PFD Heading/Roll Error

[Edwardoc]

I'm curious to see if anyone else has had a skyview boot up and the heading and roll indications indicate a roll  or turn in wrong direction and then precessing back to correct roll & heading  indication as if it were a mag compass.  On a VFR flight  the AP in HDG mode would engage and immediately start slipping as AP attempted to hold a heading when the heading and roll indications were oscillating left and right like a mag compass in turbulence.  AP would command larger and larger roll commands as it attempted to hold a continuously oscillating heading.  Altitude channel worked perfectly.  I rebooted in flight and problem was gone.  Roll and heading were good and AP engaged normally for the remainder of a 4 hour flight and subsequent 7 sorties.  This is the second time this has happened in two years.

 

[Dynon]

Does it do that when you're flying the airplane by hand (and are not banking at all, of course), or was it only observed while the AP was flying?

One thing to look at to start: does PDF > G METER look normal, with no odd spikes?

 

[Edwardoc]

It does it when hand flying or on AP.  It has only happened twice in a year.  The first time I noticed the heading was acting odd as I turned out of parking on the ramp in that it was leading the turns like a mag compass does and then spun back and over shot the correct heading and then settled on correct heading for the taxiway.  But every little turn resulted in the heading going the wrong way and then correct back and overshoot the proper heading.  After takeoff it was obvious it was not working correctly but I blamed it on the AHARS going bad.  But after landing and rebooting, it was normal.  This second time I truthfully never looked at the PDF while taxiing out but as soon as I attempted to engage the AP and the roll servo began showing a SLIP I started trying to figure out what was wrong.  While hand flying,  as I rolled to the left and held the bank, the PDF presentation indicated a roll to the right the same amount of bank and then immediate precessed back to indicate a left bank.  If I rocked the wings in level flight, the heading would swing wildly the wrong way.  The best way to describe it is just to watch a whiskey compass in a rapid turn.  The airplane symbol on the map presentation also rotated the wrong direction as it followed the PDF display.  I did not have the G-meter up so I do not know if there were any spikes but the altitude mode was working fine and it climbed and leveled off as programmed.  The problem was in the heading input.
If it does it again, I'll do additional trouble shooting and video it.

 

[Dynon]

What kind of aircraft/engine is it? Where's the ADAHRS mounted? A video would definitely help, for sure interesting, but even more so a diagnostics data file would REALLY yelp us see what you're seeing. You need to grab that within an hour of the event, and it takes some time to download on to a USB stick (during which time the display is not usable). Also, are you running 5.1? ADAHRS vibration can cause some off effects in rare installations, but, SkyView can now warn you about that in our most recent software versions.

 

[Edwardoc]

My Skywiew is in an RV-8/IO-360. Running 5.1 and am going to wait before upgrading to 6.0 for a while since I'm perfectly happy with 5.1. The ADAHRS is mounted just behind the rear baggage compartment on a shelf attached to the left upper longeron. It is within the mounting area shown in the instructions. I doubt it is vibration since it has only happened twice in a little over a year and 100 plus sorties and it always reboots and works perfectly. I'll read up on how to capture the data on a USB and if it happens again I'll get it. Thanks.