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.
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.
(Ivanov V.P. , Aircraft designer N.N. Polikarpov.-
SPb, Politechnika, 1995,ISBN 5-7325-0085-5)
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
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.
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
"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