After all the checking, it was found that there was water ingress at the L-Band connector to the antenna on the mast. This was dried and cleaned. The connectors were properly sealed with self-bonding electrical tape and cable ties.
Considerations from the above event:
- This observation reinforces the need for good practice conducting field entry/arrival DP checks making sure all DP systems are operational and healthy.
- It is unclear why the laser-based reference system was not in use but it is assumed the system was not immediately available due to distance or shadowing.
- Several recent reports indicate the use of only two enabled position reference systems (PRS), these are often both DGNSS. It cannot be stressed enough that a mixture of PRS should be used.
- Regular checks of connections which are exposed to the environment need to be carried out and included in planned maintenance systems.