Leonardo da Vinci’s rotating-air design was called the aerial screw.
Leonardo drew the aerial screw in the Codex Atlanticus, probably around 1489. The design shows a large helical surface made from reed, linen, and wire, mounted on a frame. Leonardo reasoned that turning the screw could make it “screw” upward through the air, an idea that resembles the operating principle of a modern rotorcraft.
The sketch was a conceptual study rather than a functioning helicopter. A human crew could not turn the mechanism rapidly enough, and the proposed structure would have been too heavy and aerodynamically inefficient to lift itself. Modern helicopters use powered rotors whose blades generate lift through carefully shaped airfoils, a technology unavailable in Renaissance Italy.
The aerial screw is still historically important because it shows Leonardo reasoning about vertical flight separately from birdlike flapping flight. It is often called a helicopter precursor, but it was not a helicopter in the modern engineering sense and did not lead directly to a working aircraft.