Turbulence is gusts which change the airspeed. I recall reading one account
of a thunderstorm accident where the plane encountered a 80kt vertical gust.
In the Sierra Wave Project loads of +16G and -20G were encountered in a
rotor cloud at below Va..

I think it should be understood that these are extreme examples i.e. flying
into the worst part of the worst thunderstorm at the worst time. A one in a
million event. The usual breakup story is loss of control followed by an
overspeed were the pilot pulls the wings off in the recovery.

Mike
MU-2

"Peter" wrote in message
...

I think I understand the reasoning behind Va, the max maneuvering
speed, being that the wing will stall (and thus dispose of the
loading) before it breaks. This is why Va falls as the weight falls,
because at any given IAS a higher weight takes the aircraft closer to
stall already.

So, how is it possible to have aircraft destruction due to weather,
e.g. flying into a strong updraught in a CB, if flying below Va?

A DOWNdraught would do it more easily because most aircraft designs
have a lower design limit for negative G.


Peter.
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