It seems that some Dynon EFIS users have had problems with momentary attitude display anomalies, that are possibly related to vibration from the engine. The problem is present at some specific engine rpms, but not others. Dynon is taking the problem seriously, and are working hard to find and fix it.

The following message was posted on the RV-List:

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Subject: RV-List: Dynon D-10 errorsDate: Mon, 6 Sep 2004 20:26:04 -0400From: "Stewart, Michael (ISS Atlanta)" To: --> RV-List message posted by: "Stewart, Michael (ISS Atlanta)" I want to thank those who have inquired as to the errors I have beengetting on the Dynon based on some Findings From Dan Checkoway's post onhis website here:http://www.rvproject.com/20040901.html Dan has done an excellent  goodjob summarizing the issue there. I suggest you read that first.To summarize, myself and others, have been getting errors on the horizonfunction of the Dynon EFIS. In one case it really scared me and as aresult I have grounded me 6A from any IFR work. Most of the errors are alean in the roll axis by as much as 7-10 degrees. Pitch errors in mycase have been as much as 20 degrees. Here is a brief synopsis of whatand how it is happening based on some e-mail to Dynon:I flew 6 hours today and worked the Dynon hard. I can now easilyreproduce the lean.I started after departure at 2500rm and went to 1900rmp 10rpm at a timewith 1 minute intervals, and back to 2700rpmAt 2560, the leaning happens, it slowly oscillates from right to left,and back again. I can come off it by 15rmp on either side and it resumesaccurate operation.I can give you further details but I now can quickly reproduce it, and Itook some shots of how bad it is out on the lean. You will notice thaton one shot, the bank indicator on the right shows wings completelylevel, autopilot on, and it was silky smooth air.Also I have seen it at other RPMs today. I saw it in formation at 2480but could not troubleshoot as we were practicing.I was able to see the pitch out during this activity, but not by much. 2degrees maybe, but it was out and I could watch it happen with theleaning at the same rpm, although the pitch was not as reproducible asthe roll problem.took off from home base, early turn out, climb in smooth morning air to3500'agl level off and the d10 compass heading was swinging a d10 beingerratic on the screen. That caught my eye. At the same time, d10 showedme in a 20 degree climb and I was level. In about 6 seconds the compassstabilized, and in about 20 seconds the pitch stabilized to level.Next on a different day, I saw another example of the leans in rollinformation by about 4 degrees. A very pronounced lean showing a righthand turn 4 degrees or so, autopilot flying the plane straight andlevel, compass on the d10 holding steady. It would eventually, after 1minute or so get level, then lean again. This went on for about 6minutes. Then fine. I have seen this behavior in the unit a dozen timesover the 700 hours of flight with it.In another case, the one that really scared me, I came out of 15,000' ona long hard decent to 1000'AGL and leveled off in MVFR vis 2, mist, andthe dynon showed I was in a steady climb of 20 degrees. I was clearlylevel cross checking other instruments and was low. After a min or so itcleared up and resumed normal operation. This is the largest deviationin pitch I have seen. I took a big deep breath and thanked god I was notIMC. If I were, I may not have caught the pitch error and might have putthe nose into the ground. Needless to say, no more IFR till it isresolved.So the above e-mail excerpts will give you and idea of the issue. LikeDan stated on his webpage, I have been in contact with Dynon and theyare taking this very seriously. I have been impressed with theirresponsiveness and professionalism. Clearly this is serious and Dynonsays "this is the most important item on their plate." Now, we have notfound a fix yet. I seem to be the only guy who can easily reproduce theproblem, but I would bet, as I did with the EMI item, that this is afleet wide problem. Dynon says I have the most hours on their unit inthe field. Perhaps that explains some of why I have been able to get toa reproducible stage. They are working hard and I am confident they willget to the bottom of it. They have offered to refund my money. I haven'ttaken it yet as I want to help them work out the problem. This is aterrific unit and I am confident they will nail it down. Until then,remember this is an experimental device and should be treated as such.If you have one of these in your plane, keep this in mind as you fly.Picture of a lean here: Notice bottom right Trio Autopilot shows wingslevel, as they were.http://www.mstewart.net/deletesoon/dynonlean.jpgRegards,Mike Stewart

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I've always considered the Dynon EFIS as a big experiment, and nothing has happened to change that viewpoint. I'm encouraged by Dynon's willingness to admit problems, and to work hard to fix them. I have every reason to believe they will fix this one. I am thinking very seriously at having an independent attitude source though, just in case. I just need to do a bunch more overtime to pay for it.