So the problem arises when a satellite is scheduled to be offline for whatever reason, but the status is changed to be online, and this happens between the retrieval of NOTAMS and the almanac getting to the aircraft (once again, pretty sure from training material this happens once a week only on the particular Universal FMS I use).
Airservices updates their information to correctly reflect this, NOTAMS say all ok, but the box doesn't know, so refuses to go into approach mode because it thinks it won't have RAIM but in fact it will. Thats assuming the satellite that it thinks is offline will make the number available less than that required for RAIM.
VERY rare scenario, but I guess you could say it is a reason to do the RAIM prediction in flight.
As for the flight test / instrument renewal form item - check RAIM availability - is there a RAIM warning or failure flag? If not then you have RAIM and checking for the absence of a flag IS checking its availability.
Last edited by glekichi; 21st May 2014 at 09:10.
Reason: clarification