Small Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 9.0
Situational Awareness; Communication Breakdown
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert
Airspace Structure; Human Factors
Aircraft X was enroute. I thought I issued a descent to 11000 feet. They were passing through a 11000 MVA (Minimum Vectoring Altitude) area. I saw Aircraft X descend to 10800 feet; then 10600 feet. I asked if Aircraft X was maintaining 11000 feet. Aircraft X answered that they had been cleared to 10000 feet. I issued them 11000 feet and to expect lower in one minute. Aircraft X stopped their descent but did not appear to climb back up. Aircraft X remained at 10600 feet for approximately 5 miles in the 11000 foot MVA area. Listen carefully for readbacks; especially if the aircraft has a scratchy radio.
A Center Controller reported they observed an aircraft that descended below the assigned altitude and below the Minimum Vectoring Altitude did not climb back to the assigned altitude when instructed.