Leonardo da Vinci’s flying-machine design with a rotating helical wing was called the aerial screw.
Leonardo sketched the aerial screw around 1489 in a manuscript now associated with the Institut de France. The design shows a large helical rotor made from a reed or cane framework covered with linen. Leonardo reasoned that if the screw were turned quickly enough, its spiral surface would press against the air and lift the machine. The drawing is therefore a study of vertical flight rather than a working helicopter.
The aerial screw is frequently described as a helicopter prototype, but that wording can be misleading. Leonardo did not have a lightweight engine capable of turning the rotor, and the proposed human-powered mechanism could not have supplied enough energy for sustained flight. Modern helicopters also depend on aerodynamic rotor blades, controls, and engines that are absent from the Renaissance design.
Its historical importance lies in the idea of a rotating lifting surface. Centuries later, engineers developed powered rotorcraft using principles that made the aerial screw’s basic ambition practical.