Leonardo da Vinci sketched an aerial screw as a spiral aircraft concept often described as an early helicopter idea.
The design appears in Leonardo’s famous Codex Atlanticus and is usually dated to around 1489. It shows a large helical surface wrapped around a central mast. Leonardo reasoned that, if the spiral surface were turned rapidly, it might screw upward through the air in a way similar to a screw moving through a solid material.
The drawing is important in the history of flight because it anticipates the basic idea of rotary-wing lift. Yet the proposed machine had no practical engine, and its materials and human-powered mechanism could not have produced enough thrust. It was therefore a conceptual study, not a working helicopter.
The aerial screw is sometimes called a “proto-helicopter,” but that label should not imply that Leonardo built one. It also differs from an ornithopter, which attempts to fly with flapping wings rather than a rotating spiral surface.