Light Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (mon) 1
Communication Breakdown; Distraction
Airspace Violation All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Provided Assistance
Environment - Non Weather Related
Aircraft X was under the control of Edmonton ACC (CZEG; Whitehorse Sector) on an IFR flight plan YXY...JAGIT...YOW.  Before I opened the D-side position on sectors 7/8 the R-side had approved coordination from the CZEG Controller for Aircraft X to maneuver in the vicinity of JAGIT in the block altitude 240B270.  I opened the position to assist during a period of busy traffic and did not have time to initiate a recorded position relief briefing; there had not been a D-side until that point.  I asked about Aircraft X as it was an unusual flight plan and due to be in our airspace a short time after I opened D7/8.  All coordination had been completed by the R-side and we were never going to be in control of or in radio contact with the aircraft so I continued with normal duties.  A short time later I noticed a beacon target to the east of JAGIT squawking 2000 and indicating FL240.  I assumed this was Aircraft X as it corresponded to where the aircraft was expected to be.  The aircraft was proceeding westbound when it began a slow descent out of FL240.  I called the CZEG controller to inform them of the situation and by the time he answered the line the aircraft had descended below the MIA in its area (FL218) and was continuing down.  I told the CZEG Controller of the minimum altitude and that CFNCT needed to climb immediately.  A few moments later CZEG called me indicating that he was unable to communicate with the aircraft due to its low altitude and the limitations of the frequency. I requested permission to use that frequency so that an aircraft in our airspace and in Aircraft X vicinity could relay the low altitude alert.  The R-side was able to successfully relay the instruction and had the aircraft climb to FL240. The CZEG Controller called again some time later once he had re-established communications and confirmed that the pilot had mistakenly descended below the altitude assignment.The clearance given by the CZEG Controller ensured separation from terrain and the pilot's action caused the unsafe situation.  The only way this may have been avoided is if the pilot had been monitoring a frequency with adequate coverage to reach altitudes lower than FL240.  I recommended to the CZEG Controller that low altitude aircraft in the vicinity of YAK should monitor 119.0 (the YAK RCAG) instead of 126.55 (the ORT RCAG) which he had instructed Aircraft X to monitor. If Aircraft X had been listening to 119.0 the R-side may have been able to successfully issue the low altitude alert in the blind.
CZEG (Edmonton Center) called me on the R-side prior to having a D-side with a non-radar point out on Aircraft X in the block 240B270 and advised he would be doing a couple turns in hold about 20 miles east of JAGIT.  I approved it.  I had [no] traffic and the altitudes where well above my MIAs.  A while later my D-side points out the code 2000 at FL240 in that vicinity and I tagged up the call sign.  Moments later while I was sequencing aircraft for ANC my D-side points out that Aircraft X was descending; about that time it started to MSAW as well.  My D-side immediately called CZEG to inquire; and established that nobody was in contact with him because of his altitude [low].  So we got permission to use CZEG's frequency to relay through another aircraft a low altitude alert and to climb immediately.  Aircraft X climbed and I had the other aircraft call again to assign 240; and my D-side advised CZEG of this.  A few minutes later CZEG advised they were in contact with the pilot again as he fell out of our radar coverage and the pilot admitted his descent. The appropriate coordination had been accomplished; so it was a pilot deviation; no changes recommended.
ZAN Controller reports of an aircraft descending into a lower MVA and having radio problems trying to reach this aircraft to tell it to climb.