A series of missteps and inadequate preparation by key personnel of United States destroyer USS John S. McCain were largely to blame for its collision with an oil tanker in Singapore waters on Aug 21.
When the vessel entered the congested channels, the commanding officer (CO) did not station extra manpower on the deck to help with navigation in the early hours of the morning, despite recommendations to do so from other officers.
He also ordered an unplanned shift of duties in the control room that led to confusion among the personnel and the ship's loss of steering. The move triggered an "un-commanded turn" into the path of the Liberian-registered tanker Alnic MC just before 5.24am.
These details emerged from an investigation report released by the US Navy on Wednesday, which provided a blow-by-blow account of one of the deadliest naval accidents to occur in Singapore waters.
The report also covered the collision between the USS Fitzgerald and container ship ACX Crystal in June near Japan, which was one of four incidents involving US warships in Asian waters this year. Among the four incidents, the USS John S. McCain collision resulted in the highest number of casualties, claiming the lives of 10 US sailors and intensifying questions over the US Navy's operations and procedures.
The 72-page report detailed how the first misstep took place even before the USS John S. McCain had entered Singapore waters.
A team providing additional personnel with specialised navigation to be stationed on board - known as the Sea and Anchor detail - was scheduled to come on only at 6am.
This was more than 30 minutes after the warship had entered a high traffic area of the Singapore Strait.
The report said the CO had decided not to station the Sea and Anchor detail when appropriate, despite recommendations from the Navigator, Operations Officer and Executive Officer. "If the CO had set Sea and Anchor Detail adequately in advance of entering the Singapore Strait Traffic Separation Scheme, then it is unlikely that a collision would have occurred," it added.
The CO also made an unplanned reassigning of steering and speed control duties, which "caused confusion in the watch team".
While the CO had assigned a crew member to take over the speed control duties from the helmsman, the latter's steering control duties were also assigned inadvertently and unknowingly to another station.
By the time the crew realised a loss of steering, the CO tried to slow the ship down. But the two throttles on each side of the ship were not coupled together, and the crew ended up slowing the left side more than that on the right. This led to an "un-commanded turn" to the left, among other factors, which, although corrected three minutes later, was too late to avoid the collision.
Other mistakes included how key personnel, like the officers responsible for safety and issuing steering orders, did not attend a navigation briefing the day before.
Another way it could have been prevented, said the report, was if either the destroyer or the tanker had sounded short blasts of whistle required by international rules as they came into close proximity.
If this or bridge-to-bridge communications were done in a timely manner, "then it is possible that a collision might not have occurred".
"The navy is not concerned about the mistakes made by Alnic," added the report. "Instead, the navy is focused on the performance of its ships and what we could have done differently to avoid these mishaps."
It laid most of the responsibility on CO Alfredo J. Sanchez, who was relieved of his duties last month, alongside executive officer Jessie L. Sanchez. "In the navy, the responsibility of the commanding officer for his or her ship is absolute. Many of the decisions made that led to this incident were the result of poor judgment and decision-making of the commanding officer," it said. But it added that no single person bears full responsibility for this incident, citing the crew's lack of preparation, ineffective command and control, and deficiencies in training and preparations for navigation.
Asked to comment on the report, Singapore's Transport Safety Investigation Bureau said its investigations are ongoing and it would not be appropriate to make comments at this stage. The bureau is a unit within the Ministry of Transport which investigates air and sea accidents.