“And as shown in the photo in post #20 above, when you can see these spirals off the prop, they are going the wrong way to support the myth.”

“Ahh but... The swirl theory is based on the assumption that the propeller imparts energy to the air particles that causes them to move in the same direction as the propeller. This is the source of the clockwise rotation. The problem with this is that it violates airfoil theory. Air particles moving over an airfoil are forced down and AFT. To make the slipstream work they'd have to go down and FORWARD!”

On the first statement, you cannot make any conclusions about velocity from the still photo. All we can determine is that the tips of the props have scribed a spiral path with respect to the ground and airframe in recent history. This says nothing about the actual airflow. There is no way to conclude that the spiral is twisting at all, much less one way or the other from that photo. It is however a cool pic.

On the second, that is dead wrong unless I missed something. Actually, what violates airfoil theory (not to mention the laws of thermodynamics) is what you present as correct.

First, if what you say is true, then air has a net velocity increase rearward. I.E. it gains velocity as it leaves the airfoil. If true, this net gain must react on something, i.e. the airfoil. Then the accelerated air would increase the velocity of the airfoil, pushing it faster thru the air. So once you start the prop spinning, or the wing moving, it would accelerate all on it’s own until and you could turn off the power plant. That is perpetual motion… not possible. Violates the laws of thermodynamics.

I believe the hang up is with the downward wash off an airfoil when it generates lift. Yes, the velocity of the downwash is rearward and down (with respect to lift), however, the net velocity of this air mass is moving slower than the clean air. It must… that is drag. Look at the velocity distribution of any airfoil, you will always find that the air mass at the TE of the airfoil is moving slower than the pre-airfoil air.

Then when we have a rotating wing generating lift (a propeller), the downwash will still be slightly slower than the velocity of the airfoil, it must. This will cause the slower air leaving the airfoil to follow the path of the airfoil in the same direction. Once we leave the rotating coordinate system (i.e. sit in the plane or watch from ground) the air velocity from our vantage would then be rearward and in the spiral pattern, with the rotation in the same direction as the prop movement. I think it is the jump from a rotating coordinate system to a fixed (ground or plane based) system that messes with people.

I still don’t know if there is any significant effect to yaw from this, but unless someone can point out were my logic failed, I believe the wash is in the direction of prop rotation, which could possibly lend weight to the spiral slipstream causing left yaw on standard rotating engines. Even after my proof that the spiral wash is indeed the direction I originally indicated, I am beginning to believe that while the some effect is there, p-factor dominates. Thoughts? Cheers.