Leonardo da Vinci’s flying-machine design with a spiral sail intended to lift vertically was the aerial screw.
Leonardo sketched the aerial screw around 1489–1490 in his notebooks. The design shows a large helical surface supported by a framework, with men turning a central shaft. Leonardo reasoned that the rotating spiral would screw itself into the air, much as a screw advances through a solid material.
The aerial screw is often called a helicopter prototype, but that label can mislead. It was a conceptual machine, not a tested aircraft, and its linen-covered reed frame would not have produced enough lift with human muscle. Modern helicopters use powered rotors and aerodynamic blades rather than Leonardo’s continuous spiral sail.
The sketch remains important because it shows Leonardo thinking about vertical flight centuries before practical helicopters. It should not be confused with his ornithopter, which depended on flapping wings, or his parachute, which was intended to descend safely rather than rise.