Any Unknown or Unlisted Aircraft Manufacturer
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 10; Flight Crew Total 25000; Flight Crew Type 130
Situational Awareness; Communication Breakdown
Conflict NMAC
General None Reported / Taken
Airport; ATC Equipment / Nav Facility / Buildings; Airspace Structure; Human Factors; Procedure
I was inbound to ZZZ airport; about 5 miles northeast. I reported my position on the CTAF and that I was planning a left downwind entry for the active runway. There was a fair number of trainer aircraft in the vicinity of the airport as well as numerous aircraft in the vicinity of the VOR executing practice instrument approaches. A light twin announced that he was upwind off of Runway X; then crosswind. Since I knew that his departure could result in a possible conflict; I maintained extra caution and vigilance. Even so; I did not see the northbound aircraft until it was above the horizon; about 1/8 mile away.  There wasn't enough time for evasive action; the aircraft passed behind me.This kind of incident may be a precursor to possible in-flight collisions at this airport because of very heavy training activity with many non-standard operations. Exacerbating the situation was the fact that numerous training aircraft over the VOR (7 miles to the southwest) were communicating with each other with information on altitudes; distances away from the fix; type of approaches they were doing; all on the CTAF for ZZZ. All of this continuous radio chatter precluded my opportunity to announce my position as I entered downwind; and may have been a factor as to why the other aircraft failed to see my aircraft.
Ercoupe pilot reported excessive traffic and radio congestion at a non-towered field that resulted in a NMAC.