Arjanguelsky SB-B (Russian: Архангельский СБ-Б). The SB-B was the last attempt to keep the SB in service.
Parallel to the development of the SB-RK 2M-105 model, the bureau led by Arjanguelsky began work on a short-range, high-speed bomber in 1939. Initially, the project received factory index S (with this designation tests were performed in the wind tunnel of the model in TsAGI), but soon the name was changed to B. The new design was a radical modification of the model with the aim of obtaining much higher performance and better technological processes to facilitate construction.
The crew was three: pilot, navigator and radio operator-gunner.
The main advantage of the model lay in the aerodynamic improvements. Although similar in configuration to previous models, the B featured a double-tail unit.
The biggest changes focused on improving the aerodynamics. The wingspan was reduced and the wingtips modified. In general, the wing area was reduced to 40 sq.m. The tail unit was modified to carry double tails. The power nacelles were once again aerodynamically improved.
In the structure of the SB-B it was decided to use open profiles instead of metal tubes. Also noteworthy is the extensive use of rivets and stamped parts instead of welds. Due to the war, aluminum production was scarce. For this reason, the ends and the area of the wings between the stringers were built using bakelite sheets glued to the metal structure, which allowed to obtain a higher quality and high resistance surface. To avoid perforations in this structure, the decision was made not to attach the main undecarriage into the wings.
The powerplant was again modified. The Klimov M-105TK engine included a TK-2 turbocharger that made it possible to reach 612 km / h at a height of 9000 meters. The use of the Klimov M-106 was also foreseen, with which according to the calculations it would reach 587 km / h at 7000 meters of altitude. In both engine versions, the use of 3-SMV-2 three-bladed propellers with a diameter of 3.25 m was foreseen.
The radiators were located inside the wing with the intakes on the leading edge of the central plane and the outlets to the rear. They planned to use aluminum radiators developed in the SKB of the NKAP of Leningrad.
The tail wheel of the landing gear could be retracted in flight, also to improve aerodynamics.
The normal operating capacity envisaged 600 kg of bombs, but the maximum capacity was 1000 kg, of which 800 kg could be located in the hold. The armament included bombs between 2.5 and 250 kg.
The defensive weapons included a normal caliber UltraShKAS machine gun in the nose with 600 rounds, operated by the navigator and another UltraShKAS with 800 rounds or a heavy caliber ShVAK-12 machine gun with 300 rounds, operated by the radio operator-gunner.
The performance of the new model far surpassed that of the standard SB bomber. However, the results still did not exceed the 600 km / h requested by the Defense Committee. The biggest problem was the ranga. With a cruising speed at 0.8 of the maximum speed the range with Klimov M-105TK engines, the calculations did not exceed 880 km and with Klimov M-106 engine 970 km. At the cost of reducing the offensive load, the range could be increased to 1,500 km. To solve these difficulties, the project envisaged the use of external fuel tanks of 520 kg to be located under the wings. In this case the take-off weight was 7025 kg.
In November 1939, after a detailed review of the model, the construction of the prototype was approved. By decision of the Defense Committee on 4 March 1940 two copies would be built, B-1 and B-2, at Factory No. 22. The first version would correspond to a fast bomber, while the second would correspond to a dive bomber. The B-2 would have a wider fuselage and nose with a different configuration.
The B-1 prototype with Klimov M-105 series engines was completed around October 1940 and flight tests immediately began. On October 2 the B-1 was taken off the list of Factory No.22 and ground work and test runs began. The problems presented by the Klimov M-105 engine, which ended with catastrophes in Nikolai Polikarpov’s aircraft, forced extreme care in the tests of the B-1, so it was decided to transfer the plane to the Central Airfield in Moscow where the November 6 took flight with test pilot Yu.K. Stankievich at the controls. After six flights, it was decided to return the plane to the airfield of Factory No.22 in Fili. On 26 November 1940, while landing at Fili the left landing gear was damaged.
Upon returning to the workshops, Arjangelsky decided to take the opportunity and carry out a series of improvements as a result of the test flights carried out. The plane was ready to fly again on February 20, 1941.
Between 24 March and 9 of June 1941 the factory tests piloted by Stankevich got excellent speed of 540 km / hr at 4900 meters. After minor refinements it was expected to increase this number by 20 – 25 km / h. The second prototype, the B-2, was built during the summer of 1941 and it was expected to achieve an increase of 40 to 60 km / h.
In November 1940 a high-ranking commission that included representatives of the TsAGI, the VVS and the NKAP made a comparison between the Petlyakov PB-100, the Yakovlev BB-22PB and the Arjanguelsky SB-RK and SB-B. As a result of this meeting, it was decided to promote the production of the PB-100 (future Pe-2) as the main dive bomber and to keep the BB-22 in production. The SB-B was not approved because at that time it had not yet passed the testing stage. However, the program received the green light to continue its course.
Despite the excellent results obtained by the SB-B, even superior in many respects than those of the Pe-2, the start of the war brought about the cancellation of the project. The prototype B-1 was sent to the rear deep once the decision to evacuate the KB of Arjanguelsky to the city of Omsk. What may have happened later is unknown. Arjanguelsky set about repairing the existing SB bomber and was eventually reinstated to the KB of Tupolev.
SB-B / B
Engines: 2 1050 hp М-105Р engines in the B-1
Wingspan: 16.00 m
Wing area: 46.0 m²
Length: 12.27 m
Height: 3.52 m
Empty weight: 4100 kg
Normal takeoff weight: 5980 kg
Maximum speed at sea level: 454 km / h
Maximum speed at height: 540 km / h
Cruising speed: 475 km / h
ROC: 788 m / min
Range at 80% maximum speed: 880 km
Ceiling: 10,100 m
Crew: 3: commander, navigator and radio operator-gunner.
Armament: 4 ShKAS 7.62 mm machine guns
Bombload: 8 max capacity was 1000 kg / normal weights 600 kg
All Aero 