Leonardo da Vinci sketched an aerial screw as a flying-machine concept with a helical rotor.
His drawing, usually dated to about 1489, shows a large spiral structure intended to rise by turning through the air. Leonardo compared the mechanism to a screw moving through a solid substance, imagining that a rotating helix could produce upward motion. The machine is sometimes described as an early helicopter idea.
The aerial screw was never built by Leonardo, and the design lacks several features needed for practical powered flight. It would have required a strong, lightweight frame, an efficient source of power, and a rotor able to generate lift. Human muscle alone could not have provided enough power with the materials available in Renaissance Italy.
The design should not be confused with Leonardo’s ornithopter studies, which imitate flapping bird wings. The aerial screw uses rotary motion instead. Modern helicopters also use rotating blades, but their aerodynamic principles and engineering are substantially different.