Submarines: China Gets AIP To Work


September 26, 2018: In mid-2018 the Chinese Navy proclaimed that its new AIP (air independent propulsion system) equipped submarine had performed very well. Actually, as described the Chinese AIP performed about as well as early Western AIP systems. For the Chinese that was good enough because they have had problems getting their AIP (apparently based on the Swedish Stirling AIP system) to perform adequately and reliably. China has been working on getting a working AIP system in one of their Yuan class Type 39B subs for over fifteen years but until now no Chinese AIP equipped boats were seen in action. That changed earlier this year when new Yuan class sub went to sea and operated like an AIP boat (staying underwater for more than seven days at a time). According to the Chinese press releases their AIP sub stayed under for over two weeks at a time, which is typical of what a Stirling AIP system can do.

China may now have three of these AIP equipped boats. That is because in late 2016 China apparently resumed building more of its Yuan class subs. These are based on the late model Russian Kilo class diesel-electric boats. Construction of the Yuans appeared have halted in 2013 for reasons unknown. Then at the end of 2016 three more of these Yuan class (Type 39B) subs were seen being built. The last new Type 39B appeared in late 2013 but even before that, there were indications that this was another pause to absorb user experience with the current model and plan modifications for the next batch. This new batch is apparently the three new ones that recently went to sea. When these enter service China will have ten Type 39Bs, plus three of the earlier Type 39A versions.

In late 2016 it was believed the three latest 39Bs would have many modifications and upgrades, some of them visible because of minor changes in the conning tower or hull features. China was apparently upgrading its sensor and fire control electronics but the capabilities of these won’t be detected until foreign subs encounter the new 39Bs at sea. At that point, U.S. subs will be able to construct an acoustic and electronic “signature” of the new 39Bs so they can be more easily and quickly identified in the future. That process also confirmed that the latest 39Bs had working AIP. How reliable the AIP is will come only after thousands of hours of use.

One thing was certain about the latest Type 39Bs; the Chinese are continuing their relentless effort to create world-class subs, one tweak and improvement at a time. Since the late 1980s, China has been designing and building a rapidly evolving collection of "Song" (Type 39) class diesel-electric submarines that emphasize quietness and incremental improvements. The changes have been so great that the four Songs completed in 2013 were recognized as a new type and designated the Yuan class (Type 39A). The original design (Type 39) was a 1,800 ton Kilo type sub that first appeared in the late 1990s and 13 have been built. The larger (2,800 ton) Type 39A first appeared in 2006. The Type 39A quickly involved into the larger and more lavishly equipped Type 39B showed up. The evolution continues, and there are now thirteen "Type 39 Yuan Class" subs (of at least four distinct models). These latest models were thought to have AIP along with new electronics and other internal improvements. Now the presence of AIP has been confirmed.

This rapid evolution of the Type 39 appears to be another example of China adapting Russian submarine technology to Chinese design ideas and new technology. China has been doing this for as long as it has been building subs (since the 1960s). But the recent versions of the Type 39B design shows Chinese naval engineers getting more creative. The Yuans were meant to have an AIP that would allow them to cruise underwater longer. Western AIP systems allow subs to stay underwater for two weeks or more. China has been working on AIP since 1975 and the first working prototype was available by 1998. A decade later it seemed that design was ready for regular use but it wasn’t. The first Chinese AIP had less power and reliability and does not appear to be nearly as capable as Russian or Western models. In part, this was because that AIP used lead-acid batteries. The Chinese kept improving on their AIP, and the last half dozen AIP systems were designed to use a more efficient lithium battery system. This AIP 2.0 has numerous other tweaks and appears, on paper at least, to match what most Western AIPs can do and that’s the version that was installed in one (or all three) of the latest Type 39B subs.

The Songs look a lot like the Russian Kilo class and that was apparently no accident. The 39s and 39A/Bs are both similar in appearance but the type 39A/Bs appear larger than the 1,800 ton Type 39s. Both have with crews of 60-70 sailors and six torpedo tubes. This is very similar to the Kilos (which are a bit larger). China began ordering Russian Kilo class subs, then one of the latest diesel-electric designs available, in the late 1990s. The first two Type 39Bs appeared to be a copy of the early model Kilo (the model 877), while the second pair of Type 39Bs appeared to copy the late Kilos (model 636). The latest Yuans still appear like Kilos but may be part of an evolution into a sub that is similar to the Russian successor to the Kilo, the Lada. The Type 39s were the first Chinese subs to have the teardrop shaped hull. The Type 39B was thought to be just an improved Song but on closer examination, especially by the Russians, it looked like a clone of the Kilos. The Russians now believe that the entire Song/Yuan project is part of a long-range plan to successfully copy the Kilo. If that is the case, it appears to be succeeding.

The Chinese Navy currently has 13 Song class, 12 Kilo class, 13 Type 39A/B (Yuan) class, and 18 Ming (improved Russian Romeo) class boats. But at least a dozen more Yuans are apparently planned. The Song/Yuan class subs are meant to replace the elderly Mings.

The Chinese nuclear sub program has been less successful. There are only 3 Type 91 Han class SSNs (nuclear attack subs), as the Chinese are still having a lot of problems with the nuclear power plant in subs. Despite that, the Hans are going to sea, even though they are noisy and easily detected by Western sensors. Five Hans were built (between 1974 and 1991) two have already been retired. There are six newer Type 93 Shang class SSNs in service, but these are still pretty noisy. There is one Type 95 Sui class SSN undergoing sea trials with another building, The first Type 95 is expected to enter service in 2020 and if it is as quiet as hoped, a lot more will be built. There are also ten SSBN (ballistic missile carrying nuclear subs) in two classes and these have had a lot of problems and rarely go to sea.

China is also offering their “improved Kilo” designs to export customers. In late 2016 China confirmed that final details have been agreed to on the sale of eight Chinese S20 diesel-electric submarines to Pakistan. These are export versions of the Type 39A that lack many of the advanced features. Four of these will be built in China while at the same time Chinese personnel will assist Pakistan in building another four in Pakistan. Final cost is expected to average somewhere between $500 million and $600 million each and the first one will enter service by 2023. Since early 2014 China and Pakistan have been negotiating prices and terms for the sale of the S20. At first, it was believed that Pakistan wanted six subs, but the final deal specified eight. Currently, the Pakistani Navy has five submarines and plans to use all of them against India (which is also considered a Chinese foe). In 2017 China sold three of those export model Yuan class subs to Thailand. Construction on the first one began in early September. These boats will cost over $400 million each.




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