The Sukhoi Su-47 Berkut (Russian: Су-47 Беркут - Golden Eagle), also designated S-32 and S-37 during initial development, is an experimental supersonic jet fighter developed by Sukhoi Aviation Corporation.
Although the aircraft was build as a testbed for developing fifth-generation technologies, in May 2002 Sukhoi was selected as prime contractor for the next-generation Russian PAK FA fighter programme. Although the SU-47 will be used for the PAK AF program, the design of it will probably be very different.

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. It also retains it's high manoeuvrability in supersonic flight.

Maximum turn rates and the upper and lower limits on air speed for weapon launch are important criteria in terms of combat superiority. The Su-47 aircraft has very high levels of manoeuvrability with maintained stability and controllability at all angles of attack.
Maximum turn rates are important in close combat and also at medium and long range, when a mission may involve engaging consecutive targets in different sectors of the airspace.

The high turn rate of the Su-47 allows the pilot to turn the fighter aircraft quickly towards the next target to initiate the weapon launch. The swept-forward wing, compared to a swept-back wing of the same wing area, provides a number of advantages: higher lift to drag ratio; higher capacity in dogfight manoeuvres; higher range at subsonic speed; improved stall resistance and anti-spin characteristics; improved stability at high angles of attack; a lower minimum flight speed; and a shorter take-off and landing distance.

The SU-47's initial engine, the Saturn-Lulka Al-41F thrust vectoring engine was scarcely available, they were reserved for Mikoyan's Article 1.42 tests.
The final engine, the Al-37FU uses fuel instead of hydraulic liquid to drive the nozzles, and can be operated in two modes, automatic and manual. In automatic more, the axi-symmetric nozzles are controlled by the digital fly-by-wire flight control system (FCS).

via: http://www.videocu.lt/news.php?id=55
links: http://www.airforce-technology.com/projects/s37/
http://en.wikipedia.org/wiki/PAK_FA