Intermittent systems failures in ADAHRS, EMS, GPS...

[Ben Barbour]

I have been fighting this issue for months now. It began early on with the MAP sensor intermittently going out... I didn't pay too much attention to it though because I don't NEED a MAP in my 172.

A few months later, intermittently in flight I will get an ADAHRS failure where it shows me going 500mph and at 50000 feet with an erratic compass and attitude. Cycling the power corrects it until it occurs again. This happens on all 3 screens. We've swapped out the ADARHS once and it did nothing, now my shop wants to swap it out again which to me, makes no sense. A couple days ago, I was getting a complete system failure with half of the EMS sensors failed (EGT, CHT, volts, amps, etc... not working.. volts showed 22 on my 12v system but measured 12v so I'm sure it was just erroneous data)... Carb temp, oil temp, MAP, fuel, etc.. were all reading correctly. In addition, the backlights on the physical AP and Alt/Baro/Hdg panels were flickering. I have also had my compass fail in flight where it locked in on 285 degrees and jittered between 275-290 until cycling the power.

All that seems to spell a wiring problem and not a particular unit failure. Since the massive failure of many systems, several cycles of the power restored everything to working order before it quickly went back to just the ADAHRS failure....

The system worked fantastic for about 8 months before all these problems occurred... given all the wild symptoms and the different affected systems.. where would you likely start to look for problems? Skyview network? I have 2 hubs.. maybe a hub is failing?

 

[Carl_Froehlich]

Contact Dynon service - I suspect they will want to start with you sending them the “Diagnostic Data” file.

Carl

 

[WorkingWarbirds]

With that kind of failure, makes me wonder about the installer. Check the Hub and network cable connections first I'd think.

 

[chriscalandro]

remember all those devices share power and gnd from the display. It sounds like a bad ref voltage to a bunch of stuff which suggests to be it’s getting pulled low somewhere.

I’d try replacing some network cables. Are they all single cables or do you have some splitter cables?

 

[vagregg]

We have been fighting this exact same failure for 6 months now. Replaced the ADAHRS, wiring harness, and double checked all connections with no avail. The failure seems to occur after 20-30min of flying OR on the start of a descent and then after about 2-3seconds the screen will flash back on with everything functioning properly. Makes me wonder if it's a batch of bad screens or possibly a bad network hub.

 

[Ben Barbour]

Your symptoms are very similar to mine. Through my troubleshooting I confirmed it wasn't the screens and the installer went through every bit of cable and harness, checked continuity and resistivity. Finally we replaced the ADAHRS again. So far I have almost 50 hours on it without the errors surfacing again (last time we replaced it, the errors resurfaced in less than 10 hours, the original unit had almost 150 hours on it before failure). My guess is that it's a bad batch of ADAHRS units. It's theoretically possible that I ended up with 2 ADAHRS with the same failure mode.