The Chinese navy has done a lot of modernization in the past 20 years, but some areas have been lagging behind others. Even while China was still buying large ticket items from Russia, there was a lot of talks on China's growing submarine force and anti-ship missiles. Not only did the imported ships have some over-hyped supersonic missiles, the domestic built ships and aircraft were also equipped with a fairly modern YJ-83 missile. The path to modernization in ASuW is relatively small compared to other areas, so it was not surprising that PLAN made the largest jump here at first.
By 2005, Chinese navy was in the midst of inducting Type 052C and 051C capable of providing anti-air area defense. Even including the interim Type 052B class, this was a very significant jump from point defense in most of the surface combatants to having ships capable of detecting multiple aircraft and missiles at long distance, processing them on the combat system and engaging them with modern long range vertically launched surface to air missiles. As Type 054A started to proliferate in Chinese navy and becoming the backbone of many flotillas, this became no longer an area of weakness. With more Type 052Cs joining service and the first Type 052D being commissioned, Chinese fleet has now become modernized in the area of AAW.
The one area that PLAN has always lagged is in ASW. For a long time, most of the surface combatants only had hull sonar and some ASW rockets. By the turn of century, the new ships have been installed with Yu-7 torpedo. However, China's limited number of naval helicopters mean that only a limited number of ships can travel with ASW helicopters. Since helicopters are rotated between ships, that would limit the ships training with them and their effectiveness. Before the induction of 054A, China's most advanced ASW assets were diesel submarines and Type 037 sub chasers. They are both limited to littoral waters and cannot be expected to escort a fleet. Even in littoral water, they are limited by their own noisiness and lack of speed or range. The 093s could be useful in blue waters, but they are also very loud.
Type 052As were China's most well equipped ASW ships until Type 052C came along. The Type 052C destroyers were the first of surface combatants to be installed with the new generation of Towed array sonar and acoustic decoy. The Type 052s had their original imported French variable depth sonar replaced with this new towed array sonar. The induction of Type 054A really brought a lot of added ASW capabilities. They were also equipped with towed array sonar and acoustic decoy in the back along with bow mounted sonar in the front. Lack of permanent naval helicopter remains to be an issue, but at least they can launch ASROC type of missiles from VLS. That really extended the range of engaging submarines when a helicopter is not available for such duty. Even so, the passive TAS by itself has limitations and is still more suitable for littoral water.
In the past year or so, a new generation of home grown variable depth sonar has been developed. One of those versions has been installed on Type 056, which should be able to replace Type 037 sub chasers for littoral ASW duties. With the existence of helipad that can land Z-9 helicopter, installation of Yu-7 torpedoes and this new VDS, it should be a huge leap over the Type 037s that are retiring from service. An improved version of 054A has also come out recently with this new variable depth sonar installed next to TAS (position of acoustic decoys on earlier 054As) and the new 11 barrel CIWS. This combination of active VDS and passive TAS is installed on the most recent 4 054As (2 each from HD and HP shipyard). Although more of this type could be built, my guess is that they are just testing out this new ASW combat suite and CIWS for the next class of ships. The new Type 052D destroyer (No. 172) is also fitted with this new combination of active/passive sonar in the back along with a bow mounted sonar in the front. It is also said to be able to launch a longer range ASROC type of missiles from VLS than Type 054A. All of this should give Type 052D very balanced combat capability in ASuW, AAW and ASW. A new type of ASW helicopter based on the developing Z-20 project is needed to really allow this ship to hunt and engage modern submarines. Of course, Chinese navy does have a new ASW helicopter in Z-18F, but it is probably too large to be carried in the hangar of Type 052C/D. However, Z-18F should be able to serve on CV-16 along with large future combatants likes Type 055 and LHD/LPD classes. Z-18F is larger than other ASW helicopters like SH-60, NH-90 and Ka-28. It can carry more sonobuoy and has more snobuoy openings than SH-60. It can also carry dipping sonar along with up to 4 Torpedoes. The rest of the electronics and combat system has been upgraded from Z-8 with a new large surface search radar and modern MAWS and RWR antennas. It also has the range to really hunt modern nuclear submarines. That's why it is expected to be a part of the air wing of CV-16 and future Chinese carriers.
As a whole, the hardware for ASW in PLAN has definitely modernized, but they still lack in many areas. While they finally have a Y-8 maritime patrol aircraft, it's still years behind P-3C and serving too small in number. While Z-18F is a nice addition, a Z-20 or Z-15 based ASW helicopter is badly needed for ships in the class of Type 052D and 054A. And finally, the biggest help to Chinese navy would be newer and quieter nuclear submarines with more powerful sonar. Until that happens, the Chinese navy would always be in a place of danger when it comes to underwater warfare.