What do the ICAO AGL terms mean?
ICAO gives the parts of an airfield, and the lights that serve them, exact names — so a designer, an inspector and a pilot all mean the same thing.
ICAO AGL terminology is the fixed vocabulary of Annex 14, Volume I for naming the areas of an aerodrome and the aeronautical ground lights that serve them. A light is named by where it is and what it tells the pilot: threshold lights mark the start of the part of the runway usable for landing, runway end lights mark the end of the runway, and a stop bar says stop at a holding position.
The same text separates a Standard (shall) from a Recommended Practice (should), and many terms carry a colour and a role. Using the exact term avoids ambiguity in specifications, inspection reports and fault logs.
- Find the verb. Shall marks a Standard; should marks a Recommended Practice.
- Find the noun. Is it a runway, a taxiway, an apron or a holding position? ICAO defines each, and the lighting follows the area.
- Find the light. Names like threshold, touchdown zone, centre line and stop bar say where a light sits and what it tells the pilot.
- Find the colour and role. White, green, red, yellow or blue each carries a meaning, so the colour is part of the term.
- Check the edition. Quote Annex 14 by volume, chapter and amendment, and note any national difference.
Necessary for the safety or regularity of air navigation. States comply or notify ICAO of a difference.
Desirable in the interest of safety, regularity or efficiency. States will endeavour to conform to it.
Frequently Asked Questions
Q1Is AGL an ICAO term?
Not exactly. ICAO Annex 14 speaks of aeronautical ground lights, meaning any light provided specially as an aid to air navigation. AGL (airfield ground lighting) is the everyday industry shorthand for the same lighting on the airfield.
Q2What is the difference between a Standard and a Recommended Practice?
In ICAO Annex 14 a Standard uses the word shall and is necessary for the safety or regularity of air navigation; States must comply or notify ICAO of a difference. A Recommended Practice uses the word should and is desirable, and States will endeavour to conform to it. Reading the verb correctly is the first step in reading any lighting requirement.
Q3What is the difference between a runway-holding position and a stop bar?
The runway-holding position is the place where taxiing aircraft and vehicles stop and wait for clearance, shown by markings and signs. A stop bar is the row of red lights across the taxiway at that position, switched on to say stop and off to say proceed, under the control of the tower.
Q4What is the difference between the threshold and the touchdown zone?
The threshold is the beginning of the part of the runway usable for landing, marked by green threshold lights. The touchdown zone is the part of the runway beyond the threshold where landing aeroplanes are first intended to contact the runway; touchdown zone lights are required on Category II and III precision approach runways.
Q5Where are ICAO lighting terms defined?
Definitions are in Annex 14, Volume I (Aerodrome Design and Operations), and the lighting requirements are in its chapter on visual aids for navigation. The Aerodrome Design Manual, Doc 9157, Part 5 covers electrical systems. Always check the current edition and any national differences.
Q6What is a PAPI and how does the pilot read it?
A PAPI (precision approach path indicator) is a row of four light units beside the runway, normally on the left side near the threshold. Each unit shows white when the pilot is above its set angle and red when below. Above the slope the pilot sees more white, on the slope two white and two red, and below the slope more red. It is a visual approach slope indicator, not a light that marks part of the runway. Check Annex 14, Volume I, and the national requirement for the exact arrangement.
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