Leonardo da Vinci’s aerial screw was a rotating-screw device intended to rise through the air.
Leonardo sketched the aerial screw around 1489. The drawing shows a helical sail or screw mounted on a vertical framework, with people turning controls to rotate it. Leonardo reasoned that the screw could “screw” itself upward through the air, an idea that resembles the principle of a helicopter rotor.
The machine was never built and tested by Leonardo, and it lacked the powerful, lightweight engine needed for sustained flight. Its large size and proposed human power also presented major practical problems. For that reason, it is best understood as a conceptual study of vertical lift rather than a helicopter.
The aerial screw is frequently described as a helicopter precursor, but the comparison has limits. Modern helicopters use powered rotors with carefully shaped blades, aerodynamic control systems, and engines or electric motors. Leonardo’s design had none of those mature technologies.