Date: 202106
Local time of day: 0601-1200
Location: EDF.Airport, AK
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
Airspace: Class E ZAN
ATC / advisory: TRACON A11
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Relief Pilot; First Officer
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Air Traffic Control; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: On arrival into EDF we were on ANC Approach. After initial contact; ANC asked what approach we wanted at EDF. The Pilot Monitoring replied the Visual 34. ANC instructed us to turn left heading 260 and descend and maintain 8;000 (we were at 13;000.) While rolling out on a 260 heading and still descending; ANC came back and said they were going to take us the other way and to turn back right heading 330. We rolled out on 330 still descending. At around 9;000 descending; ANC asked us if we wanted Runway 16 and that the winds were 330 at 5. Taking into account our position and high altitude relative to EDF Runway 34 and our weight; I decided that this would be acceptable; but wanted the IRO to double check the numbers before accepting this change. I said 'standby' and the Pilot Monitoring transmitted 'standby' to ANC. ANC immediately instructed us to descend and maintain 3;000. At the same time of ANC transmission; we were leveling at 8;000; and I was asking the IRO to run the numbers for 16. The Pilot Monitoring replied '3;000; Aircraft X'. I reset the altitude selector to 3;000; verified the altitude with the Pilot Monitoring; engaged FLC; set speed and we began to descend. This clearance seemed logical considering we were clearing terrain; there was no traffic on TCAS; no terrain indicating on the HSI (I was in terrain mode) and we needed to lose altitude to make the airport. There was no further contact with ANC ATC until they instructed us to maintain 8;000.Descending through approximately 6;700; ANC contacted us and instructed us to maintain 8;000; low alt alert and that the MVA in that area was 8;000. After landing and block in; I was notified by EDF Tower (via the military) that ANC TRACON wanted me to give them a call (which I did after speaking to the Chief Pilot.) They took my info and said he would be forwarding to quality control (assurance?) and they may contact me as they were looking into it. There was either an error by ANC Approach or we mistook instructions for another aircraft. After the flight while discussing with the crew; myself and the Pilot Monitoring thought we heard the same instructions. Considering we may have accepted a clearance for another aircraft on frequency; I later looked at the flights in and out of ANC at the same time. There was another flight that arrived in ANC shortly after we landed. It is possible that the instruction were meant for them. It is also possible instructions were meant for an entirely different aircraft and we mistook it for us. There was high workload at the time while considering a runway change; configuring the aircraft and checking landing data.The Pilot Monitoring immediately replied to maintain 8;000. I rolled the altitude selector back to 8;000; clicked off the autopilot; added power and hand flew the airplane back to 8;000 and then reengaged the autopilot. If in fact we did accept a clearance from a different aircraft; caution must be used when similar flight numbers are on the same transmitting frequency; especially during high work loads. Unfortunately; we were unaware of the other aircraft at the time of the event.


Second narrative: As International Relief Officer; I heard ATC instruct us to descend to 3;000 feet.  Pilot Monitoring (PM) readback 3;000 feet on the radio to ATC. Pilot Flying (PF) entered 3;000 feet into MCP.  PM acknowledged the entry of 3;000 feet into MCP.  As aircraft descended below 8;000 feet; ATC instructed us to go back to 8;000 feet.  PF reset 8;000 feet in MCP and flew aircraft to 8;000 feet.  After landing; PIC was instructed to phone call ATC when he was informed that we flew below the instructed altitude of 8;000 feet.  It is possible that we heard and responded to an altitude instruction for another aircraft.  However; PM did read back the altitude and wasn't; subsequently; corrected.  The situation was corrected quickly after being instructed to do so.  The conditions were VMC.  There were no terrain hazards at our altitude.  There didn't appear to be any traffic conflicts.


Synopsis: Air carrier flight crew reported a CFIT event during approach due to a communication breakdown between ATC and flight crew.