During the Great Patriotic War, the design bureau headed by A.S.Yakovlev presented a series of single-engine fighters and twin-engine light bmbers and transport aircraft. Conveniently, the single-engine aircraft had odd numbers [eg, Yak-1, Yak-3, etc], while the twin- engine aircraft had even numbers [eg, Yak-2, Yak-4, etc]. Not surprisingly, this simplicity did not last long.
If the Yak-2 was the fruit of the creativity of OKB-115 employees, then the Yak-4 seems to be largely a design of plant number 81. For the first time, the question of installing the M-105 engines on an aircraft 22 was raised in 1939. He was even assigned the next number "23". It was expected that the maximum speed will reach 625 km / h at an altitude of 5000 meters, the ceiling - 12,500 meters, and the range - 1,500 km. But from calculations to real data usually ran a great distance. The design was carried out under the supervision of Strongin, engineer No. 1.
Since the airframe design of the Yak-4 was similar to the Yak-2, the prototype of the new bomber was altered at the end of 1939 from the serial BB-22 No. 1002, and it received the designation product 70bis (BB-22bis) at the factory. Externally, it was distinguished not only by new motors with all-metal VISH-22E screws, but also by new uprights of the main landing gear supports with two wheels of 750 × 175 mm in size. The tail wheel was also replaced, now it was 300 × 125 mm in size. This was due to the increased take-off weight of the car. Not only more powerful engines contributed to its weighting (each of them weighed 70 kg more than its predecessor), but also additional equipment, an increased supply of fuel and oil, and an expanded composition of bomb weapons. Additionally, on four wing nodes D2MA-250, a suspension of 50 and 100 kg bombs was allowed, but not more than 200 kg.
In the first half of 1940 at plant number 1, only one BB-22bis was assembled. His inspection showed that the aircraft was performed worse than its predecessors, moreover, the position of the center of gravity, which reached 3132%, made it dangerous for flights, and the cockpit of the pilot and navigator became closer. The second car was made in November, and on this release they stopped at the plant number 1. And in this nervous situation, the aircraft was launched into serial production at one more plant - No. 381, but they never produced a single machine there, because the company was re-focused on making the Il-2, which is more important for the country's defense.
At one of the meetings with Stalin on the Pe-2 aircraft (March 15-17, 1941, one day before the approval of the report on the results of the state tests of this machine), - said the test pilot of the Air Force Scientific Research Institute N. A. Stepanov, - against the plane of Yakovlev sharply made test pilot of the Scientific Research Institute of the Air Force I. P. Piskunov, and this, it seems, was the last straw of patience. The designer himself was not at the meeting; nevertheless, Stalin ordered that the worthless aircraft be sorted out and stopped. After this meeting, the Decree of the Council of People's Commissars of the USSR No. 381 of April 12 obliged the industry to hand over the last 22 Yak-4s to the military in the second quarter.
Yak-2 and Yak-4 were very unsuccessful aircraft. And, if the prototype of the BB-22 had high speed data, then on mass-produced aircraft they were leveled by poor quality of finish. For a twin-engine plane, the mass of the bomb load was very small. In addition, the suspension of the maximum load has become impossible in practice due to unacceptable shifting of the center back. Production of the Yak-2 and Yak-4 aircraft was limited, and their service at the front was short.
|Aircraft length, m||10.18|
|Wing area, square m||29.40|
|Weight, kg: empty aircraft||4,000|
|Maximum speed, km / h||550|
|Rate of climb, m / s||15.3|
|Practical ceiling, m||9500|
|Flight range, km||960|
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