Re: ETOPS Question

Date:         01 Dec 97 02:33:56 
From:         Exiled Expat <lutsch@emirates.net.ae>
Organization: Emirates Internet
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David Lesher wrote:
> 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?
> but need it be?  I was not meaning to ask just "does anyone do it
> now?" but also "why not...?"

The 777 APU is the first commercial aircraft that I know of that now has
electrical heating pads installed onto the APU Gearbox assy which is heated
at all times that there is AC power on the aircraft to ensure better colld
temperature starts.

> 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.....

The 777 also now has a redundant starting unit that consists of a pneumatic
air driven turbine starter that is always used to start the APU over the
electric starter whenever air is availlable.
Seems to me that the aerospace designers are doing a pretty good job doing
what they are paid to do. :-)