Specifically, I'm a little confused about Sec 91.175(c)(3)(i) which states:

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.

From what I understand, I'm allowed to descend up to 100ft above the touch down zone elevation (TDZE) if I'm able to see and identify the red terminating bars on the approach light systems (ALS).

However, what happens when the ALS does not have the red terminating bars (for e.g. MALSR and MALSF)? Do I maintain my MDA even if I have part of the ALS in sight?

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    $\begingroup$ Same topic: Misunderstanding Part 91.175. $\endgroup$ – mins Sep 12 '15 at 18:22
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    $\begingroup$ "It's important to know that not all approach lighting systems have red terminating or red side row bars. [...] the MALS [...], doesn't have them as shown in Figure 8. So, if you end up at 100 feet above the TDZE and can't see one of the first nine runway references, a missed approach is necessary. This is one reason why it's very important to know what type of approach lighting is available at the airport before you shoot the approach." (source) $\endgroup$ – mins Sep 12 '15 at 18:33

You can descend down to 100ft above TDZE if you have any ALS in sight. You need an ALS with red lights (ALSF I & II) to go below that.

Red terminating bars/red side row bars help you find the threshold. Think of an ALS with red lights as being in the same category as Runway/lights/markings, Threashold/lights/markings, Touchdown Zone/lights/markings, VASI/PAPI, and REIL. Any other type of ALS (MALSR, MALSF, etc.) has the 100ft above TDZE restriction put on it when it is the only thing you can see.

@mins linked to a couple of helpful articles in the comments.


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