(3)  
Close the fueling receptacle access door 521BB or 621BB.

 S 094-023
 WARNING:_______DO THE PROCEDURE IN AMM 27-81-00/201 TO REMOVE THE LOCKS. THE FLAPS MOVE QUICKLY AND COULD CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.
 (4)  
Remove the leading edge flap locks (AMM 27-81-00/201). S 864-021

 (5)  
Remove electrical power, if it is not necessary (AMM 24-22-00/201).

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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 ALL  ú ú 01 Page 405 ú Jun 18/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 DEFUELING CHECK VALVE - REMOVAL/INSTALLATION
____________________________________________
 1.  General
_______
 A.  This procedure contains instructions to remove and install the defueling check valve.
 B.  The defueling check valve is found in each outboard main tank. The defueling check valve is installed on the front spar opposite the manual defueling valve. The manual defueling valve also must be removed since it is attached to the defueling check valve.
 C.  When persons do maintenance in the area of the wing leading edge, install safety locks on all extended leading edge flaps.
 TASK 28-26-02-004-001
 2.  Defueling Check Valve Removal (Fig. 401)
_____________________________
 A.  References
 (1)  
AMM 28-11-00/201, Fuel Tanks

 (2)  
AMM 28-26-00/201, Defueling

 (3)  
AMM 28-26-01/401, Manual Defueling Valve

 (4)  
AIPC 28-22-05 Fig. 2

 B.  
Access

 (1)  
Location Zones 543 Outbd Main Tank (Part), Front Spar to Mid Spar, Left 643 Outbd Main Tank (Part), Front Spar to Mid Spar, Right

 (2)  
Access Panels
 546AB Fuel Tank Access Door
 646AB Fuel Tank Access Door

 C.  
Procedure

 S 654-002
 (1)  Defuel the outboard main tank (AMM 28-26-00/201).
 S 864-015
 WARNING: CAREFULLY DO ALL THE SAFETY PROCEDURES TO DEFUEL AND GO INTO
_______ THE FUEL TANKS. INJURY TO PERSONS AND DAMAGE TO EQUIPMENT CAN OCCUR IF YOU DO NOT OBEY THE SAFETY PROCEDURES.
 (2)  
Purge and prepare to go into the outboard main tank
 (AMM 28-11-00/201).

 (3)  
Remove the manual defueling valve (AMM 28-26-01/401).

 S 034-005

 (4)  
From out of the tank, remove the bolts (3) (four locations) that attach the defueling check valve (1) to the front spar.

 S 014-004
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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 ALL  ú ú 01 Page 401 ú Feb 10/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 S 014-014

 (5)  
Go into the fuel tank through the applicable access opening 546AB or 646AB (AMM 28-11-00/201).

 S 034-016

 (6)  
Hold the defueling check valve (1) and disconnect the coupling (4) that attaches the defueling check valve (4) to the fuel-feed manifold.

 S 034-020

 (7)  
Discard the packings (5).

 S 024-007

 (8)  
Remove the defueling check valve (1).

 S 034-017

 (9)  
Discard the gasket seal (2).

 TASK 28-26-02-404-008
 3. Defueling Check Valve Installation (Fig. 401)
__________________________________
 A. Parts
 ~.............................................................................. | MM | | IPC | ................. ............................ | FIG | ITEM | NOMENCLATURE | SUBJECT | FIG | ITEM | ................................................................................ | 401 | 1 | Defueling Check Valve | 28-22-05 | 02 | 720 | | | 2 | Gasket Seal | | | 655 | | | 3 | Bolt | | | 725 | | | 5 | Packing | | | 465 | 2......…........…...................................…..........….....….........1
　
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