Narrative:

Air carrier X while operating at a level cruising altitude of 29000 ft, our TA and collision avoidance system (TCASII) showed a TA alerting us to another aircraft level at our altitude and converging upon our position. The TA quickly changed to an RA indicating a collision threat and demanding immediate corrective action. A visual sighting of the intruding air carrier Y confirmed to us that we needed evasive action. We immediately began a turn away from the aircraft and descended to 28200 ft to avoid the other aircraft which passed approximately 1/2 mi from our position. Just prior to our corrective action, we were assigned a new frequency by ZDC. We had just changed to this new frequency when the traffic conflict occurred. During our corrective action, we made numerous unanswered calls on this new frequency in an attempt to inform ATC of our actions. With no response on our new frequency, we reported our actions on our old frequency. After this conflict was resolved and on our climb back to 29000 ft, we noted that our altimeters were set at 30.14 instead of 29.92 resulting in a 200 ft error. We corrected our altimeters. Supplemental information from acn 219984: air carrier X apparently had an improper TCASII resolution to descend from 29000 ft. He advised ATC he was taking evasive action and descended through 28000 ft. He was nebound when we visually picked him up. Our turn towards pxt VOR was stopped and we passed behind him. No evasive maneuvers were performed, bank angles did not exceed 15 degrees. Our aircraft was not TCASII equipped.

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Original NASA ASRS Text

Title: ACR X WRONG ALTIMETER SET HAD TCASII RA DSNDED TO OCCUPIED ALT HAD LTSS FROM ACR Y. PLTDEV. ERRONEOUS TCASII RA.

Narrative: ACR X WHILE OPERATING AT A LEVEL CRUISING ALT OF 29000 FT, OUR TA AND COLLISION AVOIDANCE SYS (TCASII) SHOWED A TA ALERTING US TO ANOTHER ACFT LEVEL AT OUR ALT AND CONVERGING UPON OUR POS. THE TA QUICKLY CHANGED TO AN RA INDICATING A COLLISION THREAT AND DEMANDING IMMEDIATE CORRECTIVE ACTION. A VISUAL SIGHTING OF THE INTRUDING ACR Y CONFIRMED TO US THAT WE NEEDED EVASIVE ACTION. WE IMMEDIATELY BEGAN A TURN AWAY FROM THE ACFT AND DSNDED TO 28200 FT TO AVOID THE OTHER ACFT WHICH PASSED APPROX 1/2 MI FROM OUR POS. JUST PRIOR TO OUR CORRECTIVE ACTION, WE WERE ASSIGNED A NEW FREQ BY ZDC. WE HAD JUST CHANGED TO THIS NEW FREQ WHEN THE TFC CONFLICT OCCURRED. DURING OUR CORRECTIVE ACTION, WE MADE NUMEROUS UNANSWERED CALLS ON THIS NEW FREQ IN AN ATTEMPT TO INFORM ATC OF OUR ACTIONS. WITH NO RESPONSE ON OUR NEW FREQ, WE RPTED OUR ACTIONS ON OUR OLD FREQ. AFTER THIS CONFLICT WAS RESOLVED AND ON OUR CLB BACK TO 29000 FT, WE NOTED THAT OUR ALTIMETERS WERE SET AT 30.14 INSTEAD OF 29.92 RESULTING IN A 200 FT ERROR. WE CORRECTED OUR ALTIMETERS. SUPPLEMENTAL INFO FROM ACN 219984: ACR X APPARENTLY HAD AN IMPROPER TCASII RESOLUTION TO DSND FROM 29000 FT. HE ADVISED ATC HE WAS TAKING EVASIVE ACTION AND DSNDED THROUGH 28000 FT. HE WAS NEBOUND WHEN WE VISUALLY PICKED HIM UP. OUR TURN TOWARDS PXT VOR WAS STOPPED AND WE PASSED BEHIND HIM. NO EVASIVE MANEUVERS WERE PERFORMED, BANK ANGLES DID NOT EXCEED 15 DEGS. OUR ACFT WAS NOT TCASII EQUIPPED.

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.