What Leonardo da Vinci device used a helical sail to suggest vertical flight?

Leonardo da Vinci’s device that used a helical sail to suggest vertical flight was the aerial screw.

Leonardo sketched the aerial screw around 1489–1490 in the manuscript now known as the Codex Atlanticus. The drawing shows a large helical surface made from linen, supported by reeds, with a central mast and a platform for people to turn the mechanism. Leonardo reasoned that the rotating helix could “screw” itself upward through the air, by analogy with a screw moving through wood.

The aerial screw was a conceptual machine, not a documented working aircraft. Its proposed structure was approximately 5 metres across, and the design lacked a practical engine or a clearly workable method for producing sustained rotation. It is often called an early helicopter concept, although modern helicopters use powered rotors rather than a single fabric-covered helix.

Leonardo’s sketch belongs to his wider study of flight, which also included parachutes, wings, and ornithopters. The aerial screw therefore matters mainly as an influential early flight concept, not as a proven flying machine.