Question 1

The DPO has called the master. The master reviews the situation: position is still stable, Fanbeam is active, only the gyro divergence is concerning him. The master says: 'position is holding fine — I don't want to move out and lose the Fanbeam reflector lock. Keep monitoring.'

The DPO is not satisfied with this response. What should the DPO do?

Accepted Answer

Clearly and professionally express the specific concern: with two diverging gyros and the third offline, the heading reference cannot be trusted, and a heading error in this position could cause an uncontrolled excursion toward the rig. If the master still declines to increase standoff, the DPO has the right and duty to formally log the disagreement and the master's instruction. The DPO should ask the master to come to the bridge to see the situation directly The authority gradient is a documented DP incident cause — a junior DPO who accepts a master's "keep monitoring" instruction for a genuinely deteriorating situation has allowed the gradient to override professional safety judgement. The correct response is to re-state the concern clearly and specifically, ask the master to come to the bridge (direct observation often changes assessments), and formally log the exchange and the master's instruction. This is not insubordination — it is professional accountability. Escalating over the master's head at this stage (before the master has even come to the bridge) is premature; asking the master to attend is the right next step. The DPO's right to initiate a stop is preserved regardless.

Question 2

EMERGENCY SCENARIO — DP2 CONSTRUCTION VESSEL NEAR DRILLING RIG

Vessel: DP2 offshore construction vessel. Location: 120m from a mobile drilling rig, conducting pre-lay survey. Riser and anchor spread deployed from rig. Three gyrocompasses active. Two DGNSS units and one Fanbeam active (Fanbeam tracking reflector on rig). Sea state: 1.5m, wind 18 knots from the north. DPO on watch, approaching end of 10-hour watch. Master in cabin.

--- POINT 1 OF 10 ---

Gyro 2 suddenly reads 201° while Gyros 1 and 3 both read 187°. The DP system shows no alarm — its weighted average heading is 191.7°. The DPO notices the discrepancy on the heading display.

What is the correct immediate action?

Accepted Answer

Manually exclude Gyro 2 from the DP heading input immediately — two gyros agree at 187°, Gyro 2 has clearly jumped. A 4.7° heading error introduced by the weighted average will cause the DP system to apply incorrect thruster forces and may drive the vessel off station toward the rig If the DP system uses weighted averaging rather than true median voting, a 14° gyro jump on one unit produces a meaningful error in the heading output. A 4.7° heading error at 120m from a rig can produce a meaningful sideways force command. More critically, waiting for the DP alarm means accepting the erroneous input for however long the alarm takes to trigger. The DPO has already identified the problem — two gyros agree and one has clearly jumped. The correct action is to manually exclude the outlier immediately, inform the master, and arrange investigation of Gyro 2. The alarm is a safety net, not the trigger for action.

Question 3

Gyro 2 has been excluded. Gyros 1 and 3 are now the only heading inputs. The chief engineer is investigating Gyro 2 and expects a 45-minute assessment. The DP system is now running on two gyros. Position is stable.

With only two gyros now available, what additional operational consideration must the DPO apply?

Accepted Answer

With only two gyros, if Gyros 1 and 3 diverge, there is no way to determine which is correct. The DPO must increase monitoring frequency for heading discrepancy, inform the master of the degraded heading reference status, consider whether the ASOG requires a minimum of three gyros for this operation, and be aware that any future heading divergence between the two remaining gyros will require an immediate decision about whether to continue operations The third gyro is not a luxury — it is the tie-breaker. With three gyros, a divergent reading can be identified and rejected. With two, if they disagree, the DPO has a 50/50 problem with no way to resolve it from the heading data alone. The master must know the heading reference has degraded. The ASOG may specify minimum gyro requirements for different operation types — near a rig with a deployed anchor spread is exactly the type of sensitive operation where three-gyro minimums are commonly set. Running on two gyros 120m from a rig is not automatically acceptable: it requires a formal ASOG status reassessment.