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Instrument Flying Handbook
Human factors
illusions Leading to Spatial Disorientation

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Instrument Flying
Handbook

Preface

Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Flying
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Flying
Using an Electronic Flight
Display

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight
Display

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency
Operations

Angular Acceleration
Figure 1-5. Angular Acceleration,

When the aircraft returns to straight-and-level flight, the fluid
in the canal moves briefly in the opposite direction. This sends
a signal to the brain that is falsely interpreted as movement
in the opposite direction. In an attempt to correct the falsely
perceived turn, the pilot may reenter the turn placing the
aircraft in an out of control situation.

The otolith organs detect linear acceleration and gravity in a
similar way. Instead of being filled with a fluid, a gelatinous
membrane containing chalk-like crystals covers the sensory
hairs. When the pilot tilts his or her head, the weight of these
crystals causes this membrane to shift due to gravity and
the sensory hairs detect this shift. The brain orients this new
position to what it perceives as vertical. Acceleration and
deceleration also cause the membrane to shift in a similar
manner. Forward acceleration gives the illusion of the head
tilting backward. [Figure 1-6] As a result, during takeoff and
while accelerating, die 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 hack 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 ban king 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
Dissertation

The sensory system responsible for most of the illusions
leading to spatial disorientation is the vestibular system.
Visual illusions can also cause spatial disorientation.

Vestibular Illusions
The Leans

A condition called the leans can result when a banked attitude,
to the left for example, may be entered too slowly to set in
motion the fluid in the "roll" semicircular tubes. [Figure 7-5]
An abrupt correction of this attitude sets the fluid in motion,
creating the illusion of a banked attitude to the right. The
disoriented pilot may make the error of rolling the aircraft
into the original left banked attitude, or if level flight is
maintained, will feel compelled to lean in the perceived
vertical plane until this illusion subsides.

Linear Acceleration.
Figure 1-6. Linear Acceleration.