Yak-3 VK-107
history and images
file updated on June 6, 2005
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The powerful VK-107A engine was taken in consideration since early 1943 for equipping the new Yak-3 lightweight fighter.
The Yak-1M prototype was experimentally refitted with this powerplant, able of 1650 hp at ground level and 1500 hp at an altitude of 4500 m , but its lack of reliability let to prefer the less powerful VK-105 PF-2, giving 1240 hp at altitude, for standard Yak-3s.

Image from typi Broni

This image shows the Yak-1M prototype after having been re-engined with a VK-107A; it is distinguishable for the different exhaust stacks.
image from Replic


Image from Yakovlev's Piston Engined Fighters of Gordon and Khazanov
The idea of equipping the Yak-3s with the VK-107A engine was resumed in late 1943 under the direction of Y.G.Adler.
The propeller was the VISh -107LO with  diameter of 3,1 m. 
The aircraft had its cockpit moved 400 mm aft, the fuel tanks were increased up to 518 litres, and the armament was changed into two B-20S 20 mm syncronized guns in the nose, with 120 rounds each.
The fuel was contained in four fixed and one removable tanks. 
The capacity of oil tank was increased to 60 l.


The original wooden construction of the rear fuselage and wing outer panels was conserved on these prototypes.
The position of the air intake and of air outlet on the upper engine cowling was different to that of series aircrafts; the similar Yak-9U had the same evolution..
Note the wire antenna between the stabilizer and a small hole in the rear part of canopy.
The inclined rear armoured glass behind the pilot's head is visible too.


Image from Yakovlev's Piston Engined Fighters of Gordon and Khazanov
Two prototypes were completed in early 1944, No.1 and No.2 "dubler".
Aircraft No.1 was completed on 6 January 1944, used for factory tests and flown by Pavel Y. Fedorovi from April 15 until 20 November 1944. 
It executed 38 flights for a total time of nearly 15 hours.
Tests showed excellent speed, climb rate and handling; the engine was still unreliable, and it had problems for three times.
Although flight mass increased to 2984 kg, its specific power loading was 2.0 kg/hp, better than Me-109G-2 and FW-190A.

The problems came from the unreliability of the VK-107A engine, that had:
  • a short life of crankshaft bearings,
  • loss of fumes from the cylinders head,
  • vibration at low regime,
  • loss of oil from the reduction gear that spattered the windshield and risks to cause a fire if it comes in contact with the hot exhaust stacks;
  • supercharger pressure not constant when altitude changed;

  • irregularities in oil and fuel pressure at altitudes higher than 8000 m.
Mantaining oil and cooling water temperature at high regime required full opening of ventral air outlet shutters, that decreased the speed of 24 km/h.


No.2 (dubler) was completed on January 22, 1944.
It made factory tests from 25 to 29 January 1944, flown by test pilot Fedorovi. 
Then the state trials of NII VVS started under the supervision of leading engineer G.Sedov
Test pilots were Y.A. Antipov and A.G. Proshakov.
A first stage of flight test was made between 7 February 1944 to May 15, 1944.
Then the aircraft was modified for the correction of some defects, and the state tests were made again from 13 July to 29 August.
In all, 44 flights were made, for a total of nearly 26 hours. 

Image from Yakovlev's Piston Engined Fighters of Gordon and Khazanov

The tests went slowly, mainly because of engine misfunctions; the flight were stopped many times, once even for two months, because of this.
In particular, the life of the crankshaft bearings was short, the throttle was unreliable and oil was sprayed on the windshield compromising visibility.
Apart for the engine unreliability, other major problems were the insufficient strength of the structure, particularly of the wings, and the small anti-nose-over angle,
that prevented the possibility of normal operative use.
On the other hand, the aircraft had the best flight characteristics between all known fighters, both Soviet and foreign. Besides, it was as simple to be flown as the standard Yak-3. So, it was decided to continue the development of the aircraft.


In the spring of 1945, the Soviet government ordered the construction of 75 all-metal fighters at the Zavod n.31 at Tbilisi; they had to reutilize unfinished airframes stocked in this plant.
This factory was chosen because of its better quality standard if compared to Zavod no.292 of Saratov, that was producing Yak-3s too.
The work was made under the supervision of K. Skrzhinskiy, that modified a production machine (70-03).
A VK-107A engine of the latest batch, incorporating an additional oil pump, was fitted on the airframe.
The plywood skin of wings and rear fuselage was replaced by duraluminium, and the fabric on control surfaces was replaced by magnesium alloy.

The fuel and oil tankage was slightly increased if compared to a standard aircraft, but was inferior to that of the prototype.
Some steel parts were replaced by alluminium alloy parts to save weight.
The gross weight of the aircraft was of 2935 kg, compared to 2984 kg of the mixed construction prototypes and to 2697 kg of a standard Yak-3.
After a month of factory tests, the aircraft was sent to NII-VVS for state trials, under the supervision of  I.Kolosov, on 11 May 1945.
The test pilot was Y.A. Antipov.
The flights revealed better characteristics and better engine and brakes functioning if compared to the prototypes.
The speed and manoeuvrability were good, in spite of the impossibility to use the "combat mode" (3200 rpm, the nominal mode was 3000 rpm) of the engine due to its unreliability.

image from Replic
This image shows what is believed to be the first all-metal Yak-3VK-107A produced in Tbilisi plant. 
Panel lines are vaguely visible under the wing surface; they were absent on wooden wings.
Note that the supercharger intake over the nose is shown in front position on some photos, as on No.1 and No.2 prototypes, while it appears moved back (as on series aircrafts and series Yak-9P/U) on other photos of another aircraft, also wearing a silver and red livery.

This aircraft was different from the previous one  for the position of intakes on the nose and the different profile of oil cooler outlets under the wingroots; in both these details, this aircraft was identical to series Yak-9P.

Image from Yakovlev's Piston Engined Fighters of Gordon and Khazanov

Meanwhile, the production in Zavod 31 was continuing; the plant built 40 aircrafts in 1945 and further 8 in 1946, before switching the production line to the jet- powered Yak-15.
The Tbilisi series-built Yak-3 VK-107A were fitted with two syncronized B-20S 20 mm gunswith 120 rounds each, plus one B-20M 20 mm gun firing through the propeller's hub with 100 rounds.
Most of them were equipped with a bulletproof windshield.
Strangely, no any document on the operative life of these 48 series aircrafts is available. However, they are hardly distinguishable from Yak-9 U/P on photos.
According to the instruction sheet of the Amodel kit, they were painted with two greys camo with light blue undersurfaces.


About operative use during the Great Patrioctic War: the book "porsev'ye istrebitel YAK 1941-1945" shows a profile about an operative Yak-3 VK-107A.
Yellow 32 was the personal aircraft of Pavel Petrovic Karavay from March 1945 till Oct. 1946. He was the commander of  897 IAP.
Karavay and some other pilots went to Zavod no.31 at Tbilisi for planes and they found some new models of Yak fighters.
They took possession of them and brought to the unit by evading the usual procedures.
Karavay used the plane in fights above Hungary. He shot down one Bf-109 on 23.03.1945 above Mór and one more above lake Balaton on 22.04.1945 while flying this machine.
Karavay was made Hero of the Soviet Union on 18 August 1945.

According to the book, the aircraft was armed with 3  20 mm guns, and had an armoured windshield. 
The radio mast drawn is noteworty: it was not on Yak-9P, and it is not described on Tbilisi-built Yak-3VK-107. I wonder if a photo of this aircraft really exists.
The uppersurfaces were AMT-11 light grey, the undersurfaces AMT-7 light blue, and the spinner was red.


The aircraft was interpretated as a postwar Yak-9P on the decals sheet Aeromaster 48622.
At present time, we have not other sources or photos to decide which  identification is right.
However, Yak-3 VK-107A and Yak-9U/P are hardly distinguishable in photos, unless the main landing gear doors are visible.


A batch of 30 fighters had to be built at Zavod No.292 in Saratov in the spring of 1946.
Three production machines (01-01, 03-01 and 04-01) were effectively built and tested.
They differed from the prototypes and from Tbilisi-built Yak-3 VK-107A in many details:
  • metallic skinning of wings only;
  • fabric covered rudder and, probably, other control surfaces;
  • two B-20 S syncronized guns (plus one B-20 M with 100 rounds on the  propeller's axis on 03-01 and 04-01);
  • one-piece streghtened landing gear strut;
  • the oil radiators were enlarged, as their shutters opening (closed position: 68 mm, opened position: 250 mm);
  • front bulletproof glass on the windshield (of 01-01 and 03-01 only);
  • RSI-4 radio set replaced with RSI-6;
  •  protruding radio mast added.
The aircraft of this photo (01-01 or 03-01) looks painted with  grey AMT-11 uppersurfaces and light blue AMT-7 undersurfaces.

On these images, you can see the VK-107A engine, and observe how the stacks were made. The first one is not for hot fumes, but for some cooling device.

image from Red Stars of Geust-Keskinen-Stenman

image from Le Fana de l'Aviation n.420

The first production machines (01-01, 03-01 and 04-01) were tested by NII VVS from 10 April to 20 May 1946, giving good performances (even if slightly lower than the expected ones). The max speed at 5950 m altitude was 697 km/h, while 4,2-4,5 min were required to climb at 5,000 m.
Many defects were noted, and the aircrafts returned to the factory to be modified.
On 29 June 1946, no-01-01 returned to NII VVS for further tests that ended on 30 July.
Some serious problems were noted again, however it was suggested to build a batch of 30 aircrafts  for operative tests after the correction of the major defects.
Simulate air combats of 01-01 with Yak-9U, P-63 and Spitfire IX showed that its performances were equivalent to those of Yak-9U.
High stick forces were required by ailerons and elevators, and this made its handling unpleasant.
Besides, the engine was still not fully reliable, suffering a breakdown on one machine; occasionally overheating was observed on other machines, as well as vibrations when the throttle was moved back.
It wasn't possible to remedy to such defects, so the Yak-3s of Saratov didn't pass the state trials.
So, the production of Saratov was interrupted after the first three machines.
The work on this type of aircraft was interrupted, because the Yak-9U was preferred as the only fighter with VK-107A engine because of :


John Garric owns a real YAK 3 VK107 dismantled, recovered in Russia.
He used the original pieces as a master, reproducing them to convert Yak-11s into flying replicas.
The original wing is identical to that of Yak-11, while the fuselage was entirely rebuilt.
The engine fitted is not a VK-107, but an Allison.
Apart for some details (more protruding exhaust stacks, lack of rear armoured glass, lack of armament and sight, absence of gun hole on the spinner, Normandie-Niemen style painting), the aircraft looks an extremely convincing replica of the original subject.
Garric's own aircraft, white 6, will be followed by other ones.
For further images, see:


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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