Leonardo da Vinci called a flying-machine concept an aerial screw in a drawing from about 1489.
The design shows a large helical surface wrapped around a central mast. Leonardo reasoned that if the screw were turned rapidly, its spiral surface could bite into the air and lift the machine. The concept resembles the basic visual idea of a modern helicopter rotor, but it was not a helicopter in the engineering sense.
The aerial screw was never built by Leonardo and had no engine capable of providing the necessary power. Its structure was also too heavy and its proposed materials and propulsion method were not adequate for sustained flight.
The drawing is important because it shows Leonardo exploring vertical flight rather than only copying the flapping motion of birds. Modern helicopters use powered rotors and aerodynamic lift, not a solid spiral sail rotating around a mast.