CHAPTER 7
OXYGEN SYSTEMS
performance unless it is supplied the full amount of
A dependable supply of oxygen is an essential
oxygen that it requires. Like the engine, the body requires
element for maintaining life. Oxygen systems aboard
a means of having this oxygen supplied to it in greater
naval aircraft sustain the lives of the pilot and aircrew
amounts or under greater pressure. This need is satisfied
so they can perform their missions. AME personnel
by use of supplemental oxygen supplied directly to the
service and maintain aircraft oxygen systems.
respiratory system through an oxygen mask, and by
Therefore, it is important that AME personnel
pressurizing the aircraft to a pressure equivalent to that
understand how and why oxygen systems function as
at normal safe-breathing altitudes, or both.
they do. This chapter provides an overview of the
operating characteristics and maintenance require-
For purposes of illustration, an aviator's lungs are
ments for several aircraft oxygen systems, stressing
like a bag of air since the air in the lungs behaves in the
safety and use of the applicable maintenance instruc-
same way. If an open bag is placed in an aircraft at sea
tion manual (MIM).
level, air will escape from it continuously as the aircraft
ascends. The air pressure at 18,000 feet is only half that
IMPORTANCE OF OXYGEN
at sea level; therefore, at 18,000 feet the bag will be
subjected to only half the atmospheric pressure it was
LEARNING OBJECTIVE: Identify the im-
subjected to at sea level. For this reason, it will contain
portance of oxygen to include types, charac-
only half the oxygen molecules it had when on the
teristics, and effects of a lack of oxygen.
ground. Similarly, an aviator's lungs contain less and
No one can live without sufficient quantities of
less air as the aircraft ascends, and correspondingly less
food, water, and oxygen. Of the three, oxygen is by
oxygen. Thus the use of supplemental oxygen is neces-
far the most urgently needed. If necessary, a
sary on high-altitude flights.
well-nourished person can go without food for weeks,
living on what is stored in the body. The need for water
Up to approximately 35,000 feet, an aviator can
is more immediate, but still does not become critical for
keep sufficient oxygen in the lungs to permit normal
several days. The supply of oxygen in the body is
activity by use of oxygen equipment that supplies
limited to a few minutes. When the supply is exhausted,
oxygen upon demand (inhalation). The oxygen
death is inevitable.
received by the body on each inhalation is diluted with
decreasing amounts of air up to approximately 33,00
Oxygen starvation affects a pilot or aircrewman in
feet. Above 33,000 feet and up to approximately 35,000
much the same way that it affects an aircraft engine.
feet, this equipment provides 100 percent oxygen. At
Both the body and the engine require oxygen for the
approximately 35,000 feet, inhalation through the
burning of fuel. An engine designed for low-altitude
demand oxygen system alone will NOT provide
operation loses power and performs poorly at high
enough oxygen.
altitudes. High-altitude operation demands a means of
supplying air at higher pressure to give the engine
Above 35,000 feet and up to 43,000 feet, normal
enough oxygen for the combustion of fuel. A
activity is only possible by use of pressure demand
super-charger or compressor satisfies the engine's
equipment. This equipment consists of a super-charger
demands. What about the demands of the human body?
arrangement by which oxygen is supplied to the mask
The combustion of fuel in the human body is the
under a pressure slightly higher than that of the
source of energy for everything the aviator is required
surrounding atmosphere. Upon inhalation, oxygen is
to do with muscles, eyes, and brain. As the aircraft
forced (pressured) into the mask by the system. Upon
climbs, the amount of oxygen per unit of volume of air
exhalation, the oxygen pressure is shut off
decreases, and the aviator's oxygen intake is reduced.
automatically so that carbon dioxide can be expelled
Unless the aviator breathes additional oxygen, the eyes,
from the mask. Above 43,000 feet, the only adequate
brain, and muscles begin to fail. The body is designed
provision for the safety of the aviator is pressurization
for low-altitude operation and will not give satisfactory
of the entire body.
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