What Leonardo da Vinci concept is commonly called a helicopter?

Leonardo da Vinci’s concept commonly called a helicopter was the aerial screw.

Drawn in the Codex Atlanticus around 1489, the aerial screw featured a helical rotor made from reed, linen, and wire. Leonardo proposed that rotating the screw could make it rise by “screwing” into the air, much as a screw moves through a solid material.

It was not a working helicopter: the materials and human power available in Leonardo’s era could not provide enough lift. The design is nevertheless an important early vertical-flight concept. Modern helicopters use powered rotors and aerodynamic blades rather than Leonardo’s large, fabric-covered spiral.