Controller describes operational error due to lack of automated radar terminal system [ARTS]; which ...

Narrative:

The automated radar terminal system [ARTS] system went out and we were using primary targets for separation. Aircraft X came over from ZLC15 with multiple coordinations on descent and position due to the outage. Coordination was performed by the tower for a departing [aircraft Y] on course through the final approach course for the active runway. Aircraft X was cleared for the visual and the VFR aircraft Y was misidentified through position correlation between the tower and radar controllers. The VFR aircraft Y was never in communication with the radar controller. Instructions for collision avoidance were given to the wrong aircraft. The problem is we are always doing this type of maintenance during normal business hours and we should be doing it overnight when traffic volumes are lowest and the margin of safety would be higher. This was an unsafe situation and would not have taken place had we not given up the ARTS system.we should be giving different shift assignments to maintenance personnel when monthly/yearly pms [preventative maintenance] are due. Trying to accomplish these things during normal business hours introduces risk into the system unnecessarily. No overtime would be needed if they were just assigned a 1600 to midnight shift once or twice a month to accomplish these pms.

Original NASA ASRS Text

Title: Controller describes operational error due to lack of Automated Radar Terminal System [ARTS]; which had been released to Maintenance for preventative maintenance.

Narrative: The Automated Radar Terminal System [ARTS] System went out and we were using primary targets for separation. Aircraft X came over from ZLC15 with multiple coordinations on descent and position due to the outage. Coordination was performed by the Tower for a departing [Aircraft Y] on course through the final approach course for the active runway. Aircraft X was cleared for the visual and the VFR Aircraft Y was misidentified through position correlation between the Tower and Radar controllers. The VFR Aircraft Y was never in communication with the Radar Controller. Instructions for collision avoidance were given to the wrong aircraft. The problem is we are always doing this type of maintenance during normal business hours and we should be doing it overnight when traffic volumes are lowest and the margin of safety would be higher. This was an unsafe situation and would not have taken place had we not given up the ARTS system.We should be giving different shift assignments to maintenance personnel when monthly/yearly PMs [Preventative Maintenance] are due. Trying to accomplish these things during normal business hours introduces risk into the system unnecessarily. No overtime would be needed if they were just assigned a 1600 to midnight shift once or twice a month to accomplish these PMs.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1187885
Time
Date	201407
Local Time Of Day	1201-1800
Place
Locale Reference	BIL.TRACON
State Reference	MT
Environment
Light	Daylight
Aircraft 1
Make Model Name	Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft High Wing 1 Eng Retractable Gear
Flight Phase	Climb
Route In Use	None
Flight Plan	VFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 2
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance

Controller describes operational error due to lack of automated radar terminal system [ARTS]; which had been released to maintenance for preventative maintenance.