Originally Posted by
underfire
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Here is what you need for RAIM, minimum of 5 sats for fault detection, 6 sats for fault detection and exclusion. The HPL is also a consideration.
The FMS is always calculating RAIM, and enroute always governs over prediction, so this can have quite the effect on the flight.
Out of curiosity what is the influence of WAAS or similar systems on this?