What rotating-wing aircraft did Leonardo da Vinci design in a screw-shaped form?

Leonardo da Vinci designed an aerial screw as a rotating-wing flying machine.

His drawing, usually dated to around 1489, shows a large helical surface wrapped around a central mast. Leonardo reasoned that the screw could rise if its surface pressed against the air while the mechanism was turned. The concept resembles a helicopter rotor in its intended vertical lift, although it was not a practical powered helicopter.

The design probably could not lift itself because the materials and available human power were insufficient. It also lacked the efficient rotor blades and engine that later aircraft required. For that reason, historians generally treat it as an important conceptual predecessor rather than a working helicopter.

The aerial screw is often called a “helicopter” in popular accounts, but that label can create confusion. Leonardo’s machine had a helical sail-like surface, not the powered rotor system used by modern helicopters.