ot ▁ 3 4 6 " ▁(" Sam oly ot " ▁- ▁A ircraft ) ▁to ▁distance ▁it ▁from ▁its ▁German ▁orig ins , ▁was ▁completed ▁and ▁tested ▁in ▁Ts AG I ▁wind ▁tunnel ▁T - 1 0 1 . ▁Test s ▁revealed ▁some ▁aer od ynamic ▁def ic ien cies ▁which ▁would ▁result ▁in ▁un rec over able ▁st alls ▁at ▁certain ▁angles ▁of ▁attack . ▁This ▁phenomen on ▁involved ▁a ▁loss ▁of ▁longitud inal ▁stability ▁of ▁the ▁air frame . ▁After ▁the ▁wind ▁tunnel ▁tests , ▁two ▁wing ▁f ences ▁were ▁installed ▁on ▁a ▁more ▁advanced , ▁longer ▁version ▁of ▁the ▁D FS - 3 4 6 , ▁the ▁purpose ▁of ▁f ences ▁was ▁to ▁interrupt ▁the ▁span wise ▁movement ▁of ▁air flow ▁that ▁would ▁otherwise ▁bring ▁the ▁boundary - layer ▁break down ▁and ▁transition ▁from ▁attached ▁to ▁st alled ▁air flow ▁with ▁loss ▁of ▁lift ▁and ▁increase ▁of ▁drag . ▁ ▁This ▁solution ▁was ▁used ▁on ▁the ▁majority ▁of ▁Soviet ▁plan es ▁with ▁swe pt ▁wings ▁of ▁the ▁ 1 9 5 0 s ▁and ▁ 1 9 6 0 s . ▁In ▁the ▁meant ime , ▁the ▁escape ▁caps ule ▁system ▁was ▁tested ▁from ▁a ▁B - 2 5 J ▁and ▁proved ▁prom ising . ▁Despite ▁results ▁from ▁studies ▁showing ▁that ▁the ▁plane ▁would ▁not ▁have ▁been ▁able ▁to ▁pass ▁even ▁Mach ▁ 1 , ▁orders ▁were ▁given ▁to ▁proceed ▁with ▁construction ▁and ▁further ▁testing . ▁ ▁Oper ational ▁use ▁In ▁ 1 9 4 7 , ▁an ▁entirely