Narrative:

While in cruise flight; I turned the controls over to the captain; and I left the cockpit to check on the operation of the ipads in the cabin as they were written up for not being able to connect to the inflight entertainment system.while I was gone; the aircraft (with ap engaged); failed to make a course turn with a dog-leg at zzzzz intersection. The controller queried the captain; and the captain then noticed the deviation; and that the FMS/auto pilot had failed to make the turn at zzzzz despite being in FMS mode. The captain then re-sequenced the FMS to make the next stop leg the active way point; and the aircraft turned back onto the course. Upon my return to the flight deck; the captain described what had happened; and stated that he had probably flown no more than 3 miles past zzzzz before correcting back to the proper course.upon hearing the description; it sounded like the active leg had been suspended similar to when one would engage obs mode to change the active course using the course selector knob. I brought up the garmin 5000 manuals on my ipad; and read the description of what the obs knob does; and surmised what might have happened. Earlier; and prior to leveling off at FL400; I had used my pfd gtc (primary flight display garmin touchscreen controller) to select monitor first officer comm 2; in order to listen to guard frequency. I recall that we hit some descent turbulence just as I was trying to press the small 'mon' button; and that I had to hit it again as the first touch landed lower on the screen.well; the obs button is directly underneath the audio selector; and all we could figure is that I must have engaged obs mode; thus suspending the sequencing of the FMS way points; and when the captain forced the next leg (after zzzzz intersection) to be the active way point; obs mode was then deselected. This fit with the description of obs mode exactly. It would be better to have the obs mode button lower on the gtc; maybe where the timer button is; that way; if one accidentally touches the button while trying to select an audio mon (a commonly used function); then all that would happen is that you would bring up the timer panel. Likewise; it would be helpful to have a white cas message pop up after a certain amount of time in obs mode; as one would generally only select obs to manually make a course change; which would be a quick operation. Likewise; it would be helpful to have another alert (white cas message; or general message) if one were in obs mode while approaching a course way point; as the FMS is basically suspended while in obs mode.

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Original NASA ASRS Text

Title: CE-680 First Officer reported that the aircraft failed to make a course turn while the autopilot was engaged.

Narrative: While in cruise flight; I turned the controls over to the Captain; and I left the cockpit to check on the operation of the iPads in the cabin as they were written up for not being able to connect to the inflight entertainment system.While I was gone; the aircraft (with AP engaged); failed to make a course turn with a dog-leg at ZZZZZ intersection. The controller queried the Captain; and the Captain then noticed the deviation; and that the FMS/Auto Pilot had failed to make the turn at ZZZZZ despite being in FMS mode. The Captain then re-sequenced the FMS to make the next stop leg the active way point; and the aircraft turned back onto the course. Upon my return to the flight deck; the Captain described what had happened; and stated that he had probably flown no more than 3 miles past ZZZZZ before correcting back to the proper course.Upon hearing the description; it sounded like the active leg had been suspended similar to when one would engage OBS mode to change the active course using the course selector knob. I brought up the Garmin 5000 manuals on my iPad; and read the description of what the OBS knob does; and surmised what might have happened. Earlier; and prior to leveling off at FL400; I had used my PFD GTC (Primary Flight Display Garmin Touchscreen Controller) to select MONITOR FO COMM 2; in order to listen to guard frequency. I recall that we hit some descent turbulence just as I was trying to press the small 'MON' button; and that I had to hit it again as the first touch landed lower on the screen.Well; the OBS button is directly underneath the audio selector; and all we could figure is that I must have engaged OBS mode; thus suspending the sequencing of the FMS way points; and when the Captain forced the next leg (after ZZZZZ intersection) to be the active way point; OBS mode was then deselected. This fit with the description of OBS mode exactly. It would be better to have the OBS mode button lower on the GTC; maybe where the timer button is; that way; if one accidentally touches the button while trying to select an audio MON (a commonly used function); then all that would happen is that you would bring up the timer panel. Likewise; it would be helpful to have a white CAS message pop up after a certain amount of time in OBS mode; as one would generally only select OBS to manually make a course change; which would be a quick operation. Likewise; it would be helpful to have another alert (white CAS message; or general message) if one were in OBS mode while approaching a course way point; as the FMS is basically suspended while in OBS mode.

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.