Su-5, I-107 by P.O.Sukhoj

Three 16k views of 1/72 vacuform MPM model of the Su-5, by A.Savine

Design competing with the I-250, combining a piston engine and the VRDK jet booster. The Su-5 was a small aircraft, but due to the volume of the additional power unit, the fuselage was very deep.

In the second half of World War II, when the possibilities of the piston engined aircraft were nearly exhausted, there were new fighters, exploiting jet engines constructed in Germany, USA and United Kingdom.

In the USSR this program progressed slowly due to the evacuation of research and designing factories to the East. The priority was given to various proposals of mixed-power fighters. In 1943- 1944, an "accelerator" (VRDK) was constructed, designed by engineer Khalshchevnikov. Two prototypes were built: MiG-13/I-250 and Su-5/I-107.

76k, courtesy of Ned Avejic, see his collection

The P.O.Sukhoj Su-5 took off in spring 1945. It was powered by V.Ya.Klimov VK-107A 12-cylinder vee engine (1700hp/1240kW). The diameter of the constant four-blade propeller was 2.90m. Below the nose, there was a large air intake duct. The air was lead to the cooler and the compressor, as well. The compressed air was blown to the Khalshchevnikov's reaction engine in the rear fuselage.

To fulfill its interceptor tasks, the fighter was armed very well: a 23mm Nudelman cannon fired through the propeller spinner and two synchronized 12.7mm Berezin-UBS machine guns were housed in the engine cowling. Factory tests continued until mid June, 1945. The calculated top speed was 810km/h.

This testing program was cancelled in favor of more advanced design for "jet only" aircrafts, promising much better performance.