Is P-factor For Real?

Peter Garrison

Saturday, March 01, 2014 at 12:08 AM ET

Verified

Key Takeaways:

The article investigates the forces requiring right rudder in a climb, primarily distinguishing between P-factor, slipstream rotation, and torque.
An "inverted climb" test is proposed to differentiate P-factor (which consistently pulls the nose left) from slipstream rotation (whose effect on the fin reverses when inverted).
Experimental results from acrobatic aircraft (Extra 300s, Pitts) indicate that P-factor is the predominant cause for rudder input during climbs, often requiring left rudder when climbing inverted.
The study concludes that while P-factor dictates rudder use in climbs, slipstream rotation and ground torque are more influential during the takeoff roll when the aircraft is level.

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When climbing, you need some right rudder to keep the ball centered. If you perform a half roll and continue to climb upside-down, which rudder will you have to use to stay coordinated?

Why do we need right rudder in a climb, anyway? Is it because of slipstream rotation? The propeller drags some air around with it, and the airplane continually advances through this slipstream of deflected air. The fin, being behind the portion of the propeller disk where the blades are going left to right, feels a push to the right.