Narrative:

The traffic was increasing and the radar trnee took a request from another turbojet. He overlooked some traffic below the plane and descended him. About this time the jacks on the radar side were cutting out and they had someone from maintenance come up to take a look at it. After he left, the instrument realized that the 2 aircraft were coming together and climbed the 1 aircraft back up to regain standard sep. I believe if the equipment would have been working properly that the trainer would have been able to concentrate more on what the trnee was doing. Callback conversation with reporter revealed the following: reporter was working the manual or d-side during this incident. 2 large transport's were involved, with 1 at FL370 eastbound and the other at FL350 wbound. Trnee failed to comprehend the closeness of traffic when he acceded to the higher aircraft's request and gave the descent clearance. The instrument caught the mistake in time to prevent a very close situation, but too late to prevent less than standard separation. The closest proximity was 1000' vertical and 3.5 mi horizontal.

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Original NASA ASRS Text

Title: ACR-LGT DESCENDED TOWARD ALT OF ACR-LGT. VERTICAL AND LATERAL SEPARATION LOST BEFORE INSTRUCTOR CAN INTERVENE.

Narrative: THE TFC WAS INCREASING AND THE RADAR TRNEE TOOK A REQUEST FROM ANOTHER TURBOJET. HE OVERLOOKED SOME TFC BELOW THE PLANE AND DSNDED HIM. ABOUT THIS TIME THE JACKS ON THE RADAR SIDE WERE CUTTING OUT AND THEY HAD SOMEONE FROM MAINT COME UP TO TAKE A LOOK AT IT. AFTER HE LEFT, THE INSTR REALIZED THAT THE 2 ACFT WERE COMING TOGETHER AND CLBED THE 1 ACFT BACK UP TO REGAIN STANDARD SEP. I BELIEVE IF THE EQUIP WOULD HAVE BEEN WORKING PROPERLY THAT THE TRAINER WOULD HAVE BEEN ABLE TO CONCENTRATE MORE ON WHAT THE TRNEE WAS DOING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR WAS WORKING THE MANUAL OR D-SIDE DURING THIS INCIDENT. 2 LGT'S WERE INVOLVED, WITH 1 AT FL370 EBND AND THE OTHER AT FL350 WBOUND. TRNEE FAILED TO COMPREHEND THE CLOSENESS OF TFC WHEN HE ACCEDED TO THE HIGHER ACFT'S REQUEST AND GAVE THE DSCNT CLRNC. THE INSTR CAUGHT THE MISTAKE IN TIME TO PREVENT A VERY CLOSE SITUATION, BUT TOO LATE TO PREVENT LTSS. THE CLOSEST PROX WAS 1000' VERT AND 3.5 MI HORIZ.

Data retrieved from NASA's ASRS site as of August 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.