Stp local controller alerted to near midair collision with conflict alert and GA pilot report.

Attributes
ACN	526389
Time
Date	200110
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : stp.airport
State Reference	MN
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : stp.tower artcc : zkc.artcc
Operator	general aviation : personal
Make Model Name	Cheetah, Tiger, Traveler
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : stp.tower
Operator	other
Make Model Name	Beechcraft, Beech Aircraft Corp Undifferentiated or Other Model
Flight Phase	descent : approach
Person 1
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
ASRS Report	526389
Person 2
Affiliation	other
Function	flight crew : single pilot
Events
Anomaly	conflict : nmac non adherence : far
Independent Detector	atc equipment : conflict alert
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew faa : investigated
Miss Distance	horizontal : 0 vertical : 75
Supplementary
Problem Areas	Flight Crew Human Performance Airspace Structure
Primary Problem	Flight Crew Human Performance

Narrative:

I was working local control. Aircraft X was on an IFR approach to runway 32 at stp. I was alerted when the conflict alert sounded. Aircraft Y was on approximately a 6 mi final and I observed a VFR target passing to the east of aircraft Y. Aircraft Y then reported an near midair collision. I said 'roger.' when aircraft Y landed, I gave him the tower number.

Original NASA ASRS Text

Title: STP LCL CTLR ALERTED TO NMAC WITH CONFLICT ALERT AND GA PLT RPT.

Narrative: I WAS WORKING LCL CTL. ACFT X WAS ON AN IFR APCH TO RWY 32 AT STP. I WAS ALERTED WHEN THE CONFLICT ALERT SOUNDED. ACFT Y WAS ON APPROX A 6 MI FINAL AND I OBSERVED A VFR TARGET PASSING TO THE E OF ACFT Y. ACFT Y THEN RPTED AN NMAC. I SAID 'ROGER.' WHEN ACFT Y LANDED, I GAVE HIM THE TWR NUMBER.

Data retrieved from NASA's ASRS site as of July 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.