Narrative:

I combined the arrival sector to my departure sector and received the briefing from the arrival controller. The arrival controller told me about very strong winds from the southwest and that he was crossing over the top of the localizer and turning into the left downwind to better slow the aircraft to make the sequence on to final. He briefed me on about 6 arrs including the 2 aircraft in question; air carrier X and air carrier Y. He told me air carrier Y was established on the localizer level at 5000 ft. He told me air carrier X was out of 8000 ft for 6000 ft and since air carrier X was from the southwest I agreed with him about crossing over the top of final. He put air carrier X on a 090 degree heading to go over the top of air carrier Y. I then keyed up the frequencys and my first transmission was to descend air carrier Y to 3000 ft. The arrival controller walked down to give me his arrival strips when we both heard the conflict alert alarm. I noticed air carrier X descending through 5800 ft and air carrier Y descending through 4700 ft. I immediately climbed air carrier X back to 6000 ft and expedited air carrier Y through 4000 ft to maintain 3000 ft while separation might have been lost at that point. The controller then told me that he forgot that he descended air carrier X to 5000 ft. Contributing factors: due to forced overtime; this is my 12TH day worked out of the last 13 days. I might have caught the descent rate better on air carrier X. The arrival controller was going home within 10 mins so he was rushing. Our airspace (mtv sector) on a south flow is very small and compact to sequence the arrs; we bump up against iad airspace; there is no margin for error. I also believe that the supervisor should have stayed longer since we had a heavy arrival flow due to bad WX earlier. The bottom line: the arrival controller should have descended air carrier Y and stopped air carrier X at 6000 ft.

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Original NASA ASRS Text

Title: PCT CTLR DESCRIBED CONFLICT AFTER COMBINING DEP AND ARR POSITIONS WHEN RELIEVED CTLR FAILED TO BRIEF AND DESCEND ONE OF TWO ARR ACFT.

Narrative: I COMBINED THE ARR SECTOR TO MY DEP SECTOR AND RECEIVED THE BRIEFING FROM THE ARR CTLR. THE ARR CTLR TOLD ME ABOUT VERY STRONG WINDS FROM THE SW AND THAT HE WAS XING OVER THE TOP OF THE LOC AND TURNING INTO THE L DOWNWIND TO BETTER SLOW THE ACFT TO MAKE THE SEQUENCE ON TO FINAL. HE BRIEFED ME ON ABOUT 6 ARRS INCLUDING THE 2 ACFT IN QUESTION; ACR X AND ACR Y. HE TOLD ME ACR Y WAS ESTABLISHED ON THE LOC LEVEL AT 5000 FT. HE TOLD ME ACR X WAS OUT OF 8000 FT FOR 6000 FT AND SINCE ACR X WAS FROM THE SW I AGREED WITH HIM ABOUT XING OVER THE TOP OF FINAL. HE PUT ACR X ON A 090 DEG HDG TO GO OVER THE TOP OF ACR Y. I THEN KEYED UP THE FREQS AND MY FIRST XMISSION WAS TO DSND ACR Y TO 3000 FT. THE ARR CTLR WALKED DOWN TO GIVE ME HIS ARR STRIPS WHEN WE BOTH HEARD THE CONFLICT ALERT ALARM. I NOTICED ACR X DSNDING THROUGH 5800 FT AND ACR Y DSNDING THROUGH 4700 FT. I IMMEDIATELY CLBED ACR X BACK TO 6000 FT AND EXPEDITED ACR Y THROUGH 4000 FT TO MAINTAIN 3000 FT WHILE SEPARATION MIGHT HAVE BEEN LOST AT THAT POINT. THE CTLR THEN TOLD ME THAT HE FORGOT THAT HE DSNDED ACR X TO 5000 FT. CONTRIBUTING FACTORS: DUE TO FORCED OVERTIME; THIS IS MY 12TH DAY WORKED OUT OF THE LAST 13 DAYS. I MIGHT HAVE CAUGHT THE DSCNT RATE BETTER ON ACR X. THE ARR CTLR WAS GOING HOME WITHIN 10 MINS SO HE WAS RUSHING. OUR AIRSPACE (MTV SECTOR) ON A S FLOW IS VERY SMALL AND COMPACT TO SEQUENCE THE ARRS; WE BUMP UP AGAINST IAD AIRSPACE; THERE IS NO MARGIN FOR ERROR. I ALSO BELIEVE THAT THE SUPVR SHOULD HAVE STAYED LONGER SINCE WE HAD A HVY ARR FLOW DUE TO BAD WX EARLIER. THE BOTTOM LINE: THE ARR CTLR SHOULD HAVE DSNDED ACR Y AND STOPPED ACR X AT 6000 FT.

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.