Destination's Journey Military Photos

The Polikarpov I-153DM was one of the Soviet Union’s most unusual experimental fighter aircraft, combining the proven Polikarpov I-153 “Chaika” biplane with pioneering ramjet propulsion. The suffix DM, short for Dopolnityelnyi Motor (“supplementary engine”), referred to the installation of two underwing ramjet engines designed to boost the aircraft’s speed without replacing its conventional piston engine. Developed in 1940, the project reflected Soviet interest in advanced propulsion systems during the years immediately preceding the widespread introduction of turbojet aircraft.

The standard I-153 was powered by a Shvetsov M-62 radial engine driving a two-bladed propeller and was renowned for its exceptional manoeuvrability despite its biplane configuration. Engineers fitted experimental Merkulov DM-2 and later DM-4 gasoline-burning ramjets beneath the lower wings. Unlike turbojets, ramjets contain no moving compressor and rely entirely on the aircraft’s forward speed to compress incoming air. As a result, the ramjets could not operate from take-off and only became effective after the aircraft had reached sufficient speed under piston-engine power.

Flight testing demonstrated that the concept worked. Aircraft fitted with the smaller DM-2 ramjets achieved an increase in maximum speed of approximately 30 km/h (19 mph), while the more powerful DM-4 installation produced gains of up to 50 km/h (31 mph). A total of 74 experimental flights were conducted, proving that auxiliary ramjets could provide a measurable performance improvement without fundamentally altering the aircraft’s design.

The Nikitin-Shevchenko IS (Istrebitel Skladnoi – “Folding Fighter”) was one of the most unconventional Soviet fighter aircraft projects of the Second World War era. Designed by Vasily Nikitin and test pilot Vladimir Shevchenko, the aircraft was conceived in the late 1930s as a “polymorphic fighter” capable of transforming between a biplane and a monoplane during flight. The concept aimed to combine the excellent take-off, climb, and manoeuvrability of a biplane with the superior speed and lower drag of a monoplane.

The aircraft featured a unique retractable lower wing. During take-off and landing, the IS operated as a conventional sesquiplane, with the lower wing providing additional lift. Once airborne, the landing gear retracted into the lower wing, after which the entire wing folded upward into recesses beneath the fuselage and upper wing. The complete transformation took only a few seconds and was controlled by a simple three-position lever in the cockpit. This ingenious mechanism allowed the pilot to choose the most suitable configuration for different phases of flight.

The first prototype, designated IS-1, was powered by a Shvetsov M-63 radial engine and armed with four 7.62 mm ShKAS machine guns mounted in the upper wing. Flight testing demonstrated that the folding-wing mechanism worked reliably, validating the engineering concept. A second prototype, the IS-2, incorporated a more powerful M-88 radial engine, a slimmer fuselage, and heavier armament consisting of two 12.7 mm Berezin BS machine guns and two ShKAS guns. Plans also existed for more advanced IS-3 and IS-4 variants fitted with even more powerful engines and improved aerodynamics.