Lieutenant Ng Keng Yong made "errors of judgement" that led the anti-submarine patrol vessel RSS Courageous into the path of the Dutch-owned ANL Indonesia on January 3, investigators from the Maritime and Port Authority of Singapore (MPA) said.

A trainee officer of the watch, Lieutenant Chua Chue Teng, was in control of the vessel at the time of the collision but was under the direct supervision of Ng, who approved the trainee's instructions to change course.

As the two vessels headed towards each other in the eastern Singapore Straits near Pedra Branca island, the trainee ordered the 452-tonne RSS Courageous to change course to port, or the left side.

Ng, the officer of the watch, approved the change despite knowing that the move was against maritime collision regulations, investigators said.

Such regulations state that when two vessels are heading towards a possible smash, each shall change course to starboard, or right side, so that they would pass each other on the left side.

The 51,938-tonne ANL Indonesia took the correct action by moving starboard, the investigators said.

"The collision ... was caused by errors of judgement in assessing the situation and the wrongful application of the Collision Regulations on the part of the RSS Courageous," said MPA senior director Lee Seng Kong at a news conference.

Although the trainee officer was in control of the ship, she was under the direct supervision of Lieutenant Ng. As such, Ng "was fully responsible for the safe navigation" of the navy ship, investigators said in their report.

"By not intervening, the officer of the watch had shown that he was either not fully aware of the situation around him or had wrongly agreed with the actions and instructions given by the trainee," Lee said.

Only the bodies of three servicewomen killed in the collision were recovered. The fourth servicewoman was never found, and is presumed dead.

Defence Minister Tony Tan said the findings by the MPA were consistent with those of the Singapore Armed Forces' higher board of inquiry.

He said the Ministry of Defence agreed with the MPA's conclusion that there were "errors of judgement" by Ng, but no lawsuits have been filed.

The findings of the MPA and the higher board of inquiry will be sent to the state coroner for further action, he said.

"We will have to wait for the next stage, which is the coroner's inquiry, which will assess who is to blame. Until we know culpability, it will be premature to take action at this time," Tan told a news conference.

Chief of Navy, Rear Admiral Ronnie Yap, said the trainee was undergoing training in shiphandling as part of the navy's programme to give its officers practical experience.

The navy has described the incident as the worst in its history.

SPACE.WIRE