Thruster feedback incident
A drive-off position loss was experienced by one of our members’ vessels whilst it was operating in Class 2 alongside a platform. Upon investigation, the cause of the incident was found to be a mechanical failure in the azimuth feedback unit of one of the thrusters. More specifically, a gear wheel driving the feedback potentiometers was found to be severely worn.
The effect of the failure was that, from the information available to the DPO, the affected thruster was functioning correctly, whilst it was actually delivering thrust in a completely false direction. This was sufficient to cause position instability and made it very difficult to determine the correct course of action.
A complicating factor was the fact that the alarm for mismatch between thruster set point and feedback, which had recently been tested and adjusted, did not activate since throughout the incident the thruster appeared to follow the set points.
Fortunately this particular incident did not result in any damage or injury. The company involved has advised vessels using azimuthing thrusters that have a single mechanical drive for the azimuth feedback potentiometer to assess the situation on the vessel and to take preventative measures.
This information was notified to IMCA by Global Maritime BV. Should you require additional information please do not hesitate to contact Jan Frumau of Global Maritime (Tel: +31 (0) 10 2806900 / e-mail: [email protected]).
Safety Event
Published: 1 January 2000
Download: 
IMCA SF 01/00
IMCA Safety Flashes
Submit a Report
IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of all. The effectiveness of the IMCA Safety Flash system depends on Members sharing information and so avoiding repeat incidents. Please consider adding [email protected] to your internal distribution list for safety alerts or manually submitting information on incidents you consider may be relevant. All information is anonymised or sanitised, as appropriate.
IMCA’s store terms and conditions (https://www.imca-int.com/legal-notices/terms/) apply to all downloads from IMCA’s website, including this document.
IMCA makes every effort to ensure the accuracy and reliability of the data contained in the documents it publishes, but IMCA shall not be liable for any guidance and/or recommendation and/or statement herein contained. The information contained in this document does not fulfil or replace any individual’s or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.