The Polikarpov 2I-1N (DI-1) was a two seat fighter that was the first in a long line of biplane fighters designed by Nikolai Polikarpov. The 2I-1N was designed to serve as an escort fighter and reconnaissance aircraft. Its original designation indicated that it was a two-seat fighter (Istrebital) and the first to use the 450hp Napier Lion inline engine.
The 2I-1N had a wooden semi-monocoque fuselage constructed from layers of veneered wooden sheets. The fuselage was impressively streamlined, starting with a large propeller spinner that merged seamlessly into the rest of the aircraft. The aircraft was armed with two 7.62mm machine guns - one fixed forward firing PV-1 gun mounted above the nose (some sources say two, but photographs show one) and one flexibly mounted DA machine in the rear observer's cockpit.
The 2I-1N made its maiden flight on 12 January 1926, and eight more flights followed, with Polikarpov flying in the observer's position on the fourth and eighth flight. Tragically during the ninth flight on 31 March 1926 the skin came off the right upper wing causing a crash in which the aircraft was destroyed and both crewmen killed. The cause of the crash was later established as poor build quality, with the glue either badly applied or missing. Polikarpov's later aircraft were more solidly built - the Polikarpov I-3, which was based on the 2I-1N, had an empty weight of 3,086lb, an increase of 544lb on the 2I-1N, despite being a single seat design.
The 2I-N1 was retrospectively redesignated as the DI-1, or two-seat fighter number 1, becoming the first in a short series of aircraft that included the Polikarpov DI-2, itself developed from the I-3.
Engine: Napier Lion inline engine
Wing span: 39.38ft
Empty Weight: 2,542lb
Loaded Weight: 3,748lb
Max Speed: 166.5mph
Service Ceiling: 23,300ft
Range: 500 miles
Armament: One forward firing 7.62mm PV-1 machine gun and one flexibly mounted 7.62mm DA machine gun