Bonanza 35
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 1
Situational Awareness
ATC Issue All Types; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance
Airspace Structure; Procedure
A Bonanza took off and wanted to turn straight back to the west for a practice RNAV approach. On initial call they were at 1500 ft. on a 050 heading about a mile from the runway so I turned them to a 270 heading. The small aircraft turned very slow and it took them about 4 to 5 miles to make the full turn to the west. At that time they were in a MVA (Minimum Vectoring Altitude) area of 3000 ft. still at 1900 ft. when they entered the MVA. I turned them more to the south to get them away from the obstruction but by that time they were already reaching the height of the obstruction of 2100 ft. and I turned them back to their initial approach fix. I should have known that a student pilot in a small aircraft which can usually turn very tight is not going to fly the aircraft as someone who is not a student. Also complacency; I have turned several aircraft without issue inside of the MVA because small aircraft can turn so tight.
MLI TRACON Controller reported an aircraft executed a turn wider than they expected and flew below the Minimum Vectoring Altitude.