What spiral-powered flying device did Leonardo da Vinci sketch in 1489?

Leonardo da Vinci sketched an aerial screw as a spiral-powered flying device in 1489.

The design appears in Leonardo’s Paris Manuscript B, where he imagined a large helical surface turning around a central shaft. His notes compare the action to a screw moving through a solid medium. The machine was not built in Leonardo’s lifetime, and no surviving experiment proves that it could have lifted a pilot.

The aerial screw is often called an early helicopter concept because its rotating spiral resembles a rotor. That comparison is useful, but it should not be treated as a working helicopter blueprint. Modern helicopters use powered rotors, aerodynamic blades, and control systems that Leonardo’s sketch did not provide.

The design is also frequently confused with Leonardo’s parachute and bird-inspired flying machines. Those were separate ideas with different operating principles: the parachute descends by drag, while the aerial screw was intended to rise through rotational motion.