An air carrier was descended to an altitude occupied by another aircraft resulting in less than stan...

Attributes
ACN	110805
Time
Date	198905
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sac
State Reference	CA
Altitude	msl bound lower : 11000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mcc
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
ASRS Report	110805
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
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

On 5/X/89, I was working south feeder at XX15Z. I had several aircraft proceeding to the sacramento VOR at various altitudes. 2 arrs that needed to be descended for approach to smf, 2 departures that I restr below the arrs, and another 2 overflts. I overlooked the small transport and cleared air carrier X to 11000'. At 5 mi and closing I discovered my error and issued traffic alerts to both small transport and turned to 090 degrees, and air carrier X was turned to 270 degrees. However, I used air carrier Y call sign initially and quickly restated the turn to air carrier X, who took the turn and reported the small transport in sight. Latitude sep had decreased to 2 mi upon air carrier X sighting traffic. My scan of the traffic was hampered when the data tags of air carrier Y and small transport had overlapped. It was at this time that air carrier X called in.

Original NASA ASRS Text

Title: AN ACR WAS DESCENDED TO AN ALT OCCUPIED BY ANOTHER ACFT RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: ON 5/X/89, I WAS WORKING S FEEDER AT XX15Z. I HAD SEVERAL ACFT PROCEEDING TO THE SACRAMENTO VOR AT VARIOUS ALTS. 2 ARRS THAT NEEDED TO BE DSNDED FOR APCH TO SMF, 2 DEPS THAT I RESTR BELOW THE ARRS, AND ANOTHER 2 OVERFLTS. I OVERLOOKED THE SMT AND CLRED ACR X TO 11000'. AT 5 MI AND CLOSING I DISCOVERED MY ERROR AND ISSUED TFC ALERTS TO BOTH SMT AND TURNED TO 090 DEGS, AND ACR X WAS TURNED TO 270 DEGS. HOWEVER, I USED ACR Y CALL SIGN INITIALLY AND QUICKLY RESTATED THE TURN TO ACR X, WHO TOOK THE TURN AND RPTED THE SMT IN SIGHT. LAT SEP HAD DECREASED TO 2 MI UPON ACR X SIGHTING TFC. MY SCAN OF THE TFC WAS HAMPERED WHEN THE DATA TAGS OF ACR Y AND SMT HAD OVERLAPPED. IT WAS AT THIS TIME THAT ACR X CALLED IN.

Data retrieved from NASA's ASRS site as of August 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.

An air carrier was descended to an altitude occupied by another aircraft resulting in less than standard separation.