Narrative:

Holding was in progress at the macey intersection. After a series of step downs in the holding pattern, we were cleared to descend to 13000 ft, which is usually the inbound altitude to atl leaving the holding pattern, but we were not cleared on the arrival or for vectors to the airport. As we began the turn for the outbound holding leg, passing 15000 ft, ZTL directed us to expedite descent through 14000 ft and directed another descending aircraft to level off. In our turn, we received a TCASII traffic alert for that aircraft in our direction of turn 300 ft above us. We did acquire the aircraft visually and continued our expedited descent. The TCASII, meanwhile, changed to an RA commanding a 4000 FPM climb, which we did not follow because the other aircraft had leveled by this time. Our expedited descent was ensuring separation, and a climb would have made matters worse. We passed with 2000 ft vertical separation and about 1/4 mi lateral. The situation would have been very dangerous in IMC when in a matter of seconds we would have had to decide whether to follow the controller's instructions or the TCASII advisory which was based on the other aircraft's initial descent, but which would probably have changed to a reversal of the escape maneuver once it determined the other aircraft leveled. The controller apologized to both aircraft, and told us he thought he had cleared us for the arrival. What might have prevented the conflict would have been a query to ATC of their intentions upon clearance to 13000 ft, but ZTL often gives vectors on the outbound leg for spacing even with a descent to 13000 ft, so the instructions were not looked upon by us as extraordinary. Supplemental information from can 519190: during our outbound turn over masey intersection, the controller told us to expedite our descent through 14000 ft MSL. Almost simultaneously, the TCASII gave us a traffic alert at 1 O'clock position, 5 mi, 300 ft, above descending. The controller told the conflicting traffic to level off at 15000 ft MSL and reiterated for us to expedite through 14000 ft MSL. We were established in a 4000 FPM descent when the TCASII TA turned into an RA recommending a 3500 FPM climb to avoid this traffic descending above us. At this time we acquired the traffic visually and opted to comply with the controller's directions. We leveled at 13000 ft MSL and passed the conflicting traffic with a 2000 ft vertical separation and a 1/4 mi lateral spacing. I also don't know what the other aircraft was seeing in their cockpit. If we followed the TCASII directions and the other aircraft followed the controller's directions, we may have hit -- who knows?

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Original NASA ASRS Text

Title: A B727 FLC HAS A POTENTIAL CONFLICT WITH OTHER HOLDING TFC DURING DSCNT AT MACEY INTXN NEAR ATL, GA.

Narrative: HOLDING WAS IN PROGRESS AT THE MACEY INTXN. AFTER A SERIES OF STEP DOWNS IN THE HOLDING PATTERN, WE WERE CLRED TO DSND TO 13000 FT, WHICH IS USUALLY THE INBOUND ALT TO ATL LEAVING THE HOLDING PATTERN, BUT WE WERE NOT CLRED ON THE ARR OR FOR VECTORS TO THE ARPT. AS WE BEGAN THE TURN FOR THE OUTBOUND HOLDING LEG, PASSING 15000 FT, ZTL DIRECTED US TO EXPEDITE DSCNT THROUGH 14000 FT AND DIRECTED ANOTHER DSNDING ACFT TO LEVEL OFF. IN OUR TURN, WE RECEIVED A TCASII TFC ALERT FOR THAT ACFT IN OUR DIRECTION OF TURN 300 FT ABOVE US. WE DID ACQUIRE THE ACFT VISUALLY AND CONTINUED OUR EXPEDITED DSCNT. THE TCASII, MEANWHILE, CHANGED TO AN RA COMMANDING A 4000 FPM CLB, WHICH WE DID NOT FOLLOW BECAUSE THE OTHER ACFT HAD LEVELED BY THIS TIME. OUR EXPEDITED DSCNT WAS ENSURING SEPARATION, AND A CLB WOULD HAVE MADE MATTERS WORSE. WE PASSED WITH 2000 FT VERT SEPARATION AND ABOUT 1/4 MI LATERAL. THE SIT WOULD HAVE BEEN VERY DANGEROUS IN IMC WHEN IN A MATTER OF SECONDS WE WOULD HAVE HAD TO DECIDE WHETHER TO FOLLOW THE CTLR'S INSTRUCTIONS OR THE TCASII ADVISORY WHICH WAS BASED ON THE OTHER ACFT'S INITIAL DSCNT, BUT WHICH WOULD PROBABLY HAVE CHANGED TO A REVERSAL OF THE ESCAPE MANEUVER ONCE IT DETERMINED THE OTHER ACFT LEVELED. THE CTLR APOLOGIZED TO BOTH ACFT, AND TOLD US HE THOUGHT HE HAD CLRED US FOR THE ARR. WHAT MIGHT HAVE PREVENTED THE CONFLICT WOULD HAVE BEEN A QUERY TO ATC OF THEIR INTENTIONS UPON CLRNC TO 13000 FT, BUT ZTL OFTEN GIVES VECTORS ON THE OUTBOUND LEG FOR SPACING EVEN WITH A DSCNT TO 13000 FT, SO THE INSTRUCTIONS WERE NOT LOOKED UPON BY US AS EXTRAORDINARY. SUPPLEMENTAL INFO FROM CAN 519190: DURING OUR OUTBOUND TURN OVER MASEY INTXN, THE CTLR TOLD US TO EXPEDITE OUR DSCNT THROUGH 14000 FT MSL. ALMOST SIMULTANEOUSLY, THE TCASII GAVE US A TFC ALERT AT 1 O'CLOCK POS, 5 MI, 300 FT, ABOVE DSNDING. THE CTLR TOLD THE CONFLICTING TFC TO LEVEL OFF AT 15000 FT MSL AND REITERATED FOR US TO EXPEDITE THROUGH 14000 FT MSL. WE WERE ESTABLISHED IN A 4000 FPM DSCNT WHEN THE TCASII TA TURNED INTO AN RA RECOMMENDING A 3500 FPM CLB TO AVOID THIS TFC DSNDING ABOVE US. AT THIS TIME WE ACQUIRED THE TFC VISUALLY AND OPTED TO COMPLY WITH THE CTLR'S DIRECTIONS. WE LEVELED AT 13000 FT MSL AND PASSED THE CONFLICTING TFC WITH A 2000 FT VERT SEPARATION AND A 1/4 MI LATERAL SPACING. I ALSO DON'T KNOW WHAT THE OTHER ACFT WAS SEEING IN THEIR COCKPIT. IF WE FOLLOWED THE TCASII DIRECTIONS AND THE OTHER ACFT FOLLOWED THE CTLR'S DIRECTIONS, WE MAY HAVE HIT -- WHO KNOWS?

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.