by Roy Cochrun
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The S-37 "Berkut"

Development history

A momentous event took place at the end of 1997 in the history of domestic aviation - the flight of the first domestic fifth generation fighter, the S-37 "Berkut, took place.  The airplane, having broken away from the concrete of the airfield runway in Zhukovskiy, quickly disappeared into the gray skies outside Moscow, creating with the roar of its turbines the start of a new stage in the story of Russian fighter aviation.

Research of the fifth generation fighter's shape was begun in our country in the middle of the '70s, when the fourth generation Su-27 and MiG-29 aircraft were making out their first steps.  The leading branches of the scientific centers and design bureaus were attracted to the work.

Together with the customer (the Ministry of Defense) the basic positions of the new fighter's concept gradually were formulated - multi-role capability, that is a high effectiveness with destruction of aerial, ground surface, and underwater targets, the presence of a round-robin ((KRUGOVAYA)) information system, and the mastery of flight cruise regimes at supersonic speeds.  The achievement of a cardinal decrease of the airplane's observability in the radar and infrared ranges coupled with a transition of the on-board sensors to passive methods of receiving information also for regimes of increased security.  The integration of all information sensors and the creation of on-board expert systems was proposed.

The fifth generation airplane was supposed to possess the ability to realize all-aspect firing at targets in a dog fight and to carry out multichannel missile fire during combat at long range. High maneuverability was one of the most important requirements for the Russian fighter - the ability to maintain stability and control at angles of attack of 90 degrees and more.

As one of the solutions, which assured the receipt of the required maneuvering characteristics, the use of a forward-swept wing (KOS) was examined.  They tried to use such a wing, which provides definite lay-out advantages in comparison with a swept-back wing, as early as the 1940s.  However, the realization of all the advantages of such a wing at that time was unsuccessful because of the lack of the necessary construction materials and technologies.  They returned to the forward swept wing only in the middle of the '70s.  The use of the KOS allowed an improvement in control at low flight speeds and an increase of aerodynamic effectiveness in all flight regimes.  The configuration with a forward swept wing provided a better coupling of the wing and fuselage and optimized pressure distribution on the wing.

Work on the creation of the shape of the domestic maneuverable airplane with a KOS was led by the country's largest aviation and scientific centers - the Central Aerohydrodynamics Institute ((TsAGI)) and the Siberian Scientific Research Institute of Aviation.  In particular, at TsAGI a model of an airplane with a KOS was tested in a wind tunnel which was based on a MiG-23 airplane, and in Novosibirsk a configuration of an Su-27 with a forward swept wing was studied.  Having had this scientific margin allowed the Sukhoy OKB to come to the unheard of conclusion of the complex task of creating the first highly maneuverable combat airplane in the world with a forward swept wing.  And this work was completed successfully - on 25 September the prototype S-37 "Berkut" fifth generation fighter, piloted by test pilot Igor' Votintsev, completed its first flight.  The "Berkut" was executed in accordance with an aerodynamic "longitudinal integral triplane" scheme, which in a way the OKB built.  The well-developed wing extensions ((RAZVITYE KRYL'EVYE NAPLYVY)), beneath which fixed air intakes are located, are among the features of the configuration.  The fighter's wing has a well-developed root with a large sweep angle along the leading edge and which smoothly mates the cantilever part with forward sweep with it.

The twin ruddered vertical tail is attached to the center wing section of the wing and has a large cant to the outer side.

While armament most likely is not installed on the prototype, a large part of it will be located inside the airframe.

The S-37 is covered with radar-absorbing materials.  The prototype is equipment with two D30F6 engines (2x15,500 kg of power), which also are used on the MiG-31 fighter interceptors.  In the future, it is planned to replace the engines with new generation engines, which have a greater thrust, lower specific fuel consumption and a simpler design with the use of the newest technologies.  The location and dimensions of the antennas are evidence of the attempt of the designers to provide a circular radar view.  Besides the basic radar, which is located in the nose beneath a finned radome ((OREBRENNYJ OBTEKATEL')), the fighter has two rear view antennas which are installed between the wing and the engine nozzles.  The leading edges of the vertical tail, wing extension and canard also are occupied with antennas of various designation.

The "Berkut" is equipped also with an optical locating station, which is located in the nose part of the fuselage, in front of the airman's windscreen.  As it is too on the SU-33 and Su-35 fighters, the station housing is off-set to the right so as not to limit the view for the airman.

The main gear of the new fighter have one wheel each and are retracted into the fuselage.  The forward twin-wheel strut is retracted into the fuselage by rotating forward.   The S-37's canopy glazing is practically identical to the glazing of the Su-27 fighter.  However, on the model of the "Berkut" in "static configuration, a photograph of which ended up on the pages of the foreign press, the airplane's canopy is executed as unsegmented ((BESPEREPLETNYY)), as on the American "Raptor."  In a number of publications, without reference to sources, the characteristics of the new airplane are given.  If they correspond to reality, then the "Berkut" on the whole is in the "weight category" of the Su-27 fighter and its modified variants.  The advanced aerodynamics should assure it superiority in a maneuvering dog fight over all existing or forecast potential enemies.  All other fighters on meeting with the Russian "Berkut" have extremely modest chances of returning to their airfield.

Source:  28.06.02, Vechernyaya Ryazan'