Small Aircraft; High Wing; 1 Eng; Fixed Gear
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Conflict NMAC; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew Became Reoriented
Aircraft; Airspace Structure; Human Factors
Aircraft Y was in left closed traffic for Runway 2W (Water runway) instructed to extend upwind. Aircraft X was entering the right downwind from the north for Runway 2R. I was the Instructor to the Local Control developmental who was on the line coordinating with the radar handoff position regarding multiple different items. I looked over the trainee's shoulder at the tower radar display and observed Aircraft Y had drifted about a mile east of the upwind and was now on a collision course with Aircraft X entering the downwind.I instructed Aircraft Y to turn left crosswind immediately and issued traffic. I issued traffic to Aircraft X and told him to start a climb. Aircraft Y was observed at 1700 ft while Aircraft X was observed at 1900 ft. Traffic pattern altitude at FAI is 1500 ft. Aircraft X reported Aircraft Y in sight and was instructed to maintain visual separation. Aircraft Y passed east and above of Aircraft X. Radar data shows lateral separation of .18 NM and 200 ft. Surface wind was 020 at 10 Knots.VFR pilots must; to the greatest extent possible; maintain runway heading while in the upwind and pattern altitude while in the traffic pattern.
FAI Tower Controller reported a traffic conflict in the pattern due to an aircraft that drifted off course.