Leonardo da Vinci’s birdlike flying-machine design was an ornithopter.
An ornithopter is an aircraft intended to fly by flapping wings, rather than by using fixed wings like an airplane or rotating blades like a helicopter. Leonardo studied birds and bats closely and sketched machines whose wings would be moved by human or mechanical power.
His designs were theoretical inventions, not successful aircraft. Human muscles cannot produce enough sustained power to lift a person with flapping wings of the size Leonardo imagined. The sketches nevertheless show his interest in applying anatomy and observation of nature to engineering.
An ornithopter is sometimes confused with Leonardo’s aerial screw, which used a rotating helical surface and is often described as an early helicopter concept. Leonardo’s birdlike machines belong to the flapping-wing category, while the aerial screw belongs to the rotary-wing tradition.