Narrative:

I was approaching [the airport] to make a left downwind pattern for runway 31L. As I did this I was instructed to follow a cessna which I identified in front of me. While flying parallel to 31L; I was instructing my private student on what sort of distance we were looking for and performing our before landing checklist. I lost situational awareness temporarily and lost the cessna; but believed I identified it further on making its base turn. I watched the aircraft pass by my wing and allowed about 30 seconds more to keep us separated. I then looked ahead of me and to my left to make sure I was clear of traffic before turning base. I instructed my student on what a proper base looked like before turning final. By then I still had not been cleared to land so I was about to query the tower when another call came on saying they were on final with someone above them. Even though we have a parallel runway there was enough doubt in my mind I executed a missed approach; and banked to the right to stay clear of the traffic which I located under me and to my right. I exited the pattern and request instruction to rejoin. It was later I learned the diamond I would come in close contact with was on a right base for the same runway at a different altitude and that is why I wasn't able to pick him up in my scan as I was focused on left downwind traffic. I believe the problem was caused by a variety of factors. One being that the other aircraft and I didn't see each other; and it is my opinion this close call could have been avoided if [ATC] had intervened when he saw two aircraft on base heading towards each other.

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Original NASA ASRS Text

Title: C152 instructor pilot reported a NMAC in the airport traffic pattern.

Narrative: I was approaching [the airport] to make a left downwind pattern for Runway 31L. As I did this I was instructed to follow a Cessna which I identified in front of me. While flying parallel to 31L; I was instructing my private student on what sort of distance we were looking for and performing our before landing checklist. I lost situational awareness temporarily and lost the Cessna; but believed I identified it further on making its base turn. I watched the aircraft pass by my wing and allowed about 30 seconds more to keep us separated. I then looked ahead of me and to my left to make sure I was clear of traffic before turning base. I instructed my student on what a proper base looked like before turning final. By then I still had not been cleared to land so I was about to query the Tower when another call came on saying they were on final with someone above them. Even though we have a parallel runway there was enough doubt in my mind I executed a missed approach; and banked to the right to stay clear of the traffic which I located under me and to my right. I exited the pattern and request instruction to rejoin. It was later I learned the Diamond I would come in close contact with was on a right base for the same runway at a different altitude and that is why I wasn't able to pick him up in my scan as I was focused on left downwind traffic. I believe the problem was caused by a variety of factors. One being that the other aircraft and I didn't see each other; and it is my opinion this close call could have been avoided if [ATC] had intervened when he saw two aircraft on base heading towards each other.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.