G1000 AHRS failures

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vontresc
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Re: G1000 AHRS failures

Post by vontresc »

Magnetometers can be finicky. I had one avionics shop jokingly tell me that the best place to mount the GMU44 is on a 100' string behind the airplane.
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Boatguy
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Re: G1000 AHRS failures

Post by Boatguy »

vontresc wrote: Wed Apr 10, 2019 3:28 pm Turns out in our case that the GMU-44 would fail when the nav lights were on. We upgraded to LED nav lights, and haven't had an issue since. Lower current in the wires going past the magnetometer reduced the interference.
So the GMU 44 did not fail, it was poor installation placement that was causing the GMU44 to be influenced by the magnetic field created by the current in the nav lights wiring. That should have been identified in dynamic testing. It's the solid state version of compass deviation.
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Scotsman58
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Re: G1000 AHRS failures

Post by Scotsman58 »

I recently had an AHRS failure (in my 2005 DA40 -- non-WAAS G1000). Fortunately, it happened on the ground, following start-up. The PFD displayed the "AHRS align" screen but would not progress to initializing. I tried to shut down and restart a few times but no joy. Interestingly, the G1000 system status page was not showing any faults -- but nothing I tried could get the AHRS to initialize. I had to leave the plane at KGON (not my home base -- pain in the ***) and Columbia Aviation was able to test the system and determine (with the help of Garmin) that the GRS-77 AHRS box was not providing a good signal and had to be replaced. I ended up having to replace the GRS-77 (thanks to Columbia for their great service).

Everything is good now, but I'm thinking more about redundancy (or lack thereof) in the DA40 than I was before. I now have a Stratus III and an iPad and at least have some backup AHRS capability, in addition to the backup mechanical AI.
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