Leonardo da Vinci’s helical rotorcraft concept is called the aerial screw.
Leonardo drew the design around 1489 in a manuscript now associated with the Codex Atlanticus. It shows a large spiral sail or screw made from linen stiffened with reeds and supported by a light framework. His notes suggested that, if rotated rapidly enough, the screw might press against the air and lift the machine.
The aerial screw is often described as an early helicopter idea, but it was not a practical helicopter and Leonardo did not build a working full-scale version. Its proposed lifting principle also differs from the powered rotors used by modern helicopters. The design is especially important because it treats vertical flight as a mechanical problem rather than as imitation of bird flight.
The word “aerial” distinguishes this machine from Leonardo’s many other rotating or screw-shaped mechanisms. It should not be confused with his parachute, which was intended to descend rather than climb.