A TRACON controller reported an aircraft descended below the assigned altitude and below the minimum...

Narrative:

Aircraft X was inbound from the northeast. When the aircraft checked on they were at an altitude of approximately 12500 feet. The aircraft was over an 11000 MVA (minimum vectoring altitude). I issued a descent to 11000 feet. A minute or so later when I looked at the tag the aircraft was at 10200 feet in the 11000 foot MVA. I issued a low altitude alert and instructed the pilot to climb to 11000 feet immediately which he did. This MVA does seem like a hot spot as I have had an aircraft do this before. I do think there is something that could help. Center descends aircraft to 12000 feet; and to comply with the letter of agreement we must descend them out of their airspace without delay. So coming from the northeast; the aircraft descends to 12000 feet; then we have to descend and stop them again at 11000 feet. If we could change the letter of agreement where we have approval to leave the aircraft at 12000 feet (in this area only; not coming from all directions) I believe this would be a safer operation. The MVA is not that large where it would cause us to be in center's airspace for an unusually long amount of time. We could even have it worded whereas once the aircraft clears we shall descend the aircraft out of 12000 feet. This would leave them in center airspace for an even shorter amount of time.

Original NASA ASRS Text

Title: A TRACON Controller reported an aircraft descended below the assigned altitude and below the Minimum Vectoring Altitude.

Narrative: Aircraft X was inbound from the northeast. When the aircraft checked on they were at an altitude of approximately 12500 feet. The aircraft was over an 11000 MVA (Minimum Vectoring Altitude). I issued a descent to 11000 feet. A minute or so later when I looked at the tag the aircraft was at 10200 feet in the 11000 foot MVA. I issued a low altitude alert and instructed the pilot to climb to 11000 feet immediately which he did. This MVA does seem like a hot spot as I have had an aircraft do this before. I do think there is something that could help. Center descends aircraft to 12000 feet; and to comply with the Letter of Agreement we must descend them out of their airspace without delay. So coming from the northeast; the aircraft descends to 12000 feet; then we have to descend and stop them again at 11000 feet. If we could change the Letter of Agreement where we have approval to leave the aircraft at 12000 feet (in this area only; not coming from all directions) I believe this would be a safer operation. The MVA is not that large where it would cause us to be in Center's airspace for an unusually long amount of time. We could even have it worded whereas once the aircraft clears we shall descend the aircraft out of 12000 feet. This would leave them in Center airspace for an even shorter amount of time.

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	1530916
Time
Date	201804
Local Time Of Day	0001-0600
Place
Locale Reference	EUG.TRACON
State Reference	OR
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	Lancair IV/IVP
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 3.2
Events
Anomaly	Deviation - Altitude Overshoot Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

A TRACON controller reported an aircraft descended below the assigned altitude and below the minimum vectoring altitude.