Narrative:

Uneventful flight until cleared for localizer runway 27 at san. Approach was set up and hand flown as a localizer/VNAV, path to runway 27. After passing FAF (reebo) at 2000 ft, a descent was started to 710 ft. No TA's were issued by either approach control or tower. With aircraft on VNAV path GS, at approximately 1250 ft MSL, a TCASII alert sounded ('traffic, traffic'). Our TCASII showed a target 400 ft below and directly in front of our aircraft (less than 1 mi). No visual contact with traffic was established. Approximately 2 seconds later, TCASII sounded an RA ('climb, climb') and traffic showed same horizontal position, and 200 ft below. A go around was initiated. As power was applied on the go around and the aircraft nose raised, TCASII showed the target at 100 ft below. Go around and subsequent visual approach uneventful. Neither visual contact nor advisory from approach or tower ever received.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-800 FLC PERFORMS A GAR WHEN THEIR TCASII DETECTS AN INTRUDER JUST BELOW THEM WHILE ON A 4 MI FINAL FOR SAN, CA.

Narrative: UNEVENTFUL FLT UNTIL CLRED FOR LOC RWY 27 AT SAN. APCH WAS SET UP AND HAND FLOWN AS A LOC/VNAV, PATH TO RWY 27. AFTER PASSING FAF (REEBO) AT 2000 FT, A DSCNT WAS STARTED TO 710 FT. NO TA'S WERE ISSUED BY EITHER APCH CTL OR TWR. WITH ACFT ON VNAV PATH GS, AT APPROX 1250 FT MSL, A TCASII ALERT SOUNDED ('TFC, TFC'). OUR TCASII SHOWED A TARGET 400 FT BELOW AND DIRECTLY IN FRONT OF OUR ACFT (LESS THAN 1 MI). NO VISUAL CONTACT WITH TFC WAS ESTABLISHED. APPROX 2 SECONDS LATER, TCASII SOUNDED AN RA ('CLB, CLB') AND TFC SHOWED SAME HORIZ POS, AND 200 FT BELOW. A GAR WAS INITIATED. AS PWR WAS APPLIED ON THE GAR AND THE ACFT NOSE RAISED, TCASII SHOWED THE TARGET AT 100 FT BELOW. GAR AND SUBSEQUENT VISUAL APCH UNEVENTFUL. NEITHER VISUAL CONTACT NOR ADVISORY FROM APCH OR TWR EVER RECEIVED.

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.