CHAPTER 11
OXYGEN COMPONENTS TEST STANDS
Learning Objective: Upon completion of this chapter, you will be able to
identify, maintain, and perform periodic inspections on oxygen components
test stands.
Aircrew Survival Equipmentmen are respon-
sible for shop testing aircraft oxygen system
components, including regulators, emergency
oxygen systems, and other items. The AME is
responsible for checking system components in
the aircraft; however, in case of a suspected
malfunction and for periodic maintenance testing,
the component is removed from the aircraft and
brought to the oxygen shop where it is tested by
the PR. This testing is accomplished with the use
of various types of test equipment, some of which
are discussed in this chapter.
OXYGEN
No one can live without sufficient quantities
of food, water, and oxygen. Of the three, oxygen
is by far the most urgently needed. If necessary,
a well-nourished individual can go without food
for many days or weeks, living on what is stored
in the body. The need for water is more
immediate, but still the need does not become
critical for several days. The amount of oxygen
in the body is limited at best to a few minutes
supply. When that supply is exhausted, death is
prompt and inevitable.
Oxygen starvation affects a pilot or air-
crewman in much the same way that it affects an
aircraft engine—neither can function without it.
The engine requires oxygen for burning the fuel
that keeps it going. An engine designed for low-
altitude operation loses power and performs
poorly at high altitudes. High-altitude operation
demands a means of supplying air at higher
pressure to give the engine enough oxygen for the
combustion of its fuel. The supercharger or
compressor performs this function.
The combustion of fuel in the human body
is the source of energy for everything the aviator
is required to do with his muscles, with his eyes,
and with his brain. As the aircraft climbs, the
amount of oxygen per unit of volume of air
decreases; therefore, the aviator’s oxygen intake
is reduced. Unless he/she breathes additional
oxygen, the eyes, the brain, and the muscles
begin to fail. The body is designed for low-
altitude operation and will not give satisfactory
performance unless it is supplied the full amount
of oxygen that it requires. Like the engine, the
body requires a means of having this oxygen
supplied to it in greater amounts or under greater
pressure. This need is satisfied by the use of
supplemental oxygen supplied directly to the
respiratory system through an oxygen mask, by
pressurizing the aircraft to an atmospheric
pressure equivalent to that of safebreathing
altitudes, or both.
For purposes of illustration, an aviator’s lungs
may be compared to a bottle of air. If an open
bottle is placed in an aircraft at sea level, air
escapes from it continuously as the aircraft
ascends. The air pressure at 18,000 feet is only
half the amount as that at sea level; therefore, at
18,000 feet the bottle is subjected to only half the
atmospheric pressure it was subjected to at sea
level. For this reason, it will contain only half the
oxygen molecules it had when on the ground.
In like fashion, an aviator’s lungs contain
less and less air as he/she ascends, and
correspondingly less oxygen. Thus, the use of
supplemental oxygen is an absolute necessity on
high-altitude flights. Above 35,000 feet, normal
activity is possible up to about 43,000 feet by use
of positive pressure equipment. This equipment
consists of a “supercharger” arrangement by
which the oxygen is supplied to the mask under
a pressure slightly higher than that of the
surrounding atmosphere. Upon inhalation, the
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