as the subject of one of the former events in the American nationwide Science Olympiad event list. The event ("Flying Bird") entailed building a self-propelled ornithopter to exacting specifications, with points awarded for high flight time and low weight. Bonus points were also awarded if the ornithopter happened to look like a real bird. Aerodynamics As demonstrated by birds, flapping wings offer potential advantages in maneuverability and energy savings compared with fixed-wing aircraft, as well as potentially vertical take-off and landing. It has been suggested that these advantages are greatest at small sizes and low flying speeds, but the development of comprehensive aerodynamic theory for flapping remains an outstanding problem due to the complex non-linear nature of such unsteady separating flows. Unlike airplanes and helicopters, the driving airfoils of the ornithopter have a flapping or oscillating motion, instead of rotary. As with helicopters, the wings usually have a combined function of providing both lift and thrust. Theoretically, the flapping wing can be set to zero angle of attack on the upstroke, so it passes easily through the air. Since typically the flapping airfoils produce both lift and thrust, drag-inducing structures are minimized. These two advantages potentially allow a high degree of efficiency. Wing design If future crewed motorized ornithopters cease to be "exotic", imaginary, unreal aircraft and start to serve humans as junior members of the aircraft family, designers and engineers will need to solve not only wing design problems but many other problems involved in making them safe and reliable aircraft. Some of these problems, such as stability, controllability, and durability, are necessary for all aircraft. Other problems specific to ornithopters will appear; optimizing flapping-wing design is only one of them. An effective ornithopter must have wings capable of generating both thrust, the force that propels the craft forward, and lift, the force (perpendicular to the direction of flight) that keeps the craft airborne. These forces must be strong enough to counter the effects of drag and the weight of the craft. Leonardo's ornithopter designs were inspired by his study of birds, and conceived the use of flapping motion to generate thrust and provide the forward motion necessary for aerodynamic lift. However, using materials available at that time the craft would be too heavy and require too much energy to produce sufficient lift or thrust for flight. Alphonse Pénaud introduced the idea of a powered ornithopter in 1874. His