GMDSS and VHF distress procedures

USCG Boatswain Manual Ch. 7 §7.2

Search and Rescue Distress signalling priorities: VHF Channel 16 MAYDAY with DSC if equipped (transmits identity and position automatically), EPIRB activation if a rapid response is critical, visual flares and signal mirror as backup. Always continue to transmit MAYDAY until acknowledged.

Bowditch Pub. 9 Ch. 30 §3000

Introduction The navigator’s chief responsibility is the safety of the vessel and its crew. Fulfilling this duty consists mostly of ascertaining the ship’s position and directing its course to avoid dangers. But accidents can happen to the most cautious, and the most prudent of navigators may experience an emergency which requires outside assistance. Distress incidents at sea are more likely to be resolved without loss of vessel and life if they are reported immediately. The more information that rescue authorities have, and the sooner they have it, the more likely it is that the outcome of a distress at sea will be favorable. Global distress communication systems, ship reporting systems, emergency radiobeacons, commercial ship tracking and other technologies have greatly enhanced mariner…

Bowditch Pub. 9 Ch. 30 §3002

Ship Carriage Requirements By the terms of the SOLAS Convention, the GMDSS provisions apply to cargo ships of 300 gross tons and over and ships carrying passengers on international voyages. Unlike previous shipboard carriage regulations that specified equipment according to size of vessel, the GMDSS carriage requirements stipulate equipment according to the area in which the vessel operates (and vessel size in some cases). These sea areas are designated as follows: 464 MARITIME SAFETY SYSTEMS Sea Area A1 An area within the radiotelephone coverage of at least one VHF coast station in which continuous Digital Selective Calling is available, as may be defined by a Contracting Government to the 1974 SOLAS Convention. This area extends from the coast to about 20 miles offshore. Sea Area A2 An…

Bowditch Pub. 9 Ch. 30 §3005

SafetyNET SafetyNET is a broadcast service of Inmarsat-C’s Enhanced Group Call (EGC) system. The EGC system (Figure 3005a) is a method used to specifically address particular regions or groups of ships. Its unique addressing capabilities allow messages to be sent to all vessels in both fixed geographical areas or to predetermined groups of ships. SafetyNET is a service designated by the IMO through which ships receive maritime safety information. The other service under the EGC system, called FleetNET, is used by commercial companies to communicate directly and privately with their individual fleets. SafetyNET is an international shore to ship satellitebased service for the promulgation of distress alerts, navigational warnings, meteorological warnings and forecasts, and other safety mess…

Bowditch Pub. 9 Ch. 30 §3007

Digital Selective Calling (DSC) Digital Selective Calling (DSC) is a system of digitized radio communications which allows messages to be targeted to all stations or to specific stations, allows for unattended and automated receipt and storage of messages for later retrieval, and permits the printing of messages in hardcopy form. All DCS calls automatically include errorchecking signals and the identity of the calling unit. Digital codes allow DSC stations to transmit and receive distress messages, transmit and receive acknowledgments of distress messages, relay distress messages, make urgent and safety calls, and initiate routine message traffic. Each unit has a MAYDAY button which allows the instant transmittal of a distress message to all nearby ships and shore stations. The location o…

Bowditch Pub. 9 Ch. 30 §3008

Using DSC A distress call consists of a Format Specifier--Distress; the MMSI code; the nature of the distress (selected from a list: fire/explosion, flooding, collision, grounding, listing, sinking, disabled/adrift, or abandoning ship; defaults to Undesignated); the time of the call, and the format for subsequent communications (radiotelephone or NDBP). Once activated, a distress signal is repeated automatically every few minutes until an acknowledgment is received or the function is switched off. As soon as an acknowledgment is received by the vessel in distress, it must commence communications with an appropriate message by radiotelephone or NDBP according to the format: “MAYDAY” MMSI CODE NUMBER AND CALL SIGN NAME OF VESSEL POSITION NATURE OF DISTRESS TYPE OF ASSISTANCE NEEDED OTHER IN…