functionally test the converter assembly and air-
craft oxygen system, proceed as follows:
1. Ensure all circuit breakers associated with
the LOX quantity indicating system are set.
External electrical power must be applied to the
aircraft to perform steps 2 and 3 below.
2. Depress oxygen test switch. Check the
quantity gauge and low warning light for proper
operation. Refer to the applicable aircraft Hand-
book of Maintenance Instructions (HMI) to
determine at what quantity (indicated on quantity
gauge) that the low warning light should
3. Release test switch. Ensure gauge pointer
returns to position registered on gauge before
depressing. When test is completed, disconnect
electrical power for aircraft.
4. Ensure oxygen shutoff valve is in the OFF
5. Attach an oxygen mask, regulator and
regulator-to-seat kit hose assembly to oxygen
supply connection in aircraft.
6. Turn oxygen shutoff valve to the ON posi-
tion. There should be a flow of oxygen through
7. Place the mask against your face and
breathe. There should be a slight resistance during
exhalation. This resistance is due to the positive
pressure feature of the regulator.
8. Upon completing the functional test, turn
the oxygen shutoff valve to OFF. Disconnect the
regulator-to-seat kit hose from the aircraft supply
If discrepancies are found or suspected, notify
Components of the aircraft oxygen system that
do not pass inspection and cannot be repaired in
the aircraft are removed and replaced by ready
for issue (RFI) components.
All liquid oxygen converters are given the
calendar inspection before they are placed in
Table 12-18.Visual Inspection of Type GCU-24/A Liquid Oxygen Converter (P/N 10C-0016-10)