ARTCC radar controller failed to provide radar or altitude separation between aircraft under his con...

Attributes
ACN	143567
Time
Date	199004
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : stl
State Reference	MO
Altitude	msl bound lower : 26000 msl bound upper : 26000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zkc
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	143567
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	faa : investigated
Miss Distance	horizontal : 7200 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Light transport X was descending to FL270. Medium large transport Y was at FL260. Ntap readout later indicated the light transport X was at FL268 to FL270 while FL270 was temporarily entered in the data block. The light transport X was subsequently descended to F240 opp direction with medium large transport Y. C/a never activated and the 'snitch' patch never went off. The light transport X pilot brought the error to my attention by requesting the altitude of the traffic he just passed. At the closest point they were 1.2 mi and 700'. Although C/a often activates when temporary altitudes are used, it didn't activate this time. More attention on my part would have rectified the problem, but a little help from automation system would have been appreciated.

Original NASA ASRS Text

Title: ARTCC RADAR CTLR FAILED TO PROVIDE RADAR OR ALT SEPARATION BETWEEN ACFT UNDER HIS CONTROL.

Narrative: LTT X WAS DSNDING TO FL270. MLG Y WAS AT FL260. NTAP READOUT LATER INDICATED THE LTT X WAS AT FL268 TO FL270 WHILE FL270 WAS TEMPORARILY ENTERED IN THE DATA BLOCK. THE LTT X WAS SUBSEQUENTLY DSNDED TO F240 OPP DIRECTION WITH MLG Y. C/A NEVER ACTIVATED AND THE 'SNITCH' PATCH NEVER WENT OFF. THE LTT X PLT BROUGHT THE ERROR TO MY ATTN BY REQUESTING THE ALT OF THE TFC HE JUST PASSED. AT THE CLOSEST POINT THEY WERE 1.2 MI AND 700'. ALTHOUGH C/A OFTEN ACTIVATES WHEN TEMPORARY ALTS ARE USED, IT DIDN'T ACTIVATE THIS TIME. MORE ATTN ON MY PART WOULD HAVE RECTIFIED THE PROB, BUT A LITTLE HELP FROM AUTOMATION SYS WOULD HAVE BEEN APPRECIATED.

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.

ARTCC radar controller failed to provide radar or altitude separation between aircraft under his control.