For DP Class 2 and 3 operations, at least three Position Reference Systems should be deployed and selected into the DP system. Why should they not all be based on the same principle?

A DPO is only trained on one type of Position Reference System
B So that if one PRS fails the vessel remains fully operational
C Because of the improved accuracy available from this configuration
D To protect against Commen Mode Failure

Question

For DP Class 2 and 3 operations, at least three Position Reference Systems should be deployed and selected into the DP system. Why should they not all be based on the same principle?

A DPO is only trained on one type of Position Reference System
B So that if one PRS fails the vessel remains fully operational
C Because of the improved accuracy available from this configuration
D To protect against Commen Mode Failure

Accepted Answer

The correct answer is **D To protect against Common Mode Failure**.

In Dynamic Positioning (DP) operations, particularly for Class 2 and Class 3, redundancy is crucial for ensuring that the vessel can maintain its position even in the event of a failure in one or more systems. The requirement to have at least three Position Reference Systems (PRS) deployed and selected into the DP system, and ensuring they are not all based on the same principle, is specifically to protect against Common Mode Failure.

**Common Mode Failure** refers to a situation where multiple systems or components fail at the same time due to a single cause. This can happen if all systems are of the same type and therefore susceptible to the same types of failure. For example, if all PRS are GPS-based, then a problem that affects GPS signals (like solar flares or signal jamming) could cause all of them to fail simultaneously, leaving the vessel without a reliable position reference.

By using PRS based on different principles (e.g., combining GPS with acoustic positioning and laser-based systems), the DP system ensures that even if one principle fails, the other systems, being based on different technologies, are likely to remain operational. This diversity in technology types provides a robust safeguard against common mode failures, thus enhancing the overall reliability and safety of the DP operation.

- **A DPO is only trained on one type of Position Reference System**: This is incorrect because Dynamic Positioning Operators (DPOs) are trained to use and understand multiple types of PRS.
- **B So that if one PRS fails the vessel remains fully operational**: While this statement is true and reflects the importance of redundancy, it does not directly address the issue of avoiding common mode failures by using diverse systems.
- **C Because of the improved accuracy available from this configuration**: Using multiple systems may improve accuracy, but the primary reason for not basing all PRS on the same principle is to avoid common mode failures, not necessarily to improve accuracy.

For DP Class 2 and 3 operations, at least three Position Ref...

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