How is a distress call made at sea, what is sent, and what is the process?
Short answer
| Method | Means | Sends |
|---|---|---|
| DSC, the primary alert | VHF channel 70, MF 2187.5 kHz, HF DSC frequencies | identity (MMSI), position, nature of distress |
| EPIRB | 406 MHz Cospas-Sarsat, float-free, automatic | identity and GPS position via satellite |
| Satellite | Inmarsat or recognised mobile-satellite ship earth station | distress priority call |
| Radiotelephony | MAYDAY on VHF channel 16 and MF 2182 kHz | the full distress message |
| SART or AIS-SART | radar or AIS transponder | locating the survival craft, not an alert |
- Principle: the GMDSS (SOLAS chapter IV) requires a ship-to-shore distress alert by at least two separate and independent means, with equipment matched to sea areas A1 (VHF), A2 (MF), A3 (satellite) and A4 (HF, polar).
- Methods: DSC on VHF channel 70, MF 2187.5 kHz and HF; the 406 MHz EPIRB; satellite; spoken MAYDAY on VHF 16 and MF 2182 kHz; SART or AIS-SART for locating.
- Content: identification (MMSI, call sign, name), position and time, nature of distress, assistance required, persons on board, course, speed, intentions.
- Process: master orders the alert; DSC distress alert, then the MAYDAY message on the associated frequency; coast station or RCC acknowledges and coordinates search and rescue; nearby ships respond; the distress is cancelled when resolved, and a false alert cancelled immediately by voice.
- Priorities: MAYDAY for grave and imminent danger; PAN-PAN urgency; SÉCURITÉ safety.
- As Chief Engineer: the GMDSS depends on the emergency source of power and the reserve batteries I maintain, and my engine-room report is what triggers the master to send the alert.
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class I section of the Marine One forum, open to members enrolled for the MEO Class I exam.