Development
Originally known as the S-37, Sukhoi redesignated its advanced test aircraft as the Su-47 in 2002. Officially nicknamed Berkut (Golden Eagle), the Su-47 was originally built as Russia's principal testbed for composite materials and sophisticated fly-by-wire control systems.
TsAGI 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. Rearward-swept wings yield a higher maximum lift coefficient, reduced bending moments, and delayed stall when compared to more traditional wing shapes. At high angles of attack, the wing tips remain unstalled allowing the aircraft to retain aileron control. Conversely, forward sweep geometrically creates increased angle of incidence of the outer wing sections when the wing bends under load. This creates more lift, more load, more angle of incidence, etc. This leads to a tendency for the wings to fail structurally at lower speeds than for a straight or aft-swept wing. Forward swept wings counter this by being designed to twist downward as they bend upward. This twisting-as-it-bends is done with composite materials on the S-37, but it can also be done, to an extent, with conventional materials.
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 Su-47 was primarily a technology demonstrator for future Russian fighters; however, Sukhoi briefly attempted to market the Su-47 to the Russian military and foreign customers as a production fighter in its own right.
Read more about this topic: Sukhoi Su-47
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