Narrative:

Aircraft X was released for departure off of jac airport via the geyser departure procedure. The aircraft departed runway 01 at jac and reported on frequency. I radar identified aircraft X 2 miles north of jac and asked the pilot to confirm his altitude. I gave a control instruction to the pilot; leaving 14;000 feet MSL cleared right turn direct a fix south of aircraft X's position. The pilot read back the clearance correctly. Continuing my scan I began to ship another aircraft to ZDV and while doing so noticed a radar hit showing a right turn of aircraft X at about 10;200 feet MSL. The minimum IFR altitude in that area was just over 11;000 feet MSL. The departure procedure requires a right turn to intercept the outbound course from the jac VOR. At times a quick turn by an aircraft is translated as a bigger turn by the radar system; therefore I couldn't tell initially if that turn was due to the aircraft or the radar. I finished shipping the aircraft to ZDV and watched aircraft X for the second radar return. The second radar return showed a continuation of the right turn southbound. I immediately restated the clearance to not turn on course until leaving 14;000 feet MSL. The pilot again responded with the correct clearance given. I informed my manager of what was happening while I continued to monitor the aircraft's climb rate. Aircraft X had a climb rate that was fast enough to stay out of high terrain so no low altitude alert was issued. The manager left and I then shipped aircraft X to the next sector in ZLC after a handoff was accepted. Sector 08 received aircraft X and continued their climb. The data block was dropped leaving R16's airspace. The response by the pilot was that the fix nalsi is a fly by point instead of a fly over fix. The FMS of the aircraft X is being stated as the reason for the early turn. I have never witnessed an FMS system make a 'smart turn' 10 miles from a fix to stay on course. Not all aircraft make that early of a turn including aircraft X flown by company to many destinations from jac. I believe that fix needs to be made a fly over fix to mitigate the ability of an FMS system making that error.

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Original NASA ASRS Text

Title: ZLC Center Controller reported an aircraft turned early leading to a climb below the minimum IFR altitude.

Narrative: Aircraft X was released for departure off of JAC airport via the GEYSER Departure Procedure. The aircraft departed Runway 01 at JAC and reported on frequency. I radar identified Aircraft X 2 miles north of JAC and asked the pilot to confirm his altitude. I gave a control instruction to the pilot; leaving 14;000 feet MSL cleared right turn direct a fix south of Aircraft X's position. The pilot read back the clearance correctly. Continuing my scan I began to ship another Aircraft to ZDV and while doing so noticed a radar hit showing a right turn of Aircraft X at about 10;200 feet MSL. The minimum IFR altitude in that area was just over 11;000 feet MSL. The departure procedure requires a right turn to intercept the outbound course from the JAC VOR. At times a quick turn by an aircraft is translated as a bigger turn by the radar system; therefore I couldn't tell initially if that turn was due to the aircraft or the radar. I finished shipping the aircraft to ZDV and watched Aircraft X for the second radar return. The second radar return showed a continuation of the right turn southbound. I immediately restated the clearance to not turn on course until leaving 14;000 feet MSL. The pilot again responded with the correct clearance given. I informed my manager of what was happening while I continued to monitor the aircraft's climb rate. Aircraft X had a climb rate that was fast enough to stay out of high terrain so no low altitude alert was issued. The manager left and I then shipped Aircraft X to the next sector in ZLC after a handoff was accepted. Sector 08 received Aircraft X and continued their climb. The data block was dropped leaving R16's airspace. The response by the pilot was that the fix NALSI is a fly by point instead of a fly over fix. The FMS of the Aircraft X is being stated as the reason for the early turn. I have never witnessed an FMS system make a 'smart turn' 10 miles from a fix to stay on course. Not all aircraft make that early of a turn including Aircraft X flown by company to many destinations from JAC. I believe that fix needs to be made a fly over fix to mitigate the ability of an FMS system making that error.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.