Testing your glide. Are people doing this?

On Tue, 28 Oct 2003 at 16:27:33 in message
VNwnb.51170$HS4.234123@attbi_s01, Jay Honeck
wrote:

But is that true of all airliners? I guess I would have thought that a
600,000 pound un-powered jetliner wouldn't glide very well.

The weight makes a difference to the rate of sink but I see no obvious
reason why it should make a big difference to the glide angle. After
all, airliners need good lift drag ratios to make them economical.

The BOAC 747 that lost all engines due to volcanic ash expected to be
able to glide 141 nm from 37,000 ft taking 23 minutes. That's a glide
ratio of over 20 to 1 and around 1600 ft a minute and 240 knots.

They did worse than that because they did not know the best speed and
they needed to maintain the engine start speed. Not only that but they
had no reliable speed measurement either. One pilot had 320knots and the
other had 270 knots on their ASIs - 50 knot difference!. Then they had
to sacrifice height because of loss of pressurization. Of course when
they passed out of the ash they were able to restart.

Ref: Air Disaster Volume 2 by Macarthur Job
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