ZID controller experienced operational error at FL290.

Attributes
ACN	611314
Time
Date	200403
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : hvq.airport
State Reference	WV
Altitude	msl single value : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	general aviation : corporate
Make Model Name	Learjet 55
Operating Under FAR Part	Part 91
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 16 controller time certified in position1 : 6.5
ASRS Report	611314
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	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 : 18600
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Assumed position just 4 mins prior to error. Issued descent to #2 and overlooked #1 who was already handed off and switched frequency to next sector by previous controller. Error happened immediately after issuing clearance.

Original NASA ASRS Text

Title: ZID CTLR EXPERIENCED OPERROR AT FL290.

Narrative: ASSUMED POS JUST 4 MINS PRIOR TO ERROR. ISSUED DSCNT TO #2 AND OVERLOOKED #1 WHO WAS ALREADY HANDED OFF AND SWITCHED FREQ TO NEXT SECTOR BY PREVIOUS CTLR. ERROR HAPPENED IMMEDIATELY AFTER ISSUING CLRNC.

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.