Leonardo da Vinci’s aerial screw used a rotating helical sail as an early helicopter concept.
Leonardo sketched the aerial screw around 1489, during his investigations of flight and the movement of air. The drawing shows a large spiral surface made from reeds, linen, and wire, supported by a central mast. Leonardo reasoned that turning the structure could make it rise, much as a screw advances through a solid material.
The design was never built by Leonardo, and it could not have lifted a person with the materials and human power available in Renaissance Italy. Modern historians generally describe it as a conceptual ancestor of the helicopter rather than a working aircraft. The idea differs from Leonardo’s ornithopter, which imitated flapping bird wings.
The aerial screw is often called a helicopter precursor, but it was not a helicopter in the modern engineering sense. Powered vertical flight required lightweight engines and more efficient rotors, developed centuries later.