Air for APU compartment cooling is drawn from which location?

• A. The cooling air inlet above the APU exhaust outlet
• B. The APU intake
• C. The cabin ventilation system
• D. The main engine nacelle

Answer: (A)

Cooling for the APU compartment uses ram air drawn from a dedicated inlet located above the APU exhaust outlet. This setup provides outside, relatively cool air specifically for cooling the APU components, helps prevent recirculating cabin air or ingesting exhaust, and keeps the APU’s compressor intake separate from the cooling flow. The APU intake is reserved for supplying air to the APU itself, not for cooling, and the cabin ventilation system or main engine nacelle aren’t used for this purpose. Using the dedicated inlet above the exhaust ensures a reliable, uncontaminated cooling air source and proper airflow through the APU’s heat exchangers.