Distress Signals
When in distress and requiring assistance, vessels shall use the signals described in Annex IV (red flares, SOS, MAYDAY, DSC, EPIRB and others).
Rule 37 states that when a vessel is in distress and requires assistance, she shall use or exhibit the signals described in Annex IV to these Regulations. Recognized distress signals include:
- a gun or other explosive signal fired at intervals of about a minute - a continuous sounding with any fog-signalling apparatus - rockets or shells throwing red stars one at a time at short intervals - the signal SOS by any signalling method - the spoken word "MAYDAY" by radiotelephony - the International Code Signal of distress: NC - a square flag with a ball or anything resembling a ball above or below it - flames on the vessel - a rocket parachute flare or hand flare showing a red light - orange-coloured smoke - slowly and repeatedly raising and lowering arms outstretched to each side - a DSC distress alert, a ship-to-shore distress alert through satellite services, an EPIRB alert, or approved radiocommunication distress signals such as survival craft radar transponders
Signal Workflow
Decide the context first: manoeuvring in sight, restricted visibility, or distress. The same whistle can mean very different things in a different context.
Check both the pattern and the interval. For fog signals, the time spacing is part of the rule, not just the blast sequence.
When in doubt about another vessel's intentions, use the prescribed warning signal early rather than waiting for the situation to deteriorate.
Exam Focus
Three short blasts are astern propulsion, not a fog signal.
In restricted visibility, think 'every two minutes' for underway signals and 'every one minute' for anchor bell signals.
Key Takeaways
Annex IV recognizes both traditional visual signals and modern radio distress alerts
MAYDAY is the spoken radiotelephony distress signal and SOS remains a recognized signalling method
Red flares and orange smoke are classic visual distress signals
Distress signals must only be used when assistance is genuinely required
Common Mistakes
Using a distress signal for urgency or routine communications
Knowing only the flare signals and forgetting the DSC, satellite and EPIRB options
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