Narrative:

This letter is intended to offer my personal evaluation of the TCAS system currently in use on board air carrier. This is not sanctioned by any organization and is intended solely to benefit those who are evaluation the system nationwide. This letter is also sent to you in lieu of the questionnaires currently in use throughout the country. I read with great interest the first issue of the ttp newsletter dated 3/91. With few exceptions, the problems noted in the newsletter have occurred on board an aircraft on which I was the PIC. I have several reservations about the current system: 1) the vol of the traffic calls is too loud and very distracting. I have had several comments from passenger who became anxious after hearing, 'traffic, traffic,' call from as far away as the third row in the coach cabin. 2) I feel the system should be completely biased below 1000' AGL. At many of the busy airports we are cleared for takeoff immediately following another aircraft. On 3 separate occurrences I have had a TA as soon as the weight was off the main gear. The traffic conflict was from the aircraft that had just departed ahead of me. This is such a dangerous distraction that I feel it will eventually cause, rather than prevent an accident. Traffic this close to the airport is under rigid control by the local controller. Seldom when conditions are VFR will the trailing aircraft not be requested to maintain visibility sep on departure. When conditions are IFR, controllers will provide the sep from the ground. TCAS is completely useless in this low altitude departure environment. 3) in addition to the departure problem above, I have had 1 occurrence on arrival of a nuisance TA. The aircraft in question was a much slower small transport arriving on 26L at phx. We were conducting a visibility approach from behind and had a TA at 500' AGL on that aircraft when he was on the runway! 4) I have had several TA's (no RA's) while conducting parallel visibility approachs at ord and rdu. The ord incident I was ready for and had turned the TCAS to TA only. I wonder how TCAS will interface with the new high-speed scan radar at rdu when the reduced sep for the parallel approachs is approved. 5) my biggest concern with the system was covered rather nicely in the ttp newsletter. I was the PNF on flight from phx to dfw. We were on the acton 1 arrival approaching the hulen intersection at 11000' and 250 KTS per the STAR. Regional approach advised traffic at 1-2 O'clock climbing to 10000', an large transport. When I responded to ATC that we had the traffic in sight, we received a TA that was clearly audible in my transmission. I commented to ATC that our new toy also had contact with the traffic. His response was a short, 'ok,' with a slight snicker. Immediately after releasing the yoke microphone switch, we received a 'climb now' RA with the vsi requesting a 1500' FPM climb. The first officer reacted properly by beginning a power application which I immediately halted based on my visibility recognition of the traffic and an obvious no conflict situation. I felt that the evasive maneuver commanded by the TCAS was absolutely unnecessary and possibly unsafe since I knew the F/a's were in the aisle doing their before landing safety check. I have modified my use of the TCAS to maintain a safe environment in the cockpit. I will now select TA only on all dfw arrs until clear of the departure area for the runways in use. I will no longer turn on TCAS below 1000' AGL on departure. I have incorporated this in my mental 1000' checklist and it works very nicely. If conditions are IMC, I turn TCAS on while going into position on the runway. In VMC, it waited until 1000' AGL if there is any possibility of a nuisance TA. If the system is supposed to be biased out at 400' AGL as indicated in the ttp newsletter, it is not operating correctly on at least 3 of our aircraft. I hope that this is of some help to the evaluation of TCAS. Hopefully, the technology is available to 'iron out the bugs.'

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Original NASA ASRS Text

Title: ACR CAPT ELECTS NOT TO COMPLY WITH TCASII ALERT SINCE TRAFFIC IN SIGHT.

Narrative: THIS LETTER IS INTENDED TO OFFER MY PERSONAL EVALUATION OF THE TCAS SYS CURRENTLY IN USE ON BOARD ACR. THIS IS NOT SANCTIONED BY ANY ORGANIZATION AND IS INTENDED SOLELY TO BENEFIT THOSE WHO ARE EVALUATION THE SYSTEM NATIONWIDE. THIS LETTER IS ALSO SENT TO YOU IN LIEU OF THE QUESTIONNAIRES CURRENTLY IN USE THROUGHOUT THE COUNTRY. I READ WITH GREAT INTEREST THE FIRST ISSUE OF THE TTP NEWSLETTER DATED 3/91. WITH FEW EXCEPTIONS, THE PROBS NOTED IN THE NEWSLETTER HAVE OCCURRED ON BOARD AN ACFT ON WHICH I WAS THE PIC. I HAVE SEVERAL RESERVATIONS ABOUT THE CURRENT SYS: 1) THE VOL OF THE TFC CALLS IS TOO LOUD AND VERY DISTRACTING. I HAVE HAD SEVERAL COMMENTS FROM PAX WHO BECAME ANXIOUS AFTER HEARING, 'TFC, TFC,' CALL FROM AS FAR AWAY AS THE THIRD ROW IN THE COACH CABIN. 2) I FEEL THE SYS SHOULD BE COMPLETELY BIASED BELOW 1000' AGL. AT MANY OF THE BUSY ARPTS WE ARE CLRED FOR TKOF IMMEDIATELY FOLLOWING ANOTHER ACFT. ON 3 SEPARATE OCCURRENCES I HAVE HAD A TA AS SOON AS THE WT WAS OFF THE MAIN GEAR. THE TFC CONFLICT WAS FROM THE ACFT THAT HAD JUST DEPARTED AHEAD OF ME. THIS IS SUCH A DANGEROUS DISTR THAT I FEEL IT WILL EVENTUALLY CAUSE, RATHER THAN PREVENT AN ACCIDENT. TFC THIS CLOSE TO THE ARPT IS UNDER RIGID CTL BY THE LCL CTLR. SELDOM WHEN CONDITIONS ARE VFR WILL THE TRAILING ACFT NOT BE REQUESTED TO MAINTAIN VIS SEP ON DEP. WHEN CONDITIONS ARE IFR, CTLRS WILL PROVIDE THE SEP FROM THE GND. TCAS IS COMPLETELY USELESS IN THIS LOW ALT DEP ENVIRONMENT. 3) IN ADDITION TO THE DEP PROB ABOVE, I HAVE HAD 1 OCCURRENCE ON ARR OF A NUISANCE TA. THE ACFT IN QUESTION WAS A MUCH SLOWER SMT ARRIVING ON 26L AT PHX. WE WERE CONDUCTING A VIS APCH FROM BEHIND AND HAD A TA AT 500' AGL ON THAT ACFT WHEN HE WAS ON THE RWY! 4) I HAVE HAD SEVERAL TA'S (NO RA'S) WHILE CONDUCTING PARALLEL VIS APCHS AT ORD AND RDU. THE ORD INCIDENT I WAS READY FOR AND HAD TURNED THE TCAS TO TA ONLY. I WONDER HOW TCAS WILL INTERFACE WITH THE NEW HIGH-SPD SCAN RADAR AT RDU WHEN THE REDUCED SEP FOR THE PARALLEL APCHS IS APPROVED. 5) MY BIGGEST CONCERN WITH THE SYS WAS COVERED RATHER NICELY IN THE TTP NEWSLETTER. I WAS THE PNF ON FLT FROM PHX TO DFW. WE WERE ON THE ACTON 1 ARR APCHING THE HULEN INTXN AT 11000' AND 250 KTS PER THE STAR. REGIONAL APCH ADVISED TFC AT 1-2 O'CLOCK CLBING TO 10000', AN LGT. WHEN I RESPONDED TO ATC THAT WE HAD THE TFC IN SIGHT, WE RECEIVED A TA THAT WAS CLEARLY AUDIBLE IN MY XMISSION. I COMMENTED TO ATC THAT OUR NEW TOY ALSO HAD CONTACT WITH THE TFC. HIS RESPONSE WAS A SHORT, 'OK,' WITH A SLIGHT SNICKER. IMMEDIATELY AFTER RELEASING THE YOKE MIC SWITCH, WE RECEIVED A 'CLB NOW' RA WITH THE VSI REQUESTING A 1500' FPM CLB. THE F/O REACTED PROPERLY BY BEGINNING A PWR APPLICATION WHICH I IMMEDIATELY HALTED BASED ON MY VIS RECOGNITION OF THE TFC AND AN OBVIOUS NO CONFLICT SITUATION. I FELT THAT THE EVASIVE MANEUVER COMMANDED BY THE TCAS WAS ABSOLUTELY UNNECESSARY AND POSSIBLY UNSAFE SINCE I KNEW THE F/A'S WERE IN THE AISLE DOING THEIR BEFORE LNDG SAFETY CHK. I HAVE MODIFIED MY USE OF THE TCAS TO MAINTAIN A SAFE ENVIRONMENT IN THE COCKPIT. I WILL NOW SELECT TA ONLY ON ALL DFW ARRS UNTIL CLR OF THE DEP AREA FOR THE RWYS IN USE. I WILL NO LONGER TURN ON TCAS BELOW 1000' AGL ON DEP. I HAVE INCORPORATED THIS IN MY MENTAL 1000' CHKLIST AND IT WORKS VERY NICELY. IF CONDITIONS ARE IMC, I TURN TCAS ON WHILE GOING INTO POS ON THE RWY. IN VMC, IT WAITED UNTIL 1000' AGL IF THERE IS ANY POSSIBILITY OF A NUISANCE TA. IF THE SYS IS SUPPOSED TO BE BIASED OUT AT 400' AGL AS INDICATED IN THE TTP NEWSLETTER, IT IS NOT OPERATING CORRECTLY ON AT LEAST 3 OF OUR ACFT. I HOPE THAT THIS IS OF SOME HELP TO THE EVALUATION OF TCAS. HOPEFULLY, THE TECHNOLOGY IS AVAILABLE TO 'IRON OUT THE BUGS.'

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.