Narrative:

Center cleared us to descend at pilot's discretion to 10000 ft. About a min later, center informs the flight to maintain 12000 ft for traffic at 1 O'clock, 10 mi. Air crew calls tally traffic at 1 O'clock. Center tells crew traffic at 13000 ft at 5 mi no longer a factor. Center is now talking to other aircraft. Air crew is now mi past top of descent and starts descent. About 300 ft below cruise altitude, the crew finally tells center leaving 12000 ft. Center tells aircraft to maintain 12000 ft traffic at 1 O'clock, 10 mi at 11000 ft. Flight crew climbs to 12000 ft until clear of traffic and is reclred to descend to 10000 ft. Human performance considerations: flcs should make sure of clearance after change of instruction. Controllers should be specific in why clearance changed and number of traffic.

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Original NASA ASRS Text

Title: FREIGHTER GIVEN DSCNT, RECLRED TO MAINTAIN 12000 FT. HEAR 'NO FACTOR' COMMENT TO ANOTHER ACFT AND BEGIN DSCNT.

Narrative: CENTER CLRED US TO DSND AT PLT'S DISCRETION TO 10000 FT. ABOUT A MIN LATER, CENTER INFORMS THE FLT TO MAINTAIN 12000 FT FOR TFC AT 1 O'CLOCK, 10 MI. AIR CREW CALLS TALLY TFC AT 1 O'CLOCK. CENTER TELLS CREW TFC AT 13000 FT AT 5 MI NO LONGER A FACTOR. CENTER IS NOW TALKING TO OTHER ACFT. AIR CREW IS NOW MI PAST TOP OF DSCNT AND STARTS DSCNT. ABOUT 300 FT BELOW CRUISE ALT, THE CREW FINALLY TELLS CENTER LEAVING 12000 FT. CENTER TELLS ACFT TO MAINTAIN 12000 FT TFC AT 1 O'CLOCK, 10 MI AT 11000 FT. FLC CLBS TO 12000 FT UNTIL CLR OF TFC AND IS RECLRED TO DSND TO 10000 FT. HUMAN PERFORMANCE CONSIDERATIONS: FLCS SHOULD MAKE SURE OF CLRNC AFTER CHANGE OF INSTRUCTION. CTLRS SHOULD BE SPECIFIC IN WHY CLRNC CHANGED AND NUMBER OF TFC.

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.