The Sukhoi Design Bureau started research on thrust vectoring in 1983, when the Soviet government tasked the bureau with the separate development of the Su-27M. 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 focus on two-dimensional nozzles prevailing in the West.
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. The aircraft was rolled out in May. Two months later, the temporary engines were replaced with AL-37FUs; its nozzles could only deflect 15 degrees up or down in the
pitch axis, together or differentially. Apart from the addition of thrust-vectoring nozzles, the Su-37 did not outwardly differ much from the canard-equipped Su-27M. Instead, engineers had focused on the aircraft's avionics. Unlike previous Su-27Ms, the Su-37 had a digital (as opposed to analogue)
fly-by-wire flight control system, which was directly linked to the thrust-vectoring control system. Together with the aircraft's overall high
thrust-to-weight ratio and the engine's
full authority digital engine control feature, the integrated propulsion and flight control systems added maneuverability at high angles of attack and low speeds. The aircraft's
weapons-control system had also been improved, as it included an
N011M Bars (literally "Panther")
pulse-Doppler phased-array radar that provided the aircraft with simultaneous air-to-air and air-to-ground capability. The radar was capable of tracking twenty aerial targets and directing missiles toward eight of them simultaneously; in comparison, the Su-27M's baseline N011 could only track fifteen aerial targets and engage six of them simultaneously. The aircraft retained from the Su-27M the N012 self-defence radar located in the rearward-projecting tail boom.--> Considerable improvement had also been made to the cockpit layout. In addition to the
head-up display, the Su-37 had four
Sextant Avionique multi-function colour
liquid crystal displays arranged in a "T" configuration; they had better backlight protection than the Su-27M's monochrome
cathode-ray tube displays. The displays presented to the pilot information about navigation, systems status, and weapons selection. The pilot sat on an
ejection seat that was reclined to 30 degrees to improve
g-force tolerance. Painted in a disruptive sand and brown scheme, the aircraft was given the code
711 Blue, later changed to
711 White. The aircraft was publicly unveiled at Zhukovsky later in the year, and was redesignated Su-37. == Operational history ==