TIME - SECONDS
____ 2.5 PSIG IS THE RECOMMENDED MINIMUM TEST POINT.
NOTE:
Pressure Leakage Rate Check Chart Figure 202
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A 737-300/400/500MAINTENANCE MANUAL
S 022-004
(3) Remove the oxygen mask regulators from the oxygen system in the crew cabin (AMM 35-12-00).
NOTE: The removal of the oxygen equipment is not necessary if the
____
absolute pressure is not more than 20 psi.
S 792-005
CAUTION: MAKE SURE THAT ALL OF THE PITOT STATIC SYSTEM IS THERE AND THE
_______ LEAK TEST HAS BEEN DONE. ALSO, REMOVE ALL AIR DATA UNITS THAT ARE NOT CONNECTED TO THE PITOT STATIC SYSTEM BEFORE YOU START THE FUSELAGE LEAKAGE TEST. DAMAGE TO EQUIPMENT CAN OCCUR IF THE PITOT STATIC SYSTEM IS NOT COMPLETE AND PRESSURE TIGHT.
(4) Make sure that all of the pitot static system is there and it is leak tested (AMM 34-11-00).
(a) Remove all spare air data units and air data units that have disconnected pitot static lines from the airplane. The open pitot static lines must be sealed with a cap.
S 862-006
(5)
Start the APU and use it as a pressure source (AMM 49-11-00/401).
S 882-007
(6)
Operate the air conditioning pack (AMM 21-00-00).
NOTE: You can use the left or the right air conditioning pack.
(a)
Operate the pack in AUTO at approximately 70°F (21°C)
(AMM 21-00-00).
(b)
Make sure the outflow valve position indicator show the valve is fully open.
(c)
Move the pressurization mode selector on the forward overhead panel to MAN.
S 792-008
(7) Do the cabin pressure leakage test:
(a)
Record the cabin temperature, external ambient pressure, and external ambient temperature.
(b)
Begin to close the main outflow valve when the air condition system has become stable.
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(c)
(d)
(e)
(f)
(g)
(h)
(i)
A
737-300/400/500MAINTENANCE MANUAL
Adjust the outflow valve position to allow for a comfortable rate of change in cabin pressure.
NOTE: The increase in pressure can cause the lav or galley
____ smoke detectors to sound an alarm when there is no smoke.
Increase the cabin pressure until the cabin differential indicator shows a differential pressure of 4.0 psi.
NOTE: The indication on the differential indicator must not be
____ more than 4.0 psi during a normal test.
NOTE: Equipment cooling fans work harder at cabin pressures
____ more than 15.7 psia. Limit the operation of fans at high cabin pressure to less than 30 minutes.
If a fan overheats and stops during high cabin pressure operation, the equipment cooling OFF light will illuminate. If this occurs, select ALTERNATE to restore the equipment cooling air flow. After a cool-down period, the internal thermostats in the overheat fan will automatically reset. The fan will become operational again.
Fully close the outflow valve when you have a differential pressure of 4.0 psi. 1) Make sure the valve position indicator shows that the valve
is closed.Turn the air conditioning pack to off (Ref 21-00-00).Do the APU shutdown procedure, if it is necessary (AMM 49-11-00/401).Make a record of the pressure differential and the time during the cabin bleed down. Start the test at 4.0 psi differential (time zero). Stop the test at 2.5 psi differential.Record a minimum of 4 sets of measurements for each of the following. 1) The time on the stopwatch. 2) The cabin differential pressure.
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