Narrative:

The embraer 145 was on a westerly heading; inbound to cle runway 24R. The itinerant aircraft was nebound; arriving burke lakefront (bkl) airport. I had assumed the radar position about 3 mins prior to the situation. I initiated a descent on the E145 to 3000 ft. I erroneously assumed the bkl arrival would be descending; as they were less than 5 mi from their destination. The E145 continued wbound across the final approach course. I instructed the E145 to maintain present altitude and pointed out the traffic. I also turned him left. The embraer pilot said he had the traffic in sight previously; but had lost sight of it. (Having the traffic in sight would have been prior to the aircraft getting closer than 3 NM.) after the 2 aircraft passed; they continued on visual approachs to their destinations. I believe that my assumptions contributed to the problem. I was told the itinerant aircraft was descending into bkl; so I thought he'd probably be below the E145. I knew the itinerant was north of the runway 24R final approach course that the E145 was inbound for. I assumed the E145 was going to join this final or proceed toward the airport. As stated earlier; the E145 did not join this course.

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Original NASA ASRS Text

Title: CLE TRACON CTLR EXPERIENCED OPERROR AT APPROX 3000 FT WHEN ASSUMING CONFLICTING TFC WOULD BE DSNDING.

Narrative: THE EMBRAER 145 WAS ON A WESTERLY HDG; INBOUND TO CLE RWY 24R. THE ITINERANT ACFT WAS NEBOUND; ARRIVING BURKE LAKEFRONT (BKL) ARPT. I HAD ASSUMED THE RADAR POS ABOUT 3 MINS PRIOR TO THE SIT. I INITIATED A DSCNT ON THE E145 TO 3000 FT. I ERRONEOUSLY ASSUMED THE BKL ARR WOULD BE DSNDING; AS THEY WERE LESS THAN 5 MI FROM THEIR DEST. THE E145 CONTINUED WBOUND ACROSS THE FINAL APCH COURSE. I INSTRUCTED THE E145 TO MAINTAIN PRESENT ALT AND POINTED OUT THE TFC. I ALSO TURNED HIM L. THE EMBRAER PLT SAID HE HAD THE TFC IN SIGHT PREVIOUSLY; BUT HAD LOST SIGHT OF IT. (HAVING THE TFC IN SIGHT WOULD HAVE BEEN PRIOR TO THE ACFT GETTING CLOSER THAN 3 NM.) AFTER THE 2 ACFT PASSED; THEY CONTINUED ON VISUAL APCHS TO THEIR DESTS. I BELIEVE THAT MY ASSUMPTIONS CONTRIBUTED TO THE PROB. I WAS TOLD THE ITINERANT ACFT WAS DSNDING INTO BKL; SO I THOUGHT HE'D PROBABLY BE BELOW THE E145. I KNEW THE ITINERANT WAS N OF THE RWY 24R FINAL APCH COURSE THAT THE E145 WAS INBOUND FOR. I ASSUMED THE E145 WAS GOING TO JOIN THIS FINAL OR PROCEED TOWARD THE ARPT. AS STATED EARLIER; THE E145 DID NOT JOIN THIS COURSE.

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.