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D01 TRACON controller reported an aircraft descended below the assigned altitude and below the MVA.
| Attributes | |
| ACN | 1505970 |
| Time | |
| Date | 201712 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | D01.TRACON |
| State Reference | CO |
| Environment | |
| Flight Conditions | Marginal |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | Regional Jet 700 ER/LR (CRJ700) |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Flight Plan | IFR |
| Person 1 | |
| Function | Approach |
| Qualification | Air Traffic Control Fully Certified |
| Experience | Air Traffic Control Time Certified In Pos 1 (yrs) 3 |
| Events | |
| Anomaly | ATC Issue All Types Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT Inflight Event / Encounter Fuel Issue |
Narrative:
I was working arrivals doing ILS approaches. Aircraft X checked in on the downwind and declared minimum fuel. I verified the fuel status and advised the pilot to which runway to expect. I continued working through my other aircraft with an awareness that I needed to get aircraft X in as soon as feasible. It was low IFR and with the parallel runway configuration aircraft were doing at least 20 mile finals. At the opportune time; I based aircraft X at 9;000 ft. The aircraft took the turn and I then issued the full ILS clearance to the aircraft. The pilot read back the turn and clearance but not the altitude.as the aircraft approached the localizer; I observed aircraft X at 8;000 ft. The next hit was below 8;000 ft and now below the MVA. I asked the pilot his altitude to which he did not respond and I tried to climb him but my transmissions were blocked no less than 3 times. The aircraft was now at 7;200 ft. The low altitude alert never went off; but I issued a low altitude alert to the pilot and climbed him to 9;000 ft. He read back the clearance but was very slow to climb the aircraft. However the aircraft did accelerate. Due to the fuel situation that the pilot advised me of; I chose not to break the aircraft off the approach but rather to ask if he was able to continue the approach. He replied in the affirmative. I reissued the clearance and reduced his speed. He was now overtaking the traffic in front of him; but I didn't have time to keep him on my frequency due to the altitude of the aircraft next to him. The aircraft climbed while on the localizer until reaching the step down altitude of 9;000 ft and then descended on the approach and landed without further incident.this may have been a pilot error due to the added stress of performing a minimum fuel landing in IFR conditions. I am glad I was able to be of assistance to the pilots.
Original NASA ASRS Text
Title: D01 TRACON Controller reported an aircraft descended below the assigned altitude and below the MVA.
Narrative: I was working arrivals doing ILS approaches. Aircraft X checked in on the downwind and declared minimum fuel. I verified the fuel status and advised the pilot to which runway to expect. I continued working through my other aircraft with an awareness that I needed to get Aircraft X in as soon as feasible. It was low IFR and with the parallel runway configuration aircraft were doing at least 20 mile finals. At the opportune time; I based Aircraft X at 9;000 ft. The aircraft took the turn and I then issued the full ILS clearance to the aircraft. The pilot read back the turn and clearance but not the altitude.As the aircraft approached the localizer; I observed Aircraft X at 8;000 ft. The next hit was below 8;000 ft and now below the MVA. I asked the pilot his altitude to which he did not respond and I tried to climb him but my transmissions were blocked no less than 3 times. The aircraft was now at 7;200 ft. The Low Altitude alert never went off; but I issued a low altitude alert to the pilot and climbed him to 9;000 ft. He read back the clearance but was very slow to climb the aircraft. However the aircraft did accelerate. Due to the fuel situation that the pilot advised me of; I chose not to break the aircraft off the approach but rather to ask if he was able to continue the approach. He replied in the affirmative. I reissued the clearance and reduced his speed. He was now overtaking the traffic in front of him; but I didn't have time to keep him on my frequency due to the altitude of the aircraft next to him. The aircraft climbed while on the localizer until reaching the step down altitude of 9;000 ft and then descended on the approach and landed without further incident.This may have been a pilot error due to the added stress of performing a minimum fuel landing in IFR conditions. I am glad I was able to be of assistance to the pilots.
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.