Leonardo da Vinci sketched the aerial screw as an early concept for a helicopter-like flying machine.
Drawn around 1489, the aerial screw used a large helical surface intended to rotate and rise through the air. Leonardo compared its action to a screw moving through a solid material, proposing that a rapidly turning spiral could push against the air.
The device was not a practical helicopter. Its proposed linen-and-reed structure was large, and the design lacked a suitable lightweight engine or a fully developed system for producing continuous rotation. Modern reconstructions are demonstrations of the idea rather than evidence that Leonardo’s original machine could fly.
The aerial screw is often mentioned as a precursor to helicopter concepts, but it should not be confused with a modern rotorcraft. Modern helicopters use powered rotors, aerodynamic blades, and control systems developed centuries later.