Air Conditioning Control Panel
Pack Flow Selector
If the APU is supplying bleed air or one air conditioning pack fails, high flow is delivered regardless of pack flow selector's position.
LO - If LOW flow is selected and the temperature demand cannot be satisfied, the pack reverts to normal flow.
HI - If HIGH flow is selected on the pack flow selector, the engine IP air is normally sufficient to supply the required air flow at normal thrust power settings. When IP air is not sufficient, the HP air valve will open to provide additional air pressure.
However, at idle power the actual air flow will be LO due to insufficient air pressure from both the IP and HP.
The pack flow selector allows for selecting the desired pack flow based on the passenger load:
- LO is normally selected if less than 115 passengers are expected
- NORM is selected if 115 passengers or more are expected
- HI is selected if abnormally hot and humid conditions exist.