Small Transport; Low Wing; 2 Recip Eng
Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument
ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Procedure; Human Factors
The following is written from memory. I'm assuming audio recordings and radar tracks are available for reference by others. A small transport piloted by me was on an IFR flight plan cruising at 6;000 feet assigned and on assigned westerly heading. A VFR Aircraft Y was heading east and reported to ZMP Center query as being at 6200 feet. Center gave both aircraft progressive traffic advisories of 12 o'clock and 9 miles; then 6 miles then 4 miles distance. My response to ATC was 'looking' and two of us in the cockpit kept scanning visually. At the Center 6 mile advisory I turned on landing light and taxi lights. The strobe and rotating beacon were already on. Sometime between the 6 mile and the 4 mile advisory I heard Aircraft Y reply to Center's query for his altitude that he was at 6000 feet. At that point since neither aircraft reported seeing the other and since I had not received an instruction from Center but while still closing at about 300 knots (estimated) and understanding that both aircraft were at the same altitude; I initiated a slight deviation to the right and a slight climb. A moment later Center told me to climb. A moment later Aircraft Y acknowledged having me in sight and I acknowledged having him in sight. The Aircraft Y passed 120 feet below and about 30 feet to my left.Contributing factors:One aircraft was on an IFR flight plan. The other was VFR. I filed IFR for 6000 feet to stay below the freezing level referenced in an AIRMET for icing otherwise I would have filed higher. There was a narrow band of clouds at about 6200 feet MSL (estimated) between the two aircraft running from southwest of course to northeast of course.Human Performance Considerations:Perceptions; judgments; decisions. After the incident ZMP Center asked me over the same radio frequency if I had TCAS. I responded; negative TCAS; no TCAS. Was the controller assuming I had TCAS and expecting me to provide my own separation? Is that normal for ATC to assume aircraft have TCAS and will use that to provide their own traffic separation while operating under an IFR flight plan under ATC control? The VFR aircraft descending through the flight path of an oncoming aircraft given that both aircraft were listening and communicating respective altitudes through the ATC communications is hard to understand. The decision of the ZMP Center controller to delay providing separation instructions to either aircraft until they were closer than 4 miles and at the same altitude and closing rapidly (300 knots estimated) is questionable.Actions of Inactions:ATC did not inquire and the VFR aircraft did not offer during query for altitude report to report whether level; climbing or descending. ATC delayed too long to issue direction or altitude changes to either of the aircraft.
An IFR light twin pilot in VMC was advised by ZMP Center about a single engine VFR aircraft at the same altitude. ATC assumed the light twin had TCAS; but it did not and the aircrafts had a near miss.