An aircraft auxiliary power unit serves as an additional energy source normally used to start one of the main engines on an airliner or business jet. The APU is equipped with an extra electrical generator to create enough power to operate onboard lighting, galley electrics and cockpit avionics, usually while the aircraft is parked at the gate. Drawing bleed air from its own compressor, an APU also drives the environmental packs used to heat and cool the aircraft.
How an Auxiliary Power Unit Works
Key Takeaways:
- An Auxiliary Power Unit (APU) is a small, non-propulsive turbine engine located in the rear of an aircraft, primarily providing electrical power for onboard systems and environmental control while on the ground.
- Its main functions include starting the aircraft's main engines, powering avionics and cabin amenities, and driving environmental packs to heat or cool the cabin, thereby saving fuel and maintenance costs compared to using main engines.
- While primarily ground-operated, APUs can serve as an emergency electrical power source during flight, especially for ETOPS operations, though their noise can lead to airport restrictions.
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