Tupolev TB-3

The Tupolev TB-3, designated ANT-6 by the Tupolev design bureau, was a four-engine monoplane heavy bomber flown by the Soviet Air Force in the 1930s and in the early years of the Second World War. It was among the first heavy bombers in the world to use a cantilever wing, and its all-metal airframe of corrugated steel skin followed the construction practice pioneered by Hugo Junkers. The prototype first flew on 22 December 1930, and series production was approved in February 1931 with Mikulin M-17 engines. Production aircraft proved heavier than the prototype, and the factories paid workers for each kilogram removed. Officially withdrawn from bomber service in 1939, the type still numbered 516 operational aircraft when Germany invaded in June 1941 and flew night bombing, cargo and paratroop missions. It also served as the mothership in the Zveno project, carrying fighters, and as a transport for light tanks. No complete example survives.