When do you use MAYDAY vs PAN-PAN vs SÉCURITÉ?

MAYDAY is reserved for grave and imminent danger to vessel or life requiring immediate assistance. PAN-PAN is urgency — safety at risk but not grave (e.g. medical emergency, disabled in clear water). SÉCURITÉ is a safety message, typically a navigational or meteorological hazard warning. All three are spoken three times at the start of the call.

What goes in a Mayday message?

MAYDAY ×3, THIS IS [vessel name ×3], MAYDAY [vessel name once], callsign and 9-digit MMSI, position (lat/long or bearing and distance from a charted point), nature of distress, assistance required, persons onboard, and any other useful information (hull colour, EPIRB on, life raft launched). End with OVER.

Which channel and frequency are used for distress?

VHF Channel 16 (156.8 MHz) for short-range distress, MF 2182 kHz for medium range, and DSC alerts on VHF Ch 70 / MF 2187.5 kHz. Modern GMDSS ships transmit a DSC distress alert first, then voice on the working frequency for that band.

What is a Mayday Relay?

A Mayday Relay is sent by another vessel or coast station that hears a distress alert but cannot itself help, or that hears a distress signal go unanswered. It begins MAYDAY RELAY ×3, THIS IS [station] ×3, and includes everything from the original distress call. Anyone hearing a Mayday Relay must maintain radio silence and assist if able.

Distress — Mayday

Use a distress signal only when the vessel or a person is threatened by grave and imminent danger and immediate assistance is required. Once transmitted, a distress alert obliges every station that hears it to render assistance and to maintain radio silence on the working frequency until silence is lifted.

Speak slowly. Speak clearly. Spell unfamiliar names with the phonetic alphabet. Repeat the position twice if you have any doubt the receiving station copied it correctly.

Priority hierarchy

MAYDAY (×3) — distress. Grave and imminent danger to vessel or life; immediate assistance needed. Highest priority on all channels.
PAN-PAN (×3) — urgency. Safety of vessel or person at risk but not immediate grave danger (e.g. medical emergency, disabled propulsion in clear water). Second priority.
SÉCURITÉ (×3) — safety. A navigational or meteorological warning. Third priority. Used by coast stations and by ships reporting hazards (drifting containers, debris, ice).

Spoken Mayday format (VHF Ch 16 / MF 2182 kHz)

MAYDAY MAYDAY MAYDAY THIS IS [vessel name, three times] MAYDAY [vessel name, once] CALLSIGN [callsign]  MMSI [9-digit number] POSITION [lat/long, or true bearing and distance from a charted point] NATURE OF DISTRESS [e.g. on fire, sinking, man overboard, listing] ASSISTANCE REQUIRED NUMBER OF PERSONS ONBOARD ANY OTHER INFORMATION [hull colour, EPIRB on, life raft launched] OVER

Mayday Relay

If a vessel hears a Mayday and either there is no acknowledgement from a coast station or the calling vessel is unable to transmit further, any station may relay:

MAYDAY RELAY MAYDAY RELAY MAYDAY RELAY THIS IS [own vessel name, three times] CALLSIGN [own callsign]  MMSI [own MMSI] RECEIVED FOLLOWING DISTRESS FROM [original vessel name] [repeat the original Mayday content] OVER

DSC distress alert (SOLAS Ch IV / Rule 31)

Lift the red protective cover on the DSC controller.
If time permits, select the nature of distress (fire, flooding, collision, grounding, listing, sinking, disabled and adrift, abandoning ship, piracy, MOB, undesignated).
Press and hold the DSC distress button for ≥5 seconds. The set transmits the alert and switches automatically to channel 16.
Immediately follow with a spoken Mayday on VHF 16 (or MF 2182 kHz, or HF as appropriate to area).
If no acknowledgement is received within ~4 minutes, repeat the DSC alert.

Worked example

MAYDAY MAYDAY MAYDAY THIS IS MV EXAMPLE MV EXAMPLE MV EXAMPLE CALLSIGN 9HA1234  MMSI 248123456 MAYDAY MV EXAMPLE POSITION 36 DEGREES 15 MINUTES NORTH 014 DEGREES 30 MINUTES EAST VESSEL ON FIRE IN ENGINE ROOM, PROPULSION LOST REQUIRE FIRE-FIGHTING ASSISTANCE AND MEDEVAC 18 PERSONS ONBOARD, 2 INJURED WITH BURNS VESSEL DRIFTING SOUTHWEST AT 2 KNOTS EPIRB ACTIVATED OVER

Imposing and lifting silence

SEELONCE MAYDAY — said by the vessel in distress or by the on-scene coordinator to impose silence on all stations.
SEELONCE DISTRESS — said by any other station (e.g. an MRCC) to impose silence on its own behalf.
PRU-DONCE — restricted working may resume; only stations involved in the SAR may transmit.
SEELONCE FEENEE — distress traffic ended; channel returns to normal.

If you cannot transmit

Activate the EPIRB and the SART. The 406 MHz Cospas-Sarsat EPIRB transmits the vessel identity and a GNSS position to satellites; the X-band SART produces a 12-dot line on the radar of any vessel within ~5 nm (~30 nm if SAR aircraft is overhead). Deploy them in the open from the highest point that remains above water, and keep them with you in the life raft.

After the rescue

Cancel any false alert immediately on the same frequency: "ALL STATIONS THIS IS [vessel name], CANCEL MY DISTRESS ALERT OF [time UTC], OVER." A false alert that is not cancelled diverts SAR resources and is a serious offence under the Radio Regulations.