Definition
A combined reference to two in-pavement runway lighting systems used on precision instrument runways. Touchdown Zone Lighting (TDZ) consists of two rows of transverse white light bars installed symmetrically about the runway centerline in the touchdown zone, beginning 100 feet beyond the landing threshold and extending 3,000 feet down the runway, or to the midpoint, whichever is less. Runway Centerline Lighting (CL) consists of flush white lights spaced 50 feet apart along the runway centerline, transitioning to alternating white and red, then to all red, as the runway end approaches. When TDZ/CL is listed as inoperative, certain straight-in landing minimums on the approach chart must be raised in accordance with the inoperative components table.
Plain English
Two sets of lights built into the runway surface that help pilots see exactly where to touch down and where the centerline runs during a low-visibility landing. If either set is out of service, the published landing minimums on the approach plate may need to be raised before the approach can legally be flown.
Context Anchor
Seen in approach lighting legends, airport lighting notes, and instrument approach information when runway lighting equipment is listed or when inoperative lighting may affect landing minimums.
Why Pilots Care
Provides precise visual guidance for runway alignment and touchdown point during low-visibility approaches, reducing the risk of runway excursions or unstable landings.
Intuition Check
Do not read TDZ/CL as one single light system. It is a combined notation for two runway lighting systems: touchdown zone lights and centerline lights.
Example Sentence 1
The NOTAM listed TDZ/CL as out of service, so we checked the inoperative components table and raised our landing minimums before starting the approach.
Example Sentence 2
With the TDZ/CL system operating, the crew maintained centerline tracking through the final 1,000 feet of the approach.