Narrative:

I was flying left seat as pilot in command with a second in command pilot in the right seat. We were on an IFR flight plan in VFR conditions and were receiving vectors from wichita [TRACON] to intercept the ILS for runway 19 aao which was our final destination. After clearance to descend to 4000 and vectors to intercept the inbound course the controller advised traffic; a primary target at our location as I was turning and descending to intercept the localizer. Then the controller advised us to change to the advisory frequency. At that point I was turning inbound in the course and immediately stopped the descent while looking for the reported traffic. The sic changed to the advisory frequency; and established radio contact with the pilot of the C172. As that pilot was advising us that our aircraft was passing overhead of his aircraft; I noticed the TCAS system display a target within 300 ft of our aircraft. The sic radioed the pilot of the C172 we were on an active medevac flight and asked if he would clear the area while we completed our approach and landing into aao. He agreed and we were able to complete our approach and landing into aao without further incident or delay. At the time of this incident the aircraft flight and navigation systems were operating properly to the best of my recollection. In my opinion the controller should have had us remain on the [TRACON] frequency to assist us in remaining clear of that primary target.

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Original NASA ASRS Text

Title: Air taxi Captain reported experiencing a NMAC with a C172 on approach to the non-Towered AAO airport.

Narrative: I was flying left seat as pilot in command with a second in command pilot in the right seat. We were on an IFR flight plan in VFR conditions and were receiving vectors from Wichita [TRACON] to intercept the ILS for Runway 19 AAO which was our final destination. After clearance to descend to 4000 and vectors to intercept the inbound course the controller advised traffic; a primary target at our location as I was turning and descending to intercept the localizer. Then the controller advised us to change to the advisory frequency. At that point I was turning inbound in the course and immediately stopped the descent while looking for the reported traffic. The SIC changed to the advisory frequency; and established radio contact with the pilot of the C172. As that pilot was advising us that our aircraft was passing overhead of his aircraft; I noticed the TCAS system display a target within 300 ft of our aircraft. The SIC radioed the pilot of the C172 we were on an active Medevac flight and asked if he would clear the area while we completed our approach and landing into AAO. He agreed and we were able to complete our approach and landing into AAO without further incident or delay. At the time of this incident the aircraft flight and navigation systems were operating properly to the best of my recollection. In my opinion the controller should have had us remain on the [TRACON] frequency to assist us in remaining clear of that primary target.

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.