Narrative:

I was working aircraft X who required a lower altitude and route coordination due to a nonstandard routing. I started the coordination process then was distraction by multiple landline calls that interrupted my thought process. When I returned to handling aircraft X; I thought I had descended the aircraft to FL330; when in fact I descended the aircraft to FL320. That was the altitude the traffic was at. I switched the aircraft to the next frequency. That controller missed the bad altitude on check-in and the flts passed tail-to-tail; then standard separation was lost. It was my 4TH day of work. I had a quick turn from the previous shift I worked; approximately 4 hours rest. Prior evening shifts were busy with deviating traffic; tmu rertes; etc.

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Original NASA ASRS Text

Title: ZDC CTLR DESCRIBED OPERROR AT FL330 WHEN DESCENDING ACFT WAS ASSIGNED AN OCCUPIED ALT.

Narrative: I WAS WORKING ACFT X WHO REQUIRED A LOWER ALT AND RTE COORD DUE TO A NONSTANDARD ROUTING. I STARTED THE COORD PROCESS THEN WAS DISTR BY MULTIPLE LANDLINE CALLS THAT INTERRUPTED MY THOUGHT PROCESS. WHEN I RETURNED TO HANDLING ACFT X; I THOUGHT I HAD DSNDED THE ACFT TO FL330; WHEN IN FACT I DSNDED THE ACFT TO FL320. THAT WAS THE ALT THE TFC WAS AT. I SWITCHED THE ACFT TO THE NEXT FREQ. THAT CTLR MISSED THE BAD ALT ON CHK-IN AND THE FLTS PASSED TAIL-TO-TAIL; THEN STANDARD SEPARATION WAS LOST. IT WAS MY 4TH DAY OF WORK. I HAD A QUICK TURN FROM THE PREVIOUS SHIFT I WORKED; APPROX 4 HRS REST. PRIOR EVENING SHIFTS WERE BUSY WITH DEVIATING TFC; TMU RERTES; ETC.

Data retrieved from NASA's ASRS site as of January 2009 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.