[Exclusive] Another Submarine's Engine Stopped on the Day the Seohee Was Launched

Seawater ingress halts Jang Yeongsil's engine
April fire aboard Hong Beomdo disrupts overhaul schedule

The Navy's submarine force is facing a potential crisis. Although the Navy has launched the Seohui, concerns are growing that gaps could emerge in its operational fleet as engines on submarines being deployed have stopped running and depot maintenance schedules have fallen behind.

According to a government official on November 4, the Seohui, launched the previous day, is the second submarine in the Jang Bogo-III Batch-II (3,600-ton class). The problem lies with the first vessel, the Jang Yeongsil. It is scheduled to be delivered to the Navy in September 2027, but its engine stopped during sea trials. The Jang Yeongsil is equipped with three Rolls-Royce engines. The cause was seawater entering one of them while the submarine was operating its snorkel. The Navy believes seawater entered because an external exhaust valve did not close automatically during the operation. Rolls-Royce engineers are scheduled to visit South Korea in November and investigate the cause together with engineers from Italy's Calzoni, the manufacturer of the external exhaust valve. The Navy plans to suspend snorkel operations by the Jang Yeongsil until measures to prevent a recurrence are in place.

The navigation radar is not meeting performance requirements. Although it was successfully localized, unstable output has prevented its installation. The Navy believes the connection between the antenna and its cable is faulty. Military authorities say they aim to find a solution by the end of 2026, but some test and evaluation items are likely to be difficult to verify.

The Hong Beomdo, a Jang Bogo-II-class (1,800-ton) submarine, caught fire in April 2026 while undergoing depot maintenance at HD Hyundai Heavy Industries' Ulsan shipyard. Four months have passed: 1.5 months preserving the site for the accident investigation and 2.5 months cleaning up, including removing soot. Given that it took three years to restore a French submarine after a fire during depot maintenance in 2020, the Hong Beomdo is also likely to take a long time to restore.

The maintenance of the Hong Beomdo is also expected to delay depot maintenance for subsequent submarines. Depot maintenance refers to work performed after a submarine has carried out missions for a certain period to restore it to the same performance level as when it was first delivered. The Son Wonil is currently undergoing depot maintenance at HD Hyundai Heavy Industries, and the Jeong Ji and Sin Dolseok are due for depot maintenance starting in 2027. The Navy believes HD Hyundai Heavy Industries will be unable to carry out depot maintenance on two or more submarines, and is considering requesting that Hanwha Ocean handle the maintenance.

A Defense Acquisition Program Administration official said, "We have established measures to prevent a recurrence of seawater ingress through software improvements and completed corrective measures for components related to the navigation radar. The flooded engine will be replaced with a new one, after which we plan to complete the relevant tests and evaluation in December."

This content was produced with the assistance of AI translation services.