Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 5.0
Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
ATC Equipment / Nav Facility / Buildings
ZDV called me and informed me that Aircraft X; deviating en route was indecisive and having trouble with the weather. They gave me control and shipped me the aircraft. Aircraft X decided to divert to GCN due to the weather. They were IMC and asked for vectors through the Grand Canyon flight free zone corridors. I issued a vector. Aircraft X then asked to descend as low as possible. I informed them the lowest IFR altitude available and descended them. I observed the data block's altitude to read 300 feet below the MIA (Minimum IFR Altitude) and attempted to contact the aircraft. After several attempts to communicate with no response another aircraft on frequency told me they could hear Aircraft X responding to my calls though I could not hear them. I had the other aircraft inform Aircraft X of the MIA and told them to maintain that minimum altitude. I reestablished contact with Aircraft X a couple of minutes later and then was able to vector them to the initial approach fix for the ILS Approach to Runway 3 at GCN. They were cleared in for the approach and after giving them the frequency change they ended up going missed approach. After climbing back up to 9000 feet (the MIA in that area); I vectored them back to the IAF for the ILS approach again. I cleared them for the approach and before I could give them a frequency change; we lost communication again. I informed the Supervisor of the situation and they attempted to make contact with the FBO at the airport as the Tower had already closed for the night. A few minutes later; we were called by flight service stating Aircraft X had landed. The inability for myself and the pilot to be able to communicate due to the radio limitations in that area of my sector is the main contributor to this safety event. Though the pilot sounded nervous and was dealing with weather; they appeared to follow the instructions they had heard. I believe that improvements to the radio as well as radar coverage in that area would help prevent similar situations in the future.
ZLA Center Controller reported insufficient radio coverage in their airspace caused confusion when vectoring an aircraft that was diverting due to weather descended below the Minimum IFR Altitude.