Light Transport; Low Wing; 2 Turboprop Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 6
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
Human Factors
Training in progress and I was the CIC (Controller in Charge) at the time. Aircraft X checked in at FL180 descending to 140. The Controller gave Aircraft X 10 left and to descend and maintain 120. The Pilot read back the altitude incorrectly and it was not caught by the training team or by myself. The Pilot read back 100 and descended to that altitude in an 112 MVA. No MSAW alert went off. The Controller did not observe the Pilot until almost level at 100 and then asked if Aircraft X had the terrain and field in sight and cleared them for the visual approach. I was not aware of the event until informed by the Controllers.Don't get comfortable when the traffic is very light. As Controllers In Charge we are very hyper aware when it is busy but when the traffic is light like it was during this event we tend to let our guard down.
TRACON Controller In Charge reported a read back error which caused an aircraft to descend below the MVA.