Acceptance that the concept of the I-180 was outmoded coupled with the prospect of the availability of powerful 18-cylinder radial engines led the Polikarpov OKB to design the I-185 within an extraordinarily short period of time (25 January to 10 March 1940). Intended for the 1,750hp Shvetsov M-90 engine, the I-185 was of mixed construction, having a wooden monocoque fuselage mated with metal wings featuring automatic leadingedge slats a la Bf 109. Armament consisted of twin 12.7mm and twin 7.62mm guns, all fuselage-mounted. Development delays with the M-90 - which, by December 1940, was cleared only for restricted flight testing - resulted in dismantling of the first prototype unflown, this having been known as Samolet (Aircraft) R.
A second prototype. Samolet RM, was completed with a Shvetsov M-81 18-cylinder two-row radial and a ducted propeller spinner. This was flown on 11 January 1941, but the M-81 was found to develop insufficient power and was replaced by the Shvetsov M-71 of 1,900hp in May 1941. A third prototype, Samolet I, was completed with a 14-cylinder Shvetsov M-82 engine rated at 1,330hp (later 1,400hp), the fuselage being lengthened for CG reasons from 7.68m to 8.10m, and fuselage-mounted armament being changed to three 20mm cannon. State Acceptance Tests were conducted successfully between 13 April and 5 July 1942. A fourth prototype reverted to the M-71 engine and this underwent operational evaluation on the Kalinin Front alongside Samolet I. A redesigned wing (of single - in place of two-spar construction) was featured by this aircraft, which was tested with both the four-machine gun and three-cannon armament arrangements. A pre-production prototype, the so-called I-185 Etalon (Standard), was flown on 10 June 1942. Regarded as the forerunner of the intended production derivative, the I-186, this standardised on the M-71 engine and three-cannon armament, and had a similarly lengthened fuselage to that of Samolet I. State Acceptance Testing was conducted between November 1942 and January 1943, the NIl VVS evaluation reports describing the I-185 Etalon as "superior to all contemporary fighters." In the event, it was found impracticable to manufacture the M-71 in large numbers and airframe production capacity was unavailable.
Max take-off weight: 3735 kg / 8234 lb
Empty weight: 3130 kg / 6901 lb
Wingspan: 9.80 m / 32 ft 2 in
Length: 8.05 m / 26 ft 5 in
Wing area: 15.53 sq.m / 167.16 sq ft
Max. speed: 680 km/h / 423 mph