12.2 Emergency Distress Equipment: EPIRB, SART, Navtex & Pyrotechnics

12.2 Emergency Distress Equipment: EPIRB, SART, Navtex & Pyrotechnics

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406 MHz Emergency Position Indicating Radio Beacons (EPIRB)

An Emergency Position Indicating Radio Beacon (EPIRB) is an autonomous, buoyant transmitter designed to alert SAR authorities via satellite when a vessel is in grave distress.

The COSPAS-SARSAT Satellite System

EPIRBs operate through the international COSPAS-SARSAT satellite network:

• LEOSAR (Low Earth Orbit Search and Rescue): Satellites at 850–1,000 km altitude calculating beacon positions via Doppler shift frequency analysis as they transit overhead.
• GEOSAR (Geostationary Orbit Search and Rescue): Satellites at 36,000 km altitude over the equator providing instantaneous alerting between 70°N and 70°S without Doppler positioning.
• MEOSAR (Medium Earth Orbit Search and Rescue): Payloads aboard GPS, Galileo, and GLONASS navigation constellations at ~20,000 km altitude, combining instant alerts with multi-satellite Doppler and time-difference-of-arrival positioning.

Frequencies & Operating Characteristics

The core satellite-alerting and local-homing functions use:

1. 406 MHz Digital Distress Band (406.0 to 406.1 MHz):
   • Emits a 5-Watt digital burst lasting 0.5 seconds every 50 seconds.
   • Transmits a coded beacon identity and country code; SAR authorities use that identity to retrieve registration records ashore. The records themselves are not broadcast by the beacon.
   • GNSS-enabled (GPS/Galileo) EPIRBs encode exact satellite coordinates into the burst, achieving accuracy within 100 metres within minutes of activation.
   • Beacons without GNSS can be located independently by MEOSAR using arrival-time/frequency differences, as well as by LEOSAR Doppler processing. They are not restricted to waiting for a LEOSAR pass; location time and accuracy depend on the available detections.
2. 121.5 MHz Analogue Homing Frequency:
   • Emits a continuous low-power (50 mW) swept tone.
   • Enables SAR aircraft and RNLI all-weather lifeboats using VHF Direction Finding (VHF-DF) equipment to home in directly during the final visual approach.

Hydrostatic Release Units (HRU) & Maintenance

Float-free brackets incorporate a Hydrostatic Release Unit (HRU):

• Automatic Deployment: Water pressure activates the HRU at a depth of 1.5 to 4.0 metres, severing the plastic retaining bolt and allowing the buoyant beacon to float free.
• Water Switch Contacts: Saltwater bridges external electrodes, automatically activating transmission upon immersion.
• Manual Activation: Beacons can be released manually from the bracket by pulling the locking pin and toggling the switch to ON.
• Maintenance Lifecycle: HRUs expire every 2 years. Replace the beacon battery by its marked expiry date, after emergency activation, or when the manufacturer’s test/service instructions require it. Use an approved service provider. Keep the beacon registration record current and promptly update changes.

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UK 406 MHz Beacon Registration (MCA) vs. Ofcom Ship Radio Licensing

A critical legal and operational distinction tested in Yachtmaster examinations is the difference between registering a distress beacon and licensing ship radio equipment in the United Kingdom:

1. The UK Beacon Registry (Maritime and Coastguard Agency - MCA)

• Statutory Mandate: The Merchant Shipping (EPIRB and PLB Registration and Radiocommunications) (Amendment) Regulations2026, with the Watercraft Order2023, require registration of EPIRBs and406MHz PLBs fitted/carried on UK-registered ships and hovercraft, and watercraft within scope. MGN665 Amendment1 explains the application; MSN1924 specifies the particulars. Register UK-coded beacons with the MCA. Ownership by a UK resident alone is not this maritime carriage test.
• Registration Method: Registration is completed online via the dedicated, free UK government portal: gov.uk/register-406-beacons.
• Vital Operational Purpose: When an EPIRB or PLB activates, the alert carries a beacon identity through the Cospas-Sarsat network to the appropriate SAR authorities. The HEXidentity is15characters for first-generation beacons and23for second-generation beacons. Duty officers instantly access the registry database to retrieve the vessel's name, type, emergency point-of-contact phone numbers, usual cruising grounds, and onboard survival gear. If an unverified alert sounds, calling shore contacts confirms within minutes whether the vessel is actively at sea or if the beacon was knocked accidentally in a marina berth—preventing unnecessary search taskings while dramatically accelerating response for live casualties.
• Mandatory Updates: Keep registration details accurate and update them promptly when emergency contacts, telephone numbers, vessel ownership or beacon status change. Check the record before a passage; registration is separate from battery or HRU expiry.

2. Ofcom Ship Radio Licensing

• The Office of Communications (Ofcom) is the UK's telecommunications and radio spectrum regulator.
• Under the Wireless Telegraphy Act, Ofcom issues the Ship Radio Licence (or Ship Portable Radio Licence) and formally assigns the vessel's official Call Sign and 9-digit MMSI.
• AIS-SARTs, MOB devices and EPIRB-AIS units use manufacturer-assigned identities, commonly beginning970,972and974 respectively; these are not the ship's MMSI. A DSC-equipped personal device may separately require the intended ship's MMSI as a call destination. Follow its programming instructions and record the equipment on the appropriate radio licence.

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Search and Rescue Transponders (SART)

A Search and Rescue Transponder (SART) locates survival craft during search operations:

1. The 9 GHz Radar SART

A Radar SART operates exclusively on the 9 GHz marine radar band (3 cm wavelength, X-band radar).

• Battery Endurance: Minimum 96 hours standby, followed by 8 hours continuous transmission when interrogated by an X-band radar pulse.
• Radar Screen Signature:
  • Range > 1 NM: Paints a line of 12 distinct blips extending radially outwards ~8 NM. The innermost blip gives an approximate bearing/range to the SART; the response can plot beyond its true range.
  • Range < 1 NM: At close range, replies received through radar sidelobes can broaden the dots into arcs, indicating that the SART is nearby.
  • Very Close: Arcs may become complete concentric rings around the radar display origin. This indicates proximity, not an exact fix at the rings’ centre.

2. The AIS SART

An AIS SART operates on VHF AIS frequencies (161.975 / 162.025 MHz):

• Broadcasts AIS Message 1 and Message 14 containing internal GNSS coordinates.
• Transmits a unique 9-digit MMSI commencing with prefix 970 (e.g., 970xxxxxx).
• Displays on chartplotters/ECDIS as a circle containing an X labelled "SART ACTIVE".

SART Elevation & Radar Horizon

• SARTs must be mounted at least 1.0 metre above sea level using a telescopic pole or dedicated liferaft canopy sleeve.
• Greater antenna elevation improves detection range. Ship radar height, the deployed SART, obstructions and conditions all affect reception; a unit lying low in the water has much poorer range. Continue a systematic visual and radar search.

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Navigational Telex (Navtex) Coastal Information System

Navtex is an automated direct-printing system distributing Maritime Safety Information (MSI):

• 518 kHz (International): Broadcasts exclusively in English worldwide.
• 490 kHz (National): Broadcasts in national languages or specialized local regional reports.
• Message Preamble (ZCZC B1 B2 B3 B4):
  • B1: Transmitter station identifier (A–X) operating on allocated 10-minute time slots every 4 hours.
  • B2: Subject indicator:
    • A (Navigational warnings), B (Meteorological warnings), D (SAR distress traffic), and L (Additional nav warnings) are mandatory and non-rejectable.
    • Other subjects can be filtered, for example C (ice reports), E (meteorological forecasts) and F (pilot/VTS service messages).
  • B3 B4: Message number (01–99). 00 overrides station and subject selections and is printed/displayed whenever received; its use is strictly controlled and is not for routine or service messages.

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Marine Pyrotechnics: Flare Specifications & Handling

SOLAS pyrotechnics provide visual signalling when electrical systems are disabled:

Safe Handling, Storage & Disposal

1. Firing Direction: Follow the instructions printed on each device. Parachute rockets are normally launched vertically with a clear path overhead; hold hand flares downwind, outside the canopy and away from people, sails and buoyancy tubes.
2. Protective Gear: Wear leather gloves and eye protection; never look down the barrel.
3. Liferaft Safety: Hold flares outside canopy over water to prevent melting buoyancy tubes.
4. Expiry & Disposal: Check each device’s printed expiry date. Never dump flares, put them in household waste or fire them for disposal. Arrange an authorised third-party disposal service; HMCoastguard no longer accepts private individuals’ unwanted flares.

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Abandonment, Liferafts and Helicopter Recovery

Abandon only when the vessel no longer offers the safer refuge. Brief the crew, send distress and prepare lifejackets, warm clothing and the grab bag. Keep the raft accessible and serviced to its maker’s instructions. Secure its painter to a suitable strong point before launching; deploy and inflate as instructed, then bring it alongside. Board directly if possible, count everyone and release/cut the painter when necessary to clear the sinking or dangerous vessel. Stream the raft’s drogue, close the canopy, bail, attend to casualties and keep communicating with rescuers.

For helicopter recovery, maintain the requested radio watch and follow the aircrew’s course, speed and winching instructions. Secure loose gear and clear the working area. A hi-line guides the winchman or lifting device: tend it as directed, keep slack clear and never secure it to the yacht or a person. Allow the static-discharge lead/device to ground before touching the hook as instructed. Keep lights out of the pilot’s eyes. The helicopter crew controls the transfer; report promptly if you cannot comply.

Sources: RYA liferaft guidance, RNLI abandonment steps, IMO vessel/helicopter procedures, section16.

Coastguard Safety Information and Shore Contacts

Older syllabus references to the Coastguard boat-safety identification scheme concern CG66. It was superseded by UK RYA SafeTrx, whose app and website closed on 31 December 2025. Do not rely on either as a current trip-tracking service. HM Coastguard continues its emergency response service.

Leave a trusted shore contact your vessel description, route, people aboard, expected return and what to do if overdue. Update them when plans change and confirm safe arrival. They should call 999 and ask for the Coastguard if concerned that you are overdue. Carry appropriate independent distress communications; a shore plan cannot itself transmit an alert from the yacht.

Sources: MCA CG66/SafeTrx history, current closure and safety advice.

Seamanship Traps & Examination Pitfalls

1. MCA Registration vs. Ofcom Licensing: Never assume that licensing an EPIRB on an Ofcom Ship Radio Licence automatically registers it with rescue authorities. Beacons must be independently registered with the UK MCA Beacon Registry under MSN 1924 (M+F).
2. Radar SART Bands: Radar SARTs operate exclusively on 9 GHz (3 cm X-band); they do not respond to 3 GHz (10 cm S-band) radar.
3. Mandatory Navtex Subjects: A, B, D, and L are non-rejectable.
4. White vs. Red Flares: White flares indicate collision warning (IRPCS Rule 36), never distress.