Guardian FMS 65 Series, Owner'S Manual

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10-3 Rev. A
2018-11-7
The effects of hypoxia
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on a given person cannot be accurately predicted. For example, a person
may be relatively unaffected one day, but highly susceptible the next. It is difficult to detect
hypoxia, because its victims are seldom able to judge how seriously they are affected, or if they
are affected at all. The unpleasant sensations experienced in suffocation are absent in the case of
hypoxia. Blurring of vision, slight shortness of breath, a vague, weak feeling, and a little dizziness
are the only warnings. Even these may be absent or so slight as to go unnoticed. While still
conscious, the aviator may lose all sense of time and spend his/her last moments of consciousness
in some apparently meaningless activity. In such a condition, a person is a menace to the crew as
well as to himself. Since the aviator understands that it is the reduced air pressure at higher altitudes
that determines the effect on the body, dependence should be upon the altimeter rather than
sensations or judgment to determine when oxygen is needed. The effects of hypoxia at various
altitudes are discussed in the following paragraphs
.
Below 10,000 Feet - At or below 10,000 feet, some effects of hypoxia may be present.
Generally, the eye is the first part of the body to suffer effects of hypoxia. Even at a relatively low
altitude of approximately 5,000 feet, where no other effect of hypoxia can be detected, night
vision is appreciably reduced. At 10,000 feet, night operations may be seriously handicapped by
poor night vision, which is due to mild oxygen starvation. Thus, the use of supplemental oxygen
on night flights above 5,000 feet is required. Although hypoxia affects the eyes in the daytime
as well as at night, the results during the day are usually not as noticeable below 10,000 feet.
Between 10,000 and 15,000 Feet- Although efficiency may be considerably impaired at 10,000
to 15,000 feet, death from oxygen starvation at these altitudes is virtually unknown. The greatest
dangers are from errors in judgment or performance due to drowsiness or mental confusion. At
these altitudes, long flights without oxygen produce persistent drowsiness and excessive fatigue
for many hours afterward. Frequently, persistent headaches develop soon after completion of the
flight. For these reasons, the use of oxygen on flights above 10,000 feet is required. Portable
oxygen systems are available for aircraft that do not have oxygen equipment.
Between 15,000 and 20,000 Feet - Flights at 15,000 to 20,000 feet, even for short periods, must
not be attempted without the use of oxygen. Collapse and unconsciousness are common. Failure
to use oxygen could result in death, especially when the situation is complicated by loss of blood
in combat or by shock due to pain or fear.
Between 20,000 and 25,000 Feet - During World War II, most military flying was done in
unpressurized aircraft at altitudes of between 20,000 and 25,000 feet. Most of the resulting anoxia
deaths occurred in this altitude range. The general symptoms of drowsiness, mental confusion, dim
vision, and dizziness occur here, as at lower altitudes, but they come on much more quickly,
allowing less opportunity for corrective action. Consequently, under no circumstances should
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