FX850A Inset Runway Centreline Light

The FX850A (FAA designation L-850A(L)) is ATG's primary inset runway centreline light for Category II and III precision approach operations. Installed along the centreline of the runway at 15-metre intervals (or 7.5 m in the touchdown zone), these fixtures form the white and — in the last 900 m before the threshold — alternating white/red, and finally red-only, colour transition sequence that tells pilots their position along the runway during low-visibility approaches and rollouts.

The fixture sits 4.0 mm above grade, fully within the FAA Style 3 and ICAO Style 4 flush-fitting envelope (≤6.3 mm), and is designed to sustain repeated aircraft main-gear and nose-gear overrolling without structural damage. The flat lens with no negative slope prevents sand, silt, and standing water accumulating in the aperture — an important characteristic at Gulf airports where fine desert sand is an ever-present contaminant.

Both bidirectional and unidirectional optical configurations are available, supporting centreline-only or centreline-plus-touchdown-zone combined installations. The LED array operates on 2.8–6.6 A series circuits and is fully dimmable against the tungsten halogen response curve, ensuring intensity step calibration matches existing centreline design standards. Fail-open monitoring signals LED array degradation to the airfield management system.

With LED service life exceeding 60,000 hours, airport engineering teams can expect to reduce runway closure frequency for lamp replacement dramatically compared with halogen predecessors — a meaningful operational gain at busy international airports where runway availability directly affects capacity.