Less than standard separation between corp aircraft and air carrier. Operational error.

Attributes
ACN	92916
Time
Date	198808
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : syi
State Reference	TN
Altitude	msl bound lower : 10500 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme artcc : zdc
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	92916
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	controller : issued new clearance none taken : insufficient time
Consequence	faa : investigated
Miss Distance	horizontal : 28800 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Corp X was heading approximately north at 13000' and air carrier Y nnebound at 11000'. When the 2 aircraft were 5 NM latitude separated I instructed corp X to cross the shelbyville VOR DME at and maintain 6000'. Corp X left 13000 for 6000', still diverging away from air carrier Y at 11000'. At this time I thought I had assigned a heading of 050 degrees to air carrier Y, which would have provided latitude sep. The 050 degree heading was given to another air carrier Y company jet about 4 mins before. Air carrier Y reaching okies intersection on the shelbyville 1 arrival rocket transition turned to the nnw. When I realized air carrier Y turned I issued instructions for air carrier Y to turn right to a 090 degree heading, and corp X to turn left to a heading of 280 degrees. C/a did not activate until after the turns were issued to each aircraft. This incident occurred in the shelbyville low sector at the memphis ARTCC center. I had approximately 16 aircraft on frequency. The 2 aircraft came within 4.8 NM of each other with approximately 500' vertical sep and increasing (minor error). I made a mistake when I thought I had air carrier Y assigned 050 degree heading.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN CORP ACFT AND ACR. OPERATIONAL ERROR.

Narrative: CORP X WAS HDG APPROX N AT 13000' AND ACR Y NNEBOUND AT 11000'. WHEN THE 2 ACFT WERE 5 NM LAT SEPARATED I INSTRUCTED CORP X TO CROSS THE SHELBYVILLE VOR DME AT AND MAINTAIN 6000'. CORP X LEFT 13000 FOR 6000', STILL DIVERGING AWAY FROM ACR Y AT 11000'. AT THIS TIME I THOUGHT I HAD ASSIGNED A HDG OF 050 DEGS TO ACR Y, WHICH WOULD HAVE PROVIDED LAT SEP. THE 050 DEG HDG WAS GIVEN TO ANOTHER ACR Y COMPANY JET ABOUT 4 MINS BEFORE. ACR Y REACHING OKIES INTXN ON THE SHELBYVILLE 1 ARR ROCKET TRANSITION TURNED TO THE NNW. WHEN I REALIZED ACR Y TURNED I ISSUED INSTRUCTIONS FOR ACR Y TO TURN RIGHT TO A 090 DEG HDG, AND CORP X TO TURN LEFT TO A HDG OF 280 DEGS. C/A DID NOT ACTIVATE UNTIL AFTER THE TURNS WERE ISSUED TO EACH ACFT. THIS INCIDENT OCCURRED IN THE SHELBYVILLE LOW SECTOR AT THE MEMPHIS ARTCC CENTER. I HAD APPROX 16 ACFT ON FREQ. THE 2 ACFT CAME WITHIN 4.8 NM OF EACH OTHER WITH APPROX 500' VERT SEP AND INCREASING (MINOR ERROR). I MADE A MISTAKE WHEN I THOUGHT I HAD ACR Y ASSIGNED 050 DEG HDG.

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.