FALSE TCASII WARNING.

Narrative

GOT AN RA AT APPROX 2000 FT MSL ON APCH; TOLD US TO CLB AND SHOWED A TARGET RIGHT ON US AT '00' ALT. WE INITIATED CLB; TRIED TO GET A WORD IN EDGEWISE WITH TWR (LOTS OF TFC). TWR TOLD US TO MAINTAIN 2000 FT ON THE MISS BUT WE WERE ALREADY CLBING THROUGH 3500 FT SO WE STOPPED AT 3500 FT. THE TCASII STILL SAID '00.' CALLED DEP. THEY TURNED US; AND TCASII TARGET STAYED WITH US! OBVIOUSLY A FALSE TARGET. TURNED THE DAMN THING OFF; RESTARTED OUR HEARTS WITH ELECTROSHOCK; GOT ON THE GND WITHOUT FURTHER INCIDENT. WROTE TCASII UP IN DISCREPANCY LOG. THE MECHS CHANGED THE BOX. I DON'T THINK THERE WAS A TFC CONFLICT BUT YOU NEVER KNOW; HENCE THIS RPT. TWR TOLD US THAT THERE WAS NO TFC ANYWHERE NEAR US. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FLIES THE ATR 72 FOR A LARGE REGIONAL AIRLINE. HE HAS FLOWN THE SAAB 340 FOR THE SAME ACR. HE BELIEVES THAT THE TCASII IN THE ATR IS LESS SOPHISTICATED THAN THE TCASII IN THE SAAB. FOR INSTANCE; HE HAS NEVER HAD A FALSE TCASII WARNING IN THE SAAB; BUT HAS HAD SEVERAL IN THE ATR. THE RPTR STATES THAT; IN THE ATR ON THE ACTON STAR INTO DFW; ONE CAN OFTEN GET A FALSE WARNING PASSING DOWNTOWN FORT WORTH. THE RPTR BELIEVES THAT THIS MAY BE A REACTION FROM A MICROWAVE TWR IN FORT WORTH. HE STATES THAT THE LATEST MODIFICATION TO THE TCASII SUPPRESSES ALL RA'S BELOW 1000 FT AGL. THIS IS THE FIRST TIME THAT THE RPTR HAS HAD A FALSE ALARM THAT FOLLOWED HIS ACFT. CHANGING THE 'BOX' FIXED THE PROB AS THE RPTR IMMEDIATELY FLEW THE ACFT LATER IN THE DAY.