Aircraft X same altitude assigned had less than standard separation from aircraft Y. System error.

Attributes
ACN	275201
Time
Date	199406
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ffo
State Reference	OH
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : day
Operator	general aviation : personal
Make Model Name	Twin Beech 18
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	PA-23-250 Aztec
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller military : 4 controller radar : 8
ASRS Report	275201
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument
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	faa : investigated
Miss Distance	horizontal : 3000 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working approach control with about 8 or 9 aircraft on the frequency. The other approach controller asked if twin beech X and pazt Y were ok. Once I recognized the conflict of both aircraft at 8000 ft converging, I took action by turning the twin beech left to go behind the aztec, and also climbed him to 90000 ft. The aircraft came within 15 mi and 400 ft.

Original NASA ASRS Text

Title: ACFT X SAME ALT ASSIGNED HAD LTSS FROM ACFT Y. SYS ERROR.

Narrative: I WAS WORKING APCH CTL WITH ABOUT 8 OR 9 ACFT ON THE FREQ. THE OTHER APCH CTLR ASKED IF TWIN BEECH X AND PAZT Y WERE OK. ONCE I RECOGNIZED THE CONFLICT OF BOTH ACFT AT 8000 FT CONVERGING, I TOOK ACTION BY TURNING THE TWIN BEECH L TO GO BEHIND THE AZTEC, AND ALSO CLBED HIM TO 90000 FT. THE ACFT CAME WITHIN 15 MI AND 400 FT.

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.