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
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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
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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