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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 alcohol consumed in beer and mixed drinks is ethyl
alcohol, a central nervous system depressant. From a medical
point of view, it acts on the body much like a general
anesthetic. The "dose" is generally much lower and more
slowly consumed in the case of alcohol, but the basic effects
on the human body are similar. Alcohol is easily and quickly
absorbed by the digestive tract. The bloodstream absorbs
about 80 to 90 percent of the alcohol in a drink within 30
minutes when ingested on an empty stomach. The body
requires about 3 hours to rid itself of all the alcohol contained
in one mixed drink or one beer.

While experiencing a hangover, a pilot is still under the
influence of alcohol. Although a pilot may think he or she is
functioning normally, motor and mental response impairment
is still present. Considerable amounts of alcohol can remain
in the body for over 16 hours, so pilots should be cautious
about flying too soon after drinking.

Altitude multiplies the effects of alcohol on the brain. When
combined with altitude, the alcohol from two drinks may have
the same effect as three or four drinks. Alcohol interferes
with the brain's ability to utilize oxygen, producing a form
of histotoxic hypoxia. The effects are rapid because alcohol
passes quickly into the bloodstream. In addition, the brain
is a highly vascular organ that is immediately sensitive to
changes in the blood's composition. For a pilot, the lower
oxygen availability at altitude and the lower capability of
the brain to use what oxygen is there, add up to a deadly

Intoxication is determined by the amount of alcohol in the
bloodstream. This is usually measured as a percentage by
weight in the blood. 14 CFR part 91 requires that blood
alcohol level be less than .04 percent and that 8 hours pass
between drinking alcohol and piloting an airplane. A pilot
with a blood alcohol level of .04 percent or greater after
8 hours cannot fly until the blood alcohol falls below that
amount. Even though blood alcohol may be well below .04
percent, a pilot cannot .y sooner than 8 hours after drinking
alcohol. Although the regulations are quite specific, it is a
good idea to be more conservative than the regulations.

Pilot performance can be seriously degraded by both
prescription 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 may impair judgment, memory, alertness,
coordination, vision, and the ability to make calculations.

[Figure 16-9] Others, such as antihistamines, blood pressure
drugs, muscle relaxants, and agents to control diarrhea and
motion sickness have side effects that may impair the same
critical functions. Any medication that depresses the nervous
system, such as a sedative, tranquilizer, or antihistamine, can
make a pilot more susceptible to hypoxia.

Painkillers are grouped into two broad categories: analgesics
and anesthetics. Analgesics are drugs that reduce pain,
while anesthetics are drugs that deaden pain or cause loss
of consciousness.

Over-the-counter analgesics, such as acetylsalicylic acid
(aspirin), acetaminophen (Tylenol), and ibuprofen (Advil)
have few side effects when taken in the correct dosage.
Although some people are allergic to certain analgesics or
may suffer from stomach irritation, flying usually is not
restricted when taking these drugs. However, flying is almost
always precluded while using prescription analgesics, such
as drugs containing propoxyphene (e.g., Darvon), oxycodone
(e.g., Percodan), meperidine (e.g., Demerol), and codeine
since these drugs are known to cause side effects such as
mental confusion, dizziness, headaches, nausea, and vision

Anesthetic drugs are commonly used for dental and surgical
procedures. Most local anesthetics used for minor dental and
outpatient procedures wear off within a relatively short period
of time. The anesthetic itself may not limit flying as much
as the actual procedure and subsequent pain.

Stimulants are drugs that excite the central nervous
system and produce an increase in alertness and activity.
Amphetamines, caffeine, and nicotine are all forms of
stimulants. Common uses of these drugs include appetite
suppression, fatigue reduction, and mood elevation. Some
of these drugs may cause a stimulant reaction, even though
this reaction is not their primary function. In some cases,
stimulants can produce anxiety and mood swings, both of
which are dangerous when flying

Depressants are drugs that reduce the body's functioning in
many areas. These drugs lower blood pressure, reduce mental
processing, and slow motor and reaction responses. There are
several types of drugs that can cause a depressing effect on the
body, including tranquilizers, motion sickness medication,
some types of stomach medication, decongestants, and
antihistamines. The most common depressant is alcohol.