ATC reported flight flew through final approach course and descended below their assigned minimum ve...

Narrative:

Aircraft X was established on a downwind for the ILS approach. I issued aircraft X a left turn heading 280 and descend and maintain 4;200 feet. Aircraft X read back the correct heading and altitude. When I cleared aircraft X for the ILS approach he read back the incorrect altitude of 4;000 feet. That's when I observed aircraft X descending through 3;600 feet. The low altitude alert on the system did not go off until 3;200 feet. I issued the low altitude alert informing aircraft X of the MVA (minimum vectoring altitude) of 4;200 feet and altimeter of 29.80. I observed aircraft X half mile west of the localizer and canceled approach clearance and vectored him back around for the approach. The pilot called the facility and informed the supervisor he thought the altitude issued was 2;200 feet. The low altitude alert for the system needs to be configured to alert prior to 1;000 feet below the MVA in that area.

Original NASA ASRS Text

Title: ATC reported flight flew through final approach course and descended below their assigned Minimum Vectoring Altitude; ATC Low Altitude Alert did not activate in a timely manner.

Narrative: Aircraft X was established on a downwind for the ILS Approach. I issued Aircraft X a left turn heading 280 and descend and maintain 4;200 feet. Aircraft X read back the correct heading and altitude. When I cleared Aircraft X for the ILS approach he read back the incorrect altitude of 4;000 feet. That's when I observed Aircraft X descending through 3;600 feet. The low altitude alert on the system did not go off until 3;200 feet. I issued the low altitude alert informing Aircraft X of the MVA (Minimum Vectoring Altitude) of 4;200 feet and altimeter of 29.80. I observed Aircraft X half mile west of the localizer and canceled approach clearance and vectored him back around for the approach. The pilot called the facility and informed the Supervisor he thought the altitude issued was 2;200 feet. The low altitude alert for the system needs to be configured to alert prior to 1;000 feet below the MVA in that area.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1665874
Time
Date	201907
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Tower
State Reference	US
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 14.0
Events
Anomaly	ATC Issue All Types Deviation - Altitude Overshoot Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

ATC reported flight flew through final approach course and descended below their assigned minimum vectoring altitude; ATC low altitude alert did not activate in a timely manner.