Narrative:

I was working south departure at atl tower. Air carrier X, a B727, departed and climbed to 10000 ft. Air carrier Y, a L101, was inbound level at 11000 ft. Both aircraft were level and traffic was given when they were still 7-8 mi apart. As the targets converged, the pilot of air carrier X said he was climbing in response to an RA. Our training is not to interfere with compliance to an RA, so without telling him not to climb, I reissued the traffic, which was now almost directly above him. He said his TCASII reported traffic 700 ft below him and was advising a climb rate of 2000 FPM. I told him there was nothing below him and he quickly returned to 10000 ft. Had X continued his climb of 2000 FPM, I don't know if he would have collided with Y but it would have been a very near thing. This is the second instance we have had in atl where a departure climbed toward an arrival in response to an RA. In both cases the pilots reported an RA on traffic '700 ft below' and in both cases no traffic existed in that location.

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Original NASA ASRS Text

Title: ACR X ERRONEOUS TCASII RA NON ADHERENCE TO ATC CLRNC HAD LTSS FROM ACR Y.

Narrative: I WAS WORKING S DEP AT ATL TWR. ACR X, A B727, DEPARTED AND CLBED TO 10000 FT. ACR Y, A L101, WAS INBOUND LEVEL AT 11000 FT. BOTH ACFT WERE LEVEL AND TFC WAS GIVEN WHEN THEY WERE STILL 7-8 MI APART. AS THE TARGETS CONVERGED, THE PLT OF ACR X SAID HE WAS CLBING IN RESPONSE TO AN RA. OUR TRAINING IS NOT TO INTERFERE WITH COMPLIANCE TO AN RA, SO WITHOUT TELLING HIM NOT TO CLB, I REISSUED THE TFC, WHICH WAS NOW ALMOST DIRECTLY ABOVE HIM. HE SAID HIS TCASII RPTED TFC 700 FT BELOW HIM AND WAS ADVISING A CLB RATE OF 2000 FPM. I TOLD HIM THERE WAS NOTHING BELOW HIM AND HE QUICKLY RETURNED TO 10000 FT. HAD X CONTINUED HIS CLB OF 2000 FPM, I DON'T KNOW IF HE WOULD HAVE COLLIDED WITH Y BUT IT WOULD HAVE BEEN A VERY NEAR THING. THIS IS THE SECOND INSTANCE WE HAVE HAD IN ATL WHERE A DEP CLBED TOWARD AN ARR IN RESPONSE TO AN RA. IN BOTH CASES THE PLTS RPTED AN RA ON TFC '700 FT BELOW' AND IN BOTH CASES NO TFC EXISTED IN THAT LOCATION.

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.