What Leonardo da Vinci design used a large spiral blade to suggest human flight?

Leonardo da Vinci’s aerial screw used a large spiral blade to suggest human flight.

Leonardo drew the aerial screw in a manuscript usually dated to about 1489. The design resembles a giant helical rotor, with a linen-covered frame and a central mast. Leonardo reasoned that rotating the spiral surface could compress or “screw” through the air and lift the machine upward.

The aerial screw is frequently called a helicopter precursor, but it was not a practical helicopter. Its proposed mechanism lacked a suitable power source, and the materials and human muscle available in the Renaissance could not provide enough sustained lift. Modern helicopters instead use powered rotors with carefully shaped blades.

The sketch remains important because it shows Leonardo thinking about vertical flight separately from gliding or flapping-wing flight. It is also commonly linked to the later helicopter, although no direct engineering lineage has been established.