Details of the Sukhoi Design Bureau's work on the stealthy aspects of the T-50 PAK FA fighter aircraft emerged in late December 2013, when the company's patents were published.
According to the patent paperwork, taken together, all of the stealthy measures offer significant improvements over legacy fighter designs. The papers claim that the radar cross-section (RCS) of an Su-27 was in the order of 10-15 m 2 , with the intention being to reduce the size of the RCS in the T-50 to an " average figure of 0.1-1 m 2 " ..