COLREG / ARPA / AIS Bridge Rule 19(d)(ii) 🔒 Course / Premium

RV — Target Abaft Port Beam (Rule 19(d)(ii))

Target detected abaft your port beam, slowly closing (relative bearing ~160 port / ~200 true from your heading).

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Scenario briefing

Target detected abaft your port beam, slowly closing (relative bearing ~160° port / ~200° true from your heading). AIS identifies her as a SAILING vessel (badge "S"). Note: in clear visibility Rule 18(a)(iv) would make YOU the give-way vessel, but in RESTRICTED VISIBILITY Rule 19 applies to every vessel there is NO stand-on/give-way. Rule 19(d)(ii): avoid alteration TOWARD a vessel abeam or abaft the beam. A port alteration here is prohibited; consider a starboard turn or a speed change.

Applicable COLREG rule(s)

Rule 19(d)(ii) — 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 19(d)(ii) — Restricted visibility — target abaft port beam — radar PPI with AIS targets — Bridge-simulator scene under COLREG Rule 19(d)(ii) — Restricted visibility — target abaft port beam. Captured from the SkipperCheck COLREG / ARPA / AIS bridge simulator.

Key teaching points

In restricted visibility, Rule 19 applies to every vessel — Rules 11–18 (in-sight rules) do NOT apply.
Rule 19(d)(ii): for a target abeam or abaft the beam, do NOT alter TOWARD her.
For target abaft port beam: port alteration is forbidden; starboard turn or speed reduction is acceptable.
Sound signals: continue one prolonged blast every ≤2 minutes (Rule 35(a)).

Common mistakes to avoid

Applying Rule 18 priority logic in fog — the target may be a sailing vessel, but in RV Rule 19 governs.
Port alteration "to clear her" — Rule 19(d)(ii) prohibits this when the target is on your port side and abeam/abaft.

Why it matters

A target abaft the port beam in fog raises an extra layer of complexity — in clear visibility Rule 18 might make YOU the give-way vessel, but in fog Rule 19 supersedes and there is no give-way/stand-on. Every vessel acts on her own.

Exam relevance

The interaction between Rule 18 (in-sight) and Rule 19 (RV) is a stress-test question in Yachtmaster Offshore and STCW OOW orals.

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