Leonardo da Vinci’s aerial screw was a spiral-powered flying-machine concept sketched in the 15th century.
The drawing shows a large helical rotor made from reeds, linen, and wire. Leonardo proposed that the rotating screw could press against the air and lift the machine, an idea often compared with the principle of a modern helicopter rotor.
The sketch dates from around 1489, but it was not a practical aircraft. The proposed materials and human-powered mechanism could not produce enough lift for the machine to rise. The design nevertheless anticipated the broad idea of vertical flight by a rotating airfoil.
The aerial screw is often described as a helicopter ancestor, but it was not a helicopter in the modern engineering sense. Modern helicopters use powered rotors, carefully shaped blades, and systems for controlling lift and direction.