What was Leonardo da Vinci’s helical flying-machine concept called?

Leonardo da Vinci’s helical flying-machine concept was called the aerial screw.

Leonardo sketched the design in the 1480s, describing a large helical structure made from linen stretched over a reed framework. The device was intended to rotate and push against the air, producing upward force in a way that resembles the action of a modern rotor.

The aerial screw is often described as an early helicopter concept, but that comparison needs care. Leonardo had no lightweight engine capable of powering it, and the sketch does not show a complete practical aircraft with modern rotor controls. It therefore remained a speculative design.

The concept is distinct from Leonardo’s ornithopter. An ornithopter flaps wings like a bird, whereas the aerial screw relies on a rotating spiral surface. The design is one of the clearest examples of Leonardo applying mechanical reasoning to the problem of vertical flight.