Air carrier X TCASII TA RA evasive action taken climb had less than standard separation from light transport. System error.

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Attributes
ACN	203568
Time
Date	199203
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : sfo
State Reference	CA
Altitude	msl bound lower : 5000 msl bound upper : 5000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : oak
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 20500 flight time type : 2500
ASRS Report	203568
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 3000 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

We were operating as air carrier X (las-sfo) and were under the control of bay approach (frequency 135.65). We had been cleared for a 'quiet bridge' approach (sfo 095 degrees) and were level at 6000 ft. The controller (female voice) then cleared us to '4000 ft, turn left 20 degrees, intercept the localizer for runway 28L and tell me when you see it.' I turned left and started to descend (we were in moderate rain and still in the clouds). Shortly thereafter, the TCASII issued a TA. I looked at the display to see which traffic was the problem when the TCASII sounded an RA with instructions to climb and the correct symbology. I started the climb and the first officer informed the controller of our actions. A (male voice) controller informed us that the traffic was at 5000 ft. I had seen what appeared to be an light transport crossing in front of us as I began our pull up. The new controller vectored us around for another approach and successful landing. The TCASII performed perfectly.

Original NASA ASRS Text

Title: ACR X TCASII TA RA EVASIVE ACTION TAKEN CLB HAD LTSS FROM LTT. SYS ERROR.

Narrative: WE WERE OPERATING AS ACR X (LAS-SFO) AND WERE UNDER THE CTL OF BAY APCH (FREQ 135.65). WE HAD BEEN CLRED FOR A 'QUIET BRIDGE' APCH (SFO 095 DEGS) AND WERE LEVEL AT 6000 FT. THE CTLR (FEMALE VOICE) THEN CLRED US TO '4000 FT, TURN L 20 DEGS, INTERCEPT THE LOC FOR RWY 28L AND TELL ME WHEN YOU SEE IT.' I TURNED L AND STARTED TO DSND (WE WERE IN MODERATE RAIN AND STILL IN THE CLOUDS). SHORTLY THEREAFTER, THE TCASII ISSUED A TA. I LOOKED AT THE DISPLAY TO SEE WHICH TFC WAS THE PROBLEM WHEN THE TCASII SOUNDED AN RA WITH INSTRUCTIONS TO CLB AND THE CORRECT SYMBOLOGY. I STARTED THE CLB AND THE FO INFORMED THE CTLR OF OUR ACTIONS. A (MALE VOICE) CTLR INFORMED US THAT THE TFC WAS AT 5000 FT. I HAD SEEN WHAT APPEARED TO BE AN LTT XING IN FRONT OF US AS I BEGAN OUR PULL UP. THE NEW CTLR VECTORED US AROUND FOR ANOTHER APCH AND SUCCESSFUL LNDG. THE TCASII PERFORMED PERFECTLY.

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.