wrote in news:c2611450-2801-4cb7-9fc9-
:

On Feb 17, 3:58*pm, Bertie the Bunyip wrote:
True, but having said that, the ASI should e regarded with some
suspicion even IMC. Most pilots ( and I did this exercise in the sim
the
other day) when presented with bad airspeed info will chase it in
preference to attitude info. this has caused lots of accidensts over
the
years. Two I can remember off the top of my head are the 757 off the
coast of Peru, I think, and the 727 in upstate new york. I'm sure
there
have been lots of others in light airplanes. It's amazing to watch.
The
airspeed sems to run away and the guy just zeroes in on it and pulls
or
pushes until the whole scene is just such a mess recovery would be a
miracle.

Yeah, worst case is when the pitot freezes over or otherwise gets
sealed off, so the ASI says you're slowing down when you're speeding
up, and vice versa (because of the changing static-port pressure as
you climb or descend). In theory, the ASI should then be out-voted by
the altimeter and the attitude indicator, but I imagine it's tricky
(I've never experienced it myself).

I have a couple of times and I had no problem, but apparently it can be.
it certainly gives you a jolt when you see it. I had it in a Twin Beech
once and the airspeed instantly went to the barberpole. Had it in some
singles as well I t doesn't take much to clog them.

That's one situation where the mushy response of a slow plane, or the
stiff controls and whooshing sound in a diving one, might be
especially helpful in augmenting what the instruments are saying (at
least for the light planes I fly--dunno how well that applies to
airliners).

It's the same, though the feel is simulated through an artificial system
that is reliant on.. you guessed it, airspeed! Older airplanes had
dedicated pitots for this ( you can see them on the fin of older
Boeings) but newer machines tend to use the air data computer which is
fed by standad pitots on the nose.

Bertie