What is a fixture foundation?
The small concrete base under an elevated light. It sets the fixture’s position, height and facing, so it has to be right before the concrete cures.
A fixture foundation is a small concrete footing that supports an elevated AGL light, such as an edge light. Anchor bolts set into it carry a frangible coupling, and a conduit brings the cable up inside the footing to the fixture.
It is a civil interface because it is excavated and poured with the civil works, often in turf beside pavement. Its position, top level, orientation, anchor-bolt layout and conduit entry must match the lighting layout and the coupling, and be agreed with the AGL team before the concrete cures.
Concrete footing holding an elevated light on a frangible coupling above ground.
Buried housing for an inset or shallow-mounted light and its connections.
Frequently Asked Questions
Q1What is a fixture foundation in airfield ground lighting?
A small buried or ground-level concrete base that supports an elevated light, such as an edge light. It carries the fixture on a frangible coupling and brings the cable up through a conduit.
Q2Why is a fixture foundation a civil interface?
It is excavated and poured as civil works, often in turf beside pavement. Its position, level, orientation and anchor bolts must be set to the lighting layout and agreed with the AGL team before the concrete cures.
Q3How is a fixture foundation different from a base can?
A base can is a buried housing for an inset or shallow-mounted light and its connections. A fixture foundation is a concrete footing that holds an elevated fixture and its frangible coupling above ground.
Q4Why is the frangible coupling part of the interface?
The coupling sits between the foundation and the fixture and is designed to break if struck, so the foundation top, bolt layout and fixture height must match the coupling and the elevation requirements.
Q5What goes wrong if the foundation is set out poorly?
The fixture may sit at the wrong height, lean, or face the wrong way, and the beam may not align. These are hard to correct after the concrete cures, so setting out and template checks matter.
Q6Where are the requirements defined?
FAA AC 150/5340-30 covers installation details, AC 150/5345-45 covers low-impact-resistant (frangible) supports and AC 150/5370-10 covers concrete construction. ICAO Annex 14 Vol I Ch 5 and Aerodrome Design Manual Doc 9157 Part 6 cover frangibility, while Part 5 covers electrical systems. Confirm against the current edition and the manufacturer's data.
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