Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 27; Flight Crew Total 286; Flight Crew Type 92
Conflict Airborne Conflict; Conflict NMAC
Flight Crew Took Evasive Action
Airport; Human Factors
I departed ZZZ direct to AIO to attend a fly-in with one passenger. I communicated 10 miles northeast of AIO that I would enter the left downwind for runway 02. Aircraft Y pilot reported 6 south of AIO for a straight in approach to runway 02. A couple minutes later I communicated to the Aircraft Y pilot that I was entering the downwind to runway 02 and would land after. At this time Aircraft Z reported 5 miles northwest and would enter the downwind to runway 02. Aircraft W reported 8 to the west of AIO and would overfly the field before entering the downwind to runway 02. I again reported on the left downwind to runway 02. Not more than 20 seconds later my passenger pointed out Aircraft Z; which passed slightly behind us from the right and slightly below us. I took evasive action to avoid the aircraft and exited the pattern to the west.I reentered the pattern behind Aircraft W. Aircraft W pilot extended his downwind and eventually turned onto the upwind without landing. I suspect he thought I would overtake him and land despite me communicating that I would follow Aircraft W and land after him. Unsure what Aircraft W pilot would do; despite communicating on CTAF; I continued to follow Aircraft W through the entire pattern. The Aircraft W pilot eventually turned onto a 2 mile final on his second circuit and landed. The pilot exited 4500 down the 5000 runway. Shortly after Aircraft W pilot exited the runway I was able to land without incident. There was a lot of traffic at the airport due to the fly-in. I arrived at a particularly busy time. Despite communicating on the radio multiple times; a mid-air collision almost occurred. Based on the report of Aircraft Z being 5 miles out as I entered the pattern; I had thought that it was no factor. Aircraft Z was not in the position that it had reported on CTAF. If I don't avoid fly-in's entirely in the future. I will ensure that I communicate more directly with each pilot that could create a conflict. I made the mistake of trusting where the pilot said. His aircraft was also positioned in a location that was not visible from the pilot's seat of [my aircraft].
GA pilot reported several airborne conflicts and a near-mid-air-collision while entering the pattern at AIO CTAF airport.