Non-precision approaches and approach lights

2 Answers

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   John D Collins on Feb 22, 2018

   I interpret it that it would apply to non precision, APV, and precision Category I approaches. The approach lights are a visual cue, it is just that they can’t be used as a visual cue below 100 feet above the TDZE unless the Red terminating or side row bars are visible. Red terminating bars or side row bars are only found on the ALSF-1 or ALSF-2. The most common approach lighting systems MALSR and MALSF systems don’t have any red terminating or side row bars. You can still descend to 100 feet above the TDZE using approach light systems that do not have red terminating or side row bars, it is just that one can’t use the non existent red terminating/side row bars to continue below 100 feet above the TDZE. When there are no red terminating/side row bars, the exception to allow continuation below 100 feet above the the TDZE solely based on the approach lights does not apply, but you can continue if you see one of the other listed cues.

   The whole point of the approach lights is to provide guidance to the runway at minimum visibility or otherwise there would be no way to complete the approach under these conditions, particularly when the visibility at a DH is 1/2 mile. At 200 feet, on a 3 degree slope, the threshold is just over 0.7 miles away, so without using the approach lights to descend lower, there is no way to see any of the other visual cues. That is also why if the approach lights are OOS, the visibilty must be at least 0.75 miles because you need to at least be able to see the threshold. The same logic applies to an MDA.

   91.175 (c) reads as follows:

   (c) Operation below DA/DH or MDA. Except as provided in paragraph (l) of this section or §91.176 of this chapter, where a DA/DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, below the authorized MDA or continue an approach below the authorized DA/DH unless—

   (1) The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and for operations conducted under part 121 or part 135 unless that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing;

   (2) The flight visibility is not less than the visibility prescribed in the standard instrument approach being used; and

   (3) Except for a Category II or Category III approach where any necessary visual reference requirements are specified by the Administrator, at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:

   (i) 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.

   (ii) The threshold.

   (iii) The threshold markings.

   (iv) The threshold lights.

   (v) The runway end identifier lights.

   (vi) The visual glideslope indicator.

   (vii) The touchdown zone or touchdown zone markings.

   (viii) The touchdown zone lights.

   (ix) The runway or runway markings.

   (x) The runway lights.

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   Charles22 on Feb 22, 2018

   Many thanks for your reply and your clarifications

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