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MAYDAY and Distress Signals 

Mayday Distress Call using GMDSS - Digital Selective Calling (DSC) VHF Radio

DSC (Digital Selective Calling) is a new form of VHF Radio which allows calling of specific ships using its unique MMSI (Maritime Mobile Service Identity), a 9 digit number.  Yachts normally carry a Class D set.

GMDSS (Global Maritime Distress and Safety System) uses DSC for an automatic distress signal.

See for more details http://www.mcga.gov.uk/c4mca/gmdss.pdf

Using DSC for Mayday enables an automatic transmission of both the Mayday signal and your present position, providing your DSC set is interfaced with a GPS.

Just lift or slide the safety latch and press the red Mayday DISTRESS button (far right in the photo above).  Some sets allow you to specify the type of distress eg 'Sinking'.

Wait about 15 seconds for a DSC acknowledgement from the Coastguard or a ship station.  On Ch16, on receipt of a DSC acknowledgement or after about 15 seconds, send a voice Distress call:

Mayday, Mayday, Mayday

This is ‘YACHT NAME.................’,   spoken three times

Mayday – NAME and ‘MMSI* or call sign’, spoken once

My Position is…………….

Nature of Distress………………

Assistance required…………..

Number on board  (total crew + skipper)........

Other information

Over

*  MMSI = Mobile Maritime Service Identity – 9 digit number assigned to the radio

If no DSC acknowledgement is received, and offer of assistance is accepted from another vessel, cancel the DSC alert to prevent it automatically retransmitting.

See here for a guide to VHF Radio Mayday Guide and DSC Procedures  VHF skills chart

Acknowledgement of a DSC distress alert

When a DSC controller receives a Distress alert it will sound an audible alarm. 

Immediately cease any transmission that may interfere with Distress traffic and continue a watch on CH16.  Acknowledgement of a DSC alert by use of DSC is made only by coast stations and vessels fitted with Class A or B DSC controllers.  There is no facility on a Class D controller to acknowledge a distress alert by DSC.  If there is no DSC acknowledgement after a short interval, acknowledge by voice on CH16:

Mayday
9 digit MMSI of the vessel in distress, spoken three times
'This is' name of own vessel, spoken three times
Received Mayday
State the assistance you can give

Distress signals   

The following signals, used together or separately, indicate distress and need of assistance: 

  1. a signal sent by radio consisting of the spoken word "'Mayday";

  2. slowly and repeatedly raising and lowering arms outstretched to each side;

  3. a rocket parachute flare or a hand flare showing a red light;

  4. a smoke signal of orange-coloured smoke;

  5. a signal made by radio or by any other signalling method consisting of the group  . . . - - - . . . (SOS) in the Morse Code;

  6. a gun or explosive signal fired at intervals of a minute;

  7. a continuous sound with any fog-signalling apparatus;

  8. flames on the vessel (as from a burning tar barrel, oil barrel, etc.);

  9. rockets or shells, throwing red stars at short intervals;

  10. the International Code Signal of distress indicated by N and C flags;

  11. a signal consisting of a square flag having above or below it a ball or anything resembling a ball.

  12. a signal from an EPIRB or SART