Leading lights and directional lights
1The lesson in plain words
Leading lights form a line to follow: keep them in line and you are on the track. A directional light does the same job with one light and a narrow beam.
Leading lights
Leading lights are two or more lights placed so that, seen one above the other, they mark a leading line to follow, often through a narrow entrance. The rear light stands higher and behind the front one. The chart shows the line and its true bearing from seaward, for example Ldg Lts 270°. Holding them in line keeps you on the track.
Off the line
When approaching with the lights ahead, steer towards the front light, the lower and nearer one, if they separate. If the front light appears to the right of the rear one, you are to the left of the line: steer to starboard. Leading lights are often synchronised, flashing together, which makes them easier to pick out against shore lights. Day transits are in the Pilotage unit.
Directional lights
A directional light (Dir) shows a very narrow beam, often white, flanked by sectors of other colours or of much weaker light. It marks a line on its own, without a second light. The chart draws the line with its bearing, for example a Dir WRG light with the bearing of its white beam alongside.
Lights in line
Lts in line tells you that lights align; it does not by itself establish a safe track. They may mark an area boundary, cable alignment or anchoring limit. Check the chart and List of Lights before treating the alignment as a route.
Use with care
A leading line is safe only along its charted length; leave it at the turning point in your plan, even if the lights stay in view. In a cross-current, point the bow towards the side the current comes from by enough to keep the lights in line.
2Key data
- Leading lights
- Rear light higher; keep both in line
- Off the line
- When approaching, steer towards the front light
- Dir
- Single light with a very narrow sector marking a line
- Lts in line
- An alignment; check whether it marks a track or a limit
- Bearing on the chart
- True, as seen from seaward
3Key points
- 1
Keep leading lights in line to stay on the leading line.
- 2
When approaching with the lights ahead, steer towards the front (lower) light to regain the line.
- 3
A directional light marks a line with one narrow beam.
- 4
“Lts in line” describes an alignment; check whether it marks a track or a limit.
4Frequent mistakes
Wrong: When approaching, steer towards the rear light when the lights separate.
Right: When approaching with the lights ahead, steer towards the front, nearer light until they line up again.
Wrong: Any two lights in line mark a safe track.
Right: Check the charted purpose. “Lts in line” may show limits or cables rather than a safe track.
5Practice case & exam keys
You are entering on leading lights bearing 270°T. The front light moves left of the rear light just as you reach the planned turning point. Do you regain the line or turn?
Show the answer
Turn as planned. The front light to the left shows that you are north of the leading line, but that line is only valid along its charted length. Do not continue towards the lights to regain alignment beyond the planned turn. Before the turning point, you would correct to port.
Exam keys
- Leading lights in line = on the leading line; bearing true from seaward.
- When approaching with the lights ahead, steer towards the front light to regain the line.
- Dir = directional light, a narrow beam marking a line.
- “Lts in line” may not mark a track.
Finish this unit
When you've read it, match the terms, then answer three questions. Get them all right to finish the unit; opening the page alone doesn't count.
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