Originally Posted by
pineteam
In the very unlikely it happens, I will simply request radar vectors. Where I fly, we are under radar control 100% of the time. =)
Lucky you. My outfit still operates into procedural-only airports or with airports where SID/STARs/MAPs take you well below MRVA. In those cases, it's nice to have a backup plan.
Originally Posted by
Tomaski
If the FMS/GPS or whatever RNAV system in use can no longer meet the Required Nav Performance (RNP) for the particular phase of flight, then there will be an annunciation to that effect at which time the pilots will switch to alternate means of navigation as appropriate to their aircraft. There's no harm in having enroute navaids tuned up, but there is no requirement to do so either.
Your FMS won't know that by NOTAM the navaid has been moved to a new position and is operating on test, and will try to use that signal to calculate aircraft's position, which could obviously be grossly incorrect.
Boeing in one of the technical manuals does mention that crew should inhibit the non-operating/on test navaids:
The pilot is expected to have current NOTAM information for navaids along the intended route, and to utilize this information to blackball updating from those navaids.
EASA on the other hands as well recognizes the need for this (mainly for RNP AR operations) :
(d) NAVAID exclusion
1) The operator should establish procedures to exclude NAVAID facilities in accordance with NOTAMs (e.g. DMEs, VORs, localisers). Internal avionics reasonableness checks may not be adequate for RNP operations.