Leonardo da Vinci’s proposed vertical-flight machine with a helical rotor is commonly called the aerial screw.
Leonardo sketched the design around 1489–1490 in his notebooks. It shows a large helical framework covered with linen, intended to rotate around a central shaft. Leonardo reasoned that the screw could push against the air and lift the machine, much as a screw advances through water.
The aerial screw was not built or tested by Leonardo, and its proposed materials and human-powered mechanism would not have produced enough lift for practical flight. Modern historians therefore describe it as a conceptual precursor to the helicopter rather than a working helicopter.
The design is often confused with Leonardo’s separate wing-flapping machines, which imitate birds. The aerial screw instead uses rotary motion and a spiral lifting surface. Its importance lies in the early recognition that vertical flight could be achieved through a rotating device, centuries before powered helicopters became feasible.