mikenjulie.parkin(at)btop
Guest
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 Posted: Sun Jul 30, 2006 10:12 am Post subject: Re Wing Drop in the Stall |
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>Are the Classics more prone to wing drop? Do XS wings have the same
| Quote: | behavior? Could a minor tolerance between the wing setup (angle of
>attack, sweep) be a cause of wing drop in stall? Do i understand correctly
that stall strips are spoiling the good wing to the same quality as the bad
>wing? In what class are the speed penalties involved?
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Jos,
I think that the original foam built wings are likely to vary slightly more
in performance than the factory made wings purely because of the nature of
construction. Profiling the wing is a laborious process and the end result
is very much an 'eyeball dependent' operation. I think it would be fair to
say that the jig made factory wings are likely to produce a more consistent
result.
The original wings were fitted with flaps and ailerons made from foam
blocks, glass cloth and resin. Fitting the flap hinges and setting up the
correct washout was challenging and certainly not a precise science. Having
produced 2 of these labour intensive wings, the chances of each wing
exhibiting the same CL curve is unlikely at best. Combine these variables
with any tolerances in the wing to fuselage incidence and you could have
some work to do to make the aircraft behave. The very nature of the wing
seems to provide a useable amount of lift until the stall, at which point
the loss of lift from the wing seems to be almost total. Now if one wing
stalls before the other it is conceivable that the aircraft might roll on
its back.
The purpose of the stall strips is exactly as you suggest - to make the good
wing stall before it would if the stall strip was not fitted.
I think that the strip works by the nib of the strip disrupting the boundary
layer (at particulat angle of attack) on the wing downstream of the strip.
I have read somewhere that the strips can affect short field landing and
take-off performance - no doubt one of our aerodynamicists would be able to
explain - I can't remember the reason.
However, as I understand it, the stall strips have negligible effect at
higher speeds.
From a practical flying point of view. In the airline industry, along with
level busts, the subject of stabilised approaches is very topical with
training captains. All pilots should strive to establish a stabilised
approach (on calculated landing speed, on the centreline, on glidepath,
sensible power setting) by 200 - 300 ft finals. If you have not achieved
the ideal situation then consider going around and getting it right next
time. There is no loss off face by throwing away a poor approach - anyone
that thinks there is, is just 'flying towards the scene of his own
accident'. All pilots should know when to throw it away - and particularly
with inexperienced or non-current pilots - it should be sooner rather than
later.
Remember the old fighter pilot saying - height is might and speed is life.
All the best, and safe flying.
regards,
Mike
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