Seaways Free Article: DP deadlock on the bridge
Conflicting regulations pose a challenge for the Master
by Łukasz Jakub Grodź AFNI
Modern Dynamic Positioning (DP) operations are governed by an impressive stack of documents: the shipping company DP manual, international standards, industry guidance, Original Equipment Manufacturer (OEM) limitations, and client-specific requirements. Individually, each of them claims to enhance safety. Collectively, they can leave the Master standing on the bridge asking a simple but dangerous question: which rule do I follow when they all disagree? When alignment fails, it is not the paperwork that absorbs the risk – it is the DP team.
Conflicting guidance
A recent scenario from a DP2 vessel illustrates how conflicting guidance can generate confusion rather than clarity. The vessel was operating near a Floating Production Storage & Offloading unit (FPSO). The client’s operations manual was unequivocal: mandatory requirements (‘shall’) must be followed unless a formal dispensation was in place; DP2 operations require at least three independent Position Reference Systems (PRS); and only relative PRS may be used alongside moving assets. Absolute systems, including DGPS, were prohibited.
Further, if the vessel needed to pass a fanbeam reflector or similar positioning equipment, this had to be done manually. Once passed, the vessel was required to withdraw, configure DP at a safe distance, verify the references, and then re-approach. On paper, this is cautious. On the bridge, it feels anything but.
The FPSO was equipped only with laser targets and radius transponders. Every operation demanded a manual approach purely to ‘deliver’ a third reference target, followed by withdrawal and a second DP approach. Manoeuvring manually near a floating installation to enable a supposedly safer DP configuration challenges any intuitive understanding of risk mitigation.
Seeking clarity, the crew consulted IMCA’s DP Event database. Report DPE 03/23 recognises two methods for operations near moving assets:
- A mix of absolute and relative PRSs for vessels with Follow Target functionality.
- An absolute PRS set to monitoring only, with at least three relative PRSs for vessels without Follow Target functionality.
IMCA cautions that Option 2 is not a recommended practice and should only be used with full understanding of risks and OEM consultation. OEM advice, however, warns against using relative targets in Auto Position mode (without Follow Target functionality). The proposed mitigation – a software upgrade enabling Follow Target – depends on a mix of absolute and relative PRSs, which the client forbids. From a DP behaviour perspective, the risks are well understood. With only relative PRSs enabled in Auto Position, any movement of the reference object is interpreted by the DP system as an increase in environmental force. A modest shift of an FPSO can trigger increased thrust demand, drive-off, alarms, and corrective action – often resulting in oscillation or ‘slingshotting’. If the asset moves again, or alters heading – particularly when the vessel is operating close to the asset’s centre of gravity (CG) – the margin to contact can evaporate rapidly.
Adding to the dilemma, the company’s class-approved DP manual requires vessels without Follow Target functionality to operate in Auto Position with one absolute PRS and two relative PRSs, recalibrating DGPS as necessary – contradicting client rules.
A risk shared - or transferred?
It is also worth noting an operational reality that remains an open secret: most PSV tonnage on the market lacks Follow Target functionality. While this does not invalidate the safety argument for such systems, it highlights a disconnect between guidance, contractual expectations, and fleet capability. Where technical limitations are widespread, choosing between ‘lesser’ and ‘greater’ risk should not fall solely on the Master. Risk ownership, like risk control, must be shared – not silently transferred to the bridge.
So where does this leave the Master? Company procedures point one way. Industry guidance hedges. The client mandates another path. The OEM raises a red flag. The result is a regulatory triangle with no safe corner to stand in – all the risk falls on the Master at the DP console.
This is not an argument against client authority, industry guidance, or company procedures. It is a reminder that misalignment is itself a hazard. When rules conflict, the risk does not vanish. It is quietly and efficiently transferred to the bridge.