Defense Minister Takeshi Iwaya said Monday the crash of an Air Self-Defense Force F-35A stealth fighter in the Pacific Ocean off Aomori Prefecture two months ago was likely caused by “spatial disorientation” of the pilot rather than technical problems with the aircraft.
According to a preliminary report by the Defense Ministry, there were no signs the 41-year-old pilot tried to eject. He is believed to have lost his bearings during an ASDF exercise just before the crash.
Verification work to identify the cause of the crash has received considerable attention as Tokyo’s plan to purchase from Washington 105 F-35As, at a cost of about ¥11.6 billion ($107 million) each, could be affected by its outcome.
Iwaya told a news conference he will not review the F-35A deployment plan. He added that the ministry is taking measures such as special inspections of the remaining 12 F-35As at Misawa Air Base, in Aomori Prefecture, and more rigorous training of pilots so they can avoid losing their bearings.
The advanced fighter that crashed in April was one of the first 13 F-35As deployed in Japan, and the crash was the first involving an F-35A anywhere in the world. Since the accident the ASDF has suspended operations of the remaining 12 F-35A jets at Misawa, but plans to resume flights soon.
“We will fully enforce training to avoid spatial disorientation and will fully explain to local residents before deciding to resume flights” of the remaining F-35As, Iwaya said.
Since the cutting-edge jet went down off Aomori Prefecture at around 7:25 p.m. on April 9, the ASDF has analyzed radar data and records of communication with three other F-35A fighters that were flying alongside it during the drill.
According to the ASDF, to maintain the necessary distance from U.S. aircraft that happened to be flying nearby, the pilot began descending from an altitude of about 9,600 meters after receiving instructions from ground control.
After descending to an altitude of about 4,700 meters with a speed of at least 900 kph and receiving additional instructions, it began veering to the left and continued its descent for another 15 seconds to below an altitude of about 300 meters before going off the radar about 135 kilometers off Misawa Air Base.
It is believed that moments before it crashed the jet was traveling at a speed of at least 1,100 kph.
Right after it began veering left, the pilot said “Hi, knock it off” in a calm voice indicating his wish to suspend the drill, so the ASDF determined that the possibility of an aircraft malfunction or a loss of the pilot’s consciousness was “extremely low.”
Japan stopped searching for the single-seat stealth jet earlier this month after retrieving some fragments of it, including the flight data recorder, but that was heavily damaged.
Last Friday, the ministry confirmed the death of Maj. Akinori Hosomi, the pilot, after parts of his body were found in the ocean near the area where debris from the jet was recovered.