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 shows a large, spiral-shaped linen sail mounted around a central mast. Leonardo reasoned that if the spiral rotated rapidly, it might “screw” itself upward through the air, much as a screw moves through a solid material.
The aerial screw was not a working helicopter. Its proposed materials and human-powered mechanism could not provide enough lift with Renaissance technology. The idea is nevertheless often discussed as an early conceptual ancestor of the helicopter, because it combined a rotating lifting surface with a vertical axis.
A common mix-up is calling the drawing a helicopter. Leonardo did not build a helicopter, and the modern helicopter depends on aerodynamic principles, engines, and rotor control systems developed centuries later. His aerial screw is best understood as a visionary mechanical study, not a completed aircraft.