the need to change "275" missiles to the lighter "275A" (although total missile weight decreased to , the warhead actually grew to ). The new airframe with a smaller fuselage and a delta wing instead of the earlier swept wing was designated La-250A. The "275" missiles were now carried on underwing pylons. The lighter airframe was not enough to overcome the weaker engines, and projected performance suffered compared to La-250. While busy redesigning the aircraft, Lavochkin OKB also had to develop new variants of the "275" missile - the semi-active radar homing "277," the nuclear-armed "279," and solid fuel rocket-powered "280." The first La-250A prototype was finally rolled out on 16 June 1956. Test flights of the five prototypes were plagued by crashes caused by failures of the hydraulic boost system and landing gear as well as poor forward visibility (the latter was corrected with fitting of a new slightly "drooped" nose). La-250A made a single test flight in 1956, only 6 flights in 1957, and a mere 14 flights in 1958. Frustrated by the lack of progress, Soviet Air Force stopped all work on the K-15 system in 1959. Lessons learned with K-15 were used to develop new interceptor system requirements which led to the Tupolev Tu-28 interceptor. Survivors One of Lavochkin La-250A prototypes is on display at the Central Air Force Museum at Monino, outside of Moscow, Russia. Specifications (La-250A) See also Sources Kopenhagen, W (ed.), Das große Flugzeug-Typenbuch, Transpress, 1987, Ла-250 Анаконда – Уголок неба. 2008 250 Abandoned military aircraft projects of the Soviet Union 1950s Soviet fighter aircraft Twinjets Delta-wing aircraft Mid-wing aircraft Aircraft first flown in 1956