Narrative:

Near midair collision report. Socal instructions: cross smo at 7000 ft; expedite descent to 2500 ft; expect base in 4-5 miles. There will be an aircraft crossing behind you for runway on the left. We slowed to 210 KTS. We lowered the landing gear prematurely to help in expediting the descent. Flying just south of wilshire blvd on downwind; I saw a single engine low wing aircraft appeared heading south across downtown at a lower altitude than we were. The single engine was moving fast in the direction of flight; if maintained; that would cross underneath our aircraft once we were turned on base leg; which is exactly what happened. Socal instructions: slow to 190 KTS; slow to 170 KTS; turn right to heading 160 degrees; report the field in sight. We were 10.6 DME at 2500 ft heading 160 degrees when received the first of 4 TA/RA alerts. The first one was 'climb; climb; climb.' the HUD data indicated the aircraft flight path symbol was in the safe box and we should maintain flight path. Socal instructions: turn right to 220 degrees; intercept the localizer for runway 24R. As we were in the turn as told; the first officer to look for traffic at the 3 O'clock position; as I felt the single engine might be a conflict. The first officer visually sighted the traffic and said it was crossing underneath us and after a moment said it should be clear. Now we received the second TA/RA. This time it on the TCAS display was -.03 NM. Tower was very busy and we could not make contact. We then received the fourth TA/RA. This time 'descend; descend; descend.' in the captain's peripheral vision; on the left side of the aircraft; another carrier aircraft was co-altitude descending and passing our aircraft. Estimated distance was 300 ft or less. The first officer asked if the embraer was landing on our runway. He was so close I said; ask tower. We finally made contact with tower and they said he was landing on the left runway. The landing was uneventful. This event was caused by a failure of socal approach to provide safe separation; adequate information; and adequate instructions to the intruder aircraft. The single engine traffic was never called out to us giving us the impression that socal was not aware of it. Socal failed to instruct the air carrier aircraft to maintain adequate separation and to remain behind our aircraft. These events were fast moving and conflicting. These warnings do not occur in a vacuum. The high cockpit workload on the final approach must remain the pilot's focus. The effect of multiple conflicting TA/RA alerts of the climb and descend nature close to the ground with very little room to maneuver if necessary is unacceptable in a high threat environment. I would recommend that we at company do not accept any visual approach clrncs from the TRACON or tower. It gains us nothing. We should fly the published instrument approach to each runway. This requires ATC to provide safe separation. It does not save 1 penny of fuel or 1 min of time. Approach issues heading; altitude; and airspeed instructions to the final approach whether or not we accept the visual approach. They think that if we accept the visual their liability ends for safe separation. The only thing that accepting the visual approach accomplishes is it reduces TRACON workload which is something I feel is not in our company's best interest.

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Original NASA ASRS Text

Title: A B737 HAD AN NMAC WITH ANOTHER ACR ACFT APCHING LAX 24 RWYS.

Narrative: NMAC RPT. SOCAL INSTRUCTIONS: CROSS SMO AT 7000 FT; EXPEDITE DSCNT TO 2500 FT; EXPECT BASE IN 4-5 MILES. THERE WILL BE AN ACFT XING BEHIND YOU FOR RWY ON THE L. WE SLOWED TO 210 KTS. WE LOWERED THE LNDG GEAR PREMATURELY TO HELP IN EXPEDITING THE DSCNT. FLYING JUST S OF WILSHIRE BLVD ON DOWNWIND; I SAW A SINGLE ENG LOW WING ACFT APPEARED HDG S ACROSS DOWNTOWN AT A LOWER ALT THAN WE WERE. THE SINGLE ENG WAS MOVING FAST IN THE DIRECTION OF FLT; IF MAINTAINED; THAT WOULD CROSS UNDERNEATH OUR ACFT ONCE WE WERE TURNED ON BASE LEG; WHICH IS EXACTLY WHAT HAPPENED. SOCAL INSTRUCTIONS: SLOW TO 190 KTS; SLOW TO 170 KTS; TURN R TO HDG 160 DEGS; RPT THE FIELD IN SIGHT. WE WERE 10.6 DME AT 2500 FT HDG 160 DEGS WHEN RECEIVED THE FIRST OF 4 TA/RA ALERTS. THE FIRST ONE WAS 'CLB; CLB; CLB.' THE HUD DATA INDICATED THE ACFT FLT PATH SYMBOL WAS IN THE SAFE BOX AND WE SHOULD MAINTAIN FLT PATH. SOCAL INSTRUCTIONS: TURN R TO 220 DEGS; INTERCEPT THE LOC FOR RWY 24R. AS WE WERE IN THE TURN AS TOLD; THE FO TO LOOK FOR TFC AT THE 3 O'CLOCK POS; AS I FELT THE SINGLE ENG MIGHT BE A CONFLICT. THE FO VISUALLY SIGHTED THE TFC AND SAID IT WAS XING UNDERNEATH US AND AFTER A MOMENT SAID IT SHOULD BE CLR. NOW WE RECEIVED THE SECOND TA/RA. THIS TIME IT ON THE TCAS DISPLAY WAS -.03 NM. TWR WAS VERY BUSY AND WE COULD NOT MAKE CONTACT. WE THEN RECEIVED THE FOURTH TA/RA. THIS TIME 'DSND; DSND; DSND.' IN THE CAPT'S PERIPHERAL VISION; ON THE L SIDE OF THE ACFT; ANOTHER CARRIER ACFT WAS CO-ALT DSNDING AND PASSING OUR ACFT. ESTIMATED DISTANCE WAS 300 FT OR LESS. THE FO ASKED IF THE EMBRAER WAS LNDG ON OUR RWY. HE WAS SO CLOSE I SAID; ASK TWR. WE FINALLY MADE CONTACT WITH TWR AND THEY SAID HE WAS LNDG ON THE L RWY. THE LNDG WAS UNEVENTFUL. THIS EVENT WAS CAUSED BY A FAILURE OF SOCAL APCH TO PROVIDE SAFE SEPARATION; ADEQUATE INFO; AND ADEQUATE INSTRUCTIONS TO THE INTRUDER ACFT. THE SINGLE ENG TFC WAS NEVER CALLED OUT TO US GIVING US THE IMPRESSION THAT SOCAL WAS NOT AWARE OF IT. SOCAL FAILED TO INSTRUCT THE ACR ACFT TO MAINTAIN ADEQUATE SEPARATION AND TO REMAIN BEHIND OUR ACFT. THESE EVENTS WERE FAST MOVING AND CONFLICTING. THESE WARNINGS DO NOT OCCUR IN A VACUUM. THE HIGH COCKPIT WORKLOAD ON THE FINAL APCH MUST REMAIN THE PLT'S FOCUS. THE EFFECT OF MULTIPLE CONFLICTING TA/RA ALERTS OF THE CLB AND DSND NATURE CLOSE TO THE GND WITH VERY LITTLE ROOM TO MANEUVER IF NECESSARY IS UNACCEPTABLE IN A HIGH THREAT ENVIRONMENT. I WOULD RECOMMEND THAT WE AT COMPANY DO NOT ACCEPT ANY VISUAL APCH CLRNCS FROM THE TRACON OR TWR. IT GAINS US NOTHING. WE SHOULD FLY THE PUBLISHED INST APCH TO EACH RWY. THIS REQUIRES ATC TO PROVIDE SAFE SEPARATION. IT DOES NOT SAVE 1 PENNY OF FUEL OR 1 MIN OF TIME. APCH ISSUES HDG; ALT; AND AIRSPD INSTRUCTIONS TO THE FINAL APCH WHETHER OR NOT WE ACCEPT THE VISUAL APCH. THEY THINK THAT IF WE ACCEPT THE VISUAL THEIR LIABILITY ENDS FOR SAFE SEPARATION. THE ONLY THING THAT ACCEPTING THE VISUAL APCH ACCOMPLISHES IS IT REDUCES TRACON WORKLOAD WHICH IS SOMETHING I FEEL IS NOT IN OUR COMPANY'S BEST INTEREST.

Data retrieved from NASA's ASRS site as of May 2009 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.