Leonardo da Vinci's aerial screw was a rotating, screw-shaped machine intended to lift itself into the air.
Leonardo sketched the design in about 1489. It had a large helical sail made from linen and reed, mounted around a central shaft. He reasoned that rapidly turning the screw could force air downward and produce upward motion.
The machine was never built or flown by Leonardo, and it lacked a practical power source capable of turning its large rotor. Modern helicopters use powered rotors with carefully shaped blades, rather than a continuous spiral sail.
The aerial screw is often called a helicopter “prototype,” but that label can mislead. It anticipated the vertical-lift idea, while the engineering principles and propulsion systems of helicopters developed much later.