Narrative:

I was first officer on a flight from jfk to lax. The TCAS unit was installed on the air carrier widebody transport. The unit was in the TA/RA mode. The following are concerns of mine re: the TCAS. First is the # of aircraft which clutter up the screen on the arrival into lax, or perhaps any busy terminal area. With primary attention outside the aircraft, a quick scan should enable you to identify potential traffic. This is not the case near lax except in the 5 NM range. On final approach to 25L leaving 1000', we received a 'traffic, traffic' alert. A quick scan of the TCAS was of no help (too many aircraft, maybe some of the ground). We figured it was the aircraft in front of us. Then at 500' on G/south, in the slot with proper sink and speed, we received a 'reduce descent, reduce descent' resolution advisory. No aircraft were seen in our area other than the one leaving the runway and those in line for takeoff on 25R. I do not feel this was a safety enhancement in this phase of flight. The potential to land long was dangerous in this situation. In conclusion I feel the following should be recommended: when flying in a congested terminal area, use the 5 NM range. When commencing an approach the RA mode should be turned off. I also feel the RA mode should automatically be inhibited below 500-600' radar altitude. I don't think it should be a mandatory requirement to comply with an RA. That choice should be left to the PIC who is ultimately responsible. This is not the first time I have used TCAS nor is it the first time I have disagreed or been disappointed with its use. This is the first RA I have seen and I am not happy with it. I hope this information will be helpful in making TCAS a useful tool. Callback conversation with reporter revealed the following: callback conducted to clarify terms and abbreviations, and to discuss operational aspects of TCAS-equipped aircraft. The reporter reiterated 3 basic concerns re: TCAS implementation and operational as follows: 1) the reporter states that the TCAS units with which he is familiar tend to warn of too much traffic. Targets are being painted, although they are on the ground, when in fact they are not supposed to be painted. The reporter indicates that it is his understanding that older type 'analog' transponder units are the culprit here. 2) there are 2 many target warnings being experienced at high density airport. 3) the reporter is concerned that the FAA will, as part of the far's, mandate that TCAS RA's will become mandatory actions on the part of the flight crew. The reporter also noted 2 additional TCAS incidents. The first, in which the reporter was a jump seat rider, was identify to the subject of this report, in that the air carrier large transport was on short final at 400' and received a spurious climb command. In the other incident, the reporter was a flight crew member of an air carrier widebody transport level at FL260. An aircraft at higher altitude was cleared to descend to FL270 in proximity to the reporter's flight. The higher aircraft, an adv tech transport medium large transport, descended rapidly to its assigned altitude, apparently in excess of 1000 FPM rate of descent within 100' of its assigned altitude (a characteristic of this type medium large transport). The reporter's TCAS unit commanded a descent, although no conflict existed. The reporter recommends that the FAA reexamine its position with respect to its intent to make compliance with TCAS RA's mandatory, and that TCAS units be operated in shorter range modes in high density terminal areas in order to reduce the # of false warnings and commands.

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Original NASA ASRS Text

Title: ACR WDB FLT CREW EXPERIENCES SPURIOUS TCAS RA ON SHORT FINAL AT LAX.

Narrative: I WAS F/O ON A FLT FROM JFK TO LAX. THE TCAS UNIT WAS INSTALLED ON THE ACR WDB. THE UNIT WAS IN THE TA/RA MODE. THE FOLLOWING ARE CONCERNS OF MINE RE: THE TCAS. FIRST IS THE # OF ACFT WHICH CLUTTER UP THE SCREEN ON THE ARR INTO LAX, OR PERHAPS ANY BUSY TERMINAL AREA. WITH PRIMARY ATTN OUTSIDE THE ACFT, A QUICK SCAN SHOULD ENABLE YOU TO IDENT POTENTIAL TFC. THIS IS NOT THE CASE NEAR LAX EXCEPT IN THE 5 NM RANGE. ON FINAL APCH TO 25L LEAVING 1000', WE RECEIVED A 'TFC, TFC' ALERT. A QUICK SCAN OF THE TCAS WAS OF NO HELP (TOO MANY ACFT, MAYBE SOME OF THE GND). WE FIGURED IT WAS THE ACFT IN FRONT OF US. THEN AT 500' ON G/S, IN THE SLOT WITH PROPER SINK AND SPD, WE RECEIVED A 'REDUCE DSNT, REDUCE DSNT' RESOLUTION ADVISORY. NO ACFT WERE SEEN IN OUR AREA OTHER THAN THE ONE LEAVING THE RWY AND THOSE IN LINE FOR TKOF ON 25R. I DO NOT FEEL THIS WAS A SAFETY ENHANCEMENT IN THIS PHASE OF FLT. THE POTENTIAL TO LAND LONG WAS DANGEROUS IN THIS SITUATION. IN CONCLUSION I FEEL THE FOLLOWING SHOULD BE RECOMMENDED: WHEN FLYING IN A CONGESTED TERMINAL AREA, USE THE 5 NM RANGE. WHEN COMMENCING AN APCH THE RA MODE SHOULD BE TURNED OFF. I ALSO FEEL THE RA MODE SHOULD AUTOMATICALLY BE INHIBITED BELOW 500-600' RADAR ALT. I DON'T THINK IT SHOULD BE A MANDATORY REQUIREMENT TO COMPLY WITH AN RA. THAT CHOICE SHOULD BE LEFT TO THE PIC WHO IS ULTIMATELY RESPONSIBLE. THIS IS NOT THE FIRST TIME I HAVE USED TCAS NOR IS IT THE FIRST TIME I HAVE DISAGREED OR BEEN DISAPPOINTED WITH ITS USE. THIS IS THE FIRST RA I HAVE SEEN AND I AM NOT HAPPY WITH IT. I HOPE THIS INFO WILL BE HELPFUL IN MAKING TCAS A USEFUL TOOL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: CALLBACK CONDUCTED TO CLARIFY TERMS AND ABBREVIATIONS, AND TO DISCUSS OPERATIONAL ASPECTS OF TCAS-EQUIPPED ACFT. THE RPTR REITERATED 3 BASIC CONCERNS RE: TCAS IMPLEMENTATION AND OPERATIONAL AS FOLLOWS: 1) THE RPTR STATES THAT THE TCAS UNITS WITH WHICH HE IS FAMILIAR TEND TO WARN OF TOO MUCH TFC. TARGETS ARE BEING PAINTED, ALTHOUGH THEY ARE ON THE GND, WHEN IN FACT THEY ARE NOT SUPPOSED TO BE PAINTED. THE RPTR INDICATES THAT IT IS HIS UNDERSTANDING THAT OLDER TYPE 'ANALOG' XPONDER UNITS ARE THE CULPRIT HERE. 2) THERE ARE 2 MANY TARGET WARNINGS BEING EXPERIENCED AT HIGH DENSITY ARPT. 3) THE RPTR IS CONCERNED THAT THE FAA WILL, AS PART OF THE FAR'S, MANDATE THAT TCAS RA'S WILL BECOME MANDATORY ACTIONS ON THE PART OF THE FLT CREW. THE RPTR ALSO NOTED 2 ADDITIONAL TCAS INCIDENTS. THE FIRST, IN WHICH THE RPTR WAS A JUMP SEAT RIDER, WAS IDENT TO THE SUBJECT OF THIS RPT, IN THAT THE ACR LGT WAS ON SHORT FINAL AT 400' AND RECEIVED A SPURIOUS CLB COMMAND. IN THE OTHER INCIDENT, THE RPTR WAS A FLT CREW MEMBER OF AN ACR WDB LEVEL AT FL260. AN ACFT AT HIGHER ALT WAS CLRED TO DSND TO FL270 IN PROX TO THE RPTR'S FLT. THE HIGHER ACFT, AN ADV TECH TRANSPORT MLG, DSNDED RAPIDLY TO ITS ASSIGNED ALT, APPARENTLY IN EXCESS OF 1000 FPM RATE OF DSNT WITHIN 100' OF ITS ASSIGNED ALT (A CHARACTERISTIC OF THIS TYPE MLG). THE RPTR'S TCAS UNIT COMMANDED A DSNT, ALTHOUGH NO CONFLICT EXISTED. THE RPTR RECOMMENDS THAT THE FAA REEXAMINE ITS POS WITH RESPECT TO ITS INTENT TO MAKE COMPLIANCE WITH TCAS RA'S MANDATORY, AND THAT TCAS UNITS BE OPERATED IN SHORTER RANGE MODES IN HIGH DENSITY TERMINAL AREAS IN ORDER TO REDUCE THE # OF FALSE WARNINGS AND COMMANDS.

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.