Distress Calls
	We must remember that a distress call should only be made when a vessel or person is in grave and imminent danger. (Under GMDSS a person overboard is a distress situation, before GMDSS this was classed as an urgency situation.) If the danger is not grave and imminent, then an urgency call should be made instead. A distress call should only be made on the direct orders of the Master. With distress calls, we need to know: 1. How to send a distress alert 2. What to do if we receive a distress alert 3. How to relay a distress call from another vessel 4. What to do if we hear a distress call being relayed.
	Transmission of a Distress Alert
	See a typical Distress Alert to Circular Area transmitted by United Kingdom Coastguard. Although equipment varies, the DSC control unit will have a distress button clearly labelled, and normally protected by a safety flap. To send a distress alert: a. Press the distress button to initiate the distress mode. b. Select the band on which the alert is to be transmitted, VHF, MF, or one of the HF bands. c. The radio must be tuned to the DSC distress channel of the chosen band. The DSC control unit may do this automatically, but if not, then it must be done manually. e. If time allows, key in or select from the on-screen menu, the nature of the distress, the vessel's position (if it is not automatically included from a GPS receiver) and the time in UTC when the position was valid. e. If time allows, key in or select the nature of the distress, e.g. grounding, abandon ship, fire, piracy attack etc. f. Select type of subsequent communication - voice or telex, and the frequency to be used. g. Transmit the distress alert - usually by a second prolonged push of the distress button or by pushing another button, depending on the equipment. h. Prepare for the subsequent traffic by tuning the radio to the emergency frequency of the band used to transmit the alert. Many DSC control units will do this automatically. The receiver for the DSC control unit will continue to monitor the DSC channels for the reception of a DSC distress acknowledgement. For alerts sent by VHF or MF, if the DSC control unit can automatically tune the radio to the correct frequency, it will repeat the transmission of the distress alert at about four-minute intervals until it receives a DSC acknowledgement or the operator cancels the alert. If the radio has to be manually tuned, then any repeat alerts will have to be sent manually by repeating the above steps. On HF, the propagation conditions between the various bands vary greatly. Transmission on more than one HF band will increase the chance of it being received by a Coast Station. This can be achieved in one of two ways: 1. Transmit the distress alert twice, on one HF band, with a 45-second gap. This gives the best chance for a scanning receiver to receive the alert. Then wait a few minutes to see if it is acknowledged by a Coast Station. If there is no DSC acknowledgement received within 3 minutes, switch to another HF band and try again. This process is repeated until a DSC acknowledgement is received. 2. Most DSC control units will allow you to make a series of distress alerts, on several or all of the HF bands, with little or no pause between them. The operator then watches to see on which band the DSC acknowledgement is received and then proceeds accordingly. If time permits, the first method, a systematic attempt on the most likely bands, will usually make it easier to find and select the best band for the working of the distress traffic. Which frequency is chosen obviously depends upon the anticipated propagation between the calling station and the desired Coast Station. Under many conditions 8414.5 kHz is a good one with which to start. If it is daylight, and the Coast Station is far away, a higher frequency might be better. At night, or if the vessel is close to an A2 area, then a lower frequency could be more suitable. Whichever band permits the DSC alert to be received is likely to support the distress traffic. However, if time is short, then the so-called 'multi-hit' method gives the best chance of having at least the alert picked up. Even if there is no time to follow up the alert with any distress traffic, if the alert has been sent properly the Coast Station will have your identity, the fact that you are in distress, the nature of the distress and your position. Even if they cannot establish voice or telex contact, the alert should be enough to initiate search and rescue. When sending an HF DSC alert, if time permits, an MF and VHF DSC alert should be sent as well to alert any vessels that may be in the area but which will not hear the HF alert because of the skip zone. While waiting for a DSC acknowledgement, you should also listen on the emergency frequency of the band on which the alert was transmitted for any vessels acknowledging reception of the alert by voice. When a DSC acknowledgement is received, or if any station is heard acknowledging the alert on the emergency frequency, transmit the distress message.
	TRANSMISSION OF THE DISTRESS MESSAGE
	The ITU recommend that telex is used for distress traffic wherever possible because there is a written copy of all communications, but if time is short, voice may be quicker. Tune the radio to the voice or telex emergency frequency of the band on which the alert was transmitted or the band on which an acknowledgement was received. Voice emergency frequencies are: VHF- Channel 16 MF - 2182 kHz HF - 4125 kHz, 6215 kHz, 8291 kHz, 12290 kHz, 16420 kHz. Telex emergency frequencies are: VHF- Not applicable. MF - 2174.5 kHz HF - 4177.5, kHz, 6268 kHz, 8376.5 kHz, 12520 kHz, 16695 kHz A distress message is the only type of traffic that does not have to be addressed to somebody. A distress message is 'broadcast' to anybody who may be listening. Any distress message should follow the standard format, using the mnemonic MIPDANIO. Mayday - Mayday indicates that it is a distress message. Under GMDSS there is no need to repeat the 'Mayday' three times as we did before GMDSS. That is the call and the call has already been made by DSC. Identity - This is ........... Your MMSI number, repeated three times. This is the only identification known to other stations who have received the DSC call. If there is time, the call sign and name of your vessel can be included. Position - This may have been included in the DSC alert, but should be given again. In coastal waters a range and bearing from a prominent feature may mean more to receiving stations than a latitude and longitude from the GPS. Distress - The nature of the distress, e.g. aground, sinking, piracy/armed attack, fire/explosion, flooding, collision, listing, disabled and adrift, abandoning ship, assistance required, man overboard, etc. Assistance requested - For example, need help abandoning ship, or a tow off a lee shore etc. Number of people on board - It is useful for rescuers to know how many people are to be rescued, so that they know what sort of vessel to send and how many people they must search for in the case of an abandoned vessel. Information - Any other information which will help the rescuers, e.g. wind and sea conditions, visibility, numbers of injured persons etc. Over - Terminate the transmission with the MMSI number and/or call sign and name of the vessel and the word 'over', so that other stations know that the transmission has ended, and they may reply. Remember to release the key on the microphone, otherwise you will not be able to hear any reply. If the 'MIPDANIO' format is followed, you are sure to send all the required information at the first attempt, and if for some reason the message cannot be completed, then the most important bits have been sent first. On MF or HF, if transmitting the Distress Message by voice select J3E mode. If the distress traffic is to be conducted on telex, unless otherwise instructed by a Coast Station use the Forward Error Correction mode. FEC allows other stations to copy the traffic, as well as the station for whom it is intended. Start the transmission with at least one carriage return, a line feed, a letter shift and either the word Mayday, or SOS.
	Ends