Posts: 100
Joined: Wed May 31, 2000 10:50 am


Tue Jul 24, 2001 12:43 pm

This may be a s illy question but what is an APU on a jet aircraft?
Posts: 2682
Joined: Mon May 01, 2000 10:52 am


Tue Jul 24, 2001 2:47 pm

APU stands for Auxilury Power Unit. That aircraft has power small engine to keep supply power for electricity and air conditioner or heat while the plane is on the ground. Also, APU must running while take off or landing for in case engine failure and APU is running to re-start engine.




Tue Jul 24, 2001 8:41 pm

Can anyone confirm that the APU is running during takeoff and landing? I know it doesn't have to be, because airliners fly with inop APUs all the time. I thought they were always shut down prior to flight and not restarted until they were back on the ground. I would think that you would want all the fuel going to the engines for flight and if an engine were to fail you could use the still running engine/s to cross-start the failed engine.
Posts: 129
Joined: Sun Apr 29, 2001 1:39 am


Tue Jul 24, 2001 10:37 pm

No APU's are not running during take off and landing think about it, the APU is distibuuting power to the aircraft while the engines are not running, when the engines are running the generators are providing power so why would you need the APU?????
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Joined: Wed Jul 18, 2001 7:54 pm


Tue Jul 24, 2001 10:48 pm

APU is a gas-turbine which provides energie and hydraulic pressure, when the engines are out and the plane is on the ground. APU will be stopped after engine start and be activated at the gate before the engine shutdown. But inflight the Apu is out if you need energie for the restart of a engine
(what i truely doubt, because if an engine is giong to die inflight there is a reason, maybe I try it once but then I'll leave it off) take the energie supply of the other engine(s)

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