Unreliable position reference systems leads to incident

  • DP Event
  • Published on 29 November 2019
  • Generated on 21 September 2026
  • DPE 04/19
  • 1 minute read

Incident

The end-effect was that the deviation from the set point in surge and sway increased with each oscillation.

DPE 19.04 – Unreliable Position Reference Systems leads to DP incident – Flowchart

Comments

Only two DGNSS were online, with poor signal quality due to the location and environmental conditions. The end-effect was that the deviation from the set point in surge and sway were increasing for each oscillation.

Considerations

  • For DP2 operations, the use of only two DGNSS systems is insufficient; a minimum of three systems are to be used based on two principles.
  • The importance of monitoring the position reference systems (PRS) screen cannot be overstated; this then ensures that all the PRS agree on the position of the vessel.
  • It is evident that the selected PRS were not providing reliable position information and highlights the problems that can be experienced when at least one reliable PRS is not available.
  • It was noted that the move was paused at 2005; this should have provided the opportunity to investigate and correct the situation rather than continue with the move.
  • It is also worth considering that the erratic movement of the vessel could indicate that the DP system needs retuning.

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