ADAHRS then GPS failure at altitude

[dch@haydencorp.com]

On a flight from my home airport to another approximately 115NM away, my D1000 system demonstrated several errors I hadn't seen previously during the first 40 hours of flight testing.

The first symptom was a loss of correct altitude in the PFD. Altitude suddenly jumped from 5,500 feet or so (my cruising altitude) to more than 48,000 feet. GPS altitude remained correct, but PFD altitude failed to read correctly until descent below 5,000 feet.

Later in the flight, the attitude indicator began to wildly gyrate at times, coupled with various "message" and "warning" verbal alerts and ADAHRS and GPS Assist messages. GPS Continued to function properly for the most part. Large red arrows appeared at times on the PFD, as the artificial horizon rolled around on the display for much of the flight until descent.

Throughout the flight and the return trip, temperatures were mild and winds were light. Actual flying conditions, altitude, attitude, etc., were all placid and normal.

The return flight was much the same, with PFD initially behaving normally, and then going erratic late in ascent. I did not notice if the behavior started at a particular altitude, but the flight out was at 5,500-7,500 feet and the return flight was around 4,500 feet. GPS information was also lost occasionally during the return flight, with both screens occasionally going "red X", though the GPS and moving map was far more reliable than the PFD/ADAHRS. EMS was fine throughout. I use a three-pane split, PFD 40% EMS 20% MAP 40%.

At home, I checked the forum and found a post about intermittent failures of a similar type that ended up being a chafed wiring harness. I did check all SkyView network cables yesterday and found no chafing. I also tried to prompt the error condition by wiggling wires and connectors at all points. No luck. The PFD remained fine.

I will download logs and diagnostics in the next day or so, and will post them here as soon as I have them.

Up to this point, the system has functioned very well, though nearly all of my flight testing has been at 3,500 to 4,500 feet, I believe. I only tend to select a higher altitude when I am cruising long distances as I was on this first long trip with the aircraft.

 

[Dynon]

I think you've already spoken to us here (I see the case), and we've also gotten your log. If the power line that goes to the GPS were shorting to ground, you would see the GPS issues for sure, and it could also affect the ADAHRS. That's the most likely culprit here, so check that first. From the data, it doesn't look to be an internal failure of the ADAHRS, at least not obviously.

 

[dch@haydencorp.com]

To clarify, the GPS wiring might cause a sustained failure of ADAHRS data, but not GPS data? During the flight, although the PFD was displaying erratic data for most of the flight, the GPS was only incorrect or absent for a few short periods. Notably, the aircraft's relative position to the magenta course line was almost always correct, but the white airplane icon's orientation relative to the direction of flight was occasionally very wrong (off by approximately as much a son 90 or 180 degrees at times).

I'll recheck the entire GPS cable path, but it follows much of the same route as the ADAHRS cable, and that route was both free of chafing and moving the bundle and connectors did not generate symptoms on the display.

 

[dch@haydencorp.com]

Just checked GPS wiring throughout. The run is clean, no signs of chafe. I also powered the system as before and manually tugged and jostled the cables along their length. There was no effect of any kind on the PFD; altitude and attitude read normally.

 

[Dynon]

Those are all the right things to check. If you're still seeing that, you should probably get in touch with our support team at 425-402-0433 or support at dynonavionics dot com for further help here. Mention "case 258108" (you can also email support with "case 258108" in the subject line and it will get back to our support team in the right place.