S 862-006
(8)
Start the APU (AMM 49-11-00/201).
S 862-036
(9)
Select the engine bleed valve "on".
S 862-037
(10)
Open the wing isolation "Left and Right".
S 862-007
(11)
Start one or more air conditioning packs (AMM 21-00-00/201).
E. Procedure
S 792-032
(1) Do the leakage test.
(a)
Make sure that the outflow valve position indicators on the CPCS selector module M181, on the panel P5, show that the two valves are fully open.
(b)
Push the MAN L and MAN R switches (M181 module) to the on position.
(c)
Make sure all of the external hatches and doors that must hold pressure are tightly closed.
(d)
When the air conditioning system is stable, hold the OPEN/CLOSE toggle switch (M181 module) to the close position.
(e)
Monitor the cabin rate of climb.
(f)
When the cabin rate of climb reaches -400 ft./min., release the OPEN/CLOSE toggle switch.
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A 747-400 MAINTENANCE MANUAL
(g) Hold the OPEN/CLOSE toggle switch to the close position as necessary to maintain a cabin rate of approximately -500 ft./min.
NOTE:____ Do not let the cabin rate of climb exceed -500 ft./min.
NOTE:____ The increase in pressure can cause the lav or galley smoke detectors to sound an alarm when there is no smoke.
(2) S 972-013Make a record of the maximum cabin rate of climb.
(3) S 862-014Continue to pressurize at a maximum or a lower rate as is necessary. Do this until the cabin pressure differential is at 395-knot ASI and it becomes stable (4.0-psi gage).
NOTE:____ Make sure the pressure is not more than a 4.0-psi pressure differential.
(4) S 862-015Turn the air conditioning pack(s) to the off position (AMM 21-00-00/201).
(5) S 862-038Immediately CLOSE the outflow valves.
(6) S 972-016In less than 5 minutes after you turn off the air conditioning packs, make a record of the data. (a) Make a record of the pressure differential in knots ASI against time for cabin bleed down (minimum reading 150 knots ASI). (b) Make five to ten data sets of each of the items that follow: 1) The time on the stopwatch 2) The cabin differential pressure 3) The cabin temperature 4) The external ambient temperature and pressure.
(7) S 752-018Make a check for leakage caused by structural damage.
NOTE:____ Listen for air leaks through the fuselage, especially from the pressure bulkheads and structure hidden by fairings.
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ALL ú ú 01 Page 207 ú Oct 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
S 972-031
(8) Do the Leakage Rate Analysis
(a)
Get the correction factor from figure 201 to correct the time data. Do this if the test was done at field altitudes that are much higher than at the sea level
(b)
Make a graph from the points that follow: 1) The differential pressure data on the vertical axis of
Figure 202. 2) The time on the horizontal axis of Figure 202. 3) Make a straight line through the two axis points of
Figure 202. 4) If your line stays in the SATISFACTORY ZONE on Figure 202, the pressure leakage rate is satisfactory.
F. Put the Airplane Back to Its Initial Condition
S 862-019
(1)
Hold the OPEN/CLOSE toggle switch to the OPEN position until the two outflow valves are fully open.
S 012-020
(2)
Open all external hatches and doors that are necessary.
S 862-021
(3)
Do the APU shutdown procedure (or the alternate pressure source) (AMM 49-11-00/201).
S 442-039
(4)
To open the section 41, forward overboard valve, do the steps that follow:
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