A passive cooling system for an auxiliary power unit (10) located in an aft compartment (20) of an aircraft is provided in which cooling air is drawn into the compartment through an aft opening (54) located in the rear of the aircraft and discharged back t...

Cooling air is branched-off from a bypass flow and fed to the outside of the housing (1) via an intake channel (8) with shut-off valve (5). The air is introduced into a first chamber (6), where its volume is divided. Part of the air is fed from the chamber...