Narrative:

At approximately XX07 P.M., I heard an aircraft call on frequency but I did not hear the entire transmission. From what I heard, I concluded that it was light transport X inbound to bhm from approximately 25 mi northwest. Possibly because of data block overlap, or my own inattn, I did not notice that the aircraft had not been handed off to me. I issued a clearance for the aircraft to proceed to the LOM and descend to 4000'. Approximately 90 seconds later, I received and accepted a handoff from ZTL, thinking the aircraft had been changed to my frequency in advance of the handoff by mistake. The aircraft was at a position closer than I would have normally have expected to get the handoff, but this is not uncommon. As the aircraft was leaving 10500', ZTL called and asked if we were working light transport X. They were advised that he was on our frequency and that he was descending. They called later and requested the altitude of the aircraft and were advised that it was leaving 9000'. They then said the aircraft had been assigned a heading and an altitude of 17000', and that for reasons unknown, the pilot had left their frequency. They did not mention that there had been a conflict with other traffic, and I was not aware of any problems other than previously mentioned. The aircraft was later descended to 2500' and reported the airport insight, cleared for a visibility approach and changed to tower frequency. At the time of the incident, I was working 2 positions combined and monitoring 2 VHF and 2 UHF frequencys. There were no UHF aircraft on frequency at the time. The tapes revealed the pilot reported leaving 17500' for 17000 on initial contact. Had I heard this, I would not have descended the aircraft and would have called ZTL to coordinate. Our LOA with the center specifies that jet and turboprop aircraft at or above 11000' be descending to that altitude. Approximately 15 mins later, ZTL called and advised the bhm supervisor that there had been less than standard separation between light transport X and light transport Y at 16000'. They advised they turned light transport Y to avoid the conflict. I did not see the other aircraft, as my filter limits were not set that high. I feel the main reason for the occurrence was my not hearing the entire transmission of light transport X, and not having him repeat it. I also feel that the pilot jumping the frequency did contribute to the situation. There also appears to be a lack of concern at ZTL about getting inbound aircraft down to lower altitudes. As stated earlier, this is not uncommon and is not addressed by the LOA.

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Original NASA ASRS Text

Title: TRACON RADAR CTLR DESCENDED AN ACFT BEFORE IT WAS RELEASED TO HIS CTL WHICH RESULTED IN LESS THAN STANDARD SEPARATION.

Narrative: AT APPROX XX07 P.M., I HEARD AN ACFT CALL ON FREQ BUT I DID NOT HEAR THE ENTIRE XMISSION. FROM WHAT I HEARD, I CONCLUDED THAT IT WAS LTT X INBND TO BHM FROM APPROX 25 MI NW. POSSIBLY BECAUSE OF DATA BLOCK OVERLAP, OR MY OWN INATTN, I DID NOT NOTICE THAT THE ACFT HAD NOT BEEN HANDED OFF TO ME. I ISSUED A CLRNC FOR THE ACFT TO PROCEED TO THE LOM AND DSND TO 4000'. APPROX 90 SECS LATER, I RECEIVED AND ACCEPTED A HDOF FROM ZTL, THINKING THE ACFT HAD BEEN CHANGED TO MY FREQ IN ADVANCE OF THE HDOF BY MISTAKE. THE ACFT WAS AT A POS CLOSER THAN I WOULD HAVE NORMALLY HAVE EXPECTED TO GET THE HDOF, BUT THIS IS NOT UNCOMMON. AS THE ACFT WAS LEAVING 10500', ZTL CALLED AND ASKED IF WE WERE WORKING LTT X. THEY WERE ADVISED THAT HE WAS ON OUR FREQ AND THAT HE WAS DSNDING. THEY CALLED LATER AND REQUESTED THE ALT OF THE ACFT AND WERE ADVISED THAT IT WAS LEAVING 9000'. THEY THEN SAID THE ACFT HAD BEEN ASSIGNED A HDG AND AN ALT OF 17000', AND THAT FOR REASONS UNKNOWN, THE PLT HAD LEFT THEIR FREQ. THEY DID NOT MENTION THAT THERE HAD BEEN A CONFLICT WITH OTHER TFC, AND I WAS NOT AWARE OF ANY PROBS OTHER THAN PREVIOUSLY MENTIONED. THE ACFT WAS LATER DSNDED TO 2500' AND RPTED THE ARPT INSIGHT, CLRED FOR A VIS APCH AND CHANGED TO TWR FREQ. AT THE TIME OF THE INCIDENT, I WAS WORKING 2 POSITIONS COMBINED AND MONITORING 2 VHF AND 2 UHF FREQS. THERE WERE NO UHF ACFT ON FREQ AT THE TIME. THE TAPES REVEALED THE PLT RPTED LEAVING 17500' FOR 17000 ON INITIAL CONTACT. HAD I HEARD THIS, I WOULD NOT HAVE DSNDED THE ACFT AND WOULD HAVE CALLED ZTL TO COORDINATE. OUR LOA WITH THE CENTER SPECIFIES THAT JET AND TURBOPROP ACFT AT OR ABOVE 11000' BE DSNDING TO THAT ALT. APPROX 15 MINS LATER, ZTL CALLED AND ADVISED THE BHM SUPVR THAT THERE HAD BEEN LTSS BTWN LTT X AND LTT Y AT 16000'. THEY ADVISED THEY TURNED LTT Y TO AVOID THE CONFLICT. I DID NOT SEE THE OTHER ACFT, AS MY FILTER LIMITS WERE NOT SET THAT HIGH. I FEEL THE MAIN REASON FOR THE OCCURRENCE WAS MY NOT HEARING THE ENTIRE XMISSION OF LTT X, AND NOT HAVING HIM REPEAT IT. I ALSO FEEL THAT THE PLT JUMPING THE FREQ DID CONTRIBUTE TO THE SITUATION. THERE ALSO APPEARS TO BE A LACK OF CONCERN AT ZTL ABOUT GETTING INBND ACFT DOWN TO LOWER ALTS. AS STATED EARLIER, THIS IS NOT UNCOMMON AND IS NOT ADDRESSED BY THE LOA.

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.