At 2230 in the English Channel, ARPA shows a vessel at 8nm, bearing 040, CPA 0.3nm in 12 minutes. Your examiner asks: "What are the ARPA limitations you must account for before taking action, and how would you use the trial manoeuvre function?"

A. ARPA limitations to account for: acquisition time (1-3 radar sweeps to establish initial track — early readings of newly acquired targets are unreliable); course and speed filter lag (ARPA smooths data over several sweeps — a target that has recently manoeuvred may show incorrect CPA); beam width and pulse width cause echo distortion particularly at close range; target swap (ARPA can exchange the track of two close targets causing wrong CPA prediction); limit on number of targets simultaneously tracked. Trial manoeuvre: input proposed course/speed change; ARPA projects future positions of all tracked targets based on your trial manoeuvre; confirms CPA of all affected targets before committing to the alteration. The result must be checked against ALL targets, not just the one of concern.

B. ARPA is accurate to within 0.1nm and 0.5 knots in all conditions. No limitations need to be considered when using trial manoeuvre data for collision avoidance.

C. Trial manoeuvre shows only the future position of the vessel of concern. It does not affect the display of other tracked targets.

D. ARPA limitations only apply at ranges below 2nm. At 8nm the ARPA data is fully accurate and can be used without reference to visual observation.

A. At management level: hull fouling and speed/fuel trade-off; weather routing service integration; piracy risk assessment (Gulf of Guinea — IMB/BMP6 procedures, MSCHOA registration, citadel arrangements); regional seasonal weather (harmattan, North Atlantic gales timing); full port approach analysis for Lagos (pilot boarding area, VTS, port congestion, anchorage assessment, agent contacts); cargo condition requirements throughout (ventilation against condensation in tropical transit); crew fatigue management across the voyage duration; load line zone changes (Summer to Tropical); emergency contingency analysis (abort ports, refuge areas); environmental compliance across all jurisdictions transited.

B. The Chief Mate passage plan is identical to the OOW plan. The difference is only that the Chief Mate signs it and presents it to the master for approval.

C. At management level, the primary additional consideration is fuel consumption optimisation. Safety planning is the OOW's responsibility during the voyage itself.

D. Management-level passage planning focuses on commercial considerations such as ETA commitments and port scheduling. The safety elements are unchanged from OOW level.

A. Parallel indexing uses a radar index line set parallel to the vessel's intended track at a known distance from a fixed radar target (headland, breakwater, isolated rock). As the vessel proceeds, the radar echo should remain on or near the index line — deviation indicates the vessel is off-track. Used for: restricted visibility coastal passages; harbour approaches; narrow channel navigation where fixed marks are reliably radar-conspicuous. Limitations: requires a strong, reliable radar target that returns a consistent echo; dependent on radar accuracy (beam width, set and drift errors); can give false confidence if the target gives ambiguous echoes; does not replace visual fixing when available.

B. Parallel indexing is a technique for comparing two radar targets simultaneously. It is only used when ECDIS is not available.

C. Parallel indexing measures the distance between two vessels on radar. The index line represents the minimum CPA required and alarms when breached.

D. Parallel indexing is an ARPA function that automatically plots the vessel's track and corrects for set and drift. It requires no manual input from the navigator.