Leonardo da Vinci called his rotating aerial-screw concept the aerial screw.
The design appears in a notebook entry usually dated to about 1489. It shows a large helical structure intended to rotate and push against the air, somewhat like a modern helicopter rotor. Leonardo wrote that if the screw-shaped surface were made from linen held taut by reeds, it might rise when turned rapidly.
The aerial screw was not a working helicopter. Its proposed materials, dimensions, and power source would not have produced enough lift with Renaissance technology. Modern helicopters use powered rotors and carefully shaped blades, while Leonardo’s drawing presents a broad spiral surface.
The idea is still historically important because it demonstrates Leonardo’s attempt to reason about vertical flight. It is also distinct from his ornithopters, which depended on flapping wings, and from his parachute, which was intended to slow a descent rather than provide powered ascent.