Leonardo da Vinci's ornithopter was a human-flight design based on flapping bird wings.
Leonardo studied birds intensely and filled notebooks with observations about their wing shapes, balance, and movement. His ornithopter designs used a pilot's muscular effort to operate large wings, usually through pedals, levers, or crank mechanisms. The word ornithopter comes from Greek roots meaning “bird” and “wing.”
Leonardo understood that simply copying a bird would not make human flight practical. Humans lack the strength-to-weight ratio needed to flap wings of the required size, so his machine was never built into a working aircraft. The designs nevertheless belong to the early history of aviation because they show a systematic attempt to explain and reproduce powered flight.
A common mix-up is calling every Leonardo flying-machine sketch a helicopter. The ornithopter depends on flapping wings; his aerial screw uses a rotating spiral surface and represents a different concept.