Leonardo da Vinci’s screw-shaped rotor design is known as the aerial screw.
Leonardo drew the aerial screw in a manuscript usually dated to about 1489. Its linen-covered helical surface was intended to press against the air as the rotor turned, in a concept often compared with a modern helicopter rotor. The sketch shows four people standing on a circular platform and turning a central shaft.
The aerial screw was a theoretical machine, not a tested flying craft. Leonardo did not build a working full-scale version, and the materials and power available in Renaissance Italy could not have supplied enough lift. Its importance lies in recognizing that a rotating screw might move through air in a way analogous to a screw moving through water.
It is sometimes called Leonardo’s helicopter, but that label is retrospective. The design lacks the powered engine, controllable rotor system, and practical structure required by a modern helicopter.