Narrative:

Received clearance to climb/maintain 17000' MSL by ATC (on 070 degree vector). Passing 11500' MSL, received instructions from ATC to maintain 11000' MSL and queried about present altitude. Immediately began a descent to 11000' MSL (climb apex 11800' MSL). Visly sighted aircraft (small transport Y) approximately 2-3 NM 60 degree right. Aircraft altitude 12000' MSL (approximately 200' above). No evasive action required. Received left turn to 360 degree from ATC. Supplemental information from acn 169601. Cmh departure control assigned us a 070 degree heading and climb to 14000', the xferred us to cle center as we were on a short hop from cmh to cle. We checked on with cle center frequency and advised him we were climbing to 14000' and on an assigned heading of 070 degree. Cle center controller seemed to question the 070 degree heading but did not change it. Passing through 11500', cle controller told us to level off at 11000'. I immediately retarded throttles and nosed aircraft over to descend to 11000' as altitude peaked at 11800'. Also captain advised cle center controller of our move. Controller then immediately gave another aircraft a left turn to a southerly heading and then gave us an immediate left turn to heading 360 degree. I suspected a close encounter and then saw the commuter twin (small transport Y) in my 1 O'clock position turning with an approximately 2-3 mi range. What I suspected happened was that our original 070 degree heading would have got us real close (but not 'midair' close) to the commuter at 12000' (I'm guessing 12000' only because we were quickly assigned 11000'). This must have triggered warning indications in the cle center's control room and the appropriate action was taken by the controller. Note that no evasive action was initiated by us as both aircraft passed within 2-3 mi and no closer than 200' vertical at the worst moment (as the horizontal distance decreased as we came closer, the vertical sep increased) however, from a controller's standpoint, the required 5 mi horizontal and 1000' vertical sep standards were jeopardized, but barely in our opinion.

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Original NASA ASRS Text

Title: ATC STOPPED CLIMB OF LGT DUE TO TRAFFIC, AN SMT ON CONVERGING COURSE. LESS THAN STANDARD SEPARATION OCCURRED.

Narrative: RECEIVED CLRNC TO CLB/MAINTAIN 17000' MSL BY ATC (ON 070 DEG VECTOR). PASSING 11500' MSL, RECEIVED INSTRUCTIONS FROM ATC TO MAINTAIN 11000' MSL AND QUERIED ABOUT PRESENT ALT. IMMEDIATELY BEGAN A DSNT TO 11000' MSL (CLB APEX 11800' MSL). VISLY SIGHTED ACFT (SMT Y) APPROX 2-3 NM 60 DEG R. ACFT ALT 12000' MSL (APPROX 200' ABOVE). NO EVASIVE ACTION REQUIRED. RECEIVED L TURN TO 360 DEG FROM ATC. SUPPLEMENTAL INFO FROM ACN 169601. CMH DEP CTL ASSIGNED US A 070 DEG HDG AND CLB TO 14000', THE XFERRED US TO CLE CTR AS WE WERE ON A SHORT HOP FROM CMH TO CLE. WE CHKED ON WITH CLE CTR FREQ AND ADVISED HIM WE WERE CLBING TO 14000' AND ON AN ASSIGNED HDG OF 070 DEG. CLE CTR CTLR SEEMED TO QUESTION THE 070 DEG HDG BUT DID NOT CHANGE IT. PASSING THROUGH 11500', CLE CTLR TOLD US TO LEVEL OFF AT 11000'. I IMMEDIATELY RETARDED THROTTLES AND NOSED ACFT OVER TO DSND TO 11000' AS ALT PEAKED AT 11800'. ALSO CAPT ADVISED CLE CTR CTLR OF OUR MOVE. CTLR THEN IMMEDIATELY GAVE ANOTHER ACFT A L TURN TO A SOUTHERLY HDG AND THEN GAVE US AN IMMEDIATE L TURN TO HDG 360 DEG. I SUSPECTED A CLOSE ENCOUNTER AND THEN SAW THE COMMUTER TWIN (SMT Y) IN MY 1 O'CLOCK POS TURNING WITH AN APPROX 2-3 MI RANGE. WHAT I SUSPECTED HAPPENED WAS THAT OUR ORIGINAL 070 DEG HDG WOULD HAVE GOT US REAL CLOSE (BUT NOT 'MIDAIR' CLOSE) TO THE COMMUTER AT 12000' (I'M GUESSING 12000' ONLY BECAUSE WE WERE QUICKLY ASSIGNED 11000'). THIS MUST HAVE TRIGGERED WARNING INDICATIONS IN THE CLE CTR'S CTL ROOM AND THE APPROPRIATE ACTION WAS TAKEN BY THE CTLR. NOTE THAT NO EVASIVE ACTION WAS INITIATED BY US AS BOTH ACFT PASSED WITHIN 2-3 MI AND NO CLOSER THAN 200' VERT AT THE WORST MOMENT (AS THE HORIZ DISTANCE DECREASED AS WE CAME CLOSER, THE VERT SEP INCREASED) HOWEVER, FROM A CTLR'S STANDPOINT, THE REQUIRED 5 MI HORIZ AND 1000' VERT SEP STANDARDS WERE JEOPARDIZED, BUT BARELY IN OUR OPINION.

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.