Leonardo da Vinci designed an aerial screw with a large spiral he believed could lift a machine into the air.
Leonardo drew the concept in a manuscript usually dated to about 1489 or 1490. Its spiral surface was intended to act like a screw moving through air, while people inside the framework would turn a central mechanism. The design is commonly compared with a helicopter because it proposes vertical lift, but it was not a helicopter in the modern engineering sense.
The aerial screw could not have flown with the human power available in Leonardo's design. Its structure would have been heavy, and the crew could not produce enough power to overcome its weight. Modern replicas therefore use engines or other external assistance.
The idea is important historically because it shows Leonardo thinking about vertical flight more than four centuries before powered helicopters became practical. It was a speculative machine, not a proven aircraft.