wrote in news:1193070733.442941.237020
@v23g2000prn.googlegroups.com:

On Oct 21, 3:56 am, Bertie the Bunyip wrote:
wrote in news:1192935582.999886.201640
@t8g2000prg.googlegroups.com:



In addition to what others have said, another interesting question
to
ponder is why the airplane yaws when you bank.

The yaw is induced by the ailerons, so the only time you need to
apply
rudder is when you are changing your bank angle with the ailerons.
On
the side where the aileron is down, the wing has more lift, and
more
drag. On the other side, the lift is spoiled and there is less
drag.
The draggy wing yaws backwards, requiring opposite rudder.

that's adverse yaw. I beleive he meant why does the airplane yaw in
the
same direction (eventually) as the direction of roll?

Bertie



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Bertie,

I assumed that adverse yaw was what he was asking about since it is
the most pronounced effect.

To answer the question the other way:

The reason for rudder use in a sustained bank is due to the fact that
the airspeed of the outside wing is slightly higher than the airspeed
of the inside wing due to the difference in arc-distance that each
wing is traveling in a turn. The outside wing has a little more drag
due to the higher airspeed and a little bit of rudder is required to
compensate.



Ooops!

I don't think that is what he was asking either! Though both statements
you made are correct.

I think he was asking why, when you bank, the airplane also (eventually)
yaws in the same direction.
Simply put, if you bank without yaw, you slip (after the adverse yaw
thing settles down a bit) and that slip will apply a force to the fin,
coarsely dragging the nose into roughly the direction the airplane is
going.
But, as this poster points out, adverse yaw will cause it to initially
yaw in the opposite direction due to adverse yaw, and then rudder will
be required to ensure the yaw is tangential to the line of flight.
IOW the fin will knock the airplane in roughly the right direction but
you need to use your feet.


Bertie