Narrative:

We were flight from msp to ewr. Our position was approximately 20 NM west of bae VOR in chicago's airspace level at FL270. Listening on an assigned chicago frequency. Our TCASII, which was set in RA/TA, was providing TA's in front of us. 1 TA showed an aircraft below our altitude at 800 ft with an arrow showing a climb. The other aircraft was shown as a TCASII advisory at 1000 ft in level flight above our altitude. TCASII gave us a RA on the aircraft at 800 ft below us and climb. TCASII commanded a climb resolution at which time I disconnected the autoplt and placed the vertical speed pointer into the green area shown on the vertical speed indicator. Shortly afterwards, TCASII commanded monitor vertical speed. The vertical speed was then reduced and the vertical speed pointer was placed between the 2 red areas (the red areas above and below as shown on the vertical speed indicator). We climbed to an altitude of 27300 ft. MSL when TCASII indicated clear of conflict. We then went back to FL270. The captain immediately told ZAU of our situation. They said they were not aware of any problems. Chicago center told the captain that the traffic below us was level at FL260. The captain told me he saw the TCASII aircraft below us get as close as 700 ft on his navigation display. Further en route, we kept getting numerous TCASII TA's from other aircraft leveled at 1000 ft above and below our altitude as we were leveled at FL270. We had standard selected in heading for the altimeter setting. We felt our TCASII was not operating correctly and therefore it was written up in the aircraft logbook for maintenance to look at in newark. Supplemental information from acn 287828: possible TCASII malfunction. We had about 15 TCASII TA's en route to ewr while level at 270 degrees. All target aircraft were 1000 ft above or below our flight level. Supplemental information from acn 290316: was there any loss of separation due to the TCASII RA? If yes, what was the closest proximity: 1.5 NM and 700 ft. Were you aware the aircraft was TCASII equipped? -- Yes. If yes, did this have an effect on your handling of the aircraft? No.

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Original NASA ASRS Text

Title: TCASII RA.

Narrative: WE WERE FLT FROM MSP TO EWR. OUR POS WAS APPROX 20 NM W OF BAE VOR IN CHICAGO'S AIRSPACE LEVEL AT FL270. LISTENING ON AN ASSIGNED CHICAGO FREQ. OUR TCASII, WHICH WAS SET IN RA/TA, WAS PROVIDING TA'S IN FRONT OF US. 1 TA SHOWED AN ACFT BELOW OUR ALT AT 800 FT WITH AN ARROW SHOWING A CLB. THE OTHER ACFT WAS SHOWN AS A TCASII ADVISORY AT 1000 FT IN LEVEL FLT ABOVE OUR ALT. TCASII GAVE US A RA ON THE ACFT AT 800 FT BELOW US AND CLB. TCASII COMMANDED A CLB RESOLUTION AT WHICH TIME I DISCONNECTED THE AUTOPLT AND PLACED THE VERT SPD POINTER INTO THE GREEN AREA SHOWN ON THE VERT SPD INDICATOR. SHORTLY AFTERWARDS, TCASII COMMANDED MONITOR VERT SPD. THE VERT SPD WAS THEN REDUCED AND THE VERT SPD POINTER WAS PLACED BTWN THE 2 RED AREAS (THE RED AREAS ABOVE AND BELOW AS SHOWN ON THE VERT SPD INDICATOR). WE CLBED TO AN ALT OF 27300 FT. MSL WHEN TCASII INDICATED CLR OF CONFLICT. WE THEN WENT BACK TO FL270. THE CAPT IMMEDIATELY TOLD ZAU OF OUR SIT. THEY SAID THEY WERE NOT AWARE OF ANY PROBS. CHICAGO CTR TOLD THE CAPT THAT THE TFC BELOW US WAS LEVEL AT FL260. THE CAPT TOLD ME HE SAW THE TCASII ACFT BELOW US GET AS CLOSE AS 700 FT ON HIS NAV DISPLAY. FURTHER ENRTE, WE KEPT GETTING NUMEROUS TCASII TA'S FROM OTHER ACFT LEVELED AT 1000 FT ABOVE AND BELOW OUR ALT AS WE WERE LEVELED AT FL270. WE HAD STANDARD SELECTED IN HDG FOR THE ALTIMETER SETTING. WE FELT OUR TCASII WAS NOT OPERATING CORRECTLY AND THEREFORE IT WAS WRITTEN UP IN THE ACFT LOGBOOK FOR MAINT TO LOOK AT IN NEWARK. SUPPLEMENTAL INFO FROM ACN 287828: POSSIBLE TCASII MALFUNCTION. WE HAD ABOUT 15 TCASII TA'S ENRTE TO EWR WHILE LEVEL AT 270 DEGS. ALL TARGET ACFT WERE 1000 FT ABOVE OR BELOW OUR FLT LEVEL. SUPPLEMENTAL INFO FROM ACN 290316: WAS THERE ANY LOSS OF SEPARATION DUE TO THE TCASII RA? IF YES, WHAT WAS THE CLOSEST PROX: 1.5 NM AND 700 FT. WERE YOU AWARE THE ACFT WAS TCASII EQUIPPED? -- YES. IF YES, DID THIS HAVE AN EFFECT ON YOUR HANDLING OF THE ACFT? NO.

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.