Tupolev SB

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The Tupolev ANT-40, also known by its service name SB (Скоростной бомбардировщик - Skorostnoi Bombardirovschik - "high speed bomber"), 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". 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.

Tupolev ANT-40 (SB) at Monino

[edit] Development

The plan to build ANT-40/SB was developed in February 1934 at TsAGI. Two versions were planned: with Wright Cyclone engines and with Hispano-Suiza 12Y.

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 duties 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.

Tupolev SB-2s of the Finnish Air Force lined up.

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 thermostat controlled cooling shutters. At an early production stage, the M-100 engine gave place to improved M-100A engine, this driving ground-adjustable 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 plagued 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 license in Czechoslovakia.

The version of the SB to be supplied to and subsequently license built in Czechoslovakia was fundamentally the SB-2M-100A and, as a B-71, 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 license production program 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.

[edit] Variants

ANT-38 - prototype with radial engines. Maybe, it is ANT-40.1.
ANT-39 - related?
ANT-40.1 and ANT-40.2 - designations of two SB prototypes (2RTs 2 x Wright Cyclone engines and 2IS 2 x Hispano-Suiza engines)
ANT-40 2RTs - the first variant for Wright Cyclone (545 kW, 730 hp) built in Oct 1934. It was a bit less than most of the later SBs. Test flights (I.S.Zhurov and K.K.Popov) 7-31 October 1934 ended in landing crash. The aircraft was recovered to Feb 1935. Second test flights were done 5-Feb-1935 to 31-Jul-1935. Wing area was reduced. Became experimental (ski gears, etc). Hispano-Suiza engines were preferred.
ANT-40 2IS - built in fall 1934. Preliminary test flights in Jan 1935 shown the speed of 430 km/h (269 mph). State tests from Feb 1935 to Apr 1936. Was given to the production plant as an etalon.
SB-2M-100 - wing area grown to 56.7 m² (610 ft²). Klimov M-100 engines. First serial. Sometimes unofficially referred to simply as the SB-2
SB-2M-100A - new engines of 642 kW (860 hp). Modified engine covers. Fall 1936. Sometimes unofficially referred to as the SB-2bis
PS-40 2M-100A - cargo version for Aeroflot. 1938.
SB-2M-100A Modernized - new rear gun installation "Tur" MV-3. Tested in 1937. Accepted, but no production.
SB-2M-103/SBbis - new engines, bigger navigator cockpit, new controllable rear wheel. Tested in Sep 1937. Etalon tested 27-Jun-1938 to 19-Sep-1938. Starting from this version SB could retract ski gears. 2-Sep-1937 M.Yu.Alexeev set registered record of altitude of 40,169 ft (12,244 m) with load of 1,000 kg (2,200 lb). (1-Nov-1936 hi set unregistered record of 41,639 ft or 12,692 m). Sometimes unofficially referred to as the SB-3
USB - trainer. tested in 1938. navigator cockpit replaced for instructor pilot. small serial production.
SBbis2-2M-103 - polished wings. no serial production.
SBbis3-2M-103 - new screw/engine group. tested from 1-Nov-1937 to 17-Jan-1938. Significant speed grow. Few serial a/c were built.
SB-2M103-1939 - development of SBbis3. new radiators and partially polished wings. Screws: VISh-2, then VISh-22. Etalon tested in Sep-Oct'39. Mass production. New gunner's cockpit and guns since 1940.
PS-41-2M103U - old SBbis3 "written off" to Aeroflot for civil work.
PS-41bis-2M-103U - Mail carrier. PS-41 with additional external fuel tanks. 180 kg (396 lb) cargo load.
MMN-2M-105 - new engines, reduced wing area, 3x ShKAS only. Tested in 1939 and rejected. Used as an experimental for SB-RK.
SB-RK (also known as RK, KR, Ar-2) - dive-bomber. Two Klimov M-105R with VISh-22E props. Wing area reduced as for MMN. Radiators in wing consoles. Air inlets in wing noses. Air outcome throw the holes on the upper side of the wings. Four ShKAS. Bombs: 6x 100 kg (220 lb), 2x 250 kg (550 lb), 1x 500 kg (1,100 lb), VAP-500, ZAP-500 and others internally plus up to 1,500 kg (3,300 lb) external load. The final release of SB. Few built. The Pe-2 and Tu-2 changed it. Total 6,656 SBs and Ar-2 were built.
3-wheel SB - experimental TsAGI. Tested by M.L.Gallay. 1940-1941.
SB-2 - unofficial, but wide spread designation
DI-8/ANT-46 - two-seat heavy fighter modification with 102 mm cannon
T-1/ANT-41 - torpedo bomber modification