Capn Bloggs,
Some good points there but:
- Does the A300-600 have the gear to be RNP-AR (or indeed LPV or LNAV/VNAV) capable;
- Why doesn't KBHM 18 have a glideslope? I suspect cost or terrain (which was collided-with) prohibits (could also preclude an RNP-AR approach).
- RNP LNAV works well when the aircraft can use the FMS database-coded approach slope/VNAV (even if just following it with VS/FPA or handflying), but aircraft must be capable.
I was responding to the issues raised by Retired F4's more generic question on safety of NPAs.
An RNAV LPV does not need to follow the 'rules' of an ILS as it is not constrained by needing to be 'in the beam'. The aircraft can be 'established' on the procedure while in a turn and with varying descent rates. Look at the approach into DCA along the Potomac. This makes RNP LPV approaches and departures more suited to complex terrain: there are some in China that zigzag along mountainous valleys.
I do not know whether the particular UPS A306 fit was capable of RNP LPV. However, if crews have a choice on which approach aids and procedures to use I would hope that they use the aid/procedure that provides the highest safety level; unless there is a justified requirement for doing otherwise.
RNP arrival and departure procedures could have been rolled out US wide but the rate has been very slow. Moreover, in many cases to make procedure generation and use simple the RNP arrival procedures are merely overlays of the existing ILS procedures. This means the ROI on equipping aircraft and training crews is insufficient for companies to do so. Therefore, despite the RNP LPV capability being nearly a decade old we are still seeing NPAs in use.
This is another discussion that perhaps could move to Tech Log