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S-37 Berkut Sukhoi
(S-37 Berkut)
ASCC codename: Firkin
Advanced Fighter Prototype

Originally known as the S-37, Sukhoi redesignated this advanced test aircraft as the Su-47 in 2002. The change reflected the company's decision to market the design as a production fighter rather than as an experimental prototype. Also commonly referred to as the Berkut (Golden Eagle), the Su-47 was originally built as Russia's principle testbed for composite materials and sophisticated fly-by-wire control systems.

The aircraft made use of forward-swept wings allowing superb maneuverability and operation at angles of attack up to 45 or more. The advantages of forward sweep have long been known since such wings offer lower wave drag, reduced bending moments, and delayed stall when compared to more traditional wing shapes. Unfortunately, forward sweep also induces twisting strong enough to rip the wings off an aircraft built of conventional materials. To solve this problem, the Su-47 was built of composite materials carefully tailored to resist twisting while still allowing the wing to bend for improved aerodynamic behavior.

To reduce development costs, the S-37 borrowed the forward fuselage, vertical tails, and landing gear of the Su-27 family. Nonetheless, the aircraft incorporated several sophisticated features such as reduced radar signature (including radar absorbent materials), an internal weapons bay, and space set aside for an advanced radar. Though similar in overall concept to the American X-29 research aircraft of the 1980s, the Su-47 was about twice the size and far closer to an actual combat aircraft than the US design.

Like the X-29, the S-37 was primarily a technology demonstrator, one intended to lay the foundation for the next generation Russian fighter. Such a fighter would not only have to be as advanced as the US F-22 and Eurofighter Typhoon, but would also have to compete for Russian development funds against the more conventional MiG 1-42.

However, the advanced capabilities demonstrated by the S-37 prototype led Sukhoi to market the Su-47 to the Russian military and foreign customers as a production fighter in its own right. Initial reaction was not good, but the aircraft's performance was sufficiently impressive that the Russian government made funds available for further testing of the design at the expense of the competing MiG 1-42.

A decision was ultimately made not to put the Su-47 into production and the aircaft instead became a technology testbed for Russia's "5th Generation" fighter, which is viewed as a competitor to the American Joint Strike Fighter. However, Sukhoi has apparently decided to abandon the forward-swept wings of the S-37, and the new T-50 design planned to go into production will return to a more conventional wing layout. This decision may indicate that Sukhoi reached the same conclusion as NASA did following testing of the X-29 that the benefits of forward-swept wings are not worth the extra cost and complexity associated with their design and manufacture.

Data below subject to change as more details of the S-37 become available
Last modified 09 August 2009

First Flight 25 September 1997
Service Entry

did not enter service

CREW: one: pilot


probably $50 million+

Wing Root unknown
Wing Tip


Length 72.83 ft (22.60 m)
Wingspan 74.00 ft (16.70 m)
Height 19.33 ft (5.90 m)
Wing Area 666 ft (62.0 m)
Canard Area


Empty unknown
Normal Takeoff 57,320 lb (26,000 kg)
Max Takeoff 74,955 lb (34,000 kg)
Fuel Capacity internal: unknown
external: unknown
Max Payload


Powerplant two Aviadvigatel D-30F6 afterburning turbofans (original)
two Saturn/ Lyul'ka AL-37FU afterburning turbofans (planned)
Thrust 68,340 lb (303.8 kN) [D-30F6]
37,480 lb (166.7 kN) [AL-37U]
63,930 lb (284.4 kN) [AL-37U] with afterburner

Max Level Speed at altitude: 1,555 mph (2,500 km/h)
at sea level: 870 mph (1,400 km/h)
Initial Climb Rate 45,275 ft (13,810 m) / min
Service Ceiling 61,680 ft (18,800 m)
Range typical: 2,100 nm (3,880 km)
ferry: unknown
g-Limits unknown

Gun one 30-mm GSh-30 cannon (150 rds)
Stations one internal weapons bay
Air-to-Air Missile R-27/AA-10 Alamo, R-73/AA-11 Archer (presumably)
Air-to-Surface Missile unknown
Bomb unknown
Other unknown
S-32 Original designation seen on the first prototype
S-37 New designation for an experimental single-seat fighter prototype; 1 built
Su-47 Redesignation for the design as marketed by Sukhoi which has promoted the aircraft as a production fighter


did not enter service




S-37 Berkut

  • Covault, Craig. Russian S-37 Accelerates Fighter Technology, Aviation Week & Space Technology, vol. 152, no. 22, 29 May 2000, p. 52-54.
  • Taylor, Michael. Brassey's World Aircraft & Systems Directory 1996/1997. London: Brassey's, 1996, p. 96, Sukhoi S-32.
  • Taylor, Michael J. H. Brassey's World Aircraft & Systems Directory 1999/2000. London: Brassey's, 1999, p. 78-79, Sukhoi S-37.

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