What Leonardo da Vinci design used a helical sail to propose vertical flight?

Leonardo da Vinci’s aerial screw used a helical sail to propose vertical flight.

Drawn around 1489, the aerial screw resembles a large screw or auger mounted on a circular frame. Leonardo suggested that rotating the screw could force air downward and lift the structure upward. The idea is often described as a conceptual ancestor of the modern helicopter, although it was not a helicopter in the modern engineering sense.

The design’s lifting principle was imaginative, but the proposed materials and human power source could not have produced enough thrust. Leonardo did not build a successful flying prototype from the drawing. Its importance lies in showing that he was thinking about vertical takeoff centuries before powered helicopters appeared.

The aerial screw is commonly mixed up with the ornithopter. The ornithopter depends on flapping wings, while the aerial screw depends on a rotating helical surface.