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747-400 MAINTENANCE MANUAL
 S 864-017
 (9)  
Apply electrical power (Ref 24-22-00/201).

 S 744-018

 (10)
 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.

 (c)  
Select 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.

 (11)
 Remove electrical power (Ref 24-22-00/201).

 S 864-019
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747-400 MAINTENANCE MANUAL
 LOWER FORWARD CARGO OVERBOARD EXHAUST CHECK VALVE - REMOVAL/INSTALLATION
________________________________________________________________________
 1.  General
_______
 A.  There are two tasks in this procedure. There is one task for the removal and one task for the installation of the lower forward cargo overboard exhaust check valve.
 B.  The overboard exhaust check valve is in the floor area of the lower forward cargo compartment at station 770.
 TASK 21-26-19-004-001
 2.  Valve Removal (Fig. 401)
_____________
 A.  References
 (1)  IPC 21-58-51 Fig. 10
 B.  Access
 (1)  Location Zone
 124 Forward Cargo Compartment Aft Half, RH

 C.  Procedure
 S 034-003
 (1)  Remove the elbow duct from the overboard exhaust stack.
 NOTE: The overboard exhaust stack is in the floor area of the
____ lower forward cargo compartment at station 770.
 (a)  
Loosen the support clamp.

 (b)  
Remove the clamp from each end of the elbow duct and pull the duct from the check valve.

 S 024-006
 (2)  Remove the check valve.
 TASK 21-26-19-404-008
 3.  Valve Installation
__________________
 A.  References
 (1)  IPC 21-58-51 Fig. 10
 B.  Access
 (1)  Location Zone
 124 Forward Cargo Compartment Aft Half, RH

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747-400 MAINTENANCE MANUAL
SEE A
STA 
770 
SUPPORT 
CLAMP 
CLAMP 
CHECK VALVE 
ELBOW 
DUCT  CLAMP 
OVERBOARD 
VALVE 

LOWER FORWARD CARGO OVERBOARD
EXHAUST STACK

A

Lower Forward Cargo Overboard Exhaust Check Valve - Installation
Figure 401

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747-400 MAINTENANCE MANUAL
 C. Procedure
 S 214-010
 (1)  
Make sure the flanges on the duct and the valve are clean.
　
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