What rotating machine did Leonardo da Vinci study as a possible way to lift off?

Leonardo da Vinci studied an aerial screw as a possible way to lift off.

Drawn around 1489, the aerial screw is a helical machine with a broad, spiral-shaped surface. Leonardo reasoned that if the screw rotated rapidly enough, it might “screw” itself upward through the air. The concept is often compared with a helicopter rotor, although it does not have the same rotor-and-fuselage arrangement as a modern helicopter.

Leonardo’s design probably could not have flown as drawn. The proposed materials would have made it heavy, and human muscle power would not have supplied enough energy to rotate the large screw quickly enough. The drawing therefore represents an important aerodynamic idea rather than a tested aircraft.

The aerial screw is also called Leonardo’s helicopter in popular writing, but that label can mislead readers. Leonardo did not invent a functioning helicopter, and the machine’s rotating surface was based on analogy with a screw moving through a solid medium. Its historical importance lies in the attempt to explain vertical lift mechanically centuries before powered flight.