Is P-factor For Real?

Peter Garrison

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

Verified

Key Takeaways:

Pilots use right rudder in an upright climb to counteract left-turning forces, predominantly P-factor and slipstream rotation.
An inverted climb test helps distinguish these forces: P-factor continues to pull the nose left (requiring the pilot's left rudder), while slipstream rotation's effect reverses (requiring the pilot's right rudder).
Experimental results from acrobatic aircraft suggest P-factor is the primary cause for rudder input in most climbs, with slipstream rotation playing a lesser or negligible role.
During the takeoff roll, when the aircraft is level, P-factor is absent, and the leftward pull is primarily due to slipstream rotation and torque reaction on the ground.

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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.