(2)  
The pack flow control and shutoff valve admits hot compressed air from the pneumatic bleed air manifold to the heat exchanger when the pack selector switch is in the NORM, A, or B position. The bleed air cooled in the primary core of the heat exchanger then passes through the compressor where it is boosted in pressure. The compressor discharge air is passed through the secondary core of the heat exchanger, and is then expanded through the cooling turbine, resulting in reduced temperature and pressure. Turbine discharge air is passed through the water separator where moisture is removed, and then flows to the conditioned air plenum chamber. The temperature of this conditioned air meets the supply requirements of the cabin zone calling for the lowest inlet air temperature.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

ECS SYNOPTIC
AUXILIARY EICAS DISPLAY

Air Conditioning Pack System EICAS Displays
Figure 3

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 ú  01F  Page 11
 ú  Jun 10/93