Less than standard separation occurred. System error.

Attributes
ACN	112496
Time
Date	198905
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lax
State Reference	CA
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air taxi
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other descent other
Route In Use	arrival other enroute airway : lax
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air taxi
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller military : 4 controller non radar : 2 controller radar : 6
ASRS Report	112496
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : developmental
Events
Anomaly	conflict : airborne less severe non adherence : clearance non adherence : required legal separation non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 7500 vertical : 600
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Atx X eastbound to lax at 7000' was descended to 6000. Atx Z also eastbound to lax below atx X at 5000'. Atx Y departed lax wbound climbing to 6000'. OJT training in effect. I pointed out conflict to developmental who then turned atx Z swbound out of the way of atx X. Atx Y answered the call for company atx Y. I missed the inherent readback. I noticed that the turn hadn't had the desired result when the aircraft were approximately 5 mi apart. I then overrode the developmental and instructed atx Y to turn left heading 180 degree 'now'. I also turned atx X nebnd. The aircraft passed about 1 1/2 mi from each other and 600' vertically. I believe this error could have been prevented by careful attention to readbacks. I also feel that during training I must not allow the developmental to let a situation go to the point where only an emergency override transmission will prevent a loss of separation. To the extent possible, it also would be nice if more could be done to minimize similar sounding call signs among the carriers.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION OCCURRED. SYSTEM ERROR.

Narrative: ATX X EBND TO LAX AT 7000' WAS DESCENDED TO 6000. ATX Z ALSO EBND TO LAX BELOW ATX X AT 5000'. ATX Y DEPARTED LAX WBOUND CLIMBING TO 6000'. OJT TRAINING IN EFFECT. I POINTED OUT CONFLICT TO DEVELOPMENTAL WHO THEN TURNED ATX Z SWBOUND OUT OF THE WAY OF ATX X. ATX Y ANSWERED THE CALL FOR COMPANY ATX Y. I MISSED THE INHERENT READBACK. I NOTICED THAT THE TURN HADN'T HAD THE DESIRED RESULT WHEN THE ACFT WERE APPROX 5 MI APART. I THEN OVERRODE THE DEVELOPMENTAL AND INSTRUCTED ATX Y TO TURN LEFT HDG 180 DEG 'NOW'. I ALSO TURNED ATX X NEBND. THE ACFT PASSED ABOUT 1 1/2 MI FROM EACH OTHER AND 600' VERTICALLY. I BELIEVE THIS ERROR COULD HAVE BEEN PREVENTED BY CAREFUL ATTN TO READBACKS. I ALSO FEEL THAT DURING TRAINING I MUST NOT ALLOW THE DEVELOPMENTAL TO LET A SITUATION GO TO THE POINT WHERE ONLY AN EMER OVERRIDE XMISSION WILL PREVENT A LOSS OF SEPARATION. TO THE EXTENT POSSIBLE, IT ALSO WOULD BE NICE IF MORE COULD BE DONE TO MINIMIZE SIMILAR SOUNDING CALL SIGNS AMONG THE CARRIERS.

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.