M2017-02 M/F Sterna - Collision with transfer span pontoon, Lillmälö, Parainen, 12.6.2017

Finnferries Ltd.’s ferry, M/F Sterna was in around the clock, scheduled, road ferry traffic between Parainen and Nauvo. When approaching the ferry landing on the Parainen side, the steering gear of the ferry malfunctioned. The master of the ferry could not decrease the speed of the ferry sufficiently due to the malfunction. The master therefore steered the ferry into the pontoon of the transfer span, in order to dampen the impact. The crew consisted of master, chief engineer and deck hand. The cargo consisted of 16 cars and 24 persons, some of which were in the cars.

Minor oil wastage had earlier been detected in the ferry's propulsion system. The problem had been temporarily solved by lowering the tank for the propeller shaft's shaft seal's lubrication oil (gravitation oil), in order to decrease the flow pressure. When working with the tank, the break of the rotating motor for the azimuth thruster had, by mistake, been turned completely, or partly, to closed position. This prevented the thruster from turning normally and thus the ferry lost in manoeuvrability.

After the installation work of the tank, the crew had noticed strange sounds when turning the azimuth thruster, but the origin of the sounds had not been detected. The shipping company was informed about the observations and it was decided that the ferry would be removed from traffic after completing the scheduled trip at 15.00 from Nauvo.

When approaching the Parainen side ferry landing, about 400 meters from the transfer span, the master turned the control handle for the aft azimuth thruster to reverse position. He commenced reversing with the aft thruster maybe 200 meters from the transfer span, but the speed of the ferry did not decrease. Based on this, the master suspected that something was wrong. Since the ferry was getting closer to the shore, he nevertheless increased reverse thrust. This increased the speed of the ferry instead of decreasing it. It became clear that the aft azimuth thruster had not turned to the position indicated by the control handle. The master then began reversing with the forward thruster. The reverse thrust was not sufficient, so the master decided to steer the ferry and its “mooring-horns" into the pontoon of the transfer span. The master made this decision because steering the mooring horns into the ordinary mooring leads in the linkspan, would have caused a faster retardation and thus a more violent impact. The collision occurred at 15.09.

Two passengers informed that they had received strain injuries and six cars suffered slight damages because of the collision. The ferry's mooring-horn punctured the pontoon of the transfer span. The pontoon sank when the ferry pulled away from it. In addition the forward ramp on the ferry was bent and some hydraulic hoses broke. The passengers were evacuated to the border guard’s and the emergency response centre's boats, through a side gate on the ferry. The ferry was driven to the linkspan right next to the damaged one. There

the crew, following company policy, reversed the vehicles ashore from the ferry. When the ferry later, after the accident, was transferred to Nauvo and from there to a repair yard, the steering gear operated normally.

The steering gear had been partially renewed in the autumn 2016. At the same time the engine control system was totally renewed. In connection with those measures, the grouping and indicating of system alarms were changed. If, for example, there was a mismatch between the positioning of the azimuth thruster and its control handle, the old system would have given an asynchrony alarm, while the new system only gave a group alarm, "AQM system alarm, disturbance". Acquiring more detailed information about the cause for the group alarm would have required connecting a separate device to the system. That day, after 14.00, the engine control system had issued several "AQM system alarm, disturbance" - group alarms. The regulations by the Finnish Transport Safety Agency, Trafi, states that the engine control system must provide information for rapid identification of a fault. A large number of alarms may often result in routine responding to them, in which case they may only be reset without any immediate further action.

Trafi, the Finnish Transport Safety Agency, received information concerning the modifications to be done on M/F Sterna and M/F Falco when an application concerning postponing an inspection on Sterna's sistership Falco was filed. Trafi granted the postponing of the inspection, but did not react on the possible requirement for approval of the planned modifications. The system suppliers had, after the docking, sent the documents concerning the modifications to Trafi, but the agency had not issued a response in the matter. Trafi should have taken action in the matter.

In spite of the communication between the shipping company and the Finnish Transport Safety Agency, the approval of the modifications was not realised in accordance with the official procedures for obtaining approval. In hindsight, Trafi acknowledged that the modifications would have required obtaining approval prior to the commencement of the modification work.

The responsibility for initiating the process for obtaining approval lies with the shipping company. The shipping company must be in active contact with the supervising authority when planning modifications on vessels. Shipping companies may not always be aware of the need for the process of obtaining approval, or they may not consider the planned modifications to be of such character that they would require an approval by the authorities.

Based on this investigation The Safety Investigation Authority recommends, that

1. The Finnish Transport Safety Agency develops both its guidance and informing practises concerning the process for obtaining approval for modifications, as well as the monitoring of the actual modification work.

2. From now on, Finnferries Ltd, utilizing their Safety Management System, reviews the risks associated with the modification of critical systems and ensures with the authorities whether the modifications require obtaining their approval.

M2017-02 Report (in Finnish).pdf (pdf, 1.75 Mt)