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ANT-40 (SB)

High-speed bomber, batch-produced. The first soviet aircraft of such class, the most mass produced aircraft designed by A.N. Tupolev.



Considering the creation of a specialized high-speed bomber, which speed would be comparable with the ones of potential enemies’ fighters, began in the early 30s. By the end of 1933, enough research and development and scientific-technical reserve, which could provide the practical implementation of the concept of such aircraft, was accumulated, and the Design Bureau started designing a high-speed bomber, that received ANT-40 internal designation and the SB official one. A.A. Arkhangelskiy was appointed the project leader, and became the head of the brigade №5 created in January, 1934.

In March, 1934 the Air Force provided their mission requirements for the new airplane: maximum speed at an altitude of 4,000 meters - 330 km/h, ceiling - 8000 m, range - 700 km, bomb capacity - 500 kg, defensive weapons – 2 ShKAS machine-guns in the nose turret, 1 ShKAS in the dorsal turret and 1 ShKAS in the ventral hatch turret.




Other brigades of the Design Bureau, and divisions of TsAGI were also engaged in the work on ANT-40. Thus, the wing and control system of ailerons were developed by the brigade of V.M. Petliyakov. In the field of aerodynamics, the leader was A.K. Martynov, while A.I. Makarevskiy, S.N. Shishkin and G.A. Ozerov were solving structural problems.

As a result of hard work three months later on March 8, 1934 the preliminary design of a new bomber was submitted to the Air Force for approval. The new bomber was a twin-engine three-seat cantilever mid-wing monoplane with retractable landing gear and smooth skin of the fuselage and wing. The configuration of the aircraft was based on the requirement that for a given bomb load of 500 kg and powerful defensive weapons, dimensions of the plane should have been minimal. All payloads were arranged inside the fuselage. Aerodynamic shape of the aircraft was perfect, without any projecting parts. Thus, ANT-40 project was the logical culmination of the search for optimal solutions and development of the ideas, accepted during the work on ANT-21, ANT-29 and ANT-30 projects.



On March 10, the mockup of the aircraft was approved. At the same time, a decision to build two prototypes of ANT-40 was taken: the first one had Wright R-1820 "Cyclone" engines of 730 hp each, the second one had Hispano-Suiza 12Yrbs engines of 780 hp each.

Aircraft construction began on April 25, and on October 7, 1934, test-pilot Konstantin Popov performed the first flight of ANT-40 with "Cyclone" engines. During the ninth flight, the first aircraft crashed and was sent to the factory for recovery. Later, it was used for experimental work.
The second ANT-40 prototype with Hispano-Suiza engines became the basis for the batch production. Its construction began on May 15, 1934. On December 30, the airplane was ready and on the same day, it performed its first flight (piloted by I.S. Zhurov). Factory tests continued till January 21, 1935. The top speed of 430 km/h at an altitude of 4,000 m was recorded, which was significantly higher than specified in the mission requirements.

State joint tests of the second ANT-40 were carried out from February 8 to March 3, 1935 and were interrupted due to aileron flutter of the wing that was eliminated in several days by setting the weight compensation on ailerons (M.V. Keldysh, who later became a famous academician, was leading this work). In the summer of 1935, tests were continued and ended in April, 1936 then the aircraft was transferred to the serial factory № 22 as a standard for the batch production.



 The issue of launching batch production of the new bomber was settled much earlier, in March, 1934 already. The Soviet Air Force was in desperate need of this bomber type, so even before the end of the state tests, in March, 1935 (according to some documents – from December 5, 1934), transfer of documentation to the plant № 22 began. According to the decision of the government in mid-1936, brigade №5 led by A.A. Arhangelskiy was sent to the production plant as an independent experimental design bureau for the implementation and improvement of ANT-40 (SB).

The first production SB aircraft was produced in the spring of 1936, but with domestic M-100 engines (750 hp each), hence the name of the first production machine was SB-2M100. From March 25 to July 31, 1936, service tests of the five SB-2M100s of the first prototype batch were being performed. On the basis of these tests, the aircraft was brought into service.

SB bombers of various modifications have set different world and national records:
- On November 1, 1936 test-pilot M. Yu. Alekseev reached an altitude of 12,695 meters on the second ANT-40 prototype with payload of 1,000 kg, the achievement was recorded only as a national record;
- On September 2, 1937 test-pilot M. Yu. Alekseev established an international record of flying to maximum altitude with a payload of 1,000 kg, reaching an altitude of 12,246 meters on SB bis-2 prototype.


During the years of its batch production, SB was repeatedly modernized – its designers, considering experience of operating and combat operations, were constantly improving the aircraft, trying to maintain its performance at a proper level. Below is a summary of several versions of SB aircraft, which found application in the Air Force and Civil Air Fleet, and some others, remained as prototypes:



 - SB-2M100A, production SB airplane with M-100A engines of 860 hp each, batch production in 1937;
- SB-2M-100A with shielded turrets - prototype created from the experience of operating first SBs during the Spanish war. The airplane was being tested in 1937. Until 1940, only some production SB airplanes were manufactured with similar turrets (MV-2 and MV-3). Conversion of the air fleet began only after the war with Finland;
- SB-2M100A "cruiser". SB version with four ShVAK guns in the nose turret. The aircraft passed factory and field tests, and took part in repelling attacks on Moscow during the war as a night fighter. Only two airplanes were built;




Since 1936, mass production of SB started at the plant № 22, and next year, it was started at the plant № 125 in Irkutsk. Mass production of all-metal plane of SB class became an event in the world and domestic aircraft engineering. The production reached 10-13 airplanes a day. In total, prior to the termination of batch production in 1941, 6831 aircraft of various modifications had been produced.
- SB-2M100A with six RO-132 rocket rail launchers. Six SB production planes, reequipped with RS-132 rocket launchers, took part in the war with Finland;
- Prototype SB bis with M-103 engines (960 hp each), frontal radiators and three-bladed propellers VISh-2. The airplane was being tested in 1937-1938;
- Prototype SB bis-2 with M-103 engines and frontal radiators. The airplane became the basis for the batch production;
- Prototype SB bis-3 with M-103A engines and tunnel radiators. The airplane was being tested in 1937-1938 and became the basis for the batch production;
- Production SB-2M103 aircraft with frontal radiators of increased safe load factor, external hard points for bombs and armoured backrest, batch production in 1938 - 1939;
- production SB-2M103 airplane with duct radiators - the fastest SB (450 km/h at 4,100 m), batch production in 1939-1940;
- prototype SB-2M103 dive bomber;
- prototype SB-2M103 (SN), with ultra-quick firing SN machine guns;
- SB-2M103 "Searchlight" - one of the production SB airplanes equipped with searchlights to illuminate enemy bombers, was used in the anti-air defense of Moscow during the war;
- SB-2M103 "balloon cable cutter" – production SB airplane reequipped with cable-cutting devices;
- SB-N - SB-2M103 with the installation of ShVAK movable cannon in the NU-SB nose turret instead of machine-guns;
- SB-SH - SB-2M103 converted into a prototype attack aircraft with two ShVAK movable guns under the fuselage, bomb capacity of 400 kg and reinforced pilot and navigator cockpit’s armoring;
- SB-UK (USB) - SB-2M100A and SB-2M103 training airplanes, equipped with special training cabin. Tests were performed in the spring of 1938. Most of the bombers were reequipped combatant SB bombers, although a small batch of SB-UK 2M103s was released;
- SB-2M-104, a small batch of SBs with M-104 engines and new weapons;
- MMN ("Maximum aircraft modernization "N" "), a deep modernization of SB with the M-105 engines (1050 hp each), improved aerodynamics and advanced weapons. Tests were performed in 1939, but the aircraft was never batch produced;
- Prototype MMN-2M-104 airplane - the MMN "twin" with M-104 engines;
-SB-2M-105, a small batch of SB with M-105 engines and new weapons, produced in 1940;
- SB-2M105 TK (TK-2) - three production SB-2M105 airplanes equipped with turbochargers. The airplane was never batch produced;
- SB-2M100 on floats, project of 1934, was not implemented;
- SB-2M103 with tricycle landing gear, experimental aircraft, was tested in 1940-1941 in the LII;
- PS-40 - SB-2M100As with removed armament - transferred to CAF, used as cargo;
- PS-41 - upgraded PS-40 with M-103U engines. The first aircraft was released by the CAF’s plant № 89. Then, SB-2M103s received from the Air Force were also reequipped in the same way;
- PS-41bis – a number of PS-41s, equipped with additional external fuel tanks;
- B-71 - SB-2M100A, manufactured in Czechoslovakia since 1937 under license. The airplanes were used in the Air Force of Czechoslovakia, Germany, Slovakia, Bulgaria and Finland;
- SB-RK (Ar-2), a dive bomber, a profound modification of SB and the development of MMN. The aircraft was in batch production until the war. In total, about 200 airplanes were built.



First SBs began arriving to the Air Force combat units in 1936. Already on November 7, 1936 large units of the Air Force flew on SBs over Red Square. And even earlier, in September, Soviet crews of pilots-internationalists took part in the battles for Republican Spain, flying SB-2M100s. SB airplanes presented themselves very well in Spain and for a long time they were virtually invulnerable to German and Italian biplane fighters, speeds of which were less than the speed of the bomber. This situation continued until the appearance of Me-109 in the sky of Spain. Since autumn, 1937 SBs with the Soviet and Chinese crews took part in the battles against Japan. Then, SBs were used in military conflicts at Khasan Lake, Khalkhin Gol River and in the war with Finland. By the beginning of the Great Patriotic War, SB aircraft were considered already outdated, but they were the basis of the Soviet front-line bombers and were actively used on all fronts until 1943.


The main drawbacks of these airplanes during the war were weak defensive armament and almost total absence of armour protection for the crew and vital parts of the aircraft, which resulted in large losses of SBs under the domination of the enemy in the air and often, under the lack of fighter cover during a combat mission. After 1943, SB remained in service as a transport, a tug for cargo gliders and gunnery practice targets, a training aircraft and a liaison aircraft.

Today, only one SB airplane exists, that was rebuilt by the Design Bureau and the aircraft development plant, and it is presented in the Museum of the Air Force in Monino.

SB bombers of various modifications have set different world and national records:

- On November 1, 1936, test-pilot M. Yu. Alekseev reached an altitude of 12,695 meters on the second ANT-40 prototype with the payload of 1,000 kg, the achievement was recorded only as a national record;
- On September 2, 1937, test-pilot M. Yu. Alekseev established an international record of flying to maximum altitude with a payload of 1,000 kg, reaching an altitude of 12,246 meters on SB bis-2 prototype.



Basic characteristics of SB-2M100A production aircraft:
• aircraft length, m- 12.27
• wing span, m - 20.33
• height, m - 4.735
• wing area, m2 - 56.7
• normal takeoff weight, kg - 5,732
• bomb capacity, kg - 500/600
• maximum speed at an altitude of 4,000 m - 423 km/h
• practical ceiling, m - 9,560
• maximum range, m - 1,500
• machine-guns - 4 x ShKAS
• crew, persons - 3