Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Multiengine
Flight Crew Last 90 Days 113; Flight Crew Total 1208; Flight Crew Type 601
Training / Qualification; Situational Awareness; Confusion; Communication Breakdown; Distraction
Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
Procedure; Human Factors; Environment - Non Weather Related
My student pilot and I had just entered the pattern from a 45 degree leg to left downwind when a call on CTAF addressed us by call sign; asked our intentions; and said we were 'all over the place'.  I looked to my right and saw another airplane about 500 feet from us; also on left downwind. The pilot said on CTAF that he had just turned from crosswind to downwind and was aware of our entry from the 45 based on our position reports. He said he would extend downwind to allow us to land ahead of him. I can think of three factors that contributed to my failure to see the traffic until so late.First; the CTAF frequency for ZZZ is shared by numerous airports in the area. While I was talking my student through the pattern entry; we were hearing calls for at least four different airports without any silence; so we had to talk to each other over these calls. In such a situation it was easy to miss the one call we needed to hear.Second; the frequency was congested shortly before the traffic conflict by a lengthy and non-standard position report ending with; 'could any traffic in the area please advise'.  This may have been the pilot of the aircraft that conflicted with me; or it may have been an unrelated call at another airport that blocked the frequency.  A colleague who had just landed at the same airport later told me that the same pilot had also called him on CTAF while he was on final; asking his 'intentions after landing'. Third; my student had become disoriented while making a teardrop turn to the 45 degree entry; and I was distracted by helping her get reoriented to the airport and make a correct pattern entry.
Flight Instructor reported a NMAC when they were assisting their disoriented student enter downwind at an uncontrolled airport and failed to see another aircraft on downwind. The instructor reported CTAF congestion due to several airports sharing the same frequency was also a factor.