The ro-ro passenger ferry Hebrides ran aground due to a mechanical failure which resulted from a loose screw, the Marine Accident Investigation Branch (MAIB) informed.
Hebrides lost control of its port controllable pitch propeller and grounded while it was approaching Lochmaddy, North Uist, Scotland on September 25, 2016.
Loss of control was caused by a mechanical failure within a linear servomotor actuator in the propulsion control system, caused by a setscrew which was not secured in position with thread locking compound when it was replaced six months earlier.
The master attempted to control the ferry’s movements but he was unable to prevent it from running over several mooring pontoons and briefy grounding. There were no injuries among the passengers and crew but the ferry was damaged and had to be taken out of service and repaired in dry dock.
The MAIB investigation unveiled that neither the service engineer who ftted the setscrew nor the ferry’s engineers who subsequently inspected the actuator were aware of the actuator manufacturer’s service instruction to secure the setscrew with thread locking compound.
Additionally, the investigation showed that upgrades to the propulsion control system that had been recommended by its supplier to mitigate the consequences of a propeller control failure had not been implemented.
Furthermore, the crew’s response to the loss of control “was well intended but was un-coordinated because they were not sufciently prepared or practised to deal quickly and efectively with the loss of pitch control in the confined waters,” MAIB said.
The UK’s investigation branch made a recommendation to Rolls-Royce Marine, the provider of the propulsion control system ftted on board Hebrides, aimed at ensuring that service instructions are made available to service engineers and in documentation provided to vessels.
The ferry’s operator, CalMac Ferries, was also asked to ensure that recommendations for safety critical system upgrades received from manufacturers are properly documented and processed and that its crews are better prepared to deal efectively with propulsion failures.