Rule 27(f) — Mineclearance Vessel
NIGHT. A warship displays normal PDV lights (masthead + sidelights + sternlight) AND in addition THREE all-round GREEN lights one at the foremast head a...
Scenario briefing
NIGHT. A warship displays normal PDV lights (masthead + sidelights + sternlight) AND in addition THREE all-round GREEN lights one at the foremast head and one at each end of the fore yard. Identify her duty and the danger zone to avoid.
Applicable COLREG rule(s)
📸 Night recognition — 8 aspects
The same vessel rendered every 45° of aspect — bow, starboard bow, beam, quarter, stern, port quarter, beam, bow. Use this strip to learn how the lights present from each approach angle. Click any image to view full size.
Key teaching points
- Rule 27(f): a vessel engaged in mine-clearance shall exhibit, in addition to PDV lights, three all-round GREEN lights — one at the foremast head and one at each end of the fore yard.
- These lights indicate that it is DANGEROUS for another vessel to approach within 1000 m of the mine-clearance vessel.
- Day equivalent: three black balls, in the same arrangement.
- The 1000 m exclusion zone is generous because of the operational hazard, not the vessel itself.
Common mistakes to avoid
- Approaching closer than 1000 m — Rule 27(f) explicitly flags this as dangerous, and active minefield operations are no place for proximity.
- Reading three greens as a Rule 27(e) diving operation — diving is red-white-red plus a flag, not three greens.
Why it matters
Exam relevance
Rule 27(f) mine-clearance is a niche question in STCW OOW orals; rarely tested in recreational yachting.
Related scenarios
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