IALACOLREG
21

Definitions (Lights)

Masthead light — 225° arc, centred forward.

Rule 21 defines the types of navigation lights:

a
Masthead light: a white light over an arc of 225 degrees, visible from dead ahead to 22.5 degrees abaft the beam on each side
b
Sidelights: green on starboard and red on port, each showing over an arc of 112.5 degrees from dead ahead to 22.5 degrees abaft the beam
c
Sternlight: a white light over an arc of 135 degrees, shown from dead astern to 67.5 degrees on each side
d
Towing light: a yellow light with the same characteristics as a sternlight
e
All-round light: a light showing over an arc of 360 degrees
f
Flashing light: a light flashing at regular intervals at a frequency of 120 flashes or more per minute

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.

Ključne točke

1

Masthead light covers 225 degrees (ahead to 22.5 abaft beam)

2

Sidelights cover 112.5 degrees each

3

Sternlight covers 135 degrees

4

All-round light covers full 360 degrees

Česte pogreške

Confusing the arcs of visibility for different light types

Forgetting towing light is yellow, same arc as sternlight

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