Monday 19 January 2009

Chinese naval sonar evolves from foreign influences

Chinese naval sonar evolves from foreign influences
The types of sonars equipping Chinese warships are a barometer of Chinese naval technology and antisubmarine capability. The evolution of Chinese sonar from old Soviet equipment to series production, to indigenous designs, to French examples and finally to modern Russian vessels with sonar suites parallels Chinese naval progress. Just as these systems have grown from secondhand gear to indigenous designs supplemented by up-to-date foreign technologies, so has the Chinese navy transitioned to a force designed to serve the nation's maritime needs.
The initial phase of the Chinese sonar program began with Soviet searchlight sonars provided from 1954 to 1975. The searchlight sonars were high frequency (HF) units that transmitted and received echoes in one direction. The first sonar-equipped submarines acquired from the Soviet Union were four World War II vintage S-class submarines with the MARS-12 passive sonar delivered in 1954. Two years later, components for the first of 21 Soviet Whiskey-class diesel submarines included the TAMIR SLS active sonar. The Chinese assembled these kits in their own shipyards with Soviet assistance. China established a manufacturing plant for these sonars and produced more than 100, and they likely were exact copies of the Soviet examples.

The passive arrays could have been slightly improved MARS 24 sonars, indicating 24 instead of 12 transducer elements. This would provide much improved bearing accuracy and reduced beam side lobes. Chinese shipyards went into a large production run of the submarines, designating them as Type 031. Chinese efforts to obtain more modern Soviet submarines and sonars were thwarted by the cooling of relations in 1960 when the Soviet Union began to pull back its military technicians and engineers. China did manage to obtain plans and drawings of the Romeo-class diesel submarine. This submarine had TAMIR SL active sonar and a FENIKS passive array. China's shipyards produced 64 Romeo copies, designated Type 033. Unlike the Type 031, the Type 033 bows did have a unique fez-shaped topside transducer, which indicated that the newer sonars had been obtained. Two 033 submarines reportedly were upgraded with French DUUX-5 sonars in 1983.

Similar efforts were directed at surface vessels. In 1954, the Soviet Union provided components for four Riga-class destroyer escorts that were built in a Chinese shipyard in 1958. These ships included PEGAS-2 hull-- mounted HF searchlight sonars. Starting in 1964, Chinese shipyards produced five more copies, with no Soviet parts supplied, called Jiangnan class. The Soviet Union provided two classes of warships in 1955 that included sonar equipment. These included 10 Kronstadt patrol craft equipped with TAMIR-10 HF searchlight sonars. Based on these examples, Chinese shipyards produced 14 more copies, including the sonars. The other class comprised four T-43 ocean minesweepers equipped with HF TAMIR-11 searchlight sonars. China's Wuchang and Donglang shipyards produced 37 more T-43 sonars, designated Type 053HT by China.

China began developing indigenous sonars around 1962 when all Soviet assistance and shipments ceased, and it produced them roughly from 1975 until 1987. Because the sonar transducer dome or fairing is the only part of sonar that is visible externally, observers can detect two levels of sonar design technology. The earliest, the transducer on the keel of a ship, was initially a hoist-lower device that transmitted and listened in only one bearing-the searchlight sonar. Newer technology transmits sound around 360 degrees, and echoes are displayed on a plan position indicator cathode ray tube (CRT). This is the conventional scanning sonar. A bow dome device cannot be a hoist-lower unit because of tight space restrictions, and so it is assumed to be scanning technology. Small bow domes indicate that HF scanning equipment is present, and larger more bulbous domes likely contain medium frequency (MF) or even low frequency (LF) sonar technology, if very large.

The first mention of a People's Liberation Army Navy (PLAN) designation for a sonar was the EH-5 on the Jianghu frigate in 1975. It reportedly also was on 25 of the Jianghu frigates in variants I through IV from 1975 until 1986. Photographs show HF bow dome sonar on Jiangwei frigates. The Jiangnan V frigate had a sonar designated an EH-SA, which would seem to be an improved version. The next Chinese sonar designation was not evident until 1991 when the SO-7H was installed on the Jiangwei I (FF 539 to 542) and Jiangwei II (FF 521 to 524) frigates. Photographs of Jiangwei ships in drydock clearly show a medium-size bow dome, and models or drawings on display support this observation. This transducer location indicates very strongly that these Chinese sonars are the more modern scanning type.

Because it seems that the Soviets supplied only old searchlight sonars, the question is how did China advance into a next-generation scanning design? A crucial issue is whether China received an example of a first-generation Soviet scanning sonar or if China designed a scanning sonar from scratch. Examples of new naval equipment designed in China without foreign help usually involved many years of work before that equipment became operational, and then many times, the technology was not placed in production, indicating poor results. One notable example is the HQ-61 surface-to-air missile for two Jiangdong frigates that took 10 years to become operational. Both ships were decommissioned after a few years, and their successor ships were Jianghu frigates.
Two major events in China greatly retarded or stopped the normal design process of newer sonar-unique technology such as audio and video scanners. The Great Leap Forward from 1955 to 1959 basically moved industry to a local backyard-furnace level, where quality control standards were virtually nonexistent. Next, the 1965 Cultural Revolution featured Red-Book-waving fanatics who jailed and beat nonproletarian engineers and scientists as deviationists. These activities continued until the 1970s. This atmosphere in China impeded any significant sonar improvements for the crucial period from 1955 to 1970.
These facts contribute to a strong case for the conclusion that China received a foreign example on which to base its scanning sonar. The firstgeneration Soviet HF scanning sonar, called Titan MG-312, was developed in 1957 and installed on Petya and Kashin vessels in 1960. This sonar also is referred to by observers as one of several Herkules sonars, also known by the NATO designation Wolf Paw. The Soviet Union continued providing equipment to China until 1962, and it is certain that China had listed scanning sonar as a priority request. Because it is not considered an offensive system, the Soviet Union could have provided at least one set, possibly with drawings. This would have allowed China several years to reach full production for bow dome Jianghu frigates by the early 1980s.

China had several facilities that could contribute to the design and production of an indigenous sonar. The first leading-edge development challenge for Chinese naval construction was the Han nuclear attack submarine (SSN). Prior to this, China copied Soviet submarines, destroyer escorts and patrol craft. The largest ship was the Luda, which appeared to be very similar to the Soviet Tallinn class. The Han had sonars installed in 1970, but systems were not certified until 1975. The active sonar was designated SQZ-3 and the passive version was SQC-1. The Shanghai 22nd Radio Plant reportedly produces the SQC-1, but too little time seems to have elapsed to develop the expertise to design and build a sonar more capable than the crude TAMIRs known to be in production.

China has had several highly respected oceanographic universities. The first was established in Qingdao in 1952, and in 1958 the government created six navy research and development laboratories, including underwater acoustics and underwater weapons. In 1965, China expanded its old Bureau of Oceans into a vast network of facilities, research and forecast centers and bureaus called the State Oceanographic Agency. By 1970, it created special underwater acoustic sites in the Bohai, East China and Yellow seas. Technical institutes known to be very involved in sonar design are Institute 715 in Huangzhou and Institute 706 in Beijing. Other sonar manufacturing plants include the Dongfeng Mechanical Plant that produced the SQ2-D sonar for diesel submarines, the Jiangxin Machinery Plant, the Jiangning Mechanical Plant and the Great Wall Radio Factory in Beijing.
Although there are no photographs of indigenous Chinese sonars on warships in open sources, an interesting photograph taken in 1978 inside the J-302 vessel participating in submarine-launched ballistic missile test shots showed a "splashdown monitoring team" manning a unit. With one large CRT and three smaller CRTs above, it looked like a sonar set, although the operator was not wearing a headset.

Beginning in the mid-1970s, China opted to import modern sonars. These tend to fall into two categories. France provided modern sonar equipment from 1974 until 1993. The second period of modern Russian sonar systems extends from 1994 to the present.
The first imported French sonars were two sets of the lightweight Thomson SS-12 variable depth sonars in 1974. These can be used as a dipping sonar on antisubmarine warfare (ASW) helicopters or as a variable-depth stern-- mounted sonar on a small ASW patrol craft. The five Hanclass SSNs reportedly obtained French DUUX-5 sonar sometime around 1974, as did the single Xia nuclear ballistic missile submarine (SSBN) around 1988, although Chinese SQX- designations were used. Three Chinese diesel Song-class submarines carried French TSM-2233 and TSM-2255 sonars beginning around 1988.

In 1987, on Haiju patrol craft hulls 688 and 697, SS12 variable depth sonar (VDS) replaced the aft 57-millimeter guns. These sonars could have been copies of the two acquisitions from France. The workhorse Luda-class guided missile destroyers (DDGs) had their first notable upgrade in 1987. The lead ship built in 1972, DDG 105, received facilities for two helicopters and 57-millimeter guns but no new bow sonar. This was known as the oneof-a-kind Luda II. What is not as well-known is that another Luda, DDG 131, was in a Shanghai dry dock with a large bow sonar dome in the same year but was not called a Luda II.

The most capable French sonar provided was the DUBV-23 surface-ship scanning LF search sonar. The first example appeared on the first Luda III conversion in 1990. The two new construction Luhu DDGs had the DUBV-23 in 1993, and the larger Luhai DDG had one in 1999. The largest and best warships of the PLAN all sported the DUBV-23, and the Luhu also had the French DUBV-43 LF VDS aft. China had licensed production rights from France for both sonars.

The Russian import sonars are significant because they were included as part of a full weapon/sensor suite on modern vessels that China bought. The modern ASW torpedoes and missiles with associated fire control systems greatly enhanced the capabilities of the complex sonars.

In 1995 the first of two modern, quiet 877E Kilo submarines were procured with MKG-400 and MG-519 sonar suites. Two additional improved-636 Kilos followed in three years, but the sonar suites were nearly identical. The MKG400 was improved to the MGK-400 EM variant. In 1999 the first of two Sovremenny DDGs arrived from Russia equipped with MG-335 MF bow sonar and MG-7 HF fire control attack sonar. Because of the clustering of the most modern Kilo and Sovremenny units in the Zhoushan area, it is probable that Russia established a maintenance and support group there for the ASW suites.
China's designation for sonar systems installed on various surface ships is "SJD" followed by a unique number. The Kronstadt with TAMIR in 1955 was SJD-3, increasing with odd numbers to SJD-11 on the Luda III in 1992. It is probable that Luhu and Luhai are equipped with SJD-13 and -15, but this is not confirmed. The logistics support, maintenance and operator training are challenging because of the variety of old Soviet and modern French and Russian sonars, in addition to several indigenous searchlight and scanning sonars.Based upon 43 sets of sonar equipment provided by the Soviet Union, China produced 417 additional sonars for various classes of warships and submarines. The few ships fitted with modem French sonars are fairly certain, and the new Russian sonar suites on Kilo submarines and Sovremenny DDGs are very publicized. The sonar types of a vast number of Chinese designed combatants launched between those two known sonar installation groups are the interesting mystery. These numerous indigenously designed destroyers, frigates, patrol craft and submarines total more than 100 vessels. It is hoped that in the near future, China will be more open and the actual state of PLAN sonar technology will be revealed.

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