Leonardo da Vinci's helical flying-machine design is commonly called the aerial screw.
Leonardo sketched the aerial screw in a manuscript usually dated to about 1489. The drawing shows a large helical surface, probably covered with linen, mounted around a central vertical axis. Leonardo proposed that turning the structure could make it rise by screwing into the air.
The concept is often described as an early ancestor of the helicopter, but it was not a helicopter in the modern engineering sense. Leonardo did not provide a practical engine or a complete method for producing enough power, and the proposed machine was never known to have flown.
The aerial screw demonstrates Leonardo's interest in translating familiar mechanical ideas into flight. Its corkscrew-like form resembles the action of a screw moving through a solid material, while the surrounding air would not provide the same resistance. Modern rotorcraft use rotating blades that generate lift rather than a single continuous helical surface.