Other Variable-Sweep Projects

The reason that a British team under Dr. Barnes Wallis at Vickers-Armstrongs was available to work on variable sweep with the NASA Langley group in 1959 was that Wallis could not get British government funding for full-scale variable-sweep tests. Inspired by wartime German research, Wallis had actually started variable-sweep research in Britain in 1945, using models launched from a rocket-powered trolley After some success­ful model flights, Vickers-Armstrongs contracted for a small piston-engine variable-sweep test airplane with Heston Aircraft Ltd., but the parts built were never assembled and were eventually broken up.

In 1959, Wallis brought the Vickers-Armstrongs variable-sweep team and data to NASA’s Langley Laboratory for further research. At the time, the variable-sweep configuration of interest to the British was a high-aspect-ratio tailless arrangement in which the wing inboard ends required translation. The British called this arrowhead-like configuration “Swallow.” The Swallow was to lead to a high-subsonic airliner capable of flying nonstop from London to Australia at 50,000 feet. NASA wind-tunnel tests indicated that the Swallow would be longitudinally unstable with the wings unswept at low subsonic speeds (Figure 16.6). A return to horizontal tails and the successful outboard-hinge rotation-only arrangement followed.

Later practical applications of variable sweep were the Anglo-German-Italian Panavia Tornado and the former USSR’s MiG-23 Flogger, MiG-27, Su-17, Su-24, Tu-22M Backfire, and the Tu-160 Blackjack.

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