Real Life Accident: Towed Vessel Sinks After Colliding With Tug

An unmanned, decommissioned fisheries protection vessel was under tow when it developed a list of about 10 degrees to port. The tug’s Master informed the tug company’s managers and then called the local coastguard authority to request permission to seek shelter in a nearby bay and investigate the cause of the list.

In preparation for this, he reduced the scope of the tow from 480 metres to 200 metres and altered course towards the place of refuge. The Master was informed by the coastguard that he would need to take a pilot to enter the bay since he was not simply seeking shelter, but intending to board the towed vessel to investigate the list. The Master subsequently decided to anchor the tug and tow in the deep anchorage outside the bay where no pilot was required.

The weather at the deep anchorage was light winds, slight sea and good visibility. The tidal stream was north-easterly about 0.9kt. The Master’s plan was to anchor the tug and then board the towed vessel himself to investigate the cause of the list. He reduced the length of the tow further, to 100 metres, and stopped the tug down tide of the tow.

An officer was forward with a seaman and the Master and the chief engineer were on the bridge. The towed vessel was about 60 metres away when the Master ordered to let go the port anchor and put one shackle of chain in the water. At this point, control of the anchor windlass was transferred to the bridge and the cable was walked out. The anchoring had the effect of pivoting the tug to port, stopping it in the water, side-on to the tide and in the path of the tow, which maintained its momentum.

When 1½ shackles were in the water, the Master stopped walking out the anchor cable and used the searchlight to locate the towed vessel, which had been lost visually. A few seconds later, the towed vessel was seen closing the port side of the tug at right angles.

The Master immediately attempted evasive action to avoid a collision but the towed vessel struck the tow just aft of midships on the port side. As the Master attempted to manoeuvre clear he was informed that there was major water ingress to the engine room. The towed vessel’s bow had penetrated the tug’s shell plating below the waterline in way of the hydraulic motors in the engine room. The Master called the coastguard on VHF, advised them that the engine room was flooding and requested immediate assistance. Meanwhile, the hydraulic pump motors failed due to water ingress resulting in the immediate loss of all hydraulic power, which disabled the windlass. Concerned that the vessel might sink, the Master released the tow and put both engines full ahead in an attempt to dredge the anchor into shallower water.

Although the tug was later saved due to the actions of the Master and the quick response of local authorities, the towed vessel eventually sank.

The official investigation found the following:

• The Master’s lack of appreciation of the dangers resulting from tidal effects on the tow when anchoring was a direct contributing factor.
• The Master contacted the company as soon as he became concerned about the list on the towed vessel. However, there were no instructions or guidance in the company’s procedures regarding the use of senior, experienced staff from the management company to assist Masters in planning their response to crisis situations such as this. Had the Master developed a plan in conjunction with senior, experienced staff from the company, it is likely that the tidal conditions would have been taken into account.
• Had the Master taken a pilot, the subsequent anchoring would have been better prepared and therefore (probably) not have resulted in a collision.

Reference: nautinst

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