Air carrier was inadvertently descended to an altitude occupied by another aircraft.

Attributes
ACN	110793
Time
Date	198905
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : brv
State Reference	VA
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	110793
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : developmental
ASRS Report	110797
Events
Anomaly	non adherence : published procedure non adherence : required legal separation other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was cleared to 10000' with air carrier Y in proximity. OJT was in progress and I was the instrument. Traffic was heavy (approximately 20 aircraft) and complex. I was distracted by another traffic situation and did not catch the trnee clearing the air carrier X to 10000' instead of 11000' as was the standard procedure. The problem was discovered when the ca triggered the 'snitch' patch. There was no evasive action taken by either aircraft. I feel that the situation occurred because I was just returning from 10 days vacation and was not quite 'up to speed' to conduct OJT with heavy traffic. Recommend a few hours to work traffic after vacation to get timing back. Situation occurred 12 mins after signing on sector.

Original NASA ASRS Text

Title: ACR WAS INADVERTENTLY DESCENDED TO AN ALT OCCUPIED BY ANOTHER ACFT.

Narrative: ACR X WAS CLRED TO 10000' WITH ACR Y IN PROX. OJT WAS IN PROGRESS AND I WAS THE INSTR. TFC WAS HVY (APPROX 20 ACFT) AND COMPLEX. I WAS DISTRACTED BY ANOTHER TFC SITUATION AND DID NOT CATCH THE TRNEE CLRING THE ACR X TO 10000' INSTEAD OF 11000' AS WAS THE STANDARD PROC. THE PROB WAS DISCOVERED WHEN THE CA TRIGGERED THE 'SNITCH' PATCH. THERE WAS NO EVASIVE ACTION TAKEN BY EITHER ACFT. I FEEL THAT THE SITUATION OCCURRED BECAUSE I WAS JUST RETURNING FROM 10 DAYS VACATION AND WAS NOT QUITE 'UP TO SPD' TO CONDUCT OJT WITH HVY TFC. RECOMMEND A FEW HRS TO WORK TFC AFTER VACATION TO GET TIMING BACK. SITUATION OCCURRED 12 MINS AFTER SIGNING ON SECTOR.

Data retrieved from NASA's ASRS site as of August 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.