Small Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 6
Training / Qualification; Distraction; Situational Awareness; Communication Breakdown
ATC Issue All Types; Conflict NMAC
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors; Procedure; Aircraft; Airport
I was working the Local 1 position; training in progress. The traffic pattern was getting unwieldy; so I took over and started to clean up the sequence. Aircraft X was number 1 on 3 mile final Runway 3R. Three aircraft were on the downwind; extended to follow Aircraft X. I saw what I thought was Aircraft Y cut out Aircraft X; but realized it was Aircraft X appearing to be on right base Runway 3R; inside the downwind. I re-cleared Aircraft X; and that was when Aircraft Z advised NMAC with Aircraft X.The pilot of Aircraft X should have advised me what he was doing; especially if it was safety related (birds; for instance). I could have at the very least called traffic.
PRC Local Controller observed an aircraft that had been established on final maneuvered on its own to a base leg position on a conflicting course with downwind traffic.