Tom Imrich:
It is time to move on, to 100% RNP and GLS, globally. Then we'll finally see these unnecessarily hull losses abate.
Perhaps it was after you departed the FAA, but they have had for some time the glide-slope qualification surface (GQS). If the GQS is penetrated then the runway is disqualified from having any approach with vertical guidance, whether it be ILS, GLS, LNAV/VNAV, RNP AR, or LPV. Then there is the FAA's visual segment, which is wider than the GQS, and which every approach has. The visual segment can have obstacles but only to a point. That became much stricter after the Lear hit the trees one night.
Also, the cost of converting a large fleet's FMS and avionics to RNP AR feathering to GLS would be huge. (many of those approaches would have to be "dual string" because of low RNP requirements.) You know that Boeing, for one major OEM, charges an arm, leg, and your first born child to make such modifications.
Finally, there are airports where decent minimums cannot be obtained because of significant terrain in the missed approach segment. Related to that, the commercial operator has to also have a viable OEI path for the missed approach.
BTW, have you flown LPV? It is a great system where it can be sited. The accident runway at Halifax has a great LPV approach but apparently the airline wanted to keep their first born child.
