What did Leonardo da Vinci call his rotating aerial-machine concept?

Leonardo da Vinci called his rotating aerial-machine concept an aerial screw.

In a notebook drawing usually dated to about 1489, Leonardo proposed a large helical structure covered with reeds and linen. He imagined that turning the screw would compress or push against the air and lift the machine. The design is commonly described as an early ancestor of the helicopter, although it could not have flown as drawn with the materials and human power available at the time.

The aerial screw was not a working helicopter. It lacked a practical engine, and its heavy structure would have required far more power than people could provide. Modern helicopters use powered rotors that generate lift through carefully shaped blades, a different mechanism from Leonardo’s continuous spiral surface.

Even so, the sketch is significant because it treats vertical flight as an engineering problem. Leonardo explored several airborne concepts, and the aerial screw is one of the clearest examples of his attempt to reason about lift and propulsion.