GOC GMDSS Exam common mistakes
GOC GMDSS Exam · Understand the traps and how to avoid them.
Treating the urgency signal as interchangeable with the distress signal, for example transmitting a PAN PAN call for a vessel taking on water, or using MAYDAY for a routine medical advice request.
Candidates memorise the three signal words as a list but never attach each to its distinct legal condition (grave and imminent danger requiring immediate assistance vs. a serious situation that may develop into danger vs. a navigational or weather warning), so the choice is made by gut feel under time pressure.
What to do instead
Build a three-column decision table and rehearse it with concrete scenarios: MAYDAY only when the vessel or person is threatened by grave and imminent danger and immediate assistance is required; PAN PAN for a serious situation short of that threshold (illness, breakdown, man overboard recovered, loss of propulsion but no immediate danger); SECURITE for safety of navigation or weather. For each practice scenario, state the condition first, then derive the signal word from the definition rather than recognising the scenario.
Confusing the role of DSC and radiotelephony in a distress alert, for example sending a distress alert with a working channel specified, or expecting the follow-on voice distress message to be optional after a DSC distress alert.
The DSC alert and the subsequent distress traffic are learned as separate topics, so the link between them (alert first, then switch to the stated radiotelephony or NBDP frequency for the distress message) is never internalised.
What to do instead
Write out the full distress sequence as a numbered timeline: DSC distress alert on 156.525 MHz (or the MF/HF DSC frequency) with nature of distress and position, wait briefly for DSC acknowledgement, then transmit the MAYDAY distress call and message on 156.8 MHz (or the paired HF frequency). Practise stating which frequency carries which element, and note that the alert should not specify a working channel.
Misassigning equipment to sea areas, for example claiming a Sea Area A2 vessel needs HF, or that A3 is satisfied by VHF plus MF/HF alone without a recognised satellite service.
The sea area definitions are memorised as a list of letters without the underlying logic that each area is defined by which shore-based or satellite communication facilities provide coverage, so candidates cannot derive the carriage requirement from the definition.
What to do instead
Anchor each area to its coverage mechanism: A1 within VHF coast station range (DSC on VHF ch 70), A2 outside A1 but within MF coast station range (DSC on 2187.5 kHz), A3 outside A1 and A2 but within coverage of a recognised mobile satellite service, A4 outside all of these (HF required). Then derive carriage requirements from the area rather than memorising a table, and test yourself by deriving A2, A3 and A4 from scratch.
Handling NAVTEX and EGC/SafetyNET as if they were the same service, for example saying NAVTEX covers polar regions, or that a NAVTEX receiver needs a specific transmitter selected manually each time, or that SafetyNET delivers MSI to a NAVTEX receiver.
Both deliver MSI, so candidates collapse them into one concept and lose the distinctions in coverage, addressing, and message structure that the exam tests.
What to do instead
Contrast them explicitly on four axes: coverage (NAVTEX is MF, nominally about 200-400 nautical miles from a coastal transmitter, so no polar or mid-ocean coverage; EGC via Inmarsat covers the ocean regions), addressing (NAVTEX by transmitter and message type via B1/B2 settings; EGC by ocean region and addressed to a group or to all ships), and message numbering and cancellation rules. Use a two-column comparison sheet and redraw it from memory.
Believing an EPIRB or SART is a transmitter of position to rescuers in the ordinary sense, for example saying a SART shows the vessel's position on shore radar, or that an EPIRB transmits on VHF and is received by nearby ships.
Both are emergency devices that 'help rescue', so their very different operating principles (406 MHz satellite alert with 121.5 MHz homing vs. 9 GHz radar transponder response) are blurred.
What to do instead
State the principle for each in one sentence: the 406 MHz EPIRB transmits a coded alert via the Cospas-Sarsat satellite system to a rescue coordination centre, with a 121.5 MHz signal for local homing; the SART is a radar transponder that, when interrogated by a 9 GHz radar, produces a line of dots on that radar screen to indicate the survival craft's bearing and range. Note that AIS-SART instead transmits AIS messages, and that neither device is a two-way communicator.
Assuming VHF and MF/HF DSC distress alerts reach rescue authorities directly, or that a DSC distress alert must always be acknowledged by another ship before any voice traffic is sent.
The relay and acknowledgement conventions are intricate and are often learned as isolated rules rather than as a procedure with a purpose, so candidates cannot reason about what to do when no acknowledgement arrives.
What to do instead
Learn the purpose: the DSC alert alerts coast stations and ships, and the follow-on voice message gives detail. Know that if no acknowledgement is received, a distress alert may be transmitted again after a short interval, and that ships should acknowledge and relay where appropriate. Practise the decision points: alert sent, acknowledgement received or not, follow-on message sent, distress traffic controlled by the station in charge.
Answering propagation questions with a memorised slogan, for example saying HF skywave range always increases with frequency, or that VHF is unaffected by antenna height, or treating the ionosphere as a single fixed layer.
Propagation is taught as a list of bands and ranges rather than as the interaction of frequency, ionospheric layer ionisation, time of day and season, and path geometry, so any question that changes one variable defeats the memorised answer.
What to do instead
Reason from the mechanism: skywave depends on refraction in the ionosphere, whose ionisation varies with solar elevation (day/night, season) and sunspot cycle; lower frequencies are absorbed more in daylight and higher frequencies may penetrate rather than refract. VHF is essentially line-of-sight, so range grows with antenna height. Draw the layers, mark which dominate by day and night, and predict the effect of each change before checking.
Treating battery capacity and charging as a simple number, for example saying a battery of a given ampere-hour rating will deliver that current for any duration, or ignoring the difference between a battery in good condition and one that passes a voltage check.
Capacity, discharge rate, depth of discharge and the need for periodic capacity testing are technical details that candidates skip in favour of the headline requirement that a reserve source of energy must be provided.
What to do instead
Learn that capacity is quoted at a specified discharge rate and that available capacity falls at higher currents and with age; learn that a reserve source must be capable of supplying the required load for the specified period and that batteries must be tested and maintained. Practise explaining why a voltage reading alone does not prove capacity, and what a capacity test demonstrates.
Keeping radio records and watchkeeping logs as a memory exercise, for example being unable to state what must be entered in the radio log, or confusing the distress, urgency and safety watch frequencies for VHF and MF/HF.
The regulatory material is perceived as dry paperwork, so it is skimmed, and the frequency and logging facts are never tied to the operational reason they exist.
What to do instead
Build a one-page reference you can reproduce: the distress and calling frequencies for VHF (ch 70 for DSC, ch 16 for voice), MF (2187.5 kHz DSC, 2182 kHz voice), the HF DSC and voice pairs, and the categories of entries required in the radio log (distress and urgency traffic, watchkeeping arrangements, tests, malfunctions, position reports where required). Test yourself by writing the page from memory, then check it.
Answering licensing and equipment-testing questions from general knowledge, for example assuming any crew member may operate the radio, or that a daily test of all equipment is required in every case, or that a malfunction need not be recorded.
Candidates treat the regulatory framework as background reading and never connect the operator certificate, the ship's radio licence, the required tests and the recording of defects into one compliance chain.
What to do instead
Learn the chain as a sequence: the ship holds a radio licence, the operator holds the appropriate certificate of competence, specified daily, weekly and monthly tests and checks are carried out as required, and results, defects and remedial action are recorded. For each item, ask who is responsible and where it is recorded, and practise describing the action to take when a required item fails a test.