Leonardo da Vinci proposed an aerial screw as a rotating spiral device that might lift a flying machine.
His drawing, usually dated to around 1489, shows a helical sail wrapped around a frame. Leonardo suggested that the spiral surface could “screw” through the air if rotated rapidly, an idea that resembles the principle of a helicopter rotor. The design is often described as one of the earliest conceptual ancestors of vertical-flight machines.
The aerial screw was not a working helicopter. Leonardo did not have a lightweight engine capable of supplying the necessary power, and the proposed structure was too heavy for human-powered flight. Its importance lies in the underlying aerodynamic idea rather than in practical performance.
It is often confused with Leonardo’s ornithopter. An ornithopter uses flapping wings, while the aerial screw depends on rotary motion and a helical lifting surface.