Narrative:

The C650 was climbing swbound. The LJ35 was northbound in descent. The C650 was climbing to FL230 and the LJ35 was given clearance to cross a point approximately on the C650's route of flight at 11000 ft. As the aircraft converged at roughly a 90 degree angle; the controller decided that the issued clrncs were not going to provide separation. He then cleared the C650 to stop at 17000 ft and the LJ35 to maintain FL180. The LJ35 had already descended through FL180 although mode C showed FL187; and then climbed back to FL180. Vertical separation was not established prior to loss of lateral separation. This error occurred because controller did not issue clrncs to either aircraft to ensure positive separation; before they became an imminent situation. I was providing general supervision in the area covering 2 low altitude; 2 high altitude; 2 super high altitude sectors (6 sectors total). Most sectors had moderate traffic; 3 sectors had radar associates also on position. The sector where error occurred did not have a radar associate; I found out about the error after it occurred. I was notified by the omic that there had been an aedp alert. I then found an opportunity to question the radar controller about the incident. Practically and reasonably; the clrncs issued would have been expected to work. The C650 would have been about FL180 at the point the LJ35 had crossing at 11000 ft; but the issued clrncs did not insure separation.

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Original NASA ASRS Text

Title: ZID SUPVR CTLR DESCRIBES OPERROR AT 17000 FT INVOLVING CLBING AND DSNDING ACFT.

Narrative: THE C650 WAS CLBING SWBOUND. THE LJ35 WAS NBOUND IN DSCNT. THE C650 WAS CLBING TO FL230 AND THE LJ35 WAS GIVEN CLRNC TO CROSS A POINT APPROX ON THE C650'S RTE OF FLT AT 11000 FT. AS THE ACFT CONVERGED AT ROUGHLY A 90 DEG ANGLE; THE CTLR DECIDED THAT THE ISSUED CLRNCS WERE NOT GOING TO PROVIDE SEPARATION. HE THEN CLRED THE C650 TO STOP AT 17000 FT AND THE LJ35 TO MAINTAIN FL180. THE LJ35 HAD ALREADY DSNDED THROUGH FL180 ALTHOUGH MODE C SHOWED FL187; AND THEN CLBED BACK TO FL180. VERT SEPARATION WAS NOT ESTABLISHED PRIOR TO LOSS OF LATERAL SEPARATION. THIS ERROR OCCURRED BECAUSE CTLR DID NOT ISSUE CLRNCS TO EITHER ACFT TO ENSURE POSITIVE SEPARATION; BEFORE THEY BECAME AN IMMINENT SIT. I WAS PROVIDING GENERAL SUPERVISION IN THE AREA COVERING 2 LOW ALT; 2 HIGH ALT; 2 SUPER HIGH ALT SECTORS (6 SECTORS TOTAL). MOST SECTORS HAD MODERATE TFC; 3 SECTORS HAD RADAR ASSOCIATES ALSO ON POS. THE SECTOR WHERE ERROR OCCURRED DID NOT HAVE A RADAR ASSOCIATE; I FOUND OUT ABOUT THE ERROR AFTER IT OCCURRED. I WAS NOTIFIED BY THE OMIC THAT THERE HAD BEEN AN AEDP ALERT. I THEN FOUND AN OPPORTUNITY TO QUESTION THE RADAR CTLR ABOUT THE INCIDENT. PRACTICALLY AND REASONABLY; THE CLRNCS ISSUED WOULD HAVE BEEN EXPECTED TO WORK. THE C650 WOULD HAVE BEEN ABOUT FL180 AT THE POINT THE LJ35 HAD XING AT 11000 FT; BUT THE ISSUED CLRNCS DID NOT INSURE SEPARATION.

Data retrieved from NASA's ASRS site as of January 2009 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.