... So, back in 2010 it became clear that the aircraft was designed somewhat unsuccessfully. It could not withstand the required operational overloads, rivets were cut off at the air intakes, air-to-air heat exchangers cracked along the welds, and the fuel in tank No. 3 categorically refused to be spent completely. In order for the first car to safely reach the assigned resource at 300 hours, it was put up for revision in August 2011 (the rest was reinforced at the factory) and started designing the car of the 2nd stage (by the way, the wrench left there was removed from the keel 50-1 key). At the 2nd stage, the proportion of composites increased significantly (almost all the plating became from PCM), but the weight of the airframe, due to the gain of the SS, still increased excessively. Then they decided to replace in many units the dural B95 and AK-5 with an aluminum-lithium alloy 1461T with a specific weight of almost 20% less. In October 2012, the final decision was made on the launch of the 2nd stage in production. It was planned 2 cars - T-50-7 and T-50-8. At that time, there were 3 cars of the 1st stage at various stages of production - 4, 5, 6. But they realized in time, and decided to make 50-7 statics. And in February of the 13th they decided to make a transition model and assigned it the T-50-6 index. In order to avoid confusion, the T-50-6 of the first stage was called the T-50-6-1, and the car of the second stage was called the T-50-6-2.
But, among the imported components for the T-50 were American carbon fiber structures, widely used in the wing and tail. Our military leadership decided that this was unacceptable and decided to "import-substitute" and instructed the DGP "Technology" from Obninsk to develop domestic cellular materials. By the way, all other composites for T-50 are also made in Obninsk. It is expected, Obnitsy set all the deadlines. As a result, with grief Sagittarius (he is now PAK PAK, not Davidenko) in May, he even proposed to remove the plumage from the T-50-4 and put it on 6-2, having finished the fairings of drives and semi-axes, but a month ago the cellular fillers finally came.
Alloy 1461 turned out to be another problematic issue. It desperately cracked during machining; here it must also be said that the assembly is still being carried out according to the technologies of the 1970s, that is, the sledgehammer is still quite popular when assembling the components into an assembly. A similar treatment did not transfer the alloy at all. As a result, the reverse transformation of the material of the parts from 1461 to B-95, and sometimes again back to 1461, went. That, of course, led to the indescribable delight of all, especially the hard ones.
Thus, 2013, 2014 passed, and only in February 2015 the fuselage 6-2 was docked ...