Originally Posted by
Bluescan
Dear all.
Here's a scenario from a recent simulator exercise (a bit simplified).
On the MCP panel, both Vertical Navigation (VNAV) Switch and Approach (APP) Switch are INOP. Everything else is operational.
Can an ILS be flown to ILS DA(H) and/or can a LNAV/VNAV be flown to LNAV/VNAV DA(H), using the remaining operational functions of the autopilot (e.g. LOC+V/S or LNAV+V/S?
1️⃣ Already answered by many, but I would like to add reversion to VNAV PTH (after Glideslope mode failure) is no more allowed as per our latest FCTM. If G/s raw data signal exists, revert to V/s or FPA
2️⃣ Short Answer - NO can’t use LNAV/VNAN (DA)
You May want to read FAA AC 20-105A Appendix B for more info.
In principle, RNP APCH Approaches with LNAV/VNAV Minima are 3D Approaches. Once VNAV is lost, any other backup (A/p F/d) mode makes it a 2D Approach. You might want ask about FPA in that case, even use of FPA is considered 2D (refer DOC 8168 6th Edition 2.3.3)
The word ‘DA’ added to LNAV/VNAV minima mandates the Approach be carried out as a 3D operation. (refer DOC 8168 6th Edition 2.3.4)
(refer DOC 8168 6th Edition 2.5.5 foot note 1)
The biggest draw back is that the information on RNP APCH is scattered across many documents. If one would want to enquire if certain approaches could be carried out after certain equipment failure in their airplane it becomes difficult to determine the most legal course of action.