Date: 201812
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Mission: Personal
Flight phase: Initial Approach; Final Approach
Airspace: Class E ZZZ
ATC / advisory: CTAF ZZZ
Second aircraft: DA40 Diamond Star
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument
Human factors: Communication Breakdown; Confusion; Situational Awareness; Distraction
Anomaly: Conflict NMAC
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Airport; Human Factors; Procedure
Primary problem: Human Factors

Narrative: I entered the VFR pattern from 5 to 6 miles northwest of the field when I called in my position to saying that I would at first set up for touch and go's on Runway XX. The other aircraft then called in asking if anyone was in the pattern at which realizing he didn't give me a position report I then changed and said I would over fly the airport at 1;500 feet to not only see the windsock but also to see where he would be entering from. After overflying the field and saying I would be entering a downwind to Runway XX because winds favored it I said 'left downwind' at first to which I corrected myself and said I would be on a right downwind and make left closed traffic to Runway XX. This may have confused Aircraft Y as later on I found out he was not familiar with this airport. After one touch and go to Runway XX and turning my crosswind I spotted the pilot on a downwind to the airports closed runway and the pilot claimed that Runway XX was closed.I called back saying that Runway XX was not closed but that he attempted to land at a closed runway and I offered him to follow behind me to Runway XX if he was unfamiliar with the airport and didn't have a map (I assumed he didn't have this information due to his lack of knowledge as to which runways were available even after flying over the airport) to which the pilot refused the help. I saw the aircraft on what looked like a left downwind to Runway XX and so I followed behind him to keep a visual sight on the plane. After some long downwind to Runway XX it looked as if the pilot was turning a left base to Runway XX to which I asked if he was and he responded with 'I'm departing the pattern and will re-enter'. After that I saw his 'left base' was actually him performing a 360 degree turn about 6 miles west of the field. I then proceeded to enter my left base to Runway XX about 3 miles west while keeping some eye contact on the aircraft.After my landing I lost sight of the plane and upon entering the upwind Aircraft Y said; 'Ill be entering a 35 left downwind to Runway XX' and I then prepared to spot the aircraft while I was on crosswind. I extended out my upwind to create a larger downwind for some time to spot the pilot and when the pilot of Aircraft Y said 'On a left downwind for Runway XX' I then turned my downwind leg and made the radio call. After doing a visual scan I did not see the plane and I was just about to make a radio call asking where he was in relation to the airport when I spotted the aircraft about a 135 degree angle from my forward facing airplane at around 100 feet or less vertical and about the same altitude. He was behind me about 45 degrees on my right side and coming at a very fast power setting (assuming full throttle). I immediately applied full power while climbing as quickly as possible. The aircraft did not seem to have a visual on me and from my perspective his 'left downwind for Runway XX' was actually a left downwind to Runway XY.After the encounter I immediately departed the pattern and started a return back to [home] airport in which I heard the pilot of Aircraft Y make a call that he would be leaving the pattern to the south and make another attempt to land. The pilot had no idea what runways were active even after over flying the field in his attempt to land on a closed runway. I should have made a better decision earlier on to depart the pattern and wait for him to land after I noticed he was not familiar with the airport set up but I was in a calm manner and felt that if I kept a listen and eyes out for him I would be fine. I have dealt with pilots who haven't had communications in the pattern before so I figured there was not a big difference.




Synopsis: C172 pilot reported an NMAC in a non-towered airport traffic pattern.