Air carrier was descended through altitude occupied by another aircraft.

Attributes
ACN	111284
Time
Date	198905
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : cvg
State Reference	OH
Altitude	msl bound lower : 14000 msl bound upper : 15000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : zid
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air taxi
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 16
ASRS Report	111284
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	faa : investigated
Miss Distance	horizontal : 25200 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working the cvg low radar and non radar combined positions at ZID ARTCC. Aircraft #1 was descending to 13000' via atl-ffo-day. Aircraft #2 was at 15000' requesting FL210 routed cvg V5 ape-yye. Latitude sep was lost prior to vertical being established. Aircraft #1 was descending through 17000 to 13000' and was told 'increase rate of descent through 140.' reply was, 'I am at 4000 FPM now.' aircraft #2 was turned 30 degrees left and climbed on FL210. When aircraft #1 passed 14300', aircraft was 4.2 mi away at 15000'. Later study of the incident revealed aircraft #1's rate of descent had changed from 4000 FPM to 1800 FPM at the time sep was lost. Had the pilot advised the controller he could not maintain or increase his rate of descent through 14000', then alternative action may have helped.

Original NASA ASRS Text

Title: ACR WAS DESCENDED THROUGH ALT OCCUPIED BY ANOTHER ACFT.

Narrative: I WAS WORKING THE CVG LOW RADAR AND NON RADAR COMBINED POSITIONS AT ZID ARTCC. ACFT #1 WAS DSNDING TO 13000' VIA ATL-FFO-DAY. ACFT #2 WAS AT 15000' REQUESTING FL210 ROUTED CVG V5 APE-YYE. LAT SEP WAS LOST PRIOR TO VERT BEING ESTABLISHED. ACFT #1 WAS DSNDING THROUGH 17000 TO 13000' AND WAS TOLD 'INCREASE RATE OF DSCNT THROUGH 140.' REPLY WAS, 'I AM AT 4000 FPM NOW.' ACFT #2 WAS TURNED 30 DEGS LEFT AND CLBED ON FL210. WHEN ACFT #1 PASSED 14300', ACFT WAS 4.2 MI AWAY AT 15000'. LATER STUDY OF THE INCIDENT REVEALED ACFT #1'S RATE OF DSCNT HAD CHANGED FROM 4000 FPM TO 1800 FPM AT THE TIME SEP WAS LOST. HAD THE PLT ADVISED THE CTLR HE COULD NOT MAINTAIN OR INCREASE HIS RATE OF DSCNT THROUGH 14000', THEN ALTERNATIVE ACTION MAY HAVE HELPED.

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.