Leonardo da Vinci called his spiral flying-machine design an aerial screw.
Drawn around 1489, the aerial screw used a helical surface wrapped around a frame. Leonardo reasoned that if the screw-shaped structure rotated rapidly, it might push against the air and rise, much as a screw advances through a solid material.
The drawing is often described as an early helicopter concept, but it was not a helicopter in the modern engineering sense. Leonardo did not provide a practical engine or a complete system capable of producing the required rotation and lift.
The aerial screw is also distinct from his flapping-wing ornithopters. Its proposed motion was rotary rather than birdlike. Modern helicopters use powered rotors with carefully shaped blades, a major aerodynamic development beyond Leonardo's sketch.