What are the FAA fixture concepts?
A fixture is more than a lamp — the FAA specifies how it is designated, mounted, supported, connected and certified.
FAA fixture concepts describe a light as a complete installed unit. Each fixture type has an L-number in the FAA specification, and it is mounted either elevated on a frangible coupling or inset in the pavement. It sits on a buried light base, and an isolation transformer in the base or a separate housing connects it to the series circuit.
Equipment on FAA-funded projects is expected to come from the FAA’s certification program, so a fixture is specified by its designation, its mounting and its certified listing together, not by brightness alone.
- Find the designation. Look for the L-number in the specification, such as the L-850 series of inset runway lights.
- Note the mounting. Elevated on a frangible coupling, or inset in the pavement.
- Note the light base. Non-load-bearing for elevated fixtures, load-bearing for inset ones, and whether the transformer sits in the base or a housing.
- Check colour and direction. Uni-directional or bi-directional, and the colour for the zone, such as yellow in the caution zone.
- Confirm certification. Check the item is on the current FAA certified list and which Advisory Circular revision applies.
Stands above the surface on a frangible coupling that breaks away if struck. Sits on a non-load-bearing base.
Set flush in pavement and projects only slightly. Sits on a load-bearing base that carries aircraft wheels.
Frequently Asked Questions
Q1What does an FAA L-number mean?
It is the designation of a type of fixture or equipment in an FAA specification, such as the L-850 series of inset runway lights in AC 150/5345-46. The number identifies the type, not its brightness, so read the Advisory Circular to see what each designation covers and which revision is current.
Q2What is a frangible coupling?
The breakaway joint under an elevated light. If an aircraft or vehicle strikes the light, the coupling is designed to break cleanly so the damage is limited, and the light base and cable below are protected. Elevated lights are expected to be frangible under both FAA and ICAO rules.
Q3What is the difference between a light base and a transformer housing?
The light base is the buried can that supports and mounts a fixture, and it may also hold the isolation transformer. A transformer housing is a separate buried can for the transformer, commonly used with inset lights, which connects to the fixture by a short secondary cable. Both are covered by FAA base and housing specifications.
Q4What is the FAA's equipment certification program?
The Airport Lighting Equipment Certification Program (ALECP), described in AC 150/5345-53. Equipment is tested by approved bodies against the relevant specification and listed, so owners can specify certified equipment. Check the FAA's current list rather than relying on an older copy.
Q5Do FAA and ICAO fixtures differ?
They serve the same functions but are specified differently. Colour names are largely aligned, since both call the caution-zone colour yellow, but distances are given in feet or metres, and light output is set by an FAA specification rather than the Annex 14 photometric curves. Compare them requirement by requirement.
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