Photo/IllutrationThe main rotor head of a Ground Self-Defense Force helicopter that crashed in Kanzaki, Saga Prefecture, is retrieved on Feb. 8. (Nami Sugiura)

A key component of a Ground Self-Defense Force helicopter that crashed in Saga Prefecture on Feb. 5 was taken from used stock and not new as the Defense Ministry initially reported, sources said.

The part was the main rotor head that conveys the output of the engine to four main rotor blades. It was installed on the AH-64D attack helicopter as a replacement in regular maintenance work immediately prior to the crash, which killed the two crew members aboard.

The practice of swapping out main rotor heads with used ones is permissible. However, the Defense Ministry is investigating the possible connection between the strength of the used main rotor head and the crash.

In a news conference on Feb. 8, Koji Yamazaki, the chief of staff of the GSDF, said, “I have received a report that the part that replaced (the previous one) was a new one.”

Following that announcement, the ministry checked maintenance records and discovered that the main rotor head had been previously installed on a different helicopter of the same model, the Defense Ministry sources said.

The main rotor head had been removed from the helicopter, checked by Subaru Corp., supplied to the GSDF and then installed on the helicopter that crashed.

As for why the ministry initially said that the main rotor head was new, one of the sources said, “The confirmation was insufficient.”

Of the four rotor blades, two were found about 300 to 500 meters from the crash site in a residential area of Kanzaki still attached to parts of the main rotor head.

According to the sources, the main rotor head of the helicopter was manufactured by Boeing Co. of the United States. It was purchased by Fuji Heavy Industries Ltd. (current Subaru Corp.), based in Tokyo.

The helicopter underwent regular maintenance work from Jan. 18 to Feb. 4, during which time the used main rotor head replaced the previous one.