Leonardo da Vinci specified linen for the sail of his aerial screw design.
Drawn around 1489–1490, the aerial screw was a helical rotor intended to rise by “screwing” through the air. Leonardo’s notes describe a reed framework covered with linen, with the fabric treated to make it as airtight as possible. The design was not a working helicopter, because a human crew could not generate enough power to turn its large rotor.
The idea is often called a helicopter in popular summaries, but that label can mislead. Modern helicopters use powered rotors, aerodynamic blades, and controlled lift; Leonardo’s machine relied on a broad spiral surface and human effort. It nevertheless anticipated the general concept of vertical flight.
Leonardo’s other flying-machine studies included flapping-wing ornithopters and parachute designs. His aerial screw is especially famous because its shape resembles the later screw principle used in some vertical-lift aircraft.