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Center controller reported that an aircraft descended below the minimum IFR altitude in a non-radar area; resulting in cftt.
| Attributes | |
| ACN | 1682678 |
| Time | |
| Date | 201909 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZAN.ARTCC |
| State Reference | AK |
| Aircraft 1 | |
| Make Model Name | Super King Air 350 |
| Operating Under FAR Part | Part 135 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Person 1 | |
| Function | Enroute Instructor |
| Qualification | Air Traffic Control Fully Certified |
| Experience | Air Traffic Control Time Certified In Pos 1 (yrs) 4 |
| Events | |
| Anomaly | ATC Issue All Types Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT |
Narrative:
While conducting OJT for my trainee; I ensured separation between aircraft X and a preceding aircraft using vertical separation. Aircraft X entered a known non-radar area and the trainee asked the preceding aircraft his altitude and they responded with level at 7;000 ft. The trainee then issued aircraft X 8;000 ft. To which the replay was that he was already cleared to 4;000 ft. We asked his altitude and he told us 4;200 ft. The minimum IFR altitude in that area is 4;600 ft. And aircraft X was climbed to 6;000 ft. But no warning was issued. We did not issue this altitude to this aircraft and confirmed it by reviewing the audio recording after our training session. I do not believe longitudinal separation was lost between aircraft X and the preceding aircraft due to routings and issued holding instructions. Overall I feel that this was pilot error in a non-radar environment. Having and adsb-gbt or wam (wide area multi-lateration) in the area would have given us enough radar coverage to have noticed the early descent out of 15;000 ft. And we could have corrected it before the aircraft descended below the minimum IFR altitude.
Original NASA ASRS Text
Title: Center Controller reported that an aircraft descended below the minimum IFR altitude in a non-radar area; resulting in CFTT.
Narrative: While conducting OJT for my trainee; I ensured separation between Aircraft X and a preceding aircraft using vertical separation. Aircraft X entered a known non-radar area and the trainee asked the preceding aircraft his altitude and they responded with level at 7;000 ft. The trainee then issued Aircraft X 8;000 ft. to which the replay was that he was already cleared to 4;000 ft. We asked his altitude and he told us 4;200 ft. The minimum IFR altitude in that area is 4;600 ft. and Aircraft X was climbed to 6;000 ft. but no warning was issued. We did not issue this altitude to this aircraft and confirmed it by reviewing the audio recording after our training session. I do not believe longitudinal separation was lost between Aircraft X and the preceding aircraft due to routings and issued holding instructions. Overall I feel that this was pilot error in a non-radar environment. Having and ADSB-GBT or WAM (Wide Area Multi-lateration) in the area would have given us enough radar coverage to have noticed the early descent out of 15;000 ft. and we could have corrected it before the aircraft descended below the minimum IFR altitude.
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.