Narrative:

On civet arrival to lax runway 25L 38 ilax just inside of bremr descending to make arnes, received traffic alert at approximately 11500 ft, followed by an RA 'reduce descent.' since I was only descending at 1000-500 FPM, I leveled off at 10800 ft. We then received a 'monitor vertical speed' RA at the same time the other aircraft traveling towards us from right to left went under the nose of the aircraft. We told lax approach that we had an RA. Their response was that the aircraft had been showing at 4500 ft and after crossing our path displayed 10500 ft. The cessna aircraft's transponder was thankfully accurate for our TCASII.

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Original NASA ASRS Text

Title: TCASII RA E OF LAX, CA. SCT CLAIMS THE OFFENDING ACFT'S DATA TAG HAD INCORRECT ALT DISPLAY.

Narrative: ON CIVET ARR TO LAX RWY 25L 38 ILAX JUST INSIDE OF BREMR DSNDING TO MAKE ARNES, RECEIVED TFC ALERT AT APPROX 11500 FT, FOLLOWED BY AN RA 'REDUCE DSCNT.' SINCE I WAS ONLY DSNDING AT 1000-500 FPM, I LEVELED OFF AT 10800 FT. WE THEN RECEIVED A 'MONITOR VERT SPD' RA AT THE SAME TIME THE OTHER ACFT TRAVELING TOWARDS US FROM R TO L WENT UNDER THE NOSE OF THE ACFT. WE TOLD LAX APCH THAT WE HAD AN RA. THEIR RESPONSE WAS THAT THE ACFT HAD BEEN SHOWING AT 4500 FT AND AFTER XING OUR PATH DISPLAYED 10500 FT. THE CESSNA ACFT'S XPONDER WAS THANKFULLY ACCURATE FOR OUR TCASII.

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.