Tupolev Tu-4


The Tupolev Tu-4 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. 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, which 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 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 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 and the identification friend or foe 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 USSR had 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.

Operational history

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 and the Tupolev Tu-95 turboprop bomber. 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.

Variants

;Tu-4: main production version, originally designated B-4
;Tu-4 Variants without special designations:
;Tu-4A: 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.
;Tu-4D: troop transport. Also known as Tu-76.
;Tu-4K/KS: anti-shipping version, armed with KS-1 Komet missiles carried between the engines under the wings.
;Tu-4LL: 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.
;Tu-4NM: drone launcher aircraft with Lavochkin La-17 unmanned aerial vehicles carried underwing
;Tu-4R: long-range reconnaissance.
;Tu-4T: paratroop transport
;Tu-4TRZhK: liquid oxygen tanker aircraft.
;Tu-4UShS: navigational trainer.
;ShR-1: testbed for Myasishchev M-4 to develop a bicycle-type landing gear.
;UR-1/-2: 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.
;Tu-70: Airliner derivative, never reached mass production.
;Tu-75: Cargo aircraft derivative, never reached mass production.
;Tu-79: Tu-4 powered by M-49TK engines.
;Tu-80: Long-range bomber derivative, never reached mass production.
;Tu-85: Long-range heavy bomber derivative, never reached mass production.
;Tu-94: Tu-4 powered by Kuznetsov TV-2 turboprop engines.

Operators

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.

Survivors

;Tu-4 4114, ex-KJ-1 AEWC, "4114"
;Tu-4 4134, "4134"
;Tu-4 unknown, "01"

Specifications (Tu-4)