What is an inset runway light?
A flush-mounted fixture set into the pavement surface, so aircraft and vehicles can roll straight over it — no riser, no frangible coupling, no above-ground obstruction.
An inset runway light is a flush-mounted fixture set into the runway pavement. A low, sealed fixture body is bolted to a flange on a shallow light base cut into the pavement structure, so only a thin top with the optical window rises above the surface. Runway centreline and touchdown zone lights are inset, and edge lights may be inset too.
Because wheels run directly over it, it is built to carry aircraft wheel loads, and its heat and height are controlled so it stays safe for tyres. Without a raised stem it needs no frangible coupling; the trade-off is a more involved installation, since the base must be set into the pavement and adjusted when it is resurfaced.
Stands above grade beside the runway edge on a frangible coupling.
Sits within the pavement, so it can be rolled over and presents no obstruction.
Frequently Asked Questions
Q1What is an inset runway light?
A runway light fixture mounted flush in the pavement surface, on a shallow light base below. Aircraft and vehicles can roll over it, so it presents no above-ground obstruction.
Q2Why use an inset light instead of an elevated one?
Where an above-ground fixture would be an obstruction or be exposed to damage, or where the light must sit within the paved area itself. Runway centreline and touchdown zone lights, for example, are inset because they lie directly in the path of the wheels.
Q3Can aircraft drive over an inset runway light?
Yes. The fixture is built to withstand aircraft wheel loads, projects only slightly above the surface, and is designed so that its surface temperature stays suitable for tyres.
Q4Is an inset light frangible?
No. It is not a raised object, so it needs no frangible coupling. Its protection against impact comes from being low, flush and structurally strong.
Q5What is below an inset runway light?
A shallow light base (can) set into the pavement structure. It holds the fixture and its secondary connection; the isolation transformer is normally in a deep base or a separate transformer housing nearby, joined by a secondary lead, and connects the fixture to the airfield's series lighting circuit through the primary cable.
Q6Which runway lights are normally inset?
Runway centreline and touchdown zone lights are inset. Runway edge lights may be either elevated or inset, and stop bars may use elevated and/or inset fixtures.
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