Leonardo da Vinci’s aerial screw was a flying-machine design built around a large spiral rotor.
Leonardo drew the aerial screw around 1489 in a notebook now linked with the Codex Atlanticus. The machine was intended to rise as its helical sail rotated, somewhat like the principle later used by a helicopter rotor. Leonardo proposed a linen-covered helical surface supported by a reed or wire framework.
The sketch does not prove that the machine could have flown. Its proposed materials and human-powered mechanism would not have supplied enough power for vertical flight. Modern reconstructions generally treat it as an important early visualization of rotary-wing flight rather than a working helicopter.
The design is frequently compared with a screw because its spiral surface would push against air. That resemblance explains the name, but it should not be confused with the Archimedes screw, which is a water-raising device rather than an aircraft.