Leonardo da Vinci designed an aerial screw, a spiral machine intended to rise through the air.
His drawing shows a large helical surface wrapped around a central mast. Leonardo reasoned that if the spiral were rotated rapidly, it might screw upward through the air in a way similar to a screw moving through a solid material. The design is one of his best-known studies of vertical flight.
The aerial screw is often described as a helicopter ancestor, but it could not fly as drawn. It lacked a practical lightweight power source, and its large spiral surface would not generate useful lift in the same way as modern rotor blades. The concept therefore represents an important imaginative step, not a working helicopter.
It is also distinct from Leonardo's flapping-wing ornithopter. The aerial screw relies on a rotating helical surface, while an ornithopter imitates the flapping motion of a bird's wings.