Leonardo da Vinci’s early helicopter concept with a spiral, screw-shaped rotor was the aerial screw.
Leonardo sketched the aerial screw around 1489 in the Codex Atlanticus. Its design used a large helical surface made from reeds, linen, and wire. Leonardo reasoned that if the screw rotated quickly enough, it might push against the air and lift the structure upward.
The aerial screw is often called a helicopter precursor, but it was not a working helicopter. The materials, power source, and human muscle available in Renaissance Italy could not produce enough lift for the proposed machine. Modern helicopters instead use powered rotor blades that generate lift through aerodynamic airfoils.
The design is also different from Leonardo’s ornithopter, which imitated the flapping motion of birds. The aerial screw used rotary motion, making it conceptually closer to a modern rotorcraft than to a bird-inspired flying machine.