Leonardo da Vinci sketched an aerial screw, a rotating-wing design often compared with a helicopter.
His drawing, usually dated to about 1489, shows a large helical surface wrapped around a central mast. Leonardo proposed that the rotating structure could screw itself upward through the air, much as a screw moves through a solid material. The concept is one of the best-known flight ideas in his notebooks.
The aerial screw was not a working helicopter. Leonardo did not provide a practical engine or a sufficiently light structure, and the available materials and power sources could not have made the machine fly as drawn. Modern helicopters use powered rotors and aerodynamic principles that differ substantially from the sketch.
The design is sometimes called a helicopter prototype, but “aerial screw” is the more specific historical name for Leonardo’s concept. Its importance is conceptual: it anticipated vertical-lift thinking centuries before powered rotorcraft became practical.