Narrative:

I was working sector 80. A crj checked on climbing to FL330. I had traffic at FL360; a B737; that I knew was a factor for the crj. At the lateral airspace boundary; per normal procedure; I climbed the crj to FL350. The pilot read back the altitude correctly. I was consciously attending to the altitude read back because I knew the traffic was a factor; they were red on uret; and I was kind of busy at the time. When the two were around 25 miles or so apart; I called the traffic. During my normal scan; I saw the crj was showing FL352 when they were nearly abeam the B737 and I asked the crj pilot their altitude; thinking it might have been a mode C anomaly or sort box jump. The pilot said they were showing 300 ft high; apologized; and said they were correcting. I turned the crj 40 degrees left; told them to expedite. I turned the B737 20 degrees left in an attempt to keep some kind of separation. The conflict alert activated. The highest I saw the crj was FL355. I saw them go back down to FL350; then back up to FL351. Once I had them pried apart and back on course; I asked the crj what had happened. The pilot said that the altitude capture on the autopilot hadn't worked. They implied that it had failed twice.

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Original NASA ASRS Text

Title: Traffic assigned FL350 continued the climb above the assigned altitude conflicting with other traffic. Several versions of the factors involved are provided in this combined ATC/flight crew report.

Narrative: I was working Sector 80. A CRJ checked on climbing to FL330. I had traffic at FL360; a B737; that I knew was a factor for the CRJ. At the lateral airspace boundary; per normal procedure; I climbed the CRJ to FL350. The pilot read back the altitude correctly. I was consciously attending to the altitude read back because I knew the traffic was a factor; they were red on URET; and I was kind of busy at the time. When the two were around 25 miles or so apart; I called the traffic. During my normal scan; I saw the CRJ was showing FL352 when they were nearly abeam the B737 and I asked the CRJ pilot their altitude; thinking it might have been a Mode C anomaly or sort box jump. The pilot said they were showing 300 FT high; apologized; and said they were correcting. I turned the CRJ 40 degrees left; told them to expedite. I turned the B737 20 degrees left in an attempt to keep some kind of separation. The Conflict Alert activated. The highest I saw the CRJ was FL355. I saw them go back down to FL350; then back up to FL351. Once I had them pried apart and back on course; I asked the CRJ what had happened. The pilot said that the altitude capture on the autopilot hadn't worked. They implied that it had failed twice.

Data retrieved from NASA's ASRS site as of July 2013 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.