APU Capabilities Component List - Auxiliary Power Unit Parts

An auxiliary power unit (APU) serves as an additional and supplementary power source for the machine it is mounted on. Larger aircraft such as commercial passenger jets use APUs for multiple purposes; while normally used to start the main engines on the aircraft, the APU can also be used to power onboard lighting, cockpit avionics, and the interior heating and cooling systems of the aircraft. Using an APU instead of the aircraft’s main engines saves on fuel and maintenance devoted to a more expensive and intricate power plant.

In most situations, the APU is shut off before takeoff and reactivated when the aircraft lands. While the APU is typically only operated when on the ground, an APU can be used as an emergency power source while the aircraft is flying.

The APU is a small turbine engine installed at the rear of the fuselage, typically in the tail of the aircraft. Calling the APU an extra jet engine is not accurate, however. This is because an APU’s exhaust is vented overboard, rather than compressed and used for thrusting to propel the aircraft forward.

APUs are found on most medium-size and larger civilian and military jets. Smaller aircraft do not mount APUs because of the extra weight and structure requirements that they impose. APUs can also be found on spacecraft, naval vessels, and even semi-truck trailers and train cars carrying frozen food to run the refrigeration system.

At NSN Parts Now, owned and operated by ASAP Semiconductor, we supply APU parts and systems manufactured by Honeywell International Inc.