Question 1

A DP2 pipe-lay vessel has been exceeding its ASOG yellow wind limit by 2–4 knots on every watch for the past five days without incident. The lead DPO tells the incoming watch: 'Don't worry about the yellow alarm — it goes off in these conditions all the time and we just carry on. The old limit was too conservative anyway.'

What is the danger in the lead DPO's reasoning?

Accepted Answer

Repeated limit exceedance without incident is the definition of normalisation of deviance — each incident-free violation makes the next seem safer, eroding the original safety margin without any formal review. The ASOG limit exists because someone calculated the risk; overriding it verbally on the basis that "nothing happened" removes the agreed safety envelope without authorisation IMCA's 2024 Station Keeping Review identified normalisation of deviance as one of the most persistent human factors in DP incidents. The ASOG limit has not become less relevant because the vessel survived exceeding it five times — the safety margin has simply been eroded on each occasion without a formal risk assessment supporting that decision. If conditions deteriorate slightly further on the sixth day, the vessel may be operating at actual capability limit with a DPO team who believe the alarm is background noise. The correct action is to formally review the ASOG with the client, not to informally dismiss the threshold.

Question 2

A DPO is six hours into a twelve-hour DP watch on a cable-lay vessel. Conditions have been perfect all watch — flat calm, three good references, all systems green, no alarms. The DPO begins browsing the internet on a personal device to pass the time.

What human factor is operating here, and what is the specific risk it creates in DP watchkeeping?

Accepted Answer

Extended uneventful periods create the highest complacency risk in DP watchkeeping: the DPO's vigilance degrades precisely because nothing has demanded it. When a fault develops — a reference dropout, a thruster fluctuation, a slow position drift — the response time increases because the DPO's attention is elsewhere. Long periods of routine are when the first small signals of developing problems are most likely to be missed Complacency in long uneventful DP watches is one of the top human factors identified in IMCA incident data. The paradox is that the safest-seeming watches — calm conditions, all systems green — are when the DPO's monitoring vigilance is most degraded. DP incidents are not always sudden; many develop over minutes through progressive reference degradation, slow position drift, or incremental power system changes. A DPO whose attention is on a personal device during this development window misses the early signals that would allow a controlled response. Active, structured monitoring — regularly checking reference quality, gyro agreement, thruster load, position variance — maintains the vigilance that automated alarms cannot replace.

Question 3

A DP2 diving support vessel has been running a complex subsea installation for 11 hours. The task is 90% complete. Weather has now reached the ASOG yellow limit and the forecast shows it will build to the red limit within 90 minutes. The dive supervisor tells the DPO: 'We just need 40 more minutes — we\'ve invested too much in this dive to stop now.'

What human factor is the dive supervisor exhibiting, and why is it particularly dangerous here?

Accepted Answer

Plan continuation bias — the cognitive tendency to continue toward a goal because of the investment already made, even when conditions indicate stopping. It is particularly dangerous because the "sunk cost" of 11 hours of work is irrelevant to the safety calculation for the next 40 minutes. Those 40 minutes will be conducted in degrading conditions with a deteriorating safety margin, not in the conditions the plan was designed for Plan continuation bias — sometimes called "get-there-itis" in aviation — is the impulse to complete a task because of investment already made, ignoring signals that conditions have changed. In DP operations, it appears as "we're nearly done," "we've already invested X hours," or "just 20 more minutes." The ASOG yellow limit does not contain an exception for nearly-finished jobs. The forecast deterioration to red within 90 minutes means operating at yellow for 40 more minutes runs a real risk of reaching red with divers still in the water. IMCA incident data consistently shows plan continuation bias as a precursor to incidents that occurred when operations continued past defined limits because the team was "too close to finishing" to stop.

DP — Human Factors Practice Questions