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Yu-4 (鱼-4) torpedo is the Chinese development of the Russian SAET-50 ASuW passive acoustic homing torpedo, and it is the Russian SAET-50 torpedo incorporating active acoustic homing guidance. Yu-4 torpedo is often erroneously claimed by many sources as the Chinese version of the SAET-60 acoustic homing torpedo, but Soviets had not completed the development of SAET-60 and only fielded the weapon in 1961, by then the relationship between former-
Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
and China had already worsened and China had not received any technical assistance on SAET-60 torpedo. The background of the development of Yu-4 torpedo is identical to that of Yu-1 torpedo and Yu-2 torpedo.


Background

In August, 1958, the deputy chief-of-staff of PLA Zhang Aiping and the deputy commander-in-chief of
PLAN A plan is typically any diagram or list of steps with details of timing and resources, used to achieve an Goal, objective to do something. It is commonly understood as a modal logic, temporal set (mathematics), set of intended actions through wh ...
Luo Shunchu (罗舜初) led a military delegation to visit former-
Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
signed a deal with Soviets to produce three types of Soviet torpedoes in China. In comparison with other military programs each with dozens or even hundreds of Soviet advisors, however, the former-
Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
did not put too much emphasis on torpedo capability: the total number of Soviet advisors initially sent to China for all of its torpedo programs was only five. The
Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
quickly delivered the samples and technical information of the three types of torpedoes to China with the five advisors to China as promised. Two Soviet advisors were assigned to assist China to produce the RAT-52 rocket-powered torpedo at No. 123 Factory, while others were assigned to teach China about compressed oxygen powered torpedo and SAET-50 acoustic homing torpedoes. In July 1960, the first two samples of Chinese-built rocket propelled torpedoes were completed. Type 920 electrical propulsion system and electronics of the electrically powered passive acoustic homing torpedo had also been completed, while the basic technologies of compressed oxygen torpedoes were also mastered by China. Everything appeared to be great but the subsequent
Sino-Soviet split The Sino-Soviet split was the gradual worsening of relations between the People's Republic of China (PRC) and the Union of Soviet Socialist Republics (USSR) during the Cold War. This was primarily caused by divergences that arose from their ...
ended the promising future: from July 28 to September 1, 1960, former-
Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
had quickly withdrawn all of its advisors from China. Compounding the problem, other domestic political turmoil such as
Great Leap Forward The Great Leap Forward was an industrialization campaign within China from 1958 to 1962, led by the Chinese Communist Party (CCP). Party Chairman Mao Zedong launched the campaign to transform the country from an agrarian society into an indu ...
further hindered the Chinese development of torpedoes. The 7th Academy consequently ordered the 705th Research Institute to lead a team consisted of No. 724 Factory
Pinyang Machinery Factory
(平阳机械厂, also known as Factory 874) in
Houma, Shanxi Houma () is a county-level city in the southwest of the Shanxi province of the People's Republic of China, on the Fen River - the tributary of Yellow River; it is under the administration of Linfen City. Houma has an area of and has a population o ...
, an
East Wind Instrumentation Factory
(东风仪表厂, also known as Factory 872) in
Xi'an Xi'an is the list of capitals in China, capital of the Chinese province of Shaanxi. A sub-provincial city on the Guanzhong plain, the city is the third-most populous city in Western China after Chongqing and Chengdu, as well as the most populou ...
to indigenously manufacture Soviet compressed oxygen powered torpedo. In 1962,
Field Marshal Field marshal (or field-marshal, abbreviated as FM) is the most senior military rank, senior to the general officer ranks. Usually, it is the highest rank in an army (in countries without the rank of Generalissimo), and as such, few persons a ...
Nie Rongzhen ordered all resources to be concentrated on achieving the goal of fielding “two boats and a torpedo” (Two boats:
torpedo boat A torpedo boat is a relatively small and fast naval ship designed to carry torpedoes into battle. The first designs were steam-powered craft dedicated to ramming enemy ships with explosive spar torpedoes. Later evolutions launched variants of ...
and
submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...
, torpedo: heavy torpedo of 533 mm diameter). In July, 1962, researchers at 705th Institute concluded that despite having samples and design drawings, compressed oxygen powered torpedoes was unsafe and after numerous accidental explosions, they were rarely used by the Soviet Navy, and Chinese navy was not happy with oxygen powered torpedo either. Chinese researchers recommended steam powered torpedo instead, and in the following year,
PLAN A plan is typically any diagram or list of steps with details of timing and resources, used to achieve an Goal, objective to do something. It is commonly understood as a modal logic, temporal set (mathematics), set of intended actions through wh ...
issued an order to first develop steam powered torpedo, and then the electrically powered acoustic homing torpedo. The electrically powered Yu-4 torpedo program was put on hold despite the earlier successful development of components.


Development

The progress made in the development of the Yu-3 torpedo had encouraged the Chinese to resume the development of the Yu-4 torpedo after several years of dormancy which begun in the early 1960s. At the end of 1971, 5 samples were produced based on the experience gained in the development of the Yu-3 torpedo. However, the speed was low and other results were not satisfactory either. The Chinese researchers decided to take a prudent approach by developing two different versions, one with passive acoustic homing guidance and the other with combined passive / active acoustic homing guidance. The one with passive acoustic homing begun its development in the mid-1960s and was named as Yu-4 Jia (鱼-4甲), or sometimes as Yu-4A, while the combined active / passive acoustic homing version begun its development in the late-1960s and named as Yu-4 Yi (鱼-4乙) or sometimes as Yu-4B. Yu-4A was designed by th
East Wind Instrumentation Factory
(东风仪表厂) in
Xi'an Xi'an is the list of capitals in China, capital of the Chinese province of Shaanxi. A sub-provincial city on the Guanzhong plain, the city is the third-most populous city in Western China after Chongqing and Chengdu, as well as the most populou ...
, while Y-4B was designed jointly by Northwestern Polytechnical University (primary contractor) an
Pinyang Machinery Factory
(平阳机械厂) in
Houma, Shanxi Houma () is a county-level city in the southwest of the Shanxi province of the People's Republic of China, on the Fen River - the tributary of Yellow River; it is under the administration of Linfen City. Houma has an area of and has a population o ...
.
Pinyang Machinery Factory
(平阳机械厂) was tasked with manufacturing both Yu-4A and Y-4B. In March 1977, Yu-4A went through first oceanic tests and was considered meeting most of the requirements. Further tests in September, 1979 indicated that the last two problems still existed: the high level of noise generated by the motor and the accidental arming of the fuse. After efforts were spent to attack the problems, the sample Yu-4A torpedoes were once again tested in June, 1980, proving that the problems appeared to be solved. However, after 78 sample torpedoes had been test fired in July, 1981, it was revealed that the problem of the fuse still existed despite drastic reduction of the occurrence, and more worked was needed. Finally, in December 1982, all problems were solved and Yu-4A went into series production. Yu-4B, on the other hand, experienced more difficulties and new measures had to be developed, including replacing the original mechanically scanned equipment with electronically scanned equipment to improve the accuracy of depth setting and a new electro-magnetic fuse. In March 1987, after the final test of 63 torpedoes, Yu-4B was accepted into service and went into series production. The export version of Yu-4B designated as ET31.


Specification

*Diameter: 533 mm *Length: 7.75 m *Weight: 1,775 kg (1,628 kg for the training version) *Warhead: 309 kg *Guidance: acoustic homing: Yu-4A: passive, Yu-4B: active/passive *Propulsion: electrical, silver-zinc battery *Range: 6 km (original) @ , 15 km (upgraded) @ *Speed: 30 kt (56 km/h) or 40 kt (75 km) upgraded *Depth: N/A, ASuW torpedo


Modification

Due to the adoption of newer technologies such as the silver-zinc battery, the performance of Yu-4 torpedo has exceeded the Russian SAET-50 torpedo it is based on, and reached that of SAET-50M: the speed of the Yu-4 torpedo is increased more than 25% to , even faster than the SAET-50M, and the range is increased 50% to 6 km, equal to that of SAET-50M. For these reasons, the Yu-4 torpedo is considered at least equal or better than Russian SAET-50M torpedo, the successor of SAET-50 torpedo, and even comparable to Russian SAET-60 torpedo in some aspects. However, the 6 km range was considered rather short for modern naval warfare by the Chinese navy, which led to one of the major upgrade resulted in increased range (up to 15 km), and in comparison to Yu-1 torpedo, there were not as many Yu-4 torpedoes entering service like Yu-1 torpedo. Like Yu-1 torpedo, Yu-4 torpedoes in Chinese inventory have been continuously modified, such as incorporating ASW capability, updated electronics and propulsion system, and being converted as part of
CAPTOR mine The Mark 60 CAPTOR (Encapsulated Torpedo) is the United States' only deep-water anti-submarine naval mine A naval mine is a self-contained explosive weapon placed in water to damage or destroy surface ships or submarines. Similar to anti-p ...
type mine systems.


See also

* Export torpedoes of China


References

{{DEFAULTSORT:Yu-4 Torpedo Torpedoes of China