Question id 158 - Aircraft General Knowledge - Airframe, Systems, Powerplant - ATPL - Airline Transport Pilot license

Supplying The Heat Exchangers With Cooling Air During Cruise Flight.
Supplying the heat exchangers with cooling air during slow flights and ground operation.
Cooling of the APU compartment.
Supplying The Passenger Service Unit (psu) With Fresh Air.

Training tests and timed exam simulations ATPL - Airline Transport Pilot license