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Download Basic Propeller Principles
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Basic Propeller Principles Kevin Jung What is propeller? • Consists of two or more blades • Rotating wing • Transforms the rotary power of the engine into forward thrust The Left Turning Tendency • The propeller causes the airplane to turn left. • Four major causes are ▫ ▫ ▫ ▫ Torque Corkscrew effect (Slipstream effect) Asymmetric loading of the propeller (P-Factor) Gyroscopic effect Torque Reaction • Newton’s Third Law of Physics ▫ For every action, there is an equal and opposite reaction • When the airplane is in the air, this force is acting around the longitudinal axis, tending to make the aircraft roll to the left • When the airplane is on the ground during takeoff, torque will cause the airplane to yaw to the left. Corkscrew Effect • At high propeller speeds and low forward speed, this spiraling rotation is very compact and exerts a strong sideward force on the aircraft’s vertical tail surface • It yaws the airplane to the left Asymmetric Loading (P-Factor) • It is caused when one side of the propeller produces more thrust than the other side • At a high AOA, the downward moving blade has a higher resultant velocity, creating more lift than the upward moving blade • It yaws the airplane to the left Gyroscopic Effect • Less noticeable than other three • Produces a left yawing motion when pitching down and a right yawing motion when pitching up Summary • • • • • Propeller = Rotating Wing Torque – rolls and yaws to the left Corkscrew effect – yaws to the left P-Factor – yaws to the left Gyroscopic Effect ▫ Yaws to the left when pitching down ▫ Yaws to the right when pitching up
