Taiwan's Hai Kun submarine begins deeper sea trials on its 25th outing

Taiwan's first locally built submarine, the prototype Hai Kun (SS-711), sailed from Kaohsiung on Wednesday, 15 October 2026, for its 25th sea outing and 19th submerged test, entering a harder phase of deep-dive and long-endurance trials that stand between the boat and a planned year-end delivery to the Republic of China Navy.

Liberty Times, United Daily News and China Times all reported the morning sortie from Kaohsiung. Liberty Times said the boat appeared about 7:50 a.m. Taipei time, earlier than recent departures, as the test tempo rises. United Daily News said the navy and shipbuilder CSBC continue to verify systems and handling under open-water conditions while the programme moves into its closing stretch.

Chi Tung-yun, who heads the Taiwan Security Development Association and spoke at the quay, told reporters the sea-trial series has entered its final stage, with longer, deeper and more demanding runs now scheduled, including overnight endurance tests. He said months of tuning and foreign technical support had resolved most of the serious systems-integration problems that CSBC chairman Chen Cheng-hung had previously acknowledged.

Chi argued that Hai Kun's pace from yard start in 2018 through launch in September 2023 and toward delivery compares favourably with troubled first-of-class projects abroad. He cited South Korea's first German-designed boats that needed major post-delivery repairs, Spain's S-80 Plus buoyancy error that stretched the build to about 18 years, and Australia's Collins-class boats that still struggle to keep high availability.

Only a handful of countries can design and build submarines without a foreign turnkey yard, Chi said, and Taiwan faces extra political barriers when buying kit, so the public should judge the prototype by safety and progressive proof rather than by a calendar alone. Without submarines, he said, Taiwan would have only half a navy. China Times quoted him saying that under a safety-first approach a handover could still come soon once the harder runs are finished.

CSBC still targets delivery before the end of 2026 if the deep-dive and endurance series go smoothly, but officials and outside experts keep repeating that acceptance depends on test results and negotiated punch-list items rather than a fixed handover date. The navy will use the remaining weeks to prove the prototype can operate safely at depth before any ceremony that would put Taiwan's first indigenous boat on the fleet list.

For Taipei the stakes are operational as well as industrial. A working Hai Kun is meant to seed a follow-on class that can hunt in the waters where Chinese submarines already practise, and to show that Taiwan can finish complex undersea systems despite supply-chain friction. Wednesday's deeper trial day therefore matters less as a count of sorties than as evidence that the hardest remaining checks have begun.