Date: 201807
Local time of day: 1201-1800
Location: OSH.Airport, WI
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: PA-28R Cherokee Arrow All Series
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Initial Approach
Airspace: Class D OSH
ATC / advisory: Tower OSH
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Private
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Conflict NMAC
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Human Factors; Environment - Non Weather Related; Procedure
Primary problem: Procedure

Narrative: I entered the Fisk arrival at Ripon heading to Fisk. Traffic was extremely busy. My concentration was out of the front trying to maintain separation from other aircraft trying to get in to Oshkosh. Out of the corner of my eye to the left I caught a light colored aircraft approaching directly towards me and a little high in a left turn to intersect my path. He passed directly overhead by 20 ft and I believe slowed down and settled in behind me. Since the Piper doesn't have rear windows I could not see where he went. Evasive action wasn't safe as there were planes near me; some at lower altitudes.I believe the problem was caused by a chain of events:1. The temporary Approach ATC didn't like the bunched up gaggle of planes and told everyone at Fisk to turn left; go around and try setting up again. They wanted us to be safe. Well; what you ended up with was 40-50 planes all turning left at the same time in uncontrolled airspace. Some adhered to the NOTAM and followed procedures some did not. If anything we were in a very unsafe environment. 2. As time went on pilots were getting angry and trying to get to Oshkosh at any cost. That's where all the maverick moves were done to cut in line. Sometimes we had very good separation in front of us and someone saw that as a hole to fill with their airplane and ruined it for us. Perhaps that's what the high wing  was doing. 3. I am guessing the high wing [aircraft] may not have seen us since he was a little higher and starting in a turn. The pilot was on the left side and we were on his right.4. The weather was down below VFR minimums in the morning and when they lifted everyone was trying to get to the same place.I think something has to be done to rework the arrival into Oshkosh for AirVenture week. There were literally hundreds of planes in very tight proximity to each other trying to squeeze into one arrival path. I don't have any solutions since I don't have an ATC background but it would be nice if they gave more IFR arrivals. It seems like they only hand out a very small amount of those. The VFR approach method isn't working with the amount of traffic that this event has grown to. I am an IFR student with about 55 hours of IFR training and will be able to take advantage of that next time I go. Lastly; ATC can't wash their hands of us when they tell everyone to go back to Ripon and try it again. They are sending us out there amongst pilots of varying levels of competency and in very close proximity to remain clear of each other. There are too many planes in that situation to reliably keep track of and they aren't all following the NOTAM'd procedure. Someone is going to get killed out there.




Synopsis: PA-28 pilot reported a near mid-air collision in the vicinity of OSH; asserting that current ATC procedures for AirVenture traffic are not safe.