showing white during inhalation and black during exhalation. 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 when released. 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: 1. 2. 3. 4. 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% position. Place the supply valve control lever in the OFF position. 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 operation—fill, buildup, and supply (fig. 4-15). In the supply sequence, the converter alternates between the economy and demand modes of operation. Fill Sequence 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 sequence. Buildup Sequence SYSTEM OPERATION 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 equipment compartment. 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 valve. 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 operating pressure. 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, 4-22