As UK MAIB reports in its most recent Safety Digest, an early morning sailing of a domestic ro-ro passenger ferry nearly came to an awkward end when it lost control and headed for the beach. Fortunately, the crew were able to regain control before the ferry grounded and the voyage continued safely.
The incident
The vessel was fitted with a Voith Schneider Propeller (VSP) system that provided it with the ability to drive in any direction without the need for a rudder. The VSP could be controlled from joysticks on one of three consoles on the port, starboard or centre of the bridge. Control was exchanged by pressing a command button at one of the consoles and confirmed by pressing the button a second time. An audible tone would indicate when there was misalignment between the joysticks of the two consoles and the transfer would not take place. The angle of the control display panels made it difficult to see which console was in control.
The master was using the starboard console to manoeuvre the ferry out of port on the morning of the incident. The helmsman pressed the command button on the centre console to request control as normal and the audible tone sounded. The master, believing control had been passed, set the starboard console’s joystick to the zero position. However, the VSP audible tone continued.
This was confusing. Neither the master nor helmsman knew who was in control. The ferry slowed and swung to port, lining itself up with a man who was enjoying an early morning cup of coffee on the beach, much to his consternation. The bridge team attempted to take control at each console station and in doing so the control passed backwards and forwards many times.
The audible tone stopped shortly afterwards, indicating that the transfer process had timed out. The bridge team then zeroed all the joysticks and successfully transferred control to the centre console after pressing the command button at that station twice. The ferry was able to pull back from the beach and resume its passage.
Lessons learned
Equipment: The system for identifying which console had control at any time was unclear; at the time of transfer no one knew who had control. Modifications to the position of the VSP display panels had inadvertently made it harder to see the control indication when the crew were manoeuvring the ship. Control indications should be unambiguous and any modifications need to be carefully considered so that the fixing of one problem does not create another.
Qualified: The bridge team were familiar with the routine transfer of control between stations with the joysticks in the full ahead position, but when the VSP did not operate as expected it took time for them to regain control. The zeroing of the controls to affect a transfer was described in the ferry’s safety management system and training in this procedure may have quickened the bridge team’s response to the loss of control.