Controller descended small transport to occupied altitude with less than standard separation.

Attributes
ACN	193701
Time
Date	199111
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gsb
State Reference	NC
Altitude	msl bound lower : 14400 msl bound upper : 15000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Route In Use	enroute airway : zdc
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Retractable Gear
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 4 controller radar : 2
ASRS Report	193701
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
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : anomaly accepted
Consequence	faa : investigated
Miss Distance	horizontal : 14400 vertical : 600
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I just sat down to work R25 sector. As soon as small transport X entered my airspace, I descended that aircraft to get that propeller below jets going to rdu. Small transport X was northbound at 15000 direct to iso VORTAC. I never saw the limited data block on small aircraft Y until the conflict alert went off. When I assumed that position from a training developmental, I never saw the data block on small aircraft Y, nor did I see a limited data block. The conflict alert went off after it appeared the 2 aircraft passed each other. It is possible that data block timed out or that the previous controller took it off the scope. There were numerous data blocks in the area of the occurrence. The data block on small transport X was wward to the position off its target, possibly covering the 14000 limited data block on the small aircraft Y.

Original NASA ASRS Text

Title: CTLR DSNDED SMT TO OCCUPIED ALT WITH LTSS.

Narrative: I JUST SAT DOWN TO WORK R25 SECTOR. AS SOON AS SMT X ENTERED MY AIRSPACE, I DSNDED THAT ACFT TO GET THAT PROP BELOW JETS GOING TO RDU. SMT X WAS NBOUND AT 15000 DIRECT TO ISO VORTAC. I NEVER SAW THE LIMITED DATA BLOCK ON SMA Y UNTIL THE CONFLICT ALERT WENT OFF. WHEN I ASSUMED THAT POS FROM A TRAINING DEVELOPMENTAL, I NEVER SAW THE DATA BLOCK ON SMA Y, NOR DID I SEE A LIMITED DATA BLOCK. THE CONFLICT ALERT WENT OFF AFTER IT APPEARED THE 2 ACFT PASSED EACH OTHER. IT IS POSSIBLE THAT DATA BLOCK TIMED OUT OR THAT THE PREVIOUS CTLR TOOK IT OFF THE SCOPE. THERE WERE NUMEROUS DATA BLOCKS IN THE AREA OF THE OCCURRENCE. THE DATA BLOCK ON SMT X WAS WWARD TO THE POS OFF ITS TARGET, POSSIBLY COVERING THE 14000 LIMITED DATA BLOCK ON THE SMA Y.

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.