However, the fall of the Soviet Empire jeopardized development of the S-32/37/47 for the reborn Russian Ministry of Defense lacked the funding required to keep many programs afloat. Sukhoi continued the Berkut as a private venture, helped along by its many Su-27 sales, in the hopes the Berkut could further internal knowledge of forward-swept flight for possible integration into a future Sukhoi fighter design. The aircraft continued to progress, though at a much slower pace, and testing eventually proved the design sound. The forward-swept nature of the wings allowed for the expected improvement in agility at low speeds with enhanced maneuverability. The demonstrator netted a maximum speed of Mach 1.6 during testing.
Outwardly, and beyond the obviously forward-swept wings, the Su-37/47 remained a largely conventional aircraft design. The cockpit (taken from the Su-27) was set at the front of the fuselage and aft of a short nose cone assembly. The engines were paired at the rear in a side-by-side arrangement, set between the twin, outward-canted vertical tail fins. While the inlets of the aircraft were fixed, air scoops were embedded into the leading edge of each wing to provide additional airflow to the engines during low-speed flight. Ahead of the main wings were small forward canards to increase controllability and lift. Aft of the main wings were shallow horizontal planes. The undercarriage was fully retractable and of a tricycle arrangement, borrowed from the Su-27K model to expedite development.
The Su-32/37/47 demonstrator was outfitted with 2 x Aviadvigatel D-30F6 turbofan engines capable of afterburn (the same as fitted to the Mikoyan MiG-31 "Foxhound" interceptor). Output was listed at 18,700lbs under "dry" thrust with 32,000lbs of thrust generated through afterburning (raw fuel pumped into the exhaust for limited bursts of thrust). Advanced demonstrators were to field 2 x Lyulka brand AL-37FU/FP turbofans with thrust-vectoring. The Berkut achieved a maximum speed of 1,066 miles per hour with a cruising speed of 870 miles per hour. Range was listed at 2,050 miles with a service ceiling of 59,000 feet and rate-of-climb of 46,200 feet-per-minute.
In comparison, the Su-27SK model (and export-minded single-seater) yielded a maximum speed of 1,550 miles per hour with a rnage out to 2,070 miles. Its service ceiling was 62,500 feet with a rate-of-climb nearing 54,000 feet per minute.
Intended from the beginning as a technology demonstrator, the Su-37/47 was not officially armed. Had it reached the formal adoption stage, it may have included an internal 30mm cannon as well as various underwing and underfuselage hardpoints for the carrying of guided/unguided, powered/unpowered munitions similar in scope to the rest of the Flanker family.
As it stands, the Su-47 existed only through the four aforementioned prototypes and it is believed that all active development on the series have been stopped.
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