Leonardo da Vinci’s screw-shaped helicopter precursor is commonly called the aerial screw.
Leonardo sketched the aerial screw around 1489. The design shows a large helical surface made from reeds, linen, and wire, mounted on a central mast. Leonardo suggested that turning the structure could make it rise by forcing air downward, an idea related to the lift produced by a modern rotor.
The aerial screw is often described as a helicopter ancestor, but it was not a functioning helicopter. Its proposed materials and human-powered mechanism could not provide enough power for practical vertical flight. The sketch is therefore best understood as a mechanical investigation of flight rather than a completed aircraft.
The design is sometimes confused with Leonardo’s ornithopter. The ornithopter flaps wings like a bird; the aerial screw uses a rotating spiral surface. That distinction makes the aerial screw especially important in histories of rotorcraft concepts.