What to check on a Navigation Lights.
A deck floodlight or a signal lamp can be bought off the shelf and mounted anywhere useful; a navigation light cannot. COLREGS Annex I specifies the horizontal sector each light must cover, the vertical sector above and below the horizontal, the minimum range at which it must remain visible against a dark background, and the chromaticity coordinates of red, green and white so that a light seen at a distance is unambiguous to another vessel. The set fitted, and which ones are switched on together, tells another ship your type…
What sets navigation lights apart
A deck floodlight or a signal lamp can be bought off the shelf and mounted anywhere useful; a navigation light cannot. COLREGS Annex I specifies the horizontal sector each light must cover, the vertical sector above and below the horizontal, the minimum range at which it must remain visible against a dark background, and the chromaticity coordinates of red, green and white so that a light seen at a distance is unambiguous to another vessel. The set fitted, and which ones are switched on together, tells another ship your type, size, heading and what you are doing, which is why the rule fixes them so tightly rather than leaving design to preference.
Main components
Masthead light
White, forward-facing 225-degree sector, mounted on the fore mast and, on vessels 50 m and over, a second aft and higher masthead light showing the same sector.
Sidelights
Green to starboard, red to port, each a 112.5-degree sector from dead ahead to 22.5 degrees abaft the beam on its own side, either as two separate lanterns or a single combined bow lantern on smaller craft.
Sternlight
White, 135-degree sector centred on dead astern.
Anchor light
All-round white light, shown when at anchor instead of the underway lights.
Lamp and lens assembly
LED or filament lamp behind a coloured or clear lens sized and shaped to hold the required sector and range; a cracked or fogged lens narrows the effective sector even if the lamp itself still works.
Selection and sizing
- Vessel length class, since minimum required range increases with length under Annex I (for example 2 nm sidelights on small craft rising to 3 nm and more on larger vessels)
- LED versus filament source, since LED fixtures need a driver matched to the ship's supply and typically last far longer between lamp changes
- Certified sector and range for the specific lantern model, not the raw output of the lamp inside it
- Mounting height and any obstruction from masts, cranes or antennas that could cut into the required sector
Regulations and class
COLREGS Rule 21 defines each light type and Annex I sets the technical detail: sector angles, minimum range by vessel length, and chromaticity limits for red, green, white and yellow. Fittings are type approved against these figures, and the type approval certificate, not a general marine-grade label, is what a surveyor checks. Class and flag state surveys verify the correct lights are fitted for the vessel's length and type, that spare lamps are carried, and that the required lights actually operate together as a set rather than testing them individually in isolation.
Typical faults
| Fault | Cause | Consequence |
|---|---|---|
| Reduced range | Salt film or UV-clouded lens, or a lamp swapped for a non-certified equivalent | Light fails the measured range at survey, or is not seen in time by an approaching vessel |
| Sector cut off | Bracket bent in service or a new structure erected in the light's field | Blind arc where the light cannot be seen from a bearing it should cover |
| Wrong light shown | Anchor light left on underway, or underway lights left on at anchor | Other vessels misread the ship's status and manoeuvre incorrectly |
| Total failure undetected | No lamp-fail alarm fitted or alarm ignored on the bridge | Ship effectively unlit without anyone aboard aware of it |
What to look for in a supplier
- Type approval certificate stating the exact sector and range achieved, matched to the vessel's length category
- A lamp-fail monitoring panel compatible with the bridge navigation light control unit already fitted
- LED replacement lamps that are themselves type approved, since an uncertified LED retrofit in an old lantern voids the original approval
- Housing material and gasket quality suited to the mounting location, since a masthead light sees far more vibration and weather than a sternlight
Swapping a failed filament lamp for whatever LED bulb is in the spares locker is the fastest way to quietly lose type approval on a light that still looks lit from the bridge.
