Rule 27 prescribes lights for NUC and RAM vessels.
Day shapes: NUC shows two balls in a vertical line. RAM shows ball-diamond-ball in a vertical line.
Recognition Sequence
Classify the vessel state first: underway, making way, stopped, at anchor, aground, towing, fishing, pilotage or special condition.
Read special lights vertically from top to bottom before using sidelights and sternlight to confirm aspect.
Then confirm the answer with the day shape, vessel length and any extra signal such as towing lights, deck illumination or a cylinder.
Exam Focus
Avoid identifying a vessel from one colour alone.
Many mistakes come from spotting a red light and guessing before checking the full pattern.
If the question mentions 'making way', 'underway but stopped', 'at anchor' or 'aground', that wording usually determines which extra lights or shapes appear.
Key Takeaways
NUC: two red all-round lights vertically (day: two balls)
RAM: red-white-red all-round lights (day: ball-diamond-ball)
Dredging vessels show red on obstructed side, green on clear side
Sidelights/sternlight only when making way
Common Mistakes
Confusing NUC lights (red-red) with RAM lights (red-white-red)
Forgetting that NUC and RAM only show sidelights when making way
Test Your Knowledge
Test your knowledge and prove your mastery.
More rules in this Part
- Towing and PushingVessels towing or pushing display additional masthead lights and a yellow towing light. Three masthead lights if tow exceeds 200m.
- Sailing Vessels Underway and Vessels Under OarsSailing vessels show sidelights and sternlight. May optionally show red over green all-round lights at the masthead.
- Pilot VesselsA pilot vessel on duty shows white over red all-round lights at the masthead. When underway, also sidelights and sternlight.
- Anchored Vessels and Vessels AgroundAnchored vessels show an all-round white light forward and another aft (lower). Vessels aground additionally show two red all-round lights.
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