Leonardo da Vinci designed an aerial screw with spiral blades inspired by a screw.
His drawing, usually dated to about 1489, shows a large helical surface wrapped around a central mast. Leonardo suggested that the device could rise if its screw-shaped surface pushed against the air, an idea sometimes compared with the operating principle of a modern helicopter rotor.
The design was not a helicopter in the modern engineering sense. It lacked an engine, a practical rotor system, and a demonstrated method of generating enough lift. It was therefore a theoretical machine rather than a proven aircraft. Its importance lies in the way it translated the familiar action of a screw into a possible method of vertical flight.
The aerial screw is often called a “helicopter” in popular accounts, but that wording can be misleading. The modern helicopter developed much later and uses powered rotors rather than one large linen-covered spiral. Leonardo’s sketch is best identified by the specific term aerial screw.