Narrative:

Both pilot and first officer understood a further descent from 9000 to 7000 and commenced same after repeating clearance and call sign. At 8500' indicated, center queried us as to our altitude which we reported. The controller advised us of traffic at 8000' at which point a climb was immediately initiated. The controller then did an about face and decided to have us descend to 7000'. We descended at an extreme rate (1500 FPM) to expedite and avoid the 'traffic'. At this point we were VFR and at no time saw any flight crew. About 40 mi out of gainesville we were told to call the quality assurance people and had the number repeated as the controller was a bit unintelligible at times. Upon landing an attempt was made to call jacksonville center by phone as requested, there was no answer. The next morning the copilot called the quality assurance people and was told that the controller had not cleared us from 9-7000' but told us to maintain 9000 which was acknowledged with a '10-4' and that a traffic warning was issued due to a computer tracked 4.5 mi separation incursion. Neither of us ever use '10-4' in our conversations in the plane, neither of us ever heard a traffic advisory until we had descended to 8500' and we both recall repeating 'leaving 9 for 7' upon hearing our request granted. We do not remember if there was a change of controllers at this particular moment, however, we had a sector change shortly before or during the time this all occurred.

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Original NASA ASRS Text

Title: UNAUTH ALT CHANGE BY PLT. PLT DEVIATION.

Narrative: BOTH PLT AND F/O UNDERSTOOD A FURTHER DSCNT FROM 9000 TO 7000 AND COMMENCED SAME AFTER REPEATING CLRNC AND CALL SIGN. AT 8500' INDICATED, CENTER QUERIED US AS TO OUR ALT WHICH WE REPORTED. THE CTLR ADVISED US OF TFC AT 8000' AT WHICH POINT A CLIMB WAS IMMEDIATELY INITIATED. THE CTLR THEN DID AN ABOUT FACE AND DECIDED TO HAVE US DSND TO 7000'. WE DESCENDED AT AN EXTREME RATE (1500 FPM) TO EXPEDITE AND AVOID THE 'TFC'. AT THIS POINT WE WERE VFR AND AT NO TIME SAW ANY FLT CREW. ABOUT 40 MI OUT OF GAINESVILLE WE WERE TOLD TO CALL THE QUALITY ASSURANCE PEOPLE AND HAD THE NUMBER REPEATED AS THE CTLR WAS A BIT UNINTELLIGIBLE AT TIMES. UPON LNDG AN ATTEMPT WAS MADE TO CALL JACKSONVILLE CENTER BY PHONE AS REQUESTED, THERE WAS NO ANSWER. THE NEXT MORNING THE COPLT CALLED THE QUALITY ASSURANCE PEOPLE AND WAS TOLD THAT THE CTLR HAD NOT CLRED US FROM 9-7000' BUT TOLD US TO MAINTAIN 9000 WHICH WAS ACKNOWLEDGED WITH A '10-4' AND THAT A TFC WARNING WAS ISSUED DUE TO A COMPUTER TRACKED 4.5 MI SEPARATION INCURSION. NEITHER OF US EVER USE '10-4' IN OUR CONVERSATIONS IN THE PLANE, NEITHER OF US EVER HEARD A TFC ADVISORY UNTIL WE HAD DESCENDED TO 8500' AND WE BOTH RECALL REPEATING 'LEAVING 9 FOR 7' UPON HEARING OUR REQUEST GRANTED. WE DO NOT REMEMBER IF THERE WAS A CHANGE OF CTLRS AT THIS PARTICULAR MOMENT, HOWEVER, WE HAD A SECTOR CHANGE SHORTLY BEFORE OR DURING THE TIME THIS ALL OCCURRED.

Data retrieved from NASA's ASRS site as of August 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.