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This report discusses the August 21, 2017, collision between the US Navy destroyer John S McCain and the tanker Alnic MC. The John S McCain was overtaking the Alnic MC in the westbound lane of the Singapore Strait Traffic Separation Scheme when the destroyer had a perceived loss of steering. While the crew attempted to regain control of the vessel, the John S McCain unintentionally 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 over $100 million in damage. No one was injured on the Alnic MC, and the vessel sustained about $225,000 in damage. There was no report of pollution.  



1. Weather was not a factor in the accident. 

2. The Alnic MC’s steering and propulsion systems as well as the credentials of its crew were not factors in the accident. 

3. The functioning of the electrical, mechanical, and hydraulic components of the John S McCain’s steering and propulsion systems was not a factor in the accident. 

4. During the process of shifting control of thrust, a John S McCain watchstander unintentionally transferred control of steering from the helm to the lee helm station. 

5. The perceived loss of steering by the John S McCain helmsman was due to the unintentional transfer of steering control from the helm station to the lee helm station. 

6. Although the helmsman perceived a loss of steering, there was no malfunction of the John S McCain steering system. 

7. The unintended shift in steering control from the helm to the lee helm station on the John S McCain was likely a unilateral transfer initiated from the lee helm station. 

8. Operating the John S McCain’s steering system in backup manual mode allowed for the unintentional, unilateral transfer of steering control and contributed to the errors that led to the accident. 

9. Due to the perceived loss of steering, the bridge team on the John S McCain did not input starboard rudder orders needed to maintain the vessel’s intended heading, which initiated the destroyer’s port turn toward the Alnic MC. 

10. Had the John S McCain crew pressed the emergency-override-to-manual button at the Ship Control Console when the perceived loss of steering occurred, the watch team would have reestablished control of steering and would have likely avoided the collision. 

11. The John S McCain’s port and starboard propeller throttles were not ganged when the lee helmsman answered the order to reduce speed, and thus the throttles became unintentionally mismatched when he slowed only the port throttle.

 12. The John S McCain’s mismatched throttles resulted in an accelerated rate of turn to port toward the Alnic MC. 

13. The John S McCain bridge team was not monitoring the lee helmsman’s response to orders and therefore did not recognize that the throttles were mismatched. 

14. While attempting to reestablish rudder control on board the John S McCain, an inadvertent rudder input to port from aft steering and the resultant temporary movement of the rudders to port delayed the bridge team’s attempt to turn the destroyer away from the Alnic MC. NTSB Marine Accident Report 38 

15. The inability to maintain course due to a perceived loss of steering, the mismatch of port and starboard throttles producing an unbalanced thrust, and the brief but significant port rudder input from aft steering combined to bring the John S McCain into the path of the Alnic MC. 

16. The 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.

 17. Transmission of automatic identification system information from the John S McCain would have improved the situation awareness of watchstanders on surrounding vessels, including the Alnic MC bridge team. 

18. The John S McCain bridge team lost situation awareness in the minutes prior to the accident, and, consequently, they did not take sufficient action to avoid the collision. 

19. The lack of a very high frequency radio announcement from the John S McCain alerting nearby vessels of the destroyer’s steering casualty, as directed in the commanding officer’s standing orders, deprived the Alnic MC master of information needed to take action to avoid the collision. 

20. The Alnic MC master could not have reasonably determined that his vessel was in extremis before it was too late to maneuver the tanker to avoid the accident. 

21. The Alnic MC bridge was not manned in accordance with the requirements of the company’s safety management system. 

22. It is unlikely that the presence of additional watchstanders on the Alnic MC bridge would have changed the outcome of the accident. 

23. The design of the John S McCain’s touch-screen steering and thrust control system increased the likelihood of the operator errors that led to the collision. 

24. The steering and thrust control written operating procedures on the John S McCain’s bridge did not describe the actions needed to transfer control between stations and therefore were inadequate. 

25. Training on the operation of the Integrated Bridge and Navigation System for John S McCain watchstanders was inadequate, because it did not ensure that the crew could perform the basic functions of the watch, such as the transfer of steering and thrust control between bridge stations. 

26. John S McCain bridge watchstanders, particularly the lee helmsman, were acutely fatigued at the time of the accident, which impacted their situation awareness and their ability to respond to the perceived steering emergency. 

27. The Navy failed to provide effective oversight of the John S McCain in the areas of bridge operating procedures, crew training, and fatigue mitigation.