A tanker in ballast was on coastal passage but navigating near well charted and buoyed sandbanks; visibility was good in daylight, tra c was light but there was a strong northerly tidal stream. The master had directed the OOW to fix at 5-minute intervals when passing in close proximity to the sandbanks. The OOW, who was also the navigator, was alone on the bridge and correcting charts that had been delivered to the vessel just before sailing and were required later in the passage. When on a northerly heading, the radar alarm sounded on the bridge as the vessel crossed the safety corridor, 5 cables south of the new north-westerly heading. The OOW was not expecting the alarm and was unaware of the approaching turn; nevertheless, he plotted a fix then returned to working on the chart corrections.

Eleven minutes after the first radar alarm, it sounded again, this time to indicate that the vessel was exiting the 5 cable safety corridor plotted on the radar. When this alarm sounded the OOW realised that he had missed the turn to the new course, so applied port helm and steadied on a westerly heading with the intention of regaining the planned track. The OOW did not fix the ship’s position until 12 minutes after the turn was complete; this showed that the vessel was still signi cantly to starboard of the planned track so the OOW made a correction of a further 3o to port.

Fifteen minutes later, the OOW correctly recorded a fix in the bridge logbook but incorrectly plotted it 1 mile south of the vessel’s actual position. This error led him to assess that the vessel was regaining track; however, a few minutes later, the strong northerly tidal stream caused the vessel to ground on a sandbank.

The Lessons

    1.     The first duty of the OOW is the safety of the ship. It is understandable that the OOW, as the ship’s navigator, had a strong desire to correct the newly delivered charts as soon as possible. However, this proved a very significant distraction and the OOW lost situational awareness at a crucial point in the passage leading to the grounding. Without realising the immediate danger ahead, he also did not call for help. 


2.    Bridge management is about teamwork; there were sufficient qualified bridge watchkeepers on board for the master to have temporarily relieved the OOW so he could finish the corrections and complete the passage plan. The master’s direction  to use a 5-minute fixxing interval when passing the sandbanks was not effective mitigation of the navigational risk that had been identified. It would have been more appropriate for the lookout to close up and for the vessel’s master to have been on the bridge to monitor the navigation.

3. When the OOW took over the watch, he did not calculate the anticipated tidal stream, so was unaware of its effect. This proved critical as the heading adjustments made were insufficient to counter the tide’s effect. Other measures could have been taken to closely monitor the track of the vessel, such as radar parallel index lines and close observation of the available visual clues such as the buoys.

Source: MAIB Safety Digest