Complex sentence: In addition to the fire control system Mikoyan-Gurevich also used, for the first time, titanium alloys in the rear fuselage where high temperatures were expected, with conversion from I-3 to I-3U being completed in 1956.
Split into simpler sentences: In addition to the fire control system Mikoyan-Gurevich also used, for the first time, titanium alloys in the rear fuselage where high temperatures were expected. The conversion from I-3 to I-3U being completed in 1956.