Basic Propeller Principles

1. Basic Propeller Principles Kevin Jung

2. What is propeller? • Consists of two or more blades • Rotating wing • Transforms the rotary power of the engine into forward thrust

3. 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

4. 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.

5. 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

6. 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

7. Gyroscopic Effect • Less noticeable than other three • Produces a left yawing motion when pitching down and a right yawing motion when pitching up

8. 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