Module 18 - Signals & Communications
Complete DSC Distress Workflow
What you will learn
Lead the complete DSC-to-voice distress sequence while allocating vessel, radio, position and emergency roles and retaining a communication-failure branch.
A distress call is one stream in a concurrent emergency. The best procedure is accurate and fast, but it never leaves the yacht without control, damage action, lookout or a fallback alerting path.
When grave and imminent danger requires immediate assistance, lift the cover, select the nature of distress if time permits, and press and hold the distress control until the set confirms that the alert has been sent. Do not tap and release it. The alert should carry the vessel's MMSI and, when the radio is receiving valid GNSS data, position and time. A stale or absent position input makes the voice position even more important.
On receipt of a DSC acknowledgement, or after about 15 seconds, transmit the MAYDAY call and message on Channel 16. Give MAYDAY three times; vessel name three times; call sign or other identity and MMSI; then MAYDAY once, identity, position, nature of distress, assistance required, persons on board, and useful hazards or survival information. End with OVER and listen. If the situation changes, update the controlling station rather than allowing an obsolete message to govern the response.
The skipper should allocate tasks before pressing the button where time allows: one person controls the vessel, one transmits, one verifies and writes the position, and one prepares survival or recovery equipment. If the radio operator must leave the set, hand over the log and the exact last transmission. Preserve Channel 16 for the distress exchange and follow the Coastguard's channel instructions.
A strong command answer includes the failure branch. If DSC is unavailable, make the voice MAYDAY on Channel 16. If VHF contact is not achieved, use other available alerting appropriate to the equipment and area—such as EPIRB, PLB, another radio or satellite device—while continuing the immediate actions that protect life. Communications support the emergency plan; they do not replace damage control, recovery, firefighting, or abandonment preparation.
Worked example
The alert is sent at 2210, the voice MAYDAY follows, but no readable reply is heard and water continues to rise.
- 1Record 2210, the exact position sent, the people aboard and the current water trend.
- 2Maintain listening watch and retry with the independent handheld or other appropriate alerting equipment without abandoning damage control.
- 3Prepare survival equipment and a concise update stating whether pumping is gaining or losing and which controls remain.
- 4Use the pre-briefed abandonment or recovery trigger if the situation crosses it; do not wait for a perfect radio exchange.
Sense check: The communication plan has at least one genuinely independent branch and every attempt supports, rather than replaces, the life-saving plan.
| Function | First owner | Closed-loop report |
|---|---|---|
| Vessel | Helm/skipper | Course, traffic, sea room and control |
| Emergency | Damage/casualty lead | Trend improving, stable or worsening |
| Communications | Radio operator | Alert sent, station reached, channel and next call |
| Position/survival | Navigator/deck crew | Verified position and equipment readiness |
Run the first two minutes of a flooding response
Water is rising faster than the electric pump can clear it. Four people are aboard, one is steering away from traffic and the fixed VHF has live position data.
1. Own the functions
Assign vessel control, flooding action, radio/position and survival preparation; combine roles only deliberately on a small crew.
2. Send the alert and voice
Press and hold DSC until sent; on acknowledgement or after about 15 seconds send the Channel 16 MAYDAY with current facts.
3. Confirm and update
Log the controlling station and instruction, report the water trend and continue independent alerting if the first path is not proven.
Sense check: At the end of the first exchange, someone still owns the helm, someone is measuring the flooding trend and the crew knows the next update time.
Common mistake or limitation
- Completing the call is not the same as controlling the emergency or confirming that a coordinating station has the message.
- Do not leave the helm, lookout, pumps or casualty without an owner while everyone gathers around the radio.
- A connected display is not an independent backup when it shares the same power, antenna, GNSS or mounting failure.
- Update the controlling station when position, persons, fire, flooding or abandonment state changes.
Recap
- Press and hold DSC until the alert is sent.
- Voice MAYDAY follows on acknowledgement or after about 15 seconds.
- Allocate vessel, emergency, radio and position roles.
- Keep an independent alerting branch and continue immediate life-protection actions.
Optional quick check
Section 11 of 18
After the MAYDAY, the operator receives no readable reply while flooding worsens. What is the best command response?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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