Japan's Ground Self-Defense Force has failed to determine the cause of engine trouble that resulted in one of its helicopter crashing in waters off the southern prefecture of Okinawa in April last year, Defense Ministry sources said Sunday.
The outcome of the investigation is expected to be announced in the near future, along with measures to prevent a recurrence of any similar accident. April's crash resulted in the deaths of all 10 personnel on board.
After analyzing the wreckage and the recovered flight recorder, the GSDF and collaborating companies detected that both engines saw a reduction in power immediately before the crash, the sources said.
However, inconclusive data from the flight recorder made it impossible to determine whether it was equipment malfunction or pilot error that caused the drop in output, the sources added.
The UH-60JA helicopter disappeared from radar 10 minutes after taking off from a base on Miyako Island at 3:46 p.m. on April 6, 2023. There were no abnormalities when it communicated with air traffic control around 3:44 p.m., the sources said.
The accident was the deadliest involving an GSDF aircraft, surpassing a helicopter crash in Ehime Prefecture, western Japan, in 1968 that left eight people dead.
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