Leonardo da Vinci described an aerial screw as a rotating flying machine in one of his famous engineering sketches.
The design appears in a manuscript page generally dated to around 1489. It shows a large helical structure made from reeds and linen, supported by a framework. Leonardo reasoned that if the screw rotated rapidly enough, its helical surface might “screw” into the air and lift the machine.
The aerial screw is often called a helicopter precursor, but it was not a functioning helicopter. Leonardo did not have a practical lightweight engine, and the proposed human-powered mechanism could not provide enough energy for sustained lift. The sketch therefore represents a theoretical machine rather than a tested invention.
Modern helicopters use powered rotors that generate lift aerodynamically. Leonardo’s aerial screw used a different conceptual approach, although its central idea of rotary lift helped make it a memorable milestone in the history of flight.