From what I heard through the grapevine, Dynon had reproduced a "leaning" issue in a Cub they were working with. Apparently they're seeing an issue in the 1900 to 2000 RPM range. This is a range that I basically never use, at least not in cruise. I normally fly between 2300 and 2500 RPM. But the point is that Dynon may have reproduced a similar issue and believes it's related to vibration frequencies. I did not receive this information firsthand from Dynon, so take it with a grain of salt. But think about it...it makes sense. Depending on the sampling rate of the sensors, and depending on the frequency of the vibration, you could easily get some "constructive interference" type of interpretation due to vibration. I'm no engineer, but I can kinda visualize the wave math of it.
Meanwhile, Mike Stewart and I have been talking via email and phone quite a bit lately. Mike has put over 700 hours on the EFIS-D10 in his RV-6A, and he has seen not only "the leans" like I have, but he has also experienced pitch display excursions. I had never seen any pitch issues in my setup. One thing that Mike and I talked about was why we were the only two RV pilots out there who had mentioned having problems with the D10. My theory is that there are some who are in complete denial about the issue, or maybe haven't picked up on it yet. We know Mike and I aren't the only people who have flown in IMC with our D10s. Others have mentioned flying IFR with it as well. Is it possible that in other installations the problem hasn't occurred at all? Yes. Do I think there are other installations that are experiencing this problem? Yes. Mike and I have put quite a bit of time on our planes and on the D10, so I'm not surprised that we may be the first to encounter and isolate the problem, and possibly the most in tune with it...but it's scary to think that there may be pilots out there who are flying their D10s in IMC either without knowing that there's a problem, or in denial that it exists. It's understandable. You spend $2000 on a high-tech piece of "cool toy" for your panel, and in a way you don't want to admit that it's not perfect and it's not the best thing since sliced bread. But let's get real here. Flying on clear day with an attitude indicator that occasionally indicates a slight error is NOT a problem. But flying in instrument conditions with a gauge that isn't perfect is a risk. Be careful out there people, and SPEAK UP if you think you have even the slightest problem. This is brand new technology, and the kinks are NOT all worked out...regardless of how careful and diligent Dynon was in the R&D phase, and how they took their time releasing the EFIS to the public. They still have their work cut out for 'em.
Let me shift gears and say that I don't mean to speak negatively about the EFIS-D10 or especially not Dynon as a company. While I do believe the product is still nacent and has its issues, I also believe that the company will come up with a solution that works. I have faith that this will be resolved. I'm willing to be somewhat patient, because I do believe that Dynon's product is the best choice for my panel and the way I fly.
Ok, back to the details. A few days ago Mike did some extensive testing in his -6A, armed with the theory that the problem was vibration related. He was actually able to reliably reproduce the leaning issue. He said that he started at high RPM and gradually reduced the RPM in 10 RPM increments, each increment running for 1 minute. Mike saw the leaning happen at 2560 RPM, where it would slowly oscillate back and forth. By varying 15 RPM on either side of 2560, the D10 would become accurate again. This was done with the wings perfectly level in "silky smooth air." Mike mentioned that he saw some variation at 2480 RPM as well. He mentioned he did see some pitch excursions, but they were minor and not as reproducible.
I haven't had time to do as extensive testing as Mike has, so it has been extremely helpful that he has been so diligent in digging for the answer. Dynon has responded with a firmware update, which they gave Mike and me to try out. I upgraded my D10 with version 1.9.4 and flew for a couple of hours. Again, I haven't had time to do a strict RPM-based test...I just "went flying" (had some flyouts and stuff going on...good VFR stuff, obviously).
Version 1.9.4 did not solve the leaning problem, which happened a couple of times during the flights. Not only did I see leaning, but I saw two rapid pitch excursions at one point during a climb. It indicated an immediate pitch-up of about 10 degrees, then bounced right back down to where it was, then repeated, maybe slightly less amplitude the second time. Then, after that, it was fine for the remainder of the day pitch-wise. I had never seen any pitch excursions before...so technically, version 1.9.4 is worse than before. Leaning plus pitch.
Hey, what can I say other than I'm willing to keep testing and trying fixes? As long as Dynon is working to resolve the issue I'm happy to try stuff out. Remember -- they had this nasty EMI issue. They fixed that. Now they have this nasty attitude issue. They'll fix it in due time.
I can't stress enough...if you see any attitude deviations with your Dynon EFIS, please speak up.