200832 Grounding and near loss of tug

I was chief officer on a 35,000 dwt tanker proceeding to berth under pilotage. During our passage up a narrow channel section, the ship suddenly blacked out. Port wheel had just been ordered prior to the event, and with the rudder stuck at this angle and the residual headway, the ship rapidly veered out of the channel and ran aground before any contingency action could be taken.

She was pulled off by tugs after half a day and we continued up the channel, accompanied by a tug in case we had further problems. In order to save fuel, the tug was towed by the ship while lying alongside on a line.

Once loaded, we left the berth and the same tug was there to accompany us back down the channel. The tug was again held alongside on a single line forward. The ship left the berth and gradually went up to full manoeuvring speed. Soon, cries of distress came from the tug and looking down from the bridge wing, we saw that our bow wave was swamping the tug and water was pouring down into her engine room and accommodation through the open doors. The captain stopped the ship while I rushed down with an AB and cut the tug free. Fortunately, the tug pumped herself out and we continued on our way.

What we hadn't taken into account was that our underwater volume was a lot greater when loaded than in ballast, and our bow wave was correspondingly larger. One of us, the pilot, our captain, myself or even the tug skipper should have realised this; but none of us did.

Editor's note: It must be remembered that a complex pattern of high and low pressure zones develop in the water near the hull of a moving ship. These can attain significant values with increase in the draft and speed through the water: they can endanger tugs and even larger passing vessels when making full speed. If required to tow an idle escort tug, it may be safer to have it secured on the vessel's stern, sufficiently clear of the propeller wash. In any case, reliable communications must be maintained between tugs and the ship's bridge at all times.

FEEDBACK Aug 2008
All tugs should have an emergency hook release mechanism. For overall safety, a tug’s skipper must ensure, among other things, the following are also complied with before commencing a towing operation:
Tow winch(es) operation and quick release(s) checked, as applicable
Towing ropes / wires / gear are in good condition
The bridge radio is functioning correctly
Ship's whistle, fire and general alarms are tested
All watertight doors and openings on and below the main deck are battened down.
Vessels must not tow an idle escort tug. The Nautical Institute publication, Tug Use in Port, by Captain Henk Hensen FNI includes valuable information on the safe deployment of tugs.