Leonardo da Vinci’s screw-rotor design for vertical flight was the aerial screw.
Leonardo sketched the aerial screw around 1489, describing a large helical structure wrapped around a central mast. His notes suggest that if the screw-shaped surface rotated rapidly, it might rise by pressing against the air, in a way loosely analogous to a screw advancing through a solid material.
The design is often called a helicopter precursor, but it was not a practical helicopter. Leonardo did not specify a workable engine, and the materials and power sources available in the Renaissance could not provide enough lift for a full-scale machine. The broad concept of a rotating lifting rotor was important, even though the proposed structure would not operate like a modern helicopter rotor.
The aerial screw is also distinct from the ornithopter. The ornithopter depends on flapping wings, while the aerial screw depends on rotary motion. Modern helicopters use aerodynamic rotor blades, engines, and controls developed long after Leonardo’s sketches.