Chunchŏn-class frigate

HO-340 Chunchŏn as she appeared when commissioned.
Class overview
Builders:	Gyŏngsan Songsu-do Shipyard Kimhae Naval Yard Chŏndu New Naval Yard
Operators:	Menghe Azbekistan Sundan Ummayah
Preceded by:	Yechŏn-class frigate
Succeeded by:	Sŏnsan-class frigate
Built:	2010-present
In commission:	2013-present
Planned:	17
Building:	1
Completed:	18
Active:	18
General characteristics (Chunchŏn, 2014)
Type:	Frigate
Displacement:	5,950 tons full load
Length:	138.2 m overall 126.4 m at waterline
Beam:	17.9 m at bridge wings 15.8 m at waterline
Draught:	6.09 m to keel
Propulsion:	CODOG 2 × LM2500+ turbine (30,200 kW each) 2 × Taesan T16K diesel (6,440 kW each) 4 × Samsan 6EY22ALW aux. generator (1,435 kWe each) 2 shafts
Speed:	34 knots
Range:	5,400 nautical miles (10,000 km) at 15 knots
Complement:	23 officers 154 enlisted crew
Sensors and processing systems:	1 × SMART-S MK2 air-search radar AN/SQS-53C hull sonar Ŭ-100 variable-depth sonar AN/SQR-19 towed array sonar
Electronic warfare & decoys:	2 × JJ-9 ESM/ECM complex 2 × D-107 datalink 2 × Pigan EO scanner 2 × Baram-2 countermeasure launchers 2 × Manhwagyŏng-H torpedo countermeasure launcher
Armament:	1 × HP-130/1 single 130mm turret 32 × Mk 41 VLS cell 32 × strike-length cell 8 × YDH-29 Chŏngryong anti-ship missile 2 × Subisu CIWS 2 × 2 350mm torpedo tube
Aircraft carried:	2 × GH-28 Ppulsoeori
Aviation facilities:	landing pad with hauldown winch hangar

The Chunchŏn-class frigates (Menghean: 春川級外層護衛艦 / 춘천급 외충 호위함, Chunchŏn-gŭb Oechung Howiham) are a class of guided missile frigate built in Menghe. Developed as successors to the Yechŏn class, they share the same battlegroup escort capabilities, but are also designed to carry out coastal bombardment and anti-shipping missions. In addition to the eight units operated by the Menghean Navy, there are three units operated by Azbekistan, four units operated by Sundan, and three units operated by Ummayah, with a fourth scheduled for delivery in mid-2024.

Since 2014, Menghe has replaced the Chunchŏn class with the Sŏnsan class in all new construction for the Menghean Navy, while continuing production of the Chunchŏn class for foreign customers. The Sŏnsan class uses the same hull as the Chunchŏn, but with a quieter and more reliable powerplant, making it more effective at anti-submarine warfare.

Development

Requirements

The Menghean Navy ordered design work on a new frigate class in the mid-2000s, while the Yechŏn-class frigates were still entering service. As "outer-layer escort ships" (oechung howiham, HO), the Yechŏns and their subclasses were designed to operate at the edges of a carrier battle group or other formation, sitting on the threat axis between the core escorted asset and a likely enemy approach. This role called for strong self-defense capabilities, as these ships would be the first to come under air or missile attack, but also a relatively inexpensive sensor and armament fit, as they would be needed in large numbers and would have a high probability of being lost. Accordingly, compared with the Haeju-class destroyers, the Yechŏns sacrificed long-range air search radar, VLS cell count, and anti-surface capabilities while retaining powerful ASW sensors and the ability to fire medium-range surface-to-air missiles.

By 2004, the Menghean Navy was already conducting conceptual work on a new frigate class, but the Ummayan Civil War and the diplomatic shift around it mandated faster development and new requirements. For one, Menghe now faced a possible war with Innominada, which shared a coastline on the South Menghe Sea. This raised the need for naval operations along an enemy-controlled coast, in support of small amphibious units or Army forces on land. Navy planners concluded that many features of the HO ship concept carried over well to shore bombardment work: frigates of this type were relatively inexpensive, but also possessed powerful self-defense capabilities, making them well-suited to a threat-dense littoral environment. The Yechŏn-class frigates, however, only sported 76mm guns for shore bombardment work, and only carried YDH-26 missiles to engage enemy surface ships. Thus emerged a new requirement for a frigate similar to the Yechŏn class but armed with a 130mm main gun.

Along similar lines, the Navy required that the new class be better-equipped for anti-shipping missions. The Chŏndong-class destroyers had proven effective in naval combat during the Ummayan Civil War, and Menghe hoped to use later batches of this frigate class to replace them. The YDH-29 Chŏngryong missile, still in development at the time, would serve as the prospective main armament.

These requirements caused some debate in the Navy, as more conservative officers viewed them as a form of mission creep: as initially envisioned, HO-type frigates were supposed to sacrifice all capabilities not directly relevant to the battlegroup defense mission in order to minimize cost and reduce the loss in capability from a sinking. Prospective designs for the new frigate class would increase displacement by up to 1,000 tonnes and bring overall capabilities closer to those of the Haeju-class destroyer. Advocates for the expanded ship concept argued that the new capabilities required relatively little space, cost, and mass, and coincided with the baseline HO hull's demands for a high-speed, low-cost ship with good self-defense capabilities.

Proposals

The first blueprint, Plan 84, was submitted in 2007. It resembled the Chŏndong-class destroyers, with four forward-facing missile launch boxes on either side of a narrow bridge structure. The 32 Mk41 cells were split between two 16-cell modules, one forward of the bridge and one at the rear end of the superstructure. Just forward of the aft Mk41 module was a helipad and a single telescoping hangar. Gun armament consisted of an HP-130/2 Type 82 twin 130mm autoloading naval gun in a low-RCS angular mount. Propulsion would have been the same CODOG system used on the Yechŏn class. Though conservative in its capabilities, this design offered little growth potential, especially as the exact size of the YDH-29 launch box was not yet known so the spaces flanking the bridge could prove to be too narrow.

Plan 85 was submitted in 2008, after a more thorough design process. It more closely resembled the Yechŏn class, with a single 130mm gun turret forward (taken from the Haeju class), a two-helicopter hangar, and a more conventional squared-off funnel, all requiring a larger hull. To compensate for the increased displacement, the powerplant was upgraded, with uprated LM2500+ turbines for sprinting and larger Taesan T16K diesels for cruising. These engines were still coupled in a CODOG arrangement, which, though louder and slightly slower, would also be a more reliable bet compared with less familiar options. Otherwise, the overall layout was similar to the Dŏkju-subclass frigates already under construction, with a SMART-S MK2 air search radar on an hourglass-pyramid mast, 32 Mk41 VLS cells forward, and reloadable Subisu CIWS mounts replacing the non-reloadable Dungji CIWS in roughly the same locations.

A design called Plan 86 took the size increases even further, with a fully enclosed bow to eliminate the radar reflection from the anchor handling gear and the VLS cells split between a 32-cell group forward and a 16-cell group aft. Plan 86 was the most capable of the entries, but it was also the largest, with a waterline length of about 140 meters. This would have made it too large for the existing drydocks for the construction and maintenance of frigates. On this basis, and on the basis of increased cost, it was rejected early on. Plan 87 did, however, provide design experience for the Insŏng-class destroyers which followed later in the decade.

Plan 87 was the final entry to receive a formal plan number from the Navy's evaluation office, being registered in early 2009. Like Plan 86, it offered a CODLAG powerplant with quiet direct-drive electric motors for cruising and LM2500+ gas turbines for high-speed sprints. Because of its all-electric gearless transmission, it would have been quieter at low speeds than the Plan 84 or Plan 85, and also more fuel-efficient, due to the ability to run both shafts on power from one diesel generator rather than trailing the other shaft while running on a single diesel engine. Its distribution of equipment also made it more survivable in the event of a hull breach or missile impact. In all other respects, it closely resembled the Plan 85 design.

Approval and construction

At first, Plan 87 seized the advantage in theoretical evaluations, as its CODLAG powerplant would be superior for ASW work and would allow the same range on less fuel. But as the deadline for the first keel laid down grew near, Plan 87 stumbled over practical issues. To run its powerplant, it would require two 5,000-kW low-speed brushles electric motors from Taesan and four high-power-density 3,500-kWe diesel generators from Samsan. These contractors had the required systems in development, but both reported that they were several years away from a mass-production-ready design. In the end, unwilling to order an additional batch of Dŏkju-class frigates to fill the delay until the required powerplants were ready, the Ministry of National Defense selected the Plan 85 design at the start of 2010.

The first ship in the class, named HO-340 Chunchŏn, was laid down on 20 August 2010 at the Chŏndu New Naval Yard, which had been expanded specifically to support new frigate construction. A sister ship, HO-341 Myŏngju, was laid down in the neighboring assembly hall three months later. Chunchŏn was commissioned on 17 September 2013.

Characteristics

Propulsion and machinery

Comparison of the powerplants of the Plan 85 (Chunchŏn) and Plan 858 (Sŏnsan) frigate designs.

The Chunchŏn-class frigates use a CODOG powerplant in which each shaft is coupled to an LM2500+ gas turbine provided by Glasic General Electric (30,200 kW) and a T16K diesel engine supplied by Taesan Heavy Machinery (8,050 kW). The clutch system of the transmission only supports using one powerplant at a time to power each shaft, with no combined diesel and gas power and no cross-coupling between shafts. Electricity for the ship's systems comes from four Samsan 6EY22ALW diesel generators, each producing 1,425 kWe. The engines and generators are split across two watertight compartments separated by a blastproof and fireproof double bulkhead, with both gas turbines and two generators in the forward compartment and both diesels and two generators in the aft compartment. Because both transmission units are in the aft compartment, damage confined to that compartment could still immobilize both propeller shafts, but even in this case the ship would be able to limp to port under the power of an electric retractable bow thruster which can also rotate through 360 degrees to aid with maneuvering in port.

For efficient cruising at speeds of up to 19 knots, the Chunchŏn-class frigates can run one diesel engine while trailing the other shaft with feathered propeller blades. Adding in the second diesel engine on its own shaft brings top speed up to 24 knots at full load. At peak power, with both gas turbines running, the ships are rated for a top speed of 33.4 knots at full load, though speeds of over 35 knots were achieved on trials when running at reduced fuel load.

All machinery components are fitted to rafted mounts, which partially isolate vibration from the hull to reduce the ship's acoustic signature. A Prairie-Masker system further reduces cavitation and machinery noise. The forward Masker belt is fed with bleed air from the gas turbine engine, while the aft Masker belt and the Prairie system are fed by electrically-powered air compressors, allowing them to be used when the gas turbines are shut off. As on the Jedong-class corvettes built around the same time, the Chunchŏn-class frigates use a newer model of air compressor produced by Samsan Heavy Machinery. Unfortunately, at-sea trials concluded that while Samsan's compressors were moderately more reliable than the type used by the Yechŏn and Mirun classes, they still required frequent downtime for maintenance and could not be run continuously on long anti-submarine patrols. This issue was confirmed during early operational tests with Chunchŏn, and it motivated the development of the Sŏnsan-class frigate.

Gun armament

While the Yechŏn class carried a 76mm dual-purpose gun forward, the Yechŏn is armed with a 130mm HP-130/1 Type 03 gun turret. This system has a rate of fire of 30 rounds per minute, and fires from two 20-round carousels at the bottom level of the hull, well below the waterline. It can fire programmable time-fuse shells, as well as point-detonation contact-fused shells, laser-guided shells, and Chŏl-u cluster munition shells. With a rocket-propelled long range shell, it has a claimed maximum firing range of over 100 kilometers.

Self-defense gun armament comes in the form of two Subisu CIWS installations, one on either side of the hull just forward of the helicopter hangar. This is the same approximate arrangement used by the Dŏkju-class frigates, but the Chunchŏn's mounts are one deck higher, allowing each mount to fire its guns directly forward over the sides of the wheelhouse and slightly across the centerline aft, resulting in full 360-degree coverage. In peacetime, each mount's traverse range is restricted to reduce the risk of damage to sensors and equipment, but in a combat scenario the crew can deactivate this restriction to engage targets directly forward and aft at the cost of endangering searchlights, radio antennas, and life raft containers in the field of fire.

Despite its intended coastal role and despite the threat of Innominadan fast inshore attack craft, the Chunchŏn class does not carry dedicated autocannons for defense against small boats. Instead, standard practice is to rely on the GBM-23/5 guns, which have a reduced rate-of-fire setting for use against surface targets. The ships are fitted for but not with three 12.7mm heavy machine guns, with one pintle mount on the bow and one on each rear corner of the helicopter hangar. HMGs were often seen on these positions during the Innominadan Crisis, but since 2015 the mounts have almost always been stowed.

Missile and torpedo armament

The Chunchŏn class carries four eight-cell strike-length Mark 41 VLS modules, for 32 launch cells in total. This is the same VLS armament as the Yechŏn-class frigates, mounted in the same arrangement, with all cells forward between the bridge and the 130mm gun The following loadouts are typical:

• Battlegroup escort mission
  • 16 × YDG-60 long-range SAM
  • 8 × HŎ-3 Ryongorŭm anti-submarine rocket
  • 32 × YDG-64 medium-range SAM (quadpacked, 8 cells)
• Surface attack mission
  • 20 × YDH-28 anti-ship missile
  • 32 × YDG-64 medium-range SAM (quadpacked, 8 cells)
  • 4 × HŎ-3 Ryongorŭm anti-submarine rocket
• Coastal bombardment mission
  • 20 × SY-26 or SY-28 cruise missile
  • 32 × YDG-64 medium-range SAM (quadpacked, 8 cells)
  • 4 × HŎ-3 Ryongorŭm anti-submarine rocket

Between the funnel and the helicopter hangar are eight angled box launchers for the YDH-29 Chŏngryong supersonic anti-ship missile. When launched from a stationary surface platform like a Chunchŏn-class frigate, the YDH-29 has a range of 400 kilometers on an all-high trajectory, 300 kilometers on a hi-lo trajectory with a sea-skimming terminal approach, and 250 kilometers on an all-lo trajectory, which would minimize the missile's chances of detection.

In addition to its two 23mm rotary autocannons, each Subisu mount is also fitted with 32 YDG-61 surface-to-air missiles, including eight at the ready and 24 in a magazine below the deck. This brings the total to 64 missiles.

Torpedo armament consists of two twin 350mm torpedo tubes on each side of the superstructure, under the Subisu CIWS mounts. These fire the YŎ-35/2 torpedo, which is also used by the ship's helicopters. The YŎ-35/2 has a range of 8 kilometers at 54 knots or 25 kilometers at 26 knots, and exists as a backup option against unexpected undersea threats at close range, with HŎ-3 Ryongorŭm missiles and heliborne torpedoes serving as the ship's main anti-submarine weapons. No other short-range anti-submarine armament, such as the HBDJ-21/12, is fitted.

Sensors and countermeasures

The tower over the superstructure carries a SMART-S MK2 air-search radar. This system operates in the E/F band and has an instrumented range of 250 kilometers at 13.5 RPM and 150 kilometers at 27 RPM. Mounted over 28 meters above the waterline, it has a surface-level radar horizon of 22 kilometers. Though less capable than the AN/SPY-1D system on the Haeju-class destroyers, the SMART-S radar confers adequate range to target YDG-60 missiles against patrol aircraft and detect anti-ship missiles incoming on the horizon.

To complement this radar system, the ships carry two Pigan electro-optical cameras, one on each side of the superstructure flanking the waist of the hourglass mast. These sensors automatically sweep back and forth horizontally, taking 15 seconds for each 180 degree sweep. Working in the infrared band, they scan the horizon for surface vessels, periscopes, or incoming anti-ship missiles, and can be programmed to stop on a target to allow closer inspection. This allows the ship to remain on alert against incoming threats even with the air search radar switched off. Each Pigan unit is stabilized to point at the horizon even as the ship pitches and rolls, though there is no way to program them to scan higher or lower angles.

For missile guidance and fire control, the Chunchŏn class carry two CPAR-X traversing I-band phased array antennas, one forward and one aft. Each director can each provide simultaneous terminal guidance for four missiles and simultaneous mid-course guidance for eight, using multiple beam steering to track and illuminate multiple targets in the same 120-degree arc. Instrumented range is limited to 150 kilometers. Compared with the STIR 2.4 antennas used by the Yechŏns and their subclasses, this reduces the frigate's maximum range for illuminating a target, restricting a favored strategy of using a frigate to illuminate targets for long-range surface-to-air missiles fired from a destroyer operating under radio silence. The enhanced multiple engagement capability, however, greatly improves the Chunchŏn's ability to fend off large waves of anti-ship missiles in a jamming-intensive environment.

The forward antenna can also provide fire solutions and fire correction for the ship's 130mm naval gun.

The shipboard electronic warfare suite is built around two JJ-9 ESM/ECM modules, which are designed to detect radar signals from incoming anti-ship missiles, classify them, and jam them in the same frequency. Two Baram-2 countermeasure launchers provide an inner layer of defense, complemented by four Munje fast-deploying inflatable radar decoys which float on the surface of the water, mimicking the ship's radar signature. Two Manhwagyŏng torpedo countermeasure launchers centered over the helicopter hangar can distract incoming torpedoes, buying time for the ship to escape.

Aviation facilities

The aft hangar structure can accommodate two GH-28 helicopters, double the capacity of the Yechŏn-class frigates. Hauldown devices on tracks running into the hangars allow recovery operations in strong winds and heavy seas. The flight deck control room is centered between the hangars overlooking the landing area.

YŎ-35/2 torpedoes for the ship's helicopters are stored in a magazine room below the waterline and lifted on a hoist which runs between the two helicopter parking spaces. Previously, this type of internal torpedo magazine was only used by the Haeju-class destroyers; on all other Menghean frigate and corvette classes, torpedo reloads were stored on the main deck level. The internal magazine reduces the risk of explosion due to damage above the waterline.

Ryoju subclass

HO-345 Ryoju, HO-346 Raenghae, and HO-347 Suju were completed to a slightly different design from the first five Menghean hulls. Up top, their upper sensor mast was extended to make room for an HG-54 omnidirectional VHF and UHF acquisition and direction-finding array, to help locate enemy radio emissions. The Pigan EO units flanking the tower were replaced by Hongmoja models, which are more sensitive and can also scan at higher elevations to detect enemy aircraft and high-altitude missiles. This change necessitated the relocation of some UHF antennas. Because the changes are minor, the Menghean Navy does not consider these ships to constitute a separate subclass in their own right, but ship identification guides note that the "beehive" structure on the upper mast and the more angular cameras flanking the hourglass mast set these three ships apart from the others.

Sŏnsan subclass

Main article: Sŏnsan-class frigate

HO-348 Sŏnsan as built.

The Sŏnsan-class frigates (designed as Plan 858) were originally developed as a subclass of the Chunchŏn-class frigates, but owing to the depth of the differences between the designs, they are now generally treated as a separate frigate class in their own right.

Export deals

Sundan

In 2011, the government of Sundan signed an agreement with Menghe for the construction of four Chunchŏn-class frigates. This was one of the first major warship export orders which Menghe had received from a country outside of the future Namhae Front. All three ships were built at the Chŏndu New Naval Yard, with the first delivered on 5 February 2015 and the last delivered on 28 November 2018. All three follow the baseline Chunchŏn design, even though the first ship in the Ryoju subclass was built in between the first two and the second two.

Azbekistan

Azbekistan inked a deal for three new Chunchŏn-class frigates in 2012, hoping to replace earlier Menghean frigates lost or damaged in a conflict with Khalistan. The first ship, delivered in 2016, followed the baseline Chunchŏn design. The second and third, however, incorporate the changes made to HO-345 Ryoju, featuring improved ESM and EO equipment.

Ummayah

Ummayah ordered four Chunchŏn-class frigates in 2016, as replacements for the three aging Yobu-class destroyers which Ummayah acquired from Menghe in 2005. Because of Banbhan export restrictions, and because of the unusual timing of their construction (Menghe had already laid down five Sŏnsan-class frigates by the time the first Ummayan ship was laid down), these four frigates follow a different design and are often regarded as their own subclass. Their main air search radar is the HR-827 Pioran, which has a range of only 140 kilometers but is of entirely Menghean design and construction. For missile guidance and gun fire control, they use the Jj-0403 phased array radar, an experimental Menghean design not used by any Menghean Navy ship. Because the YDG-60, YDG-64, and YDG-66 all use too many foreign components, Ummayah was only sold YDG-7N surface-to-air missiles to arm these ships. The YDH-29, YDH-28, SY-28, and HŎ-3 are all Menghean domestic products and were not affected.

Ships in the class

The table below shows all Chunchŏn and Sŏnsan-class frigates in service or under construction as of February 2023. Dates in italics are predicted launching and commissioning periods, as of that point in time.

Menghean Navy

Subclass	Name	Hull No.	Builder	Launched	Commissioned	Notes
Chunchŏn	Chunchŏn	HO-340	Chŏndu	2012-02-26	2013-09-17
	Myŏngju	HO-341	Chŏndu	2012-07-19	2014-01-07
	Sŏlsan	HO-342	Kimhae	2013-10-28	2015-05-06
	Misu	HO-343	Songsu-do	2014-01-30	2015-08-06
	Cheho	HO-344	Songsu-do	2014-04-07	2015-11-10
	Ryoju	HO-345	Kimhae	2015-06-18	2017-02-14
	Raenghae	HO-346	Songsu-do	2015-08-07	2017-03-21
	Suju	HO-347	Songsu-do	2015-10-04	2017-06-27
Sŏnsan	Sŏnsan	HO-348	Kimhae	2016-10-27	2018-08-28
	Pungsan	HO-349	Songsu-do	2017 01 22	2018 10 24
	Juta	HO-350	Songsu-do	2017 04 01	2018 12 15
	Ichŏn	HO-351	Kimhae	2018 02 17	2019 12 14
	Bunju	HO-352	Songsu-do	2018 06 25	2020 01 30
	Wando	HO-353	Songsu-do	2019 09 08	2021
	Chŏngsŏng	HO-354	Kimhae	2019 09 15	2021
	Pyŏnghae	HO-355	Chŏndu	2020 06 22	2022
	Takgye	HO-356	Songsu-do	2021	2022
	Daejŏ	HO-357	Kimhae	2021	2022
	Hajŏn	HO-358	Chilsan	2021	2023
	Dagye	HO-359	Chilsan	2021	2023
	Jŏngpae	HO-1300	Chŏndu	2022	2023
	Chŏnghwa	HO-1300	Songsu-do	2022	2023