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A Navy E-2C Hawkeye early-warning aircraft arrives at NASA's Dryden Flight Research Center. Courtesy


A mechanical device that produces motion in some kinds of airplanes or ships. A propeller consists of two or more twisted blades that rotate around a central hub. As the propeller spins, air or water is pushed in one direction, pushing the craft in the opposite direction. [Propeller comes from a Latin word meaning “to thrust forward.”]