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This is an attempt to answer the frequent question "Why is my aircraft turning left all the time? This occurs only in aircraft with propellers at the front of the aircraft.
And yes, it does occur in real life. Four distinct phenomena cause the effect, all causing the aircraft to turn in the same direction.
They are:. A propeller pushes air not just horizontally to the back, but more in a twisting helix around the fuselage clockwise as seen from the cockpit. As the air whirls around the fuselage it pushes against the left side of the vertical tail assuming it is located above the propeller's axis , causing the plane to yaw to the left.
The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i. Torque effect is the influence of engine torque on aircraft movement and control. It is generally exhibited as a left turning tendency in piston single engine propeller driven aircraft. According to Newton's law, "for every action there is an equal and opposite reaction," such that the propeller, if turning clockwise when viewed from the cockpit , imparts a tendency for the aircraft to rotate counterclockwise.
Since most single engine aircraft have propellers rotating clockwise, they rotate to the left, pushing the left wing down.
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Typically, the pilot is expected to counter this force through the control inputs. To counter the aircraft roll left, the pilot applies right aileron. It is important to understand that torque is a movement about the roll axis. Aileron controls roll. Prop torque is not countered by moving the rudder or by setting rudder trim.
It is countered by moving or trimming the aileron. This correction induces adverse yaw, which is corrected by moving or trimming the rudder right rudder. On aircraft with contrarotating propellers propellers that rotate in opposite directions the torque from the two propellers cancel each other out, so that no compensation is needed.
Further Reading: Propeller Torque Factor. 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. This is the tendency of a spinning object to precess or move about its axis when disturbed by a force. The engine and propeller act as a big gyroscope. However, gyroscopic precession is likely to be minimal in a typical aircraft.
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Understanding Propeller Torque and P-Factor
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