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.