The S-37 Berkut [Golden Eagle] is a testbed for developing technologies for the next generation of aircraft. The basic dimensions and weight of the S-37 "Berkut" are similar to those of Su-37, although they are different aircraft, and the tail, nose and canopy are similar to those of the Su-35. The first two prototypes of this aircraft were evidently designated the S-32, and the S-37 designation was previously applied to an unrelated fighter project for a smaller delta wing single aircraft that was cancelled due to lack of funding.
The S-37 features forward-swept wings, which promises a range of benefits in aerodynamics at subsonic speeds and at high angles of attack. The forward-swept wing, which enables the aircraft to increase its range and its manoeuvrability at high altitude, makes extensive use of composite materials. The aircraft has large canards mounted on the intake side, close to the leading edge of the wing. The vertical stabilizers are canted slightly outward [not inward, as previously believed], and two large auxiliary intake doors are visible on the center fuselage section. It is still unclear which engines are used on this aircraft. The two powerplants are at the moment D-30F6 turbojets which are normaly used at the MiG-31M, while the second prototype uses the Ljulka AL-37FU turbojet with thrust vectoring. The S-37 is an experimental programme for developing fifth-generation technologies, and any decision on serial production of this aircraft would be taken by the Ministry of Defence at a later date.