Figure 102 (Sheet 14)

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A

747-400
FAULT ISOLATION/MAINT MANUAL

RIGHT WHEEL WELL 
SEE  C 
AFT CARGO TRIM AIR 
MODULATION VALVE (REF) 
AIR CONDITIONING 
BAY (REF)  INBOARD 
FWD  BULKHEAD 
AIR CONDITIONING EQUIPMENT 
BAY AND WHEEL WELL
AFT CARGO 
TRIM AIR 
SHUTOFF 
VALVE 
SEE  D 
OUTBD  FWD 
RIGHT WHEEL WELL 
C 

AFT CARGO TRIM AIR SHUTOFF VALVE D
Distribution - Component Location Figure 102 (Sheet 15)
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 1.

2.

3.

4.

5.

A
747-400 MAINTENANCE MANUAL
 MAIN DISTRIBUTION MANIFOLD - DESCRIPTION AND OPERATION
______________________________________________________
General (Fig. 1)
_______
 A.  The main distribution manifold includes the air conditioning packs outlet ducts and the conditioned air plenum.
 B.  Cooled air from the air conditioning packs is collected by a plenum, discharged through riser ducts, and directed to the zones of the airplane through distribution ducts. Ground service conditioned air enters the system ahead of the plenum through connections in the pack 1 and pack 3 discharge ducts.
Conditioned Air Plenum
______________________
 A.  The conditioned air plenum consists of two molded chambers interconnected by a crossover duct. The plenum is between the wing center section and the main deck floor. Uneven conditioned air supply volume and pressures are balanced between plenum chambers by the crossover duct.
 B.  Pack output ducts go aft, enter the wing gear wheel wells, and then up and forward over the wing center section to the aft end of the plenum. Air flows from the conditioned air plenum into the zone risers where trim air is added.
Conditioned Air Check Valves
____________________________
 A.  Check valves are in each pack manifold between the pack and the plenum to prevent reverse flow from the plenum. The valves are dual flapper spring-loaded type valves attached to the wheel well side of the wheel well forward bulkhead where the 9-inch (228 mm) ducts from the packs enter the space above the wings.
Ground Service Connectors (Fig. 1)
_________________________
 A.  Ground service conditioned air connectors tee into the air conditioning pack output ducts downstream from the water separators in packs 1 and 3. Some airplanes have a ground service conditioned air connector downstream from the water separator in pack 2. A swing check valve in each connector prevents air loss when the air conditioning packs are operating.
Operation
_________
 A.  Functional Description
 (1)  Conditioned air from the air conditioning packs or from a conditioned air ground cart flows into the conditioned air plenum. Air from the plenum goes to the zone risers where trim air is added as required by the temperature control system.
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A
747-400
MAINTENANCE MANUAL

SEE A
FORWARD M/DCARGO RISERS
AFT M/D CARGO RISER
(REF) SYSTEM TRIM AIR 
F/D, U/D, CRA RISER CARGO RISERS AFT M/D  CARGO COMPARTMENT TO FORWARD TO AFT CARGO COMPARTMENT 
SEE  B 
A  SYSTEM (REF) TRIM AIR 
Figure 1 (Sheet 1) Conditioned Air Manifold 
　
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