Yak-1 with M-106 engine, A.S.Yakovlev

High altitude interceptor variant of the Yak-1. Its major difference from other siblings - M-106 engine, which was designed at Mikulin KB under Governmental Order issued on January 9, 1941.

M-106 (also known as M-106-1sk) was a M-105PF variation. Major distinction - single-speed centrifugal supercharger, providing intake pressure 1175mm.Hg. As a result, engine gained up to 150hp of output. The supercharger was designed by V.A.Dollezhal.

Other engine changes included:

• compression reduced from 7.5 to 6.0
• oil pumps of increased productivity
• constructive strength of vital parts (shaft, gearbox etc)was increased

Single-speed supercharger allowed to eliminate a power drop at 1850m, where M-105PF supercharger had a speed change. Elimination of this power drop (known to and exploited by Luftwaffe pilots) could provide Soviet pilots with certain advantage at low and medium altitudes, where most of dogfight took place.

Airframe modifications were minor weight saving changes and installation of the VISh-61P variable-pitch propeller. Yak-1 M-106 had fuselage of series Yak-1 (which one? - A.S.), metal tail stabilizer and rudder from Yak-7, metal wing spars, two wing fuel tanks. Oil coolers (9' diameter) were installed in wing tunnels. Tunnel of the water cooler was modified according to recent TsAGI recommendations.

Yak-1 M-106 was armed with engine-mounted 20mm ShVAK and 12.7mm UBS guns. Other equipment was identical to series Yak-1 M-105PF.

Engine progressed slowly, and only on December 12, 1942 assembly of test fighter was ordered by GKO. Yak-1 M-106 was assembled in end of December, 1942. In January 1943 trials were undertaken by test-pilot A.I.Kokin, senior engineer K.N.Mkrtychan and aircraft mechanic F.Z.Sbitnev.

Flight performance obtained during factory trials was substantially better than of series Yak-1 M-105PF. But... those advantages could not be obtained at air temperatures above 15°C. Cooling system productivity, despite was increased compared to standard M-105PF, could not coup with increased engine heat output on maximum climb rate.

Factory trials revealed also that the engine needs more work on it. Vibration on transitional (1800 to 2000rpm) rates, frequent spark plug failures, smoke, excessive fuel consumption and 'diseling' required serious attention of engine designers. It was transferred to LII.

Also in January (8 to 13) 1943 another Yak-1 with M-106 engine was tested at LII. This was a series Yak-1 M-105PF with standard airframe. It had lower assembly quality and was heavier than specially-built modified stalemate. Performance worsened, and engine had same toothing problems.

Nonetheless, production of the Yak-1 M-106 was launched. 47 aircraft were assembled at Saratov until February 18, 1943. 32 of them had standard cooling system and were designated for winter conditions combat trials. But this was the end of the story. None of those machines saw action, because all were rejected by military representatives. Temperature regimes were found not acceptable, M-106 engines were graded as unsuitable and replaced by standard M-105PF.

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Created November 20, 2000 by

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