Jun 162014

Assumptions led to collision

Merely responding “Okay” isn’t the best way of ensuring that the other vessel actually understands your intentions. And, as Germany’s Bundesstelle für Seeunfalluntersuchung, BSU report into the collision between xontainerships CMV CCNI Rimac and CMV CSAV Petorca near the port of Yangshan, China, shows:  Assume nothing.

Under conditions of reduced visibility at 1148, on 21 June 2011, VTS Yangshan, told the Petorca that she was outside the fairway and that a vessel in the fairway was approaching her. Petorca  acknowledged the information and told the traffic centre that she intended to return to the northern part of the fairway immediately after the outbound ship  passed. She did not mention the ship by name but was referring to the Rimac. VTS Yangshan repeated the information from the Petorca and acknowledged her intentions.

Rimac called VTS Yangshan about 15 seconds later and asked about the oncoming vessel now some 1.5 nm away. The Petorca heard this query and requested the Rimac to maintain her course at 1150. Petorca intended to alter her course a  little further to port.

While it was clearly the intention of the Petorca that the two vessels should pass green-green Rimac apparently understood the Petorca’s request incorrectly. Although “Okay” was her reply, this “Okay” was combined with the information that she would now move to starboard. However, this misunderstanding was not recognised by the Petorca and she merely replied with a brief ‘thank you’ to the master.

Rimac started to make the stated course alteration to starboard immediately after the radio contact was finished. The Petorca altered her course slightly to port. The two vessels came within sight of each other shortly afterwards at a distance of about 0.8 nm, prior to which they had observed one another only on the radar.

However, they could not prevent the collision at 1153, which was caused by the opposing evasion manoeuvres. Petorca touched the Rimac’s superstructure on the port side at an angle of about 50 degrees with her bow and then scraped along several container stacks stowed in front of the superstructure. As a result of the collision, the Rimac took on water due to a hole in the area of the port side of cargo hold 5; however, this did not compromise her buoyancy. 26 of the containers on the ship went overboard. The Petorca was damaged only slightly in the area of the bow and bulbous bow, consequently, she remained completely seaworthy.

After the water ingress in the cargo hold, a dangerous situation occurred in the roads of Yangshan on the following day. A chemical reaction followed by heat and smoke occurred inside at least one dangerous goods container stowed in cargo hold 5
because of water ingress. The crew of the Rimac was temporarily evacuated from the vessel as a precaution. A special team discharged 9 the four dangerous goods containers affected as a priority, thus eliminating the ensuing hazardous situation.
The collision did not result in any injuries and there was no pollution of any significance.

Says BSU: “Once more, the finding that manoeuvring arrangements made to prevent collisions are very problematic and for various reasons involve the risk of ill-fated misunderstandings was confirmed. It would appear that this is true even when there are no doubts as to the identity of the communicating parties and immediate verification of the implementation of (supposed) agreements is easily possible using modern technology (ARPA, AIS). Once again, the collision between the Rimac and Petorca  illustrates that the risks inherent in any close-quarters situation – in restricted visibility, in particular – should never be underestimated. Within just a few minutes, a situation that appeared relatively uncomplicated only eight minutes before the subsequent accident developed into a collision, which could have claimed human lives had the course of events been
less favourable”.

BSU believes it is likely that the Rimac initially tried to implement a port side to port side (‘red-red’) encounter with the Petorca  by making moderate course alterations to starboard. The RIMAC probably interpreted the Petorca’s initial continuous course alteration to starboard as her action in mirror image.

The two communicating parties failed to inform the Rimac about the ‘green-green’ pass – occurring in less than three minutes – which stood in contrast to the ‘red-red’ encounter usually practised on fairways and, in particular, contravened Rule 19 COLREGs.

Petorca assumed a green-green pass with the Rimac because of the supposed agreement. Rimac’s alteration of course to starboard initiated immediately after the end of the radio contact, which was diametrically opposed to the supposed arrangement, should have been noticed and led to an immediate response. Instead, the ship’s command of Petorca seemed to stick to its planned green-green pass with Rimac until the very end purely on the basis of the supposed arrangement and without considering the actual and clearly disparate events.

So, assumptis were maintained even though they weren’t supported by what was actually happening.

Just listening isn’t enough, one has to know what one’s listened to if your mental models are going

Download Investigation Report

See also:

Spring Bok/Gas Arctic – Knocked By Fatigue, Distraction And Poor Lookout

Marti Princess/Renate Schultze – Poor Situational Awareness

Far Swan/Miclyn 131 Collision – Lights, Lookout And Mental Models

Scottish Viking/Homeland Collision

Collision: Bonking Birka Too Little Too Late



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