ARTCC radar controller was vectoring 2 air carrier aircraft for separation and descending one at the same time. Reporter controller misjudged the spacing and the aircraft ended up with less than standard separation.

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Attributes
ACN	338127
Time
Date	199605
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : loz
State Reference	KY
Altitude	msl bound lower : 30000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid artcc : zlc
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 4 controller non radar : 16 controller radar : 16
ASRS Report	338127
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance flight crew : took evasive action other
Consequence	Other
Miss Distance	horizontal : 15000 vertical : 1000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X, DC9, at FL330 direct vxv was issued a 220 degree heading until receiving gqo and descended to FL290. Air carrier Y, MD80, was at FL310 heading 10 degrees. Air carrier Y was additionally turned to a 35 degree heading. I anticipated air carrier X to proceed to gqo on a rerte by tmu placing the aircraft 10-15 mi west of air carrier Y. Apparently air carrier X thought he was receiving gqo and only was tracking approximately 190 degrees. This placed air carrier X head on with air carrier Y. Air carrier X in addition only descended 2000 ft in 30 mi. I subsequently issued air carrier X an expedite descent to FL290 and turned him to a 270 degree heading. Air carrier Y was turned to a 90 degree heading and air carrier Y responded with 'I have traffic in sight and am responding to an RA. TCASII alert climbing to a higher altitude.' the end result is I misjudged air carrier X's rate of descent and ability to navigation direct gqo. My clrncs to separate air carrier X and air carrier Y was 'too little too late!'

Original NASA ASRS Text

Title: ARTCC RADAR CTLR WAS VECTORING 2 ACR ACFT FOR SEPARATION AND DSNDING ONE AT THE SAME TIME. RPTR CTLR MISJUDGED THE SPACING AND THE ACFT ENDED UP WITH LTSS.

Narrative: ACR X, DC9, AT FL330 DIRECT VXV WAS ISSUED A 220 DEG HDG UNTIL RECEIVING GQO AND DSNDED TO FL290. ACR Y, MD80, WAS AT FL310 HDG 10 DEGS. ACR Y WAS ADDITIONALLY TURNED TO A 35 DEG HDG. I ANTICIPATED ACR X TO PROCEED TO GQO ON A RERTE BY TMU PLACING THE ACFT 10-15 MI W OF ACR Y. APPARENTLY ACR X THOUGHT HE WAS RECEIVING GQO AND ONLY WAS TRACKING APPROX 190 DEGS. THIS PLACED ACR X HEAD ON WITH ACR Y. ACR X IN ADDITION ONLY DSNDED 2000 FT IN 30 MI. I SUBSEQUENTLY ISSUED ACR X AN EXPEDITE DSCNT TO FL290 AND TURNED HIM TO A 270 DEG HDG. ACR Y WAS TURNED TO A 90 DEG HDG AND ACR Y RESPONDED WITH 'I HAVE TFC IN SIGHT AND AM RESPONDING TO AN RA. TCASII ALERT CLBING TO A HIGHER ALT.' THE END RESULT IS I MISJUDGED ACR X'S RATE OF DSCNT AND ABILITY TO NAV DIRECT GQO. MY CLRNCS TO SEPARATE ACR X AND ACR Y WAS 'TOO LITTLE TOO LATE!'

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.