Originally Posted by
pilotnik
I think some of you guys confuse ABAS, SBAS and even GBAS. I've read through dozens of documents on PBN and interchangeable use of augmentation types is nowhere to be found. You can't just use GBAS or SBAS to compensate for lack of satellites in order to perform LNAV/VNAV. Am I crazy or am I missing something important here?
You're still stuck on "Do we have RAIM" The requirement for a RNP approach (or any RNP operation) is not; "do we have RAIM", it is; "Do we have the required navigation performance" My FMS system (SBAS/WAAS capable GPS receivers and triple IRU's ) doesn't tell me RAIM/No RAIM, (although I can find that if I'm interested) it tells me what the current navigation performance is, and if that is more accurate the the minimum accuracy required for the operation, then we're good to go. The system as a whole is not dependent on RAIM to determine the current navigation performance. there are other ways that it automatically verifies the performance, and augmentation is one of the ways it does that.