Mikoyan-Gurevich I-3

The Mikoyan-Gurevich I-3 was the first of three closely related fighter prototype programs developed by the Mikoyan-Gurevich design bureau in the Soviet Union in the mid/late 1950s - starting with the I-3, continuing with the I-7 and finally evolving into the I-75. On several occasions airframes were re-built and/or re-used both within a program or in a succeeding program. All the aircraft in the I-3 program were affected by delays in the development of the Klimov VK-3 turbojet engine, its cancellation and replacement by the Lyulka AL-7F turbojet engine.

Design and development
Both the I-3 and I-3P were ordered by the Council of Ministers on June 3, 1953 – the I-3 as a front-line fighter and the I-3P as an all-weather interceptor. They were developed in parallel with the I-1/2 program but with nothing in common except for a similar wing. On the other hand, the I-3’s visual appearance was so similar to the Sukhoi S-1 (the Su-7 prototype) that a common design specification and fundamental research source seems likely. Compared to the Mikoyan-Gurevich MiG-19 the I-3U was slightly larger and heavier, but aerodynamically very similar.

I-3 (I-380)
The I-3 had a longer forward fuselage compared to the I-1 and the cockpit was positioned further ahead of the 60 degree swept wing. Armament consisted of three 30 mm Nudelman-Richter NR-30 cannons each with 65 rounds – one in left wing root and two on the right side. The Klimov VK-3 turbojet was never provisioned or fitted to the airframe. In 1956 the I-3 was converted into the I-3U.

I-3P
Developed in parallel with the I-3 but equipped with the same Almaz search radar as the I-1. Armament consisted of two 30 mm Nudelman-Richter NR-30 cannons. In addition two ORO-57K rocket launchers each with 16 55 mm ARS-57 (S-5) unguided rockets or two 190 mm TRS-190 unguided rockets or two 212 mm ARS-212 unguided rockets or two 250 kg bombs could be carried on pylons under the wing. Development was halted in late 1954.

I-3U (I-5)
The I-3U was modified from the unfinished I-3; the fuselage was stretched 93 cm (from 12.27 m to 13.20 m), the nose redesigned to accommodate the Uragan-1 fire control system (hence the U in the designation) above the inlet and an Almaz search radar with a search/track range of 17 km was fitted in the cone centered in the inlet. Armament consisted of two 30 mm Nudelman-Richter NR-30 cannons with symmetrical auto ranging connected to the radar. 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 was completed in 1956.

Flight testing took place on an irregular basis in 1956-1958 due to engine flaws and frequent modifications. A total of 34 test flights were carried out, with design bureau test pilot Georgiy Mossolov reaching a speed of 1960 km/h at attitude on one flight. The program was cancelled on June 17, 1958.

Source criticism
The sources generally agree on which airframes from the I-3 program that was rebuilt (I-3 into I-3U). But one of the external links says it was I-3P that was rebuilt into I-3U. The sources all agree on that the I-3 is the same as the I-380 (using the old design bureau designation series), but they all disagree on the (old) designations for the I-3P and the I-3U. One says that the I-3U was the I-400 while another uses I-410 for the I-3U and also puts the label I-5 on it. One source even uses the I-420 designation for the later I-7U. The online source and the external links all use I-410 for the I-3P and I-420 for the I-3U.