Leonardo da Vinci’s helical flying-machine concept was the aerial screw. His 1489 drawing shows a large spiral rotor made from reeds, covered with linen, and mounted on a circular platform.
Leonardo reasoned that the screw could climb if its rotating surface “screwed” into the air, much as a screw moves through a solid material. The design was not powered by an engine; the sketch appears to assume people would turn the mechanism, making sustained flight unrealistic.
The aerial screw is often called a helicopter precursor, but it was not a working helicopter. Modern helicopters use powered rotors, aerodynamic blades and control systems. Leonardo’s idea is historically important because it recognized that a rotating airfoil could generate lift, a principle later used in rotorcraft.