(5)  
Install a cover on the duct opening to prevent entry of unwanted objects.

 S 024-011
 TASK 21-26-17-404-004
 3.  Valve Installation
__________________
 A.  References
 (1)  
AMM 21-26-00/501, Ventilation System

 (2)  
24-22-00/201, Manual Control

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747-400 MAINTENANCE MANUAL
SEE A
STA 770
LOWER FORWARD CARGO OVERBOARD VALVE
CLAMPS (QTY 2)
LOWER FORWARD CARGO OVERBOARD BACK-UP VALVE (REF)
ELECTRICAL
CONNECTOR

LOWER FORWARD CARGO OVERBOARD
EXHAUST STACK

A
Lower Forward Cargo Overboard Valve - Installation Figure 401
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747-400
MAINTENANCE MANUAL

 (3)  
IPC 21-58-51 Fig. 10

 (4)  
SSM 21-23-02

 (5)  
WDM 21-23-22

 B. Access
 (1)  Location Zone
 124 Forward Cargo Compartment Aft Half, RH

 C. Procedure
 S 434-004
 (1)  
Remove the cover from the duct opening.

 S 214-005

 (2)
Make sure the mating surfaces of the valve and duct are clean.

 S 424-006

 (3)  
Install the valve with the flow arrow pointed away from the overboard back-up valve and install the clamps (2 locations).

 S 214-011

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

 S 434-007

 (5)  
Install the bonding jumper on the valve.

 S 434-006

 (6)  
Install the electrical connector DV526 on the valve.

 S 864-007

 (7)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:

 (a)  
P6 Main Power Distribution Panel
 1) 6E34 CARGO AIR COND PCA

 (b)  
P180 DC Power Distribution Panel
 1) 180E27 FWD CGO OVBD VLV PWR

 S 864-008
 (8)  
Apply electrical power (Ref 24-22-00/201).

 S 744-009

 (9)  
Do a ground test for the forward cargo overboard system on the CMC CDU (AMM 21-26-00/501).

 (a)  
Make sure the conditioned air FLOW SELECTOR switch in the area of the forward cargo door is set to OFF.

 (b)  
Select GROUND TEST from the CMC main menu.

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 (c)
Select Chapter 21 - AIR CONDITIONING from the ground test menu.

 (d)
Select FWD CARGO OVBD from the air conditioning menu.

 (e)
Make sure IN PROGRESS shows on the CMC CDU.

 (f)
Make sure that after 1.5 minutes, PASS shows on the CMC CDU.

 S 864-010
 (10) Remove electrical power (Ref 24-22-00/201).
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747-400 MAINTENANCE MANUAL
 LOWER FORWARD CARGO OVERBOARD BACK-UP VALVE - REMOVAL/INSTALLATION
　
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