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Aviation Glossary :: APU  Aviation Glossary :: APU FAA Written Test Preparation
Aviation Glossary Welcome to the Dauntless Aviation Glossary!

At Dauntless, our editorial staff maintains the web's largest unified glossary of aviation terms. This glossary is built from a combination of official, quasi-official, and proprietary sources (including original material that we develop oursselves). Uniquely, we often provide multiple definitions of a given term so that you can find that which best applies to you. In order to maximize your learning efficiency, this glossary (and similar ones for our international users) is incresingly fully integrated into our aviation learning apps, including our FAA written test prep and FAA practical test prep software and apps. If you like this glossary, you'll love them with their polished learning environments and world's best and clearest content (please do give them a try.).

APU
APU
A small turbine or reciprocating engine that drives a generator, hydraulic pump, and air pump. The APU is installed in the aircraft and is used to supply electrical power, compressed air, and hydraulic pressure when the main engines are not running.
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source: FAA Aviation Maintenance Technician Airframe Handbook (FAA-H-8083-31)

Auxiliary power unit. A small turbine- or reciprocating engine-powered generator, hydraulic pump, and air pump. APUs are installed in the aircraft and are used to supply electrical power, air, and hydraulic pressure when the main engines are not running.
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source: FAA Aviation Maintenance Technician Powerplant Handbook (FAA-H-8083-32)

Auxiliary Power Unit: a small gas turbine engine, usually located in the tail cone, which is used on the ground when the engines are shut down to generate electricity, to provide air conditioning and high pressure air to start the engines. The APU can also be used in flight up to 25,000 feet for back-up electrical power in the event of an engine failure
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source: ICAO English Pro Aviation Glossary

An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft, naval ships, as well as some large land vehicles. Aircraft APUs generally produce 115 V alternating current (AC) at 400 Hz (rather than 50/60 Hz in mains supply), to run the electrical systems of the aircraft; others can produce 28 V direct current (DC). APUs can provide power through single or three-phase systems.
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source: Wikitionary / Wikipedia and Related Sources (Edited)


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Disclaimer: While this glossary in most cases is likely to be highly accurate and useful, sometimes, for any number of editorial, transcription, technical, and other reasons, it might not be. Additionally, as somtimes you may have found yourself brought to this page through an automated term matching system, you may find definitions here that do not match the cotext or application in which you saw the original term. Please use your good judgement when using this resource.


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