A New Look for Night Lights
An Update on the FAA’s Approach Lighting LED Migration Plan
By Tom Hoffman, FAA Safety Briefing Magazine
LED technology offers many benefits to the aviation industry, particularly with airport lighting, including longer bulb life, lower usage costs, and enhanced light quality. However, there are specific safety and viability factors that the FAA must also consider, such as bulb brightness, color conspicuity, and visibility variations that may exist in different low-visibility environments. After a significant amount of testing and research, the FAA is now ready to move forward with its plan to get LEDs installed in approach lighting systems (ALS) nationwide. Let’s look at how we got here and shed some light on what’s in store for the future.
LED technology offers many benefits, including longer bulb life, lower usage costs, and enhanced light quality.
PAR for the Course
The LED transition effort began back in 2007 under the direction of the Energy Independence and Security Act. This act mandated improved light bulb efficiency and required the FAA to transition incandescent lamps to LED technology within the various ALS arrays, namely the PAR 38 and PAR 56 bulbs used in these systems.
For those wondering, PAR stands for parabolic aluminized reflector. As the name implies, these bulbs use a highly reflective aluminum coating in a parabola-shaped housing that helps create a focused beam of light. You’ll likely find this design with many accent, landscaping, and stage lighting applications. The number refers to the size of the bulb in one-eighth-inch increments, so a PAR 38 bulb is 4.75 inches wide and a PAR 56 is 7 inches wide.
The larger PAR 56 bulbs are used with the more sophisticated High-Intensity Approach Lighting System with Sequenced Flashing Lights (ALSF-2), which is only found at roughly 150 airports. The ALSF-2 uses a mix of more than 250 steady and flashing lights that extend out 2,400 feet from the runway threshold to provide visual information on not only runway alignment, but also height, roll, and horizontal reference for Category II/III precision instrument approaches. The ALSF-2 system also includes a high-intensity flasher system known as a “rabbit,” which looks like a giant ball of light sliding toward the runway two times per second. (Note: The PAR 56 LED replacement is still a work in progress given the added complexities and scrutiny the ALSF-2 systems demand.) More on that a bit later.
The FAA is moving forward with its plan to get LEDs installed in approach lighting systems nationwide.
PAR 38 bulbs are mainly used with the ALSF-2’s smaller sibling — and quite possibly the FAA’s lengthiest acronym — the Medium Intensity Approach Lighting System with Runway Alignment Indicator Lights (MALSR). With 940 locations, this is the system you will more likely encounter. MALSR uses threshold lamps, light bars, and flashers to provide guidance for Category I approaches.
A typical MALSR uses 18 green PAR 56 lamps along the runway threshold spaced 10 feet apart, nine white light bars with five lights separated every 200 feet, and five sequenced flashers also separated every 200 feet over a distance of 2,400 feet from the runway threshold. At the 1,000-foot point, there are three light bars (15 lamps) for added visual reference for the pilot on final approach. Sequenced flashing lights provide added visual guidance down the runway centerline path.
A Literal Light Bulb Moment
The FAA has long considered using LEDs to replace the less efficient incandescent lights in the ALSF-2 and MALSR systems to improve reliability and reduce maintenance. Early operational field tests with MALSRs at Phoenix Sky Harbor International Airport (PHX) and Grand Forks International Airport (GFK) were very encouraging. However, the FAA decided to research a few issues further.
One area the FAA reviewed was flicker. “LEDs can blink or flicker since they are not a steady-state light,” says Matt Harmon, an aviation safety inspector with the FAA’s Flight Technologies and Procedures Division. “After extensive research, we were able to eliminate LED flicker by varying pulse width modulations and voltage inputs, which can change the way your eyes perceive the light.”
These pulse width modulation adjustments were also used to better control dimming with LED bulbs, addressing the issue of excessive brightness that concerned some pilots early on. When it comes to dimming, Harmon is quick to point out another unique advantage of LEDs — no color shifting. “LEDs stay the exact same color all the time, whereas a white incandescent might appear yellower as it dims.”
Play It Cool
Although rife with operational advantages, there is one LED benefit that wound up being a liability in certain cases. Hand in hand with an LED’s greater efficiency comes a drop in the heat produced per watt. In fact, LEDs emit nearly 100% of their energy as light, compared to incandescent light, which can waste as much as 98% of its energy as heat. However, the lack of heat — and heat in the form of infrared radiation (IR) — will not allow some legacy night-vision goggles (NVG) and enhanced flight vision systems (EFVS) to detect these lights on their display.
The agency changed specifications in 2020 to add IR emitters to red LED obstruction lights (see Advisory Circular 70/7460–1M), however, the requirement to have an electronic means to see approach lights if you can’t see them with your naked eye will not change (Title 14, Code of Federal Regulations (14 CFR), section 91.176 (a) and (b)). NVG and EFVS manufacturers are working on adopting new technology that can better detect LED lights. In the meantime, the FAA is planning to start charting LED approach light installations in the U.S. Chart Supplement to help EFVS users know where to expect LEDs. The change is expected to take place with the December 2024 chart cycle. In addition, FAA’s Flight Standards Service has a spreadsheet of all LED approach light system locations.
Lighting the Way
With several years of research under its belt, the FAA is now well on its way to installing LEDs at ALSs nationwide. “We have awarded a contract to a company to develop production units of PAR 38 LEDs, and we’re now in the final phase of development tests,” says Donald Lampkins, project lead with the FAA’s Visual Guidance Lighting Systems Group. “We should be through the testing phase by next April and ready to install at different airports by the end of September 2025.” While the timeline for completion is predicated on funding, Lampkins expects to have the MALSRs all transitioned to LED within six to 10 years.
“With MALSRs, we don’t have to change any of the infrastructure,” Lampkins continues. “We are able to swap out the existing lamps with LED ones.” The new FAA specification for MALSR lights is fairly similar to the previous specification for incandescent lights, with the exception of some voltage requirements and a few other items specific to LEDs. “This keeps it a simple replacement for 98% of the system. We were able to achieve this by using a new smart LED lamp that can detect the different voltage requirements and provide the correct light output for each section.”
The higher-intensity ALSF-2 systems, on the other hand, have presented a few additional challenges for LED transition. Lampkins notes that these lights demand higher scrutiny and more certification parameters given the different architecture and the extremely precise Category II and III approach systems they support.
“Lamps within an ALSF-2 have different requirements and must work within a constant current-based lamp monitoring system, so it’s more complicated. The good news is that we can use all of the hard work and lessons learned from the MALSR lights research to help write the specifications for ALSF-2.” The FAA’s ALSF-2 Project Team is currently working on those details, along with finding a bulb supplier, and expects to have a solution in place within three to four years.
Many Hands Make Light Work
Coordination is key when it comes to the actual installation of the new approach light LEDs. The FAA’s MALSR Project Team schedules the replacements according to available funding and resources and will try to coincide with other planned airport maintenance activities to limit operational downtimes. With MALSRs, there are approximately 63 bulbs to replace in lighting rows spaced out 200 feet and within a 2,400-foot footprint. “A single MALSR can take anywhere from two hours to two days to complete,” says Lampkins. Factors such as terrain and accessibility, including whether any lights are located within a runway safety area, can affect the schedule.
It’s also worth noting that the FAA does not plan to install approach lighting LEDs piecemeal. This is to comply with existing requirements that direct airports to convert to LED lights on a single runway or taxiway at the same time to avoid any visual perception differences for pilots. That said, there is the potential to see LED lights on the airfield (e.g., runway centerline lights, taxiway lights) along with incandescents used for approach lighting before the transition is complete.
A Happy PAPI
MALSRs and ALSF-2 systems are not the only approach aids in store for an LED makeover. Also included in the replacement schedule are the Precision Approach Path Indicators or PAPIs. A PAPI consists of four light boxes arranged perpendicular to the edge of the runway. It projects a pattern of red and white lights that provide visual approach slope information.
A key difference with the transition to LED PAPIs is that existing PAPI units will be completely replaced instead of just changing the bulbs. Currently, the priority is to use PAPIs to replace the older Visual Approach Slope Indicator (VASI) systems. These more antiquated systems with numerous variations are approaching 60 years old. As such, VASIs have become increasingly unreliable, with spare parts becoming harder to find. The FAA also adopted this change to conform to International Civil Aviation Organization (ICAO) requirements that use PAPI as the new international standard for visual glide slope indicators.
“We still have about 400 VASIs out there,” says Lampkins, whose efforts are helping direct about 20 replacements a year with new LED PAPIs. There are currently 1,356 PAPI systems in the National Airspace System (NAS), 139 of which have LEDs. There’s still a long way to go to have everything fully updated with LEDs, but there’s a strong incentive to get it done soon due to market forces that have driven manufacturers away from producing incandescent lamps.
Also fueling the drive for replacement are the impressive power consumption savings that the switch to LED provides. “When we replaced VASIs with LED PAPIs we noticed a 60–70% reduction in power consumption from the old units, which translated into significant cost savings.” It was these cost savings that led the LED PAPI Program to win the Department of Transportation’s 2023 Sustainability Award. Lampkins expects that the MALSR LEDs will have similar power savings, going from 14,000 watts to just 4,000 watts to operate. An even greater savings may be realized in the future with the much more power-hungry ALSF-2 lamps.
Passing with Flying Colors
In addition to heeding the advice of researchers about LED use, the FAA is also keenly focused on pilot feedback. “We’re seeing a lot of the same positive feedback from before in recent years,” says Harmon. “Pilots have indicated that the LEDs work well, can be easily spotted in bad weather, and that they’re able to detect color differences.” He admits that while the volume of overall feedback is down, that’s to be expected as LEDs have become more the norm in the NAS.
Lampkins adds that the transition has been “a positive change for pilots that will definitely improve visual cues.”
This feedback, coupled with numerous financial and environmental benefits, paints a bright future for LED technology and helps solidify its successful role in the NAS.
Learn More
- FAA’s Visual Guidance Lighting Systems web page
- FAA Engineering Brief 67, Light Sources Other than Incandescent and Xenon for Airports
- SAFO 18010, Procedures for Avoiding Obstacles Lighted with LED Obstruction Lights While Utilizing Night Vision Goggles
- AC 70/7460–1M, Obstruction Marking and Lighting
- FAA Report AM-22/08, LEDs in Airfield Lighting Applications (PDF download)
Tom Hoffmann is the editor of FAA Safety Briefing. He is a commercial pilot and holds an A&P certificate.
