Leonardo da Vinci called his 1480s flying-machine concept with two spiral blades an aerial screw.
The aerial screw appears in Leonardo’s notebooks as a large helical device intended to rise by forcing air downward. Its design resembles a modern helicopter rotor in broad concept, but it would not have worked with the materials and human power available in Renaissance Italy. Leonardo proposed a linen-covered spiral frame, with reeds or other light supports helping maintain its shape.
The machine is often described as a helicopter prototype, but that wording can mislead. It had no powered rotor system comparable to a modern helicopter and was never built or flown by Leonardo. The famous drawing is important because it shows Leonardo reasoning about vertical flight centuries before powered helicopters became practical.