Golden Eagle 421
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Communication Breakdown; Confusion; Distraction; Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Airspace Structure; Human Factors; Procedure
I had been sitting at the sector for about 15 mins. BigSky APCH (Boise) flashed Aircraft X; a (C421) probably 15 minutes before the aircraft would be in my airspace. The Aircraft X had a final altitude of 090 in the data block. I brought up my MIAs knowing that this altitude would be below the MIA along the route. After doing this; I came to the conclusion that 100 would be a safe altitude for Aircraft X. BigSky APCH called me for something (don't remember now) and I asked the controller to climb Aircraft X to 100 for terrain. She responded 'wilco' and took the hand off back. I continued to work and sometime later accepted the hand off on Aircraft X at 120. 'Even better;' I thought to myself. I issued the BOI altimeter to Aircraft X when the aircraft checked on and went back to working without re-checking my MIAs. Aircraft X was now between 5 and 10 nm north of the original route that I had looked at earlier. The MSAW alert went off on Aircraft X for a 129 MIA ahead. I measured Aircraft X's current heading and believe it was like a 092. I issued a right turn to a heading of 110 to Aircraft X thinking that I went more then needed on the heading. I continued to work and kept checking back on Aircraft X. It looked close to me; but I believed the heading was working and would ultimately work. The MSAW never stopped flashing that kept me second guessing. I felt that the aircraft was on the boundary of the 129 MIA; but still clear. But; the fact that the MSAW didn't stop flashing until the aircraft was clear of the MIA makes me question if I was safe or not?First off; I should have re-examined Aircraft X's route and the MIA's along it. Secondly I should have issued a stronger turn to the aircraft ensuring that it would stay plenty clear of the higher MIA.
Salt Lake Center Controller reported an unsafe situation where an aircraft was given an altitude to maintain below the Minimum IFR Altitude.