Mikoyan/Gurevich MiG-13 (I-250)
|Virtual Aircraft Museum / USSR / Russia / Mikoyan/Gurevich
In February 1944, the MiG OKB initiated the design of a mixed-power single-seat fighter with the Izdeliye designation N. Conceived to use the so-called "accelerator", or VRDK (Vozdushno-reaktivny dvigatyel kompressorny, or Air-reaction engine compressor), which had been developed at the TsIAM under the leadership of K V Kholshchevnikov, the N preliminary design was finished on 28 March 1944. Drawings were completed by 30 November 1944, by which time the official designation I-250 had been applied to the project, and three months later, on 26 February 1945, the first of two prototypes, the N-1, left the factory. Primary power was provided by a Klimov M-107A (VK-107A) 12-cylinder Vee-type engine rated at 1650hp for take-off and armament consisted of three 20mm G-20 cannon, one between the engine cylinder banks and the others flanking the engine.
The first flight took place on 3 March 1945, and the VRDK was fired for the first time during the third test flight. The VRDK consisted of an engine-driven compressor which fed compressed air via a water radiator to a mixing chamber in which fuel was introduced under pressure, the mixture being ignited in a double-walled combustion chamber and then ejected through a variable orifice. This provided 300kg of thrust for up to 10 minutes, boosting speed by 100km/h. N-1 crashed during mid-May when the permissible load factor was exceeded and the horizontal tail collapsed at low altitude, but a second prototype, the N-2, was rolled out on 26 May 1945. This lacked armament and the vertical tail was enlarged to rectify some longitudinal instability, but this prototype, too, was destroyed in an accident. In July 1945, the OKB received instructions to supervise the construction of 10 I-250 aircraft to participate in the Air Parade that was planned for 7 November 1945, barely four months later.
Nine I-250s were ready on time, but inclement weather resulted in cancellation of the Parade. These aircraft, together with a further seven, were subsequently delivered to the Navy as MiG-13s, equipping an evaluation unit based at Skultye airfield, near Riga. Several of the pre-series MiG-13s were experimentally fitted with sabre-shaped propeller blades, and official NII VVS trials were conducted between 9 October 1947 and 8 April 1948. Production of the I-250 alias MiG-13 had totalled 16 pre-series aircraft, and although the fighter was essentially successful, it had been overtaken by pure jet fighters and surviving examples were retired by the Navy in May 1948. The following performance data relate to the N-1, weights and dimensions being applicable to the MiG-13.