Leonardo da Vinci’s four-bladed vertical-flight design was called the aerial screw.
Leonardo sketched the aerial screw around 1489–1490 in his notebooks. Its large helical surface was intended to push against the air and lift the structure upward, much as a screw advances through a solid material. The drawing is often described as an early conceptual ancestor of the helicopter, although it was never built and tested by Leonardo.
The design was probably inspired partly by the Chinese flying top, a toy known in Europe through illustrations and objects. Leonardo proposed a linen-covered framework, with the fabric made airtight by coating it with starch. A rotating mechanism would have turned the screw, but the proposed human-powered system could not have generated enough lift with the materials and technology available at the time.
The aerial screw is therefore best understood as a remarkably early flight concept, not a working helicopter. Its name refers to the screw-shaped rotor, not to a conventional aircraft propeller.