Narrative:

Approximately xa:30 I started to relieve departure control low at washington tower. During the briefing, I heard him tell a medium large transport X to turn right heading 150 degree and climb to 13000'. He also briefed me that an small transport Y was heading 120 degree at 10000'. Medium large transport X and small transport Y were 10-15 mi apart. Small transport Y at 10000', medium large transport X turning in front of small transport Y leaving 8000' for 13000'. I was subsequently briefed on other factors to flight and additional traffic. Shortly after assuming control of the position, the controller who I had relieved brought to my attention that medium large transport X did not appear to be turning. When I questioned medium large transport X he advised that he received a climb but no turn. I told medium large transport X to turn to a heading of 180 degree expedite his turn and his climb through 11000' for 13000'. I then turned small transport Y heading 090 degree, at this time medium large transport X and small transport Y were about 8 mi apart with medium large transport X leaving 9500'. Medium large transport X turn brought him to within 3 mi of small transport Y. Maybe closer. I thought 2, the controller I relieved said 3 mi. Although the conflict alert had activated by the computer the switch patch did not appear to activate as is the case when sep is lost. I am 100 percent positive the previous controller issued the instructions to medium large transport X. Neither I or the other controller can recall medium large transport X readback. Just making relief I was not prepared to have to make such a decision that had such a small margin of error. Although medium large transport X had not started his turn when I questioned him, our airspace constraints to the northwest of washington (over gai) lead me to turn him, naturally anticipating better performance from the medium large transport X aircraft and crew, rather than continue and pass behind the small transport Y and take on the burden of remaining clear of iad and bwi airspace.

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Original NASA ASRS Text

Title: RELIEVING DEP CTLR CLIMBED MLG THROUGH ALT OF SMT WITH LESS THAN STANDARD SEPARATION.

Narrative: APPROX XA:30 I STARTED TO RELIEVE DEP CTL LOW AT WASHINGTON TWR. DURING THE BRIEFING, I HEARD HIM TELL A MLG X TO TURN R HDG 150 DEG AND CLB TO 13000'. HE ALSO BRIEFED ME THAT AN SMT Y WAS HDG 120 DEG AT 10000'. MLG X AND SMT Y WERE 10-15 MI APART. SMT Y AT 10000', MLG X TURNING IN FRONT OF SMT Y LEAVING 8000' FOR 13000'. I WAS SUBSEQUENTLY BRIEFED ON OTHER FACTORS TO FLT AND ADDITIONAL TFC. SHORTLY AFTER ASSUMING CTL OF THE POS, THE CTLR WHO I HAD RELIEVED BROUGHT TO MY ATTN THAT MLG X DID NOT APPEAR TO BE TURNING. WHEN I QUESTIONED MLG X HE ADVISED THAT HE RECEIVED A CLB BUT NO TURN. I TOLD MLG X TO TURN TO A HDG OF 180 DEG EXPEDITE HIS TURN AND HIS CLB THROUGH 11000' FOR 13000'. I THEN TURNED SMT Y HDG 090 DEG, AT THIS TIME MLG X AND SMT Y WERE ABOUT 8 MI APART WITH MLG X LEAVING 9500'. MLG X TURN BROUGHT HIM TO WITHIN 3 MI OF SMT Y. MAYBE CLOSER. I THOUGHT 2, THE CTLR I RELIEVED SAID 3 MI. ALTHOUGH THE CONFLICT ALERT HAD ACTIVATED BY THE COMPUTER THE SWITCH PATCH DID NOT APPEAR TO ACTIVATE AS IS THE CASE WHEN SEP IS LOST. I AM 100 PERCENT POSITIVE THE PREVIOUS CTLR ISSUED THE INSTRUCTIONS TO MLG X. NEITHER I OR THE OTHER CTLR CAN RECALL MLG X READBACK. JUST MAKING RELIEF I WAS NOT PREPARED TO HAVE TO MAKE SUCH A DECISION THAT HAD SUCH A SMALL MARGIN OF ERROR. ALTHOUGH MLG X HAD NOT STARTED HIS TURN WHEN I QUESTIONED HIM, OUR AIRSPACE CONSTRAINTS TO THE NW OF WASHINGTON (OVER GAI) LEAD ME TO TURN HIM, NATURALLY ANTICIPATING BETTER PERFORMANCE FROM THE MLG X ACFT AND CREW, RATHER THAN CONTINUE AND PASS BEHIND THE SMT Y AND TAKE ON THE BURDEN OF REMAINING CLR OF IAD AND BWI AIRSPACE.

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.