Large Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 24
Situational Awareness; Confusion; Training / Qualification
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Separated Traffic; Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Aircraft; Human Factors
Aircraft X was in the Tower VFR pattern. Local Control coordinated with Approach that Aircraft X will follow traffic on the ILS Approach. Aircraft Y was turned on the approach at 2;000 feet and was tracking the approach inbound. I was conducting training and we were discussing how Aircraft X will fall in nice behind Aircraft Y. Right before Approach was going to switch Aircraft Y to the Tower I noticed Aircraft X turning his base turn. He was only 2 miles off the approach course opposite direction as it was. The trainee on Approach issued a traffic alert and gave Aircraft Y a turn to the right heading 270 degrees. This put the aircraft nose to nose. I took over the frequency and gave Aircraft Y a left turn 040 away from Aircraft X.Aircraft Y did not see Aircraft X due to a cloud. There was maybe a mile between the 2 aircraft and closing. It was close. Closer than anything I have seen in [all my] years. The pilot of [Aircraft X] later called the Approach Control and spoke to the Supervisor admitting to the error. I was able to watch the radar replay and it was close. Disturbing.
A TRACON Controller reported an aircraft on downwind turned base leg on its own toward traffic established on short final.