On July 9, JR East announced the progress of its investigation and interim measures regarding the E8 Series train issues that occurred on the Yamagata Shinkansen in June.
Overview of the Trouble
On June 17, four incidents of auxiliary power unit failures occurred on the new E8 Series trains operating on the Yamagata and Tohoku Shinkansen lines.
These failures led to:
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Loss of power to lighting, air conditioning, and control systems
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Inoperability of the main converter system
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Resulting in complete immobilization of the train
Investigation Progress
As of June 25, damaged semiconductor components were confirmed inside the failed auxiliary power units.
However, the root cause remains unidentified.
Similar malfunctions have also been found on other E8 Series units that were not in active operation and had been parked at maintenance depots.
Environmental factors such as temperature are also under investigation.
Current Operational Measures
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Standalone operations of E8 Series trains are suspended.
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The "Tsubasa" service on the Yamagata Shinkansen is currently turning back at Fukushima Station.
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Passengers traveling between the Tokyo area and Yamagata must transfer at Fukushima Station.
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Only one round-trip direct train is operating between Tokyo and Shinjo.
Measures from July 19
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The number of direct round-trips will be increased from 1 to 3 per day.
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Due to limited operational E8 trainsets, service between Fukushima and Yamagata may be reduced.
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E8 trains currently stationed in Yamagata will be moved to the Tohoku Shinkansen line at night to enable 17-car operations and additional service.
Outlook
JR East stated that the current system will continue at least through July.
Plans for August and beyond will be announced separately once more information is available.
