Leonardo da Vinci's aerial screw used a large helical surface to suggest vertical flight.
Leonardo drew the aerial screw in a manuscript generally dated to about 1489. The machine has a central mast and a helical canvas surface supported by reeds. His notes suggest that, if the screw were turned rapidly, its helical shape might bite into the air and lift the structure.
The aerial screw is often called a helicopter prototype, but that description needs care. Leonardo had no lightweight engine, and the drawing does not establish that the machine could actually fly. Modern helicopters use powered rotors that generate lift through rotating blades, while the aerial screw was a speculative mechanical concept.
Its importance lies in identifying vertical flight as a separate engineering problem. The idea later became a visual ancestor of helicopter concepts, even though practical powered helicopters required advances in engines, materials, and aerodynamics.