Polikarpov I-1M-5 (IL-400)

Working at the former Duks factory (GAZ 1) at Khodinka, Moscow, Nikolai N Polikarpov, assisted by I M Kostkin, designed a conceptually advanced single-seat fighter, the IL-400, which flew on 15 August i923. A cantilever low-wing monoplane of wooden construction powered by a 400hp Liberty water-cooled engine, the IL-400 proved longitudinally unstable and crashed shortly after becoming airborne on its first flight. Extensive redesign, both aerodynamic and structural, resulted in the IL-400b (also to be known as the IL-2), which, flown on 18 July 1924, retained a plywood-covered wooden fuselage mated with an entirely new, shorter span, thinner-section wing with dural ribs and corrugated dural skinning. Armament comprised two 7.62mm machine guns. Following State trials, contracts were placed for eight and then a further 25 of a modified version of the fighter which reverted to all-wood construction. Designated I-1M-5 (and also referred to as the IL-3) and powered by an M-5 engine - the licence-built version of the 400hp Liberty - this completed State tests on 16 March 1926. The series I-1M-5 suffered from low manufacturing standards, however, was seriously overweight and dangerously unstable. It was not, therefore, delivered to service units.