Radio Operating Procedures: Distress, Urgency, and Safety Communications
Priority order
Traffic priority descends: distress, urgency, safety, then routine. Distress uses MAYDAY, spoken three times, on VHF Channel 16 (156.800 MHz) or MF 2182 kHz. Urgency uses PAN-PAN (three times) for a serious but not immediately dangerous situation. Safety uses SECURITE (three times) for navigational or weather warnings.
The distress call
Format: MAYDAY three times, "This is" plus vessel name and call sign/MMSI, position, nature of distress, assistance required, number of persons aboard, other useful information, then "Over." A station hearing it should acknowledge; if no coast station answers, another station may relay using MAYDAY RELAY.
Control of the frequency
The station in distress, or the coast station coordinating, imposes silence with SEELONCE MAYDAY (distress traffic) or SEELONCE DISTRESS (other distress traffic). When normal working may resume, the controlling station sends SEELONCE FEENEE (silence finished). PRU-DONCE marks a reduced silence.
Good operating practice
Use standard phonetics (Alfa, Bravo, Charlie...), procedure words (Roger, Wilco, Say again, Out), and count figures digit by digit. "Over" invites a reply; "Out" ends the exchange, so never say "over and out."
Traps
Silent periods on 2182 kHz are the first three minutes after the hour and after the half hour. Channel 70 (156.525 MHz) is DSC only, with no voice permitted. A false distress alert must be cancelled at once and reported; it is a criminal offense.
Rule of thumb: MAYDAY = grave and imminent danger; PAN-PAN = urgency; SECURITE = safety.