Source of quotes: [[PHAK Ch5]] # Overview > the left turning tendency of the airplane is made up of four elements that cause or produce a twisting or rotating motion around at least one of the airplane’s three axes ![[Axes of Airplane.jpeg]] > The effects of each of these four elements of torque vary in value with changes in flight situations. In one phase of flight, one of these elements may be more prominent than another. In another phase of flight, another element may be more prominent. --- # Four Tendencies ## Torque Reaction > Torque reaction involves Newton’s Third Law of Physics— for every action, there is an equal and opposite reaction. As applied to the aircraft, this means that as the internal engine parts and propeller are revolving in one direction, an equal force is trying to rotate the aircraft in the opposite direction. ![[Torque Reaction.jpeg]] ### Impact During cruise flight, the aircraft is designed to negate this. During takeoff roll, however, this can be felt as a left turn. Since the clockwise propeller forces the left tire harder to the ground, causing more friction and making the airplane pivot left. ### Mitigation Use right rudder as needed to align with centerline on takeoff roll. --- ## Spiral Slipstream > The high-speed rotation of an aircraft propeller gives a corkscrew or spiraling rotation to the slipstream. At high propeller speeds and low forward speed (as in the takeoffs and approaches to power-on stalls), this spiraling rotation is very compact and exerts a strong sideward force on the aircraft’s vertical tail surface. ![[Spiral Slipstream.jpeg]] ### Impact Slipstream striking the right side of the vertical fin, especially as slow speeds, yaws the nose left.^[The spiral slipstream also causes a right rolling motion, but notice this is offset by the left rolling motion from the [[Torque Reaction]]. They often counteract each other, but in practice the forces involved vary and the pilot should apply proper corrective action to accommodate.] At faster speeds, the slipstream elongates and is not as impactful. ### Mitigation Use right rudder ([[Step on the Ball]]) to keep the airplane coordinated. --- ## [[P-Factor]] (Asymmetric Loading) > When an aircraft is flying with a high AOA, the “bite” of the downward moving blade is greater than the “bite” of the upward moving blade. This moves the center of thrust to the right of the prop disc area, causing a yawing moment toward the left around the vertical axis.^[This is a great one to look at on an actual plane. It's easier to see when you have a real propeller in front of you to look at.] ![[Propeller Blade AOA.jpeg]] ![[P-Factor Asymmetric Loading.jpeg]] ### Impact When the aircraft is at a high [[AOA]], the downward moving propellor generates more forward pull then the upward moving blade. Airplanes in the US have propellers which rotate clockwise, so the propeller right side (viewed from flight deck) generates more force forward then the left side, yawing the nose left. ### Mitigation Use right rudder ([[Step on the Ball]]) to keep the airplane coordinated. --- ## Gyroscopic Precession The propeller is also a good gyroscope, and so is affected by precession. > Precession is the resultant action, or deflection, of a spinning rotor when a deflecting force is applied to its rim. ... when a force is applied, the resulting force takes effect 90° ahead of and in the direction of rotation. > > Any time a force is applied to deflect the propeller out of its plane of rotation, the resulting force is 90° ahead of and in the direction of rotation and in the direction of application, causing a pitching moment, a yawing moment, or a combination of the two depending upon the point at which the force was applied. ![[Gyroscopic Precession.jpeg]] ### Impact This is most frequently experienced in tailwheel aircraft when the tail is raised for takeoff. ![[Raising Tail Causes Gyroscopic Precession.jpeg]] ### Mitigation Use elevator and rudder to prevent undesired pitching and yawing. Be ready for gyroscopic precession especially when raising the tail of a tailwheel aircraft on the takeoff roll.