HD, my interest is to avoid CFIT incidents / accidents, and the requirement for crew to have and use a check height. ATC assistance is always welcome; however, range calls, particularly on Non Precision Approaches (NPA) could give crews a false sense of security unless there is a corresponding check of altitude.
OZEx, thanks for the ILS info, this is as I had hoped, however the hazards of NPAs remain particularly for those procedures without DME.
In addition, there could be a further hazard when the crew defines a continuous descent path using VNAV, i.e. an error in waypoint entry, and they commence the descent early. The EFIS display of VNAV path is very ‘ILS like’ and thus very compelling; maybe some crews fly a VNAV approach like an ILS. Yet apparently there are no other means checking the progress of a VNAV NPA other than at MDA, it is an open loop procedure.
In extreme circumstances with a very early descent, the flight path could be below an intermediate platform/check altitude defined in the originating NPA. Thus, it appears many of the benefits of a continuous descent are lost, but of course this is applies to most procedures when human error is considered. Therefore, perhaps crews should use a double check procedure when manually entering VNAV waypoints, or only use database procedures.
The
draft JAA Notice of Proposed Amendment NPA-OPS 20 relates to the introduction of continuous descent approaches, it will require operators to have procedures to circumvent errors such as above. The obvious procedure is to use distance to waypoint to check altitude, but of course, a waypoint error could be the source of any flight path error and thus not show any offset. I am seeking some safety defences.