Which Leonardo da Vinci design used a large helical blade to suggest powered flight?

Leonardo da Vinci’s aerial screw used a large helical blade to suggest powered flight. Drawn around 1489, the design resembles a giant screw intended to push against the air and lift a platform vertically.

Leonardo’s sketch shows a circular platform, a reed-and-cane framework, and a helical surface covered with linen. The proposed machine was roughly 5 meters across. His notes suggested that several people could turn a central mechanism, although the available materials and human power would not have been sufficient for sustained flight.

The aerial screw is often described as a conceptual ancestor of the helicopter, but it was not a working helicopter. Modern helicopters use powered rotors that generate lift through carefully shaped blades, while Leonardo’s design depended on a continuous spiral surface. Its importance lies in recognizing that rotation could be used to produce vertical lift.