Leonardo da Vinci’s spiral rotor aircraft concept is commonly called the aerial screw.
Leonardo drew the design around 1489 in a manuscript now associated with the Codex Atlanticus. It consists of a large helical surface mounted around a vertical frame. Leonardo proposed that, if the screw rotated rapidly enough, its spiral surface would “screw” upward through the air.
The aerial screw is often described as a distant precursor to the modern helicopter, but it was not a working helicopter. The sketch does not provide a practical engine, lightweight structure, or complete system for controlling flight. Its proposed lifting mechanism also differs from the aerodynamic rotor blades used by helicopters.
The design is important because it shows Leonardo thinking about vertical flight rather than only about gliding or flapping wings. He also explored several other flight concepts, including parachutes and ornithopters.
No evidence shows that Leonardo built or tested a full-scale aerial screw. Its importance is chiefly historical and conceptual.