Before jets, propellers powered everything. They still do, on small aircraft, regional turboprops, and drones. A propeller is a set of rotating airfoil blades that converts engine power into thrust by accelerating air backward.

Blade shape changes along the length. The tips move faster than the roots, so the twist varies to keep the angle of attack consistent. Fixed-pitch propellers work well at one speed. Variable-pitch propellers adjust blade angle to stay efficient across a range of conditions.

Common propeller types

• Fixed-pitch, simple and cheap
• Constant-speed, maintaining RPM automatically
• Controllable-pitch, adjustable by the pilot
• Feathering, aligning blades to reduce drag after engine failure

Efficiency drops at high speed because the tips approach the speed of sound. That is why jet engines took over long-distance and high-speed flying.