GMA OOW Deck common mistakes
GMA OOW Deck · Understand the traps and how to avoid them.
Calculating a great-circle or Mercator sailing distance and initial course but reporting the final course without applying conversion between quadrantal and 360-degree notation, so the answer points the wrong way (e.g. giving N45W as 045 instead of 315).
Candidates learn the formulas (haversine, Mercator ratio, plane sailing triangles) in isolation and practise them until the arithmetic is automatic, but the exam marks the stated bearing, not the intermediate values. Under time pressure the last step, converting the quadrant letter into a true bearing, is the one skipped.
What to do instead
Adopt a fixed answer template: latitude difference, departure, then course as both quadrantal and true bearing, then distance, and check the true bearing against a sketch of the two positions on a plotting sheet. Practise ten mixed north/south, east/west cases until the conversion is part of the routine rather than an afterthought.
Treating variation and deviation as interchangeable or applying them with the wrong sign, so a compass-to-true conversion is off by twice the error. For example, adding westerly deviation when converting from compass to true.
The mnemonic 'Cadbury Dairy Milk Gives Children Headaches' (compass, deviation, magnetic, variation, true) is memorised as a sequence but not as a direction rule. Candidates also forget that deviation depends on the ship's heading and must be read from the deviation card for the compass heading, not the true heading.
What to do instead
Write the conversion chain out in full every time, with an explicit easterly-add/westerly-subtract note at each arrow, and work from compass heading through deviation to magnetic, then variation to true. When the question gives a deviation table, interpolate for the compass heading actually being converted and state the interpolated value.
Answering a stability question with an initial (small-angle) formula such as GM = KM - KG when the heel exceeds about 10 degrees, or quoting GZ from the wall-sided formula for a vessel with large free surface or a box-shaped deck cargo.
The small-angle formulae are the ones drilled in class and are easy to apply, so candidates reach for them regardless of the angle stated in the question. The assumption behind them (metacentre fixed, GZ proportional to sin of heel) is not usually restated in the question, so nothing prompts a check.
What to do instead
Before calculating, classify the problem: small angle (under roughly 10 degrees) use GM and GZ = GM sin(theta); large angle use the cross curves or the stability booklet GZ table. State the assumption explicitly in the answer and, where free surface exists, apply the free surface correction to KG before computing GM.
Computing a loading or ballast condition and reporting only the final draught, omitting the check on transverse list, longitudinal trim, and the resulting stresses (shear force and bending moment) against the allowable curve.
Draught and deadweight arithmetic feels like the whole question, and the stress check requires reading a second set of curves that candidates find harder to use. In practice the examiner is testing whether the officer would actually let the ship sail in that condition.
What to do instead
Structure every loading answer as four checks: deadweight and draught, list (transverse moments about centreline), trim (LCG against LCB), and hull stress against the allowable shear force and bending moment curves. If any check is outside limits, say so and propose a redistribution of cargo or ballast.
Describing a tropical revolving storm avoidance manoeuvre by 'steering to keep the wind on the same bearing' without first identifying the hemisphere and the vessel's position relative to the storm track, and without stating the dangerous and navigable semicircles.
The rule of thumb is memorable and gets repeated, but it only works once the hemisphere and the vessel's quadrant relative to the track are known. Candidates skip that step because the question often gives wind direction only, and they do not practise deriving the bearing of the centre from it.
What to do instead
Answer in a fixed order: determine hemisphere from the wind veering or backing, plot the bearing of the storm centre (wind direction plus roughly 90 degrees to the right in the Northern Hemisphere, left in the Southern), classify the semicircle, then state the course to steer and speed to maximise distance from the track. Name the dangerous semicircle explicitly.
Quoting a GMDSS distress procedure from memory without the correct sequence and content, for example sending a DSC distress alert without the nature of distress, or failing to follow the alert with a Mayday radiotelephony call on the correct frequency.
The procedure has several steps (alert, then distress call and message, then silence and traffic) and candidates compress it. They also mix up the DSC alert format fields with the voice Mayday content, and forget that a ship-to-shore alert must still be followed by a voice Mayday on the associated radiotelephony frequency.
What to do instead
Write the DSC distress alert fields in order (format, nature of distress, position, time, subsequent communication) and then the Mayday call content (Mayday three times, name three times, Mayday plus name once, position, nature of distress, assistance required, persons on board, other information). Practise on a real or simulated DSC controller so the key sequence is muscle memory.
Describing an emergency drill or muster as a list of actions without assigning responsibility, timing, or the reporting chain, so the answer never says who does what, in what order, and who reports to the master.
Candidates revise the drill as a narrative of events rather than as a set of roles. The examiner is looking for the officer's understanding of the muster list, the on-scene commander, and the communication to shore, not a generic description of a fire or abandon-ship.
What to do instead
Answer drills in role terms: alarm and initial response, muster and headcount, team leaders and their tasks, boundary cooling or lifeboat preparation as applicable, bridge communications including urgency or distress alerting, and the master's decision points. State the timing expectations and the person responsible for each report.
Answering a COLREGS question by naming the rule number and paraphrasing the principle, but not stating the action required (alteration of course and/or speed, which vessel gives way, what the stand-on vessel may and must do) for the specific crossing, overtaking or head-on situation given.
Rule numbers are easy to memorise and give a false sense of a complete answer. The scenario in the question usually contains a detail (a vessel restricted in ability to manoeuvre, a traffic separation scheme, a vessel in sight of another) that changes which rule applies, and candidates miss it.
What to do instead
For each scenario, identify the vessels by category first, then state the applicable rule and the required action, including the timing ('early and substantial'), the aspect (give-way or stand-on), and any modifying rule. Where a special category vessel is present, say how it changes the ordinary obligations.
When asked about a machinery or propulsion problem at deck officer level, giving an engineer-level diagnosis (fuel injection timing, bearing clearances) or a purely administrative answer, instead of the bridge-level response and the limitations it imposes on the ship.
The syllabus boundary is unclear to candidates, so they either overreach into engineering detail they cannot verify or retreat into 'inform the chief engineer'. The question is testing whether the officer can manage the ship's operation and safety around a degraded machinery state.
What to do instead
Answer at the interface: what indication the bridge would see, what immediate precautions follow (reduced speed, tug or pilot arrangements, anchor readiness, drift and set assessment), what the master must be told, and what the ship must not attempt until the chief engineer confirms. Keep diagnosis to 'report the symptom and await advice'.
Treating a cargo stowage question as a list of segregation requirements without applying the IMDG segregation table to the specific classes given, and without addressing lashing, securing and the cargo's own documentation.
Candidates memorise 'keep away from' and 'separated from' as phrases but do not practise looking up the actual table for the pair of classes in the question. They also forget that the stowage answer must cover securing and the dangerous goods declaration, not only segregation.
What to do instead
For each pair of classes, look up the segregation term in the IMDG segregation table and translate it into a distance or compartment requirement on the actual ship, then state the securing method and the documents required (dangerous goods declaration, stowage plan, placards). Name the classes and the resulting term explicitly in the answer.