Pia approach controller reported regional jet was below the MVA. Controller missed incorrect read ba...

Narrative:

Aircraft X came over level at 060 inbound for bmi. On initial contact; I instructed the plane to descend to 040 and turn 20 degrees right for the ILS runway 29 approach. The pilot read back 10 degrees right; but I decided to let that be and give him a hard heading in a bit. After a few more miles; I instructed the plane to descend to 031 (the altitude for the approach) and fly heading 010. I thought that the pilot gave a correct readback; but after my air traffic managers (atm) and front line manager (flm) reviewed the tapes; they told me he readback 021. The MVA is 024. I can't remember if it was before or after that transmission that my flm began prebriefing; but I gave the position to him shortly after. Around the time he cleared the plane for the approach at 031; we were starting to lose radar on the plane and the pilot stated that he was now at 021. The pilot stated that he had the airport in sight and was cleared for a visual approach.

Original NASA ASRS Text

Title: PIA approach controller reported Regional Jet was below the MVA. Controller missed incorrect read back while aircraft was in an area of limited radar coverage.

Narrative: Aircraft X came over level at 060 inbound for BMI. On initial contact; I instructed the plane to descend to 040 and turn 20 degrees right for the ILS Runway 29 approach. The pilot read back 10 degrees right; but I decided to let that be and give him a hard heading in a bit. After a few more miles; I instructed the plane to descend to 031 (the altitude for the approach) and fly heading 010. I thought that the pilot gave a correct readback; but after my Air Traffic Managers (ATM) and Front Line Manager (FLM) reviewed the tapes; they told me he readback 021. The MVA is 024. I can't remember if it was before or after that transmission that my FLM began prebriefing; but I gave the position to him shortly after. Around the time he cleared the plane for the approach at 031; we were starting to lose radar on the plane and the pilot stated that he was now at 021. The pilot stated that he had the airport in sight and was cleared for a visual approach.

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	1534898
Time
Date	201804
Local Time Of Day	1201-1800
Place
Locale Reference	PIA.TRACON
State Reference	IL
Aircraft 1
Make Model Name	Bombardier/Canadair Undifferentiated or Other Model
Flight Phase	Final Approach
Flight Plan	IFR
Events
Anomaly	ATC Issue All Types Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

Pia approach controller reported regional jet was below the MVA. Controller missed incorrect read back while aircraft was in an area of limited radar coverage.