Re: ailerons and adverse yaw

[John Denker <jsd@MONMOUTH.COM>]

At 01:57 AM 8/14/99 -0500, brian whatcott wrote:
> This comment offers insight into another misconception.
> People are often aware that the Wright Flyer was the first truly
> controlable airplane.

Correct.  The Wrights went to a lot of trouble to enforce their patent on
roll control.

> It did not use ailerons - they had yet to be invented
> - or at least named by the French,

Alexander Graham Bell is generally credited with the invention of ailerons
_per se_.  Initially they were called flaps.  Nowadays flaps means
something else.  See
  http://www.curtisswright.com/hist/warp.htm

> but the Flyer used something rather
> similar called wing warping.

Correct.  The aileron is an improvement over wing warping, but not
categorically different.

>    But people conceive that the low trailing edge lifted the wing - wrongly.
> The low wing dropped and slowed the Flyer as it turned towards it.

Uhhh, it's tautological to say the low wing dropped.  I assume you mean the
wing with the lowered aileron dropped.

Even with that emendation, I suspect that's not quite right.

I suspect you read something like

http://www.always-online.com/jayhawker/Pictures/Virginia_Beach/Wright_Bros/H
istory/First_flight_history.htm
which is correct and well-written but easily misinterpreted.

The tricky point is that in an airplane, there are two separate concepts:
the way is the airplane *pointing* is not necessarily the same as the way
is it *going*.  In cars, bikes, typical boats, and practically everything
else except airplanes, this distinction is lost, because you control the
direction of motion by controlling the heading.

In an airplane in normal flight, lowering the left aileron will cause the
left wing to rise, as desired.  When the left wing is up, the airplane's
center-of-mass motion will turn to the right, as desired.

The quirk is that while the aileron is deflected, it will cause the
airplane to *yaw* to the left, which is not desired.  The Wrights
discovered that they needed to deflect the rudder to overcome this adverse
yaw, to keep the airplane pointing the same way it is going.

The effect is quite noticeable even on modern airplanes.  For more on this, see
  http://www.monmouth.com/~jsd/how/htm/yaw.html