How Often Does Airfield Lighting Need Photometric Testing?

There is no single interval. For a CAT II or III runway, EU guidance and ICAO recommend measuring in-pavement lights at least twice a year and other lights once a year. The FAA circular says not less than twice a year on a precision approach runway and lists monthly testing in its tables. Part 139 sets none.

Part 139 itself names no photometric testing interval. The FAA interval comes from AC 150/5340-26C , which is mandatory only on projects funded through AIP grants or PFC revenue and recommended guidance everywhere else. A test means measuring what each fixture emits with equipment proven accurate and repeatable. Looking at the lights at night does not count.

What photometric testing of runway lights is

Photometric testing measures the light a fixture gives out, in the field, and compares it with the specification. Annex 14 10.5.3 and 10.5.4 describe it as in-field measurement of the intensity, beam spread and orientation of the lights, covering all lights as far as practicable. 10.5.5 asks for a mobile measuring unit accurate enough to analyse each light. In the FAA circular, the result is judged against the output required for the fixture in AC 150/5345-46.

What Part 139 says and does not say

14 CFR 139.311 is the lighting rule. Paragraph (c) requires a certificate holder to provide and maintain lighting for air carrier operations, including runway lighting that meets the specifications for the minimums authorised for each runway. Paragraph (d) says to “properly maintain” means cleaning, replacing or repairing anything faded, missing or non-functional, keeping it unobscured and clearly visible, and making sure it gives the user an accurate reference.

Neither paragraph names photometric testing or an interval. Paragraph (f) points to FAA advisory circulars as containing methods and procedures that are acceptable to the Administrator. Section 139.327 adds the daily self-inspection, with a record of the conditions found and the corrective action taken, kept for at least 12 consecutive calendar months. It does not call for photometric measurement.

Where does your interval live, then? In the Airport Certification Manual. Section 139.203 lists, among its required contents, a description of and procedures for maintaining the marking, signs and lighting systems.

What the circular asks for

The status matters first. Paragraph 2 says use of the circular is in general not mandatory, and mandatory for projects funded through the Airport Improvement Program and the Passenger Facility Charges Program. The circular calls itself recommended guidelines. Everything below is guidance unless your funding makes it binding.

Two readings follow. The tables treat photometric testing as monthly work, and the text treats twice a year as a floor for a precision approach runway, with the real interval set by local conditions. Both say the interval may be tuned once the airport has data. The text is guidance in the form of “should”, so the floor is not a regulation unless your manual or grant makes it one.

On HIRL the circular says regular photometric measurements are the only practical way to learn whether elevated runway edge lights emit the specified light and to find misalignment. For in-pavement lights it calls photometric measurement the most direct way to check output.

What counts as a test

Paragraph 4.1.12 describes the method. In the past, in situ measurements were possible only with a hand-held spot meter, and the circular says that method proved very ineffective: it detects only gross differences between lights and cannot account for alignment errors. It points instead to mobile systems that test individual fixtures at high speed and high accuracy. Some produce an isocandela diagram per light, flag misaligned fixtures or give a GPS position for each light. The equipment must be proven capable of high accuracy and repeatability so that no erroneous data is collected.

So a qualifying test has three parts.

• An instrument that measures output per fixture. A calibrated photometer reports intensity in candela , and the fixture is judged against the output required for it in AC 150/5345-46.
• A reading before and after maintenance. The circular asks for testing before cleaning, relamping or realignment, to learn whether work is needed, and after, to show the work had an effect.
• A criterion. A light measuring below 70 percent of the minimum output required when operated at maximum intensity should be targeted for cleaning or maintenance, and the circular calls it ineffective in high background brightness and low visibility. For elevated lights the circular states this for high intensity runway edge lights.

Viewing the lights at night is a different check. The circular offers it as a way to spot lenses out of orientation, with testing as the alternative. The daily twilight drive looks for burned-out or dimly burning lamps. For in-pavement lights the circular says nightly photometric testing is not practical, so an airport can develop its own guidance on what “dim” means on a daily check.

Do not mix the 70 percent figure with the serviceability limits. Table A-8 counts how many lights are on or serviceable, for example 85 percent of runway edge lights on, and 95 percent serviceable on CAT II and CAT III runways. That is a count of lights. The 70 percent figure is a measure of output and a trigger for maintenance.

How the EU and ICAO compare

For a European aerodrome the order is different. ADR.OPS.C.015(b) requires a preventive and corrective maintenance programme for the individual lights and does not print an interval. AMC1 to ADR.OPS.C.015(b) and (f) says that, irrespective of runway type, the operator should ensure serviceability by photometric measurements at appropriate intervals set in the programme. For a category II or III precision approach runway, it adds the floor. Annex 14 carries the same floor as a Recommendation in 10.5.6.

The FAA text applies one floor to elevated and in-pavement lights, where the European text splits them. It also says precision approach runway where the European text says category II or III. Annex 14 10.5.2, a Standard, requires a system of preventive maintenance and names no interval. The interval sits in the Recommendation 10.5.6.

Testing outside the calendar

Some tests do not wait for a date. The circular asks for testing before cleaning, re-lamping or realignment, and again after. It says weekly checks of centreline lights may be needed where rubber builds up, especially on CAT II and CAT III runways. When the FAA declares a lighted navigation aid out of service as suspect in an aircraft accident, paragraph 3.7 asks the operator to inspect it at once and record the as-found functional parameters against Appendix A. It does not say photometric.

What the results feed

A test is only useful if the number changes what happens next. The circular ties the two together in its cleaning paragraphs. Its general cleaning schedule in 5.3.3.6 asks for each light to be cleaned thoroughly at least once a year and says regular photometric measurements may show a need for a more aggressive schedule. For in-pavement lights it names rubber deposits and runway de-icing fluids as having an extremely detrimental effect on light output, and asks for cleaning when output falls below 70 percent of the minimum required. A light that keeps showing output below that level after cleaning should be scheduled for removal and servicing.

That is the practical meaning of “regular”. A fixed calendar date tells you when to measure. The results tell you whether that date was right, and the circular expects the interval to move once the airport has experience with its own equipment and traffic.

What this means for a programme

Write the interval into the maintenance procedures your manual describes, with the reason: traffic, pollution, fixture age and what earlier results showed. Test before and after cleaning, so the record shows whether the work helped. Keep the instrument, its calibration state and the intensity step with every reading.

A drone survey does not replace that test. The circular names no platform, and whether a drone-based method meets a particular programme is a question for the programme and its FAA contacts. TarmacView reports each unit as lit or dark, its colour, its output relative to its neighbours and to the commanded step, and its surveyed position. It does not measure candela, which needs a calibrated photometer. What it adds is a light-by-light look between measured campaigns, so the next test goes to the units that need it. The runway edge lights service describes that work.

For the procedure itself, see the photometric measurement guide . For the serviceability percentages, see runway light serviceability limits .