Hmm. It seems there is a lack of traction on the issue of automatic versus manual RAIM events.
2bigmelons,
In flight, pilots-in-command should use the RAIM prediction facility of their GPS equipment for RAIM availability predictions.
All pilots use the RAIM prediction facility of their TSO'd receiver. It's automatic, prior to all GPS approaches.
Presence of RAIM should be continuously monitored whenever GPS is used for navigation.
And indeed it is; continuous and automatic, for any TSO'd GPS receiver in NAV mode.
The issue is,
will the pilot notice the little flashing light or little blinking message that tells you RAIM isn't or won't be available. That's what needs monitoring, and that is at the heart of the NAIPS & CASA advice.
iPahlot,
I don't think the RAIM prediction is that smart that it will look in to the future and predict that a satellite will develop a fault while you are enroute.
You are right, of course. But here is the problem: if you do a manual prediction 30mins before ETA, I can ask you to do another one at 29mins. Or 28, or 27. At any stage, a hitherto unpredicted fault might develop. Where does it end? The law requires a prediction before flight (NOTAM) and a prediction before the approach begins (automatic). Where do the extra checks end? How can you justify a manual check at time T, but not at time T+1?
I mentioned good airmanship. Here's when I might do a manual prediction:
Proceeding to destination, then having to divert to a destination,
a) for which I will need a GPS approach and
b) for which I don't have a NOTAM prediction and
c) knowing I will have limited fuel on arrival for go arounds and holding.
That I think would require a manual receiver prediction as soon as possible.
Regards all,
O8