How is fixture alignment checked in service?
Making sure each light still points the way it was installed — square to the runway axis, level and at the right height — and re-aiming it when it has drifted.
A light that is on is not necessarily a light that is aimed correctly. Replacement, resurfacing, impact, jet blast and loose bolts can all turn or tilt a fixture without putting it out, so alignment is checked in service against a reference. For an inset runway light the reference is the runway axis or a surveyed line, and an alignment tool set on the fixture’s alignment mark shows any rotation error directly.
Level and height are checked at the same visit, because a tilted fixture shifts the vertical aim and one that stands proud of the pavement is more exposed to damage. Alignment is always confirmed after the final torque pass, since tightening can turn the fixture slightly. What alignment means and why it matters is covered in Fixture alignment (Runway Lighting); this entry is the maintenance routine.
- Prepare. Agree runway access with ATC or airside operations, isolate and lock out the circuit under your permit-to-work, and get the alignment instructions and tolerance for that fixture model.
- Reference. Locate the runway axis or surveyed line and set the alignment tool on the fixture’s alignment mark.
- Read. Compare tool and reference to find the rotation error; check level and height above the pavement.
- Adjust. Loosen the fixture, rotate it to the mark, and bring it level.
- Re-torque. Tighten in a cross pattern to the data-sheet value, then re-check alignment.
- Record. Log the fixture, the error found and the correction made.
Frequently Asked Questions
Q1What is fixture alignment checking in maintenance?
Confirming that an in-service light is still aimed as installed: rotated square to the runway axis, sitting level and at the correct height. If it has drifted, it is re-aimed, re-torqued and checked again.
Q2What can knock a fixture out of alignment?
Fixture replacement, resurfacing or grooving, impact from vehicles or snow clearing, jet blast, and bolts that have worked loose. Any of these can turn or tilt a fixture without it going out.
Q3How is rotation checked on an inset light?
An alignment tool or jig is set on the fixture's alignment mark and compared with the runway axis or a surveyed reference line. Any angle between the tool and the line is the rotation error.
Q4Why check level and height as well as rotation?
A tilted fixture changes the vertical aim of the beam, and one that stands too high or sits too low is more exposed to wheel and snow-plough damage. The correct height above the pavement comes from the manufacturer's data.
Q5Why re-check alignment after tightening the bolts?
Tightening can turn a fixture slightly. Alignment is therefore confirmed after the final torque pass (see Torque checking), not only before it.
Q6How is this different from the Fixture alignment entry in Runway Lighting?
That entry explains what alignment is and why a beam must be aimed correctly. This one covers how alignment is checked and corrected on a fixture already in service.
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