High-speed aircraft, in wind tunnels and out, flap their wings like birds | National Geographic Magazine, vol. 104 1953

Engineers used to treat wings as rigid units, but the long, thin, narrow wings of today's jet bombers pose a new problem: aeroelasticity.

In flight through turbulent air the Boeing B-52's wing tips may move in a 20-foot arc. To study such flapping and its effect on performance, these Seattle engineers mount an aeroelastic model of balsa segments strung on metal wingspars. They wear soft cloth overshoes to protect the tunnel's polished steel. The flexible model and steel-rod mount, both new to aeronautical research, were developed by the Boeing Airplane Company.

A slow-motion camera records the flexing wings as this B-52 model rides up and down on its monkey-on-a-stick mount. Boeing's transonic wind tunnel, based on designs of the NACA, is the only one of its kind operated by private industry.

Kodachrome photos by Luis Marden, National Geographic Staff, and NACA