I've been looking at FAA RNP. Guess it must be different...5nm seems pretty poor precision.
Yes... all that "RNP" stuff goes back to the goode olde days when pilots were real men with sextants, and a jet pilot coming off the oceanic route was doing damn well if his INS drifted off by just 5nm.
Today it is basically meaningless, because both INS with GPS or DME/DME fixing yields accuracies of a fraction of a nm (equivalent to RNP 0.3 or better).
A Garmin 496 is RNP0.0-something and that's before you get EGNOS.....
The funniest thing being that a handheld is allowed to receive EGNOS whereas a certified unit isn't
But there is such a huge army of assorted well paid hangers-on around the national regulators safeguarding "RNP" based performance specs, and all the associated avionics certification garbage, and turkeys have never voted for xmas.
BRNAV is RNP5 I think. PRNAV is RNP1, I think. GPS approaches are RNP0.3 or something like that, which is why PRNAV (which requires weird equipment
and crew certification, despite being less accurate than GPS approaches for which even EASA has a straight path today) is now completely irrelevant. But does that stop the PRNAV machinery in its tracks? No way. It will be 10-20 years before they realise that the "RNP" boat has left the port (sunk, actually) a few years ago.
The problem with GPS is the inherrent inability of MOST owners to keep the database up to date - and despite protestations to the contrary, things do change from time to time.
I am sure that's true but have not seen evidence that this statistically features in CAS busts. Let's face it, the CAA VFR charts update once a year, and they are as "official" as you can get... And the typical handheld, with its fairly hopeless Jeppesen mapping, needs to be used together with the printed chart anyway.
It's different and more critical for airways/IFR where all nav is 100% GPS and ATC are constantly feeding you waypoints. I should update the KLN94 database every 28 days but in practice I don't bother if I am not flying airways in those 28 days, so I skip that cycle and save myself a few bob. I did one airways flight 2 weeks or so ago and the next one will be to Germany on 9th April and I see there is a download becoming valid on 8th April so I will grab that one.