Leonardo da Vinci’s aerial screw used a large helical rotor to imitate a flying screw.
Drawn around 1489, the design shows a broad spiral sail mounted on a central shaft and supported by a circular wooden platform. Leonardo appears to have reasoned that the spiral surface could push against air and lift the structure.
The aerial screw is often described as a helicopter precursor, but it was not a working helicopter. Its proposed materials, size, and power source would not have produced practical powered flight with Renaissance technology. The sketch is best understood as an ingenious aeronautical concept.
The idea is frequently confused with Leonardo’s ornithopter, which copied the flapping motion of bird wings. The aerial screw instead relied on rotary motion, making it conceptually closer to a rotorcraft.