Radio communication procedures
This domain tests GMDSS and radiotelephony: which priority, on which channel, in what order, with which words. Marks are lost on procedure rather than vocabulary, so examiners look for the alert, the follow-up and the correct level of priority.
The three priorities
- MAYDAY - grave and imminent danger, immediate assistance required (fire, sinking, man overboard at night, abandon ship).
- PAN PAN - urgency: the safety of the ship or a person is concerned but there is no immediate danger (breakdown, injury needing medical advice, dismasting).
- SECURITE - safety of navigation or a meteorological warning (a drifting container, a storm warning).
Channels and carriage
- VHF 16: distress, safety and calling, radiotelephony.
- VHF 70: DSC only - never voice, and never used for a radio check.
- VHF 13: bridge-to-bridge intership safety; 06 intership working; 09 port operations and routine working.
- Sea areas A1–A4 determine carriage: A1 VHF with DSC, A2 adds MF, A3 adds Inmarsat, A4 adds HF. NAVTEX receives on 518 kHz.
Distress sequence
Send the VHF DSC alert on channel 70 with the nature of distress, position and time, then the voice call on 16: MAYDAY three times, this is plus ship's name three times, callsign or MMSI, position, nature of distress, assistance required, persons on board, any other information, over. If there is no DSC acknowledgement within about five minutes, escalate to another means rather than waiting. A MAYDAY RELAY is used when you hear a distress from a station unable to transmit it herself.
Worked example
At 0300, in position 47°12′N 003°45′W, one crew member is missing overboard, eight persons on board, wind SW 6. This is an imminent danger to life, so it is a MAYDAY, not a PAN PAN. The DSC alert goes first with the nature 'man overboard' and the position; then the voice call on 16 follows the standard order, ending with over. The ship keeps a listening watch on 16, plots any assisting vessel, and only ends the distress traffic when the case is closed - with silence mayday traffic controlled by the coordinating station, not by any ship that happens to hear it.
Traps that cost marks
- Using channel 70 for a voice call, or channel 16 for a radio check - use a working channel such as 09.
- Sending a PAN PAN for a genuine MAYDAY (fire, flooding, abandonment) or a SECURITE for a medical evacuation.
- Crying MAYDAY only once, or omitting the position - the two facts a coast station needs first.
- Forgetting to cancel a false DSC alert on 16 immediately, which triggers a full search-and-rescue response.