What is the function of an APU?

The function of an APU, or Auxiliary Power Unit, is crucial within aviation systems. An APU is a small turbine engine typically located at the rear of an aircraft that provides energy for various functions while the plane is on the ground and the main engines are not operational. This includes supplying electrical power, air conditioning, and starting the main engines.

This setup allows the aircraft to maintain necessary systems without relying on the main engines, which can be particularly valuable during pre-flight checks and when parked at gates. The APU helps improve efficiency and comfort by ensuring that essential services remain available while the aircraft is stationary.

The other definitions do not pertain to the functions performed by an APU. The term Air Pressure Unit does not relate to the auxiliary power tasks typical of aircraft, nor do the concepts of Automatic Power Usage or Advanced Propulsion Unit describe the APU's role in ground support operations. Thus, identifying the APU as the Auxiliary Power Unit is essential for understanding its significance in aircraft operations.