Date: 201509
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: DA20-A1 Katana
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Passenger
Flight phase: Landing
Airspace: Class E ZZZ
ATC / advisory: CTAF ZZZ
Reporter organization: Personal
Reporter function: Instructor; Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Flight Instructor
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Airport; Airspace Structure; Human Factors
Primary problem: Human Factors

Narrative: Approaching into traffic pattern; all appropriate position radio calls were made. Just before turning onto Base leg; I looked up to see a [single engine Beechcraft] just above me and to my left. He had overtaken me from behind but had not seen me either visually or on his TCAS. No evasive action was required to maintain separation; but I gave way to him and turned to my right; level altitude. I glanced at my radio to discover I have been making all my radio calls on 122.7 instead of 122.8; which is ZZZ's CTAF. 122.7 is the CTAF for ZZZ1; where we had just come from. 122.8 was in my stand-by freq slot. I switched over to 122.8 and communicated with the [other aircraft]. He admitted that he never saw me as I was below him and slightly to his right; and nothing appeared on his TCAS. He also mentioned that he never heard my radio calls. I confessed that I was making radio calls; but on the wrong frequency.Both aircraft landed without incident; and no evasive maneuvers were required by either aircraft. However; as stated; I gave way to the [other aircraft] by making a right 360 and re-entered the pattern on the left 45; ensuring I was on the correct radio frequency.I feel both pilots could have broken the chain of events. I; as the pilot of the Diamond could have broken the chain of events simply by having been on the correct radio frequency. Having been ahead and below the [other aircraft]; it would not have been possible to have seen the plane overtake us on the downwind leg. I entered the traffic pattern on the 45 at pattern altitude and was able to complete my downwind leg and did not see the aircraft overtake us. Had I heard the [other] pilot's radio calls; I could have easily known where to look for him and maintain situational awareness. I never saw the [other aircraft] on downwind at any time.The [other] pilot could have broken the chain of events if his focus was looking for traffic. A [single engine Beechcraft] in the pattern is flying at higher air speeds than a Diamond DA-20; so it can be surmised that the pilot had time to see the DA-20 enter the downwind from the 45; as he would have had to been on crosswind or just starting his downwind at the time. The [other] pilot admitted he didn't see me on his TCAS; and never saw me visually during the entire event. His plane did not appear on my Traffic Information Service.




Synopsis: Diamond DA-20 pilot reported a near-mid-air-collision while entering the traffic pattern of a non-towered airport. He discovered that his radio had not been tuned to the correct CTAF frequency.