DSC Distress Alert Not Acknowledged on MF/HF
You are the sole radio operator on a 180 m bulk carrier in sea area A3, about 900 nm east of Japan, at 0340 UTC. A crew member reports a fire in the engine room. You transmit a distress alert on 2187.5 kHz DSC with distress nature 'fire' and position from the GPS. Within 5 minutes no DSC distress acknowledgement is received. You then switch the MF/HF radio to radiotelephony and transmit a Mayday on 2182 kHz; still no reply. The vessel is making 8 knots and the fire is spreading. Your Inmarsat-C terminal shows no distress priority queue activity, and the VHF DSC on channel 70 shows no acknowledgement either. The master asks you what you are doing next and whether the ship should be abandoned.
1. Explain why the lack of DSC acknowledgement does not mean the alert was not received, and state what distress communications you should now initiate under GMDSS procedures.
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A DSC distress alert is a one-way broadcast; many coast stations and ships receive it without sending a DSC acknowledgement. Absence of acknowledgement therefore does not prove non-reception. The correct action is to follow the distress alert's own retransmission logic: if no acknowledgement arrives within about 5 minutes, retransmit the DSC distress alert, and if still unanswered, transmit a Mayday radiotelephony distress call and message on the associated distress and safety frequency (2182 kHz for MF, or the appropriate HF band). Because the vessel is in A3, you should also use an Inmarsat distress priority call to an RCC (for example a distress priority message or call via the Inmarsat terminal) to guarantee shore-side reception, and continue to attempt acknowledgement. Do not wait indefinitely on one medium. The master should be informed that distress traffic is ongoing and that a distress alert has been transmitted; abandonment is a separate decision based on fire progression, not on radio acknowledgement alone.
2. The fire worsens and the master orders abandonment. Describe the distress traffic you should send and the sequence of actions for the survival craft.
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Transmit a Mayday on 2182 kHz (and on VHF channel 16 if within range of other vessels) stating 'Mayday, Mayday, Mayday', the vessel's name and call sign, position, nature of distress (fire), assistance required, number of persons, and any other useful information. If no acknowledgement, repeat at intervals. Activate the Inmarsat distress priority call to the RCC. On abandonment, ensure the EPIRB is carried to the survival craft and activated manually if it has not floated free and activated automatically; confirm its strobe and that it is transmitting on 406 MHz. Take the portable VHF transceivers, the SART (or AIS-SART) and the portable GMDSS VHF radios into the liferaft. Switch the SART on when clear of the vessel and monitor channel 16. Keep the EPIRB upright and clear of metal. Log all transmissions, times and frequencies in the radio log. The distress traffic should continue until the RCC or a rescuing vessel assumes control, at which point you send 'Silence' procedures only if directed by the coordinator.
3. The vessel's Inmarsat-C terminal shows no activity. What could explain this and what should you check?
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Possible explanations include: the terminal is not logged on to the satellite (no GPS fix or no network registration), the antenna is obstructed or the cable damaged, the terminal is in a non-distress state because the distress button was not pressed or the distress priority was not enabled, or the terminal has a fault. Check the terminal display for 'logged in' or 'registered' status, confirm the GPS position is being received, check that the distress button/priority is correctly set, and verify the antenna and cabling. If the terminal cannot be made to work, use the MF/HF DSC and radiotelephony as the primary distress route and inform the RCC by any available means. Do not rely on a single terminal; cross-check with the VHF DSC and the EPIRB.