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Geg approach controller reported an A320 descended below the MVA due to a blocked altitude readback.
| Attributes | |
| ACN | 1551053 |
| Time | |
| Date | 201806 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | GEG.TRACON |
| State Reference | WA |
| Aircraft 1 | |
| Make Model Name | A320 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Route In Use | Vectors |
| Flight Plan | IFR |
| Person 1 | |
| Function | Approach |
| Qualification | Air Traffic Control Fully Certified |
| Events | |
| Anomaly | ATC Issue All Types Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT Inflight Event / Encounter Weather / Turbulence |
Narrative:
Busy traffic day for the sector. Usually a slow sector; however; there was a fly-in so traffic was higher; and a greater mix of GA traffic. Aircraft X was issued a descent to 090; when the pilot was reading back the clearance mso tower called for a release covering the readback. I thought I heard a 090 readback; but did not verify with aircraft X. Released an aircraft off mso with tower and was trying to identify a VFR aircraft trying to get through weather into mso. Automated low altitude alert went off on aircraft X at 086 MSL and low altitude alert was issued to aircraft X with a climb to 090. Aircraft X stated they were descending to 050 and I restated they needed to climb to 090. While they were climbing; but still 400 feet below the MVA I issued a turn to join the localizer to keep them away from rising terrain on the other side of the localizer. Listening to the tape; I still cannot hear if aircraft X read back 050 or 090 because the tower call blocked the readback. I am positive I would have caught a 050 readback if it had not been blocked; because that is 2;500 feet lower than any MVA in our airspace.a handoff should have been staffed to answer calls from mso tower and help with VFR's trying to get through the weather. Not normally this busy and the controller in charge was helping with strips; but not working handoff. Supervisor was out of the operation for three hours before and during the incident. Controller in charge could have staffed the handoff if the supervisor had been in to work the osr.
Original NASA ASRS Text
Title: GEG Approach Controller reported an A320 descended below the MVA due to a blocked altitude readback.
Narrative: Busy traffic day for the sector. Usually a slow sector; however; there was a fly-in so traffic was higher; and a greater mix of GA traffic. Aircraft X was issued a descent to 090; when the pilot was reading back the clearance MSO Tower called for a release covering the readback. I thought I heard a 090 readback; but did not verify with Aircraft X. Released an aircraft off MSO with Tower and was trying to identify a VFR aircraft trying to get through weather into MSO. Automated Low Altitude alert went off on Aircraft X at 086 MSL and low altitude alert was issued to Aircraft X with a climb to 090. Aircraft X stated they were descending to 050 and I restated they needed to climb to 090. While they were climbing; but still 400 feet below the MVA I issued a turn to join the localizer to keep them away from rising terrain on the other side of the localizer. Listening to the tape; I still cannot hear if Aircraft X read back 050 or 090 because the Tower call blocked the readback. I am positive I would have caught a 050 readback if it had not been blocked; because that is 2;500 feet lower than any MVA in our airspace.A handoff should have been staffed to answer calls from MSO Tower and help with VFR's trying to get through the weather. Not normally this busy and the CIC was helping with strips; but not working handoff. Supervisor was out of the operation for three hours before and during the incident. CIC could have staffed the handoff if the Supervisor had been in to work the OSR.
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.