Narrative:

Air carrier X takeoff normal on runway 15 with first officer at the controls. At about 1000' tower switched us to departure control departure clearance was heading 210 degrees and 10000'. We turned to 210 degrees and continued climb after takeoff check was completed. Departure clearance was 300 degrees, but stopped climb at 6000' due to VFR traffic at 6500'. We both cleared right during the turn to 300 degrees. I changed the heading on the MCP. As wings rolled level at about 4900', the first officer engaged the right autoplt and changed the MCP altitude to 6000'. The first officer yelled 'look,' as we both saw traffic at 12 O'clock and slightly high. We both grabbed the yoke and pushed forward. The first officer also disengaged the autoplt and put in some nose down trim. I saw about 5340' on the captain's altimeter, but I do not know if the aircraft was going up or starting down. We leveled at 5000'. I told departure we just had a close one. I said to departure the traffic must have been at 5500' and asked him to check. Departure said he would check with another controller. In a few seconds departure said the traffic was at 5500' and not 6500'. Departure then cleared us to 10000' and ZBW. The evasive action was abrupt, but everyone was seated and there were no injuries. After arrival in atl, a conference call between me, flight control and ATC was held. ATC had determined that an small aircraft Y with no mode C, altitude readout, had been cleared out of 6500' to 5500', but the controller had gotten busy and had failed to change the altitude tag on the scope. Therefore the controller handling my flight did not know of the altitude change of small aircraft Y. The ATC supervisor on the phone with me listened to several parts of the tape during our conversation. I am satisfied that this was a simple case of human error but I am not aware of what events caused the controller to fail to change the altitude tag. I am convinced that had we not seen small aircraft Y and taken evasive action we would have collided at about a 70 degree angle on his left side. Supplemental information from acn 153763: shortly after, we were told to turn to a 300 degree heading and to stop our climb at 6000' because of VFR traffic ahead of us at 6500'. As the captain was occupied talking to departure and selecting the new heading, I engaged the right autoplt and changed the altitude selection from 10000' to 6000', completing these adjustments as we passed 5000' at 250 KTS. I then spotted our traffic, a white, single engine, low wing light aircraft crossing directly ahead and slightly above us, much closer than expected. I immediately pushed forward on the yoke, disengaged the autoplt, and saw the captain pushing forward on his yoke as well our aircraft was briefly in slightly negative G acceleration as we abruptly transitioned from a climb to a shallow descent, bottoming out around 5000' and then resuming our climb. We were close enough to see his side #south and to see sky through his cabin windows. He did not appear to take evasive action.

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Original NASA ASRS Text

Title: ACR X HAD NMAC WITH SMA Y. SEE AND AVOID CONCEPT. CTLR FAILED TO PROPERLY UPDATE ARTS DATA TAG. OPERATIONAL DEVIATION.

Narrative: ACR X TKOF NORMAL ON RWY 15 WITH F/O AT THE CTLS. AT ABOUT 1000' TWR SWITCHED US TO DEP CTL DEP CLRNC WAS HDG 210 DEGS AND 10000'. WE TURNED TO 210 DEGS AND CONTINUED CLB AFTER TKOF CHK WAS COMPLETED. DEP CLRNC WAS 300 DEGS, BUT STOPPED CLB AT 6000' DUE TO VFR TFC AT 6500'. WE BOTH CLRED RIGHT DURING THE TURN TO 300 DEGS. I CHANGED THE HDG ON THE MCP. AS WINGS ROLLED LEVEL AT ABOUT 4900', THE F/O ENGAGED THE RIGHT AUTOPLT AND CHANGED THE MCP ALT TO 6000'. THE F/O YELLED 'LOOK,' AS WE BOTH SAW TFC AT 12 O'CLOCK AND SLIGHTLY HIGH. WE BOTH GRABBED THE YOKE AND PUSHED FORWARD. THE F/O ALSO DISENGAGED THE AUTOPLT AND PUT IN SOME NOSE DOWN TRIM. I SAW ABOUT 5340' ON THE CAPT'S ALTIMETER, BUT I DO NOT KNOW IF THE ACFT WAS GOING UP OR STARTING DOWN. WE LEVELED AT 5000'. I TOLD DEP WE JUST HAD A CLOSE ONE. I SAID TO DEP THE TFC MUST HAVE BEEN AT 5500' AND ASKED HIM TO CHK. DEP SAID HE WOULD CHK WITH ANOTHER CTLR. IN A FEW SECS DEP SAID THE TFC WAS AT 5500' AND NOT 6500'. DEP THEN CLRED US TO 10000' AND ZBW. THE EVASIVE ACTION WAS ABRUPT, BUT EVERYONE WAS SEATED AND THERE WERE NO INJURIES. AFTER ARR IN ATL, A CONFERENCE CALL BTWN ME, FLT CTL AND ATC WAS HELD. ATC HAD DETERMINED THAT AN SMA Y WITH NO MODE C, ALT READOUT, HAD BEEN CLRED OUT OF 6500' TO 5500', BUT THE CTLR HAD GOTTEN BUSY AND HAD FAILED TO CHANGE THE ALT TAG ON THE SCOPE. THEREFORE THE CTLR HANDLING MY FLT DID NOT KNOW OF THE ALT CHANGE OF SMA Y. THE ATC SUPVR ON THE PHONE WITH ME LISTENED TO SEVERAL PARTS OF THE TAPE DURING OUR CONVERSATION. I AM SATISFIED THAT THIS WAS A SIMPLE CASE OF HUMAN ERROR BUT I AM NOT AWARE OF WHAT EVENTS CAUSED THE CTLR TO FAIL TO CHANGE THE ALT TAG. I AM CONVINCED THAT HAD WE NOT SEEN SMA Y AND TAKEN EVASIVE ACTION WE WOULD HAVE COLLIDED AT ABOUT A 70 DEG ANGLE ON HIS LEFT SIDE. SUPPLEMENTAL INFO FROM ACN 153763: SHORTLY AFTER, WE WERE TOLD TO TURN TO A 300 DEG HDG AND TO STOP OUR CLB AT 6000' BECAUSE OF VFR TFC AHEAD OF US AT 6500'. AS THE CAPT WAS OCCUPIED TALKING TO DEP AND SELECTING THE NEW HDG, I ENGAGED THE RIGHT AUTOPLT AND CHANGED THE ALT SELECTION FROM 10000' TO 6000', COMPLETING THESE ADJUSTMENTS AS WE PASSED 5000' AT 250 KTS. I THEN SPOTTED OUR TFC, A WHITE, SINGLE ENG, LOW WING LIGHT ACFT XING DIRECTLY AHEAD AND SLIGHTLY ABOVE US, MUCH CLOSER THAN EXPECTED. I IMMEDIATELY PUSHED FORWARD ON THE YOKE, DISENGAGED THE AUTOPLT, AND SAW THE CAPT PUSHING FORWARD ON HIS YOKE AS WELL OUR ACFT WAS BRIEFLY IN SLIGHTLY NEGATIVE G ACCELERATION AS WE ABRUPTLY TRANSITIONED FROM A CLB TO A SHALLOW DSNT, BOTTOMING OUT AROUND 5000' AND THEN RESUMING OUR CLB. WE WERE CLOSE ENOUGH TO SEE HIS SIDE #S AND TO SEE SKY THROUGH HIS CABIN WINDOWS. HE DID NOT APPEAR TO TAKE EVASIVE ACTION.

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.