B737-300 flight crew respond to TCASII event on approach to bur from other unknown aircraft descending through WX under sct control.

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Attributes
ACN	609125
Time
Date	200402
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bur.airport
State Reference	CA
Altitude	msl bound lower : 6700 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sct.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : lynxx
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : sct.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent : intermediate altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	609125
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne critical inflight encounter : weather other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action flight crew : returned to assigned altitude flight crew : overrode automation
Miss Distance	vertical : 0
Supplementary
Problem Areas	Weather Flight Crew Human Performance Environmental Factor ATC Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

On the lynxx 7 arrival from las into bur, past janny at 8000 ft MSL, talking to socal approach, we were IMC, estimating tops at 9000 ft and burbank reporting 4500 ft broken. We saw traffic on the TCASII at 5 mi, 12 O'clock position and closing. His initial altitude was either 8400 ft or 8300 ft, descending slowly. We queried socal when he was 4 mi away. Socal asked the traffic if he was still 8500 ft. Very bad. Traffic is 3 mi now, co-altitude. We got a TA followed immediately by an RA, commanding a maximum 'climb.' we initiated our climb, traffic started to climb also. The RA changed to maximum 'descend.' I unloaded the aircraft, banked left 60 degrees, and commenced a radio descent. Our TCASII symbols started to merge. Socal ordered traffic to descend. Very, very bad. I jumped on radio and said something to the effect of 'negative, I'm descending.' I leveled around 6700 ft MSL after the TCASII stopped yelling at us. This all happened very fast. We climbed back to 8000 ft after telling socal our altitude.

Original NASA ASRS Text

Title: B737-300 FLT CREW RESPOND TO TCASII EVENT ON APCH TO BUR FROM OTHER UNKNOWN ACFT DSNDING THROUGH WX UNDER SCT CTL.

Narrative: ON THE LYNXX 7 ARR FROM LAS INTO BUR, PAST JANNY AT 8000 FT MSL, TALKING TO SOCAL APCH, WE WERE IMC, ESTIMATING TOPS AT 9000 FT AND BURBANK RPTING 4500 FT BROKEN. WE SAW TFC ON THE TCASII AT 5 MI, 12 O'CLOCK POS AND CLOSING. HIS INITIAL ALT WAS EITHER 8400 FT OR 8300 FT, DSNDING SLOWLY. WE QUERIED SOCAL WHEN HE WAS 4 MI AWAY. SOCAL ASKED THE TFC IF HE WAS STILL 8500 FT. VERY BAD. TFC IS 3 MI NOW, CO-ALT. WE GOT A TA FOLLOWED IMMEDIATELY BY AN RA, COMMANDING A MAX 'CLB.' WE INITIATED OUR CLB, TFC STARTED TO CLB ALSO. THE RA CHANGED TO MAX 'DSND.' I UNLOADED THE ACFT, BANKED L 60 DEGS, AND COMMENCED A RADIO DSCNT. OUR TCASII SYMBOLS STARTED TO MERGE. SOCAL ORDERED TFC TO DSND. VERY, VERY BAD. I JUMPED ON RADIO AND SAID SOMETHING TO THE EFFECT OF 'NEGATIVE, I'M DSNDING.' I LEVELED AROUND 6700 FT MSL AFTER THE TCASII STOPPED YELLING AT US. THIS ALL HAPPENED VERY FAST. WE CLBED BACK TO 8000 FT AFTER TELLING SOCAL OUR ALT.

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.