BA 777 crash at Heathrow

Big John wrote in
:

On Fri, 18 Jan 2008 02:59:24 +0000 (UTC), Bertie the Bunyip
wrote:

"Ridge" wrote in
:


I saw one report that said the pilot reported loosing all
electronics
on final.

Well, the news, ya know?

If they lost both engines they would have lost a lot of electrics
unless
they had the APU runnning, which they would not have done most likely.


Bertie


------------------------------------
Bertie

Whar rpm would the 777 engines windmill on final approach speed if you
know.

Well, modern jets are all expressed in percentage ( TO RPM would be
about 100%) You'd be looking at around 60% N1 when you're dirty and
stabilised, and they would have been so at 600'.

Also what RPM would the generators/alternators drop off line?

Pretty low. They have a constant speed drive to keep the freq steady and
that can cope down to about 45% N2 ( I think it's a two spool engine,
but it might be three) You lose a genny pretty quickly after an engine
failure. The APU door was open, so they may have been runing it for the
approach, or they may have tried to start it after the failure, but I
reckon that at 600 feet they had other things on their minds than a few
clocks going black.

Do any of those brds have a RAT?

Yeah,It should be on the right wing root just behing the leading edge.
It'll run hydraulics and electrics. The airplane also has battery power
to provide both essential DC and AC for probably an hour and a half as
well. I was talking briefly to a friend who flies the 777.
They have a lot of additional generators dedicated to the computers. Of
course if they engines aren't running you won't have those either, but
something provided enough for the flight controls, it appears, or they
would have had no control. So something was making sparks.


Bertie