ZTL controller experienced loss of separation because of pilot error.

Attributes
ACN	593345
Time
Date	200309
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : hsv.airport
State Reference	AL
Altitude	msl single value : 18500
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : ztl.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	descent : intermediate altitude descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : ztl.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
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 22
ASRS Report	593345
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	controller : issued new clearance
Consequence	faa : investigated
Miss Distance	horizontal : 700 vertical : 2480
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft a was cleared to FL200. Aircraft B ws level at FL190. Was starting in trail to atl. Looked at other end of sector to switch airplanes. Data blocks were overlapped on aircraft a&B. Something looked wrong, so I moved data blocks. Aircraft a was descending through aircraft B and out of FL186. I made sure aircraft B stayed at FL190. Aircraft a was turned to heading 180 degrees from 110 degrees and told to descend. I got a call from the supervisor in charge when he called aircraft a was out of FL180 and I told him aircraft a was out of FL186.

Original NASA ASRS Text

Title: ZTL CTLR EXPERIENCED LOSS OF SEPARATION BECAUSE OF PLT ERROR.

Narrative: ACFT A WAS CLRED TO FL200. ACFT B WS LEVEL AT FL190. WAS STARTING IN TRAIL TO ATL. LOOKED AT OTHER END OF SECTOR TO SWITCH AIRPLANES. DATA BLOCKS WERE OVERLAPPED ON ACFT A&B. SOMETHING LOOKED WRONG, SO I MOVED DATA BLOCKS. ACFT A WAS DSNDING THROUGH ACFT B AND OUT OF FL186. I MADE SURE ACFT B STAYED AT FL190. ACFT A WAS TURNED TO HDG 180 DEGS FROM 110 DEGS AND TOLD TO DSND. I GOT A CALL FROM THE SUPVR IN CHARGE WHEN HE CALLED ACFT A WAS OUT OF FL180 AND I TOLD HIM ACFT A WAS OUT OF FL186.

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.