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68 (Tu-4)

 

 

 

Before the beginning of the World War II, modern four-engine long-range bomber TB-7, developed by EDB of A.N. Tupolev, with performance on the level of similar airplanes of world's leading aviation powers, entered service with the Air Force of the Red Army. However, the actual conditions of the Great Patriotic War did not allow deploying a full-scale production and assimilation of the aircraft in the Air Force units. The brunt of the struggle in the air over the Soviet-German front was borne by the front-line aviation unit, that’s why during the war contribution of four-engine heavy bombers to the Soviet Air Force, such as TB-7, was small. These airplanes were part of the Long Range Aviation, and by the end of the war, it consisted of about 2,000 of different airplanes. They were mostly middle-class twin-engine bombers, such as DB-3F (IL-4), Er-2 and B-25 under Lend-Lease, as well as Li-2 and C-47 transport aircraft. Four-engine bombers were represented by several tens of TB-7s and outdated TB-3s. At the end of the war, the long-range aviation gained a small number of repaired four-engine B-17 and B-24 US bombers, captured by the Red Army in Eastern Europe. In total, soviet aviation industry has produced 93 TB-7 aircraft, compared with the US aviation industry that has produced about 30,000 four-engine bombers such as B-17, B-24, B-29, and the UK aviation industry that has produced about 10,000 four-engine bombers.

 

 

 

In 1943, the military-political leadership of the USSR began to receive regular information on the developing of B-29 "Superfotress" - the US long-range high-speed high-altitude bomber. It was decided in the USSR to begin the work on the aircraft, with performance similar to that of American aircraft, with an eye to getting a similar aircraft into service with Soviet Air Force by the end of the war. Besides, it should be noted that it was 1943 when the Soviet Union intensified work on its own atomic bomb project - new "super weapon" needed a decent aircraft carrier.
In the second half of 1943, several domestic aviation bureaus were given the task of the preliminary engineering of a modern four-engine long-range high-speed high-altitude bomber, with similar performance to that of B-29. In particular, within the framework of the project, design bureau of I.F. Nezval was working on deep modernization of TB-7 and on the project of the new four-engine bomber, while design bureau of S.V. Ilyushin was working on IL-14 bomber, and design bureau of V.M. Myasischev – on DVB-202 and DVB-302 aircraft projects. The biggest progress in the creation of a new long-range bomber was achieved at this stage by design bureau of A.N. Tupolev, which started developing project "64" since 1943.
In September, 1943 the Bureau was suggested to develop a preliminary design and build up a mockup of the high-altitude heavy bomber with M-71TK-M engines, pressurized cabins and cannon defensive weapons. The aircraft was to have the following basic performance:

maximum speed at an altitude of 10,000 m 500 km/h
range at a speed of 400 km/h and full bomb load 5,000 km
with 7,000-8,000 kg bomb load 6,000 km
 bomb bay capacity 10,000 kg

The Bureau was to design a heavy bomber similar to the American B-29 in its class and performance, given that the new bomber had to be built using the existing domestic technologies, materials and equipment. Designing a new aircraft that got "64" designation within the Bureau, and the official Tu-10 designation, was carried out in two directions: a bomber and a transport-passenger aircraft. Evaluation of the given task, carried out within the framework of the started project, showed that aircraft "64", given that the selected dimensions were close to those of ANT-42, had to be twice heavier. Thus, designers and structural engineers faced number of challenges, because stresses in structural elements of "64" aircraft were almost 2 times higher than in the corresponding elements of ANT-42. There was a war, and one couldn’t count on provision with new materials, semi-fabricated products, modern equipment and machines. All that American aircraft engineers had, designing B-29, we could only find in special aviation magazines, at best.
Despite all the difficulties, in August, 1944 preliminary design of the airplane was ready, according to which airplane "64" represented a heavy four-engine bomber, designed for daily operations deep behind enemy lines. High speed and ceiling, as well as powerful defensive cannon weapons provided aircraft operability in the areas with the strongest enemy air defense. The aircraft could carry a bomb load up to 18,000 kg, with bombs caliber up to 5,000 kg. The bombs were placed in two capacious bays: in front of the center-wing and behind it.

 

 

 

Pressurized crew cabins allowed the aircraft to fly at altitudes of up to 8,000-10,000 m. The aircraft was an all-metal monoplane with a mid-wing. Its fuselage had monocoque construction with a thick stressed skin. Two-spar wing was equipped with powerful high-lift system. The aircraft had H-tail and a three-wheeled landing gear with nose wheel. It was supposed to use one of the following types of engines on the airplane: AM-42TK or AM-43TK-300B, or diesel engines ACh-30BF, or ASh-83FN, or M-250. Structural design calculations and calculations of flight characteristics were performed for all types of these engines. Defensive cannons were to be placed in four- or two-cannon fuselage turrets with drive-by-wire control and in tail turret for one or two cannons (cannon caliber of 20-23 mm). Navigation, radio communication and radio equipment were supposed to be the most modern of all that the domestic industry could give. Plane "64" was supposed to have a high level of electrification - all major aircraft systems were electrified, except the most stressed ones, which had hydraulic actuators.
During the design, several variants of aircraft "64" were considered, that differed from each other in geometrical dimensions, layout of the fuselage, set of the equipment, weapons and crew arrangement.
In August, 1944 on the basis of preliminary work on aircraft "64", the Air Force prepared a draft of mission requirements for the long-range high-altitude bomber with four AM-42TK engines that could be replaced for AM-46TK or M-84. Long-range bomber aircraft version had to have an operating altitude of flight of 9,000-10,000 m, combat radius of at least 2,000 km, bomb capacity of at least 18,000 kg and powerful defensive armament (12 cannons of 20-23 mm caliber with a capability for transition to 45-57 mm cannon at the tail turret in future).
By September, 1944 a mockup of "64" was ready and was inspected by the representatives of the Air Force. A lot of remarks were made; in particular, a requirement for installation of panoramic bombing radar similar to B-29’s radar was added. On April 7, 1945, mission requirements for the airplane were approved. Air Force wanted to get a bomber with the following performance:

maximum speed at rated power of the engines
610 km/h
maximum speed at engines’ combat mode
630 km/h
service ceiling  

11,000 m

 range with 5,000 kg of bombs
5,000 km
tactical range with 14,000 kg of bombs
2,000 km
 take-off run
800 m

It was proposed to use turbocharged engines (AM-43TK-300B or AM-46TK-300) in the power plant.

 

 

 

On April 27, 1945 the mockup was approved. After the war with Germany, the Bureau started releasing drawings for the airplane, and preparations for the construction of the first prototype aircraft began. There were almost no issues on the airframe and power plant, except turbochargers, but equipping the aircraft in the required time limits with modern equipment that met the requirements of the Air Force was a stumbling block. At this stage, subcontracting enterprises could not supply airplane "64" with neither necessary navigation and radio equipment, nor automated remote control system for the cannon armament.
It was clear that creation of the first Soviet strategic aircraft carrier was coming to a deadlock. The country's leaders, concerned about the situation with aircraft "64", made a decision to deploy Soviet mass production of a copy of the American B-29 bomber, on the basis of four bombers interned in the Far East. The work on copying B-29 bomber was committed to the Tupolev Design Bureau, so, it focused on this priority work. Gradually, all the works on aircraft "64" were stopped, although it was in the production schedule for nearly two years more. However, another aircraft project was prepared – it was completely redesigned, regarding the experience of studying B-29. The airplane switched to the low-wing scheme that simplified transition to the passenger version, it received AM-46TK-3PB engines of 2,300 hp each, radar of "Cobalt" type, etc.

 

The basic project data of aircraft "64" with four AM-46TK-3PB engines

aircraft length, m
30
wing span, m
42.0
aircraft height, m
7,2
wing area, m2
150.3
normal takeoff weight, kg
38,000
normal bomb load, kg
5,000
maximum speed with normal takeoff weight, km/h
650
service ceiling, m
11,000
maximum range with 4,000 kg of bombs, km
6,500
cannon weapon

10 x B-20

crew, persons
10

By early 1945 it became clear that due to the gap in development of domestic aircraft equipment, work on aircraft "64" came to a deadlock. For the near future the country could be left without a strategic bomber. Having assessed the situation, the country's leadership and Stalin personally took an unusual decision - to copy and launch long-range American B-29 bomber into production. Four "Super fortress" bombers, that had made emergency landing on the territory of the Soviet Far East after raids on Japan and interned under non-aggression agreement with Japan of May, 1941 were to become the prototypes.

 

 

 
 
 

Work on creation of analogue of B-29 and its launch into serial production have been committed to the Tupolev Design Bureau. On June 6, 1945 the State Defense Committee issued a decree № 8934 on the organization of batch production of B-4 - such a designation was given to the "Soviet" B-29 at the factory in Kazan.
Three B-29 bombers were transferred to Moscow. One of them was transferred to the LII for staff training and preparation of operating manuals, the second one was transferred to the Design Bureau for disassembly, study, copy and preparation of documentation for batch production, while the third one remained as a reference.
After inspection of the aircraft, Tupolev estimated the time limits of forthcoming works as three years, grounding this period by the fact that American technology was very different from the domestic one, and was on a higher level, not only in aircraft engineering but also in other related industries. In response to the arguments of Tupolev, Stalin gave him the most extensive powers and full support of Beria’s administration, while limiting the term of B-4 development with two years. About 900 enterprises and organizations of various commissariats were engaged in the works on the bomber, with several enterprises specially created for B-4 project.
A.N. Tupolev began preparations for the work with the creation of a "brain-storm center" of the Bureau’s brigade leaders, each of them was responsible for specific work area. D.S. Markov was appointed the project leader.

 

 

 

In the summer of 1945, immediately after the arrival of the first aircraft, a task group for designing the basic units of the aircraft structure was organized. An album with sketches, which became the basis for further work on the copy, was prepared. The designing showed that without a radical change in technology of aircraft metal industry it would be impossible to reproduce this plane in the Soviet Union. It was necessary to introduce new manufacturing processes and materials into production, also there were big problems with the equipment - many components of the systems and equipment simply were not manufactured in the USSR.
In accordance with the order of Stalin, any deviation in any detail and any unit from American prototypes was not allowed. This was strictly inspected by the main Bureau, headed by A.N. Tupolev. Any deviations from the prototype made by the specialized design bureaus and allied enterprises could lead to additional dislocations and redesign. They possessed, at best, missed deadlines, and or worse – task failure. To understand, to some extent, how the copy problem was being solved, one can trace the work of structural engineers of the Bureau, who together with the technologists had to develop requirements for the domestic equivalent of the American construction materials. Structural engineers headed by A.M. Cheriomukhin had to solve difficult "inverse" problem: by measuring parts of B-29 and studying strength characteristics of the American materials those parts were made of, they gave requirements for new alloys to metallurgists. This hard work was performed on virtually all elements of the airframe.

 

 

 

 

Production of engineering drawings for the production plant № 22 began with sequential disassembly of the aircraft. During it, each individual unit was processed by its own team of designers and technologists. Then, all removable equipment was dismounted until the unit’s frame was free from it. 40,000 drawings of A4 format were released on the base of these studies. Drafting was finished in March, 1946. Almost all the equipment removed from the aircraft during disassembly was sent for studying and copying to specialized design bureaus.
The issue with engines for B-4 was tackled rather easy, as since 30s, the design bureau of A.D. Shvetsov was working on the production mastering of licensed engines of the American Curtiss-Wright Corporation.
In the late 30's - early 40's, the bureau of A.D. Shvetsov has prepared M-71 engines followed by M-72, that were close in their design and performance to the powerful engines of the Curtiss-Wright Corporation, mounted on bomber B-29. That’s why, the American R-3350-23A engine was not copied, and domestic ASh-73TK engine of 2000/2400 hp was put into serial production. The turbocharger with its control system, magnetos and heat-resistant bearings were copied from the American engine.
Defensive armament of B-4 differed from that used on B-29. 12.7 mm machine guns were replaced by B-20 cannons at first, and then - by NR-23 cannons, while maintaining defensive weapons’ control system.
The mastering of complex bomber B-4 by the Soviet aviation industry and industries related to it, became that basis, which, to a large extent, allowed the Soviet aviation moving to a global level in the 50s.
In the spring of 1947, a little less than two years after the start of works, the first production aircraft B-4 was finished at the plant № 22. On May 19, 1947 the plane piloted by a crew headed by test-pilot N.S. Rybko (including leading engineer V.N. Saginov), performed its first flight. The second and the third production airplanes left the airfield of the plant, piloted by the crews of M.L. Gallay and A.G. Vasilchenko. Till the end of the year, 20 production planes B-4 were ready, which were subjected to nearly two-year set of tests and developments.
Tu-4 modifications and variants of use:
- Tu-4 - bomber, the main version of production aircraft that was batch produced until 1952;
- Tu-4P - long-range photo reconnaissance planes that were converted from production Tu-4s;
- Tu-4 ECM aircraft - several production Tu-4 bombers, equipped with electronic reconnaissance and warfare equipment.
- Tu-4A - atomic bomb carrier - 10 production Tu-4 airplanes, adapted for transportation and use of the first Soviet atomic bombs;
- Tu-4K (Tu-4KS) - carrier of KS-1 aircraft-like missiles. A batch of 50 airplanes was produced which were operated in the Air Force;
- Tu-4D (aircraft "76") - landing transport aircraft, converted from Tu-4 production airplane. In total, 300 Tu-4 were converted;
- Tu-4T (aircraft "4T") - troop-carrier – a single Tu-4, converted into a prototype with advanced capabilities for transportation and landing of troops, cargo and military equipment;
- Tu-4UShS - navigational training aircraft, conversion of production Tu-4 aircraft, designed to train bomber navigators;
- Tu-4 "Command aircraft" – several Tu-4 production airplanes, equipped as command aircraft;
- Tu-4 (order "20") - radiation reconnaissance aircraft, specially equipped with sensors for monitoring the US nuclear tests;
- Tu-4 relay aircraft - equipped with radio equipment for communication between Navy ships and coastal command posts;
- Tu-4 "Barge Haulers" - Tu-4, equipped with a system of towing two MiG-15bis;
- Tu-4 flying cinematographic laboratory for the filming according to the "circorama" system;
- Tu-4 long-range ice reconnaissance aircraft - decommissioned Tu-4s which were transferred to the polar aviation;
- aircraft  "79" - Tu-4 project with M-49TK engines;
- aircraft "94" - Tu-4 project with TV-2 type turboprop engines;
- Tu-4 tankers - several Tu-4 equipped with flight refueling system, of the "hose-and-drogue" type for front-line airplanes and "from wing to wing" type for airplanes of the Long Range Aviation;
- Tu-4 LL - flying laboratories for testing aircraft engines. Several Tu-4 aircraft that were in operation till the 60s were converted in Tu-4 LL. They became testbed airplanes for flight tests and development of the following engines: piston - ASh-2TK and ASh-2K, VD-3TK and VD-4K, turboprop - TV-2, TV-2F and TV-2M, 2TV-2F, NK-12, NK-4, AI-20, turbojet - AM-3 and RD-3, AL-7 and AL-7F, VD-5 and VD-7, AM-5, RD-9, R-11, D-20P, etc.
Conversion crews of Long Range Aviation for Tu-4 began already in 1946, when the first production B-4 was still under construction. The mass transferring of Tu-4 to the units of Long Range Aviation began in 1949. The first Tu-4s, as was customary in the USSR during the rearming, were received by the western military districts. The airplanes were transferred to the squadrons, located at the airfields of Ukraine, near Leningrad, in Karelia, Estonia and Belarus. During military exercises and periods of aggravation of the international situation, Tu-4s were transferred to the forward airfields in Eastern Europe, ready at any time to bomb NATO troops located in Europe.

 

 

 

As well as the American B-29s and B-50s, the Soviet Tu-4s were scrambled and then, they flew to the borders of the Eastern block. Individually or in groups, they were patrolling the borders of potential enemies. Sometimes, even Tu-4As, carrying the atomic bombs, took part in these "games".
As the Air Force was being gradually saturated with Tu-4s, the airplanes began arriving in the Soviet Navy aviation – to the mine-torpedo squadrons. In this regard, a system of mine and torpedo weapons has been developed for Tu-4.
Crews of Tu-4As were engaged in the Soviet nuclear weapons tests over the nuclear test areas at Semipalatinsk and Novaya Zemlya archipelago. Also, Tu-4A dropped atomic bomb during military exercises of the Soviet troops at Totsk, in 1954.
Tu-4K airplanes with a "Cometa" (Comet) complex were a real threat to warships and ships of western union’s convoys. The complex was mastered in the army within a short time and was successfully used during Navy exercises, which involved Tu-4K.
Tu-4D landing transport airplanes entered service with Air Force transport squadrons, and were actively used for troops and military equipment transportation till the 60s. As such, they were used for troops and cargo transportation to the rebellious Hungary. Tu-4s, which started off for Budapest bombing, were returned to their bases on the way to the Hungarian border.
Several dozens of Tu-4 were supplied to China, where they were used till 80s.
Since 1954, Tu-4 began to be gradually replaced in the units of Long Range Aviation with Tu-16 airplane. By the early 60s, Tu-4s, were operated only in the Air Force transport units, flying schools and as flying laboratories in the Air Force and the Ministry of Aircraft Production. There is only one Tu-4 airplane in Russia that was saved and now presented at the exhibition of Monino museum.

Basic data of Tu-4 production aircraft
aircraft length, m
30.179
wing span, m
43.047
height of the aircraft parked, m
8.460
wing area, m2
161.7
normal takeoff weight, kg
47850
bomb load, kg
3,000-8,000
maximum speed at an altitude of 10,250 m, km/h
558
service ceiling, m
11,200
range with takeoff weight of 63,600 kg and 3,000 kg of bombs, km

6,200

defensive armament
11 x B-20E cannons (10 x NR-23 cannons)
crew, persons
11