What rotating flying machine did Leonardo da Vinci sketch around 1489?

Leonardo da Vinci sketched the aerial screw around 1489 as a proposed rotating flying machine.

The drawing shows a helical rotor made from a linen-like material stretched over a reed framework. Leonardo reasoned that the spiral surface could “screw” upward through the air if it rotated fast enough. The concept is often compared visually with a modern helicopter rotor, although it would not have been practical with the power sources available in Renaissance Italy.

The aerial screw was a design study, not a working aircraft. Leonardo did not build a documented full-scale version, and surviving notes do not establish that he solved the problems of weight, propulsion, stability, or control.

The idea is frequently described as a helicopter precursor. That description is useful for explaining its appearance, but it should not imply that Leonardo invented the modern helicopter. Powered flight required later engines and aerodynamic knowledge.