What did Leonardo da Vinci call his screw-shaped flying-machine concept?

Leonardo da Vinci called his screw-shaped flying-machine concept the aerial screw.

Leonardo sketched the design around 1489. It featured a large helical surface made from reed, linen, and wire, mounted around a central framework. His notes suggest that turning the mechanism could force air downward and lift the structure upward.

The aerial screw is often described as a distant forerunner of the helicopter, but it was not a working helicopter. Leonardo did not provide a practical engine, and the materials and human power available in Renaissance Italy could not generate enough lift for the proposed machine.

The resemblance to a modern helicopter rotor is mainly conceptual. A helicopter uses powered rotating blades that produce lift; Leonardo’s design relied on a rotating spiral surface. Its historical importance lies in recognizing that a screw-like device might rise through air, centuries before powered flight became possible.