The Sukhoi Su-47 ''Berkut'' () (

NATO reporting name NATO uses a system of code names, called reporting names, to denote military aircraft and other equipment used by post-Soviet states, former Warsaw Pact countries, China, and other countries. The system assists military communications by providi ...

Firkin), also designated S-32 and S-37 during initial development, was a Russian experimental

supersonic Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...

jet fighter Fighter aircraft (early on also ''pursuit aircraft'') are military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the air ...

developed by the JSC Sukhoi Company. A distinguishing feature of the aircraft was its

forward-swept wing A forward-swept wing or reverse-swept wing is an aircraft wing configuration in which the quarter-chord line of the wing has a forward sweep. Typically, the leading edge also sweeps forward. Aircraft with forward-swept are more maneuverable, due ...

Russian Aviation Page: Sukhoi S-37 Berkut (S-32)
which gave the aircraft excellent agility and maneuverability. While serial production of the type never materialized and the configuration was not further pursued, the sole aircraft produced served as a technology demonstrator prototype for a number of advanced technologies later used in the

fourth-generation fighter The fourth-generation fighter is a class of jet fighters in service from around 1980 to the present, and represents design concepts of the 1970s. Fourth-generation designs are heavily influenced by lessons learned from the previous generation o ...

Su-35 The Sukhoi Su-35 (-35; NATO reporting name: Flanker-E/M, occasionally nicknamed "Super Flanker") is the designation for two improved derivatives of the Su-27 air-defence fighter. They are single-seat, twin-engine, supermaneuverable, 4.5 ge ...

and the

fifth-generation fighter A fifth-generation fighter is a Jet fighter generations, jet fighter aircraft classification which includes major technologies developed during the first part of the 21st century. these are the most advanced fighters in operation. The characteri ...

Su-57 The Sukhoi Su-57 (; NATO reporting name: Felon) is a Twinjet, twin-engine stealth aircraft, stealth Multirole combat aircraft, multirole fighter aircraft developed by Sukhoi. It is the product of the PAK FA (, prospective aeronautical comp ...

Development

Originally known as the S-37, Sukhoi redesignated its advanced test aircraft as the Su-47 in 2002. Officially nicknamed ''Berkut'' () (the Russian word for the

golden eagle The golden eagle (''Aquila chrysaetos'') is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known bird of pr ...

), the Su-47 was originally built as Russia's principal testbed for composite materials and sophisticated fly-by-wire control systems, as well as new airframe technologies.

TsAGI The Central Aerohydrodynamic Institute (also (Zhukovsky) Central Institute of Aerodynamics, , TsAGI) is a Russian national research centre for aviation. It was founded in Moscow by Russian aviation pioneer Nikolai Yegorovich Zhukovsky on Decemb ...

has long been aware of the advantages of forward-swept wings, with research including the development of the Tsibin LL and study of the captured Junkers Ju 287 in the 1940s. At high angles of attack, the wing tips remain retracted allowing the aircraft to retain aileron control. Conversely to more conventional rear-swept wings, forward sweep geometrically creates increased angle of incidence of the outer wing sections when the wing bends under load. The wings experience higher bending moments, leading to a tendency for the wings to fail structurally at lower speeds than for a straight or aft-swept wing. The project was launched in 1983 on order from the Soviet Air Force. But when the USSR dissolved, funding was frozen and development continued only through funding by Sukhoi. Like its US counterpart, the

Grumman X-29 The Grumman X-29 is an American experimental aircraft that tested a forward-swept wing, canard control surfaces, and other novel aircraft technologies. Funded by NASA, the United States Air Force and DARPA, the X-29 was developed by Grumman, a ...

, the Su-47 was primarily a technology demonstrator for future Russian fighters such as the

Sukhoi Su-57 The Sukhoi Su-57 (; NATO reporting name: Felon) is a twin-engine stealth multirole fighter aircraft developed by Sukhoi. It is the product of the PAK FA (, prospective aeronautical complex of front-line aviation) programme, which was in ...

. The forward-swept wing configuration was ultimately not pursued because it was mainly advantageous at transonic speeds while an aft-swept wing was superior at supersonic speeds. Sukhoi Su-47 outline

The Su-47 is of similar dimensions to previous large Sukhoi fighters, such as the

. To reduce development costs, the Su-47 borrowed the forward fuselage, vertical tails, and landing gear of the Su-27 family. Nonetheless, the aircraft includes an internal weapons bay, and space set aside for an advanced radar. Like its immediate predecessor, the Su-37, the Su-47 is of tandem-triple layout, with canards ahead of wings and

tailplane A tailplane, also known as a horizontal stabilizer, is a small lift (force), lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters ...

s. The Su-47 has two tailbooms of unequal length outboard of the exhaust nozzles, carrying rearward-facing

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

and a breaker-chute.

Maneuverability

The Su-47 has extremely high agility at subsonic speeds, enabling the aircraft to alter its angle of attack and its flight path very quickly while retaining maneuverability in supersonic flight. The forward-swept wings give the Su-47 an unconventional appearance. The inner portion of the wing generates a substantial part of the lift. This lift is not restricted by wingtip stall, and the lift-induced wingtip vortex generation is thus reduced. The

aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement aroun ...

remain effective at the highest angles of attack, and controllability of the aircraft is retained even in the event of airflow separating from the remainder of the wings' surface. A disadvantage of such a forward-swept wing design is that it twists when under load, resulting in greater stress on the wing than occurs with a similar straight or aft-swept wing. This requires the wing be designed to twist as it bends—opposite to the geometric twisting. This is done by the use of composite wing skins laid-up to twist. The aircraft was initially limited to Mach 1.6. Because the forward sweep was primarily beneficial at transonic speed while losing out to aft-swept wing at supersonic speed, it was not pursued further.

Thrust vectoring

The

thrust vectoring Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to Aircraft flight control system, control the Spacecra ...

(with PFU engine modification) of ±20° at 30°/second in pitch and yaw would have greatly supported the agility gained by other aspects of the design.

Stealth

According to some sources, the Su-47 was treated with

radar absorbent material In materials science, radiation-absorbent material (RAM) is a material which has been specially designed and shaped to absorb incident RF radiation (also known as non-ionising radiation), as effectively as possible, from as many incident direc ...

(RAM) in order to reduce its radar signature. However, the airframe itself has no specific features characteristic of true stealth aircraft that would more significantly reduce its radar cross-section.

Specifications (Su-47)

Gallery

File:Sukhoi Su-47 Berkut (S-37) in 2001.jpg File:Russian Air Force, 01, Sukhoi Su-47 Berkut (49581076306).jpg File:Sukhoi Su-35UB and Su-47 at MAKS-2003 airshow.jpg, Su-47 next to a Sukhoi Su-35UB at the MAKS-2003 air show. File:Sukhoi Su-47 in formation, 2005.jpg, Sukhoi Su-47 Berkut in the lead, followed by a Su-27SKM (top) and a Su-30MKK (bottom).

References

Bibliography

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External links

S-37 Berkut at Fighter-Planes.com
{{Authority control 1990s Soviet and Russian experimental aircraft 1990s Russian fighter aircraft Abandoned military aircraft projects of Russia Aircraft first flown in 1997 Canard aircraft Forward-swept-wing aircraft Relaxed-stability aircraft Su-47 Twinjets