Dynamic Positioning

DP Mini Guide: Motion & Wind Sensor Failure (MRU/VRU)

🕑 8 min read 1300 words Dp-academy

Crew Connect DP Academy · Mini Guide 26

Motion & Wind Sensor Failure (MRU/VRU)

Topic: Sensors · Sub-topic: Motion & Wind Sensors  ·  Level: DPO  ·  Read time: 8 min

Training scenario only. In an actual operation, follow the approved vessel- and activity-specific procedures, ASOG/CAM/TAM, FMEA and emergency response arrangements; apply the Master’s authority and escalate through the applicable command structure. This guide is Crew Connect educational content — it does not override your vessel’s approved documents.

1. What / Why / How

Motion Reference Units (MRU/VRU) measure the vessel's actual motion (roll, pitch, heave), used to correct other sensor readings for vessel movement. Wind sensors feed the DP system's feed-forward thrust calculation directly. Both carry genuinely different information than position or heading alone — degraded data from either can distort the whole picture even while PRS and gyro look perfectly healthy.

2. Recognition / Risk / But

Erratic wind readings, while actual vessel motion shows no such variation, risk the DP system applying thrust corrections that don't match real conditions. But: before assuming the DP system is being actively misled, check whether the wind-sensor voting/selection logic has already detected the inconsistency and is handling it.

3. Now / What next / Decision / Why

If the system has already down-weighted the erratic sensor in favour of a healthy one, confirm the healthy sensor's data is genuinely representative and monitor the erratic one — automatic resilience handling one failed input doesn't remove the DPO's job of understanding what's happening.

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