CHAPTER 4
OXYGEN SYSTEMS
Terminal Objective: Upon completion of this chapter, you will be able to
recognize the importance, characteristics, and uses of oxygen and identify
oxygen systems, components, and their functions.
A dependable supply of oxygen is an essential
element for the sustainment of life. Oxygen
systems aboard naval aircraft sustain the lives of
the pilot and aircrew so they can perform their
missions. AME personnel service and maintain
aircraft oxygen systems. Therefore, it is very
important that AME personnel understand how
and why oxygen systems function as they do. This
chapter provides an overview of the operating
characteristics and maintenance requirements for
several specific aircraft oxygen systems, stressing
safety and the use of the applicable Maintenance
Instructions Manual (MIM).
IMPORTANCE OF OXYGEN
Learning Objective: Recognize the impor-
tance of oxygen to include types,
characteristics, and the effects of a lack of
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 person 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 will not become critical for several days.
The supply of oxygen in the body is limited to a
few minutes. When that supply is exhausted,
death is inevitable.
Oxygen starvation affects a pilot or air-
crewman in much the same way that it affects an
aircraft engine. Both the body and the engine
require oxygen for the burning of fuel. 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 fuel. A super-
charger or compressor satisfies the engines
demands. What about the demands of the human
body?
The combustion of fuel in the human body
is the source of energy for everything the aviator
is required to do with muscles, eyes, and brain.
As the aircraft climbs, the amount of oxygen per
unit of volume of air decreases, and the aviator’s
oxygen intake is reduced. Unless the aviator
breathes additional oxygen, the eyes, brain, and
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 use of
supplemental oxygen supplied directly to the
respiratory system through an oxygen mask, and
by pressurizing the aircraft to a pressure
equivalent to that at normal safe-breathing
altitudes, or both.
For purposes of illustration, an aviator’s lungs
are like a bag of air since the air in the lungs
behaves in the same way. If an open bag is placed
in an aircraft at sea level, air will escape from it
continuously as the aircraft ascends. The air
pressure at 18,000 feet is only half that at sea level;
therefore, at 18,000 feet the bag will be 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 necessary on high-
altitude flights.
4-1
