IR.VI.E.K2FAA-S-ACS-8C · Nov 2023Knowledge
Airport signs, markings, and lighting, including approach lighting systems.
Airport signs, markings, and lighting, including approach lighting systems.
Bottom line
The approach light system, except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable. When viewed from the landing threshold, the runway centerline lights are white until the last 3,000 feet of the runway. The white lights begin to alternate with red for the next 2,000 feet, and for the last 1,000 feet of the runway, all centerline lights are red.
Key numbers
| Number | What it means |
|---|---|
| 50-foot intervals along the runway centerline | Centerline spacing |
| last 1,000 feet of the runway | All-red segment |
| last 3,000 feet, viewed from the landing threshold | White-to-red start |
| 100 feet above TDZE, unless red terminating bars or red side row bars visible | Approach light limit |
FAA references
- 14 CFR 91.175 (Takeoff and landing under IFR.) — eCFR current as of 2026-03-05
- AFH Glossary (p. G-13) — FAA-H-8083-3C
- IFH ch. 1 (p. 1-27) — FAA-H-8083-15B
- AFH ch. 6 (p. 6-1) — FAA-H-8083-3C
- RMH ch. 3 (p. 3-8) — FAA-H-8083-2A
- 14 CFR 91.189 (Category II and III operations: General operating rules.) — eCFR current as of 2026-03-05
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