What is one function of the APU in an aircraft?

The Auxiliary Power Unit (APU) in an aircraft serves several important functions, one of which is to generate electrical power. This is particularly vital when the aircraft is on the ground and the main engines are not running, as the APU acts as a backup source of electricity for various systems. This includes powering cockpit instruments, cabin lighting, and other electrical systems until the main engines can provide sufficient power upon startup.

While the APU does assist in providing environmental control, such as cabin temperature regulation, and it is sometimes used to start the main engines, its primary and most critical role is the generation of electrical power. This makes it essential for maintaining operations when the aircraft is stationary, and it also supports systems that are necessary for pre-flight checks and passenger comfort.