Date: 201506
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 30
Light: Daylight
Aircraft: Cessna Single Piston Undifferentiated or Other Model
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Mission: Personal
Flight phase: Initial Approach
Airspace: Class E ZZZ
ATC / advisory: CTAF ZZZ
Second aircraft: Cessna Single Piston Undifferentiated or Other Model
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Commercial
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: Several other pilots encouraged me to file it in the interest of underscoring the importance of CTAF use by all pilots of radio-equipped aircraft in the vicinity of a busy; uncontrolled airport.This event occurred on a sunny; clear Saturday afternoon near airport ZZZ; which is the busiest airport [in the area]. I was on a VFR flight plan to ZZZ and was approaching ZZZ from the south for landing. At 25 miles out; I called FSS on frequency X to extend my flight plan; and at 10 miles out; I received the Aerodrome Flight Information Service (AFIS) information and called ZZZ Traffic on the CTAF (also frequency X) to announce my intentions to enter left traffic for RWY 36. The FSS reported that there were approximately nine aircraft approaching within 10 miles from the northwest and three(?) Cessnas approaching from the south; one of which I assume was my Cardinal. I diverted to the west; away from the traffic pattern; to watch the line of Otters and Beavers approaching from the northwest; and to look for other aircraft; before finding a safe time and location to enter the pattern for landing. At approximately 1510; there was a break in the traffic entering the downwind from the northwest so I reported entering a long left base #3 or #4 for landing (I forget which) following an Otter. I believed that entering from a long left base would allow me to spot any further traffic entering the downwind and to watch for traffic approaching from the south.Immediately after announcing my intentions; my wife in the right seat became startled and pointed out an aircraft that came from behind about 200 feet away; over our left wing; approximately 50-100 feet above us; descending. I immediately turned away to the right to increase our distance and keep this aircraft in sight as it descended ahead of us. The aircraft; a Cessna 172; continued ahead of us; roughly toward the airport but possibly headed farther downstream along the Susitna River. I heard no radio calls from this aircraft. Eventually the 172 made a sharp left toward the ZZZ airport; clearly intending to land. Still there were no calls from the 172 on the CTAF. After looking again for other aircraft; I re-announced my position on long left base for RWY 36; now #2 following the 172.After landing; I approached the pilot of the 172 and asked if he ever saw my Cardinal; and why I didn't hear him report his positions and intentions on the CTAF. His answer was that he never saw me; and he was communicating on frequency Y; which is one of two other FSS frequencies for ZZZ (the third being frequency Z). He stated that it was OK to be using any of the three frequencies; as long as he was talking to flight service; especially since the CTAF was so busy with multiple aircraft in the traffic area. To me; this assumption defeats the purpose of the CTAF; particularly in high-density traffic situations.The next morning before returning to my home base; I went into the ZZZ FSS and talked to the person who was on duty the previous afternoon. He remembered communicating with me on the CTAF and knew the 172 I was referring to. He stated that he had asked the 172 pilot to change to the CTAF for traffic advisories; but the pilot had not complied. He also reminded me that communicating on the CTAF is not a legal requirement; numerous aircraft without radios operate out of ZZZ. Nevertheless; I believe that the fact we did not see each other (until I did after he cut in front of me); and the 172 pilot was not using the CTAF; contributed to the significant potential for a mid-air collision. (There had been a mid-air collision at ZZZ less than two weeks prior; which fortunately all occupants of both aircraft survived because it occurred just above the runway and both aircraft were able to land; albeit one on top of the other.)




Synopsis: The pilot of a single engine Cessna was surprised by a near-mid-air-collision with another Cessna in the traffic pattern of a busy uncontrolled airport.  After taking evasive action and adjusting for the unforeseen traffic; both pilots successfully landed.  A post flight conversation identified several inconsistences with CTAF operations.