Pilot’s Improper Flanking a Bend Resulted in Collision

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The National Transportation Safety Board has issued a Marine Accident Brief regarding the collision of Crimson Gem Tow with Bulk Carrier Yangtze Ambition docked at the bottom of a river bend.

Specifically, on January 28, 2016, at 04:30 local time, the uninspected towing vessel Crimson Gem was pushing 20 barges downbound during high-water conditions on the Lower Mississippi River in Ama, Louisiana, when two of its barges collided with the bulk carrier Yangtze Ambition. Damages to the vessel and the barges, including a third barge that made contact with the dock, was estimated to be $575,000. There was no injury or pollution reported.

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The Crimson Gem pilot told investigators that he should have backed down sooner than he did after passing the Dennis Fromenthal. By slowing down sooner, he would have better positioned the Crimson Gem tow to account for the slide effect of the current in the 67-degree bend. Consequently, he could have kept his vessel farther away from the right descending bank where the Yangtze Ambition was docked.

The pilot also said he would it have backed down at all had it not been for his ARTCO Tulane fleet area destination, just 0.9 mile away on the left descending bank from the accident site. Backing down in the current reduced his ability to control the tow.

The pilot would have preferred to have “flanked” the bend, as he told investigators. Flanking allows tows to pivot around the point of a bend, similar to how a large log might drift downriver. A vessel operator may decide to flank around a bend if the combined forward speed of the vessel and the current might otherwise push the tow onto the outside riverbank before the turn can be completed.

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Compared with steering around a bend, flanking requires more time to navigate through relatively short stretches of the river (as the forward speed is slower) but reduces the risk of running aground. Flanking is possible only when the current pushes the vessel from astern and carries the vessel through the turn. As the Crimson Gem approached the bend in Ama, the river current was pushing the tow from astern at as much as 6.7 mph.

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Probable Cause

The National Transportation Safety Board determines that the probable cause of the collision of the Crimson Gem tow with the moored bulk carrier, Yangtze Ambition was the Crimson Gem pilot’s ineffective maneuvering for the prevailing current along a river bend.

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Source: NTSB

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