Re: "Frise-type" ailerons...

From:         barr@netcom.com (Keith Barr)
Organization: NETCOM On-line Communication Services (408 261-4700 guest)
Date:         15 Jun 95 01:13:58 
References:   1
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In article <airliners.1995.749@ohare.chicago.com>,
Nick Strauss <pilot@leland.stanford.edu> wrote:
>Are "frise" ailerons different from the usual up-down articulated flap at end
>of wing thing that I've grown comfortable with after all these years?

In essence, they are the same thing you have known, but they have an extra
feature which helps counteract adverse yaw in a turn.

Ailerons bank the aircraft by creating a lift differential between the
wings.  The aileron on the wing on the inside of the turn is raised, which
reduces lift, and the aileron on the outside of the wing is lowered, which
increases lift.  Induced drag is increased when lift is increased, so there
is a drag differential as well between the wings, with the high wing having
more lift and drag.  This drag imbalance tends to move the nose of the
aircraft in the opposite direction of the turn, and is called adverse yaw.
Usually rudder is applied to remove this effect, but Frise ailerons were
created to minimize the need for rudder.

A Frise aileron has a tab built in to the leading edge, so that when the
aileron is raised (such as on the low wing in a turn) the tab is exposed to
the slipstream, which creates drag, thereby (more or less) equalizing the
drag between the high and low wing, thus minimizing the adverse yaw.
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