Leonardo da Vinci sketched an aerial screw as a helical-rotor aircraft concept.
The drawing appears in the Codex Atlanticus and is usually dated to about 1489. It shows a large spiral structure made from reeds, covered with linen, and supported by a framework. Leonardo reasoned that the rotating spiral could “screw” upward through the air, much as a screw moves through a material.
The design is often called an early helicopter concept, but it was not a working helicopter. Its proposed rotor was too large and heavy for the materials and power sources available in Renaissance Italy. Modern helicopters also use powered rotors, but their aerodynamic principles and engineering are substantially more developed.
The aerial screw should also be distinguished from Leonardo’s ornithopter, which imitated flapping bird wings. Both belonged to his broader investigations into human flight, but they used different mechanical ideas.