Leonardo da Vinci’s helical-rotor flying-machine design was called the aerial screw.
Leonardo drew the aerial screw around 1489–1490 in his notebooks. The design used a large spiral surface made from linen stiffened with reeds, mounted around a central mast. Leonardo reasoned that turning the screw could make it rise by “screwing” through the air, much as a screw moves through a solid material.
The aerial screw is often called an early helicopter concept, but it was not a working helicopter. Leonardo did not have a sufficiently powerful, lightweight engine, and the drawing does not provide a complete practical method for producing the required rotation. Its importance lies in the idea of vertical flight and rotary lift. The design is also sometimes mistakenly described as the first helicopter; modern helicopters depend on powered rotor blades, aerodynamic lift, and control systems that Leonardo’s sketch did not solve.