Robert Ehrlich wrote:
Jim wrote:

...
In a descending turn, which is what gliders do in turns, it is not the
case that both wings have the same vertical component of velocity. In
a stable descending turn the inside wing is always undergoing a
downward motion relative to the outer wing. This is one cause for the
inside wing to be at a higher AOA than the outer wing, and one reason
for the resulting earlier stall than the outer wing. In an ascending
turn, power airplanes I guess, it is the outer wing that is always
undergoing a downward moovement relative to the inner wing.

I found this difficult to visualize at first, but if you try "flying"
a stable descending "turn" with your hand you will experience it
clearly.



Can't understand that. If both wingtips have a different vertical component
of velocity, the vertical distance between them should change,
increasing the bank angle if the inner wing sinks faster than the outer
one. This difference must anyway stop at 90 degrees bank. But as long
as the bank angle remains constant, both wings should have the same
vertical component of velocity.
Relative to what? - is the point.

You are correct that their vertical component of velocity must be the
same because of geometry, if the bank angle remains constant. However,
because the inner wing is describing a smaller diameter spiral the
relative wind will present at a higher angle of attack on the inner wing
tip - relative to the outer wingtip. Velocity relative to the ground is
not entirely sufficient to understand what is happening in three dimensions.

In the same time the inner tip travels a smaller distance, but descends
the same vertical distance, hence the greater angle of descent, not
rate. People seem to continuously confuse rates and angles? Airflow
behavior is very dependent on angles and chord wise component of airflow
velocity...