B737-800
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Communication Breakdown; Training / Qualification
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Procedure
Training was in progress on Final. We received notification Aircraft X was a medical emergency from the southwest. I told the plan to my trainee; we would descend the Aircraft on the approach to 16R to 2100 feet to allow Aircraft X descend for the visual approach. I also instructed the trainee to vector Aircraft X through the bay for the right base. I told him to start issuing traffic for pilot applied visual separation. Aircraft X reported Aircraft Z; a B737; in sight and told to maintain visual separation from the B737; we received a confirmation from Aircraft X for pilot applied visual separation. Aircraft Y reported Aircraft X insight; was told to maintain visual separation from Aircraft X; we did not receive a confirmation. Separation was lost before pilot applied visual separation was obtained. Aircraft X was cleared for a visual approach to 16L and began a descent while crossing over the top of Aircraft Y. Aircraft Y notified us he received a RA from Aircraft X.
S46 TRACON Controller reported separation was lost; before pilot applied visual separation was obtained.