Air carrier X descended through altitude occupied by air carrier Y.

Attributes
ACN	112169
Time
Date	198905
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : fcm airport : msp
State Reference	MN
Altitude	msl bound lower : 6000 msl bound upper : 7000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : msp
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 5
ASRS Report	112169
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe inflight encounter : weather non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 9000 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was vectoring air carrier X to final approach course of msp descending from 7000 to 5000' MSL. An aircraft, air carrier Y turbo jet, was being vectored at 6000' MSL by departure control on a westerly heading. There was a cold front moving through the area with severe thunderstorms in vicinity causing considerable route deviation for most aircraft. In my interest to provide a smoother altitude and vector clear of a known thunderstorm cell near the airport, I prematurely descended air carrier X into the proximity of the air carrier Y turbojet. By the time the error was detected, sep standards had been compromised. Air carrier X was a commuter descending from 7000' MSL to 5000' MSL on a radar vector to final approach course for runway 11R at msp.

Original NASA ASRS Text

Title: ACR X DESCENDED THROUGH ALT OCCUPIED BY ACR Y.

Narrative: I WAS VECTORING ACR X TO FINAL APCH COURSE OF MSP DSNDING FROM 7000 TO 5000' MSL. AN ACFT, ACR Y TURBO JET, WAS BEING VECTORED AT 6000' MSL BY DEP CTL ON A WESTERLY HDG. THERE WAS A COLD FRONT MOVING THROUGH THE AREA WITH SEVERE TSTMS IN VICINITY CAUSING CONSIDERABLE ROUTE DEVIATION FOR MOST ACFT. IN MY INTEREST TO PROVIDE A SMOOTHER ALT AND VECTOR CLR OF A KNOWN TSTM CELL NEAR THE ARPT, I PREMATURELY DSNDED ACR X INTO THE PROX OF THE ACR Y TURBOJET. BY THE TIME THE ERROR WAS DETECTED, SEP STANDARDS HAD BEEN COMPROMISED. ACR X WAS A COMMUTER DSNDING FROM 7000' MSL TO 5000' MSL ON A RADAR VECTOR TO FINAL APCH COURSE FOR RWY 11R AT MSP.

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.