Aviation Air Conditioning Pack Problems

Pack Problems

PACK TRIP OFF

Cause: Pack temp has exceeded limit. (Note this is pack temp not output temp)
Remedy: Select warmer temp (to make the pack work less hard) then trip reset.

PACK (-4/8/900 only)

Cause: Pack temp has exceeded limit or failure of pack controls.
Remedy: Select warmer temp (to make the pack work less hard) then trip reset.

On the ground: 1-500’s: Use only one pack from the APU because packs are working hardest when delivering cold air. NG APU’s are more powerful so can use both packs for cooling or heating. In fact using both packs causes the APU to burn slightly less fuel than single pack operation.

If one pack fails with the pack switches in AUTO, the other will regulate to high flow (unless flaps are down). Note series 1/200’s do not have an AUTO mode, the pack switch is simply ON/OFF.

If you dispatch with one pack inoperative, then max altitude is FL250. If a pack fails when above this level, then you may continue at the higher level. Note if a pack should fail, even at the aircrafts maximum certified altitude it should be able to maintain cabin pressure. If both packs fail the cabin altitude will climb, probably between 2000 & 4000fpm depending upon the condition of the aircraft seals.

 

-3/5/6/700 Pneumatics panel

Source: http://www.b737.org.uk/airconditioning.htm