Leonardo da Vinci’s bird-inspired wing-flapping aircraft was an ornithopter.
An ornithopter is an aircraft designed to fly by flapping wings, rather than by using a propeller or fixed wings. Leonardo studied birds and bats and produced several drawings of human-powered ornithopter mechanisms during the late fifteenth and early sixteenth centuries.
His sketches explored how a pilot might move large wings using pedals, levers, and body power. The designs were inventive, but a person could not supply enough energy to flap wings large enough to lift a complete machine. Leonardo’s ornithopters therefore remained plans and models rather than practical aircraft.
The term is broader than Leonardo’s work: modern engineers have also built small experimental ornithopters. It should not be confused with the aerial screw, whose proposed lifting mechanism rotated instead of flapping.