Sct controller experienced operational error at 4000 ft during in-trail spacing vectors to sna.

Attributes
ACN	628045
Time
Date	200404
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sna.airport
State Reference	CA
Altitude	msl single value : 4000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sna.tower
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller military : 2 controller non radar : 7 controller radar : 25 controller time certified in position1 : 20 flight time total : 1400
ASRS Report	628045
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne critical non adherence : required legal separation
Independent Detector	atc equipment : conflict alert aircraft equipment : tcas other controllera
Resolutory Action	controller : issued new clearance controller : issued alert flight crew : took evasive action
Consequence	faa : investigated
Miss Distance	horizontal : 5600 vertical : 300
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft #1 was vectored 300 degrees across the ILS final at sna. Aircraft #2 was in-trail. Aircraft #1 was given a 070 degree heading and then when aircraft #2 rechked approximately the same point where aircraft #1 turned, aircraft #2 was told turn right heading 350 degrees. Aircraft #1 was at 4000 ft and aircraft was descending to 4000 ft. Aircraft #2 cut across the path of aircraft #1. When I realized aircraft #2 was converging on aircraft #1, I asked aircraft #2 if he had #1 in sight. When he said no, I told aircraft #2 to turn left, heading 300 degrees, immediately. Aircraft #2 passed behind aircraft #1 by .9 NM and 300 ft. I told aircraft #1 to descend but his TCASII told him to climb. I intended to tell aircraft #2 to climb. But, his TCASII told him to descend. My action, while not solving a separation standards problem, would have increased separation. The TCASII alerts did not maximize the near miss distance. Our conflict alert system did not activate in time to allow any course of action on my part had I relied on it for a timely alert. Aircraft #1 and aircraft #2 would have passed closer.

Original NASA ASRS Text

Title: SCT CTLR EXPERIENCED OPERROR AT 4000 FT DURING IN-TRAIL SPACING VECTORS TO SNA.

Narrative: ACFT #1 WAS VECTORED 300 DEGS ACROSS THE ILS FINAL AT SNA. ACFT #2 WAS IN-TRAIL. ACFT #1 WAS GIVEN A 070 DEG HDG AND THEN WHEN ACFT #2 RECHKED APPROX THE SAME POINT WHERE ACFT #1 TURNED, ACFT #2 WAS TOLD TURN R HDG 350 DEGS. ACFT #1 WAS AT 4000 FT AND ACFT WAS DSNDING TO 4000 FT. ACFT #2 CUT ACROSS THE PATH OF ACFT #1. WHEN I REALIZED ACFT #2 WAS CONVERGING ON ACFT #1, I ASKED ACFT #2 IF HE HAD #1 IN SIGHT. WHEN HE SAID NO, I TOLD ACFT #2 TO TURN L, HDG 300 DEGS, IMMEDIATELY. ACFT #2 PASSED BEHIND ACFT #1 BY .9 NM AND 300 FT. I TOLD ACFT #1 TO DSND BUT HIS TCASII TOLD HIM TO CLB. I INTENDED TO TELL ACFT #2 TO CLB. BUT, HIS TCASII TOLD HIM TO DSND. MY ACTION, WHILE NOT SOLVING A SEPARATION STANDARDS PROB, WOULD HAVE INCREASED SEPARATION. THE TCASII ALERTS DID NOT MAXIMIZE THE NEAR MISS DISTANCE. OUR CONFLICT ALERT SYS DID NOT ACTIVATE IN TIME TO ALLOW ANY COURSE OF ACTION ON MY PART HAD I RELIED ON IT FOR A TIMELY ALERT. ACFT #1 AND ACFT #2 WOULD HAVE PASSED CLOSER.

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.