Narrative:

Aircraft Y level at FL240 frequency changed to low altitude sector (rod, 32) at XA21:37. My expectation was that he would begin descent. At XA23:29 aircraft X called on my frequency 'leaving FL220 for FL230.' his mode C indicated FL223 (climbing). After asking his rate of climb, and he responding 1500 FPM, I issued climb instruction to FL310, expecting that I could climb above aircraft Y. After instructing the rod controller to descend aircraft Y (to make it easier to attain vertical separation), I instructed aircraft X to expedite climb through FL250. At XA24:11, aircraft X reported that he was responding to a TCASII RA to descend. The next mode C (XA24:15) report was FL233 (indicating he'd actually been higher than that prior to the TCASII maneuver). At that time aircraft Y showed FL231 on mode C. The aircraft X flight was already higher than the aircraft Y flight, and had TCASII not intervened (instructing the climbing (higher) aircraft to descend, and the descending (lower) aircraft to climb) I only needed 400 ft more from each aircraft in the direction of the control instructions to attain approved separation. Unfortunately, both aircraft received TCASII RA's opposite to the control instructions, and maneuvered back toward each other, rather than away. Supplemental information from acn 448070: aircraft #1 started down out of FL240. Aircraft #2 started up and told to expedite. Aircraft were on the good side of each other by 200-300 ft when TCASII RA told both aircraft to reverse direction of climb/descent. TCASII was late in the RA causing an near midair collision. It is unknown if required 7110.65 separation would have been maintained if TCASII had not gone off. The control decision (human) to expedite aircraft #2 up and aircraft #1 down was a poor one. We learned later in the evening that aircraft #1 filed an near midair collision and also injured a flight attendant during the RA. Callback conversation with reporter acn 448502 revealed the following information: reporter advised that the xferred low altitude controller expressed surprise that the high altitude controller was attempting the opposite direction climb. The developmental controller stated that the climbing air carrier appeared to him as leveling, and that reinitiating a climb appeared questionable. Since the radar display was about 2 sweeps behind, he could not determine for sure when both aircraft started the respective TCASII maneuvers.

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Original NASA ASRS Text

Title: ZID CTLR ISSUES CLB CLRNC TO TOP XING ACR WHICH RESULTS IN AN OPERROR WHEN TCASII CONTRADICTS CTLR INSTRUCTIONS.

Narrative: ACFT Y LEVEL AT FL240 FREQ CHANGED TO LOW ALT SECTOR (ROD, 32) AT XA21:37. MY EXPECTATION WAS THAT HE WOULD BEGIN DSCNT. AT XA23:29 ACFT X CALLED ON MY FREQ 'LEAVING FL220 FOR FL230.' HIS MODE C INDICATED FL223 (CLBING). AFTER ASKING HIS RATE OF CLB, AND HE RESPONDING 1500 FPM, I ISSUED CLB INSTRUCTION TO FL310, EXPECTING THAT I COULD CLB ABOVE ACFT Y. AFTER INSTRUCTING THE ROD CTLR TO DSND ACFT Y (TO MAKE IT EASIER TO ATTAIN VERT SEPARATION), I INSTRUCTED ACFT X TO EXPEDITE CLB THROUGH FL250. AT XA24:11, ACFT X RPTED THAT HE WAS RESPONDING TO A TCASII RA TO DSND. THE NEXT MODE C (XA24:15) RPT WAS FL233 (INDICATING HE'D ACTUALLY BEEN HIGHER THAN THAT PRIOR TO THE TCASII MANEUVER). AT THAT TIME ACFT Y SHOWED FL231 ON MODE C. THE ACFT X FLT WAS ALREADY HIGHER THAN THE ACFT Y FLT, AND HAD TCASII NOT INTERVENED (INSTRUCTING THE CLBING (HIGHER) ACFT TO DSND, AND THE DSNDING (LOWER) ACFT TO CLB) I ONLY NEEDED 400 FT MORE FROM EACH ACFT IN THE DIRECTION OF THE CTL INSTRUCTIONS TO ATTAIN APPROVED SEPARATION. UNFORTUNATELY, BOTH ACFT RECEIVED TCASII RA'S OPPOSITE TO THE CTL INSTRUCTIONS, AND MANEUVERED BACK TOWARD EACH OTHER, RATHER THAN AWAY. SUPPLEMENTAL INFO FROM ACN 448070: ACFT #1 STARTED DOWN OUT OF FL240. ACFT #2 STARTED UP AND TOLD TO EXPEDITE. ACFT WERE ON THE GOOD SIDE OF EACH OTHER BY 200-300 FT WHEN TCASII RA TOLD BOTH ACFT TO REVERSE DIRECTION OF CLB/DSCNT. TCASII WAS LATE IN THE RA CAUSING AN NMAC. IT IS UNKNOWN IF REQUIRED 7110.65 SEPARATION WOULD HAVE BEEN MAINTAINED IF TCASII HAD NOT GONE OFF. THE CTL DECISION (HUMAN) TO EXPEDITE ACFT #2 UP AND ACFT #1 DOWN WAS A POOR ONE. WE LEARNED LATER IN THE EVENING THAT ACFT #1 FILED AN NMAC AND ALSO INJURED A FLT ATTENDANT DURING THE RA. CALLBACK CONVERSATION WITH RPTR ACN 448502 REVEALED THE FOLLOWING INFO: RPTR ADVISED THAT THE XFERRED LOW ALT CTLR EXPRESSED SURPRISE THAT THE HIGH ALT CTLR WAS ATTEMPTING THE OPPOSITE DIRECTION CLB. THE DEVELOPMENTAL CTLR STATED THAT THE CLBING ACR APPEARED TO HIM AS LEVELING, AND THAT REINITIATING A CLB APPEARED QUESTIONABLE. SINCE THE RADAR DISPLAY WAS ABOUT 2 SWEEPS BEHIND, HE COULD NOT DETERMINE FOR SURE WHEN BOTH ACFT STARTED THE RESPECTIVE TCASII MANEUVERS.

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.