If you’ve been to any major airport at night, you may have noticed on the runway there are a lot of different kinds of lights, ranging from flashing white or pulsating yellow to steady red and even blue. And the lights are spaced at defined intervals. Runway lighting is important for aircraft operating at night. Here’s how they’re spaced, and how these lights can make your next night flight safer.
Colors Found In The Runway Edge Lighting
According to the FAA’s most up-to-date airfield Standards publication. There are roughly nine color combinations of lighting you’ll notice around the edges of runways.
Runway Edge light Spacing and Color
Both High-Intensity Runway Lights (HIRLs) and Medium Intensity Runway Lights (MIRLs) require a maximum spacing of two hundred feet between each runway edge light. For runways with intersecting taxiways or alternative runways, the maximum gap cannot exceed four hundred feet. In addition, the runway edge lights must be two to ten feet offset from the full-strength paved runway edge.
Runway edge lights are white until you start getting close to the departure end of the runway. On instrument runways, edge lights are yellow on the last 2,000′, or half the runway length, whichever is less. This forms a caution zone for landing on instrument runways at nighttime. Keep in mind, however, that if you’re not landing on an instrument runway, the edge lights are white all the way to the end of the runway.
Runway centerline Lighting and Color
Runway centerline lights and touchdown zone lights are required for CAT II and CAT III runways, and for CAT I runways used for landing operations below 2,400 foot RVR. Runway line lights are needed on runways used for takeoff operations below 1,600-foot RVR unless specifically approved by the Federal Aviation Agency in an airline operator’s specification for that runway.
Runway centerline lights are spaced at fifty feet apart. Similar to runway centerline markings, knowing this distance can help you perfect landings at nighttime and ensure you don’t float too far. The line of runway centerline lights may be uniformly offset laterally to the same side of the physical runway centerline by a maximum of 2.5 feet.
When viewed from the landing threshold, runway centerline lights are white until the last 3,000 feet. Where they start to alternate red and white for 2,000 feet and eventually solid red for the final 1,000 feet.
Whether you’re VFR or IFR, approach lights can help you identify and line up with the runway at nighttime.
Beyond that, approach lights help instrument pilots transition from IMC to VMC conditions. Once you’re flying an instrument approach, if you can see the white approach light system and nothing else, you can descend all the way down to 100′ above touchdown zone elevation, regardless of the kind of approach you’re flying (even if it’s a non-precision approach). But at the 100′ point, you need alternative visual references to descend lower. Here are some examples of approach light systems that get you down to 100′ above the touchdown zone.
VASI and PAPI Lights
The Visual Approach Slope Indicator (VASI) is a system of lights arranged to supply visual descent guidance information throughout the approach to a runway for VFR and IFR pilots. These lights are visible from 3-5 miles throughout the day and up to twenty miles or more at night. The visual approach path of the VASI provides safe obstruction clearance within plus or minus ten degrees of the extended runway centerline and to four NM from the runway threshold.
If you see two red lights over two white lights, you’re on the approach path. Although normal glide path angles are three degrees, VASI lights at some airports may be as high as 4.5 degrees to grant proper obstacle clearance.
The precision approach path Indicator (PAPI) is another quite common visual glide path indicator light. PAPIs use lights similar to the VASI, but are installed in a single row of either two or four light units. These lights are visible from about five miles during the day and up to twenty miles at night.
The visual approach path of the PAPI generally provides safe obstruction clearance within plus or minus ten degrees of the extended runway centerline and to 3.4 NM from the runway threshold.
Two white lights and 2 red lights mean you’re on the established glide path on a PAPI.
Using Runway Lights to make Your Flight Safer
Flying at night is difficult, however, understanding the runway lighting system for your airport is a key to staying safe. Use the approach, visual approach path and runway lights at your airport, and you’ll stay on-glide and clear of obstructions all the way to the touchdown.