How is a sign selected?
Four decisions, taken in order, that narrow the choice to the right airfield sign for its message, its pilot and its place on the airfield.
A sign only works if the pilot reads it in time, so it is chosen for its message and its reader. The function sets the colour scheme, red for mandatory and yellow and black for information. The legend size follows the sign type and runway, the lighting method sets the housing depth, and the site decides how it is powered and mounted.
The flowchart only narrows the choice. The final sign is confirmed against the signage plan for colour and inscription, legend height, lit-face luminance, frangibility and its transformer and driver, and against the standard it must meet.
Frequently Asked Questions
Q1How is an airfield sign selected?
By working through a few decisions in order: what the sign must tell the pilot, how large its legend must be, how the face is lit, and what circuit and site it must suit. The result is then checked against the data sheet, the standard and the airport’s signage plan.
Q2Why does the sign function come first?
Colour carries the meaning. A mandatory sign is red with a white inscription and marks a position an aircraft or vehicle must not pass without clearance (a holding position, for example), or prohibits entry. An information sign only guides, as a location sign with a yellow inscription on black or a direction sign with a black inscription on yellow. Each panel carries one colour scheme: a red mandatory panel is not combined with yellow-and-black information on the same panel, although a location sign may stand beside it as a separate panel.
Q3What decides the size of the legend?
Annex 14 sets minimum character heights of 200, 300 and 400 mm, and the sign face is at least twice the legend height. Which height applies depends on the sign type and the runway it serves, so the airport’s design and the standard decide, not the manufacturer’s catalogue alone.
Q4What is the difference between a back-lit and an edge-lit sign?
A back-lit sign has its LED sources behind the face and needs a deeper housing so the light can spread. An edge-lit sign has LEDs along the edges feeding a light guide plate, which gives even luminance in a thinner housing. Either must deliver the luminance and colour the standard requires.
Q5What should be checked before the choice is final?
That the colour, inscription and legend height match the signage plan, that the lit face meets the required luminance, that the sign is low and frangible with a sealed housing, and that its transformer and driver suit the series circuit. The manufacturer’s data sheet and the standard decide.
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