Mikoyan-Gurevich MiG-15UTI, part one

The Mikoyan-Gurevich MiG-15UTI was the two-seat trainer variant of the Mikoyan-Gurevich MiG-15bis. It has been regarded as one of the most successful jet-trainer aircraft of all time and, with almost 5500 exemplars having built it's also one of the most produced aircrafts in history.
It was designed by Mikoyan-Gurevich OKB (which stands for "design bureau") and flew for the first time on 27th June 1949. It was produced from 1950 until 1959, just in Soviet factories and, the licensed variants like the Czechoslovak Aero CS-102 ,the Chinese Shenyang JJ-2/FT-2 or the Polish WSK-Mielec SB Lim-1 and Lim2 were still under production as late as 1958 and, in the Chinese case most probably until early-to-mid 1960s. The first factory to produce the UTI variant was the Kuybyshev Aircraft Factory No.1 "Stalin", located at Kuybyshev which manufactured the UTI from 1950 until 1953 which, manufactured 881 exemplars. The second factory to manufacture it was Ulan-Ude's Aircraft Factory No.99, in Ulan-Ude. This one, with 1117 exemplars manufactured from 1951 until 1959 has the record of being the one that most MiG-15UTIs manufactured. The third factory to manufacture it was Kharkov's Aircraft Factory No. 135, in Kharkov which produced 511 of them from 1950 until 1954 and the fourth factory to manufacture it was Novosibirsk's Aircraft Factory No.153, in Novosibirsk which made 924 exemplars making it the second most productive one.
Just like the regular Mikoyan-Gurevich MiG-15, the UTI version was powered by a single Klimov RD-45F which delivered a thrust power of 5005lb (22.26KN), had an internal fuel tank of 1080L (238 imp. gal. or 250 US gal.) with the possibility of carrying two additional external fuel tanks on the wings with a capacity of 400L (88imp. gal, 106 US gal.) each. It was armed with a single 12,7mm (0,5in) UBK-machine gun placed under the nose and could also mount a single 23mm NR-23 cannon also under the nose. It had also hardpoints to carry either two 50kg (110lb) or 100kg (221lb) bombs underwings.
Due to its high success and popularity, it was quickly adopted as the VVS main trainer and remained in that role until the fall of the USSR in 1992 and, some of the ex-Soviet republics still kept it in active combat service during the conflicts of the 1990s. At VVS's command was used not only in the trainer role but also in the recon role during the 1960s (and more exactly to watch the Czechoslovak-German border during the Soviet Invasion of Czechoslovakia, AKA the Prague Spring) and the type became famous because the first man in space, Yuri Gagarin, was killed in a crash during a training flight in a MiG-15UTI due to poor visibility.
A sub-variant, the MiG-15UTI-P was a single prototype designed in Czechoslovakia by the "1st Aviation Repair Division" (translation not 100% precise) in 1957 which was unarmed but was equipped with a Izumrud RP-1 radar mounted in the nose (which was the same radar type the MiG-17PF had) and was intended to train pilots in the usage of airborne radar. However it wasn't accepted into production as there was already another type covering that need.

Sources:
1. https://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-15
2. https://forum.valka.cz/topic/view/22676
3. https://forum.valka.cz/topic/view/12489