Narrative:

I was on the radar associate position during a moderate to heavy session. The radar controller was waiting to descend a wbound regional jet as a twin cessna was crossing sbound. I answered a handoff line for coordination. While I was off frequency; the radar controller gave traffic to the regional jet. The radar controller only used the last 3 digits of each call sign (both call signs ended with the same digits). The radar controller told the wbound regional jet to maintain FL270 and there was traffic sbound -- a twin cessna at FL260. When I came back on frequency; 2 aircraft were talking. The radar controller immediately told the twin cessna to maintain FL260 and his traffic was wbound at FL270. The twin cessna said that he was going back down. The radar controller told him to report level. The twin cessna did; but separation was lost during his short climb. The radar controller should have done 2 things to avoid the confusion: 1) advise both aircraft that similar call signs were on frequency; 2) used full call signs on either of those 2 aircraft on any transmission to them. I could have advised the radar controller to advise the 2 aircraft of similar sounding call signs. Any or all 3 of these possibilities might have avoided the error.

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Original NASA ASRS Text

Title: ZOB ASSOCIATE CTLR DESCRIBED OPERROR AT APPROX FL260 WHEN CTLR ISSUED CTL CLRNCS TO ACFT WITH SIMILAR CALL SIGNS RESULTING IN A CONFLICT.

Narrative: I WAS ON THE RADAR ASSOCIATE POS DURING A MODERATE TO HVY SESSION. THE RADAR CTLR WAS WAITING TO DSND A WBOUND REGIONAL JET AS A TWIN CESSNA WAS XING SBOUND. I ANSWERED A HDOF LINE FOR COORD. WHILE I WAS OFF FREQ; THE RADAR CTLR GAVE TFC TO THE REGIONAL JET. THE RADAR CTLR ONLY USED THE LAST 3 DIGITS OF EACH CALL SIGN (BOTH CALL SIGNS ENDED WITH THE SAME DIGITS). THE RADAR CTLR TOLD THE WBOUND REGIONAL JET TO MAINTAIN FL270 AND THERE WAS TFC SBOUND -- A TWIN CESSNA AT FL260. WHEN I CAME BACK ON FREQ; 2 ACFT WERE TALKING. THE RADAR CTLR IMMEDIATELY TOLD THE TWIN CESSNA TO MAINTAIN FL260 AND HIS TFC WAS WBOUND AT FL270. THE TWIN CESSNA SAID THAT HE WAS GOING BACK DOWN. THE RADAR CTLR TOLD HIM TO RPT LEVEL. THE TWIN CESSNA DID; BUT SEPARATION WAS LOST DURING HIS SHORT CLB. THE RADAR CTLR SHOULD HAVE DONE 2 THINGS TO AVOID THE CONFUSION: 1) ADVISE BOTH ACFT THAT SIMILAR CALL SIGNS WERE ON FREQ; 2) USED FULL CALL SIGNS ON EITHER OF THOSE 2 ACFT ON ANY XMISSION TO THEM. I COULD HAVE ADVISED THE RADAR CTLR TO ADVISE THE 2 ACFT OF SIMILAR SOUNDING CALL SIGNS. ANY OR ALL 3 OF THESE POSSIBILITIES MIGHT HAVE AVOIDED THE ERROR.

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.