When teaching instructors how to draw the relative wind acting on a propeller blade, I teach the following:
- Draw the propeller from side on, showing the downgoing blade. Draw an arrow pointing down from the blade, representing plane of rotation.
- Draw an arrow from the bottom of the plane-of-rotation arrow, pointing forwards. This represents the forward speed of the aircraft.
- Draw an arrow diagonally from the forwards-pointing arrow to the propeller blade.
- You should now have a right-angled triangle, consisting of Plane of Rotation, Forward Speed and finally Relative Wind.
It's easy to draw variations showing the effect of higher forward speed, increased or decreased RPM etc. The only time the relative wind is the same as plane of rotation is when forward speed is zero. It is also easy to see that it is not possible for the relative wind to be the same as the wing's relative wind (that is, straight forwards) unless the propeller is not rotating at all.
Secondly, there are several corrections to be made with this statement...
As a propellor climbs, (and with a counterclockwise rotation), the descending blade has more lift than the ascending blade, which will exacerbate torque issues, requiring more rudder input. (Single).
The effect you're describing occurs when the aircraft is operating at high angles of attack. The aircraft need not be climbing, and often is not (e.g. on rotation during take-off, but before a significant ROC has developed).
It doesn't matter whether the propeller rotates counterclockwise or not.
This effect is not directly related to torque issues. The thrust developed by the entire propeller slightly favors (as you said) the downgoing blade, tending to cause yaw. Torque causes roll, which may lead to yaw...
The effect is not limited to single engine aircraft. I fly a light twin which has a pair of clockwise rotating propellers, and tends to yaw quite strongly during / after rotation.
All the best,
O8