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Pilot's Handbook of Aeronautical Knowledge
Aeromedical Factors

Health and Physiological Factors Affecting Pilot Performance

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Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




The semicircular canals lie in three planes and sense motions of roll, pitch, and yaw.
Figure 16-3. The semicircular canals lie in three planes and sense motions of roll, pitch, and yaw.

Sinus block can be avoided by not flying with an upper
respiratory infection or nasal allergic condition. Adequate
protection is usually not provided by decongestant sprays
or drops to reduce congestion around the sinus openings.
Oral decongestants have side effects that can impair pilot
performance. If a sinus block does not clear shortly after
landing, a physician should be consulted.

Spatial Disorientation and Illusions
Spatial disorientation specifically refers to the lack of
orientation with regard to the position, attitude, or movement
of the airplane in space. The body uses three integrated
systems working together to ascertain orientation and
movement in space.
• Vestibular system—organs found in the inner ear that
sense position by the way we are balanced.
• Somatosensory system—nerves in the skin, muscles,
and joints, which, along with hearing, sense position
based on gravity, feeling, and sound.
• Visual system—eyes, which sense position based on
what is seen.

All this information comes together in the brain and, most
of the time, the three streams of information agree, giving
a clear idea of where and how the body is moving. Flying
can sometimes cause these systems to supply conflicting
information to the brain, which can lead to disorientation.

During flight in visual meteorological conditions (VMC),
the eyes are the major orientation source and usually prevail
over false sensations from other sensory systems. When
these visual cues are removed, as they are in instrument
meteorological conditions (IMC), false sensations can cause
a pilot to quickly become disoriented.

The vestibular system in the inner ear allows the pilot to
sense movement and determine orientation in the surrounding
environment. In both the left and right inner ear, three
semicircular canals are positioned at approximate right angles
to each other. [Figure 16-3] Each canal is filled with fluid
and has a section full of fine hairs. Acceleration of the inner
ear in any direction causes the tiny hairs to deflect, which
in turn stimulates nerve impulses, sending messages to the
brain. The vestibular nerve transmits the impulses from
the utricle, saccule, and semicircular canals to the brain to
interpret motion.

The somatosensory system sends signals from the skin, joints,
and muscles to the brain that are interpreted in relation to the
Earth's gravitational pull. These signals determine posture.
Inputs from each movement update the body's position to the
brain on a constant basis. "Seat of the pants" flying is largely
dependent upon these signals. Used in conjunction with visual
and vestibular clues, these sensations can be fairly reliable.
However, the body cannot distinguish between acceleration
forces due to gravity and those resulting from maneuvering
the aircraft, which can lead to sensory illusions and false
impressions of an aircraft's orientation and movement.