine Aircraft Position Over an NDB/
Compass Locator: .................................................7-29
To Determine Aircraft Position Over a Fix Made
up of an NDB/Compass Locator Bearing
Crossing a VOR/LOC Course: .............................7-30
To Hold Over an NDB/Compass Locator: ...........7-30
IFR Flight Using GPS ...........................................7-30
GPS Instrument Approaches .................................7-31
Departures and Instrument Departure
Procedures (DPs) ..................................................7-33
GPS Errors ............................................................7-33
System Status ........................................................7-33
GPS Familiarization ..............................................7-34
Differential Global Positioning Systems (DGPS) ....7-34
Wide Area Augmentation System (WAAS) ............7-34
General Requirements ..........................................7-34
Instrument Approach Capabilities ........................7-36
Local Area Augmentation System (LAAS) .............7-36
Inertial Navigation System (INS) .............................7-36
INS Components ...................................................7-37
INS Errors .............................................................7-37
Instrument Approach Systems .....................................7-37
Instrument Landing Systems (ILS) ..........................7-37
ILS Components ...................................................7-39
Approach Lighting Systems (ALS) ..........................7-40
ILS Airborne Components ....................................7-42
ILS Function .............................................................7-42
ILS Errors .................................................................7-44
Marker Beacons ....................................................7-44
Operational Errors ................................................7-45
Simplifi ed Directional Facility (SDF) ......................7-45
Localizer Type Directional Aid (LDA) ....................7-45
Microwave Landing System (MLS) .........................7-45
Approach Azimuth Guidance ...............................7-45
Required Navigation Performance ...............................7-46
Flight Management Systems (FMS) ............................7-48
Function of FMS ......................................................7-48
Head-Up Display (HUD) .............................................7-49
Radar Navigation (Ground Based) ...............................7-49
Functions of Radar Navigation ................................7-49
Airport Surface Detection Equipment ..................7-50
Radar Limitations .....................................................7-50
Chapter 8
The National Airspace System ...........................8-1
Introduction ....................................................................8-1
Airspace Classifi cation ...............................................8-2
Special Use Airspace ..................................................8-2
Federal Airways .........................................................8-4
Other Routing .............................................................8-5
IFR En Route Charts ......................................................8-6
Airport Information ....................................................8-6
Charted IFR Altitudes ................................................8-6
Navigation Features ....................................................8-7
Types of NAVAIDs ................................................8-7
Identifying Intersections .........................................8-7
Other Route Information .......................................8-10
Weather Information and Communication
Features .................................................................8-10
New Technologies .......................................................8-10
Terminal Procedures Publications ...............................8-12
Departure Procedures (DPs) .....................................8-12
Standard Terminal Arrival Routes (STARs) ............8-12
Instrument Approach Procedure (IAP) Charts ............8-12
Margin Identifi cation ................................................8-12
The Pilot Briefi ng .....................................................8-16
The Plan View ..........................................................8-16
Terminal Arrival Area (TAA) ......................................8-18
Course Reversal Elements in Plan View and
Profi le View ..............................................................8-20
Procedure Turns ....................................................8-20
Holding in Lieu of Procedure Turn ......................8-20
Teardrop Procedure ..............................................8-21
The Profi le View ...................................................8-21
Landing Minimums ..................................................8-23
Airport Sketch /Airport Diagram .............................8-27
Inoperative Components ..........................................8-27
RNAV Instrument Approach Charts ........................8-32
Chapter 9
The Air Traffi c Control System ...........................9-1
Introduction ....................................................................9-1
Communication Equipment ...........................................9-2
Navigation/Communication (NAV/COM)
Equipment ..................................................................9-2
Radar and Transponders .............................................9-3
Mode C (Altitude Reporting) ..................................9-3
Communication Procedures ...........................................9-4
Communication Facilities ..............................................9-4
xv
Automated Flight Service Stations (AFSS) ...............9-4
ATC Towers ...............................................................9-5
Terminal Radar Approach Control (TRACON) .........9-6
Tower En Route Control (TEC) .................................9-7
Air Route Traffi c Control Center (ARTCC) ..............9-7
Center Approach/Departure Control ..........................9-7
ATC Infl ight Weather Avoidance Assistance ..............9-11
ATC Radar Weather Displays ..................................9-11
Weather Avoidance Assistance ................................9-11
Approach Control Facility ...........................................9-12
Approach Control Advances ........................................9-12
Precision Runway Monitor (PRM) ..........................9-12
Precision Runway Monitor (PRM) Radar ............9-12
PRM Benefi ts ........................................................9-13
Control Sequence .........................................................9-13
Letters of Agreement (LOA) ....................................9-14
Chapter 10
IFR Flight ............................................................10-1
Introduction ..................................................................10-1
Sources of Flight Planning Information .......................10-2
Aeronautical Information Manual (AIM) ................10-2
Airport/Facility Directory (A/FD) ............................10-2
Notices to Airmen Publication (NTAP) ...................10-2
POH/AFM ................................................................10-2
IFR Flight Plan .............................................................10-2
Filing in Flight ..........................................................10-2
Cancelling IFR Flight Plans .....................................10-3
Clearances ....................................................................10-3
Examples ..................................................................10-3
Clearance Separations ..............................................10-4
Departure Procedures (DPs) ........................................10-5
Obstacle Departure Procedures (ODP) ....................10-5
Standard Instrument Departures ...............................10-5
Radar Controlled Departures ....................................10-5
Departures From Airports Without an
Operating Control Tower .........................................10-7
En Route Procedures ....................................................10-7
ATC Reports ............................................................10-7
Position Reports .......................................................10-7
Additional Reports ...................................................10-7
Planning the Descent and Approach ........................10-8
Standard Terminal Arrival Routes (STARs) ............10-9
Substitutes for Inoperative or Unusable
Components ..............................................................10-9
Holding Procedures ......................................................10-9
Standard Holding Pattern (No Wind) .......................10-9
Standard Holding Pattern (With Wind) ....................10-9
Holding Instructions .................................................10-9
Standard Entry Procedures .....................................10-11
Time Factors ...........................................................10-12
DME Holding .........................................................10-12
Approaches ................................................................10-12
Compliance With Published Standard Instrument
Approach Procedures .............................................10-12
Instrument Approaches to Civil Airports ...............10-13
Approach to Airport Without an Operating
Control Tower .....................................................10-14
Approach to Airport With an Operating
Tower, With No Approach Control ....................10-14
Approach to an Airport With an Operating
Tower, With an Approach Control .....................10-14
Radar Approaches ..................................................10-17
Radar Monitoring of Instrument Approaches ........10-18
Timed Approaches From a Holding Fix ................10-18
Approaches to Parallel Runways ............................10-20
Side-Step Maneuver ...............................................10-20
Circling Approaches ...............................................10-20
IAP Minimums .......................................................10-21
Missed Approaches ................................................10-21
Landing ...................................................................10-22
Instrument Weather Flying ........................................10-22
Flying Experience ..................................................10-22
Recency of Experience .......................................10-22
Airborne Equipment and Ground Facilities ........10-22
Weather Conditions ................................................10-22
Turbulence ..........................................................10-23
Structural Icing ...................................................10-24
Fog ......................................................................10-24
Volcanic Ash ......................................................10-24
Thunderstorms ....................................................10-25
Wind Shear .........................................................10-25
VFR-On-Top ..........................................................10-26
VFR Over-The-Top ................................................10-27
Conducting an IFR Flight ..........................................10-27
Prefl ight ..................................................................10-27
Departure ................................................................10-31
En Route .................................................................10-32
Arrival ....................................................................10-33
Chapter 11
Emergency Operations .....................................11-1
Introduction ..................................................................11-1
Unforecast Adverse Weather .......................................11-2
Inadvertent Thunderstorm Encounter .......................11-2
Inadvertent Icing Encounter .....................................11-2
Precipitation Static ...................................................11-3
Aircraft System Malfunctions ......................................11-3
Electronic Flight Display Malfunction .....................11-4
Alternator/Generator Failure ....................................11-4
Techniques for Electrical Usage ..............................11-5
xvi
Master Battery Switch ..........................................11-5
Operating on the Main Battery .............................11-5
Loss of Alternator/Generator for Electronic Flight
Instrumentation .........................................................11-5
Techniques for Electrical Usage ..............................11-6
Standby Battery ....................................................11-6
Operating on the Main Battery .............................11-6
Analog Instrument Failure ...........................................11-6
Pneumatic System Failure ............................................11-7
Pitot/Static System Failure ...........................................11-7
Communication/Navigation System Malfunction .......11-8
GPS Nearest Airport Function .....................................11-9
Nearest Airports Using the PFD ...............................11-9
Additional Information for a Specifi c Airport ......11-9
Nearest Airports Using the MFD ...........................11-10
Navigating the MFD Page Groups .....................11-10
Nearest Airport Page Group ...............................11-10
Nearest Airports Page Soft Keys ........................11-10
Situational Awareness ................................................11-11
Summary .............................................................11-12
Traffi c Avoidance ...................................................11-14
Appendix A
Clearance Shorthand .........................................A-1
Appendix B
Instrument Training Lesson Guide ...................B-1
Glossary ..............................................................G-1
Index ......................................................................I-1
1-1
Introduction
Human factors is a broad fi eld that examines the interaction
between people, machines, and the environment for the
purpose of improving performance and reducing errors. As
aircraft became more reliable and less prone to mechanical
failure, the percentage of accidents related to human factors
increased. Some aspect of human factors now accounts for
over 80 percent of all accidents. Pilots who have a good
understanding of human factors are better equipped to plan
and execute a safe and uneventful fl ight.
Flying in instrument meteorological conditions (IMC) can
result in sensations that are misleading to the body’s sensory
system. A safe pilot needs to understand these sensations and
effectively counteract them. Instrument fl ying requires a pilot
to make decisions using all available resources.
The elements of human factors covered in this chapter
include sensory systems used for orientation, illusions in
fl ight, physiological and psychological factors, medical
factors, aeronautical decision-making, and crew resource
management (CRM).
Human
Factors
Chapter 1
1-2
Figure 1-1. Rubic’s Cube Graphic.
Sensory Systems for Orientation
Orientation is the awareness of the position of the aircraft
and of oneself in relation to a specifi c reference point.
Disorientation is the lack of orientation, and spatial
disorientation specifi cally refers to the lack of orientation
with regard to position in space and to other objects.
Orientation is maintained through the body’s sensory organs
in three areas: visual, vestibular, and postural. The eyes
maintain visual orientation. The motion sensing system in
the inner ear maintains vestibular orientation. The nerves in
the skin, joints, and muscles of the body maintain postural
orientation. When healthy human beings are in their natural
environment, these three systems work well. When the
human body is subjected to the forces of fl ight, these senses
can provide misleading information. It is this misleading
information that causes pilots to become disoriented.
Eyes
Of all the senses, vision is most important in providing
information to maintain safe flight. Even though the
human eye is optimized for day vision, it is also capable
of vision in very low light environments. During the day,
the eye uses receptors called cones, while at night, vision is
facilitated by the use of rods.
Both of these provide a level
of vision optimized for the
lighting conditions that they
were intended. That is, cones
are ineffective at night and
rods are ineffective during
the day.
Rods, which contain rhodopsin
(called visual purple), are
especially sensitive to light
and increased light washes out
the rhodopsin compromising
the night vision. Hence, when
strong light is momentarily
introduced at night, vision
may be totally ineffective as
the rods take time to become
effective again in darkness.
Smoking, alcohol, oxygen
deprivation, and age affect
vision, especially at night. It
should be noted that at night,
oxygen deprivation such as one
caused from a climb to a high
altitude causes a significant
reduction in vision. A return
back to the lower altitude will
not restore a pilot’s vision in the same transitory period used
at the climb altitude.
The eye also has two blind spots. The day blind spot is the
location on the light sensitive retina where the optic nerve
fi ber bundle (which carries messages from the eye to the
brain) passes through. This location has no light receptors,
and a message cannot be created there to be sent to the brain.
The night blind spot is due to a concentration of cones in an
area surrounding the fovea on the retina. Because there are
no rods in this area, direct vision on an object at night will
disappear. As a result, off-center viewing and scanning at
night is best for both obstacle avoidance and to maximize
situational awareness. [See the Pilot’s Handbook of
Aeronautical Knowledge and the Aeronautical Information
Manual (AIM) for detailed reading.]
The brain also processes visual information based upon color,
relationship of colors, and vision from objects around us.
Figure 1-1 demonstrates the visual processing of information.
The brain assigns color based on many items to include an
object’s surroundings. In the fi gure below, the orange square
on the shaded side of the cube is actually the same color
as the brown square in the center of the cube’s top face.
1-3
Figure 1-2. Shepard’s Tables.
Isolating the orange square from surrounding infl uences
will reveal that it is actually brown. The application to a real
environment is evident when processing visual information
that is infl uenced by surroundings. The ability to pick out an
airport in varied terrain or another aircraft in a light haze are
examples of problems with interpretation that make vigilance
all the more necessary.
Figure 1-2 illustrates problems with perception. Both tables
are the same lengths. Objects are easily misinterpreted in
size to include both length and width. Being accustomed to
a 75-foot-wide runway on fl at terrain is most likely going
to influence a pilot’s perception of a wider runway on
uneven terrain simply because of the inherent processing
experience.
Vision Under Dim and Bright Illumination
Under conditions of dim illumination, aeronautical charts and
aircraft instruments can become unreadable unless adequate
fl ight deck lighting is available. In darkness, vision becomes
more sensitive to light. This process is called dark adaptation.
Although exposure to total darkness for at least 30 minutes is
required for complete dark adaptation, a pilot can achieve a
moderate degree of dark adaptation within 20 minutes under
dim red fl ight deck lighting.
Red light distorts colors (fi lters the red spectrum), especially
on aeronautical charts, and makes it very diffi cult for the
eyes to focus on objects inside the aircraft. Pilots should
use it only where optimum outside night vision capability is
necessary. White fl ight deck lighting (dim lighting) should
be available when needed for map and instrument reading,
especially under IMC conditions.
Since any degree of dark adaptation is lost within a few
seconds of viewing a bright light, pilots should close one eye
when using a light to preserve some degree of night vision.
During night fl ights in the vicinity of lightning, fl ight deck
lights should be turned up to help prevent loss of night vision
due to the bright fl ashes. Dark adaptation is also impaired by
exposure to cabin pressure altitudes above 5,000 feet, carbon
monoxide inhaled through smoking, defi ciency of Vitamin A
in the diet, and by prolonged exposure to bright sunlight.
During fl ight in visual meteorological conditions (VMC),
the eyes are the major orientation source and usually provide
accurate and reliable information. Visual cues usually
prevail over false sensations from other sensory systems.
When these visual cues are taken away, as they are in IMC,
false sensations can cause the pilot to quickly become
disoriented.
An effective way to counter these false sensations is to
recognize the problem, disregard the false sensations, rely
on the fl ight instruments, and use the eyes to determine the
aircraft attitude. The pilot must have an understanding of
the problem and the skill to control the aircraft using only
instrument indications.
1-4
Figure 1-4. Angular Acceleration and the Semicircular Tubes.
Figure 1-3. Inner Ear Orientation.
Ears
The inner ear has two major parts concerned with orientation,
the semicircular canals and the otolith organs. The
semicircular canals detect angular acceleration of the body
while the otolith organs detect linear acceleration and gravity.
The semicircular canals consist of three tubes at right angles
to each other, each located on one of three axes: pitch, roll,
or yaw as illustrated in Figure 1-4. Each canal is fi lled with
a fl uid called endolymph fl uid. In the center of the canal is
the cupola, a gelatinous structure that rests upon sensory
hairs located at the end of the vestibular nerves. It is the
movement of these hairs within the fl uid which causes
sensations of motion.
Because of the friction between the fl uid and the canal, it
may take about 15–20 seconds for the fl uid in the ear canal
to reach the same speed as the canal’s motion.
To illustrate what happens during a turn, visualize the aircraft
in straight and level fl ight. With no acceleration of the aircraft,
the hair cells are upright and the body senses that no turn
has occurred. Therefore, the position of the hair cells and the
actual sensation correspond.
Placing the aircraft into a turn puts the semicircular canal and
its fl uid into motion, with the fl uid within the semicircular
canal lagging behind the accelerated canal walls.
This lag creates a relative movement of the fl uid within the
canal. The canal wall and the cupula move in the opposite
direction from the motion of the fl uid.
The brain interprets the movement of the hairs to be a turn in
the same direction as the canal wall. The body correctly senses
that a turn is being made. If the turn continues at a constant
rate for several seconds or longer, the motion of the fl uid in
1-5
Figure 1-6. Linear Acceleration.
Figure 1-5. Angular Acceleration.
the canals catches up with the canal walls. The hairs are no
longer bent, and the brain receives the false impression that
turning has stopped. Thus, the position of the hair cells and the
resulting sensation during a prolonged, constant turn in either
direction will result in the false sensation of no turn.
When the aircraft returns to straight-and-level fl ight, the fl uid
in the canal moves briefl y in the opposite direction. This sends
a signal to the brain that is falsely interpreted as movement
in the opposite direction. In an attempt to correct the falsely
perceived turn, the pilot may reenter the turn placing the
aircraft in an out of control situation.
The otolith organs detect linear acceleration and gravity in a
similar way. Instead of being fi lled with a fl uid, a gelatinous
membrane containing chalk-like crystals covers the sensory
hairs. When the pilot tilts his or her head, the weight of these
crystals causes this membrane to shift due to gravity and
the sensory hairs detect this shift. The brain orients this new
position to what it perceives as vertical. Acceleration and
deceleration also cause the membrane to shift in a similar
manner. Forward acceleration gives the illusion of the head
tilting backward. As a result, during takeoff and
while accelerating, the pilot may sense a steeper than normal
climb resulting in a tendency to nose-down.
Nerves
Nerves in the body’s skin, muscles, and joints constantly
send signals to the brain, which signals the body’s relation to
gravity. These signals tell the pilot his or her current position.
Acceleration will be felt as the pilot is pushed back into the
seat. Forces created in turns can lead to false sensations of
the true direction of gravity, and may give the pilot a false
sense of which way is up.
Uncoordinated turns, especially climbing turns, can cause
misleading signals to be sent to the brain. Skids and slips
give the sensation of banking or tilting. Turbulence can create
motions that confuse the brain as well. Pilots need to be aware
that fatigue or illness can exacerbate these sensations and
ultimately lead to subtle incapacitation.
Illusions Leading to Spatial
Disorientation
The sensory system responsible for most of the illusions
leading to spatial disorientation is the vestibular system.
Visual illusions can also cause spatial disorientation.
Vestibular Illusions
The Leans
A condition called the leans can result when a banked attitude,
to the left for example, may be entered too slowly to set in
motion the fl uid in the “roll” semicircular tubes.
An abrupt correction of this attitude sets the fl uid in motion,
creating the illusion of a banked attitude to the right. The
disoriented pilot may make the error of rolling the aircraft
into the original left banked attitude, or if level fl ight is
maintained, will feel compelled to lean in the perceived
vertical plane until this illusion subsides.
1-6
Figure 1-7. Graveyard Spiral.
Coriolis Illusion
The coriolis illusion occurs when a pilot has been in a turn
long enough for the fl uid in the ear canal to move at the same
speed as the canal. A movement of the head in a different
plane, such as looking at something in a different part of the
fl ight deck, may set the fl uid moving and create the illusion
of turning or accelerating on an entirely different axis.
This action causes the pilot to think the aircraft is doing a
maneuver that it is not. The disoriented pilot may maneuver
the aircraft into a dangerous attitude in an attempt to correct
the aircraft’s perceived attitude.
For this reason, it is important that pilots develop an instrument
cross-check or scan that involves minimal head movement.
Take care when retrieving charts and other objects in the fl ight
deck—if something is dropped, retrieve it with minimal head
movement and be alert for the coriolis illusion. Graveyard Spiral
As in other illusions, a pilot in a prolonged coordinated,
constant rate turn, will have the illusion of not turning.
During the recovery to level fl ight, the pilot will experience
the sensation of turning in the opposite direction. The
disoriented pilot may return the aircraft to its original turn.
Because an aircraft tends to lose altitude in turns unless the
pilot compensates for the loss in lift, the pilot may notice
a loss of altitude. The absence of any sensation of turning
creates the illusion of being in a level descent. The pilot may
pull back on the controls in an attempt to climb or stop the
descent. This action tightens the spiral and increases the loss
of altitude; hence, this illusion is referred to as a graveyard
spiral. At some point, this could lead to a loss
of control by the pilot.
Somatogravic Illusion
A rapid acceleration, such as experienced during takeoff,
stimulates the otolith organs in the same way as tilting the
head backwards. This action creates the somatogravic illusion
of being in a nose-up attitude, especially in situations without
good visual references. The disoriented pilot may push the
aircraft into a nose-low or dive attitude. A rapid deceleration
by quick reduction of the throttle(s) can have the opposite
effect, with the disoriented pilot pulling the aircraft into a
nose-up or stall attitude.
Inversion Illusion
An abrupt change from climb to straight-and-level fl ight can
stimulate the otolith organs enough to create the illusion of
tumbling backwards, or inversion illusion. The disoriented
pilot may push the aircraft abruptly into a nose-low attitude,
possibly intensifying this illusion.
Elevator Illusion
An abrupt upward vertical acceleration, as can occur in
an updraft, can stimulate the otolith organs to create the
illusion of being in a climb. This is called elevator illusion.
The disoriented pilot may push the aircraft into a nose-low
attitude. An abrupt downward vertical acceleration, usually
1-7
Figure 1-8. Sensations From Centrifugal Force.
in a downdraft, has the opposite effect, with the disoriented
pilot pulling the aircraft into a nose-up attitude.
Visual Illusions
Visual illusions are especially hazardous because pilots rely
on their eyes for correct information. Two illusions that lead
to spatial disorientation, false horizon and autokinesis, are
concerned with only the visual system.
False Horizon
A sloping cloud formation, an obscured horizon, an aurora
borealis, a dark scene spread with ground lights and stars,
and certain geometric patterns of ground lights can provide
inaccurate visual information, or false horizon, for aligning
the aircraft correctly with the actual horizon. The disoriented
pilot may place the aircraft in a dangerous attitude.
Autokinesis
In the dark, a stationary light will appear to move about when
stared at for many seconds. The disoriented pilot could lose
control of the aircraft in attempting to align it with the false
movements of this light, called autokinesis.
Postural Considerations
The postural system sends signals from the skin, joints, and
muscles to the brain that are interpreted in relation to the
Earth’s gravitational pull. These signals determine posture.
Inputs from each movement update the body’s position to
the brain on a constant basis. “Seat of the pants” fl ying is
largely dependent upon these signals. Used in conjunction
with visual and vestibular clues, these sensations can be
fairly reliable. However, because of the forces acting upon
the body in certain fl ight situations, many false sensations
can occur due to acceleration forces overpowering gravity.
These situations include uncoordinated turns,
climbing turns, and turbulence.
Demonstration of Spatial Disorientation
There are a number of controlled aircraft maneuvers a pilot
can perform to experiment with spatial disorientation. While
each maneuver will normally create a specifi c illusion, any
false sensation is an effective demonstration of disorientation.
Thus, even if there is no sensation during any of these
maneuvers, the absence of sensation is still an effective
demonstration in that it shows the inability to detect bank
or roll. There are several objectives in demonstrating these
various maneuvers.
1. They teach pilots to understand the susceptibility of
the human system to spatial disorientation.
2. They demonstrate that judgments of aircraft attitude
based on bodily sensations are frequently false.
3. They help lessen the occurrence and degree of
disorientation through a better understanding of the
relationship between aircraft motion, head movements,
and resulting disorientation.
4. They help instill a greater confi dence in relying on
fl ight instruments for assessing true aircraft attitude.
1-8
A pilot should not attempt any of these maneuvers at low
altitudes, or in the absence of an instructor pilot or an
appropriate safety pilot.
Climbing While Accelerating
With the pilot’s eyes closed, the instructor pilot maintains
approach airspeed in a straight-and-level attitude for several
seconds, and then accelerates while maintaining straight-andlevel
attitude. The usual illusion during this maneuver, without
visual references, will be that the aircraft is climbing.
Climbing While Turning
With the pilot’s eyes still closed and the aircraft in a straightand-
level attitude, the instructor pilot now executes, with a
relatively slow entry, a well-coordinated turn of about 1.5
positive G (approximately 50° bank) for 90°. While in the
turn, without outside visual references and under the effect of
the slight positive G, the usual illusion produced is that of a
climb. Upon sensing the climb, the pilot should immediately
open the eyes and see that a slowly established, coordinated
turn produces the same feeling as a climb.
Diving While Turning
Repeating the previous procedure, with the exception that
the pilot’s eyes should be kept closed until recovery from
the turn is approximately one-half completed can create this
sensation. With the eyes closed, the usual illusion will be
that the aircraft is diving.
Tilting to Right or Left
While in a straight-and-level attitude, with the pilot’s eyes
closed, the instructor pilot executes a moderate or slight skid
to the left with wings level. This creates the illusion of the
body being tilted to the right.
Reversal of Motion
This illusion can be demonstrated in any of the three planes of
motion. While straight and level, with the pilot’s eyes closed,
the instructor pilot smoothly and positively rolls the aircraft to
approximately a 45° bank attitude while maintaining heading
and pitch attitude. This creates the illusion of a strong sense
of rotation in the opposite direction. After this illusion is
noted, the pilot should open his or her eyes and observe that
the aircraft is in a banked attitude.
Diving or Rolling Beyond the Vertical Plane
This maneuver may produce extreme disorientation. While
in straight-and-level fl ight, the pilot should sit normally,
either with eyes closed or gaze lowered to the fl oor. The
instructor pilot starts a positive, coordinated roll toward a
30° or 40° angle of bank. As this is in progress, the pilot
tilts his or her head forward, looks to the right or left, then
immediately returns his or her head to an upright position.
The instructor pilot should time the maneuver so the roll is
stopped as the pilot returns his or her head upright. An intense
disorientation is usually produced by this maneuver, and the
pilot experiences the sensation of falling downward into the
direction of the roll.
In the descriptions of these maneuvers, the instructor pilot is
doing the fl ying, but having the pilot do the fl ying can also
be a very effective demonstration. The pilot should close his
or her eyes and tilt the head to one side. The instructor pilot
tells the pilot what control inputs to perform. The pilot then
attempts to establish the correct attitude or control input with
eyes closed and head tilted. While it is clear the pilot has no
idea of the actual attitude, he or she will react to what the
senses are saying. After a short time, the pilot will become
disoriented and the instructor pilot then tells the pilot to
look up and recover. The benefi t of this exercise is the pilot
experiences the disorientation while fl ying the aircraft.
Coping with Spatial Disorientation
To prevent illusions and their potentially disastrous
consequences, pilots can:
1. Understand the causes of these illusions and remain
constantly alert for them. Take the opportunity to
understand and then experience spatial disorientation
illusions in a device such as a Barany chair, a
Vertigon, or a Virtual Reality Spatial Disorientation
Demonstrator.
2. Always obtain and understand preflight weather
briefi ngs.
3. Before fl ying in marginal visibility (less than 3 miles)
or where a visible horizon is not evident such as fl ight
over open water during the night, obtain training and
maintain profi ciency in airplane control by reference
to instruments.
4. Do not continue fl ight into adverse weather conditions
or into dusk or darkness unless profi cient in the use of
fl ight instruments. If intending to fl y at night, maintain
night-fl ight currency and profi ciency. Include crosscountry
and local operations at various airfi elds.
5. Ensure that when outside visual references are used,
they are reliable, fi xed points on the Earth’s surface.
6. Avoid sudden head movement, particularly during
takeoffs, turns, and approaches to landing.
7. Be physically tuned for fl ight into reduced visibility.
That is, ensure proper rest, adequate diet, and, if fl ying
at night, allow for night adaptation. Remember that
illness, medication, alcohol, fatigue, sleep loss, and
mild hypoxia are likely to increase susceptibility to
spatial disorientation.
1-9
Water Refraction
Rain on the windscreen can create an illusion of being at a
higher altitude due to the horizon appearing lower than it is.
This can result in the pilot fl ying a lower approach.
Haze
Atmospheric haze can create an illusion of being at a greater
distance and height from the runway. As a result, the pilot
will have a tendency to be low on the approach. Conversely,
extremely clear air (clear bright conditions of a high attitude
airport) can give the pilot the illusion of being closer than he
or she actually is, resulting in a high approach, which may
result in an overshoot or go around. The diffusion of light
due to water particles on the windshield can adversely affect
depth perception. The lights and terrain features normally
used to gauge height during landing become less effective
for the pilot.
Fog
Flying into fog can create an illusion of pitching up. Pilots
who do not recognize this illusion will often steepen the
approach quite abruptly.
Ground Lighting Illusions
Lights along a straight path, such as a road or lights on moving
trains, can be mistaken for runway and approach lights. Bright
runway and approach lighting systems, especially where
few lights illuminate the surrounding terrain, may create the
illusion of less distance to the runway. The pilot who does not
recognize this illusion will often fl y a higher approach.
How To Prevent Landing Errors Due to
Optical Illusions
To prevent these illusions and their potentially hazardous
consequences, pilots can:
1. Anticipate the possibility of visual illusions during
approaches to unfamiliar airports, particularly at
night or in adverse weather conditions. Consult
airport diagrams and the Airport/Facility Directory
(A/FD) for information on runway slope, terrain, and
lighting.
2. Make frequent reference to the altimeter, especially
during all approaches, day and night.
3. If possible, conduct aerial visual inspection of
unfamiliar airports before landing.
8. Most importantly, become profi cient in the use of
flight instruments and rely upon them. Trust the
instruments and disregard your sensory perceptions.
The sensations that lead to illusions during instrument
fl ight conditions are normal perceptions experienced by
pilots. These undesirable sensations cannot be completely
prevented, but through training and awareness, pilots can
ignore or suppress them by developing absolute reliance
on the flight instruments. As pilots gain proficiency in
instrument fl ying, they become less susceptible to these
illusions and their effects.
Optical Illusions
Of the senses, vision is the most important for safe fl ight.
However, various terrain features and atmospheric conditions
can create optical illusions. These illusions are primarily
associated with landing. Since pilots must transition from
reliance on instruments to visual cues outside the fl ight
deck for landing at the end of an instrument approach, it is
imperative they be aware of the potential problems associated
with these illusions, and take appropriate corrective action.
The major illusions leading to landing errors are described
below.
Runway Width Illusion
A narrower-than-usual runway can create an illusion the
aircraft is at a higher altitude than it actually is, especially
when runway length-to-width relationships are comparable.
The pilot who does not recognize this illusion
will fl y a lower approach, with the risk of striking objects
along the approach path or landing short. A wider-than-usual
runway can have the opposite effect, with the risk of leveling
out high and landing hard, or overshooting the runway.
Runway and Terrain Slopes Illusion
An upsloping runway, upsloping terrain, or both, can create
an illusion the aircraft is at a higher altitude than it actually
is. The pilot who does not recognize this
illusion will fl y a lower approach. Downsloping runways and
downsloping approach terrain can have the opposite effect.
Featureless Terrain Illusion
An absence of surrounding ground features, as in an
overwater approach, over darkened areas, or terrain made
featureless by snow, can create an illusion the aircraft is at
a higher altitude than it actually is. This illusion, sometimes
referred to as the “black hole approach,” causes pilots to fl y
a lower approach than is desired.
1-10
Figure 1-9. Runway Width and Slope Illusions.
6. Recognize that the chances of being involved in an
approach accident increase when some emergency or
other activity distracts from usual procedures.
7. Maintain optimum profi ciency in landing procedures.
4. Use Visual Approach Slope Indicator (VASI) or
Precision Approach Path Indicator (PAPI) systems
for a visual reference, or an electronic glide slope,
whenever they are available.
5. Utilize the visual descent point (VDP) found on many
nonprecision instrument approach procedure charts.
1-11
Figure 1-10. Stress and Performance.
Physiological and Psychological Factors
Physiological or psychological factors can affect a pilot
and compromise the safety of a fl ight. These factors are
stress, medical, alcohol, and fatigue. Any of these factors,
individually or in combination, signifi cantly degrade the
pilot’s decision-making or fl ying abilities.
Stress
Stress is the body’s response to demands placed upon it. These
demands can be either pleasant or unpleasant in nature. The
causes of stress for a pilot can range from unexpected weather
or mechanical problems while in fl ight, to personal issues
unrelated to fl ying. Stress is an inevitable and necessary part
of life; it adds motivation to life and heightens an individual’s
response to meet any challenge. The effects of stress are
cumulative and there is a limit to a person’s adaptive nature.
This limit, called the stress tolerance level (or channel
capacity), is based on the ability to cope with the situation.
At fi rst, some amount of stress can be desirable and can
actually improve performance. However, higher stress levels,
particularly over long periods of time, can adversely affect
performance. Performance will generally increase with the
onset of stress, but will peak and then begin to fall off rapidly
as stress levels exceed the ability to cope.
At this point, a pilot’s performance begins to decline and
judgment deteriorates. Complex or unfamiliar tasks require
higher levels of performance than simple or overlearned
tasks. Complex or unfamiliar tasks are also more subject to
the adverse effects of increasing stress than simple or familiar
tasks.
The indicators of excessive stress often show as three types
of symptoms: (1) emotional, (2) physical, and (3) behavioral.
Emotional symptoms may surface as over-compensation,
denial, suspicion, paranoia, agitation, restlessness, or
defensiveness. Physical stress can result in acute fatigue
while behavioral degradation will be manifested as sensitivity
to criticism, tendency to be argumentative, arrogance, and
hostility. Pilots need to learn to recognize the symptoms of
stress as they begin to occur.
There are many techniques available that can help reduce
stress in life or help people cope with it better. Not all of the
following ideas may be a solution, but some of them should
be effective.
1. Become knowledgeable about stress.
2. Take a realistic self-assessment. (See the Pilot’s
Handbook of Aeronautical Knowledge).
3. Take a systematic approach to problem solving.
4. Develop a lifestyle that will buffer against the effects
of stress.
5. Practice behavior management techniques.
6. Establish and maintain a strong support network.
Good fl ight deck stress management begins with good life
stress management. Many of the stress coping techniques
practiced for life stress management are not usually practical
in fl ight. Rather, pilots must condition themselves to relax and
think rationally when stress appears. The following checklist
outlines some methods of fl ight deck stress management.
1. Avoid situations that distract from fl ying the aircraft.
2. Reduce fl ight deck workload to reduce stress levels.
This will create a proper environment in which to make
good decisions. Typically, fl ying involves higher stress
levels during takeoff and landing phases. Between the
two generally lies a period of low activity resulting
in a lower stress level. Transitioning from the cruise
phase to the landing phase is generally accompanied
by a significant workload that, if not properly
accommodated, will increase stress significantly.
Proper planning and prioritization of flight deck
duties are key to avoiding events that affect the pilot's
capacity to maintain situational awareness. 1-12
3. If a problem occurs, remain calm. If time is not a
pressing factor, follow the analytical approach to
decision-making: think for a moment, weigh the
alternatives, select and take an appropriate course of
action, and then evaluate its effects.
If an emergency situation occurs, remain calm and
use the aeronautical decision-making (ADM) process
to resolve the emergency. This process relies on the
pilot’s training and experience to accurately and
automatically respond to an emergency situation.
Constant training in handling emergency procedures
will help reduce pilot stress when an emergency
occurs.
4. Become thoroughly familiar with the aircraft, its
operation, and emergency procedures. Also, maintain
fl ight profi ciency to build confi dence.
5. Know and respect personal limits. Studies have
suggested that highly experienced pilots have taken
more chances when flying into potential icing
conditions than low time or inexperienced pilots.
Very low time pilots without experience may analyze
and interpret the likelihood for “potential” fl ight into
icing without the benefi t of life experience, thereby
making decisions closely aligned with the compilation
of their training and recent academic knowledge.
Highly experienced pilots may evaluate the current
situation based upon the empirical information
(sometimes diluted with time) coupled with their
vast experience. This may lead to a level of greater
acceptability of the situation because their experience
has illustrated successful navigation of this problem
before. Therefore, the automatic decision may be in
error because not all salient facts are evaluated.
6. Do not allow small mistakes to be distractions during
fl ight; rather, review and analyze them after landing.
7. If flying adds stress, either stop flying or seek
professional help to manage stress within acceptable
limits.
Medical Factors
A “go/no-go” decision based on a pilot’s medical factors is
made before each fl ight. The pilot should not only prefl ight
check the aircraft, but also himself or herself before
every fl ight. A pilot should ask, “Can I pass my medical
examination right now?” If the answer is not an absolute
“yes,” do not fl y. This is especially true for pilots embarking
on fl ights in IMC. Instrument fl ying is much more demanding
than fl ying in VMC, and peak performance is critical for the
safety of fl ight.
Pilot performance can be seriously degraded by both
prescribed and over-the-counter medications, as well as
by the medical conditions for which they are taken. Many
medications, such as tranquilizers, sedatives, strong pain
relievers, and cough suppressants, have primary effects
that impair judgment, memory, alertness, coordination,
vision, and the ability to make calculations. Others, such
as antihistamines, blood pressure drugs, muscle relaxants,
and agents to control diarrhea and motion sickness, have
side effects that impair the same critical functions. Any
medication that depresses the nervous system, such as a
sedative, tranquilizer, or antihistamine, makes a pilot much
more susceptible to hypoxia.
Title 14 of the Code of Federal Regulations (14 CFR) prohibits
pilots from performing crewmember duties while using any
medication that affects the faculties in any way contrary to
safety. The safest rule is not to fl y as a crewmember while
taking any medication, unless approved to do so by the
Federal Aviation Administration (FAA). If there is any doubt
regarding the effects of any medication, consult an Aviation
Medical Examiner (AME) before fl ying.
Alcohol
14 CFR part 91 prohibits pilots from performing crewmember
duties within 8 hours after drinking any alcoholic beverage or
while under the infl uence. Extensive research has provided a
number of facts about the hazards of alcohol consumption and
fl ying. As little as one ounce of liquor, one bottle of beer, or
four ounces of wine can impair fl ying skills and render a pilot
much more susceptible to disorientation and hypoxia. Even
after the body completely metabolizes a moderate amount of
alcohol, a pilot can still be impaired for many hours. There
is simply no way of increasing the metabolism of alcohol or
alleviating a hangover.
Fatigue
Fatigue is one of the most treacherous hazards to fl ight safety,
as it may not be apparent to a pilot until serious errors are
made. Fatigue can be either acute (short-term) or chronic
(long-term).
Acute Fatigue
A normal occurrence of everyday living, acute fatigue is
the tiredness felt after long periods of physical and mental
strain, including strenuous muscular effort, immobility, heavy
mental workload, strong emotional pressure, monotony, and
lack of sleep. Adequate rest, regular exercise, and proper
nutrition prevent acute fatigue.
1-13
Indications of fatigue are generally subtle and hard to
recognize because the individual being assessed is generally
the person making the assessment, as in single pilot
operations. Therefore, the pilot must look at small errors
that occur to provide an indication of becoming fatigued.
These include:
• Misplacing items during the prefl ight;
• Leaving material (pencils, charts) in the planning
area;
• Missing radio calls;
• Answering calls improperly (read-backs); and
• Improper tuning of frequencies.
Chronic Fatigue
Chronic fatigue occurs when there is not enough time for a
full recovery from repeated episodes of acute fatigue. Chronic
fatigue’s underlying cause is generally not “rest-related” and
may have deeper points of origin. Therefore, rest alone may
not resolve chronic fatigue.
Chronic fatigue is a combination of both physiological
problems and psychological issues. Psychological problems
such as fi nancial, home life, or job related stresses cause a
lack of qualifi ed rest that is only resolved by mitigating the
underpinning problems. Without resolution, performance
continues to fall off, judgment becomes impaired, and
unwarranted risks are taken. Recovery from chronic fatigue
requires a prolonged and deliberate solution. In either case,
unless adequate precautions are taken, personal performance
could be impaired and adversely affect pilot judgment and
decision-making.
IMSAFE Checklist
The following checklist, IMSAFE, is intended for a pilot’s
personal prefl ight use. A quick check of the items on this
list will help a pilot make a good self-evaluation prior to any
fl ight. If the answer to any of the checklist questions is yes,
then the pilot should consider not fl ying.
Illness
Do I have any symptoms?
Medication
Have I been taking prescription or over-the-counter drugs?
Stress
Am I under psychological pressure from the job? Do I have
money, health, or family problems?
Alcohol
Have I been drinking within 8 hours? Within 24 hours?
Fatigue
Am I tired and not adequately rested?
Eating
Have I eaten enough of the proper foods to keep adequately
nourished during the entire fl ight?
Hazard Identifi cation
In order to identify a hazard, it would be useful to defi ne what
a hazard is. The FAA System Safety course defi nes a hazard
as: “a present condition, event, object, or circumstance that
could lead or contribute to an unplanned or undesired event.”
Put simply, a hazard is a source of danger. Potential hazards
may be identifi ed from a number of internal and external
sources. These may be based upon several concurrent factors
that provide an indication and ultimate identifi cation of a
hazard. Consider the following situations:
Situation 1
The pilot has just taken off and is entering the clouds. Suddenly,
there is an explosive sound. The sudden noise is disturbing and
occurs as the pilot is given a new heading, a climb restriction,
and the frequency for the departure control.
Situation 2
The pilot took off late in a rented aircraft (fi rst time fl ying
this model), and is now in night conditions due to the delay,
and fl ying on an instrument fl ight rules (IFR) fl ight plan in
IMC conditions. The radios do not seem to work well and
develop static. They seem to be getting weaker. As the pilot
proceeds, the rotating beacon stops fl ashing/rotating, and the
lights become dimmer. As the situation progresses, the pilot
is unaware of the problem because the generator warning
light, (on the lower left of the panel) is obscured by the chart
on the pilot’s lap.
Both situations above represent hazards that must be dealt
with differently and a level of risk must be associated with
each depending on various factors affecting the fl ight.
Risk Analysis
Risk is defi ned as the future impact of a hazard that is not
eliminated or controlled. It is the possibility of loss or injury.
Risk analysis is the process whereby hazards are characterized
by their likelihood and severity. Risk analysis evaluates
the hazards to determine the outcomes and how abrupt that
outcome will occur. The analysis applied will be qualitative
to the degree that time allows resulting in either an analytical
or automatic approach in the decision-making process.
1-14
In the fi rst situation, the decision may be automatic: fl y the
airplane to a safe landing. Since automatic decision-making
is based upon education and experience, an inexperienced
pilot may react improperly to the situation which results in
an inadequate action. To mitigate improper decision-making,
immediate action items from emergency procedures should
be learned. Training, education, and mentorship are all key
factors in honing automatic decision-making skills.
In the second situation, if the pilot has a fl ashlight onboard, it
can be used for illumination, although its light may degrade
night vision. After changing the appropriate transponder
code, and making calls in the blind, awareness of present
location becomes imperative, especially if the pilot must
execute a controlled descent to VMC conditions. Proper
prefl ight planning conducted before departure and constant
awareness of location provide an element of both comfort
(reduces stress) and information from which the pilot can
draw credible information.
In both cases, the outcomes can be successful through
systems understanding, emergency procedures training, and
correctly analyzing the risks associated with each course
of action.
Crew Resource Management (CRM)
and Single-Pilot Resource Management
(SRM)
Crew resource management (CRM) and single-pilot resource
management (SRM) is the ability for the crew or pilot to
manage all resources effectively to ensure the outcome of the
fl ight is successful. In general aviation, SRM will be most
often used and its focus is on the single-pilot operation. SRM
integrates the following:
• Situational Awareness
• Flight Deck Resource Management
• Task Management
• Aeronautical Decision-making (ADM) and Risk
Management
SRM recognizes the need to seek proper information from
these sources to make a valid decision. For instance, the
pilot may have to request assistance from others and be
assertive to resolve situations. Pilots should understand the
need to seek information from other sources until they have
the proper information to make the best decision. Once a
pilot has gathered all pertinent information and made the
appropriate decision, the pilot needs to perform an assessment
of the action taken.
Situational Awareness
Situational awareness is the accurate perception of
operational and environmental factors that affect the fl ight. It
is a logical analysis based upon the machine, external support,
environment, and the pilot. It is knowing what is going on.
Flight Deck Resource Management
CRM is the effective use of all available resources: human,
equipment, and information. It focuses on communication
skills, teamwork, task allocation, and decision-making.
While CRM often concentrates on pilots who operate in
crew environments, the elements and concepts also apply to
single-pilot operations. Human Resources
Human resources include everyone routinely working with the
pilot to ensure fl ight safety. These people include, but are not
limited to: weather briefers, fl ight line personnel, maintenance
personnel, crew members, pilots, and air traffi c personnel.
Pilots need to effectively communicate with these people.
This is accomplished by using the key components of the
communication process: inquiry, advocacy, and assertion.
Pilots must recognize the need to seek enough information
from these resources to make a valid decision. After the
necessary information has been gathered, the pilot’s decision
must be passed on to those concerned, such as air traffi c
controllers, crew members, and passengers. The pilot may
have to request assistance from others and be assertive to
safely resolve some situations.
Equipment
Equipment in many of today’s aircraft includes automated
fl ight and navigation systems. These automatic systems, while
providing relief from many routine fl ight deck tasks, present a
different set of problems for pilots. The automation intended
to reduce pilot workload essentially removes the pilot from the
process of managing the aircraft, thereby reducing situational
awareness and leading to complacency. Information from
these systems needs to be continually monitored to ensure
proper situational awareness. Pilots should be thoroughly
familiar with the operation of and information provided by
all systems used. It is essential that pilots be aware not only
of equipment capabilities, but also equipment limitations in
order to manage those systems effectively and safely.
Information Workload
Information workloads and automated systems, such as
autopilots, need to be properly managed to ensure a safe
1-15
Figure 1-11. The Margin of Safety.
fl ight. The pilot fl ying in IMC is faced with many tasks, each
with a different level of importance to the outcome of the
fl ight. For example, a pilot preparing to execute an instrument
approach to an airport needs to review the approach chart,
prepare the aircraft for the approach and landing, complete
checklists, obtain information from Automatic Terminal
Information Service (ATIS) or air traffi c control (ATC), and
set the navigation radios and equipment.
The pilot who effectively manages his or her workload
will complete as many of these tasks as early as possible
to preclude the possibility of becoming overloaded by last
minute changes and communication priorities in the later,
more critical stages of the approach. Figure 1-11 shows the
margin of safety is at the minimum level during this stage
of the approach. Routine tasks delayed until the last minute
can contribute to the pilot becoming overloaded and stressed,
resulting in erosion of performance.
By planning ahead, a pilot can effectively reduce workload
during critical phases of fl ight. If a pilot enters the fi nal
phases of the instrument approach unprepared, the pilot
should recognize the situation, abandon the approach, and
try it again after becoming better prepared. Effective resource
management includes recognizing hazardous situations and
attitudes, decision-making to promote good judgment and
headwork, and managing the situation to ensure the safe
outcome of the IFR fl ight.
Task Management
Pilots have a limited capacity for information. Once
information fl ow exceeds the pilot’s ability to mentally
process the information any additional information will
become unattended or displace other tasks and information
already being processed. This is termed channel capacity and
once reached only two alternatives exist: shed the unimportant
tasks or perform all tasks at a less than optimal level. Like an
electrical circuit being overloaded, either the consumption
must be reduced or a circuit failure is experienced.
The pilot who effectively manages the tasks and properly
prioritizes them will have a successful fl ight. For example,
do not become distracted and fi xate on an instrument light
failure. This unnecessary focus displaces capability and
prevents the pilot’s ability to appreciate tasks of greater
importance. By planning ahead, a pilot can effectively reduce
workload during critical phases of a fl ight.
Aeronautical Decision-Making (ADM)
Flying safely requires the effective integration of three
separate sets of skills. Most obvious are the basic stick-andrudder
skills needed to control the airplane. Next, are skills
related to profi cient operation of aircraft systems, and last,
but not least, are ADM skills.
ADM is a systematic approach to the mental process used
by pilots to consistently determine the best course of action
in response to a given set of circumstances. The importance
of learning effective ADM skills cannot be overemphasized.
While progress is continually being made in the advancement
of pilot training methods, airplane equipment and systems, and
services for pilots, accidents still occur. Despite all the changes
in technology to improve fl ight safety, one factor remains the
same—the human factor. While the FAA strives to eliminate
errors through training and safety programs, one fact remains:
humans make errors. It is estimated that approximately 80
percent of all aviation accidents are human factors related.
1-16
The ADM process addresses all aspects of decision making
in the fl ight deck and identifi es the steps involved in good
decision making. While the ADM process will not eliminate
errors, it will help the pilot recognize errors, and in turn
enable the pilot to manage the error to minimize its effects.
These steps are:
1. Identifying personal attitudes hazardous to safe
fl ight;
2. Learning behavior modifi cation techniques;
3. Learning how to recognize and cope with stress;
4. Developing risk assessment skills;
5. Using all resources; and
6. Evaluating the effectiveness of one’s ADM skills.
Historically, the term “pilot error” has been used to describe
the causes of these accidents. Pilot error means that an action
or decision made by the pilot was the cause, or a contributing
factor that led to the accident. This defi nition also includes
the pilot’s failure to make a decision or take action. From
a broader perspective, the phrase “human factors related”
more aptly describes these accidents since it is usually not a
single decision that leads to an accident, but a chain of events
triggered by a number of factors.
The poor judgment chain, sometimes referred to as the “error
chain,” is a term used to describe this concept of contributing
factors in a human factors related accident. Breaking one link
in the chain normally is all that is necessary to change the
outcome of the sequence of events.
The Decision-Making Process
An understanding of the decision-making process provides
a pilot with a foundation for developing ADM skills.
Some situations, such as engine failures, require a pilot to
respond immediately using established procedures with a
little time for detailed analysis. This is termed automatic
decision-making and is based upon training, experience, and
recognition. Traditionally, pilots have been well trained to
react to emergencies, but are not as well prepared to make
decisions requiring a more refl ective response where greater
analysis is required. Typically during a fl ight, there is time
to examine any changes that occur, gather information, and
assess risk before reaching a decision. The steps leading to
this conclusion constitute the decision-making process.
Defi ning the Problem
Problem defi nition is the fi rst step in the decision-making
process. Defi ning the problem begins with recognizing that
a change has occurred or that an expected change did not
occur. A problem is perceived fi rst by the senses, then is
distinguished through insight and experience. One critical
error that can be made during the decision-making process
is incorrectly defi ning the problem. For example, a low oil
pressure reading could indicate that the engine is about to
fail and an emergency landing should be planned, or it could
mean that the oil pressure sensor has failed. The actions to be
taken in each of these circumstances would be signifi cantly
different. One requires an immediate decision based upon
training, experience, and evaluation of the situation; whereas
the latter decision is based upon an analysis. It should be
noted that the same indication could result in two different
actions depending upon other infl uences.
Choosing a Course of Action
After the problem has been identifi ed, the pilot must evaluate
the need to react to it and determine the actions that may
be taken to resolve the situation in the time available.
The expected outcome of each possible action should be
considered and the risks assessed before deciding on a
response to the situation.
Implementing the Decision and Evaluating the
Outcome
Although a decision may be reached and a course of action
implemented, the decision-making process is not complete.
It is important to think ahead and determine how the decision
could affect other phases of fl ight. As the fl ight progresses, the
pilot must continue to evaluate the outcome of the decision
to ensure that it is producing the desired result.
Improper Decision-Making Outcomes
Pilots sometimes get in trouble not because of defi cient basic
skills or system knowledge, but rather because of faulty
decision-making skills. Although aeronautical decisions
may appear to be simple or routine, each individual decision
in aviation often defi nes the options available for the next
decision the pilot must make and the options, good or
bad, they provide. Therefore, a poor decision early on in
a fl ight can compromise the safety of the fl ight at a later
time necessitating decisions that must be more accurate and
decisive. Conversely, good decision-making early on in an
emergency provide greater latitude for options later on.
FAA Advisory Circular (AC) 60-22, defi nes ADM as a
systematic approach to the mental process of evaluating a
given set of circumstances and determining the best course of
action. ADM thus builds upon the foundation of conventional
decision-making, but enhances the process to decrease
the probability of pilot error. Specifi cally, ADM provides
a structure to help the pilot use all resources to develop
comprehensive situational awareness.
1-17
Figure 1-12. The 3P Model for Aeronautical Decision-Making.
Models for Practicing ADM
Two models for practicing ADM are presented below.
Perceive, Process, Perform
The Perceive–Process–Perform (3P) model for ADM offers
a simple, practical, and systematic approach that can be
used during all phases of fl ight. To use it,
the pilot will:
• Perceive the given set of circumstances for a fl ight;
• Process by evaluating their impact on fl ight safety;
and
• Perform by implementing the best course of action.
In the fi rst step, the goal is to develop situational awareness
by perceiving hazards, which are present events, objects, or
circumstances that could contribute to an undesired future
event. In this step, the pilot will systematically identify and
list hazards associated with all aspects of the fl ight: pilot,
aircraft, environment, and external pressures. It is important
to consider how individual hazards might combine. Consider,
for example, the hazard that arises when a new instrument
pilot with no experience in actual instrument conditions wants
to make a cross-country fl ight to an airport with low ceilings
in order to attend an important business meeting.
In the second step, the goal is to process this information
to determine whether the identifi ed hazards constitute risk,
which is defi ned as the future impact of a hazard that is not
controlled or eliminated. The degree of risk posed by a given
hazard can be measured in terms of exposure (number of
people or resources affected), severity (extent of possible
loss), and probability (the likelihood that a hazard will cause
a loss). If the hazard is low ceilings, for example, the level
of risk depends on a number of other factors, such as pilot
training and experience, aircraft equipment and fuel capacity,
and others.
In the third step, the goal is to perform by taking action to
eliminate hazards or mitigate risk, and then continuously
evaluate the outcome of this action. With the example of low
ceilings at destination, for instance, the pilot can perform
good ADM by selecting a suitable alternate, knowing where
to fi nd good weather, and carrying suffi cient fuel to reach
it. This course of action would mitigate the risk. The pilot
also has the option to eliminate it entirely by waiting for
better weather.
Once the pilot has completed the 3P decision process and
selected a course of action, the process begins anew because
now the set of circumstances brought about by the course of
action requires analysis. The decision-making process is a
continuous loop of perceiving, processing and performing.
The DECIDE Model
Another structured approach to ADM is the DECIDE model,
which is a six-step process intended to provide a logical
way of approaching decision-making. As in the 3P model,
the elements of the DECIDE model represent a continuous
loop process to assist a pilot in the decision-making
required when faced with a situational change that requires
judgment. The model is primarily focused
on the intellectual component, but can have an impact on
the motivational component of judgment as well. If a pilot
continually uses the DECIDE Model in all decision-making,
it becomes natural and results in better decisions being made
under all types of situations. The steps in this approach are
listed in Figure 1-13C.
In conventional decision-making, the need for a decision is
triggered by recognition that something has changed or an
expected change did not occur. Recognition of the change,
or lack of change, is a vital step in any decision making
process. Not noticing change in a situation can lead directly
to a mishap. The change indicates that an
appropriate response or action is necessary in order to modify
the situation (or, at least, one of the elements that comprise it)
and bring about a desired new situation. Therefore, situational
awareness is the key to successful and safe decision making.
At this point in the process, the pilot is faced with a need to
evaluate the entire range of possible responses to the detected
change and to determine the best course of action.
Figure 1-13B illustrates how the ADM process expands
conventional decision-making, shows the interactions of the 1-18
Figure 1-13. Decision-Making.
ADM steps, and how these steps can produce a safe outcome.
Starting with the recognition of change, and following with an
assessment of alternatives, a decision to act or not act is made,
and the results are monitored. Pilots can use ADM to enhance
their conventional decision-making process because it:
1. Increases their awareness of the importance of attitude
in decision-making;
2. Teaches the ability to search for and establish relevance
of information; and
3. Increases their motivation to choose and execute actions
that ensure safety in the situational timeframe.
Hazardous Attitudes and Antidotes
Hazardous attitudes, which contribute to poor pilot judgment,
can be effectively counteracted by redirecting that hazardous
attitude so that correct action can be taken. Recognition of
hazardous thoughts is the fi rst step toward neutralizing them.
After recognizing a thought as hazardous, the pilot should
label it as hazardous, then state the corresponding antidote.
Antidotes should be memorized for each of the hazardous
attitudes so they automatically come to mind when needed.
Each hazardous attitude along with its appropriate antidote
is shown in Figure 1-14.
1-19
Figure 1-14. The Five Antidotes to Hazardous Attitudes.
Research has identifi ed fi ve hazardous attitudes that can affect
a pilot’s judgment, as well as antidotes for each of these fi ve
attitudes. ADM addresses the following:
1. Anti-authority (“Don’t tell me!”). This attitude is
found in pilots who do not like anyone telling them
what to do. They may be resentful of having someone
tell them what to do or may regard rules, regulations,
and procedures as silly or unnecessary. However, there
is always the prerogative to question authority if it is
perceived to be in error.
2. Impulsivity (“Do something quickly!”). This attitude
is found in pilots who frequently feel the need to do
something—anything—immediately. They do not
stop to think about what they are about to do, they do
not select the best course of action, and they do the
fi rst thing that comes to mind.
3. Invulnerability (“It won’t happen to me!”). Many
pilots feel that accidents happen to others, but never
to them. They know accidents can happen, and they
know that anyone can be affected. They never really
feel or believe that they will be personally involved.
Pilots who think this way are more likely to take
chances and increase risk.
4. Macho (“I can do it!”). Pilots who are always trying to
prove that they are better than anyone else are thinking,
“I can do it—I’ll show them.” Pilots with this type of
attitude will try to prove themselves by taking risks in
order to impress others. This pattern is characteristic
in both men and women.
5. Resignation (“What’s the use?”). These pilots do not
see themselves as being able to make a great deal of
difference in what happens to them. When things go
well, these pilots are apt to think it is due to good luck.
When things go badly, they may feel that someone is
out to get them, or attribute it to bad luck. The pilot
will leave the action to others, for better or worse.
Sometimes, they will even go along with unreasonable
requests just to be a “nice guy.”
1-20
2-1
Introduction
Several factors affect aircraft performance including the
atmosphere, aerodynamics, and aircraft icing. Pilots need an
understanding of these factors for a sound basis for prediction
of aircraft response to control inputs, especially with regard
to instrument approaches, while holding, and when operating
at reduced airspeed in instrument meteorological conditions
(IMC). Although these factors are important to the pilot fl ying
visual fl ight rules (VFR), they must be even more thoroughly
understood by the pilot operating under instrument fl ight
rules (IFR). Instrument pilots rely strictly on instrument
indications to precisely control the aircraft; therefore, they
must have a solid understanding of basic aerodynamic
principles in order to make accurate judgments regarding
aircraft control inputs.
Aerodynamic
Factors
Chapter 2
2-2
Figure 2-1. The Airfoil.
Figure 2-2. Angle of Attack and Relative Wind.
The Wing
To understand aerodynamic forces, a pilot needs to
understand basic terminology associated with airfoils.
Figure 2-1 illustrates a typical airfoil.
The chord line is the straight line intersecting the leading
and trailing edges of the airfoil, and the term chord refers
to the chord line longitudinal length (length as viewed from
the side).
The mean camber is a line located halfway between the
upper and lower surfaces. Viewing the wing edgewise, the
mean camber connects with the chord line at each end. The
mean camber is important because it assists in determining
aerodynamic qualities of an airfoil. The measurement of
the maximum camber; inclusive of both the displacement
of the mean camber line and its linear measurement from
the end of the chord line, provide properties useful in
evaluating airfoils.
Review of Basic Aerodynamics
The instrument pilot must understand the relationship
and differences between several factors that affect the
performance of an aircraft in fl ight. Also, it is crucial to
understand how the aircraft reacts to various control and
power changes, because the environment in which instrument
pilots fl y has inherent hazards not found in visual fl ying. The
basis for this understanding is found in the four forces acting
on an aircraft and Newton’s Three Laws of Motion.
Relative Wind is the direction of the airfl ow with respect to
an airfoil.
Angle of Attack is the acute angle measured between the
relative wind, or fl ight path and the chord of the airfoil.
Flight path is the course or track along which the aircraft is
fl ying or is intended to be fl own.
The Four Forces
The four basic forces acting upon an aircraft in
fl ight are lift, weight, thrust, and drag.
Lift
Lift is a component of the total aerodynamic force on an
airfoil and acts perpendicular to the relative wind. Relative
wind is the direction of the airfl ow with respect to an airfoil.
This force acts straight up from the average (called mean)
center of pressure (CP), which is called the center of lift. It
should be noted that it is a point along the chord line of an
airfoil through which all aerodynamic forces are considered
to act. The magnitude of lift varies proportionately with
speed, air density, shape and size of the airfoil, and angle
of attack. During straight-and-level fl ight, lift and weight
are equal.
2-3
Figure 2-3. The Four Forces and Three Axes of Rotation.
Weight
Weight is the force exerted by an aircraft from the pull of
gravity. It acts on an aircraft through its center of gravity
(CG) and is straight down. This should not be confused
with the center of lift, which can be signifi cantly different
from the CG. As an aircraft is descending, weight is greater
than lift.
Thrust
Thrust is a force that drives an aircraft through the air and can
be measured in thrust and/or horsepower. It is a component
that is parallel to the center of thrust and overcomes drag
providing the aircraft with its forward speed component.
Drag
Drag is the net aerodynamic force parallel to the relative
wind and is generally a sum of two components: induced
drag and parasite drag.
Induced drag
Induced drag is caused from the creation of lift and increases
with airspeed. Therefore, if the wing is not producing lift,
induced drag is zero. Conversely, induced drag increases
with airspeed. Parasite drag
Parasite drag is all drag not caused from the production of
lift. Parasite drag is created by displacement of air by the
aircraft, turbulence generated by the airfoil, and the hindrance
of airfl ow as it passes over the surface of the aircraft or
components. All of these forces create drag not from the
production of lift but the movement of an object through an
air mass. Parasite drag increases with speed and includes skin
friction drag, interference drag, and form drag.
• Skin Friction Drag
Covering the entire “wetted” surface of the aircraft is a thin
layer of air called a boundary layer. The air molecules on the
surface have zero velocity in relation to the surface; however,
the layer just above moves over the stagnant molecules
below because it is pulled along by a third layer close to
the free stream of air. The velocities of the layers increase
as the distance from the surface increases until free stream
velocity is reached, but all are affected by the free stream.
The distance (total) between the skin surface and where free
stream velocity is reached is called the boundary layer. At
subsonic levels the cumulative layers are about the thickness
of a playing card, yet their motion sliding over one another
creates a drag force. This force retards motion due to the
viscosity of the air and is called skin friction drag. Because
skin friction drag is related to a large surface area its affect
on smaller aircraft is small versus large transport aircraft
where skin friction drag may be considerable.
• Interference Drag
Interference drag is generated by the collision of airstreams
creating eddy currents, turbulence, or restrictions to smooth
fl ow. For instance, the airfl ow around a fuselage and around
the wing meet at some point, usually near the wing’s root.
These airfl ows interfere with each other causing a greater
2-4
Figure 2-4. Newton’s First Law of Motion: the Law of Inertia.
drag than the individual values. This is often the case when
external items are placed on an aircraft. That is, the drag of
each item individually, added to that of the aircraft, are less
than that of the two items when allowed to interfere with
one another.
• Form Drag
Form drag is the drag created because of the shape of a
component or the aircraft. If one were to place a circular
disk in an air stream, the pressure on both the top and bottom
would be equal. However, the airfl ow starts to break down
as the air fl ows around the back of the disk. This creates
turbulence and hence a lower pressure results. Because the
total pressure is affected by this reduced pressure, it creates
a drag. Newer aircraft are generally made with consideration
to this by fairing parts along the fuselage (teardrop) so that
turbulence and form drag is reduced.
Total lift must overcome the total weight of the aircraft, which
is comprised of the actual weight and the tail-down force used
to control the aircraft’s pitch attitude. Thrust must overcome
total drag in order to provide forward speed with which to
produce lift. Understanding how the aircraft’s relationship
between these elements and the environment provide proper
interpretation of the aircraft’s instruments.
Newton’s First Law, the Law of Inertia
Newton’s First Law of Motion is the Law of Inertia. It states
that a body at rest will remain at rest, and a body in motion
will remain in motion, at the same speed and in the same
direction until affected by an outside force. The force with
which a body offers resistance to change is called the force of
inertia. Two outside forces are always present on an aircraft
in fl ight: gravity and drag. The pilot uses pitch and thrust
controls to counter or change these forces to maintain the
desired fl ight path. If a pilot reduces power while in straightand-
level fl ight, the aircraft will slow due to drag. However,
as the aircraft slows there is a reduction of lift, which causes
the aircraft to begin a descent due to gravity.
Newton’s Second Law, the Law of Momentum
Newton’s Second Law of Motion is the Law of Momentum,
which states that a body will accelerate in the same direction
as the force acting upon that body, and the acceleration
will be directly proportional to the net force and inversely
proportional to the mass of the body. Acceleration refers
either to an increase or decrease in velocity, although
deceleration is commonly used to indicate a decrease. This
law governs the aircraft’s ability to change fl ight path and
speed, which are controlled by attitude (both pitch and bank)
and thrust inputs. Speeding up, slowing down, entering
climbs or descents, and turning are examples of accelerations
that the pilot controls in everyday fl ight.
Newton’s Third Law, the Law of Reaction
Newton’s Third Law of Motion is the Law of Reaction,
which states that for every action there is an equal and
opposite reaction. As shown in Figure 2-6, the action of
the jet engine’s thrust or the pull of the propeller lead to the
reaction of the aircraft’s forward motion. This law is also
responsible for a portion of the lift that is produced by a wing,
from the downward defl ection of the airfl ow around it. This
downward force of the relative wind results in an equal but
opposite (upward) lifting force created by the airfl ow over
the wing.
Atmosphere
The atmosphere is the envelope of air which surrounds the
Earth. A given volume of dry air contains about 78 percent
nitrogen, 21 percent oxygen, and about 1 percent other gases
such as argon, carbon dioxide, and others to a lesser degree.
Although seemingly light, air does have weight and a one
square inch column of the atmosphere at sea level weighs
approximately 14.7 pounds. About one-half of the air by
weight is within the fi rst 18,000 feet. The remainder of the air
is spread over a vertical distance in excess of 1,000 miles.
Air density is a result of the relationship between temperature
and pressure. Air density is inversely related to temperature
and directly related to pressure. For a constant pressure to be
2-5
Figure 2-5. Newton’s Second Law of Motion: the Law of Figure 2-6. Newton’s Third Law of Motion: the Law of Reaction.
Momentum.
maintained as temperature increases, density must decrease,
and vice versa. For a constant temperature to be maintained
as pressure increases, density must increase, and vice versa.
These relationships provide a basis for understanding
instrument indications and aircraft performance.
Layers of the Atmosphere
There are several layers to the atmosphere with the
troposphere being closest to the Earth’s surface extending to
about 60,000 feet. Following is the stratosphere, mesosphere,
ionosphere, thermosphere, and fi nally the exosphere. The
tropopause is the thin layer between the troposphere and
the stratosphere. It varies in both thickness and altitude but
is generally defi ned where the standard lapse (generally
accepted at 2° C per 1,000 feet) decreases signifi cantly
(usually down to 1° C or less).
International Standard Atmosphere (ISA)
The International Civil Aviation Organization (ICAO)
established the ICAO Standard Atmosphere as a way
of creating an international standard for reference and
performance computations. Instrument indications and
aircraft performance specifi cations are derived using this
standard as a reference. Because the standard atmosphere is
a derived set of conditions that rarely exist in reality, pilots
need to understand how deviations from the standard affect
both instrument indications and aircraft performance.
In the standard atmosphere, sea level pressure is 29.92" inches
of mercury (Hg) and the temperature is 15° C (59° F). The
standard lapse rate for pressure is approximately a 1" Hg
decrease per 1,000 feet increase in altitude. The standard lapse
rate for temperature is a 2° C (3.6° F) decrease per 1,000 feet
increase, up to the top of the stratosphere. Since all aircraft
performance is compared and evaluated in the environment
of the standard atmosphere, all aircraft performance
instrumentation is calibrated for the standard atmosphere.
Because the actual operating conditions rarely, if ever, fi t the
standard atmosphere, certain corrections must apply to the
instrumentation and aircraft performance. For instance, at
10,000 ISA predicts that the air pressure should be 19.92" Hg
(29.92" - 10" Hg = 19.92") and the outside temperature at -5°C
(15° C - 20° C). If the temperature or the pressure is different
than the International Standard Atmosphere (ISA) prediction
an adjustment must be made to performance predictions and
various instrument indications.
Pressure Altitude
There are two measurements of the atmosphere that affect
performance and instrument calibrations: pressure altitude
and density altitude. Pressure altitude is the height above the
standard datum pressure (SDP) (29.92" Hg, sea level under
ISA) and is used for standardizing altitudes for fl ight levels
(FL). Generally, fl ight levels are at or above 18,000 feet
(FL 180), providing the pressure is at or above 29.92"Hg.
For calculations involving aircraft performance when the
altimeter is set for 29.92" Hg, the altitude indicated is the
pressure altitude.
Density Altitude
Density altitude is pressure altitude corrected for nonstandard
temperatures, and is used for determining aerodynamic
performance in the nonstandard atmosphere. Density altitude
increases as the density decreases. Since density varies
directly with pressure, and inversely with temperature, a
wide range of temperatures may exist with a given pressure
altitude, which allows the density to vary. However, a
known density occurs for any one temperature and pressure
altitude combination. The density of the air has a signifi cant
effect on aircraft and engine performance. Regardless of the
2-6
Figure 2-7. Relationship of Lift to Angle of Attack.
actual altitude above sea level an aircraft is operating at, its
performance will be as though it were operating at an altitude
equal to the existing density altitude.
If a chart is not available the density altitude can be estimated
by adding 120 feet for every degree Celsius above the ISA. For
example, at 3,000 feet pressure altitude (PA), the ISA prediction
is 9° C (15° C - ).
However, if the actual temperature is 20° C (11° C more than
that predicted by ISA) then the difference of 11° C is multiplied
by 120 feet equaling 1,320. Adding this fi gure to the original
3,000 feet provides a density altitude of 4,320 feet (3,000 feet
+ 1,320 feet).
Lift
Lift always acts in a direction perpendicular to the relative
wind and to the lateral axis of the aircraft. The fact that lift is
referenced to the wing, not to the Earth’s surface, is the source
of many errors in learning fl ight control. Lift is not always
“up.” Its direction relative to the Earth’s surface changes as
the pilot maneuvers the aircraft.
The magnitude of the force of lift is directly proportional to
the density of the air, the area of the wings, and the airspeed. It
also depends upon the type of wing and the angle of attack. Lift
increases with an increase in angle of attack up to the stalling
angle, at which point it decreases with any further increase
in angle of attack. In conventional aircraft, lift is therefore
controlled by varying the angle of attack and speed.
Pitch/Power Relationship
An examination of Figure 2-7 illustrates the relationship
between pitch and power while controlling fl ight path and
airspeed. In order to maintain a constant lift, as airspeed is
reduced, pitch must be increased. The pilot controls pitch
through the elevators, which control the angle of attack.
When back pressure is applied on the elevator control, the tail
lowers and the nose rises, thus increasing the wing’s angle of
attack and lift. Under most conditions the elevator is placing
downward pressure on the tail. This pressure requires energy
that is taken from aircraft performance (speed). Therefore,
when the CG is closer to the aft portion of the aircraft the
elevator downward forces are less. This results in less energy
used for downward forces, in turn resulting in more energy
applied to aircraft performance.
Thrust is controlled by using the throttle to establish or
maintain desired airspeeds. The most precise method
of controlling flight path is to use pitch control while
simultaneously using power (thrust) to control airspeed. In
order to maintain a constant lift, a change in pitch requires a
change in power, and vice versa.
If the pilot wants the aircraft to accelerate while maintaining
altitude, thrust must be increased to overcome drag. As
the aircraft speeds up, lift is increased. To prevent gaining
altitude, the pitch angle must be lowered to reduce the
angle of attack and maintain altitude. To decelerate while
maintaining altitude, thrust must be decreased to less than the
value of drag. As the aircraft slows down, lift is reduced. To
prevent losing altitude, the pitch angle must be increased in
order to increase the angle of attack and maintain altitude.
Drag Curves
When induced drag and parasite drag are plotted on a graph,
the total drag on the aircraft appears in the form of a “drag
curve.” Graph A of Figure 2-8 shows a curve based on thrust
versus drag, which is primarily used for jet aircraft. Graph B
of Figure 2-8 is based on power versus drag, and it is used
for propeller-driven aircraft. This chapter focuses on power
versus drag charts for propeller-driven aircraft.
Understanding the drag curve can provide valuable insight
into the various performance parameters and limitations of
the aircraft. Because power must equal drag to maintain a
steady airspeed, the curve can be either a drag curve or a
power required curve. The power required curve represents
the amount of power needed to overcome drag in order to
maintain a steady speed in level fl ight.
The propellers used on most reciprocating engines achieve
peak propeller effi ciencies in the range of 80 to 88 percent.
As airspeed increases, the propeller effi ciency increases until
it reaches its maximum. Any airspeed above this maximum
point causes a reduction in propeller effi ciency. An engine
that produces 160 horsepower will have only about 80
percent of that power converted into available horsepower,
2-7
Figure 2-8. Thrust and Power Required Curves.
Figure 2-9. Regions of Command.
approximately 128 horsepower. The remainder is lost energy.
This is the reason the thrust and power available curves
change with speed.
Regions of Command
The drag curve also illustrates the two regions of command:
the region of normal command, and the region of reversed
command. The term “region of command” refers to the
relationship between speed and the power required to
maintain or change that speed. “Command” refers to the input
the pilot must give in terms of power or thrust to maintain a
new speed once reached.
The “region of normal command” occurs where power must
be added to increase speed. This region exists at speeds higher
than the minimum drag point primarily as a result of parasite
drag. The “region of reversed command” occurs where
additional power is needed to maintain a slower airspeed.
This region exists at speeds slower than the minimum drag
point (L/DMAX on the thrust required curve, Figure 2-8) and
is primarily due to induced drag. Figure 2-9 shows how one
power setting can yield two speeds, points 1 and 2. This is
because at point 1 there is high induced drag and low parasite
drag, while at point 2 there is high parasite drag and low
induced drag.
Control Characteristics
Most fl ying is conducted in the region of normal command:
for example, cruise, climb, and maneuvers. The region of
reversed command may be encountered in the slow-speed
phases of fl ight during takeoff and landing; however, for
most general aviation aircraft, this region is very small and
is below normal approach speeds.
Flight in the region of normal command is characterized
by a relatively strong tendency of the aircraft to maintain
the trim speed. Flight in the region of reversed command is
characterized by a relatively weak tendency of the aircraft to
maintain the trim speed. In fact, it is likely the aircraft exhibits
no inherent tendency to maintain the trim speed in this area.
For this reason, the pilot must give particular attention to
precise control of airspeed when operating in the slow-speed
phases of the region of reversed command.
Operation in the region of reversed command does not imply
that great control diffi culty and dangerous conditions exist.
However, it does amplify errors of basic fl ying technique—
making proper fl ying technique and precise control of the
aircraft very important.
Speed Stability
Normal Command
The characteristics of fl ight in the region of normal command
are illustrated at point A on the curve in Figure 2-10. If the
aircraft is established in steady, level fl ight at point A, lift is
equal to weight, and the power available is set equal to the
power required. If the airspeed is increased with no changes
2-8
Figure 2-10. Region of Speed Stability.
to the power setting, a power defi ciency exists. The aircraft
has a natural tendency to return to the initial speed to balance
power and drag. If the airspeed is reduced with no changes
to the power setting, an excess of power exists. The aircraft
has a natural tendency to speed up to regain the balance
between power and drag. Keeping the aircraft in proper
trim enhances this natural tendency. The static longitudinal
stability of the aircraft tends to return the aircraft to the
original trimmed condition.
An aircraft fl ying in steady, level fl ight at point C is in
equilibrium. If the speed were increased
or decreased slightly, the aircraft would tend to remain at
that speed. This is because the curve is relatively fl at and
a slight change in speed does not produce any signifi cant
excess or defi ciency in power. It has the characteristic of
neutral stability, i.e., the aircraft’s tendency is to remain at
the new speed.
Reversed Command
The characteristics of fl ight in the region of reversed command
are illustrated at point B on the curve in Figure 2-10. If the
aircraft is established in steady, level fl ight at point B, lift is
equal to weight, and the power available is set equal to the
power required. When the airspeed is increased greater than
point B, an excess of power exists. This causes the aircraft
to accelerate to an even higher speed. When the aircraft is
slowed to some airspeed lower than point B, a defi ciency
of power exists. The natural tendency of the aircraft is to
continue to slow to an even lower airspeed. This tendency toward instability happens because the
variation of excess power to either side of point B magnifi es
the original change in speed. Although the static longitudinal
stability of the aircraft tries to maintain the original trimmed
condition, this instability is more of an infl uence because of
the increased induced drag due to the higher angles of attack
in slow-speed fl ight.
Trim
The term trim refers to employing adjustable aerodynamic
devices on the aircraft to adjust forces so the pilot does not
have to manually hold pressure on the controls. One means is
to employ trim tabs. A trim tab is a small, adjustable hinged
surface, located on the trailing edge of the elevator, aileron,
or rudder control surfaces. (Some aircraft use adjustable
stabilizers instead of trim tabs for pitch trim.) Trimming is
accomplished by defl ecting the tab in the direction opposite
to that in which the primary control surface must be held.
The force of the airfl ow striking the tab causes the main
control surface to be defl ected to a position that corrects the
unbalanced condition of the aircraft.
Because the trim tabs use airfl ow to function, trim is a
function of speed. Any change in speed results in the need
to re-trim the aircraft. An aircraft properly trimmed in pitch
seeks to return to the original speed before the change. It is
very important for instrument pilots to keep the aircraft in
constant trim. This reduces the pilot’s workload signifi cantly,
allowing attention to other duties without compromising
aircraft control.
Slow-Speed Flight
Anytime an aircraft is fl ying near the stalling speed or the
region of reversed command, such as in fi nal approach for a
normal landing, the initial part of a go around, or maneuvering
in slow fl ight, it is operating in what is called slow-speed
fl ight. If the aircraft weighs 4,000 pounds, the lift produced
by the aircraft must be 4,000 pounds. When lift is less
than 4,000 pounds, the aircraft is no longer able to sustain
level fl ight, and consequently descends. During intentional
descents, this is an important factor and is used in the total
control of the aircraft.
However, because lift is required during low speed fl ight
and is characterized by high angles of attack, fl aps or other
high lift devices are needed to either change the camber of
the airfoil, or delay the boundary level separation. Plain
and split fl aps are most commonly used to
change the camber of an airfoil. It should be noted that with
the application of fl aps, the aircraft will stall at a lower
angle of attack. The basic wing stalls at 18° without fl aps
but with the application of the fl aps extended (to CL-MAX
position) the new angle of attack at which point the aircraft
will stall is 15°. However, the value of lift (fl aps extended
to the CL-MAX position) produces more lift than lift at 18°
on the basic wing.
Delaying the boundary layer separation is another way to
increase CL-MAX. Several methods are employed (such as
suction and use of a blowing boundary layer control), but the
2-9
Figure 2-11. Various Types of Flaps. Figure 2-12. Vortex Generators.
If allowed to slow several knots, the airplane could enter
the region of reversed command. At this point, the airplane
could develop an unsafe sink rate and continue to lose speed
unless the pilot takes a prompt corrective action. Proper pitch
and power coordination is critical in this region due to speed
instability and the tendency of increased divergence from
the desired speed.
Large Airplanes
Pilots of larger airplanes with higher stall speeds may fi nd the
speed they maintain on the instrument approach is near 1.3
VSO, putting them near point C the entire time
the airplane is on the fi nal approach segment. In this case,
precise speed control is necessary throughout the approach. It
may be necessary to temporarily select excessive, or defi cient
thrust in relation to the target thrust setting in order to quickly
correct for airspeed deviations.
most common device used on general aviation light aircraft
is the vortex generator. Small strips of metal placed along
the wing (usually in front of the control surfaces) create
turbulence. The turbulence in turn mixes high energy air from
outside the boundary layer with boundary layer air. The effect
is similar to other boundary layer devices.
Small Airplanes
Most small airplanes maintain a speed well in excess of 1.3
times VSO on an instrument approach. An airplane with a
stall speed of 50 knots (VSO) has a normal approach speed
of 65 knots. However, this same airplane may maintain 90
knots (1.8 VSO) while on the fi nal segment of an instrument
approach. The landing gear will most likely be extended at
the beginning of the descent to the minimum descent altitude,
or upon intercepting the glide slope of the instrument landing
system. The pilot may also select an intermediate fl ap setting
for this phase of the approach. The airplane at this speed has
good positive speed stability, as represented by point A on
Figure 2-10. Flying in this regime permits the pilot to make
slight pitch changes without changing power settings, and
accept minor speed changes knowing that when the pitch is
returned to the initial setting, the speed returns to the original
setting. This reduces the pilot’s workload.
Aircraft are usually slowed to a normal landing speed when
on the fi nal approach just prior to landing. When slowed to
65 knots, (1.3 VSO), the airplane will be close to point C.
At this point, precise control of the pitch and
power becomes more crucial for maintaining the correct speed.
Pitch and power coordination is necessary because the speed
stability is relatively neutral since the speed tends to remain
at the new value and not return to the original setting. In
addition to the need for more precise airspeed control, the pilot
normally changes the aircraft’s confi guration by extending
landing fl aps. This confi guration change means the pilot must
be alert to unwanted pitch changes at a low altitude.
2-10
Figure 2-13. Forces In a Turn.
Turns
Like any moving object, an aircraft requires a sideward force
to make it turn. In a normal turn, this force is supplied by
banking the aircraft in order to exert lift inward, as well as
upward. The force of lift is separated into two components
at right angles to each other. The upward
acting lift together with the opposing weight becomes the
vertical lift component. The horizontally acting lift and its
opposing centrifugal force are the horizontal lift component,
or centripetal force. This horizontal lift component is the
sideward force that causes an aircraft to turn. The equal and
opposite reaction to this sideward force is centrifugal force,
which is merely an apparent force as a result of inertia.
The relationship between the aircraft’s speed and bank angle
to the rate and radius of turns is important for instrument
pilots to understand. The pilot can use this knowledge to
properly estimate bank angles needed for certain rates of
turn, or to determine how much to lead when intercepting
a course.
Rate of Turn
The rate of turn, normally measured in degrees per second,
is based upon a set bank angle at a set speed. If either one of
these elements changes, the rate of turn changes. If the aircraft
increases its speed without changing the bank angle, the rate
of turn decreases. Likewise, if the speed decreases without
changing the bank angle, the rate of turn increases.
Changing the bank angle without changing speed also causes
the rate of turn to change. Increasing the bank angle without
changing speed increases the rate of turn, while decreasing
the bank angle reduces the rate of turn.
For example, a pilot is on an instrument approach at 1.3
VSO, a speed near L/DMAX, and knows that a certain power
setting maintains that speed. The airplane slows several knots
below the desired speed because of a slight reduction in the
power setting. The pilot increases the power slightly, and the
airplane begins to accelerate, but at a slow rate. Because the
airplane is still in the “fl at part” of the drag curve, this slight
increase in power will not cause a rapid return to the desired
speed. The pilot may need to increase the power higher
than normally needed to maintain the new speed, allow the
airplane to accelerate, then reduce the power to the setting
that maintains the desired speed.
Climbs
The ability for an aircraft to climb depends upon an excess
power or thrust over what it takes to maintain equilibrium.
Excess power is the available power over and above that
required to maintain horizontal fl ight at a given speed.
Although the terms power and thrust are sometimes
used interchangeably (erroneously implying they are
synonymous), distinguishing between the two is important
when considering climb performance. Work is the product of
a force moving through a distance and is usually independent
of time. Power implies work rate or units of work per unit of
time, and as such is a function of the speed at which the force
is developed. Thrust, also a function of work, means the force
which imparts a change in the velocity of a mass.
During take off, the aircraft does not stall even though it
may be in a climb near the stall speed. The reason is that
excess power (used to produce thrust) is used during this
fl ight regime. Therefore, it is important if an engine fails
after take off, to compensate the loss of thrust with pitch
and airspeed.
For a given weight of the aircraft, the angle of climb depends
on the difference between thrust and drag, or the excess
thrust. When the excess thrust is zero, the inclination of the
fl ight path is zero, and the aircraft is in steady, level fl ight.
When thrust is greater than drag, the excess thrust allows a
climb angle depending on the amount of excess thrust. When
thrust is less than drag, the defi ciency of thrust induces an
angle of descent.
Acceleration in Cruise Flight
Aircraft accelerate in level fl ight because of an excess of
power over what is required to maintain a steady speed. This
is the same excess power used to climb. Upon reaching the
desired altitude with pitch being lowered to maintain that
altitude, the excess power now accelerates the aircraft to its
cruise speed. However, reducing power too soon after level
off results in a longer period of time to accelerate.
2-11
Figure 2-14. Turns.
The standard rate of turn, 3° per second, is used as the main
reference for bank angle. Therefore, the pilot must understand
how the angle of bank varies with speed changes, such
as slowing down for holding or an instrument approach.
Figure 2-14 shows the turn relationship with reference to a
constant bank angle or a constant airspeed, and the effects on
rate of turn and radius of turn. A rule of thumb for determining
the standard rate turn is to divide the airspeed by ten and
add 7. An aircraft with an airspeed of 90 knots takes a bank
angle of 16° to maintain a standard rate turn (90 divided by
10 plus 7 equals 16°).
Radius of Turn
The radius of turn varies with changes in either speed or bank.
If the speed is increased without changing the bank angle,
the radius of turn increases, and vice versa. If the speed is
constant, increasing the bank angle reduces the radius of
turn, while decreasing the bank angle increases the radius of
turn. This means that intercepting a course at a higher speed
requires more distance, and therefore, requires a longer lead.
If the speed is slowed considerably in preparation for holding
or an approach, a shorter lead is needed than that required
for cruise fl ight.
Coordination of Rudder and Aileron Controls
Any time ailerons are used, adverse yaw is produced. Adverse
yaw is caused when the ailerons are defl ected as a roll motion
(as in turn) is initiated. In a right turn, the right aileron is
defl ected downward while the left is defl ected upward. Lift
is increased on the left side and reduced on the right, resulting
in a bank to the right. However, as a result of producing lift
on the left, induced drag is also increased on the left side.
The drag causes the left wing to slow down, in turn causing
the nose of the aircraft to initially move (left) in the direction
opposite of the turn. Correcting for this yaw with rudder, when
entering and exiting turns, is necessary for precise control of
the airplane when fl ying on instruments. The pilot can tell if
the turn is coordinated by checking the ball in the turn-andslip
indicator or the turn coordinator.
As the aircraft banks to enter a turn, a portion of the wing’s
vertical lift becomes the horizontal component; therefore,
without an increase in back pressure, the aircraft loses altitude
during the turn. The loss of vertical lift can be offset by
increasing the pitch in one-half bar width increments. Trim
may be used to relieve the control pressures; however, if used,
it has to be removed once the turn is complete.
In a slipping turn, the aircraft is not turning at the rate
appropriate to the bank being used, and the aircraft falls to
the inside of the turn. The aircraft is banked too much for the
rate of turn, so the horizontal lift component is greater than
the centrifugal force. A skidding turn results from excess of
centrifugal force over the horizontal lift component, pulling
the aircraft toward the outside of the turn. The rate of turn
is too great for the angle of bank, so the horizontal lift
component is less than the centrifugal force.
The ball instrument indicates the quality of the turn, and
should be centered when the wings are banked. If the ball
is off of center on the side toward the turn, the aircraft is
slipping and rudder pressure should be added on that side to
increase the rate of turn or the bank angle should be reduced.
If the ball is off of center on the side away from the turn,
the aircraft is skidding and rudder pressure toward the turn
should be relaxed or the bank angle should be increased.
If the aircraft is properly rigged, the ball should be in the
center when the wings are level; use rudder and/or aileron
trim if available.
The increase in induced drag (caused by the increase in angle
of attack necessary to maintain altitude) results in a minor
loss of airspeed if the power setting is not changed.
Load Factor
Any force applied to an aircraft to defl ect its fl ight from a
straight line produces a stress on its structure; the amount of
this force is termed load factor. A load factor is the ratio of
2-12
Figure 2-15. Adverse Yaw.
the aerodynamic force on the aircraft to the gross weight of
the aircraft (e.g., lift/weight). For example, a load factor of 3
means the total load on an aircraft’s structure is three times
its gross weight. When designing an aircraft, it is necessary
to determine the highest load factors that can be expected in
normal operation under various operational situations. These
“highest” load factors are called “limit load factors.”
Aircraft are placed in various categories, i.e., normal, utility,
and acrobatic, depending upon the load factors they are
designed to take. For reasons of safety, the aircraft must be
designed to withstand certain maximum load factors without
any structural damage. The specifi ed load may be expected in terms of aerodynamic
forces, as in turns. In level fl ight in undisturbed air, the
wings are supporting not only the weight of the aircraft, but
centrifugal force as well. As the bank steepens, the horizontal
lift component increases, centrifugal force increases, and the
load factor increases. If the load factor becomes so great that
an increase in angle of attack cannot provide enough lift to
support the load, the wing stalls. Since the stalling speed
increases directly with the square root of the load factor, the
pilot should be aware of the fl ight conditions during which the
load factor can become critical. Steep turns at slow airspeed,
structural ice accumulation, and vertical gusts in turbulent
air can increase the load factor to a critical level.
Icing
One of the greatest hazards to fl ight is aircraft icing. The
instrument pilot must be aware of the conditions conducive to
aircraft icing. These conditions include the types of icing, the
effects of icing on aircraft control and performance, effects
of icing on aircraft systems, and the use and limitations of
aircraft deice and anti-ice equipment. Coping with the hazards
of icing begins with prefl ight planning to determine where
icing may occur during a fl ight and ensuring the aircraft is
2-13
Figure 2-16. Clear Ice.
free of ice and frost prior to takeoff. This attention to detail
extends to managing deice and anti-ice systems properly
during the fl ight, because weather conditions may change
rapidly, and the pilot must be able to recognize when a change
of fl ight plan is required.
Types of Icing
Structural Icing
Structural icing refers to the accumulation of ice on the
exterior of the aircraft. Ice forms on aircraft structures and
surfaces when super-cooled droplets impinge on them and
freeze. Small and/or narrow objects are the best collectors
of droplets and ice up most rapidly. This is why a small
protuberance within sight of the pilot can be used as an “ice
evidence probe.” It is generally one of the fi rst parts of the
airplane on which an appreciable amount of ice forms. An
aircraft’s tailplane is a better collector than its wings, because
the tailplane presents a thinner surface to the airstream.
Induction Icing
Ice in the induction system can reduce the amount of air
available for combustion. The most common example of
reciprocating engine induction icing is carburetor ice. Most
pilots are familiar with this phenomenon, which occurs when
moist air passes through a carburetor venturi and is cooled. As
a result of this process, ice may form on the venturi walls and
throttle plate, restricting airfl ow to the engine. This may occur
at temperatures between 20° F (-7° C) and 70° F (21° C). The
problem is remedied by applying carburetor heat, which uses
the engine’s own exhaust as a heat source to melt the ice or
prevent its formation. On the other hand, fuel-injected aircraft
engines usually are less vulnerable to icing but still can be
affected if the engine’s air source becomes blocked with ice.
Manufacturers provide an alternate air source that may be
selected in case the normal system malfunctions.
In turbojet aircraft, air that is drawn into the engines creates
an area of reduced pressure at the inlet, which lowers the
temperature below that of the surrounding air. In marginal
icing conditions (i.e., conditions where icing is possible),
this reduction in temperature may be suffi cient to cause ice
to form on the engine inlet, disrupting the airfl ow into the
engine. Another hazard occurs when ice breaks off and is
ingested into a running engine, which can cause damage to
fan blades, engine compressor stall, or combustor fl ameout.
When anti-icing systems are used, runback water also can
refreeze on unprotected surfaces of the inlet and, if excessive,
reduce airfl ow into the engine or distort the airfl ow pattern
in such a manner as to cause compressor or fan blades to
vibrate, possibly damaging the engine. Another problem
in turbine engines is the icing of engine probes used to set
power levels (for example, engine inlet temperature or engine
pressure ratio (EPR) probes), which can lead to erroneous
readings of engine instrumentation operational diffi culties
or total power loss.
The type of ice that forms can be classifi ed as clear, rime, or
mixed, based on the structure and appearance of the ice. The
type of ice that forms varies depending on the atmospheric
and fl ight conditions in which it forms. Signifi cant structural
icing on an aircraft can cause serious aircraft control and
performance problems.
Clear Ice
A glossy, transparent ice formed by the relatively slow
freezing of super cooled water is referred to as clear ice.
The terms “clear” and “glaze” have been used
for essentially the same type of ice accretion. This type of
ice is denser, harder, and sometimes more transparent than
rime ice. With larger accretions, clear ice may form “horns.”
Temperatures close to the freezing point, large
amounts of liquid water, high aircraft velocities, and large
droplets are conducive to the formation of clear ice.
Rime Ice
A rough, milky, opaque ice formed by the instantaneous or
very rapid freezing of super cooled droplets as they strike
the aircraft is known as rime ice. The rapid
freezing results in the formation of air pockets in the ice,
giving it an opaque appearance and making it porous and
brittle. For larger accretions, rime ice may form a streamlined
extension of the wing. Low temperatures, lesser amounts of
liquid water, low velocities, and small droplets are conducive
to the formation of rime ice.
2-14
Figure 2-19. Aerodynamic Effects of Icing.
Figure 2-17. Clear Ice Buildup. Figure 2-18. Rime Ice.
Mixed Ice
Mixed ice is a combination of clear and rime ice formed on
the same surface. It is the shape and roughness of the ice that
is most important from an aerodynamic point of view.
General Effects of Icing on Airfoils
The most hazardous aspect of structural icing is its aerodynamic
effects. Ice alters the shape of an airfoil, reducing
the maximum coeffi cient of lift and angle of attack at which
the aircraft stalls. Note that at very low angles of attack, there
may be little or no effect of the ice on the coeffi cient of lift.
Therefore, when cruising at a low angle of attack, ice on the
wing may have little effect on the lift. However, note that the
ice signifi cantly reduces the CL-MAX, and the angle of attack
at which it occurs (the stall angle) is much lower. Thus, when
slowing down and increasing the angle of attack for approach,
the pilot may fi nd that ice on the wing, which had little effect
on lift in cruise now, causes stall to occur at a lower angle of
attack and higher speed. Even a thin layer of ice at the leading
edge of a wing, especially if it is rough, can have a signifi cant
effect in increasing stall speed. For large ice shapes, especially
those with horns, the lift may also be reduced at a lower angle
of attack. The accumulation of ice affects the coeffi cient
of drag of the airfoil. Note that the effect is
signifi cant even at very small angles of attack.
A signifi cant reduction in CL-MAX and a reduction in the angle
of attack where stall occurs can result from a relatively small
ice accretion. A reduction of CL-MAX by 30 percent is not
unusual, and a large horn ice accretion can result in reductions
of 40 percent to 50 percent. Drag tends to increase steadily
as ice accretes. An airfoil drag increase of 100 percent is not
unusual, and for large horn ice accretions, the increase can
be 200 percent or even higher.
2-15
Figure 2-20. Effect of Ice and Frost on Lift.
Figure 2-21. Downward Force on the Tailplane.
Figure 2-22. Ice on the Tailplane.
Ice on an airfoil can have other effects not depicted in these
curves. Even before airfoil stall, there can be changes in the
pressure over the airfoil that may affect a control surface at
the trailing edge. Furthermore, on takeoff, approach, and
landing, the wings of many aircraft are multi-element airfoils
with three or more elements. Ice may affect the different
elements in different ways. Ice may also affect the way in
which the air streams interact over the elements.
Ice can partially block or limit control surfaces, which
limits or makes control movements ineffective. Also, if the
extra weight caused by ice accumulation is too great, the
aircraft may not be able to become airborne and, if in fl ight,
the aircraft may not be able to maintain altitude. Therefore
any accumulation of ice or frost should be removed before
attempting fl ight.
Another hazard of structural icing is the possible uncommanded
and uncontrolled roll phenomenon, referred to as roll upset,
associated with severe in-fl ight icing. Pilots fl ying aircraft
certifi cated for fl ight in known icing conditions should be
aware that severe icing is a condition outside of the aircraft’s
certifi cation icing envelope. Roll upset may be caused by
airfl ow separation (aerodynamic stall), which induces selfdefl
ection of the ailerons and loss of or degraded roll handling
characteristics . These phenomena can result
from severe icing conditions without the usual symptoms of
ice accumulation or a perceived aerodynamic stall.
Most aircraft have a nose-down pitching moment from the
wings because the CG is ahead of the CP. It is the role of the
tailplane to counteract this moment by providing a downward
force. The result of this confi guration is
that actions which move the wing away from stall, such
as deployment of fl aps or increasing speed, may increase
the negative angle of attack of the tail. With ice on the
tailplane, it may stall after full or partial deployment of fl aps.
Since the tailplane is ordinarily thinner than the wing, it is a
more effi cient collector of ice. On most aircraft the tailplane
is not visible to the pilot, who therefore cannot observe how
well it has been cleared of ice by any deicing system. Thus, it
is important that the pilot be alert to the possibility of tailplane
stall, particularly on approach and landing.
Piper PA-34-200T (Des Moines, Iowa)
The pilot of this fl ight, which took place on January 9,
1996, said that upon crossing the runway threshold and
lowering the fl aps 25°, “the airplane pitched down.” The
pilot “immediately released the fl aps and added power, but
the airplane was basically uncontrollable at this point.” The
pilot reduced power and lowered the fl aps before striking
the runway on its centerline and sliding 1,000 feet before
2-16
coming to a stop. The accident resulted in serious injury to
the pilot, the sole occupant.
Examination of the wreckage revealed heavy impact
damage to the airplane’s forward fuselage, engines, and
wings. Approximately one-half inch of rime ice was
observed adhering to the leading edges of the left and right
horizontal stabilizers and along the leading edge of the
vertical stabilizer.
The National Transportation Safety Board (NTSB)
determined the probable cause of the accident was the pilot’s
failure to use the airplane’s deicing system, which resulted
in an accumulation of empennage ice and a tailplane stall.
Factors relating to this accident were the icing conditions and
the pilot’s intentional fl ight into those known conditions.
Tailplane Stall Symptoms Any of the following symptoms, occurring singly or in
combination, may be a warning of tailplane icing:
• Elevator control pulsing, oscillations, or vibrations;
• Abnormal nose-down trim change;
• Any other unusual or abnormal pitch anomalies
(possibly resulting in pilot induced oscillations);
• Reduction or loss of elevator effectiveness;
• Sudden change in elevator force (control would move
nose-down if unrestrained); and
• Sudden uncommanded nose-down pitch.
If any of the above symptoms occur, the pilot should:
• Immediately retract the fl aps to the previous setting
and apply appropriate nose-up elevator pressure;
• Increase airspeed appropriately for the reduced fl ap
extension setting;
• Apply sufficient power for aircraft configuration
and conditions. (High engine power settings may
adversely impact response to tailplane stall conditions
at high airspeed in some aircraft designs. Observe the
manufacturer’s recommendations regarding power
settings.);
• Make nose-down pitch changes slowly, even in
gusting conditions, if circumstances allow; and
• If a pneumatic deicing system is used, operate the
system several times in an attempt to clear the tailplane
of ice.
Once a tailplane stall is encountered, the stall condition
tends to worsen with increased airspeed and possibly may
worsen with increased power settings at the same flap
setting. Airspeed, at any fl ap setting, in excess of the airplane
manufacturer’s recommendations, accompanied by uncleared
ice contaminating the tailplane, may result in a tailplane stall
and uncommanded pitch down from which recovery may not
be possible. A tailplane stall may occur at speeds less than
the maximum fl ap extended speed (VFE).
Propeller Icing
Ice buildup on propeller blades reduces thrust for the same
aerodynamic reasons that wings tend to lose lift and increase
drag when ice accumulates on them. The greatest quantity
of ice normally collects on the spinner and inner radius of
the propeller. Propeller areas on which ice may accumulate
and be ingested into the engine normally are anti-iced rather
than deiced to reduce the probability of ice being shed into
the engine.
Effects of Icing on Critical Aircraft Systems
In addition to the hazards of structural and induction icing,
the pilot must be aware of other aircraft systems susceptible
to icing. The effects of icing do not produce the performance
loss of structural icing or the power loss of induction icing
but can present serious problems to the instrument pilot.
Examples of such systems are flight instruments, stall
warning systems, and windshields.
Flight Instruments
Various aircraft instruments including the airspeed indicator,
altimeter, and rate-of-climb indicator utilize pressures
sensed by pitot tubes and static ports for normal operation.
When covered by ice these instruments display incorrect
information thereby presenting serious hazard to instrument
flight. Detailed information on the operation of these
instruments and the specifi c effects of icing is presented in
Chapter 3, Flight Instruments.
Stall Warning Systems
Stall warning systems provide essential information to pilots.
These systems range from a sophisticated stall warning vane
to a simple stall warning switch. Icing affects these systems
in several ways resulting in possible loss of stall warning to
the pilot. The loss of these systems can exacerbate an already
hazardous situation. Even when an aircraft’s stall warning
system remains operational during icing conditions, it may
be ineffective because the wing stalls at a lower angle of
attack due to ice on the airfoil.
Windshields
Accumulation of ice on fl ight deck windows can severely
restrict the pilot’s visibility outside of the aircraft. Aircraft
equipped for fl ight into known icing conditions typically have
some form of windshield anti-icing to enable the pilot to see
2-17
outside the aircraft in case icing is encountered in fl ight. One
system consists of an electrically heated plate installed onto
the airplane’s windshield to give the pilot a narrow band of
clear visibility. Another system uses a bar at the lower end
of the windshield to spray deicing fl uid onto it and prevent
ice from forming. On high performance aircraft that require
complex windshields to protect against bird strikes and
withstand pressurization loads, the heating element often is
a layer of conductive fi lm or thin wire strands through which
electric current is run to heat the windshield and prevent ice
from forming.
Antenna Icing
Because of their small size and shape, antennas that do not lay
fl ush with the aircraft’s skin tend to accumulate ice rapidly.
Furthermore, they often are devoid of internal anti-icing
or deicing capability for protection. During fl ight in icing
conditions, ice accumulations on an antenna may cause it to
begin to vibrate or cause radio signals to become distorted
and it may cause damage to the antenna. If a frozen antenna
breaks off, it can damage other areas of the aircraft in addition
to causing a communication or navigation system failure.
Summary
Ice-contaminated aircraft have been involved in many
accidents. Takeoff accidents have usually been due to failure
to deice or anti-ice critical surfaces properly on the ground.
Proper deicing and anti-icing procedures are addressed in
two other pilot guides, Advisory Circular (AC) 120-58, Pilot
Guide: Large Aircraft Ground Deicing and AC 135-17, Pilot
Guide: Small Aircraft Ground Deicing.
The pilot of an aircraft, which is not certifi cated or equipped
for fl ight in icing conditions, should avoid all icing conditions.
The aforementioned guides provide direction on how to do
this, and on how to exit icing conditions promptly and safely
should they be inadvertently encountered.
The pilot of an aircraft, which is certifi cated for fl ight in
icing conditions can safely operate in the conditions for
which the aircraft was evaluated during the certifi cation
process but should never become complacent about icing.
Even short encounters with small amounts of rough icing
can be very hazardous. The pilot should be familiar with all
information in the Aircraft Flight Manual (AFM) or Pilot’s
Operating Handbook (POH) concerning flight in icing
conditions and follow it carefully. Of particular importance
are proper operation of ice protection systems and any
airspeed minimums to be observed during or after fl ight
in icing conditions. There are some icing conditions for
which no aircraft is evaluated in the certifi cation process,
such as super-cooled large drops (SLD). These subfreezing
water droplets, with diameters greater than 50 microns,
occur within or below clouds and sustained fl ight in these
conditions can be very hazardous. The pilot should be familiar
with any information in the AFM or POH relating to these
conditions, including aircraft-specifi c cues for recognizing
these hazardous conditions within clouds.
The information in this chapter is an overview of the hazards
of aircraft icing. For more detailed information refer to AC
91-74, Pilot Guide: Flight in Icing Conditions, AC 91-51A,
Effect of Icing on Aircraft Control and Airplane Deice and
Anti-Ice Systems, AC 20-73A, Aircraft Ice Protection and
AC 23.143-1, Ice Contaminated Tailplane Stall (ICTS).
2-18
3-1
Introduction
Aircraft became a practical means of transportation when
accurate fl ight instruments freed the pilot from the necessity
of maintaining visual contact with the ground. Flight
instruments are crucial to conducting safe fl ight operations
and it is important that the pilot have a basic understanding
of their operation. The basic fl ight instruments required
for operation under visual fl ight rules (VFR) are airspeed
indicator (ASI), altimeter, and magnetic direction indicator.
In addition to these, operation under instrument fl ight rules
(IFR) requires a gyroscopic rate-of-turn indicator, slip-skid
indicator, sensitive altimeter adjustable for barometric
pressure, clock displaying hours, minutes, and seconds with
a sweep-second pointer or digital presentation, gyroscopic
pitch-and-bank indicator (artifi cial horizon), and gyroscopic
direction indicator (directional gyro or equivalent).
Flight Instruments
Chapter 3
3-2
Figure 3-1. A Typical Electrically Heated Pitot-Static Head.
Aircraft that are fl own in instrument meteorological conditions
(IMC) are equipped with instruments that provide attitude
and direction reference, as well as navigation instruments that
allow precision fl ight from takeoff to landing with limited or
no outside visual reference.