Leonardo da Vinci’s spiral-powered flying-machine sketch is commonly called the aerial screw.
Leonardo drew the design around 1489. It shows a large helical surface wrapped around a central mast, with a platform and framework for people to turn the mechanism. His idea was that the spiral would “screw” itself upward through the air, much as a screw advances through a solid material.
The aerial screw is frequently described as an early helicopter concept, but it was not a helicopter in the modern engineering sense. Leonardo did not provide a working propulsion system capable of producing enough lift, and the proposed materials and human power would not have made the craft practical.
The sketch is nevertheless historically important because it demonstrates Leonardo’s interest in vertical flight. It is distinct from his ornithopter, which uses flapping wings, and from his parachute, which is intended to descend rather than climb.