Air carrier X had less than standard separation from small transport Y. System error.

Attributes
ACN	136033
Time
Date	199002
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : rod
State Reference	OH
Altitude	msl bound lower : 22000 msl bound upper : 23000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute : on vectors enroute : direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 16
ASRS Report	136033
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 24000 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was en route from ord J178 ape.cmh. Small transport Y was en route dtw V47 rod.lex. Air carrier X was cleared from FL230 down to FL200. Small transport Y was level at FL220. When air carrier X started descent, forward speed increased and air carrier X appeared to be drifting south of course. When it appeared that lateral might be diminishing, I turned air carrier X to 'fly heading 020.' however, lateral reduced to 4 NM at closest point.

Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM SMT Y. SYSTEM ERROR.

Narrative: ACR X WAS ENRTE FROM ORD J178 APE.CMH. SMT Y WAS ENRTE DTW V47 ROD.LEX. ACR X WAS CLRED FROM FL230 DOWN TO FL200. SMT Y WAS LEVEL AT FL220. WHEN ACR X STARTED DSCNT, FORWARD SPEED INCREASED AND ACR X APPEARED TO BE DRIFTING S OF COURSE. WHEN IT APPEARED THAT LATERAL MIGHT BE DIMINISHING, I TURNED ACR X TO 'FLY HDG 020.' HOWEVER, LATERAL REDUCED TO 4 NM AT CLOSEST POINT.

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.