AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

How Auxiliary Power Units (APU) Serve Aircraft?

Auxiliary power units, or APUs, are common elements found on fixed-wing aircraft, serving as energy sources that are in addition to the standard engines and batteries used for flight operations. APUs are very important for a number of reasons, providing various systems power while the aircraft is parked for safety. While electricity is necessary for the operation of many systems and apparatuses during the passenger boarding phase, having an engine operating near personnel and the airport terminal is very hazardous. As a result, the APU is a common item on numerous medium to large aircraft.

Auxiliary power units are considered to be a type of gas turbine, featuring a power section, load compressor, and gearbox. The power section comes in the form of a turbine engine, allowing for the system to be provided with power. With the use of the load compressor, a pneumatic pressure supply is provided while the gearbox transmits power between the APU and electric generator. As the final section of a standard APU, the electric generator supplies the electrical power it receives from the gearbox to the various systems and components situated across the aircraft.

With an auxiliary power unit, everything from on-board lighting fixtures to mission critical avionics are operational while parked at an airport terminal. As the APU also features its own compressor that can provide bleed air, a parked aircraft can even have heating and cooling for the cabin before takeoff. While an auxiliary power unit is often compared to standard jet engines as a result of their compressors, gearbox, engine, and general design, they are unable to provide propulsion. Alongside providing an aircraft with ample power while parked near a terminal or hanger, APUs also save operators money as fuel expenditures and engine wear are both reduced. With their ability to be activated as needed, APUs are also an emergency power system in the instance that main power sources fail.

The location of an auxiliary power unit will often vary based on the design of the aircraft in question. Most of the time, the APU is situated in the tail cone of the aircraft, though some might have the assembly within an engine nacelle or wheel well instead. While the APU can provide ample power for most needs, it requires energy from an onboard battery first before operations can begin.

When searching for an APU or APU parts for your particular needs, it is important that you carefully choose components so that compatible systems are established. Generally, the manufacturer of a given aircraft will determine the APU requirements of an aircraft based on the size of the cabin, the amount of bleed air needed for powering environmental packs, and the generator necessary for powering cockpit instruments and starting engine operations. Then, once a given APU is certified for use in flight, it can then be used as required for additional electrical power.

If you find yourself in need of various auxiliary power unit parts and components, let the experts at Emergent Aviation help you source all that you are interested in while saving you time and money. Owned and operated by ASAP Semiconductor, we present customers access to over 2 billion new, used, obsolete, and hard-to-find components that have been sourced from leading global manufacturers we trust. If you come across any item of interest, we encourage you to fill out and submit an RFQ form at your earliest convenience, and a dedicated account manager will contact you within 15 minutes to provide a personalized quote for your comparisons. Get started today and see how Emergent Aviation can serve as your strategic sourcing partner for all your operational needs.


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