Distress, urgency, and safety communications: alerting, SAR coordination, and on-scene communications
This domain tests the hierarchy of distress, urgency and safety communications, the difference between alerting and on-scene traffic, and how a ship supports SAR coordination. The exam expects you to know who acknowledges, who controls the scene, and which channel carries the working traffic.
Alerting and priority
A distress alert is sent by DSC, EPIRB or other GMDSS means. A MAYDAY voice call has absolute priority. A distress relay, MAYDAY RELAY, is sent only when the station in distress cannot transmit, when a coast station requests it, or when a station controlling the scene considers it necessary. Urgency (PAN PAN) covers serious illness, a disabled vessel without immediate danger, or a hazard that could become distress. Safety (SECURITE) covers navigational warnings and weather messages.
SAR coordination and on-scene work
The Rescue Coordination Centre (RCC) coordinates the search and rescue. A ship already on scene may be designated On-Scene Coordinator (OSC) until a rescue unit or coast station takes over. The OSC assigns search areas, keeps a listening watch, and controls on-scene communications. Initial voice contact is on channel 16; working traffic normally moves to channel 06, or another designated channel, to leave channel 16 clear.
Worked example
You receive a DSC distress alert from a vessel eight nautical miles away; no coast station acknowledgement is heard. You acknowledge by radiotelephony on channel 16, not by sending a DSC acknowledgement as a ship. You notify the RCC, proceed to the position, and establish on-scene contact on channel 06. Because no other unit has arrived, you act as OSC, assign a nearby fishing vessel to search a sector, and log times, positions and actions. When a coast guard vessel arrives, you transfer the OSC role.
Traps that cost marks
Do not transmit a MAYDAY RELAY for every distress alert you hear; relay only when it is needed. Do not use MAYDAY for a disabled vessel that is in no immediate danger. Do not abandon channel 16 without arranging the working channel. Failing to log the alert, acknowledgement and on-scene actions is a common practical weakness.