Operating Procedures - Distress, Urgency, and Safety Communications
The three priority calls
Distress outranks urgency, which outranks safety, which outranks routine traffic - no exceptions. MAYDAY, spoken three times, means grave and imminent danger and immediate assistance is required. PAN PAN means urgency: a serious problem without immediate peril (medical advice, a vessel disabled but not in danger, a drifting hazard). SÉCURITÉ (say-cure-ee-tay) announces a safety message such as a storm warning or navigational hazard.
Alerting in practice
On a DSC-equipped VHF, the distress alert goes on Channel 70: the button is held for about five seconds and the alert carries your MMSI, position, time, and nature of distress. Channel 70 is data-only - never speak there. Follow the alert with a voice MAYDAY on Channel 16. On MF, the voice distress frequency is 2182 kHz, which has silence periods of three minutes after the hour and after the half hour (00–03 and 30–33 minutes). VHF Channel 16 has no silence period.
A station hearing a distress alert addressed elsewhere should wait briefly for a coast station or rescue coordination centre to acknowledge; if nothing happens, acknowledge and/or relay as MAYDAY RELAY. To impose silence use SILENCE MAYDAY; when distress traffic is finished, SILENCE FINI (seelonce feenee). If you accidentally send a distress alert, cancel it immediately by voice on Channel 16 and notify the Coast Guard.
Worked example:
MAYDAY, MAYDAY, MAYDAY THIS IS BLUE HERON, BLUE HERON, BLUE HERON, WDC1234 MAYDAY, BLUE HERON, WDC1234 POSITION THREE MILES SOUTH OF POINT X FIRE IN ENGINE ROOM, ABANDONING TO LIFERAFT FOUR PERSONS ON BOARD, OVER
Traps: speaking on Channel 70, using PAN PAN for a vessel in imminent danger, and omitting the threefold repetition of the distress signal and vessel identity.