The F-16 Multi-Axis Thrust-Vectoring (MATV) program originally began as a joint General Electric/General Dynamics privately-funded program for a thrust-vectored version of the Fighting Falcon. The USAF initially declined to support the program, so the two companies agreed to collaborate with the Israel Defense Force/Air Force, which was highly interested in the program for its own F-16s. Under the terms of the agreement, the IDF/AF was to supply a F-16D for the tests, with the two American companies doing the conversion. However, in 1991 the USAF's Wright Laboratory became interested in the project, and the USAF now assumed an active role. Israel withdrew from the program in 1992. The project was now known as the F-16 Multi-Axis Thrust-Vectoring (MATV) program.
The USAF loaned the Lockheed Fort Worth Company (LWFC) a F-16D Block 30 (serial number 86-0048) to be modified into a thrust vectoring research aircraft. The aircraft is known as VISTA, which was an acronym which stood for "Variable-stability In-flight Simulator Test Aircraft".
The heart of the VISTA is its Axisymmetric Vectoring Exhaust Nozzle (AVEN), which is attached to the exhaust of the aircraft's General Electric F110-GE-100 engine. The AVEN achieves the required thrust vectoring within the divergent (supersonic flow) portion of the nozzle, which prevents pressure fluctuations from being fed back into the engine where they could cause a compressor stall. The divergent flaps are angled individually by means of a ring that is positioned by three additional hydraulic actuators located at 120-degree intervals, with power being supplied by an independent system. The exhaust nozzle can be deflected in any direction through an angle of up to 17 degrees. Axial and side forces imposed by the jet exhaust on the nozzle are transferred into the jetpipe and thus back into the engine. The advantage of the AVEN is that it could be retrofitted to any F-16 that was powered by the F110 engine and which had a digital flight control system.
The movement of the three actuators is commanded by a Vector Electronic Control (VEC), which is a modified version of the full-authority digital engine control used by the F110-GE-129 engine. In order to counterbalance the additional weight of the AVEN, 700 pounds of ballast were added on the inlet hardpoints to keep the center of gravity ahead of 38% chord in order to avoid the danger of deep stalls should the thrust vectoring system fail. As an additional safety measure, a spin-recovery parachute was installed high over the rear end of the aircraft to assist in recovery from deep stalls should they occur.
The VISTA F-16D was redesignated NF-16D, the N prefix meaning that the aircraft had a special test status and that the modifications were sufficiently drastic that it would be impractical to restore the plane to its original condition. The MATV aircraft first flew in this modified form on July 2, 1993. The aircraft was transferred to Edwards AFB on the 15th. Thrust vectoring in flight was first used on July 30.
The program objectives included the demonstration of the tactical utility of thrust vectoring in close-in air combat and in the use of integrated control of thrust vectoring in flight. The aircraft has demonstrated a steady angle of attack of as much as 86 degrees and a transient angle of attack of up to 180 degrees. In other words, the aircraft can fly BACKWARDS for a brief time. Thrust vectoring provides a significant advantage in terms of bringing armament to bear on a threat more quickly and in avoiding the risk of departure from controlled flight during violent maneuvers. However, the use of really high AoA maneuvers should only be a last-ditch operation in aerial combat in view of the increased vulnerability of the aircraft when it is in a low-energy state.