The Tupolev ANT-40, also known by its service name Tupolev SB , and development co-name TsAGI-40, was a high speed twin-engined three-seat monoplane bomber, first flown in 1934.
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.
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.
converted to trainer aircraft