"Robert Moore" wrote in message
. 7...
There is NO weathervaning effect until the wheels touch the ground.

Of course there is. There is "weathervaning" any time the relative wind is
not parallel to the longitudinal axis.

Banking an airplane (putting a wing down) causes it to turn.

Actually, in some aircraft, banking an airplane causes it to turn in a
direction *opposite* of the bank. Rudder is necessary in a turn, to make
sure the turn is coordinated and is as efficient as possible. Many
airplanes, without the use of rudder, will simply slip sideways without any
change in heading at all.

You
use opposite rudder simply to keep it from turning due to the bank.

That's one way to look at it. But think about why the airplane is turning
due to the bank. The yaw occurs because bank alone causes a slip, which
causes the relative wind to come from an angle to the vertical stabilizer,
which causes yaw. That yaw can be described as "weathervaning" and the
rudder is used to counteract it.

Pete