Originally Posted by
chimbu warrior
It is neither BS nor technique.
As the above extract from the approach plate shows, the 3 degree profile brings the aircraft to the MDA (420 feet) at the MAP, which is 2.2 nautical miles from the threshold. Simple maths tells us that a 3 degree profile should have the aircraft at 700 feet when 2.2 nm from the threshold. As per the dashed lines (circled on the plan form view) there is then a visual segment (provided the aircraft is visual) of almost 1 mile to intercept the 3 degree profile at about 1.3 nm from the threshold.
It is unfortunate that the profile view of the procedure suggests that the descent from the MDA to the touchdown zone is coincident with the 3 degree path. It is not. If the aircraft descended on a 3 degree path from the MAP, it would very likely land short.
I'll let the NTSB do the investigating, but just point out that such procedures are not uncommon in this part of the world.
Regarding “Cloud Break procedure” - The point I was making was this; There is no such thing in ICAO (gone) AIP, AIM or any other Instrument Approach manual or regulation. Africa and Papua are the only places that I’m aware of it remaining on approach charts. If it’s in Air Niugini manuals then I bow to your superior knowledge. What you’re describing to me is the visual segment post MDA/DDA/DA. ie. the portion of an Instrument approach where the aircraft is maneuvering to landing. It may have a level segment, it may even be a curved one (RNAV RNP 01).
Terminology
- If this RNAV GPS approach is flown to an MDA of 420 in LNAV/VNAV the missed approach is conducted at 420ft, If the runway isn’t in sight. If it is, continue and land. If a portion is flown level to intercept the (missing) PAPI or visual path then so be it.
- If flown in VS (dive and drive, or continuous descent) then in is flown to a MAP.
There is no MAP in an RNAV GPS flown in LNAV/VNAV. It’s an MDA that triggers the missed approach or Visual segment. How long have Air Niugini been doing RNAV RNP Approaches in the 73NG ?