Sukhoi Su-47

Sukhoi Su-47 Berkut

Company type	Experimental aircraft
Industry	Aerospace
Founded	1983
Headquarters	Russia
Products	Supersonic technology demonstrator aircraft

This article is about the aircraft once identified as S-37. For the aircraft known as Su-37, see Sukhoi Su-37.

The Sukhoi Su-47 Berkut (Russian: Сухой Су-47 «Беркут», lit. 'Eagle' in Kazakh) (NATO reporting name Firkin), initially designated S-32 and later S-37 during its early development stages, was a Russian experimental supersonic technology demonstrator crafted by the Sukhoi design bureau. Its most notable characteristic was the use of forward-swept wings, intended to enhance the aircraft’s agility and maneuverability. Although it never entered mass production and the forward-swept wing design was not adopted for subsequent models, the single prototype served as a test platform for numerous innovations later integrated into the Sukhoi Su-35—a fourth-generation fighter—and the Sukhoi Su-57, Russia’s fifth-generation fighter jet.

Development

Initially referred to as the S-37, this advanced test aircraft was rebranded as the Su-47 by Sukhoi in 2002. Bearing the official nickname Berkut (Russian: Беркут), which translates to "Eagle" from Kazakh, the Su-47 was primarily constructed to serve as Russia’s main experimental platform for composite materials, advanced fly-by-wire flight control systems, and innovative airframe technologies.

The Russian aerospace research center TsAGI had long recognized the benefits of forward-swept wings, with earlier investigations including work on the Tsibin LL and analysis of the captured German Junkers Ju 287 during the 1940s. At elevated angles of attack, this wing configuration maintains retracted wingtips, preserving aileron effectiveness. Unlike conventional rearward-swept wings, forward sweep increases the angle of incidence on outer wing sections when bending occurs under aerodynamic load. This results in greater bending stresses, making these wings more prone to structural failure at lower speeds compared to straight or aft-swept wings.

The project began in 1983 under commission from the Soviet Air Force. Following the dissolution of the USSR, government financing was halted; however, Sukhoi continued development using private funding. Similar to its American counterpart, the Grumman X-29, the Su-47 chiefly functioned as a technology demonstrator for future Russian fighter designs such as the Sukhoi Su-57. Ultimately, the forward-swept wing approach was abandoned because it offered advantages primarily at transonic speeds, whereas aft-swept wings performed better at supersonic velocities.

File:Sukhoi Su-47 outline.svg

Outline of the Sukhoi Su-47

Dimensionally, the Su-47 is comparable to earlier large Sukhoi fighters like the Su-35. To minimize development expenses, it incorporated components from the Sukhoi Su-27 family—including its forward fuselage section, vertical stabilizers, and landing gear assemblies. Despite this commonality, it featured an internal weapons bay and provisions for housing an advanced radar system.

Mirroring its predecessor, the Su-37, the Su-47 employs a tandem-triple wing configuration with canards positioned ahead of the main wings and tailplanes aft. It is equipped with two asymmetrical tailbooms situated outside of its exhaust nozzles; these house rear-facing radar equipment and a drogue parachute system.

Maneuverability

The Su-47 exhibits exceptional agility at speeds below Mach 1, allowing it to rapidly adjust both its angle of attack and flight trajectory while maintaining maneuverability even during supersonic flight.

Its forward-swept wing configuration gives the aircraft a distinctive silhouette. A significant portion of lift is generated by the wing's inner section, which remains unaffected by wingtip stall. Consequently, the formation of lift-induced vortices near the wingtips is minimized. The ailerons retain their effectiveness at very high angles of attack, ensuring that the aircraft remains controllable even when airflow separates from other parts of the wing surface.

One drawback of the forward-swept wing design is the twisting effect experienced under aerodynamic loads, which imposes higher stress on the wing compared to straight or rearward-swept wings. To counteract this, the wing structure is engineered to twist in opposition to the aerodynamic forces—known as aeroelastic tailoring—achieved through composite materials arranged to induce this counter-twist. Initially, the Su-47's top speed was limited to Mach 1.6. Because forward sweep provides advantages primarily in transonic flight but is less effective than aft-swept wings at supersonic speeds, further development along this line was not pursued.

Thrust vectoring

The aircraft’s thrust vectoring capability, enabled by modifications to the PFU engine, allows for ±20° deflections at a rate of 30° per second in both pitch and yaw axes. This system was designed to enhance the maneuverability already afforded by other design elements.

Stealth

Some reports indicate that the Su-47’s surface was coated with radar absorbent material (RAM) to lower its radar detectability. Nonetheless, the airframe lacks specialized stealth features that would substantially diminish its radar cross-section in comparison to dedicated stealth aircraft.

Gallery

• File:Sukhoi Su-47 Berkut (S-37) in 2001.jpg
• File:Russian Air Force, 01, Sukhoi Su-47 Berkut (49581076306).jpg
• Su-47 displayed alongside a Sukhoi Su-35UB during the MAKS-2003 exhibition.
  Su-47 displayed alongside a Sukhoi Su-35UB during the MAKS-2003 exhibition.
• Leading formation flight of the Sukhoi Su-47 Berkut, followed by a Su-27SKM (above) and a Su-30MKK (below).
  Leading formation flight of the Sukhoi Su-47 Berkut, followed by a Su-27SKM (above) and a Su-30MKK (below).

External links

• Detailed information on the S-37 Berkut at Fighter-Planes.com