Narrative:

Cpr X, a westwind 24, was climbing sbound from toronto. The handoff was made to the high altitude sector, who released FL330 and gave the handoff to the next sector. X was inadvertently issued an altitude of FL350. He was then switched to the next sector's frequency, X never checked onto the next sector's frequency, and 6 mins later climbed through FL330 toward FL350, which placed the aircraft in conflict with air carrier Y, an MD80/right wbound to ord at FL350. The conflict alert activated, and the controller working turned that aircraft to the right. Also, Y responded to a TCASII RA and climbed to FL370. The controller on whose frequency X was, was unaware that he was there and attempted to locate the aircraft, eventually calling him in the blind. X was questioned about his altitude and immediately descended back to FL330. Separation was lost, however, 37 seconds after the activation of the conflict alert. Human error is the only explanation. In my memory I was certain that I had cleared the aircraft to FL330, however, on the tapes it was clear that the clearance was to FL350.

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Original NASA ASRS Text

Title: CPR X CLB THROUGH OCCUPIED ALT HAD LTSS FROM ACR Y TCASII RA CLB. SYS ERROR. EVASIVE ACTION TAKEN.

Narrative: CPR X, A WESTWIND 24, WAS CLBING SBOUND FROM TORONTO. THE HDOF WAS MADE TO THE HIGH ALT SECTOR, WHO RELEASED FL330 AND GAVE THE HDOF TO THE NEXT SECTOR. X WAS INADVERTENTLY ISSUED AN ALT OF FL350. HE WAS THEN SWITCHED TO THE NEXT SECTOR'S FREQ, X NEVER CHKED ONTO THE NEXT SECTOR'S FREQ, AND 6 MINS LATER CLBED THROUGH FL330 TOWARD FL350, WHICH PLACED THE ACFT IN CONFLICT WITH ACR Y, AN MD80/R WBOUND TO ORD AT FL350. THE CONFLICT ALERT ACTIVATED, AND THE CTLR WORKING TURNED THAT ACFT TO THE R. ALSO, Y RESPONDED TO A TCASII RA AND CLBED TO FL370. THE CTLR ON WHOSE FREQ X WAS, WAS UNAWARE THAT HE WAS THERE AND ATTEMPTED TO LOCATE THE ACFT, EVENTUALLY CALLING HIM IN THE BLIND. X WAS QUESTIONED ABOUT HIS ALT AND IMMEDIATELY DSNDED BACK TO FL330. SEPARATION WAS LOST, HOWEVER, 37 SECONDS AFTER THE ACTIVATION OF THE CONFLICT ALERT. HUMAN ERROR IS THE ONLY EXPLANATION. IN MY MEMORY I WAS CERTAIN THAT I HAD CLRED THE ACFT TO FL330, HOWEVER, ON THE TAPES IT WAS CLR THAT THE CLRNC WAS TO FL350.

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.