How is serviceability measured and reported?
A serviceability level only means something if it is measured the same way every time and reported to the people who need it. Each light is checked against the 50 per cent line, the lights are counted by type, the result is compared with the objective and the adjacency rule, and the outcome is logged and passed on.
Serviceability is a calculation made from checks. A light counts only if its main-beam average intensity is at least 50 per cent of the specified value (Entry 26), the count is made per light type against the objective (Entry 27), and adjacency is checked separately (Entry 28). The record then shows whether the level was held.
1Checking each light
A visual patrol finds lights that are out, dirty, obscured or damaged. For CAT II/III runways, Annex 14 recommends that preventive maintenance include checks of intensity, beam spread and orientation, made with a mobile measuring unit accurate enough to assess individual lights, and of the electrical characteristics of each circuit and of the intensity settings used by air traffic control. The frequency depends on traffic density, local pollution, equipment reliability and earlier results, and for in-pavement lights should not be less than twice a year.
Quick and frequent. Shows a light is out, dirty or obscured, but not that a lit light has fallen below 50%.
Slower and periodic. The only way to show a lit light has dropped below the 50% line.
2Turning checks into a figure
Count by light type and circuit. Lights below the 50 per cent line are unserviceable even if lit. The percentage is serviceable divided by installed: 57 of 60 is 95 per cent. Then check adjacency, and judge stop bars by their count, not a percentage (Entry 29).
3Reporting
Record the result in the log, and tell airfield control straight away when an objective is not met or a critical light is affected. Where an outage affects operations and will last, aerodrome and air traffic services arrange for it to be published, for example by NOTAM, under your State’s rules. Record the restoration too. Trends in the log, such as the same circuit or fixture type recurring, show where to look.
- Log counts and positions, not just “OK”
- Time-stamp when a fault was found and restored
- Report below-objective results to control at once
- Record only a total with no positions
- Wait for the repair before reporting
- Count a lit light as serviceable without measuring
| Item | What to record |
|---|---|
| Light type and circuit | Which system and which circuit were checked |
| Installed and unserviceable | Counts, and the positions of every outage |
| Intensity results | Lights found below 50% of the specified value |
| Objective applied | The percentage or count, the adjacency check and the result |
| Timing | When each fault was found and when it was restored |
| Notification | Who was told, and whether a NOTAM was needed |
Frequently Asked Questions
Q1How is the serviceability of a light measured?
Three ways work together. A visual patrol finds lights that are out, dirty, obscured or damaged. A mobile measuring unit checks intensity, beam spread and orientation, which is the only way to show a lit light has dropped below 50 per cent of its specified intensity. Where fitted, a monitoring system reports lamp and circuit status to the control room.
Q2How often must intensity be measured?
Annex 14 ties the frequency to traffic density, local pollution, the reliability of the installed equipment and the results of earlier measurements. For CAT II/III in-pavement lights it should not be less than twice a year. Confirm the current wording and your regulator's requirement.
Q3How do I calculate the serviceability percentage?
Count the serviceable lights in one light type and divide by the number installed. For example, 57 serviceable out of 60 installed is 95 per cent. A light below 50 per cent of its specified intensity counts as unserviceable even if it is lit. Then check adjacency separately.
Q4Who must be told when the objective is not met?
Airfield control straight away, so operations can be adjusted under the site procedure. Where the outage affects operations and will last, aerodrome and air traffic services arrange for it to be published, for example by NOTAM, following your State's rules.
Q5What should the maintenance record contain?
The light type and circuit, how many are installed and how many are out, the positions of the outages, any lights found below 50 per cent, the objective applied and the result, the time found and restored, and who was told.
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