Near midair collision -- in IMC on localizer.

Attributes
ACN	295000
Time
Date	199501
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : ont
State Reference	CA
Altitude	msl bound lower : 7500 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ont
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Phase	descent : approach
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 14000 flight time type : 4000
ASRS Report	295000
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	conflict : nmac inflight encounter : vfr in imc non adherence : far other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : took evasive action other other
Consequence	Other
Miss Distance	horizontal : 400 vertical : 100
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

We were on the ziggy 3 arrival into ont. WX was 3000 ft broken with tops about 10000 ft. Approach control's primary radar was out and he was getting a secondary feed from center which had a considerable delay for mode C information. We were descended to 8000 ft and vectored across the localizer and then turned 180 degree back to the north. As we were crossing the localizer the first time we heard another airline flight given traffic and a subsequent RA (TCASII) and further conversation with the controller about a near miss and at the same time I observed the event on our TCASII ehsi. The 2 targets merged at 5000 ft about 2 mi east of petis on the localizer. As we proceeded south through the localizer and were vectored back north the intruder aircraft continued climbing and proceeding east, generally out the runway 26L localizer and up the GS. We turned as he turned and we were issued traffic by the controller with a 300-400 ft lag on TCASII readout of his altitude and what the controller was seeing. The TCASII 'TA' was interrupted by the TCASII RA 'descend crossing descend.' we descended about 500 ft and caught a glimpse of the aircraft through a small break in the clouds. In my opinion there was no way this aircraft was keeping VFR cloud separation. He was trying to climb out to get on top by tracking out a very busy ILS. The intruder was probably a single engine (possibly light twin) with a t-tail. I filed a near mid-air report so that an investigation would be pursued.

Original NASA ASRS Text

Title: NMAC -- IN IMC ON LOC.

Narrative: WE WERE ON THE ZIGGY 3 ARR INTO ONT. WX WAS 3000 FT BROKEN WITH TOPS ABOUT 10000 FT. APCH CTL'S PRIMARY RADAR WAS OUT AND HE WAS GETTING A SECONDARY FEED FROM CTR WHICH HAD A CONSIDERABLE DELAY FOR MODE C INFO. WE WERE DSNDED TO 8000 FT AND VECTORED ACROSS THE LOC AND THEN TURNED 180 DEG BACK TO THE N. AS WE WERE XING THE LOC THE FIRST TIME WE HEARD ANOTHER AIRLINE FLT GIVEN TFC AND A SUBSEQUENT RA (TCASII) AND FURTHER CONVERSATION WITH THE CTLR ABOUT A NEAR MISS AND AT THE SAME TIME I OBSERVED THE EVENT ON OUR TCASII EHSI. THE 2 TARGETS MERGED AT 5000 FT ABOUT 2 MI E OF PETIS ON THE LOC. AS WE PROCEEDED S THROUGH THE LOC AND WERE VECTORED BACK N THE INTRUDER ACFT CONTINUED CLBING AND PROCEEDING E, GENERALLY OUT THE RWY 26L LOC AND UP THE GS. WE TURNED AS HE TURNED AND WE WERE ISSUED TFC BY THE CTLR WITH A 300-400 FT LAG ON TCASII READOUT OF HIS ALT AND WHAT THE CTLR WAS SEEING. THE TCASII 'TA' WAS INTERRUPTED BY THE TCASII RA 'DSND XING DSND.' WE DSNDED ABOUT 500 FT AND CAUGHT A GLIMPSE OF THE ACFT THROUGH A SMALL BREAK IN THE CLOUDS. IN MY OPINION THERE WAS NO WAY THIS ACFT WAS KEEPING VFR CLOUD SEPARATION. HE WAS TRYING TO CLB OUT TO GET ON TOP BY TRACKING OUT A VERY BUSY ILS. THE INTRUDER WAS PROBABLY A SINGLE ENG (POSSIBLY LIGHT TWIN) WITH A T-TAIL. I FILED A NEAR MID-AIR RPT SO THAT AN INVESTIGATION WOULD BE PURSUED.

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.