Lois Larson
Airport approach lights are a crucial component of aviation safety, especially during low-visibility conditions or nighttime operations. These lighting systems are designed to guide pilots during the approach and landing phases of flight, providing visual cues to help them align their aircraft with the runway and make safe landings. The approach lighting systems (ALS) typically consist of a combination of lightbars, strobe lights, and other configurations, ensuring that pilots can identify the runway environment and make well-informed decisions.
| Characteristics | Values |
|---|---|
| Name | Approach lighting system (ALS) |
| Purpose | Help pilots visually identify the runway environment and align the aircraft with the runway during landing and takeoff |
| Types | Pulsating visual approach slope indicators, sequenced flashing lights (SFL), runway edge lights, in-pavement lights, touchdown zone lights (TDZL), high-intensity runway lights (HIRL), runway end identifier lights (REIL), runway alignment indicator lights (RAIL) |
| Controls | Radio control, Aircraft Radio Control of Aerodrome Lighting (ARCAL) system, pilot's microphone |
| Colors | White, yellow, red, green, blue |
| Visibility | Up to 4 miles during the day and up to 10 miles at night |
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What You'll Learn
Approach lighting systems (ALS)
The history of approach lighting systems can be traced back to the post-World War II era when the U.S. Navy and United Airlines collaborated to develop methods for safe aircraft landings at their California air base. This early system consisted of 38 towers, each 75 feet high, with a 5000-watt natural gas light. These early lights were soon replaced by strobe lights, dubbed "Strobeacon" lights, which offered greater brightness and efficiency. New York City's John F. Kennedy International Airport became the first large commercial airport to adopt a strobe light ALS system around 1956, setting a precedent for other major airports to follow.
Today, several ALS configurations are recognized by the International Civil Aviation Organization (ICAO), although non-standard configurations can also be found at certain airports. Typically, these systems are high-intensity and are often complemented by various on-runway light systems, such as runway end identifier lights (REIL), touchdown zone lights (TDZL), and high-intensity runway lights (HIRL). The most common approach light system configurations incorporate sequenced flashing lights, commonly known as the rabbit or the running rabbit. These lights are typically strobes positioned in front of the runway along its extended centerline, flashing in a sequence that begins with the farthest light and ends at the Decision Bar.
The Decision Bar, a feature common to all approach lighting systems in the United States, is situated 1000 feet away from the threshold in the direction of the incoming aircraft. It serves as a visual horizon, aiding pilots in transitioning from instrument flight to visual flight. The spacing of the short bars in the approach lighting system helps pilots determine flight visibility, with more precise 100-foot spacing systems being used for lower minimum visibility conditions.
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Runway lights and colours
Runway approach lights are part of an approach lighting system (ALS), which consists of a series of lightbars, strobe lights, or a combination of the two that extend outward from the runway end. These lights are used to guide pilots during takeoff and landing, especially in low-light or low-visibility conditions.
Runway lights are almost direct replacements for runway markings that are only visible during the day. The lights typically indicate the runway edge, threshold, centre line, and touchdown zone. Runway lights are colour-coded to provide specific information to pilots. Runway edge lights are white, except for the last 2,000 feet or half the runway length (whichever is less) on instrument runways, where they are yellow to indicate a caution zone for landing or takeoff. Runway centre line lights are spaced at 50-foot intervals and are white until the last 3,000 feet, where they alternate red and white for 2,000 feet to warn pilots that the end of the runway is approaching. The lights are then solid red for the final 1,000 feet. Runway threshold lights are green and span the landing threshold at the beginning of a runway, indicating the point at which pilots can land.
There are also several other types of runway lighting systems, including:
- Runway End Identifier Lights (REIL): These provide rapid identification of the approach end of a runway. They consist of a synchronised pair of flashing lights on each side of the runway threshold, which can be either omnidirectional or unidirectional.
- Touchdown Zone Lights (TDZL): These indicate the touchdown zone when landing in reduced visibility conditions. They consist of two rows of steady-burning white lights that start 100 feet beyond the landing threshold and extend to 3,000 feet beyond it.
- High-Intensity Runway Lights (HIRL): These are the brightest type of runway edge lighting and are used on runways with high-intensity operations.
- Medium-Intensity Runway Lights (MIRL): These are the second-brightest type of runway edge lighting.
- Low-Intensity Runway Lights (LIRL): These are the least bright type of runway edge lighting and typically have only one intensity setting.
- Sequenced Flashing Lights (SFL): These lights are typically strobes mounted in front of the runway on its extended centre line. They flash in sequence, usually at a speed of two consecutive sequences per second, beginning with the light farthest from the runway and ending at the Decision Bar.
The intensity of runway lights can often be controlled and adjusted to meet pilots' requests. Radio control of lighting is available at selected airports, providing airborne control of lights by keying the aircraft's microphone.
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History of airport approach lights
Airport approach lights, also known as an approach lighting system (ALS), have been crucial to the safety of air travel since the birth of air transport as a large-scale phenomenon. The first airport lighting systems were installed in the late 1920s, with approach lighting coming into use in the 1930s.
After World War II, the U.S. Navy and United Airlines collaborated on various methods to enable aircraft to land safely at night and under zero-visibility weather conditions, such as rain or heavy fog. The result was the predecessor of today's ALS: a 3,500-foot visual approach consisting of 38 towers, with 17 on each side, and atop each 75-foot-high tower, a 5,000-watt natural gas light.
The U.S. Navy's development of these lighted towers was soon followed by the adoption of more efficient and brighter strobe lights, initially known as Strobeacon lights. The first large commercial airport to install a strobe light ALS visual approach path was New York City's John F. Kennedy International Airport, in 1956.
Since then, approach lighting systems have become increasingly sophisticated, with the addition of computer-controlled systems. Modern ALS configurations are highly complex in design and significantly enhance aircraft safety, especially in conditions of reduced visibility. These systems consist of a series of lightbars, strobe lights, or a combination of both, extending outward from the end of a runway.
The International Civil Aviation Organization (ICAO) recognizes several ALS configurations, and non-standard configurations are also installed at some airports. Typically, these systems are of high intensity and are complemented by various on-runway light systems, such as runway end identifier lights (REIL), touchdown zone lights (TDZL), and high-intensity runway lights (HIRL).
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Airport beacon lights
The importance of fully operational airport beacon lights in ensuring pilot safety is paramount, and these visual aids must adhere to strict Federal Aviation Administration (FAA) standards. The FAA has specific criteria for the location, light intensity, rate of flashing, and colour patterns of the beacons, which are widely replicated worldwide.
Daily, bi-monthly, and yearly checks are essential for maintaining optimal operation and functionality of the beacon lights. The glass in any rotating airport beacon should be inspected twice a month to ensure maximum clarity and proper light dispersion. Electrical components and connections must be inspected annually to ensure proper fit and function.
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Pilot-controlled lighting systems
An approach lighting system (ALS) is a lighting system installed at the end of an airport runway, consisting of lightbars, strobe lights, or a combination of both. Modern approach lighting systems are designed to be highly complex, significantly improving aircraft safety, especially in low-visibility conditions.
Pilot-controlled lighting (PCL) systems are standard at airfields without air traffic controllers and allow pilots to activate the lighting without assistance. These systems are also known as Aircraft Radio Control of Aerodrome Lighting (ARCAL) and monitor a specific radiofrequency UNICOM (Universal Communications). After tuning into these frequencies, the pilot will click the push-to-talk button to connect to the radio receiver at the airport.
The pilot can then control the lighting intensity, which is crucial during low-visibility conditions. Pilots can also activate the Precision Approach Path Indicators (PAPI). While PAPI is typically operated by air traffic controllers, pilots can operate them at smaller airfields using the same radio system.
There are two types of ARCAL systems: type J and type K. Type J systems are activated by keying the microphone five times within five seconds, while type K is initially activated by clicking seven times within five seconds. Once activated, the intensity of type K systems can be adjusted by keying the microphone three, five, or seven times within five seconds, respectively, for low, medium, or high-intensity settings.
The pilot-controlled lighting system is beneficial for small airports, helping them save money and reduce light pollution in the surrounding areas.
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Frequently asked questions
Airport approach lights are called an approach lighting system (ALS).
An ALS consists of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end. The most common approach light system configurations include sequenced flashing lights (SFL) or runway alignment indicator lights (RAIL).
Runway lights are almost direct replacements for runway markings that are only visible during the day. Runway light colors have specific meanings. For example, white lights change to yellow for the last 2,000 feet or half the runway length (whichever is less) to form a caution zone. A horizontal line of red lights marks the end of the runway.
Airport approach lights are controlled by air traffic controllers (ATCOs) at towered airports. At non-towered airports, the lights may be on a timer or controlled by Flight Service Station (FSS) personnel. Pilots may request that lights be turned on or off and can also request a specified intensity.
