The Polikarpov I-185 was a high performance fighter that almost entered production, before problems with its engine caused the project to be cancelled.
The entire project was dogged by engine problems. After the cancellation of the I-180 Polikarpov decided to develop a new fighter using the most powerful experiment engine he could find, in this case the Nazarov M-90. This was a radial engine that was hoped to produce 2,000hp, but in practise it failed to reach this level of power. The I-185 was a low-wing monoplane, similar in appearance to the I-180, but with a small thin all-metal two-spar wing covered with a duralumin stressed skin.
The first prototype was developed during 1940. It was originally powered by the developmental M-90 engine, and was to be armed with two 7.62mm and two 12.7mm machine guns. It was expected to reach 444mph at 24,000ft, but taxiing trials reveals that the engine didn’t even have enough power to get the aircraft off the ground. Another new engine, the Shvetsov M-81, was installed instead, but this too was under-powered, and after a single flight on 11 January 1941 this aircraft was grounded. In May of the same year development of the M-81 engine itself was also cancelled.
Late in 1940 Polikarpov began work on a second prototype, this time powered by the 1,700hp Shvetsov M-82A, which had a smaller diameter than either of the earlier engines. This reduced drag, and this improved the aircrafts speed. This second prototype was armed with three 20mm ShVAK cannon, all mounted in the nose. Flight tests began in May 1941. Although this aircraft never entered production, it did provide valuable data for the development of the La-5 and a version of the Yak-7 powered by the same engine.
A third prototype soon followed, this time powered by the Shvetsov M-71 engine, a 2,000hp 18-cylinder radial engine. The tests on this version were interrupted by the German invasion in the summer of 1941, which forced Polikarpov and zavod 51 to move east, but they were successful enough to justify further work, and to see the first prototype re-engined with the M-71. This model performed very well in tests, with a top speed at 20,250ft of 391mph, and was judged to be equal or better than every current production fighter.
In the spring of 1942 it was decided to place the I-185 M-71 into production. A production standard prototype was produced, and went to state trials on 18 November. This coincided with the start of service trials with the 728th IAP of the 3rd Air Army. The I-185 was very popular with this unit's pilots, but once again the engine would prove to be its weakest point. The trials had to be halted between mid December 1942 and mid-January 1943 until a new engine arrived, and this failed after only 24 hours of running. A few days, on 27 January 1943, a test pilot was killed while attempting to land after yet another engine failure, and the first prototype was destroyed in a crash on 5 April. It was clear that the M-71 engine was not yet ready for front line service, while the only valid alternative, the M-82, was needed for the La-5. As a result production of the I-185 was cancelled.
I-185 M-71 (production prototype)
Wing span: 32.2ft
Empty Weight: 5,973lb
Take-off Weight: 8,000lb
Max Speed: 403mph at 20,000ft
Service Ceiling: 36,000ft
Range: 497 miles
Armament: Three 20mm cannon