Leonardo da Vinci proposed an aerial screw as a rotating device for lifting a craft into the air.
Leonardo drew the aerial screw in a manuscript dated to about 1489. The design used a large helical surface wrapped around a central mast. He reasoned that, if the screw were turned quickly enough, its surface would push against the air and raise the machine.
The aerial screw is often described as a conceptual ancestor of the helicopter, but it was not a working helicopter. Leonardo did not provide a practical engine or a sufficiently light structure capable of producing the necessary lift. Modern helicopters use powered rotors with carefully shaped blades rather than a continuous cloth-covered screw.
The idea is important because it shows Leonardo exploring vertical flight separately from wing-based flight. It is also commonly confused with his ornithopter designs, which attempted to imitate the flapping motion of birds.