Are You Meeting Part 139 Requirements for Airfield Lighting?

Don’t answer that question too quickly! Airport operators generally have the misconception that if the lights are on, all is well. Tests, however, show that nothing could be further from the truth. The human eye is simply unable to detect reductions in the photometric performance of working fixtures, and this can potentially have serious safety implications.  

As an airfield lighting consultant and educator on the topic, I am concerned about an inconsistency that pervades at U.S. airports. In order to maintain Part 139 certification, airports must comply with FAA standards regarding the performance of runway and taxiway lighting. However, the FAA does not test the photometric performance of such lighting. 

This malaise can be compounded by management’s wish to avoid the expense of performing required inspections and conducting regular and required maintenance. If only photometric testing and/or test equipment were eligible for AIP funding! According to the Part 139 regulation, specifically 139.311, certificate holders must maintain lighting in accordance with guidelines in the Advisory Circulars. So for Part 139 airports, there is a requirement to perform the necessary inspections and to maintain the lighting to FAA operational tolerances. (AC 150/5340-26C, Table A-8).

Our aviation system is designed so that no single failure can, on its own, cause a fatal accident. The redundancies and checks/balances are a justifiable source of pride throughout the industry. Runway lighting is but one important piece of this system, albeit a very vital one in low visibility conditions.

Unfortunately, there is a systematic shortfall. FAA and ICAO perform considerable research to develop requirements for specific types of fixtures based on the photometric levels of lighting required to help aircraft land and taxi safely in various weather conditions. Lighting manufacturers then design and test fixtures to ensure compliance with the requirements, and airports invest in purchasing and installing these certified fixtures. That’s when and where the paradox emerges. After installation, little time is spent inspecting and testing the photometric output of the lights to ensure that they’re still operating within the safety margins defined by FAA.

Despite all the time and money invested in compliant lighting, photometric testing at Part 139 airports consistently shows that runway edge lights, centerline lights and touchdown zone lights don’t meet the minimum requirements. This defeats the whole purpose of why the lights are installed. We take the time to design airfield lights to perform in all conditions; and then there is no enforced requirement to check them on a regular basis to ensure the continued photometric compliance necessary to maintain the airport’s certification.

By the Numbers

Advisory Circular 150/5345-46 contains charts of minimum outputs for specific runway and taxiway lights. Even though airports install fixtures that have been certified to these specific standards, many do not have lights that are performing accordingly. Many do not meet the requirements outlined in 150/5345-46, often due to installation or natural degradation over time.

The only way to determine proper lighting performance is through photometric testing. It is not a lengthy process—about two hours for a 10,000-foot runway—when done with equipment designed and certified for the task.

The FAA states the following:

“Any in-pavement runway light exhibiting a light output of less than 70% of the minimum output required, when operated at maximum intensity, is ineffective (unserviceable) for high background brightness, low visibility conditions and should be targeted for maintenance and cleaning. Again, the only way to determine this is through photometric testing.”

In Table A-8 Runway and Taxiway Lighting Systems (AC 150/5340-26C), the FAA requires runway centerline lights to be 95% serviceable, touchdown zone lights to be 90% serviceable, and edge lights for CAT II and III runways to be 95% serviceable. 

Onsite photometric testing after installation and at specified intervals is a requirement. But historically, that requirement has not been enforced.

Information from MALMS Navaid Inc., the primary qualified tester of photometric performance at U.S. airports, indicates serious shortfalls. In 731 post-installation tests of edge lights performed not a single runway met FAA serviceability requirements for an average main beam candela output of at least 70% of the minimum. The results for other systems tested are equally bad. (See chart above). 

If runway lighting is found to be deficient, the situation must be remedied. Photometric testing shows airports which of their light fixtures are unserviceable. After the fixtures have been cleaned, repaired or replaced, MALMS can retest to ensure compliance.

It may seem obvious that complying with FAA standards for runway lighting is a necessary requirement for Part 139 certification, but it is surprising that runway lighting is not tested by the FAA. Some airports take the initiative and perform photometric testing to ensure they are meeting the operational requirements stated by FAA for safe operations. But there is no FAA oversight, or apparent interest by the federal agency, regarding testing or checking records for test results. 

More Help is Needed

One major reason for the lack of photometric testing is that many airports don’t realize the importance of fixture maintenance to ensure proper light output. Moreover, airport personnel can’t see when output levels drop below required minimum levels. That requires special equipment.

Fortunately, the American Association of Airport Executives (AAAE) has stepped up in the last few years to offer certification training for airport lighting maintenance personnel.

FAA, the developer of light fixture criteria and requirements, has surprisingly minimal influence over testing to ensure compliance with photometric requirements. During certification inspections, there is nothing that indicates whether runway lighting meets FAA requirements. There is no test report provided or requested that indicates whether lighting conforms to Part 139 requirements. If that were the case and it was a requirement, there would be more incentive for airports to test. In addition, FAA inspectors would better realize the importance of proper fixture performance since part of their requirement would be to ensure that the system is operating properly.

Lighting consultants like myself have talked about this disconnect for years, but nothing gets done to enhance or assure photometric performance after fixtures are installed. We have qualified equipment able to test and verify that requirements are met, but there is no enforced incentive for airports or the FAA to ensure this happens. Regulations and performance criteria are wonderful, but they must be monitored to provide the safety benefits they are designed to promote.

We have already have requirements for testing in AC 150-5340-26. If enforced, we could be assured that all the work going into fixture development and installation actually enhances safety for the flying public. When most airports don’t meet the minimum requirements, and there is no regular testing, the process has failed. The solution is to enforce the requirement for testing by involving airports and the FAA. In order to maintain a Part 139 certificate, an airport should be required to prove that its airfield lighting meets photometric requirements, and it should be required to provide this information to an inspector.

The configuration and minimum intensity requirements for airfield lighting are designed to help pilots during low visibility conditions. As a pilot descends past the decision height on a given runway, the view of the runway, as represented by its lighting, should increase. However, if fixtures have not been maintained to the required standards, the field of view may instead decrease, and the runway perspective may be lost altogether.

Another important factor that is often overlooked is the potential impact runway lighting can have on Runway Visual Range (RVR) values that are reported to pilots in low visibility conditions. In addition to the atmospheric conditions that are calculated, RVR equipment measures the current in the circuits supplying power to runway edge and centreline lights. This data is then interpreted by algorithms in the program to equate to a specific light output based on the runway lights operating at their optimum performance for that brightness step. Unfortunately, using current in the RVR calculation can be misleading. A reading of the current can be correct, but if the fixture’s lens is dirty, the output is not adequate. This could result in overstating the RVR. One can readily ascertain that if the lights are not functioning as required, skewed RVR values reported pilots could prove to be problematic.

This is why in situ photometric testing is the only effective means of maintaining compliant (serviceable) airfield lighting. The problem is that the FAA doesn’t enforce the requirement stated in AC 150/5340-26 as part of its Part 139 certification program.

Ultimately, airfield lighting is a safety issue. Former U.S. Transportation Secretary Ray LaHood put it into perspective when he said, “We put rules and regulations in place to keep the flying public safe. We expect operators to perform inspections and conduct regular and required maintenance in order to prevent safety issues. There can be no compromises when it comes to safety.”

Seward Ford is president of Visual Aids Services LLC, a provider of support and consulting services for the FAA and others regarding various airfield visual aids. For the last 20 years, Ford has been an instructor for the AAAE Airport Certified Employee course on Airport Lighting Maintenance. He is a member emeritus and past chairman of the IESALC and chaired the IES subcommittee that developed the FAA third-party testing and certification program that qualifies airfield lighting products for FAA Advisory Circulars.