Rule 23(b) — Air-Cushion Vessel (Hovercraft)
NIGHT. A wide low craft skims across the surface on an inflated skirt, leaving no wake.
Scenario briefing
NIGHT. A wide low craft skims across the surface on an inflated skirt, leaving no wake. She shows normal PDV lights (masthead + sidelights + sternlight) AND an additional all-round FLASHING YELLOW light. Which vessel type is this?
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 23(b): an air-cushion vessel when operating in the non-displacement mode shall, in addition to the lights for PDV, exhibit an all-round FLASHING YELLOW light.
- When OFF cushion (displacement), she shows normal PDV lights without the yellow flash.
- Hovercraft travel at 40–60 kt and can manoeuvre over water and shoals — give wide berth.
- Day equivalent: no special day shape.
Common mistakes to avoid
- Reading the flashing yellow as a hazard warning or a special-purpose light — Rule 23(b) makes it hovercraft-specific.
- Forgetting that hovercraft can transit shoals and beaches — your assumption of a deep-water track may be wrong.
Why it matters
Exam relevance
Rule 23(b) hovercraft lights are a niche probe in STCW OOW; less common in yachting exams unless local hovercraft traffic exists.
Related scenarios
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