Narrow Channel — Keep Starboard (Rule 9(a))
You are transiting a narrow channel marked by the two dashed yellow lines on the PPI.
Scenario briefing
You are transiting a narrow channel marked by the two dashed yellow lines on the PPI. Rule 9(a): keep as near to the outer limit of the channel on your STARBOARD side as is safe and practicable. Maintain your position east of the channel centreline (x > 0) while transiting.
Applicable COLREG rule(s)
📸 Bridge simulator scene
Captured directly from the SkipperCheck COLREG bridge simulator at scenario T = 0 — the moment the encounter begins.
Key teaching points
- Keep as near to the outer limit of the channel on your STARBOARD side as is safe and practicable (Rule 9(a)).
- Vessels under 20 m, sailing vessels and vessels engaged in fishing shall not impede vessels constrained to the channel (Rule 9(b)–(d)).
- Cross-channel traffic must not impede vessels following the channel (Rule 9(d)).
- Sound signals: one short = "I am altering to starboard"; the doubt signal (five short) is mandatory if intentions are unclear.
Common mistakes to avoid
- Steering the centreline because the chart shows the channel as a strip — the rule demands the starboard edge, not the middle.
- Crossing the channel diagonally to save time, impeding a power-driven vessel constrained to the channel.
Why it matters
Exam relevance
Narrow channel handling is a staple of RYA Yachtmaster Coastal/Offshore and ICC orals — examiners often combine Rule 9 with a sound-signal question (Rule 34).
Related scenarios
About SkipperCheck simulators
SkipperCheck offers two browser-based maritime training simulators:
- ARPA · AIS · COLREG Bridge Simulator — 54 scenarios covering Rules 2, 5–10, 12–19, 23–30, 34 and 35.
- VHF SRC Radio Simulator — 15 scenarios: voice Mayday, DSC distress, Mayday Relay, Pan-Pan, Sécurité, routine.
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