Leonardo da Vinci’s 1489 flying-machine design using a helical sail was called the aerial screw.
Leonardo recorded the design in a manuscript generally dated to around 1489. It shows a large spiral surface, or helical screw, intended to rotate and lift a central frame into the air. His notes compared the action to a screw moving through a solid medium, although air does not provide the same resistance as wood or another solid material.
The aerial screw is often described as a forerunner of the modern helicopter, but it was not a working helicopter. Leonardo did not have a suitable lightweight engine, and the design’s proposed human-powered mechanism could not have generated enough lift. The sketch therefore belongs to the history of aviation concepts rather than successful aircraft.
It is also easy to confuse the aerial screw with Leonardo’s ornithopter and parachute designs. The aerial screw relies on rotary lift, while the ornithopter imitates flapping wings and the parachute is intended for descent.