IMO: Guidance for responding to DSC distress alerts

This circular contains a procedure to be followed by radio personnel on board ships when responding to VHF, MF and HF distress alerts, in accordance with chapter IV of the International Convention for the Safety of Life at Sea, 1974.

Flow diagrams 1 and 2 in the annex are recommended to be displayed on ships’ bridges as A4 size posters.

Member Governments are invited to bring the annexed Procedure to the attention of seafarers and all other parties concerned.

This circular becomes effective on 1 January 2024, superseding COMSAR/Circ.25 as from that date.

Distress relays

• Radio personnel serving on ships should be made aware of the consequences of transmitting a distress call relay and of routeing a DSC distress alert relay to destinations other than coast stations (CS).
• The number of unintended activations of DSC distress alerts and DSC distress alert relays creates extra workload and confusion for (M)RCCs and also causes delay in the response-time. The original distress alert from a ship in distress should not be disrupted by other ships, by transmitting a DSC distress alert relay.
• Recommendation ITU-R M.541 on Operational procedures for the use of digital selective-calling equipment in the maritime mobile service identifies only two situations in which a ship would transmit a distress call relay (distress alert relay):

1. On receiving a distress alert on an HF channel, which is not acknowledged by a coast station within five minutes. The distress call relay should be addressed to the appropriate coast station (annex 1, paragraph 3.4.2 and annex 3, paragraph 6.1.4); and
2. On knowing that another ship in distress is not itself able to transmit the distress alert and the master of the ship considers that further help is necessary
3. The distress call relay should be addressed to “all ships” or to the appropriate coast station (annex 3, paragraph 1.4).

• In no case is a ship permitted to transmit a DSC distress alert relay on receipt of a DSC distress alert on either VHF or MF channels.
• Distress calls relay on HF channels should be initiated manually.
• Compliance with operational and technical provisions above would prevent
  transmissions of inappropriate distress calls relay.

All coast stations call

• Recommendation ITU-R M.493 on Digital selective-calling systems for use in the maritime mobile service provides for “group calls” an address consisting of the characters corresponding to the station’s maritime mobile service identity (MMSI) and a number of Administrations have already assigned a “group call” MMSI to their coast stations in addition to the coast station’s individual MMSI.
• By multilateral agreements, a “group call” MMSI could be assigned to all coast stations of a specific region, e.g. an RCC area, and could comply with IMO’s requirement without need of introducing further modifications to GMDSS equipment.
• An alternative method to implement an “all coast stations” call without the need to modify Recommendation ITU-R M.493 could be to use the reserved MMSI worldwide as an address for all coast stations, in accordance with Recommendation ITU-R M.585 on Assignment and use of identities in the maritime mobile service. However, this solution is not applicable to MF or HF coast stations and would also require a modification of the set-up at each VHF coast station participating in the GMDSS.

Authorization

• It should be noted that on ships, distress alerts, distress acknowledgements and distress call relays can only be transmitted with the permission of the master of the ship.

Flow diagrams

• The simplified flow diagrams 1 and 2 describe actions to be taken aboard ships upon receipt of distress alerts from other ships. Administrations distribute these flow diagrams widely to ships and training institutions.
• Member Governments are invited to bring the above guidance and the attached flow diagrams to the attention of their shipowners, seafarers, coast stations, RCCs and all others concerned.