DSC distress alert with no voice reply in the Hauraki Gulf
You are the officer of the watch on the 35 m charter vessel Tūhono, steering 310° at 10 knots in the Hauraki Gulf at 0210. Visibility is good, sea slight, wind northwest 10 knots. Your DSC controller sounds a distress alarm: a single distress alert on Channel 70 from an unknown MMSI. The display gives a position 12 nautical miles northwest of your own, nature of distress 'unspecified'. There is no GPS-derived name. You call on Channel 16 for two minutes; there is no voice reply, and no coast station appears to acknowledge. Five minutes later a white hand flare is sighted on the bearing of the reported position. You have radar, a searchlight and four crew. Your own passage is not urgent. You must decide what to transmit, whether to acknowledge, and how to avoid making the situation worse.
1. What are your immediate actions on receiving the DSC alert?
Read the worked answer
First, record the time, the MMSI, the position and the nature of distress exactly as displayed. Do not transmit a voice call on Channel 70; it is a DSC channel, not a voice channel. Keep a continuous listening watch on Channel 16 and check whether a coast station acknowledges the alert. Inform the master and the crew, plot the position, and assess whether you can assist without hazard to your own vessel.
I would try to establish voice contact on Channel 16 using the distress format, but I would not immediately send a DSC acknowledgement. In GMDSS practice, a ship station that receives a distress alert addressed to another station should not acknowledge it by DSC; it should allow a short period for a coast station to acknowledge, then acknowledge by radiotelephony if appropriate. I would also check the DSC log for any follow-up alert and keep the radar watching the bearing. If the position is within reach, I would alter course toward it at safe speed and inform Maritime Radio that I am investigating.
2. No voice reply is received, then a white flare is sighted. Do you acknowledge the DSC alert, and what do you transmit?
Read the worked answer
The flare corroborates that someone is in distress, so I would now acknowledge by voice, not by DSC. The DSC acknowledgement is not the priority; a coast station needs to know that a vessel has seen the flare and is responding. I would transmit on Channel 16:
MAYDAY, [unknown station], this is Tūhono, Tūhono, Tūhono. I have received your DSC distress alert and sighted a white flare. Acknowledge. What is your position and nature of distress? Over.
If there is still no reply, I would send a MAYDAY RELAY to all stations, giving the time, MMSI, position, nature of distress, and the fact that a white flare has been sighted. I would then inform Maritime Radio and RCCNZ of the situation and my actions. I would not keep repeating the relay; one clear relay followed by a working-channel report is better than filling Channel 16. I would keep the flare bearing under observation and prepare to recover survivors.
3. You locate a liferaft with three people aboard. What now?
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I would report immediately to Maritime Radio or RCCNZ: position, time, number of persons, condition, sea state, and whether I can recover them. I would approach slowly and from a safe angle, keep the searchlight on the raft, and use a throwing line or lifebuoy rather than putting crew in the water. Once alongside, I would take the people aboard, check for hypothermia and injuries, and account for everyone; the raft may have been occupied by more than three.
I would not cancel the search on my own authority. I would tell RCCNZ exactly who has been recovered and ask whether any other persons are missing. If the condition of a survivor is critical, I would request urgent medical advice and helicopter evacuation, using PAN PAN on Channel 16 only if I could not reach RCCNZ on the working channel. I would keep a log of times, names and medical details, and preserve the liferaft or its markings if possible for later investigation.