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
hypoxire 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
breathing.
8-1-4. Carbon Monoxide Poisoning in
Flight
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
hypoxia occur.
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
monoxide poisoning.
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

Fitness for Flight

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
of altitude.
(d) Somatogravic illusion. A rapid acceleration during takeoff can create the illusion of being

8-1-5