Atx X had possible near midair collision with BE35. See and avoid concept.

Attributes
ACN	265729
Time
Date	199403
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gmn
State Reference	CA
Altitude	msl bound lower : 11500 msl bound upper : 11500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : cor
Operator	common carrier : air taxi
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : bfl
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Bonanza 35
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller military : 4 controller non radar : 1 controller radar : 13 controller supervisory : 3
ASRS Report	265729
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : developmental
Events
Anomaly	conflict : nmac non adherence : far
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Miss Distance	horizontal : 500 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

During an on-the-job (OJT) training session, developmental controller issued a vector to atx X northbound around heavy congestion of VFR and IFR traffic on V23, for descent purposes. When IFR separation was ensured, X was descended from 12000 ft MSL to 7000 ft MSL. Shortly after descent clearance, an untagged VFR target was observed sbound at 11500 ft directly in the path of X. Traffic was passed as 12 O'clock 1 mi altitude indicates 11500 ft sbound. Pilot of X indicated traffic in sight. After passing the traffic, pilot inquired if we were working the bonanza. Our reply was negative. Contributing factors: beacon (ARTS iia data block on X) was in CST 'coast track' when traffic was observed and issued, thus making it impossible to determine altitude for consideration of TA. At times, it seems that it is physically impossible to speak fast enough to issue traffic calls when groupings of aircraft converge on the same point at the same time.

Original NASA ASRS Text

Title: ATX X HAD POSSIBLE NMAC WITH BE35. SEE AND AVOID CONCEPT.

Narrative: DURING AN ON-THE-JOB (OJT) TRAINING SESSION, DEVELOPMENTAL CTLR ISSUED A VECTOR TO ATX X NBOUND AROUND HVY CONGESTION OF VFR AND IFR TFC ON V23, FOR DSCNT PURPOSES. WHEN IFR SEPARATION WAS ENSURED, X WAS DSNDED FROM 12000 FT MSL TO 7000 FT MSL. SHORTLY AFTER DSCNT CLRNC, AN UNTAGGED VFR TARGET WAS OBSERVED SBOUND AT 11500 FT DIRECTLY IN THE PATH OF X. TFC WAS PASSED AS 12 O'CLOCK 1 MI ALT INDICATES 11500 FT SBOUND. PLT OF X INDICATED TFC IN SIGHT. AFTER PASSING THE TFC, PLT INQUIRED IF WE WERE WORKING THE BONANZA. OUR REPLY WAS NEGATIVE. CONTRIBUTING FACTORS: BEACON (ARTS IIA DATA BLOCK ON X) WAS IN CST 'COAST TRACK' WHEN TFC WAS OBSERVED AND ISSUED, THUS MAKING IT IMPOSSIBLE TO DETERMINE ALT FOR CONSIDERATION OF TA. AT TIMES, IT SEEMS THAT IT IS PHYSICALLY IMPOSSIBLE TO SPEAK FAST ENOUGH TO ISSUE TFC CALLS WHEN GROUPINGS OF ACFT CONVERGE ON THE SAME POINT AT THE SAME TIME.

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.