Leonardo da Vinci's aerial screw used a helical rotor to suggest vertical flight.
Leonardo drew the design around 1489 in a manuscript now associated with the Codex Atlanticus. The machine had a large spiral surface made from linen, supported by reeds, and mounted around a central shaft. Leonardo reasoned that turning the shaft could make the spiral “screw” move upward through the air, much as a screw moves through a solid material.
The device is often described as an ancestor of the modern helicopter, but it could not have lifted itself with the human-powered mechanism Leonardo proposed. The materials, available power, and aerodynamic understanding were insufficient for practical flight.
Its historical value is conceptual. Leonardo separated vertical lift from the wing-based forward flight of birds and gliders. Modern helicopters use powered rotors rather than a single fabric-covered helical surface, but the aerial screw remains one of his most famous aviation studies.