Leonardo da Vinci sketched an aerial screw as a flying-machine design with rotating helical blades.
Leonardo drew the aerial screw around 1489, during his studies of flight and air. The machine used a large, linen-covered helical surface mounted on a frame. Leonardo appears to have believed that rapidly turning the screw could make it rise by pressing against the air, an idea that resembles the principle of a modern helicopter rotor.
The drawing is often called a helicopter precursor, but it was not a working helicopter. The materials and human power available in Renaissance Italy could not have supplied enough lift to raise the heavy structure. Leonardo’s design also lacked the practical control systems and lightweight engines needed for powered flight.
The aerial screw is sometimes confused with Leonardo’s ornithopter, which copied the flapping motion of birds. The screw instead used rotary motion, making it one of his most recognizable studies of vertical flight.