What are the minimum serviceable lamp percentages by light type?
The share of lights that must be working is set per light type and per operation. A CAT II/III centreline is held tighter than a CAT I edge row, and runway end lights are held looser than most. Stop bars and taxiway centreline lights are counted, not averaged.
Each figure is a minimum share of installed lights that should be serviceable in that light type while the operation is in progress. A light counts as serviceable only if its main-beam average intensity is at least 50 per cent of the specified value (Entry 26). On top of the percentage, unserviceable lights should not be adjacent where that would lapse guidance (Entry 28).
1Precision approach runways
For CAT II/III, the objective is 95% of runway centreline, threshold and runway edge lights, 95% of the inner 450 m of the approach lighting system, 90% of touchdown zone lights and of the approach lighting beyond 450 m, and 75% of runway end lights. For CAT I, it is 85% in each of the approach lighting system, threshold, runway edge and runway end lights.
2Take-off in low visibility
For take-off in RVR below 550 m: 95% of runway centreline lights (where provided) and edge lights, and 75% of runway end lights. For take-off in RVR of 550 m or more: 85% of runway edge and runway end lights.
3Critical lights are counted
A stop bar used with RVR below 350 m should have no more than two unserviceable lights, and no two adjacent unless the spacing is significantly closer than specified. On a taxiway used in RVR below 350 m, no two adjacent centreline lights should be unserviceable.
A runway edge row of 60 lights at 95% allows 3 unserviceable lights, and none of them side by side.
Work from the lights actually installed in that light type and round the allowed outages down, so the share is never exceeded.
- Apply the figure for the operation in progress
- Count each light type on its own
- Check adjacency as well as the percentage
- Average across light types
- Count a dimmed light as serviceable
- Treat the percentage as permission to leave lights out
| Operation | Light type | Minimum serviceable |
|---|---|---|
| CAT II/III | Runway centreline, threshold, runway edge | 95% |
| CAT II/III | Approach lighting, inner 450 m | 95% |
| CAT II/III | Touchdown zone, approach lighting beyond 450 m | 90% |
| CAT II/III | Runway end | 75% |
| CAT I | Approach lighting, threshold, runway edge, runway end | 85% |
| Take-off, RVR below 550 m | Runway centreline (where provided), runway edge | 95% |
| Take-off, RVR below 550 m | Runway end | 75% |
| Take-off, RVR 550 m or more | Runway edge, runway end | 85% |
| Stop bar, RVR below 350 m | Stop bar | No more than 2 out, none adjacent |
| Taxiway, RVR below 350 m | Taxiway centreline | No two adjacent out |
Frequently Asked Questions
Q1What minimum percentages apply to CAT II/III runways?
Annex 14 sets the objective at 95 per cent serviceable for runway centreline, threshold and runway edge lights, 95 per cent for the inner 450 m of the approach lighting system, 90 per cent for touchdown zone lights and the approach lighting beyond 450 m, and 75 per cent for runway end lights, held during CAT II or III operations.
Q2What minimum percentage applies to a CAT I runway?
At least 85 per cent of the lights should be serviceable in each of the CAT I approach lighting system, the threshold lights, the runway edge lights and the runway end lights.
Q3What applies to runways used for low-visibility take-off?
Where take-off is meant for RVR below 550 m, 95 per cent of runway centreline lights (where provided) and edge lights, and 75 per cent of runway end lights. For RVR of 550 m or more, 85 per cent of runway edge and runway end lights.
Q4Do stop bars and taxiway centreline lights use percentages?
No, they are counted. For a stop bar used with RVR below 350 m, no more than two lights should be unserviceable and two adjacent lights should not be out unless the spacing is significantly closer than specified. For a taxiway used in RVR below 350 m, no two adjacent centreline lights should be unserviceable.
Q5How do I turn a percentage into a number of lights?
Apply it to the lights actually installed in that light type, then round the allowed outages down so you never exceed it. For example, a row of 60 edge lights at 95 per cent allows 3 unserviceable lights, and none of them adjacent.
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