Narrative:

Air carrier X checked on frequency. He was cleared for the sjc runway 30L ILS. Shortly thereafter, VFR small aircraft Y informed me he wished to cross the final approach course at 5500 ft. He was between 5 and 10 mi southeast of sjc. Traffic was issued to both aircraft. Small aircraft Y reported air carrier X in sight and was told to maintain visual separation. I then informed air carrier X visual separation was being applied and reissued the traffic. Traffic was issued again at approximately 2 mi. I then observed small aircraft Y turning to parallel the traffic. Air carrier X informed me he was climbing due to an RA. In my estimate, the aircraft involved passed 1 mi laterally and 400 ft vertically. Supplemental information from acn 255277: on ILS 30L approach to sjc descending on the GS, bay TRACON issued VFR traffic at 10 O'clock converging. The traffic was not visible to us in reduced visibility of 3 NM or less in haze and smoke, but we had a TCASII target. The controller issued our aircraft as traffic to the VFR aircraft, referring to our aircraft as an medium large transport. The VFR aircraft said that he had our aircraft in sight and was instructed by the controller to keep our aircraft in sight. A TCASII TA was activated at about 3000 ft followed almost immediately by a TCASII RA. A pull-up maneuver was initiated during which the VFR aircraft was observed visually at 10 O'clock, 1/4 to 1/2 NM, less that 500 ft below. During the RA pull-up 600 ft below was observed on the TCASII target. A missed approach was then executed because of our position far above the GS. At no time did the controller issue any positive instructions to either aircraft other than 'keep that aircraft in sight' that would have prevented the 2 aircraft from flying so close together. Supplemental information from acn 255211: while crossing the sjc runway 30 ILS approach course, ATC called airline traffic at our 2 O'clock position. We sighted the traffic, reported to approach, and turned to parallel the approach course until the traffic passed us. At that point we turned to pass behind the traffic. The airliner didn't report visual contact and their TCASII system evidently reported a conflict. The airliner started to climb after it had passed us. It is my opinion that the TCASII system required an unwarranted climb response on the part of the airline crew. The conditions were VFR and we had reported the traffic in sight and had maneuvered to avoid any conflict.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR X TCASII TA RA WITH VFR SMA Y IN ARSA. EVASIVE ACTION TAKEN.

Narrative: ACR X CHKED ON FREQ. HE WAS CLRED FOR THE SJC RWY 30L ILS. SHORTLY THEREAFTER, VFR SMA Y INFORMED ME HE WISHED TO CROSS THE FINAL APCH COURSE AT 5500 FT. HE WAS BTWN 5 AND 10 MI SE OF SJC. TFC WAS ISSUED TO BOTH ACFT. SMA Y RPTED ACR X IN SIGHT AND WAS TOLD TO MAINTAIN VISUAL SEPARATION. I THEN INFORMED ACR X VISUAL SEPARATION WAS BEING APPLIED AND REISSUED THE TFC. TFC WAS ISSUED AGAIN AT APPROX 2 MI. I THEN OBSERVED SMA Y TURNING TO PARALLEL THE TFC. ACR X INFORMED ME HE WAS CLBING DUE TO AN RA. IN MY ESTIMATE, THE ACFT INVOLVED PASSED 1 MI LATERALLY AND 400 FT VERTICALLY. SUPPLEMENTAL INFO FROM ACN 255277: ON ILS 30L APCH TO SJC DSNDING ON THE GS, BAY TRACON ISSUED VFR TFC AT 10 O'CLOCK CONVERGING. THE TFC WAS NOT VISIBLE TO US IN REDUCED VISIBILITY OF 3 NM OR LESS IN HAZE AND SMOKE, BUT WE HAD A TCASII TARGET. THE CTLR ISSUED OUR ACFT AS TFC TO THE VFR ACFT, REFERRING TO OUR ACFT AS AN MLG. THE VFR ACFT SAID THAT HE HAD OUR ACFT IN SIGHT AND WAS INSTRUCTED BY THE CTLR TO KEEP OUR ACFT IN SIGHT. A TCASII TA WAS ACTIVATED AT ABOUT 3000 FT FOLLOWED ALMOST IMMEDIATELY BY A TCASII RA. A PULL-UP MANEUVER WAS INITIATED DURING WHICH THE VFR ACFT WAS OBSERVED VISUALLY AT 10 O'CLOCK, 1/4 TO 1/2 NM, LESS THAT 500 FT BELOW. DURING THE RA PULL-UP 600 FT BELOW WAS OBSERVED ON THE TCASII TARGET. A MISSED APCH WAS THEN EXECUTED BECAUSE OF OUR POS FAR ABOVE THE GS. AT NO TIME DID THE CTLR ISSUE ANY POSITIVE INSTRUCTIONS TO EITHER ACFT OTHER THAN 'KEEP THAT ACFT IN SIGHT' THAT WOULD HAVE PREVENTED THE 2 ACFT FROM FLYING SO CLOSE TOGETHER. SUPPLEMENTAL INFO FROM ACN 255211: WHILE XING THE SJC RWY 30 ILS APCH COURSE, ATC CALLED AIRLINE TFC AT OUR 2 O'CLOCK POS. WE SIGHTED THE TFC, RPTED TO APCH, AND TURNED TO PARALLEL THE APCH COURSE UNTIL THE TFC PASSED US. AT THAT POINT WE TURNED TO PASS BEHIND THE TFC. THE AIRLINER DIDN'T RPT VISUAL CONTACT AND THEIR TCASII SYS EVIDENTLY RPTED A CONFLICT. THE AIRLINER STARTED TO CLB AFTER IT HAD PASSED US. IT IS MY OPINION THAT THE TCASII SYS REQUIRED AN UNWARRANTED CLB RESPONSE ON THE PART OF THE AIRLINE CREW. THE CONDITIONS WERE VFR AND WE HAD RPTED THE TFC IN SIGHT AND HAD MANEUVERED TO AVOID ANY CONFLICT.

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.