Small Aircraft; High Wing; 1 Eng; Fixed Gear
Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Commercial
Flight Crew Last 90 Days 34; Flight Crew Total 357; Flight Crew Type 30
Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
While (left) downwind in the pattern following other traffic in the pattern; another aircraft about 100-200 ft. below us headed in the opposite direction flew straight at us. We initiated a climb and turned left to avoid traffic; then departed the pattern due to the event. We believe that the other aircraft might have been maneuvering to the 45 to the downwind; but being so low and flying opposite to traffic pattern (with the existing traffic already flying at altitude) was dangerous. We do not know if he was on the radios; and did not hear him radio his intentions; so there was a lack of communication. The airport is uncontrolled and people often do not use their radios; but the entry procedure of this aircraft could have caused serious issues.
Pilot reported an NMAC event with a nonreporting aircraft while in landing pattern.