Leonardo da Vinci designed an aerial screw as a helical-rotor flying machine that anticipated the helicopter.
Leonardo sketched the design around 1489–1490 in his Codex Atlanticus. It shows a large spiral sail made from reeds, covered with linen, and stiffened with wire. Leonardo reasoned that rotating the screw could make the structure rise by pushing against the air.
The aerial screw was never built and tested by Leonardo, and its proposed mechanism would not have provided enough practical lift with the materials and human power available in Renaissance Italy. Modern historians therefore describe it as an imaginative aeronautical concept rather than a working helicopter.
It is often confused with Leonardo’s ornithopter studies, which imitate flapping wings. The aerial screw instead uses rotary motion, making it conceptually closer to a helicopter rotor. Later engineers built experimental models inspired by the sketch, but those reconstructions are not evidence that Leonardo flew the original.