Originally Posted by
404 Titan
If there isn’t something wrong with the way GPS NPA approaches in Australia are designed then can someone please tell me why there is a ban at my airline (and I assume others) doing such an approach in Airbus aircraft (not sure about Boeing) using “Managed” vertical guidance. This ban is world wide but the problem lies in the design of the approaches in Australia. I have seen one demonstrated in the sim for BNE rwy 19 and the bl**dy thing tries to land you several miles short in the water. I believe there are many other airports in Australia with the same problem. So far no other airports anywhere else in the world have been identified with this same problem.
the problem with the procedures you've identified are to do with the acft equipment. the honeywell fmc in airbus acft does not comply with the ARINC424 standard [let alone the current standard]. it assumes that ALL missed approach waypoints are at the threshold and as such assumes you want to be at 50' abv thr ht at this point. if your MAPt is not at the THR due ATC or climb or turn requirements then ANY app which is coded as an RNAV will fly the same profile to a point short of the rwy. if it were coded as GPS rather than RNAV [as they used to be] then they will fly correctly!!
The ARINC424 standard states where the MAPt is not coincident with the RWY THR then a calculated xing ht must be inserted at the MAPt. Honeywell FMCs don't do this! Jeppesen have confirmed that they have coded the procedure in accordance with the ARINC standard.