What is the approach area?
The ground beyond the runway threshold, along the extended centreline, where the approach lighting system stands — 420 m long on a simple system, 900 m where precision approaches are flown, with crossbars at fixed distances from the threshold.
In an airfield layout, the approach area is the strip of ground that continues the runway outward from each threshold, under the path an aircraft follows on final approach. For AGL it is the land the approach lighting system occupies, so it decides where foundations, cable routes and power for those lights have to go, and what has to stay clear around them.
1How far it is lit
Annex 14 sets the length of the lighting by the type of approach the runway supports. A simple approach system extends 420 m or more from the threshold. A precision approach system, for CAT I and CAT II/III, extends 900 m wherever possible. Along that length, lights sit on the extended runway centreline at 30 m spacing in a precision system (normally 60 m in a simple one), and a crossbar of lights crosses the centreline at fixed distances from the threshold. A CAT II/III system also carries red side rows in the inner 270 m.
2What the layout has to protect
The lights are set as low as practicable and, when elevated, are frangible, because an aircraft that touches down short could strike them. Beyond 300 m, tall structures need to be frangible only in their top 12 m. The approach area also has to stay clear of obstacles above the approach surfaces, which are an obstacle-limitation matter handled in the airport design. For where the lighting begins, see Threshold Lights.
| System | Length | Crossbars |
|---|---|---|
| Simple approach lighting | 420 m or more | 300 m |
| Precision approach, CAT I | 900 m wherever possible | 300 m |
| Precision approach, CAT II/III | 900 m | 300 m and 150 m |
Frequently Asked Questions
Q1What is the approach area in an airfield lighting layout?
The ground beyond the runway threshold, along the extended runway centreline and beneath the final approach path. It is where the approach lighting system is installed and where the layout has to keep obstacles clear.
Q2How long is an approach lighting system?
A simple system extends 420 m or more from the threshold. Precision approach systems, for CAT I and CAT II/III, extend 900 m wherever possible. Both lengths are Standards in ICAO Annex 14, Volume I, Chapter 5, written as wherever possible, so where site limits stop the full length, the shortfall is a matter to assess and agree with the regulator.
Q3Where is the crossbar on an approach lighting system?
300 m from the threshold on simple and CAT I systems. CAT II/III systems add a second crossbar at 150 m.
Q4Why must approach lights be frangible?
An aircraft that touches down short could strike them, so the structures are built to break away. Annex 14 requires elevated approach lights and their supports to be frangible, with an allowance for the top 12 m only on tall structures beyond 300 m.
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