Two ECDIS, One Position Source
A 2018-built 38,000 GT bulk carrier holds SOLAS certificates for unrestricted service and uses two ECDIS units as its primary means of navigation; no paper charts are carried. During a flag-State inspection at anchor, the inspector asks for a demonstration of the back-up arrangement. Both ECDIS units are connected through one network switch to GNSS receiver A. A second GNSS receiver is installed in the wheelhouse but its output cable is coiled and tagged 'spare'. Both displays are also fed from the same 24 V distribution board. When receiver A is switched off, both ECDIS show 'position lost' within seconds and revert to dead reckoning. The vessel is waiting to enter a traffic separation scheme with visibility of about 2 nautical miles. The master explains that the arrangement was accepted at delivery because two ECDIS units were fitted. The inspector is preparing a deficiency report and asks the master what the ship will do before departure.
1. Explain whether the arrangement satisfies SOLAS V/19 and identify the specific deficiency.
Read the worked answer
The ship is a 38,000 GT cargo ship, so SOLAS V/19 requires ECDIS as the primary means of navigation. Where ECDIS is used, the convention requires a back-up arrangement that is independent of the primary system. Two ECDIS displays are not automatically two independent systems.
In this case both displays take position from GNSS receiver A and both take power from the same 24 V board. Receiver B is installed but not connected. The inspector's test proves a common-cause failure: switching off one receiver removes position from both displays. That is precisely the failure the back-up arrangement is meant to survive.
The deficiency is therefore not the absence of a second screen; it is the absence of an effective, independent back-up. The lack of paper charts makes the consequence worse because there is no alternative means of navigation. The master's delivery explanation does not cure the deficiency. The inspector should record it against the ECDIS back-up requirement and the safety management system, and should require a demonstrated correction rather than a document.
2. What immediate measures should be taken before the vessel proceeds, and what should the inspector require?
Read the worked answer
The first step is to make the second ECDIS genuinely independent: connect GNSS receiver B to the second ECDIS, give it a separate power feed from an independent distribution board, and prove by test that failure of receiver A or of the main 24 V board does not remove position or power from both displays. The configuration should be documented and the bridge team familiarised with the changeover.
If that cannot be completed before departure, the master should not treat the two-screen arrangement as compliant. The realistic options are to remain at anchor until the correction is made, or to obtain flag-State and class acceptance for a restricted passage supported by paper charts, an additional position source such as radar parallel indexing, reduced speed and an enhanced bridge watch. Those measures are compensatory, not a substitute for compliance.
The inspector should verify the correction by witnessing a failure test, not by accepting a work order. The deficiency should remain open until the independent position and power supplies are demonstrated, and the report should note the absence of paper charts as an aggravating factor.
3. What records and evidence should demonstrate the corrected arrangement, and how should the crew be familiarised?
Read the worked answer
The evidence should include an as-built bridge network diagram showing each ECDIS, its GNSS source, its power source and the changeover method; a signed test record showing loss of GNSS A and loss of the main distribution board separately; confirmation that the second ECDIS has its own configuration backup; and a risk assessment in the safety management system covering the transitional period.
Familiarisation should be practical: the officer of the watch should demonstrate the changeover, explain which alarms indicate loss of position, and show where the independent power breaker is located. The master should record the training. A paper procedure alone is weak because the failure mode is a hidden common supply, not a lack of instructions.