Narrative:

We were cleared for a civet 1 arrival, assigned speed 320 KIAS. After passing civet at approximately XA40 PDT, we were cleared for an ILS runway 25L approach, assigned speed 250 KIAS. In the vicinity of the fuelr intersection we were instructed to slow to 220 KIAS, because approach control was turning an L1011 ahead of us. When we had a visual on the L1011 we were instructed to slow to 190 KIAS and follow the L1011 to runway 25L. At approximately 10 mi (3000 ft MSL) we got a TA with a target at 2-3 O'clock. Within 10 seconds we got an RA with a 'descend command,' quickly followed by 'increase descent rate' command. Almost simultaneously, we saw an aircraft in a steep descending r-hand turn belly up to us at approximately 1500-3000 ft laterally (approximately 500 ft above our position). I took immediate visual evasive action and increased my rate of descent below the GS to avoid a collision. The threat aircraft appeared to be correcting his dive into a climb ( I assume he was reacting to his corresponding RA climb command). After receiving a 'clear of conflict' we continued our approach to an uneventful landing. At no time did we receive any VHF radio warning of the threat aircraft (the impending midair collision).

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Original NASA ASRS Text

Title: WHILE ON APCH AND CLOSE TO THE OM, RPTR ACFT HAD TCASII RA, CONFIRMED INTRUDER DSNDING ON TOP OF THEM, RPTR TOOK EVASIVE ACTION AND DSNDED. INTRUDER APPARENTLY ALSO RECEIVED RA AND CORRECTED BY CLBING. NEITHER TWR NOR APCH CTL ADVISED OF CONFLICTING TFC. THE INTRUDING ACFT WAS POSSIBLY A RWY 24L-R VISUAL APCH THAT OVERSHOT THE FINAL APCH.

Narrative: WE WERE CLRED FOR A CIVET 1 ARR, ASSIGNED SPD 320 KIAS. AFTER PASSING CIVET AT APPROX XA40 PDT, WE WERE CLRED FOR AN ILS RWY 25L APCH, ASSIGNED SPD 250 KIAS. IN THE VICINITY OF THE FUELR INTXN WE WERE INSTRUCTED TO SLOW TO 220 KIAS, BECAUSE APCH CTL WAS TURNING AN L1011 AHEAD OF US. WHEN WE HAD A VISUAL ON THE L1011 WE WERE INSTRUCTED TO SLOW TO 190 KIAS AND FOLLOW THE L1011 TO RWY 25L. AT APPROX 10 MI (3000 FT MSL) WE GOT A TA WITH A TARGET AT 2-3 O'CLOCK. WITHIN 10 SECONDS WE GOT AN RA WITH A 'DSND COMMAND,' QUICKLY FOLLOWED BY 'INCREASE DSCNT RATE' COMMAND. ALMOST SIMULTANEOUSLY, WE SAW AN ACFT IN A STEEP DSNDING R-HAND TURN BELLY UP TO US AT APPROX 1500-3000 FT LATERALLY (APPROX 500 FT ABOVE OUR POS). I TOOK IMMEDIATE VISUAL EVASIVE ACTION AND INCREASED MY RATE OF DSCNT BELOW THE GS TO AVOID A COLLISION. THE THREAT ACFT APPEARED TO BE CORRECTING HIS DIVE INTO A CLB ( I ASSUME HE WAS REACTING TO HIS CORRESPONDING RA CLB COMMAND). AFTER RECEIVING A 'CLR OF CONFLICT' WE CONTINUED OUR APCH TO AN UNEVENTFUL LNDG. AT NO TIME DID WE RECEIVE ANY VHF RADIO WARNING OF THE THREAT ACFT (THE IMPENDING MIDAIR COLLISION).

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.