Narrative:

Air carrier X was at FL330 inbound to pit. Air carrier Y was at FL310. Air carrier X was eastbound and south of air carrier Y (wbound). I issued a 20 degree right turn to air carrier X and directed that when he was established on the new heading to descend to FL290. As air carrier X was already about 3 mi south of air carrier Y's track, I believed the turn was more than sufficient to ensure separation. I then issued clrncs to other aircraft, then I noticed conflict alert activating between air carrier X and air carrier Y. Air carrier X track histories and leader line both showed a constant left turn. The aircraft were basically now head on at about 8 mi with air carrier X descending through 32000 ft. I told the pilot he had turned left and he replied that he had turned right. As I could not be sure what he was doing I did not believe it was safe to issue a vector to air carrier Y, I told air carrier X to fly a heading of 360 degrees and to expedite a descent to FL280. I issued the continued descent in an effort to maintain a safe situation as air carrier X was already descending. Air carrier X advise that he was getting a TCASII RA and climbing. I told him to continue the turn to heading 360 degrees for other traffic at FL330, then descended him to FL240 when clear of air carrier Y. I was then relieved until the edp could be investigated. Supplemental information from acn 388003: in level cruise at FL330 ZID instructed us to turn right 20 degrees and descend to FL290. The first officer replied 'right 20 degrees, descend to FL290,' but I heard the clearance as (left 20 degrees). While I began a gentle 10 degree bank turn to left, the first officer reset the cabin and turned his attention to his flight kit for the appropriate charts. The first officer had not monitored the actual aircraft turn or descent, but upon selecting 360 degrees on the heading bug he noted that I had made little progress toward the original 20 degree right. At almost the same time that the instruction to turn left 360 degrees was given, we began to experience moderate chop which further led to confusion/distraction as the seat belt sign and airspeed were checked. Very shortly after these events (approximately 15-20 seconds) the TCASII RA sounded. I immediately added power and began to climb to follow the TCASII vertical guidance. The first officer reported to ZID that we were responding to a TCASII RA and had the aircraft in sight and were climbing. The TCASII then sounded 'clear of conflict.' I resumed descent to FL290. I didn't hear the clearance properly and the first officer didn't ensure my response to the clearance. Distraction from turbulence and confusion from the controller's words also contributed. Supplemental information from acn 387924: in level cruise at FL330 ZID instructed 'turn right 20 degrees, then descend to FL290.' first officer read back clearance. Problem can be avoided by ensuring clrncs are fully understood by both pilots, and closer monitoring by PNF.

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Original NASA ASRS Text

Title: ACR DC9 INBOUND TO PIT WAS ISSUED R TURN FOR VECTOR CLR OF OPPOSITE DIRECTION TFC AND DSCNT TO FL290. PIC THOUGHT L TURN WAS ISSUED. FO DID NOT INITIALLY OBSERVE PIC TURNING L. CTLR OBSERVED TURN INTO OPPOSITE DIRECTION TFC, ISSUED L TURN TO 360 DEGS. FLC RECEIVED TCASII RA AND CLBED.

Narrative: ACR X WAS AT FL330 INBOUND TO PIT. ACR Y WAS AT FL310. ACR X WAS EBOUND AND S OF ACR Y (WBOUND). I ISSUED A 20 DEG R TURN TO ACR X AND DIRECTED THAT WHEN HE WAS ESTABLISHED ON THE NEW HEADING TO DSND TO FL290. AS ACR X WAS ALREADY ABOUT 3 MI S OF ACR Y'S TRACK, I BELIEVED THE TURN WAS MORE THAN SUFFICIENT TO ENSURE SEPARATION. I THEN ISSUED CLRNCS TO OTHER ACFT, THEN I NOTICED CONFLICT ALERT ACTIVATING BTWN ACR X AND ACR Y. ACR X TRACK HISTORIES AND LEADER LINE BOTH SHOWED A CONSTANT L TURN. THE ACFT WERE BASICALLY NOW HEAD ON AT ABOUT 8 MI WITH ACR X DSNDING THROUGH 32000 FT. I TOLD THE PLT HE HAD TURNED L AND HE REPLIED THAT HE HAD TURNED R. AS I COULD NOT BE SURE WHAT HE WAS DOING I DID NOT BELIEVE IT WAS SAFE TO ISSUE A VECTOR TO ACR Y, I TOLD ACR X TO FLY A HDG OF 360 DEGS AND TO EXPEDITE A DSCNT TO FL280. I ISSUED THE CONTINUED DSCNT IN AN EFFORT TO MAINTAIN A SAFE SIT AS ACR X WAS ALREADY DSNDING. ACR X ADVISE THAT HE WAS GETTING A TCASII RA AND CLBING. I TOLD HIM TO CONTINUE THE TURN TO HDG 360 DEGS FOR OTHER TFC AT FL330, THEN DSNDED HIM TO FL240 WHEN CLR OF ACR Y. I WAS THEN RELIEVED UNTIL THE EDP COULD BE INVESTIGATED. SUPPLEMENTAL INFO FROM ACN 388003: IN LEVEL CRUISE AT FL330 ZID INSTRUCTED US TO TURN R 20 DEGS AND DSND TO FL290. THE FO REPLIED 'R 20 DEGS, DSND TO FL290,' BUT I HEARD THE CLRNC AS (L 20 DEGS). WHILE I BEGAN A GENTLE 10 DEG BANK TURN TO L, THE FO RESET THE CABIN AND TURNED HIS ATTN TO HIS FLT KIT FOR THE APPROPRIATE CHARTS. THE FO HAD NOT MONITORED THE ACTUAL ACFT TURN OR DSCNT, BUT UPON SELECTING 360 DEGS ON THE HEADING BUG HE NOTED THAT I HAD MADE LITTLE PROGRESS TOWARD THE ORIGINAL 20 DEG R. AT ALMOST THE SAME TIME THAT THE INSTRUCTION TO TURN L 360 DEGS WAS GIVEN, WE BEGAN TO EXPERIENCE MODERATE CHOP WHICH FURTHER LED TO CONFUSION/DISTR AS THE SEAT BELT SIGN AND AIRSPD WERE CHKED. VERY SHORTLY AFTER THESE EVENTS (APPROX 15-20 SECONDS) THE TCASII RA SOUNDED. I IMMEDIATELY ADDED PWR AND BEGAN TO CLB TO FOLLOW THE TCASII VERT GUIDANCE. THE FO RPTED TO ZID THAT WE WERE RESPONDING TO A TCASII RA AND HAD THE ACFT IN SIGHT AND WERE CLBING. THE TCASII THEN SOUNDED 'CLR OF CONFLICT.' I RESUMED DSCNT TO FL290. I DIDN'T HEAR THE CLRNC PROPERLY AND THE FO DIDN'T ENSURE MY RESPONSE TO THE CLRNC. DISTR FROM TURB AND CONFUSION FROM THE CTLR'S WORDS ALSO CONTRIBUTED. SUPPLEMENTAL INFO FROM ACN 387924: IN LEVEL CRUISE AT FL330 ZID INSTRUCTED 'TURN R 20 DEGS, THEN DSND TO FL290.' FO READ BACK CLRNC. PROB CAN BE AVOIDED BY ENSURING CLRNCS ARE FULLY UNDERSTOOD BY BOTH PLTS, AND CLOSER MONITORING BY PNF.

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.