Distress, urgency and safety communications procedures
Priority and signal words
Distress is grave and imminent danger requiring immediate assistance: MAYDAY, spoken three times. Urgency concerns safety of a ship or person but no immediate grave danger: PAN PAN. Safety is a navigational or meteorological warning: SECURITE. Distress traffic has absolute priority; urgency and safety traffic must not interfere with it. A distress call names the station, MAYDAY, position, nature of distress, assistance required, persons on board and other useful information.
Control and silence
A coast station acknowledging distress becomes the distress traffic controller and imposes silence with SEELONCE MAYDAY. Other stations must keep silent unless they can assist or are involved. When distress traffic ends, the controller sends SEELONCE FEENEE. An urgency message may use PRU-DONCE if silence is needed for a medical or other urgent transmission. An on-scene coordinator may be appointed to coordinate assisting ships.
Worked example
A vessel loses its engine 20 nm offshore but is not in immediate danger; another vessel is nearby. Reasoning: this is urgency, not distress-there is no grave and imminent danger. Transmit PAN PAN, identify the vessel, position, nature of trouble and assistance needed. If the vessel later begins to sink, upgrade to MAYDAY; do not use MAYDAY for a tow request.
Traps
Do not use MAYDAY for a breakdown with no immediate danger. Do not acknowledge a distress alert if a coast station is already handling it, unless asked. Do not resume normal working until SEELONCE FEENEE. Do not forget to cancel a false alert and inform the coast station.