COLREG / ARPA / AIS Bridge Rule 7 🔒 Course / Premium

CPA/TCPA Recognition (Rule 7)

A single target is inbound. Under Rule 7 you must use all available means (radar, AIS) to determine if risk of collision exists.

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Scenario briefing

A single target is inbound. Under Rule 7 you must use all available means (radar, AIS) to determine if risk of collision exists. Observe the target for at least 3 minutes sim-time, then click EVALUATE to declare whether risk of collision exists.

Applicable COLREG rule(s)

Rule 7 — referenced in this scenario. Practising this scenario reinforces correct application under realistic time pressure.

📸 Bridge simulator scene

Captured directly from the SkipperCheck COLREG bridge simulator at scenario T = 0 — the moment the encounter begins.

SkipperCheck bridge simulator — COLREG Rule 7 — CPA / TCPA risk-of-collision recognition — radar PPI with AIS targets — Bridge-simulator scene under COLREG Rule 7 — CPA / TCPA risk-of-collision recognition. Captured from the SkipperCheck COLREG / ARPA / AIS bridge simulator.

Key teaching points

Steady compass bearing on a closing target = risk of collision (Rule 7(d)(i)).
Even a slowly-changing bearing can hide risk at close range or with a very large vessel (Rule 7(d)(ii)).
Use ALL available means: radar/ARPA plotting, AIS, visual bearings — Rule 7(b) makes this mandatory.
Observe for at least 3 minutes (ARPA needs that long to stabilise CPA) before declaring "no risk".

Common mistakes to avoid

Declaring "no risk" after a 30-second look. ARPA-class CPA estimates need 3+ minutes of tracking.
Trusting a single tool — AIS alone if AIS is off on the other vessel, or radar alone in heavy clutter.

Why it matters

Rule 7 forbids assuming risk is absent from scanty information. The single skill behind every COLREG decision is the ability to recognise — quickly and unambiguously — when risk of collision exists. Watchkeepers who guess this from a single glance miss developing situations.

Exam relevance

Rule 7 application is examined in RYA Day Skipper through STCW OOW orals — candidates must demonstrate they use multiple instruments and patient observation, not snap judgement.

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