Re: ETOPS Question

Date:         03 Nov 97 19:20:03 
From:         Steve Lacker <look@the.sig>
Organization: Applied Research Laboratories - The University of Texas at Austin
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Rob Wells (WLL) wrote:
> In Oz it was reported that the APU was definitely non-op. I seem to
> remember that there was only enough compressed air left for one more
> attempt to turn over an engine. But perhaps that was an embelishment
> added by the local tabloids.

I would say "embellishment." As far as I know, there is NO storage of
compressed air on board a commercial aircraft- certainly not enough for
engine starts. The compressed air is fed from a *running* APU straight
to the engine starter.

The intended reference was probably to "air-starting" the engine,
wherein the ram air flow from the planes forward speed spins the
turbines up enough to start the engine, provided the combustors are
sufficiently clear of debris, fuel and igniter systems are working, etc.
As you run out of altitude and airspeed, this becomes impossible. As I
recall, one of the engines was *finally* successfully air-started, and
provided enough compressed air for normal starts of the remaining
engines.

-
Stephen Lacker
Applied Research Laboratories, The University of Texas at Austin
PO Box 8029, Austin TX 78713-8029
512-835-3286 slacker@arlut.utexxas.edu (Remove the extra 'x' to mail me)