TAIPEI (Taiwan News) — A preliminary investigation of the Sikorsky S-70C anti-submarine helicopter crash on Wednesday (June 22) points to a failure of the tail rotor, Navy Chief of Staff Chiang Cheng-kuo (蔣正國) said on Thursday.

Chiang said that after reviewing communication logs, neither the pilot nor the co-pilot mentioned mechanical failures or other issues. He added that based on what the control tower observed and the pilot's description of events, it is suspected that the helicopter's tail rotor failed, CNA reported.

Chiang said further assessment of the accident is needed to concretely determine the cause of the crash. He said that since the military began operating S-70C helicopters in the 1980s, there have been 4 Level 1 flight safety incidents. The first three occurred in 1983, 1994, and 1997.

The military will continue to maintain personnel training and implement a flight incident assessment mechanism, the Navy chief of staff added.

Four Navy officers were injured when their S-70C came in for a hard landing at the Zuoying Naval Base during a training mission Wednesday afternoon. The Navy has grounded all Sikorsky-made helicopters of the same type for inspection, and a special task force has been set up to investigate the crash.