Leonardo da Vinci called his screw-shaped flying-machine concept an aerial screw.
Drawn around 1489, the design shows a large helical surface wrapped around a central mast. Leonardo reasoned that if the screw were rotated rapidly, its spiral surface might push against the air and lift the structure upward. The concept resembles a very large version of a screw moving through a substance.
The aerial screw was not a working helicopter. Renaissance materials and human power could not provide the necessary lift or rotation. Nevertheless, the drawing is often discussed as an early conceptual ancestor of the helicopter, although modern rotorcraft depend on aerodynamic rotor blades rather than a continuous fabric-covered helix.