Airbus Industrie Undifferentiated or Other Model
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Confusion; Distraction; Situational Awareness; Training / Qualification; Communication Breakdown
ATC Issue All Types; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Human Factors; Procedure; Airspace Structure
Aircraft X was issued 3;500 ft. by my Trainee and we heard a good read back of 3;500 ft. I observed the aircraft at 3;100 ft. and I issued a climb immediately as the aircraft was a few miles from a 3;500 ft. MVA. The aircraft continued to descend further before he was able to climb. To be honest I let the Trainee go too far in running his own sequence.  Had I been working I would typically not have the aircraft that low and close to the airport if he wasn't number one for the runway. I think this may have contributed to the Pilot mistaking thinking he was cleared for the visual approach.
TRACON Controller reported during that OJT an aircraft descended below its assigned altitude and flew below the Minimum Vectoring Altitude.