Research aircraft rocket powered aircraft. The LL had a streamlined Bell X-1 looking fuselage and swept tail plane. It seems to have been intended to fit it with a rocket engine, but it is not sure whether this was ever done.
According to other sources ("Osprey Encyclopedia of Russian Aircraft 1875-1995" by Bill Gunston), LL was flown in 1949. Three LL's were built - with straight wing LL-1, with normal swept wing LL-2 and LL-3 with 40° forward swept wing.