I-15 was a small biplane fighter, development of the I-5 and I-6 with improved aerodynamic. 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. Upper wing shape improved pilot view and reduced drag.
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 fading, and in 1939 during clashes with Japanese I-15 was already obsolete.
I-15 deserves special honor from American military pilots. It was flown by ace of Spanish War Frank G. Tinker, who became the first American to shot down Messerschmitt Bf-109.
I-152 (I-15bis) was development of the I-15 with a straight upper wing and a more powerful engine. The I-152 was used in Spain and China, and also fought in WWII.
After the Spanish civil war, the USSR wrongly concluded that there would be a role in the future for a maneuverable biplane fighter. The I-153 was a refinement of the earlier I-15 and I-152 with retractable landing gear; the gull-wing of the I-15 was employed.
I-153 / I-15ter Chaika (Sea Gull) with six RS82/RS132 "Katusha" rockets under wings.
