There were no mechanical, electrical or control system failures onboard the council’s tug Solan when she collided with the tanker Loch Rannoch at Sullom Voe in December 2011.
That was the verdict of an investigation into the incident presented to councillors at a special meeting of the harbour board in the town hall this afternoon.
The report found that the underlying cause of the incident was related to an electronic solution the shipbuilder had applied to control the directional instability problem the Solan and Bonxie had suffered since they were built.
According to the incident panel which carried out the investigation, this was a rare, random, multi-factor event, with a number of contributory factors, including:
The original directional stability issue, and the subsequent electronic vectoring system which was installed by the builders to address it;
The operational issues associated with the towing winch which were experienced immediately before the incident, and which were a distraction for the bridge team, one of whom was under training;
Darkness, and the layout and poor illumination and labelling of the engine speed control buttons.
The incident investigation panel consisted of four master mariners and a chief engineer from SIC’s ports and harbour operations service.
At this afternoon’s meeting, the harbour board was also told of a potential solution to the stability issues affecting both Solan and Bonxie. This involves the fitting of relatively small horizontal stabiliser wings, and plans are in place to have both vessels modified over the next few months. This is expected to cost in the region of £60,000.
Harbour board chairwoman Andrea Manson said: “I am pleased to see the professional manner in which this investigation has been conducted, and it is clear from the report that there were several factors which led up to the incident.
“The board was satisfied to see details of a potential fix for the problems these vessels have suffered from since they were delivered. This should cost much less than was originally anticipated, and see the Bonxie and Solan operational before too long.
“The report, as is required by law, will now be sent to the Marine Accident Investigation Branch for their consideration, but I’m confident that this concludes this long-running matter.”