An unassociated failure of one part of a gyro system affected the DP system – DP undesired event

Comments from the report:

A new gyro was installed as a replacement but failed to start with first attempt. Further investigation revealed that the ‘Gyro 2 remote control unit’ located on the forward bridge had a fault, failure of it caused Gyro 2 to shut down. When the ‘Gyro 2 remote control unit’ was disconnected the new gyro was switched on with no further problems. After a stabilisation period the Gyro was tested, found operational and the signal to DP reinstated. DP operations were resumed. In conclusion the original Gyro 2 was and remains healthy.

Considerations of the IMCA Marine DP Committee from the above event:

  • It can be assumed that good operational activity planning took place and the ASOG indicated a yellow alert to be activated with the loss of one gyro
  • The logic of systems connected to the DP system need to be fully understood so that a failure in one part of a connected system does not affect the DP system
  • With the availability of so many position reference systems it may be better to use 2 DGNSS and keep the other 2 DGNSS as monitoring
  • It is unclear what the gyro 2 remote control unit is required for, but it appears to have introduced an additional failure mode of the gyro and should have been identified in the DP FMEA.