What rotating aerial machine did Leonardo da Vinci design with a helical sail?

Leonardo da Vinci designed an aerial screw, a rotating machine with a helical sail intended to rise through the air.

Leonardo drew the device around 1489–1490 in a manuscript now associated with the Institut de France. The design uses a large spiral surface made from linen, reeds, and wire. Leonardo reasoned that rotating the spiral rapidly would cause it to screw upward through the air, much as a screw moves through a material.

The aerial screw is often described as a helicopter precursor, but it was not a helicopter in the modern engineering sense. It lacked a practical powered rotor system, and the proposed human-powered mechanism could not supply enough energy for sustained flight.

The concept remains important because it shows Leonardo thinking about vertical lift rather than relying only on wings. Modern helicopters use rotating airfoils and powered rotors, while Leonardo’s sail was a different aerodynamic idea.