Phil Squares: under which authority do you operate? Under the EU ones which I've been subjected to a solo BRNAV approach is not allowed. It is an FMC approach flown in LNAV/VNAV with raw data back-up reference, subject to RNP & ANP being correct. Thus the aids need to be working. Amazingly, because it happened to me, even on my IRS/GPS equipped a/c our MEL stated that 2 VOR's, 2 ILS's and 1 ADF & DME was required for IFR controlled airspace operations. I was shocked. A re-set of the CB solved the problem, and I notified FLT OPs if this could really be correct. No reply.
A further question about the SOP to check the ANP/RNP on approach, and what to do if it was outside limits, also went un-replied. Common sense says you can not use LNAV/VNAV, but the youngsters asked the question. If you have to check something as an SOP to be allowed to use it they wanted an SOP of what to do if it was bust. Trained robots, but there we are.