Korean Submarine Suffers Equipment Malfunction During First Overseas Exercise

The South Korean Navy's submarine Anmu (KSS-III, 3,000-ton class), the second vessel of the Dosan Ahn Chang-ho class and the first domestically designed submarine to participate in overseas joint exercises, experienced performance degradation while abroad, prompting the emergency dispatch of Korean technical personnel for urgent repairs, the Seoul Economic Daily has learned.

According to the Seoul Economic Daily's investigation on the 5th, the Anmu crossed the Pacific Ocean to participate in the 2025 Silent Shark Korea-U.S. combined anti-submarine warfare exercise, arriving in Guam last November. The submarine departed from Jinhae Naval Base on November 4 and arrived in Guam 13 days later on November 17.

Prior to departure, the Anmu underwent approximately one month of comprehensive safety inspections covering all facilities and equipment. The mission carried significant meaning as the first overseas joint exercise participation by a submarine independently designed and built with domestic Korean technology.

However, an unexpected performance degradation occurred during the 3,500-kilometer Pacific voyage. Increased strain on the cooling system during the long-distance ocean transit revealed a seawater leakage problem in the air conditioning seawater pump.

Upon detecting the issue while crossing the Pacific, the Anmu reported to the Submarine Command. The Navy immediately dispatched technical personnel from the Submarine Command's Submarine Repair Depot to Guam, timing their arrival with the vessel's port call for emergency repairs.

"It is true that the Anmu discovered the air conditioning seawater pump leakage problem while crossing the Pacific and that we urgently dispatched Submarine Repair Depot technicians for emergency repairs," a Navy official stated. "It was not a major malfunction. The problematic component was immediately replaced, and the scheduled combined anti-submarine exercise was completed successfully."

Typically, when incidents occur, military branches conduct comprehensive safety inspections of all weapons systems of the same type. However, the Navy did not conduct safety inspections on the first vessel (Dosan Ahn Chang-ho) or third vessel (Shin Chae-ho) of the Dosan Ahn Chang-ho class.

Regarding this, the Navy explained, "This maintenance addressed simple leakage in an auxiliary equipment component, which does not require immediate safety inspections of all submarines of the same class. The Navy conducts regular safety inspections of all vessel equipment according to regulations."

Silent Shark is a Korea-U.S. combined anti-submarine warfare exercise in which the Korean Navy conducts submarine tracking and attack drills, free-play warfare exercises, and aviation anti-submarine warfare with U.S. forces in waters near Guam for approximately one month to strengthen combined operational capabilities.

Rep. Kang Sun-young of the People Power Party stated, "Just as Heinrich's Law indicates that one major accident is preceded by 29 minor accidents and 300 warning signs, concealing or downplaying military incidents without accurate investigation or identification of causes can lead to larger accidents." She added, "The Ministry of National Defense must conduct comprehensive safety inspections of all vessels of the same class and thoroughly investigate suspicions of concealing the malfunction."

The Anmu, the Navy's second 3,000-ton submarine developed with indigenous Korean technology, measures 83.3 meters in length and 9.6 meters in width. It is a diesel submarine equipped with an Air Independent Propulsion (AIP) system that extends submerged operation time.

The AIP system enables underwater operations for up to several weeks without surfacing, unlike older submarines, significantly enhancing the stealth capability essential to submarine operations. With numerous domestically developed systems including combat systems and sonar, the vessel achieves a 76% domestic content ratio.

Maximum underwater speed exceeds 20 knots (37 km/h), with a crew of approximately 50. Like the first vessel Dosan Ahn Chang-ho, it is reported to be equipped with six vertical launch tubes capable of firing submarine-launched ballistic missiles (SLBMs).

Vertical launch systems are typically found on nuclear-powered submarines, making their installation on diesel submarines rare worldwide. The vessel is also evaluated as having superior operational endurance and significantly enhanced stealth and survivability through the application of the latest fuel cell technology and cutting-edge noise reduction technology.