G1000 AHRS failures

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Boatguy
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G1000 AHRS failures

Post by Boatguy »

A couple of recent posts and personal discussions have triggered me to try to investigate the frequency of G1000 AHRS (GRS79) failures. Watching lots of ASI crash analysis videos, I don't think I've seen a single video with LOC due to G1000 AHRS / partial panel issues. That said, I know the system does fail. So at the risk of appearing totally naive, how frequently does this happen? Not "what if", but first, second or maybe even third hand stories of G1000 AHRS failures.

Maybe later we can get into other sorts of G1000 partial panel situations, or someone can start another thread. For the moment, let's focus on AHRS.

Cheers!
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TwinStarScott
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Re: G1000 AHRS failures

Post by TwinStarScott »

After some quick internet searching Russ, here's a generic article from 2008 on the subject of glass panel failures:

https://blog.aopa.org/aopa/2008/07/30/n ... ggo-wrong/

yet follow-up comments posted (below) by other pilots reference the G1000 specifically 12 different times.

One post in particular caught my attention:

"but I will only fly my family with backups for my backup. As the technology gets better it gets more complex, it get more mission critical but we should always have a reliable backup plan. I always have two independent GPS systems, EFB, hand held NAV com and the “steam gauge backup”. My AHRS for the G1000 has failed without warning in CAVU weather but at least it told me it had gone AWOL whereas the vacuum pump may not be obvious"
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Chris B
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Re: G1000 AHRS failures

Post by Chris B »

Proving a negative is obviously difficult, but AFAICT G1000 AHRS failures are exceedingly rare. Hasn't happened to me yet in >2300 hrs. In fact, aside from rare PFT boot failures (probably due to movement), I have never had a G1000 failure. Well, other than having the GFC700 follow instructions rather than intentions. :oops:

Our backup electric AIs also have an excellent reliability record. The main risk is probably total electrical failure, which has nearly happened to me once (see: link to 2014 DAN thread). That was a self-inflicted issue, but an alternator or main battery failure would be memorable. No panel, radio, transponder, boost pump, or flaps. :shock:

The emergency battery should keep the AI alive, but unfortunately there is no ongoing way to ensure that the wiring & lithium cells are functional. Engaging the backup battery also requires pilot intervention in what will presumably be a very busy time, *before* the AI spins down.

Personally I am hoping to keep the existing electric AI, but eventually replace the backup altimeter with a "mini glass panel" having integrated battery backup, like the Aerovonics AV-30 (see: https://aerovonics.com/av-30) or Garmin/Dynon equivalent. Under most circumstances this would make partial panel a relatively straightforward problem.

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Re: G1000 AHRS failures

Post by Colin »

Back in August 2013 in our DA40 I had an alternator failure which was uneventful because we were daytime VFR on a clear day. The G1000 screens went black after landing.

In January 2017 I had an actual failure of the AHRS the G1000 uses, which turned out to be five bent pins in the connector certainly caused by work at the factory. I wrote it up in some dryer (and shorter) detail after the fact.

My DPE for the instrument checkride said, "There's no reason for me to make you practice partial panel because of how redundant everything is in here..." I don't agree with him. I practice flying by the standby instruments and I have practiced flying at night by the iPad. And I don't really feel comfortable flying IMC or at night unless that iPad is currently, charged, and connected. It is my backup for my backup.

It was 1,600 hours in the DA40 and another 600 in the DA42. I would say I have had one true AHRS failure entirely due to poor maintenance practices at the factory.
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vontresc
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Re: G1000 AHRS failures

Post by vontresc »

Our DA-40 hasn't had any AHRS issues AFAIK, but we had plenty of grief with the magnetometer. Not as bad as an AHRS failure but still frustrating.

So this stuff does fail.
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Re: G1000 AHRS failures

Post by Boatguy »

vontresc wrote: Tue Apr 09, 2019 7:32 pm Our DA-40 hasn't had any AHRS issues AFAIK, but we had plenty of grief with the magnetometer. Not as bad as an AHRS failure but still frustrating.

So this stuff does fail.
By magnetometer you mean the heading sensor/electronic compass via GMU44? What was the resolution of the problem?

The backup for heading is of course the magnet compass, and then two separate GPS's which provide Track which is arguably more valuable than heading anyway.

Of course everything can fail, the question is how often? I think of it as a risk equation which is the product of Severity of Failure X Likelihood to Fail. So for example EFATO has a very high Severity and a low, but significant Likelihood (engine is under max load) so that's a big issue which is why we train for it (even if only one engine for the ME folks). For IFR AHRS has a very high Severity and I'm trying to understand the Likelihood.
Last edited by Boatguy on Wed Apr 10, 2019 3:30 am, edited 1 time in total.
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vontresc
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Re: G1000 AHRS failures

Post by vontresc »

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.
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Re: G1000 AHRS failures

Post by Rich »

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.
Curious. I could see a potential problem with the strobe lights (which are supposed to be on all the time), due to the ballast and the synch signal that has to pass between the wings. But just the nav lights, which are straight DC, this is interesting. Especially since the LEDs are also straight DC circuits, albeit it at lower current.

I'm now LED'ed also, and have been wondering about the GMU 11 that is part of the G5 installation. The installation manual has a very involved procedure for validating the proper operation of the GMU 11 in each airframe.
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vontresc
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Re: G1000 AHRS failures

Post by vontresc »

We have the older whelen incandescent/strobe light unit. The ballast for the strobes is mounted out past the the magnetometer. Not sure on how much that draws. IIRC the incandescent bulbs are rated at 25W a piece. So at 28V that's around 1.8amps. In testing the fault, no impact was caused by the strobes, but turning on the nav lights failed it pretty consistently.

The LED drop ins are only drawing 12W total now. Seems to be working so far.

We got the bulbs here.
https://www.aero-lites.com/
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Rich
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Re: G1000 AHRS failures

Post by Rich »

vontresc wrote: Wed Apr 10, 2019 7:53 pm We got the bulbs here.
https://www.aero-lites.com/
I replaced the A600 assemblies with Orion units a couple of years ago, so the wingtips are now all-LED. Shaved off about 4 lbs. of weight and about .75 in. of wingspan :D

Still curious. I certainly never had any problem with the original nav lights with my King KMT112 units and haven't heard of the GMU44/nav lights being a widespread problem.
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