▁the ▁N II - V VS ▁( N auch no - I ss led ov atel ' ski y ▁Institut ▁Vo yen no - V oz do osh ny kh ▁Se el ▁– ▁air ▁force ▁scientific ▁test ▁inst itute ) ▁conducted ▁state ▁tests ▁which ▁revealed ▁tail plane ▁buff eting , ▁which ▁was ▁alle vi ated ▁by ▁fitting ▁en larg ed ▁elev ators . ▁The ▁next ▁flight ▁encountered ▁radi ator ▁damage ▁and ▁an ▁engine ▁failure , ▁but ▁in ▁spite ▁of ▁this , ▁the ▁ ▁AN T - 7 ▁passed ▁the ▁state ▁accept ance ▁tests . ▁ ▁Oper ational ▁history ▁Production ▁aircraft ▁were ▁designated ▁ ▁R - 6 ▁by ▁the ▁Soviet ▁Air ▁Force . ▁The ▁first ▁production ▁aircraft ▁was ▁rolled ▁off ▁the ▁G A Z - 2 2 , ▁( GA Z ▁– ▁G os ud ar st ven ny ▁A vi ats ion ny y ▁Z av od ▁– ▁state ▁av iation ▁plant / factory ), ▁assembly ▁line ▁in ▁November ▁ 1 9 3 1 , ▁a ▁year ▁after ▁production ▁started . ▁Another ▁ 4 1 0 ▁aircraft ▁were ▁made ▁during ▁the ▁following ▁three ▁years : ▁ 3 8 5 ▁at ▁G A Z - 2 2 ▁in ▁Moscow ▁( one ▁of ▁these ▁was ▁the ▁R - 6 ▁Lim uz in ), ▁five ▁at ▁G A Z - 3 1 ▁in ▁Tag an rog ▁( float plan es ▁designated ▁K R - 6 P ), ▁and ▁ 2 0 ▁more ▁at ▁G A Z - 1 2 ▁in ▁K oms om ol sk -