Narrative:

B737 was inbound to ind, descending to 15000 ft. LJ35 was an overflt at 11000 ft. I issued to B737 a crossing clearance to a fix at 11000 ft. I had entered a temporary altitude on the B737's data block of 12000 ft, thinking that is what I issued, 12000 ft. Traffic was issued to the LJ35 that the B737 was at 1 O'clock position, 12 mi, northbound, at 12000 ft. The LJ35 did not acknowledge the traffic call. Traffic was issued to the B737 that the LJ35 was at 10 O'clock position, 12 mi, eastbound, at 11000 ft. The B737 acknowledged the traffic call. The B737 descended to 11000 ft and separation was lost. I was surprised that the B737 did not question his clearance to 11000 ft at this time since it was obvious that there would not be separation. Supplemental information from acn 548053: I was 'controller in charge' at the time of the incident. I was busy performing supervisory duties and managing the area when the event occurred. I was not aware of the situation until after it occurred. Controller did not have a d-side and was not busy enough to warrant one. He issued traffic calls to both aircraft but neither the aircraft or the controller caught the error before the conflict alert activated.

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Original NASA ASRS Text

Title: ZID ARTCC RADAR CTLR ISSUES AN 11000 FT XING CLRNC TO A B737 THAT IS IN THE PATH OF A LJ35 AT 11000 FT.

Narrative: B737 WAS INBOUND TO IND, DSNDING TO 15000 FT. LJ35 WAS AN OVERFLT AT 11000 FT. I ISSUED TO B737 A XING CLRNC TO A FIX AT 11000 FT. I HAD ENTERED A TEMPORARY ALT ON THE B737'S DATA BLOCK OF 12000 FT, THINKING THAT IS WHAT I ISSUED, 12000 FT. TFC WAS ISSUED TO THE LJ35 THAT THE B737 WAS AT 1 O'CLOCK POS, 12 MI, NBOUND, AT 12000 FT. THE LJ35 DID NOT ACKNOWLEDGE THE TFC CALL. TFC WAS ISSUED TO THE B737 THAT THE LJ35 WAS AT 10 O'CLOCK POS, 12 MI, EBOUND, AT 11000 FT. THE B737 ACKNOWLEDGED THE TFC CALL. THE B737 DSNDED TO 11000 FT AND SEPARATION WAS LOST. I WAS SURPRISED THAT THE B737 DID NOT QUESTION HIS CLRNC TO 11000 FT AT THIS TIME SINCE IT WAS OBVIOUS THAT THERE WOULD NOT BE SEPARATION. SUPPLEMENTAL INFO FROM ACN 548053: I WAS 'CTLR IN CHARGE' AT THE TIME OF THE INCIDENT. I WAS BUSY PERFORMING SUPERVISORY DUTIES AND MANAGING THE AREA WHEN THE EVENT OCCURRED. I WAS NOT AWARE OF THE SIT UNTIL AFTER IT OCCURRED. CTLR DID NOT HAVE A D-SIDE AND WAS NOT BUSY ENOUGH TO WARRANT ONE. HE ISSUED TFC CALLS TO BOTH ACFT BUT NEITHER THE ACFT OR THE CTLR CAUGHT THE ERROR BEFORE THE CONFLICT ALERT ACTIVATED.

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.