FAA Instrument Flight Instructor (FII)IFR Procedures and ApproachesHard
During an ILS approach at night, the pilot reaches decision altitude with only the approach light system in sight; the runway environment itself is not visible. Per 14 CFR 91.175, below what height may the pilot NOT continue descent using the approach lights alone unless red terminating bars or red side-row bars are also distinctly visible?
- A50 feet above the runway threshold
- B200 feet above the touchdown zone elevation
- CThe published decision altitude itself
- D100 feet above the touchdown zone elevation
Show answer & explanationAnswer & explanation
Correct answer: D. 100 feet above the touchdown zone elevation
14 CFR 91.175(c)(3)(ii) specifically prohibits descent below 100 feet above the touchdown zone elevation using only the approach light system as visual reference, unless the red terminating bars or red side-row bars are also distinctly visible, indicating proximity to the runway.
Why the other options are wrong
- A. 50 feet AGL relates to other visual reference criteria, not this specific rule.
- B. 200 feet is not the specified threshold in the regulation.
- C. The DA is where the visual reference decision is made, not the floor for approach-light-only descent.
91.175 Red Terminating/Side-Row Bars Rule
A pilot may not descend below 100 feet above the touchdown zone elevation using the approach light system as the sole visual reference unless red terminating bars or red side-row bars are also distinctly visible.
- Applies specifically to approach-light-only visual references
- 100 feet above TDZE is the hard floor without additional red bar visibility
- Red terminating/side-row bars indicate close proximity to the runway threshold
Memory trick: 'Red Bars or Bust' below 100 feet.