A small tanker was manoeuvring to leave port without tug assistance. The departure manoeuvre began at twilight, with winds from the south of about 10 knots. The pilot, Master, OOW and helmsman were on the bridge. The departure plan, as discussed by the bridge team, was to let go aft and bring the forward spring lines under tension with the engine dead slow ahead and wheel hard to port, swinging the stern away from the berth to starboard. With the stern clear the engine was to be put astern and the vessel backed away from the berth, as shown in the simplified diagram below, steps 1 and 2. The vessel was equipped with a controllable-pitch left-handed-turning propeller. The berthed vessel forward was not seen as a hindrance.
On the first attempt, the wind, which was pressing the vessel on to the berth, brought the vessel’s stern back close to the berth, nullifying the manoeuvre. It was agreed to moor the vessel again and make another attempt. As the vessel was closing the berth it had some speed astern.
Image Credits: nautinst.org
Ahead engine was applied but the vessel still bumped the fender astern. Then, because too much ahead power had been used, the vessel surged forward and came into contact with the vessel moored ahead, its port bow contacting the starboard aft quarter of the other vessel. The port side anchor remained entangled on the stern railings and deck fittings of the moored vessel.
Image Credits: nautinst.org
Lessons learned
- Although winds were light they nonetheless did not help the planned manoeuvre. When manoeuvring always look to use the elements to your favour. If this is not possible, consider the use of one or more tugs.
- The left-turning CP propeller, which will normally cant the stern to port irrespective of ahead or astern thrust applied, should have been an early indicator that carrying out this plan without tug assistance was not advisable.
- In dark conditions a person’s visual acuity is not as sharp as in daytime. Missed visual cues while manoeuvring in tight quarters in darkness could contribute to less than adequate performance.
Reference: nautinst.org
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