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Understanding Propeller Torque and P-Factor: Difference between revisions
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Understanding Propeller Torque and P-Factor (view source)
Revision as of 11:28, 24 February 2014
, 24 February 2014→P-Factor: The propeller may even have a fixed pitch, but in relation *to the oncoming air* the angle of attack, not of the aircraft, but the ascending and descending propeller will differ
(→P-Factor: The propeller may even have a fixed pitch, but in relation *to the oncoming air* the angle of attack, not of the aircraft, but the ascending and descending propeller will differ) |
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=== P-Factor === | === P-Factor === | ||
P-factor is the term for asymmetric propeller loading, causes the airplane to yaw to the left when at high angles of attack. | P-factor is the term for asymmetric propeller loading, that causes the airplane to yaw to the left when at high angles of attack. | ||
Assuming a clockwise rotating propeller it is caused by the descending right side of the propeller (as seen from the rear) having a higher angle of attack relative to the oncoming air, and thus generating a higher air flow and thrust than the ascending blade on the left side, which at the other hand will generate less airflow and thrust. This will move the propellers aerodynamic centre to the right of the planes centreline, thus inducing an increasing yaw moment to the left with increasing angle of attack or increasing power. With increasing airspeed and decreasing angle of attack less right rudder will be required to maintain coordinated flight. | |||
This occurs only when the propeller is not meeting the oncoming airflow head-on, for example when an aircraft is moving down the runway at a nose-high attitude (in essence at high angle of attack), as is the case with tail-draggers. Aircraft with tricycle landing gear maintain a level attitude on the takeoff roll run, so there is little P-factor during takeoff roll until lift off. | |||
When having a negative angle of attack the yaw moment will instead be to the right and and left rudder will be required to maintain coordinated flight. However negative angles of attack is rarely encountered in normal flight. In all cases, though, the effect is weaker than prop wash. | |||
=== Gyroscopic Precession === | === Gyroscopic Precession === | ||