What rotating-air design by Leonardo da Vinci inspired the modern helicopter?

Leonardo da Vinci’s rotating-air design that inspired the modern helicopter was the aerial screw.

Leonardo sketched the aerial screw in 1489, describing a helical rotor-like surface intended to “screw” upward through the air. The design used a large framework and a spiral sail made from reed, linen, and wire. Leonardo reasoned that rotation could produce an upward force, much as a screw moves through a solid or liquid medium.

The aerial screw was not a functioning helicopter. Its proposed materials, scale, and human power source would not have provided the thrust needed for controlled flight. Modern helicopters use powered rotors with carefully shaped blades, aerodynamic control systems, and engines or electric motors. Leonardo’s design had none of those modern systems.

Despite its limitations, the aerial screw is historically important because it recognized the possibility of vertical lift through rotary motion. The word “helicopter” was coined much later. Leonardo’s sketch is therefore best understood as an early conceptual ancestor of rotary-wing aircraft, not as a completed aircraft.