Cardinal 177/177RG
Flight Crew Private
Situational Awareness
Conflict NMAC
Flight Crew Took Evasive Action
Human Factors
Level @ 5;500 feet; 108kts GS; on frequency with Center. ATC notified of traffic 12 o'clock 5 miles E direction. I identified aircraft immediately at same altitude and reported traffic in sight. Noticed aircraft landing light and determined that aircraft was turning north in my direction. ATC advised she had no contact with aircraft and noted that distance was closing. I disengaged AP and began immediate descent and turn to south southwest. Aircraft passed approx. 250' overhead. ATC confirmed that I was okay and I responded that evasive action was necessary to avoid a mid-air collision. ATC voiced concern and [said] that shouldn't have happened. Within 2 minutes the aircraft reported on frequency; ATC responded with a question 'had the pilot seen me?' Pilot responded that she had but it was okay because we had missed each other. I feel that was not an acceptable response by the pilot. ATC apologized for the incident. I'm reporting this because there may be something that can be done to avoid an incident such as this. I believe the problem was that pilot of [the other aircraft] was not on ATC frequency so as to avoid other traffic and pilot was very 'nonchalant' about the incident.
C177 pilot reported a NMAC with a turboprop aircraft in the vicinity of THA airport.