FMS-3000 Theory of Operation
 

I'm trying to figure out how this FMS works. I know it gets GPS and DME/DME information to compute a navigation solution. It can also use VOR/DME if there aren't any DME/DME signals available. The question is "Does the FMS use the GPS and DME information at the same time, constantly comparing the signals for the best solution or does it use only the GPS signal and when the GPS reliability falls below a certain threshold revert to DME/DME for the solution?

Thanks in advance for the help!

FMS
 

The CMA-900,FMS has GPS ,DME-DME, VOR-DME. GPS is the highest priority.The FMS continuosly x check the GPS position against the nex best sensor (DME-DME) to ensure that the position is within the required accuracy.If the main sensor (GPS) becames unavailable for navigation,the FMS will revert to the nex best IFR-approved nav mode .

Thanks Pichu17, that's the answer I was looking for!