What was Leonardo da Vinci’s screw-shaped flying-machine concept called?

Leonardo da Vinci’s screw-shaped flying-machine concept was called the aerial screw.

Leonardo sketched the aerial screw in a manuscript usually dated to about 1489. The design has a large helical surface wrapped around a central structure. Leonardo appears to have reasoned that turning the screw could press against the air and lift the machine, an idea that resembles the operating principle of a modern helicopter rotor.

The aerial screw was a conceptual drawing, not a tested aircraft. Its proposed materials and human-powered mechanism would not have supplied enough energy for practical flight. It is therefore more accurate to describe it as an early helicopter-like concept than as a working helicopter.

People sometimes call the drawing Leonardo’s helicopter, but “aerial screw” is the historical name most closely associated with it. The sketch is one of several examples of Leonardo applying mechanical engineering ideas to the problem of flight.