Narrative:

Air carrier X departed from atl during a high traffic arrival and departure time. WX was VMC with the first officer flying. Departing east, cleared to 10000', turned over to departure control. We had been further cleared to 14000' and headed 170 degrees when climbing through, then above, scattered clouds. About 6300' the controller called us to, 'maintain 6000'.' I advised that we were climbing through 6300' and that we would stop climb and return to 6000'. While I was speaking the first officer smoothly stopped the climb, reaching about 6450', and descended toward 6000'. The controller called out traffic at our 1-2 O'clock position as I visually observed aircraft Y. I reported to the controller that we had the reported traffic and were leveling at 6000'. About that time aircraft Y passed directly overhead with a sep estimated at 1000'. I reported to the controller that we were clear of aircraft Y and shortly thereafter we were cleared to continue our climb. At no time were we near enough to aircraft Y to require evasive action, since stopping the climb preserved our altitude sep. Although this conflict did not become serious it was only because the controller saw the problem in time for us to correct it. Had he not stopped our climb at that point a collision was a distinct possibility. I had just gotten into performing a checklist at that point which distracted me from looking out. In addition, we had been in and out of scattered clouds early in the climb and I had switched off the landing lights temporarily so we were not as visible to the other aircraft. Aircraft Y showed only the required navigation lights and beacon(south) and I was unable to determine its type. In retrospect, I've noted that I should relegate other duties below watching for traffic, particularly in the terminal area. In atl, as other high density airports, the sky is literally filled with aircraft lights during busy periods and keeping them sorted out is very challenging. One tends to rely on the radar controller, especially in a TCA. I seriously question the validity of see and avoid as a traffic sep tenet in today's environment, but it will always be the final safeguard available to pilots and as such continues to deserve emphasis.

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Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACFT Y. SYSTEM ERROR.

Narrative: ACR X DEPARTED FROM ATL DURING A HIGH TFC ARR AND DEP TIME. WX WAS VMC WITH THE F/O FLYING. DEPARTING E, CLRED TO 10000', TURNED OVER TO DEP CTL. WE HAD BEEN FURTHER CLRED TO 14000' AND HEADED 170 DEGS WHEN CLBING THROUGH, THEN ABOVE, SCATTERED CLOUDS. ABOUT 6300' THE CTLR CALLED US TO, 'MAINTAIN 6000'.' I ADVISED THAT WE WERE CLBING THROUGH 6300' AND THAT WE WOULD STOP CLB AND RETURN TO 6000'. WHILE I WAS SPEAKING THE F/O SMOOTHLY STOPPED THE CLB, REACHING ABOUT 6450', AND DSNDED TOWARD 6000'. THE CTLR CALLED OUT TFC AT OUR 1-2 O'CLOCK POS AS I VISUALLY OBSERVED ACFT Y. I RPTED TO THE CTLR THAT WE HAD THE RPTED TFC AND WERE LEVELING AT 6000'. ABOUT THAT TIME ACFT Y PASSED DIRECTLY OVERHEAD WITH A SEP ESTIMATED AT 1000'. I RPTED TO THE CTLR THAT WE WERE CLR OF ACFT Y AND SHORTLY THEREAFTER WE WERE CLRED TO CONTINUE OUR CLB. AT NO TIME WERE WE NEAR ENOUGH TO ACFT Y TO REQUIRE EVASIVE ACTION, SINCE STOPPING THE CLB PRESERVED OUR ALT SEP. ALTHOUGH THIS CONFLICT DID NOT BECOME SERIOUS IT WAS ONLY BECAUSE THE CTLR SAW THE PROB IN TIME FOR US TO CORRECT IT. HAD HE NOT STOPPED OUR CLB AT THAT POINT A COLLISION WAS A DISTINCT POSSIBILITY. I HAD JUST GOTTEN INTO PERFORMING A CHKLIST AT THAT POINT WHICH DISTRACTED ME FROM LOOKING OUT. IN ADDITION, WE HAD BEEN IN AND OUT OF SCATTERED CLOUDS EARLY IN THE CLB AND I HAD SWITCHED OFF THE LNDG LIGHTS TEMPORARILY SO WE WERE NOT AS VISIBLE TO THE OTHER ACFT. ACFT Y SHOWED ONLY THE REQUIRED NAV LIGHTS AND BEACON(S) AND I WAS UNABLE TO DETERMINE ITS TYPE. IN RETROSPECT, I'VE NOTED THAT I SHOULD RELEGATE OTHER DUTIES BELOW WATCHING FOR TFC, PARTICULARLY IN THE TERMINAL AREA. IN ATL, AS OTHER HIGH DENSITY ARPTS, THE SKY IS LITERALLY FILLED WITH ACFT LIGHTS DURING BUSY PERIODS AND KEEPING THEM SORTED OUT IS VERY CHALLENGING. ONE TENDS TO RELY ON THE RADAR CTLR, ESPECIALLY IN A TCA. I SERIOUSLY QUESTION THE VALIDITY OF SEE AND AVOID AS A TFC SEP TENET IN TODAY'S ENVIRONMENT, BUT IT WILL ALWAYS BE THE FINAL SAFEGUARD AVAILABLE TO PLTS AND AS SUCH CONTINUES TO DESERVE EMPHASIS.

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.