Less than standard separation between air carrier and commuter. Operational error.

Attributes
ACN	173980
Time
Date	199103
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : ont
State Reference	CA
Altitude	msl bound lower : 5000 msl bound upper : 5000
Environment
Flight Conditions	Marginal
Light	Night
Aircraft 1
Controlling Facilities	tracon : ont
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller military : 8 controller radar : 19
ASRS Report	173980
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated faa : reviewed incident with flight crew
Miss Distance	horizontal : 2000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

While working ont arrival and other en route radar sectors, I was working air carrier X and commuter Y for the ILS to ont. Traffic was moderate and complex due to an emergency widebody transport trying to locate a suitable fuel dump sight to return to ont for landing. (No designated fuel dump area presently exists for ont area.) when first observed the radar tracks of both X and Y appeared to be no factor, but when air carrier X was cleared for approach he slowed quite a bit and somewhat prematurely. Aircraft Y didn't slow and this created a conflict. Due to the distraction of the fuel dump and an IFR GA aircraft at 12000' which the radar would not track properly, attention was diverted away from the pending conflict. When I went back to rechk the air carrier and commuter's tracks, I observed the conflict and had already lost approved IFR sep. The C/a feature of FAA radar went into alarm approximately 20 seconds after the aircraft had already passed. Further investigation by FAA showed that aircraft had seen each other and had already taken action on their own to avoid each other. Aircraft Y pilot advised that this was a near miss, but didn't file formally to my knowledge.

Original NASA ASRS Text

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

Narrative: WHILE WORKING ONT ARR AND OTHER ENRTE RADAR SECTORS, I WAS WORKING ACR X AND COMMUTER Y FOR THE ILS TO ONT. TFC WAS MODERATE AND COMPLEX DUE TO AN EMER WDB TRYING TO LOCATE A SUITABLE FUEL DUMP SIGHT TO RETURN TO ONT FOR LNDG. (NO DESIGNATED FUEL DUMP AREA PRESENTLY EXISTS FOR ONT AREA.) WHEN FIRST OBSERVED THE RADAR TRACKS OF BOTH X AND Y APPEARED TO BE NO FACTOR, BUT WHEN ACR X WAS CLRED FOR APCH HE SLOWED QUITE A BIT AND SOMEWHAT PREMATURELY. ACFT Y DIDN'T SLOW AND THIS CREATED A CONFLICT. DUE TO THE DISTR OF THE FUEL DUMP AND AN IFR GA ACFT AT 12000' WHICH THE RADAR WOULD NOT TRACK PROPERLY, ATTN WAS DIVERTED AWAY FROM THE PENDING CONFLICT. WHEN I WENT BACK TO RECHK THE ACR AND COMMUTER'S TRACKS, I OBSERVED THE CONFLICT AND HAD ALREADY LOST APPROVED IFR SEP. THE C/A FEATURE OF FAA RADAR WENT INTO ALARM APPROX 20 SECS AFTER THE ACFT HAD ALREADY PASSED. FURTHER INVESTIGATION BY FAA SHOWED THAT ACFT HAD SEEN EACH OTHER AND HAD ALREADY TAKEN ACTION ON THEIR OWN TO AVOID EACH OTHER. ACFT Y PLT ADVISED THAT THIS WAS A NEAR MISS, BUT DIDN'T FILE FORMALLY TO MY KNOWLEDGE.

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.