Distress, Urgency and Safety Communications (DSC and Voice)
The three priorities and their signals
MAYDAY means grave and imminent danger requiring immediate assistance: sinking, fire, man overboard, abandoning ship. PAN PAN means urgency - a problem threatening safety but not yet life-threatening, such as engine failure in a shipping lane, a medical consultation, or obstructing a fairway. SECURITE announces a safety message: navigation or meteorological warnings, or a station identifying itself before a safety broadcast. The signal word is spoken three times, and the correct one must be used; upgrading or downgrading wrongly loses marks and, at sea, credibility.
The distress routine
Alert first, voice second. On a DSC set, lift the cover, press the distress key for five seconds, and the alert - carrying MMSI, position and time - goes on Ch 70. Then switch to Ch 16 and transmit: "MAYDAY, MAYDAY, MAYDAY. This is [name, name, name, callsign, MMSI]. MAYDAY. This is [name, callsign]. My position is [latitude and longitude, or bearing and distance from a landmark]. I am [nature of distress]. I require immediate assistance. Number of persons on board [x]. Any other information. Over." Keep the watch on Ch 16 afterwards and follow instructions from the coast station or rescue unit.
Acknowledgements, relays and silence
A DSC distress alert is acknowledged by a coast station, or by a ship only when the coast station instructs it. If you hear a MAYDAY that nobody answers, or see a casualty that cannot transmit, send MAYDAY RELAY using the same format prefixed by "MAYDAY RELAY" three times, identifying yourself as the relaying station. A station in distress or the rescue authority may impose radio silence with "silence MAYDAY"; obey immediately until "silence FINI" is heard.
Worked example
You hear MAYDAY three times but the transmission is broken, no position is given, and no coast station replies within two minutes. Reasoning: someone is in grave and imminent danger but cannot communicate effectively, so a distress relay is justified. You transmit MAYDAY RELAY on Ch 16 giving the casualty's identity if known, your own name and callsign, your position, and the nature of the problem as heard, then stand by on Ch 16.
Traps
- Using MAYDAY for a tow or a lost engine; that is PAN PAN.
- Sending the DSC alert and then going quiet instead of following up on Ch 16.
- Failing to cancel a false alert both by DSC and by voice on Ch 16.
- Acknowledging another vessel's distress by voice without authority.