When fog settles over the Manukau Harbour at 2am, pilots aren’t reading painted lines. They’re reading lights. This guide to airfield lighting covers how those lights work, what each colour means, the standards New Zealand aerodromes must meet, and how long a system should last before it needs replacing.
This guide is written for aerodrome operators and airfield managers. If you need hands-on help, our airfield lighting team installs, maintains, and upgrades systems across New Zealand.
What Is Airfield Lighting?
Airfield lighting, also called airfield ground lighting (AGL), is the network of lights that guides aircraft during take-off, landing, and taxiing. It includes runway, taxiway, and approach lights, PAPI units, illuminated signs, and the control equipment behind them.
Most AGL runs on series circuits powered by constant current regulators (CCRs). These hold the current steady, typically 6.6 amps at full brightness, so every light on the circuit glows at the same intensity. An isolation transformer at each fitting keeps the circuit running if a single lamp fails.
When it works properly, pilots get a clear picture of the runway in darkness, fog, and heavy rain, cutting the risk of misaligned landings, runway incursions, and ground collisions.
Reading the Runway: Runway Lighting Visibility Explained
Here’s runway lighting explained simply. Every colour and position tells the pilot something specific, and the system is standardised through ICAO, so a pilot reads the same cues in Auckland as in Singapore. New Zealand applies ICAO standards through CAA Part 139, so the figures below are metric rather than the US FAA figures many overseas guides quote.
Runway edge, threshold, and end lights
Edge lights outline both sides of the runway in white. On instrument runways, the final 600m (or the last third of the runway, whichever is shorter) can switch to yellow to warn a pilot on take-off that the end is close. Green threshold lights mark where the landing runway begins, and red end lights show where it stops.
Centreline and touchdown zone lights
Centreline lights sit flush with the pavement. They’re white until 900m from the runway end, alternate red and white from 900m to 300m, then turn solid red for the final 300m. Touchdown zone lights add white light bars on either side, giving pilots an aiming point when visibility is low.
Approach lighting systems
Approach lights extend from the threshold out into the approach path. They help pilots line up and switch from instruments to visual references on final approach. Part 139 sets which runways need which system, from a simple approach lighting system on non-precision runways to full Category II and III systems for low-visibility landings.
Taxiway lights, stop bars, and runway guard lights
Taxiway lights guide aircraft between the runway, apron, and terminal. Edge lights are blue, and centreline lights are green. Where a taxiway centreline leads onto or off a runway, the lights alternate green and yellow. A row of red stop bar lights means hold, and flashing yellow runway guard lights warn pilots they’re about to enter an active runway.
| LIGHT | COLOUR | WHAT IT TELLS THE PILOT |
| Runway edge | White (yellow in caution zone) | Where the runway sides are, and when the end is near |
| Threshold | Green | Where the landing runway starts |
| Runway end | Red | Where the runway finishes |
| Runway centreline | White, then red/white, then red | Alignment and distance remaining |
| Taxiway edge | Blue | The edges of the taxiway |
| Taxiway centreline | Green (green/yellow near runways) | The taxi route, and when a runway is close |
| Stop bar | Red | Hold position until cleared |
| Runway guard lights | Flashing yellow | An active runway is just ahead |
Guiding the Final Approach: What Are PAPI Lights?
So, what are PAPI lights? They show pilots whether they’re on the correct glide path as they descend, helping them maintain a safe angle to touchdown.
PAPI stands for Precision Approach Path Indicator. It’s a row of four light units, usually on the left-hand side of the runway near the touchdown point. Each unit projects a beam that looks white from above a set angle and red from below it.
PAPI light meaning depends on how many units show red versus white. The standard glide path is usually around 3 degrees.
| WHAT THE PILOT SEES | WHAT IT MEANS |
|---|---|
| Two red, two white | On the correct glide path |
| Three white, one red | Slightly high |
| Four white | Too high |
| Three red, one white | Slightly low |
| Four red | Too low |
Under Part 139 Appendix E, a visual approach slope indicator is required where a runway serves jet aircraft, where the approach crosses water or featureless terrain, or where obstacles or terrain make undershooting risky. Smaller aerodromes can use APAPI, a two-unit version.
Because each unit must be precisely aimed, alignment checks are vital to PAPI maintenance. LED units cut lamp changes dramatically too. Halogen PAPI bulbs typically last around 1,000 hours, compared with roughly 50,000 hours for LED versions.
Meeting the Rules: A Guide to Airfield Lighting Standards in NZ
This quick guide to airfield lighting standards covers the documents CAA NZ uses to set requirements for intensity, colour, and placement.
- CAA Rule Part 139 governs certificated aerodromes. Appendix E sets out the required visual aids for navigation, and Appendix H covers electrical systems.
- Advisory Circular AC139-6 sets out the acceptable means of compliance for aerodrome design, including light colours, spacing, and intensity. Revision 8 was published on 10/07/2025.
- ICAO Annex 14 is the international standard that Part 139 and AC139-6 align with.
- AC139-3 covers aerodrome inspection programmes, including periodic condition evaluations of every visual aid.
The detail matters. Part 139 requires intensity controls so brightness can be adjusted for the conditions, with approach, edge, threshold, centreline, and touchdown zone lights all able to run at compatible intensities.
Compliance is also ongoing. Regular inspections, testing, and clear records keep an aerodrome audit-ready and avoid penalties or restrictions.
Tackling the Biggest Challenges in Airfield Lighting
The biggest challenges in airfield lighting rarely come from the lights themselves. They come from the environment, and the tight windows crews work within.
Weather, moisture, and water ingress
Rain, fog, and salty coastal air test every seal. Once water gets into an inset fitting or cable joint, it causes corrosion, insulation breakdown, and hard-to-trace intermittent faults. That’s why seal checks and insulation resistance testing matter so much at coastal aerodromes like Auckland’s.
Aircraft loads, rubber build-up, and inset fitting damage
Inset lights carry the weight of aircraft wheels every day, and Part 139 requires them to withstand being run over without damage to the aircraft or the fitting. Over time, rubber deposits in touchdown zones dim the lenses, and constant vibration loosens fittings.
Tight maintenance windows
Busy airports can’t just close a runway. During Auckland Airport’s LED runway upgrade, the physical work could only happen between 1.30am and 4.30am on Saturday and Monday, the only times with no scheduled flights.
Legacy infrastructure and LED compatibility
Many aerodromes run a mix of old and new equipment, and fittings from different manufacturers often aren’t interchangeable. Getting compatibility right at the design stage avoids expensive surprises later on.
Working safely on live series circuits
Series circuits can run at high voltages, and a failed isolation transformer can put dangerous voltage where it shouldn’t be. Safe work means proper isolation and lock-out, airside-trained staff, and strict adherence to NZ health and safety law and CAA guidance on aerodrome works (AC139-5).
Keeping Every Light Working: Airfield Lighting Maintenance
A dark section of edge lighting or a misaligned PAPI can mean restricted operations, delayed flights, or a finding at your next CAA audit. Regular maintenance catches those problems before a pilot does, and it costs far less than emergency repairs on an active airfield. A good programme includes:
| TASK | WHY IT MATTERS |
| Visual inspections and lens cleaning | Spots failed lamps, cracked lenses and moisture, and removes rubber and grime that dim output |
| Photometric testing | Confirms each light still meets its required intensity |
| Insulation resistance testing | Picks up cable and joint deterioration before it causes a failure |
| PAPI alignment checks | Keeps glide path information accurate |
| Wiring, voltage, and CCR checks | Confirms circuits and brightness settings are working correctly |
| Record keeping | Gives CAA NZ inspectors a clear audit trail |
Planning for Airfield Lighting System Lifespan
Airfield lighting system lifespan depends on the component, as each part wears out on its own timeline.
Auckland Airport’s LED runway lights have a life expectancy of around 75,000 hours, against about 5,000 hours for the halogen lamps they replaced. At roughly 12 hours a day, that’s about 17 years versus just over one. Heat, moisture, and vibration all shorten that in practice.
Cables, isolation transformers, CCRs, and control systems age too, often without obvious signs. Falling insulation readings and more frequent faults are the early warnings. So plan replacements component by component based on test results, rather than waiting for failures.
