An air carrier flight crew is advised of VFR traffic ahead on their route. They do not see the traffic, but got a TCASII 'RA' and acted on it. The TCASII displayed the traffic at less than 1 mi.

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Attributes
ACN	346140
Time
Date	199608
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lax
State Reference	CA
Altitude	msl bound lower : 17500 msl bound upper : 18500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Aircraft 2
Make Model Name	PA-28 Cherokee Arrow IV
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 16000 flight time type : 1700
ASRS Report	346140
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : far non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 4500 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error other

Narrative:

On civet arrival ATC called out VFR traffic 12 O'clock 17500 ft. I was descending through 18500 ft. First officer said 'we'll level off.' center said 'no need to, she (cherokee) has you in sight.' as I was starting a level off I got an 'RA.' the traffic was not in sight so I followed the 'RA.' I told the controller I was not comfortable with VFR traffic on the civet arrival. He replied 'I didn't see a problem -- I was controling both of you and I had a mi separation.' I don't think VFR departures out the civet course is a good or safe idea. My TCASII showed less than 1 mi horizontal separation.

Original NASA ASRS Text

Title: AN ACR FLC IS ADVISED OF VFR TFC AHEAD ON THEIR RTE. THEY DO NOT SEE THE TFC, BUT GOT A TCASII 'RA' AND ACTED ON IT. THE TCASII DISPLAYED THE TFC AT LESS THAN 1 MI.

Narrative: ON CIVET ARR ATC CALLED OUT VFR TFC 12 O'CLOCK 17500 FT. I WAS DSNDING THROUGH 18500 FT. FO SAID 'WE'LL LEVEL OFF.' CTR SAID 'NO NEED TO, SHE (CHEROKEE) HAS YOU IN SIGHT.' AS I WAS STARTING A LEVEL OFF I GOT AN 'RA.' THE TFC WAS NOT IN SIGHT SO I FOLLOWED THE 'RA.' I TOLD THE CTLR I WAS NOT COMFORTABLE WITH VFR TFC ON THE CIVET ARR. HE REPLIED 'I DIDN'T SEE A PROB -- I WAS CTLING BOTH OF YOU AND I HAD A MI SEPARATION.' I DON'T THINK VFR DEPS OUT THE CIVET COURSE IS A GOOD OR SAFE IDEA. MY TCASII SHOWED LESS THAN 1 MI HORIZ SEPARATION.

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.