ZOB controller experienced operational error at FL370 when descending through occupied altitude.

Attributes
ACN	677399
Time
Date	200511
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : zob.artcc
State Reference	OH
Altitude	msl single value : 37000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : charter
Make Model Name	Canadair/Bombardier Undifferentiated or Other Model
Operating Under FAR Part	Part 135
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 10
ASRS Report	677399
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 15
ASRS Report	676917
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment : conflict alert aircraft equipment : tcas other controllera
Resolutory Action	controller : issued new clearance controller : issued alert
Consequence	faa : investigated
Miss Distance	horizontal : 12000 vertical : 600
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

MD80 (FL370) was an overflt sebound. CL60 was southwest landing at ind. I looked at CL60 and thought he needed lower; and proceeded to descend to FL360; the base of my altitudes. Not seeing MD80 was a complete oversight for which I have no explanation. I worked an evening shift the night before and didn't get much sleep before my day shift. The error happened in early morning. I do think it would help if the conflict alert would have gone off as soon as I entered FL360. The conflict alert didn't flash until the aircraft left FL377.

Original NASA ASRS Text

Title: ZOB CTLR EXPERIENCED OPERROR AT FL370 WHEN DSNDING THROUGH OCCUPIED ALT.

Narrative: MD80 (FL370) WAS AN OVERFLT SEBOUND. CL60 WAS SW LNDG AT IND. I LOOKED AT CL60 AND THOUGHT HE NEEDED LOWER; AND PROCEEDED TO DSND TO FL360; THE BASE OF MY ALTS. NOT SEEING MD80 WAS A COMPLETE OVERSIGHT FOR WHICH I HAVE NO EXPLANATION. I WORKED AN EVENING SHIFT THE NIGHT BEFORE AND DIDN'T GET MUCH SLEEP BEFORE MY DAY SHIFT. THE ERROR HAPPENED IN EARLY MORNING. I DO THINK IT WOULD HELP IF THE CONFLICT ALERT WOULD HAVE GONE OFF AS SOON AS I ENTERED FL360. THE CONFLICT ALERT DIDN'T FLASH UNTIL THE ACFT LEFT FL377.

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.