Polikarpov DI-1
{{Short description|Soviet aircraft}}
{{good article}}
| {{Infobox aircraft begin
| name=DI-1 (2I-N1) | image=Polikarpov DI-1.jpg | caption= }}{{Infobox aircraft type | type=Fighter | national origin=Soviet Union | manufacturer=Polikarpov | designer=Nikolai Nikolaevich Polikarpov | first flight=12 January 1926 | introduced= | retired= | status=Cancelled | primary user= | number built=1 | developed from= | variants with their own articles= }} |
The Polikarpov DI-1 (DI - Dvukhmesnyy Istrebitel - two-seat fighter), also known as 2I-N1, {{langx|ru|Поликарпов ДИ-1 (2И-Н1)}}, was a prototype Soviet two-seat fighter designed during the 1920s. The sole prototype built crashed on its ninth flight, due to manufacturing defects, and the program was cancelled.
Design and development
Nikolai Nikolaevich Polikarpov began design of a two-seat fighter initially designated as the 2I-N1 (two-seat Istrebitel{{'}} (fighter) with a single Napier engine) in October 1924 at Zavod (Factory) Nr. 1 at Khodynka Aerodrome, Moscow. It was the first Soviet indigenous two-seat fighter.Gordon and Dexter, p. 5 It was a single-bay biplane with its wings arranged in a sesquiplane configuration. The oval-shaped, semi-monocoque fuselage was made of 'shpon', molded birch plywood. The wings were also covered with 'shpon'. The upper wing had two spars, but the lower wing only had one. Internal bracing wires were not used in the wings as it was built up from plywood ribs with large lightening holes and stringers. V-struts made from Duralumin separated the wings and connected the upper wing to the fuselage. Steel bracing wires were used externally. An airfoil enclosed the axle of the fixed undercarriage and a small ski served as a tailskid. It had an imported {{convert|336|kW|adj=on}} Napier Lion engine enclosed in a metal cowling. It carried {{convert|547|kg|abbr=on}} of fuel and oil. The armament consisted of a single fixed {{convert|7.62|mm|abbr=on}} synchronized PV-1 machine gun and a 7.62 mm DA machine gun mounted on a ring in the observer's cockpit.
The first flight of the prototype took place on 12 January 1926 and the DI-1, as it was now known, demonstrated excellent performance. Polikarpov himself flew as the observer on the fourth and eighth test flights. However, during the ninth flight on 31 March 1926, the aircraft was making speed runs over the measured kilometer at Khodynka Airfield at a height of {{convert|100|m|0}} when the upper surface of the right upper wing ripped off, followed by the lower skin. Both right wings then collapsed and the DI-1 crashed, killing both the pilot, V. N. Filippov, and the observer, V. V. Mikhailov.Gunston, p. 288
Examination of the wreckage revealed that large portions of the wings' skin were badly glued and that a number of rib caps and stringers were not glued at all. Many panel pins were not connected to the structure at all and many of the bradawl holes necessary to equalize pressure between the inside of the wing and the outside were missing entirely. The crash of such an advanced aircraft shocked the entire industry and caused a six-month hiatus in design work. Polikarpov overreacted to its loss and built the structure of a number of his subsequent aircraft stronger, and thus, heavier, than it needed to be. All further work on the project was abandoned following the crash, nominally for lack of a suitable engine.
Specifications
{{Aircraft specs
|ref=Istoriia konstruktskii samoletov v SSSR do 1938 {{cite book|author=Shavrov V.B.|year=1985|title=Istoriia konstruktskii samoletov v SSSR do 1938 g. (3izd.)|language=Russian|publisher=Mashinostroenie|isbn=5-217-03112-3}}
|prime units?=met
|crew=2
|length m=9.75
|length note=
|span m=12
|span note=
|height m=
|height note=
|wing area sqm=27.15
|wing area note=
|aspect ratio=
|airfoil=
|empty weight kg=1153
|empty weight note=
|gross weight kg=1700
|gross weight note=
|max takeoff weight kg=
|max takeoff weight note=
|fuel capacity=
|more general=
|eng1 number=1
|eng1 name=Napier Lion
|eng1 type=W-12 water-cooled piston engine
|eng1 kw=336
|eng1 note=
|prop blade number=2
|prop name=fixed-pitch propeller
|prop dia m=
|prop dia note=
|max speed kmh=268
|max speed note=
|cruise speed kmh=
|cruise speed note=
|stall speed kmh=
|stall speed note=
|never exceed speed kmh=
|never exceed speed note=
|range km=800
|range note=
|combat range km=
|combat range note=
|ferry range km=
|ferry range note=
|endurance=
|ceiling m=7100
|ceiling note=
|g limits=
|roll rate=
|climb rate ms=
|climb rate note=
|time to altitude={{cvt|5000|m}} in 13 minutes
|wing loading kg/m2=63
|wing loading note=
|fuel consumption kg/km=
|power/mass={{cvt|0.2|kW/kg}}
|more performance=
- Horizontal turn time: 12 sec
|guns= 2 × 7.62 mm (0.30 in) machine guns
}}
References
{{reflist}}
Further reading
{{refbegin}}
- {{cite book|last=Gunston|first=Bill|authorlink=Bill Gunston |title=The Osprey Encyclopedia of Russian Aircraft 1875-1995|publisher=Osprey|location=London|date=1995|isbn=1-85532-405-9}}
- {{cite book |last=Gordon |first=Yefim |author2=Dexter, Keith |title= Polikarpov's Biplane Fighters|year=2002 |publisher= Midland Publishing|location=Hinckley, England |isbn=1-85780-141-5}}
{{refend}}
{{Polikarpov aircraft}}
{{Soviet fighter designations}}