Yachtmaster Passage Planning: Make Every Decision Defendable

What makes a passage plan defendable?

A defendable plan shows where each important assumption came from and what would invalidate it. That includes chart edition and corrections, weather timing, tidal data, under-keel clearance, expected traffic, pilotage information and vessel performance.

The point is not to produce the largest possible document. It is to show that the skipper has found the constraints that can change the outcome and has made them visible to the crew.

How should limits and decision points be recorded?

Write limits in observable terms. “Turn back if the weather is bad” is weak. A useful decision point names the location or time, the forecast or observed condition being checked, and the action that remains available.

Apply the same method to tidal gates, daylight, fuel, crew fatigue and harbour access. If a late arrival removes the safe alternative, the decision must be made earlier while that alternative still exists.

How should electronic navigation be explained?

An electronic route is part of the evidence, not the whole plan. Explain chart-data currency, safety settings, cross-track limits, alarm use, power resilience and the independent information that will detect a misleading display or poor position.

Keep the route connected to the real environment. Depth, visual bearings, radar, buoyage, tidal stream and the vessel's observed progress should agree with the electronic picture.

What does command-level reasoning sound like?

Begin with the risk or constraint, state the evidence, give the decision, then explain the contingency. This makes the reasoning clear without reciting every calculation in the order it was completed.

Be ready for one assumption to change. A revised wind direction, delayed departure or unavailable destination should trigger a coherent update across tides, pilotage, crew plan and alternatives rather than a single isolated correction.