In aeronautics, an aircraft propeller, also called an airscrew, converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type.

William Frederick Durand was a United States naval officer and pioneer mechanical engineer. He contributed significantly to the development of aircraft propellers. He was the first civilian chair of the National Advisory Committee for Aeronautics, the forerunner of NASA.