Leonardo da Vinci sketched an aerial screw in 1489, a rotating device often described as an early helicopter concept.
The drawing shows a large helical rotor made from linen supported by reeds. Leonardo proposed that if the screw rotated quickly enough, its spiral surface would bite into the air and lift the machine. The design was roughly 15 feet across, according to descriptions associated with the drawing.
The machine was not a helicopter in the modern engineering sense. It had no demonstrated engine capable of turning the rotor, and Leonardo did not build or test a full-size version. Modern helicopters use powered rotors, aerodynamic blades, and systems for controlling lift and direction.
The aerial screw nevertheless shows Leonardo thinking about vertical flight rather than relying on wings or a runway. His drawing is preserved among his notebooks and is one of the most recognizable examples of his studies of aviation.