A center radar controller descended an LR55 through the altitude of a same direction SF34 level at FL200. Due to speed difference, the LR55 overtook the SF34 and headings to maintain separation were not sufficient to prevent a loss of separation.

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Attributes
ACN	409571
Time
Date	199807
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : tvt
State Reference	OH
Altitude	msl bound lower : 20000 msl bound upper : 20000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	SF 340A
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Learjet 55
Operating Under FAR Part	Part 91
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	409571
Person 2
Affiliation	government : faa
Function	oversight : supervisor
Qualification	controller : radar pilot : instrument pilot : private
Experience	flight time total : 1000
ASRS Report	408910
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 25200 vertical : 800
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X northbound direct djb at FL200. Air carrier X switched to mfd low. Ape high radar controller asked for lower on cga Y. I gave him FL210. Cga Y called on descending to FL210. I assigned him present heading (V050) for air carrier X traffic and I also descended him to 15000 ft. I monitored the situation and turned cga Y to heading of 090 degrees. When I realized heading of 090 degrees was not sufficient, I turned cga Y to heading of 120 degrees. Aedp activated. Reason for error: poor judgement on my (controller's) part. The aircraft did not turn as quickly as I thought. Vector would have worked if turn was issued at call on of cga Y. Overall, should have kept aircraft XXX at FL210 until turn was completed, ensuring 5 NM separation. I apologize for my use of poor judgement. This has been a humbling but motivational experience so as to improve my skills and to provide better service to the flying public. Please feel free to phone me with any questions.

Original NASA ASRS Text

Title: A CTR RADAR CTLR DSNDED AN LR55 THROUGH THE ALT OF A SAME DIRECTION SF34 LEVEL AT FL200. DUE TO SPD DIFFERENCE, THE LR55 OVERTOOK THE SF34 AND HDGS TO MAINTAIN SEPARATION WERE NOT SUFFICIENT TO PREVENT A LOSS OF SEPARATION.

Narrative: ACR X NBOUND DIRECT DJB AT FL200. ACR X SWITCHED TO MFD LOW. APE HIGH RADAR CTLR ASKED FOR LOWER ON CGA Y. I GAVE HIM FL210. CGA Y CALLED ON DSNDING TO FL210. I ASSIGNED HIM PRESENT HDG (V050) FOR ACR X TFC AND I ALSO DSNDED HIM TO 15000 FT. I MONITORED THE SIT AND TURNED CGA Y TO HDG OF 090 DEGS. WHEN I REALIZED HDG OF 090 DEGS WAS NOT SUFFICIENT, I TURNED CGA Y TO HDG OF 120 DEGS. AEDP ACTIVATED. REASON FOR ERROR: POOR JUDGEMENT ON MY (CTLR'S) PART. THE ACFT DID NOT TURN AS QUICKLY AS I THOUGHT. VECTOR WOULD HAVE WORKED IF TURN WAS ISSUED AT CALL ON OF CGA Y. OVERALL, SHOULD HAVE KEPT ACFT XXX AT FL210 UNTIL TURN WAS COMPLETED, ENSURING 5 NM SEPARATION. I APOLOGIZE FOR MY USE OF POOR JUDGEMENT. THIS HAS BEEN A HUMBLING BUT MOTIVATIONAL EXPERIENCE SO AS TO IMPROVE MY SKILLS AND TO PROVIDE BETTER SVC TO THE FLYING PUBLIC. PLEASE FEEL FREE TO PHONE ME WITH ANY QUESTIONS.

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.