The Sukhoi Su-37 (-37; NATO reporting name: Flanker-F; popularly nicknamed "Terminator") was a single-seat twin-engine aircraft designed by the Sukhoi Design Bureau that served as a technology demonstrator. It allowed for the need to enhance pilot control of the Su-27M (later renamed Su-35), which was a further development of the Su-27. The sole aircraft had originally been built as the eleventh Su-27M (T10M-11) by the Komsomolsk-on-Amur Aircraft Production Association before having its thrust-vectoring nozzles installed. In addition, it was modified with updated flight- and weapons-control systems. The aircraft made its maiden flight in April 1996. Throughout the flight-test program, the Su-37 demonstrated its supermaneuverability at air shows, performing manoeuvres such as a 360-degree somersault. The aircraft crashed in December 2002 due to structural failure. The Su-37 did not enter production; despite a report in 1998 which claimed that Sukhoi had built a second Su-37 using the twelfth Su-27M airframe, T10M-11 remained the sole prototype. Sukhoi had instead applied the aircraft's systems to the design bureau's other fighter designs. Design and development The Sukhoi Design Bureau started research on thrust vectoring as early as 1983, when the Soviet government tasked the bureau with the separate development of the Su-27M, which was an upgrade of the Su-27. At the insistence of General Director Mikhail Simonov, who had been the chief designer of the Su-27, Sukhoi and the Siberian Aeronautical Research Institute studied axisymmetrical vectoring nozzles. This was in contrast to the prevailing focus on two-dimensional nozzles in the Western press. Lyulka (later Lyulka-Saturn) also began studies of thrust-vectoring engines in 1985. By the late 1980s, Sukhoi were evaluating their research using its flying test beds. During test flights of the Su-27Ms, which began in 1988, engineers discovered that pilots failed to maintain active control of the aircraft at high angles of attack due to the ineffectiveness of flight control surfaces at low speeds. Engineers therefore installed thrust-vectoring engines to the eleventh Su-27 (factory code T10M-11), which had been built by the Komsomolsk-on-Amur Aircraft Production Association in the country's Far East and was being used as a radar test bed. Following the airframe's completion in early 1995, the aircraft was delivered to the design bureau's experimental plant near Moscow, where engineers started installing the nozzles on the aircraft. Although Sukhoi had intended the Lyulka-Saturn AL-37FU to power the aircraft, the engine had not yet been flight-cleared. The aircraft was temporarily fitted with the