Less than standard separation between two air carrier. Operational error.

Attributes
ACN	106043
Time
Date	198903
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : esl
State Reference	WV
Altitude	msl bound lower : 30000 msl bound upper : 31100
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	106043
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	other other : unspecified atc
Resolutory Action	controller : issued new clearance none taken : unable
Consequence	faa : investigated
Miss Distance	horizontal : 27000 vertical : 1100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was given clearance X25 west esl FL290. Air carrier Y was given clearance X25 west esl FL250. Situation was monitored from beginning to end. When X started his descent there was approximately 10 miles. I then started Y down. Y showed an initial descent rate of 2500 to 2750 FPM. When I saw that separation was getting minimal I turned X 15 degrees right. No evasive action was required. This error occurred because of bad judgement. More positive control should have been used.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN TWO ACR. OPERATIONAL ERROR.

Narrative: ACR X WAS GIVEN CLRNC X25 W ESL FL290. ACR Y WAS GIVEN CLRNC X25 W ESL FL250. SITUATION WAS MONITORED FROM BEGINNING TO END. WHEN X STARTED HIS DSCNT THERE WAS APPROX 10 MILES. I THEN STARTED Y DOWN. Y SHOWED AN INITIAL DSCNT RATE OF 2500 TO 2750 FPM. WHEN I SAW THAT SEPARATION WAS GETTING MINIMAL I TURNED X 15 DEGS RIGHT. NO EVASIVE ACTION WAS REQUIRED. THIS ERROR OCCURRED BECAUSE OF BAD JUDGEMENT. MORE POSITIVE CONTROL SHOULD HAVE BEEN USED.

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.