What did Leonardo da Vinci call his 1489 design for a vertical-flight machine?

Leonardo da Vinci called his 1489 vertical-flight concept the aerial screw.

The aerial screw was drawn in a manuscript usually dated to 1489. Its design used a large helical structure made from reeds, linen, and wire. Leonardo imagined that rotating the screw would force air downward and lift the machine upward, an idea that resembles the principle of a modern rotor.

The machine was not powered or tested in Leonardo’s lifetime. Its structure was also too heavy and its proposed human power source too weak for practical flight. Nevertheless, the sketch is frequently discussed as an important early concept in the history of helicopters.

The aerial screw should not be confused with Leonardo’s ornithopter designs, which attempted to imitate the flapping motion of birds. The screw relied on rotary motion and a helical lifting surface instead.