Air Flow Control With both air conditioning pack switches in AUTO and both packs operating, the packs provide normal air flow. However, with one pack not operating, the other pack automatically switches to high air flow in order to maintain the necessary ventilation rate. This automatic switching is inhibited when the airplane is on the ground, or inflight with the flaps extended, to insure adequate engine power for single engine operation. Automatic switching to high air flow occurs if both engine bleed air switches are OFF and the APU bleed air switch is ON, regardless of flap position, air/ground status or number of packs operating. With the air conditioning pack switch in HIGH, the pack provides high air flow. Additionally, APU high air flow rate is available when the airplane is on the ground, the APU bleed air switch is ON and either or both pack switches are positioned to HIGH. This mode is designed to provide the maximum airflow when the APU is the only source of bleed air.