related to the Su-57's Saturn AL-41F1 (izdeliye 117), differing primarily in the engine control system. The engines are equipped with thrust-vectoring nozzles, which have their rotational axes canted at an angle; the nozzles operate in one plane for pitch, but the canting allows the aircraft to produce both roll and yaw by vectoring each engine nozzle differently; this configuration was first implemented on the Su-30MKI and is also used on the Su-57. The Su-35's thrust-vectoring system and integrated flight- and propulsion-control systems allow the aircraft to attain "supermaneuverability", enabling it to perform post-stall manoeuvres at low speeds. This differs from Western air combat doctrine, which emphasises the maintenance of a fighter aircraft's kinetic energy. The engine gives the Su-35 the limited ability to sustain supersonic speed without the use of afterburners. According to Carlo Kopp of the think tank Air Power Australia, such a "supercruise" feature allows the Su-35 to engage an opponent at a greater speed and altitude and increases the range of its long-range missiles by 30–40 percent. He cites the aircraft's mature airframe and carefully balanced combination of advanced technology as allowing the Su-35 to achieve a favourable exchange rate against the F-35 stealth fighter. The US Department of Defense and Lockheed Martin had refuted criticisms of the F-35, saying that it is 400 percent more effective in air-to-air combat than any aircraft other than the F-22. Testing and production Following the completion of design work, KnAAPO constructed the first prototype, which was finished in mid-2007. The prototype, Su-35-1, was then transferred to the Gromov Flight Research Institute at Zhukovsky Airfield, in preparation for its maiden flight. On 19 February 2008, Sergey Bogdan took the aircraft aloft for its 55-minute first flight from Zhukovsky. Bogdan later piloted the second prototype on its maiden flight on 2 October from KnAAPO's Dzyomgi Airport. The flight-test programme was expected to involve three flying prototypes, but on 26 April 2009, a day before its scheduled maiden flight, the fourth Su-35 (there's a static test aircraft) crashed during a taxi run at Dzyomgi Airport. The aircraft struck a barrier at the end of the runway and was destroyed by fire; the pilot ejected and sustained burn injuries. The cause of the accident was the failure of the engine management system, as a result of which the afterburner was not turned off. The Su-35 project was aimed primarily at the export market. During