Narrative:

Medium large transport XXX following large transport zxx to ewr (eastbound, 15 mi in trail). Mdt Y northbound at 13000' direct avp after deviating east of course for WX. Large transport zxx then medium large transport XXX both cleared to 14000'. Next 3 radio contact necessary to obtain medium large transport's attention for speed reduction. After clearing 13000' traffic, I cleared the large transport to cross sweet intersection at and maintain 7000'. Medium large transport XXX answered clearance, which was not caught by controller. Medium large transport XXX issued, 'traffic 12 O'clock, 13000', northbound, 8 mi, lower when clear.' response: 'medium large transport XXX.' controller noticed medium large transport XXX's data block descending and climbed medium large transport XXX immediately to 14000'. Loss of sep occurred. Supplemental information from acn 145485: during the slate run arrival I received ATC instructions to 'cross sweet at 7000,' and replied, 'blank X90, cross sweet at 7000.' there was no response from ATC. Shortly thereafter first officer began descent from 14000' and I called center saying, 'blank X90, descending to 7, also asking for information concerning which way traffic might be deviating around trws ahead.' ATC quickly replied, 'blank X90, climb to level 140 immediately! That clearance was for blank blank Q90!' we climbed back (approximately 1500' deviation) to 14000' and reported level. Factors: not insisting on radio response from ATC, concentration on trws ahead, expecting descend clearance within only a few mi of position, day in and day out, and fatigue--crew up since X30Z.

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Original NASA ASRS Text

Title: PLT READBACK DESCENT CLRNC FOR ANOTHER ACFT. ACFT STARTED DESCENT WHICH RESULTED IN LESS THAN STANDARD SEPARATION.

Narrative: MLG XXX FOLLOWING LGT ZXX TO EWR (EBND, 15 MI IN TRAIL). MDT Y NBND AT 13000' DIRECT AVP AFTER DEVIATING E OF COURSE FOR WX. LGT ZXX THEN MLG XXX BOTH CLRED TO 14000'. NEXT 3 RADIO CONTACT NECESSARY TO OBTAIN MLG'S ATTN FOR SPD REDUCTION. AFTER CLRING 13000' TFC, I CLRED THE LGT TO CROSS SWEET INTXN AT AND MAINTAIN 7000'. MLG XXX ANSWERED CLRNC, WHICH WAS NOT CAUGHT BY CTLR. MLG XXX ISSUED, 'TFC 12 O'CLOCK, 13000', NBND, 8 MI, LOWER WHEN CLR.' RESPONSE: 'MLG XXX.' CTLR NOTICED MLG XXX'S DATA BLOCK DSNDING AND CLBED MLG XXX IMMEDIATELY TO 14000'. LOSS OF SEP OCCURRED. SUPPLEMENTAL INFO FROM ACN 145485: DURING THE SLATE RUN ARR I RECEIVED ATC INSTRUCTIONS TO 'CROSS SWEET AT 7000,' AND REPLIED, 'BLANK X90, CROSS SWEET AT 7000.' THERE WAS NO RESPONSE FROM ATC. SHORTLY THEREAFTER F/O BEGAN DSNT FROM 14000' AND I CALLED CENTER SAYING, 'BLANK X90, DSNDING TO 7, ALSO ASKING FOR INFO CONCERNING WHICH WAY TFC MIGHT BE DEVIATING AROUND TRWS AHEAD.' ATC QUICKLY REPLIED, 'BLANK X90, CLB TO LEVEL 140 IMMEDIATELY! THAT CLRNC WAS FOR BLANK BLANK Q90!' WE CLBED BACK (APPROX 1500' DEVIATION) TO 14000' AND RPTED LEVEL. FACTORS: NOT INSISTING ON RADIO RESPONSE FROM ATC, CONCENTRATION ON TRWS AHEAD, EXPECTING DSND CLRNC WITHIN ONLY A FEW MI OF POS, DAY IN AND DAY OUT, AND FATIGUE--CREW UP SINCE X30Z.

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.