Here is a quote of the relevant portion of the regulation:ĩ1.175 (c) Operation below DA/ DH or MDA. If you clearly have the approach lights at the DA/MDA, you may continue the descent, but by 100 feet above the TDZE, you must have one of the other visual cues to continue the descent as the red side row/threshold bars don’t exist. When there is an approach lighting system such as the MALSF/MALSR installed, there are no red side row or terminating bars. In effect either is a visual cue that indicates the runway end in the immediate vicinity. You must be able to see all of the side row bars. When there is an ALSF-I system installed, the red terminating bars are within a hundred feet of the threshold and with an ALSF-II is installed, the red side row bars are located in 100 foot increments beginning 900 feet from the threshold and ending at 100 feet before the runway threshold. If you can’t see one of the other runway cues, then the flight visibility is below minimums. At 100 feet above the TDZE, the pilot is 0.36 miles from the threshold. So the approach lights guide the pilot to the point they must be able to see the other cues or abandon the approach. That is why when the ALS is OOS, visibility minimums go the 0.75 mile. At the typical ILS Category 1 approach with minimums of 200 feet and a half mile, when the conditions are truly at minimums, geometry says it is impossible to see the runway threshold at the DA as it is 0.72 miles away. The whole point of the approach light systems is to aid the pilot in getting to the runway in low visibility conditions. The point 100 feet above the runway TDZE is not a new MDA for either a vertically guided approach or a non precision approach. The DA is the altitude where you decide to initiate the missed approach or have the required visual cues to continue the landing. Level off at an MDA is acceptable until reaching the MAP, but never permitted when the approach has vertical guidance with a DA. Mae, you wrote: “I am not sure why I was taught to level off at DA, MDA even when the ALS was visible.” But if all you can see is the ALS and none of the red terminating or side row bars, you’re stuck at 100′ up until you see more of it. If you see any of those parts, AND you’re in a position for normal approach and landing, AND the flight visibility is at or above approach minimums, then you can continue your approach and landing visually as long as you keep those things in sight. The threshold (itself, the markings, or lights) The touchdown zone (itself, the markings, or lights) The runway (itself, the markings, or lights) Runway end identifier lights (REIL, the flashing strobes on either side of the threshold) If you can’t see those terminating or side row bars you’d have to maintain that 100′ altitude above TDZE until or unless you can see any other part of the runway environment. This applies whether it’s ALSF 1 or 2 because those numbers only refer to different layouts of the lights. The regulation 91.175, which I take it you’re talking about, says that if you see those lights of the ALS you’re allowed to descend to 100′ above the TDZE “unless the red terminating bars or the red side row bars are also distinctly visible and identifiable”, in which case you’d be allowed to continue the descent to landing. The approach lighting system (ALS) is the set of light bars and/or moving strobes out ahead of the runway. I also looked up FAA order on ALS and it says it is not really required for CAT-ll and CAT-lll approaches and unfortunately does not state anything on ALSF-I. Reg clearly states 'one of the visual reference' for intended landing runway including red bars but they are not the runway I am intending to land. Now my question is, you see the red terminating bars/ side row bards and descend to whatever the altitude but you do not see the runway, should I continue descending or go around? So I did the internet research and found out they are only seen when the runway is equipped with either I or II version, and we are allowed to descend below 100ft above TDZE but no other types of ALS, if I am correct. I was going through the regulation part which was bit vague in meaning but I grew to digging into ALSF-I and II when I read the text saying 'red terminating bar/ side row bar.
I am currently working on my instrument, and I will be soon doing my check ride with DE next week.
Asked by: Mae 5547 views FAA Regulations, Flight Instructor, Instrument Rating
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