In its latest Safety Digest, UK MAIB describes a case of a dredger grounding resulted from loss of steering control. MAIB noted that the loss of steering occurred during the transfer of control between the consoles.
The incident
Having completed cargo discharge, a suction hopper dredger got underway. The master was in control of the ship at the port bridge wing console. It was about 2½ hours after high water and the tidal stream was ebbing south; there was a gentle breeze in fine, clear daylight conditions.
Using propulsion, the rudder and bow thruster, the master turned the dredger at rest in preparation for the outward passage along the adjacent narrow channel. With the turn nearly complete, the master moved to the centreline of the bridge and went through the procedure to transfer control of the ship from the port bridge wing to the centre console.
The master stopped the swing to starboard using the bow thruster and then increased speed to head down the channel. As the dredger gathered headway, the master realised that the rudder was not responding – steering control had been lost.
In response to the loss of control, the master reduced speed and attempted to steer the ship using the bow thruster. The master then repeated the procedure for transferring steering control between the consoles, which resulted in regaining control of the rudder from the centreline.
However, the recovery of steering control came too late to prevent the dredger grounding gently at about 2kts on the mud bank opposite the berth and a short distance downstream. The dredger was undamaged and refloated at the next high water.
Lessons learned
- Loss of steering occurred during the transfer of control between the consoles. The procedure included a requirement to acknowledge the transfer by pressing an ‘accept’ button on the receiving console. However, there was no indication on the panel that control had been successfully transferred. The procedure also took a few moments to complete as there were separate transfer buttons for propulsion, steering and bow thruster controls. There was also no procedure to immediately test that control had been successfully transferred. As a result, the master was unaware that the transfer of steering control had failed at a crucial moment in the transition from unberthing to heading down the channel.
- Transferring control between bridge consoles always involves a brief moment without immediate control of the ship. The time to do this should be chosen carefully, ideally at a point in the passage plan where there is sufficient sea room to recover from any delay in completing the procedure. In this case, there was very little sea room and the tide was falling, so it might have been more appropriate to delay the changeover. Alternatively, the unberthing and transition into the channel could have been controlled from the centre console with an additional crewman on the bridge to call out distances to the berth from the port bridge wing. This would have eliminated the risks associated with changing consoles.
- When MAIB made some enquiries about this accident, it became apparent that this was the third grounding of the vessel in the same channel in just over 3 months. The dredger had been recently introduced into service and it was larger than the company’s previous vessel. When the navigational situation changes in this way, it is important for the company and the harbour authority to work together to update the risk assessments and pilotage plans, taking into account the characteristics of the new vessel. In this case, the tidal ‘window’ needed to be adjusted for safe entry and exit of the dredger along the shallow and narrow channel to the aggregates berth.
