Leonardo da Vinci sketched the aerial screw in 1489 as an early helicopter concept.
The design appears in Leonardo’s Codex Atlanticus and uses a helical surface, or screw, intended to rotate and push against the air. Leonardo compared its action to a screw moving through a solid material, but the drawing does not provide a complete working engine or practical control system.
The aerial screw is often called a helicopter ancestor, but it was not a helicopter in the modern engineering sense. Its linen-covered helical rotor would have needed far more power than a human crew could supply. Leonardo’s idea nevertheless anticipated the basic principle of vertical lift from rotating blades.
It should not be confused with his ornithopter, which depended on flapping wings. The aerial screw uses rotary motion, making it closer conceptually to a modern rotorcraft.