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The X-29 is an experimental aircraft built by the Grumman Aerospace Corp. for the US Defense Research Projects Agency. Relaxed static stability, one of the aircraft's key design features, means that the pilot must depend exclusively on computers to fly the plane. The X-29's computers monitor and adjust the positions of the plane's control surfaces every 25 milliseconds to follow the pilot's directions. Because it is designed to be unstable, the X-29 has its center of lift ahead of the center of gravity rather than behind it, unlike most stable aircraft. The way that the aircraft's canards and flaperons contribute to maneuverability is explained, and an account is given of how a computer-aided design and manufacturing system was used to design the composite wing. The aircraft has three digital computers backed up by three analog computers. The three digital computers are linked to one another by data buses in a ring-like configuration.
Date of Publication: June 1985