Narrative:

First officer was flying the ziggy 3 arrival into ont. After hitop (palmdale 104 degree radial at 41 mi), we were given a heading of 150 degrees for the runway 26L localizer and a descent to 8000 ft. During the arrival, we were previously given several altitude restrs for traffic, most of which we did not see. We were held at 8000 ft, and then given a heading of 230 degrees to intercept the localizer and a descent to 4200 ft. We received a TA at 10 O'clock and 400 ft below. I was looking for the unrpted traffic in the haze, and we received an RA of 'climb, climb.' the first officer added power to stop the descent and commenced climbing and turning away from the unseen threat. I reported our action to ont approach and they asked us if we were able to get down (7500 ft 14 mi) and the first officer said 'yes' and turned back to intercept the localizer. Descending through 6500 ft, we received another TA at 9-10 O'clock at our altitude. I saw a small plane converging and told the first officer to level off and come right. We cleared this threat and I told approach that we had another conflict. Approach said, 'that was the traffic at 2 O'clock and 2 mi that I reported.' (we never heard that transmission.) I replied, 'no, it was 10 O'clock and a mi.' the first officer rejoined the localizer, increased the rate of descent and made a stabilized approach to an uneventful landing. The ont area is extremely hazardous. The WX is usually marginal VFR (haze, smoke) with high terrain in the area. There are many other aircraft, both VFR and IFR that air traffic does not see or report. In addition, ont approach often clears aircraft for a 'slam-dunk' ILS and then tells them to maintain visual separation with other traffic, which is usually unseen. Without TCASII, we would probably have had a midair collision. I was surprised to hear that a part 121 cargo carrier (who frequents ont) does not have TCASII installed!

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Original NASA ASRS Text

Title: TCASII SAVES THE DAY AGAIN BY TURNING A POSSIBLE NMAC INTO A POTENTIAL CONFLICT.

Narrative: FO WAS FLYING THE ZIGGY 3 ARR INTO ONT. AFTER HITOP (PALMDALE 104 DEG RADIAL AT 41 MI), WE WERE GIVEN A HDG OF 150 DEGS FOR THE RWY 26L LOC AND A DSCNT TO 8000 FT. DURING THE ARR, WE WERE PREVIOUSLY GIVEN SEVERAL ALT RESTRS FOR TFC, MOST OF WHICH WE DID NOT SEE. WE WERE HELD AT 8000 FT, AND THEN GIVEN A HDG OF 230 DEGS TO INTERCEPT THE LOC AND A DSCNT TO 4200 FT. WE RECEIVED A TA AT 10 O'CLOCK AND 400 FT BELOW. I WAS LOOKING FOR THE UNRPTED TFC IN THE HAZE, AND WE RECEIVED AN RA OF 'CLB, CLB.' THE FO ADDED PWR TO STOP THE DSCNT AND COMMENCED CLBING AND TURNING AWAY FROM THE UNSEEN THREAT. I RPTED OUR ACTION TO ONT APCH AND THEY ASKED US IF WE WERE ABLE TO GET DOWN (7500 FT 14 MI) AND THE FO SAID 'YES' AND TURNED BACK TO INTERCEPT THE LOC. DSNDING THROUGH 6500 FT, WE RECEIVED ANOTHER TA AT 9-10 O'CLOCK AT OUR ALT. I SAW A SMALL PLANE CONVERGING AND TOLD THE FO TO LEVEL OFF AND COME R. WE CLRED THIS THREAT AND I TOLD APCH THAT WE HAD ANOTHER CONFLICT. APCH SAID, 'THAT WAS THE TFC AT 2 O'CLOCK AND 2 MI THAT I RPTED.' (WE NEVER HEARD THAT XMISSION.) I REPLIED, 'NO, IT WAS 10 O'CLOCK AND A MI.' THE FO REJOINED THE LOC, INCREASED THE RATE OF DSCNT AND MADE A STABILIZED APCH TO AN UNEVENTFUL LNDG. THE ONT AREA IS EXTREMELY HAZARDOUS. THE WX IS USUALLY MARGINAL VFR (HAZE, SMOKE) WITH HIGH TERRAIN IN THE AREA. THERE ARE MANY OTHER ACFT, BOTH VFR AND IFR THAT AIR TFC DOES NOT SEE OR RPT. IN ADDITION, ONT APCH OFTEN CLRS ACFT FOR A 'SLAM-DUNK' ILS AND THEN TELLS THEM TO MAINTAIN VISUAL SEPARATION WITH OTHER TFC, WHICH IS USUALLY UNSEEN. WITHOUT TCASII, WE WOULD PROBABLY HAVE HAD A MIDAIR COLLISION. I WAS SURPRISED TO HEAR THAT A PART 121 CARGO CARRIER (WHO FREQUENTS ONT) DOES NOT HAVE TCASII INSTALLED!

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.