electrical coaxial cable. The quantity gauge is
marked in liters from zero to the systems
maximum storage capacity (i.e., 0 to 10). The
gauge constantly shows the remaining liquid in
the converter. The low quantity warning light is
also connected to the coaxial cable and illuminates
when the quantity of liquid in the converter falls
below 1 liter. The maintenance of the quantity
indicating and warning light system is the
responsibility of the AE rating. You, as an AME,
must understand the operation of the electrical
portion of the LOX system in order to
troubleshoot the indicator and warning systems.
Oxygen Shutoff Valve
The oxygen shutoff valve is installed in the
system to control the flow of oxygen to the pilot
or flight crew, as required. Figure 4-11 illustrates
a typical manually operated two-position valve.
This valve has an inlet port, outlet port, and a
relief port. The pressure-relief valve is located in
the inlet chamber to protect the oxygen regulator
and crew member from excessive system pressure
if there is a malfunction of the liquid oxygen
converter. Also, excessive pressure due to thermal
expansion of gaseous oxygen trapped within the
system when not in use is relieved by this valve.
If the oxygen system incorporates a console-
mounted regulator, the shutoff valve is a part of
the regulator.
Composite Quick-Disconnect Coupling
The purpose of the composite quick-dis-
connect coupling is to provide a single-point
connection for quickly connecting and dis-
connecting the pilot with aircraft oxygen, anti-g,
communications, and ventilation air services.
Oxygen Lines
LOX systems are classed as low-pressure
systems. As such, low-pressure tubing is used in
the manufacture and repair of LOX lines. All low-
pressure tubing used in LOX systems are
aluminum alloy 5052 tubing and is nonheat-
treatable. It is manufactured in seamless, round
lengths, and is annealed to provide greater
flexibility. Aircraft oxygen systems are fitted with
5/16-, 3/8-, and 1/2-inch sizes. Low-pressure
tubing is also installed from the pressure reducer
to the outlets in reduced high-pressure oxygen
systems.
Oxygen Regulators
Regulators used with LOX systems are either
console-mounted or miniature mask-mounted.
Figure 4-11.—Oxygen shutoff valve.
The miniature mask-mounted regulator was
especially designed for use with aircraft that have
ejection seats. The console-mounted regulator is
normally used in large nonelection seat equipped
multiplace aircraft such as the E-2 and the P-3.
Miniature Oxygen Breathing
Regulator
The miniature mask oxygen regulator, shown
in a cutaway view in figure 4-12, is intended
primarily for use in aircraft having a low-pressure
LOX system and ejection seats. It is often
referred to as a miniature mask-mounted
regulator. Since it weighs only 2.3 ounces and
measures approximately 2 5/8 inches in length
and width, it is easily mounted on the oxygen
mask or user’s torso harness. It is designed so that
4-16
