Yakovlev Yak-1 - Design and Development

Design and Development

Prior to World War II Yakovlev was best known for building light sports aircraft, his Yak-4 light bomber impressed the Soviet government enough to order the OKB to design a new fighter with a Klimov M-106 V-12 liquid-cooled engine. Formal specifications released on 29 July 1939, called for two prototypes - I-26-1 with a top speed of 620 km/h (385 mph) at 6,000 m (16,685 ft), combat range of 600 km (375 mi), a climb to 10,000 m (32,808 ft) of under 11 minutes, and armament of 2 × 7.62 mm ShKAS machine guns and 1 × 12.7 mm (0.5 in) Berezin BS heavy machine gun, and I-26-2 with a turbocharged M-106 engine with a top speed of 650 km/h (404 mph) at 10,000 m (32,808 ft) and armament of 2 × 7.62 mm (.3 in) ShKAS machine guns. The design took full advantage of Yakovlev OKB's experience with sports aircraft and promised agility as well as high top speed. Since the M-106 was delayed, the design was changed to incorporate the Klimov M-105P V-12 engine, with a 20 mm (.8 in) ShVAK cannon in the "vee" of the engine block.

I-26-I first flew on 13 January 1940. The prototype suffered from oil overheating problems which were never completely resolved resulting in 15 emergency landings during early testing. Then, on 27 April 1940, I-26-1 crashed, killing its test pilot Yu.I. Piontkovskiy. The investigation of the crash found that the pilot performed two consecutive barrel rolls at low altitude which was in violation of test flight plan. It was believed that during the first roll, the main landing gear became unlocked, causing it to crash through the wing during the second roll. It has been hypothesized that Piontkovskiy's deviation from the flight plan was caused by frustration that his aircraft was being used for engine testing while I-26-2, built with the lessons of I-26-1 in mind, was already performing aerobatics.

Technical issues with subassemblies provided by different suppliers raised the I-26-2's weight 400 kg (882 lb) above projected figures, which restricted the airframe to only 4.4 G while overheating oil was still a problem. The many defects caused I-26-2 to fail government testing in 1940. Fortunately for Yakovlev, its competitors I-200 (future Mikoyan-Gurevich MiG-3) and I-301 (future LaGG-3) also failed testing. Requested improvements were incorporated into I-26-3 which was delivered for testing on 13 October 1940. Although it passed on 9 December 1940, the aircraft was still very much unfinished with unresolved engine problems.

Troublesome and slow testing and development must have been quite worrisome for Soviet officials considering the fact that the I-26 was ordered into production under the name "Yak-1" on 19 February 1940, a mere month after I-26-1 made its maiden flight. The goal of this gamble was to reduce lag time between prototype and production aircraft. As a backup, the I-200 and I-301 were also ordered into production. Although the Yak-1 was slower than the I-200 and less heavily armed than the I-301, it enjoyed the advantage of having been started earlier which gave it a consistent lead in testing and development over its competitors. Beginning of the Axis invasion of the Soviet Union on 22 June 1941 made development and implementation of several other upcoming promising designs like Polikarpov I-185 unfeasible. The fact that Yakovlev might have been Joseph Stalin's personal favorite may have also played in the Yak-1's favor.

Simultaneous manufacturing and testing of a design that required as many improvements as I-26 wreaked havoc on the production lines. Almost 8,000 changes were made to the aircraft's blueprints by 1941 with an additional 7,000 implemented the following year with 5,000 more changes coming in 1942. Production was further slowed by shortages of engines, propellers, radiators, wheels and cannons. Shortages of quality materials resulted in plywood being torn off the wings on several aircraft. To make matters worse, Factory No.292 which was the main manufacturer of Yak-1s was bombed on 23 June 1943 and burned to the ground. Amazingly, production resumed among the ruins on 29 June. Due to loose tolerances, each aircraft was essentially unique with workers performing the final assembly having the unenviable task of mating what often proved to be somewhat dissimilar components. For example, left and right main landing gear could be of different lengths and different angles relative to the aircraft which required adjusting their attachments to ensure an even stance for the completed aircraft. Parts were often non-interchangeable between aircraft. Production of Yak-1 ended in July 1944 with somewhere around 8,700 built.