TADTE 2025: Sea acceptance trials of Taiwan's new submarine programme delayed

A model of Taiwanʼs Indigenous Defense Submarine at the Taipei Aerospace & Defense Technology Exhibition 2025. (Janes/Akhil Kadidal)

Efforts to conclude sea trials of Taiwan's Indigenous Defense Submarine (IDS) prototype have been delayed due to technical challenges, a Republic of China Navy (RoCN) source has confirmed to Janes.

The prototype, which will become the ROCS Hai Kun (Narwhal) once it is commissioned, is intended to enhance the service's submarine fleet. Under production by Taiwan shipbuilder CSBC Corporation, the submarine was subject to over a year of harbour trials. The vessel was due to complete its sea trials in September.

However, the RoCN source told Janes on 19 September, during the Taipei Aerospace & Defense Technology Exhibition (TADTE) 2025 held from 18 to 20 September, that the sea acceptance trials phase had encountered “technical issues”.

This follows a 17 September statement by CSBC president Tsai Kun-tsung, who said, “completing the sea acceptance trials in September was ‘impossible', judging by the current progress”, as reported by state-owned Central News Agency (CNA).

“The issues experienced all have solutions from an engineering point of view,” the RoCN source said. “But it will require some time to [implement].”

According to a CSBC source, the submarine began initial sea trials in June. However, it appears that there are concerns about the vessel's ability to conduct a fully submerged test.

A CSBC statement presented at TADTE 2025 said the submarine “was currently in dry dock to calibrate the performance of various systems and equipment”. According to the statement, the submarine's underwater equipment has been inspected and the vessel has been subject to watertight testing.