Airport Lighting Aids

Airport Lighting Aids

            1. Runway approach ramps

            Simple version of approach lights

 A simple form of approach lighting consists of a low intensity white  centerline and cross bar. It starts 500 meters earlier to the runway edge (the green lights).

Figure 1: Simple Approach Light System

Precision version of approach lights

Airfields can have more difficult approach lighting systems used mainly in link with ILS equipped runways. A well-known system is the Calvert Approach lighting system. The Calvert system consists of a white centerline and 5 white cross bars. It starts 900 meters earlier to the runway edge. At airfields where CAT II and III approaches are conducted, supplementary approach lights are added to the system. Supplementary approach lights are installed the last 300 meters earlier the runway edge, consist of a white Centerline barrette and two red side barrettes.

	Figure 2: Calvert Approach light system

          2.  Visual Approach Slope Control

Precision Approach Path Indicator (PAPI)

The PAPI provides a visual aid to determine the correct approach path. It contains    single row of 4 red and white lights. The color is depending on the vertical angle as shown in the diagram hereunder.

Figure 3a: PAPI light system

Figure 3b: PAPI light arrangement

PAPI’s are not designed to be used outside 15° of the runway centerline. PAPI’s are usually located to the left side of the runway. But, where this is impossible, it can be mounted on the right side of the runway. There also are airfields where PAPI’s are placed on both sides of the runway. Where a PAPI is used together with an ILS, it is located to align both glide slopes as much as possible.

Visual Approach Slope Indicator (VASI)

A VASI system does greatly the same as a PAPI system. It is just a different arrangement.

It contains two rows of two red and white lights which the arrangement is as shown below:

Figure 4: VASI light arrangement

VASI systems may consist of 2, 4, 6, 12, or 16 light units arranged in bars referred to as near, middle, and far bars. Most VASI systems consist of 2 bars, near and far, and may consist of 2, 4, or 12 light units. Some VASIs consist of three bars, near, middle, and far, which provide an additional visual glide path to accommodate high cockpit aircraft. This installation may consist of either 6 or 16 light units. VASI installations consisting of 2, 4, or 6 light units are located on one side of the runway, usually the left. Where the installation consists of 12 or 16 light units, the units are located on both sides of the runway.

T - VASI

A variation of the VASI is the T-VASI, which presentation is as shown below:

Figure 5:T-light arrangement

    Runway lighting

    All runways certified for night operations shall have:

          ·          Runway Edge Lights

          ·         Runway Threshold and Runway End Lights

             Note that centerline and touchdown zone lights are additional                                guidance in support of low visibility operations.

           

          Runway edge lights

           Edge Lights are white lights situated along the edges of the stated                        runway width spaced at 60 meters.

                                                                                                                                                                  

                               Figure 6a: Runway edge lights

Figure 6b: Runway edge lights

They are white except for:

·         Caution Zone Lights

·         Pre-Threshold Lights

·         Runway Exit Lights

·         Stop way Lights

Caution Zone Lights

Yellow caution zone lights are installed on ILS equipped runways without centerline lights, on the last 600 meter.

Pre- Threshold Lights

On a runway with a displaced landing threshold (an available area in front of the threshold for the take-off run and not the landing), the runway edge lights from the beginning of the pavement up to the displaced threshold are red. Where the area in front of the threshold is narrower than the associated runway width, the edges are lighted is blue.

Runway Exit Lights

One or two Omni-directional blue lights may replace or supplement the edge lights to indicate an exit taxiway.

Stop way Lights

Where a stop way is provided the edge lights are red and facing one way so only the landing traffic is able to see them. A stop way is for emergency use only, and not for routine landings.

Runway threshold and runway end lights

Runway Threshold lights are always seen green by a pilot on final, indicating the start of the available landing distance. Runway End lights are always seen red, indicating the boundary of the runway available for guiding.

                          

                                     Figure 7: Runway threshold and runway end lights

Runway centerline lights

For runways supporting low visibility operations high intensity runway centerline lights are installed.

Runway centerline lights are color coded:

·         From the threshold until 900 meters from the runway end the centerline lights are white.

·         The next 600 meters are alternating red and white lights.

·         The last 300 meters are only red lights.

Runway centerline lights are spaced each 30 meters. However for CAT III runway operations, they are spaced each 15 meters.

             Figure 8: Runway centerline lights

Touchdown zone (TDZ) lights

For runways supporting low visibility operations additional touchdown zone lights, consisting of two rows of white barrettes are installed. The touchdown zone lights extend from the threshold light bar for 900 meters or the midpoint of the runway, whichever is the shorter distance.

Figure 9: Touchdown zone lights

Rapid Exit Taxiway Indicator Lights (RETIL)

Rapid exit taxiway indicator lights consist of six yellow lights in a three/two/one configuration, spaced 100 meters apart (Where the single yellow light is situated 100 meters from the start of the turn).

            Figure 10:Rapid Exit Taxiway indicator lights

3.  Taxiway Lighting

Taxiway edges are provided with blue edge lighting. Green taxiway centerline lights are provided for low visibility procedures (Where green centerline lights are provided, blue edge lights may also be provided).

                    Figure 11: Taxiway Lighting

Stop bar

Airfields approved for low visibility operations have stop bars lights. Stop bars lights consist of equally spaced red lights across the taxiway at a 90° angle to the taxiway centerline. Stop bars are situated at runway entry’s and holding points. They may also be installed at taxiway intersections (e.g. connected with a taxiway guidance system).  Normally stop bars are installed connected with green lead-on lights.

                 Figure 12:stop bar

Runway guard lights

Runway  guard  lights  are  two  pairs  of  alternately  flashing  yellow  lights.  Each pair located next to the taxiway indicating close proximity to the runway. Where a taxiway is wider than usual an alternate variation may be installed, where additional pairs of alternately flashing yellow lights are installed into the taxiway across the full width.

     Figure 13:Runway guard light