What is an omnidirectional fixture?
One light, every direction: it shows around the full circle, so the pilot sees it from wherever they approach.
An omnidirectional fixture shows light at all angles in azimuth, a full 360° around it. There is no front or back, so it is used where aircraft or vehicles can come from any side.
Elevated taxiway edge lights are the standard example, showing blue all round, because an aircraft may arrive from either direction or at an angle. Obstacle lights and heliport perimeter lights follow the same logic. Omnidirectional describes the fixture, not every installation: at taxiway intersections, exits and curves, edge lights are shielded as far as practicable so they are not seen from azimuths where they could be confused with other lights. Coverage is all round in azimuth, but the intensity still varies with angle and taxiway edge lights must still show up to at least 75° above the horizontal, so the photometric data governs.
All directions in azimuth. Seen from any side, so orientation is not critical.
One beam, or two beams 180° apart. Aimed at specific observers.
Frequently Asked Questions
Q1What is an omnidirectional fixture in airfield ground lighting?
A fixture that shows its light at all angles in azimuth, a full 360 degrees around it, so an observer sees it from any side.
Q2Which AGL lights are normally omnidirectional?
Elevated taxiway edge lights show blue in all directions. Obstacle lights and heliport perimeter lights are also commonly omnidirectional, because aircraft can approach from any side.
Q3Why use an omnidirectional fixture?
On a taxiway, an aircraft can arrive from either direction, turn, or approach at an angle. One all-round light is seen from wherever the pilot is, with no aiming or orientation to get wrong.
Q4Is an omnidirectional fixture equally bright in every direction?
Not necessarily. It covers all azimuths, but the intensity is shaped to the requirement and varies with angle, and is concentrated at low elevation angles, although a taxiway edge light must still show up to at least 75 degrees above the horizontal. The photometric data sets the actual distribution.
Q5Does orientation matter for an omnidirectional fixture?
Much less than for a one-way or two-way fixture, because the beam covers every direction. Height, levelness and a clean, unobstructed lens still matter.
Q6How does it differ from bidirectional and unidirectional fixtures?
A unidirectional fixture has one beam, a bidirectional fixture has two beams 180 degrees apart, and an omnidirectional fixture covers every direction around it.
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