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Yak-2/BB-22

Short- range Bomber

Yakovlev

Yak-2/BB-22

The Yakovlev Yak-2 (BB-22) was a short range bomber with two Klimov M-103 V-12 engines.

In the Yakovlev Design Bureau, which until 1938 was engaged exclusively in light-engine aviation, L. Shekhter proposed the idea of ​​creating a high-speed twin-engine multipurpose aircraft. The main "highlight" of the project, he considered obtaining the highest flight speed, which should have been provided by the minimum size of the machine, equipped with two M-103 engines with a capacity of 960 hp. These motors were created on the basis of licensed French 12-cylinder engines of the Hispano-Suiza company with liquid cooling. With a design flight weight of 4000 kg, the specific power load was record low - only 2.05 kg / hp. (for comparison: the Soviet I-16 type 24 fighter has 2.09 kg / hp, and the German Bf 109E-3 has 2.44 kg / hp). The wing area of ​​the new aircraft in the draft design was determined to be 27 m², which provided a rather high specific load on the wing at that time - 148 kg / m². In order to reduce the weight, the designers decided to use a one-piece all-wood wing with a span of 13.5 m and a truss (made of steel pipes) fuselage, i.e. use a scheme already well tested on light Yakovlev sports aircraft.

In the Air Force Research Institute, during the tests in the fifth flight, it was possible to accelerate "aircraft number 22" to a maximum speed of 567 km / h at an altitude of 4900 m (taking into account the compressibility of air - 558 km / h). It took only 5.75 minutes to climb 5,000 m, and the ceiling exceeded 10,000 m. According to these data (without taking into account the carrying capacity and flight range), the new aircraft took one of the first places among the machines of its class both in the USSR and abroad ... Comparison with Italian Breda 88, French Breguet 690 and Pote 63, Polish PZL-38 "Vilk" was favorable for our aircraft. The test report emphasized that the speed obtained was not the limit: it could well have been increased to 600 km / h with an improvement in the engine cooling system, a change in the exhaust system and a better selection of propellers.

Plant No. 1 named Aviakhim, one of the most powerful in the country, in March 1940 presented a serial BB-22 with serial number 1012 for testing. The production performance of the machine was so poor that its maximum speed at a design altitude of 5000 m did not exceed 515 km / h.

The lead aircraft, the so-called "aircraft of the first ten" or "aircraft of the military series" in the spring of 1940 passed military tests at the Air Force Research Institute. Their results looked, to put it mildly, disappointing. Once again, the lack of knowledge of the propeller group, the insufficient strength of the wheels of the main landing gear struts. Poor visibility from the navigator's cockpit made it difficult to navigate and reach the target. The armament of the aircraft again turned out to be unsettled: the bomb bay doors did not open, huge efforts were required to drop bombs using the MSH-8, the rear gun mount could not be used for its intended purpose, since the pneumatic system for raising the canopy and the arc of the turret did not have time to work properly.

According to the test pilots, the machines were distinguished by a relatively high landing speed, an unusually steep glide path, and insufficient lateral and track stability. At high alignment, the aircraft would quickly fall through, and the rigid shock absorption of the landing gear was unable to effectively absorb the resulting shock. From the point of view of the operators, the BB-22 was a real nightmare: it took a good half hour to dig up and bury the engines alone. Access to the units turned out to be inconvenient, there were more than 20 drain taps in the cooling system ... The general bleak picture was completed by the vibration of the tail unit, due to which the military tests had to be stopped.

On machines built in the summer of 1940, it was necessary to increase the flow area of ​​the radiator channels again, introduce one more oil cooler (eight-inch) with an air intake on the inner (facing the fuselage) surface of the engine nacelles, and install the twin wheels on the main landing gear legs. The midsection of the engine nacelles has grown somewhat due to the turn of the water coolers perpendicular to the air flow. To improve the defenses on serial vehicles, the gargrot behind the navigator's cabin was lowered according to the model tested during military trials. A DI-6 rifle mount with a ShKAS machine gun was mounted in the navigator's cabin. Starting with vehicle No. 1045, the BB-22 began to install a standard turret of the high-speed aircraft TSS-1, which provided an increase in firing angles and was distinguished by higher reliability.

The production quality of the airframe was still low: the wing skin had waviness, was not smoked, the painted surfaces were rough. The flight weight of the vehicle increased again and reached 5660 kg. At the same time, the specific load on the wing increased to 192.5 kg/m². The maximum flight speed, measured on the serial BB-22 No. 1041, at a design altitude of 4600 m dropped to 478 km / h even in the absence of bombs on the external sling! With a load of 400 kg of bombs in the fuselage and two FAB-50s under the wing, the car could no longer accelerate faster than 445 km / h. Thus, in terms of flight speed, it practically equaled the SB!

Little by little it became clear that in order to turn the BB-22 into a full-fledged bomber, it would not be possible to do with the elimination of the identified defects. Improvement of flight (especially stability in flight) and performance of the machine could only be achieved by radical changes in the geometry and design of the airframe.


                                                                                                                                                                                                              
BB-22, Yak-2, Yak-4
BB-22
prototype
BB-22
serial
Yak-2
serial
Як-2
serial
No - 1012 1041 70204
Factory of origin # 115 # 1 # 1 # 81
The ending of tests 2.1940 3.1940 9.1940 10.1940
Crew Two
Dimensions
Length, m 10.17 (33 ft 5 in)
Wing span, m 14.00 (45 ft 11 in)
Wing area 29.40 m²(316 ft²)
Powerplant
Engine 2 x M-103 2 x M-103 2 x M-103 2 x M-103
Power, hp 2 x 960 2 x 960 2 x 960 2 x 960
Weight
Load weight, kg 5315 5380 5660 5630
Performance
Max speed, km/h at sea level 449 439 399 410
at altitude 535 515 478 498
altitude, m 5,000 5,000 4,600 4,800
Time to level 5000 m, min 7.4 7.7 9.5 8.0
Service ceiling, m 8,900 8,900 8,100 8,700
Photo Description
Drawing Yak-2 Drawing Yak-2
The M-103 engine of # 22 airplane The M-103 engine of # 22 airplane
Yak-2 with M-103 engine Yak-2 with M-103 engine

Bibliography

  • "The history of designs of planes in USSR 1938-1950" /Vadim Shavrov/
  • "Planes of Stalin falcons" /Konstantin Kosminkov and Dmitriy Grinyuk/
  • "Stories of the aircraft designer" /Alexander Yakovlev/
  • "The Soviet planes" /Alexander Yakovlev/