Narrative:

I was working the calvert intermediate sector by myself. I had been there for over 1 hour working moderate traffic west/O incident. Mlt X, an fgt aircraft, was on my frequency at 12000'. Air carrier Y, an medium large transport aircraft, was also on my frequency at 14000' and was landing at ric. I issued air carrier Y a descent clearance with a crossing restriction to be level at 9000'. I thought he would be well under mlt X before I lost latitude sep. I was wrong. He maintained altitude, then proceeded to descend at about 3500 FPM. When I realized there was going to be a conflict, air carrier Y's mode C indicated 13400', so I told him to stop his descent at 13000'. He responded that he would climb back up to 13000'. His descent continued down to 12400' where he leveled for 20-30 seconds before climbing back up. In the mean time, I issued about a 110 degree turn to mlt X who immediately read back the clearance correctly. About 10 seconds later mlt X questioned the assigned heading. 2 more times I issued the heading to him. Some 25 seconds after he acknowledged the initial heading he began his turn. By that time, minimum sep was lost. I think there were several causes to this problem. First, during the week preceding this event I had driven over 2000 mi and had minimal sleep due to the illness of a family member. My mind was not completely on my work, by any means, and I recognized the problem much later than I normally would have. Secondly, air carrier Y, I think, forgot about the restriction until I reminded him, thus necessitating a later and steeper than normal descent. And finally, I think mlt X had a less than adequate radio in it because he questioned the clearance twice. Then a couple of mins after the incident I lost total radio contact with him on my normal frequency and had to revert to calling him on guard 243.0.

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Original NASA ASRS Text

Title: ACR WAS ISSUED A DESCENT THROUGH AN OCCUPIED ALT RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: I WAS WORKING THE CALVERT INTERMEDIATE SECTOR BY MYSELF. I HAD BEEN THERE FOR OVER 1 HR WORKING MODERATE TFC W/O INCIDENT. MLT X, AN FGT ACFT, WAS ON MY FREQ AT 12000'. ACR Y, AN MLG ACFT, WAS ALSO ON MY FREQ AT 14000' AND WAS LNDG AT RIC. I ISSUED ACR Y A DSNT CLRNC WITH A XING RESTRICTION TO BE LEVEL AT 9000'. I THOUGHT HE WOULD BE WELL UNDER MLT X BEFORE I LOST LAT SEP. I WAS WRONG. HE MAINTAINED ALT, THEN PROCEEDED TO DSND AT ABOUT 3500 FPM. WHEN I REALIZED THERE WAS GOING TO BE A CONFLICT, ACR Y'S MODE C INDICATED 13400', SO I TOLD HIM TO STOP HIS DSNT AT 13000'. HE RESPONDED THAT HE WOULD CLB BACK UP TO 13000'. HIS DSNT CONTINUED DOWN TO 12400' WHERE HE LEVELED FOR 20-30 SECS BEFORE CLBING BACK UP. IN THE MEAN TIME, I ISSUED ABOUT A 110 DEG TURN TO MLT X WHO IMMEDIATELY READ BACK THE CLRNC CORRECTLY. ABOUT 10 SECS LATER MLT X QUESTIONED THE ASSIGNED HDG. 2 MORE TIMES I ISSUED THE HDG TO HIM. SOME 25 SECS AFTER HE ACKNOWLEDGED THE INITIAL HDG HE BEGAN HIS TURN. BY THAT TIME, MINIMUM SEP WAS LOST. I THINK THERE WERE SEVERAL CAUSES TO THIS PROB. FIRST, DURING THE WK PRECEDING THIS EVENT I HAD DRIVEN OVER 2000 MI AND HAD MINIMAL SLEEP DUE TO THE ILLNESS OF A FAMILY MEMBER. MY MIND WAS NOT COMPLETELY ON MY WORK, BY ANY MEANS, AND I RECOGNIZED THE PROB MUCH LATER THAN I NORMALLY WOULD HAVE. SECONDLY, ACR Y, I THINK, FORGOT ABOUT THE RESTRICTION UNTIL I REMINDED HIM, THUS NECESSITATING A LATER AND STEEPER THAN NORMAL DSNT. AND FINALLY, I THINK MLT X HAD A LESS THAN ADEQUATE RADIO IN IT BECAUSE HE QUESTIONED THE CLRNC TWICE. THEN A COUPLE OF MINS AFTER THE INCIDENT I LOST TOTAL RADIO CONTACT WITH HIM ON MY NORMAL FREQ AND HAD TO REVERT TO CALLING HIM ON GUARD 243.0.

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.