Leonardo da Vinci sketched an aerial screw as a proposed flying device with a spiral rotor in the 1480s.
The design appears in Leonardo’s notebooks and is often compared with a modern helicopter because its rotating helical surface was intended to lift the machine. Leonardo wrote that a linen-covered reed framework, strengthened with wire, could turn rapidly enough to rise. The idea was theoretical rather than a tested aircraft.
The aerial screw is sometimes called a helicopter precursor, but it did not use a powered engine or the aerodynamic rotor system used by helicopters. Its shape also differs from Leonardo’s other flying-machine studies, especially the ornithopter, which imitated flapping bird wings.
Leonardo’s drawing is important because it shows him reasoning about vertical flight centuries before practical powered helicopters existed. The concept influenced later popular histories of aviation, although historians generally describe it as an ingenious mechanical proposal rather than a working invention.