What was Leonardo da Vinci’s proposed aerial screw intended to use as its lifting surface?

Leonardo da Vinci’s proposed aerial screw was intended to use a helical screw as its lifting surface. The design showed a large spiral-shaped structure that would supposedly push against the air and raise the machine.

Leonardo drew the aerial screw around 1489 while studying flight. His notes compared the idea to a screw moving through a solid material, but air does not resist motion in exactly the same way. The proposal therefore anticipated the broad concept of a rotor without providing a practical power source or a proven method of flight.

The aerial screw is often casually called Leonardo’s helicopter, but that label can mislead. Modern helicopters use powered rotors with carefully shaped blades, engines or motors, control systems and a lightweight airframe. Leonardo’s design had none of those modern systems and was never demonstrated as a working aircraft.

Its historical value is conceptual. The drawing shows Leonardo trying to translate a familiar mechanical principle into an aerial machine, making it an important landmark in the history of rotorcraft ideas.