I-403

I-403. The Mikoyan-Gurevich I-403 was a Soviet experimental fighter aircraft developed in the immediate post-World War II era. It was a further development of the earlier Mikoyan-Gurevich I-250 (N) design, which itself was a unique hybrid powered by a combination of a conventional Klimov VK-107 piston engine and a Kompressor jet engine in the tail. The I-403 was intended to explore the limits of mixed-powerplant technology and high-speed flight, competing with emerging pure-jet designs from rivals like Yakovlev and Lavochkin.

Design and development

The design bureau of Artem Mikoyan and Mikhail Gurevich initiated the I-403 project to refine the concept proven by the earlier Mikoyan-Gurevich I-250. The core innovation remained the VRDK (Vozdushno-Reaktivnyy Dvigatel Kompressornyy) motorjet system, where the Klimov VK-107 piston engine drove a compressor that forced air into a combustion chamber, creating additional jet thrust. This configuration was intended to offer the high-speed performance of early jet engines while mitigating their notorious fuel consumption and slow throttle response. The airframe was of all-metal construction, with a laminar-flow wing and a pressurized cockpit for the pilot. Armament was planned to be heavy, consisting of multiple Nudelman-Suranov NS-23 autocannons. The development took place amidst intense postwar technological competition with other Soviet bureaus and the rapid advancements being captured from Germany, such as those from BMW and Junkers.

Operational history

The sole I-403 prototype was completed and made its first flight in 1947, with test pilot Aleksey Grinchik at the controls. Flight testing revealed that while the aircraft could achieve impressive speeds for its time, the complex hybrid powerplant was notoriously unreliable and difficult to maintain. The emergence of more advanced, purpose-built turbojet engines like the Klimov RD-45 (a Soviet copy of the Rolls-Royce Nene) rendered the VRDK concept obsolete. Projects like the Mikoyan-Gurevich MiG-9 and the Mikoyan-Gurevich MiG-15, which utilized these simpler, more powerful jet engines, demonstrated superior performance and development potential. Consequently, the Soviet Air Forces showed no interest in ordering the I-403 into production, and the program was terminated after only a brief test cycle. The aircraft never entered squadron service or participated in any major military exercises like those held at Kubinka Air Base.

Specifications (I-403)

General characteristics * **Crew:** 1 * **Powerplant:** 1 × Klimov VK-107 V-12 liquid-cooled piston engine driving a Kompressor for the VRDK jet thrust. * **Armament:** Proposed 4 × 23 mm Nudelman-Suranov NS-23 autocannons

Performance * **Maximum speed:** Estimated 825 km/h (513 mph)