How are approach lights tested?
Instrument measurements that show how the circuit really performs, finding faults that an inspection cannot see.
Where inspection looks, testing measures. An approach lighting circuit is tested at five points: insulation resistance, circuit current, earth continuity, light output and control function.
Tests are made at commissioning, at regular intervals, and after any repair or fault. Results are recorded and compared with required and previous values, so a slow decline, such as falling insulation resistance, is caught before it becomes a failure.
Frequently Asked Questions
Q1What is approach-light testing?
Measuring how an approach lighting circuit performs, using instruments, rather than only looking at it. Typical tests cover insulation, circuit current, earthing, light output and control function.
Q2How is testing different from inspection?
Inspection is a visual and physical check. Testing takes measurements and compares them with required or baseline values, which can reveal faults that cannot be seen.
Q3When are approach lights tested?
At commissioning, at regular intervals under the airport’s maintenance programme, and after any repair, fault or circuit change.
Q4What is an insulation resistance test?
A test made with a megohmmeter on the isolated circuit, with the CCR disconnected. It applies a test voltage and measures the resistance between the cable and earth, and the cable is discharged afterwards. A falling reading warns of insulation damage before it causes an earth fault.
Q5Who should carry out the tests?
Trained and authorised AGL personnel. Series circuits carry hazardous current, so testing follows the site isolation, lock-out and permit procedures. Insulation and earth tests are made with the circuit isolated; current, output and control checks are made energised, never by opening a live loop.
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