N.N.Polikarpov I-15

spanish language version
(Ye.Gordon, V.Zenkin, V. Titov, Biplane fighters of N.N. Polikarpov,
Moscow, Gonchar, 1992,ISBN 5-88541-002-X)
front view

August 1932 when the works on I-5 fighter were completed a big goup of engineers of VT design bureau was moved to AGOS TsAGI. The group was headed by Ye.N. Paufler and N.N.Polikarpov was in this group also.
It's nesessary to note than Paufer was a person from NKVD. The structure of AGOS TsAGI was changed after uniting of these teams.
4th of May 1932 Kharlamov N.M. (at the time - head of the TsAGI) issued an order to make N.N.Polikarpov and G.I.Bertosh deputys of P.O.Sukhoj - head of brigade 3. According to the plan of 1933 the brigade was deriving two new high speed fighters: I-13 (Polikarpov) with M-32 engine and I-14 (Sukhoi) with M-38 engine. .
Having faced with M-32 engine development problems N.N.Polikarpov derived advanced draft on the base of I-13 named initially I-14a, which gradually evolved into the I-15 design.
I-14a project
(Ivanov V.P. , Aircraft designer N.N. Polikarpov.- SPb, Politechnika, 1995,ISBN 5-7325-0085-5)
Mock-ups of the I-14 (P.O.Sukhoj) and I-14A (N.N.Polikarpov) were presented in November 1932. On December 8 both projects were approved, I-14 as a high speed interceptor and I-15 as a highly maneuverable dogfighter. At the time N.N.Polikarpov got his separate design brigade.
January 1933 TseKaBe design bureau at the factory No39 was formed. The fighters brigade was headed by N.N.Polikarpov. So October 1933 the experimental I-15 version creation finished. The same month it was tested in flight by V.P. Chkalov.
I-15 was a small biplane fighter, development of the I-5 and I-6 with improved airdynamic. The most distinctive features were gulled upper wing and very clean fixed landing gear, often covered with fairing. Roots of the upper wing were included into fuselage structure. (sometimes this is called "The wing of Pulawsky") Upper wing shape improved pilot view and reduced drag (wing-fuselage interference).
Front section of the fuselage from engine to cockpit was covered with duralumin sheets, the rest of aircraft - with fabric. Wheels were equipped with disk brakes. First aircraft was equipped by imported 630/715hp high altitude Wright-Cyclone SGR-1820 F-3 engine. Armament included pair of synchronized PV-1 machineguns and 40kg of bombs (overload). Interestingly, the tail of the first TsKB-3 carried same letters VT as the VT-11 prototype of the I-5.
Flight tests were performed in October-November 1933 by V.P.Chkalov. The second prototype - on skis - was flown in December. During continuous dive one of skis was lost, and aircraft turned over during landing.
Series production of I-15 started.
Early series were powered by Wright-Cyclone engine. Planned production of its license version M-25 was delayed, and during 1934-36 few hundred of I-15 were equipped with M-22. Interestingly, low altitude performance did not suffer despite less powerful engine was used. Since 1936 all production aircraft had M-25 engine, demonstrating improved performance at high altitudes. Production aircraft carried four PV-1 machineguns or (in 1938) pair of 12.7mm BS heavy machineguns.
Stripped version of the I-15 was used in 1935 by V.K.Kokkinaki to set the World altitude record (14,575m). Series of trials were performed in 1937 with pressurized cockpit. They had no value for series I-15 (due to ceiling), but those were first successful tests of pressurized cockpits on Soviet fighters.
Gull-wing caused heated debates among specialists and pilots, despite the I-15 was superior compared with other contemporary fighters. As a result N.N.Polikarpov had to convert design back to conventional wing. This conversion forced production delay in 1936 (only 12 I-15 rolled out). But while large series with straight wing started in 1937 (picture below), extensive airdynamic tests at TsAGI proved advantage of the gull wing at high speeds. As a result in 1938 I-15 production continued with (modified) gull wing.

The I-15 was used in combat in Spain and proved to be one of the best fighter biplanes of its time. Performance was high enough to force pilots of early Bf-109 to avoid close combat with more agile and well-armed 'Chato'. But biplane era was already fadin.
In 1939 during clashes with Japanese I-15 was already obsolete.
More Links:

  • "History of aircraft construction in the USSR" by V.B.Shavrov, Vol.1 p.75-77;
  • Ye.Gordon, V.Zenkin, V. Titov, Biplane fighters of N.N. Polikarpov, Moscow, Gonchar, 1992,ISBN 5-88541-002-X
  • Ivanov V.P. , Aircraft designer N.N. Polikarpov.- SPb, Politechnika, 1995,ISBN 5-7325-0085-5
  • Technical information
    Type I-15 M-22
    Function fighter
    Year 1934
    Crew 1
    480hp M-22
    6.1 m
    Wing area 23.55sq.m
    Empty weight 1106kg
    Loaded weight 1415kg
    Wing load 60.2kg/sq.m
    Power load
    Speed at 0m 286km/h
    Speed at 3000m 350 km/h
    Turn time 8.5s
    Landing Speed 90 km/h
    Landing Roll 70m
    Takeoff Run 70m
    Ceiling 7520m
    Guns 2X7.62 PV-1
    Bombs 100 kg
    Created by Alexandre Savine
    Modified December 8, 2000 by
    Sergey Andreev;