A ZID ARTCC radar controller lost legal separation when he misjudged lateral spacing between an LJ55...

Attributes
ACN	636736
Time
Date	200411
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : hyk.vortac
State Reference	KY
Altitude	msl bound lower : 43000 msl bound upper : 45000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	general aviation : corporate
Make Model Name	Learjet 55
Operating Under FAR Part	Part 91
Flight Phase	cruise : enroute altitude change cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	general aviation : corporate
Make Model Name	Citation X
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller limited radar : 1 controller military : 6 controller radar : 1.5 controller time certified in position1 : 1 controller time certified in position2 : 3
ASRS Report	636736
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne critical non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment : conflict alert atc equipment other atc equipment : radar/mode c other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	faa : investigated
Miss Distance	horizontal : 13800 vertical : 1400
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft X (LJ55) was heading east, nebound at FL450 and requested FL430. Aircraft Y (C750) was wbound to FL430. I had cleared aircraft X (LJ55) direct to psb which was a left turn. I thought that I had lateral separation so I descended aircraft X (LJ55) to FL430. I lost required lateral separation, then I turned aircraft X to a 360 degree heading.

Original NASA ASRS Text

Title: A ZID ARTCC RADAR CTLR LOST LEGAL SEPARATION WHEN HE MISJUDGED LATERAL SPACING BTWN AN LJ55 AND A C750.

Narrative: ACFT X (LJ55) WAS HDG E, NEBOUND AT FL450 AND REQUESTED FL430. ACFT Y (C750) WAS WBOUND TO FL430. I HAD CLRED ACFT X (LJ55) DIRECT TO PSB WHICH WAS A L TURN. I THOUGHT THAT I HAD LATERAL SEPARATION SO I DSNDED ACFT X (LJ55) TO FL430. I LOST REQUIRED LATERAL SEPARATION, THEN I TURNED ACFT X TO A 360 DEG HDG.

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.

A ZID ARTCC radar controller lost legal separation when he misjudged lateral spacing between an LJ55 and a C750.