The US National Transportation Safety Board has attributed the causes of the collision between US Navy Destroyer John S McCain and Tanker Alnic MC (IMO 9396725) in the Singapore Strait on August 21st 2017 to insufficient training, inadequate bridge operating procedures and a lack of operational oversight.
In its Marine Accident Report, released this week, the report recounted that the John S McCain was overtaking the Liberian-flagged tanker Alnic MC while both vessels were transiting the westbound lane in the Middle Channel passage of the Singapore Strait Traffic Separation Scheme. The destroyer crew suffered a loss of steering and, while the crew attempted to regain control of the vessel, she turned to port into the path of the Alnic MC. As a result of the collision, 10 John S McCain sailors died, 48 were injured, and the vessel sustained more than $100m worth of damage. No one was injured on the Alnic MC; the vessel sustained about $225,000 worth of damage. There was no report of pollution.
Contributing to the accident were the John S McCain bridge team’s loss of situation awareness and a failure to follow loss of steering emergency procedures, which included the requirement to inform nearby traffic of their perceived loss of steering. Also contributing to the accident was the operation of the steering system in backup manual mode, which allowed for an unintentional, unilateral transfer of steering control.
As the John S McCain entered the Singapore Strait, steering and thrust were being controlled by a single watchstander – the helmsman – from the helm station. The commanding officer directed the lee helm station be manned as well and the crew took actions intended to transfer propeller thrust control from the helm to the lee helm station. The NTSB concluded that during the process of shifting thrust control, a John S McCain watchstander unintentionally transferred control of steering from the helm to the lee helm station, which resulted in a perceived loss of steering by the John S. McCain’s helmsman, however, steering control was available at all times in the accident sequence. The NTSB further concluded the unintentional transfer was possible because the system was being operated in backup manual mode, which removed a safeguard against inadvertent transfer of steering control.
The throttles on the John S McCain became mismatched at 05:22:20, about 18 seconds before the Alnic MC master would have had to slow his vessel to avoid the collision. Prior to the mismatch, the vessels were not on a collision course, as the Alnic MC master had assessed, although they would have passed close to each other. After the mismatch, the John S McCain’s rate of turn toward the tanker increased while its overall speed decreased. Investigators considered the ability of the Alnic MC’s bridge team to detect the change in the destroyer’s rate of turn and whether it should have triggered additional concern regarding risk of collision.
Reviewing the time span of 20 seconds prior to the John S McCain’s throttle mismatch, the destroyer’s change in heading was 4.9 degrees; in the 20 seconds after the mismatch, the change in heading was 7.8 degrees—a difference of less than 3 degrees. In darkness, viewing primarily the destroyer’s navigation lights, the change in the John S McCain’s rate of turn after the throttle mismatch would have been difficult to perceive and would have taken time to develop—likely longer than the estimated 18 seconds that the master had to act.
The NTSB concluded that it was unlikely that the presence of additional watchstanders on the Alnic MC bridge would have changed the outcome of the accident.
The NTSB report also concluded that the inability to maintain course due to a perceived loss of steering, the mismatch of port and starboard throttles producing an unbalanced thrust, and a brief but significant port rudder input from after steering combined to bring the John S McCain into the path of the Alnic MC.
This decision to change the configuration of the John S McCain’s critical controls while the destroyer was in close proximity to other vessels increased the risk of an accident, the NTSB said.
Based on its investigation of the collision, the NTSB has issued seven safety recommendations to the US Navy, which are listed below:
- Issuance of permanent guidance directing destroyers equipped with the Integrated Bridge and Navigation System to operate in computer-assisted steering modes, except during an emergency.
- Issuance of guidance to crews emphasizing the importance of appropriate use of very high frequency radio for safe navigation.
- Ensuring design principles in ASTM International Standard F1166 are incorporated when modernizing complex systems such as steering and control systems within the Integrated Bridge and Navigation System.
- Revision of written instructions for bridge watchstanders on destroyers equipped with the Integrated Bridge and Navigation System to include procedures for shifting steering and thrust control between all bridge stations.
- Revision of Integrated Bridge and Navigation system technical manuals to include a description of and procedures for ganging and unganging throttles.
- Revision of training standards for helmsman, lee helmsman and boatswain’s mate of the watch for destroyers equipped with the Integrated Bridge and Navigation System to require demonstrated proficiency in all system functions including transfer of steering and thrust control between all bridge control stations.
- Instituting Seafarers’ Training, Certification and Watchkeeping Code rest standards for all crewmembers aboard naval vessels.
|Vessels||John S McCain||Alnic MC|
|Owner/operator||US Navy||Energetic Tank Inc/Stealth Maritime Corporation|
|Homeport/port of registry||Yokosuka, Japan (homeport)||Monrovia, Liberia|
|Flag||United States||Republic of Liberia|
|Classification Society||N/A||Bureau Veritas|
|Length||504.5 ft (153.8 m)||600.4 ft (183.0 m)|
|Draft||32.5 ft (9.9 m)||42.2 ft (12.9 m)|
|Beam/width||66.4 ft (20.2 m)||105.6 ft (32.2 m)|
|Displacement||8,261 long tons (8,394 metric tons)||37,204 long tons (37,801 metric tons)|
|Persons on board||280||24|