With acceptance of the I-3 for series production, Polikarpov and his team commenced work on a smaller, lighter fighter, the I-6, powered by a 450hp Gnome- Rhone Jupiter VI air-cooled radial.
A single-bay, unequal span biplane of wooden construction with fabricskinned wings and a monocoque fuselage, the I-6 was flown on 30 March 1930, two prototypes appearing in the annual May Day fly-past over Moscow in that year. Prior to the commencement of flight testing, Polikarpov had been arrested (in September 1929), accused of "exercising insufficient energy in bringing assigned work to fruition", and, together with Dmitri P Grigorovich, was already working whilst in detention on a further fighter (the I-5). Comparative trials were subsequently performed between the I-6 and the I-5, the latter being selected for series manufacture after prolonged evaluation. The I-6 was the faster in level flight, but offered a poorer rate of climb and was less manoeuvrable. Development was therefore discontinued in favour of the I-5.
Max take-off weight: 1280 kg / 2822 lb
Empty weight: 868 kg / 1914 lb
Wingspan: 9.70 m / 32 ft 10 in
Length: 6.78 m / 22 ft 3 in
Wing area: 20.50 sq.m / 220.66 sq ft
Max. speed: 280 km/h / 174 mph
Range: 700 km / 435 miles