What was Leonardo da Vinci’s rotating aerial-machine concept called?

Leonardo da Vinci’s rotating aerial-machine concept was called the aerial screw.

In a drawing usually dated to about 1489, Leonardo imagined a large helical structure made from reed, linen, and wire. He proposed that the spiral surface could screw upward through the air if rotated rapidly. The design is often discussed as an ancestor of the helicopter, although it was never built and tested by Leonardo.

The aerial screw differs from his flapping-wing ornithopter. Instead of imitating a bird’s wing beats, it uses a rotating spiral surface to suggest lift. Leonardo’s notes show that he was exploring several different mechanisms rather than pursuing one settled aircraft design.

Modern helicopters achieve vertical lift with rotating rotor blades and a powered engine. Leonardo’s sketch lacked a practical power source and a lightweight structure, so its historical importance lies mainly in the concept of rotary-wing flight.