Which Leonardo da Vinci invention was designed to fly by flapping wings?

Leonardo da Vinci’s flapping-wing flying-machine concept was an ornithopter.

An ornithopter is an aircraft designed to fly by moving its wings like a bird or an insect. Leonardo studied bird anatomy and flight closely, hoping that a human-built mechanism could reproduce the same motion.

His surviving drawings show several ideas involving wings, frames, pedals, and hand-operated mechanisms. These machines were intended to imitate biological flight rather than use propellers or fixed wings. Leonardo understood that weight, balance, and wing movement were major problems, but his proposed power systems could not produce enough energy for sustained human flight.

No Leonardo ornithopter is known to have flown. The term applies to a broad class of flapping-wing machines, including later experimental aircraft. Leonardo’s studies nevertheless contributed to the history of aeronautical thinking by treating flight as a problem that could be investigated through observation, anatomy, and mechanical design.