Leonardo da Vinci designed an aerial screw as a flying-machine concept with a large rotating helical surface.
His drawing, usually dated to about 1489, shows a platform beneath a linen-covered screw. Leonardo proposed that the screw would move upward by “screwing” through the air, an idea that resembles the principle of a modern helicopter rotor.
The machine could not have flown as drawn because its human-powered mechanism would not have supplied enough energy, and the design lacked a practical way to control rotation and stability. It was therefore an imaginative study, not a working aircraft.
The aerial screw is frequently described as a helicopter ancestor, but it was not a helicopter in the modern engineering sense. Its importance lies in identifying vertical flight as a mechanical problem centuries before powered helicopters became possible.