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Old January 19th 05, 03:13 AM
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Actually, the reason that a dirty plane has vortices that are less
intense than a clean airplane is that the vortices coming off the flaps
themselves act destructively with the vortices coming off the wingtips.
Same principal is in play on a turbulent day when the vortices are
broken up more quickly than on a day with smooth air.

Dave
Eric Nospam wrote:
You get the strongest wingtip vortices when an aircraft is flying

heavy,
clean and slow. But why?

It has to do with the amount of lift being generated by the wing.

HEAVY I
can understand. Heavier aircraft - you need more lift to keep it

aloft.

But CLEAN? SLOW? Why do you get less vortex with the flaps down?

Why does
a slow-moving aircraft generate a stronger vortex than a fast-moving
aircraft generating the same amount of lift? Is it because of the

larger
angle of attack necessary to generate the same lift at a lower

airspeed? If
so, why?

Eric