Operational error.

Attributes
ACN	286263
Time
Date	199410
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : bkw
State Reference	WV
Altitude	msl bound lower : 28000 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 25
ASRS Report	286263
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 26400 vertical : 300
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X jet sbound at FL280. Air carrier Y jet east bound at FL290. Heavy traffic at end of shift/overlapping data blocks/had worked mostly D sides during shift. Descended air carrier Y from FL290 to FL260 do not observe or remember air carrier X jet off his left sbound. When I observed problem it was too late, air carrier Y had passed off air carrier X's left side 400-500 ft above his descending.

Original NASA ASRS Text

Title: OPERROR.

Narrative: ACR X JET SBOUND AT FL280. ACR Y JET E BOUND AT FL290. HVY TFC AT END OF SHIFT/OVERLAPPING DATA BLOCKS/HAD WORKED MOSTLY D SIDES DURING SHIFT. DSNDED ACR Y FROM FL290 TO FL260 DO NOT OBSERVE OR REMEMBER ACR X JET OFF HIS L SBOUND. WHEN I OBSERVED PROB IT WAS TOO LATE, ACR Y HAD PASSED OFF ACR X'S L SIDE 400-500 FT ABOVE HIS DSNDING.

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.