An outstanding mid-30s flying machine which became obsolete by the start of WWII
The two ANT-40 light bomber prototypes of Andrei N. Tupolev's design bureau, designed and developed by a team led by A. A. Arkhangelski, were years ahead of their time when they first flew in October 1934: the all-metal construction, enclosed cockpit and retractable landing gear were then comparatively novel features. Indeed the ANT-40's maximum speed of 325km/h at operating height was faster than the biplane interceptor fighters that equipped most of the peacetime air forces.
The initial production version as selected for export and service with the V-VS was based on the second prototype, and was known as the SB-2 (skorostnoi bombardirovshchik, or fast bomber); the engines were two 619kW licence-built Hispano-Suiza 12Ybr engines, termed M-100 by Soviet industry, and initially they were fitted with two-bladed fixed-pitch propellers.
The first SB-2s were passed to the V-VS's bomber aviation regiments in February 1936, and in October of that year the first of 210 were transferred with Soviet crews to Spain to fight on the side of the Republican air force against the insurgent Nationalists. Over Spain the performance of the SB-2 caused considerable concern to the Nationalist fighter units which were equipped with Heinkel He-51 and Fiat CR.32 biplanes, and the urgent call went out for fighters of better speed and climb properties.
At the time SB-2s were passed to the Chinese Nationalist air force to fight aganst the Japanese, and to Czechoslovakia, where the type went into licensed manufacture as the B.71 bomber. The version of the SB to be supplied to, and subsequently license-built as the Avia B-71 was fundamentally the SB 2M-100A but fitted with the Avia-built Hispano-Suiza 12-Ydrs engine. A single 7.92 mm ZB-30 machine gun supplanted the twin ShKAS machine guns in the nose and similar weapons were provided for the dorsal and ventral stations.
In general the SB-2 performed well until faced with sterner fighter opposition, which occurred over Spain in 1938 and in particular over Finland during the Winter War of 1939-40, when many were shot down.
Steps were taken to improve performance by installing the 641kW M-100A engine with variable-pitch propellers. Increased fuel capacity and two 716kW M-103 engines were installed in the Tupolev SB-2bis, the performance of which was improved by three-bladed VISh-22 propellers. In addition to the PS-40 and PS-41 transport versions the SB-RK (Arkhangelskii Ar-2) was a modified SB-2bis dive-bomber with reduced wing area and powered by two supercharged M-105R engines.
The SB-2's record as a day bomber came to an abrupt end during the fierce fighting following the German invasion of the USSR on 22 June 1941. Those that were not destroyed on the ground ventured into the air on numerous and gallantly-flown missions over the front line, and paid a heavy price to the Luftwaffe's Messerschmitt Bf 109F fighters.
Czechoslovakian Air Force received 60 Russian-built SB with Hispano Suiza 12Ybrs engines in April and May 1938. Another 101 bombers and 60 reconnaissance aircraft were license-built Avia B-71.
Finnish Air Force operated 24 SB bombers. The first eight aircraft (seven powered by M-103 engines, one by M-100 engines) were captured during the Winter War, another 16 aircraft were converted from German-captured material from 5 November 1941-27 August 1942. All aircraft were refitted with M-103 engines and were used as anti-submarine aircraft in the LeLv 6 squadron. Two aircraft were rebuilt and were used as trainers. The Finnish Air Force withdrew all SB aircraft in 1945, and all were scrapped in 1950.
Luftwaffe operated captured aircraft, Czech-built Avia B-71 and Soviet SB.
Polish Air Force operated few USB-2M-103 aircraft for training after World War II.
Republican Spanish Air Force received its first 31 SB-2M-100A bombers on 14 October 1936. The second batch of 31 aircraft was delivered in June–July 1937 and a final batch of 31 following in 1938. The Soviet Union delivered a total of 93 SBs to Spain.
Nationalist Spanish Air Force captured 19 SB-2M-100A bombers. All were overhauled and Soviet M-100 engines were replaced with French Hispano Suiza 12Ybrs. These aircraft were used operationally and later for training duties, and were retired in 1950. Spanish pilots called captured SB bombers Katiuska.