 As a test bed for the new engine, OKB-155 was authorised on 20 April 1951 to convert one of the prototype MiG-17s, replacing the single Klimov VK-1 engine with two AM-5s (later replaced by AM-5As), with the testbed, designated SM-1 (or I-340), flying late in 1951.While the SM-1 was a useful testbed, its performance was less than expected, and first resulted in an afterburner being designed for the AM-5, resulting in the AM-5F (reaching with reheat).While the SM-1 was a test bed, the SM-2 (or I-360) was intended as the required supersonic escort fighter, with work authorised on 10 August 1951.