On December 5, 2024, the Defense Acquisition Program Administration (DAPA) announced that it held a meeting with HJ Heavy Industries to discuss upgrades for the Yoon Youngha-class Guided Missile Patrol Vessel (PKG). A few weeks ago, on November 27, HJ Heavy Industries announced that it secured a 124.7 billion KRW (87.2 millions USD) contract from DAPA to develop a performance improvement program (PIP) for 18 Yoon Youngha-class PKGs. These are 440-ton high-speed combat vessels dedicated to patrol duties in the NLL area. HJ Heavy Industries was responsible for constructing eight of these vessels, including the first ship, Yoon Youngha, in 2008, and all 18 ships were commissioned by 2018. HJ Heavy Industries will conduct an upgrade of all 18 ships, modernizing combat systems, software upgrades and adding auxiliary features to its sensors.
The PKG PIP is planned to be carried out sequentially until 2030, in conjunction with the ships’ depot maintenance. This upgrade aims to enhance the vessels’ survivability, combat capabilities, and their ability to safeguard the Republic of Korea’s Northern Limit Line (NLL) against North Korean threats. Notable upgrades will include implementation of RCWS for the 12.7mm K6 machine guns, upgrade for the air search radar, new decoy launch system (DLS), and addition of function to the EOTS.
The integration of the RCWS for K6 machine guns is anticipated to significantly enhance crew survivability by enabling remote operation of the weapon from within the vessel, utilizing the platform’s advanced surveillance and detection system. Naval News confirmed with DAPA that the SPS-540K 3D air search radar will undergo a software upgrade and frequency optimization to minimize interference and maximize performance. Furthermore, the SAQ-540K EOTS will be upgraded with a de-icing capability to prevent the sensor from freezing and ensure reliable operation in harsh conditions.
Lastly, the Mk36 SRBOC decoy launch system (DLS) will be replaced with a modern decoy system to enhance soft-kill capabilities and improve the survivability of the PKG. According to DAPA, the specific decoy system to be implemented has not yet been determined, and HJ Heavy Industries will make the final decision after testing. The three major decoy systems under consideration for the upgrade program are Rheinmetall’s MASS, Safran’s Dagaie NG (local partner SNT Dynamics), and TS Tech’s K-RBOC-NG.
Rheinmetall’s MASS has been widely applied to the latest Republic of Korea Navy vessels, including the recently commissioned ROKS Jeongjo the Great and the soon-to-be-delivered Chunnam-class frigates. However, concerns have been raised both domestically and internationally regarding whether MASS is sufficient to counter the advanced anti-ship missile threats posed by potential adversaries to the Republic of Korea Navy. Traditional countermeasures, such as chaff, are increasingly ineffective against modern missile systems equipped with advanced seekers capable of distinguishing chaff. To address this issue, integrating technologies such as corner reflectors and infrared imaging (IIR) decoy systems has become essential. Given the growing sophistication of modern anti-ship missiles and the advancements in North Korea’s military technology through NK-Russia cooperation, the ROK Navy’s investment in advanced soft-kill systems appears crucial to prepare for the increasingly complex challenges of future maritime operations.
We can never forget our comrades who were sacrificed in the surprise attack by North Korean patrol boats 22 years ago. DAPA will ensure the seamless execution of projects so that our military can respond to provocations with superior combat power.
RDML Hyun-seung Shin, Head of the Naval Ship Program Department, DAPA
Yoon Youngha-class Guided Missile Patrol Vessel (PKG)
The Yoon Youngha-class Guided Missile Patrol Vessel (PKG – Patrol Killer Guided) was developed as part of the Next-Generation Patrol Boat Project (PKX – Patrol Killer Experimental). The PKX program incorporated lessons learned from previous engagements near the Northern Limit Line (NLL). To protect the crew and critical equipment, ballistic protection was enhanced, and structural analysis results were used to improve shock resistance. On top of that, the vessel was designed to enhance survivability against enemy attacks by compartmentalizing sections to prevent the spread of flooding between compartments. Additionally, it became the first vessel in the ROK Navy to adopt a waterjet propulsion system. The lead ship was named Yoon Youngha in honor of Lieutenant Commander Yoon Young-ha, the commanding officer of PKM 357 who was killed in action during the Second Battle of Yeonpyeong. The first six ships were named after the crew members of PKM 357 who sacrificed their lives during the battle in 2002.
The vessel has a displacement of approximately 450 tons, measures 63 meters in length, and has a beam of 9 meters. It accommodates a crew of 40 personnel. Powered by two GE LM500 gas turbines and two MTU diesel engines in a CODAG (Combined Diesel and Gas) configuration, its waterjet propulsion system allows a maximum speed of 40 knots. The PKG’s armament includes a 76mm main gun, a 40mm twin gun, two inclined launchers for four C-Star anti-ship missiles (SSM-700K), two K6 12.7mm machine guns, and depth charges for anti-submarine missions.
For sensors and countermeasures, the vessel is equipped with LIG Nex1’s SPS-540K 3D air search radar, STX’s SPS-100K 2D surface search radar, the SPG-540K fire control radar, Hanwha Systems’ SAQ-540K electro-optical targeting system (EOTS), Mk36 SRBOC decoy launchers, and LIG Nex1’s SLQ-200(V)K SONATA (search-only) electronic support measures (ESM).
In addition to the recently announced upgrade plan, DAPA announced in August this year its plans to mass-produce 76mm armor-piercing high-explosive (APHE) rounds for the Yoon Youngha-class PKG and Chamsuri-class PKMR. Unlike conventional high-explosive shells that detonate immediately upon impact, the new APHE rounds are designed to penetrate the enemy hull and detonate inside using an impact-delay fuse. This development is expected to significantly enhance the strike capability of the 76mm main gun.
Regarding future vessels, it was recently mentioned during a seminar on the Navy’s Manned-Unmanned Teaming (MUM-T) systems that the Republic of Korea Navy plans to replace the PKGs with 800-ton Offshore Patrol Vessels (OPVs). These new OPVs will have the capability to control 100-ton large combat unmanned surface vessels (USVs), with air defense capabilities. Designed to address the demands of future battlefields and a decreasing availability of manpower, the 800-ton OPVs will incorporate advanced automation and unmanned technologies. They will also control unmanned aerial vehicles (UAVs) and surrounding USVs through low-earth orbit communication satellites.
