Different runway fixtures
Edge, centreline, touchdown zone and threshold/end: four runway lights that differ in what they mark, how they are mounted, their colour and the direction of their light.
A runway is lit by several fixtures, each with a job. Four common ones are the elevated edge light, the inset centreline light, the inset touchdown zone light and the threshold and end light. They differ in what they mark, whether they stand above the pavement or sit flush in it, their colour, and the direction their light is shown.
Lights beside or at the ends of the runway can be raised on a frangible coupling that breaks first if an aircraft strikes them. Lights on the paved surface are set flush and built to carry wheel loads. A threshold and end fixture shows green to a pilot approaching and red toward the runway, so the colour on each face matters as much as the fixture itself.
Edge, and threshold and end lights. Raised on a frangible coupling above a base can, so the upper part breaks away and the base stays in the ground.
Centreline and touchdown zone lights. Flush in the pavement, so no break point, but they carry wheel loads and must be re-set after resurfacing.
| Aspect | Edge light | Centreline light | Touchdown zone light | Threshold / end light |
|---|---|---|---|---|
| Marks | Runway edges | Runway axis | Touchdown zone | Threshold (start) and runway end |
| Mounting | Elevated on a frangible coupling above a base | Inset, flush in the pavement | Inset, flush in the pavement | Elevated on a frangible coupling; inset where the design requires |
| Colour | White; yellow near the far end of the runway as the standard allows (ICAO: last 600 m or one-third, whichever is less) | White, changing to red-and-white then red near the runway end | White | Green toward the approach, red toward the runway |
| Light direction | Seen along the runway; direction per the design | One or both landing directions, per the design | Toward the landing direction | Green faces the approach; red faces the runway |
| Break point | Frangible coupling at grade | None: flush, not a raised object | None: flush, not a raised object | Frangible coupling when elevated |
| Watch points | Height, aim and coupling as built; window clean | Height after resurfacing; sealed joint; wheel damage | Same as centreline; keep paired lights matched | Correct colour on each face; aim; coupling as built |
What to check on runway fixtures
Break point as built
Keep the manufacturer’s coupling and fasteners on elevated lights. Never add bracing or a stronger fixing across the break point.
Window and lens
Keep the window or lens clean and undamaged. Dirt, scratches and cracks reduce and distort the light.
Colour on each face
Check the filter or LED colour is correct for each face, especially on threshold and end lights.
Height and flushness
Check elevated height, and inset height against the pavement. Re-check inset height after resurfacing.
Aim and alignment
Check each fixture points the way the design says. Re-check aim after maintenance or a strike.
Seals and water
Check seals, joints and sealant. Water in a fixture or base damages the lamp, connectors and insulation.
Frequently Asked Questions
Q1What are the main types of runway light fixture?
Four common ones are the elevated edge light, the inset centreline light, the inset touchdown zone light and the threshold and end light. They differ in what they mark, whether they stand above the pavement or sit flush in it, their colour and the direction their light is shown. Details vary by product and standard.
Q2Why are some runway lights elevated and others inset?
Edge, threshold and end lights stand beside or at the ends of the runway, so they can be raised on a frangible coupling that breaks away if an aircraft strikes them. Centreline and touchdown zone lights lie on the paved surface that aircraft run over, so they are set flush in the pavement and built to carry wheel loads.
Q3Why is the direction of the light important?
A runway light is seen from particular directions, such as by a pilot landing or taking off. Some fixtures show light in one direction only, some in two opposite directions, and some in all directions. The wrong direction or aim can make the pattern hard to read, so direction is part of the design and is checked in service.
Q4Why do threshold and end lights use two colours?
A combined threshold and end fixture shows green toward a pilot approaching to land and red toward the runway, marking the start of the runway for one pilot and the end of it for another. Colour is set by the filter or LED colour on each face, so each face must be the correct colour.
Q5What changes when the runway is resurfaced?
Inset fixtures must be re-set so their top stays at the correct height relative to the new surface, and joints and sealant checked. Elevated fixtures may need their height and aim re-checked. Resurfacing is a common time for inset fixtures to end up too high or too low.
Q6What limits and requirements apply?
Light colour, spacing, intensity, heights and frangibility limits come from the standard (ICAO or FAA), the regulator, the airport's design and the manufacturer's instructions. Always use the requirements for your site rather than a generic list, and isolate and lock out the circuit before working on any fixture.
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