What is the function of the Auxiliary Power Unit (APU)?

The Auxiliary Power Unit (APU) serves a vital role in an aircraft by providing power and essentially acting as a backup power source when the main engines are not operational. One of its primary functions is to operate a generator that supplies electrical power to the aircraft, especially when the engines are shut down. This capability is crucial during ground operations, where the APU ensures that essential systems remain functional without the need to run the main engines, thus providing power for lighting, air conditioning, and other electrical systems.

The APU's ability to generate electricity allows for smoother operations and maintenance procedures on the ground. By using the APU instead of relying on the main engines, it also contributes to noise reduction and fuel conservation during pre-flight preparations. This makes the APU an essential component for efficient and effective aircraft operations.