But I had a strange, progressive failure of the AHRS. But my mechanic is unsure where the source of the trouble is. (I asked if there was a mechanical AI somewhere that could be falling over, whether my recent upgrade work may have damaged the backplace of the LRU unit, and what MAY have failed. Since it was an intermittent failure, should we send units back to Garmin for bench testing?) Quoting:
I’ve never seen a “check attitude” annunciator before. If it were just the wind malfunctioning I’d say ADC or a blockage somewhere. If the heading is drifting I’d say GMU. If both then probably GRS.
1. No mechanical instruments. You used to have a turn coordinator only for the KAP140
2. The rack shouldn’t have changed much since the new GIAs and GTX are the same size as the old ones. The fan should be enough and it would give you a fail message if it stopped.
3. I wouldn’t rule out the GIAs since they are new and can fail the AHRS (usually with GPS faults too, and if you lose GPS I think you lose wind)
4. Sending LRUs to Garmin sounds pretty time consuming and expensive. It would be more ideal get loaners to swap in and see if the problem persists.
I am certain there is not a blockage somewhere. The airspeed and everything else matched the independent GPS readings from the G1000 itself and the Stratus 2s. I don't think the avionics guy on the field in Midland is going to be able to do much. I have a feeling I'm flying it home VFR on Thursday.
Colin Summers, PP Multi-Engine IFR, ~3,000hrs colin@mightycheese.com * send email rather than PM http://www.flyingsummers.com
N972RD DA42 G1000 2.0 s/n 42.AC100 (sold!)
N971RD DA40 G1000 s/n 40.508 (traded)
Sorry to hear about this. I read the post on your web site.
I would start by removing all LRUs, vacuum cleaning the rack backplane (I had copper debris sitting there once) , cleaning the contacts and reassembling.
Do the same with the external connectors that are possible candidates.
And if this does not work, I believe the idea of starting by suspecting the newly installed parts of being dead on arrival makes sense. The infamous "U shaped" failure rate curve. If under warranty, it should be possible to get loaner parts?
As Antoine suggested, plug-in connections on the backplane (or elsewhere) are the most common failure point for this type of gear. I would remove all of the boxes, clean all of the connectors as well as I could, and then treat them with something like Stabilant 22 (http://www.stabilant.com/appnt17.php). I has a noisy NAV/COM in my aircraft where simply cleaning and replugging the box did not cure the static, but one application of this stuff did (for > 1 year, so far).
I really hope it's something simple like a backplane connection, but based on the symptoms you described, it sounds more like a failing component in the AHRS. Looking forward to hearing what it turns out to be.
Thanks Steve. Stabilant is the name of the miracle cleaner I was looking for. I actually ordered a bottle of this many moons ago and still have it handy. Used it once to clean up magnetometer contacts on my previous DA40.
Worked well.
Colin, yes, bathtub!
I could not find the world in english anymore
I had a "progressive" failure actually with similar AHRS data drop out that was down to bad crimps between the GMU and AHRS. The failure was progressive as it was temperature related: the crimps concerned were right on the limit and as the temperatures increased the connections got gradually worse/became more intermittent, so more failures. Found by pulling the cables (gently) at the crimps. So as well as the G 1000 chassis suggest that it may be worth a gentle tug test on the cables.
Wasn't there a post on this thread that mentioned the wingtip lights being replaced and it affecting the magnetometer? (Possible thread drift inside my head, so it could have been elsewhere.) Thanks.
Colin Summers, PP Multi-Engine IFR, ~3,000hrs colin@mightycheese.com * send email rather than PM http://www.flyingsummers.com
N972RD DA42 G1000 2.0 s/n 42.AC100 (sold!)
N971RD DA40 G1000 s/n 40.508 (traded)
