P-factor
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P-factor is an aerodynamic phenomenon experienced by a moving propeller with a high angle of attack that produces an asymmetrical center of thrust[1]
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[edit] Causes
The p-factor is caused by the difference in angle of attack between the ascending and decending blades of a rotating propeller blade. Specifically, the decending blade has a higher angle of attack, relative to the ascending blade. In accordance with the Bernoulli Principle, the propeller blade with the higher angle of attack will provide more force, in this case, measured as thrust[2]. With the decending blade providing more thrust than the ascending blade, the center of thrust is moved away from the center and out towards a parallel point somewhere along the decending blade.
[edit] Effects
The effects of the p-factor, on a single engine propeller aircraft, are observed through the aircrafts tendancy to have left yaw on the vertical axis. These effects are most noticable during take off[3] or in flights with high power and high angle of attack[4].In multi engine, propeller-driven aircraft, P-factor is also important in determining the critical engine.
[edit] Sources
- [1997] (2004) Willits, Pat: Guided Flight Discovery - Private Pilot, Abbot, Mike Kailey, Liz, Jeppesen Sanderson, Inc.. ISBN 0-88487-333-1.
- Ramskill, Clay. Prop Effects. Retrieved on 2006-12-5.
