Todd Pattist wrote:

Jim wrote:

(Chris OCallaghan) wrote:
I'm having some trouble visualizing this.

Is it possible that Sammy has posited a reference frame that looks
only at AOA,

I think he's looking at the ground reference. If an
aircraft is making a pure level skidding turn, it's turning
in yaw only. If it's rolled knife edge in the level turn,
it's making a pure pitching turn. If it's pointed straight
down (Mike's "vertical barrel roll") it's making a pure
rolling turn. Different banks and descent/climb rates from
the level turn produce the combinations of the above that
Sammy describes.
...

But nevertheless it seems there is a confusion about what
are the pitch, yaw and roll axis. The usual convention is
that these axis are tied to the airframe, independantly of
the attitude and the airflow. In this case, most gliders
when they are near stall have a nose up attitude despite
their strongly descending path. In this case Sammy's description
would be an ascending turn, with a difference of AOA between
wings opposite to what is observed (remember the extreme case
of the half wingspan equal to turn radius yielding an AOA
over 90 degrees (90 degrees + nose up attitude + incidence)
for the inner wingtip). Sammy's description would probably
be correct if we redefine the roll axis as parallel to the
airflow, pitch axis unchanged from wintip to wingtip and yaw
axis perpendicular to both others. This is in some way implied
by this description as being the case of a descending turn, as the
fact that the aircraft is descending is tied to the direction
of the airflow, not the pitch attitude. In this case this description
and the previous one involving the speed difference of both
wing tips are equivalent.