Leonardo da Vinci designed an aerial screw with a helical rotor intended to rise through the air.
The design appears in a manuscript from around 1489 and is often compared with the basic idea of a modern helicopter rotor. Leonardo proposed a large spiral surface made from reeds and linen, supported by a framework. He reasoned that rotating the spiral could screw its way upward through the air.
The machine was not a helicopter in the modern engineering sense. It lacked a powered engine, and the proposed materials and human power would not have produced enough lift for practical flight. The design was therefore a theoretical flying-machine study rather than a demonstrated aircraft.
The aerial screw is frequently described as an early helicopter concept, but that label can mislead readers into imagining a working prototype. Its lasting importance lies in its recognition that rotary lift could be explored separately from birdlike flapping wings.