Narrative:

At XA41Z, large transport X nebound in level flight at FL240, was issued 2 communications transfer instructions. Light transport Y was, at that time, proceeding sbound in level flight at FL240. I feel certain that I did not accept the handoff on light transport Y. As specified by facility operations standards, the controller to whom large transport X was transferred was required to descend the aircraft below my altitude stratum upon initial contact or notify me that he/she was unable to do so. Taking into account the mileage between the 2 aircraft, in conjunction with the facility operations standards, these 2 aircraft were not, in my opinion, in conflict at XA41Z. I received no notification that the florence low controller was unable to descend large transport X. Had I been made aware that the aircraft had not changed frequencys, there was more than sufficient time to take steps to avoid the incident. Large transport X continued in level flight, and came into confliction with light transport Y. At XA43Z, I issued light transport Y an immediate turn to a heading of 270 in an attempt to avoid an error. At the same time, large transport X contacted me. I advised large transport X to make an immediate turn to a heading of 090 degrees. Large transport X, instead of acknowledging my clearance, replied with a report on a TCASII alert. Unaware that large transport X was in a climb, I issued a descent clearance to FL210. (The florence low controller had approved descent into his airspace). Only then did large transport X acknowledge my immediate clearance by asking what heading I wanted him to fly. By this time, the error had occurred, and separation was increasing, so I cleared large transport X direct to sdz. I then instructed large transport X to contact ZDC liberty low who by now had a handoff on the aircraft. At approximately XA47Z, large transport X was still on the aiken high frequency, and had to again be told to change frequencys. Supplemental information from acn 192656. We were on a flight from atl to rdu. Approximately XX43 local, 40 NM southwest of sandhill VOR at 24000 ft, jax center called. The transmission was cut out. We tried 3 times to call back, but with no answer. Our TCASII gave a RA telling us to climb. We climbed immediately toward 24500 ft. TCASII indicated the other aircraft 400 ft below us. We never saw the traffic. Another call to jax center was successful. We remained on that frequency (127.87) for several mins. The controller was relieved shortly by another controller. This new controller had us contact jax on another frequency. This new sector controller said they had tried to contact us 3 times. The remainder of the flight was uneventful. There definitely seemed to be a breakdown in communications. The TCASII did its job and possibly prevented a mid air.

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Original NASA ASRS Text

Title: FREQ CHANGE MISSED BY ACR LGT PLUS FREQ CONGESTION CAUSES LTSS WITH AN LTT AT SAME ALT. TCASII RA ON LGT CAUSES ALTDEV.

Narrative: AT XA41Z, LGT X NEBOUND IN LEVEL FLT AT FL240, WAS ISSUED 2 COMS TRANSFER INSTRUCTIONS. LTT Y WAS, AT THAT TIME, PROCEEDING SBOUND IN LEVEL FLT AT FL240. I FEEL CERTAIN THAT I DID NOT ACCEPT THE HDOF ON LTT Y. AS SPECIFIED BY FACILITY OPS STANDARDS, THE CTLR TO WHOM LGT X WAS TRANSFERRED WAS REQUIRED TO DSND THE ACFT BELOW MY ALT STRATUM UPON INITIAL CONTACT OR NOTIFY ME THAT HE/SHE WAS UNABLE TO DO SO. TAKING INTO ACCOUNT THE MILEAGE BTWN THE 2 ACFT, IN CONJUNCTION WITH THE FACILITY OPS STANDARDS, THESE 2 ACFT WERE NOT, IN MY OPINION, IN CONFLICT AT XA41Z. I RECEIVED NO NOTIFICATION THAT THE FLORENCE LOW CTLR WAS UNABLE TO DSND LGT X. HAD I BEEN MADE AWARE THAT THE ACFT HAD NOT CHANGED FREQS, THERE WAS MORE THAN SUFFICIENT TIME TO TAKE STEPS TO AVOID THE INCIDENT. LGT X CONTINUED IN LEVEL FLT, AND CAME INTO CONFLICTION WITH LTT Y. AT XA43Z, I ISSUED LTT Y AN IMMEDIATE TURN TO A HDG OF 270 IN AN ATTEMPT TO AVOID AN ERROR. AT THE SAME TIME, LGT X CONTACTED ME. I ADVISED LGT X TO MAKE AN IMMEDIATE TURN TO A HDG OF 090 DEGS. LGT X, INSTEAD OF ACKNOWLEDGING MY CLRNC, REPLIED WITH A RPT ON A TCASII ALERT. UNAWARE THAT LGT X WAS IN A CLB, I ISSUED A DSCNT CLRNC TO FL210. (THE FLORENCE LOW CTLR HAD APPROVED DSCNT INTO HIS AIRSPACE). ONLY THEN DID LGT X ACKNOWLEDGE MY IMMEDIATE CLRNC BY ASKING WHAT HDG I WANTED HIM TO FLY. BY THIS TIME, THE ERROR HAD OCCURRED, AND SEPARATION WAS INCREASING, SO I CLRED LGT X DIRECT TO SDZ. I THEN INSTRUCTED LGT X TO CONTACT ZDC LIBERTY LOW WHO BY NOW HAD A HDOF ON THE ACFT. AT APPROX XA47Z, LGT X WAS STILL ON THE AIKEN HIGH FREQ, AND HAD TO AGAIN BE TOLD TO CHANGE FREQS. SUPPLEMENTAL INFO FROM ACN 192656. WE WERE ON A FLT FROM ATL TO RDU. APPROX XX43 LCL, 40 NM SW OF SANDHILL VOR AT 24000 FT, JAX CENTER CALLED. THE XMISSION WAS CUT OUT. WE TRIED 3 TIMES TO CALL BACK, BUT WITH NO ANSWER. OUR TCASII GAVE A RA TELLING US TO CLB. WE CLBED IMMEDIATELY TOWARD 24500 FT. TCASII INDICATED THE OTHER ACFT 400 FT BELOW US. WE NEVER SAW THE TFC. ANOTHER CALL TO JAX CENTER WAS SUCCESSFUL. WE REMAINED ON THAT FREQ (127.87) FOR SEVERAL MINS. THE CTLR WAS RELIEVED SHORTLY BY ANOTHER CTLR. THIS NEW CTLR HAD US CONTACT JAX ON ANOTHER FREQ. THIS NEW SECTOR CTLR SAID THEY HAD TRIED TO CONTACT US 3 TIMES. THE REMAINDER OF THE FLT WAS UNEVENTFUL. THERE DEFINITELY SEEMED TO BE A BREAKDOWN IN COMS. THE TCASII DID ITS JOB AND POSSIBLY PREVENTED A MID AIR.

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.