Tupolev SB-2
The Tupolev SB, developed as the ANT-40, was a Soviet twin-engined high-speed bomber designed in Andrei Tupolev's bureau by a team led by A. A. Arkhangelski and first flown in 1934. Two Soviet factories built 6,831 of them; the type fought in Spain, China, Mongolia and Finland, and still formed 94 percent of the Soviet operational bomber force when Germany invaded in 1941, by which time modern fighters had overtaken the speed that had once protected it.
Why It Mattered
The SB took its service name from the Russian words for "high-speed bomber", and speed was the whole idea: when it appeared in the mid-1930s it could outrun the biplane fighters then in service. It was the first modern stressed-skin aircraft built in quantity in the Soviet Union, and Wikipedia describes it, by the late 1930s, as numerically the most important bomber in the world. Two Soviet factories built 6,831 of them, and when Germany invaded in June 1941 the type still made up 94 percent of the Soviet operational bomber force. By then, though, fighter speeds had risen past it, and the type was obsolete.
Design Notes
The SB was designed and developed in Andrei Tupolev's design bureau by a team led by A. A. Arkhangelski, answering a Soviet requirement issued in 1933 for a high-speed bomber. Two ANT-40 prototypes flew in 1934, the Wright Cyclone-powered one first, on 7 October, and a Hispano-Suiza-powered one on 30 December that showed superior performance and set the pattern for production. The production aircraft was an all-metal monoplane seating three, powered by two Klimov M-100 engines — the Hispano-Suiza 12Y built under licence — behind honeycomb frontal radiators. Its broad, high-aspect-ratio wing gave it good performance at altitude, and Soviet crews nicknamed the aircraft the "Pterodactyl". Defensive armament was four 7.62 mm ShKAS machine guns: two in the nose, and one each in dorsal and ventral positions. The design was advanced but short on refinement, and teething trouble on the production prototype drew from Stalin the remark that there are no trivialities in aviation. Engines improved in steps: the M-100 gave way to the more powerful M-100A, and from 1938 to the yet more powerful M-103, and later installations slung the radiators under the engines.
Operational History
The first production SB came off the line before the end of 1935 and entered full production in 1936; some 400 had been delivered by the end of that year. In October 1936 the first batch of 31 reached Spain, where the SBs equipped Grupo 12 of the Republican air force, at first mainly manned by Soviet volunteers and under Soviet control. There its speed made interception difficult — Nationalist fighters had to dive from altitude to catch it — and the type acquired the popular name "Katyusha". The arrival of Messerschmitt Bf 109s with the Condor Legion ended that protection: the SB could no longer evade fighters by sheer speed, losses rose, and 73 had been lost by the time the Civil War ended in April 1939. SBs next fought over China: from December 1937 Soviet forces attacked Japanese ships on the Yangtze River, and on 23 February 1938 they made a long-range attack on Japanese airfields on Taiwan. In Mongolia in 1939, two SB regiments deployed in June and flew their first missions on 26 June; the type later worked above 6,100 metres, where interception by Japanese fighters was difficult. The Winter War against Finland cost at least 100 SBs, with the Finns claiming nearly 200 shot down; formations often flew unescorted and at low level, vulnerable to anti-aircraft fire and fighters. When Germany invaded in June 1941, between 1,500 and 2,000 SBs were deployed along the western border districts; losses in the first days forced most of the remaining aircraft to switch to night attacks. By December 1941 almost all had been replaced or lost, but the type kept secondary duties — supply dropping, glider towing and training — and remained in use in the Far East until 1945.
Afterlife
Most ANT-40s that survived the Second World War were scrapped in Stalin's post-war cleanup of the 1950s. One exception was an aircraft that had force-landed in a snow storm in the Yuzhne Muiski mountains in the Baikal region: recovered in the late 1970s, it was returned to Moscow, restored by volunteer Tupolev employees, and unveiled at the Central Air Force Museum at Monino in April 1982. A second ANT-40 is displayed at Verkhnyaya Pyshma; the source names no other survivors. The design outlived the SB itself in one descendant: the SB-RK dive bomber, renamed the Arkhangelsky Ar-2 after its designer, was ordered into production, and 200 were built before the Pe-2 and Tu-2 superseded it.