SEE  A 
A 
A 
A  VALVE APU CHECK 
A 
BSEE COUPLING SEAL (2 LOCATIONS) 
FWD 
COUPLING (2 LOCATIONS)  A 
VALVE BODY APU CHECK  VALVE FLAPPER 
|10`  FWD 
FLANGE DUCT  O-RING SEAL (2 LOCATIONS)  FLANGE VALVE  A  A 
(SECTION THRU JOINT) COUPLING SEAL B  A-A FLAPPER VALVE SHAFT 
Figure 401 APU Check Valve Installation 

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A
747-400 MAINTENANCE MANUAL
 S 864-005
 (5)  
Put the APU BLEED switch, on the P5 overhead panel, to the ON position

 S 864-006

 (6)  
Put one or more of the wing ISLN switches, on the P5 overhead panel, to the OPEN position.

 S 864-007

 (7)
Remove the pressure in the pneumatic system (AMM 36-00-00/201).

 S 024-008

 (8)
Remove the couplings from each side of the APU check valve.

 S 024-025

 (9)  
Remove the APU check valve.

 S 034-009

 (10)
 Remove the seals from the duct flanges.

 (a)  
If a seal has damage, it must be replaced.

 S 034-010
 (11) Put the covers on the open ducts to keep out unwanted objects.
 TASK 36-11-08-404-011
 3.  Install the APU Check Valve (Fig. 401)___________________________
 A. Consumable Materials
 (1)  
G00095 Detector - Leak, Leak-Tek (160X)

 B.
References

 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 32-00-30/201, Landing Gear Door Locks

 (3)  
AMM 36-00-00/201, Pneumatic System

 (4)  
AMM 49-11-00/201, Auxiliary Power Unit

 (5)  
IPC 36-11-60 Fig. 1

 C.
Access

 (1)  
Location Zone
 755 Body Landing Gear Wheel Well, LH

 D.
Install the Valve

 (1)  
Remove the covers from the ducts.

 (2)  
Install the seals in the duct flanges.

 S 424-014

 (3)  
Install the APU check valve in the correct position between the duct flanges.

 (a)  
Make sure that the flow arrow points in the downward direction.

 S 434-012
 S 434-013
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 (b)  Make sure that the flapper valve shaft points to within 10 degrees from the airplane's longitudinal axis.
 S 434-015
 (4)  
Install the couplings on each side of the valve.

 (a)  
Tighten the couplings to 70-80 inch-pounds (7.9-9.0 N.m.).

 S 794-026
 (5)  
Do the steps that follow for the leakage test for the APU check valve.

 (a)  
Apply the leak detector to the valve flanges.

 (b)  
Put the two wing ISLN switches, on the P5 overhead panel, to the CLOSED position.

 (c)  
Use the APU to pressurize the pneumatic system (AMM 36-00-00/201).

 (d)  
Examine the valve flanges for leakage. 1) If bubbles come slowly into view, the quantity of leakage is satisfactory.

 2)  If bubbles come quickly into view, or if jet blast leakage occurs, you must repair the cause of the leakage.

 (e)  
Stop the operation of the APU (AMM 49-11-00/201).

 E.  Put the Airplane to Its Usual Condition
 S 864-021
 (1) Release the pressure in the pneumatic system (AMM 36-00-00/201).
 S 094-022
 WARNING: YOU MUST CAREFULLY DO THE STEPS IN THE TASK BELOW TO REMOVE THE
_______ DOOR LOCKS ON THE LANDING GEAR DOORS. THE DOORS CAN CLOSE QUICKLY IF YOU DO NOT REMOVE THE DOOR LOCKS CORRECTLY. THIS CAN CAUSE INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT.
　
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