Narrative:

Over louisville (iiu) we were cleared direct to pocket city (pxv) and were climbing through approximately 25500 ft to a cleared FL260. Our VNAV had begun to capture at about 25000 ft. We received a TCASII alert followed within a few seconds by an RA commanding a 4000 FPM descent. The red traffic indicator on the TCASII screen indicated traffic at 12 O'clock level at FL270. The first officer (PF) followed the commanded descent per (air carrier X) directives, and descent was accomplished to about 24500 ft. We immediately advised ZID of our TCASII commanded descent and queried him about the unannounced traffic. His response was simply that 'yes, there was traffic (opposing) at FL270, and he requested us to climb back through FL250 (for FL260) as soon as possible. We were already doing so and leveled shortly at FL260. This TCASII RA may have been brought about by the computer assumption of our climb rate (VNAV had begun to capture about 1000 ft below 26000 ft (assigned). However, there were several targets on the TCASII screen, the controller was busy at the time and had given us no notification of opposing traffic. Needless to say, the event was very unsettling, and points out the problems yet to be corrected in the TCASII system.

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Original NASA ASRS Text

Title: FLC OF AN MLG STOPPED CLB TO DSND IN RESPONSE TO A TCASII RA.

Narrative: OVER LOUISVILLE (IIU) WE WERE CLRED DIRECT TO POCKET CITY (PXV) AND WERE CLBING THROUGH APPROX 25500 FT TO A CLRED FL260. OUR VNAV HAD BEGUN TO CAPTURE AT ABOUT 25000 FT. WE RECEIVED A TCASII ALERT FOLLOWED WITHIN A FEW SECONDS BY AN RA COMMANDING A 4000 FPM DSCNT. THE RED TFC INDICATOR ON THE TCASII SCREEN INDICATED TFC AT 12 O'CLOCK LEVEL AT FL270. THE FO (PF) FOLLOWED THE COMMANDED DSCNT PER (ACR X) DIRECTIVES, AND DSCNT WAS ACCOMPLISHED TO ABOUT 24500 FT. WE IMMEDIATELY ADVISED ZID OF OUR TCASII COMMANDED DSCNT AND QUERIED HIM ABOUT THE UNANNOUNCED TFC. HIS RESPONSE WAS SIMPLY THAT 'YES, THERE WAS TFC (OPPOSING) AT FL270, AND HE REQUESTED US TO CLB BACK THROUGH FL250 (FOR FL260) ASAP. WE WERE ALREADY DOING SO AND LEVELED SHORTLY AT FL260. THIS TCASII RA MAY HAVE BEEN BROUGHT ABOUT BY THE COMPUTER ASSUMPTION OF OUR CLB RATE (VNAV HAD BEGUN TO CAPTURE ABOUT 1000 FT BELOW 26000 FT (ASSIGNED). HOWEVER, THERE WERE SEVERAL TARGETS ON THE TCASII SCREEN, THE CTLR WAS BUSY AT THE TIME AND HAD GIVEN US NO NOTIFICATION OF OPPOSING TFC. NEEDLESS TO SAY, THE EVENT WAS VERY UNSETTLING, AND POINTS OUT THE PROBS YET TO BE CORRECTED IN THE TCASII SYS.

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.