Leonardo da Vinci’s early helicopter-like design with a helical rotor was the aerial screw.
Leonardo sketched the aerial screw around 1489–1490 in his notebooks. The machine used a large spiral surface made from reeds, linen, and wire. Leonardo reasoned that turning the spiral would make it “screw” upward through the air, much as a screw moves through a solid material.
The aerial screw was a design study, not a proven flying machine. Its proposed rotor was far too large and heavy for the materials and power sources available in Renaissance Italy. It also lacked a practical engine and a reliable way to control flight.
The design is often called a helicopter precursor, but it was not a modern helicopter. Modern helicopters use powered rotary wings, aerodynamic blades, and controlled lift; Leonardo’s sketch expressed the idea of vertical flight in a very different mechanical form.