Leonardo da Vinci’s 1489 flying-machine concept using a helical rotor was the aerial screw.
Leonardo described the device in a notebook associated with his studies of flight. His design showed a large spiral surface intended to push against the air and lift the machine, somewhat like a modern helicopter rotor. The drawing was probably a theoretical exploration rather than a tested aircraft.
The aerial screw is often called an early helicopter ancestor, but it was not powered by an engine and could not have flown with the materials and human power available in Renaissance Italy. Its importance lies in the idea of vertical lift produced by a rotating screw.
It is sometimes confused with Leonardo’s ornithopter, which depended on flapping wings. The aerial screw instead used a helical, rotating structure, making it a distinct invention concept.