Narrative:

Air carrier X was cleared to FL260. Air carrier X was stopped at FL260 for military Y at FL250 proceeding direct ewm. At the time of this occurrence, I was allowing a developmental (plugged into the D side) to issue clrncs. Air carrier X reported about to level at FL260 and requested lower. Relative position at this time: military Y was in the air carrier X 1 O'clock and 5 mi. After air carrier X request for lower, the developmental issued descent to 14000 ft and gave the tus altimeter. At this point, I intervened and issued a clearance for air carrier X to maintain FL260 and called traffic. The response was 'blocked.' I again cleared to maintain FL260. The aircraft responded 'center, we're already out of FL250 and we have the traffic, no factor.' at this point conflict alert activated and the loss of separation was recorded. Supplemental information from acn 217148: air carrier X was a tus arrival out of FL350 descending to FL260 because of military Y at FL250. Air carrier X called about to level off. Without analyzing the situation, I cleared air carrier X down to 14000 ft and issued the altimeter. The radar controller tried to reclr air carrier X after he had acknowledged but he was apparently 'stepped on.' the radar controller tried again but air carrier X stated he had already passed FL260 and that he had the traffic in sight. Conflict alert was activated and we were relieved of the position. Poor judgement, combined with inexperience on my part, were the primary causal factors.

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Original NASA ASRS Text

Title: ACR X DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM MIL Y. SYS ERROR.

Narrative: ACR X WAS CLRED TO FL260. ACR X WAS STOPPED AT FL260 FOR MIL Y AT FL250 PROCEEDING DIRECT EWM. AT THE TIME OF THIS OCCURRENCE, I WAS ALLOWING A DEVELOPMENTAL (PLUGGED INTO THE D SIDE) TO ISSUE CLRNCS. ACR X RPTED ABOUT TO LEVEL AT FL260 AND REQUESTED LOWER. RELATIVE POS AT THIS TIME: MIL Y WAS IN THE ACR X 1 O'CLOCK AND 5 MI. AFTER ACR X REQUEST FOR LOWER, THE DEVELOPMENTAL ISSUED DSCNT TO 14000 FT AND GAVE THE TUS ALTIMETER. AT THIS POINT, I INTERVENED AND ISSUED A CLRNC FOR ACR X TO MAINTAIN FL260 AND CALLED TFC. THE RESPONSE WAS 'BLOCKED.' I AGAIN CLRED TO MAINTAIN FL260. THE ACFT RESPONDED 'CTR, WE'RE ALREADY OUT OF FL250 AND WE HAVE THE TFC, NO FACTOR.' AT THIS POINT CONFLICT ALERT ACTIVATED AND THE LOSS OF SEPARATION WAS RECORDED. SUPPLEMENTAL INFO FROM ACN 217148: ACR X WAS A TUS ARR OUT OF FL350 DSNDING TO FL260 BECAUSE OF MIL Y AT FL250. ACR X CALLED ABOUT TO LEVEL OFF. WITHOUT ANALYZING THE SITUATION, I CLRED ACR X DOWN TO 14000 FT AND ISSUED THE ALTIMETER. THE RADAR CTLR TRIED TO RECLR ACR X AFTER HE HAD ACKNOWLEDGED BUT HE WAS APPARENTLY 'STEPPED ON.' THE RADAR CTLR TRIED AGAIN BUT ACR X STATED HE HAD ALREADY PASSED FL260 AND THAT HE HAD THE TFC IN SIGHT. CONFLICT ALERT WAS ACTIVATED AND WE WERE RELIEVED OF THE POS. POOR JUDGEMENT, COMBINED WITH INEXPERIENCE ON MY PART, WERE THE PRIMARY CAUSAL FACTORS.

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.