Auxiliary Power Unit (APU)
An Auxiliary Power Unit (APU) is a self-contained device that provides supplementary electrical power to an aircraft. Generally, APUs are small jet engines that are fuelled directly from the aircraft’s primary tanks. They are primarily used to power essential systems such as lighting, air conditioning, and communication in case of power interruption from the main engines.
Before the main engine start, the APU is typically engaged to supply power to the cabin, cockpit and other electrical subsystems. During flight, the APU is shut down but can be restarted when necessary. It can also be utilized in emergency situations like power failure or engine inoperability.
The APU functions are critical in ensuring the safe operation of all the aircraft’s onboard systems. It provides backup power when a primary source fails and delivers electrical energy to the airplane even when on the ground before engine start. An APU’s ability to provide reliable backup power – an emergency generator- makes it an essential component of any aircraft.
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