:Polikarpov I-6

Development of the I-6 (Istrebitel{{'}}—fighter) began in September 1928 with a deadline for delivery for the first prototype of 1 August 1929 after the first prototypes of the Polikarpov I-3 were completed. Although the new fighter shared many of the characteristics of the earlier design, including the staggered sesquiplane, single-bay, layout of the wings, it was a new design which used a nine-cylinder, single-row, air-cooled Bristol Jupiter radial engine rather the water-cooled inline engine of its predecessor. It was designed by the OSS ({{langx|ru|Otdel Sookhoputnykh Samolyotov}}—Landplane Department), later redesignated as OPO-1 ({{langx|ru|Opytnyy Otdel}}—Experimental Department) of Aviatrest ("Aviation Trust") under the supervision of Nikolai Polikarpov, head designer of the department. It was originally intended to be compared to the I-3, but this was changed to an evaluation of construction methods with the wooden construction I-6 compared to the mixed construction Polikarpov I-5. Both aircraft used the Jupiter VI engine for which a license had recently been negotiated.Gordon and Dexter, p. 11

The I-6 had an oval-section semi-monocoque fuselage covered with 'shpon', molded birch plywood, with a small headrest faired into the fuselage, although the engine was enclosed in a metal cowling that left the cylinder heads exposed for better cooling. The two-spar wings were covered in plywood and fabric and had a Clark Y profile. Internal bracing wires were fitted to reinforce the wings. The control surfaces were framed in duralumin, but covered in fabric. The duralumin N-type struts that separated the wings, and attached the upper wing to the fuselage, had a teardrop profile. They were reinforced with steel bracing wires. The conventional undercarriage was fixed with rubber shock absorbers. The wooden propeller was given a spinner.Gunston, pp. 298–299 The lighter weight of the air-cooled Jupiter engine, which required neither a heavy radiator nor coolant, meant that the I-6 had an empty weight only 62% of that of the I-3.

Polikarpov was arrested and imprisoned by the OGPU in September 1929 for the crime of industrial sabotage when neither the I-6 nor the I-5 projects met their stipulated deadlines,Gordon and Dexter, p. 13 and this delayed the first flight of the I-6 until 30 March 1930. The second prototype was completed shortly thereafter and both aircraft appeared in that year's May Day fly-past over Moscow. Both aircraft likely used imported engines before they were replaced by the Soviet-built copy of the Jupiter, the Shvetsov M-22. One I-6 crashed on 13 June 1930 after the test pilot bailed out, without justification, in the opinion of the Soviet aviation historian Vadim B. Shavrov.

The I-5 and the I-6 were virtually identical in performance, although the I-6 took 15 seconds to complete a full circle versus the 9.5 seconds of the I-5. Both aircraft were armed with two 7.62 mm (0.3 in) PV-1 machine guns, but the production model of the I-5 was expected to be armed with four, although this proved to impose too great a penalty to the I-5's performance. The exact reasons for the selection of the I-5 over the I-6, which was debated for a full year, are not known, but likely relate to both of these factors. Curiously, Polikarpov was not informed of the selection of the I-5 until his release in 1933 after his initial sentence of death had been commuted to ten years of imprisonment in a labor camp.Gordon and Dexter, p. 4

{{Aircraft specs

|ref=Istoriia konstruktskii samoletov v SSSR do 1938 g.{{cite book|last=Shavrov|first=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=1

|length m=6.8

|length note=

|span m=10

|span note=

|height m=

|height note=

|wing area sqm=20.5

|wing area note=

|aspect ratio=

|airfoil=

|empty weight kg=868

|empty weight note=

|gross weight kg=1280

|gross weight note=

|max takeoff weight kg=

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|more general=

|eng1 number=1

|eng1 name=Shvetsov M-22

|eng1 type=9-cylinder air-cooled radial piston engine

|eng1 kw=313

|eng1 note=

|prop blade number=2

|prop name=fixed-pitch propeller

|prop dia m=

|prop dia note=

|max speed kmh=280

|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=700

|range note=

|combat range km=

|combat range note=

|ferry range km=

|ferry range note=

|endurance=

|ceiling m=7500

|ceiling note=

|g limits=

|roll rate=

|climb rate ms=

|climb rate note=

|time to altitude={{cvt|5000|m}} in 10 minutes

|wing loading kg/m2=62

|wing loading note=

|fuel consumption kg/km=

|power/mass={{cvt|0.245|kW/kg}}

|more performance=

• Horizontal turn time: 15 sec

|guns=2 × 7.62  mm (0.30  in) PV-1 machine guns

|avionics=

}}

{{aircontent

|related=

• Polikarpov I-5

|similar aircraft=

• Heinkel HD 37
• Curtiss P-6 Hawk
• Bristol Bulldog

|lists=

}}

{{Reflist}}

{{refbegin}}

• {{cite book|last=Gordon|first=Yefim|author2=Dexter, Keith|title=Poliarpov's Biplane Fighters|publisher=Midland Publishing|location=Hinckley, England|date=2002|series=Red Star|volume=6|isbn=1-85780-141-5}}
• {{cite book |last=Green |first=William |author2=Gordon Swanborough |title=The Complete Book of Fighters |publisher=Salamander Books|location=Godalming, UK|pages=415}}
• {{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}}

{{refend}}

{{Polikarpov aircraft}}

{{Soviet fighter designations}}

Category:1930s Soviet fighter aircraft

I-006

Category:Sesquiplanes

Category:Single-engined tractor aircraft

Category:Aircraft first flown in 1930