Leonardo da Vinci's aerial screw was a helical flying-machine design intended to rise by turning a large screw through the air.
Leonardo drew the concept around 1489. The design used a linen-covered helical surface stretched over a light frame, with a central mast and a platform for operators. His notes suggest that people would turn the mechanism to make the screw press against the air and produce lift.
The aerial screw is often described as a helicopter ancestor, but it was not a practical helicopter. Human muscle could not supply enough power to lift the heavy structure, and the design lacked the lightweight engine and rotor-control systems required for sustained flight. It is better understood as a speculative study of vertical lift.
The idea resembles an Archimedes screw, which moves water rather than air. Leonardo adapted the screw form to a new medium, showing his interest in using geometry and mechanical principles to investigate flight.