2024-07 · NASA ASRS report 2147991
Air Traffic Controller reported an aircraft descended below its assigned altitude resulting with the aircraft flying below the minimum vectoring altitude. ATC issued a low altitude alert; a climb; and vectored the aircraft to the airport where they landed without further incident.
Aircraft X was inbound for ZZZ from the southwest. Due to the aircraft's speed and altitude; I had to take it across the final and bring it in from the east side. Once he was east of the final; I issued a 020 heading and a descent to 040. The pilot read back both instructions correctly (confirmed by tape). He then turned; and a few moments later; descended below 040. I didn't notice anything wrong at that moment because there was no traffic to miss; and the MVA in that area is 026; so I just assumed I issued a descent to that altitude. I turned the aircraft to a 290 heading for the base leg; and then the aircraft descended to 025. The LA activated; and I issued the Low Altitude Alert immediately; telling the aircraft to check his altitude immediately; that the MVA was 26; and he was cleared to 26. He replied that I had descended him to 020; and that he would climb back up. He did; I vectored him and cleared him for the approach; and he landed without incident. I informed the Supervisor a few minutes later; after getting relieved; and had QC (Quality Control) pull the tapes. In fact; I never descended him below 040; which was read back correctly. I did not issue a Brasher on frequency; as I assumed I must have missed his bad readback of 2000; but I did not. Our QC person called Aircraft X to issue the Brasher.Recommendation - None. It was a pilot deviation.
While being vectored for the approach and deviating around convective cells on approach to ZZZ; we were directed on a base turn heading and cleared to 2000 feet. The PM read back the clearance and we heard nothing further from the Approach Controller. At 2300 feet the Approach Controller issued a low altitude alert and stated the minimum vectoring altitude was 2600 feet. We immediately corrected our altitude to 2600 feet and were subsequently cleared for a visual approach. We were in VMC conditions for the duration of this event.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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