A DC9 FLT CREW RECEIVES A TCASII COMMAND TO DSND FOR TFC; BUT LEVEL OFF BECAUSE THEY NOTICE THAT THE TFC IS BELOW THEM.

Narrative

THE FLT WAS PROCEEDING FROM HNN TO DJB FOR THE CETUS 2 ARR INTO DTW. WE WERE AT FL220 BECAUSE OF BEING DISPATCHED WITH ONLY 1 PACK. TCASII CALLED 'TFC' TA AND INDICATOR SHOWED A YELLOW TFC 500 FT ABOVE AT THE 2 MI RING AT THE 10 O'CLOCK POS. WE IMMEDIATELY GOT AN RA WITH THE TARGET TURNING RED AND THE TCASII DIRECTING A DSCNT AT 1500 FPM. THE FO INITIALLY BEGAN THE DSCNT TO COMPLY WITH THE RA; AS I SCANNED THE AIRSPACE WHERE WE WERE GOING AND WHERE THE TARGET WAS. THE TCASII TARGET DISAPPEARED MOMENTARILY AND THEN REAPPEARED. I PICKED UP THE TFC; BUT TO MY SURPRISE IT WAS NOT ABOVE US; BUT IT WAS ABOUT 500 FT BELOW US AND THE TCASII CONTINUED TO DIRECT US TO DSND! THE ACFT I SAW WAS A TWIN ENG WHITE ACFT WITH SILVER PROP SPINNERS AND APPEARED TO BE IN LEVEL FLT AND WAS NOT MANEUVERING. I DIRECTED THE FO TO LEVEL OFF AND RETURN TO OUR ASSIGNED ALT. WE HAD DSNDED TO FL217 AND RETURNED TO FL220. THE TCASII CONTINUED TO DIRECT US TO DSND AS THE TCASII TARGET WENT DIRECTLY THROUGH OUR DISPLAY UNTIL IT PASSED AND WE THEN RECEIVED THE TCASII 'CLR OF CONFLICT.' I CALLED THE CTLR AND INFORMED HIM WE HAD RECEIVED THE RA AND ASKED HIM IF THE OTHER ACFT HAD RECEIVED AN RA ALSO. THE OTHER ACFT PLT WAS ON THE FREQ AND SAID THEY HAD TCASII AND SAW US; BUT THEY DID NOT HAVE THE ABILITY TO RECEIVE AN RA. I THEN EXPLAINED TO THE CTLR WHAT HAD HAPPENED AND I TOLD HIM I WOULD BE SUBMITTING A RPT OF THE INCIDENT. ON THE NEW ATC ZOB SECTOR I ASKED THE CTLR IF HE COULD GET MORE INFO ON THE TWIN'S TCASII EQUIP; BUT HE NEVER GOT BACK TO US. I WROTE UP OUR TCASII FOR THE MAINT PERSONNEL TO INSPECT OUR EQUIP WHEN WE ARRIVED INTO DETROIT. I MADE CALLS TO THE DISPATCH; CHIEF PLT; UNION SAFETY AND DC9 FLEET TRAINING CAPT.