Safety Publications/Articles

Light Up Your Night: A Guide to Airport Lighting Systems

Runways designed for use at night are equipped with a variety of lighting systems to identify the runway?s features.

Finding an airport isn?t always easy. When I first learned to fly I was amazed at how difficult it could be to find a mile-long stretch of aviation-grade asphalt. Even when I knew where it was, when it was right in front of me, the runway of my destination airport could just as easily slip beneath my wings undetected.

I fear that I might not find the airport, and my stress level was high as I embarked on those first solo cross-country flights. But as I gained experience, airports became easier to see. Somehow, my eyes began to pick out the subtle cues such as an opening in the trees, a change in pattern to the cityscape or a break on the horizon that suggested an airport?s location.

Night flying added a new element of apprehension, but I quickly learned that many airports and runways are easier to find in the darkness than in daylight hours, thanks to a broad spectrum of airport lighting systems.

A quick glance at a sectional chart during your preflight planning will tell you whether an airport is equipped for night operations. A star at the top of the airport symbol denotes an airport beacon, and an ?L? denotes runway lighting of some sort. You can find specific information on airport lighting, including the types of lighting and how each operates, in the Airport/Facility Directory (A/FD) and on instrument approach charts. But there?s more to know about lighting systems and how to use them than you?ll find in these publications, and this knowledge can help you find your way in both darkness and daylight.

Beacons in the Night

Many airports have rotating beacons to help guide pilots who are flying VFR at night. Airport beacons are most visible from one to 10 degrees above the horizon, and you can usually see them from a distance of 10 miles or more, depending on the weather conditions and surrounding lighting. An alternating white and green light that flashes 24 to 30 times a minute marks a civilian airport. Military airports display two quick white flashes followed by a green flash.

Not all airports have rotating beacons, so look for that star at the top of the airport symbol on the sectional chart. Airport beacons normally operate from dusk to dawn, or as indicated in the A/FD. An airport beacon that is operating during daylight hours signifies that instrument meteorological conditions (IMC) prevail.

Runway Lights

Runways designed for use at night are equipped with a variety of lighting systems to identify the runway?s features. An ?L? in the airport information block on a sectional chart identifies the presence of runway lighting, but not much else. The A/FD provides more detail on specific types of lighting available and when and how it operates.

The most basic component of airport lighting is the runway edge lights. These white lights border the sides of the runway at maximum intervals of 200 feet. Bordered in bright white runway lights, the runways stand out against the dark terrain.

Runway edge lights generally are classified by their intensity ? low, medium, and high. Some runways are equipped only with low intensity runway lights (LIRL), but others have medium (MIRL) and high intensity (HIRL) as well. Many runways have variable intensity lights that can be set to low, medium, or high intensity.

High intensity is great for spotting the runway from a distance, but most pilots prefer a medium or low intensity setting on short approach and during the flare and landing. At a tower-controlled airport, the tower generally manages the runway illumination and, depending on the circumstances, the active runways may be the only ones illuminated. To change the lighting intensity, or to turn lights on or off, simply ask the tower controller.

Typically, the rows of lights that mark the ends of a runway are bi-directional. As you approach the runway from the air, these lights appear green to indicate the beginning of the runway. If you face the opposite direction on the runway, these lights appear red, to mark the end of the runway. If a runway has a displaced threshold, a row of green lights on both sides of the runway mark the location where the landing portion of the runway begins.

Blue edge lights are used to border taxiways and ramp areas. Except in an emergency, never line up to land on a piece of pavement outlined in blue. That is a serious mistake.

Pilot-Controlled Lighting

Many nontower airports have pilot-controlled lighting (PCL), which allows pilots to turn on the runway lights and to select the desired intensity. Within a five-mile radius of the airport, pilots activate PCL by keying the microphone button with the radio tuned to Unicom frequency. Once activated, the lights remain illuminated for 15 minutes. Pilots set the lights? intensity by keying the microphone button a specific number of times: three for low, five for medium, and seven for high intensity. Changing the intensity by clicking the transmit button the requisite number of times not only resets the intensity, it restarts the 15-minute timer.

In addition to the runway lights, PCL may also activate visual approach slope indicators (VASI), precision approach path indicators (PAPI), and runway end identifier lights (REIL) lights. To conserve energy, some nontower airports put their VASI and PAPI on PCL during the day. If the VASI or PAPI lights are off during a daylight approach, try turning them on with the PCL. In some locations, PCL also controls the taxiway lights.

Ordinarily, pilot-controlled lighting uses the airport?s Unicom frequency, but you?ll find exceptions. Airports sometimes use a different frequency to prevent pilots from activating the lighting systems at a neighboring airport that shares a common Unicom frequency. Part of any pilot?s preflight preparation for a night flight should be to consult the A/FD for the proper frequency.

Runway End Identifier Lights

Even at night, some airports are difficult to spot. Awash in a sea of city lights, some airports seem to blend into the surrounding nightscape and escape detection. At these airports, you?ll find runway end identifier lights (REILs) positioned at the corners of the approach end of the runway. These high-intensity, synchronized strobe lights flash brightly to help pilots find the approach end of the runway. At airports with PCL, you usually activate REILs along with the runway lights. Because the REILs can be annoyingly bright on short final, some runway lighting systems are configured so the REILs are off when the runway lights are set to low intensity.

Instrument Runways

Runways with instrument approaches have additional features to assist the pilot in the transition from instrument to visual flight, and to complete a landing rollout safely.

Runways designed for precision instrument approaches, particularly those at larger airports, often have in-runway lighting to mark the runway?s centerline and touchdown zone. Centerline and threshold lights are required for instrument approaches in visibility less than a half-mile.

Centerline lights are nearly flush-mounted and, starting 75 feet from the threshold, are spaced in 50-foot intervals in a single line for the length of the runway. Pilots who take off or land precisely on the centerline should expect the slight bumpiness caused by the nose wheel rolling over the protruding lights.

Touchdown zone lights appear as transverse rows of white lights emanating from the centerline lights along the first 3,000 feet of the runway centerline.

Runway lighting is often designed to indicate the length of remaining runway. This is especially important at night or in low visibility when distances are more difficult to judge. The last 2,000 feet of centerline lighting is bi-directional to indicate remaining runway lengths. Pilots see alternating red and white centerline lights from 2,000 to 1,000 feet remaining, and the last 1,000 feet of centerline lights appear red.

On runways with straight-in instrument approaches, the edge lights on the last half or 2,000 feet of the runway (whichever is less) are bi-directional and appear yellow as the pilot completes his landing roll toward the end of the runway. As you approach from the opposite direction (i.e. land on the opposite direction runway), these same lights appear white.

Approach Lighting Systems

Perhaps the most difficult time to find an airport is when it?s obscured by a blanket of fog or haze. Even with an instrument approach to guide pilots until they?re within a few hundred feet of the tarmac in broad daylight, the runway can remain invisible.

To help alleviate this problem, runways with instrument approach procedures often have one or more types of an approach lighting system (ALS). ALS comes in a variety of configurations, but all are designed to guide pilots onto the runway in low-visibility conditions.

The designations for the ALS are an alphabet soup and may be a bit confusing for the uninitiated (see sidebar). All ALSs begin with a row of green lights that indicate the approach end of the runway.

Extending into the approach area from the green lights are multiple rows of five steady white lights. Placed at intervals, they extend out from the approach end of the runway to 2,400 to 3,000 feet (see diagram). ALSF-1 and -2 have these lights set at intervals of 100 feet, and the other approach light systems have them set at 200-foot intervals. Additional transverse rows of steady white lights are set at the 1,000 foot mark. The ALSF-2 configuration also has additional transverse rows of steady white lights set at both the 500 and 1,000 foot marks.

ALSF-1 and -2, SSALR and SSALF all incorporate high intensity white lights, whereas the medium intensity MALSR and MALSF have (you guessed it) medium intensity lights.

ALSF-1 and -2 also employ red lights. The ALSF-1 has two rows of red lights that extend 200 feet from the threshold, and ALSF-2 has a row of three red lights to either side of the five steady white lights in a series that extend 1,000 feet.

An important component of many approach lighting systems (ALSF-1 and -2, MALSR, SSALSR) is the Runway Alignment Indicator Light (RAIL) or Sequenced Flashing Light (SFL). These single, blue-white strobes are set between the rows of steady lights beginning at 1,000 to 1,400 feet and extend 2,400 feet to 3,000 feet into the approach area. The strobes flash in sequence toward the approach end of the runway. Flashing at a rate of twice per second, the effect is like a ball of light streaking toward the runway.

RAIL and sequenced flashing lights are angled to be clearly visible only when you?re approaching the runway. The omnidirectional approach lighting system (ODALS), a less common flashing light system, operates in a similar fashion but is visible from all directions.

Generally, runways with precision instrument approaches (e.g., an ILS) have ALSF-1 or ALSF-2, but they may have MALSR or SSALSR instead. Non-precision approaches are more likely to have SSALS or ODALS, but may have the more sophisticated lighting systems as well.

The Right Lights

When you fly an instrument approach, it?s important to know what type of approach lighting is available for the runways at your destination airport. Knowing which type of lights to expect can help pilots avoid landing on the wrong runway during low visibility at an airport with parallel runways. If you know what type of approach lighting is available and operating, other lighting in the airport?s vicinity is less apt to confuse you. Even experienced airline crews have been fooled, leading them to descend below minimums when they thought street lights or lights in a parking lot were part of the runway environment. Such a mistake can be fatal.

The Airport/Facilities Directory (A/FD) and instrument approach charts identify the type of runway lighting available for each runway and how to activate the lighting system. Be sure to check NOTAMs to ensure that the lighting system is operational, because inoperative lighting systems may require higher instrument approach minimums. If the ALS is inoperative, visibility requirements for instrument approaches are usually increased to .75 miles or RVR (runway visual range) 4000.

Whether you fly VFR or IFR, day or night, airport lighting is an important factor. Understanding the systems, their configurations, and operation of airport lighting not only improves your margin of safety, but it can ease any concern about finding your way to your destination.

Abbreviations for Airport and Approach Light Systems

ALSF-1 = Approach Lighting System with Sequenced Flashing Lights

ALSF-2 = Approach Lighting System with Sequenced Flashing Lights

MALS = Medium Intensity Approach Lighting System

MALSR = Medium intensity Approach Lighting System w/ Runway alignment indicator lights

ODALS = Omni-Directional Approach Lighting System

SALS = Short Approach Light System

SSALS = Simplified Short Approach Light System

SSALSR = Simplified Short Approach Light System w/ Runway alignment indicator lights

LIRL = Low Intensity Runway Lights

MIRL = Medium Intensity Runway Lights

HIRL = High Intensity Runway Lights

RAIL = Runway Alignment Indicator Lights

REIL = Runway End Identifier Lights

By Robert N. Rossier

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