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Old January 18th 05, 03:30 AM
Dan Girellini
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emove (AJW) writes:


You get the strongest wingtip vortices when an aircraft is flying heavy,
clean and slow. But why?


Not so sure about dirty v clean, but at low speeds clean isn't very effecient
at generating lift. That means larger angles of attack, more air displaced,
maybe a bigger vortex.


From http://av8n.com/how/htm/airfoils.html#sec-wake-vortices:

You would think that...flaps extended would be the absolute worst, but that
is not quite true. The flaps do increase the circulation-producing
capability of the wing, but they do not extend over the full
span. Therefore a part of the circulation is shed where the flaps end, and
another part is shed at the wingtips. If you fly into the wake of another
plane, two medium-strength vortices will cause you less grief than a single
full-strength vortex. Therefore, you should expect that the threat from
wake vortices is greatest behind an airplane that is heavy, slow, and
unflapped.

d.