Staff Writer (Updated: 5/1/2015):
The SB-2's initial design came from the Tupolev firm in the form of two light bomber prototypes designated as the ANT-40. The second prototype was selected as the production model and came to be known as the SB-2. The system featured twin license-built Hispano-Suiza piston engines generating about 830 horsepower each, giving the SB-2 a top speed of over 200 miles per hour which was, at that time, faster than most of the fighters available in any one country. The maiden flight took place in 1934 and the system was hitting frontline units by early 1936.
The SB-2 was fielded with Soviet crews fighting in the Spanish Civil War for a time. Examples were also passed on to China in an effort to thwart the Japanese incursion occurring on that side of the globe. Additionally, Czechoslovakia was allowed to license-produce the system as the B-71. By war's end, some 6,900 examples would have been produced.
The SB-2 aircraft was a typical two-engine design when compared to other World War Two fast bombers of this type. Engines were mounted on a low-wing monoplane design with a slender single-rudder fuselage. The crew of three consisted of the pilot, a nose gunner and a dorsal gunner. Armament was defensive and consisted of 2 x 7.62mm machine guns in the nose, 1 x 7.62mm machine gun in a dorsal gun position (sometimes fitted to a turret instead) and 1 x 7.62mm machine gun in a ventral gun position. Maximum bombload capacity was limited to 2,205lbs of internally-held stores.
Tupolev SB-2's operated with success in the early years of operation. It was not until the more capable and advanced German Messerschmitt Bf 109 fighters arrived that the system's drawbacks truly shown through. In an effort to keep the system as a viable weapons platform, the SB-2 was modified the addition of increased fuel capacity, three-bladed propellers and M-103 type engines generating some 960 horsepower each. Nevertheless, the system still under-performed and took on heavy losses in the day bomber role. As such, the system was relegated to after hours work as a dedicated nightfighter.