B2/2000M ms FINNFELLOW, grounding near Överö in Aland, April 2, 2000
The Finnish-flagged passenger ferry ms FINNFELLOW grounded on her way from Kappelskär to Naantali at 02:32 on 2 April 2000 on the north shore of Föglö in the Aland archipelago. There were 81 people on board, 58 of whom were passengers. The vessel ran aground at a speed of about 14 knots as a result of a gyrocompass malfunction. The grounding was soft and damage was limited to the vessel's bow-thruster compartment and a few of the bottom tanks adjacent to it. No oil leaks occurred.
The FINNFELLOW was constructed in 1973 but her steering system had been renewed a few years before the grounding. In addition, a modern integrated navigation system and two gyrocompasses had been installed on the bridge.
The voyage had proceeded normally. Visibility was good, the night was dark and the speed of the northerly wind was approximately 15 m/s. Three men were manning the bridge: the watch officer, the company pilot and the lookout. The pilot was steering the vessel on autopilot. In the cockpit there are two radars, plus seating, located side by side forming part of the vessel's navigation system; the pilot was in the right-hand seat navigating and the watch officer was in the left-hand seat monitoring activity.
The events that led to the grounding occurred when the vessel was nearing the end of a turn to starboard. During the turn, when only 2.5 degrees remained of a 50-degree change of heading, the gyrocompass jammed at the same reading for 66 seconds. When the vessel grounded, the autopilot was set to its heading mode in which the vessel's turn radius is predetermined.
Because the autopilot received incorrect heading information, indicating that the vessel had not yet turned to the desired course, it started to turn the vessel to starboard by gradually increasing the rudder angle. The bridge personnel were not immediately aware of this unplanned turn off the fairway. Factors contributing to their lack of awareness included the slowing of the vessel's rate of turn, the absence of alarms, and the dark night in which only a few of the lights marking the fairway were visible. The watch officer only realised that the vessel was turning to starboard about 30 seconds after the gyrocompass jammed. A turn to port and a reduction in speed were effected immediately, but they did not have the desired effect and the FINNFELLOW grounded 85 seconds after the gyrocompass malfunction.
During the investigation it was established that the immediate cause of the gyro fault was radio frequency interference. The exact frequency of the interference, and how it entered the system to pass to the compass, could not be determined. It was also observed that the safety systems designed to prevent a heading error from affecting the navigation system had failed. The conventional compass system based on the IMO declaration A.424(XI) was not sufficiently reliable to act as the only sensor providing the heading. The conventional compass system is vulnerable as it stands; this is why the investigation board recommends that the actual navigation system be further protected, and that there are additional heading references to act in parallel with those from the gyrocompass.