A propeller is really a set of rotating wings. Each blade is an airfoil that produces thrust the same way a wing produces lift. Here is how a propeller works, and the difference between fixed-pitch and constant-speed props.
Part of our How Airplanes Work guide.
A propeller is a rotating wing
Each propeller blade has an airfoil shape, like a wing. As the engine spins it, the blade meets the air at an angle of attack and produces a force, thrust, that pulls the airplane forward. The blade is twisted from root to tip because the tip travels much faster than the root, so the twist keeps the angle of attack effective along the whole blade.
Blade angle and pitch
The blade’s pitch is the angle of the blade relative to its rotation. A lower pitch takes a smaller bite of air (good for acceleration and climb), while a higher pitch takes a bigger bite (efficient at cruise). How pitch is managed defines the two main propeller types.
Fixed-pitch vs. constant-speed propellers
Fixed-pitch propellers have one blade angle set by the manufacturer, a compromise for either climb or cruise. They are simple and common on basic trainers; you control power with the throttle alone, reading RPM.
Constant-speed propellers use a governor to automatically change blade pitch and hold a selected RPM. You set RPM with a propeller control and power with the throttle, reading manifold pressure. This lets the engine and prop operate efficiently across a wide range of conditions, and it is a complex-aircraft feature you may train on later.
Left-turning tendencies
Spinning propellers create several forces that tend to yaw the airplane left at high power and low airspeed, including P-factor (the descending blade taking a bigger bite), torque reaction, spiraling slipstream, and gyroscopic precession. You counter them with right rudder, especially on takeoff and climb.
What you'll need
The FAA handbooks that explain how your airplane works, from PilotMall.com.
Frequently asked questions
How does a propeller create thrust?
Each blade is an airfoil. As it spins, it produces a forward force the same way a wing produces lift.
What is the difference between fixed-pitch and constant-speed props?
A fixed-pitch prop has one blade angle; a constant-speed prop uses a governor to change pitch and hold a selected RPM for efficiency.
Why do I need right rudder on takeoff?
To counter the left-turning tendencies (P-factor, torque, spiraling slipstream, and gyroscopic precession) that are strongest at high power and low speed.