SR22
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4
Communication Breakdown; Training / Qualification; Situational Awareness; Confusion
ATC Issue All Types; Airspace Violation All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Air Traffic Control Separated Traffic
Human Factors; Procedure
We were training on Delmar. Aircraft X was at 4;000 east of OKB. Aircraft Y was coming missed off OKB climbing eastbound toward Aircraft X. I told the trainee to stop Aircraft Y at 3;000 to ensure separation. The trainee cleared Aircraft X for the visual and switched him to the Tower.Even though; we hadn't ensured separation from the two aircraft; I thought Aircraft X would pull away from Aircraft Y because of his speed and turn toward the airport. Instead; the Aircraft X slowed down and widened out to the north. I told the trainee to turn Aircraft Y below the Minimum Vectoring Altitude (MVA) to ensure separation. We then had to call Tower and ask them to square the base turn of Aircraft X so he wouldn't turn back into our Aircraft Y.In the future; I need to consider trainee hours when working a position. I'm really vigilant at ensuring separation; however; when the trainee cleared Aircraft X for the visual; even though I wouldn't have done it so soon; I assumed that Aircraft X would turn toward the airport and wouldn't slow until he was close to the runway. I shouldn't assume this; every pilot flies their plane differently; however I didn't even consider Aircraft X would widen out to the north.The trainee definitely learned that they need to control this approach to ensure separation from OKB.
SCT Instructor while instructing developmental had a loss of separation due to developmental clearing an aircraft for a visual approach while another aircraft was in close proximity.