Steve Walker wrote:
On Mon, 19 Apr 2010 16:32:48 +0100, Dave wrote:

Nightjar "cpb"@ insertmysurnamehere wrote:
Chris J Dixon wrote:
"Nightjar \"cpb\"@" "insertmysurnamehere wrote:

It was not a fall, but a deliberate fast descent to a level where
oxygen was not needed - one of the crew's oxygen masks was broken -
and where engine restart procedures might be expected to work, which
they did.

It's a pretty steep glide angle isn't it? I reckon it would feel
close enough to a fall for the passengers
The glide angle is 15:1, but he had to go down a lot faster than that
because of the oxygen mask problem.
The angle of attack would also be beneficial to re staring the engines
as well, by using the ram air to turn the compressor fan blades

Dave

Apparently they had to keep varying their angle, as the engines require a
specific range of airspeed to re-ignite,

I never went into this in any depth, so I have to accept what you say,
but I have my doubts. I dabbled in spin trials many years ago, but
didn't get to meet the aircrew till many years later to ask them.

but they'd lost their airspeed
indication.

I can't see that happening. There is a pitot static system on aircraft
that doesn't require power.
Pitot reads the air speed from probes that point forward and this air is
transferred to a simple gauge that measures and displays the speed.
Usually duplicated so that the co pilot gets a reading from a separate
probe from the pilots source.

The static side of the system relies on static wedges fitted to the side
of the aircraft, whose orifices are pointing sideways and are protected
from being pressurised by the wedges I mentioned. They are designed to
measure accurately the air pressure and calculate the altitude from air
pressure, this is a measure of vacuum from ground QFE (ground air
pressure at the time they are about to taxi out. They get this from the
control tower and on route from air traffic controllers, who get their
info from any number of ships when they fly over the sea.

They chanced losing altitude more quickly than required in
return for continual variations, hoping that one of their ignition attempts
would co-incide with the right airspeed.

That's something I'll look into, thanks.

I don't know how true this is, but that was what was stated on Air Crash
Investigation - funnily enough repeated a couple of nights ago.

I've watched that a few times and I always thought it was either padded,
or bulled up for TV.

I have spent some time working with our UK Aircraft Accident
Investigation Branch on three crashes and they didn't work like the ones
in the US prog.


Dave