747-400
MAINTENANCE MANUAL

SEE A
SCREEN
VENT DUCT
EXHAUST VALVE
CLAMP (2)
AIRPLANE
SKIN NOZZLE
ELECTRICAL CONNECTOR
VALVE POSITION INDICATOR(MANUAL OPERATION)
FWD
A
Forward Overboard Valve Installation Figure 401
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A
747-400 MAINTENANCE MANUAL
 TASK 21-26-15-404-007
 3.  Forward Overboard Valve Installation (Fig. 401)____________________________________
 A. Consumable Materials
 (1)  
B00600 Alcohol - Isopropyl

 (2)  
G01043 Cloth - Lint-Free

 B. References
 (1)  
AMM 21-31-00/501, Cabin Pressure Control System

 (2)  
24-22-00/201, Manual Control

 (3)  
IPC 21-26-15 Fig. 1

 (4)  
WDM 21-23-11

 (5)  
SSM 21-23-01

 C. Access
 (1)  Location Zone 115 Area Between Nose Gear Well and Fuselage, LH
 D. Procedure
 S 114-008
 (1)  
Clean the mating surfaces of the valve and duct with a clean, lint-free cloth that is moist with isopropyl alcohol.

 S 424-009

 (2)  
Put the exhaust valve into position with the electrical connector pointed inboard (Fig. 401) and install the clamps on each end of the check valves.

 S 714-011

 (3)  
Use the valve position indicator to open and close the valve. Make sure the valve moves freely.

 S 214-012

 (4)  
Examine the valve installation to make sure the clamps are tight and the valve is correctly aligned with the duct.

 (5)  
Install the electrical connector DV462 on the valve.

 S 864-014

 (6)
Close circuit breakers as follows for the overboard valve:

 S 434-013
 (a)  P6 Main Power Distribution Panel
 1) 6J32 FWD OVBD VLV CONT

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A 747-400 MAINTENANCE MANUAL
 (b)  2) 6J33 ECS MISC PC ASSYP180 DC Power Distribution Panel 1) 180J20 FWD OVBD VALVE POWER
 (7)  S 864-015Apply electrical power (Ref 24-22-00/201).
 (8)  S 744-016Do a ground test for the forward overboard valve on any CMC CDU (AMM 21-31-00/501). (a) On the CMC main menu select GROUND TEST. Select Chapter 21 -AIR CONDITIONING - OVBD VALVE SYSTEM. (b) Make sure IN PROGRESS is shown on the CMC CDU. (c) Make sure PASS is shown on the CMC CDU.
 (9)  S 864-017Remove electrical power if it is not necessary (Ref 24-22-00/201).

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747-400 MAINTENANCE MANUAL
 FORWARD OVERBOARD VALVE - CLEANING
__________________________________
 1.  General_______
 A.  This procedure has one task to clean the screen on the forward overboard valve.
 TASK 21-26-15-107-006
 2.  Forward Overboard Valve Screen Cleaning (Fig. 701)_______________________________________
 A.  Standard Tools and Equipment
 (1)  Brush - Stiff Bristle
 B.  Consumable Materials
 (1)  
G01043 Cloth - Lint-Free

 (2)  
Soap - Commercially available

 C.  References
 (1)  
IPC 21-26-15 Fig. 1

 (2)  
WDM 21-23-11

 (3)  
SSM 21-23-01

 D.  Access
 (1)  Location Zone 115 Area Between Nose Gear Well and Fuselage, LH
　
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