Chapter 8. Medical Facts for Pilots
Section 1. Fitness for Flight
8-1-1. Fitness For Flight
a. Medical Certification.
1. All pilots except those flying gliders and free
air balloons must possess valid medical certificates in
order to exercise the privileges of their airman
certificates. The periodic medical examinations
required for medical certification are conducted by
designated Aviation Medical Examiners, who are
physicians with a special interest in aviation safety
and training in aviation medicine.
2. The standards for medical certification are
contained in 14 CFR Part 67. Pilots who have a
history of certain medical conditions described in
these standards are mandatorily disqualified from
flying. These medical conditions include a
personality disorder manifested by overt acts, a
psychosis, alcoholism, drug dependence, epilepsy,
an unexplained disturbance of consciousness,
myocardial infarction, angina pectoris and diabetes
requiring medication for its control. Other medical
conditions may be temporarily disqualifying, such as
acute infections, anemia, and peptic ulcer. Pilots who
do not meet medical standards may still be qualified
under special issuance provisions or the exemption
process. This may require that either additional
medical information be provided or practical flight
tests be conducted.
3. Student pilots should visit an Aviation
Medical Examiner as soon as possible in their flight
training in order to avoid unnecessary training
expenses should they not meet the medical standards.
For the same reason, the student pilot who plans to
enter commercial aviation should apply for the
highest class of medical certificate that might be
necessary in the pilot's career.
The CFRs prohibit a pilot who possesses a current
medical certificate from performing crewmember duties
while the pilot has a known medical condition or increase
of a known medical condition that would make the pilot
unable to meet the standards for the medical certificate.
1. Even a minor illness suffered in day-to-day
living can seriously degrade performance of many
piloting tasks vital to safe flight. Illness can produce
fever and distracting symptoms that can impair
judgment, memory, alertness, and the ability to make
calculations. Although symptoms from an illness
may be under adequate control with a medication, the
medication itself may decrease pilot performance.
2. The safest rule is not to fly while suffering
from any illness. If this rule is considered too
stringent for a particular illness, the pilot should
contact an Aviation Medical Examiner for advice.
1. Pilot performance can be seriously degraded
by both prescribed 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-suppressant preparations, 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 a sedative, tranquilizer or
antihistamine, can make a pilot much more
susceptible to hypoxia.
2. The CFRs prohibit pilots from performing
crewmember duties while using any medication that
affects the faculties 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.
1. Extensive research has provided a number of
facts about the hazards of alcohol consumption and
flying. As little as one ounce of liquor, one bottle of
beer or four ounces of wine can impair flying skills,
with the alcohol consumed in these drinks being
detectable in the breath and blood for at least 3 hours.
Even after the body completely destroys a moderate
amount of alcohol, a pilot can still be severely
impaired for many hours by hangover. There is
simply no way of increasing the destruction of
alcohol or alleviating a hangover. Alcohol also
renders a pilot much more susceptible to disorientation and hypoxia.
2. A consistently high alcohol related fatal
aircraft accident rate serves to emphasize that alcohol
and flying are a potentially lethal combination. The
CFRs prohibit pilots from performing crewmember
duties within 8 hours after drinking any alcoholic
beverage or while under the influence of alcohol.
However, due to the slow destruction of alcohol, a
pilot may still be under influence 8 hours after
drinking a moderate amount of alcohol. Therefore, an
excellent rule is to allow at least 12 to 24 hours
between "bottle and throttle," depending on the
amount of alcoholic beverage consumed.
1. Fatigue continues to be one of the most
treacherous hazards to flight safety, as it may not be
apparent to a pilot until serious errors are made.
Fatigue is best described as either acute (short-term)
or chronic (long-term).
2. A normal occurrence of everyday living,
acute fatigue is the tiredness felt after long periods of
physical and mental strain, including strenuous
muscular effort, immobility, heavy mental workload,
strong emotional pressure, monotony, and lack of
sleep. Consequently, coordination and alertness, so
vital to safe pilot performance, can be reduced. Acute
fatigue is prevented by adequate rest and sleep, as
well as by regular exercise and proper nutrition.
3. Chronic fatigue occurs when there is not
enough time for full recovery between episodes of
acute fatigue. Performance continues to fall off, and
judgment becomes impaired so that unwarranted
risks may be taken. Recovery from chronic fatigue
requires a prolonged period of rest.
4. OBSTRUCTIVE SLEEP APNEA (OSA).
OSA is now recognized as an important preventable
factor identified in transportation accidents. OSA
interrupts the normal restorative sleep necessary for
normal functioning and is associated with chronic
illnesses such as hypertension, heart attack, stroke,
obesity, and diabetes. Symptoms include snoring,
excessive daytime sleepiness, intermittent prolonged
breathing pauses while sleeping, memory impairment and lack of concentration. There are many
available treatments which can reverse the day time
symptoms and reduce the chance of an accident. OSA
can be easily treated. Most treatments are acceptable
for medical certification upon demonstrating effective treatment. If you have any symptoms described
above, or neck size over 17 inches in men or 16 inches
in women, or a body mass index greater than 30 you
should be evaluated for sleep apnea by a sleep
english_bmi_calculator/bmi_calculator.html) With treatment you can avoid or delay
the onset of these chronic illnesses and prolong a
1. Stress from the pressures of everyday living
can impair pilot performance, often in very subtle
ways. Difficulties, particularly at work, can occupy
thought processes enough to markedly decrease
alertness. Distraction can so interfere with judgment
that unwarranted risks are taken, such as flying into
deteriorating weather conditions to keep on schedule.
Stress and fatigue (see above) can be an extremely
2. Most pilots do not leave stress
ground." Therefore, when more than usual difficulties are being experienced, a pilot should consider
delaying flight until these difficulties are satisfactorily resolved.
Certain emotionally upsetting events, including a
serious argument, death of a family member,
separation or divorce, loss of job, and financial
catastrophe, can render a pilot unable to fly an aircraft
safely. The emotions of anger, depression, and
anxiety from such events not only decrease alertness
but also may lead to taking risks that border on
self-destruction. Any pilot who experiences an
emotionally upsetting event should not fly until
satisfactorily recovered from it.
h. Personal Checklist. Aircraft accident statistics show that pilots should be conducting preflight
checklists on themselves as well as their aircraft for
pilot impairment contributes to many more accidents
than failures of aircraft systems. A personal checklist,
which includes all of the categories of pilot
impairment as discussed in this section, that can be
easily committed to memory is being distributed by
the FAA in the form of a wallet-sized card.
i. PERSONAL CHECKLIST. I'm physically
and mentally safe to fly; not being impaired by:
8-1-2. Effects of Altitude
1. Hypoxia is a state of oxygen deficiency in the
body sufficient to impair functions of the brain and
other organs. Hypoxia from exposure to altitude is
due only to the reduced barometric pressures
encountered at altitude, for the concentration of
oxygen in the atmosphere remains about 21 percent
from the ground out to space.
2. Although a deterioration in night vision
occurs at a cabin pressure altitude as low as
5,000 feet, other significant effects of altitude
hypoxia usually do not occur in the normal healthy
pilot below 12,000 feet. From 12,000 to 15,000 feet
of altitude, judgment, memory, alertness, coordination and ability to make calculations are impaired,
and headache, drowsiness, dizziness and either a
sense of well-being (euphoria) or belligerence occur.
The effects appear following increasingly shorter
periods of exposure to increasing altitude. In fact,
pilot performance can seriously deteriorate within
15 minutes at 15,000 feet.
3. At cabin pressure altitudes above 15,000 feet,
the periphery of the visual field grays out to a point
where only central vision remains (tunnel vision). A
blue coloration (cyanosis) of the fingernails and lips
develops. The ability to take corrective and protective
action is lost in 20 to 30 minutes at 18,000 feet and
5 to 12 minutes at 20,000 feet, followed soon
thereafter by unconsciousness.
4. The altitude at which significant effects of
hypoxia occur can be lowered by a number of factors.
Carbon monoxide inhaled in smoking or from
exhaust fumes, lowered hemoglobin (anemia), and
certain medications can reduce the oxygen-carrying
capacity of the blood to the degree that the amount of
oxygen provided to body tissues will already be
equivalent to the oxygen provided to the tissues when
exposed to a cabin pressure altitude of several
thousand feet. Small amounts of alcohol and low
doses of certain drugs, such as antihistamines,
tranquilizers, sedatives and analgesics can, through
their depressant action, render the brain much more
susceptible to hypoxia. Extreme heat and cold, fever,
and anxiety increase the body's demand for oxygen,
and hence its susceptibility to hypoxia.
5. The effects of hypoxia are usually quite
difficult to recognize, especially when they occur
gradually. Since symptoms of hypoxia do not vary in
an individual, the ability to recognize hypoxia can be
greatly improved by experiencing and witnessing the
effects of hypoxia during an altitude chamber
"flight." The FAA provides this opportunity through
aviation physiology training, which is conducted at
the FAA Civil Aeromedical Institute and at many
military facilities across the U.S. To attend the
Physiological Training Program at the Civil
Aeromedical Institute, Mike Monroney Aeronautical
Center, Oklahoma City, OK, contact by telephone
(405) 954-6212, or by writing Aerospace Medical
Education Division, AAM-400, CAMI, Mike
Monroney Aeronautical Center, P.O. Box 25082,
Oklahoma City, OK 73125.
To attend the physiological training program at one of the
military installations having the training capability, an
application form and a fee must be submitted. Full
particulars about location, fees, scheduling procedures,
course content, individual requirements, etc., are contained in the Physiological Training Application, Form
Number AC 3150-7, which is obtained by contacting the
accident prevention specialist or the office forms manager
in the nearest FAA office.
6. Hypoxia is prevented by heeding factors that
reduce tolerance to altitude, by enriching the inspired
air with oxygen from an appropriate oxygen system,
and by maintaining a comfortable, safe cabin
pressure altitude. For optimum protection, pilots are
encouraged to use supplemental oxygen above
10,000 feet during the day, and above 5,000 feet at
night. The CFRs require that at the minimum, flight
crew be provided with and use supplemental oxygen
after 30 minutes of exposure to cabin pressure
altitudes between 12,500 and 14,000 feet and
immediately on exposure to cabin pressure altitudes
above 14,000 feet. Every occupant of the aircraft
must be provided with supplemental oxygen at cabin
pressure altitudes above 15,000 feet.
b. Ear Block.
1. As the aircraft cabin pressure decreases
during ascent, the expanding air in the middle ear
pushes the eustachian tube open, and by escaping
down it to the nasal passages, equalizes in pressure
with the cabin pressure. But during descent, the pilot
must periodically open the eustachian tube to
equalize pressure. This can be accomplished by
swallowing, yawning, tensing muscles in the throat,
or if these do not work, by a combination of closing
the mouth, pinching the nose closed, and attempting
to blow through the nostrils (Valsalva maneuver).
2. Either an upper respiratory infection, such as
a cold or sore throat, or a nasal allergic condition can
produce enough congestion around the eustachian
tube to make equalization difficult. Consequently, the
difference in pressure between the middle ear and
aircraft cabin can build up to a level that will hold the
eustachian tube closed, making equalization difficult
if not impossible. The problem is commonly referred
to as an "ear block."
3. An ear block produces severe ear pain and
loss of hearing that can last from several hours to
several days. Rupture of the ear drum can occur in
flight or after landing. Fluid can accumulate in the
middle ear and become infected.
4. An ear block is prevented 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 eustachian tubes. Oral
decongestants have side effects that can significantly
impair pilot performance.
5. If an ear block does not clear shortly after
landing, a physician should be consulted.
c. Sinus Block.
1. During ascent and descent, air pressure in the
sinuses equalizes with the aircraft cabin pressure
through small openings that connect the sinuses to the
nasal passages. Either an upper respiratory infection,
such as a cold or sinusitis, or a nasal allergic condition
can produce enough congestion around an opening to
slow equalization, and as the difference in pressure
between the sinus and cabin mounts, eventually plug
the opening. This "sinus block" occurs most
frequently during descent.
2. A sinus block can occur in the frontal sinuses,
located above each eyebrow, or in the maxillary
sinuses, located in each upper cheek. It will usually
produce excruciating pain over the sinus area. A
maxillary sinus block can also make the upper teeth
ache. Bloody mucus may discharge from the nasal
3. A sinus block is prevented 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
4. If a sinus block does not clear shortly after
landing, a physician should be consulted.
d. Decompression Sickness After Scuba
1. 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, decompression sickness due to evolved gas can
occur during exposure to low altitude and create a
serious inflight emergency.
2. The recommended waiting time before going
to flight altitudes of up to 8,000 feet is at least
12 hours after diving which has not required
controlled ascent (nondecompression stop diving),
and at least 24 hours after diving which has required
controlled ascent (decompression stop diving). The
waiting time before going to flight altitudes above
8,000 feet should be at least 24 hours after any
SCUBA dive. These recommended altitudes are
actual flight altitudes above mean sea level (AMSL)
and not pressurized cabin altitudes. This takes into
consideration the risk of decompression of the
aircraft during flight.
8-1-3. Hyperventilation in Flight
a. Hyperventilation, or an abnormal increase in
the volume of air breathed in and out of the lungs, can
occur subconsciously when a stressful situation is
encountered in flight. As hyperventilation "blows
off" excessive carbon dioxide from the body, a pilot
can experience symptoms of lightheadedness,
suffocation, drowsiness, tingling in the extremities,
and coolness and react to them with even greater
hyperventilation. Incapacitation can eventually result
from incoordination, disorientation, and painful
muscle spasms. Finally, unconsciousness can occur.
b. The symptoms of hyperventilation subside
within a few minutes after the rate and depth of
breathing are consciously brought back under
control. The buildup of carbon dioxide in the body
can be hastened by controlled breathing in and out of
a paper bag held over the nose and mouth.
c. Early symptoms of hyperventilation and
hypoxia are similar. Moreover, hyperventilation and
hypoxia can occur at the same time. Therefore, if a
pilot is using an oxygen system when symptoms are
experienced, the oxygen regulator should immediately be set to deliver 100 percent oxygen, and then the
system checked to assure that it has been functioning
effectively before giving attention to rate and depth of
8-1-4. Carbon Monoxide Poisoning in
a. Carbon monoxide is a colorless, odorless, and
tasteless gas contained in exhaust fumes. When
breathed even in minute quantities over a period of
time, it can significantly reduce the ability of the
blood to carry oxygen. Consequently, effects of
b. Most heaters in light aircraft work by air
flowing over the manifold. Use of these heaters while
exhaust fumes are escaping through manifold cracks
and seals is responsible every year for several
nonfatal and fatal aircraft accidents from carbon
c. A pilot who detects the odor of exhaust or
experiences symptoms of headache, drowsiness, or
dizziness while using the heater should suspect
carbon monoxide poisoning, and immediately shut
off the heater and open air vents. If symptoms are
severe or continue after landing, medical treatment
should be sought.
8-1-5. Illusions in Flight
a. Introduction. Many different illusions can be
experienced in flight. Some can lead to spatial
disorientation. Others can lead to landing errors.
Illusions rank among the most common factors cited
as contributing to fatal aircraft accidents.
b. Illusions Leading to Spatial Disorientation.
1. Various complex motions and forces and
certain visual scenes encountered in flight can create
illusions of motion and position. Spatial disorientation from these illusions can be prevented only by
visual reference to reliable, fixed points on the ground
or to flight instruments.
2. The leans. An abrupt correction of a banked
attitude, which has been entered too slowly to
stimulate the motion sensing system in the inner ear,
can create the illusion of banking in the opposite
direction. The disoriented pilot will roll the aircraft
back into its original dangerous attitude, or if level
flight is maintained, will feel compelled to lean in the
perceived vertical plane until this illusion subsides.
(a) Coriolis illusion. An abrupt head movement in a prolonged constant‐rate turn that has ceased
stimulating the motion sensing system can create the
illusion of rotation or movement in an entirely
different axis. The disoriented pilot will maneuver the
aircraft into a dangerous attitude in an attempt to stop
rotation. This most overwhelming of all illusions in
flight may be prevented by not making sudden,
extreme head movements, particularly while making
prolonged constant-rate turns under IFR conditions.
(b) Graveyard spin. A proper recovery
from a spin that has ceased stimulating the motion
sensing system can create the illusion of spinning in
the opposite direction. The disoriented pilot will
return the aircraft to its original spin.
(c) Graveyard spiral. An observed loss of
altitude during a coordinated constant-rate turn that
has ceased stimulating the motion sensing system can
create the illusion of being in a descent with the wings
level. The disoriented pilot will pull back on the
controls, tightening the spiral and increasing the loss
(d) Somatogravic illusion. A rapid acceleration during takeoff can create the illusion of being
in a nose up attitude. The disoriented pilot will push
the aircraft into a nose low, or dive attitude. A rapid
deceleration by a quick reduction of the throttles can
have the opposite effect, with the disoriented pilot
pulling the aircraft into a nose up, or stall attitude.
(e) Inversion illusion. An abrupt change
from climb to straight and level flight can create the
illusion of tumbling backwards. The disoriented pilot
will push the aircraft abruptly into a nose low attitude,
possibly intensifying this illusion.
(f) Elevator illusion. An abrupt upward
vertical acceleration, usually by an updraft, can create
the illusion of being in a climb. The disoriented pilot
will push the aircraft into a nose low attitude. An
abrupt downward vertical acceleration, usually by a
downdraft, has the opposite effect, with the
disoriented pilot pulling the aircraft into a nose up
(g) False horizon. Sloping cloud formations, an obscured horizon, a dark scene spread with
ground lights and stars, and certain geometric
patterns of ground light can create illusions of not
being aligned correctly with the actual horizon. The
disoriented pilot will place the aircraft in a dangerous
(h) Autokinesis. In the dark, a static light
will appear to move about when stared at for many
seconds. The disoriented pilot will lose control of the
aircraft in attempting to align it with the light.
3. Illusions Leading to Landing Errors.
(a) Various surface features and atmospheric
conditions encountered in landing can create illusions
of incorrect height above and distance from the
runway threshold. Landing errors from these
illusions can be prevented by anticipating them
during approaches, aerial visual inspection of
unfamiliar airports before landing, using electronic
glide slope or VASI systems when available, and
maintaining optimum proficiency in landing
(b) Runway width illusion. A narrower-than-usual runway can create the illusion that the aircraft is at a higher altitude than it actually is. The pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects along the approach path or landing short. A wider-than-usual runway can have the opposite effect, with the risk of leveling out high and landing hard or overshooting the runway.
(c) Runway and terrain slopes illusion. An
upsloping runway, upsloping terrain, or both, can
create the illusion that the aircraft is at a higher
altitude than it actually is. The pilot who does not
recognize this illusion will fly a lower approach. A
downsloping runway, downsloping approach terrain,
or both, can have the opposite effect.
(d) Featureless terrain illusion. An
absence of ground features, as when landing over
water, darkened areas, and terrain made featureless
by snow, can create the illusion that the aircraft is at
a higher altitude than it actually is. The pilot who does
not recognize this illusion will fly a lower approach.
(e) Atmospheric illusions. Rain on the
windscreen can create the illusion of greater height,
and atmospheric haze the illusion of being at a greater
distance from the runway. The pilot who does not
recognize these illusions will fly a lower approach.
Penetration of fog can create the illusion of pitching
up. The pilot who does not recognize this illusion will
steepen the approach, often quite abruptly.
(f) Ground lighting illusions. Lights along
a straight path, such as a road, and even lights on
moving trains can be mistaken for runway and
approach lights. Bright runway and approach lighting
systems, especially where few lights illuminate the
surrounding terrain, may create the illusion of less
distance to the runway. The pilot who does not
recognize this illusion will fly a higher approach.
Conversely, the pilot overflying terrain which has few
lights to provide height cues may make a lower than
8-1-6. Vision in Flight
a. Introduction. Of the body senses, vision is the
most important for safe flight. Major factors that
determine how effectively vision can be used are the
level of illumination and the technique of scanning
the sky for other aircraft.
b. Vision Under Dim and Bright Illumination.
1. Under conditions of dim illumination, small
print and colors on aeronautical charts and aircraft
instruments become unreadable unless adequate
cockpit lighting is available. Moreover, another
aircraft must be much closer to be seen unless its
navigation lights are on.
2. In darkness, vision becomes more sensitive to
light, a process called dark adaptation. Although
exposure to total darkness for at least 30 minutes is
required for complete dark adaptation, a pilot can
achieve a moderate degree of dark adaptation within
20 minutes under dim red cockpit lighting. Since red
light severely distorts colors, especially on aeronautical charts, and can cause serious difficulty in focusing
the eyes on objects inside the aircraft, its use is
advisable only where optimum outside night vision
capability is necessary. Even so, white cockpit
lighting must be available when needed for map and
instrument reading, especially under IFR conditions.
Dark adaptation is impaired by exposure to cabin
pressure altitudes above 5,000 feet, carbon monoxide
inhaled in smoking and from exhaust fumes,
deficiency of Vitamin A in the diet, and by prolonged
exposure to bright sunlight. Since any degree of dark
adaptation is lost within a few seconds of viewing a
bright light, a pilot should close one eye when using
a light to preserve some degree of night vision.
3. Excessive illumination, especially from light
reflected off the canopy, surfaces inside the aircraft,
clouds, water, snow, and desert terrain, can produce
glare, with uncomfortable squinting, watering of the
eyes, and even temporary blindness. Sunglasses for
protection from glare should absorb at least
85 percent of visible light (15 percent transmittance)
and all colors equally (neutral transmittance), with
negligible image distortion from refractive and
c. Scanning for Other Aircraft.
1. Scanning the sky for other aircraft is a key
factor in collision avoidance. It should be used
continuously by the pilot and copilot (or right seat
passenger) to cover all areas of the sky visible from
the cockpit. Although pilots must meet specific visual
acuity requirements, the ability to read an eye chart
does not ensure that one will be able to efficiently spot
other aircraft. Pilots must develop an effective
scanning technique which maximizes one's visual
capabilities. The probability of spotting a potential
collision threat obviously increases with the time
spent looking outside the cockpit. Thus, one must use
timesharing techniques to efficiently scan the
surrounding airspace while monitoring instruments
2. While the eyes can observe an approximate
200 degree arc of the horizon at one glance, only a
very small center area called the fovea, in the rear of
the eye, has the ability to send clear, sharply focused
messages to the brain. All other visual information
that is not processed directly through the fovea will be
of less detail. An aircraft at a distance of 7 miles
which appears in sharp focus within the foveal center
of vision would have to be as close as 7/10 of a mile
in order to be recognized if it were outside of foveal
vision. Because the eyes can focus only on this
narrow viewing area, effective scanning is accomplished with a series of short, regularly spaced eye
movements that bring successive areas of the sky into
the central visual field. Each movement should not
exceed 10 degrees, and each area should be observed
for at least 1 second to enable detection. Although
horizontal back-and-forth eye movements seem
preferred by most pilots, each pilot should develop a
scanning pattern that is most comfortable and then
adhere to it to assure optimum scanning.
3. Studies show that the time a pilot spends on
visual tasks inside the cabin should represent no more
that 1/4 to 1/3 of the scan time outside, or no more than
4 to 5 seconds on the instrument panel for every
16 seconds outside. Since the brain is already trained
to process sight information that is presented from
left to right, one may find it easier to start scanning
over the left shoulder and proceed across the
windshield to the right.
4. Pilots should realize that their eyes may
require several seconds to refocus when switching
views between items in the cockpit and distant
objects. The eyes will also tire more quickly when
forced to adjust to distances immediately after
close-up focus, as required for scanning the
instrument panel. Eye fatigue can be reduced by
looking from the instrument panel to the left wing
past the wing tip to the center of the first scan quadrant
when beginning the exterior scan. After having
scanned from left to right, allow the eyes to return to
the cabin along the right wing from its tip inward.
Once back inside, one should automatically commence the panel scan.
5. Effective scanning also helps avoid
"empty-field myopia." This condition usually occurs when flying above the clouds or in a haze layer that provides nothing specific to focus on outside the aircraft. This causes the eyes to relax and seek a comfortable focal distance which may range from 10 to 30 feet. For the pilot, this means looking without seeing, which is dangerous.
8-1-7. Aerobatic Flight
a. Pilots planning to engage in aerobatics should
be aware of the physiological stresses associated with
accelerative forces during aerobatic maneuvers.
Many prospective aerobatic trainees enthusiastically
enter aerobatic instruction but find their first
experiences with G forces to be unanticipated and
very uncomfortable. To minimize or avoid potential
adverse effects, the aerobatic instructor and trainee
must have a basic understanding of the physiology of
G force adaptation.
b. Forces experienced with a rapid push-over
maneuver result in the blood and body organs being
displaced toward the head. Depending on forces
involved and individual tolerance, a pilot may
experience discomfort, headache, "red-out," and
c. Forces experienced with a rapid pull-up
maneuver result in the blood and body organ
displacement toward the lower part of the body away
from the head. Since the brain requires continuous
blood circulation for an adequate oxygen supply,
there is a physiologic limit to the time the pilot can
tolerate higher forces before losing consciousness.
As the blood circulation to the brain decreases as a
result of forces involved, a pilot will experience
"narrowing" of visual fields, "gray-out," "black-out," and unconsciousness. Even a brief loss of consciousness in a maneuver can lead to improper control movement causing structural failure of the aircraft or collision with another object or terrain.
d. In steep turns, the centrifugal forces tend to
push the pilot into the seat, thereby resulting in blood
and body organ displacement toward the lower part of
the body as in the case of rapid pull-up maneuvers and
with the same physiologic effects and symptoms.
e. Physiologically, humans progressively adapt to
imposed strains and stress, and with practice, any
maneuver will have decreasing effect. Tolerance to
G forces is dependent on human physiology and the
individual pilot. These factors include the skeletal
anatomy, the cardiovascular architecture, the nervous
system, the quality of the blood, the general physical
state, and experience and recency of exposure. The
pilot should consult an Aviation Medical Examiner
prior to aerobatic training and be aware that poor
physical condition can reduce tolerance to accelerative forces.
f. The above information provides pilots with a
brief summary of the physiologic effects of G forces.
It does not address methods of "counteracting" these
effects. There are numerous references on the subject
of G forces during aerobatics available to pilots.
Among these are "G Effects on the Pilot During
Aerobatics," FAA-AM-72-28, and "G Incapacitation in Aerobatic Pilots: A Flight Hazard"
FAA-AM-82-13. These are available from the
National Technical Information Service, Springfield,
FAA AC 91-61, A Hazard in Aerobatics: Effects of G-forces on Pilots.
8-1-8. Judgment Aspects of Collision
a. Introduction. The most important aspects of
vision and the techniques to scan for other aircraft are
described in paragraph 8-1-6, Vision in Flight. Pilots
should also be familiar with the following information to reduce the possibility of mid-air collisions.
b. Determining Relative Altitude. Use the
horizon as a reference point. If the other aircraft is
above the horizon, it is probably on a higher flight
path. If the aircraft appears to be below the horizon,
it is probably flying at a lower altitude.
c. Taking Appropriate Action. Pilots should be
familiar with rules on right-of-way, so if an aircraft is
on an obvious collision course, one can take
immediate evasive action, preferably in compliance
with applicable Federal Aviation Regulations.
d. Consider Multiple Threats. The decision to
climb, descend, or turn is a matter of personal
judgment, but one should anticipate that the other
pilot may also be making a quick maneuver. Watch
the other aircraft during the maneuver and begin your
scanning again immediately since there may be other
aircraft in the area.
e. Collision Course Targets. Any aircraft that
appears to have no relative motion and stays in one
scan quadrant is likely to be on a collision course.
Also, if a target shows no lateral or vertical motion,
but increases in size, take evasive action.
f. Recognize High Hazard Areas.
1. Airways, especially near VORs, and Class B,
Class C, Class D, and Class E surface areas are places
where aircraft tend to cluster.
2. Remember, most collisions occur during days
when the weather is good. Being in a "radar
environment" still requires vigilance to avoid
g. Cockpit Management. Studying maps,
checklists, and manuals before flight, with other
proper preflight planning; e.g., noting necessary
radio frequencies and organizing cockpit materials,
can reduce the amount of time required to look at
these items during flight, permitting more scan time.
h. Windshield Conditions. Dirty or bug-smeared windshields can greatly reduce the ability of pilots to see other aircraft. Keep a clean windshield.
i. Visibility Conditions. Smoke, haze, dust, rain,
and flying towards the sun can also greatly reduce the
ability to detect targets.
j. Visual Obstructions in the Cockpit.
1. Pilots need to move their heads to see around
blind spots caused by fixed aircraft structures, such as
door posts, wings, etc. It will be necessary at times to
maneuver the aircraft; e.g., lift a wing, to facilitate
2. Pilots must ensure curtains and other cockpit
objects; e.g., maps on glare shield, are removed and
stowed during flight.
k. Lights On.
1. Day or night, use of exterior lights can greatly
increase the conspicuity of any aircraft.
2. Keep interior lights low at night.
l. ATC Support. ATC facilities often provide
radar traffic advisories on a workload-permitting
basis. Flight through Class C and Class D airspace
requires communication with ATC. Use this support
whenever possible or when required.