What did Leonardo da Vinci call his helicopter-like flying-machine concept?

Leonardo da Vinci’s helicopter-like flying-machine concept was the aerial screw.

Leonardo drew the design around 1489–1490 in the manuscript known as the Codex Atlanticus. It shows a large helical linen sail mounted around a central mast. Leonardo reasoned that rotating the screw could make the device rise by “screwing” into the air, much as a screw advances through a solid material.

The aerial screw is often called a helicopter prototype, but that description needs care. Leonardo did not build a successful flying machine, and the drawing does not show a practical engine or a modern rotor system. The design would have required several people to turn the mechanism, while its heavy frame and sail would have made flight difficult.

It remains important because it demonstrates Leonardo’s interest in lift, rotation, and mechanical flight centuries before powered helicopters appeared.