PACK COOLING AIR CONTROL - DESCRIPTION AND OPERATION

** ON A/C NOT FOR ALL

1. General
The zone controller 8HK signals the required pack outlet temperature to the pack controllers 7HH (27HH). To get this temperature, the pack controller modulates the bypass valve 10HH (30HH) and the ram air inlet/outlet flaps. This is done in a pre-determined sequence, and is a compromise between the following:

minimum ram-air flow,
maintaining adequate heat transfer rates,
sufficient pack flow.

A priority control overrides this ram-air optimization, if the compressor outlet temperature gets to 180 DEG.C (356.00 DEG.F). During takeoff and landing, the ram-air inlet doors are fully closed to stop the ingestion of foreign matter.

For a more detailed description of the pack cooling/temperature-control system refer to 21-61-00.
The Air Conditioning System Controller 1 (ACSC1) 47HH in normal mode calculates the required pack outlet temperature and transmits it to the ACSC2 (57HH). To get this temperature, ACSC modulates the bypass valve 10HH (30HH) and the ram air inlet flap. This is done in a pre-determined sequence, and is a compromise between the following:

minimum ram-air flow,
maintaining adequate heat transfer rates,
sufficient pack flow.

[Rev.10 from 2021] 2026.04.02 06:48:23 UTC