Narrative:

ATC cleared our flight from 20000' to cross 30 east of obk VOR at 10000'. Passing approximately 14000' the copilot and I both observed an air carrier medium large transport at 11 O'clock and about 1/2 mi, at what appeared to be 13000', heading northeast. I requested the air carrier altitude. ATC replied that they showed one primary target, but they weren't working him. A few mins later ATC said the target was at 13000'. After landing at ord, I called the ATC supervisor for that area, and he indicated they were investigating the incident. Supplemental information from acn 140929: departed ord eastbound at about XA17. Somehow ord approach control lost contact with the aircraft, whose transponder became inoperative. No handoff to the center was made, but the aircraft was switched to the cribb sector frequency, which then tried to locate the aircraft. I was working kubbs sector (as a trnee), which is adjacent to cribb. At XA25, air carrier Y inbound to ord was on my frequency, descending out of 14000' to cross 30 east of obk at 10000'. Air carrier Y was 50 east of obk, and inquired as to whether I had traffic for him. As I told him, I only saw a primary target, fast moving, off his right. My first thought was that the primary was high altitude traffic that I was getting as a hit from a second radar site. In this area, these occurrences are not uncommon. In addition, we had other numerous primary targets (anomalous propagation) caused by temperature inversion. When air carrier Y reported the traffic was below him, my trainer and I tried to figure out why we had a primary target out there above 10000'. The air carrier X jet was subsequently idented, as his transponder came on about 10 mi further east. I would say the main causes involved were air carrier X's faulty transponder, ord approach's failure to realize that, and the unreliable center radar, which routinely gives us false targets. Since we are accustomed to false targets, and we expected a real target to also be false. Supplemental information from acn 140776: air carrier X IFR from ord to bdl via elx, crl, preferential arrival route, checked on frequency level at 13000'. At the time I was busy, so I acknowledged his call with, 'roger.' I had not received a radar handoff or any other coordination on this aircraft from ord approach. I then asked the aircraft his position. The reply was 35 mi west of elx VOR. The cribb sector owns airspace 35 mi west of elx (my airspace). I became concerned, for there were other aircraft in that vicinity, yet no air carrier X, limited data block or primary target. Supplemental information from acn 140799: while conducting OJT on north and east departure an aircraft departing was observed west/O working transponder. The deviation issued instructions to the aircraft to recycle, at which time the transponder came on indicating 4444. The aircraft was issued a turn and climbed to 13000'. Subsequently the aircraft again dropped his tag prior to the automated handoff to the center. He was shipped to the center with the deviation's assumption that the aircraft was already off. The scope and the automated handoff had been effected. This incident occurred during a peak departure rush eastbound.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR DEP PROCEEDED UNDETECTED BY ATC AND CAME IN CLOSE PROX TO ANOTHER ACR.

Narrative: ATC CLRED OUR FLT FROM 20000' TO CROSS 30 E OF OBK VOR AT 10000'. PASSING APPROX 14000' THE COPLT AND I BOTH OBSERVED AN ACR MLG AT 11 O'CLOCK AND ABOUT 1/2 MI, AT WHAT APPEARED TO BE 13000', HDG NE. I REQUESTED THE ACR ALT. ATC REPLIED THAT THEY SHOWED ONE PRIMARY TARGET, BUT THEY WEREN'T WORKING HIM. A FEW MINS LATER ATC SAID THE TARGET WAS AT 13000'. AFTER LNDG AT ORD, I CALLED THE ATC SUPVR FOR THAT AREA, AND HE INDICATED THEY WERE INVESTIGATING THE INCIDENT. SUPPLEMENTAL INFO FROM ACN 140929: DEPARTED ORD EBND AT ABOUT XA17. SOMEHOW ORD APCH CTL LOST CONTACT WITH THE ACFT, WHOSE XPONDER BECAME INOP. NO HDOF TO THE CENTER WAS MADE, BUT THE ACFT WAS SWITCHED TO THE CRIBB SECTOR FREQ, WHICH THEN TRIED TO LOCATE THE ACFT. I WAS WORKING KUBBS SECTOR (AS A TRNEE), WHICH IS ADJACENT TO CRIBB. AT XA25, ACR Y INBND TO ORD WAS ON MY FREQ, DSNDING OUT OF 14000' TO CROSS 30 E OF OBK AT 10000'. ACR Y WAS 50 E OF OBK, AND INQUIRED AS TO WHETHER I HAD TFC FOR HIM. AS I TOLD HIM, I ONLY SAW A PRIMARY TARGET, FAST MOVING, OFF HIS RIGHT. MY FIRST THOUGHT WAS THAT THE PRIMARY WAS HIGH ALT TFC THAT I WAS GETTING AS A HIT FROM A SECOND RADAR SITE. IN THIS AREA, THESE OCCURRENCES ARE NOT UNCOMMON. IN ADDITION, WE HAD OTHER NUMEROUS PRIMARY TARGETS (ANOMALOUS PROPAGATION) CAUSED BY TEMP INVERSION. WHEN ACR Y RPTED THE TFC WAS BELOW HIM, MY TRAINER AND I TRIED TO FIGURE OUT WHY WE HAD A PRIMARY TARGET OUT THERE ABOVE 10000'. THE ACR X JET WAS SUBSEQUENTLY IDENTED, AS HIS XPONDER CAME ON ABOUT 10 MI FURTHER E. I WOULD SAY THE MAIN CAUSES INVOLVED WERE ACR X'S FAULTY XPONDER, ORD APCH'S FAILURE TO REALIZE THAT, AND THE UNRELIABLE CENTER RADAR, WHICH ROUTINELY GIVES US FALSE TARGETS. SINCE WE ARE ACCUSTOMED TO FALSE TARGETS, AND WE EXPECTED A REAL TARGET TO ALSO BE FALSE. SUPPLEMENTAL INFO FROM ACN 140776: ACR X IFR FROM ORD TO BDL VIA ELX, CRL, PREFERENTIAL ARR RTE, CHKED ON FREQ LEVEL AT 13000'. AT THE TIME I WAS BUSY, SO I ACKNOWLEDGED HIS CALL WITH, 'ROGER.' I HAD NOT RECEIVED A RADAR HDOF OR ANY OTHER COORD ON THIS ACFT FROM ORD APCH. I THEN ASKED THE ACFT HIS POS. THE REPLY WAS 35 MI W OF ELX VOR. THE CRIBB SECTOR OWNS AIRSPACE 35 MI W OF ELX (MY AIRSPACE). I BECAME CONCERNED, FOR THERE WERE OTHER ACFT IN THAT VICINITY, YET NO ACR X, LIMITED DATA BLOCK OR PRIMARY TARGET. SUPPLEMENTAL INFO FROM ACN 140799: WHILE CONDUCTING OJT ON N AND E DEP AN ACFT DEPARTING WAS OBSERVED W/O WORKING XPONDER. THE DEV ISSUED INSTRUCTIONS TO THE ACFT TO RECYCLE, AT WHICH TIME THE XPONDER CAME ON INDICATING 4444. THE ACFT WAS ISSUED A TURN AND CLBED TO 13000'. SUBSEQUENTLY THE ACFT AGAIN DROPPED HIS TAG PRIOR TO THE AUTOMATED HDOF TO THE CENTER. HE WAS SHIPPED TO THE CENTER WITH THE DEV'S ASSUMPTION THAT THE ACFT WAS ALREADY OFF. THE SCOPE AND THE AUTOMATED HDOF HAD BEEN EFFECTED. THIS INCIDENT OCCURRED DURING A PEAK DEP RUSH EBND.

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.