Distress, Urgency and safety calls - Tx + Dx

Transmitting, Receiving and Relaying Distress, Urgency and Safety Calls

Reception of a Distress Alert

A vessel receiving a DSC distress alert should not normally acknowledge the alert by DSC, but should do so by voice or telex on the emergency frequency indicated in the alert. A DSC acknowledgement is usually done only by a Coast Station, because acknowledging the alert by DSC will stop the transmitting station from sending further alerts. Generally, it is much better for all concerned if a Coast Station hears and acknowledges the alert, and then assumes control of the operation. Another vessel should only acknowledge the alert by DSC if it is being transmitted on VHF or MF, and if it seems that no Coast Station has received the call and the transmission of the distress alert is continuing. In this situation, the receiving vessel may acknowledge the call by DSC to terminate the transmissions. But the receiving vessel is then required to contact the nearest Coast Station by any practical means and inform them of the situation. A DSC distress alert on HF should never be acknowledged by DSC by another vessel, because by the nature of HF propagation the two vessels are likely to be many hundreds of miles apart. Transmission of a DSC acknowledgement will stop the transmission of further alerts, and it would be better for the distressed vessel to continue sending alerts in the hope that a Coast Station will receive the call directly and take control of the situation. A vessel receiving an alert on HF should relay the alert to a Coast Station.

Reception of a DSC DISTRESS ALERT on VHF or MF

If a DSC distress alert is received on VHF or MF, the normal procedure to follow is: (a) Watch the DSC control unit for reception of a DSC acknowledgement from a Coast Station. Such an acknowledgement will stop further transmissions of the distress alert. (b) Tune the radio to the frequency and mode indicated in the DSC alert. (c) Acknowledge the receipt of the distress alert on the frequency indicated, either by voice or by telex as indicated in the DSC alert. The message acknowledging the distress alert should be as follows: Mayday - The word Mayday indicates that it is a distress message. Identity of Distressed vessel - This will be their MMSI, repeated three times - neither the name nor the call sign of the distressed vessel will be indicated on the DSC alert. This is......... - Your identity - your MMSI and/or name and call sign, repeated three times. Received Mayday. Over. If there is a Coast Station, or Rescue Co-ordination Centre controlling the operation and they want you to help, they will call you back. If no Coast Station nor RCC has taken control, the distressed vessel should hear your acknowledgement and may call you back to ask for your assistance if it is needed. If no Coast Station nor RCC has taken control and you do not hear any response to your acknowledgement by the distressed vessel, then you should send a distress alert relay.

Reception of a DISTRESS ALERT on HF

Vessels operating in Areas A3 and A4 are expected to monitor at least two of the DSC HF emergency frequencies. Normally 8414.5 kHz is designated as one and the other is chosen according to conditions - a lower frequency by night or a higher one by day. Many DSC watch-keeping receivers will in fact scan through all the DSC emergency frequencies; which are: 4207.5 kHz 6312 kHz 8414.5 kHz 12577 kHz 16804.5 kHz If you receive a DSC distress alert on HF from another ship you must not acknowledge it by DSC. Because of the likely propagation of the HF signal it is probable that the other vessel is several hundreds, or possibly thousands of miles away. If the distress alert was acknowledged by DSC then no further distress alerts would be transmitted by the distressed station, and this could well reduce the chances of it being heard by a shore station who could co-ordinate rescue attempts. If you do receive an HF DSC distress alert then the correct procedure is: a. Note on which band or bands the DSC alert was received. b. Note the position of the distressed vessel, and compare to your own. Unless the HF signal was received on ground wave, it is likely to be many hundreds of miles from your own position. c. Tune the HF radio to the mode and frequency indicated in the alert, or if no frequency and mode was specified then to the emergency frequency in the band on which the DSC alert was received. The HF emergency frequencies are: Voice emergency frequencies: 4125 kHz 6215 kHz 8291 kHz 12290 kHz 16420 kHz Telex emergency frequencies: 4177.5 kHz 6268 kHz 8376.5 kHz 12520 kHz 16695 kHz If telex was specified in the alert then the telex frequency should be monitored, but if it is possible to monitor the voice frequency on the same band as well then this should be done. If the DSC alert was received on several frequencies then monitor the most likely band, probably 8 MHz if the alert was received on this band. d. If no distress traffic is heard on the frequency to which you tuned within two minutes, then switch to the emergency frequency on another band on which the DSC alert was received or another of the emergency frequencies that might be appropriate, considering the position of the other vessel in relation to you and the likely propagation. e. If distress working is heard, then the situation should be monitored until it is obvious that the Coast Station has the situation under control. If no distress working is heard and no DSC acknowledgement has been transmitted by a Coast Station, then transmit a DSC distress alert relay to inform the nearest Rescue Co-ordination Centre or Coast Station by any means possible.

Transmission of a Distress Alert Relay

A vessel should transmit a distress alert relay if: (a) the distressed vessel herself is not able to transmit a distress alert. (b) the master of the relaying ship considers that more assistance is required. (c) a distress alert has been received but no contact with the distressed vessel has been possible and no Coast Station has responded to the alert. The distress alert relay could be sent to 'all stations', to vessels in a particular area or to a specific Coast Station or RCC. On VHF or MF an 'all stations' call might be considered appropriate to alert vessels in the vicinity as well as any Coast Stations within range. Usually, in the case of an HF DSC alert relay, it will be better to send it to a specific Coast Station or Rescue Co-ordination Centre, and let them co-ordinate the rescue. Do not do an 'all stations' call. There is no point in alerting vessels, for example, in the Indian Ocean for a vessel in distress in the North Atlantic. A DSC distress alert relay is sent as follows. a. Tune the radio to the DSC emergency frequency of the most suitable band. b. Select 'distress relay' on the DSC control unit. c. Address the call as 'all stations', or to the MMSI of a specific Coast Station or RCC. d. Key in the MMSI of the distressed vessel, if known. e. Select the nature of the distress, if known. f. Key in position of distressed vessel. g. Key in UTC time that the position was valid. h. Indicate frequency and mode for subsequent traffic. i. Transmit the DSC distress alert relay. j. Watch on the DSC control unit for a DSC acknowledgement. Tune the radio to the stipulated frequency and mode, and transmit the distress relay message. The distress relay message should take the format: Mayday relay - Mayday indicates that there is a distress situation, but by adding the word 'relay' it indicates at once that it is not you in distress. This is......... - Your MMSI, name of vessel, and call sign. Text of message - Indicating identity and position of distressed vessel, nature of distress, assistance needed and number of persons on board if known.

Reception of a Distress Alert Relay

See a typical Mayday Relay transmitted via Inmarsat-A by JRCC PIRAEUS. When a Coast Station, RCC, or indeed another vessel, has received, and acknowledged a DSC distress alert it may elect to transmit a distress alert relay to other vessels. It can do this to all stations, a group of vessels, vessels in a particular geographic area, or to one specific vessel. Vessels receiving such a DSC alert should not acknowledge it by DSC, but instead should tune to the indicated frequency and mode and acknowledge it on the appropriate frequency on the same band as it was received. The procedure is: - a. Do not acknowledge by DSC. Tune the radio to the appropriate frequency and mode indicated in the relay call. b. Acknowledge the alert relay by voice or telex as appropriate. The format of the acknowledgement message is: Mayday - The word Mayday indicates that it is a distress message. Identity of Distressed vessel - This will be their MMSI, repeated three times. (Neither the name nor the call sign of the distressed vessel will have been indicated on the DSC alert. This is......... - Your identity, including your MMSI and/or name and call sign, repeated three times. Received Mayday. Over. If there is a Coast Station or Rescue Go-ordination Centre controlling the operation and they want you to help, they will call you back. Continue to monitor the frequency after you have transmitted the acknowledgement. If a DSC distress alert relay is received from another ship who has perhaps done an 'all stations' distress alert relay, the procedure is exactly the same. Do not acknowledge by DSC, instead acknowledge by voice or telex as appropriate, in exactly the same way as above.

Urgency Calls

An urgency call is for serious situations but not one where the ship or a person is in 'grave and imminent' danger. An example of an urgency call might be a vessel which has lost her engines and may be swept ashore in the next hour or so. The danger is grave, but not yet imminent, so the correct call is an urgency call rather than a distress call. A serious medical problem may warrant an urgency call for assistance or evacuation. An urgency call must not be broadcast to the world in general, it must be addressed to somebody, even if it is to 'all stations.'

Transmission of an Urgency Alert

DSC is used to alert other stations that an urgency message is about to be transmitted on a nominated frequency. The message itself is then transmitted on an appropriate frequency in the normal way. The procedure is: a Select 'urgency call' on the DSC control unit. b. Select on which band you want to transmit the DSC alert. c. Tune the radio to the DSC frequency of the chosen band. The DSC control unit may do this for you. d. Address the call to 'all stations' or to the MMSI of a particular Coast Station or vessel, or group of vessels. e. Key in the mode and frequency on which the urgency message will be transmitted. f. Transmit the DSC urgency alert.

Transmission of an Urgency Message

The radio can now be tuned to the emergency frequency of the band on which the DSC alert was sent for transmission of the urgency message. The format of an urgency message is: Pan Pan - The words Pan Pan indicate that the message is an urgency message, and as such, it should have priority over all but distress traffic. In the case of a request for medical assistance, the signal is Pan Pan Medico. Note that this is for medical assistance. A request for medical advice is not a Pan Pan. Address - All messages except distress must be addressed to somebody. A general call, perhaps for a tow, would be addressed to 'all stations'. A Pan Pan Medico is more likely to be addressed to a specific Coast Station, but under some circumstances that too could be addressed to 'all stations'. Identity - You must identify yourself in all transmissions. Any station that has received your urgency call on DSC has received your MMSI number as part of the call, so your identity should include the MMSI number as well as the name and call-sign of your vessel. Position - This may have been included in the DSC call, but it should be repeated here. If somebody is to help you, they need to know where you are. As in the distress message, your position as a distance and bearing from a prominent landmark may mean more to the receiving station than a latitude and longitude. Assistance - State what assistance is needed. Over - Terminate the message with Pan Pan, name of your vessel and call-sign, and the word 'over', so the other stations know you have finished, and they can respond. Once communications have been established with a suitable station, the subsequent traffic will normally transfer off the emergency frequency onto a working channel. If the communication is on VHF and the traffic is inter-ship, then channel 6 could be used. If the communication is with the Coastguard, then they will probably transfer operations to channel 67 in the UK or 22A in the USA. A Coast Station will move communications to one of their working channels.

Reception of an Urgency Alert

Vessels receiving a DSC urgency alert should not acknowledge by DSC but should switch to the indicated channel, normally the emergency frequency for the band where the DSC alert was received, and listen for the urgency message.

Safety Calls

A safety call is to warn other vessels of a particular danger. It may be some danger to navigation, such as a drifting derelict or it could be an urgent weather warning. Again, the call and the message must be addressed to somebody even if it is to 'all stations'. The DSC safety alert can be addressed to 'all stations', a particular Coast Station, a group of vessels, vessels in a specified geographic area, or an individual vessel. Safety messages if they are short (less than a minute in duration), and if they are primarily intended for vessels in the immediate vicinity can be transmitted on the emergency frequency, but any longer messages should be transmitted on a working channel. If the message is addressed to 'all stations' and is primarily intended for reception by other vessels in the vicinity, then VHF will be used both for the DSC alert and the subsequent traffic and the message itself could be transmitted on channel 6, the inter-ship safety channel, or channel 13, the bridge-to-bridge navigational safety channel. For example, if you were entering a narrow channel in thick fog and you wanted to warn other vessels of your location, you would do this on channel 13.

Transmission of a Safety Alert

As with the urgency call, DSC is used to alert a station or stations that there is a safety message about to be transmitted and advises them of the frequency and mode. To send a DSC safety alert: a. Tune the radio to the DSC frequency of the band on which it is desired to transmit the alert. b. Select 'safety call' on the DSC control unit. c. Address the call to 'all stations' or to the MMSI of a particular Coast Station or vessel or group of vessels. d. Key in the channel on which the urgency message will be transmitted. For most safety messages a working channel (such as VHF channel 13 or 6) is selected, rather than the emergency channel. e. Transmit the DSC safety alert.

Transmission of a Safety Message

The radio can now be tuned to the appropriate channel and the message transmitted. The message should be in the format: Securite - The word securite - pronounced securitay - indicates that this is a safety message. Address - The message must be addressed to somebody, very often in this case to 'all stations'. Identity - Give your MMSI, which will have been given in the DSC call, and the name of your vessel and/or call-sign. All transmissions must be identified, even if you are not expecting a reply. Message - The text of the safety message. Out- Terminate the transmission with the name/call-sign of the vessel, and the word 'out', which signifies the end of the transmission and that you are not expecting a reply. 'Over' signifies the end of that part of the transmission and that you are standing by for a reply. Although one hears it every day, it is incorrect to say 'over and out' - the two together are contradictory.

Reception of a Safety Alert

Another vessel may want to issue a safety message to warn of a danger to navigation, or perhaps a Coast Station has an urgent gale warning or navigational warning to transmit. The DSC alert may be addressed to 'All Stations', a group of vessels, vessels in a particular area, or it may be addressed to you specifically. If the DSC control unit recognises that the safety call concerns you, you will be alerted. a. Do not acknowledge by DSC, unless the alert is addressed only to your vessel. b. Tune the radio to the frequency and mode indicated in the call c. Listen for the transmitted message. Non-DSC equipped vessels should make distress, urgency, or safety calls on the emergency frequency of a suitable band prior to transmitting the message. The call is Mayday, repeated three times, for a distress call; Pan Pan repeated three times for an urgent call; or Securite repeated three times for a safety call. This should be followed by your vessel's name and/or call sign again repeated three times. Then the message should be transmitted in exactly the same way as if a DSC alert had been sent, e.g., MIPDANIO for distress. Under the GMDSS regulations there is no obligation for anybody to monitor any of the emergency frequencies other than the DSC frequencies, although hopefully somebody will hear you.