Narrative:

Assigned mxe departure sector, phila departure control xa:40-xb:05 UTC tue july 1990. Combined with dupont low satellite sector. Swap procedures new york ARTCC in effect. Tower delays up to 200 min due to previous stop of all mxe/ptw departure due to earlier thunderstorms. In trail restrictions to mxe/ptw VOR's of 15-20 mi in effect due to volume from earlier stoppages. Due to above backlog of aircraft ARTS IIIA system was at capacity of discrete beacon codes and number of aircraft in primary tab list. A non discrete beacon code of 1600 assigned to aircraft when discrete 4 digit codes are all used up when system becomes overloaded. These 1600 beacon codes must be track started manually. At time of occurrence approximately 10-11 aircraft were on frequency and 5 aircraft with no ARTS tag. Due to this and the spacing from the tower which was 3 mi I lost track of several aircraft while attempting to positively identify above aircraft. With aid of tower extra ARTS personnel I was able to vector aircraft for spacing to mxe and ptw VOR using both vertical and lateral sep, however, in the earlier confusion of trying to positively identify non-tagged targets, I assigned 9000' to air carrier X to ptw and 9000' to air carrier Y to mxe thinking I assigned 10000' to air carrier Y. Air carrier X vectored 090 degree for spacing and air carrier Y vectored direct mxe both at 9000'. At last second I noticed both aircraft at same altitude. Immediately climbed air carrier Y to 10000' and turned air carrier X 360 degree heading. Control instructions issued too late. Air carrier X reported visibility with air carrier Y and vice versa. Air carrier X then requested to report near midair collision and air carrier Y responded 'we concur'. One aircraft requested an explanation after stating 'philly that was close.' I attempted to explain I had in my opinion too many aircraft at once to adequately sep due to extra procedures I had to initiate to start manual tags. I advised air carrier Y that I thought I had assigned 10000' but in reality only 9000' was assigned. I was responsible and I clearly erred however, I lost valuable time earlier in the scenario doing tasks which are normally automatic. At time of system error both had ARTS tags. Callback conversation with reporter revealed the following information. Reporter gave ATC experience. Incident occurred just outside the TCA. System error filed by facility, but not known if near midair collision filed. Reporter was working 10-11 aircraft with only one aircraft on code 1600. Air carrier X was a departure and distracted reporter at a time when he was busy by being on the wrong code. In addition, another aircraft also came off on the wrong code. Supervisor was busy at another position when the incident happened. When the reporter asked for more help, the supervisor added two more controllers to help, but it was too late. Swap stands for 'severe WX advisory procedures.' reporter was decertified for 4 days before returning to control duties. Supplemental information from acn 152703. After extensive 'south' turns vectors, we were assigned a 090 degree heading, maintain 9000'. Just prior to roll out, I saw landing lights of an opp direction aircraft and alerted the copilot. As it became obvious that we were at the same altitude, I stopped the turn and then turned back to the left (we had ben in a right turn) and climbed to about 9300'. We passed an large transport jet approximately 1/4 to 1/2 mi off our right at about the same altitude. It was obvious the controller was overloaded, even remarking 'oh my god' several occasions. Supplemental information from acn 152986. Shortly after we heard controller say, 'oh god less than a mi' second officer made first visibility contact with air carrier X after hearing ATC's comment and advised captain 'traffic 12 O'clock.' captain took immediate evasive action by the following. Turned left 30 degree bank, 10 degree nose down pitch, power levers to idle. Observed air carrier X in left bank with nose up attitude. ATC did not advise of conflicting traffic. Afterward the ATC controller stated 'I was overloaded with too many aircraft, I thought I cleared you to 10000'. It's my fault, and we have started filing a report.'

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Original NASA ASRS Text

Title: A DEPARTING ACR LGT CAME IN CLOSE PROX TO A PREVIOUS DEPARTING ACR LGT AND REPORTED A NMAC.

Narrative: ASSIGNED MXE DEP SECTOR, PHILA DEP CTL XA:40-XB:05 UTC TUE JULY 1990. COMBINED WITH DUPONT LOW SATELLITE SECTOR. SWAP PROCS NEW YORK ARTCC IN EFFECT. TWR DELAYS UP TO 200 MIN DUE TO PREVIOUS STOP OF ALL MXE/PTW DEP DUE TO EARLIER TSTMS. IN TRAIL RESTRICTIONS TO MXE/PTW VOR'S OF 15-20 MI IN EFFECT DUE TO VOLUME FROM EARLIER STOPPAGES. DUE TO ABOVE BACKLOG OF ACFT ARTS IIIA SYS WAS AT CAPACITY OF DISCRETE BEACON CODES AND NUMBER OF ACFT IN PRIMARY TAB LIST. A NON DISCRETE BEACON CODE OF 1600 ASSIGNED TO ACFT WHEN DISCRETE 4 DIGIT CODES ARE ALL USED UP WHEN SYS BECOMES OVERLOADED. THESE 1600 BEACON CODES MUST BE TRACK STARTED MANUALLY. AT TIME OF OCCURRENCE APPROX 10-11 ACFT WERE ON FREQ AND 5 ACFT WITH NO ARTS TAG. DUE TO THIS AND THE SPACING FROM THE TWR WHICH WAS 3 MI I LOST TRACK OF SEVERAL ACFT WHILE ATTEMPTING TO POSITIVELY IDENT ABOVE ACFT. WITH AID OF TWR EXTRA ARTS PERSONNEL I WAS ABLE TO VECTOR ACFT FOR SPACING TO MXE AND PTW VOR USING BOTH VERT AND LATERAL SEP, HOWEVER, IN THE EARLIER CONFUSION OF TRYING TO POSITIVELY IDENT NON-TAGGED TARGETS, I ASSIGNED 9000' TO ACR X TO PTW AND 9000' TO ACR Y TO MXE THINKING I ASSIGNED 10000' TO ACR Y. ACR X VECTORED 090 DEG FOR SPACING AND ACR Y VECTORED DIRECT MXE BOTH AT 9000'. AT LAST SEC I NOTICED BOTH ACFT AT SAME ALT. IMMEDIATELY CLBED ACR Y TO 10000' AND TURNED ACR X 360 DEG HDG. CTL INSTRUCTIONS ISSUED TOO LATE. ACR X RPTED VIS WITH ACR Y AND VICE VERSA. ACR X THEN REQUESTED TO RPT NMAC AND ACR Y RESPONDED 'WE CONCUR'. ONE ACFT REQUESTED AN EXPLANATION AFTER STATING 'PHILLY THAT WAS CLOSE.' I ATTEMPTED TO EXPLAIN I HAD IN MY OPINION TOO MANY ACFT AT ONCE TO ADEQUATELY SEP DUE TO EXTRA PROCS I HAD TO INITIATE TO START MANUAL TAGS. I ADVISED ACR Y THAT I THOUGHT I HAD ASSIGNED 10000' BUT IN REALITY ONLY 9000' WAS ASSIGNED. I WAS RESPONSIBLE AND I CLRLY ERRED HOWEVER, I LOST VALUABLE TIME EARLIER IN THE SCENARIO DOING TASKS WHICH ARE NORMALLY AUTOMATIC. AT TIME OF SYS ERROR BOTH HAD ARTS TAGS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR GAVE ATC EXPERIENCE. INCIDENT OCCURRED JUST OUTSIDE THE TCA. SYS ERROR FILED BY FAC, BUT NOT KNOWN IF NMAC FILED. RPTR WAS WORKING 10-11 ACFT WITH ONLY ONE ACFT ON CODE 1600. ACR X WAS A DEP AND DISTRACTED RPTR AT A TIME WHEN HE WAS BUSY BY BEING ON THE WRONG CODE. IN ADDITION, ANOTHER ACFT ALSO CAME OFF ON THE WRONG CODE. SUPVR WAS BUSY AT ANOTHER POS WHEN THE INCIDENT HAPPENED. WHEN THE RPTR ASKED FOR MORE HELP, THE SUPVR ADDED TWO MORE CTLRS TO HELP, BUT IT WAS TOO LATE. SWAP STANDS FOR 'SEVERE WX ADVISORY PROCS.' RPTR WAS DECERTIFIED FOR 4 DAYS BEFORE RETURNING TO CTL DUTIES. SUPPLEMENTAL INFO FROM ACN 152703. AFTER EXTENSIVE 'S' TURNS VECTORS, WE WERE ASSIGNED A 090 DEG HDG, MAINTAIN 9000'. JUST PRIOR TO ROLL OUT, I SAW LNDG LIGHTS OF AN OPP DIRECTION ACFT AND ALERTED THE COPLT. AS IT BECAME OBVIOUS THAT WE WERE AT THE SAME ALT, I STOPPED THE TURN AND THEN TURNED BACK TO THE L (WE HAD BEN IN A R TURN) AND CLBED TO ABOUT 9300'. WE PASSED AN LGT JET APPROX 1/4 TO 1/2 MI OFF OUR R AT ABOUT THE SAME ALT. IT WAS OBVIOUS THE CTLR WAS OVERLOADED, EVEN REMARKING 'OH MY GOD' SEVERAL OCCASIONS. SUPPLEMENTAL INFO FROM ACN 152986. SHORTLY AFTER WE HEARD CTLR SAY, 'OH GOD LESS THAN A MI' S/O MADE FIRST VIS CONTACT WITH ACR X AFTER HEARING ATC'S COMMENT AND ADVISED CAPT 'TFC 12 O'CLOCK.' CAPT TOOK IMMEDIATE EVASIVE ACTION BY THE FOLLOWING. TURNED L 30 DEG BANK, 10 DEG NOSE DOWN PITCH, PWR LEVERS TO IDLE. OBSERVED ACR X IN L BANK WITH NOSE UP ATTITUDE. ATC DID NOT ADVISE OF CONFLICTING TFC. AFTERWARD THE ATC CTLR STATED 'I WAS OVERLOADED WITH TOO MANY ACFT, I THOUGHT I CLRED YOU TO 10000'. IT'S MY FAULT, AND WE HAVE STARTED FILING A RPT.'

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.