ORIGINAL: Red B.
Majortomski wrote:
... Again no swirl in the slipstream...
The twist of the propeller slipstream has been experimentally shown to exist, no doubt about it! (See my previous post for links)
As I previously stated the twist angle is of the order of a few degrees and thus you will not see the slipstream spiral around the fuselage simply by observing an aircraft in flight by eye. In controlled experimental conditions however the twist is easily measured.
When in doubt about theories trust nature!
/Red B.
Yep Red B finally found what I was looking for however...
The old report from the 30's finally gives an equation to the amount of twist imparted in the slipstream, and at cruise it is only 3 degrees. Doesn't say which way, or what happens at slower airspeed and higher angle of attack.
The second report, and now I've got to go hunt down a full copy of it, basically assumes that the swirl exists because the left wing stalled before the right wing by surprise...the three degrees from the first report! But they didn't go into the detail of how was the test aircraft rigged, or was it a damaged airframe in the first case.
Now under this new light I have a new set of criteria to examine. But I'm beginning to believe that over the course of the years the two minor forces involved in slow flight yawing (spiraling slipstream and angle of attack on the propeller) have been over emphasized the the significant forces actually at work (propeller rotational velocities and P factor thrust) are being almost completely over looked!