Leonardo da Vinci sketched an airscrew as a rotating-air machine with a helical sail.
His drawing, made around 1489, shows a large spiral surface wrapped around a central mast. Leonardo wrote that if the screw-shaped surface were well made from reed, linen, and wire, it could rise into the air when rotated rapidly. The idea was based on the principle that a screw moves through a material by pushing against it.
The device was not a helicopter in the modern engineering sense. Leonardo did not provide a practical engine, a clear control system, or a lightweight structure capable of producing sustained lift. Modern historians therefore treat it as an imaginative flight concept rather than a demonstrated aircraft.
The airscrew remains important because its spiral rotor resembles the later principles behind helicopter rotors and propellers. It should not be confused with Leonardo's ornithopter, which attempted to imitate the flapping motion of bird wings.