Mikoyan/Gurevich I-230 (MiG-3U)

With the primary objective of improving the aerodynamics of the basic MiG-3 design, the OKB began work late in 1941 on an enhanced version of the fighter to which it gave the Izdeliye designation of D. Known officially as the I-230, and later as the MiG-3U - the suffix letter signifying uluchshenyi (improved) - the new fighter was first flown in August 1942. Whereas the fuselage of the MiG-3 was primarily of steel tube with duralumin skinning, that of the I-230 was almost entirely of wood owing to the contemporary metal shortages. By comparison with the MiG-3, the fuselage was lengthened by 37cm, but the Mikulin AM-35A engine was retained and the wing of the first prototype was unchanged, armament consisting of two 20mm SP-20 (ShVAK) cannon mounted above the engine. The second prototype differed in having a larger wing of 18.00m² area and spanning 11.00m. Performance proved good during factory and state trials, but it was not possible to reinstate production of the AM-35A and production of the I-230 was therefore restricted to a pre-series of five aircraft which were assigned to a Guards Regiment (1 GvIAP) on the Kalinin front for service evaluation.