Narrative:

On final approach to runway 25L, we received a TCASII traffic alert followed immediately by a resolution advisory. TCASII commanded a climb, and the vsi arc was all red except a small green sector at nearly 2000 FPM up. As I added power and started a climb, neither of us could acquire traffic visually, the red DOT on our vsi appeared to be an aircraft behind us and a few hundred ft above us. I immediately reversed the climb, topping out at the same altitude as the traffic on the vsi. Only then did TCASII call for a descent and the green sector switched to the bottom of the vsi. Remainder of approach was uneventful. On short final however, TCASII gave some garbled commands and I switched the TCASII off. It appears that our TCASII directed us to climb towards a collision during a critical phase of flight. Perhaps it should be a checklist item to turn TCASII to TA for approach. Callback conversation with reporter revealed following information. The red DOT warning is indeed on the vsi. The traffic was crossing from the left behind the rptrs and never was a real threat. Perhaps when detected by TCASII the intruder was in a descent so the TCASII resolution was a climb initially. Reporter says it is company policy to select the TA in the terminal area but sometimes the flight crew forget and it is not on a checklist.

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Original NASA ASRS Text

Title: ACR LGT ALTDEV EXCURSION FROM CLRNC ALT GS IN RESPONSE TO TCASII RA.

Narrative: ON FINAL APCH TO RWY 25L, WE RECEIVED A TCASII TFC ALERT FOLLOWED IMMEDIATELY BY A RESOLUTION ADVISORY. TCASII COMMANDED A CLB, AND THE VSI ARC WAS ALL RED EXCEPT A SMALL GREEN SECTOR AT NEARLY 2000 FPM UP. AS I ADDED PWR AND STARTED A CLB, NEITHER OF US COULD ACQUIRE TFC VISUALLY, THE RED DOT ON OUR VSI APPEARED TO BE AN ACFT BEHIND US AND A FEW HUNDRED FT ABOVE US. I IMMEDIATELY REVERSED THE CLB, TOPPING OUT AT THE SAME ALT AS THE TFC ON THE VSI. ONLY THEN DID TCASII CALL FOR A DSCNT AND THE GREEN SECTOR SWITCHED TO THE BOTTOM OF THE VSI. REMAINDER OF APCH WAS UNEVENTFUL. ON SHORT FINAL HOWEVER, TCASII GAVE SOME GARBLED COMMANDS AND I SWITCHED THE TCASII OFF. IT APPEARS THAT OUR TCASII DIRECTED US TO CLB TOWARDS A COLLISION DURING A CRITICAL PHASE OF FLT. PERHAPS IT SHOULD BE A CHKLIST ITEM TO TURN TCASII TO TA FOR APCH. CALLBACK CONVERSATION WITH RPTR REVEALED FOLLOWING INFO. THE RED DOT WARNING IS INDEED ON THE VSI. THE TFC WAS XING FROM THE L BEHIND THE RPTRS AND NEVER WAS A REAL THREAT. PERHAPS WHEN DETECTED BY TCASII THE INTRUDER WAS IN A DSCNT SO THE TCASII RESOLUTION WAS A CLB INITIALLY. RPTR SAYS IT IS COMPANY POLICY TO SELECT THE TA IN THE TERMINAL AREA BUT SOMETIMES THE FLT CREW FORGET AND IT IS NOT ON A CHKLIST.

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.