Air carrier X had less than standard separation from air carrier Y. System error.

Attributes
ACN	178964
Time
Date	199105
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : aml
State Reference	VA
Altitude	msl bound lower : 9000 msl bound upper : 9000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 22 controller supervisory : 10
ASRS Report	178964
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : anomaly accepted
Consequence	faa : investigated
Miss Distance	horizontal : 25800 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X from over mol doccs iad was being vectored behind air carrier Y who was out of west en route to doccs iad. While this was going on, my other 2 events were occurring. Air carrier X was on a 350 degree then 2 more headings to fall behind air carrier Y. Air carrier X was at 90 and air carrier Y was descending to 90. This was in my mind the only event which I thought I had complete control. At no time did I think I had less than 5 mi. But the computer proved me wrong. The only suggestion I could give is that this situation that occurs every day at this same time has to be worked on and corrected. As I said in the other report, it happens only for about 30 mins each day. In all my 30 some odd yrs of controling and supervision, I have never seen a situation where a sector could blow up as fast as this and deteriorate just as fast.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: ACR X FROM OVER MOL DOCCS IAD WAS BEING VECTORED BEHIND ACR Y WHO WAS OUT OF W ENRTE TO DOCCS IAD. WHILE THIS WAS GOING ON, MY OTHER 2 EVENTS WERE OCCURRING. ACR X WAS ON A 350 DEG THEN 2 MORE HDGS TO FALL BEHIND ACR Y. ACR X WAS AT 90 AND ACR Y WAS DSNDING TO 90. THIS WAS IN MY MIND THE ONLY EVENT WHICH I THOUGHT I HAD COMPLETE CTL. AT NO TIME DID I THINK I HAD LESS THAN 5 MI. BUT THE COMPUTER PROVED ME WRONG. THE ONLY SUGGESTION I COULD GIVE IS THAT THIS SITUATION THAT OCCURS EVERY DAY AT THIS SAME TIME HAS TO BE WORKED ON AND CORRECTED. AS I SAID IN THE OTHER RPT, IT HAPPENS ONLY FOR ABOUT 30 MINS EACH DAY. IN ALL MY 30 SOME ODD YRS OF CTLING AND SUPERVISION, I HAVE NEVER SEEN A SITUATION WHERE A SECTOR COULD BLOW UP AS FAST AS THIS AND DETERIORATE JUST AS FAST.

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.