Fatigue
Fatigue is frequently associated with pilot error. Some of
the effects of fatigue include degradation of attention and
concentration, impaired coordination, and decreased ability
to communicate. These factors seriously influence the
ability to make effective decisions. Physical fatigue results
from sleep loss, exercise, or physical work. Factors such as
stress and prolonged performance of cognitive work result
in mental fatigue.
Like stress, fatigue falls into two broad categories: acute
and chronic. Acute fatigue is short term and is a normal
occurrence in everyday living. It is the kind of tiredness
people feel after a period of strenuous effort, excitement, or
lack of sleep. Rest after exertion and 8 hours of sound sleep
ordinarily cures this condition.
A special type of acute fatigue is skill fatigue. This type of
fatigue has two main effects on performance:
• Timing disruption—appearing to perform a task as
usual, but the timing of each component is slightly off.
This makes the pattern of the operation less smooth
because the pilot performs each component as though it
were separate, instead of part of an integrated activity.
• Disruption of the perceptual field—concentrating
attention upon movements or objects in the center of
vision and neglecting those in the periphery. This is
accompanied by loss of accuracy and smoothness in
control movements.
Acute fatigue has many causes, but the following are among
the most important for the pilot:
• Mild hypoxia (oxygen deficiency)
• Physical stress
• Psychological stress
• Depletion of physical energy resulting from
psychological stress
• Sustained psychological stress
Sustained psychological stress accelerates the glandular
secretions that prepare the body for quick reactions during
an emergency. These secretions make the circulatory and
respiratory systems work harder, and the liver releases energy
to provide the extra fuel needed for brain and muscle work.
When this reserve energy supply is depleted, the body lapses
into generalized and severe fatigue.
Acute fatigue can be prevented by proper diet and adequate
rest and sleep. A well-balanced diet prevents the body from
needing to consume its own tissues as an energy source.
Adequate rest maintains the body’s store of vital energy.
Chronic fatigue, extending over a long period of time, usually
has psychological roots, although an underlying disease is
sometimes responsible. Continuous high-stress levels produce
chronic fatigue. Chronic fatigue is not relieved by proper diet
and adequate rest and sleep and usually requires treatment
by a physician. An individual may experience this condition
in the form of weakness, tiredness, palpitations of the heart,
breathlessness, headaches, or irritability. Sometimes chronic
fatigue even creates stomach or intestinal problems and
generalized aches and pains throughout the body. When the
condition becomes serious enough, it leads to emotional illness.
If suffering from acute fatigue, stay on the ground. If fatigue
occurs in the flight deck, no amount of training or experience
can overcome the detrimental effects. Getting adequate rest
is the only way to prevent fatigue from occurring. Avoid
flying without a full night’s rest, after working excessive
hours, or after an especially exhausting or stressful day. Pilots
who suspect they are suffering from chronic fatigue should
consult a physician.
Exposure to Chemicals
When conducting preflight and post-flight inspections, pilots
must verify that the fluid levels in their aircraft meet the
levels specified for safe operations as stated in the Pilot's
Operating Handbook. These fluids include, but are not limited
to hydraulic fluid, engine oil, and fuel.
It is important that every pilot recognize the potential hazards
of working with these fluids as well as the recommended first
aid measures to follow should any of these fluids come in
contact with their eyes, skin, and/or respiratory system. As
the specific first aid measures for dealing with exposure to
these chemicals can vary by chemical type, it is important that
every pilot be familiar with the location and use of the Material
Safety Data Sheet (MSDS) for each chemical they encounter.
The procedures described in the following sections are
minimum guideline for first aid for each of the indicated
scenarios. Ultimately, the pilot should consult the MSDS
for first aid procedures specific to the type of chemical and
exposure scenario.
Hydraulic Fluid
• Eye Contact—immediately flush the eyes with clean
water and seek medical attention if irritation occurs.
• Skin Contact—remove all contaminated clothing and
thoroughly cleanse the affected areas with mild soap
and water or a waterless hand cleaner. If irritation or
redness develops and persists, seek medical attention.
Should the hydraulic fluid get into or under the skin,
or into any other part of the body, regardless of the
appearance of the wound or its size, seek medical
attention immediately.
• Inhalation—if respiratory symptoms develop, move
away from the source of exposure and into fresh air
in a position comfortable for breathing. If symptoms
persist, seek medical attention.
• Ingestion—first aid is not normally required; however,
if swallowed and symptoms develop, seek medical
attention.
Engine Oil
• Eye Contact—immediately flush the eyes with clean
water and seek medical attention if irritation occurs.
• Skin Contact—remove all contaminated clothing and
thoroughly cleanse the affected areas with soap and
water. Launder contaminated clothing before reuse.
• Inhalation—move away from the source of exposure
and into fresh air. If respiratory irritation, dizziness,
nausea, or unconsciousness occurs, seek immediate
medical attention. If breathing stops, assisted
ventilation is required via a bag-valve-mask or
cardiopulmonary resuscitation (CPR).
• Ingestion—seek immediate medical attention. If
immediate medical attention is not available, contact
a regional poison control center or emergency medical
professional regarding the induction of vomiting or
use of activated charcoal. Vomiting should never be
induced to a person who is groggy or unconscious.
Fuel
• Eye Contact—immediately flush the eyes with
clean water for at least 15 minutes and seek medical
attention immediately.
• Skin Contact—remove all contaminated clothing
and thoroughly cleanse the affected areas with mild
soap and water or a waterless hand cleaner. If skin
surface is damaged, apply a clean dressing and seek
medical attention. If irritation or redness develops,
seek medical attention. Launder contaminated clothing
before reuse.
• Inhalation—move away from the source of exposure
and into fresh air. If breathing stops, assisted
ventilation is required via a bag-valve-mask or
cardiopulmonary resuscitation (CPR). Once breathing
is restored, the use of additional oxygen may be
necessary. Seek medical attention immediately.
• Ingestion—seek immediate medical attention. Do not
induce vomiting or take anything by mouth as this may
cause the material to enter the lungs and cause severe
lung damage. Should vomiting occur, keep head below
the hips to reduce the risks of aspiration. Monitor for
breathing difficulties. Rinse out any material which
enters the mouth until the taste is dissipated.
Dehydration and Heatstroke
Dehydration is the term given to a critical loss of water from
the body. Causes of dehydration are hot flight decks and
flight lines, wind, humidity, and diuretic drinks—coffee, tea,
alcohol, and caffeinated soft drinks. Some common signs of
dehydration are headache, fatigue, cramps, sleepiness, and
dizziness.
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 turns 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
intake.
• Staying ahead—not relying on the thirst sensation as
an alarm. If plain water is not preferred, 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 urine).
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 upon complete collapse.
Type Beverage Typical Serving Pure Alcohol
(oz) Content (oz)
Table wine
Light beer
Aperitif liquor
Champagne
Vodka
Whiskey
4.0
12.0
1.5
4.0
1.0
1.25
.48
.48
.38
.48
.50
.50
0.01–0.05% average individual appears normal
(10–50 mg)
0.03–0.12%* mild euphoria, talkativeness, decreased
(30–120 mg) inhibitions, decreased attention, impaired
judgment, increased reaction time
0.09–0.25% emotional instability, loss of critical
(90–250 mg) judgment, impairment of memory and
comprehension, decreased sensory
response, mild muscular incoordination
0.18–0.30% confusion, dizziness, exaggerated
(180–300 mg) emotions (anger, fear, grief), impaired
visual perception, decreased pain
sensation, impaired balance, staggering
gait, slurred speech, moderate muscular
incoordination
0.27–0.40% apathy, impaired consciousness, stupor,
(270–400 mg) significantly decreased response to
stimulation, severe muscular
incoordination, inability to stand or walk,
vomiting, incontinence of urine and feces
0.35–0.50% unconsciousness, depressed or
(350–500 mg) abolished reflexes, abnormal body
temperature, coma, possible death from
respiratory paralysis (450 mg or above)
* Legal limit for motor vehicle operation in most states is 0.08
or 0.10% (80–100 mg of alcohol per dL of blood).
Figure 17-8. Impairment scale with alcohol use.
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 a 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
Alcohol impairs the efficiency of the human body.
[Figure 17-8] Studies have shown that consuming alcohol
is closely linked to performance deterioration. 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 ability, 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 can occur from consuming as little as
one drink.
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 the oxygen that is available can add up to a
deadly combination.
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 aircraft. 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 fly 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.
Drugs
The Federal Aviation Regulations include no specific
references to medication usage. Two regulations, though,
are important to keep in mind. Title 14 of the CFR part 61,
section 61.53 prohibits acting as pilot-in-command or in any
other capacity as a required pilot flight crewmember, while
that person:
1. Knows or has reason to know of any medical condition
that would make the person unable to meet the
requirement for the medical certificate necessary for
the pilot operation, or
2. Is taking medication or receiving other treatment for
a medical condition that results in the person being
unable to meet the requirements for the medical
certificate necessary for the pilot operation.
Further, 14 CFR part 91, section 91.17 pro hibits the use
of any drug that affects the person’s faculties in any way
contrary to safety.
There
are several thousand medications currently approved
by the U.S. Food and Drug Administration (FDA), not
including OTC (over the counter) drugs. Virtually all
medications
have the potential for adverse side effects in
some people. Additionally, herbal and dietary supplements,
sport and energy boosters, and some other “natural” products
are derived
from substances often found in medications that
could also have adverse side effects. While some individuals
experience
no side effects with a particular drug or product,
others may be noticeably affected. The FAA regularly
r
eviews FDA and other data to assure that medications found
acceptable
for aviation duties do not pose an adverse safety
risk. Drugs that cause no apparent side effects on the ground
can create
serious problems at even relatively low altitudes.
Even at typical general aviation altitudes, the changes in
concentrations of atmospheric gases in the blood can enhance
the
effects of seemingly innocuous drugs that can result in
impaired judgment, decision-making, and performance. In
addition, fatigue, stress, dehydration, and inadequate nutrition
can increase an airman’s susceptibility to adverse effects from
various drugs, even if they appeared to tolerate them in the
past. If multiple medications are being taken at the same time,
the adverse effects can be even more pronounced.
Ano ther important consideration is that the medical
condition
for which a medication is prescribed may itself be
disqualifying. The FAA will consider the condition in the
context
of risk for medical incapacitation, and the medication
as well for cognitive impairment, and either or both could be
found
unacceptable for medical certification.
Some of the most commonly used OTC drugs, antihistamines
and decongestants, have the poten tial to cause noticeable
adverse side effects, including drowsiness and cognitive
deficits. The symptoms associated with common
upper respiratory infections, including the common
cold,
often suppress a pilot’s desire to fly, and treating
symptoms with a drug that causes adverse side effects
only compo unds the problem. Particularly,
medications
containing diphenhydramine (e.g.,
Benadryl) are known to cause drowsiness and have a
prolonged half-life, meaning the drugs stay in one’s system
for an extended time, which lengthens the time that side
effects are present.
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 17-9] 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 problems.
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.
There is evidence taking illicit drugs significantly elevates
the risk of having an aviation accident. Even though the
Drug Enforcement Administration (DEA) defines
marijuana as a Schedule I drug on its controlled substances
list, states have taken steps to allow the possession, sale,
Figure 17-9. Adverse affects of various drugs.
Substance Possible Side Effects Generic Or
Brand Name
Treatment
for
Alcohol
Nicotine
Amphetamines
Caffeine
Antacid
Antihistamines
Aspirin
Beer
Liquor
Wine
Cigars
Cigarettes
Pipe tobacco
Chewing tobacco
Snuff
Ritalin
Obetrol
Eskatrol
Coffee
Tea
Chocolate
No-Doz
Alka-2
Di-Gel
Maalox
Coricidin
Contac
Dristan
Dimetapp
Omade
Chlor-Trimeton
Diphenhydramine
Bayer
Bufferin
Alka-Seltzer
N/A
N/A
Obesity (diet pills)
Tiredness
N/A
Stomach acids
Allergies
Colds
Headaches
Fevers
Aches
Pains
Impaired judgment and perception
Impaired coordination and motor control
Reduced reaction time
Impaired sensory perception
Reduced intellectual functions
Reduced tolerance to G-forces
Inner-ear disturbance and spatial disorientation (up to 48 hours)
Central nervous system depression
Sinus and respiratory system infection and irritation
Impaired night vision
Hypertension
Carbon monoxide poisoning (from smoking)
Prolonged wakefulness
Nervousness
Impaired vision
Suppressed appetite
Shakiness
Excessive sweating
Rapid heart rate
Sleep disturbance
Seriously impaired judgment
Impaired judgment
Reduced reaction time
Sleep disturbance
Increased motor activity and tremors
Hypertension
Irregular heart rate
Rapid heart rate
Body dehydration (through increased urine output)
Headaches
Liberations of carbon dioxide at altitude (distension may cause
acute abdominal pain and may mask other medical problems)
Drowsiness and dizziness (sometimes recurring)
Visual disturbances (when medications also contain antispasmodic drugs)
Irregular body temperature
Variation in rate and depth of respiration
Hypoxia and hyperventilation (two aspirin can contribute to)
Nausea, ringing in ears, deafness, diarrhea, and hallucinations when taken in
excessive dosages
Corrosive action on the stomach lining
Gastrointestinal problems
Decreased clotting ability of the blood (clotting ability could be the difference
between life and death in a survival situation)
and use of marijuana withing their border. The
FAA has stated, "Marijuana is an illicit drug per
federal law and its use by airmen is pro hibited."
Stimulants are drugs that excite the cen tral nerv ous
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.
Some drugs that are classified as neither stimulants nor
depressants have adverse effects on flying. For example,
some antibiotics can produce dangerous side effects, such
as balance disorders, hearing loss, nausea, and vomiting.
While many antibiotics are safe for use while flying, the
infection requiring the antibiotic may prohibit flying. In
addition, unless specifically prescribed by a physician, do
not take more than one drug at a time, and never mix drugs
with alcohol because the effects are often unpredictable.
The dangers of illegal drugs also are well documented.
Certain illegal drugs can have hallucinatory effects that occur
days or weeks after the drug is taken. Obviously, these drugs
have no place in the aviation community.
14 CFR prohibits pilots from performing crewmember
duties while using any medication that affects the body in
any way contrary to safety. The safest rule is not to fly as a
crewmember while taking any medication, unless approved to
do so by the FAA. If there is any doubt regarding the effects
of any medication, consult an AME before flying.
Prior to each and every flight, all pilots must do a proper
physical self-assessment to ensure safety. A great mnemonic,
covered in Chapter 2 on Aeronautical Decision-Making,
is IMSAFE, which stands for Illness, Medication, Stress,
Alcohol, Fatigue, and Emotion.
For the medication component of IMSAFE, pilots need to
ask themselves, “Am I taking any medicines that might affect
my judgment or make me drowsy? For any new medication,
OTC or prescribed, you should wait at least 48 hours after
the first dose before flying to determine you do not have any
adverse side effects that would make it unsafe to operate an
aircraft. In addition to medication questions, pilots should
also consider the following –
• Do not take any unnecessary or elective medications;
• Make sure you eat regular balanced meals;
• Bring a snack for both you and your passengers for
the flight;
• Maintain good hydration - bring plenty of water;
• Ensure adequate sleep the night prior to the flight; and
• Stay physically fit.
Additionally, you should wait at least five maximal dosing
intervals, the time between recommended or prescribed
dosing, (e.g., a dosing interval of 5 to 6 hours would require
you to wait 30 hours) before flying after taking any medication
that has potentially adverse side effects (e.g., sedating or
dizziness). Observing the recommended dosing interval
doesn’t eliminate the risk for adverse side effects because
everyone metabolizes medications differently. However,
five times the dosing interval is a reasonable rule of thumb.
Altitude-Induced Decompression Sickness (DCS)
Decompression sickness (DCS) describes a condition
characterized by a variety of symptoms resulting from
exposure to low barometric pressures that cause inert gases
(mainly nitrogen), normally dissolved in body fluids and
tissues, to come out of physical solution and form bubbles.
Nitrogen is an inert gas normally stored throughout the
human body (tissues and fluids) in physical solution. When
the body is exposed to decreased barometric pressures (as in
flying an unpressurized aircraft to altitude or during a rapid
decompression), the nitrogen dissolved in the body comes out
of solution. If the nitrogen is forced to leave the solution too
rapidly, bubbles form in different areas of the body causing a
variety of signs and symptoms. The most common symptom
is joint pain, which is known as “the bends.” [Figure 17-10]
What to do when altitude-induced DCS occurs:
• Put on oxygen mask immediately and switch the
regulator to 100 percent oxygen.
• B egin an emergency descent and land as soon as
possible. Even if the symptoms disappear during
descent, land and seek medical evaluation while
continuing to breathe oxygen.
• If one of the symptoms is joint pain, keep the affected
area still; do not try to work pain out by moving the
joint around.
• Upon landing, seek medical assistance from an FAA
medical officer, AME, military flight surgeon, or
a hyperbaric medicine specialist. Be aware that a
physician not specialized in aviation or hypobaric
medicine may not be familiar with this type of medical
problem.
• Definitive medical treatment may involve the use of
a hyperbaric chamber operated by specially-trained
personnel.
• Delayed signs and symptoms of altitude-induced DCS
can occur after return to ground level regardless of
presence during flight.
DCS After Scuba Diving
Scuba diving subjects the body to increased pressure, which
allows more nitrogen to dissolve in body tissues and fluids.
[Figure 17-11] The reduction of atmospheric pressure that
accompanies flying can produce physical problems for scuba
divers. A pilot or passenger who intends to fly after scuba
diving should allow the body sufficient time to rid itself of
excess nitrogen absorbed during diving. If not, DCS due to