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Yak-3 VK-108
history and images
file updated on January 1, 2005
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The powerful VK-108 engine (also called VK-107B) of 1800 hp differed from the VK-107A mainly for his new supercharger.
This 12-cylinders engine gave a power of 1800 hp at altitude.
This engine never entered in series production, 
Less than 50 VK-108 were built, plus some VK-108NV injection engines; it development was stopped because of the advent of the jet age.
A VK-108 was intalled on a Yak-3 airframe in 1944 for experiment only.

The prototype building started on 1 August 1944.
The most recognizable characteristic  of the Yak-3 VK-108 prototype was the presence of 24 exhaust stacks, aligned in four lines of six, on the nose sides and upper cowling.
Besides, the supercharger air intake was divided from those of oil coolers at the wingroot, and moved under the nose as on Spitfire.
The armament was reduced to the NS-23 gun  only, firing through the propeller's hub.
The leader of the project was eng. A. Kanookov.


The aircraft rolled out on 1st October 1944,
flown by test pilot V. Rastorguyev.
The factory tests started on 7 October 1944.
On 21st December, 1944, the aircraft was flown after having been lightened to 2830 kg by omitting the gun and part of the fuel.
It took off on three points (without raising the tail), climbed to 5000 m in 3.5 mins only, and reached 745 km/h at 6290 m. 
These impressing performances were inficiated by strong overheating, vibrations, smoke emission and many engine faults.
After this flight, the aircraft was landed to replace the engine.
The work was discontinued on 8 March, 1945, after the first flight with the new engine, still badly functioning.
Some further trying to improve the aircraft were made since August 1, 1945 under the supervision of ing. G.Grigoryev; the prototype was armed with two syncronized B-20S guns with 120 rounds each, but the work didn't give the hoped results.
In 1946, the NKAP ordered the construction of 3 further prototypes, but the project was soon abandoned due to the advent of jets.

standard Yak-3  Yak-3 VK-107 prototype Yak-3 VK-107 
Tbilisi production
Yak-3 VK-107
Saratov production
Yak-9U  Yak-3 VK-108
year of production 1943 1944 1945 1946 1944 1944
engine M-105PF-2 VK-107A VK-107A VK-107A VK-107A VK-108
power 1240 1500 1500 1500 1500 1800
length (m) 8.5 8.5 8.5 8.5 8.6 8.5
wingspan (m) 9.2 9.2 9.2 9.2 9.74 9.2
wing area (sqm) 14.85 14.85 14.85 14.85 17.15 14.85
empty weight (kg) 2128             2512  
gross weight (kg) 2697 2984 2935   3204 2830
Max speed at sea level (km/h) 565 611  604 600      
Max speed  640 720  706 697    746
at altitude of 4400 5750  5900 5900    6000
Climb to 5000 m (min) 4.1 3.9   4.2-4.5 5.0 3.5
Ceiling (m) 10400 11800 11800 10880 10650   
turn time (s) 19 18 18   20   
range (km) 850 1060 850 1000 675   
armament 1x20 mm+
2x12,7 mm UBS
2x20 mm 2-3 20 mm guns 2-3x 20 mm  1x20 mm+
2x12,7 mm UBS
1x23 mm

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