Narrative:

At FL310 inbound to abq VOR, cleared to cross 45 southwest of abb at FL240. First officer programmed FMS to accomplish this crossing restr. First officer did not manually tune to abb. I was using my VOR/DME to find a VOR combination for the FMS to tune. We were down to 2 FMS DME stations and occasionally down to 1 VOR/DME station. The FMS, however, showed our position as well as top of descent and end of descent (at 45 southwest of abb). At about 60 DME southwest of abb (FMS map) in the descent, center asked us to stop the descent at FL290. About 30 seconds later the FMS map failed (without warning). Center then turned us to a northwest heading and asked us our descent clearance and our distance from abb. I manually tuned abb and we were about 46 DME southwest of abb. I asked center if there was a conflict and was told that the stopped descent at FL290 and the turn off course prevented a conflict. We were unable to recover FMS for remainder of flight. Factors affecting this problem: 1) unexplained and unexpected FMS failure. 2) one crew member not manually tuning of abb VOR as a backup. 3) accepting FMS data for navigation (however, is this not a system certified for accurate RNAV). 4) too much trust in the automation for 100 percent reliability.

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Original NASA ASRS Text

Title: XING RESTR NOT MET. FMS FAILURE.

Narrative: AT FL310 INBOUND TO ABQ VOR, CLRED TO CROSS 45 SW OF ABB AT FL240. FO PROGRAMMED FMS TO ACCOMPLISH THIS XING RESTR. FO DID NOT MANUALLY TUNE TO ABB. I WAS USING MY VOR/DME TO FIND A VOR COMBINATION FOR THE FMS TO TUNE. WE WERE DOWN TO 2 FMS DME STATIONS AND OCCASIONALLY DOWN TO 1 VOR/DME STATION. THE FMS, HOWEVER, SHOWED OUR POS AS WELL AS TOP OF DSCNT AND END OF DSCNT (AT 45 SW OF ABB). AT ABOUT 60 DME SW OF ABB (FMS MAP) IN THE DSCNT, CTR ASKED US TO STOP THE DSCNT AT FL290. ABOUT 30 SECONDS LATER THE FMS MAP FAILED (WITHOUT WARNING). CTR THEN TURNED US TO A NW HDG AND ASKED US OUR DSCNT CLRNC AND OUR DISTANCE FROM ABB. I MANUALLY TUNED ABB AND WE WERE ABOUT 46 DME SW OF ABB. I ASKED CTR IF THERE WAS A CONFLICT AND WAS TOLD THAT THE STOPPED DSCNT AT FL290 AND THE TURN OFF COURSE PREVENTED A CONFLICT. WE WERE UNABLE TO RECOVER FMS FOR REMAINDER OF FLT. FACTORS AFFECTING THIS PROB: 1) UNEXPLAINED AND UNEXPECTED FMS FAILURE. 2) ONE CREW MEMBER NOT MANUALLY TUNING OF ABB VOR AS A BACKUP. 3) ACCEPTING FMS DATA FOR NAV (HOWEVER, IS THIS NOT A SYS CERTIFIED FOR ACCURATE RNAV). 4) TOO MUCH TRUST IN THE AUTOMATION FOR 100 PERCENT RELIABILITY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.