Leonardo da Vinci designed an aerial screw with a helical, screw-shaped rotor.
His drawing, usually dated to about 1489, shows a large spiral surface wound around a vertical framework. Leonardo reasoned that if the spiral could rotate quickly enough, it might screw itself upward through the air, much as a screw moves through a solid material.
The concept is often described as an early helicopter idea, but it was not a helicopter in the modern engineering sense. Leonardo did not provide a complete powered engine, and the proposed materials and human power would not have produced enough lift for practical flight.
The aerial screw is also distinct from his flapping-wing studies. It relies on a rotating helical surface rather than bird-like wings. Its historical importance comes from imagining vertical lift through rotation centuries before powered helicopters became possible.