The design was very advanced, but lacked refinement, much to the dismay of crews and maintenance personnel – and of Stalin, who pointed out that "there are no trivialities in aviation".
Numerically the most important bomber in the world in the late 1930s, the SB was the first modern stressed skin aircraft produced in quantity in the Soviet Union and probably the most formidable bomber of the mid-1930s. Many versions saw extensive action in Spain, the Republic of China, Mongolia, Finland and at the beginning of the War against Germany in 1941. It was also used in various duties in civil variants, as trainers and in many secondary roles.
Successful in the Spanish Civil War because it outpaced most fighters, the aircraft was obsolete by 1941. By June 1941, 94% of bombers in the Red Army air force (VVS RKKA) were SBs.
Operational historyThere were a number of foreign customers for the SB. They were mostly satisfied with the aircraft's performance. There were some complaints about the high noise level, cramped crew compartments, hard undercarriage suspension and in particular about the front gunner's position, that could be reached only through a hatch under the fuselage. Consequently, in case of a ditching or belly landing, the gunner could not escape.
Spanish Civil WarWhile only 54 SBs had been delivered to the Soviet Air Forces by 1 July 1936, this did not stop the new Tupolev bomber being amongst the first shipments of military equipment sent by the Soviet Union to support the Spanish Republicans when the Spanish Civil War broke out on 17 July 1936. An initial batch of 31 SBs arrived in Cartagena aboard the Soviet Freighter Komsomol in October 1936, flying their first mission, a bombing raid by four SBs against Tablada airfield, Seville on 28 October. The SBs were used to equip Grupo 12 of the Spanish Republican Air Force, which at first was mainly manned by Soviet volunteers and under Soviet control.
The SB could outpace the Fiat CR.32 and Heinkel He 51 biplane fighters of the nationalist forces, and was therefore difficult to intercept, with dives from high altitude being the only way to intercept the SB. On 29 May 1937 two SBs attacked the German pocket battleship Deutschland, mistaking it for the Nationalist cruiser Canarias, killing 31 and injuring a further 83 German sailors. In June–July, a second consignment of 31 SBs were received, allowing Grupo 12 to return to full strength, and a new unit, Grupo 24, to be established. The delivery of Messerschmitt Bf 109s to re-equip the German Condor Legion meant that the SB could no longer evade Nationalist fighters by sheer speed, and losses rose.
A third and final batch of 31 SBs arrived in June 1938, allowing operations to continue, although losses continued to be high. By the time the Civil War ended in March 1939, 73 SBs had been lost, 40 of them to enemy action. Nineteen SBs were taken over by the Nationalists, and used to form a bomber squadron. Although some were re-engined with French Hispano-Suiza 12Ybrs engines to aid maintenance, they were still subject to spares shortages, and in April 1943 only three were airworthy. When Junkers Ju 88s were received in December 1943, the remaining SBs were used for occasional training flights until withdrawn and scrapped in 1948.
In July 1937, the Second Sino-Japanese War broke out. The Soviet Union signed the Sino-Soviet Non-Aggression Pact on 21 August 1937, and as part of this agreement, supplied large amounts of military equipment to the Chinese Nationalists, as well as deploying complete air force units, nominally manned by Soviet volunteers. An initial delivery of 62 SBs was made in September–October 1937, with combat operations by Soviet forces starting in December with attacks on Japanese ships on the Yangtze River. On 23 February 1938, to celebrate Soviet Army Day, Soviet SBs carried out a long range attack on Japanese airfields on Taiwan, claiming 40 Japanese aircraft destroyed on the ground.
A further 60 SBs were delivered to China in early 1938, these being heavily used to attack Japanese forces during the Battle of Wuhan. Losses were heavy, forcing the Chinese SB units to be temporarily withdrawn from combat. The Soviet units operating the SB over China re-equipped with the Ilyushin DB-3 in 1939, allowing their SBs to be transferred to Chinese units, but the Chinese made limited use of these reinforcements.
The Soviet Union supplied a further 100 SBs in 1941, just before it signed the Soviet–Japanese Neutrality Pact. The SB was gradually phased out of front-line operations against the Japanese with the delivery of more modern American bombers from 1942, being partly replaced by Lockheed Hudsons and B-25 Mitchells. Limited numbers of SBs continued in non-combat use, including operations against opium plantations, before being used against the Communists when the Chinese Civil War flared up in 1945, being finally withdrawn in 1946.
MongoliaAs well as the aircraft operated by volunteers against the Japanese over China, SBs were used in combat against the Japanese during the Fighting near Lake Khasan on the border between the Soviet Union and Manchuria in July–August 1938, one SB being lost. Fighting between Soviet and Japanese forces broke out again at Khalkhin Gol in Eastern Mongolia in May 1939. While SBs were not involved in the May air battles, where the Soviet forces received heavy losses, two Regiments of SBs were deployed to Mongolia in June, flying their first missions on 26 June. SBs were used heavily against Japanese forces when they attacked in early July. The Soviet SB regiments consisted of a mixture of early and later SBs, whose differing speeds caused problems in maintaining formation, while Japanese Nakajima Ki-27 fighters proved adept in exploiting the poor defensive armament of the SB, with the radio operator operating both the dorsal and ventral guns. To minimise losses to Japanese fighters, the Soviets changed tactics, flying SB missions at over 6,100 m (20,000 ft) where it was difficult for the Japanese to intercept. SBs continued to be used against the Japanese as the Soviets and Mongolian forces commanded by Georgy Zhukov carried out a successful offensive until a cease-fire was signed in September 1939.
Winter WarOn 30 November 1939, the Soviet Union attacked Finland in the conflict that became known as the Winter War, with the forces deployed against Finland including several hundred SBs. Losses were heavy, with bomber formations often un-escorted, and forced to operate at low level, where they were vulnerable to Finnish anti-aircraft fire and fighters. While in 1936 in Spain, the SB could outpace enemy fighters, by now it was vulnerable and poorly armed. SBs were fitted skis for operation from snow covered airfields, slowing the aircraft and making them more vulnerable, while the need to wear heavy winter clothing made the gunner's job even harder. By the end of the 15 week war, at least 100 SBs had been lost, with the Finns claiming nearly 200 shot down, 92 of them to Finnish fighters.
Eastern FrontWhen Germany invaded the Soviet Union in June 1941, re-equipment with more modern aircraft such as the Pe-2 had begun. Still, 94% of the Soviet operational bomber force was equipped with SBs, with 1,500–2,000 SBs deployed along the Western border districts of the Soviet Union.The Luftwaffe started Operation Barbarossa with co-ordinated strikes against 66 major Soviet airfields, destroying a large proportion of Soviet air strength on the ground or air on the first day of the invasion. The SBs that survived the carnage of the first day continued to be poorly used, many being frittered away in unescorted low-level attacks against German tanks, where the SB's relatively large size and lack of armour made it highly vulnerable to German light Flak, while German fighters continued to take a heavy toll. Within a few days, losses forced most of the remaining SBs to switch to night attacks.
SBs continued to be used, in the defense of Leningrad and Moscow, mainly at night by attacking German artillery. By December 1941 almost all of the SBs had either been replaced or lost, although it remained in large-scale use until March 1942 in the North against Finland. SBs continued in use for non-combat roles such as supply dropping, glider towing and training, and continued in use in the Far East until 1945.
Many Soviet SBs crashed or force-landed on Finnish soil during the Winter War, with the Finns salvaging as many aircraft as possible, with those in the best condition being sent to Valtion lentokonetehdas for possible repair for use by the Finnish air force. By the time of the Continuation War against the Soviet Union, when Finland moved to recover the territory lost in the Winter War, five SBs had been repaired (with a further three added later), being used to equip Lentolaivue 6, flying Maritime patrol and attack missions. These aircraft were supplemented by a further 16 SBs purchased from Germany, who had captured them during the initial weeks of the invasion of the Soviet Union. These SBs employed the first air-dropped depth charges used in combat. Finland lost seven SBs to accidents during the Continuation War, with none being lost in combat, with Finnish SBs claiming three Soviet submarines and a 4,000 ton merchant ship sunk.
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"Just had luck ... / Nochmal Glück gehabt ... ! "