Lesson previewScenario Method: Brief Before Touching Controls1 section shown
Preview lesson
Scenario Method: Brief Before Touching Controls
What you will learn
Build a traceable radar scenario brief that names the question, display state, evidence, safe state, decision trigger and verification plan before action.
A scenario is not solved by recognising one screen pattern; it is solved by controlling the vessel while evidence is gathered, challenged and checked after action.
Begin with the operational question: collision risk, feature identity, lateral track, progress, entrance recognition or equipment health. Record orientation, motion mode, range scale, heading and speed inputs, control state and observation time. A tidy picture without that state is not an auditable observation.
Build an evidence ledger rather than a verdict. Separate raw radar observations, tracked-target forecasts, AIS reports, chart or electronic overlay, depth, visual or sound evidence and vessel response. Name which sources share an input, what is missing and what result would disprove the leading interpretation.
Choose a safe state before choosing an answer: speed, sea room, water to hold or turn, engine readiness, lookout and an abort or wait option. Then state the decision trigger and the observations required after action. A scenario is complete only when the result is verified and recovery remains controlled.
Radar scenario transfer board
Keep the method stable while the problem changes
Select a scenario. Question, evidence, safe state and release remain available as text as well as the schematic.
1 · Question
A target trend is risk evidence, not a vessel role
Does the timed relative picture indicate collision risk, which visibility-dependent Rules apply, and what action remains safe for every target?
2 · Evidence
Keep time, compass bearing, range, continuity, track age, display mode and input health together. Visual classification is separate from radar geometry.
3 · Safe state
Preserve time, sea room and engine/helm capacity. Do not wait for an exactly constant bearing or assign an in-sight role when Rule 19 applies.
4 · Release
Test action across all contacts, mark own manoeuvre and obtain fresh observations until passing geometry is safe and finally past and clear.
Change scenario without changing method: frame the question, separate evidence, protect a safe state and release only a monitored decision.
Worked example
A coherent contact is 4.0 M away and its measured relative range is closing at about 12 kn while a harbour entrance lies 5 M ahead. The track is new and the display has just changed range scale.
- 1Frame two questions separately: the contact's collision risk and whether the planned harbour approach still has enough assessment and manoeuvre time.
- 2At 12 kn relative closure, a simple unchanged straight-line range budget is 4.0 ÷ 12 × 60 = 20 minutes. This is not CPA or TCPA and assumes the measured closure remains valid.
- 3Record the new scale, rebuild a timed track, identify fixed references, cross-check inputs and protect water to slow, hold outside or turn away before committing to the entrance.
Sense check: A displayed TCPA or AIS identity cannot turn the 20-minute range budget into a safe passing forecast; the scenario still needs geometry, source quality and post-action verification.
| Brief field | Record | Failure it prevents |
|---|---|---|
| Question | Collision, identity, track, progress, entrance or system-health decision | Solving the wrong problem |
| Set-up | Orientation, motion mode, range, inputs, controls and time | Reading an untraceable picture |
| Evidence | Raw observation, trend, source, independence, uncertainty and disconfirming cue | Turning agreement into false certainty |
| Control | Safe speed/state, trigger, action, abort, verification and recovery | Acting without room to discover error |
Say the whole brief aloud
A second crew member takes the radar while the vessel approaches traffic and confined water.
1. Question
Name the decision the watch is trying to make and the time or distance boundary.
2. Evidence
State observed values, trends, sources, shared inputs, uncertainty and the strongest contradictory cue.
3. Control
State present safe speed/state, next trigger, available action and abort water.
4. Verify
Name what will be observed after action and what must be true before route or speed recovery.
Sense check: If the brief cannot distinguish observation from forecast, the decision is not yet ready for release.
Common mistake or limitation
- Starting with the nearest or brightest echo before defining the decision.
- Treating several displays fed by one sensor as independent evidence.
- Choosing an action before protecting a safe state and verification plan.
Recap
- Question, set-up, evidence, safe state, decision and verification form one scenario method.
- Display precision does not remove source or timing uncertainty.
- A disconfirming cue is part of the brief, not an afterthought.
- Release includes recovery and monitoring, not merely a button or helm order.
Optional quick check
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