RAIM Check requirements.

[Bluemeaway]

Hi.

Regarding the requirements to check RAIM.

I have always been told and I do carry out a RAIM check as a part of my approach briefs when doing an RNAV.

However, I can only find a mention of it saying it needs to be done on the ground during flight planning..

I cannot find anything about the inflight check requirement. Only that there are 3 methods to check RAIM in CaaP 179A-1

Being software.
NOTAM
Or GPS unit ( mentions they might not have an complete up to date almanac of the constellation so the other 2 options are better?)

Any solid tips on this?


Cheers

Blue.

[mcgrath50]

RAIM is based on a time, usually your ETA for the missed approach fix. You're RAIM check needs to be accurate to within +/- a certain amount of time (I actually couldn't find the number in the CAAP but I'm thinking 10mins). I always check RAIM on the ground before flight, cuts down workload prior to the approach, but obviously it can mean if you are delayed, or quicker than planned, your RAIM check needs to be redone.