B727 APU (was:MD-80: Lawn Dart or Efficient Design?)

From:         mikem727@aol.com (MikeM727)
Organization: America Online, Inc. (1-800-827-6364)
Date:         03 Nov 96 19:56:59 
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In article <airliners.1996.2155@ohare.Chicago.COM>, "Keith R. Thompson"
<keithrt@earthlink.net> writes:

>The APU uses a flow multiplier which draws from the right wheel well.

Only the -200 uses a flow multiplier.  The flow multiplier allows the
running of both a/c packs on the APU. The -100 can only run one pack on
the APU.

>The main problem with this installation is that in extremely hot
>environments, high temperatures in the wheelwell when the APU is operating
>can result in a Lower Aft Body overheat warning light illuminating on the
>engineer's panel.

Never heard of that.  Generally, there would have to be some kind of bleed
air duct rupture to result in a Lower Aft Body overheat warning.  However,
if the APU is not shut down prior to takeoff, when the gear is retracted a
Wheel Well Fire warning light and bell could result.

>That's why under these conditions ground crew will
>frequently drop the main gear doors if the aircraft will be idle for
>awhile. This aids airflow to the APU and reduces the likelihood of
>getting the warning light.

Never heard of, seen, or done that.  The only time I am aware of the
inboard gear doors being dropped is for maintenance.  Seems like it might
help with cooling, though.

Mike,
ATP/FE, Boeing 727
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Props are for boats!
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