Leonardo da Vinci's rotating aerial-machine concept, drawn around 1489, was called the aerial screw.
The design has a large helical surface, or screw, intended to rise by rotating through the air. Leonardo compared its action with a screw moving through a solid material. The drawing is among his studies of flight and mechanical motion, and it is often described as an early helicopter-like concept.
The aerial screw could not have flown as drawn with the materials and power sources available in Renaissance Italy. Its frame was large, and human muscle alone would not have supplied enough power to turn the rotor fast enough. The design therefore belongs to the history of theoretical flight rather than to successful aircraft engineering.
It is often called a helicopter in popular accounts, but “aerial screw” is the more precise name for Leonardo's concept. The modern helicopter uses powered rotors and aerodynamic blades, while Leonardo's design used a helical surface. Its historical importance lies in identifying vertical lift as a mechanical problem long before powered flight.