Basic Propeller Principles

Basic Propeller PrinciplesKevin Jung

What is propeller?Consists of two or more bladesRotating wingTransforms the rotary power of the engine into forward thrust

The Left Turning TendencyThe propeller causes the airplane to turn left. Four major causes areTorqueCorkscrew effect (Slipstream effect)Asymmetric loading of the propeller (P-Factor) Gyroscopic effect

Torque ReactionNewtons Third Law of PhysicsFor every action, there is an equal and opposite reactionWhen the airplane is in the air, this force is acting around the longitudinal axis, tending to make the aircraft roll to the leftWhen the airplane is on the ground during takeoff, torque will cause the airplane to yaw to the left.

Corkscrew EffectAt high propeller speeds and low forward speed, this spiraling rotation is very compact and exerts a strong sideward force on the aircrafts vertical tail surfaceIt 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 sideAt a high AOA, the downward moving blade has a higher resultant velocity, creating more lift than the upward moving bladeIt yaws the airplane to the left

6Gyroscopic EffectLess noticeable than other threeProduces a left yawing motion when pitching down and a right yawing motion when pitching up

SummaryPropeller = Rotating WingTorque rolls and yaws to the leftCorkscrew effect yaws to the leftP-Factor yaws to the leftGyroscopic Effect Yaws to the left when pitching downYaws to the right when pitching up