What did Leonardo da Vinci call his rotating-aircraft design?

Leonardo da Vinci called his rotating-aircraft concept the aerial screw.

Leonardo sketched the aerial screw around 1489, describing a device with a helical surface intended to push against the air and rise. The design is often compared visually with a modern helicopter rotor, but it did not include the powered engine, control systems, or rotor arrangement needed for practical flight.

The drawing has a large spiral structure supported by a framework. Leonardo reasoned that if the helical surface turned rapidly enough, it might force air downward and lift the machine upward. His proposal was theoretical and has never been demonstrated as a viable human-powered aircraft.

The aerial screw is frequently called a “helicopter” in popular summaries, but that label can blur an important distinction. It was an early rotorcraft concept, not a functioning helicopter. Modern helicopters use powered rotors and aerodynamic blades rather than Leonardo’s continuous spiral surface.