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 can lead to emotional illness.
If suffering from acute fatigue, stay on the ground. If fatigue occurs in the basket, no amount of training or experience can
overcome the detrimental effects. Getting adequate rest and nutrition 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.
Dehydration & Heatstroke
Dehydration is the term given to a critical loss of water from the body. The first noticeable effect of dehydration is fatigue,
which in turn makes top physical and mental performance difficult, if not impossible. As a pilot, flying for long periods in
hot summer temperatures or at high altitudes increases the susceptibility of dehydration since the dry air at altitude tends to
increase the rate of water loss from the body. If this fluid is not replaced, fatigue progresses to dizziness, weakness, nausea,
tingling of hands and feet, abdominal cramps, and extreme thirst. [Figure 9-4]
Figure 9-4. Hydration is important both before and after participating in outdoor activities. While for obvious reasons during hot
weather, an individual can dehydrate during cold weather, too.
Heatstroke is a condition caused by inability of the body to control its temperature. Onset of this condition may be
recognized by the symptoms of dehydration, but it has also been recognized only by complete collapse.
To prevent these symptoms, it is recommended that a pilot carry an ample supply of water to drink at frequent intervals on
any long flight, whether thirsty or not.
Alcohol
Alcohol impairs the efficiency of the human body. Studies have proven 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 can occur after
consuming only one alcoholic drink.
The alcohol consumed in beer and mixed drinks is ethyl alcohol, a powerful central nervous system depressant. 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 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 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.
When experiencing a hangover, a pilot is still under the influence of alcohol. Although a pilot may think that they are
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, section 91.17 requires that blood alcohol level be less than 0.04 percent and that 8 hours pass
between drinking alcohol and piloting an aircraft. A pilot with a blood alcohol level of 0.04 percent or greater after 8 hours
cannot fly until the blood alcohol falls below that amount. Even though blood alcohol may be well below 0.04 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
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. 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 sedatives, tranquilizers, or antihistamines can make a pilot more susceptible to hypoxia.
Painkillers can be 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 (e.g., Tylenol), and ibuprofen (e.g.,
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 may 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 so 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.
Some drugs, which can be classified as neither stimulants nor depressants, have adverse effects on flying. For example,
some forms of 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 part 65 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.
Scuba Diving
Scuba diving subjects the body to increased pressure, which allows more nitrogen to dissolve in body tissues and fluids.
The reduction of atmospheric pressure that accompanies flying can produce physical problems for scuba divers. Reducing
the pressure too quickly allows small bubbles of nitrogen to form inside the body as the gas comes out of solution. These
bubbles can cause a painful and potentially incapacitating condition called the bends. (An example is dissolved gas forming
bubbles as pressure decreases by slowly opening a transparent bottle of carbonated beverage.) Scuba training emphasizes
how to prevent the bends when rising to the surface, but increased nitrogen concentrations can remain in tissue fluids for
several hours after a diver leaves the water. The bends can be experienced from as low as 8,000 feet MSL, with increasing
severity as altitude increases. As noted in the Aeronautical Information Manual (AIM), the minimum recommended time
between scuba diving on non-decompression stop dives and flying is 12 hours, while the minimum time recommended
between decompression stop diving and flying is 24 hours. [Figure 9-5]
Figure 9-5. The reduction of atmospheric pressure that accompanies flying can produce physical problems for scuba divers.
Vision in Flight
Of all the senses, vision is the most important for safe flight. Most of the things perceived while flying are visual or heavily
supplemented by vision. As remarkable and vital as it is, vision is subject to some limitations, such as illusions and blind
spots. The more a pilot understands about the eyes and how they function, the easier it is to use vision effectively and
compensate for potential problems.
The eye functions much like a camera. Its structure includes an aperture, a lens, a mechanism for focusing, and a surface
for registering images. Light enters through the cornea at the front of the eyeball, travels through the lens, and falls on the
retina. The retina contains light sensitive cells that convert light energy into electrical impulses that travel through nerves
to the brain. The brain interprets the electrical signals to form images. There are two kinds of light-sensitive cells in the
eyes: rods and cones. [Figure 9-6]
The rods and
cones (film) of
the retina are
the receptors
which record
the image and
transmit it
through the
optic nerve to
the brain for
interpretation.
Rods and
Cones
Fovea
(All Cones)
The pupil (aperture) is the opening at
the center of the iris. The size of the
pupil is adjusted to control the amount
of light entering the eye.
PUPIL
Light passes through the cornea (the
transparent window on the front of the
eye) and then through the lens to
focus on the retina.
CORNEA
Lens
Iris
Rod Concentration
Retina
Optic Nerve
Figure 9-6. The human eye.
The cones are responsible for all color vision, from appreciating a glorious sunset to discerning the subtle shades in a fine
painting. Cones are present throughout the retina, but are concentrated toward the center of the field of vision at the back
of the retina. There is a small pit called the fovea where almost all the light sensing cells are cones. This is the area where
most “looking” occurs (the center of the visual field where detail, color sensitivity, and resolution are highest).
While the cones and their associated nerves are well suited to detecting fine detail and color in high light levels, the rods are
better able to detect movement and provide vision in dim light. The rods are unable to discern color but are very sensitive
at low light levels. However, a large amount of light overwhelms the rods, and they take a long time to “reset” and adapt
to the dark again. There are so many cones in the fovea that the very center of the visual field has virtually no rods at
all. Therefore, the middle of the visual field is not very sensitive in low light. Farther from the fovea, the rods are more
numerous and provide the major portion of night vision.
The area where the optic nerve enters the eyeball has no rods or cones, leaving a blind spot in the field of vision. Normally,
each eye compensates for the other’s blind spot. Figure 9-7 provides a dramatic example of the eye’s blind spot. Cover the
right eye and hold this page at arm’s length. Focus the left eye on the X in the right side of the windshield, and notice what
happens to the balloon while slowly bringing the page closer to the eye.
Figure 9-7. The eye’ s blind spot.
Empty-Field Myopia
Another problem associated with flying at night or in reduced visibility is empty-field myopia, or induced nearsightedness.
With nothing on which to focus, the eyes automatically focus on a point just slightly ahead of the aircraft. Searching out
and focusing on distant light sources, no matter how dim, helps prevent the onset of empty-field myopia.
Night Vision
It is estimated that once fully adapted to darkness, the rods are 10,000 times more sensitive to light than the cones, making
them the primary receptors for night vision. [Figure 9-8] Since the cones are concentrated near the fovea, the rods are also
responsible for much of the peripheral vision. The concentration of cones in the fovea can create a night blind spot in the
center of the field of vision. To see an object clearly at night, the pilot should expose the rods to the image. This can be done
by looking 5° to 10° off center of the object to be seen. This can be tried in a dimly lighted room. When looking directly at
the light, it dims or disappears altogether. When looking slightly off center, it becomes clearer and brighter.
Cones active
Rods active
Night blind spot
Figure 9-8. Night blind spot
When looking slightly off center, it becomes clearer and brighter. Refer to Figure 9-8. When looking directly at an object,
the image is focused mainly on the fovea, where detail is best seen. At night, the ability to see an object in the center of the
visual field is reduced as the cones lose much of their sensitivity and the rods become more sensitive. Looking off center
can help compensate for this night blind spot. Along with the loss of acuity (sharpness) and color at night, depth perception
and judgment of size may be lost.
Balloon pilots, while not normally conducting flight operations at night, can experience similar issues when flying in low
light conditions, particularly if there is haze or reduced visibility. In those instances where the balloon is operated at night,
such as during a night “glow” or tether, night vision can be immediately destroyed by the light from the burner. It may take
several minutes for the pilot to recover their vision, time in which complete awareness of their surroundings is lost. If those
surroundings include people, a potentially dangerous situation can ensue. Closing one eye during a burn and not looking
at the burner flame will minimize this momentary blindness.
Diet and general physical health have an impact on how well a pilot can see in the dark. Deficiencies in vitamins A and
C have been shown to reduce night visual acuity. Other factors, such as carbon monoxide poisoning, smoking, alcohol,
certain drugs, and a lack of oxygen also can greatly decrease night vision.
Chapter Summary
Balloon pilots and glider pilots are unique in that they “self-certify” they are physically fit to conduct flight duties. This
is an individual responsibility and must not be abused. The ability to “self-certify” becomes particularly problematic after
the balloon pilot has had a major medical issue arise, such as a heart attack, angina, major surgery, and other items in this
category. While they may be perfectly capable of piloting a balloon after triple bypass surgery, for example, it may not be
the recommended course of action.
The best recommendation is to be aware of the provisions of 14 CFR part 67 and 14 CFR part 61, section 61.53. A
balloon pilot who is not required to hold a medical certificate would still be well advised to consult with an AME or a
physician who is familiar with aeromedical factors regarding medical issues which may be medically disqualifying and
obtain recommendations on how best to proceed.