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 turbine engine providing essential electrical power, bleed air for environmental control (heating/cooling), and the capability to start main engines while an aircraft is on the ground.
- Its primary benefit is saving significant fuel and reducing wear on the main engines by handling ground power needs and ensuring passenger comfort before departure.
- Primarily used before takeoff and after landing, APUs can also serve as an emergency airborne power source and are critical for ETOPS flights, though their noise can lead to operational restrictions at some airports.
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