What Leonardo da Vinci design used wings modeled on a bat for human flight?

Leonardo da Vinci’s bat-winged human-flight design was an ornithopter.

An ornithopter is an aircraft intended to fly by flapping wings, rather than by using fixed wings or a propeller. Leonardo studied birds and bats closely and filled his notebooks with sketches of wing structures, joints, and control systems. His proposed machine was powered by the pilot’s arms and legs through a system of levers and pedals.

Leonardo’s design was never built as a successful flying aircraft. The main difficulty was power: human muscles cannot produce enough sustained energy to flap wings large enough to lift a person. His work nevertheless helped record important observations about lift, balance, and wing movement.

An ornithopter is not the same as Leonardo’s later glider concepts, which relied on fixed lifting surfaces. The word comes from Greek roots meaning “bird” and “wing,” and modern experimental ornithopters use motors, springs, or other mechanical power sources.