TAIPEI, — Taiwan’s first domestically built submarine, Hai Kun (SS-711), also known as Narwhal, completed its 23rd sea trial and 17th submersible test on October 2 near Kaohsiung. Shipbuilder CSBC Corporation, Taiwan, is accelerating testing as it works toward handing over the submarine to the Republic of China (ROC) Navy by the end of 2026.
Military expert Chi Tung-yun, chair of the Taiwan Association for Security and Development, said sea trials are expected to continue on a near-weekly basis to complete the remaining acceptance requirements. Navy officials have not announced a firm delivery date, emphasizing that safety and quality standards take priority over the schedule.
Submarine Design and Testing
Construction of Hai Kun began in November 2021 at CSBC’s Kaohsiung facility, and the submarine was launched in September 2023. The diesel-electric attack submarine has an estimated submerged displacement of 2,500 to 3,000 tons and incorporates lithium-ion battery technology and a Lockheed Martin combat system.
The submarine is designed to carry U.S.-made Mk 48 heavyweight torpedoes and Harpoon anti-ship missiles. Sea trials began with surface operations in mid-2025, followed by the first submerged test on January 29, 2026. Subsequent tests have covered propulsion, sonar, hull integrity and combat systems.
In May 2026, Hai Kun successfully launched training torpedoes, testing functions associated with target detection, fire-control calculations, launch and guidance. CSBC continues equipment calibration and adjustments based on trial data. Weather and technical requirements have occasionally delayed individual tests, while the program has progressed through surface, shallow-water and deeper submerged phases.
Delivery Delays and Financial Penalties
CSBC missed the original contractual delivery deadline in November 2025 and has been paying daily penalties of approximately NT$190,000 (about US$6,200). The company has maintained that safety and quality take priority over meeting the original deadline.
Although handover is planned by the end of 2026, delivery will not mean immediate operational service. After receiving the submarine, the ROC Navy must complete further certification, systems integration and operational testing before declaring it combat-ready.
Chi estimated that post-delivery evaluation could take at least six months and potentially more than a year, depending on the submarine’s performance during advanced testing and tactical assessments.
Role in Taiwan’s Submarine Fleet
Taiwan currently operates two aging Chien Lung-class submarines acquired from the Netherlands in the 1980s. Hai Kun is the prototype of the Indigenous Defense Submarine (IDS) program, which aims to expand Taiwan’s undersea capabilities through domestic submarine construction.
Funding for follow-on submarines remains contingent on the successful completion of the prototype’s trials and related legislative reporting. The remaining sea trials and acceptance procedures will determine when Hai Kun can be transferred to the Navy, with additional evaluations required before it enters operational service.
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