What Leonardo da Vinci invention is commonly called the aerial screw?

Leonardo da Vinci’s aerial-screw design is commonly described as an early helicopter concept.

Leonardo sketched the aerial screw around 1489. Its spiral linen sail was intended to rotate and push against the air, lifting the machine vertically. The design was never built or tested by Leonardo, and it could not have flown as drawn because the proposed materials and human power were insufficient.

The helicopter connection is historical rather than technological. Modern helicopters use powered rotors with carefully shaped blades, while Leonardo’s device used a helical surface more like a screw moving through air. That difference is why historians usually call it a precursor or conceptual ancestor, not the first working helicopter.

Leonardo’s drawing appeared in his notebooks among studies of flight, wind, and mechanical motion. It is often confused with his wing-flapping machine, but the two ideas used different methods: the aerial screw relied on rotary lift, whereas the other design imitated bird wings.