No HF DSC acknowledgement during a medical emergency
At 0200 local time your 8,000 GT tanker is 1,700 nm from the nearest coast earth station. The second officer has severe right lower abdominal pain, fever and vomiting; the master suspects appendicitis and wants medical advice and possible evacuation. The MF/HF radio has DSC and radiotelephony. You first send a DSC distress alert on 8,414.5 kHz, but there is no acknowledgement after two attempts over 10 minutes. On 8 MHz you hear several broadcast carriers but no coast station; 12 MHz is very noisy; 16 MHz is quiet. The Inmarsat-C terminal is operational for messaging, but the satellite telephone battery is flat and the spare is missing. The vessel is in a recognized HF distress watch area but beyond reliable VHF range.
1. Was the DSC distress alert on 8,414.5 kHz appropriate? Explain the band choice, propagation, and what you should do after the two unanswered calls.
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A DSC distress alert on 8,414.5 kHz is a valid HF distress frequency, and a suspected appendicitis with fever and vomiting 1,700 nm from help can reasonably be treated as a distress situation if there is imminent danger to life; if the master judges the danger is not yet imminent, urgency (PAN PAN) would be more appropriate. The lack of acknowledgement does not prove the alert was not transmitted. At 0200 local, 8 MHz often supports long-distance skywave, but it can also suffer heavy atmospheric noise and fading in tropical areas; 12 MHz is noisy and 16 MHz may be too high for reliable nighttime propagation over that path. You should not keep repeating on the same frequency indefinitely. After two unanswered calls, try another HF DSC distress frequency (for example 6,312 kHz or 12,577 kHz) and its associated radiotelephony frequency, while continuing to listen on 8,291 kHz for a reply.
2. What radiotelephony procedure and content would you use on the associated 8 MHz frequency?
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Use the associated radiotelephony frequency for 8,414.5 kHz, which is 8,291 kHz. Transmit: 'MAYDAY MAYDAY MAYDAY, all stations, this is [ship name, call sign, MMSI], position [lat/long], medical emergency, one person with severe abdominal pain, fever and vomiting, suspected appendicitis, request medical advice and possible evacuation, over.' If using urgency, substitute PAN PAN PAN and state that medical advice is required. Keep the call short, give the position in a standard format, and say what assistance is needed. Listen for an acknowledgement and be ready to switch to a working frequency. If a coast station replies, follow its instructions and pass the patient's age, temperature, pulse, pain location and history. Do not read a long medical history on the distress frequency unless asked.
3. What alternative communications and escalation should you use if HF remains unanswered?
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Use the Inmarsat-C terminal to send an urgency or distress-priority message to the appropriate RCC/coast earth station if the terminal is configured for that service; do not assume a routine message will be seen promptly. Charge or obtain a battery for the satellite telephone; if another ship is within VHF/HF range, ask it to relay. Notify the company medical adviser and the ship's agent. Do not activate the 406 MHz EPIRB unless the vessel is in imminent danger and may need to be abandoned; an EPIRB is not a medical evacuation request. If the patient's condition deteriorates, upgrade to MAYDAY and consider diverting toward the nearest suitable port. Record all calls and times.