S 424-011

 (2)  
Install the check valve.

 NOTE: The valve flapper must open in the down direction.
____
 S 824-020
 (3)  
Push the valve flapper down to make sure the valve flapper moves freely from open to close.

 S 434-012

 (4)  
Install the elbow duct.

 (a)  
Install the clamps on each end of the elbow duct.

 (b)  
Install the support clamp on the elbow duct.

 S 214-013
 (5)  Make sure the clamps are tight and the valve aligns with the duct sections.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-26-19
 ALL  ú ú 03 Page 403 ú Feb 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 CARGO COMPARTMENT CONDITIONED AIR DISTRIBUTION - DESCRIPTION AND OPERATION
__________________________________________________________________________
 1.  General_______
 A.  The cargo air conditioning system uses dedicated pack air to provide conditioned air at variable temperature and flow rate to the lower lobe cargo compartments. Trim air from the pneumatic mainfold goes through a trim air shutoff valve and trim air modulation valve and then connects to the cargo conditioned air duct to regulate the temperature of the supplied air.
 B.  The forward cargo compartment is supplied by dedicated pack 3 conditioned air and the aft cargo compartment is supplied by dedicated pack 2 conditioned air.
 C.  The flow rate of air to the forward and aft compartments can be selected with the LOWER LOBE CARGO COND AIR FLOW RATE selector on the overhead P461 panel.
 (1)  
When the selector is in the OFF position, the air conditioning packs supply all their air to the main and upper deck areas.

 (2)  
When the selector is rotated to one of the flow positions, air is diverted from the applicable pack to the cargo compartment.

 D.  The packs can supply conditioned air to both the forward and aft cargo compartments in the low flow mode.
 E.  In the high flow mode, the packs can only supply conditioned air to the forward or the aft cargo compartment, but not to both.
 2.  Cargo Air Conditioning Flow Regulating Valves (Fig. 1)_____________________________________________
 A.  There are two flow regulating valves, one for the forward and one for the aft cargo compartment.
 (1)  
The forward cargo air conditioning valve is in the right air conditioning bay.

 (2)  
The aft cargo air conditioning valve is in the right hand wheel well.

 B.  The flow regulating valves allow airflow from pack 2 and pack 3 to enter the aft and forward cargo compartments, respectively.
 C.  The valves are 9-inch diameter disk type valves that are operated by 115 volts ac power.
 D.  When the cargo air conditioned flow rate is set to LOW, the valve will be partially open.
 E.  When the cargo air conditioned flow rate is set to HIGH, the valve will be fully open.
 F.  The valves have a visual position indicator on the valve actuator.
 3.  Forward and Aft Cabin Shutoff Valves (Fig. 1)____________________________________
 A. There are two cabin shutoff valves, one for pack 2 and one for pack 3.
 (1)  
The aft cabin shutoff valve (for pack 2) is in the main distribution manifold area.

 (2)  
The forward cabin shutoff valve (for pack 3) is in the right wing gear wheel well.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 21-28-00
 ALL  ú ú 02F Page 1 ú Jun 18/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

FLIGHT COMPARTMENT 
SEE  B 
FORWARD CARGO 
CONDITIONED 
AIR SUPPLY 
SEE  A 
FORWARD CARGO AIR 
CONDITIONING FLOW 
REGULATING VALVE 
SEE  C  PACK 3 WATER 
SEPARATOR (REF) 
FORWARD CARGO CONDITIONED AIR SUPPLY
(IN RIGHT AIR CONDITIONING EQUIPMENT BAY) 
　
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