Air carrier X had less than standard separation from air carrier Y. System error.

Attributes
ACN	134023
Time
Date	199001
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sat
State Reference	TX
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sat tower : fxe
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
ASRS Report	134023
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 non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	unspecified : 12600 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X checks in at 10,000 cleared to 6000. Air carrier Y checks in out of 14,000 descending to 12,000 located over air carrier X with 130K overtake. I instructed air carrier Y to descend and maintain 7000. Air carrier X doesn't descend and air carrier Y descends at faster than normal rate. The ARTS tags overlap with no conflict alert. When vertical separation is lost, air carrier Y is 2.1 mi in front.

Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACR Y. SYSTEM ERROR.

Narrative: ACR X CHECKS IN AT 10,000 CLRED TO 6000. ACR Y CHECKS IN OUT OF 14,000 DESCENDING TO 12,000 LOCATED OVER ACR X WITH 130K OVERTAKE. I INSTRUCTED ACR Y TO DSND AND MAINTAIN 7000. ACR X DOESN'T DSND AND ACR Y DESCENDS AT FASTER THAN NORMAL RATE. THE ARTS TAGS OVERLAP WITH NO CONFLICT ALERT. WHEN VERTICAL SEPARATION IS LOST, ACR Y IS 2.1 MI IN FRONT.

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.