(h)
If the decay time is more than the MINIMUM PASS TIME, then the right bleed air system and precooler is satisfactory.
(i)
If the decay time is less than the MINIMUM PASS TIME, then do the Pneumatic Duct Section Leakage test.
S 795-017
(5) To do a check for leakage on the left bleed air system, do these steps:
(a)
Put the ISOLATION VALVE switch on the P5-10 panel to the OPEN position (Fig. 501).
(b)
Put the APU BLEED switch to the ON position.
(c)
Pressurize the pneumatic system with the APU
(AMM 36-05-00/201).
(d)
Put the ISOLATION VALVE switch on the P5-10 panel to the CLOSED position.
(e)
When the bleed air duct pressure is stable, record the left duct pressure shown on the P5-10 panel.
(f)
Make sure that the left manifold is pressurized to a minimum of 20 psig.
(g)
Put the APU BLEED switch on the P5-10 panel to the OFF position.
(h)
Measure the time necessary for the left manifold duct pressure to decrease to 5 psi (INDICATOR END value) from one of the Duct Pressure Start values shown in the chart below.
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737-300/400/500MAINTENANCE MANUAL
~................................................... | DUCT PRESSURE| INDICATOR END | MINIMUM PASS TIME | | START (PSI) | (PSI) | (SEC) | ..................................................... | 50 | 5 | 17 | ..................................................... | 40 | 5 | 14 | ..................................................... | 30 | 5 | 11 | ..................................................... | 20 | 5 | 8 | 2..............…................…...................1
(i)
If the decay time is more than the MINIMUM PASS TIME, then the left bleed air system and precooler is satisfactory.
(j)
If the decay time is less than the MINIMUM PASS TIME, then do the Pneumatic Duct Section Leakage test.
E. Put the Airplane Back to Its Usual Condition
S 865-024
(1)
Stop the APU if necessary.
S 865-025
(2)
Remove the pressure from the pneumatic system (AMM 36-05-00/201).
S 025-026
(3)
AIRPLANES WITH ASPIRATED TAT TUBE;
Do the steps that follow:
(a)
Remove the cap from the open end of the aspirated TAT tube.
(b)
Remove the cap from the open boss from the pneumatic manifold duct.
(c)
Reconnect the aspirated TAT tube to the open boss on the pneumatic duct.
S 415-027
(4) Close the access doors and panels that were opened for the test.
TASK 36-12-25-795-053
4. Pneumatic Duct Section Leakage Test___________________________________
A. General
(1)
This task will do a check of the pneumatic duct section and valves for the left (right) bleed air system for leaks.
(2)
This task is for airplanes with a left (right) bleed air system and a precooler that are not satisfactory.
B. References
(1)
AMM 12-31-01/201, Zone Diagrams
(2)
AMM 12-31-31/201, Body Section 46 Access Doors and Panels
(3)
AMM 12-31-41/201, Body Section 48 Access Doors and Panels
(4)
AMM 12-31-61/201, Wing Lower Surface Access Doors and Panels
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737-300/400/500MAINTENANCE MANUAL
(5)
AMM 12-31-91/201, Nacelle and Engine-to-Fairing Access Doors and Panels
(6)
AMM 24-22-00/201, Manual Control
(7)
AMM 36-05-00/201, Pneumatic System
(8)
AMM 49-52-11/401, APU Bleed Air Valve
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