Cause of Japan GSDF Helicopter Crash in Okinawa Pref. in April 2023 Concluded to Be Unidentified; UH-60JA Crash

From the Ground Self-Defense Force’s website
A Ground Self-Defense Force UH-60JA helicopter

The Ground Self-Defense Force’s investigation committee has concluded that the direct cause of a crash of its helicopter off Miyako Island in Okinawa Prefecture in April last year could not be identified, according to government sources.

There were 10 GSDF members on board the UH-60JA multipurpose helicopter, all of whom died in the accident. The GSDF will release a report about the crash as early as the end of this week.

The accident occurred in the afternoon on April 6, 2023. The helicopter took off at 3:46 p.m. from the Air Self-Defense Force’s Miyakojima Sub Base to confirm information such as the geography of Miyako Island. It made contact with the control tower at nearby Shimojishima Airport, but it dropped off the radar about two minutes later.

Ten GSDF members included Yuichi Sakamoto, who at the time was the commander of the 8th Division headquartered in Kumamoto Prefecture.

A UH-60JA helicopter has one engine on the right and left side of the body, and the aircraft is designed to be able to continue flying even if either of the two engines malfunctions.

After the accident, the GSDF salvaged the main parts of the helicopter from the seabed and recovered the flight recorder to analyze recorded data of engine power outputs and altitude and confirmed the existence of recordings of voices of the crew who responded after noticing an abnormality.

According to the sources, the GSDF accident investigation committee found that the right-side engine’s power output rapidly declined, and the left-side engine’s power output gradually declined in about two minutes. Aviation experts said it is very unlikely that both engines on that type of helicopter would simultaneously malfunction. The committee’s main focus was on the cause of the power output decline of the left-side engine as that caused the crash.

However, some of the data in the flight recorder was damaged and unreadable. Therefore, the committee could not identify whether mechanical trouble or pilot error caused the decline of the left-side engine’s power output.

As a measure to prevent a recurrence, the GSDF plans to reinforce maintenance of its helicopters’ bodies and conduct educational training for pilots.