IRIA News

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Taiwan’s first domestically built submarine, the Hai Kun, also known as the Narwhal, entered a new and critical phase of testing with the start of underwater dive trials on January 26, 2026.

Hai Kun conducted its sixth sea acceptance and first dive test off the coast near Kaohsiung Harbor. The trial drew close attention from military observers and photographers, underscoring the strategic importance of the program both domestically and across the region.

The submarine was escorted out of the harbor by military vessels amid strong winds and rough sea conditions, according to local media reports.

Shipbuilder CSBC Corp., which is overseeing construction and testing, declined to disclose specific details about the content of the latest trial or to confirm a final delivery date. The company emphasized that submarine testing is inherently complex and time-consuming, particularly for a prototype vessel.

“Submarine testing procedures are highly complex and often take a very long time, especially for a prototype vessel, which, based on foreign experience, can sometimes take more than a year,” CSBC said in a statement.

Surface Trials to Underwater Testing

The latest test was the submarine’s first confirmed dive trials, a step that moves the program beyond surface and harbor testing that has taken place over the past year. According to Taiwanese media, the Hai Kun conducted its initial submersion test on Sunday, entering controlled underwater conditions for the first time since construction was completed.

Since its launch earlier in 2024, the submarine has undergone a series of land-based checks, harbor trials, and surface navigation tests at Kaohsiung port. Land-based testing began in July 2024, followed by incremental sea trials designed to validate propulsion, navigation, and basic platform systems.

CSBC stated that not all onboard systems need to be fully operational during every test phase. The company said safety is the top priority during sea trials, followed by engineering validation, with individual subsystems evaluated in stages.

The Hai Kun is expected to undergo three distinct cycles of underwater trials: tests at periscope depth, shallow-water dives, and deep-sea trials. These evaluations will assess the submarine’s structural integrity, buoyancy control, propulsion performance, and systems integration at varying depths.

Setbacks and Technical Challenges

The submarine program has faced several technical setbacks that have contributed to delays. In September 2024, the Hai Kun reportedly suffered a main engine failure during sea trials after a rupture occurred in internal piping systems. The incident forced a temporary halt to testing while repairs were carried out.

Following those repairs, the submarine resumed trials in mid-2025. Taiwanese media reported that departure trials were completed in June 2025, followed by floating tests in November. Surface trials officially began on June 17, 2025, and were only recently concluded, later than initially planned.

One of the most significant issues affecting the schedule involved the submarine’s integrated platform management system. According to sources cited by local outlets, the electronic management system initially failed to link effectively with other onboard sensor and weapons systems, creating compatibility problems that delayed progress.

United Daily News reported that incompatibility between the platform management system and other electronic systems was the primary reason for the delayed delivery. The issue was provisionally resolved with the assistance of dozens of foreign consultants, the report said, after which signal connectivity returned to normal.

Taiwanese media also reported that foreign engineers assisted in resolving the technical problems, though officials have not disclosed the identities or nationalities of the specialists involved.

Revised Timeline for Delivery

Taiwan’s Ministry of National Defense is now targeting June 2026 for the submarine’s formal handover to the navy, roughly seven months later than originally planned. Earlier schedules had envisioned sea trials beginning in April 2025, concluding by September, with commissioning set for November 2025.

According to local media, defense authorities expect the full testing program to be completed by mid-2026, provided no further major technical issues emerge during the underwater trial phase. Some reports suggest delivery could take place as early as June if remaining tests proceed smoothly.

CSBC reiterated that extended testing timelines are not unusual for first-of-class submarines and cited international experience to support its assessment.

Strategic Importance and Future Plans

The Hai Kun is the lead boat of a planned class of eight indigenous diesel-electric submarines that Taiwan aims to build and deploy by 2027. Taiwanese authorities have already approved plans to construct a further seven Narwhal-class submarines at a Kaohsiung shipyard, although implementation will depend heavily on the successful completion of trials for the first vessel.

The program is a central component of Taiwan’s efforts to strengthen its undersea deterrence in the Taiwan Strait and reduce reliance on foreign-built platforms. Submarines are viewed by Taiwan’s defense planners as a survivable and asymmetric capability that could complicate Chinese naval operations in the event of a conflict.

By developing domestic submarine production capabilities, Taiwan is also seeking to build long-term expertise in advanced naval engineering, systems integration, and sustainment. The Hai Kun program has therefore attracted intense scrutiny from both supporters and critics, who see it as a test case for Taiwan’s broader defense industrial ambitions.

Regional Attention

The start of dive testing has placed the Hai Kun among the most closely watched naval programs in East Asia. Military analysts across the region are monitoring the trials for indications of the submarine’s operational capabilities and the pace at which Taiwan can bring indigenous platforms into service.

While delays have raised questions about execution and technical risk, Taiwanese officials continue to frame the program as a long-term investment rather than a short-term fix. With underwater trials now underway, the coming months are expected to be decisive in determining whether the Hai Kun can meet performance expectations and pave the way for the rest of the class.

If testing proceeds as planned, Taiwan’s first domestically built submarine could enter service in 2026, marking a milestone in the island’s efforts to enhance its naval deterrent and defense self-sufficiency.