At one point, Mikhail Pashinin was employed by the Polikarpov aircraft concern and this served him well when attempting to develop his I-21 fighter - an all-new, all-modern monoplane intended to succeed the aging Polikarpov I-16 line in Soviet Air Force service. Pashinin was keen to implement lessons learned from Soviet involvement in the Spanish Civil War (1936-1939) as well as clashes with the Japanese and produced a sleek offering with good overall performance. However, the I-21 offered little in the way of gains when compared to competing designs from Mikoyan-Gurevich and Yakovlev - leaving just three flyable prototypes to show for the program.
Externally, the I-21 was given a sleek design with an aerodynamically refined fuselage. The cockpit was positioned aft of midships with the wing mainplanes set ahead of the cockpit and low against the fuselage sides. The nose contained the engine installation and this drove a traditional three-bladed propeller. The tail unit involved a single vertical fin with low-set horizontal planes. A tail-dragger undercarriage (retractable) was featured for ground running. The canopy was framed and offered generally adequate views of the action surrounding the aircraft but its placement so far aft meant that the wing mainplanes and long nose obstructed much of the action ahead and below.
Internally, the aircraft was constructed of welded steel tubing (forward fuselage) and wood (rear fuselage). The wings were metal with plywood skinning. Power would come from the in-development Klimov M-107 inline piston engine promising the needed output.
Proposed armament was 1 x 20mm ShVAK or 1 x 23mm BT-23 automatic cannon in the nose firing through the propeller hub and 2 x 7.62mm ShKAS machine guns, one per wing element. This provided good firepower against contemporary enemy aircraft types - particularly the 23mm cannon fit buried within the engine.
Prior to a first-flight, it became apparent that the M-107 inline would not be available as it ran into development troubles all its own. This forced the Klimov M-105P V12 of 1,050 horsepower to be used instead. A first-flight by way of first prototype was had on May 18th, 1940 with the Soviet Union having just wrapped up its "Winter War" with neighboring Finland back in March. Further examination of the aircraft showcased inadequate stability which led to a revision of the wings that greeted the second prototype. Handling issues persisted which led to a more refined third prototype, this example with further modified wing mainplanes, in January of 1941. The mainplanes now sported slight sweepback beyond mid-span and were given "clipped" tips but this did little to improve the design as a whole.
Despite promising straight-line performance from the prototypes, unresolved issues persisted and this eventually led a five-strong pre-series production order to be dropped - leaving just the three aforementioned prototypes. Soviet authorities elected to go with competing designs leaving the I-21 to the pages of history.
The I-21 designation was earlier used by the Ilyushin TsKB-32 which can add confusion.
(OPERATORS list includes past, present, and future operators when applicable)
✓Air-to-Air Combat, Fighter
General ability to actively engage other aircraft of similar form and function, typically through guns, missiles, and/or aerial rockets.
✓X-Plane (Developmental, Prototype, Technology Demonstrator)
Aircraft developed for the role of prototyping, technology demonstration, or research / data collection.
28.7 ft (8.75 m)
31.2 ft (9.50 m)
8.7 ft (2.65 m)
4,630 lb (2,100 kg)
5,886 lb (2,670 kg)
+1,257 lb (+570 kg)
(Showcased structural values pertain to the base Pashinin I-21 production variant)
1 x Klimov M-105P V12 liquid-cooled inline piston engine developing 1,050 horsepower and driving three-bladed propeller unit at the nose.
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