What Leonardo da Vinci flying-machine concept used a large rotating screw?

Leonardo da Vinci’s rotating-screw flying-machine concept is known as the aerial screw.

Leonardo drew the aerial screw in a manuscript generally dated to about 1489. The design shows a helical linen surface wrapped around a framework, with a central mast and a platform for people to turn. Leonardo reasoned that the screw might rise by pressing against the air, an idea analogous to a screw moving through a solid material.

The drawing is often called a helicopter prototype, but that description can be misleading. The design was not built and tested by Leonardo, and the materials and human power available in the Renaissance would not have made practical flight likely. Modern helicopters use powered rotors, aerodynamic blades, and controlled lift rather than a large fabric-covered screw.

The aerial screw remains important because it shows Leonardo thinking about vertical flight centuries before powered helicopters. It should not be confused with his separate bird-inspired ornithopter studies.