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Instrument Flying Handbook
Human factors

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Instrument Flying


Table of Contents

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

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

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

Inner Ear Orientation.
Figure 1-3. Inner Ear Orientation.

The inner ear has two major parts concerned with orientation,
the semicircular canals and the otolith organs. [Figure 1-3] The
semicircular canals detect angular acceleration of the body
while the otolith organs detect linear acceleration and gravity.
The semicircular canals consist of three tubes at right angles
to each other, each located on one of three axes: pitch, roil,
or yaw as illustrated in Figure 1-4 Each canal is filled with
a fluid called endolymph fluid. in the center of the canal is
the cupola, a gelatinous structure that rests upon sensory
hairs located at the end of the vestibular nerves. It is the
movement of these hairs within the fluid which causes
sensations of motion.

Because of the friction between the fluid and the canal, it
may take about I 5—20 seconds for the fluid in the ear canal
to reach the same speed as the canal's motion.

To illustrate what happens during a turn, visualize the aircraft
in straight and level flight. With no acceleration of the aircraft,
the hair cells are upright and the body senses that no turn
has occurred. Therefore, the position of the hair cells and the
actual sensation correspond.

Placing the aircraft into a turn puts the semicircular canal and
its fluid into motion, with the fluid within the semicircular
canal lagging behind the accelerated canal walls.[Figure 1-5]
This lag creates a relative movement of the fluid within the
canal. The canal wall and the cupula move in the opposite
direction from the motion of the fluid.

The brain interprets the movement of the hairs to be a turn in
the same direction as the canal wall. The body correctly senses
that a turn is being made. if the turn continues at a constant
rate for several seconds or longer, the motion of the fluid in
the canals catches up with the canal walls. The hairs are 110
longer bent, and the brain receives the false impression that
turning has stopped. Thus, die 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.

Angular Acceleration and the Semicircular Tubes.
Figure 1-4. Angular Acceleration and the Semicircular Tubes.