What Leonardo da Vinci design used a helical rotor to rise into the air?

Leonardo da Vinci’s helical-rotor design was called the aerial screw.

Leonardo sketched the aerial screw around 1489 in his notebooks. The design shows a large spiral structure made from reed, linen, and wire, intended to compress air and lift the machine. Its shape resembles a giant screw turning through the air.

The aerial screw is often described as an early helicopter concept, but it was never built or tested by Leonardo. The materials and human power available in Renaissance Italy could not have supplied enough lift for the proposed machine. Modern helicopters use powered rotors and aerodynamic blades rather than a linen-covered spiral.

A common mix-up is calling the aerial screw Leonardo’s first working helicopter. It was a theoretical flying-machine design, not a completed aircraft. Leonardo also studied wings, parachutes, and gliders, making his flight investigations broader than one invention.