A Mayday call is only to be used when a boat or person is in grave and imminent danger and requires immediate assistance. Depending on whether or not your radio is fitted with DSC or not, a Mayday call consists of two or three parts: a DSC alert, the distress alert and the distress message.
To trigger a DSC alert, lift the tab over the distress button. On some radio sets you may have to press the button once and then press again and hold for 5 seconds, while on others you may only need to press the button for 5 seconds. Assuming the DSC controller is connected to a working GPS receiver, pressing the button will send a digital distress call in less than half a second. The call automatically includes your identity, your position and the time of the call. It will continue to send a digital distress every 4 minutes until it is acknowledged. The DSC alert needs to be followed by a voice Mayday call.
The voice Mayday call is made up of two parts: the distress alert and the distress message. The distress alert consists of:
• ‘Mayday, Mayday, Mayday’
• 'This is … (name of boat said three times)'
• 'Mayday … (name of boat) … (if the call follows a DSC alert, then add the MMSI).'
The distress message is:
• 'Position … (either in latitude and longitude or distance and bearing from a known point)'
• Say what type of distress you are experiencing, for example 'sinking', 'on fire', 'man overboard' or other distress.
• 'Require further assistance'
• Say how many people you have onboard.
• Further information, such as 'abandoning to liferaft'
For more information, see Sea Safety: The Complete Guide.