Re: ETOPS Question

Date:         29 Nov 97 03:24:29 
From: (David Lesher)
Organization: NRK Clinic for habitual NetNews Abusers - Beltway Annex
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Steve Lacker <look@the.sig> writes:

>> Could you not just heat the APU's normally, given you will be
>> starting it ASAP if you lose an engine anyhow?

>"Heating the APU normally" is descending into warm air and allowing it
>to warm up due to the ambient temperature :-)

but need it be?  I was not meaning to ask just "does anyone do it
now?" but also "why not...?"

>You're short of waste heat if all the engines are windmilling and you
>need to start the APU. Even if an engine is running, I think there's
>probably no provision for "heating" the APU from engine bleed air.

Err, even given the difference between Diesels and turbines,
I doubt a warmed APU could go back to "too cold to start" in
the few seconds I mention. And while there many not be bleed heat
in use, today, does that preclude same? I can easily see the oil
being kept toasty-warm, and THAT keeping the injector thawed.

That same bleed air feed might start the beast. ISTM a redundant
starting method would not hurt. And don't you get bleed even from a
windmilling engine? I can think of one immediate advantage to
bleed-air starting. If you overcrank an electric starter, you get a
pool of melted copper. At least on {yes, I know, they are
different..} Diesels, the air starters are self-cooling -- you can
keep cranking until you run out of air. On a balky EMC 1250 hp
stationary engine, this was a Godsent.....
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