Narrative:

After a normal departure from clt I was climbing on vectors to the SID altitude of 4;000 feet MSL. My autopilot (an stec 55X) was engaged with altitude capture. It is connected to a garmin G500 pfd. I had entered the correct altimeter setting (30.34) in the G500 prior to takeoff and entered 4000 feet as my cruise altitude.during climb; well prior reaching 4;000 feet; I noticed that my heading information on the G500 had failed as indicated by a small red 'X' and the word 'heading'. This happens occasionally and can be caused by various forms of interference. It rarely lasts more than a minute and then the warning goes away. Prior to reaching my assigned altitude; the G500 was operating normally again.when my autopilot leveled off at 4;000; ATC called and said 'I show you at 4;400 feet. Descend to 4;000 altimeter 30.34.' I acknowledged and looked at my altimeter setting and it was 29.92. Somehow during the failure of the heading mode; the G500 had reset the altimeter setting. I later contacted garmin and they said this should not have happened. I am still investigating this. Lessons learned: cross check altitudes when leveling off. I have a backup; classic steam gauge altimeter but I never looked at it - only my primary G500 altimeter. Second; if there is any glitch or anomaly with the pfd; all settings must be checked (even though garmin says they shouldn't be lost). An observation: many GA pilots have upgraded their panels from the old mechanical instruments to 'glass.' I suspect only a small fraction of these are familiar with all the various failure modes of their new equipment. Moreover; when we go to training; the instructors we fly with are not familiar with the failure modes either so we don't learn them there. I know it is the PIC responsibility to be familiar with their equipment but how many pilots read the hundreds of pages of the operators' manual?

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Original NASA ASRS Text

Title: The pilot of a turbocharged Cessna twin was climbing to his cleared altitude of 4;000 MSL when he noted the latest example of a recurring nuisance heading failure alert on his GARMIN PFD. As before; the alert went away shortly and the climb was continued. After leveling; ATC advised he was reporting 4;400 MSL vice 4;000 as cleared and provided the altimeter setting of 30.34; the same as was set in the PFD prior to departure. When the reporter checked he was surprised to note that the setting had changed to 29.92; apparently during the previous PDF heading anomaly. Of particular interest is his last paragraph addressing the little discussed but widely realized fact that few converts to glass cockpit retrofits in their aircraft are totally familiar with all that is included in the several hundred page users' manuals.

Narrative: After a normal departure from CLT I was climbing on vectors to the SID altitude of 4;000 feet MSL. My autopilot (an STEC 55X) was engaged with altitude capture. It is connected to a Garmin G500 PFD. I had entered the correct altimeter setting (30.34) in the G500 prior to takeoff and entered 4000 feet as my cruise altitude.During climb; well prior reaching 4;000 feet; I noticed that my heading information on the G500 had failed as indicated by a small red 'X' and the word 'Heading'. This happens occasionally and can be caused by various forms of interference. It rarely lasts more than a minute and then the warning goes away. Prior to reaching my assigned altitude; the G500 was operating normally again.When my autopilot leveled off at 4;000; ATC called and said 'I show you at 4;400 feet. Descend to 4;000 altimeter 30.34.' I acknowledged and looked at my altimeter setting and it was 29.92. Somehow during the failure of the heading mode; the G500 had reset the altimeter setting. I later contacted Garmin and they said this should not have happened. I am still investigating this. Lessons learned: cross check altitudes when leveling off. I have a backup; classic steam gauge altimeter but I never looked at it - only my primary G500 altimeter. Second; if there is any glitch or anomaly with the PFD; all settings must be checked (even though Garmin says they shouldn't be lost). An observation: Many GA pilots have upgraded their panels from the old mechanical instruments to 'glass.' I suspect only a small fraction of these are familiar with all the various failure modes of their new equipment. Moreover; when we go to training; the instructors we fly with are not familiar with the failure modes either so we don't learn them there. I know it is the PIC responsibility to be familiar with their equipment but how many pilots read the hundreds of pages of the operators' manual?

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.