Leonardo da Vinci studied an ornithopter, a human-powered flight machine designed to fly by flapping wings.
The word ornithopter means a machine that flies through wing beats, modeled on birds or bats. Leonardo filled several notebooks with observations of bird anatomy, air currents, wing movement, and mechanical flight. His designs included a frame, large wings, and pedals or levers intended to transfer human power to the wings.
Leonardo correctly recognized that flight depended on lift, balance, and the movement of air. However, human muscles could not provide enough power for a practical flapping aircraft of the scale he envisioned. No Leonardo ornithopter is known to have flown.
His work is often confused with his separate studies of gliders and rotary-wing machines. Those designs used different aerodynamic principles, while an ornithopter specifically imitates flapping flight.