Some great advice seen here re sound flying procedures for NPAs.
The self built vs database appch consids are important, as Airbus at least does not endorse any changes to a database appch after the FAF, thus to fly a managed self- built rwy appch would be a definite no-no.
The idea of using an ILS overlay to fly an NPA is certainly creative, but I doubt if the acft or FMS manufacturer would support such an activity. Those who trust their airline SOPs to support them in the event of an incident/accident during such an appch may find themselves out in the cold. Is it actually written in balck and smudge somewhere? I would certainly doubt that CASA would go out on a limb and endorse such a procedure. Perhaps a creative Airline Trng manager is writing cheques that his position can't actually cash.
In any case a database appch will not guarantee a correctly flown managed appch as per the plate, as they are often riddled with mistakes, do not align with the raw data all that closely and are sometimes unable to fly steep vert profiles with changing descent gradients and thus undercut the steps on final. Additionally, you may suffer a 'map shift' or loss of GPS primary & thus sufficient nav accuracy, thus the green/magenta line is no longer accurate. It is human nature to follow the neat fltpln Nav Display line, so very few pilots will manually select lat navigation in such cases, even with the raw data out of tolerance (automation complacency). Those who don't believe me simply haven't seen enough examples in the sim. All the above instances are commonplace in the area of the world where I commit aviation. I am yet to see a managed database appch here that flies with reasonable accuracy according to the IAP plate and raw data upon which it is predicated. Infact, due to the above safety consids, many of the pilots in my company will only fly an NPA in selected modes vertically and laterally. I think more emphasis needs to be placed on these types of simple real world problems during airline sim training.
The bottom line is, some NPAs are too tricky (read poorly designed) to be coded correctly thus the automation won't handle it effectively, that's why we pilots still have jobs! When PF on an NPA, I would say knowing your vertical profile is paramount and don't expect the other guy to feed you all the info as his mind might be elsewhere, as seen in the Thai incident.
I suppose the real bottom line is for regulators to hurry up and approve GPS NPAs at all airports.
