Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Situational Awareness
ATC Issue All Types; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Chart Or Publication; Airspace Structure; Human Factors; Procedure
Aircraft X was on a vector descending to 5;500 feet for the GPS approach. Aircraft X read the heading and altitude assignment correctly. Aircraft X was issued a base turn heading 060. After traffic passed below Aircraft X at 4;000 feet; I began to Precision Turn Altitude Clearance (PTAC) Aircraft X for GPS Approach. It was at the moment when I finished transmitting that I realized Aircraft Y was leveling at 5;000 feet. Immediately; the pilot read back the clearance. However it was incorrect due to the pilot stating 'maintain altitude until established in the localized... I immediately told the pilot to disregard the PTAC and to climb to 5;500 feet. I then told the pilot to 'check their altitude immediately' and that the MVA (Minimum Vectoring Altitude) in the area was 5;400 feet. I received no response so I repeated the climbing instruction with an amendment to maintain 5;400 feet instead. I then asked the pilot to read back the altitude assignment. The pilot did not read back the numeric altitude. I then instructed Aircraft X to join the final approach course upon reaching 5;400 feet. I observed Aircraft X reach 5400 feet quickly and safely. Aircraft X was cleared for the RNAV/GPS Approach and landed without incident.I recommend having a quarterly conversation with the local flying community around BTV's airspace. There are a multitude of flying clubs and academies that can benefit from a conversation with BTV ATC. The format for these conversations could include in person tours; sit-downs; or e-mail correspondence. Events like this can be avoided; in my opinion; by explaining the importance of understanding altitude assignments; approach information for our lengthy; step-down; ILS and RNAV/GPS Approaches and expectations. Most of the flying community around BTV flies in and out of uncontrolled airports."
TRACON Controller reported an aircraft descended below the assigned altitude and flew below the Minimum Vectoring Altitude.