Date: 201908
Local time of day: 1201-1800
Location: FBK.Airport, AK
Light: Daylight
Aircraft: Small Transport
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Flight phase: Descent
Airspace: Class E FAI
ATC / advisory: TRACON FAI
Reporter organization: Government
Reporter function: Instructor; Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Training / Qualification; Situational Awareness; Distraction; Communication Breakdown
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance
Contributing factors: Human Factors; Airspace Structure
Primary problem: Human Factors

Narrative: Prior to accepting the handoff from Center; there were high winds; approximately 240 at 55 knots. A C208 had checked in and was being vectored around a large weather cell that turbulence had been reported. The C208 was keeping their altitude high reference the weather build up. At this time; Tower requested; using automated request; for a release on an RNAV SID. This departure procedure would place the [departing] B190 in the vicinity of the C208 coming from the northwest. Since we only had 2 aircraft on frequency; and it was slow; I utilized the display to bring up the SID and help answer questions regarding it with my trainee. At that time; Aircraft X was handed off from Center descending out of 10000 ft. for 8000 ft. I was instructing as an OJTI (On-the-Job Training Instructor). My trainee gave the Pilot his clearance direct to the IAF and pilot's discretion descent to 6500 ft.; expecting clearance for the GPS RNAV Approach at FBK. At the time; I believed that Aircraft X had read back correctly all information given; but upon further review of the audio replay; Aircraft X had read back the altitude of 6000 ft. The MVA that Aircraft X was currently in was 6400 ft. The [wrong] read back was missed. Further distractions from releases off FBK; and the assignment of runway heading from the aircraft departing allowed for a break down in the initial scan. Aircraft X was the only aircraft northeast of our airspace; with the focus of discussion being to the west and northwest. Aircraft X descended below the MVA by 400 ft. There were no LA alerts or Climb Alerts or MSAW (Minimum Safe Altitude Warning) Alerts sounded; to draw attention back to the aircraft below the MVA. After issuing more weather to the other aircraft involved; the scan back to Aircraft X; who would be expecting further descent shortly revealed that they were below the MVA. I keyed up the frequency; since no alert had sounded and asked Aircraft X to verify his altitude. Prior to this; there had been a few aircraft from the airport that have had faulty or inaccurate Mode C's that required reassignment of altimeter. When I asked him to verify altitude at 6500 ft.; he said 'Negative; six thousand.' I immediately climbed him to an altitude above the MVA. I notified my CIC (Controller in Charge) in the room. During this occurrence; it was the second of a long; combined stint of training for this particular trainee. The new requirements from our region of having our trainees get 12-15 hours of live traffic training a week has caused a bit of fatigue in all the controllers within the facility. We are required; with short staffing numbers; to force these trainees on position even when there isn't any traffic. This does not include time to go over book work with their OJTI's which is making us have to perform book work while on position. I believe this was a partial factor in the event; as attentions were held on the IDS4 and the approach plates. Since the traffic volume was so low; we had to not waste the 2 hour session by not going over anything.My recommendation is that trainees be allowed to utilize their 3 hour required training a day to be given at least 1 hour of that training to go over book work instead of 3 straight hours of live traffic. This would allow for better transfer of knowledge; while still allowing the trainee at least 2 hours of position time. Typically; 2 hours of position time wouldn't be difficult if there were plenty of staffing; to include CIC's to supervisor operations. During this particular stretch; every available body was on position with training occurring both in Tower and in Radar.




Synopsis: FAI TRACON Controller reported not hearing an aircraft read back an incorrect altitude which caused the aircraft to descend below the Minimum Vectoring Altitude.