Narrative:

Once again I have had a TCASII incident while approaching sjc in california. While on an extended left base approximately 10 mi south of sjc in day VFR, on a visual approach to 30L, we were given a TA by ATC but did not spot the traffic. 30 seconds to 1 min later our TCASII system gives us a TA followed very shortly by an RA. In this case telling us to reduce descent, which we are required by regulation to respond to. Moments later we spotted the small aircraft passing 700 ft directly beneath us traveling south. Without TCASII we would have had a very near miss or possible collision. My concern is that of the 4 RA's I have encountered in the past yr, 3 of them have occurred while approaching sjc under very similar circumstances. Keep in mind an RA requires the crew to deviate, a climb or descent, from a flight path. In every case ATC issued a TA, we did not spot the traffic, heard nothing more from ATC, then moments later had a TCASII RA requiring a deviation averting a near miss or possible collision. Even when ATC is controling the other traffic we frequently are unable to acquire visual contact with the other aircraft. I feel that ATC relies far too heavily on visual contact for separation in sjc. This is more than just a busy area. I feel it is ATC's inability to adequately separate IFR and VFR traffic. We should not have to rely on TCASII for basic ATC separation. I write this in the hopes someone will compile data on the numbers of TCASII incidents in sjc. I have not encountered this much of a problem anywhere else in the country. I hope that in the future better ATC separation can be provided.

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Original NASA ASRS Text

Title: CLOSE PROX ACR-MLG GA-SMA S OF SJC.

Narrative: ONCE AGAIN I HAVE HAD A TCASII INCIDENT WHILE APCHING SJC IN CALIFORNIA. WHILE ON AN EXTENDED L BASE APPROX 10 MI S OF SJC IN DAY VFR, ON A VISUAL APCH TO 30L, WE WERE GIVEN A TA BY ATC BUT DID NOT SPOT THE TFC. 30 SECONDS TO 1 MIN LATER OUR TCASII SYS GIVES US A TA FOLLOWED VERY SHORTLY BY AN RA. IN THIS CASE TELLING US TO REDUCE DSCNT, WHICH WE ARE REQUIRED BY REG TO RESPOND TO. MOMENTS LATER WE SPOTTED THE SMA PASSING 700 FT DIRECTLY BENEATH US TRAVELING S. WITHOUT TCASII WE WOULD HAVE HAD A VERY NEAR MISS OR POSSIBLE COLLISION. MY CONCERN IS THAT OF THE 4 RA'S I HAVE ENCOUNTERED IN THE PAST YR, 3 OF THEM HAVE OCCURRED WHILE APCHING SJC UNDER VERY SIMILAR CIRCUMSTANCES. KEEP IN MIND AN RA REQUIRES THE CREW TO DEVIATE, A CLB OR DSCNT, FROM A FLT PATH. IN EVERY CASE ATC ISSUED A TA, WE DID NOT SPOT THE TFC, HEARD NOTHING MORE FROM ATC, THEN MOMENTS LATER HAD A TCASII RA REQUIRING A DEV AVERTING A NEAR MISS OR POSSIBLE COLLISION. EVEN WHEN ATC IS CTLING THE OTHER TFC WE FREQUENTLY ARE UNABLE TO ACQUIRE VISUAL CONTACT WITH THE OTHER ACFT. I FEEL THAT ATC RELIES FAR TOO HEAVILY ON VISUAL CONTACT FOR SEPARATION IN SJC. THIS IS MORE THAN JUST A BUSY AREA. I FEEL IT IS ATC'S INABILITY TO ADEQUATELY SEPARATE IFR AND VFR TFC. WE SHOULD NOT HAVE TO RELY ON TCASII FOR BASIC ATC SEPARATION. I WRITE THIS IN THE HOPES SOMEONE WILL COMPILE DATA ON THE NUMBERS OF TCASII INCIDENTS IN SJC. I HAVE NOT ENCOUNTERED THIS MUCH OF A PROBLEM ANYWHERE ELSE IN THE COUNTRY. I HOPE THAT IN THE FUTURE BETTER ATC SEPARATION CAN BE PROVIDED.

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.