ACR X TCASII TA RA DSND NON COMPLIANCE WITH TCASII RA HAD LTSS FROM ACR Y. SYS ERROR.

Narrative

CLBING OUT OF ORD; WE WERE CLRED TO FL290. I (FO) WAS HAND FLYING THE ACFT. APCHING FL280 WE NOTICED A TARGET ON TCASII AT FL280; 10 O'CLOCK; ABOUT 6 MI AND CLOSING; FOLLOWED SHORTLY BY A TCASII TA. AT APPROX FL282; CHICAGO CTR CALLED THE TFC AND DIRECTED A TURN FROM 170 DEGS TO 260 DEGS AND 'EXPEDITE CLB.' AT THE SAME TIME TCASII DIRECTED AN RA DSCNT AT 2000 FT FPM. AT THIS POINT THE CAPT PICKED UP THE TFC VISUALLY AND I ELECTED TO CONTINUE THE CLB; AS WE WERE ALREADY ABOVE THE TARGET (AN LGT) THE TARGET DID NOT APPEAR TO MANEUVER IN ALT AND THE ESTIMATED MISS DISTANCE (FROM TCASII) WAS ABOUT 1-2 NM HORIZLY. LATER CONVERSATION WITH THE CTLR REVEALED HIS RADAR SHOWED A 4 NM MISS. NOT A RELIABLE ESTIMATE; DUE TO INHERENT INACCURACIES IN ATC RADAR. THE POINT OF THIS RPT IS TO BRING TO LIGHT THE PROBS OF TCASII DIRECTING 1 MANEUVER AND THE CTLR CALLING FOR THE OPPOSITE. IN THIS CASE I BELIEVE WE MADE THE PROPER DECISION; BUT ALL FACTORS NEED TO BE CONSIDERED. THE TARGET ACFT WAS NOT TCASII EQUIPPED. HAD HE BEEN; THE RESULT MIGHT HAVE BEEN MORE EXCITING. BOTTOM LINE: TCASII MAY BE A TOOL; BUT IT IS NO SUBSTITUTE FOR HUMAN JUDGEMENT! SUPPLEMENTAL INFO FROM ACN 241826: ACR X GIVEN AN ASSIGNED HDG FOR CLB TO FL280. SHORTLY AFTER TKOF GIVEN DIRECT BVT. AFTER TURNING OVER BVT TO FLY THE BVT 287 DEG RADIAL; I NOTED ACR X IN A HARD R TURN AT APPROX 2-3 NM. CHK WITH COMPANY RADIO REVEALED THAT ACR X HAD RECEIVED A TCASII RA AND TOOK EVASIVE ACTION TO PRECLUDE A NEAR MISS. WE TOOK NO EVASIVE ACTION AS WE SAW ACR X AFTER HE HAD COMMENCED HIS EVASIVE MANEUVER AND NO THREAT EXISTED TO US. OUR ACFT WAS NOT TCASII EQUIPPED AND WE RECEIVED NO ADVISORY FROM ZID THAT ACR X WAS IN OUR VICINITY. ALTHOUGH IT IS PROBABLE WE WOULD HAVE SEEN EACH OTHER VISUALLY; ACR X TCASII RA KEPT AN EXCITING SIT FROM BECOMING A DANGEROUS ONE AS BOTH ACFT WERE AT FL280. DO NOT KNOW WHY BOTH ACFT WERE AT FL280 ON CONVERGING HDGS. WE KNOW OF NO CREW OMISSIONS.