Leonardo da Vinci’s aerial screw used a screw-shaped rotor as a proposed way to lift a craft into the air.
His drawing, generally dated to about 1489, shows a large helical surface mounted around a central mast. Leonardo reasoned that if the screw were rotated rapidly, its spiral surface might press against the air and produce upward motion. The concept is often compared with a helicopter rotor, although it would not operate efficiently with the materials and power sources available in the Renaissance.
The aerial screw was a design study, not a flight-tested helicopter. It also should not be confused with Leonardo’s other flying-machine ideas, including flapping-wing ornithopters and gliders. The famous sketch influenced later popular accounts of helicopter history, but modern helicopters use aerodynamic rotor blades rather than a continuous fabric-covered helix. Its importance lies in identifying rotary lift as a possible route to flight long before powered aviation.