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Old 5th Apr 2011, 08:08
  #3005 (permalink)  
HazelNuts39
 
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high altitude stalls

I like this quote from the opening sentences of D.P. Davies discussion on "Stalling" (but must admit I'm taking it completely out of context):
Stalling is one of the major areas which always come up for discussion whenever responsible pilots get together. (...) Stalling appears to drive even the most rational of pilots to completely opposing points of view.
In many minds, including mine, stalling is something you get close to during takeoff and and landing, i.e. at relatively low altitude. In thirty-odd pages related to stalling, mr. Davies devotes only a single (not quite accurate) sentence to the effect of altitude:
At very high altitude the EAS stall speed occurs at a significant Mach number (180 knots = 0.61 Mach number, for example); the pressure pattern is disturbed and a higher stall speed results.
The point I wish to make is that stall at high altitude involves fundamentally different (transonic) phenomena compared to low altitude. For example, for the A330 in clean configuration, alpha max is of the order of 14 degrees up to Mach 0.275, 8 degrees at Mach 0.6, and 4 degrees at Mmo.

Regards,
HN39

Last edited by HazelNuts39; 5th Apr 2011 at 09:36. Reason: correction of amax/M.275
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