MiG 19P / SM12/3 / SM12/1 / SM12/2

Plans for the SM-12/3 originated in the PVO’s need for a fast, high-alti – tude interceptor. Compared with the MiG-19 prototype, the SM-12/3 had a longer forward fuselage and thinner rims around the engine air intake, which encircled a two-position nose dome housing the radar antenna. This arrangement was chosen to reduce the ram pressure losses in the intake. The AM-9B (RD-9B) turbojets were replaced by R3- 26s rated at 3,725 daN (3,825 kg st) and built by a subsidiaiy of the Mikulin OKB managed by V. N. Sorokin. This change of power unit forced engineers to modify the nozzle throats and to install new heat shields in the engine bay

Other modifications included: more reliable BU-13MSK and BU – 13MK servo-controls for the slab tailplane and ailerons; the new APS – 4MD electric stabilator trim actuator, cutting to a quarter the time required to set up the slab tailplane on the MiG-19S; and more unguid­ed rockets to offset removal of the NR-30 cannon from the fuselage. These and other changes greatly enhanced the performance of the SM – 12/3 over that of the MiG-19S. Maximum speed jumped from 1,430

km/h (772 kt) to 1,930 km/h (1,042 kt), and service ceiling improved from 17,500 m (57,400 feet) to 18,000 m (59,000 feet). The latter alti­tude could be reached in just 3.2 minutes. Thus a significant increase in speed and ceiling had been achieved without modifying the aircraft’s structure noticeably and increasing its weight or the thrust of its power unit appreciably.