Leonardo da Vinci’s aerial screw used a helical screw to imitate the lifting action of a modern helicopter rotor.
Leonardo drew the aerial screw in a manuscript usually dated to around 1489. The design showed a large spiral surface made from reeds and linen, supported by a framework. Leonardo reasoned that if the screw rotated rapidly, its helical surface might press against the air and lift the machine.
The aerial screw was an important theoretical step in the history of vertical flight, but it was not a helicopter. Leonardo had no lightweight engine capable of turning the structure fast enough, and the proposed materials and human power would not have produced sufficient lift. The design’s resemblance to a helicopter rotor is therefore conceptual rather than technological.
The drawing is also sometimes called Leonardo’s “helicopter.” That nickname is convenient but anachronistic: the modern helicopter developed much later and uses powered rotors with aerodynamic blades rather than a single linen-covered screw.