Narrative:

At 2200 ft MSL after takeoff from ord we got a TCASII RA 'descend, descend now' with RA traffic showing level with us but not in sight visually. Since we were only 1500 ft AGL and in a 25-30 degree left bank, climbing out over a densely populated area, I elected to attempt to level the aircraft and continue the banked turn beyond our assigned heading of 140 degrees to about 105 degrees, instead of descending to avoid the traffic. The transponder was in TA/RA with my associated switches in 'normal' and 'absolute' on the transponder head, and I believe the first officer's switches were in the same position as mine. After the warning stopped and no traffic was spotted visually, the climb was once again started to 5000 ft MSL along with an immediate return to our assigned heading of 140 degrees. Passing through 3500 ft MSL we received a TA with the words, 'traffic, traffic.' ord radar, upon being questioned, said they showed no traffic in our immediate vicinity, and we saw no traffic visually and contacted ARTCC with no further problems until our descent into boston- logan airport. At 4200 ft MSL descending to 2000 ft MSL in contact with bos approach, we received a TA to 'climb, climb now', which once again proved to be a false warning with no traffic reported by approach and none seen visually. The TCASII tested normally at the gate prior to departure, and was in TA/RA on takeoff before and after gear and flaps were up. I believe with this experience (my first with TCASII on the line) of having several false warnings at low altitudes and in takeoff and landing regimes (potentially critical periods of flight) we need to reexamine exactly when to have it on or off and to ascertain if in fact this type of warning can ever be truly reliable. Where do we go from here without further testing on both the software and hardware of these units. Can I really trust TCASII for reliable traffic avoidance inputs? Further testing is needed to 'de-bug' this system before regular line use on commercial acrs.

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Original NASA ASRS Text

Title: ACR MLG GOT A FALSE TCASII WARNING ON CLB OUT FROM ORD REPEATED ON DSCNT INTO BOS.

Narrative: AT 2200 FT MSL AFTER TKOF FROM ORD WE GOT A TCASII RA 'DSND, DSND NOW' WITH RA TFC SHOWING LEVEL WITH US BUT NOT IN SIGHT VISUALLY. SINCE WE WERE ONLY 1500 FT AGL AND IN A 25-30 DEG L BANK, CLBING OUT OVER A DENSELY POPULATED AREA, I ELECTED TO ATTEMPT TO LEVEL THE ACFT AND CONTINUE THE BANKED TURN BEYOND OUR ASSIGNED HDG OF 140 DEGS TO ABOUT 105 DEGS, INSTEAD OF DSNDING TO AVOID THE TFC. THE TRANSPONDER WAS IN TA/RA WITH MY ASSOCIATED SWITCHES IN 'NORMAL' AND 'ABSOLUTE' ON THE TRANSPONDER HEAD, AND I BELIEVE THE FO'S SWITCHES WERE IN THE SAME POS AS MINE. AFTER THE WARNING STOPPED AND NO TFC WAS SPOTTED VISUALLY, THE CLB WAS ONCE AGAIN STARTED TO 5000 FT MSL ALONG WITH AN IMMEDIATE RETURN TO OUR ASSIGNED HDG OF 140 DEGS. PASSING THROUGH 3500 FT MSL WE RECEIVED A TA WITH THE WORDS, 'TFC, TFC.' ORD RADAR, UPON BEING QUESTIONED, SAID THEY SHOWED NO TFC IN OUR IMMEDIATE VICINITY, AND WE SAW NO TFC VISUALLY AND CONTACTED ARTCC WITH NO FURTHER PROBLEMS UNTIL OUR DSCNT INTO BOSTON- LOGAN ARPT. AT 4200 FT MSL DSNDING TO 2000 FT MSL IN CONTACT WITH BOS APCH, WE RECEIVED A TA TO 'CLB, CLB NOW', WHICH ONCE AGAIN PROVED TO BE A FALSE WARNING WITH NO TFC RPTED BY APCH AND NONE SEEN VISUALLY. THE TCASII TESTED NORMALLY AT THE GATE PRIOR TO DEP, AND WAS IN TA/RA ON TKOF BEFORE AND AFTER GEAR AND FLAPS WERE UP. I BELIEVE WITH THIS EXPERIENCE (MY FIRST WITH TCASII ON THE LINE) OF HAVING SEVERAL FALSE WARNINGS AT LOW ALTS AND IN TKOF AND LNDG REGIMES (POTENTIALLY CRITICAL PERIODS OF FLT) WE NEED TO REEXAMINE EXACTLY WHEN TO HAVE IT ON OR OFF AND TO ASCERTAIN IF IN FACT THIS TYPE OF WARNING CAN EVER BE TRULY RELIABLE. WHERE DO WE GO FROM HERE WITHOUT FURTHER TESTING ON BOTH THE SOFTWARE AND HARDWARE OF THESE UNITS. CAN I REALLY TRUST TCASII FOR RELIABLE TFC AVOIDANCE INPUTS? FURTHER TESTING IS NEEDED TO 'DE-BUG' THIS SYS BEFORE REGULAR LINE USE ON COMMERCIAL ACRS.

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.