Passage planning — an extensive resource
Passage planning — an extensive resource (including Tom Cunliffe's sayings)
Before departing the berth, there is no safer or more efficient task than passage planning. This is also NOT simply plotting a course on a chart. It is a thorough, disciplined, and documentable steps-and-processes approach to gaining an understanding of the uncertainty involved, then putting that uncertainty to work and managing the risk. What is found in the International Maritime Organization’s Guidelines for Voyage Planning (IMO A.893(21)) is but a mere sample of the minutiae involved in a passage plan. Guides such as Tom Cunliffe draw on the nuances of years of hands-on experience in small-boat cruising and river pilotage.
What is the purpose of a passage plan?
There is a legal and professional obligation the skipper has: to ensure the vessel is navigated safely. This is NOT an easy task, and the passage plan helps fulfil that obligation.
It is important, from the point of view of safe vessel navigation, to identify hazards and plan for contingencies to avoid fatigue or rushing. Good planning will also increase operational efficiency. It will also increase crew satisfaction, as they will have greater confidence and be able to enjoy the planning effort, as it is designed to reduce the number of surprises and improve the overall project. Good passage planning will improve the project's overall efficiency.
The four phases of a passage plan (IMO + practical steps)
1. Appraisal — gather everything relevant
- Collect all information for the route:
- Charts (paper and digital), ADMIRALTY or national chart corrections and Notices to Mariners.
- Pilot guides, local sailing directions, pilotage notes and recent cruising reports.
- Tidal data and tidal stream atlases for the entire passage time window.
- Forecast weather (barometer trend), wind and visibility, and swell and sea-state.
- Vessel particulars (draught, air-draught, manoeuvring characteristics, fuel range, electrical and communications capability).
Crew
Experience, watch rotation and any medical or equipment limitations.
Tom Cunliffe stresses local knowledge and simple, common-sense checks: walk the approaches in your head (or on paper), visualise the critical parts of the route, and pinpoint where you must be at a given position or time.
2. Planning — make the plan from berth-to-berth
- Segment the voyage into stages: departure, offshore/coastal leg(s), and arrival. For each stage, specify:
- Waypoints and courses (bearing and distance), track lines and turning points.
- Minimum safe depth margins and under-keel clearance at the planned time (account for tide).Traffic segregation sites, suggested pathways, and potential traffic bottlenecks.
- Contingent strategies: secure anchor points, diversion harbours, and places to turn back.
- Travel times including potential delays; determine ETAs at critical points and the destination.
- Cunliffe advocates conservative margins — assume traffic delays and adverse weather, and aim to arrive at the tidal gateways at the safe rather than the slackest time. During watches, he cites annotated photos and sketch charts as invaluable.
3. Implementation — follow the plan, but engage your own judgement
- Brief your team. Pass the watch over with clear positions, bearings, and anticipated actions.
- Lookout and position yourself to integrate the plan, GPS, and visual bearings.
- Record the GPS path and update your ETA.
- Use the appropriate channel on the VHF/ CPDLC to communicate with other ships or traffic on the quay.
Cunliffe’s advice: Make the plan straightforward and keep it visible (a laminated “destination card” works well), and use it as a training tool so everyone is familiar with the plan and the most likely contingencies.
4. Review – the cycle of verification and adjustment
- Check the plan often to validate your current position and speed.
- Review the plan based on changes to the weather and the tide. Modify the plan to reflect material changes.
- If any of the described factors place you outside of the safe margins, including depth, traffic, or visibility, implement your contingency plan without delay.
Practical aids and templates
- Minimum passage plan checklist (print or pdf)
- Vessel name, contact info, and emergency contact info.
- Brief description of route (from berth to berth).
- Main waypoints (lat/long), bearing/distance/ETA with margin.
- Tidal heights/streams at key times and positions
- Minimum depth and underkeel clearance you used to plan.
- Safe and expected speed is used to determine ETA.
- Contingency ports/anchorages and notes for approaching them.
- Communications plan (VHF channels, AIS, mobile/shore)
- Crew briefing and watch schedule.
- Fuel, power, and safety equipment (that has been) checked.
Simple example, short coastal transit
Departure: Hamble Marina 09:00
Leg 1: Hamble Bar buoy to Southampton Water (course 270 T, 6 nm) ETA 09:30.
Leg 2: Southampton Water to The Needles Channel (course 245 T, 20 nm), ETA 12:30 (arrive at slack +30min).
Contingency: If wind >25 kts or visibility <1 nm, divert to Solent harbour X, call marina Y.
(Numbers are illustrative; always calculate with your vessel’s actual speed and the relevant tidal streams)
Most common pitfalls (and how to avoid them)
Relying on one source of navigation: always cross-check your chart, your electronic chart, your radar and your visual bearings.
Ignoring tidal streams and under-keel clearance: small errors in tide and time can become significant.
Overly complex plans: The watch-usable elements of the plan should be kept clear and simple (essential bearings, distance, and time).
Cunliffe highlights the importance of looking after the simple things under pressure.
Try our Bareboat Skipper, Yachmaster Coastal & Offshore courses to improve/refresh your passage plan skills.
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