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).

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).