Five DP Bulletins From September 2026: An Uncalibrated Joystick, a New Antenna, Dirty Fuel and a Swell That Rolled the Sensors

Why These Five

This is the bulletin before October’s, and it is the one that carries the closest thing to a collision in this run of IMCA writing: a DP2 vessel that hit an installation twice after a fuel transfer nobody had risk assessed. The other four are quieter, and in some ways more useful, because each shows a way a DP vessel can lose its margin without anyone deciding to. For the October set, see our DPE 03/26 guide.

1. Know Your Equipment, or at Least Where to Find the Answers

A DP2 vessel was at anchor with an OEM technician aboard, receiving system updates in good conditions. Two of three generators were on an open bus, four thrusters were running and two DGNSS were selected. During an update in Follow Target mode the crew noticed that with the joystick at zero, the system was commanding 10% power ahead.

The joystick had become uncalibrated after the update. The crew and technician found the calibration section in the manual and recalibrated it. Records showed this was not the first time: the joystick needed recalibrating after every update.

The bulletin’s point: the calibration was not the lesson. Nobody had understood what an update does to the system’s behaviour, and a recurring problem had not been handled through change management. A simple event like this could easily have gone unreported as a routine update. IMCA recommends a robust management of change process that includes the OEM software change process and a test method to verify function afterwards. (IMCA HSS001 covers management of change.)

2. New Equipment, Unexpected Consequences

A DP2 vessel was working subsea with two ROVs deployed, three DGPS and an acoustic reference, six of seven thrusters and four of six generators on an open bus, in 2 m waves, 14 knots of wind and 2.3 knots of current. At 14:47 DGNSS corrections were lost on DGPS 1 and 2, and DGPS 3 received them only intermittently. The DPO told the relevant departments and stopped operations. The ROV was moved clear of the pumping unit and landed on the seabed to give a stable acoustic position reference. The degraded DGPS 3 and the acoustic system together gave enough redundancy to hold position.

The first suspicion was external. Correction providers reported elevated solar activity. But other vessels in the field had no loss of corrections. Troubleshooting with the provider (rebooting the demodulator, swapping antennas, reconfiguring constellations and frequencies) did not help. The onboard survey team’s own DGNSS units also showed severe degradation. Isolation testing found that a recently installed survey antenna, operated independently on the vessel, was interfering with all three DGNSS units. Disconnecting it restored normal operation, and later testing showed the new antennas were defective.

The bulletin’s point: independent equipment on board can harm DP-critical systems. Fault-finding should consider onboard hardware, not just external causes, even during known scintillation and jamming. The bulletin lists no formal recommendations; its conclusion implies structured troubleshooting, checking everything recently installed or modified, and verifying compatibility of project equipment before starting.

3. A Chain of Small Failures Leads to a Major Consequence

A DP2 vessel was alongside an installation doing cargo operations on DP, in a closed bus with all five thrusters running, a 20 knot north-easterly and a 4 m swell. Two of three generators were online: DG1 (1665 kW) and DG3 (2600 kW). DG2, also 2600 kW, was on standby and not connected to the power system.

DG3 shut down unexpectedly, causing a partial blackout. The power management system cut thruster load to protect the smaller remaining generator, DG1, from overload. The DPO tried to take manual control with the thruster levers, but the thruster control system was not in command at the active console, so the thrusters did not respond, even in emergency mode. With manoeuvrability gone, the vessel hit the installation twice.

What the bulletin found:

1. Fuel had been transferred from the sludge tank to the clean drain tank and filtered back to the day tanks without an appropriate risk assessment or permit to work. The contaminated fuel tripped DG3.
2. With the standby generator disconnected, the plant was less resilient than intended, and the set-up did not reflect the redundancy philosophy in the DP documents.
3. The bulletin says it is unclear whether a consequence analysis warning was raised or considered.
4. The crew did not know the vessel-specific control transfer arrangements and emergency modes, so the recovery action failed when time mattered.
5. Documentation and training did not cover the critical systems adequately.

Take-away: five small gaps lined up. Any one of them might have been survivable. Keep the power configuration consistent with the FMEA and ASOG, treat fuel handling as a controlled job, and make sure the people on the console have practised the control transfer.

4. Holding Position, Losing References

A DP2 vessel was on final approach to a turret-moored, weathervaning FPSO, with two DGNSS, Radius and CyScan in Follow Target mode and its heading fixed relative to the FPSO. A long-period swell close to the vessel’s natural roll period produced resonance, and the vessel rolled up to 15 to 20 degrees. Because the heading was tied to the FPSO’s weathervane position, the crew could not turn the vessel to reduce its exposure to the swell.

The relative references became unstable and were intermittently lost because of the motion. The vessel moved away and stabilised. The absolute references stayed available throughout, but close-proximity cargo operations needed reliable relative references, so the approach was not continued. A second approach produced the same rolling and the same loss, and the operation was suspended until the sea state improved.

The bulletin’s point: this was not an equipment fault. It was the interaction of swell, vessel response, the FPSO’s weathervane behaviour and the way relative reference sensors degrade with motion. Early recognition and a conservative decision, repeated once to confirm it, were the right calls.

5. DP Drill: Loss of Seawater Cooling Pump Redundancy

The page gives only the drill’s purpose and its reference: the scenario itself is in two images and a downloadable PDF that we have not seen. The stated aim is to let crews observe how key DP personnel react and to make sure they know the various DP system set-ups and failure modes. The template is meant to be usable on any DP vessel. The bulletin points to Appendix A of IMCA M273, A guide to conducting DP drills and ensuring preparedness for DP failures.

The Pattern

• Change without a test. A software update, a new antenna, an unassessed fuel transfer: each changed the vessel, and none was followed by a check of what had changed.
• Looking outward first. The DGNSS team blamed solar activity before the survey antenna.
• The operator did not know the system’s emergency modes. The levers did not respond because control was not in command at that console.
• Conservative calls worked. Landing the ROV for a reference, and suspending the FPSO approach, were both decisions to give up an operation.

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Related Reading

• The October 2026 DP bulletins (DPE 03/26)
• Eight times a DP console did what the operator did not mean
• Five real DP incidents from 2026 (DPE 01/26)