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 primarily used on the ground to provide electrical power, bleed air for environmental control, and assist in starting the main engines.
- APUs save fuel and reduce wear on main engines by powering onboard systems and ensuring passenger comfort before departure, and can also act as an emergency airborne power source.
- While essential for most medium to large aircraft, their weight can prohibit use in smaller jets, and noise output often leads to operational restrictions at some airports.
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