Narrative:

We had a group of 4 aircraft over geg. Sector was busy (19 aircraft total). I heard my r-side giving speed restrs. I noted one of the aircraft my r-side was trying to sequence into sea was going to yvr and I advised the r-side. The r-side cleared the aircraft 'direct bacon,' maintain FL390. I did not hear the readback. I notice the aircraft at FL382 and alert had gone off, r-side verified altitude and pilot responded descending FL290 as assigned. R-side climbed aircraft back to FL390. No one from management called to ask about alert. Maybe they thought due to close proximity of a number of aircraft that we had a bad mode C or a mode C swap.

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Original NASA ASRS Text

Title: ARTCC RADAR CTLR WITH 19 ACFT ON FREQ ISSUED A DIRECT INTXN CLRNC AND MAINTAIN FL390. THE PLT THOUGHT THE CLRNC WAS TO DSND TO FL290 AND STARTED DSCNT. THE RADAR CTLR CAUGHT THE MISTAKE WHEN CONFLICT ALERT WENT OFF AND THEN CLBED THE ACFT BACK UP TO FL390. HOWEVER, LOSS OF SEPARATION HAD ALREADY OCCURRED.

Narrative: WE HAD A GROUP OF 4 ACFT OVER GEG. SECTOR WAS BUSY (19 ACFT TOTAL). I HEARD MY R-SIDE GIVING SPD RESTRS. I NOTED ONE OF THE ACFT MY R-SIDE WAS TRYING TO SEQUENCE INTO SEA WAS GOING TO YVR AND I ADVISED THE R-SIDE. THE R-SIDE CLRED THE ACFT 'DIRECT BACON,' MAINTAIN FL390. I DID NOT HEAR THE READBACK. I NOTICE THE ACFT AT FL382 AND ALERT HAD GONE OFF, R-SIDE VERIFIED ALT AND PLT RESPONDED DSNDING FL290 AS ASSIGNED. R-SIDE CLBED ACFT BACK TO FL390. NO ONE FROM MGMNT CALLED TO ASK ABOUT ALERT. MAYBE THEY THOUGHT DUE TO CLOSE PROX OF A NUMBER OF ACFT THAT WE HAD A BAD MODE C OR A MODE C SWAP.

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.