Leonardo da Vinci called his 1489 rotating-air machine an aerial screw.
The drawing shows a large helical structure made from reeds, linen, and wire, with a central mast and a platform. Leonardo proposed that rotating the screw would make it rise by driving against the air, an idea that resembles the principle of a helicopter rotor. The machine was not built and tested by Leonardo, and its proposed human-powered mechanism could not have supplied enough lift.
The aerial screw is often called a helicopter prototype, but that label needs care. A modern helicopter uses powered rotors, aerodynamic blades, and controlled lift; Leonardo’s device was a speculative sketch rather than a practical aircraft. Its importance lies in showing that Leonardo considered vertical flight separately from winged flight.
The drawing is preserved in the Codex Atlanticus, which contains many of his engineering studies.