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Old 16th Jan 2009, 02:03
  #2492 (permalink)  
HarryMann
 
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Thanks JustMe, kept us well informed all along

A small point on Ground Effect:
In practice, ground effect came into play, allowing both aircraft to reach a low altitude, where the loss of ground effect, and the high drag, took over.
Say 'Ground effect' to an aerodynamicist and the the first thing he thinks of is 'reduced induced drag', not increased Clmax.... because Clmax doesn't 'necessarily' improve, in fact can go either way, even reduce if circulation is reduced with some wing/ground configurations.

The intuitive effect that I imagine pilots feel, sense, and commentators are meaning, is 'dynamic stall' - that is the momentary Clmax increase due to 'rate of rotation' - an effect that birds and especially insects (operating in a thick air medium with thin wings) utilise to get instantaneous Cl's (up to 2) way over steady state ones.


So 'yanking it off' the ground at a significant rate of rotation, could, even can, give a false impression.. and get the aircarft airborne below steady-state stall speeds. As the starting vortex sheds and flow settles down, the true situation then asserts itself.. which is not necessarily because you are 40 or 50 foot up!

I happen to agree with those that are suggesting more instinctive flying responses might have reduced the casaulties in this awful accident... nose down, firewall the throttles and keep it straight - what an horrendous airfield to lose directional control on - yet something else to be factored in to the 'blame game'!

And failing the production of a clear systems flowchart for those awkwad relay failure symptons, that indicates a clear course of action, the engineer on the spot should be treated with a bit more respect by the investigating judge?
Quite why straightforward failure flowcharts for critically linked MEL/non-MEL system items aren't always to hand is beyond me -

A very, very sad and sorry story.

Last edited by HarryMann; 16th Jan 2009 at 02:20.
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