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Fitness for Flight



3. Hyperventilation in Flight


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.


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.


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 immediate-

ly 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




4. Carbon Monoxide Poisoning in



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

hypoxia occur.


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

monoxide poisoning.


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.



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.


Various complex motions and forces and

certain visual scenes encountered in flight can create

illusions of motion and position. Spatial disorienta-

tion 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 move-

ment 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

of altitude.

(d) Somatogravic illusion.

A rapid accel-

eration during takeoff can create the illusion of being

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