Date: 201707
Local time of day: 0601-1200
Location: OKB.Airport, CA
Flight conditions: VMC
Weather elements / visibility: Haze / Smoke; 30
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Cruise
Airspace: Class E SCT
ATC / advisory: TRACON SCT
Second aircraft: Single Engine Turboprop Undifferentiated
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument
Anomaly: Conflict NMAC
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: While on an IFR flight plan in VMC conditions (though hazy because of smoke from fires in the vicinity) roughly 10 miles east north east of the OCN VOR; while on radar vectors from SoCal Approach being vectored to ILS runway 24 at CRQ; I was advised by a SoCal Approach controller on frequency 127.3 that a single engine turboprop operating at OKB was at my 3 o'clock position at approximately 7;500 feet and descending; while I was level at 5;000 feet. I was in a Cessna 172; and was unable to see traffic to my right and high because of the high wing. I advised the controller that I did not have the traffic in sight because of my wing; but was looking for traffic. The turboprop aircraft advised the controller that he had me in sight and would maintain visual separation. The approach controller acknowledged. I continued to visually scan for the aircraft. Approximately 30 seconds to a minute later I saw the low wing; single engine turboprop aircraft just to the front and right of my aircraft; between 12 and 1 o'clock. It was descending rapidly on a roughly north by northwest heading; heading apparently into my course and passing through my altitude. I immediately took evasive action by banking hard to the left; deviating from my assigned course by approximately 30 to 45 degrees to the north to avoid an imminent collision. The turboprop also immediately banked right into an approximately 45 degree or more bank and continued descending to the south. I estimate that at the closest point; the low wing turboprop was at my same altitude and descending; and within 200 feet of my aircraft. I immediately notified SoCal Approach of my taking evasive action to avoid the aircraft and told the controller something to the effect that the other airplane 'was right on top of me'. The approach controller acknowledged and had me return to my previously assigned vector of approximately a 90 degree heading. The low wing turboprop pilot reported he had my plane in visual sight the entire time. The controller asked if I wanted to 'make a report.' Ultimately; I decided against it; as in my opinion the controller did nothing wrong when the other aircraft reported me in sight. However; the other aircraft caused me to deviate from my assigned radar vector from approach control; though only for approximately a total of 30 seconds. My flight continued on without incident; and the turboprop pilot apologized on the frequency for 'scaring me.' Ultimately; it is my belief that either the turboprop lost sight of me in his descent which is why he came so close to my airplane; or almost as worryingly; he did have me in sight the entire time; but thought it would be fun to 'buzz' my aircraft.




Synopsis: GA pilot reported a NMAC while being vectored for an ILS Ruwnay 24 Approach to CRQ.