LESS THAN STANDARD SEPARATION BETWEEN CLIMBING AND DESCENDING ACFT ON CROSSING COURSES. INCIDENT JUST AFTER POSITION RELIEF HAD TAKEN PLACE.

Narrative

I WAS WORKING AS A RADAR CTLR AT ZDC ARTCC ON SECTOR 19; 3/MON/88. I TOOK THE HDOF ON LGT X AT FL240 AND DSNDED HIM TO FL210; I ACCEPTED THE HDOF ON MLG Y CLBING TO FL210. I THOUGHT THE MLG Y WAS TURNING NE BOUND OVER OOD. I BRIEFED THE NEXT CTLR AND WALKED AWAY. HE CALLED ME BACK AND SHOWED ME WHAT HAPPENED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: SEPARATION WAS LOST BTWN THE LGT AND THE MLG. ACFT WERE ON XING COURSES AND RPTR HAD THOUGHT THEY WOULD BE PARALLEL. ACFT GOT WITHIN 1.4 MI AND 400' BY ODEP READOUT. THE CTLR THAT RELIEVED THE RPTR HAD BEEN PLUGGED IN FOR ABOUT 2-3 MINS AND THEN WAS GIVEN THE SECTOR AS THE RPTR TOOK A BREAK. RPTR WAS STILL IN THE AREA WHEN THE RELIEVING CTLR SAID TO COME BACK AND SEE WHAT WAS HAPPENING. RELIEVING CTLR WAS VERY EXPERIENCED AND HAD TRAINED THE RPTR. TFC VOL WAS LIGHT; 6 ACFT; AND WX WAS NOT A FACTOR. CTLR WORKING SECTOR AT TIME OF LTSS WAS WORKING ALONE IN COMBINED POS CONFIGN. RPTR ADMITS THAT RELIEF BRIEFING WAS NOT THOROUGH AND THAT IS WHY THE RPTR WAS CLASSIFIED AS CTLR (A) IN THIS INCIDENT. RELIEVER WAS CTLR (B). ACTION TAKEN BY RELIEVER WAS INCOMPLETE TO MAINTAIN LEGAL SEP. NOT KNOWN IF TFC WAS GIVEN OR SIGHTED.