Leonardo da Vinci called his 1480s device with a helical sail for rising through air an aerial screw.
The aerial screw is one of Leonardo’s best-known flight concepts. His sketch shows a large helical structure wrapped around a central mast. Leonardo reasoned that if the screw were turned rapidly, its surface might press against the air and lift the machine, an idea analogous to a screw advancing through a solid material.
The concept is frequently described as a distant precursor to the helicopter, but it was not a helicopter and was never demonstrated as a working aircraft. Leonardo did not have an engine light and powerful enough to rotate the proposed mechanism, and the design’s aerodynamics would not have produced practical flight as drawn.
The phrase “aerial screw” refers to Leonardo’s particular concept. It is more precise than simply calling the sketch a helicopter, since the first successful helicopters appeared centuries later and used powered rotors with different engineering.