replacing the navigator. Over 120 built, powered by the M-100A or M-103. SB-MN (Men'she nesushchye – reduced area) or MMN (Modifikatsiya men'she nesushchye) — second generation level bomber powered by 783 kW (1,050 hp) M-105 engines and with new wings with NACA 22 high lift airfoils, reduced wing area and span (18.0 m (59 ft 0¾ in). One built. SB-RK (Razreznoye krilo – slotted wing) – Dive bomber developed in parallel with SB-MN. Same wings as SB-MN, but with large slotted flaps usable as dive brakes. The cooling radiators were buried within the wings, with an air intake on the leading and the exhaust on the wing's upper surface. Equipped with three ShKAS machine guns, and it could carry six bombs or two bombs internally or bombs externally. Ordered into production as Arkhangelskii Ar-2. 200 built before it was superseded by the Pe-2 and Tu-2. SBB-1 — Archangelskii's last iteration of the SB, based on SB-MN and -RK, with even smaller wings (16.0 m (52 ft 5⅞ in) span) twin tail and other changes. Alternative designation B. One prototype flown 1940 but no production. Avia B-71 – SB 2M-100A licence built in Czechoslovakia. PS-40 – cargo version for Aeroflot, powered by M-100A engines and with all military equipment removed. Capable of carrying cargo or six passengers. 100 supplied during 1938. PS-41 – Conversion of SB 2M-103 as freighter for Aeroflot. PS-41bis fitted with underwing fuel tanks. Pterodactyl – SB 2M-103 fitted with fixed tricycle landing gear. One converted 1940. Operators Bulgarian Air Force operated 32 Avia B-71 aircraft redesignated Avia-Katiusza Ě-8. Chinese Nationalist Air Force received 62 SB 2M-100 bombers in the autumn 1937. The Soviet Union delivered 3 more SB 2M-100 and SB 2M-105 bombers from August 1938 – June 1941. China-Nanjing The Reorganized Republic of China Air Force had two Tupolev bombers that had been flown by defected Nationalist pilots. Czechoslovak Air Force received 60 Russian-built SB with Hispano Suiza 12Ybrs engines in April and May 1938. Another 101 bombers and 60 reconnaissance aircraft were ordered to be built under license as the Avia B-71 but only 101 were built. Finnish Air Force operated 24 SB bombers. The first eight aircraft (seven powered by M-103 engines, one by M-100 engines) were captured during the Winter War, another 16 aircraft were converted from German-captured material from 5 November 1941 – 27 August 1942. All aircraft were refitted with M-103