Leonardo da Vinci’s spiral aerial machine is commonly called the aerial screw.
Leonardo drew the aerial screw around 1489 in his notebooks. The design shows a large helical rotor made from reeds, linen, and a supporting frame. He reasoned that the spiral surface could screw upward through the air if turned rapidly, much as a screw moves through a solid material.
The aerial screw was a concept rather than a demonstrated aircraft. It had no engine capable of supplying the necessary power, and its structure would have been difficult to control. For that reason, historians generally describe it as an imaginative ancestor of helicopter ideas, not a working helicopter.
The design is often confused with Leonardo’s bird-inspired flapping machines. Those machines used wings, whereas the aerial screw relied on rotary lift. Modern helicopters use powered rotors and aerodynamic principles that are far more advanced than Leonardo’s proposal.