ARTCC radar controller descended an air carrier B727 through the altitude of an opposite direction B737 with less than standard separation. Both aircraft given vectors, but system error occurred anyway.

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Attributes
ACN	389151
Time
Date	199712
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mod
State Reference	CA
Altitude	msl bound lower : 31000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 11 controller radar : 9
ASRS Report	389151
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 21000 vertical : 1000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I descended aircraft X from FL350 to FL310 with aircraft Y opposite direction at FL330 and 30 mi away. After aircraft X began his descent and conflict alert went off, I turned aircraft X to miss aircraft Y. Other controller working aircraft Y coordinated to turn aircraft Y away from X.

Original NASA ASRS Text

Title: ARTCC RADAR CTLR DSNDED AN ACR B727 THROUGH THE ALT OF AN OPPOSITE DIRECTION B737 WITH LTSS. BOTH ACFT GIVEN VECTORS, BUT SYS ERROR OCCURRED ANYWAY.

Narrative: I DSNDED ACFT X FROM FL350 TO FL310 WITH ACFT Y OPPOSITE DIRECTION AT FL330 AND 30 MI AWAY. AFTER ACFT X BEGAN HIS DSCNT AND CONFLICT ALERT WENT OFF, I TURNED ACFT X TO MISS ACFT Y. OTHER CTLR WORKING ACFT Y COORDINATED TO TURN ACFT Y AWAY FROM X.

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.