How to Do The VHF Radio Distress Call

The unthinkable has happened; your boat, you and your crew are in grave and imminent danger. To raise the alarm, you sent a distress call by voice on VHF Channel 16. That distress call, with “Mayday” spoken three times followed by your vessel’s identification information, alerted your potential rescuers to immediately standby for the distress message which will contain all the pertinent details to aid in your rescue.

It is critical that you remember as many of the particulars that are needed for the Mayday message, so it can be transmitted coherently. The mnemonic “MIPDANIO” gives you a crutch to lean on when it’s difficult to focus your thoughts in an emergency.

History and Background of Maritime Distress Signals

Keep this acronym posted by your VHF radio or write it down on a notepad prior to broadcasting your Mayday, as it will guide you through the distress message:

M – Mayday I – Identity P – Position D – Distress A – Assistance N – Number I – Information O – Over

During an actual emergency, your Mayday message will unfold as follows:

Mayday – Say Mayday just once to begin the distress message. Identity – Broadcast the vessel’s name preceded by a descriptor to better identify the type of boat. For example: “sailing vessel Morning Star” or “motor yacht Diana’s Dream.” The vessel’s radio call sign and Maritime Mobile Service Identity (MMSI) number, also spoken once, complete the identification portion of the message. Position – Your latitude and longitude are the easiest position locators to give, as they can be read right off the GPS display. However, until the listener plots these coordinates on a chart they may be of little value. Instead, it can be preferable to use a familiar charted landmark as a point of reference. First give the direction from the landmark to your vessel, followed by name of the landmark and then the distance to your vessel. “My position is one-two-seven degrees true from the Miami safe water buoy, seven point six nautical miles,” is the proper format. These descriptions give the search vessel or helicopter the information needed to set out on their rescue mission. Distress – There’s no need for a lengthy explanation, just a short description such as “sinking”, “taking on water” or “on fire.” Assistance – In most cases, “request immediate assistance” is sufficient. Additional information, such as a request for pumps or a tow can be helpful. Number – The number of people on board that need to be rescued. Information – Give any other information pertinent to a rescue. That can be actions being taken, such as “abandoning to a liferaft,” or a brief description of the boat’s features (the color of the hull, number of masts, monohull or multihull). Over – The procedural word “over” concludes the distress message, and also means a response is expected.

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What do you do if you hear a distress call?

The International Telecommunication Union (ITU), which sets the Radio Regulations by international treaty, states the following rules: If it is likely that a coast radio station (such as the Coast Guard) will have received the message, you should allow five minutes for them to respond before doing so yourself. If you are in a position to offer effective assistance, you should acknowledge the message. Unless you are acknowledging and assisting, you must maintain radio silence on any channel being used for distress communications.

If the Coast Guard does not respond in the duly allotted time and you can offer help, acknowledge the call to the vessel in distress, let them know where you are, your boat speed and your estimated time of arrival.

The station in control of the distress radio traffic may transmit the procedural words: “Seelonce Mayday” (from the French), to remind any boaters in range not to break radio silence. Once the need for radio silence has ended, they will announce: “Seelonce Feenee.” Sometimes a Mayday will go unheard by search and rescue authorities due to a poor quality signal or too great a distance from the vessel in distress. In such a case, when it is clear that the call was not acknowledged you can act as a relay to the Coast Guard or all ships in range. The Mayday relay call begins with the words “Mayday Relay” spoken three times, plus the name and call sign of your vessel. It is followed by repeating the exact Mayday message from the vessel in distress. This can only be done verbatim if you wrote down the distress message. The next article of this series will cover the use of the Digital Selective Calling (DSC) distress alert as part of the Global Maritime Distress and Safety System (GMDSS).

The VHF Radio Distress Call: Digital Selective Calling (DSC)

Capt. Jeff Werner is a 23 year veteran of the yachting industry. In addition to working as a captain on private and charter yachts, both sail and power, he is a certified instructor for the RYA, MCA, USCG and US Sailing.

Digital Selective Calling (DSC): The One-Button Distress Alert

When a vessel is in distress, the faster that search and rescue authorities can be alerted the quicker that a coordinated search and rescue operation can begin. That premise was the impetus behind the International Maritime Organization’s call for the development of a Global Maritime Distress and Safety System (GMDSS) in 1979. Today, GMDSS is a reality. It allows the mariner to use an amalgam of communications equipment, both satellite and radio, in order to have the best chance of alerting authorities in the event of a life threatening situation. When far out at sea the EPIRB (Emergency Position Indicating Radio Beacon) is the perfect method to alert search and rescue services since it transmits directly to a constellation of satellites. Closer to shore, within about 20 nautical miles, the VHF radio is the go to device to use in the event of a Mayday situation.

However, when a yacht is rapidly taking on water and all efforts are aimed at keeping the vessel afloat, the captain may be unable to transmit a timely Mayday call. Wouldn’t it be nice, during this high stress moment, to just push one button to quickly alert the Coast Guard? That is exactly what Digital Selective Calling (DSC) is all about.

All new VHF radios have a red ‘distress’ button that will automatically establish initial contact with a coast radio station and nearby vessels equipped with a DSC VHF radio, and will continue to repeat the distress call until acknowledged by the coast authorities. DSC VHF radios must first be programmed with the vessel’s registered Maritime Mobile Service Identity (MMSI), a unique identifying number that can be looked up in a worldwide database to find the boat’s emergency contact information. Next, the radio must be connected to the boat’s GPS receiver. This will allow the vessel’s latitude and longitude, as well as the current time, to be transmitted with the automated distress call. The latest generation of DSC VHF radios have an internal GPS that eliminates the need to hard wire the radio to the boat’s GPS. One of ten pre-programmed ‘nature of distress’ options can be transmitted to assist in marshaling the proper resources by the search and rescue team. These predefined distress designations are: Fire or explosion, flooding, collision, grounding, listing, sinking, disabled and adrift, abandoning ship, man overboard and piracy. If time is of the essence, then the message can be immediately sent in the default mode with an ‘undesignated’ nature of the distress.

Until a coast station acknowledges the DSC alert, the vessel’s VHF radio will continue to broadcast the alert approximately every four minutes. Once acknowledged, the boat’s distress alert is automatically stopped and simultaneously switched to channel 16. At this point, the boat’s radio operator can begin transmitting a standard voice Mayday call and message to start the detailed conversation needed with the search and rescue coast station. A marine VHF DSC radio has a built-in dedicated receiver that constantly monitors channel 70, the sole digital channel on the radio. This allows the boat’s radio to receive any DSC distress alerts from nearby vessels. When sending a DSC distress alert, the radio is automatically switched to channel 70 when the distress button is pushed. It then broadcasts an ‘all stations’ coded digital Mayday message over Channel 70 to any VHF DSC radios within range. The radios receiving the alert hear a loud two-tone warble as the details of the alert are shown on the radio’s visual display. Channel 70 is only used for DSC communication, and voice communication is not allowed on that frequency.

Spotlight on Digital Selective Calling (DSC)

To avoid a false alert the distress button is protected by a plastic cover, and the button itself must be pushed and held down for several seconds before the transmission will begin. In the event of an accidental false distress alert, the radio should first be turned off to stop the repetition of the alert. Next, broadcast an all stations voice message on channel 16 cancelling the distress alert, making sure to include the boat’s MMSI number. While VHF DSC technology is a boon to safety, the United States Coast Guard tracks major issues that cause digital distress alerts to be less effective. The biggest problem is the lack of a follow-up voice Mayday call after the distress alert is acknowledged. Next are distress alerts that are sent without accurate location information, followed by calls using unregistered MMSI numbers.

History and Background of Maritime Distress Signals

Capt. Jeff Werner has written for ALL AT SEA since 2014.