GMDSS and the ETO: Who Does What Onboard?

What You Should Learn

• What equipment normally forms part of a GMDSS installation.
• Why operating the equipment and maintaining it are separate responsibilities.
• How GMDSS duties should be divided between the SMS, PMS and radio log.
• When an ETO can troubleshoot or repair a fault, and when specialist support is required.

A System Shared Between Departments

GMDSS is one of those systems that never belongs neatly to a single department.

Most of the controls are on the bridge. The deck officers use the radios, maintain the listening watches and complete the operational tests. Behind the console, however, the system depends on batteries, chargers, power distribution, antennas, cabling, earth connections and position data. When one of those fails, the ETO is usually the first person called.

That arrangement is perfectly workable. The problem comes when “call the ETO if it fails” gradually turns into “the ETO is responsible for GMDSS.”

Those statements do not mean the same thing.

An ETO may be responsible for maintaining parts of the installation without being the vessel’s designated GMDSS operator. Equally, a bridge officer can complete a successful daily test without proving that the reserve battery will still support the equipment for its required endurance.

A sensible onboard arrangement recognises both sides.

What Actually Belongs to GMDSS?

It helps to think of GMDSS as a set of communication functions rather than a fixed equipment list. The exact fit depends on the vessel’s sea areas, flag, size and operating status.

The installation will normally include:

• VHF radiotelephone equipment with digital selective calling.
• MF or MF/HF equipment where required for the operating area.
• A ship earth station using a recognised GMDSS mobile satellite service where applicable.
• Equipment for receiving maritime safety and search-and-rescue information, such as NAVTEX or an enhanced group call service.
• A float-free 406 MHz EPIRB.
• Radar SARTs or AIS-SARTs.
• Portable two-way GMDSS VHF radios for survival craft.
• Automatic position information from a navigation receiver.
• The reserve batteries, chargers, antennas, cabling and emergency lighting needed to keep the installation working.

The required combination changes across sea areas A1 to A4. The current equipment matrix is set out in IMO COMSAR.1/Circ.32/Rev.3.

This boundary matters on modern yachts because many other communication systems are fitted nearby. VSAT, Starlink-style broadband, cellular routers and internal crew radios may be operationally important, but they are not automatically part of GMDSS. Normal AIS, LRIT and SSAS installations also have separate purposes, although an AIS-SART may form part of the survival-craft equipment.

The test is not whether a device communicates with shore. The question is whether it forms part of the vessel’s approved distress and safety communications arrangement.

Where the Regulations Leave the ETO

SOLAS Chapter IV describes what the ship must be capable of doing. It covers the radio installation, required watches, reserve energy, maintenance arrangements, qualified radio personnel and radio records.

STCW then deals with competence. Chapter III covers the ETO, while Chapter IV covers GMDSS radio operators. These are related but separate qualifications.

This is the point most likely to be missed onboard.

An ETO certificate does not automatically make its holder a GMDSS radio operator. If an ETO is expected to conduct radio watches, transmit test calls or perform operational radio duties, that person must also hold the appropriate radio-operator qualification and be assigned the duty onboard.

The reverse is also true. Holding a General Operator’s Certificate or Restricted Operator’s Certificate does not qualify a bridge officer to open equipment, carry out electronic repairs or perform maintenance reserved for an authorised technician.

For UK ships, MCA guidance recognises three ways of maintaining GMDSS availability:

• Duplication of equipment.
• Shore-based maintenance.
• At-sea electronic maintenance.

The vessel may use one method or a combination, depending on its operating area and the arrangement accepted by the Administration. If at-sea electronic maintenance forms part of that arrangement, the person doing the work must be suitably qualified and the ship must carry the necessary technical information, tools, test equipment and spares. MCA MGN 641 Amendment 1

Not every ETO is automatically cleared for that work. MCA certification can include a limitation stating that the holder is not permitted to maintain radio equipment. The ETO’s CoC, radio-maintenance training and any vessel-specific authorisation therefore need to be checked rather than assumed. MCA MSN 1860 Amendment 1

Put the Responsibility in the Right Place

The division of responsibilities belongs in the vessel’s Safety Management System.

The SMS should identify who operates the equipment, who completes each test, who receives a defect report and who has authority to engage a service provider. It should also establish the point at which the Master, company, flag Administration or recognised organisation must become involved.

The Planned Maintenance System has a different job. It schedules and records the technical work that supports the SMS arrangement. Battery-capacity tests, charger inspections, terminal checks, antenna inspections and service intervals may all sit in the PMS, but the PMS should not be relied upon to define command responsibility.

The GMDSS radio log provides the operational record. It captures radio watches, distress and safety traffic, prescribed equipment checks, failures and the Master’s review or agreement where required.

In practical terms:

The names and job titles may vary between yachts. What matters is that the split is written down and understood before a fault occurs.

Routine Checks Do Not All Prove the Same Thing

The routine test schedule is another area where responsibilities can become blurred.

For UK large yachts of 300 GT or more, MCA guidance describes daily, weekly and monthly radio checks. The bridge will normally carry out and record the operational side of these checks.

The daily routine includes an internal DSC test without radiating a signal, a check of the radio batteries and confirmation that any required printer is ready. Weekly checks include a DSC test call when the yacht is within range of a suitable coast station.

The monthly routine goes further. It includes the EPIRB self-test, SART or AIS-SART test, portable survival-craft radios, aerials and the security and condition of the radio batteries and their connections.

The ETO may help with many of these checks, particularly where the result indicates a technical problem. That does not mean the bridge should simply hand the complete routine to the technical department. The operator still needs familiarity with the installed equipment and must be able to recognise and report a failure.

Battery testing shows why the distinction matters.

A daily voltage or charger indication says something about the battery’s immediate state. It does not prove available capacity. A tired battery bank can sit at a convincing float voltage and collapse once a meaningful load is applied.

IMO guidance therefore calls for radio-battery capacity to be checked at intervals not exceeding 12 months and while the vessel is not at sea. The method must test the reserve supply itself, with the main and emergency supplies—and the battery charger—properly excluded from the result.

That is technical work. It needs an approved procedure, safe isolation, suitable test equipment and an understanding of the actual connected load. The test record should remain in the PMS or technical file, while the resulting availability or defect is communicated to the Master and reflected in the appropriate radio records.

When the ETO Is Called to a Fault

The first question should not be, “Which box has failed?”

Start by asking what GMDSS function has been lost. Can the vessel still transmit a distress alert? Can it receive maritime safety information? Is the problem limited to one handset, or has a common power supply affected several pieces of equipment?

That conversation needs to happen with the bridge. The operator knows what the equipment was doing when it failed, and the ETO needs that information before isolating power or disturbing the installation.

From there, the technical investigation usually begins with the supporting systems.

Check the normal, emergency and reserve supplies. Look at charger condition, battery alarms, protective devices and changeover arrangements. Confirm that position and time are reaching the radio equipment. Inspect accessible antenna feeders, connections and earth arrangements. Consider whether recently installed electronics, LED drivers or transmitters could be introducing interference.

Configuration deserves particular care. MMSIs, call signs, satellite identities and EPIRB codes are tied to the ship’s licence and registration. They should not be altered casually during fault-finding. Software updates and replacement equipment can also affect type approval and survey status.

There should be a clear stopping point. Sealed equipment, live RF measurements, EPIRB servicing, manufacturer-controlled programming and work requiring calibrated specialist instruments may belong with an approved shore-based maintainer.

For UK ships using shore-based maintenance, the provider should meet the MCA’s requirements for GMDSS maintenance companies. The ETO’s role is then to produce a useful defect history, provide drawings and access, attend the work and make sure the final handover is complete—not to duplicate the surveyor’s or service company’s authority. MCA MGN 417 Amendment 1

The Battery That Passed the Morning Check

Consider a familiar situation.

The bridge completes the morning radio check. The charger indication is normal, the battery voltage looks healthy and the entry is made in the radio log. During a later inspection, the ETO finds heat discolouration at a battery connection and discovers that the annual capacity test is overdue.

The bridge entry was not necessarily wrong. The equipment passed the check that was performed. The technical inspection has now revealed another problem that the daily routine was never designed to prove.

The ETO should document the finding, notify the Master and establish whether the required reserve-power capability can still be demonstrated. That may lead to a controlled capacity test, battery replacement or shore assistance.

What the ETO should not do is quietly repair the connection, clear the PMS task and assume the matter is closed. Once the finding calls the availability of a required GMDSS function into question, it has become an operational issue for the Master and company.

Testing Without Creating Another Problem

Distress equipment cannot be tested like ordinary electronics.

A live distress transmission should never be used as a troubleshooting shortcut. EPIRBs must be checked through the prescribed self-test mode or with suitable test equipment. Annual testing is normally performed by trained and approved personnel, while the more extensive shore-based maintenance must be completed at the interval set by the flag Administration and no later than five years under the IMO guidance.

The same caution applies to DSC testing. A test call is an operational transmission and should be conducted by a qualified operator using the correct procedure. If an accidental distress alert is transmitted, it must be cancelled through the proper route and reported to the relevant rescue coordination centre.

Applicability

The exact requirements depend on the yacht’s flag, gross tonnage, private or commercial status, passenger numbers, operating area, surveyed equipment fit and safe-manning arrangements.

Under the 2024 REG Yacht Code Part A, yachts of 300 GT and above follow the cargo-ship requirements of SOLAS Chapter IV and COMSAR/Circ.32. Yachts below 300 GT also follow much of that framework, but with specific differences in maintenance and reserve-energy requirements. REG Yacht Code Part A, 2024 edition

The vessel’s own flag instructions, Record of Equipment, radio licence, statutory certificates and SMS must therefore be checked before turning this guidance into an onboard procedure.