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The Grumman X-29 explored a number of new technologies, the most immediately obvious being the forward-swept wings and canard control surface. The inherent aerodynamic instability of this arrangement required the use of computerized fly-by-wire control, and advanced composite materials were needed to make the wing sufficiently rigid without being unacceptably heavy.
Development
Two X-29As were built by Grumman Aerospace Corporation, the first flight taking place in 1984. The aircraft were adapted from existing Northrop F-5A Freedom Fighter airframes (after the airframe had been chosen over a competing proposal involving a General Dynamics F-16 Fighting Falcon); the modified design was known internally as the G-712. The test program of the two planes continued for over a decade, and on December 13, 1985 one of them became the first forward swept wing aircraft to fly supersonically in level flight. The earlier Junkers Ju 287 had been the first jet aircraft with forward-swept wings.
The X-29A demonstrated excellent control and maneuvering qualities at an angle of attack up to 45 degrees. There was also a decrease in turbulence.
The wing configuration made the craft inherently unstable. It could fly only with the constant corrections (up to 40 per second) provided by the computerized flight control system. The system was made up of three redundant digital computers backed up by three redundant analog computers. It was estimated that a total failure of the system was as unlikely as a mechanical failure in a normal airplane.
The first craft built is now on display in the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio.
Specifications (X-29)
References
American X-Vehicles (.pdf)
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"Grumman X-29"