Leonardo da Vinci’s aerial screw used a helical rotor concept and is often compared with a modern helicopter.
Leonardo sketched the aerial screw around 1489. The drawing shows a large helical surface wrapped around a central mast, with a framework intended to support people turning the mechanism. Leonardo wrote that the object might rise if its screw-shaped surface were made from linen and reinforced with reeds.
The design is not a helicopter in the modern engineering sense. It had no engine, no independently powered rotor, and no demonstrated method of producing enough lift. Human operators would not have been able to supply the continuous power required for sustained flight. For that reason, historians generally describe it as a speculative flying-machine concept.
The aerial screw is also separate from Leonardo’s ornithopter sketches, which sought flight through flapping wings. Its significance lies in the idea of rotary lift and in the way the drawing anticipates a visual feature associated with later rotorcraft. No evidence shows that Leonardo built or flew the aerial screw.