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

Attributes
ACN	134184
Time
Date	199001
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : oma
State Reference	NE
Altitude	msl bound lower : 4400 msl bound upper : 4400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : oma
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	approach : visual enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 16
ASRS Report	134184
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 3000 vertical : 300
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X, medium large transport inbound from northeast direct to oma VOR. Aircraft Y, small transport, inbound from southeast direct VOR landing oma. Air carrier X was cleared for a visual to follow a widebody transport. Anticipating turn in to airport, aircraft Y was descended to 3000 to follow medium large transport traffic issued when 5 mi apart. Air carrier X didn't descend as planned and did not turn in towards airport as planned. Air carrier X continued towards airport until evasive action taken by controller.

Original NASA ASRS Text

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

Narrative: ACR X, MLG INBND FROM NE DIRECT TO OMA VOR. ACFT Y, SMT, INBND FROM SE DIRECT VOR LNDG OMA. ACR X WAS CLRED FOR A VISUAL TO FOLLOW A WDB. ANTICIPATING TURN IN TO ARPT, ACFT Y WAS DESCENDED TO 3000 TO FOLLOW MLG TFC ISSUED WHEN 5 MI APART. ACR X DIDN'T DSND AS PLANNED AND DID NOT TURN IN TOWARDS ARPT AS PLANNED. ACR X CONTINUED TOWARDS ARPT UNTIL EVASIVE ACTION TAKEN BY CTLR.

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.