Narrative:

Flight was approximately 30 NM wsw of hmv on a vector to intercept the sweed 2 arrival northwest of hmv. The flight was climbing at approximately 1000 FPM through FL260 with a clearance to FL290 when we received a 'traffic' aural warning with a red 'traffic' message on the ivsi and a 2000 FPM minimum climb command. I disconnected the autoplt and initiated an immediate climb while the first officer informed ATC. I selected my TCASII display and it showed a red -07 target in the 8 O'clock position, merging with the aircraft symbol. Passing approximately FL280 the RA ended and I continued a normal climb to FL290. After the RA ended I expanded the range and envelope of the TCASII display and was unable to reacquire the target. There was no deviation from an ATC clearance or assigned altitude because we were already climbing to a higher assigned altitude. During the RA the first officer notified ATC that we were following a TCASII RA and inquired about any traffic in our immediate vicinity. ATC advised us that all they had was a flight of 4 kc-135 tanker aircraft underneath us at approximately FL220 (or 230). During the RA, prior to ATC's message I saw 2 aircraft (lights only) in a loose formation, in my 8 O'clock and several thousand ft below us. The first officer reported to ATC that we had an aircraft pass under us by a couple of hundred ft. The first officer saw the threat aircraft pass behind and to our right within 400-500 ft vertical separation. ATC didn't see anything in our immediate area but they asked us if the TCASII commanded a climb or a descent. We informed them that we received a climb command. Lack of advanced warning: the first thing I recall was hearing the 'traffic' aural warning. I immediately looked down at the ivsi and it was already in the RA mode with a red 'traffic' message and a vertical command. We never heard or saw a TA. I did not hear a climb or descend aural warning. Later the first officer said that he thought he heard the TCASII say something, possibly a 'monitor vertical speed' or a 'climb' message, but he wasn't sure. He also said that the aural message came from the left side speaker, not through his headset. After landing in cvg, I ran the TCASII through several test cycles and it tested ok except the only audio I could hear was a weak 'TCASII test ok' through the left speaker. I could not hear the aural warning through my headset. (Note: in-flight I was using the telex.) on the ground I got out my david clarks and still couldn't hear the aural warning through the headset.) I then wrote up the TCASII aural warning and left the aircraft at the maintenance hangar so I don't know what avionics did to fix the problem. Possible scenarios: 1) erroneous TCASII indication. 2) a military aircraft passing underneath us initiated a very steep vertical climb, possibly after refueling from one of the kc-135 aircraft. A rapid vertical maneuver may have taken the threat aircraft rapidly through the normal TA range so that it became an RA before the TCASII could display it as a TA. 3) TCASII didn't detect the threat aircraft until it was well within the RA envelope. It has been noted that the TCASII system installed in the cl-65 does not always display traffic within the selected envelope. We have reports of the TCASII taking as long as 10-15 mins to display a target that is obviously within the selected range. Other times a target, well within the selected range, will drop on and off the TCASII display. It is not known whether or not this is a display problem or the TCASII actually is not aware of the other aircraft. Update: commercial radio is looking into this too, ZTL quality control reported no loss of separation. There have been reports of erroneous TCASII RA's due to anomalies with military xponders, particularly kc-135's.

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Original NASA ASRS Text

Title: MDT HAS TCASII TA, RA DURING CLB.

Narrative: FLT WAS APPROX 30 NM WSW OF HMV ON A VECTOR TO INTERCEPT THE SWEED 2 ARR NW OF HMV. THE FLT WAS CLBING AT APPROX 1000 FPM THROUGH FL260 WITH A CLRNC TO FL290 WHEN WE RECEIVED A 'TFC' AURAL WARNING WITH A RED 'TFC' MESSAGE ON THE IVSI AND A 2000 FPM MINIMUM CLB COMMAND. I DISCONNECTED THE AUTOPLT AND INITIATED AN IMMEDIATE CLB WHILE THE FO INFORMED ATC. I SELECTED MY TCASII DISPLAY AND IT SHOWED A RED -07 TARGET IN THE 8 O'CLOCK POS, MERGING WITH THE ACFT SYMBOL. PASSING APPROX FL280 THE RA ENDED AND I CONTINUED A NORMAL CLB TO FL290. AFTER THE RA ENDED I EXPANDED THE RANGE AND ENVELOPE OF THE TCASII DISPLAY AND WAS UNABLE TO REACQUIRE THE TARGET. THERE WAS NO DEV FROM AN ATC CLRNC OR ASSIGNED ALT BECAUSE WE WERE ALREADY CLBING TO A HIGHER ASSIGNED ALT. DURING THE RA THE FO NOTIFIED ATC THAT WE WERE FOLLOWING A TCASII RA AND INQUIRED ABOUT ANY TFC IN OUR IMMEDIATE VICINITY. ATC ADVISED US THAT ALL THEY HAD WAS A FLT OF 4 KC-135 TANKER ACFT UNDERNEATH US AT APPROX FL220 (OR 230). DURING THE RA, PRIOR TO ATC'S MESSAGE I SAW 2 ACFT (LIGHTS ONLY) IN A LOOSE FORMATION, IN MY 8 O'CLOCK AND SEVERAL THOUSAND FT BELOW US. THE FO RPTED TO ATC THAT WE HAD AN ACFT PASS UNDER US BY A COUPLE OF HUNDRED FT. THE FO SAW THE THREAT ACFT PASS BEHIND AND TO OUR R WITHIN 400-500 FT VERT SEPARATION. ATC DIDN'T SEE ANYTHING IN OUR IMMEDIATE AREA BUT THEY ASKED US IF THE TCASII COMMANDED A CLB OR A DSCNT. WE INFORMED THEM THAT WE RECEIVED A CLB COMMAND. LACK OF ADVANCED WARNING: THE FIRST THING I RECALL WAS HEARING THE 'TFC' AURAL WARNING. I IMMEDIATELY LOOKED DOWN AT THE IVSI AND IT WAS ALREADY IN THE RA MODE WITH A RED 'TFC' MESSAGE AND A VERT COMMAND. WE NEVER HEARD OR SAW A TA. I DID NOT HEAR A CLB OR DSND AURAL WARNING. LATER THE FO SAID THAT HE THOUGHT HE HEARD THE TCASII SAY SOMETHING, POSSIBLY A 'MONITOR VERT SPD' OR A 'CLB' MESSAGE, BUT HE WASN'T SURE. HE ALSO SAID THAT THE AURAL MESSAGE CAME FROM THE L SIDE SPEAKER, NOT THROUGH HIS HEADSET. AFTER LNDG IN CVG, I RAN THE TCASII THROUGH SEVERAL TEST CYCLES AND IT TESTED OK EXCEPT THE ONLY AUDIO I COULD HEAR WAS A WEAK 'TCASII TEST OK' THROUGH THE L SPEAKER. I COULD NOT HEAR THE AURAL WARNING THROUGH MY HEADSET. (NOTE: INFLT I WAS USING THE TELEX.) ON THE GND I GOT OUT MY DAVID CLARKS AND STILL COULDN'T HEAR THE AURAL WARNING THROUGH THE HEADSET.) I THEN WROTE UP THE TCASII AURAL WARNING AND LEFT THE ACFT AT THE MAINT HANGAR SO I DON'T KNOW WHAT AVIONICS DID TO FIX THE PROB. POSSIBLE SCENARIOS: 1) ERRONEOUS TCASII INDICATION. 2) A MIL ACFT PASSING UNDERNEATH US INITIATED A VERY STEEP VERT CLB, POSSIBLY AFTER REFUELING FROM ONE OF THE KC-135 ACFT. A RAPID VERT MANEUVER MAY HAVE TAKEN THE THREAT ACFT RAPIDLY THROUGH THE NORMAL TA RANGE SO THAT IT BECAME AN RA BEFORE THE TCASII COULD DISPLAY IT AS A TA. 3) TCASII DIDN'T DETECT THE THREAT ACFT UNTIL IT WAS WELL WITHIN THE RA ENVELOPE. IT HAS BEEN NOTED THAT THE TCASII SYS INSTALLED IN THE CL-65 DOES NOT ALWAYS DISPLAY TFC WITHIN THE SELECTED ENVELOPE. WE HAVE RPTS OF THE TCASII TAKING AS LONG AS 10-15 MINS TO DISPLAY A TARGET THAT IS OBVIOUSLY WITHIN THE SELECTED RANGE. OTHER TIMES A TARGET, WELL WITHIN THE SELECTED RANGE, WILL DROP ON AND OFF THE TCASII DISPLAY. IT IS NOT KNOWN WHETHER OR NOT THIS IS A DISPLAY PROB OR THE TCASII ACTUALLY IS NOT AWARE OF THE OTHER ACFT. UPDATE: COMMERCIAL RADIO IS LOOKING INTO THIS TOO, ZTL QUALITY CTL RPTED NO LOSS OF SEPARATION. THERE HAVE BEEN RPTS OF ERRONEOUS TCASII RA'S DUE TO ANOMALIES WITH MIL XPONDERS, PARTICULARLY KC-135'S.

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.