Leonardo da Vinci called his spiral helicopter-like concept an aerial screw.
Leonardo sketched the aerial screw around 1489, describing a large spiral surface that would supposedly rise if rotated rapidly. The design is commonly compared with a modern helicopter because it aimed to generate lift through a rotating structure.
The concept used a linen-covered helical frame, with the screw imagined as roughly 5 meters in diameter. Leonardo reasoned that the rotating surface could “screw” itself into the air, much as a screw moves through a solid material. However, the design lacked a practical power source and was never demonstrated as a working aircraft.
The aerial screw should not be called a helicopter in the strict historical sense. Modern helicopters rely on powered rotors, aerodynamic blades, and controllable flight systems. Leonardo’s drawing is better understood as an early conceptual study of vertical flight and rotary lift.