Leonardo da Vinci envisioned an aerial screw with a large rotating spiral blade.
His drawing, usually dated to about 1489, shows a helical structure wrapped around a central mast. Leonardo proposed that the screw could rise if its surface pushed against the air, an idea analogous to a screw moving through a solid material. The design is often described as an ancestor of the helicopter, although it was not a helicopter in the modern mechanical sense.
The concept had no engine or practical lightweight power source. Leonardo suggested human-powered mechanisms in some flying-machine studies, but human muscles could not produce enough sustained power to lift the proposed structure. The aerial screw therefore remained a theoretical machine rather than a tested aircraft.
Its importance lies in the principle it explored: vertical lift produced by rotating blades. Modern helicopters use powered rotors with airfoils and carefully controlled pitch, not a single fabric-covered spiral. The aerial screw is thus best understood as an early conceptual precursor to rotary-wing flight.