What are touchdown zone lights?
A system of paired white light bars (barrettes) that identifies the touchdown zone and gives pilots precise visual guidance during the landing phase.
Touchdown zone lights provide visual guidance to pilots during the landing phase by identifying the touchdown zone of the runway. They consist of two rows of white transverse light bars (barrettes) disposed symmetrically about the runway centre line — each barrette made up of at least three light units set close together (ICAO: spacing not more than 1.5 m, barrette 3 m to 4.5 m long). They are fixed, unidirectional lights showing variable white.
The system extends from the threshold for 900 m, or to the runway midpoint, whichever is less: on a runway shorter than 1 800 m the system is shortened so that it does not extend beyond the midpoint. With 60 m spacing the first pair sits 60 m in from the threshold and successive pairs follow every 60 m along the runway. ICAO also allows 30 m spacing, with the first pair then 30 m in, which is advisable for operations at the lowest visibility minima. The lateral spacing between the innermost lights of each pair matches the touchdown zone marking. This is distinct from the runway centreline lights, which run as a single longitudinal row down the middle rather than paired rows to each side.
Frequently Asked Questions
Q1What are touchdown zone lights?
A system of fixed, unidirectional, variable-white lights arranged as paired transverse light bars (barrettes), disposed symmetrically about the runway centre line, that identifies the touchdown zone and provides visual guidance during landing.
Q2How far does the touchdown zone lighting system extend?
From the threshold for 900 m, or to the runway midpoint, whichever is less, with the first pair 60 m in from the threshold and successive pairs 60 m apart (30 m spacing, with the first pair 30 m in, is also allowed).
Q3What is the abbreviation for touchdown zone lights?
TDZL.
Q4How is TDZL different from runway centreline lights?
TDZL uses paired transverse barrettes disposed to each side of the centreline, while runway centreline lights run as a single longitudinal row down the middle.
Q5Are touchdown zone lights required on every runway?
No. ICAO Annex 14 requires touchdown zone lights in the touchdown zone of a precision approach runway Category II or III. Whether they are provided on other runways is a decision for the aerodrome authority under the applicable standard.
Q6How many lights are in each touchdown zone barrette?
At least three light units, spaced not more than 1.5 m apart, in a barrette 3 m to 4.5 m long set across (at right angles to) the runway centreline.
See It. Understand It. Then Learn How to Engineer It.
Recognising an AGL system visually is the first step. The next step is knowing how to design, install, test, commission and maintain them correctly.
Build Practical AGL Engineering Skills
Go deeper with structured training from Precision AGL Academy, covering:
Learn how each light, sign and circuit works as part of a complete airport lighting system, not just as an isolated diagram.