VHF DSC Distress Alert With a Stale Own Position
At 1145 local a Kazakhstan-flagged 3,000 GT coaster, 22 nm south-west of Aktau, receives an unaddressed VHF DSC distress alert on channel 70 from a fishing vessel, giving position 43°12'N 050°48'E and nature of distress 'flooding'. There is no voice follow-up on channel 16 after two minutes. The ship's VHF DSC controller is displaying her own position from a manual entry made 40 minutes ago and not updated since; the MF/HF set has just been switched off to run a battery test, and the Inmarsat terminal is logged in but its wheelhouse handset is faulty - the master's cabin satphone works. The vessel is making 10 kn and is about 55 minutes from the distressed position. Weather is fine, and the coast station at Aktau normally keeps a continuous VHF watch.
1. State what you transmit and what you deliberately do not transmit, with reasons, in the first five minutes.
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Do not transmit a DSC acknowledgement on channel 70. The alert was not addressed to this ship, and the coast station at Aktau holds a continuous VHF watch; a ship's DSC acknowledgement would compete with, and can effectively pre-empt, the shore acknowledgement that the system is designed to produce. Channel 70 is a one-way, narrow bandwidth channel and jamming it with acknowledgements from several ships is the classic failure of DSC distress handling.
Why it matters practically: the vessel in distress needs one clear, authoritative acknowledgement and then a working voice circuit - not six ships answering at once.
What to do: keep a continuous listening watch on channel 16 for at least five minutes and monitor channel 70 for a distress acknowledgement or a distress relay from the coast station. Log the time of receipt, the vessel's identity, position and nature of distress. If the coast station has not acknowledged within about five minutes, or if it is clear the alert has not been received ashore, acknowledge by radiotelephony on channel 16 in the standard form: MAYDAY, the distressed vessel's name three times, this is (own name and call sign), received your DSC distress alert, position ..., over - then establish the nature of assistance required, how many persons on board, and whether they are abandoning.
Then inform MRCC Aktau of the alert you received and of what you have transmitted, using the satphone if the Inmarsat handset cannot be relied on.
2. Deal with the three equipment defects: stale own position, MF/HF switched off for a test, and the faulty Inmarsat handset.
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Stale position first, because it is the defect that can actively misdirect a rescue. The DSC controller's own position must be updated from the GNSS, either automatically or by manual entry at intervals not exceeding four hours while underway and after every significant change of position, and certainly before any transmission that may be acted upon. Right now a distress relay or acknowledgement would carry a 40-minute-old position - at 10 kn that is about 6.7 nm of error, which in a shallow coastal area is enough to send a helicopter to the wrong place. Update it, confirm the lat/long on the display, and check which receiver is feeding it.
MF/HF: determine the sea area honestly. Within VHF coverage of Aktau the vessel is in A1 and VHF DSC plus channel 16 satisfies the watch requirement; if she is at or beyond the A1/A2 boundary, an MF watch on 2187.5 kHz is required and the set must be on. Either way the battery test was a routine maintenance act and can be aborted the moment a distress is live - a GMDSS battery is sized for hours, not for convenience. Abort the test, restore the set to normal supply, record the residual battery capacity and the time of the test interruption.
Inmarsat handset: treat the master's satphone as the interim shore link, log the defect, tell the master and the company, and raise it for repair at the next port; the radio log must show what equipment was unavailable and when. Do not sail from the next port with the defect unrecorded.
3. The master decides to proceed to the position. Set out the message you send, the assistance you plan, and the seamanship limits.
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First send a distress relay on channel 16 only if it is warranted - typically when the alert has not been acknowledged by a coast station, or when the distressed vessel cannot transmit herself, or when this ship is not in a position to assist and must hand the case to others. Keep it short: MAYDAY RELAY, own name and call sign three times, then the distressed vessel's identity, position, nature of distress (flooding), number of persons, and the fact that this ship is proceeding. Then report to MRCC Aktau by satphone with own course, speed and ETA.
The obligation to assist comes from SOLAS Chapter V Regulation 33 and UNCLOS Article 98: the master must proceed with all speed to the assistance of persons in distress if he can do so without serious danger to his own ship and persons on board. That is a duty, and a decision to deviate is not a commercial decision - the reason for proceeding, and any later decision to stop, must be recorded with times.
Plan the approach for the casualty's conditions, not just the position: a fishing vessel with flooding may be low in the water, may have gear in the water, and may be over a shoal the coaster cannot enter with her draft. Prepare for the lee side, rescue boat and ladder, lifebuoys with lines, heaving lines, floodlights, first aid and warm blankets, and a VHF handheld for talking to the casualty. Stop well clear if the depth is uncertain, verify soundings continuously, and be ready to become on-scene coordinator if no other ship or aircraft is present.