Thursday, March 15, 2012

Lost at Sea—PART 2

Lost at Sea—PART 2: A small fishing trawler’s sudden sinking and loss of its young crew leave questions unanswered.

Excerpt from U.S. Coast Guard Proceedings of the Marine Safety and Security Council magazine by Ms. Daisy R. Khalifa, technical writer.

The Casualty
According to the Coast Guard investigation, the most likely cause of the casualty was capsizing due to water on deck or flooding due to a very rapid event that did not allow the crew time to respond or access lifesaving gear.

The ROV revealed no catastrophic damage to the vessel’s hull or superstructure. Two of the three freeing ports on the starboard side were closed; the port side was not visible. The ROV also provided images of the life raft, which was deployed but still attached to the cradle,  indicating that the painter may have fouled, that there was a failure of the weak link that should have freed the raft, or that the weak link was improperly installed.

Possible Causes: Collision, Flooding, Capsizing
Possible causes that were explored in the investigation included a ship strike or collision, flooding, and capsizing.

The notion that a ship strike or collision could have caused the vessel to sink was considered the most unlikely cause. Coast Guard Sector Northern New England compiled a list of deep-draft vessels potentially in the area of the fishing vessel, and they determined that there were no large vessels close enough to the small trawler within the specified time frame. The ROV footage indicated there was no visible damage to the vessel that would be consistent with a collision.

The Coast Guard investigation asserts that capsizing due to a rapid loss of stability was the most likely cause of the sinking.

The MSC analysis focused on degradation of stability from water on deck. Based on the computer model, only limited amounts of water were needed to negatively affect stability. The vessel’s course exposed it to a quartering sea, making it susceptible to shipping seas from the stern, and if any freeing ports were closed, water on deck would cause a free surface effect, causing the vessel to further lose stability.

In part 3 we will outline the recommendations and lessons learned.

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