Leonardo da Vinci called his rotating vertical-flight concept an aerial screw.
He sketched the machine around 1489, using a helical sail made from linen stretched over a framework of reeds. Leonardo reasoned that the rotating spiral surface could screw upward through the air in much the same way that a threaded screw moves through a solid material. The drawing is one of his best-known studies of flight.
The aerial screw was not a working helicopter. Leonardo did not have a practical lightweight engine, and the human-powered mechanism shown in related flight studies could not generate enough lift. Modern reconstructions generally treat the design as an important conceptual predecessor to the helicopter rather than as a successful aircraft.
The term is sometimes confused with a conventional propeller. A propeller pushes air backward to move an aircraft forward, whereas Leonardo’s aerial screw was intended to produce upward motion directly through a rotating helical surface.