Spanish Air Force Bomber The SB (Skorostnoy Bombardirovschik – High-speed Bomber) was one of the world’s first twin-engined bombers with smooth metal plating and retractable chassis. SB (ANT-40) has constructed in the A. N. Tupolev design bureau under the supervision of A.A. Archangelsky. It made its maiden flight in October 7, 1934. M-100 engines powered first serial aircraft. They took part in Spanish Civil War (nicknamed “Katiushka” by Republicans and “Martin Bomber” by Nationalists). Since 1937 it were produced SB with M-100A engines and three-blade propellers. These aircraft became the basis of Soviet bomber aviation. SB took part in many armed conflicts in late 30s and in the initial stage of the Soviet-German War. In 1938 began license building of SB 2M-100 in Czechoslovakia as Avia B-71. These aircraft later served in Bulgarian Air Force and German Luftwaffe.