Feb 222011
 

Schleswig-Holstein lightly scratched

Germany’s BSU report on the collision between the ro-ro ferry Schleswig-Holstein and the sailing yacht Mahdi in calm, clear conditions highlights the fact that at night navigation lights are effectively point-sources and  they can deceive the unwary. Often, by the time someone realises that a collision is imminent it’s too late to react.

As the BSU analysis says: Looked at superficially, the collision was purely the result of inadequate monitoring of the sea-room as defined in
COLREG Rule 5 by the bridge crew of the Schleswig-Holstein and consequent non-observance of right of way by the ferry. However, such an assessment of the situation is most certainly too simplistic.

The skipper of Mahdi did not use a passive radar reflector because he had assumed that his 13.7 metre steel hull would provide an unambiguous radar signature. He did not have his own radar switched on because he believed that given the heavy vessel traffic, nearby drilling rig and its auxiliary vessels there would be too much interference for the radar to enhance safety. In his communications with other vessels he did not he gave no position information.

He saw the green navigation light of Schleswig-Holstein as it departed the harbour and assumed he was visible on radar, that his own lights would be seen and that it would honour his right of way.

That was not the way things worked out. The very conditions that led to the Mahdi skipper switching off his radar made Mahdi’s radar image weak and difficult to spot on the bridge of Schleswig-Holstein as it was often in the radar shadow of other vessels, a situation made worse by his decision to sail close to the larger vessels.

Adjustments to the radars aboard Schleswig-Holstein might have increased the chances of spotting Madhi, something to bear in mind when small vessels are in similar operating environments, but was she not spotted by visual lookouts?

At night lights become point-sources and it can be difficult to assess distance and motion. The mights of a vessel may make it appear to be on a parallel course until, within seconds, the light appears to suddenly swing towards one’s one vessel. In this case, however, the high red light of  light of Madhi suddenly appeared just 200 metres two degrees to starboard, much to the surprise of the officers aboard Schleswig-Holstein.

Under certain circumstances a light mounted at the top of the mast of a sailing boat located at close range is easily confused with a navigation light presumed to be situated much further away on the horizon. The eyes of the bridge crew – if they were on the horizon – were focused primarily on the drilling platform, the brightly illuminated cruise ship, and two other vessels.

BSU gives an illustration of the phenomenon, taken from the Cruiser Section of the German
Sailing Association e.V. (DSV)24 website www.praxistraining-navigation.de:

The actions taken on board the ferry after the accident were marked by a high degree of professionalism. A lifeboat was deployed very quickly, the situation on board the yacht was clarified and assistance was offered to her crew.

Download the full report here.

http://www.bsu-bund.de/cln_005/nn_91228/SharedDocs/pdf/EN/Investigation__Report/2010/Investigation__Report__251__09,templateId=raw,property=publicationFile.pdf/Investigation_Report_251_09.pdf

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