Error in judgement whilst towing in a channel

The incident

On 18 February 2011, an AHTS was towing an accommodation barge down a Channel on a SW’ly course. At approximately 21:50 the Master on the AHTS alleged that the steering had malfunctioned and was not responding to starboard helm commands. The current (3 kts x S’ly) set the vessel to drift off the channel towards an offshore installation (jacket) on her port side.

By effective use of the engines on the AHTS the Master managed to avoid vessel contact with the jacket. However, the tow wire contacted the jacket legs and the barge was carried away in a southeasterly direction around the jacket. The effect of the current and tension on the tow wire pulled the jacket over to one side slightly misaligning it from vertical.

The AHTS thereafter paid out more of her towline and altered her course to North, albeit with a lot of difficulty, to eventually clear the towline and the barge off the jacket.

Observations

• Detailed investigations by the Member revealed no equipment failure on board and all checks on the steering system also showed no malfunction.
• The towline at the incident was about 50 to 70 metres which, considering the width of the navigable water available, was considered to be long. The towline, at the time of the incident, was also under tension.
• No attempt was made to use the bow thruster.
• The influence of the current and the tow wire under tension were considered as the two factors that hampered the vessel to turn to starboard.

This case highlights the severity of the consequences for failing to adequately compensate for prevailing conditions and not being familiar with own vessel’s manoeuvring characteristics. The importance of proper tug handling, including an initial and  ongoing assessment of the length of tow being used, cannot be over-emphasised.

Financial cost

The cost of this laimwasUS$1,602,658.