Leonardo da Vinci designed the aerial screw, a flying-machine concept built around a rotating screw-shaped rotor.
His drawing, usually dated to about 1489, shows a large helical surface mounted on a central vertical structure. Leonardo reasoned that rotating the screw could make it rise by pressing against the air, much as a screw advances through a solid material.
The aerial screw is frequently called a helicopter prototype, but that description needs care. Leonardo did not have an engine capable of supplying the required power, and the drawing does not provide a practical modern rotorcraft design.
The concept nevertheless anticipated a central idea of helicopter flight: a rotor can generate lift while turning around a vertical axis. Modern helicopters use airfoils and powered rotors, not Leonardo’s continuous helical surface.