|Tupolev Tu-4 at Monino Central Air Force Museum, Moscow|
|National origin||Soviet Union|
|First flight||19 May 1947|
|Primary users||Soviet Air Force|
PLA Air Force
|Developed from||Boeing B-29 Superfortress|
|Developed into||Tupolev Tu-70 |
The Tupolev Tu-4 (Russian: Туполев Ту-4; NATO reporting name: Bull) is a piston-engined Soviet strategic bomber that served the Soviet Air Force from the late 1940s to mid-1960s. It was reverse-engineered from the American Boeing B-29 Superfortress.
Design and development
Toward the end of World War II, the Soviet Union saw the need for a strategic bombing capability similar to that of the United States Army Air Forces. The Soviet VVS air arm had the locally designed Petlyakov Pe-8 four-engined "heavy" in service at the start of the war, but only 93 had been built by the end of the war and the type had become obsolete. The U.S. regularly conducted bombing raids on Japan, from distant Pacific forward bases using B-29 Superfortresses. Joseph Stalin ordered the development of a comparable bomber.
The U.S. twice refused to supply the Soviet Union with B-29s under Lend Lease. However, on four occasions during 1944, individual B-29s made emergency landings in Soviet territory and one crashed after the crew bailed out. In accordance with the Soviet–Japanese Neutrality Pact, the Soviets were neutral in the Pacific War and the bombers were therefore interned and kept by the Soviets. Despite Soviet neutrality, the U.S. demanded the return of the bombers, but the Soviets refused. Three repairable B-29s were flown to Moscow and delivered to the Tupolev OKB. One B-29 was dismantled, the second was used for flight tests and training, and the third one was left as a standard for cross-reference. The aircraft included one Boeing-Wichita −5-BW, two Boeing-Wichita −15-BWs and the wreckage of one Boeing-Renton −1-BN – three different models from two different production lines (respectively Wichita and Renton factories). Only one of the four had de-icing boots as used on the Tu-4. The fourth B-29 was returned to the US along with its crew with the end of the Russo-Japanese entente following the Soviet declaration of war against Japan two days after the atomic bombing of Hiroshima, in accordance with the Yalta agreement.
Stalin told Tupolev to clone the Superfortress in as short a time as possible instead of continuing with his own comparable ANT-64/Tu-10. The reverse-engineering effort involved 900 factories and research institutes, who finished the design work during the first year; 105,000 drawings were made. By the end of the second year, the Soviet industry was to produce 20 copies of the aircraft, ready for State acceptance trials.
The Soviet Union used the metric system, so sheet aluminium in thicknesses matching the B-29's imperial measurements were unavailable. The corresponding metric-gauge metal was of different thicknesses. Alloys and other materials new to the Soviet Union had to be brought into production. Extensive re-engineering had to take place to compensate for the differences, and Soviet official strength margins had to be decreased to avoid further redesign, yet despite these challenges, the prototype Tu-4 weighed only about 340 kg (750 lb) more than the B-29, a difference of less than 1%.
The engineers and suppliers of components were under pressure from Tupolev, Stalin, and the government to create an exact clone of the original B-29 to facilitate production and Tupolev had to overcome substantial resistance in favor of using equipment that was not only already in production but in some cases better than the American version. Each alteration (and every component made) was scrutinized and was subject to a lengthy bureaucratic process. Kerber, Tupolev's deputy at the time, recalled in his memoirs that engineers needed authorization from a high-ranking general to use Soviet-made parachutes. Differences were limited to the engines, the defensive weapons, the radio (a later model used in lend-lease B-25s was used in place of the radio in the interned B-29s) and the identification friend or foe (IFF) system – the American IFF being unsuitable. The Soviet Shvetsov ASh-73 engine was a development of the Wright R-1820 but was not otherwise related to the B-29's Wright R-3350 The ASh-73 also powered some of Aeroflot's remaining obsolescent Petlyakov Pe-8 airframes, a much earlier Soviet four-engined heavy bomber whose production was curtailed by higher priority programs. The B-29's remote-controlled gun turrets were redesigned to accommodate the Soviet Nudelman NS-23, a harder hitting and longer ranged 23 mm cannon. Additional changes were made as a result of problems encountered during testing, related to engine and propeller failures and equipment changes were made throughout the aircraft's service life.
The Tu-4 first flew on 19 May 1947, piloted by test pilot Nikolai Rybko. Serial production started immediately, and the type entered large-scale service in 1949. Entry into service of the Tu-4 threw the USAF into a panic, since the Tu-4 possessed sufficient range to attack Chicago or Los Angeles on a one-way mission, and this may have informed the maneuvers and air combat practice conducted by US and British air forces in 1948 involving fleets of B-29s. The tests were conducted by the RAF Central Fighter Establishment and co-operative US B-29 groups, and involved demonstration of recommended methods of attack against B-29/Tu 4-type bombers using RAF Gloster Meteor and de Havilland Vampire jet fighters. The Russians developed four different midair refueling systems to extend the bomber's range, but these were fitted to only a few aircraft and only a small number of the final design was installed on operational aircraft before the Tu-4 was superseded by the Tu-16.
First public appearance
The aircraft was first displayed during a flyover at the Aviation Day parade on 3 August 1947 at the Tushino Airport in Moscow. Three aircraft flew overhead. It was assumed that these were merely the three B-29 bombers that were known to have been diverted to the USSR during World War II. Minutes later a fourth aircraft appeared. Western analysts realized that the Soviets must have reverse-engineered the B-29. The appearance of an obviously Superfortress-derived Tu-70 transport over the crowd removed any doubt about the success of the reverse-engineering.
A total of 847 Tu-4s had been built when production ended in the Soviet Union in 1952, some going to China during the later 1950s. Many experimental variants were built and the valuable experience launched the Soviet strategic bomber program. Tu-4s were withdrawn in the 1960s, being replaced by more advanced aircraft including the Tupolev Tu-16 jet bomber (starting in 1954) and the Tupolev Tu-95 turboprop bomber (starting in 1956). By the beginning of the 1960s, the only Tu-4s still operated by the Soviets were used for transport or airborne laboratory purposes. A Tu-4A was the first Soviet aircraft to drop a nuclear weapon, the RDS-1.
- main production version, originally designated B-4
- Tu-4 Variants without special designations:
- Tu-4 ELINT and ECM
- Tu-4 mothership for the DFS 346A.(Note:other DFS346 prototypes were carried by one of the Boeing B-29s interned during the war).
- Tu-4 escort fighter mothership (Project Burlaki)
- Tu-4 remotely controlled target drone converted from time expired bombers.
- Tu-4 fuel carrier
- Tu-4 in-flight refuelling testbeds (four different systems were trialled)
- Tu-4 radiation reconnaissance aircraft
- Tu-4 communications relay aircraft
- nuclear capable bomber used to test Soviet RDS-1 RDS-3 and RDS-5 nuclear bombs. The standard Tu-4 was not capable of carrying these weapons.
- troop transport (300 conversions). Also known as Tu-76.
- anti-shipping version, armed with KS-1 Komet missiles carried between the engines under the wings.
- engine testbed for the Mikulin AM-3 jet engine, the Ivchenko AI-20, Kuznetsov NK-4 and Kuznetsov 2TV-2F turboprop engines, the Dobrynin VD-3K radial engine and AV-28 contra-rotating propellers.
- drone launcher aircraft with Lavochkin La-17 unmanned aerial vehicles carried underwing
- long-range reconnaissance.
- paratroop transport (one example only)
- liquid oxygen tanker aircraft.
- navigational trainer.
- testbed for Myasishchev M-4 to develop a bicycle-type landing gear.
- testbed for Myasishchev M-4 powered controls.
- Tu-4 AWACS
- Chinese prototype with KJ-1 AEWC, "AWACS" radar and powered by Ivchenko AI-20K turboprop engines. Two converted to allow the Chinese to monitor US nuclear weapons tests in the Pacific.
- Airliner derivative, never reached mass production.
- Cargo aircraft derivative, never reached mass production.
- Tu-4 powered by M-49TK engines.
- Long-range bomber derivative, never reached mass production.
- Long-range heavy bomber derivative, never reached mass production.
- Tu-4 powered by Kuznetsov TV-2 turboprop engines.
The Soviet Air Force operated 847 Tupolev Tu-4 bombers between 1948 and early 1960. They were initially used as long-range bombers. In 1954 the Soviets began phasing out the Tu-4 as units upgraded to Tupolev Tu-16 bombers and, beginning in 1956, to Tupolev Tu-95 bombers. Tu-4s withdrawn from front line units were used for transport duties.
On 28 February 1953, Joseph Stalin gave China ten Tu-4 heavy bombers，and in 1960 two additional aircraft configured as navigational trainers arrived in Beijing. 11 Tu-4s were refitted with AI-20K turboprop engines between 1970 and 1973. The last PLAAF Tu-4 retired in 1988.
In 1969, China developed its first airborne early warning aircraft based on the Tu-4 airframe. The project was named KJ-1 and mounted a Type 843 rotodome above the fuselage of the aircraft. However, due to clutter noise the KJ-1 failed to meet the PLAAF's requirements. The project was canceled in 1979 although further projects were proposed based on Tu-4 platform. The airframe was already obsolete however and the Tu-4 was ruled out for future developments. The single prototype is displayed at the PLAAF museum north of Beijing.
- Tu-4 4114 (c/n 2805601), ex-KJ-1 AEWC, "4114"
- Stored at Datangshan, China 
- Tu-4 4134 (c/n 2205008), "4134"
- Stored at Datangshan, China 
- Tu-4 unknown (c/n 2805103), "01"
- Stored at the Central Air Force Museum, Monino, Russia 
Data from Tupolev Tu-4 Soviet Superfortress
- Crew: 11
- Length: 30.179 m (99 ft 0 in)
- Wingspan: 43.047 m (141 ft 3 in)
- Height: 8.46 m (27 ft 9 in)
- Wing area: 161.7 m2 (1,741 sq ft)
- Aspect ratio: 11.5
- Empty weight: 36,850 kg (81,240 lb)
- Gross weight: 47,850 kg (105,491 lb)
- Max takeoff weight: 55,600 kg (122,577 lb) – 63,600 kg (140,214 lb)
- Powerplant: 4 × Shvetsov ASh-73TK 18-cyl. air-cooled radial piston engines, 1,790 kW (2,400 hp) each
- Propellers: 4-bladed V3-A3 or V3B-A5, 5.06 m (16 ft 7 in) diameter
- Maximum speed: 558 km/h (347 mph; 301 kn) at 10,250 m (33,629 ft)
- Range: 5,400 km (3,355 mi; 2,916 nmi) at 3,000 m (9,843 ft) with 63,600 kg (140,214 lb) take-off weight including 3,000 kg (6,614 lb) of bombs and 10% fuel reserves
- Service ceiling: 11,200 m (36,700 ft)
- Rate of climb: 4.6 m/s (910 ft/min) at 1,000 m (3,281 ft)
- Time to altitude: 5,000 m (16,404 ft) in 18.2 minutes
- Wing loading: 400 kg/m2 (82 lb/sq ft)
- Power/mass: 0.11 kW/kg
- 10 × 23 mm Nudelman-Suranov NS-23 aircraft cannon, two cannon in each of the four turrets and two cannon in the tail barbette
- 2 × KS-1 Komet standoff missiles (Tu-4K only; these anti-ship missiles resembled a scaled-down MiG-15)
- 6 × 1,000 kg (2,200 lb) bombs
Aircraft of comparable role, configuration and era
- Gordon, 2002, p.3
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- "Chinese Airborne Early Warning (AEW)." fas.org. Retrieved: 31 July 2011.
- Photo of the Tu-4 (c/n 286501) at the FAS.org website
- "Photo of the Tu-4 (4114, cn 2806501) AWACS example exhibited in the Datangshan Museum, China." airliners.net. Retrieved: 29 December 2009.
- "Photo of the Tu-4 (4134, cn 225008) "missile carrier" exhibited in the Datangshan Museum, China." airliners.net. Retrieved: 29 December 2009.
- "Photo of the Tu-4 exhibited in the Central Air Force Museum in Monino, Russia." airliners.net. Retrieved: 29 December 2009.
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