Pyŏng'an-class destroyer

The Pyŏng'an-class destroyers are a group of four guided missile destroyers built for the Menghean Navy. They are armed with the Letnian S-300FM long-range surface-to-air missile, giving them a much longer surface-to-air engagement range than any previous Menghean destroyer class. This made them the first Menghean warship class to use a vertical launching system for its missiles, albeit in an inefficient revolver-type cold launch configuration. Later, in 2001, Menghe obtained a license to produce the Mark 41 VLS, making the Pyŏng'ans the first and last Menghean warship class to carry the YDG-39.

Development

Area Air Defense Ship program

During the 1980s and 1990s, Menghe's main air defense ship was the Yobu-class destroyer (along with its Hyŏngnam subclass). These ships were armed with the YDG-32 surface-to-air missile, a licensed derivative of the S-125 Neva/Pechora. In its upgraded 1990s model, this missile had a range of 40 kilometers, relatively short compared with more modern systems elsewhere. These ships also carried their YDG-32s on twin-arm mounts, limiting their rate of fire, and had only 16 missiles per magazine for a total of 32. Given that many Menghean warship classes carried either no radar-guided SAMs (Nunbora, Mugunghwa, Ginam) or relatively ineffective ones (Chŏndong), this was seen as a serious problem.

In response, the Menghean Navy launched a design competition for an Area Air Defense Ship specialized in protecting surface ships against aerial attack. Anti-submarine capabilities were added to the requirements list as well. The new ships would be given the hull type juryŏk howiham (주력 호위함 / 主力護衛艦), or "main force escort ship," to contrast them with the Yobu and Hyŏngnam-class escort ships and the Ansa-class outer escorts (wichung howiham). These main force escort ships would accompany the aircraft carrier Haebang and escort surface action groups composed of anti-shipping destroyers or anti-submarine warships.

Competition with Plan 351

Cross-section drawing of the Plan 351 design.

Initially, the Navy responded with a modified version of the Chanjok Jachido-class cruisers, modified with S-300FM launch cylinders in place of the helicopter hangar. The radar masts were also replaced with solid pyramid structures containing boiler exhaust pipes and electronics, and a smaller hangar structure for two helicopters was added aft, though the powerplant and the forward one-third remained unchanged. The command deck was retained, allowing these ships to operate as command centers for a formation of surface ships. Previously, the Yobu-class destroyers had been used as destroyer squadron leaders, but their makeshift command facilities were not adequate for coordinating large groups of ships. This design was designated Plan 351, and given the name Yerihan ("Keen"), though this was only a codename for the project rather than a prospective ship name, as sometimes erroneously reported.

The Yerihan design initially received a favorable evaluation from the Navy's general staff, and Choe Sŭng-min personally endorsed the design. A model was unveiled at a domestic defense exposition in 1994, and Dayashinese satellite intelligence mistakenly reported that the first ship in the class was laid down the following year (in fact, it was the Kungnaejok Jachido, third ship in the Chanjok Jachido class). Further evaluation, however, began to tip the balance against the Plan 351 design. The added superstructure aft and heavier pyramid masts added considerably to the ship's weight and shifted the center of gravity, requiring new structural bracing. This eliminated many of the expected benefits of using an existing hull. The Navy also projected that the operating costs of these ships would be relatively high, due to their large crewing requirements and inefficient steam turbine machinery.

As debate on the viability of the Plan 351 continued, the Navy commissioned a separate design team to draw up a more compact, less expensive alternative. This prototype, designated Plan 332, became the basis for the Pyŏng'an class. To reduce space, the 8-tube S-300 launch cells were replaced by 6-tube cells with outward-angled launch points, and the total number of missiles was reduced. The intermediate-range SAM battery was also removed, in favor of the short-range YDG-61, still in early development. The overall layout was more conventional, resembling foreign destroyers such as the Yakaze class.

Another breakthrough in the Plan 332 design came in 1995, when representatives of the Hallian Navy offered to covertly transfer LM2500 gas turbine engines to Menghe under the guise of a private ship-scrapping contract. Menghean engineers used these to achieve further reductions in powerplant mass, making the design more compact while retaining an adequate top speed.

Unpon further evaluation, the Menghean Navy projected that it would be able to build and operate five Plan 332 ships for the same cost as three Plan 351 ships. Given the stagnation in the military budget, which was barely keeping pace with inflation during the mid-1990s, the original procurement plan of five Plan 351 ships was deemed infeasible. With five Plan 332 hulls, however, the Navy could disperse its anti-air area coverage more widely, especially as either projection assumed that 20% of ships (1 in 3 or 1 in 5) would be out of service for maintenance at any given time. The balance of opinion gradually shifted in favor of the smaller Plan 332, and in 1996 the Navy's annual budget plan allocated funds for the construction of five hulls over the following six years. The larger Yerihan design was abandoned, like several other Menghean cruisers before it.

Construction

The first ship in the new class was laid down on August 27, 1996, at the Number 1 drydock of the Gyŏngsan Songsu-do Naval Yard. The same drydock had just launched the cruiser Kungnaejok Jachido for her fitting-out.

Because Dayashina still objected to any licensing deal which would transfer Dayashinese military technology to Menghe, the Menghean Navy was unable to secure gas turbine engines through legal means. Hallian military officials, however, believed that they could strengthen their position against the Entente Cordiale by helping the Menghean Navy modernize its fleet. As part of a secret agreement between the two countries, the Hallian Navy transferred two partially scrapped destroyer hulls to a state-owned Menghean shipbuilder for breaking up. Both ships had already been stripped of their radar and sonar equipment, but their powerplants remained intact, yielding a total of eight used but operable LM2500 turbines. These were transferred to the Navy for installation in the first four destroyer hulls, at a rate of two each.

The first ship was launched on 3 January, 1988, and commissioned on 13 September 1999 as Pyŏng'an. She was assigned to the carrier battle group of the Haebang. The next three ships were laid down and completed on schedule. While the fourth hull was halfway complete, however, Dayashina relented on its sensitive technology policy over the resolution of the Renkaku Islands dispute, and Menghe signed an agreement with Tír Glas to produce the Mark 41 Vertical Launching System and the SM-2 missile. This new system was far more flexible and efficient than the rotary launchers for the YDG-39, and by extension rendered the Pyŏng'an class obsolete for new construction. The Navy decided to complete the third and fourth hulls as they were originally designed, because construction work was already too far along to rebuild them. The fifth hull, however, was cancelled in favor of a modified design built around the new vertical launch system. This, in turn, became the Haeju class.

Description (as built)

Armament

The most important armament on the Pyŏng'an-class ships was their powerful battery of 54 YDG-39 surface-to-air missiles - Menghe's licensed copy of the Letnian S-300FM. With a maximum engagement range of 150 kilometers and a maximum engagement ceiling of 27 kilometers, these missiles brought a dramatic increase in capability compared with the YDG-32 and YDG-37 on other Menghean warships, allowing the Pyŏng'ans to provide true wide-area air defense to dispersed formations of friendly ships.

These missiles were arranged in "revolver" carousels of six missiles. As on the eight-cell S-300 launcher, one position in the ring had a cold launch pressure valve at the base, and the carousel would rotate to bring loaded cylinders over this launch point one by one. In addition to reducing the number of tubes per launcher to 6, the Menghean system also angled each tube outward from the pivot point by 5 degrees, and angled the pivot point outward by 5 degrees from the centerline. This had two major effects. First, the footprint of the launch system became much narrower at the base, allowing it to be installed further forward in the hull. Second, because the missiles launched from the 10-degree positions furthest to port and starboard, if a missile's second stage failed, it would continue on its ballistic arc into the sea rather than falling directly down onto the deck. The Pyŏng'ans were built with nine revolver arrays - six forward, and three astern - for a total of 54 missiles.

A single 30N6E radar antenna just forward of the helicopter hangars provides guidance for the YDG-39 missiles. This antenna can simultaneously guide 12 missiles toward 6 targets, but only over a single 60-degree sector. This makes the Pyŏng'an class vulnerable to saturation attacks from multiple directions.

The YDG-39 has a minimum practical engagement range of 5 kilometers, due to the delay in arming and redirecting the missile after its vertical launch. To cover this minimum engagement bubble, the Pyŏng'an-class ships were designed to carry short-range surface-to-air missile launchers on the forward and aft ends of the superstructure. Designated HYB-61/24 Bŏdŭl, these mounts each consist of 24 ready YDG-61 missiles on either side of a target acquisition array with electro-optical sights and a ranging radar. Because of delays in development, the YDG-61 was not operational until 2001; Pyŏng'an and Baekjin were both commissioned in an incomplete status, with empty pedestals where the short-range SAM launchers were expected to be. Foreign media sources at first erroneously reported that these empty mounts were intended for YDG-36 box launchers, but the Menghean Navy already considered the YDG-36 obsolete.

Further close range armament consisted of four GBM-30/6 CIWS mounts amidships, with each pair directed by a single MR-123 fire-control radar. Due to their amidships location, these guns each covered a 160-degree arc to port and starboard, leaving 10-degree gaps in gun coverage directly forward and aft.

Like previous Menghean warships, the Pyŏng'an class carried two types of anti-submarine armament as originally built, in addition to the helicopter facilities. Just aft of the bridge, and one deck below the YDH-24 anti-ship missile boxes, each ship carried four 533mm torpedo tubes per side. The chief difference with other postwar ships was the tubes' arrangement: they were fixed in place at a roughly 60-degree angle from directly ahead, and staggered so that all opened directly through hinged ports in the hull. The internal angling appears to have been chosen mainly in order to leave a roughly meter-wide space between the opposing ends of the tubes inside the ship, allowing personnel to move back and forth on that deck. No torpedo reloads were carried, though folding cranes on the deck above were meant to assist with reloading in port. Each tube could carry either a wire-guided homing torpedo or an HŎ-2 Poksŏl anti-submarine standoff rocket.

For close-range anti-submarine defense, the ships carry two HBDJ-21/12 rocket-propelled depth charge projectors. These are typically loaded with a mix of sonar decoy rounds and torpedo hardkill rounds, and were retained during refits.

Gun armament is unusually light for a 7,000-ton warship, consisting of a single 76mm HP-76/1 gun turret forward. This can engage aircraft and missiles as well as surface targets. The small caliber reflects the Pyŏng'an-class's intended role as an area air defense platform; in a typical late-90s or early-00s surface formation, Nunbora-class destroyers or Chŏndong-class destroyers would provide anti-surface escort and conduct shore bombardment operations, so a 130mm gun was deemed unnecessary.

Propulsion

The Pyŏng'an-class destroyers use a mixed foreign-and-domestic CODAG powerplant, as opposed to the steam turbine powerplants common on earlier Menghean destroyers and cruisers. The "cruise" diesel engines are domestic Samsan S9000H units, the same type used in the Sŏwicho-class corvettes, and each generate 8,000 shaft horsepower (5,970 kW). The gas turbines are used LM2500 units from Hallia, and each generate 33,600 shp (25,100 kW), for a total output of 83,200 horsepower (58,140 kW) at top speed with the diesel and turbine engines running in tandem. Top speed is reportedly 32 knots.

The Pyŏng'an-class destroyers were the first Menghean warships to install the gas turbines underneath a wide funnel to allow easy removal and servicing. The diesel engines and transmission units can also be removed through the gas turbine funnel, though their own exhaust vents through the aft radar mast.

Because the original gas turbines were first-generation LM2500 models with decades of existing use salvaged from a scrap hull, they suffered from poor reliability and efficiency in Menghean service. This contributed to a low readiness rate for Pyŏng'an during her first few years, especially as spare parts and replacement engines could not be legally imported. These concerns contributed to the use of a CODAG powerplant, rather than a full COGAG configuration, on subsequent frigate and destroyer classes.

See also

• Plan 351 "Yerihan," a competing design for Menghe's next-generation air defense ship
• Yakaze-class destroyer