Air carrier was descended to occupied altitude resulting in less than standard separation.

Attributes
ACN	120834
Time
Date	198908
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ott
State Reference	MD
Altitude	msl bound lower : 11000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute airway : v308
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : developmental
ASRS Report	120834
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance
Consequence	Other
Miss Distance	horizontal : 0 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

A swbound aircraft was at 14,000 on V229 and 2 wbound air carriers on V308. The first wbound aircraft was at 12,000 descending to 9000. I had the second wbound descending to 13,000 (expeditiously) to get under the 1400 traffic, and stay vertically separated. I had previously coordinated with balance approach to hand off at 9000 and 11,000. At this time I was told to descend air carrier 3 to 11,000 by my OJT instructor. I verbally questioned this to him whereas he responded 'descend him and we'll monitor it. 'I questioned because air carrier 2 was only out of 120 for 9000. So then I issued clearance to descend and maintain 11,000. Shortly after that air carrier 2's altitude started to XXX-out and the conflict alert went off. My OJT instructor seized the frequency and stated 'I've got it' to me. He asked air carrier 2 to say altitude. Reply 'just leaving 11,000', then told air carrier 3 to climb immediately to 12,000. I assume to try and avoid loss of separation. When air carrier 2 left 10,000, air carrier 3 was descended to 11,000 and both were switched. I don't know if it can be considered a 'contributing factor' but air carrier 2's slow response to leave 11,000 was definitely a factor in the matter. Supplemental information from acn 120700: received clearance from ZDC to continue descent to 9000' (vertical speed 1000 FPM) speed reduction in progress to 250 KIAS. Observed air carrier 3. Descended directly over our aircraft to an altitude of 11,000'. Air carrier 3 was then advised to climb to 12,000'.

Original NASA ASRS Text

Title: ACR WAS DESCENDED TO OCCUPIED ALT RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: A SWBOUND ACFT WAS AT 14,000 ON V229 AND 2 WBOUND AIR CARRIERS ON V308. THE FIRST WBOUND ACFT WAS AT 12,000 DESCENDING TO 9000. I HAD THE SECOND WBOUND DESCENDING TO 13,000 (EXPEDITIOUSLY) TO GET UNDER THE 1400 TFC, AND STAY VERTICALLY SEPARATED. I HAD PREVIOUSLY COORDINATED WITH BAL APCH TO HAND OFF AT 9000 AND 11,000. AT THIS TIME I WAS TOLD TO DSND ACR 3 TO 11,000 BY MY OJT INSTRUCTOR. I VERBALLY QUESTIONED THIS TO HIM WHEREAS HE RESPONDED 'DSND HIM AND WE'LL MONITOR IT. 'I QUESTIONED BECAUSE ACR 2 WAS ONLY OUT OF 120 FOR 9000. SO THEN I ISSUED CLRNC TO DSND AND MAINTAIN 11,000. SHORTLY AFTER THAT ACR 2'S ALT STARTED TO XXX-OUT AND THE CONFLICT ALERT WENT OFF. MY OJT INSTRUCTOR SEIZED THE FREQ AND STATED 'I'VE GOT IT' TO ME. HE ASKED ACR 2 TO SAY ALT. REPLY 'JUST LEAVING 11,000', THEN TOLD ACR 3 TO CLIMB IMMEDIATELY TO 12,000. I ASSUME TO TRY AND AVOID LOSS OF SEPARATION. WHEN ACR 2 LEFT 10,000, ACR 3 WAS DESCENDED TO 11,000 AND BOTH WERE SWITCHED. I DON'T KNOW IF IT CAN BE CONSIDERED A 'CONTRIBUTING FACTOR' BUT ACR 2'S SLOW RESPONSE TO LEAVE 11,000 WAS DEFINITELY A FACTOR IN THE MATTER. SUPPLEMENTAL INFORMATION FROM ACN 120700: RECEIVED CLRNC FROM ZDC TO CONTINUE DSCNT TO 9000' (VERT SPEED 1000 FPM) SPEED REDUCTION IN PROGRESS TO 250 KIAS. OBSERVED ACR 3. DESCENDED DIRECTLY OVER OUR ACFT TO AN ALT OF 11,000'. ACR 3 WAS THEN ADVISED TO CLIMB TO 12,000'.

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.