showing white during inhalation and black
While at ground level, the regulator will not
normally supply oxygen from the supply system
to the mask. Therefore, the emergency pressure
control lever must be used to check the oxygen
supply function of the regulator at low altitudes.
The emergency lever is spring loaded at the
NORMAL position, and will return to NORMAL
4. Hold the emergency pressure control lever
in the TEST MASK position and observe the flow
indicator. Flow indicator should be white./
indicating a flow through the regulator.
Upon completion of the functional test, secure
the regulator as follows:
Disconnect the mask from the supply hose.
Ensure that the emergency pressure control
lever returns to the NORMAL position.
Place the diluter control lever in the 100%
Place the supply valve control lever in the
discrepancies are found or suspected.
maintenance-control should be notified.
Regulators that do not pass inspection and
cannot be repaired in the aircraft are removed and
replaced by RFI regulators. Non-RFI regulators
should be forwarded to the nearest maintenance
activity having repair capability.
make up the converter assembly. The LOX
converter has three sequences of operationfill,
buildup, and supply (fig. 4-15). In the supply
sequence, the converter alternates between the
economy and demand modes of operation.
The fill sequence begins automatically when
the servicing trailer hose filler nozzle is connected
to the filler port on the filler, buildup, and vent
valve. The hose nozzle, when attached to the fill
valve, actuates a plunger within the valve, which
places the valve in the fill and vent condition
(fig. 4-15, fill sequence, view A). The valve, when
in this position, provides an opening from the top
of the converter to the atmosphere. This open-
ing is used to vent gaseous oxygen during filling
and liquid oxygen after the converter is full.
During transfer, liquid oxygen flows into the
converter through a passage located in the
bottom of the converter. This arrangement allows
gaseous oxygen to vent through the converter top
as it is being displaced by liquid flow in the
bottom. When the converter is full, liquid flows
overboard through the vent line, giving an
indication that the converter is full. Removal of
the filler hose nozzle from the fill valve
automatically places the converter in the buildup
The LOX system shown in figure 4-7 is an
example of a typical system. This system converts
LOX to gaseous oxygen and delivers it to the crew.
The oxygen source of this system is a supply of
LOX stored in a 10-liter converter. System
pressure is maintained at 75 to 110 psi by a
pressure control valve and a pressure relief valve.
The converter in this system is installed in an aft
Through a process of controlled evaporation
within the converter assembly, LOX is converted
to gaseous oxygen as required by the occupant of
the aircraft. The oxygen is delivered to the
pilot after being warmed to a safe breathing
temperature in the heat exchanger. The flow of
oxygen is controlled in the cockpit by the shutoff
The major part of the operation of the LOX
system is controlled automatically by the units that
The buildup sequence (fig. 4-15, buildup
sequence, view B) begins when the filler hose is
removed from the converter. This sequence
provides for rapid pressure buildup to system
During this sequence, LOX from the converter
fills the buildup coil by gravity feed. Liquid in
the coil absorbs heat from the ambient air around
the coil and vaporizes, causing the pressure to
build up. The gaseous oxygen formed in the coil
then circulates through the pressure closing valve
and back to the top of the converter. This causes
more liquid to flow into the buildup coil. This
circulation continues to build up pressure until
approximately 75 psi is reached. At this pressure,
the pressure closing valve is forced closed.
Pressure continues to buildup within the system
at a slower rate, and at approximately 82 psi, the
pressure opening valve opens. When this occurs,
oxygen is available at the supply outlet. A pressure
relief valve, which is set at approximately 110 psi,