Controller issued a descent clearance to aircraft Z. Aircraft X read back clearance and started desc...

Attributes
ACN	427713
Time
Date	199812
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lhs
State Reference	CA
Altitude	msl bound lower : 8000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
ASRS Report	427713
Person 2
Affiliation	Other
Function	flight crew : single pilot
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	none taken : insufficient time
Consequence	faa : investigated
Miss Distance	horizontal : 18000 vertical : 500
Supplementary
Air Traffic Incident	Operational Error

Narrative:

A third aircraft was involved, an SF34 (aircraft Z). I descended the SF34 from 11000 ft to 8000 ft and the E120 (aircraft X) read back and commenced the descent. I missed the readback. I was focused on an untagged target that was traffic for the SF34 and another traffic situation on my scope. As I was scanning my scope, I observed the E120 (aircraft X) in a descent that would conflict head-on with the PA28 (aircraft Y). I 'broke in' to the frequency and took evasive action with the E120 (aircraft X) and the PA28 (aircraft Y). At no time did the conflict alert activate. It is unknown if the E120 (aircraft X) received a TCASII resolution. I called my supervisor and alerted him to the situation. I was relieved of duties and an investigation was started. There were no other witnesses besides myself and I never stated that I lost IFR separation. Based upon the audio tape, the situation was and is classified as an operational error. With our new ARTS 3E equipment, there is no longer the capability to perform a data resolution or actually chart the aircraft. My facility tried to demonstrate that I did not lose IFR separation, however, the western pacific regional office refused to overturn because we could not 'prove' beyond a 'shadow of a doubt' that we did not lose IFR separation. This ruling against me -- also really anyone else that could be caught in a similar situation -- defies all logic! Could someone please investigate?

Original NASA ASRS Text

Title: CTLR ISSUED A DSCNT CLRNC TO ACFT Z. ACFT X READ BACK CLRNC AND STARTED DSCNT, WHICH NOW BECAME TFC FOR ACFT Y. CTLR MISSED THE READBACK FROM WRONG ACFT. LATER, CTLR ATTEMPTED TO SEPARATE ACFT X FROM ACFT Y, TOO LATE, LOST LEGAL SEPARATION.

Narrative: A THIRD ACFT WAS INVOLVED, AN SF34 (ACFT Z). I DSNDED THE SF34 FROM 11000 FT TO 8000 FT AND THE E120 (ACFT X) READ BACK AND COMMENCED THE DSCNT. I MISSED THE READBACK. I WAS FOCUSED ON AN UNTAGGED TARGET THAT WAS TFC FOR THE SF34 AND ANOTHER TFC SIT ON MY SCOPE. AS I WAS SCANNING MY SCOPE, I OBSERVED THE E120 (ACFT X) IN A DSCNT THAT WOULD CONFLICT HEAD-ON WITH THE PA28 (ACFT Y). I 'BROKE IN' TO THE FREQ AND TOOK EVASIVE ACTION WITH THE E120 (ACFT X) AND THE PA28 (ACFT Y). AT NO TIME DID THE CONFLICT ALERT ACTIVATE. IT IS UNKNOWN IF THE E120 (ACFT X) RECEIVED A TCASII RESOLUTION. I CALLED MY SUPVR AND ALERTED HIM TO THE SIT. I WAS RELIEVED OF DUTIES AND AN INVESTIGATION WAS STARTED. THERE WERE NO OTHER WITNESSES BESIDES MYSELF AND I NEVER STATED THAT I LOST IFR SEPARATION. BASED UPON THE AUDIO TAPE, THE SIT WAS AND IS CLASSIFIED AS AN OPERROR. WITH OUR NEW ARTS 3E EQUIP, THERE IS NO LONGER THE CAPABILITY TO PERFORM A DATA RESOLUTION OR ACTUALLY CHART THE ACFT. MY FACILITY TRIED TO DEMONSTRATE THAT I DID NOT LOSE IFR SEPARATION, HOWEVER, THE WESTERN PACIFIC REGIONAL OFFICE REFUSED TO OVERTURN BECAUSE WE COULD NOT 'PROVE' BEYOND A 'SHADOW OF A DOUBT' THAT WE DID NOT LOSE IFR SEPARATION. THIS RULING AGAINST ME -- ALSO REALLY ANYONE ELSE THAT COULD BE CAUGHT IN A SIMILAR SIT -- DEFIES ALL LOGIC! COULD SOMEONE PLEASE INVESTIGATE?

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.

Controller issued a descent clearance to aircraft Z. Aircraft X read back clearance and started descent, which now became traffic for aircraft Y. Controller missed the readback from wrong aircraft. Later, controller attempted to separate aircraft X from aircraft Y, too late, lost legal separation.