Maybe this write up will help someone else...
About a year ago during VFR flight, one of the dual AHRS rebooted resulting in EFISes displaying divergent flight information. I can totally see event could really become a fatal distraction if it ever happened at just the wrong time.
My panel includes 3 GRT HX EFISes driven by Dual AHRS and dual magnetometers. The electrical system is Z14 architecture (dual alternators and dual batteries). EFIS displays can be swapped but are normally set so that EFIS1 shows Primary Flight information, EFIS2 Map, and EFIS3 Engine. AHRS1 goes to the Primary flight EFIS1 display and AHRS2 goes to the EFIS2 display.
. . .
The first symptom that something was not right was "Dual AHRS" indication replaced by "AHRS x" which means something took a powder and only one AHRS was on line.
The Primary flight EFIS FROZE showing pitch up and roll left (takes several minutes to come back on line). But would you really trust it afterwards?
Ok, no problem. Just switch the backup EFIS2 (with AHRS2) to display Primary flight information. It showed good (?) data but it still disagreed with EFIS1.
It was SO TEMPTING to troubleshoot. The glaringly obvious problem was that neither EFIS could be trusted, so you REALLY need a tie breaker. Thankfully my panel includes backup AS, Alt and Attitude steam gauges. It wasn't difficult to switch over to steam gauges, but the EFISes were a huge distraction.
I'm very thankful this happened in VFR conditions and I learned a few valuable lessons.
1) Assume something will break and you will never be disappointed
Although my panel is very capable, I had assumed that my fancy multi-display, dual everything gizmos would always be there. Not so much!
2) Practice
Backups are worthless if you don't practice using them. We have SO much packed into EFIS displays. It's really distracting if one fails and there's little time to troubleshoot if in the soup. Even problems in VFR conditions can be equally fatal if they happen at the wrong time.
3) Remove the distraction
Do EFISes include an OFF switch? Mine don't and I didn't add any. Note to self, if an EFIS appears to fail, switch it to display that shows something else, such as engine parameters, or simply cover it up so there's no temptation to fixate on it.
Conclusion
After a good deal of troubleshooting on the ground, the reboot issue was traced to an AHRS power crimp. I fixed the crimp and then added a SECOND power wire input to each AHRS.
I now regularly practice switching to backups in flight... and have adjusted expectations that something will break regardless of every effort to prevent problems. Oh, and a totally low tech wet compass is still your best friend in case everything if all else fails.
Regards,
Jay
RV10 N433RV
About a year ago during VFR flight, one of the dual AHRS rebooted resulting in EFISes displaying divergent flight information. I can totally see event could really become a fatal distraction if it ever happened at just the wrong time.
My panel includes 3 GRT HX EFISes driven by Dual AHRS and dual magnetometers. The electrical system is Z14 architecture (dual alternators and dual batteries). EFIS displays can be swapped but are normally set so that EFIS1 shows Primary Flight information, EFIS2 Map, and EFIS3 Engine. AHRS1 goes to the Primary flight EFIS1 display and AHRS2 goes to the EFIS2 display.
. . .
The first symptom that something was not right was "Dual AHRS" indication replaced by "AHRS x" which means something took a powder and only one AHRS was on line.
The Primary flight EFIS FROZE showing pitch up and roll left (takes several minutes to come back on line). But would you really trust it afterwards?
Ok, no problem. Just switch the backup EFIS2 (with AHRS2) to display Primary flight information. It showed good (?) data but it still disagreed with EFIS1.
It was SO TEMPTING to troubleshoot. The glaringly obvious problem was that neither EFIS could be trusted, so you REALLY need a tie breaker. Thankfully my panel includes backup AS, Alt and Attitude steam gauges. It wasn't difficult to switch over to steam gauges, but the EFISes were a huge distraction.
I'm very thankful this happened in VFR conditions and I learned a few valuable lessons.
1) Assume something will break and you will never be disappointed
Although my panel is very capable, I had assumed that my fancy multi-display, dual everything gizmos would always be there. Not so much!
2) Practice
Backups are worthless if you don't practice using them. We have SO much packed into EFIS displays. It's really distracting if one fails and there's little time to troubleshoot if in the soup. Even problems in VFR conditions can be equally fatal if they happen at the wrong time.
3) Remove the distraction
Do EFISes include an OFF switch? Mine don't and I didn't add any. Note to self, if an EFIS appears to fail, switch it to display that shows something else, such as engine parameters, or simply cover it up so there's no temptation to fixate on it.
Conclusion
After a good deal of troubleshooting on the ground, the reboot issue was traced to an AHRS power crimp. I fixed the crimp and then added a SECOND power wire input to each AHRS.
I now regularly practice switching to backups in flight... and have adjusted expectations that something will break regardless of every effort to prevent problems. Oh, and a totally low tech wet compass is still your best friend in case everything if all else fails.
Regards,
Jay
RV10 N433RV