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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 first noticeable effect of dehydration is fatigue, which
in turn makes top physical and mental performance difficult,
if not impossible. Flying for long periods in hot summer
temperatures or at high altitudes increases the susceptibility
to dehydration because these conditions tend to increase the
rate of water loss from the body.

To help prevent dehydration, drink two to four quarts of
water every 24 hours. Since each person is physiologically
different, this is only a guide. Most people are aware of the
eight-glasses-a-day guide: If each glass of water is eight
ounces, this equates to 64 ounces, which is two quarts. If
this fluid is not replaced, fatigue progresses to dizziness,
weakness, nausea, tingling of hands and feet, abdominal
cramps, and extreme thirst.

The key for pilots is to be continually aware of their condition.
Most people become thirsty with a 1.5 quart deficit, or a loss
of 2 percent of total body weight. This level of dehydration
triggers the "thirst mechanism." The problem is that the thirst
mechanism arrives too late and is turned off too easily. A
small amount of fluid in the mouth will turn this mechanism
off and the replacement of needed body fluid is delayed.
Other steps to prevent dehydration include:
• Carrying a container in order to measure daily water
• Staying ahead—not relying on the thirst sensation as
an alarm. If plain water is offensive, add some sport
drink flavoring to make it more acceptable.
• Limiting daily intake of caffeine and alcohol (both
are diuretics and stimulate increased production of

Heatstroke is a condition caused by any inability of the body
to control its temperature. Onset of this condition may be
recognized by the symptoms of dehydration, but also has been
known to be recognized only by complete collapse.
To prevent these symptoms, it is recommended that an ample
supply of water be carried and used at frequent intervals on
any long flight, whether thirsty or not. The body normally
absorbs water at the rate of 1.2 to 1.5 quarts per hour.
Individuals should drink one quart per hour for severe heat
stress conditions or one pint per hour for moderate stress
conditions. If the aircraft has a canopy or roof window,
wearing light-colored, porous clothing and a hat will help
provide protection from the sun. Keeping the flight deck well
ventilated aids in dissipating excess heat.

Alcohol impairs the efficiency of the human body.
[Figure 16-8] Studies have proved that drinking and
performance deterioration are closely linked. Pilots must

make hundreds of decisions, some of them time-critical,
during the course of a flight The safe outcome of any flight
depends on the ability to make the correct decisions and take
the appropriate actions during routine occurrences, as well
as abnormal situations. The influence of alcohol drastically
reduces the chances of completing a flight without incident.
Even in small amounts, alcohol can impair judgment,
decrease sense of responsibility, affect coordination, constrict
visual field, diminish memory, reduce reasoning power, and
lower attention span. As little as one ounce of alcohol can
decrease the speed and strength of muscular reflexes, lessen
the efficiency of eye movements while reading, and increase
the frequency at which errors are committed. Impairments
in vision and hearing occur at alcohol blood levels due to as
little as one drink.

Impairement scale with alcohol use.
Figure 16-8. Impairment scale with alcohol use.