Leonardo da Vinci's aerial screw was a screw-shaped rotor concept intended to lift a flying machine.
Leonardo sketched the aerial screw around 1489–1490. The drawing shows a large helical surface wrapped around a central mast, with a platform and people positioned to turn the mechanism. Leonardo reasoned that if the screw could bite into the air, it might rise in a manner analogous to a screw moving through a solid material.
The design is often described as a helicopter ancestor, but it was not a helicopter in the modern engineering sense. Human-powered flight using Leonardo's proposed mechanism would not have produced enough lift, and the design lacks the powered rotor, controls, and aerodynamic structure required by modern helicopters.
The aerial screw is distinct from Leonardo's ornithopter studies, which attempted to imitate the flapping motion of birds. It is also distinct from his parachute, which was intended to slow descent rather than create powered ascent.