Despite the rejection of 2B-P2, at the end of 1926 the subject of a heavy bombload of a mixed design had to be returned. And the question was put so sharply and suddenly that even the possibility of launching the French Karman "Goliath" was considered. A commission was created from all interested parties. December 2, 1926 at a meeting of the technical section of the Air Force NC, the permanent member of the Scientific Committee, PM M. Kreyson reported on the results of the commission's work - the commission was inclined towards Goliath. These bombers were exploited in the Soviet Union for a second year and largely met the basic requirements of the Air Force.
Nikolai Polikarpov objected that the development of such an aircraft in production will take 14-16 months. And hardly more time could be required for the design and construction of a new apparatus. The arguments were adopted, from copying "Goliath" decided to abstain. Polikarpov was instructed to create a bomb type of French type with two Lorren-Dietrich engines with a capacity of 450 liters.
The aircraft was considered as a wooden night bomber, and it was believed that the main purpose of its construction is insurance in case of failure with the launch of TB-1.
In September 1926, the Experimental Department of GAZ M1, by order of Aviatrust, was reorganized into the Department of Land Aircraft Construction (OSS) of the Central Design Bureau. The chief of the OSS was NN Polikarpov. The new organization for some time was found in the territory of the aircraft plant # 1, then moved to a neighboring aircraft factory # 25 - the former factory "Moska".
L2-2LD450 was included in the program of experimental construction for 1927-28. Variants of a biplane and a half-plan were developed; designers finally settled on the latter. The draft project was considered on September 14, 1927, at one of the meetings of Aviatrust. The project was unanimously approved, the Air Force leadership regarding the aircraft already used the designation TB-2 . Present at the consideration of A.N. Tupolev spoke in a capacious and definite way: "The general scheme of the aircraft is recognized as one of the best."
In terms of appearance and layout, the TB-2 resembled a two-engine version of the R-5 army reconnaissance vehicle, the draft design of which was approved a month earlier. The same, but twice as large, wing of a wooden structure with linen plating. The wing of constant width in scope had elegant elliptical tips. The fuselage is wooden, rather narrow, with plywood plating. The crew was to consist of five people.
During the period of constructive work on TB-2, the engines changed again - now the choice was made for the German BMW-VI production which, under a license, was supposed to be organized in the Soviet Union. At the same time it was proposed to unify the chassis of TB-2 and TB-1 for simultaneous ordering them abroad. Although the idea was robust, it was not possible to implement it in practice for a number of reasons related to different layouts, different landing gear chassis and other design differences.
In February 1928, a full-sized wooden model was completed, which until May examined several commissions. The result of their activities were changes in equipment and weapons. In particular, the representatives of the Air Force proposed to make a lower version of the fuselage to accommodate an additional rifle installation. Polikarpov, in turn, suggested installing removable rifle installations behind each engine. This proposal was endorsed and endorsed by the NTC of the Air Force.
Although TB-2 was calculated for a maximum load of 1500 kg, in the final version it was decided to bring it up to 2000 kg. With two tons of bombs, the aircraft was significantly ahead of TB-1 in terms of cargo capacity and was approaching TB-3.
All the described changes led to alterations and strengthening of the structure, after which the TsAGI conducted purges and static tests of individual elements.
Originally, it was planned to build and test TB-2 before the end of 1928 and start the production at the Taganrog aviation plant # 31. However, the infamous statement of I.V. Stalin about the intensification of the class struggle and the subsequent arrests of workers in industry hampered many undertakings, including work on TB-2. The time of departure was first moved to the autumn of 1929, then he moved again and again ... The TB-2 was taken out to the airfield only in the summer of 1930. Although the aircraft fully met the requirements, its flights were not properly appreciated, and the machine was almost forgotten - it was believed that next year the TB-3 will go into production, and aircraft like TB-2 would quickly become obsolete.
|Wing span, m||27.00|
|Length, m||18.20 / 59.2 feet|
|Wing area, m2||127.70|
|engine's type||2 PD BMW VI|
|Power, hp||2 x 680|
|Maximum speed, km / h||216|
|Cruising speed, km / h||182|
|Practical range, km||1200|
|Maximum climb rate, m / min||313|
|Practical ceiling, m||6800|
|Armament:||Bomb load up to 2000 kg|
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