COLREG / ARPA / AIS Bridge Rule 19(d)(i) Rule 8 🔒 Course / Premium

RV — Target on Starboard Bow (Rule 19(d)(i))

Fog. Target detected on your starboard bow, forward of the beam. Rule 19(d)(i) forbids alteration to port. Altering toward the target (i.e.

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Scenario briefing

Fog. Target detected on your starboard bow, forward of the beam. Rule 19(d)(i) forbids alteration to port. Altering toward the target (i.e. to starboard when the target is fine on the starboard bow) may also be unsafe prefer a substantial starboard alteration to pass astern, or reduce speed.

Applicable COLREG rule(s)

Rule 19(d)(i) — referenced in this scenario. Practising this scenario reinforces correct application under realistic time pressure.

Rule 8 — 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)(i) — Restricted visibility — target on starboard bow — radar PPI with AIS targets — Bridge-simulator scene under COLREG Rule 19(d)(i) — Restricted visibility — target on starboard bow. Captured from the SkipperCheck COLREG / ARPA / AIS bridge simulator.

Key teaching points

Rule 19(d)(i): port alteration is forbidden for any target forward of the beam.
A starboard alteration toward a starboard-bow target must be substantial enough to pass clearly astern, not just nudge.
A speed reduction is often the cleaner answer when the geometry is awkward (Rule 19(e), Rule 6).
Take action in AMPLE time — fog visibility means very short warning if anything goes wrong.

Common mistakes to avoid

Holding course "to let her pass on my starboard side". Rule 19 demands action; you are not the stand-on vessel.
A small starboard turn that closes CPA. The alteration must put you behind her track, not into it.

Why it matters

A target on the starboard bow in fog is the most counter-intuitive Rule 19 case — the rule forbids port alteration, but a starboard alteration draws you TOWARD the target. The correct answer is often a substantial starboard turn to pass well astern, OR a speed reduction.

Exam relevance

The starboard-bow-in-fog case is a probing variation in Yachtmaster Offshore orals — the candidate must reason aloud why starboard turn or speed reduction is correct.

Related scenarios

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