What rotating-wing aircraft concept did Leonardo da Vinci sketch in the 1480s?

Leonardo da Vinci sketched an aerial screw as a rotating-wing aircraft concept in the 1480s.

His design shows a large helical sail made from linen stretched over a reed framework. Leonardo reasoned that turning the screw would make it rise by pushing against the air, an idea that resembles the operating principle of a modern helicopter rotor.

The drawing appears in Leonardo's notebooks, but there is no evidence that he built or tested a full-size aerial screw. It is therefore better described as an early helicopter-like concept than as the first helicopter. Modern helicopters use powered rotors, aerodynamic airfoils, and control systems that Leonardo's design did not provide.

The aerial screw is also commonly confused with Leonardo's ornithopter, another flying-machine concept based on flapping wings. The two designs represent different approaches: one uses rotary motion, while the other imitates bird flight.