Tom Imrich:
The KRIL RNP based approach minima at RNP .1 could still safely be even lower, if the present obsolete and unnecessary limitations were removed that are still being placed on RNP procedure design. The fully allocated real VEB could easily provide for DA(H) down to and even somewhat below 200' HAT compared to the higher DA(H) shown for the RNAV(RNP) Z Rwy 8. The present 250' HAT floor limit was only put there for largely political reasons, not due to any technical limitation of engineering or physics. That potential additional advantage for RNP is particularly valid considering that any aircraft with RA available could also use an RA floor to additionally bound improbable to extremely improbable VNAV non-normal events. Unlike with TERPS or PANS-Ops, with [real] RNP, particular non-normal as well as rare-normal events are already suitably addressed and accommodated.
Tom, you are missing the climb gradient limitations on both runway ends at KRIL. That's a fact of RNP AR life, although you may not agree with it.
When you were at the FAA TERPs was in the dark ages compared to today. You know, I was involved then as well.
We have the GQS, which we did not have circa 1975. We have the visual segment, which we did not have back then. And, as tentative as it is on some NPAs, we have the VDA, which we did not have back then.
As you well know, there are runway ends that you can't make a silk purse out of a sow's ear.
Speaking of RNP AR, let's get away from baro in the final segment by having the avionics switch from RNP to LPV for the last 2, or so, miles to the runway end. Or, would Boeing not like that idea?
As we all know, the original model of RNP AR was predicated upon the equipage of Boeing transports at the time.