Tupolev SB

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".
It was successful in the Spanish Civil War because it outpaced most fighters, but obsolete in 1941.
By June, 1941 94% of bombers in the Red Army air force (VVS RKKA) were SB.

Development

The skill gathered with MI-3 and DIP aircraft design was widely used.
All the development, tests and serial production had no major problems.

The SB was designed and developed in the Tupolev's KB by a team of A. A. Arkhangelski.
The aircraft entered serial production in 1936 on 2 plants until 1941.

Numerically the most important bomber in the world in late 1930s, SB was the first modern stressed-skin aircraft produced in quantity in the Soviet Union and probably the most formidable bomber of mid-1930 era. Many versions saw extensive action in Spain, China, Mongolia, Finland and in the beginning of the War against Germany in the year 1941. It was also used in various daties in civil variants, as trainers and in many secondary roles.

In the year 1933 Administration of Air Force (UVVS) had drawn up an outline requirement for a high-speed bomber. Work began in Jan 1934, two prototypes were designed as ANT-40(.1 and .2). ANT-40.2 was considered a production prototype, it's performance was impressive. The series aircraft designation was SB-2, the first series SB rolled of production line before the end of 1935 and before ANT-40.2 had completed its flight test programme.

The SB-2 was all-metal monoplane powered by two M-100 12 cylinder water-cooled engines (license production version of HS-12-Yrds engine) which drove fixed-pitch two bladed metal propellers. The engines were provided with honeycomb type frontal radiators enclosed by vertical termostat controlled cooling shutters. At an early production stage, the M-100 engine gave place to improved M-100A engine, this driving ground-ajustable three-pitch propellers, speed being boosted to 423 km/h (264 mph) at 4,000 meters (13,100 ft).

Despite the fact that the assembly lines were playned with a constant string of modifications, some 400 SB's were to be delivered by the end of 1936 - a number of these being diverted to Spain - and 24 VVS squadrons were in process of working up with the new bomber. Outstanding well recorded performance in Spanish civil war acquired popular name "Katyushka" In the year 1937 were successfully concluded negotiations between the Soviet and Czechoslovak governments for manufacture of the SB under licence in Czechoslovakia.

The version of the SB to be supplied to and subsequiently licence built in Czechoslovakia was fundamentally the SB-2M-100A and, as a B-71, thes was to be fitted with the Avia-built Hispano-Suiza 12-Ydrs engine. A single 7.92 mm vz. 30 machine gun supplanted the twin ShKAS weapons in the extreme nose and similar weapon was provided for the dorsal and ventral stations.

60 aircraft were to be flown to Czechoslovakia by the summer of 1938. The planned licence production programme was to take a decidedly leisurely course, despite the increasingly dangerous political situation. Than, by 15-Mar-1939, when the Wehrmacht was to occupy Bohemia and Moravia, not one Czech built aircraft was to have been delivered.

Variants